JPH0760927B2 - Method for manufacturing printed wiring board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a through-hole printed wiring board having through holes.

[Conventional technology]

The conventional printed wiring board manufacturing methods are roughly classified into two types: a photo printing method of forming an etching resist layer through an exposure / developing plate process and a screen printing method of forming an etching resist layer by using a screen board. To be done. recent years,
As the application of fine patterns such as three pins between pins has progressed with the development of higher density printed wiring boards, the proportion of photo printing methods has been increasing year by year. In the case of the photo printing method, a photosensitive resin film, a so-called dry film, has been frequently used, but in the dry film resist, (3) 4 to 4 pins are the limit in terms of fine line formation. However, there is a defect that the yielding cannot be improved because of poor coverage for scratches and dents on the copper plating, and as a new construction method for compensating for this defect, a method for producing a printed wiring board using an electrodeposition resin is beginning to be adopted.

Conventionally, there have been the following methods for manufacturing a printed wiring board using an electrodeposition resin.

(A) Conductive layer 2 with copper plating on the inner wall and front and back surfaces of the hole
The substrate 1 on which the film has been formed is dipped in a photolytic (hereinafter referred to as positive) or photopolymerizable (hereinafter referred to as negative) electrodeposition photosensitive resin solution and subjected to direct current electrolysis to form conductive layers on inner walls and front and back surfaces of the holes. A photosensitive resin layer is formed on the entire surface of 2 and exposed and developed to form an etching resist layer 7 as shown in FIG. 2 (a). Next, there is a method of manufacturing a printed wiring board in which a desired circuit pattern is formed by etching and then peeling off the etching resist layer 7.

(B) Also, as in (a), a photosensitive resin film is applied to a substrate having a conductive layer formed by copper plating on the inner wall of the hole and the front and back surfaces, exposed and developed to form a plating resist layer 8, and then the substrate 2 is immersed in an electrodeposition resin solution, and a resin layer 5a is formed on the inner wall of the hole and the conductive layer 2 not covered with the plating resist on the front and back surfaces by direct current electrolysis as shown in FIG. ． There is a method of manufacturing a printed wiring board in which a circuit pattern is formed by etching and peeling a resin layer.

[Problems to be Solved by the Invention]

The conventional printed wiring board manufacturing method described above has the following drawbacks.

In the manufacturing method of (a), when a negative photosensitive resin is used, the photosensitive resin adhered to the inner wall surface of the hole is not sufficiently exposed to light during exposure, and the photosensitive resin on the inner wall surface of the hole is not exposed. Since it cannot be photopolymerized, it has a drawback that it cannot be applied to a through-hole printed wiring board. In order to compensate for this drawback, it has been made to use an exposure machine that emits scattered light or to increase the sensitivity of the photosensitive resin, but even in this case there is a limit to the through hole diameter of the printed wiring board that can be manufactured, 0.4φ
There is a problem that it cannot be applied to such small diameters. However, as surface mounting technology has been widely used in recent years, 0.3
The application ratio of small-diameter through-holes of ~ 0.4φ is also increasing year by year, and the ability to form such small-diameter through-holes is indispensable for manufacturing printed wiring boards.

On the other hand, in the method using the positive type photosensitive resin, the above-mentioned negative type defects can be solved and a small diameter through hole can be formed, but the film thickness of the photosensitive resin that can be electrodeposited is as thin as about 5 to 8 μm. It is easy to produce, and the photosensitivity is extremely poor. Even at 5 to 8 μm, a considerably high exposure amount of 500 to 1,000 mj / cm ³ is required, and there are problems in terms of yield and productivity.

In the manufacturing method (b), since the plating resist is formed by using the photosensitive resin film, the conductive layer and the plating resist are poorly adhered to each other and a bridge is apt to occur. Further, when the plating resist is peeled off, the resin layer formed by electrodeposition and the plating resist are likely to come into close contact with each other, so that a special device is required for the peeling, and complete peeling is difficult.

The object of the present invention is to eliminate the conventional drawbacks, form a small-diameter through-hole and support surface mounting, and there is no occurrence of pinholes, high yield can be obtained, and productivity is also high. An object of the present invention is to provide a method for manufacturing a printed wiring board with high reliability and low cost.

[Means for Solving the Problems]

The method for producing a printed wiring board of the present invention comprises a step of depositing a resin mask on the front and back surfaces of a substrate having conductive layers formed on the inner wall surface and front and back surfaces of the hole, and immersing the substrate in an electrodeposition resin solution. ,
A step of forming a resin layer on the conductive layer on the inner wall surface of the hole by direct current electrolysis, a step of removing the resin mask and immersing it in an electrodeposition photosensitive resin solution to form a photosensitive resin layer by direct current electrolysis, and a photosensitive resin layer A step of selectively etching and removing the exposed portion of the conductive layer using the etching resist layer as a mask after exposing and developing through a mask to form an etching resist layer, and a step of removing the resin layer and the photosensitive resin layer It is characterized by including and.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

1 (a) to 1 (h) are cross-sectional views of a printed wiring board shown in the order of steps for explaining an embodiment of the present invention.

First, as shown in FIG. 1A, holes are formed and copper plating is performed to form the conductive layer 2 by copper plating on the inner wall surface of the holes 3 and the front and back surfaces of the substrate 1. Next, as shown in FIG. 1B, the resin mask 4 is applied and dried on the front and back surfaces of the substrate 1. Next, as shown in FIG. 1C, the substrate 1 is immersed in an electrodeposition resin solution, and direct current electrolysis is applied to electrodeposit a resin layer 5 on the conductive layer 4 on the inner wall of the hole 3. Next, after removing the resin masks 4 on the front and back surfaces of the substrate 1 as shown in FIG. 1 (d), the substrate is immersed in a negative electrodeposition photosensitive resin solution as shown in FIG. 1 (e), and DC electrolysis is applied. The photosensitive resin layer 6 is formed on the front and back surfaces of the substrate 1. Then, the resin layer 5 is exposed through a mask and developed to form a resin layer 5 as shown in FIG.
After forming an etching resist consisting of the photosensitive resin layer 6 and the etching resist as shown in FIG. 1 (g), the resin layer 5 and the photosensitive resin layer 6 are peeled and removed as shown in FIG. A printed wiring board having a circuit pattern was obtained.

The photosensitive resin layer 6 shown in FIG. 1 (e) of the above embodiment
Was formed by immersing in a negative type electrodeposition photosensitive resin solution and applying DC electrolysis, but the present invention can be similarly carried out by using a positive type electrodeposition photosensitive resin instead of the negative type. You can

〔The invention's effect〕

As is apparent from the above description, the present invention has the following effects.

(1) A small-diameter through hole can be formed, and a printed wiring board compatible with surface mounting can be manufactured.

(2) A printed wiring board having no pinholes, high yield, high productivity, high reliability, and low cost can be manufactured.

[Brief description of drawings]

1 (a) to 1 (h) are cross-sectional views of a printed wiring board shown in order of steps for explaining an embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are conventional printing methods. It is sectional drawing of the printed wiring board formed by the conventional method for demonstrating the manufacturing method of a wiring board. 1 ... Substrate, 2 ... Conductive layer, 3 ... Hole, 4 ... Resin mask, 5, 5a
... Resin layer, 6 ... Photosensitive resin, 7 ... Etching resist layer, 8 ... Plating resist layer.

Claims (1)

[Claims] 1. A step of depositing a resin mask on the front and back surfaces of a substrate on which conductive layers are formed on the inner wall surface and front and back surfaces of a hole, and immersing the substrate in a first electrodeposition resin solution for direct current electrolysis. A step of forming a resin layer on the conductive layer on the inner wall surface of the hole by removing the resin mask, and then dipping the substrate in an electrodeposition photosensitive resin solution to form a photosensitive resin layer by direct current electrolysis. A step of exposing and developing the resin layer and the photosensitive resin layer through a mask to form an etching resist layer, and then selectively etching away an exposed portion of the conductive layer using the etching resist layer as a mask, A step of removing the resin layer and the photosensitive resin layer, the method for producing a printed wiring board.