Component carrier with embedded component exposed by blind hole

Abstract

The present invention relates to an embedded printed circuit board including: an insulation substrate including a cavity; a sensor device disposed on the cavity; an insulating layer disposed on the insulation substrate, having an opening part exposing the sensor device; and a pad part disposed on the lower surface of the opening part exposing the sensor device.

Claims

1. A method of manufacturing a component carrier, comprising: providing a stack comprising at least one electrically conductive layer structure and at least one electrically insulating layer structure; embedding a component in the stack; creating a blind hole in the stack towards the embedded component; and thereafter extending the blind hole by etching to thereby expose a surface portion of the embedded component, wherein the blind hole has at least partially curved sidewalls with a curved section and a step at an interface with the component, wherein at least one of the curved section and the step is delimited by at least one of a first electrically insulating layer structure.

2. The method according to claim 1, wherein the method comprises drilling the blind hole by laser drilling.

3. The method according to claim 1, wherein the method comprises exposing the surface portion by plasma etching.

4. The method according to claim 1, wherein the method comprises carrying out the etching for extending the blind hole over the last few micrometers up to the embedded component.

5. The method according to claim 1, wherein the method comprises carrying out the etching for extending the blind hole over less than 5 μm up to the embedded component.

6. The method according to claim 1, wherein the method comprises cleaning the exposed surface portion and/or the blind hole by said etching.

7. The method according to claim 1, wherein the method comprises cleaning the exposed surface portion and/or the blind hole by a laser treatment.

8. A component carrier, comprising: a stack comprising at least one electrically conductive layer structure and at least one electrically insulating layer structure; a component embedded in the stack; and a blind hole in the stack exposing a surface portion of the embedded component and having at least partially curved sidewalls delimited by the stack, wherein the at least partially curved sidewalls have a curved section and a step at an interface with the component, wherein at least one of the curved section and the step is delimited by at least one of a first electrically insulating layer structure.

9. The component carrier according to claim 8, wherein the component is an optical component selected from the group consisting of an optical sensor, an optical emitter, a light-emitting device, and an optically receiving and/or emitting device.

10. The component carrier according to claim 8, wherein the component has an aperture at the exposed surface portion.

11. The component carrier according to claim 10, further comprising: an optical element accommodated at least partially in the aperture.

12. The component carrier according to claim 8, wherein a width of the exposed surface portion is less than 100 μm.

13. The component carrier according to claim 8, wherein a maximum width of the blind hole is less than 150 μm.

14. The component carrier according to claim 8, wherein the at least partially curved sidewalls are at least partially concavely curved.

15. The component carrier according to claim 8, wherein the curved section is delimited by a first one of the at least one electrically insulating layer structure of a first electrically insulating material, and the step is delimited by a second one of the at least one electrically insulating layer structure of a second electrically insulating material being different from the first electrically insulating material.

16. The component carrier according to claim 8, wherein the at least partially curved sidewalls taper towards the embedded component.

17. The component carrier according to claim 8, wherein the exposed surface portion is a sensor-active surface of the component.

18. The component carrier according to claim 8, comprising at least one of the following features: wherein the component is 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 optical element, a bridge, 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 the group consisting of copper, aluminum, nickel, silver, gold, palladium, and tungsten; wherein the at least one electrically insulating layer structure comprises at least one of the group consisting of reinforced or non-reinforced resin, 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 material, 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 the group consisting of a printed circuit board, and a substrate; wherein the component carrier is configured as a laminate-type component carrier.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a cross-sectional view of a preform of a component carrier during carrying out a method of manufacturing a component carrier according to an exemplary embodiment of the invention.

(2) FIG. 2 illustrates a cross-sectional view of a component carrier according to an exemplary embodiment of the invention which may be obtained based on the preform shown in FIG. 1.

(3) FIG. 3 illustrates a detail of the blind hole of the component carrier of FIG. 2.

(4) FIG. 4 illustrates images of component carriers manufactured according to exemplary embodiments of the invention.

(5) FIG. 5 illustrates a cross-sectional view of a component carrier according to another exemplary embodiment of the invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

(6) The illustrations in the drawings are schematically presented. In different drawings, similar or identical elements are provided with the same reference signs.

(7) 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.

(8) Conventionally, sensor packages are created utilizing a complex molded-package process flow with low robustness mechanical molding barriers for protecting a sensor aperture. Another conventional approach implements a release layer forming access to an encapsulated component.

(9) An exemplary embodiment of the invention provides a manufacturing method for manufacturing component carriers with embedded or encapsulated component (in particular embedded sensor component), in which an aperture of the embedded component is accessed and cleaned by a laser and plasma process. Preferably, said encapsulation is accomplished by a lamination of multiple layer structures with the component in between. By a combined laser and plasma process, formation of an access blind hole for exposing the embedded component becomes possible without the need of cumbersome molding processes or release layers. Furthermore, such a manufacturing method may allow the creation of miniature access holes without the risk of damaging the sensitive embedded component. This may be accomplished by stopping a laser drilling process sufficiently early before reaching the embedded components, and by removing the remaining laminate material for finally exposing the embedded component by etching, for instance plasma etching.

(10) According to exemplary embodiments of the invention, a sensor package manufacturing method may be provided which synergistically combines a laser cleaning process and a plasma cleaning process. This may ensure exposure of a functionally active surface portion of an embedded component, preferably in the framework of an embedded sensor package.

(11) Exemplary embodiments of the invention provide a highly advantageous manufacturing architecture in which an embedded optical sensor package is created by encapsulation and by additionally forming and cleaning an aperture window by laser and plasma treatment. Such a manufacturing technology provides multiple benefits in terms of reliability and involves a significantly reduced manufacturing effort compared to the conventional concept of molding barriers. In particular, exemplary embodiments of the invention may allow to realize smaller opening dimensions without the need to form additional molding barriers or release layers.

(12) Exemplary applications of exemplary embodiments of the invention are sensor packages (in particular optical sensor packages), cameras (for instance for mobile phones or automotive applications), light sources, and optoelectronic packages (for instance for optical data transmission).

(13) FIG. 1 illustrates a cross-sectional view of a preform of a component carrier 100 obtained during carrying out a method of manufacturing component carriers 100, as shown in FIG. 2, according to an exemplary embodiment of the invention.

(14) As illustrated in FIG. 1, a component 108 is placed in a cavity (not shown) formed in a layer stack 102.

(15) Stack 102 may be a plate-shaped laminate-type layer stack composed of a plurality of electrically conductive layer structures 104 and a plurality of 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) and optionally reinforcing particles therein (for instance glass fibers or glass spheres). For instance, the electrically insulating layer structures 106 may be made of FR4 or ABF. In the shown embodiment, the thick central electrically insulating layer structure 106 may be a fully cured core.

(16) The above-mentioned cavity may be defined by a through-hole in the thick central electrically insulating layer structure 106 of the stack 102 which may be closed on a bottom side by attaching a temporary carrier (not shown) to a lower main surface of the core. The temporary carrier may for instance be a sticky tape. The component 108 with (here downwardly protruding) pads 150 may be attached with direct physical contact on the temporary carrier in the cavity. The function of the temporary carrier is to provide stability as long as the component 108 is not yet glued in place within the cavity.

(17) The structure shown in FIG. 1 can be obtained by laminating one or more further electrically insulating layer structures 106 and one or more further electrically conductive layer structures 104 to the upper main surface of the central electrically insulating layer structure 106 accommodating component 108. For instance, a prepreg layer (as further electrically insulating layer structure 106) and one or more copper foils (as further electrically conductive layer structure 104) may be laminated on top. During the lamination process, uncured material of the further electrically insulating layer structure 106 may become flowable or melt and may flow in gaps between stack 102, temporary carrier and component 108. Upon curing (for instance cross-linking, polymerizing, etc.) of the material of the further electrically insulating layer structure 106, filling medium in said gaps may become solid. In particular, underfill 152 material may be formed in the gaps by said now solidified resin material.

(18) As an alternative to the described lamination, it is also possible to glue component 108 in place in the cavity formed in stack 102 by filling liquid adhesive material in the gaps in between. Upon curing said adhesive material, the component 108 is again glued in place in cavity.

(19) After having glued the component 108 in place within the cavity and thus having provided an integral connection with stack 102, the temporary carrier may be removed. When the temporary carrier is a sticky tape, it may be simply peeled off from the lower main surface of the structure shown in FIG. 1. One or more further electrically conductive layer structures 104 and electrically insulating layer structures 106 may be connected to the lower surface of the obtained structure to thereby obtain stack 102 as shown in FIG. 1.

(20) By carrying out the described manufacturing process, the illustrated laminated stack 102 of electrically conductive layer structures 104 and electrically insulating layer structures 106 with embedded component 108 is obtained. In the shown embodiment, the embedded component 108 is an optical component, for instance an optical sensor configured for detecting visible light in an environment of the component carrier 100 been presently manufactured. For instance, the embedded component 108 is a photodiode or a camera. Hence, the described manufacturing method relates to a sensor embedding encapsulation using lamination technology. As can be taken from FIG. 1 as well, the bottom main surface of the component 108 has an aperture 114 in form of a recess. Within the aperture 114 at a bottom side of the component 108, a light-sensitive detection surface of the optical component 108 is located. Hence, a lower main surface of the embedded component 108 is provided with an aperture opening at which the sensor-active surface is located, which should be made accessible to the environment.

(21) FIG. 2 illustrates a cross-sectional view of a component carrier 100 according to an exemplary embodiment of the invention which may be obtained based on the preform described referring to FIG. 1 by carrying out the further manufacturing processes which will be described in the following. FIG. 3 illustrates a detail 180 of a blind hole 110 of the component carrier 100 of FIG. 2 which is created by said further manufacturing processes.

(22) As shown in FIG. 2, blind hole 110 is created in the lower main surface of the stack 102. More specifically, said blind hole 110 extends from a bottom main surface of the structure shown in FIG. 1 towards the embedded component 108.

(23) The major portion of the blind hole 110 from an exterior bottom main surface of the stack 102 through the lowermost electrically insulating layer structure 106 extends almost, but not entirely up to the component 108 and can be formed by laser drilling. By laser drilling, i.e., the irradiation of a central portion of the lower main surface of the stack 102 with a laser beam (not shown), dielectric material of the stack 102 may be efficiently removed with a high removal rate and thus quickly. Highly advantageously, the laser drilling process may stop at some distance (preferably a few micrometers) away from a surface portion 112 of the optical component 108 to be exposed. This may ensure that the sensor-active surface of the optical component 108, i.e., surface portion 112, is not reached by the laser beam and is therefore reliably protected from being deteriorated or damaged by excessive laser energy. By taking this measure, a rapid formation of the blind hole 110 may be combined with a reliable protection of the component 108 against damage. Highly advantageously, laser drilling may be capable of creating a blind hole 110 with a small maximum width, D, of for instance 90 μm, see detail 180 of FIG. 3. As illustrated in FIG. 3 as well, a width, W, of the exposed portion 112 may be even smaller, for instance 60 μm. A width, L, of aperture 114 in a lower main surface of the component 108 may be still smaller, for instance 50 μm. Thus, the described manufacturing method is properly compatible with the trend of continuous miniaturization of embedded components 108 and corresponding component carriers 100.

(24) After having completed the laser drilling procedure several micrometers away from the surface portion 112 to be exposed (and being presently still partially covered with dielectric material of stack 102), the method may continue by extending the already formed exterior portion of the blind hole 110 by etching further inwardly into the stack 102 to thereby expose the above-mentioned sensor-active surface portion 112 of the embedded component 108. Highly preferably, the method may comprise exposing the surface portion 112 by plasma etching. Alternatively, other etching procedures may be carried out (for instance wet etching with an etchant selected for maintaining surface portion 112 intact). Thus, the method may comprise etching for extending the blind hole 110 over the last few micrometers up to the embedded component 108 to thereby expose the latter. The extension of the blind hole 110 by etching may occur over less than 5 μm remaining up to the embedded component 108 after laser drilling. The thickness of the portion of the stack 102 removed by plasma etching is denoted in FIG. 3 with “d”, wherein d may be for example in a range between 1 μm and 5 μm. Highly advantageously, the described plasma etching process completes the formation of the blind hole 110 up to the surface portion 112 of the embedded component 108 to be exposed.

(25) Simultaneously, the etching process cleans the blind hole 110 and in particular the exposed bottom surface of the blind hole 110 delimited by the exposed surface portion 112. Also, a laser process may be used for supporting said cleaning. After laser drilling, residues of the laser-burnt dielectric material of the stack 102 may remain in the blind hole 110 and may disturb the sensor functionality of the embedded sensor component 108. However, exposing surface portion 112 may be synergistically and simultaneously combined with cleaning of the blind hole 110 by etching without damaging component 108. More specifically, cleaning the exposed surface portion 112 and/or the blind hole 110 may be accomplished by said etching process which exposes the exposed surface portion 112. Additionally or alternatively, an efficient cleaning of the exposed surface portion 112 and/or the blind hole 110 may be accomplished by laser treatment. Said laser treatment may be the same or an additional one as the one used for drilling the exterior portion of the blind hole 110. In particular the synergistic combination of plasma etching and laser processing for exposing and cleaning the exposed surface portion 112 and the blind hole 110 may be of utmost advantage.

(26) As a result, the blind hole 110 in the stack 102 may be obtained with the shape as shown in FIG. 2 and FIG. 3. The blind hole 110 exposes surface portion 112 of the embedded component 108 and has partially curved sidewalls 120. In other words, the blind hole 110 is delimited by a sloped sidewall 120 of the stack 102.

(27) More specifically, the partially curved sidewalls 120 are partially concavely curved. This is a consequence of laser drilling, since the laser beam has a stronger impact on the exterior of the stack 102 as compared to an interior thereof. More precisely, the partially curved sidewalls 120 have an exterior curved section 122 and an interior step 124 at an interface with the component 108. The formed step 124 is the consequence of the plasma etching. Furthermore, the partially curved sidewalls 120 taper towards the embedded component 108. This is as further consequence of the energy impact characteristic of the laser beam used for laser drilling the exterior main portion of the blind hole 110.

(28) As shown in FIG. 3 as well, the curved section 122 is delimited by a first one of the electrically insulating layer structures 106, in particular by a first electrically insulating material 126 thereof. In contrast to this, the step 124 may be delimited by a second one of the electrically insulating layer structures 106, in particular by a second electrically insulating material 128 being different from the first electrically insulating material 126. By a corresponding material selection of the electrically insulating materials 126, 128, the characteristic shape of the blind hole 110 as shown in FIG. 2 may be further promoted. The shape of the blind hole 110 as shown in FIG. 2 is also highly advantageous for the sensor function of the embedded component 100, since its funnel-shape promotes propagation of light to be sensed between an exterior and an interior of the component carrier 100 while additionally providing a proper shielding against ambient light. Thus, the described geometry also promotes a high signal-to-noise ratio.

(29) As shown as well in FIG. 2, the component carrier 100 may further comprise an optional optical element 116, such as a convex lens, which may for instance be accommodated partially or entirely in the aperture 114. Such an optical element 116 may further promote the optical performance of the sensor-package type component carrier 100.

(30) In a nutshell, the manufacturing process is characterized by a laser ablation process with ultra-soft parameters followed by a plasma etch. As a result, the component carrier 100 with embedded and exposed component 108 is obtained being properly protected against damage and being configured for detecting light with high accuracy.

(31) FIG. 4 illustrates images of component carriers 100 manufactured according to exemplary embodiments of the invention.

(32) The corresponding component carriers 100 have been manufactured by a process similar to that described referring to FIG. 1 to FIG. 3. Windows formed in the stack 102 by laser processing followed by plasma etching may have a width slightly above 100 μm.

(33) FIG. 5 illustrates a cross-sectional view of a component carrier 100 according to another exemplary embodiment of the invention.

(34) The embodiment of FIG. 5 differs from the embodiment of FIG. 2 in particular in that the exterior portion of the blind hole 110 has a different shape in FIG. 5 as compared to FIG. 2. According to FIG. 5, the exterior portion of the blind hole 110 has straight walls as obtained for instance by mechanically drilling, for instance using a drill bit (not shown) for removing material of the stack 102. The mechanical drilling process may stop several micrometers (in particular between 1 μm and 5 μm) away from the surface portion 112 to be exposed. By such a stopping of the mechanically drilling process sufficiently remote from the surface portion 112 to be exposed, damage of the embedded component 108 during drilling can be reliably prevented. Thereafter, exposing the surface portion 112 as well as cleaning of the blind hole 110 may be accomplished by a subsequent etching process, preferably plasma etching.

(35) 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.

(36) 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 variants use the solutions shown and the principle according to the invention even in the case of fundamentally different embodiments.