Method for copper filling of a hole in a component carrier

Abstract

A method of filling a hole formed in a component carrier with copper is disclosed. The method comprises i) forming a layer of an electrically conductive material covering at least part of a surface of a wall, wherein the wall delimits the hole, and subsequently ii) covering at least partially the layer and filling at least partially an unfilled volume of the hole with copper using a plating process including a bath. Hereby, the bath comprises a concentration of a copper ion, in particular Cu.sup.2+, in a range between 50 g/L and 75 g/L, in particular in a range between 60 g/L and 70 g/L.

Claims

1. A method of filling a hole formed in a component carrier with copper, the method comprising: forming a layer of an electrically conductive material covering at least part of a surface of a wall, wherein the wall delimits the hole; and subsequently, covering at least partially the layer and filling at least partially an unfilled volume of the hole with copper using a plating process including a bath, wherein the bath comprises a concentration of a copper ion in a range between 50 g/L and 75 g/L, and wherein at least partially covering the layer and at least partially filling the hole are done by flash-plating.

2. The method according to claim 1, further comprising: supplying the bath with copper sulfate (CuSO.sub.4) and/or copper sulfate pentahydrate (CuSO.sub.4*5H.sub.2O).

3. The method according to claim 1, wherein the bath further comprises: sulfuric acid (H.sub.2SO.sub.4) with a concentration in a range between 80 g/L and 110 g/L.

4. The method according to claim 1, wherein the bath further comprises: at least one of the group consisting of iron ions, chloride (Cl.sup.) a brightening agent, and a leveler agent.

5. The method according to claim 1, further comprising: filling at least partially a remaining volume of the hole with copper using a further plating process including a further bath, wherein the further bath comprises at least approximately the same composition of chemical ingredients and/or at least approximately the same concentration of chemical ingredients as the first bath.

6. The method according to claim 1, further comprising: filling at least partially a remaining volume of the hole with copper using a further plating process including a further bath, wherein the further bath comprises a different composition of chemical ingredients and/or a different concentration of chemical ingredients as the first bath.

7. The method according to claim 1, wherein a formed layer of electrically conductive material comprises a thickness in a range between 0.1 m and 1 m, and/or wherein a copper material, which has been formed above the formed layer of electrically conductive material, comprises a thickness in a range between 0.3 m and 15 m.

8. The method according to claim 1, wherein forming the layer of electrically conductive material is done by electro-less plating.

9. The method according to claim 1, further comprising: drilling the hole with a laser; and removing waste products caused by laser drilling.

10. The method according to claim 1, further comprising: drilling the hole with a laser; and wherein the forming of the layer is performed without previously removing waste products caused by laser drilling.

11. The method according to claim 1, wherein an aspect ratio of the hole is in a range between 0.5 and 1.5.

12. The method according to claim 1, wherein the hole is configured as a through hole or as a blind hole.

13. The method according to claim 1, wherein the electrically conductive material comprises at least one of the group consisting of copper, aluminum, and nickel.

14. The method according to claim 1, wherein the copper ion is Cu.sup.2+.

15. The method according to claim 1, wherein the bath comprises a concentration of the copper ion in a range between 60 g/L and 70 g/L.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the component carrier can be better understood with reference to the following drawings. The elements and features in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the structures and principles of operation of the assemblies.

(2) FIG. 1A, FIG. 1B, FIG. 1C and FIG. 1D illustrate a method for failure-free filling of a hole in a component carrier with copper according to an exemplary embodiment of the invention.

(3) FIG. 2 illustrates an exemplary embodiment of a component carrier, which has been manufactured with the method.

(4) FIG. 3A and FIG. 3B illustrate a prior art example of filling a hole in a component carrier.

(5) FIG. 4A and FIG. 4B illustrate a prior art example of filling a hole in a component carrier by using chemical additives.

(6) FIG. 5 illustrates a prior art example of a conventional hole in a conventional component carrier.

(7) FIG. 6A and FIG. 6B illustrate experimental data of a conventional hole according to the prior art and a hole according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

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

(9) 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.

(10) According to exemplary embodiments of the invention the filling capability of holes in a component carrier is improved and better reliability of the component carrier, in particular a PCB, regarding functionality is achieved. Usually, the copper ion concentration in a plating environment is around 35 g/L. On one hand, when the concentration is lower, the formation of failures such as cracks increases. On the other hand, when the copper concentration is too high, not all copper will be soluble anymore and crystallization of the copper will take place. A copper concentration in such a high range between 50 g/L and 80 g/L, in particular around 65 g/L, would not have been considered as appropriate in a plating environment, because the probability of copper crystallization is increased. However, and most surprisingly, in this specific concentration range, the electro-plating is improved towards providing a method for filling holes in a PCB with copper, while failures such as cracks and voids are avoided.

(11) FIGS. 1A, 1B, 1C, and 1D illustrate the method of filling a hole 120 in a component carrier 100 with copper 110 according to an exemplary embodiment.

(12) According to FIG. 1A, the component carrier 100 comprises a blind hole 120. The hole 120 is delimited by walls 130 in the horizontal direction, which walls 130 comprise respective surfaces 131. The hole 120 has been drilled with a laser and waste products, in particular black oxides, have been removed.

(13) According to FIG. 1B, the method comprises forming a layer of an electrically conductive material 111 covering at least part of the surface 131 of the wall 130, wherein the wall 130 delimits the hole 120. This layer forming is done by an electro-less plating process. The formed layer of electrically conductive material 111 comprises a thickness in the range between 0.1 m and 1 m, in particular in the range between 0.3 m and 0.7 m. The hole 120 is a blind hole and therefore also comprises a bottom structure 133, which delimits the hole 120 in a vertical direction. The aspect ratio of the hole 120 is approximately 0.9. It should be noted that the layer of electrically conductive material 111 above the bottom structure 133 is thicker than the layer of electrically conductive material 111 above the walls 130.

(14) Furthermore, the surface of the electrically conductive material 111 is smooth. In summary, the thickness of the layer of electrically conductive material 111 at the walls 130, and at the bottom 133 is comparatively thick and regularly shaped. As a consequence, the filling of the hole 120 with electrically conductive material is not hampered and will be performable in an efficient manner.

(15) According to FIG. 1C, the method further comprises subsequently covering at least partially the layer 111 and filling at least partially an unfilled volume 121 of the hole 120 with copper 110 using an electro-plating process including a bath. The growing directions of the copper material 110 are illustrated with bold arrows. It can be seen that the growing takes place in a regular manner and no unfilled gaps remain within the copper material 110. Hereby, it is mandatory that the bath comprises a concentration of a copper ion, in particular Cu.sup.2+, in a range between 50 g/L and 75 g/L, in particular in a range between 60 g/L and 70 g/L.

(16) According to the specific embodiment described here the thickness of the layer of electrically conductive material 111 and the copper layer 110 at the bottom 133 is 10.84 m, while the thickness at the left wall 130 is 7.31 m and the thickness at the right wall 130 is 7.48 m. Hereby, the hole 120 is 67.36 m in height and the largest diameter of the hole 120 is 83.26 m. Above shoulders 132 to the left and right side of the top of the hole 120, the thickness is 2.93 m.

(17) According to FIG. 1D, the hole has been completely filled with copper 110 and the filled copper material 110 does not comprise any failures such as cracks and/or voids.

(18) FIG. 2 illustrates an exemplary embodiment of a component carrier 200. The component carrier 200 consists of a stack of a plurality of electrically insulating layer structures 202 and a plurality of electrically conductive layer structures 204. The component carrier 200 has been manufactured by the method described above and comprises a high quality electrically conductive material 210 without failures such as cracks and/or voids. The material 210 is copper, which has been filled into a hole of the component carrier 200 by means of an electro-plating process on top of an electrically conductive layer 211. In this manner, a first layer 200a and a second layer 200b of the component carrier 200 can be electrically interconnected.

(19) FIGS. 6A and 6B illustrate experimental data in the form of photograph of a hole in a component carrier according to an exemplary embodiment of the invention (FIG. 6A) and a photograph of a conventional hole in a component carrier according to the prior art (FIG. 6B).

(20) FIG. 6A corresponds, from a technical point of view, to the exemplary embodiment of FIG. 1C. A hole in a component carrier has been plated with electrically conductive material, wherein the hole is arranged above a further electrically conductive layer structure below the hole. The dimensions in these experimental data are as follows: 83.26 m (L1), 7.48 m (L2), 2.93 m (L3), 67.36 m (L4), 10.84 (L5), and 7.31 m (L6).

(21) FIG. 6B corresponds from a technical point of view, to FIG. 5. According to the prior art, a conventional hole in a conventional component carrier has been plated with electrically conductive material. Hereby the conventional hole is arranged above a further electrically conductive layer structure below the conventional hole. The layer thicknesses in these experimental data are as follows: 83.36 m (PL1), 4.84 m (PL2), 4.18 (PL3), 63.68 m (PL4), 4.18 (PL5), and 4.27 m (PL6).

(22) 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.

(23) 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

(24) 100 component carrier

(25) 110 copper material

(26) 111 layer of electrically conductive material

(27) 120 hole

(28) 121 unfilled volume

(29) 130 wall

(30) 131 surface

(31) 132 shoulder

(32) 133 bottom structure

(33) 200 failure-free component carrier

(34) 200a first layer

(35) 200b second layer

(36) 202 electrically insulating layer structure

(37) 204 electrically conductive layer structure

(38) 210 copper material

(39) 211 layer of electrically conductive material

(40) 300 conventional component carrier

(41) 310 copper material

(42) 320 unfilled volume

(43) 330 wall

(44) 332 shoulder

(45) 333 bottom structure

(46) 345 gap

(47) 350 crack and void

(48) 400 conventional component carrier

(49) 450 chemical additives source

(50) 451 chemical additives drain

(51) 500 conventional component carrier

(52) 520 conventional hole