Method for manufacturing printed wiring board

Abstract

To hold a degree of freedom of design of a printed wiring board at a high level.SOLUTION: A method for manufacturing a printed wiring board includes: preparing a copper-clad laminate; dividing a high density area into a first area and a second area other than the first area; forming a first through hole in a first area of a low density area and the high density area of the copper-clad laminate; forming a first through hole conductor on the inner wall of the first through hole and a copper foil; filling the first through hole with a first resin; polishing the first through hole conductor on the first resin and the copper foil, and forming a first intermediate body; forming a second through hole in a second area of a high density area of the first intermediate body; forming a second through hole conductor on the inner wall of the second through hole and the surface of the first intermediate body; filling the second through hole with a second resin; and polishing the second through hole conductor on the second resin and the first intermediate body, and forming a second intermediate body.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a printed wiring board having a high-density area with a high through-hole arrangement density and a low-density area with a low through-hole arrangement density.

Background Art

[0002] The printed wiring board disclosed in Patent Document 1 discloses a technique for making the thickness of the through-hole conductor on the surface of a copper-clad laminate uniform even when the arrangement density of through-holes (TH) formed in the copper-clad laminate varies depending on the location. In Patent Document 1, when forming through-holes in a copper-clad laminate, the arrangement density of the through-holes varies depending on the location. Subsequently, a through-hole conductor is formed by plating on the inner wall of the through-hole and on the copper foil. However, due to the difference in the arrangement density of the through-holes, a difference in plating thickness occurs on both the inner wall of the through-hole and the copper foil of the through-hole conductor. The plating thickness difference is such that the plating thickness in the high-density area < the plating thickness in the low-density area. To eliminate this plating thickness difference, in Patent Document 1, additional plating is performed only in the high-density area, and then the through-hole conductor on the copper foil is polished to make the plating thickness of the through-hole conductor on the surface of the printed wiring board uniform.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method for manufacturing a printed wiring board disclosed in Patent Document 1, the plating thickness of the through-hole conductors on the surface of the printed wiring board can be made uniform. However, the plating thickness of the through-hole conductors differed between the high-density area and the low-density area, and the resistance of the through-hole conductors also differed between the high-density area and the low-density area. Therefore, in the technique disclosed in Patent Document 1, the transmission speed through the through-hole conductors in the high-density area and the transmission speed through the through-hole conductors in the low-density area were different, resulting in a problem of reduced design freedom.

Means for Solving the Problems

[0005] The method for manufacturing a printed wiring board according to the present invention is a method for manufacturing a printed wiring board having a high-density area with a high through-hole arrangement density and a low-density area with a low through-hole arrangement density, including: preparing a copper-clad laminate provided with a copper foil on the surface of a core substrate; dividing the high-density area into a first area in which substantially the same number of through-holes are to be arranged and are spaced apart from each other and a second area other than the first area; forming first through-holes in the low-density area of the copper-clad laminate and the first area of the high-density area; forming first through-hole conductors on the inner walls of the first through-holes and on the copper foil; filling the first through-holes with a first resin; polishing the first resin and the first through-hole conductors on the copper foil to form a first intermediate; forming second through-holes in the second area of the high-density area of the first intermediate; forming second through-hole conductors on the inner walls of the second through-holes and on the surface of the first intermediate; filling the second through-holes with a second resin; polishing the second resin and the second through-hole conductors on the first intermediate to form a second intermediate; performing panel plating on the surface of the second intermediate; and forming a conductor circuit on the second intermediate.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 2D

Figure 2E

Figure 2F

Figure 2G

Figure 2H

Figure 2I

Figure 3

Embodiments for Carrying Out the Invention

[0007] Hereinafter, an embodiment of a printed wiring board targeted by the method for manufacturing a printed wiring board according to the present invention, each step in an embodiment of the method for manufacturing a printed wiring board according to the present invention, and a subtractive method for forming a circuit in the method for manufacturing a printed wiring board according to the present invention will be described. In the examples shown in the following figures, the dimensions of each member, particularly the dimensions in the height direction, are described with dimensions different from the actual dimensions in order to better understand the features of the present invention.

[0008] <Regarding an embodiment of the printed wiring board targeted by the present invention> FIGS. 1(a) and 1(b) are diagrams for explaining an embodiment of a printed wiring board targeted by the method for manufacturing a printed wiring board according to the present invention. In the examples shown in FIGS. 1(a) and 1(b), only the arrangement positions of the through holes are described on the surface of the printed wiring board to make it easier to understand the arrangement of the through holes. In the embodiment shown in FIGS. 1(a) and 1(b), the printed wiring board 1 has, on its surface, a high-density area AH with a high arrangement density of through holes and a low-density area AL with a low arrangement density of through holes. Then, the high-density area AH is divided into a first area AH-1 and a second area AH-2 that are spaced apart from each other and in which approximately the same number of through holes should be arranged. In the high-density area AH, the first area AH-1 and the second area AH-2 may be arranged in any manner as long as they are spaced apart from each other. However, as shown in FIGS. 1(a) and 1(b), it is preferable that the first area AH-1 and the second area AH-2 are arranged alternately.

[0009] In the present invention, the formation of through-holes is carried out in two steps. The first through-hole formation is performed in the first areas of the low-density area AL and the high-density area AH, and then the second through-hole formation is carried out in the second area of the remaining high-density area AH. Specifically, first, as the first through-hole formation, as shown in Fig. 1(a), a first through-hole 2-1 is formed in the low-density area AL and the first area AH-1 of the high-density area AH. Next, as the second through-hole formation, as shown in Fig. 1(b), a second through-hole 2-2 is formed in the second area AH-2 of the high-density area AH. In the examples shown in Figs. 1(a) and 1(b), a high-density area AH exists in the central portion of the printed wiring board 1, and a low-density area AL exists in the outer peripheral portion around it. However, this embodiment is an example, and the positions where the high-density area AH and the low-density area AL exist are not limited to this example. Similarly, the first area AH-1 and the second area AH-2 are not limited to this example.

[0010] <Regarding each step of the method for manufacturing a printed wiring board according to the present invention> Figs. 2A to 2I are diagrams for explaining one step in an embodiment of the method for manufacturing a printed wiring board according to the present invention. Hereinafter, an embodiment of the method for manufacturing a printed wiring board according to the present invention will be described with reference to Figs. 2A to 2I.

[0011] First, as shown in Fig. 2A, a copper-clad laminate 13 provided with copper foils 12 on the surfaces 11a and 11b of a core substrate 11 is prepared. Here, as the copper-clad laminate 13, a commercially available copper-clad laminate (CCL) can be used.

[0012] Next, as shown in Fig. 2B, a first through-hole 14-1 is formed in the low-density area AL of the copper-clad laminate 13 and the first area AH-1 of the high-density area AH. The formation of the first through-hole 14-1 can be carried out by subjecting the copper-clad laminate 13 to a conventionally known method, for example, drilling or laser (CO2, UV-YAG, excimer, etc.) processing.

[0013] Next, as shown in FIG. 2C, a first through-hole conductor 15-1 is formed on the inner wall of the first through-hole 14-1 and on the copper foil 12. The first through-hole conductor 15-1 can be formed by electroless copper plating followed by electrolytic copper plating.

[0014] Next, as shown in FIG. 2D, the first through-hole 14-1 is filled with a first resin 16-1. As is conventionally known, for example, a thermosetting epoxy resin composition can be used as the first resin 16-1. Also, as is conventionally known, filling of the first resin 16-1 can be performed using a printing method, a vacuum printing method, or the like. Thereafter, the first through-hole conductor 15-1 on the first resin 16-1 and on the copper foil 12 is polished to form a first intermediate 17-1 shown in FIG. 2D. As the polishing method, as is conventionally known, methods such as buff polishing, belt polishing, and planar polishing can be used, and the polishing method is selected according to the product specifications.

[0015] Next, as shown in FIG. 2E, a second through-hole 14-2 is formed in a second area AH-2 of the high-density area AH of the first intermediate 17-1. The formation of the second through-hole 14-2 can be performed by subjecting the first intermediate 17-1 to a conventionally known method, for example, drilling or laser (CO2, UV-YAG, excimer, etc.) processing, in the same manner as the formation of the first through-hole 14-1.

[0016] Next, as shown in FIG. 2F, a second through-hole conductor 15-2 is formed on the inner wall of the second through-hole 14-2, on the first through-hole conductor 15-1, and on the first resin 16-1. The second through-hole conductor 15-2 can be formed by electroless copper plating followed by electrolytic copper plating, similar to the first through-hole conductor 15-1.

[0017] Next, as shown in FIG. 2G, the second through hole 14-2 is filled with the second resin 16-2. Similar to the first resin 16-1, as is conventionally known, for example, a thermosetting epoxy resin composition can be used as the second resin 16-2. Also, for filling the second resin 16-2, similar to the first resin 16-1, as is conventionally known, printing methods, vacuum printing methods, etc. can be used. Thereafter, the second through hole conductor 15-2 on the second resin 16-2 and on the first intermediate 17-1 is polished to form the second intermediate 17-2 shown in FIG. 2G. As the polishing method, as is conventionally known, methods such as buff polishing, belt polishing, and planar polishing can be used, and the polishing method is properly selected according to the product specifications.

[0018] Next, as shown in FIG. 2H, panel plating 18 is applied to the surface of the second intermediate 17-2. Thereafter, by forming the conductor circuit 19 on the second intermediate 17-2, the printed wiring board 1 of the present invention can be obtained as shown in FIG. 2I.

[0019] <Regarding the method of forming a conductor circuit in the method of manufacturing a printed wiring board according to the present invention> FIGS. 3(a) to (c) are diagrams showing the steps of one embodiment of forming the conductor circuit 19 according to the subtractive process. First, as shown in FIG. 3(a), a resist 20 is formed at the position where the conductor circuit 19 is to be formed on the second intermediate 17-2 (corresponding to FIG. 2H) in a state where the panel plating 18 is formed. Thereafter, the second intermediate 17-2 on which the resist 20 is formed is etched to remove the panel plating 18 other than the resist 20, the second through hole conductor 15-2, the first through hole conductor 15-1, and the copper foil 12 as shown in FIG. 3(b) to expose the core substrate 11. Finally, as shown in FIG. 3(c), the resist 20 is removed to form the conductor circuit 19. For the formation of the resist 20, etching, and removal of the resist 20, any known method can be employed.

[0020] According to the method for manufacturing a printed wiring board according to the present invention described above, since the plating thickness of the through-hole conductor can be made uniform between the high-density area and the low-density area, the transmission speed through the through-hole conductor in the high-density area and the transmission speed through the through-hole conductor in the low-density area can be made substantially the same, and the degree of freedom in the design of the printed wiring board can be kept high.

[0021] In the above embodiment, first, the first through-hole 14-1 is formed in the low-density area AL and the first area AH-1 of the high-density area AH, and then the second through-hole 14-2 is formed in the second area AH-2 of the high-density area AH. However, even if the order of forming the through-holes is reversed, the present invention can be achieved.

Explanation of Reference Numerals

[0022] 1 Printed wiring board 2 Through-hole 11 Core substrate 11a, 11b Surfaces 12 Copper foil 13 Copper-clad laminate 14-1 First through-hole 14-2 Second through-hole 15-1 First through-hole conductor 15-2 Second through-hole conductor 16-1 First resin 16-2 Second resin 17-1 First intermediate 17-2 Second intermediate 18 Panel plating 19 Conductor circuit 20 Resist AH High-density area AH-1 First area AH-2 Second area AL Low-density area

Claims

1. A method for manufacturing a printed wiring board having a high-density area with a high through-hole arrangement density and a low-density area with a low through-hole arrangement density, comprising: preparing a copper-clad laminate having a copper foil provided on the surface of a core substrate; dividing the high-density area into a first area and a second area other than the first area, the first area having substantially the same number of through-holes to be arranged and being spaced apart from each other; forming first through-holes in the low-density area of the copper-clad laminate and the first area of the high-density area; forming a first through-hole conductor on the inner wall of the first through-hole and on the copper foil; filling the first through-hole with a first resin; polishing the first resin and the first through-hole conductor on the copper foil to form a first intermediate; forming second through-holes in the second area of the high-density area of the first intermediate; forming a second through-hole conductor on the inner wall of the second through-hole and on the surface of the first intermediate; filling the second through-hole with a second resin; polishing the second resin and the second through-hole conductor on the first intermediate to form a second intermediate; performing panel plating on the surface of the second intermediate; forming a conductor circuit on the second intermediate; A method for manufacturing a printed wiring board including the above steps.

2. The method for manufacturing a printed wiring board according to claim 1, wherein in the high-density area, the first area and the second area are arranged alternately.

3. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein forming a conductor circuit on the second intermediate is performed by a subtractive process.

Images