Component Carrier For Waveguide Applications

Abstract

A component carrier which includes a stack having at least one electrically conductive layer structure, at least one electrically insulating layer structure, and a recess being at least partially formed in the stack, optionally having an electrically conductive coating, and being configured as waveguide, wherein a plurality of edges delimiting the recess are formed by electrically conductive material of the at least one electrically conductive layer structure and/or of the optional electrically conductive coating.

Claims

1. A component carrier, comprising: a stack comprising at least one electrically conductive layer structure and at least one electrically insulating layer structure; and a recess for example a cavity, being at least partially formed in the stack, optionally having an electrically conductive coating, and being configured as a waveguide; wherein a plurality of edges delimiting the recess are formed by electrically conductive material of the at least one electrically conductive layer structure and/or of the optional electrically conductive coating.

2. The component carrier according to claim 1, comprising at least one of the following features: wherein all vertical edges delimiting the recess are formed by electrically conductive material of the at least one electrically conductive layer structure and/or of the electrically conductive coating; wherein all edges delimiting the recess are formed by electrically conductive material of the at least one electrically conductive layer structure and/or of the electrically conductive coating; wherein at least two sidewalls of the recess are completely covered with electrically conductive material of the at least one electrically conductive layer structure and/or of the electrically conductive coating; wherein at least one of a top wall, a bottom wall, and at least one sidewall of the recess is or are partially or completely covered with electrically conductive material of the at least one electrically conductive layer structure and/or of the electrically conductive coating; wherein the recess is completely surrounded by electrically conductive material of the at least one electrically conductive layer structure and/or of the electrically conductive coating with the only exception of at least one opening for feeding a signal; wherein at least one edge, for example at an upper side and/or at a lower side of the recess, comprises a metal-metal oxide-metal succession.

3.-8. (canceled)

9. The component carrier according to claim 1, wherein a width of the recess varies along a length of the recess by not more than 75 m.

10. The component carrier according to claim 1, comprising at least one of the following features: wherein the width of the recess varies along the length of the recess by not more than 20 m, for example by not more than 15 m; wherein the width is smaller than the length.

11. (canceled)

12. The component carrier according to claim 1, wherein the stack has a sidewall, delimiting the recess, which has a roughness Rz of not more than 75 m, for example in a range from 15 m to 75 m.

13. The component carrier according to claim 1, comprising at least one of the following features: wherein at least part of the sidewall is covered with an electrically conductive coating; wherein at least one of the at least one electrically conductive layer structure is exposed at at least part of the sidewall; wherein the sidewall extends continuously in a vertical direction; wherein the sidewall has at least one step.

14. (canceled)

15. The component carrier according to claim 1, comprising at least one of the following features: wherein at least one of the at least one electrically conductive layer structure defines a bottom of the recess; wherein the at least one electrically conductive layer structure defining the bottom of the recess is a patterned layer, patterned in the region of the bottom of the recess; wherein an uppermost of the at least one electrically conductive layer structure is a patterned layer; a frequency filter structure in the recess and/or at material of the stack delimiting the recess, wherein the frequency filter structure is formed by a plurality of webs of at least one of the at least one electrically insulating layer structure at at least part of the sidewall, and by an electrically conductive structure formed on and/or between the webs; wherein a horizontal surface of at least one of the at least one electrically conductive layer structure has a roughness Rz of not more than 1 m, for example of not more than 0.5 m, for example of not more than 0.2 m; an antenna structure in the recess and/or at material of the stack delimiting the recess, wherein the antenna structure is a free-standing structure in the recess, is circumferentially spaced with respect to surrounding material of the stack by a gap, and comprises part of at least one of the at least one electrically conductive layer structure.

16.-24. (canceled)

25. A method of manufacturing a component carrier, the method comprising: providing a stack comprising at least one electrically conductive layer structure and at least one electrically insulating layer structure; forming a recess at least partially in the stack, wherein a width of the recess varies along a length of the recess by not more than 75 m; and configuring said recess (43) as a waveguide.

26. The method according to claim 25, wherein the method comprises: forming a poorly adhesive structure in an interior of the stack; forming a circumferentially closed trench in the stack extending up to the poorly adhesive structure; and removing a material piece, delimited by the trench and the poorly adhesive structure, from the stack.

27. The method according to claim 26, comprising at least one of the following features: wherein the method comprises forming the trench by laser cutting, for example by pulsed laser cutting, for example using a picosecond laser or a femtosecond laser; wherein the method comprises forming a laser stop structure in the stack adjacent to the poorly adhesive structure; wherein the method comprises forming a further poorly adhesive structure in an interior of the stack: forming a further circumferentially closed trench in the stack extending up to the further poorly adhesive structure, the further circumferentially closed trench having another diameter and/or depth than and/or being laterally displaced with respect to the circumferentially closed trench; and removing a further material piece, delimited by the further trench and the further poorly adhesive structure, from the stack.

28.-29. (canceled)

30. The component carrier according to claim 1, further comprising: a wiring structure forming part of the at least one electrically conductive layer structure and being arranged on top of said recess; and a ridge surrounding the recess, wherein the wiring structure is electrically coupled with the waveguide via the ridge.

31. The component carrier according to claim 30, comprising at least one of the following features: an electrically conductive lining on at least part of the ridge and electrically coupling the waveguide with the wiring structure; wherein for example the electrically conductive lining circumferentially surrounds the ridge; wherein the ridge is a ring with a central through hole aligned with the recess; wherein the ridge comprises an electrically insulating material; wherein the wiring structure is located on top of the ridge; wherein the wiring structure is the uppermost of the at least one electrically conductive layer structure; an at least partially dielectric layer having a central through hole accommodating the ridge and having substantially the same height as the ridge plus electrically conductive material on the ridge; wherein the wiring structure comprises a feedline structure for coupling a signal between the wiring structure and the waveguide.

32.-40. (canceled)

41. The component carrier, in particular according to claim 1, wherein at least one of the at least one electrically insulating layer structure is made of a poorly adhesive structure; a metallic electroless plating structure formed on a surface of the stack apart from the poorly adhesive structure; and wherein the poorly adhesive structure covers a bottom and/or at least one sidewall of the recess, and wherein the metallic electroless plating structure is formed on at least part of a sidewall of the stack delimiting the recess.

42. The component carrier according to claim 41, comprising at least one of the following features: wherein the poorly adhesive structure is made of a hydrophobic material; wherein the recess is configured as a waveguide; wherein at least one of the at least one electrically conductive layer structure comprises a patterned metal layer at the bottom of the recess under the poorly adhesive structure.

43.-47. (canceled)

48. The component carrier according to claim 1, further comprising: an electrically conductive coating on at least part of sidewalls of the stack which laterally delimit the recess; wherein the electrically conductive coating is curved outwardly on an upper end of the sidewalls.

49. The component carrier according to claim 48, comprising at least one of the following features: wherein a beak-shaped extension of the recess is formed between the electrically conductive coating and one of the at least one electrically conductive layer structure at the upper end of the sidewalls; wherein the recess is delimited at a lower end of the sidewalls by a tilted metallic section formed in an interface region between the electrically conductive coating and one of the at least one electrically conductive layer structure; wherein the electrically conductive coating tapers downwardly in a central part of the sidewalls; wherein, over a horizontal range between two opposing intersections between the electrically conductive coating and one of the at least one electrically conductive layer structure at the bottom of the recess, a height of the recess varies by not more than 20%, for example by not more than 10%; wherein a locally thickened metallic region is formed as an intersection between the electrically conductive coating and one of the at least one electrically conductive layer structure at the bottom of the recess; wherein the electrically conductive coating is substantially S-shaped at at least one of the sidewalls.

50.-55. (canceled)

56. A component carrier, comprising: a stack comprising at least one electrically conductive layer structure and at least one electrically insulating layer structure; a recess being at least partially formed in the stack; and a structured metallic electroless plating structure formed at least partially on at least one sidewall of the stack.

57. The component carrier according to claim 56, comprising at least one of the following features: a structured poorly adhesive structure on said at least one sidewall apart from the structured metallic electroless plating structure; wherein the recess is configured as a waveguide.

58.-60. (canceled)

61. A method of using a component carrier for a high-frequency application, the method comprising: providing a stack comprising at least one electrically conductive layer structure and at least one electrically insulating layer structure; forming a recess at least partially in the stack, optionally having an electrically conductive coating, and being configured as a waveguide; wherein a plurality of edges delimiting the recess are formed by electrically conductive material of the at least one electrically conductive layer structure and/or of the optional electrically conductive coating; and coupling a signal to the waveguide.

62. The method according to claim 61, comprising at least one of the following features: wherein the component carrier is used for wireless communication, it for example according to 5G or 6G; wherein the component carrier is used for high-frequency applications above 1 GHz, for example above 28 GHz.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0094] FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, and FIG. 8 illustrate cross-sectional views of structures obtained during carrying out a method of manufacturing a component carrier according to an exemplary embodiment of the disclosure, shown in FIG. 8.

[0095] FIG. 9 is a flow diagram of a method of manufacturing a component carrier according to an exemplary embodiment of the disclosure.

[0096] FIG. 10 is a flow diagram of a method of manufacturing a component carrier according to another exemplary embodiment of the disclosure.

[0097] FIG. 11 is a flow diagram of a method of manufacturing a component carrier according to still another exemplary embodiment of the disclosure.

[0098] FIG. 12 illustrates a component carrier according to an exemplary embodiment of the disclosure.

[0099] FIG. 13 illustrates a component carrier according to another exemplary embodiment of the disclosure.

[0100] FIG. 14 illustrates a component carrier according to still another exemplary embodiment of the disclosure.

[0101] FIG. 15 illustrates a component carrier according to yet another exemplary embodiment of the disclosure.

[0102] FIG. 16 illustrates a component carrier according to yet another exemplary embodiment of the disclosure.

[0103] FIG. 17 illustrates a component carrier according to yet another exemplary embodiment of the disclosure.

[0104] FIG. 18 illustrates a component carrier according to yet another exemplary embodiment of the disclosure.

[0105] FIG. 19 illustrates a component carrier according to yet another exemplary embodiment of the disclosure.

[0106] FIG. 20 illustrates dimensions of a waveguide-type recess of a component carrier according to an exemplary embodiment of the disclosure.

[0107] FIG. 21 illustrates a cross-sectional image of a manufactured component carrier with interior waveguide-type recess according to an exemplary embodiment of the disclosure.

[0108] FIG. 22 illustrates a cross-sectional view of a component carrier with interior waveguide-type recess according to an exemplary embodiment of the disclosure and corresponding to the image of FIG. 21.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

[0109] The illustrations in the drawings are schematically presented. In different drawings, similar or identical elements are provided with the same reference signs.

[0110] Before referring to the drawings, exemplary embodiments will be described in further detail, some basic considerations will be summarized based on which exemplary embodiments of the disclosure have been developed.

[0111] According to an exemplary embodiment of the disclosure, a compact component carrier with integrated low-loss waveguide or hollow conductor may be provided. In a structured hollow conductor according to an exemplary embodiment of the disclosure, a bottom-side copper layer is first structured, after which a non-sticky coating, which is not metallized in a subsequent metallization process, is printed on the structured layer. Hence, a release layer is applied to a structured copper layer. After a further build-up of the stack and a laser cutting process, a recess is obtained. Sidewalls of the recess or cavity may then be selectively coated with metal, while the release layer is inert against electroless metal deposition and is thus selectively protected from being metal coated, and can then be removed. A selective coating with chemical copper is thus carried out for structuring the hollow conductor. In particular, metallized sidewalls may be manufactured without metal edges in the sidewall. Consequently, signal losses may be avoided. In addition, signal losses may be suppressed by the construction of a ridge or elevation as well as by covering the ridge with a copper foil, which can be structured. Furthermore, the described manufacturing method may allow to produce component carriers with integrated waveguide function on an industrial scale and with high throughput.

[0112] According to an exemplary embodiment of the disclosure, a fully metallized hollow waveguide may be provided which may include a structured feeding line on a bottom or top wall. A corresponding manufacturing process may allow to produce a transition between a structured metallized microstrip and a hollow waveguide. Advantageously, no structural artifacts (which may occur conventionally due to a layer shift resulting from a connection of two stacks for forming a component carrier) occurs in the middle of the waveguide wall according to exemplary embodiments.

[0113] In particular, a structured bottom cavity for a waveguide with metallized walls may be provided allowing to create an electrically closed waveguide. Such a waveguide may be a fully metallized air-filled waveguide with signal feeding structure on bottom. An air-filled substrate integrated waveguide may advantageously allow to obtain a low loss. At high frequencies and in particular at frequencies above 28 GHz, radar signal transmission may be achieved with high bandwidth. The high performance and low losses of the component carrier with integrated waveguide may be achieved by creating a corresponding recess using an embedded release layer which, in combination with laser cutting, allows to create the recess with high surface quality. This may allow to manufacture a component carrier-integrated waveguide without structural artifacts in the metallized sidewall. A ridge or wall may be built below a top copper layer for improving reliability of the electric coupling between waveguide and feedline. Advantageously, sidewalls of a recess in the stack constituting a waveguide may be electrically connected to top and bottom. In particular, a feeding structure on the bottom of the waveguide may be protected during an electroless copper process by release layer ink or another non-sticky or poorly adhesive structure.

[0114] For manufacturing a recess in the component carrier for forming the waveguide, a high accuracy may be achieved by implementing a picosecond laser cutter allowing to obtain a high accuracy (for instance tolerances of 15 m or less).

[0115] Exemplary embodiments of the disclosure provide structured, metallized hollow conductors and a transition between a strand-conductor and a hollow conductor. Furthermore, manufacturing processes for the manufacture of structured, metallized hollow conductors and strip conductor-hollow conductor transitions are provided. In particular, a manufacture of metallized hollow waveguides including structured bottom or top walls are possible.

[0116] Advantages of exemplary embodiments are that no dielectric signal loss occurs in an air-filled waveguide according to an exemplary embodiment of the disclosure. Further advantageously, a high bandwidth may be achieved in particular for frequencies above 28 GHz. Furthermore, it may be possible to manufacture a component carrier with waveguides and integrated three-dimensional antenna structures, for instance arranged along a vertical axis. Advantageously, no special low Dk or low Df dielectric materials are needed which may reduce the manufacturing effort. Hence, high effort due to the use of low Dk materials with high glass transition temperature can be avoided. Moreover, reliable single material type stack-ups can be produced with low effort and may be used for instance for different radar performance. Moreover, a structured fully metallized air-filled waveguide with low signal loss and high bandwidth may be provided.

[0117] Exemplary applications of exemplary embodiments of the disclosure are in particular 5G, 6G, an infrastructure base station and small cells. Further possible applications are automotive radar, industrial sensors, and THz range sensors for example for medical applications. Furthermore, exemplary embodiments allow to provide high-frequency component carriers (in particular for frequencies above 30 GHz). Further applications are internet of things applications, optical waveguides, etc.

[0118] Exemplary embodiments of the disclosure relate to structured, metallized hollow conductors and transitions between a strand-conductor and a hollow conductor which are integrated in a multilayer printed circuit board. Furthermore, a manufacturing process for these integrated structured, metallized hollow conductors and transitions between strand conductor and hollow conductor is provided. The application of the structured hollow conductor and strip conductor-hollow conductor transitions can serve as a connection between at least one antenna and at least one chip (or any other component which may be embedded in the stack or surface mounted on the stack). Furthermore, the structured hollow guide may function as a fiber optic or sound guide, as a transition component of waveguide to strip conductor, as antennas as well as part of pressure, sound, or light sensors. Furthermore, the hollow conductors according to an embodiment of the disclosure can also be used for transporting liquids and gases.

[0119] Multi-layer printed circuit boards comprise a stack of electrically conductive copper layers and electrically insulating layers of dielectric and are equipped with electronic components in or on the layer sequence. Hollow conductors are waveguides and are used for the transmission of waves, especially electromagnetic waves, light waves or sound waves. A hollow conductor can also serve as a channel for liquids such as cooling fluids and gases. In order to be able to conduct electromagnetic waves or light in a hollow conductor, a transition between a strip conductor and a hollow conductor may be desired.

[0120] An advantage of hollow conductors covered with metal is that these hollow conductors have low signal transmission losses and energy losses compared to those waveguides that are filled with dielectric and/or have at least partially opened sidewalls. Due to the cut-off frequency, hollow conductors have a frequency-dependent defined width and height. The higher the frequency of the wave to be directed, the smaller the wavelength and thus also the geometry of the hollow conductor. For the manufacture of PCBs, hollow conductors and transitions between strip conductor and hollow conductor with small dimensions are particularly appropriate in the high GHz frequency range for being integrated into the printed circuit board.

[0121] For example, the dimensions of a hollow conductor for the Ka band of 26-40 GHz are 7.1 mm in width and 3.6 mm in height, for the W band of 75-100 GHz 2.5 mm in width and 1.3 mm in height. The dimensions of a hollow conductor for the G band of 140-220 GHz are 1.3 mm in width and 0.6 mm in height and for the Y band of 750-1100 GHz are 0.25 mm in width and 0.13 mm in height.

[0122] As the frequency range increases, so do the requirements for the accuracy of the manufacture of the hollow conductors and transitions between strip conductor and hollow conductor. Thus, in the frequency range above 30 GHz, manufacture of hollow conductors and strip conductor hollow conductor transitions should preferably have tolerances below 40 m to avoid noise and signal loss.

[0123] An embodiment of the disclosure relates to structured, metallized hollow conductors and transitions between strip conductor and hollow conductor which are integrated in the printed circuit board. Furthermore, a corresponding manufacturing process for producing such a structured, metallized hollow conductor and transitions between strip conductor and hollow conductor may be provided. Copper structures at the bottom of the hollow conductor according to an embodiment of the disclosure may be covered with at least one poorly adhesive structure formed of, for example, a fluorocarbon compound. The poorly adhesive structure may be inert in a process of physically and/or chemically applying a conductive catalytic layer such as for example chemical copper. The copper layer under the copper cover layer is preferably provided with at least one ridge or elevation in the area of the hollow conductor which is stable in the chemical copper process. Furthermore, the hollow conductor in the area of the ridge may be cut out by at least one high-precision separation process such as for example a laser cutting process. The resulting edge of the ridge as well as the sidewalls may be selectively coated with copper in a structured hollow conductor according to an embodiment of the disclosure. However, a structured metal area at the bottom is not additionally metallized. Beyond this, the cavity is covered in the further structuring process and in a subsequent build up during which at least one prepreg layer with openings around the copper edges of the ridge may be applied. The top layers of the obtained component carrier may be formed by a structured copper layer and an electrically conductive material in the area of the metallic wall.

[0124] Before applying a poorly adhesive structure to protect the copper structures at the bottom of the hollow conductor according to an embodiment of the disclosure, the copper structures at the bottom of the hollow conductor can be protected by end surface processes, which may include but are not limited to processes such as chemical silver, tin, ENIG or OSP processes.

[0125] Before applying the top layer(s), the structured hollow conductor, which may have sidewalls of copper, may be subjected to further processes such as galvanic copper processing for applying further metal to the sidewalls, laser drilling processes, photo processes and etching processes for structuring a copper layer under the copper top layer. Furthermore, end surfaces may be treated by processes including chemical silver, tin, ENIG, ENIPIG, hard gold or OSP. The structuring of the top copper layer, which closes the hollow conductor on the top, can include further processes such as galvanic copper for further copper construction of the sidewalls, laser drilling processes, photo processes and etching processes for structuring a copper layer under the copper top layer, as well as end surface processes such as chemical silver, tin, ENIG, OSP or a fluorocarbon coating which includes PTFE, PVDF, etc.

[0126] The issue of layer offset in the middle of the hollow conductor wall can be solved by embodiments of the present disclosure surprisingly by the fact that the high-precision separation process (such as the laser cutting process) cuts through the applied ridge and at the same time also through the underlying layers of the circuit board up to the laser stop position. It has been surprisingly found that, after the high-precision separation process (such as a laser cutting process), a copper plating of the edge of the ridge occurs together with a copper plating of the sidewalls of the hollow conductor, while the poorly adhesive structure simultaneously protects a structured metal layer on the bottom of the hollow conductor from copper deposition. This makes it possible to produce hollow conductors with sidewalls which are completely coated with metal, without compromising on the patterned character of the bottom metal layer.

[0127] For example, the structured hollow conductors can be used for the connection between antenna and chip as well as for the manufacture of a transition between hollow conductor and strip conductor. Furthermore, the structured hollow conductors may be employed in the GHz or THz frequency range as well as for the conduction of light or sound waves. Hollow conductors according to exemplary embodiments may have a higher bandwidth and lower signal losses than conventional waveguides. Furthermore, in the manufacturing process for the structured metallized hollow conductors according to an embodiment of the disclosure, well-defined processes of printed circuit board manufacturing technology such as printing processes, laser cutting processes and chemical copper processes, photo and etching processes as well as end surface processes, may be used for enabling a mass manufacture of the integrated hollow conductors with high precision and deviations below 30 m.

[0128] FIG. 1 to FIG. 8 illustrate cross-sectional views of structures obtained during carrying out a method of manufacturing a component carrier 100, such as a printed circuit board (PCB), according to an exemplary embodiment of the disclosure, shown in FIG. 8.

[0129] Referring to FIG. 1, a stack 102 is provided which comprises a plurality of electrically conductive layer structures 41 and a plurality of electrically insulating layer structures 40. The electrically insulating layer structures 40 may for instance comprise resin (such as epoxy resin), optionally comprising reinforcing particles such as glass fibers. For instance, the electrically insulating layer structures 40 may be made of prepreg. The electrically conductive layer structures 41 may comprise continuous and/or patterned copper layers and/or vertical through connections (not shown in FIG. 1) such as copper filled laser vias.

[0130] More specifically, in the embodiment shown in FIG. 1, a first electrically conductive layer structure 41 is a patterned metal layer embedded in the stack 102. A second electrically conductive layer structure 41 is another patterned metal layer located at a top surface of the stack 102.

[0131] Furthermore, a non-sticky or poorly adhesive structure 124 is embedded in an interior of the stack 102 and may be one of the electrically insulating layer structures 40. The poorly adhesive structure 124 may also be denoted as a release layer, because the adhesion of the poorly adhesive structure 124 with respect to neighboured layer structures 40, 41 in stack 102 is so poor that the stack 102 can be easily delaminated at the poorly adhesive structure 124 without the need of overcoming adhesion forces. For instance, the poorly adhesive structure 124 may be made of Teflon. During the further manufacturing process, the poorly adhesive structure 124 can be advantageously used for two purposes: On the one hand, a recess 43 can be formed in the stack 102 by taking out a material piece 142 defined by a circumferential trench 126 and by the upper main surface of the poorly adhesive structure 124 thanks to its poor adhesion or release layer function (compare FIG. 3 and FIG. 4). On the other hand, the poorly adhesive structure 124 may remain on the patterned electrically conductive layer structure 41 directly beneath the poorly adhesive structure 124 for protecting said patterned electrically conductive layer structure 41 from an undesired metal coating during a chemical metal coating process described below in further detail (compare FIG. 5). Consequently, the patterned property of the underlying electrically conductive layer structure 41 may be maintained during said chemical metal coating process.

[0132] A further advantage of the described construction of stack 102 according to FIG. 1 is that the patterned electrically conductive layer structure 41 directly under the poorly adhesive structure 124 may synergistically function as a laser stop structure 128 in the stack 102 adjacent to the poorly adhesive structure 124, i.e. may stop a laser cutting process described below referring to FIG. 3. Alternatively, a separate laser stop structure may be provided in stack 102 in addition to the patterned electrically conductive layer structure 41 directly beneath the poorly adhesive structure 124.

[0133] Referring to FIG. 2, an elevation or ridge 42 is formed on or attached to the stack 102. The ridge 42 may be a ring of dielectric material, which may for instance be printed on top of the stack 102 and may be subsequently cured.

[0134] Referring to FIG. 3, a circumferentially closed trench 126 is formed in the stack 102 extending up to the embedded poorly adhesive structure 124. Formation of the trench 126 may be carried out by laser cutting using a laser source 152 emitting a laser beam 154 and being preferably movable relative to the stack 102. The laser stop structure 128 in the stack 102 may stop the laser cutting process at a pre-defined position, as mentioned above. Preferably, the laser beam 154 may be pulsed and may be most preferably a picosecond laser. It has turned out that this kind of cutting the stack 102 provides excellent spatial accuracy and hence formation of trench 126 with very low tolerances and without structural artefacts. Inner vertical sidewalls of the ridge 42 may be preferably aligned with the trench 126.

[0135] By formation of the circumferential trench 126 extending up to the poorly adhesive structure 124, a material piece 142 is separated from the rest of the stack 102. The material piece 142 is circumferentially delimited by the trench 126 and is delimited at its bottom side by the poorly adhesive structure 124 which does not adhere neither to the material piece 142 nor to the rest of the stack 102.

[0136] Referring to FIG. 4, said separated material piece 142 delimited by the trench 126 and the poorly adhesive structure 124 may then be removed from the stack 102 to thereby form blind hole-type recess 43 in the stack 102. Highly advantageously and also referring to FIG. 20, a width W of the recess 43 varies along a length L of the recess 43 by not more than 75 m. According to a FIG. 4, the width W and the length L of the recess 43 are the dimensions of the recess 43 in the two horizontal dimensions extending in the paper plane and perpendicular to the paper plane, respectively, whereas a height H corresponds to a dimension of the recess 43 in a vertical direction according to FIG. 4 (compare FIG. 20). The mentioned design rule means that a difference between a maximum value and a minimum value of the width W along the length L does not exceed 75 m. Furthermore, recess 43 may be characterized by exactly vertical sidewalls 110 being free of undesired micro-steps and having an extremely small surface roughness Rz of for example 15 m. The small tolerance of the width W along the length L of the recess 43, to which also the continuously smooth circumferential surface of the sidewalls 110 of stack 102 defining the recess 43 contributes, is highly advantageous, since this promotes the quality of the electromagnetic wave formation in the waveguide. A metallic structure 140 (see FIG. 5) formed subsequently on the sidewalls 110 may also have very smooth sidewalls when formed on low-roughness interior sidewalls 110 of stack 102. Consequently, the readily manufactured component carrier 100 may have excellent high-frequency properties, since signal transport along such a smooth metallic structure 110 may be possible with very low losses. Descriptively speaking, according to the skin effect, a high-frequency signal will propagate substantially only in a thin surface skin of such a metallic structure 110 and will therefore highly benefit from the low roughness. The high-frequency signal can thus propagate with only lowest distortions around the hollow conductor or waveguide being presently produced.

[0137] As shown in FIG. 4 as well, the poorly adhesive structure 124 is exposed at a bottom 48 of the recess 43 by removing material piece 142 and remains on the beneath electrically conductive layer structure 41 as a protective structure to provide protection in a subsequent electroless plating process.

[0138] Referring to FIG. 5, a metallic structure 140 is formed by electroless plating selectively on a surface of the stack 102 apart from the poorly adhesive structure 124. For instance, chemical copper may be formed for lining the recess 43 and the ridge 42 with the metallic structure 140. Highly advantageously, no or substantially no electroless deposited metal adheres to the exposed surface of the poorly adhesive structure 124 due to its non-sticky properties. Further advantageously, the poorly adhesive structure 124 protectively covers the beneath patterned electrically conductive layer structure 41 and therefore prevents undesired deposition of metal thereon. This ensures that the structured or patterned character of said electrically conductive layer structure 41 is maintained. Since patterning said electrically conductive layer structure 41 at the bottom of the recess 43 would be at least extremely difficult, this protection is of utmost advantage.

[0139] As shown in FIG. 5, the metallic structure 140 may also be in direct physical contact with the lowermost structured electrically conductive layer structure 41 shown in FIG. 5.

[0140] If desired or required, the electroless deposited metallic material of metallic structure 140 may be further thickened by a subsequent optional galvanic metal deposition process by which additional metallic material may be galvanically deposited on exposed surfaces of the metallic structure 140. Consequently, the sidewalls 110 may be covered with an electrically conductive coating 44 of adjustable thickness.

[0141] By the formation of the metallic structure 140, said recess 43 is configured as waveguide or hollow conductor. As shown, the metallic structure 140 not only covers vertical sidewalls of the recess 43, but also exposed surface portions of the elevation or ridge 42 in form of electrically conductive lining 134.

[0142] Referring to FIG. 6, the poorly adhesive structure 124 can be removed after forming the metallic structure 140. For instance, this can be accomplished by etching, dissolving, or evaporating the poorly adhesive structure 124. Thereby, also the patterned electrically conductive layer structure 41 which had initially been protected by the poorly adhesive structure 124 can be exposed at bottom 48. This may make it possible to subsequently subject said electrically conductive layer structure 41 to a surface treatment process.

[0143] However, it is alternatively also possible that the poorly adhesive structure 124 remains at the bottom of recess 43 and forms part of the readily manufactured component carrier 100. Advantageously, appropriate materials for the poorly adhesive structure 124 as disclosed herein (for instance Teflon) may be compatible with high-frequency applications and to not involve noteworthy losses.

[0144] Referring to FIG. 7, an optional electrically conductive adhesive 47 such as an electrically conductive paste (for instance comprising copper and/or silver) may be applied to the exposed top surface of the ridge 42 for electrically coupling the waveguide with a subsequently attached further electrically conductive layer structure 41 (see FIG. 8). The electrically conductive adhesive 47 may for instance be printed or dispensed on the top surface of ridge 42. This significantly improves the electric reliability of an electric coupling between the electrically conductive coating 44 delimiting the hollow recess 43 of the waveguide and the subsequently attached further electrically conductive layer structure 41 (see FIG. 8).

[0145] Hence, ridge 42preferably but not necessarily in combination with the electrically conductive adhesive 47may significantly improve the reliability of an electric connection between a stripline of the electrically conductive layer structures 41 and the waveguide with its electrically conductive coating 44 delimiting the hollow recess 43. Consequently, a highly reliable and low-loss transition between stripline and waveguide can be achieved with excellent electrical properties.

[0146] Moreover, a dielectric layer 136 (for example a prepreg layer) having a central through hole may be attached from above. Said through hole may accommodate the ridge 42. Dielectric layer 136 may have approximately the same height as the ridge 42 plus electrically conductive material (see reference signs 134 and 47) on the ridge 42. As a result, the obtained arrangement is planarized which is advantageous for the further build-up.

[0147] Referring to FIG. 8, the above-mentioned uppermost additional electrically conductive layer structure 41 and a continuous further electrically insulating layer structure 40 may be attached on top of said recess 43, on the electrically conductive adhesive 47 (or, when the latter is not present, on electrically conductive lining 134 being integrally connected with electrically conductive coating 44) and on annular dielectric layer 136. Said uppermost most electrically conductive layer structure 41 may also be patterned (in particular in its portion above recess 43) to thereby form a wiring structure 130 for conducting signals. Thereby, a highly reliable electric contact between the electrically conductive coating 44 of the waveguide and the wiring structure 130 may be established by the electrically conductive lining 134 and the electrically conductive adhesive 47. The electrically conductive adhesive 47 may be cured, for instance by pressure and/or heating.

[0148] As an alternative to the described manufacturing process, it is also possible that the electrically conductive adhesive 47 is applied onto a lower main surface of the uppermost electrically conductive layer structure 41 and is connected to the upper surface of the electrically conductive lining 134 upon connecting the uppermost electrically conductive layer structure 41 with the annular dielectric layer 136 and the ridge 42, with the electrically conductive lining 134 thereon.

[0149] As a result of the described manufacturing method, the component carrier 100 according to an exemplary embodiment of the disclosure according to FIG. 8 is obtained.

[0150] The illustrated component carrier 100 is configured as printed circuit board with integrated waveguide and connected stripline. The component carrier 100 comprises the laminated layer stack 102 composed of electrically conductive layer structures 41 (preferably made of copper) and electrically insulating layer structures 40 (for instance made of prepreg). The hollow recess 43 in stack 102 is coated continuously with electrically conductive coating 44 (for instance also made of copper) and is thereby configured as waveguide. Advantageously, the entire sidewall 110 of the stack 102 delimiting the recess 43 has a roughness Rz of preferably not more than 5 m. More specifically, the sidewall 110 may be preferably circumferentially closed and may extend completely and continuously vertically.

[0151] As already mentioned, the entire vertical sidewall 110 of the recess 43 is covered with the continuous electrically conductive coating 44. This provides a significantly better waveguide function in comparison with conventional metallic fence architectures. Furthermore, a patterned electrically conductive layer structure 41 is exposed at a bottom 48 of the recess 43. Also, the uppermost electrically conductive layer structure 41 according to FIG. 8 is a patterned layer.

[0152] Further advantageously, a horizontal surface of any of the electrically conductive layer structures 41 may have a roughness Rz of not more than 0.2 m. Hence, the horizontal surfaces of at least one of the electrically conductive layer structures 41 may be even smoother than the surface of the sidewall 110 which can be accomplished by polishing, etc. Due to the skin effect, also a very low roughness Rz of said electrically conductive layer structures 41 may be highly advantageously for the high-frequency performance.

[0153] As furthermore shown in FIG. 8, the component carrier 100 may compriseadvantageously but optionallyan antenna structure 120 in the recess 43. Said antenna structure 120 may be preferably embodied as a free-standing structure in the recess 43, may thus be circumferentially spaced with respect to surrounding material of the stack 102 by an air gap of the hollow recess 43, and may comprise an arrangement of electrically conductive layer structures 41 (for example horizontal copper pads and copper vias) preferably embedded in dielectric material of at least one electrically insulating layer structure 40 for providing stability. By antenna structure 120, high-frequency signals 120 may be properly guided within the waveguide or hollow conductor.

[0154] Moreover, component carrier 100 comprises wiring structure 130 forming part of the uppermost electrically conductive layer structures 41 and being arranged on top of said recess 43. Signals may be guided through traces of wiring structure 130. More specifically, the wiring structure 130 may comprise a feedline structure 138 for coupling a signal between the wiring structure 130 and the waveguide.

[0155] Advantageously, ring-shaped ridge 42 (wherein ridge 42 may be alternatively configured as layer with central through hole) surrounds the recess 43 along its entire perimeter. For instance, ridge 42 may be made of a dielectric material, which allows to print or dispense material forming the ridge 42 on stack 102. As shown, the wiring structure 130 located on top of the ridge 42 is electrically coupled with the waveguide via the ridge 42, more specifically via electrically conductive lining 134 covering ridge 42. In the side view of FIG. 8, the electrically conductive lining 134 in combination with an electrically conductive layer structure 41 beneath the ridge 42 fully circumferentially surround the ridge 42. As can be taken from FIG. 8 as well, the wiring structure 130 is the uppermost of the electrically conductive layer structures 41.

[0156] Annular dielectric layer 136 has a central through hole and has the same height as the ridge 42 including its electrically conductive coating. The dielectric layer 136 may be arranged around the ridge 42 to achieve planarity.

[0157] Although not shown in FIG. 8, the poorly adhesive structure 124 may alternatively also remain covering bottom 48 of the recess 43 rather than being removed before completing manufacture of the component carrier 100. Advantageously, poorly adhesive structure 124 does not disturb high-frequency applications, so that maintaining poorly adhesive structure 124 as part of component carrier 100 may allow to skip a separate process of removing poorly adhesive structure 124.

[0158] Still referring to FIG. 8 (see also FIG. 20), the illustrated component carrier 100 comprises the recess 43 being configured as a waveguide-type cavity. As shown, a plurality of edges 67 delimit the recess 43 which are formed by electrically conductive material of the electrically conductive layer structure 41 and of the electrically conductive coating 44, and option-ally also by electrically conductive adhesive 47. The metallized edges 67 may be vertical ones and/or horizontal ones. Preferably, all edges 67 delimiting the recess 43 are formed by such electrically conductive material. Moreover, a plurality of (and preferably all four) vertical sidewalls 110 may be completely covered with said electrically conductive material, in particular of the electrically conductive coating 44.

[0159] According to FIG. 8, also a top wall and a bottom wall of the recess 43 are partially covered with electrically conductive material.

[0160] Optionally and although not shown, the recess 43 may be completely surrounded by electrically conductive material of the electrically conductive layer structures 41 and of the electrically conductive coating 44 (and optionally also by electrically conductive adhesive 47) with the only exception of an opening for feeding a radiofrequency signal (not shown in FIG. 8).

[0161] However, it may also be advantageously possible to directly provide a structures electrically conductive layer (in particular an antenna structure) at the waveguide bottom. Advantageously, the patterned (for instance antenna) structure can be placed on any sidewall of the recess, wherever needed or desired.

[0162] By the metallic coverage of corners, edges 67 and faces (in particular sidewalls 110) delimiting the cavity-type recess 43 forming a waveguide, a metallic cage may be created which maintains radiofrequency waves within the recess 43 during operation of the component carrier 100. This avoids signal loss and increases the signal transmission quality.

[0163] FIG. 9 is a flow diagram 200 of a method of manufacturing a component carrier 100 according to an exemplary embodiment of the disclosure. More specifically, a manufacturing method for providing a structured metal-coated hollow conductor and a transition between a strip conductor and a hollow conductor is shown in FIG. 9.

[0164] First, a copper layer at a bottom 48 of the structured hollow conductor to be manufactured is structured, see block 202 in FIG. 9. Methods of structuring the copper layer include and are not limited to etching methods, printing methods and mechanical processes for structuring.

[0165] Referring to a block 204, a poorly adhesive structure 124 and a laser stop structure 128 may then be printed on the bottom 48 of the recess 43 to be produced. After the process according to block 202, the previously structured copper layer, which represents the bottom 48 of the structured hollow conductor, is covered in the area of the hollow conductor to be provided with a chemical compound which represents a poorly adhesive structure 128 for the other layer structures 40, 41. Preferably, the poorly adhesive structure 124 is made of a hydrophobic material. This is advantageous, as the hydrophobic behavior leads to a decreased wettability, which is believed to promote a limited or even completely eliminated copper deposition on such films. At the same time, the poorly adhesive structure 124 is inert in a subsequent metallization process and is not coated in a chemical copper metallization process. These chemical compounds include, but are not limited to lipids, waxes, alcohols, lipid acid esters, and their mixtures, various polymers wie PP, PEEK, PEK, PVC, PS, fluorocarbons, PFC, PCTFE, fluoroelastomers, silicones, PFA, fluoropolymers such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and their polymers. Particularly preferred compounds are fluorocarbon compounds which comprise PTFE, PFC, PCTFE or fluoroelastomers or wax compounds.

[0166] In addition to the above-mentioned compounds of the poorly adhesive structure 124 (functioning as adhesion prevention material), organic and/or inorganic sulfur, phosphorus or nitrogen containing compounds can be added which act as catalysts for complexing agents during the catalytic deposition of metals (such as palladium, PdSn, Pt, or Ag) and thereby prevent formation of the chemical copper metal layer. It may also be possible to print a combination of the above-mentioned compounds on the area of the structured bottom 48 of the hollow conductor according to an embodiment of the disclosure.

[0167] Referring to a block 206, further copper layers and prepreg layers may then be attached and connected by lamination for creating a further build-up of the component carrier 100 to be manufactured. Thus, further layer structures 40, 41 (such as copper layers and prepreg layers) of the hollow conductor are connected to the stack 102. The copper layer under the copper top layer of the structured hollow conductor can be structured and provided with laser holes.

[0168] Thereafter, a ridge 42 may be printed and cured on the uppermost copper layer of the stack 102 in which a recess 43 is to be formed (compare block 208). Hence, the ridge 42 is applied in the region of the cavity or recess 43 on the uppermost copper layer under the copper cover layer. Materials for the elevation or ridge 42 include and are not limited to varnishes, polymer mixtures, resins or resin mixtures, plug-in paste, solder stop varnish, polymers, and resins as well as resin mixtures which are stable in chemical copper processes of PCB manufacture.

[0169] The manufacturing processes for the creation of the ridge 42 can be carried out by a printing process and may include screen printing, three-dimensionally printing or other printing methods, in particular having an accuracy of less than 5 m, preferably having an accuracy of less than 2 m along x-, y- and z-axis. After printing, the ridge 42 may be subjected to a curing process. The curing process may be adapted to the applied material and can include the following processes: ultraviolet radiation, microwave radiation or thermal curing in an oven at a temperature in a range from 50 C. to 150 C. The metallization processes include and are not limited to a chemical copper process, a galvanic copper process, an electroless nickel immersion gold process and a chemical silver process.

[0170] Block 210 indicates a separation process (preferably by laser cutting) and subsequent activation of sidewalls 110 of the stack 102 as well as a removal of a material piece 142 in the center of the recess 43. After curing the ridge 42, a material piece 142 may be cut out from the stack 102 for exposing sidewalls 110 of the stack 102 by carrying out a precise separation method, preferably a laser cutting process. The ridge 42 as well as the underlying prepreg layers may be cut up to the laser stop position defined by laser stop structure 128. If laser cutting is used as a separation method, it is for instance possible to use a CO.sub.2 laser or a UV laser. Preferably, pulsed laser beams (in particular nanosecond pulses, picosecond pulses or even femtosecond pulses) or alternatively continuous laser beams can be used. The cutting width of the laser cutter may be in the range from 10 m to 30 m, preferably less than 25 m, especially preferably less than 20 m. The accuracy of the laser cutting process may be 30 m, preferably 20 m, most preferably less than 18 m. An advantage of the method according to an embodiment of the disclosure is to produce the structured hollow conductor by cutting out a material piece 142 along sidewall 110 of the hollow conductor from stack 102 in the separation process. Therefore, no sidewall misalignment or edge can arise from layer offset in the hollow conductor.

[0171] According to the above-mentioned precise separation method, which includes, for example, a laser cutting process, a plasma smear process can be carried out to oxidize or activate cut-out sidewalls 110 of the structured cavity or recess 43 according to an embodiment of the disclosure. By taking this measure, it may be possible to properly prepare the sidewalls 110 for the chemical copper process. At the same time, laser holes of the outer copper layer can be cleaned with the plasma process, and the surface can be oxidized or activated for a chemical copper process. Usable gases of the plasma process include pure gases and their mixtures. As gas(es), it is possible to use for example oxygen, argon, helium, carbon tetrafluoride carbon, hydrogen and/or nitrogen.

[0172] After the precise separation process and plasma activation, the cut-out material piece 142 in the middle of the cavity or recess 43 is removed from the stack 102.

[0173] As shown by block 212, a metallization process may selectively apply metal on sidewalls 110 of the recess 43, preferably for creating a chemical copper structure and a galvanic copper structure. Hence, it may be possible to selectively cover the sidewalls 110 of the resulting structured hollow conductor and at the same time of the ridge 42 by a metallization method which, for example, includes chemical copper formation, but is not limited to this. Subsequently, said chemical copper may be covered with galvanic copper as well as chemical silver, chemical tin or a nickel-gold surface. During the chemical copper metallization process, the structured metal on the bottom 48 of the hollow conductor is not coated with the copper and remains protected by its coating with a poorly adhesive structure 124. If a chemical copper process is carried out as a metallization process, a galvanic copper structure can then be formed selectively on the sidewalls 110 of the structured hollow conductor.

[0174] Thereafter, the poorly adhesive structure 124 or protection layer may be removed from the patterned bottom 48 of the recess 43, compare block 214. After the formation of metal selectively on sidewalls 110 of the recess 43 constituting the waveguide or hollow conductor, the non-metallized poorly adhesive structure 124 (which may be embodied as adhesion prevention layer) at the bottom 48 of the structured hollow conductor may be removed. Appropriate processes for said removal are aqueous and acidic processes or plasma etching methods capable of removing the poorly adhesive structure 124. It may also be possible to carry out thermal procedures to evaporate the poorly adhesive structure 124.

[0175] Alternatively, it may also be possible that the poorly adhesive structure 124 remains on the structured hollow conductor at the bottom 48 of the recess 43 and is not removed, if a removal is not necessary for the use of the structured hollow conductor according to an embodiment of the disclosure. Advantageously, no significant signal loss arises in high frequency applications by the poorly adhesive structure 124 which therefore does not impair the function of the hollow conductor. An example of a poorly adhesive structure 124 or adhesive prevention layers that can remain in the hollow conductor without compromising the high-frequency properties of the component carrier 100 are coatings of fluoropolymers, since these have a low dielectric constant.

[0176] As shown by block 216, a copper layer around the recess 43 may then be patterned. After the removal of the non-coppered poorly adhesive structure 124 at the bottom 48 of the structured hollow conductor according to an embodiment of the disclosure, an outer copper layer may be structured. Dry resist or liquid resist can be used for this purpose, wherein the cavity or recess 43 of the structured hollow conductor can be covered during this structuring process in order to be protected during the etching process.

[0177] Referring to block 218, the patterned surfaces and the sidewall 110 of the recess 43 may then be subjected to one or more end surface processes (such as chemical tin, chemical silver, ENIG, ENIPIG, hard gold and/or OSP). In addition to the copper structuring, the structured copper surfaces at the bottom 48 of the structured hollow conductor and the selectively coppered sidewalls 110 may be additionally metallized by a final surface process. For this purpose, it may be for example possible to carry out a chemical tin process, to silver-plate by a chemical silver process, to gold-plate by an ENIG process, or to coat with an organic coating by means of an OSP process or with compounds such as at least one fluorocarbon compound which includes PTFE, PFC, PCTFE or a fluoroelastomer.

[0178] As a method variant to the copper structuring process, the structured copper surfaces at the bottom 48 of the structured hollow conductor can continue to remain protected by the poorly adhesive structure 124. The selectively coppered sidewalls 110 may be additionally metallized by a final surface process for instance using a chemical tin process, silver plating by a chemical silver process, gold plating by an ENIG process or coating by an OSP process with an organic material.

[0179] In order to close the recess 43 and finish the structured hollow conductor according to an embodiment of the disclosure, a cut-out prepreg (which may have the same height as the coppered ridge 42) may be placed around the coppered ridge 42. Subsequently, the structured hollow conductor according to an embodiment of the disclosure may be provided with an electrically conductive adhesive 47 (such as an electrically conductive silver or copper paste) which may be printed on a structured copper layer in the area of the ridge 42. The coppered sidewall 110 may then be closed by pressing one or more additional layers onto a top side of the recessed stack 102 in a pressing process.

[0180] In particular, the so obtained structured hollow conductor can be used for the connection between at least one antenna and at least one chip used in the GHz or THz frequency range. Additionally or alternatively, it may be possible to use the obtained component carrier 100 with hollow conductor for further applications such as the conduction of light or sound waves, gases and liquids. What concerns high-frequency applications, such a component carrier 100 with hollow conductor may have a high bandwidth and may show only low signal losses.

[0181] FIG. 10 is a flow diagram 230 of a method of manufacturing a component carrier 100 according to another exemplary embodiment of the disclosure. Substantially, the flow diagram 230 differs from flow diagram 200 by an additional block 222 between blocks 212 and 214.

[0182] In FIG. 10, a variant of the manufacturing method according to another embodiment of the disclosure it is shown for the preparation of a structured hollow conductor and a transition between a strip conductor and a hollow conductor.

[0183] After the precise printing process (preferably with a tolerance of less than +2 m) for applying the ridge 42 and after curing the ridge 42 according to block 208, a precise separation process for separating a material piece 142 above the poorly adhesive structure 124 is carried out twice in blocks 210 and 222 between which a metallization process according to block 212 may be carried out. Preferably, the precise separation process according to blocks 210, 222 may be carried out by laser cutting. In the first precise separation process according to block 210, which can comprise a laser cutting process, one or more parts of the structured hollow conductor according to an embodiment of the disclosure may be precisely cut out which is or are to be covered with chemical copper. Those areas of the structured hollow conductor according to an embodiment of the disclosure which should remain free of metal (such as Cu, CuAg, CuSn, CuNiAu) are cut out in the first precise separation process with smaller dimensions. For instance, the first precise separation process may be a laser cutting process cutting out a structure which may be smaller (for example 20 m to 100 m smaller) than a material piece cut out in a subsequent second precise separation process. After a metallization process (which can for instance encompass a chemical copper, an electroplating copper, a chemical silver, a chemical tin, an OSP or an ENIG process) and a selective metal formation on the sidewalls 110 of the structured hollow conductor (see block 212), the previously smaller cut-out parts of the metallized sidewalls 110 may be cut away in a second precise separation process (such as for example a second laser cutting process). The second laser cutting process according to block 222 serves to expose signal lines in the hollow conductor to enable the functionality of the structured hollow conductor according to an embodiment of the disclosure. After the second precise separation process (such as a further laser cutting process), a further material piece is removed inside the structured hollow conductor.

[0184] After the copper formation in the chemical copper process and the galvanic copper process selectively on the sidewalls 110 of the recess 43 and at the ridge 42 of the structured hollow conductor according to an embodiment of the disclosure, the non-coated poorly adhesive structure 124 or adhesion prevention layer at the bottom 48 of the structured hollow conductor is removed. Said removal may be carried out by any process that sprays aqueous and/or solvent-containing solutions to remove the layer, or by thermal processes or by plasma etching processes, to etch or evaporate the layer.

[0185] The poorly adhesive structure 124 can alternatively remain in the structured hollow conductor according to an embodiment of the disclosure. For example, the poorly adhesive structure 124 may remain part of the component carrier 100 if the removal of said poorly adhesive structure 124 is not necessary for the use of the structured hollow conductor according to an embodiment of the disclosure. Advantageously, no significant signal loss arises by the poorly adhesive structure 124 which thereby does not impair the function of the hollow conductor. Correspondingly appropriate materials for the poorly adhesive structure 124 include, but are not limited to lipids, waxes, alcohols, fatty acid esters, and their mixtures, various polymers such as PP, PEEK, PEK, PVC, PS, fluorocarbons, PFC, PCTFE, fluoroelastomers, silicones, PFA, fluoropolymers such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and their polymer mixtures. In particular, fluorocarbon compounds which include PTFE, PFC or fluoroelastomers may be preferred.

[0186] In addition to the above-mentioned compounds in the poorly adhesive structure 124, organic and/or inorganic sulfur, phosphorus or nitrogen containing compounds can be added which may act as complexing agents during the catalytic deposition of metals (such as palladium, PdSn, Pt, or Ag) and thereby prevent the build-up of the chemical copper metal layer. The poorly adhesive structure 124 can also be printed as a combination of above-mentioned compounds on the area of the structured bottom 48 of the hollow conductor according to an embodiment of the disclosure. The poorly adhesive structure 124 can also permanently remain at the bottom 48 of the hollow conductor without being removed, in particular when such a coating has a low dielectric constant and comprises at least one compound selected from the group of fluoropolymers (such as PTFE, PVDF, PFC or PCTFE).

[0187] After the removal of the non-coppered poorly adhesive structure 124 at the bottom 48 of the structured hollow conductor according to an embodiment of the disclosure, the outer copper layer may be structured. The cavity or recess 43 can be covered with photoresist, which may be applied for instance by printing. In addition to this structuring process, copper surfaces of the structured hollow conductor at the structured bottom 48 and the selectively coppered sidewalls 110 can be additionally metallized by a final surface process such as a chemical tin process, silver-plated by a chemical silver process or gold-plated by an ENIG process and coated with an organic protective layer by OSP or with a compound such as a fluorocarbon compound which comprises PTFE, PFC, PCTFE or fluoroelastomers.

[0188] In order to close the structured hollow conductor according to an embodiment of the disclosure, a cut-out prepreg can be placed around the coppered ridge 42 which has the same height as the coppered ridge 42. Subsequently, a structured copper layer on which an electrically conductive adhesive 47 (such as a silver or copper paste) is applied in the area around the metallized sidewalls 110, is applied to close the recess 43 and is pressed with the stack 102 by a printed circuit board pressing process. In addition to the structuring, structured copper surfaces of the top layer of the structured hollow conductor according to an embodiment of the disclosure can additionally be metallized by a final surface process such as a chemical tin process, silver-plated by a chemical silver process or gold-plated by an ENIG process or provided with an organic protective layer by an OSP process or with a connection in form of at least one fluorocarbon compound which comprises PTFE, PFC, PCTFE or fluoroelastomers. The electrically conductive adhesive 47, which can comprise copper or silver particles, may be applied to the upper copper layer after the final surface process and before the pressing process.

[0189] The obtained structured hollow conductors can be used for the connection between at least one antenna and at least one chip used in the GHz or THz frequency range. Further possible applications include and are not limited to the conduction of light or sound waves, gases and liquids and have a higher bandwidth and lower signal losses as compared with conventional approaches.

[0190] FIG. 11 is a flow diagram 250 of a method of manufacturing a component carrier 100 according to still another exemplary embodiment of the disclosure. Substantially, the flow diagram 250 differs from flow diagram 200 by additional blocks 224 and 226 between blocks 214 and 216 and by a shift of block 212 between blocks 224 and 226. According to FIG. 11, poorly adhesive structure 124 is removed after having removed material piece 142 from stack 102, and another protection layer is formed on the bottom 48 for protecting a structured electrically conductive layer structure 41 on the bottom 48 against metallization during a subsequent electroless plating process. Said protection layer may also be poorly adhesive or non-sticky for metal, in particular for metal applied by electroless plating.

[0191] Block 224 indicates a process of printing protection layer on patterned bottom 48 of the recess 43. Block 226 indicates a removal of the protection layer from the patterned bottom 48 of the recess 43 after electroless plating and after optionally additionally galvanically plating according to block 212.

[0192] Hence, FIG. 11 shows a further variant of the method for manufacturing a structured hollow conductor and the transition between a strip conductor and a hollow conductor according to still another embodiment of the disclosure.

[0193] In said embodiment, the poorly adhesive structure 124 is removed after the (in particular first) laser cutting process. Thereafter, a protective film is applied as the protection layer to the structured bottom 48 of the hollow conductor. The protective film is inert in the subsequent chemical copper metallization process and is not coated with metal. Exemplary materials for this protective film are greases, waxes, alcohols, fatty acid esters, and their mixtures, various polymers such as PP, PEEK, PEK, PVC, PS, fluorocarbons, PFC, PCTFE, fluoroelastomers, silicones, PFA, fluoropolymers such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and their polymer mixtures.

[0194] In addition to the above-mentioned compounds of the adhesion prevention material, organic and/or inorganic sulfur, phosphorus or nitrogen containing compounds can be added which act as complexing agents during the catalytic deposition of metals (such as palladium, PdSn, Pt, or Ag) and thereby prevent the formation of a chemical copper metal layer thereon. Such a poorly adhesive structure can also be printed as a combination of the above-mentioned compounds on the area of the structured bottom 48 of the hollow conductor according to an embodiment of the disclosure.

[0195] After the selective metallization process, the protective film with suitable solvents is removed from the structured bottom 48 of the structured hollow conductor according to an embodiment of the disclosure with a spray process or with a plasma etching process with oxygen- or hydrogen-containing plasma gases and their mixtures. In addition, at least one vent hole may be included for pressure equalization or for filling gases or for the evacuation of the hollow conductor.

[0196] Copper surfaces of the structured hollow conductor such as the structured bottom 48 and the selectively copper-plated sidewalls 110 as well as a structured copper top layer can additionally be metallized by a final surface process which can be a chemical tin process, silver plating by a chemical silver process, gold-plating by an ENIG process, or treatment by an OSP process for applying an organic protective layer. Also, ENIPIG or hard gold processes may be executed for forming a protective layer.

[0197] An obtained structured hollow conductor can be used for the connection between at least one antenna and at least one chip used in the GHz or THz frequency range, and/or may be used for further applications such as the conduction of light or sound waves, gases, and liquids. Advantageously, a component carrier 100 with a corresponding waveguide may have a higher bandwidth and lower signal losses than conventional devices.

[0198] In the following FIG. 12 to FIG. 19, exemplary embodiments of component carriers 100 with structured metallized hollow conductors and transitions between conductor strips and hollow conductors will be described.

[0199] FIG. 12 illustrates a component carrier 100 according to an exemplary embodiment of the disclosure.

[0200] In FIG. 12, a structured hollow conductor in cavity or recess 43A, 43B according to an embodiment of the disclosure is shown. The illustrated component carrier 100 shows copper layers 41A, 41B, 41C and 41D as well as prepreg layers 40A, 40B, 40C, 40D and 40E. The thickness of the copper layers 41A, 41B, 41C and 41D can be between 10 m and 35 m and the thickness of the prepreg layers 40A, 40B, 40C, 40D and 40E can be between 20 m and 200 m. Ridges with copper-plated edge connected to the copper layer 41D are shown with reference signs 42A and 42B. The copper-coated sidewalls of the structured hollow conductor are shown with reference signs 44A and 44B. A structured bottom of the hollow conductor or waveguide is shown with reference signs 48A and 48B. Furthermore, a structured sidewall 45B is shown which is formed by copper structures of laser holes filled with copper and by one or more structured copper layers 41B, 41C and 41D. Component carrier 100 according to FIG. 12 can be manufactured by a manufacturing process as it is shown in FIG. 10 and may involve a first and a second laser cutting process. The copper surfaces of the structured hollow conductor can be refined after removal of the poorly adhesive structure 124 (which is not shown in FIG. 12 to FIG. 19, but may be present in other embodiments of component carriers 100) and after structuring the copper layer 41D with various end surface processes such as chemical tin, ENIG, chemical silver or OSP. At least one prepreg 40D may be applied. The prepreg 40D has the same layer thickness as that of the metallized edge of the ridge and contains cut openings corresponding to a size of the edges of the ridge. Said prepreg 40D is placed around the edges of the ridge 42A, 42B during the manufacturing process. Thereafter, a structured copper layer 41Don which an electrically conductive silver or copper-containing adhesive 47A, 47B may be applied in the area of the metallized ridgeis applied. Thereafter, a prepreg 40E is pressed onto the top in a pressing process and closes the structured hollow conductor. In addition, at least one vent hole may be included for pressure equalization or for filling gases or for the evacuation of the recess(es) of the hollow conductor.

[0201] According to the embodiment of FIG. 12, some of the electrically conductive layer structures 41 are exposed at the respective sidewall 110 in cavity 43B.

[0202] FIG. 13 illustrates a component carrier 100 according to another exemplary embodiment of the disclosure.

[0203] In FIG. 13, a component carrier 100 with a structured hollow conductor in the cavities or recesses 43A, 43B according to another embodiment of the disclosure is shown. The illustrated printed circuit board shows the copper layers 41A, 41B, 41C and 41D as well as the prepreg layers 40A, 40B, 40C, 40D and 40E. The thickness of the copper layers can be between 10 m and 35 m and the prepreg thickness of the prepreg layers can be between 20 m and 200 m. The copper-plated polymer ridge on the copper layer 41C is shown with reference signs 42A and 42B. The copper-plated sidewalls of the structured hollow conductor are shown with reference signs 44A and 44B. The structured bottom of the copper layer 41A of the structured hollow conductor is shown with reference signs 48A and 48B. Furthermore, a structured sidewall 45B is shown which represents a copper structure of laser holes filled with copper and at least one structured copper layer 41B, 41C. The formation of the structured, non-coppered sidewall 45B of the structured hollow conductor may be carried out by a manufacturing process with a second laser cutting process as shown in FIG. 10. The structured hollow conductor can be refined after removing the internal poorly adhesive structure (which is inert in the chemical copper process). Said refining can be carried out with various end surface processes such as chemical tin, ENIG, chemical silver or OSP. At least one prepreg 40D can be attached around ridges 42A, 42B. The prepreg 40D has the same layer thickness as that of the metallized edge of the ridge 42A, 42B, contains cut openings in the size of the edges of the ridge 42A, 42B, and can be placed around the edges of the ridge 42A and 42B respectively during the manufacturing process. Thereafter, the structured hollow conductor is closed with the structured copper layer 41D and a prepreg 40E which may be pressed onto the stack 102 in a pressing process.

[0204] FIG. 14 illustrates a component carrier 100 according to still another exemplary embodiment of the disclosure.

[0205] In FIG. 14, component carrier 100 with a structured hollow conductor in a cavities or recesses 42A, 42B is shown. The component carrier 100 has a stack 102 comprising copper layers 41A, 41B, 41C and 41D as well as prepreg layers 40A, 40B, 40C, 40D and 40E. The thickness of the copper layers can be between 10 m and 35 m and the thickness of the prepreg layers can be between 20 m and 200 m. The copper plated ridges on the copper layer 41C are shown with reference signs 42A and 42B. The copper-plated sidewalls of the structured hollow conductor are shown with reference signs 44A and 44B. The structured copper layer 41A at the bottom of the structured hollow conductor is shown with reference signs 48A and 48B. Chemical compounds which may be included in a poorly adhesive structure (which is already removed according to FIG. 14 and which is used for forming recesses 43A, 43B as well as for protecting patterned bottoms 48A and 48B against metallization) may be for example lipids, waxes, alcohols, fatty acid esters, and their mixtures, various polymers such as PP, PEEK, PEK, PVC, PS, fluorocarbons, PFC, PCTFE, fluoroelastomers, silicones, PFA, fluoropolymers such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and their polymer mixtures.

[0206] In addition to the above-mentioned compounds of the poorly adhesive structure 124, organic and/or inorganic sulfur, phosphorus or nitrogen containing compounds can be added which act as complexing agents during the catalytic deposition of metals (such as palladium, PdSn, Pt, or Ag) and thereby prevent the build-up of the chemical copper metal layer at patterned bottoms 48A and 48B. The poorly adhesive structure 124 can also be printed as a combination of several of the above-mentioned compounds on the area of the structured bottom of the hollow conductor.

[0207] Furthermore, structured sidewalls 65A, 66A and 66B are shown which represent a copper structure of laser holes filled with copper and at least one structured copper layer 41A, 41B, 41C and 41D. The structured, non-coppered sidewall 65A of the structured hollow conductor can be created by a manufacturing process as described referring to FIG. 10, i.e. implementing a second laser cutting process in addition to a first one. The structured hollow conductor can be refined after removing the poorly adhesive structure 124 by plasma etching (and optionally after structuring of copper layer 41D) with various end surface processes such as chemical tin, ENIG, chemical silver or OSP. At least one prepreg 40D may be attached which has the same layer thickness as that of the metallized edge of the ridge and contains cut openings in the size of the edges of the ridge. Prepreg 40D may be placed around the edges of the ridge 42A and 42B, respectively, during the manufacturing process. Thereafter, the structured copper layer 41Don which an electrically conductive silver or copper-containing adhesive 47A, 47B is applied in the area of the metallized ridgeis applied. A prepreg 40E closes the structured hollow conductor and is pressed in a pressing process.

[0208] FIG. 15 illustrates a component carrier 100 according to yet another exemplary embodiment of the disclosure.

[0209] In FIG. 15, a side view (on top of FIG. 15) with closed top layers and a top view (on the bottom of FIG. 15) in an open state of a component carrier 100 with a structured hollow conductor according to still another embodiment of the disclosure are shown. The structured hollow conductor according to the described embodiment of the disclosure is shown with recesses 43A, 43B. The stack 102 of the printed circuit board-type component carrier 100 comprises copper layers 41A, 41B, 41C and 41D as well as prepreg layers 40A, 40B, 40C, 40D and 40E. The thickness of the copper layers can be between 10 m and 35 m and the thickness of the prepreg layers can be between 20 m and 200 m. The copper-plated ridge on the copper layer 41C is shown with reference signs 42A and 42B. The selectively non-coppered walls of a transition element from a stripline to the hollow conductor are shown with reference signs 74A, 74B and 76A. The structured bottom in the copper layer 41A of the structured hollow conductor is shown with reference signs 48A and 48B. The formation of the selectively non-coppered walls of the transition element from stripline in the structured hollow conductor 74A, 74B and 76A can be accomplished by a manufacturing process as shown in FIG. 10 which comprises a second laser cutting process in addition to a first laser cutting process. The structured hollow conductor can be coated after the removal of the poorly adhesive structure (which is inert in the chemical copper process) by plasma etching and after structuring the copper layer 41D with various end surface processes (such as chemical tin, ENIG, chemical silver or OSP or with a compound consisting of at least one fluorocarbon compound which comprises PTFE, PFC, PCTFE or fluoroelastomers). At least one prepreg 40D may be attached to the stack 102 for planarization. The prepreg 40D has the same layer thickness as that of the metallized edge of the ridge and contains cut openings in the size of the edges of the ridge. The prepreg 40D can be placed around the edges of the ridge 42A and 42B during the manufacturing process. Thereafter, a pressing process can be carried out with structured copper layer 41D on which an electrically conductive silver or copper-containing adhesive 47A, 47B is applied in the area of the metallized ridge. The formed recess can be closed by structured copper layer 41D and a prepreg 40E by a pressing process. In addition, at least one vent hole may be included for pressure equalization or for filling gases or for the evacuation of the hollow conductor.

[0210] FIG. 16 illustrates a component carrier 100 according to yet another exemplary embodiment of the disclosure.

[0211] In FIG. 16, the structured hollow conductor is shown in a side view with reference signs 43A, 43B and 43C. The illustrated printed circuit board-type component carrier 100 comprises copper layers 41A, 41B, 41C and 41D as well as prepreg layers 40A, 40B, 40C, 40D and 40E. The thickness of the copper layers can be between 10 m and 35 m and the thickness of the prepreg layers can be between 20 m and 200 m. The copper-plated ridge on the copper layer 41C is shown with reference signs 42A and 42B. The structured bottom at the copper layer 41A of the structured hollow conductor is shown with reference signs 48A and 48B. The creation of the selectively non-coppered sidewalls of a transition element of a stripline to the structured hollow conductor, indicated with reference signs 85A, 85B and 86, can be accomplished by a manufacturing process as described referring to FIG. 10. The structured hollow conductor can be refined after removing the poorly adhesive structure (which is inert in the chemical copper process) and structuring the copper layer 41D with various end surface processes such as chemical tin, ENIG, chemical silver or OSP. The structured hollow conductor can be covered with at least one prepreg 40D. The prepreg 40D has the same layer thickness as that of the metallized edge of the ridge and contains cut openings in the size of the edges of the ridge. The prepreg 40D is placed around the edges of the ridge 42A and 42B during the manufacturing process. Thereafter, the structured copper layer 41Don which an electrically conductive silver or copper-containing adhesive 47A, 47B is applied at an underside in the area of the metallized ridgeis applied and a prepreg 40E closes the structured hollow conductor in a pressing process. FIG. 16 shows a U-shaped patch antenna structure 120 at the edge of recess 43A.

[0212] FIG. 17 illustrates a component carrier 100 according to yet another exemplary embodiment of the disclosure.

[0213] The embodiment of FIG. 17 comprises a frequency filter structure 114 at the recess 43A. Said frequency filter structure 114 is formed by a plurality of webs 98 of electrically insulating layer structures 40 at the sidewall 110, and by an electrically conductive structure 118 which may be formed on and/or between the webs 98. For instance, the frequency filter structure 114 may fulfil a high-pass, a low-pass or a band-pass filter functionality concerning high-frequency signals.

[0214] In FIG. 17, the structured hollow conductor is shown once with copper cover layer closed in a side view (see top of FIG. 17) and once in the open state in a top view. Recesses of the structured hollow conductor are shown with reference signs 43A, 43B and 43C. The stack 102 of the printed circuit board comprises copper layers 41A, 41B and 41C as well as prepreg layers 40A, 40B, 40C and 40D. The thickness of the copper layers can be between 10 m and 35 m and the thickness of the prepreg layers can be between 20 m and 200 m. The copper-plated ridge on the copper layer 41B is shown with reference signs 42A, 42B. The selectively non-coppered sidewalls of a transition element from a stripline to the hollow conductor are shown with reference signs 95A, 95B and 99. It is also possible, as indicated by reference sign 99, to provide interior sidewalls of the stack 102 without copper. The structured bottom in the copper layer 41A of the structured hollow conductor is shown with reference sign 48A. The formation of the non-coppered sidewalls of a transition element from a stripline to the hollow conductor (see reference signs 95A, 95B and 96A and 99 of the structured hollow conductor can be achieved by carrying out a manufacturing process according to FIG. 10 with a second laser cutting process. The structured hollow conductor can be refined after removing the poorly adhesive structure and structuring the copper layer 41B with various end surface processes such as chemical tin, ENIG, chemical silver or OSP. At least one further prepreg 40C may be applied which may have the same layer thickness as that of the metallized edge of the ridge and contains cut openings in the size of the edges of the ridge. The at least one further prepreg 40C is placed around the edges of the ridge 42A and 42B during the manufacturing process. Thereafter, the structured copper layer 41C (on which an electrically conductive silver or copper-containing adhesive 47A is applied in the area of the metallized ridge) and a prepreg 40D may close the structured hollow conductor, for instance by lamination.

[0215] FIG. 18 illustrates a component carrier 100 according to yet another exemplary embodiment of the disclosure.

[0216] In this embodiment, the circumferentially close sidewalls 110 have several steps 122.

[0217] In FIG. 18, a step-shaped structured hollow conductor is illustrated in a side view. The step-shaped hollow conductor is shown with recesses 43A, 43B. The shown printed circuit board configuration comprises copper layers 41A, 41B, 41C, 41D and 41E as well as prepreg layers 40A, 40B, 40C, 40D, 40E and 40F. The thickness of the copper layers can be between 10 m and 35 m and the prepreg thickness can be between 20 m and 200 m. The copper-plated ridges on the copper layer 41D are shown with reference signs 42A, 42B. The selectively non-coppered sidewalls of a transition element of a stripline at copper layer 41C of the structured stepped hollow conductors are shown at both ends of the prepreg 40C. The production of the selectively non-coppered sidewalls of the prepreg layer 40C of the transition element can be carried out by a manufacturing process according to FIG. 10. The structured bottom of the structured hollow conductor is shown in the copper layer 41A as well as in the copper layer 41B and with reference sign 101. The structured hollow conductor can be refined after removing the poorly adhesive structure (which is also inert in the chemical copper process) and structuring the copper layer 41D with various end surface processes such as chemical tin, ENIG, chemical silver or OSP. A prepreg 40E has the same layer thickness as that of the metallized edge of the ridge and contains cut openings in the size of the edges of the ridge. Prepreg 40E may be placed around the edges of the ridge 42A and 42B during the manufacturing process. Thereafter, structured copper layer 41E (on which an electrically conductive silver or copper-containing adhesive 47A is applied at an underside in the area of the metallized ridge) and a prepreg 40F may be laminated to the top of the stack 102 to thereby close the structured hollow conductor.

[0218] FIG. 19 illustrates a component carrier 100 according to yet another exemplary embodiment of the disclosure.

[0219] In FIG. 19, another embodiment with stepped structured hollow conductors is illustrated in a side view. Different geometries of recesses of the structured hollow conductors are shown with reference signs 43A, 43B, 43C, 43D, 43E, 43F. The selectively non-coppered sidewalls of a transition element of a stripline in copper layer relating to reference signs 113 and 117 of the structured stepped hollow conductor are shown in the cavity relating to reference sign 43C. The manufacture of the selectively non-coppered sidewalls as well as selectively non-coppered processes in some of the illustrated cavities may be carried out by a manufacturing process with several laser cutting processes of the type described referring to FIG. 10.

[0220] Structured bottoms and walls are shown in the structured hollow conductors according to recesses 43A, 43B, 43C, 43D, 43E, 43F. The copper structure 113 is connected to the bottom side of recess 43C via a copper layer and the copper structure 117 is connected to the top side of recess 43C via a respective copper layer.

[0221] The examples of structured metallized hollow conductors described referring to FIG. 12 to FIG. 19 and the corresponding manufacturing methods allow a precise mass manufacture and can be used particularly appropriately in a frequency range above 20 GHz, preferably over 28 GHz. These structured hollow conductors can be used in particular for the connection between at least one antenna and at least one chip or as a transition component between stripline and hollow conductor in the GHz or THz frequency range. Possible applications include and are not limited to the conduction of light or sound waves, gases and liquids and have a high bandwidth and low signal loss.

[0222] Exemplary embodiments of the disclosure relate to structured, metallized hollow conductors and transitions between a strip conductor and a hollow conductor integrated in a component carrier such as a printed circuit board (PCB). Furthermore, a corresponding manufacturing process is provided. In such a hollow conductor and transition, copper structures at the bottom of the hollow conductor and transition may be temporarily or permanently coated with at least one poorly adhesive structure such as an adhesive prevention or non-sticky layer. The latter may comprise or consists of at least one compound of the group of fluoropolymers such as PTFE or PVDF and may be advantageously inert in a chemical copper metallization process. A copper layer under a copper cover layer may be provided with at least one ridge in the area of the hollow conductor, which is preferably stable in the chemical copper formation process. The hollow conductor may be cut out in the area of the ridge preferably by at least one laser cutting process. A resulting edge of the ridge as well as sidewalls of the structured hollow conductor may be coated with chemical copper, wherein the structured, protected bottom is not metallized with chemical copper thanks to the poorly adhesive structure covering the structured bottom during chemical copper formation. In a subsequent structuring process, the hollow conductor may be covered. More specifically, at least one prepreg layer with opening may be placed around the coppered edges of the ridge. Said at least one prepreg layer may have the same height as the metallized edges of the ridge. A top layer comprising at least one structured copper layer and an electrically conductive adhesive in the area of the ridge may then be attached to the top side of the obtained stack.

[0223] For instance, the thickness of the ridge is in the range from 10 m to 1000 m, preferably from 15 m to 800 m. Preferably, the material of the ridge is stable during the chemical copper process and the PCB manufacture. For instance, said material can include varnishes, polymer mixtures, resins or resin mixtures, plug-in paste, solder stop varnish, polymers, various resins as well as resin mixtures.

[0224] For instance, the poorly adhesive structure may have a thickness in a range from 1 nm to 100 m, preferably a thickness in a range from 2 nm to 80 m. Moreover, the poorly adhesive structure may comprise at least one compound, which is chosen from the following chemical compounds: lipids, waxes, alcohols, fatty acid esters, and their mixtures, various polymers such as PP, PEEK, PEK, PVC, PS, fluorocarbons, PFC, PCTFE, fluoroelastomers, silicones, PFA, fluoropolymers such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) as well as organic and/or inorganic sulfur, phosphorus or nitrogen-containing compounds which act as complex formation agent during the catalytic deposition of metals such as palladium, PdSn, Pt, or Ag catalysts.

[0225] Preferably, the structured copper top layer may be covered in the area of the copper-plated sidewall with an electrically conductive connection material before the pressing process. For instance, the electrically conductive connection material can comprise silver and copper particles, preferably in the form of a paste. The electrically conductive connection material may be printed on the copper top layer or on the ridge in order to produce an electrical contact between the metallized sidewalls of the metallized hollow conductor and the copper top layer.

[0226] In one embodiment, the poorly adhesive structure (for instance configured as adhesive prevention layer) is used for the protection of the structured copper surface of the bottom of the hollow conductor against coverage with copper material during chemical copper formation. It is possible that this poorly adhesive structure is maintained or preserved during a further selective metallization of the copper sidewalls of the structured hollow conductor. Such coatings may be formed for example by final surface processes such as chemical silver, chemical tin, ENIG and/or OSP.

[0227] Preferably, the structured copper surface of the top layer may be coated by final surface processes such as chemical silver, chemical tin, ENIG or OSP.

[0228] FIG. 20 illustrates dimensions L, W, and H of a waveguide-type recess 43 of a component carrier 100 according to an exemplary embodiment of the disclosure.

[0229] As shown in FIG. 20, the width W and the length L of the recess 43 denote the horizontally extending axes of the cuboid recess 43. In other words, the width W and the length L of the recess 43 are the dimensions of the recess 43 in the two horizontal dimensions, whereas height H corresponds to a dimension of the recess 43 in a vertical direction according to FIG. 20, i.e. perpendicular to the main surfaces of the component carrier 100. Preferably, a difference between a maximum value and a minimum value of the width W along the length L does not exceed 75 m, more preferably does not exceed 20 m and most preferably does not exceed 15 m, in order to ensure a low loss wave propagation (schematically indicated in FIG. 20 as oscillating wave) within the waveguide.

[0230] Technical effects correlated with the mentioned small width tolerance will be explained in the following: Without wishing to be bound to a specific theory, it is presently believed that the size and accordingly the dimensions of the cavity or recess 43 defining the waveguide are partly dependent on the wavelength of the signal to be transported. This pre-defined width W of the cavity or recess 43 should not deviate by more than 75 m along the length L of the cavity, in particular not more than 20 m, more particularly not more than 15 m. It is believed that a low roughness Rz (for instance in a range from 15 m to 75 m) of sidewalls 110 delimiting the recess 43 may have a positive impact on the mentioned low width tolerance. The absolute value of the width W may depend on the wavelength of an electromagnetic signal to be transported by the waveguide.

[0231] FIG. 21 illustrates a cross-sectional image of a manufactured component carrier 100 with interior waveguide-type recess 43 according to an exemplary embodiment of the disclosure. Hence, FIG. 21 shows a cross-section of a practically manufactured component carrier 100 obtained by carrying out a manufacturing process similar to FIG. 1 to FIG. 8 with properly adjusted manufacturing parameters (in particular in terms of laser cutting and metal deposition). FIG. 22 illustrates a cross-sectional view of a component carrier 100 with interior waveguide-type recess 43 according to an exemplary embodiment of the disclosure and corresponding to the image of FIG. 21. Several features of the component carrier 100 according to FIG. 21 are illustrated more schematically in FIG. 22 as a basis for the below description.

[0232] First referring to FIG. 21, the illustrated cross section of the hollow waveguide in form of metal cladded recess 43 shows some specific and advantageous features:

[0233] As indicated with 1 in FIG. 21, a curved shape of copper at the top edges of recess 43 may be obtained.

[0234] As indicated with 2 in FIG. 21, it is optionally possible to create a tilted copper structure at the bottom edges of recess 43. In the shown embodiments, this feature is more pronounced in the left bottom edge than in the right bottom edge.

[0235] As indicated with 3 in FIG. 21, a tapered sidewall 110 may be adjusted for the cavity forming the waveguide.

[0236] As indicated with 4 in FIG. 21, a difference of the height from one bottom edge to the other bottom edge is preferably not more than 20%, in particular not more than 10%.

[0237] More generally, and now referring to FIG. 22, the illustrated component carrier 100 comprises a laminated layer stack 102 composed of several electrically conductive layer structures 41 and several electrically insulating layer structures 40 being connected by the application of pressure and temperature, i.e. by lamination. A recess 43 is formed in an empty area of the stack 102 and is configured as a (in particular hollow or low DK-filled) waveguide. An electrically conductive coating 44 lines sidewalls 110 of the stack 102 which laterally delimit the recess 43.

[0238] As indicated with reference signs 180, the electrically conductive coating 44 is curved outwardly on an upper end of the sidewalls 110. This geometry may buffer mechanical stress occurring when laminating layer structures 41, 40 on top of the recess 43. Thus, the mentioned feature may improve the mechanical integrity of the component carrier 100.

[0239] As shown in FIG. 1 as well, a narrow beak-shaped extension 172 of the recess 43 is formed between the electrically conductive coating 44 and the electrically conductive layer structure 41 at the upper end of the sidewalls 110. Also, the beak-shaped extension 172 may have an advantageous stress damping and force balancing function during applying vertical pressing forces during lamination. Adjusting the properties of the beak-shaped extension 172, fine-tuning of the RF properties of the component carrier 100 may be achieved.

[0240] Again referring to FIG. 22, the recess 43 is delimited at a lower end of the sidewalls 110 by a tilted metallic section 174 formed in an interface region between the slanted or tilted electrically conductive coating 44 and a horizontal electrically conductive layer structure 41. This is indicated with slanted dotted lines in FIG. 22. In addition, the electrically conductive coating 44 tapers downwardly in a central part of the sidewalls 110. This outwardly tapering geometry of the recess 43 in a vertical direction also contributes to a proper mechanical force distribution without significantly influencing the high-frequency properties of the waveguide in an excessive way.

[0241] As shown as well in FIG. 22, over a horizontal range D between two opposing intersections between the electrically conductive coating 44 and one of the at least one electrically conductive layer structure 41 at the bottom of the recess 43, a height d1, d2 of the recess 43 does not vary substantially. More specifically, it is preferred that d1 and d2 do not deviate from each other by more than 20%, and most preferably by not more than 10%. Consequently, well-defined and homogeneous RF properties of the waveguide may be ensured.

[0242] Advantageously, a locally thickened metallic region 176 is formed as an intersection between the electrically conductive coating 44 and one of the at least one electrically conductive layer structure 41 at the bottom of the recess 43. Locally thickening metal at the shown critical region may function as a reinforcing structure capable of taking up forces acting on the constituents of the component carrier 100 during a lamination process.

[0243] Further advantageously, the electrically conductive coating 44 is substantially S-shaped at each of the sidewalls 110. Such an S-shaped copper structure may function in an analogous way as a leaf spring for damping forces during the manufacturing process.

[0244] In a nutshell, the structural features described referring to FIG. 21 and FIG. 22 may be obtained by recess formation by laser cutting in combination with metal deposition by plating, while appropriately setting the process parameters. The smooth sidewalls obtained during laser cutting ensure low loss RF signal transmission. At the same time, the mentioned structural features allow a fine-tuning of the high-frequency properties as well as a mechanically robust configuration preventing damage during manufacture.

[0245] Still referring to the embodiments of FIG. 20 and FIG. 21, edges 67 at an upper side (and additionally or alternatively at a lower side) of the recess 43 may comprise a metal-metal oxide-metal succession, more specifically a copper-copper oxide-copper succession. Hence, an oxide layer may be formed between two connected metal layers which may suppress the formation of grain boundaries in between.

[0246] It should be noted that the term comprising does not exclude other elements or steps and the article a or an does not exclude a plurality. Also, elements described in association with different embodiments may be combined.

[0247] Implementation of the disclosure is not limited to the preferred embodiments shown in the figures and described above. Instead, a multiplicity of variants are possible which variants use the solutions shown and the principle according to the disclosure even in the case of fundamentally different embodiments.