JPS5826192B2 - Printed wiring board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a printed wiring board, and more particularly to an improvement in the method for manufacturing a printed wiring board using a fully additive method.

Generally, the fully additive method for manufacturing printed wiring boards involves coating the surface of an insulating substrate with a chemical plating adhesive layer containing acrylonitrile rubber, epoxy resin, and phenolic resin as main components, and then applying a circuit pattern to the adhesive layer. The method used is to mask the area other than the area to be formed with a mesh resist, then perform a hydrophilic treatment and an activation treatment, and further perform a chemical plating treatment to deposit a chemical plating film on the adhesive layer exposed from the mesh resist to form a circuit pattern. It is.

However, in this method, a chemical plating film is selectively deposited using the metskily resist as a mask, so that the metskily resist may have an adverse effect on the chemical plating bath during the chemical plating process, or the chemical plating may be abnormally deposited on the surface of the metskily resist, causing damage to the predetermined circuit. This method has drawbacks such as interfering with pattern formation.

In particular, when the plating resist is removed after chemical plating, it does not interfere with circuit pattern formation so much, but when the plating resist is used as a permanent mask, short circuits occur between circuit patterns.

In order to overcome this drawback, the inventors of the present invention have conducted extensive research to overcome the above-mentioned drawbacks, and as a result, they coated the surface of an insulating substrate with an adhesive layer for chemical plating, provided recesses in the area of the circuit pattern to be formed on this substrate, and created a hydrophilic substrate. After performing the chemical plating treatment and the chemical plating treatment, the surface of the insulating substrate is mechanically polished to remove the chemical plating film deposited on the convex portions of the substrate. We have discovered a method that allows circuit patterns to be formed using the chemical plating film that remains in the recesses without using it, thereby preventing contamination of the chemical plating bath, and producing a highly reliable printed wiring board without short circuits between the circuit patterns.

That is, the present invention includes a step of forming an adhesive layer for chemical plating mainly composed of a thermosetting resin in which rubber particles are uniformly dispersed on the surface of an insulating substrate, and a process of forming a desired depth in a circuit pattern area of the insulating substrate to be formed. a step of providing a concave portion of the insulating substrate, a step of performing a chemical plating treatment after hydrophilizing and activating the adhesive layer of the insulating substrate, and a step of mechanically polishing the surface of the insulating substrate to form a convex portion of the substrate. This method is characterized by sequentially performing the step of removing the deposited chemical plating film.

Examples of insulating substrates used in the present invention include paper-phenolic resin laminates, paper-epoxy resin laminates, glass fiber-containing phenolic resin laminates, glass fiber-containing epoxy resin laminates, phenolic resin laminates, epoxy resin laminates,
Examples include polyester resin laminates.

The adhesive layer for chemical plating in the present invention serves as a base for firmly adhering a chemical plating film to an insulating substrate.

Examples of the rubber particles that are a component of such an adhesive include one or a mixture of two or more selected from natural rubber and synthetic rubbers such as acrylonitrile rubber, butadiene rubber, and acrylonitrile-butadiene rubber.

However, since the rubber particles contribute to roughening of the surface of the adhesive layer by the hydrophilic treatment, it is necessary that the rubber particles are not unevenly distributed in the adhesive layer and are uniformly dispersed.

Examples of thermosetting resins that are other constituents of the adhesive include phenolic resins such as novolak phenolic resins, resol phenolic resins, and xylene resins, or polycondensates of epichlorohydrin and bisphenol, and J]Wfi epoxy. Examples include one type or a mixture of two or more types selected from resins and epoxy resins such as epoxidized polybutadiene resins.

In particular, it is desirable to use a mixture of a phenolic resin and an epoxy resin as the thermosetting resin.

The blending ratio of each component in the adhesive is 25 to 60 rubber particles.
It is desirable that the weight of the thermosetting resin be within the range of 75 weight plates.

In addition to the above two components, the adhesive may optionally contain inorganic fine powder such as colloidal silica to improve coating properties and adhesion, sulfur as a vulcanizing agent for rubber particles, and mercaptan as an accelerator. Additives such as system compounds may be used in combination.

In the present invention, the means for forming four parts on the insulating substrate is as follows:
For example, when coating an insulating substrate with an adhesive layer for chemical plating, a method of forming a recess of a desired depth in a circuit pattern to be formed, and a circuit to be formed after coating an adhesive layer for chemical plating on the surface of an insulating substrate. Examples include a method of forming recesses by pressing using a mold having a convex pattern of the same shape as the pattern.

Since a circuit pattern is formed in the recess thus formed by chemical plating and polishing, it is desirable that the depth is selected to be equal to or larger than the thickness of the chemically plated film to be deposited.

Examples of the chemical plating means in the present invention include chemical copper plating and chemical nickel plating.

Examples of polishing means for polishing the surface of the insulating substrate after chemical plating in the present invention include a puff polishing method.

Next, embodiments of the present invention will be described with reference to FIGS. 1 to 5.

[[] First, 40 parts by weight of acrylonitrile rubber, 20 parts by weight of resol-type phenol resin, 20 parts by weight of bisphenol-type epoxy resin, 10 parts by weight of silica gel, and 10 parts by weight of a curing agent were added to one side of polyester films 1a and 1b using methyl ethyl ketone-butyl cellosolve. Adhesives dissolved in a mixed solvent were applied, dried and cured to form chemical plating adhesive layers 2a and 2b having a thickness of about 30 #1.

Subsequently, these polyester films 1a and 1b are arranged so that their adhesive layers 2a and 2b face each other, and a plurality of prepregs 3... are interposed between these polyester films 1a and Ib, and then a circuit to be formed is formed. The film la is formed by upper and lower molds 5a and sb having convex patterns 4a, 4b, . . . at locations corresponding to the patterns.

1b and prepreg 3... were bonded by thermocompression (as shown in Figure 1)
.

By thermocompression bonding and peeling off the polyester films 1a and 1b, both surfaces of the insulating substrate 6 are coated with adhesive layers 2a and 2b as shown in FIG. 2, and recesses 7 are formed in the circuit pattern area to be formed.・was formed.

[ii] Next, through-hole holes 8 that vertically penetrate through a portion of the recesses 7 of the insulating substrate 6 were drilled (as shown in Figure 3).

Next, chromic acid 500g/A and sulfuric acid 250g/A
After roughening the adhesive layers 2a and 2b by making them hydrophilic for 7 minutes with a mixed solution having the composition of No. 11 (liquid temperature: 40°C), the adhesive layers 2a and 2b were further subjected to an activation treatment represented by the chemical plating process of Silaplay Co., Ltd. in the United States. , a chemical copper plating film 9 was deposited on the entire surface including the through-hole holes 8 (as shown in FIG. 4).

Continuing, both sides of the insulating substrate 6 are polished by puff polishing.
The chemical copper plating film 9 portions deposited on the convex portions were removed to produce a printed wiring board having a circuit pattern 10 made of the chemical copper plating film remaining in the recesses and through holes 11 connected to the circuit pattern 10 (as shown in Fig. 5). ).

Therefore, in the present invention, the circuit pattern 10 can be formed using the chemical copper plating film remaining in the recesses 7 of the insulating substrate 6 without using any metal resist.

Therefore, it is possible to prevent contamination of the chemical copper plating bath due to the use of Metsuki Resist+, and to obtain a highly reliable printed wiring board that eliminates short circuits between circuit patterns caused by chemical copper plating deposited on the Metsuki Resist. can.

Note that the present invention is not limited to the method of puff-polishing the surface of an insulating substrate after chemical copper plating to form a circuit pattern as in the above-described embodiment; The catalyst adhering to the adhesive layer may be removed, followed by chemical copper plating treatment to selectively deposit a chemical copper plating film in the recesses of the adhesive layer where the catalyst remains, thereby forming a circuit pattern.

As detailed above, according to the present invention, a circuit pattern made of a chemically plated film can be formed in the recessed portion without using a metal resist, thereby preventing contamination of the chemical plating bath and improving the service life of the plating bath. At the same time, it has remarkable effects such as being able to manufacture highly reliable printed wiring boards without short circuits between circuit patterns.

[Brief explanation of drawings]

1 to 5 are cross-sectional views showing the manufacturing process of a printed wiring board in an embodiment of the present invention. 2a, 2b...Adhesive layer for chemical plating, 5
a t5b...Mold, 6...Insulating substrate, 7...Concavity, 8...Through hole, 9...Chemical copper plating Membrane, 10...Circuit pattern, 11...Through hole.

Claims (1)

[Claims] 1. A step of forming a chemical plating adhesive layer mainly composed of a thermosetting resin in which rubber particles are uniformly dispersed on the surface of an insulating substrate, and forming a recess of a desired depth in the circuit pattern area on which the insulating substrate is to be formed. a step of applying a chemical plating treatment after hydrophilizing and activating the adhesive layer of the insulating substrate; and a step of mechanically polishing the surface of the insulating substrate to deposit chemical plating on the convex portions of the substrate. 1. A method for manufacturing a printed wiring board, comprising sequentially performing a step of removing a film.