JPS63187694A - Method of forming through-hole 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 [Field of Industrial Application] The present invention relates to a method for forming a printed wiring board having through holes, a so-called through hole board.

[Invention (already required)]

The present invention is a method for forming a through-hole board, in which after forming through-holes and performing through-hole plating, an alkali-soluble resist layer is formed on the surface of the board with a pattern opposite to the circuit pattern, and then a resist layer corresponding to the circuit pattern is formed on the surface of the board. A 1A solvent-soluble electrodeposition paint layer is formed along the pattern, the resist layer is removed with an alkaline aqueous solution, and the metal layer on the substrate surface is etched using the electrodeposition paint layer as a mask to form a circuit pattern. Thereafter, by removing the electrodeposition paint layer using an organic solvent, a through-hole substrate having a fine circuit pattern can be obtained with a high yield.

[Conventional technology]

FIG. 3 shows an example of a conventional method for forming a through-hole substrate.

For example, copper 7F3 (2) is placed on both sides of the insulating substrate (1).
A so-called double-sided copper-clad substrate (3) having a copper-clad substrate (3) adhered thereto is prepared, and through holes (4) are formed at required positions on this substrate (3) (FIG. 3A).

Next, after performing through-hole plating, that is, copper plating (5) (Fig. 3B), an alkali-soluble resist layer (6) is formed on both sides of the board (3) with a pattern opposite to the circuit pattern.
(Figure 3C). Next, an alkali-soluble electrodeposition paint (7) is formed on the surface of the substrate (3) including the through holes (4) in a pattern corresponding to the circuit pattern (third
Figure D). Next, the resist layer (6) is removed with an alkaline aqueous solution, and the copper plating (5) and copper foil (2) are etched with a ferric chloride solution using the electrodeposition paint (7) as a mask to form a circuit pattern (8). ) (Fig. 3E).

Next, remove the electrodeposited coating $4 (7+) on the circuit pattern (3) with an alkaline aqueous solution containing additives.
A through-hole substrate (9) on which a predetermined circuit pattern (8) is formed is obtained (FIG. 3F).

[Problem that the invention seeks to solve]

In the conventional through-hole substrate forming method described above, since an alkali-soluble electrodeposition paint (7) is used, the resist layer (6) is removed with an alkaline aqueous solution after the third step. Electrodeposition paint with a very thin pattern (
7) was difficult to leave normally, and therefore only a rough circuit pattern could be formed.

In view of the above-mentioned points, the present invention provides a method for forming a through-hole substrate that can form a through-hole substrate having a fine circuit pattern.

[Means for solving problems]

The present invention provides: a metal layer (2) on both sides, for example, a double-sided copper-clad board;
a step of forming through holes (4) on a substrate (3) having
) Forming on the surface an alkali-soluble resist layer (6) having a pattern opposite to the circuit pattern to be formed; d) Applying an organic solvent on the pattern corresponding to the circuit pattern not covered by the resist layer (6) on the substrate surface. Step of forming a soluble electrodeposited paint layer (7), e Step of removing the resist layer 1'6) with an alkaline aqueous solution, f Etching the metal layer (2) using the electrodeposited paint layer (7) as a mask. The method is characterized by comprising a step of forming a circuit pattern (8), and a step of removing the electrodeposition paint layer (7) with a solvent.

[For production]

In the step (d), organic solvent soluble electrodeposition paint N
By forming (7), when the resist layer (6) is removed with an alkaline aqueous solution in the next step (e), the electrical paint layer (7) corresponding to the circuit pattern can be removed normally without being damaged. Only the resist layer (6) is removed while remaining.

In other words, the dissolution resistance of the resist layer (6) and the electrodeposition paint layer (7) is greatly different, and even when the electrodeposition paint layer (7) is formed in a fine pattern, it is necessary to ensure that this is maintained when removing the resist layer (6). can be left in.

Therefore, it is possible to correspond to the formation of a high-density through-hole substrate having a fine circuit pattern.

〔Example〕

Hereinafter, embodiments of a method for forming a through-hole substrate according to the present invention will be described with reference to the drawings.

Embodiment 1 First, a so-called double-sided copper-clad board Q31 in which copper foil 021 is coated on both sides of an insulating substrate αυ is prepared, and through holes 04 are formed in required portions of the board (see FIG. 1).

Next, electroless plating is performed, followed by post-panel plating (plating thickness 10 to 30 μm) to form copper plating 09 on the surface of the substrate α including the inside of through hole C141 (first
Figure B). Next, the surface of the substrate 01 is coated with an alkali-soluble photosensitive dry film (for example, PIIT-865AF).
1-50 (manufactured by Hitachi Chemical Co., Ltd.) is laminated, exposed to a reverse pattern (negative pattern) of the circuit pattern to be molded, and developed to form a resist layer α5) with a reverse pattern (first
Figure C).

Next, using this resist layer Q61 as a mask, an organic solvent-soluble electrodeposition paint layer 0η is formed on the surface of the substrate Q31 including the inside of the through hole a. That is, this electrodeposition paint layer 07) is formed on a pattern corresponding to a circuit pattern other than the resist layer 0e (FIG. 1D). here,
As the organic solvent-soluble electrodeposition coating, resins such as alkyd, epoxy, acrylic, maleated oil, melamine, polybutadiene, polyester, phenol, and melamine alkyd can be used.

Next, the resist layer αυ is removed with a 3% sodium hydroxide aqueous solution (Fig. 1E), and then the copper plating layer 09 and the copper foil Q21 are removed using a cupric chloride solution using the electrodeposition paint layer 0'71 as a mask. is selectively etched to form a circuit pattern 0 (first
Figure F). After that, organic solvent (e.g. methylene chloride etc.)
The electrodeposited paint layer OD is removed to obtain the desired landless through-hole substrate (a substrate having through-holes without land portions for soldering) 0ω (FIG. 1G).

In this example, a circuit pattern with a pattern width of 80 μm could be manufactured with good yield.

As a comparative example, when an alkali-soluble electrodeposition paint was used in the first drawing process, circuit patterns up to a pattern width of 300 μm could be produced with good yield.

Example 2 A double-sided copper-clad board (22) for a multilayer board on which an inner layer circuit pattern (21) has been formed in advance is prepared, and through holes 00 are formed in required portions of the board (22) (FIG. 2A).

Next, electroless copper plating (23) with a thickness of 0.5 to 3 μm is applied (Fig. 2B), and then an alkali-soluble photosensitive dry film (for example, PL+R-865) is applied to the surface of the substrate 2).
AFT-50 manufactured by Hitachi Chemical Co., Ltd.) is laminated, exposed to a reverse pattern (negative pattern) of the circuit pattern to be formed, and developed to form a resist layer Qυ of the reverse pattern (
Figure 2C). Next, after acid treatment, copper sulfate plating (24) with a thickness of about 10 to 40 μm is performed (Fig. 2D), and after that,
Using resist N0119 as a mask, an organic solvent-soluble electrodeposition paint layer αη is formed on the surface of the substrate (22) including the through-hole coating layer (FIG. 2E). Next, the resist layer 061 is removed with a 5% sodium hydroxide aqueous solution (FIG. 2F), and then a copper plating layer (23) is formed using a ferric chloride solution using the electrodeposition paint layer αη as a mask.

(24) and copper foil are selected and etched to form a circuit pattern 081 (FIG. 2G). Thereafter, the electrodeposition paint layer α7) is removed using an organic solvent to obtain the desired landless through-hole board (2) with multilayer wiring (Fig. 2H).
.

In this example, a circuit pattern with a pattern width of 60 μm could be manufactured with good yield.

As a comparative example, when an alkali-soluble electrodeposition paint is used in the process shown in Fig. 2E, the circuit pattern is 20%.
It was possible to manufacture patterns with a good yield only up to a pattern width of 0 μm.

In each of Examples 1 and 2, the resist layer αQ having a reverse pattern was formed by a photographic method, but it can also be formed by a printing method.

Moreover, although the above method is applied to the formation of a landless through-hole substrate, it can also be applied to the formation of a through-hole substrate having a land portion continuous to the through-hole coating layer.

〔Effect of the invention〕

According to the present invention, after forming an alkali-soluble type resist +-IEI with an inverse pattern of a circuit pattern on the surface of a substrate having a double-sided conductive layer with through holes formed therein, an organic solvent-soluble type resist which becomes an etching resist is formed. By forming the electrodeposited paint layer, when the resist a is subsequently dissolved and removed with an alkaline aqueous solution, the electrodeposition paint layer remains intact without being damaged.

Therefore, this electrodeposition paint layer is suitable as an etching resist for fine patterns. Therefore, a high-density through-hole substrate having a fine circuit pattern can be provided easily and inexpensively.

[Brief explanation of the drawing]

FIGS. 1A-G are process diagrams showing one embodiment of the method for forming a through-hole substrate of the present invention, and FIGS. 2A-H are process diagrams showing another embodiment of the method for forming a through-hole substrate of the present invention. , FIGS. 3A to 3F are process diagrams showing an example of a conventional method for forming a through-hole substrate. 0υ is an insulated board, αZ is a copper foil, α-cover is a double-sided copper-clad board,
The α ship is a through hole, Q61 is an alkali-soluble resist layer, Q7+ is an organic solvent-soluble electrodeposition paint layer, and 0 is a circuit pattern.

Claims (1)

[Claims] a. A step of forming through holes on a substrate having metal layers on both sides; b. A step of plating the through holes; c. A step of forming an alkali-soluble resist layer having a pattern opposite to the circuit pattern to be formed on the surface of the substrate. d) forming an organic solvent-soluble electrodeposition paint layer on a pattern corresponding to the circuit pattern on the surface of the substrate; e) removing the resist layer with an alkaline aqueous solution; f) the electrodeposition paint layer. a step of etching the metal layer using a mask to form a circuit pattern; g. a step of removing the electrodeposition paint layer with an organic solvent.