Component Carrier Comprising a Copper Filled Mechanical Drilled Multiple-Diameter Bore

Abstract

A component carrier includes a layer stack formed of an electrically insulating structure and an electrically conductive structure with a bore extending into the layer stack. The bore includes a first bore section with a first diameter and a connected second bore section with a second diameter differing from the first diameter. The component carrier further comprises a thermally conductive material filling substantially the entire bore. The bore is in particular formed by mechanical drilling.

Claims

1. A component carrier, comprising: a layer stack formed of an electrically insulating structure and an electrically conductive structure; a bore extending into the layer stack and having a first bore section with a first diameter and a connected second bore section with a second diameter differing from the first diameter; a thermally conductive material filling substantially the entire bore.

2. The component carrier according to claim 1, wherein the layer stack comprises a first surface and a second surface opposing the first surface, wherein the bore extends between the first surface and the second surface.

3. The component carrier according to claim 2, wherein the first bore section extends from the first surface into the layer stack and the second bore section extends from the second surface into the layer stack.

4. The component carrier according to claim 2, wherein the thermally conductive material forms a pad section onto the second surface.

5. The component carrier according to claim 2, wherein the thermally conductive material extends along the first surface for forming a heat radiation section.

6. The component carrier according to claim 5, wherein the heat radiation section forms a first covering area onto the first surface and the pad forms a second covering area onto the second surface, wherein the first covering area is larger than the second covering area.

7. The component carrier according to claim 2, further comprising: a further bore extending into the layer stack, wherein the further bore is spaced apart from the bore, wherein the further bore extends between the first surface and the second surface, wherein the thermally conductive material is filling substantially the entire further bore.

8. The component carrier according to claim 7, wherein the thermally conductive material extends along the first surface between the bore and the further bore.

9. The component carrier according to claim 1, wherein the first diameter of the first bore section is larger than the second diameter of the second bore section.

10. The component carrier according to claim 1, wherein between the first bore section and the second bore section a transition section is formed, wherein in the transition section the first diameter merges into the second diameter.

11. The component carrier according to claim 10, wherein the transition section has a step-like shape so that the first diameter merges into the second diameter in a stepwise manner.

12. The component carrier according to claim 10, wherein the transition section has a conical shape so that the first diameter merges into the second diameter in a conical manner.

13. The component carrier according to claim 10, wherein the bore is formed by mechanical drilling such that the shape of the transition section is formable.

14. The component carrier according to claim 1, wherein the at least one electrically insulating structure comprises at least one of the group consisting of resin, cyanate ester, glass, prepreg material, polyimide, liquid crystal polymer, epoxy-based Build-Up Film, FR4 material, a ceramic, and a metal oxide.

15. The component carrier according to claim 1, wherein the at least one electrically conductive structure comprises at least one of the group consisting of copper, aluminum, and nickel.

16. The component carrier according to claim 1, wherein the component carrier is shaped as a plate.

17. The component carrier according to claim 1, 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 in particular a laminate-type component carrier.

18. An electronic device, the electronic device comprising: an electronic component with electric terminals, a component carrier according to claim 1 in which the electronic component is packaged.

19. The electronic device according to claim 18, wherein the electronic component is selected from a group consisting of 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, a sensor, an actuator, a microelectromechanical system, a microprocessor, a capacitor, a resistor, an inductance, a battery, a switch, a camera, an antenna, a magnetic element, and a logic chip.

20. Method of manufacturing a component carrier, the method comprising: forming a layer stack of an electrically insulating structure and an electrically conductive structure; boring a bore extending into the layer stack, wherein the bore has a first bore section with a first diameter and a connected second bore section with a second diameter differing from the first diameter; and filling substantially the bore with a thermally conductive material, wherein the bore is in particular formed by mechanical drilling.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0052] FIG. 1 shows a cross-sectional plan view of an embodiment of a component carrier having two bores according to the present invention and a further bore having a uniform diameter.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

[0053] The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

[0054] The illustrations in the drawings are schematical. In different drawings, similar or identical elements are provided with the same reference signs.

[0055] FIG. 1 illustrates a component carrier 100 into which an electrical component can be embedded or mounted thereon. The component carrier 100 comprises a layer stack 101 formed of an electrically insulating structure and an electrically conductive structure and a bore 110, 110′ extending into the layer stack 101 and having a first bore section 111, 111′ with a first diameter D1, D1′ and a connected second bore section 112, 112′ with a second diameter D2, D2′ differing from the first diameter D1, D1′. The component carrier further comprises a thermally conductive material 102 filling substantially the entire bore 110, 110′. The bore 110, 110′ is in particular formed by mechanical drilling. In the exemplary embodiment shown in FIG. 1, the first bore hole diameter D1, D1′ is larger than the second bore hole diameter D2, D2′.

[0056] The bore 110, 110′ is filled with the thermally conductive material 102. Besides the proper thermal conduction properties, the thermally conductive material 102 may also be electrically conducting. In an exemplary embodiment, the thermally conductive material 102 is copper or a copper compound.

[0057] For example, a multiple-diameter mechanical drilling (e.g. by a drill bit having two different diameter sections to form the bore in a counter bore or counter sink shape) may be used to replace the standard single diameter drill bit or stacked laser.

[0058] The bore 110, 110′ filled with the thermally conductive material 102 may form a via connection between two or more layers within the layer stack 101 of the component carrier 100. By providing the bore 110, 110′ with different diameters D1, D1′, D2, D2′ a small diameter target pad size of a pad section 105, 105′ made of the thermally conductive material 102 and formed at an exit section of the bore 110, 110′ and additionally a better heat transfer by the thermally conductive material 102 within the larger second bore section 111, 111′ of the bore 110, 110′ is achieved.

[0059] The layer stack 101 comprises a first surface 103 and a second surface 104 opposing the first surface 103, wherein the bore 110, 110′ extends between the first surface 103 and the second surface 104. The first bore section 111, 111′ extends from the first surface 103 into the layer stack 101 and the second bore section 112, 112′ extends from the second surface 104 into the layer stack 101.

[0060] The thermally conductive material 102 forms a pad section 105, 105′ onto the second surface 104. The pad section 105, 105′ may be connected e.g. to a printed circuit board track. Furthermore, the pad section 105, 105′ is part of the thermally conductive material 102 which fills the bore 110, 110′ so that a via (vertical connection) through the layer stack 101 is formed. The via connects other embedded components and electrically layer structures within the layer stack 101 to the pad section 105, 105′. Typically, the pad section 105, 105′ has a larger diameter than the printed circuit board track. However, it is possible to form the printed circuit board track and to fill the bore 110, 110′ with the thermally conductive material 102 in one operating step. Hence, the pad section 105, 105′ size may be reduced and has the same size (width) as the printed circuit board track.

[0061] The thermally conductive material 102 extends along the first surface 103 for forming a heat radiation section 106. The larger the heat radiation section 106 along the first surface 103, the larger the heat that may be transported away from the component carrier 100. The heat radiation section 106 forms a first covering area onto the first surface 103 and the pad section 105, 105′ forms a second covering area onto the second surface 104. The first covering area is larger than the second covering area.

[0062] Regarding the size of the heat radiation section 106, the surface area of the heat radiation section 105, 105′ which is defined between a circumference of the heat radiation section 105, 105′ and an edge of the first bore section 111, 111′ at the first surface 103 is limited in size, because if the overhang exceeds a certain threshold size, the risk of voids, cracks and other plating defects during a plating proceeding, where the thermally conductive material 102 flows into the bores 110, 110′, increases.

[0063] The threshold size may be given in an aspect ratio AR which is defined by the thickness (length) A (according to FIG. 1 the length L1, L1′ of the first bore section 111, 111′ and the length L2, L2′ of the second bore section 112, 112′) of a bore 110, 110′ with respect to an opening diameter R (according to FIG. 1 the diameter D1, D1′ of the first bore section 111, 111′ and the diameter D2, D2′ of the second bore section 112, 112′ of the second bore section 112, 112′) of the bore at a respective surface of the component carrier:

AR=A/R

[0064] As can be taken from FIG. 1, the first bore section 111, 111′ has a larger diameter D1, D1 than the second bore section 112, 112′ and the opening diameter R (i.e. D1, D1′) of the first bore section 111, 111′ is increased in order to provide a large overhang of the heat radiation section 106. However, the diameter R (i.e. D2, D2′) of the second bore section 112, 112′ is reduced in order to provide a small sized pad section 105, 105′ along the second surface 104.

[0065] For example, in a conventional bore 120 having a uniform diameter, a 101 of a component carrier 100 has a thickness A of 1 mm with 0.1 mm opening diameter R (also called mechanical drilled PTH (plated through hole) will have an aspect ratio AR=A/R of 10:1=10.

[0066] For example, the second bore section 112, 112′ may have length L2, L2′ of A=⅓ of the overall thickness (e.g. 1 mm) of the 101 and an opening diameter R (i.e. second diameter D2, D2′) of R=0.1 mm. The first bore section 111, 111′ may have ⅔ of the overall thickness (e.g. 1 mm) of the 101 drilled with a diameter R (i.e. first diameter D1, D1′) of R=0.2 mm opening diameter. Hence, the total aspect ratio will be AR=3.33. The new aspect ratio lowers the risk for inclusion and other reliability defects during plating as the difficulty of the solution exchange inside the PTH is reduced. At the same time, a smaller pad section 105, 105′ by the second bore section 112 is formed.

[0067] In comparison to the further bore 120 which is the bore 120 located between the two bores 110, 110′ of the present invention, the aspect ratio AR is 10 for a diameter R=0,1 and the overall thickness A of 1 mm of the 101.

[0068] Summarizing, by the differently sized bore sections 111, 111′, 112, 112′, a high aspect ratio AR limitation for the copper filling process is reduced and a tight/small target pad annular ring breakout is prevented. Furthermore, the total volume of copper (functioning as the thermally conductive material) in the filled via (bores 110, 110′) for better heat transfer is increased. Hence, less heat remains in the via (i.e. the bores 110, 110′) which causes lower temperature and less expansion of the layer stack 101.

[0069] The thermally conductive material 102 extends along the first surface 103 between the bore 110, 110′ and the further bore 120. Hence, along the first surface 103, a common heat radiation section 106 for the bore 110, 110′ and the further bore 120 is generated.

[0070] Between the first bore section 111, 111′ and the second bore section 112, 112′ a transition section 113, 113′ is formed. In the transition section 113, 113′ the first diameter D1, D1′ merges into the second diameter D2, D2′.

[0071] In the bore 110 shown at the left side in FIG. 1 (bore design I), the transition section 113 has a step-like shape 114 with a flat design (so that the first diameter D1 merges into the second diameter D2 in a stepwise and abrupt manner). The step defines a short transition between the first bore section D1, D1′ and the second bore section D2. For example, the step forms an edge between the first bore section 111 and the second bore section 112.

[0072] The first bore section 111 and the second bore section 112 comprise a common bore axis 107. The step of the transition section 113 has a step surface extending within a plane having a normal, wherein the step surface is formed such that an angle between the normal and the common bore axis 107 is approximately ±15 degree. Specifically, the step surface is formed such that the normal is approximately or exactly parallel with the common bore axis 107.

[0073] In the bore 110′ shown at the right side in FIG. 1 (bore design II), the transition section 113′ has a conical shape 115 (i.e. with a slope design) so that the first diameter D1′ merges into the second diameter D2′ in a conical manner.

[0074] In the mentioned example, the transition section 113′ has an inclined and sloping surface extending within a plane having a normal, wherein the step surface is formed such that an angle between the normal and the common bore axis 107′ is approximately 30 to 60 degree, specifically 45 degree.

[0075] It should be noted that the term “comprising” does not exclude other elements or steps and the “a” or “an” does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims. Implementation of the invention is not limited to the preferred embodiments shown in the figures and described above. Instead, a multiplicity of variants are possible which use the solutions shown and the principle according to the invention even in the case of fundamentally different embodiments.

REFERENCE SIGNS

[0076] 100 component carrier [0077] 101 layer stack [0078] 102 thermally conductive material [0079] 103 first surface [0080] 104 second surface [0081] 105, 105′ pad section [0082] 106 heat radiation section [0083] 107, 107′ common bore axis [0084] 110, 110′ bore [0085] 111, 111′ first bore section [0086] 112, 112′ second bore section [0087] 113, 113′ transition section [0088] 114 step-like shape [0089] 115 conical shape [0090] 120 further bore [0091] D1, D1′ first diameter [0092] D2, D2′ second diameter [0093] L1, L1′ first length [0094] L2, L2′ second length [0095] I first bore design [0096] II second bore design