Method for forming metal bumps

Abstract

We propose a method for forming metal bumps that can reduce variations in the height of metal bumps without using special components such as shielding plates. [Solution] The present invention provides a method for forming metal bumps, comprising: a dummy pattern formation step of forming a dummy pattern on the solder resist layer surrounding the metal bumps simultaneously with the formation of the metal bumps; and a dummy pattern removal step of removing the dummy pattern after the formation of the metal bumps and dummy pattern to form the metal bumps. The contact area between the dummy pattern and the solder resist layer is 170 μm². 2 More than 290μm 2 The following is preferable:

Description

Technical Field

[0001] The present invention relates to a method for forming metal bumps capable of reducing variation in the height of metal bumps.

Background Art

[0002] Conventionally, a method for forming metal bumps capable of reducing variation in the height of metal bumps is known, for example, in Patent Document 1. FIG. 3 is a diagram for explaining one embodiment of a conventional metal bump forming method disclosed in Patent Document 1.

[0003] In the conventional metal bump forming method disclosed in Patent Document 1, as shown in FIG. 3, in electrolytic plating for forming a plating film on the entire surface of a substrate 51 placed in a plating tank, a shielding plate 53 having predetermined openings formed corresponding to the chip pattern of the substrate 51 is provided between an anode 52 and the substrate 51. By forming a plating film over the entire substrate 51 via the shielding plate 53, variation in height is prevented from occurring in copper pillars formed on the substrate 51 (corresponding to the metal bumps of the present invention).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] As described above, in the conventional metal bump forming method, as shown in FIG. 3, in electrolytic plating for forming a plating film over the entire substrate 51, it is necessary to dispose the shielding plate 53 having a complicated configuration between the substrate 51 and the anode 52. For this reason, it is necessary to prepare the shielding plate 53 with a complicated configuration in advance, and there has been a problem that when the arrangement of copper pillars is changed, the shielding plate 53 must be prepared for each different arrangement.

Means for Solving the Problem

[0006] The present invention provides a method for forming metal bumps, which includes a dummy pattern formation step of forming a dummy pattern around the metal bumps at the same time as forming the metal bumps, and a dummy pattern removal step of removing the dummy pattern after the formation of the metal bumps and dummy pattern to form the metal bumps. [Brief explanation of the drawing]

[0007] [Figure 1A] This figure illustrates one embodiment of a top view of the substrate mounting surface in the method for forming metal bumps according to the present invention. [Figure 1B] This is a cross-sectional view along line AB in Figure 1A illustrating one embodiment of the method for forming metal bumps according to the present invention. [Figure 1C] This is a cross-sectional view along line AB in Figure 1A illustrating one embodiment of the method for forming metal bumps according to the present invention. [Figure 2A] This is a cross-sectional view along line AB in Figure 1A illustrating the dummy pattern formation step in one embodiment of the metal bump formation method of the present invention. [Figure 2B] This is a cross-sectional view along line AB in Figure 1A illustrating the dummy pattern formation step in one embodiment of the metal bump formation method of the present invention. [Figure 2C] This is a cross-sectional view along line AB in Figure 1A illustrating the dummy pattern formation step in one embodiment of the metal bump formation method of the present invention. [Figure 2D] This is a cross-sectional view along line AB in Figure 1A illustrating the dummy pattern formation step in one embodiment of the metal bump formation method of the present invention. [Figure 2E] This is a cross-sectional view along line AB in Figure 1A illustrating the dummy pattern formation step in one embodiment of the metal bump formation method of the present invention. [Figure 2F]This is a cross-sectional view along line AB in Figure 1A illustrating the dummy pattern formation step in one embodiment of the metal bump formation method of the present invention. [Figure 2G] This is a cross-sectional view along line AB in Figure 1A illustrating the dummy pattern formation step in one embodiment of the metal bump formation method of the present invention. [Figure 2H] This is a cross-sectional view along line AB in Figure 1A illustrating the dummy pattern formation step in one embodiment of the metal bump formation method of the present invention. [Figure 2I] This is a cross-sectional view along line AB in Figure 1A illustrating the dummy pattern removal step in one embodiment of the metal bump formation method of the present invention. [Figure 3] This figure illustrates one embodiment of a conventional method for forming metal bumps disclosed in Patent Document 1. [Modes for carrying out the invention]

[0008] Hereinafter, an embodiment of the method for forming a metal bump according to the present invention will be described with reference to the drawings. In the examples shown in Figures 1A to 1C and Figures 2A to 2I, the dimensions in the width and height directions of each member are described using dimensions different from the actual dimensions in order to better understand the features of the present invention.

[0009] <Outline of the present invention's method for forming metal bumps> Figure 1A is a diagram illustrating one embodiment of the top view of the substrate mounting surface in the metal bump formation method of the present invention. Figures 1B to 1C are cross-sectional views along line A and B of Figure 1A, illustrating one embodiment of the metal bump formation method of the present invention. The outline of the metal bump formation method of the present invention will be described below with reference to Figures 1A to 1C.

[0010] The present invention relates to a method for forming metal bumps, which reduces variations in the height of metal bumps formed by electroplating. To this end, first, as shown in the top view of the mounting surface in Figure 1A, a metal bump region is defined in the central part of the substrate 1, and a dummy pattern region is defined around the metal bump region of the substrate 1. Then, as shown in Figure 1B, a metal bump 2 is formed in the metal bump region, and at the same time, a dummy pattern 3 is formed in the dummy pattern region. Subsequently, as shown in Figure 1C, the metal bump 2 of the present invention can be formed in the metal bump region by removing the dummy pattern 3 in the dummy pattern region.

[0011] According to the metal bump formation method of the present invention described above, a dummy pattern is formed around the metal bump simultaneously with the formation of the metal bump, and then the dummy pattern is removed to form the metal bump. Therefore, variations in the height of the metal bump can be reduced without using special members such as shielding plates. Furthermore, when using shielding plates as in the conventional method, if the arrangement of the metal bumps changes, a new shielding plate must be created for each arrangement. However, with the metal bump formation method of the present invention, which does not use shielding plates, such trouble is eliminated.

[0012] <Regarding each step in one embodiment of the method for forming metal bumps according to the present invention> As described above, the present invention's method for forming metal bumps includes a dummy pattern formation step of forming a dummy pattern around the metal bumps simultaneously with the formation of the metal bumps, and a dummy pattern removal step of forming the metal bumps by removing the dummy pattern after the formation of the metal bumps and dummy pattern. The dummy pattern formation step and the dummy pattern removal step will be described below.

[0013] (1. Regarding the dummy pattern formation process) In the metal bump forming method of the present invention, the dummy pattern forming step comprises: forming a base insulating layer; forming a conductor layer on the base insulating layer; forming a solder resist layer on the base insulating layer and the conductor layer; forming an opening in the solder resist layer that exposes a part of the conductor layer as a conductor pad; forming a seed layer on the conductor layer, on the surface of the solder resist layer and on the side surface of the opening; and forming a metal bump on the conductor pad via the seed layer, and forming a dummy pattern on the surface of the solder resist layer around the metal bump via the seed layer.

[0014] Hereinafter, a specific dummy pattern forming step will be described with reference to FIGS. 2A to 2H. Note that FIGS. 2A to 2H each show a cross-section taken along line A-B of FIG. 1A, similarly to FIGS. 1B to 1C.

[0015] First, as shown in FIG. 2A, a base insulating layer 12 is formed on a substrate 11. As the substrate 11, a build-up layer formed by alternately laminating conductor layers having a predetermined circuit pattern and resin insulating layers on one or both sides of a core substrate can also be used. Next, as shown in FIG. 2B, a conductor layer 13 is formed in a metal bump region on the base insulating layer 12. The base insulating layer 12 can be formed of, for example, a resin composition containing an inorganic filler such as silica or alumina and an epoxy resin. The conductor layer 13 is formed of a conductive metal, for example, a metal mainly composed of copper.

[0016] Next, as shown in FIG. 2C, a solder resist layer 14 is formed on the base insulating layer 12 and the conductor layer 13. Next, as shown in FIG. 2D, an opening 15 that exposes a part of the conductor layer 13 as a conductor pad 13a is formed in the solder resist layer 14. The opening 15 can be formed using a carbon dioxide laser, a UV-YAG laser, or the like. Next, as shown in FIG. 2E, a seed layer 16 is formed on the conductor pad 13a, on the surface of the solder resist layer 14 and on the side surface of the opening 15. The seed layer 16 can be formed by, for example, electroless copper plating.

[0017] Next, metal bumps 17 are formed on the conductor pads 13a of the metal bump region via a seed layer 16, and dummy patterns 18 are formed on the surface of the solder resist layer 14 that constitutes the dummy pattern region around the metal bumps 17 via a seed layer 16.

[0018] To achieve this, first, as shown in Figure 2F, a plating resist 19 is formed on the seed layer 16, having an opening 19a in the area where metal bumps 17 are to be formed in the metal bump region, and an opening 19b in the area where dummy patterns 18 are to be formed in the dummy pattern region. Next, as shown in Figure 2G, metal bumps 17 are formed in the opening 19a, and dummy patterns 18 are formed in the opening 19b. The metal bumps 17 and dummy patterns 18 can be formed by electroplating copper, nickel, and tin in sequence, for example. After that, as shown in Figure 2H, the metal bumps 17 and dummy patterns 18 can be formed by removing the plating resist 19.

[0019] (2. Regarding the dummy pattern removal process) In the metal bump formation method of the present invention, the dummy pattern removal step involves removing the dummy pattern after the formation of the metal bump and dummy pattern to form the metal bump. The specific dummy pattern removal step will be described below with reference to Figure 2I. Figure 2I, like Figures 1B to 1C, shows cross-sections along the AB line in Figure 1A.

[0020] In the specific dummy pattern removal process, as shown in Figure 2H, after forming the metal bumps 17 and dummy pattern 18, as shown in Figure 2I, when the seed layer 16 between the metal bumps 17 is removed, the dummy pattern 18 peels off and is removed from the solder resist layer 14. Other examples of dummy pattern 18 removal include mechanical removal, vacuum removal, and removal with tape.

[0021] The contact area between the dummy pattern 18 and the solder resist layer 14 is 170 μm².2 More than 290μm 2 The following is preferable. This is because this range is suitable for achieving both a reduction in the height variation of the metal bumps 17 and the elimination of the dummy patterns 18. [Explanation of Symbols]

[0022] 1 circuit board 2 Metal Bump 3 Dummy Patterns 11 circuit boards 12 Base insulating layer 13 Conductor layer 13a Conductor Pad 14 Solder Resist Layers 15 Aperture 16 Seed Layer 17 Metal Bump 18 Dummy Patterns 19 Plating Resist 19a, 19b opening

Claims

1. A dummy pattern formation process in which a dummy pattern is formed around the metal bump at the same time as the metal bump is formed, After forming the metal bumps and dummy patterns, the dummy patterns are removed, which constitutes a dummy pattern removal step for forming the metal bumps. A method for forming a metal bump, including the following.

2. In the method for forming a metal bump according to claim 1, The dummy pattern formation step is To form a base insulating layer, Forming a conductive layer on the aforementioned base insulating layer, Forming a solder resist layer on the base insulating layer and the conductor layer, The solder resist layer is formed to expose a portion of the conductor layer as a conductor pad, A seed layer is formed on the conductor layer and on the surface and side of the opening of the solder resist layer. This includes forming metal bumps on the conductor pad via the seed layer, and forming the dummy pattern on the surface of the solder resist layer around the metal bumps via the seed layer, The dummy pattern removal step is, This includes removing the dummy pattern by removing the seed layer on the surface of the solder resist layer other than the metal bumps.

3. In the method for forming a metal bump according to claim 2, The contact area between the dummy pattern and the solder resist layer is 170 μm². ２ 290 μm or more ２ The following applies:

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