JPS624398A - Manufacture of double-side through hole circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a double-sided through-hole circuit board.

[Prior art] Conventionally, double-sided through-hole circuit boards were manufactured by drilling through holes in a copper-clad laminate with copper foil pasted on the front and back sides of an insulating base material, forming a circuit by etching, and using an electroless active liquid. (catalyst) to activate the entire surface. After that, a plating-resistant resist was applied to the areas other than the through-holes and lands, that is, the areas that were not to be electrolessly plated.Then, electroless plating was applied to the through-holes and lands, and circuits were formed on the front and back surfaces of the copper-clad laminate. This is done by connecting them with an electroless plating film.

However, with this manufacturing method, the catalyst adheres to areas that are not electroless plated during the activation process, and the catalyst remains on the circuit area during the electroless plating process, which tends to cause insulation defects. was there.

As a method to solve this problem,
As shown in No. 487 and Japanese Unexamined Patent Publication No. 59-155994, there is a method in which through-holes are made in a copper-clad laminate and a catalyst is applied to the entire surface thereof. In these methods,
The land portion and the portion that will become the circuit pattern are covered with a plating resist and etched to remove unnecessary copper foil and the catalyst, followed by electroless plating.

By this method, it is possible to produce a double-sided through-hole circuit board with high insulation properties and no residual catalyst between the circuits.

[Problems to be Solved by the Invention] However, in the conventional method for manufacturing double-sided through-hole circuit boards, the resist used has a high viscosity of 300P (poise), so the inner walls of the through-holes are not covered with the resist. During etching, side etching occurs in which the copper layer on the inner wall of the through hole is dissolved and removed by the etching solution. When side etching occurs, a laminate with no catalyst attached appears on the inner wall of the through-hole, and during the electroless plating process, no plating layer is attached to this area, and the circuit formed on the front and back surfaces of the double-sided through-hole circuit board is removed. The connection sometimes became poor.

[Object of the Invention] The present invention was made to solve the problems of the conventional method for manufacturing double-sided through-hole circuit boards, and its purpose is to coat not only the entire surface of the circuit board but also the inner walls of the through-holes with resist. By doing so, it is possible to prevent side etching in which the copper foil portion of the inner wall of the through hole is dissolved and removed during the etching process, and to provide a method for manufacturing a double-sided through hole circuit board that does not cause poor connections between circuits formed on the front and back surfaces. be.

[Means for Solving Problems 1-1] The present invention provides a first method for drilling through holes in a double-sided copper-clad laminate.
a second step of applying a catalyst to the surface of the laminate and the inner wall of the through hole; a third step of coating the inner wall of the through hole and the circuit pattern forming portion with a resist; and a portion of the copper layer not covered with the resist. and a fifth step of performing electroless plating on the through-hole inner walls and circuit pattern forming portions where the catalyst remains after removing the resist on the through hole inner walls and circuit pattern forming portions. ing.

[Function] In the present invention, since the resist coating is applied to the inner wall of the through hole by the above manufacturing method, night etching does not occur on the inner wall of the through hole. Therefore, a good electroless plating film is formed on the inner wall of the through hole. Ru.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3.

First, let's talk about the liquid resist method, which is the first example.
This will be explained with reference to the figures. Note that FIG. 1 shows the manufacturing steps in order.

The liquid resist method consists of the following steps, and in the first step,
A substrate 1 is formed by drilling through holes 13 in a double-sided steel-clad laminate consisting of a laminate 11 and a copper foil 12 using a drill or a punch, as shown in FIG. 1(a).

In the second step, the substrate 1 shown in FIG. 1 (a) is immersed in a palladium chloride solution, and the catalyst 14 (-1 Then, a substrate 2 is formed.

In the third step, the substrate 2 shown in FIG. 1(b) is immersed in the etching resist 15. The etching resist 15 used at this time is made by dissolving a photosensitive resist such as urethane acrylate resin, which hardens in the portion irradiated with ultraviolet rays, in an organic solvent such as butylene chloride or lucersolv to form a liquid.
Its viscosity is as low as 15C-P (centi-poise). Therefore, the substrate 2 is connected to the eratin body 1 to 1.
5, a substrate 3 is formed in which the etching resist 15 is adhered not only to the entire surface but also to the inner wall portion 13a of the through hole 13, as shown in FIG. 1(C). Then, ultraviolet rays are irradiated to form circuit patterns and land portions 16 on the front and back surfaces of the blocking plate 3 and the inner wall portions 13 of the through holes 13.
The eratin breaths 1 to 15 covering part a are cured.

In the fourth step, the portion of the copper foil 12 that is not covered with the hardened etching resist 15 is dissolved and removed by the etching solution, and at the same time, the catalyst 14 in that portion is also removed.
A substrate 4 shown in Figure (d) is formed. At this time, Figure 1 (
As shown in the substrate 3 in C), the hardened etching resist 15 covers the inner wall 13a of the through hole 13, so side etching in which the copper layer portion of the inner wall 13a is dissolved and removed by the etching solution does not occur. do not have.

In the fifth step, after removing the hardened etching resist 15 made of the substrate 4 using an organic solvent, the land portion 1
A plating resist 17 is applied to the parts other than the inner wall 13a of the through hole 13 and the substrate 5 shown in FIG. 1(e).
form. This substrate 5 is subjected to electroless plating, and the first
As shown in figure (f), the land portion 16 and the through hole 13
Due to the action of the catalyst 14 remaining on the inner wall portion 13a, a substrate 6 coated with a copper plating layer 18 is formed. This copper plating layer 18 connects circuits formed on the front and back surfaces of the substrate 6.

As described above, in the liquid resist method, since the etching resist 15 covers the inner wall 13a of the through hole 13, no nid etching occurs on the inner wall 13a during etching. Therefore, a good copper plating layer 18 is formed in the through hole 13, and the circuits formed on the front and back surfaces of the substrate 6 are reliably connected.

Next, a printing method as a second embodiment will be explained.

In the printing method, the first and second steps are as shown in FIG. ) A substrate 2 having a catalyst 14 attached thereto is formed.

In the next third step, (2) a zing resist 15 is printed on the front and back surfaces of the substrate 2 on the portions that will become the circuit pattern using a screen printing method. The etching resist 15 used here is similar to that used in the liquid resist method, and is made by dissolving a photosensitive resist such as urethane acrylate resin in an organic solvent such as Butil Cellsolve, and its viscosity is 250 P (poise). be. By the way, the etching resist 15 is also printed on the through hole 13 and has a viscosity of 250P, so the etching resist 15 printed on the through hole 13 flows into the inner wall portion 13a, and as shown in FIG. The copper layer portion of the inner wall portion 13a is coated. And etching resist 15
The printed portion is irradiated with ultraviolet rays to harden the etching resist 15 covering the circuit pattern, the portion that will become the land portion 16, and the inner wall portion 13a of the through hole 13.

After that, in the fourth and fifth steps similarly to the liquid resist method, the portions of the copper foil 12 that are not covered with the etching resist 15 that has been hardened by the etching solution and the catalyst attached to those portions are simultaneously etched. Dissolved and removed. At this time, since the copper layer portion of the inner wall portion 13a of the through hole 13 is covered with the hardened etching resist 15, no one-side etching occurs. Then, the hardened etching resist 15 is removed, and the portions other than the land portion 16 and the inner wall portion 13a of the through hole 13 are covered with the plating resist 17. In this state, electroless plating is performed to form a copper plating layer 18 on the land portion 16 and the inner wall portion 13a of the through hole 13.

Like the liquid resist method, the printing method described above can cover at least the copper layer portion of the inner wall 13a of the through hole 13, so the through hole 13 can be coated during etching.
No wall edging occurs on the inner wall portion 13a. Therefore, a good copper plating layer 18 is formed in the through hole 13, and the circuits formed on the front and back surfaces of the substrate are reliably connected.

Next, a third embodiment of the fill-in-the-blank method will be described.

The first step, second step, fourth step, and fifth step are the same as the liquid resist method and printing method of the first and second embodiments, so a description thereof will be omitted.

In the third step, in the hole filling method, an etching resist 15 is applied onto the through hole 13 so as to cover the opening. Then, the etching resist 15 is embedded in the through holes 13 by reciprocating the roller on the substrate. After the through holes 13 are filled with the etching resist 15,
A circuit pattern using etching resist 15 is printed on the substrate, and the etching resist 15 is cured by irradiating ultraviolet rays. These operations are performed on the front and back surfaces of the substrate to form the 'rj substrate 8 shown in FIG. The etching resist 15 used at this time is the same etching resist 15 used in the liquid resist method and the printing method, and has a viscosity of 200 P (poise).

Even if the etching process is performed in the next fourth step, as shown in FIG. 3, the through hole 13 is filled with the etching resist 15 up to the opening and its surface is hardened, so that the inner wall 13a of the through hole 13 is hardened. No etching occurs at all,
In the fifth step, electroless plating is performed, and a good copper plating layer 18 is formed in the through hole 13.

The above describes the liquid resist method, printing method, and hole-filling method.
Even if the M-shift manufacturing method is used, at least the copper layer portion of the inner wall portion 13a of the through hole 13 will not be exposed to the etching resist 1.
5, side etching does not occur during etching. Therefore, the inner wall 13 of the through hole 13
A good copper plating layer 18 is formed on a.

[Effects of the Invention] As described above, the double-sided through-hole circuit board according to the present invention! ! If the manufacturing method is selected, through holes are made in the double-sided copper-clad laminate, a catalyst is applied and activated, and the circuit pattern forming area and the inner wall of the through hole are covered with resist. After that, etching processing and electroless plating are performed, so that side etching, in which the copper foil portion on the inner wall of the through hole is dissolved and removed, does not occur during the etching processing. Therefore,
It is possible to provide a double-sided through-hole circuit board in which a good mating layer is formed on the inner wall of the through-hole, and connection failures between circuits formed on the front and back surfaces do not occur.

[Brief explanation of the drawing]

FIG. 1 shows a liquid resist method according to a first embodiment of the present invention, and is a diagram showing enlarged cross-sectional views of main parts in the order of IJA manufacturing steps. FIG. 2 is an enlarged cross-sectional view of a main part showing a printing method according to a second embodiment of the present invention, and FIG. 3 is an enlarged cross-sectional view of a main part showing a third embodiment of the present invention. In the figure, 13 is a through hole, 13a is an inner wall thereof, 14 is a catalyst, and 15 is an etching resist (to resist 1).

Claims (1)

[Claims] 1. A first step of drilling through holes (13) in a double-sided copper-clad laminate, and a second step of applying a catalyst (14) to the surface of the laminate and the inner wall of the through holes (13a). , a third step of covering the through-hole inner wall portion (13a) and the circuit pattern forming portion with a resist (15); a fourth step of etching away the copper layer portion not covered with the resist; 13a) and a fifth step of performing electroless plating on the through-hole inner wall portion (13a) where the catalyst remains and the circuit pattern forming portion after removing the resist (15) on the circuit pattern forming portion. A method for manufacturing a double-sided through-hole circuit board.