Component Carrier Comprising Embedded Magnet Stack

Abstract

A component carrier includes a base material stack having at least one electrically conductive layer structure and/or at least one electrically insulating layer structure, and a magnet stack with a plurality of magnetic layers and at least one bonding layer, each of the at least one bonding layer bonding two respectively neighboured magnetic layers, wherein the magnet stack is embedded in the base material stack.

Claims

1. A component carrier, comprising: a base material stack having at least one electrically conductive layer structure and/or at least one electrically insulating layer structure; and a magnet stack having a plurality of magnetic layers and at least one bonding layer, the at least one bonding layer bonding two respectively neighboured magnetic layers; wherein the magnet stack is embedded in the base material stack.

2. The component carrier according to claim 1, further comprising at least one of the following features: wherein the at least one bonding layer is temperature-stable, in particular at least up to a temperature of 300 C.; wherein the at least one bonding layer comprises or consists of epoxy resin, and is in particular free of reinforcing structures, more particularly free of reinforcing fibers; wherein at least part of the magnetic layers is made of nanocrystalline magnetic material; wherein at least part of the magnetic layers comprises an iron-silicon compound; wherein at least part of the magnetic layers has a magnetic permeability of at least 10000, in particular of at least 50000.

3. The component carrier according to claim 1, further comprising: a coil structure coupled with the magnet stack, in particular at least partially accommodating at least part of the magnet stack.

4. The component carrier according to claim 3, further comprising at least one of the following features: wherein the coil structure is arranged as a planar coil, in particular spirally formed, and in particular on an outermost electrically conductive layer structure or two outermost electrically conductive layer structures of the base material stack; wherein the coil structure comprises a plurality of helical windings and/or a plurality of annular windings; wherein the coil structure comprises or consists of copper and/or material of the at least one electrically conductive layer structure.

5. The component carrier according to claim 1, further comprising at least one of the following features: at least one surface mounted component, in particular at least one active component and/or at least one passive component, wherein in particular the at least one surface mounted component is mounted on a main surface of the component carrier opposing another main surface of the component carrier at and/or in which the coil structure is formed; wherein a thickness of a respective one of the at least one bonding layer is in a range between 1 m and 20 m; wherein a thickness of a respective one of the magnetic layers is in a range between 3 m and 70 m, in particular in a range between 10 m and 50 m; wherein an entire thickness of the magnet stack is in a range between 100 m and 1 mm, in particular in a range between 200 m and 500 m; wherein the magnet stack is formed as an annulus; wherein a dielectric disc inserted as an inlay in a central through hole of the annulus; wherein at least part of dielectric material in contact with at least part of the magnetic layers has a thermal conductivity of at least 1 W/mK, in particular of at least 3 W/mK; wherein the magnet stack extends only along a sub-portion of a lateral and/or a vertical extension of the base material stack.

6. The component carrier according to claim 1, wherein the magnet stack has at least one gap, in particular a plurality of circumferentially distributed gaps, more particularly three gaps.

7. The component carrier according to claim 6, wherein the at least one gap is filled with a dielectric solid material or is an air gap.

8. The component carrier according to claim 1, wherein the component carrier forms at least one of a group consisting of a wireless charger, in particular for wirelessly charging an electronic device such as a mobile phone, an inductor, a transformer, and a power converter, in particular a DC/DC converter.

9. The component carrier according to claim 1, further comprising at least one of the following features: at least one component surface mounted on and/or embedded in the base material stack, wherein the at least one component is in particular selected from a group consisting of an electronic component, an electrically non-conductive and/or electrically conductive inlay, a heat transfer unit, a light guiding element, an energy harvesting unit, an active electronic component, a passive electronic component, an electronic chip, a storage device, a filter, an integrated circuit, a signal processing component, a power management component, an optoelectronic interface element, a voltage converter, a cryptographic component, a transmitter and/or receiver, an electromechanical transducer, an actuator, a microelectromechanical system, a microprocessor, a capacitor, a resistor, an inductance, an accumulator, a switch, a camera, an antenna, a magnetic element, a further component carrier, and a logic chip; wherein the at least one electrically conductive layer structure comprises at least one of a group consisting of copper, aluminum, nickel, silver, gold, palladium, and tungsten, any of the mentioned materials being optionally coated with supra-conductive material such as graphene; wherein the at least one electrically insulating layer structure comprises at least one of a group consisting of resin, in particular reinforced or non-reinforced resin, for instance epoxy resin or bismaleimide-triazine resin, FR-4, FR-5, cyanate ester, polyphenylene derivate, glass, prepreg material, polyimide, polyamide, liquid crystal polymer, epoxy-based build-up film, polytetrafluoroethylene, a ceramic, and a metal oxide; wherein the component carrier is shaped as a plate; wherein the component carrier is configured as one of a group consisting of a printed circuit board, and a substrate; wherein the component carrier is configured as a laminate-type component carrier.

10. A method of manufacturing a component carrier, the method comprising: providing, in particular laminating, a base material stack having at least one electrically conductive layer structure and/or at least one electrically insulating layer structure; and embedding a magnet stack in the base material stack, wherein the magnet stack includes at least two magnetic layers and at least one bonding layer in between, the at least one bonding layer bonding two respectively neighboured magnetic layers.

11. The method according to claim 10, further comprising: embedding the magnet stack as an inlay in a cavity of the base material stack.

12. The method according to claim 10, further comprising: embedding the magnet stack as an inlay in a through hole of the base material stack being temporarily closed by a temporary carrier.

13. The method according to claim 10, further comprising: forming the magnet stack by adhering respective ones of the magnetic layers together by a respective one of the at least one bonding layer.

14. The method according to claim 10, further comprising: forming the magnet stack by forming a plurality of double sheets, each formed by connecting a respective magnetic layer with a respective bonding layer, in particular at a temperature below a curing temperature of the bonding layer; thereafter connecting the plurality of double sheets with each other, in particular at a temperature at or above the curing temperature of the bonding layers.

15. A method, comprising: forming a magnet stack as an alternating sequence of substantially planar magnetic layers and substantially planar dielectric bonding layers between each pair of adjacent magnetic layers, wherein the planar magnetic layers include a nanocrystalline magnetic material and each bonding layer is thermally stable at least up to 300 C.; inserting the magnetic stack as an inlay for embedding into a printed circuit board.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] FIG. 1 illustrates a cross-sectional view of a component carrier with an embedded magnet stack according to an exemplary embodiment of the invention.

[0061] FIG. 2 illustrates a cross-sectional view of a magnet stack of a component carrier according to an exemplary embodiment of the invention.

[0062] FIG. 3 illustrates a three-dimensional top view of a component carrier configured as wireless charging device according to an exemplary embodiment of the invention.

[0063] FIG. 4 illustrates a three-dimensional bottom view of the component carrier configured as wireless charging device according to FIG. 3.

[0064] FIG. 5 illustrates a three-dimensional view of the component carrier configured as wireless charging device according to FIG. 3 and

[0065] FIG. 4 with a mobile phone to be charged thereon in a wireless manner.

[0066] FIG. 6 illustrates an image showing a cross-sectional view of a magnet stack to be embedded in a component carrier according to an exemplary embodiment of the invention.

[0067] FIG. 7, FIG. 8, FIG. 9, FIG. 10 to FIG. 11 illustrate arrangements of magnet stacks and coil structures of component carriers according to other exemplary embodiments of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0068] The illustrations in the drawings are schematically presented. In different drawings, similar or identical elements are provided with the same reference signs.

[0069] 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 invention have been developed.

[0070] According to an exemplary embodiment of the invention, a component carrier (in particular a printed circuit board, PCB) may be provided with one or more magnet stacks having an alternating sequence of magnetic layers and dielectric bonding layers in between the magnetic layers. For instance, the stacked magnetic layers being separated by the bonding layers in between may function as magnetic core material of a coil structure. For example, the magnetic layers may comprise magnetic nanoparticles. One or more magnet stacks may be embedded in a base material stack (which may be composed of FR4 and copper) of the component carrier. A correspondingly obtained magnet stack may be embedded below coil layers in the base material stack of the component carrier. Such an architecture is highly flexible and compatible with many different component carrier designs, for instance for printed circuit boards having a number of electrically conductive layers in a range from two to eight.

[0071] FIG. 1 illustrates a cross-sectional view of a component carrier 100 with an embedded magnet stack 108 according to an exemplary embodiment of the invention. FIG. 2 illustrates a cross-sectional view of the magnet stack 108 of the component carrier 100 according to FIG. 1. However, the inlay type magnet stack 108 shown in FIG. 2 may also be used for other applications.

[0072] The component carrier 100 is here embodied as a printed circuit board (PCB). The component carrier 100 comprises a laminated base material stack 102 composed of electrically conductive layer structures 104 and electrically insulating layer structures 106. For example, the electrically conductive layer structures 104 may comprise patterned copper foils and vertical through connections, for example copper filled laser vias. The electrically insulating layer structures 106 may comprise a resin (such as epoxy resin), optionally comprising reinforcing particles therein (for instance glass fibers or glass spheres). For instance, the electrically insulating layer structures 106 may be made of prepreg or FR4. The layer structures 104, 106 may be connected by lamination, i.e. the application of pressure and/or heat.

[0073] Furthermore, the component carrier 100 comprises an inlay type magnet stack 108 embedded in a cavity of the base material stack 102. As shown in FIG. 1, the magnet stack 108 is embedded as a whole in the base material stack 102 and is thus implemented as an inlay being readily manufactured at the time of its embedding. Consequently, the magnet stack 108 has a smaller lateral extension than the base material stack 102 and therefore extends only along a sub-portion of the lateral or horizontal extension of the base material stack 102. Moreover, the magnet stack 108 has a smaller vertical extension than the base material stack 102 and therefore extends only along a sub-portion of the vertical extension of the base material stack 102.

[0074] Referring to FIG. 2, the magnet stack 108 comprises an alternating sequence of a plurality of magnetic layers 110 and a plurality of dielectric bonding layers 112. The magnetic layers 110 and the bonding layers 112 are arranged parallel to one another and alternatingly along a vertical direction, so that each of the bonding layers 112 bonds two respectively neighbored magnetic layers 110 at one of two opposing main surfaces of the respective bonding layer 112. As shown in FIG. 2 as well, a thickness, d, of a respective one of the bonding layers 112 may be for example in a range between 1 m and 20 m, for instance 5 m. A sufficiently small thickness, d, of the bonding layers 112 ensures that the magnetic performance of the magnet stack 108 is high. A thickness, D, of the magnetic layers 110 may be in a range between 10 m and 50 m, for instance 20 m. This ensures a high magnetic performance of the magnet stack 108 as a whole, while simultaneously preventing damage of the brittle material of the magnetic layers 110 which may become unstable at higher thicknesses. An entire thickness, L, of the magnet stack 108 may be for example in a range between 200 m and 500 m, for instance 300 m.

[0075] The bonding layers 112 are made of an epoxy material (preferably without glass fibers) which is temperature-stable at least up to a temperature of 300 C. Thus, the material of the bonding layers 112 is reflow stable. This allows embedding the magnet stack 108 in the base material stack 102 without the risk of damage of the magnet stack 108 during further processing or operation of the component carrier 100. The magnetic layers 110 are made of nanocrystalline magnetic material and may comprise an iron-silicon compound having a very high magnetic permeability of for instance more than 50000. Although being quite brittle, the material of the magnetic layers 110 is mechanically stable in the stack compound of the magnet stack 108 thanks to the presence of the bonding layers 112, providing some degree of elasticity.

[0076] As can be taken from FIG. 1, the component carrier 100 moreover comprises a coil structure 114 being magnetically coupled with the magnet stack 108 and forming a coil with multiple windings cooperating with the magnet stack 108. In particular, the coil structure 114 may be substantially helically wound and may be formed of copper material of the electrically conductive layer structures 104 of the base material stack 102. Since the magnet stack 108 is embedded in an interior of the base material stack 102 with electrically conductive layer structures 104 on both opposing main surfaces thereof, the configuration of FIG. 1 is highly compact.

[0077] FIG. 1 also shows that the component carrier 100 comprises a plurality of surface mounted components 116, for instance embodied as active devices such as semiconductor chips and/or passive devices such as capacitors. Advantageously, the surface mounted components 116 are mounted on an upper main surface 144 of the base material stack 102 opposing a lower main surface 146 of the base material stack 102 in which the coil structure 114 is formed. In other words, the magnet stack 108 is arranged vertically in between the surface mounted components 116 on the one hand and the coil structure 114 on the other hand. Thus, the surface mounted components 116 do not disturb a wireless charging performance of the component carrier 100 (compare FIG. 3 to FIG. 5).

[0078] As can be taken from FIG. 1 as well, it is also possible to embed one or more further components 116 in the base material stack 102. In the shown example, one embedded component 116 is arranged side-by-side with and at the same vertical level as the magnet stack 108 to thereby contribute as well to the compact configuration of the component carrier 100. Preferably, the vertical thickness of the embedded component 116 may be the same as the vertical thickness, D, of the magnet stack 108. Such a thickness adaptation may be achieved by correspondingly selecting a number of magnet layers 110 and bonding layers 112 of the magnet stack 100, as shown in FIG. 2.

[0079] The surface mounted and embedded components 116 may be electrically connected to the coil structure 114.

[0080] As already mentioned, the component carrier 100 forms a wireless charger for a mobile phone. In other embodiments, a corresponding component carrier 100 may function as an inductor, a transformer, a DC/DC converter, etc.

[0081] What concerns wireless charging, a high coupling ratio between a transmitter and a receiver may be advantageous. The height increase due to the coil structure 114 of the shown wireless charger may be reduced by embedding also the coil structure 114 in base material stack 102. According to the shown embodiment, the magnet stack 108 made of bonded high permeability magnetic layers 110 (for instance nanocrystalline magnetic sheets) may be embedded inside the PCB or other kind of component carrier 100 forming the core of the magnet stack 108. Windings of the coil structure 114 may be formed as a copper structure within the component carrier 100, i.e. may be formed as part of the electrically conductive layer structures 104 of the base material stack 102. Additional components 116, which may for instance be used for communication and/or power transfer, can be mounted as surface mounted device (SMD) components on top and/or bottom of the component carrier 100 and/or can be embedded in the component carrier 100.

[0082] Again, referring in particular to FIG. 1 and FIG. 2 (but also more generally also to other embodiments of the invention), the nanocrystalline materials of the magnetic layers 110 may have very high permeability (up to 1000000) which makes them highly appropriate for a variety of magnetic applications. However, such a material is usually quite thin (for instance with a thickness of 20 m or less), since it may otherwise be prone to damage due to its brittle characteristics. According to an exemplary embodiment, such magnetic layers 110 may be stacked together with adhesive bonding layers 112 in between to achieve higher power transfer rates. Thus, nanocrystalline magnetic layers 110 may be stacked by using (for instance epoxy-based) bonding sheets or bonding layers 112 to achieve a desired thickness of for example 300 m. Such a method of stacking magnetic layers 110 together with bonding layers 112 can be applied, for example, from two layers above. As the magnet stack 108 may be embedded into the inner layers of the PCB type component carrier 100, a temperature stable adhesive may be advantageously used for the sheet shaped bonding layers 112 to achieve reflow resistance in the final component carrier 100.

[0083] Advantageously, epoxy resin in the form of the bonding layers 112 may be applied to stack the magnetic layers 110 together. Instead of epoxy resin, another reflow resistant polymer can be used for the bonding layers 112. Preferably, such a bonding material may be temperature stable at least up to 300 C. Apart from such a sheet application, it is also possible to apply the adhesive material of the bonding layer(s) 112 in liquid form.

[0084] Using an adhesive material for the one or more bonding layers 112 having reflow stability has the advantage that it is not necessary to glue a magnet stack 108 as a surface mounted device on a component carrier 100, which would increase the thickness of the component carrier 100. In contrast to this, embedding magnet stack 108 in a preformed cavity of the base material stack 102 of the component carrier 100 may result in a compact component carrier 100. In contrast to a conventional approach of gluing patches of magnetic material to a backside of a PCB after assembly, the distance to coil structure 114 may thus be made smaller. As a result, a more compact component carrier 100 may be obtained. Thus, it may be possible according to an exemplary embodiment of the invention to embed magnet stack 108 in a PCB directly above or below coil structure 114 so as to obtain a compact configuration. Consequently, an assembly process may be improved and thick and heavy component carriers may be avoided by exemplary embodiments.

[0085] Thus, a highly advantageous aspect of an exemplary embodiment of the invention is the stacking of nanocrystalline sheet material in form of magnet layers 112 with one more bonding layers 110 made of a thermally stable adhesive to create a reflow resistant inlay which may then be embedded into the inner layers of PCB type component carrier 100.

[0086] Such a nanocrystalline magnet stack 108 can be embedded just next to coil structure 114 to create sophisticated electronic functions while keeping the compactness of the component carrier 100 high. As a result, a further miniaturization of magnetic applications in a component carrier 100 (such as the realization of a DC/DC converter) can be achieved by embedding a reflow resistant magnet stack 108 in inner layers of a base material stack 102 of a component carrier 100.

[0087] A corresponding process of producing the component carrier 100 may be as follows. For the stacking of the layers 110, 112 of the magnet stack 108, adhesive sheets with a carrier film may be used as one or more bonding layers 112. For instance, it may be possible to first laminate material at a lower temperature onto the nanocrystalline material of the magnetic layers 110 without curing the adhesive material of the one or more bonding layers 112. Then, the carrier film may be removed. A stack of coated sheets may then be laminated at full curing temperature to yield a preform of the magnet stack 108. Pieces of desired shapes can then be cut out of the laminated magnet stack 108, for instance with a laser machine. Correspondingly obtained inlay type magnet stacks 108 may then be embedded into a PCB material type base material stack 102, for instance by using a center core production method.

[0088] In an embodiment, the inlay type magnet stack 108 may remain electrically unconnected to any other copper structure of the component carrier 100. The procedure can be used to create a wireless-charging transmitter and/or receiver units with PCB embedded magnetic material as well as DC/DC converters (both isolated and non-isolated) with an embedded inductor or transformer.

[0089] What concerns the wireless charging function of the component carrier 100, applying an electric current to the coil structure 114 generates an electromagnetic field in the environment of the component carrier 100. The magnet stack 108 with the magnetic layers 112 of very high magnetic permeability enhances the electromagnetic field. In FIG. 1, the electromagnetic field is indicated schematically by arrows 136. When a mobile phone or other electronic device to be charged in a wireless manner is positioned in the region where the arrows 136 are shown and when such an electronic device comprises a corresponding receiver unit, the electromagnetic field generated by the component carrier 100 may be used for charging the electronic device.

[0090] FIG. 3 illustrates a three-dimensional top view of a component carrier 100 configured as wireless charging device according to an exemplary embodiment of the invention. FIG. 4 illustrates a three-dimensional bottom view of the component carrier 100 configured as wireless charging device according to FIG. 3. FIG. 5 illustrates a three-dimensional view of the component carrier 100 configured as a wireless charging device according to FIG. 3 and FIG. 4 with a mobile phone as an electronic device 134 to be charged thereon. The component carrier 100 is connected via a plug 130 with a USB connector 132 to be supplied with electric current.

[0091] FIG. 6 illustrates an image showing a cross-sectional view of a magnet stack 108 to be embedded in a component carrier 100 according to an exemplary embodiment of the invention. FIG. 6 shows that the various layers 110, 112 have a homogeneous thickness and well-defined properties.

[0092] FIG. 7 to FIG. 11 illustrate arrangements of magnet stacks 108 and coil structures 114 of component carriers 100 according to other exemplary embodiments of the invention. The shown magnet stacks 108 correspond to different inductor configurations.

[0093] Referring to FIG. 7, the magnet stack 108 is formed as an annulus with a gap 120. The annulus is surrounded by windings of an annular coil structure 114. The gap 120 may be filled with resin (for instance of one of the electrically insulating layer structures 106) or is an air gap, i.e. remains unfilled. The gap design may allow fine tuning of the magnetic properties of the corresponding component carrier 100.

[0094] Referring to FIG. 8, the magnet stack 100 is formed as a pillar surrounded by the windings of the coil structure 114.

[0095] Referring to FIG. 9, the magnet stack 100 is shaped as a double rectangle, wherein the coil structure 114 surrounds a central post of the magnet stack 100. Two lateral posts of the magnet stack 100 are not surrounded by windings of coil structure 114.

[0096] Referring to FIG. 10, the magnet stack 100 is shaped as a rectangle, wherein the coil structure 114 surrounds one post of the magnet stack 100, whereas another post of the magnet stack 100 is not surrounded by windings of coil structure 114.

[0097] FIG. 11 illustrates an embodiment having an annular magnet stack 108 composed of three arcuate sections separated by three circumferentially arranged gaps 120. FIG. 11 also illustrates a coil structure 114 composed of substantially planar electrically conductive structures 142 (preferably made of copper) being interconnected by vertical through connections 138 (such as copper filled laser vias).

[0098] Providing the magnet stack 108 from multiple separate bodies (three in the example of FIG. 11) may simplify handling and assembly during the manufacturing procedure.

[0099] Number, arrangement and shape of the gaps 120 are design parameters for configuring the component carrier 100, for instance in terms of electromagnetic compatibility (EMC) behavior. The gaps 120 can be air gaps (i.e. may be void regions) or can be filled with a solid material (for instance can be filled with FR4 material or a high electric and/or magnetic permeability material), depending on the requirements of a certain application. For instance, thermal prepreg material with a thermal conductivity of at least 3 W/mK can be inserted into the gaps 120 for promoting heat removal during operation of the component carrier 100.

[0100] As shown, a dielectric disc 140 (for instance an FR4 inlay) may be placed in the central through hole of the substantially annular magnet stack 108. By taking this measure, excessive voids may be avoided within the component carrier 100. This may reduce warpage and mechanical stress of the component carrier 100.

[0101] 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.

[0102] Implementation of the invention is not limited to the preferred embodiments shown in the figures and described above. Instead, a multiplicity of variants is possible which use the solutions shown and the principle according to the invention even in the case of fundamentally different embodiments.