JPS5838960B2 - Method for manufacturing printed circuit boards - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a printed circuit board used when forming a printed circuit by an additive process.

Conventionally, when producing additive process printed circuit boards, a thermosetting resin laminate obtained by pre-forming is used as a base, and one surface of the board is coated with phenol resin and two I-IJ.
A method is used in which a plating adhesive layer containing lucom as a main component is applied and then heated and cured.

However, in this method, the thickness of the coating film of the adhesive layer inevitably becomes uneven, and as a result, the properties such as insulation resistance and surface resistance of the finally obtained printed circuit board cannot be stably obtained.

Furthermore, the adhesive strength between the conductor circuit and the board is insufficient, and
Because of the non-uniformity, there is a drawback that the conductor circuit peels off from the board when soldering at high temperatures after components are mounted.

The present invention has been made in view of the above points, eliminates the various drawbacks of the conventional ones, and provides a method for manufacturing a printed circuit board that has good precision and durability, and can function for a long period of time. This is what we are trying to provide.

The method of the present invention first involves using a resol resin, for example 100-1
50 parts of nitrile rubber, for example 100 parts,
For example, a varnish for adhesion of electroless plating is obtained by dissolving a solvent such as MEK.

Next, the plating adhesion varnish is applied to the surface of the aluminum foil coated with lecithin in advance, and
C. to form an electroless plating adhesive layer.

Then, the adhesive layer obtained in this manner is applied onto the surface of an appropriate number of prepregs impregnated with phenol resin or epoxy resin, and the two are integrally bonded together, e.g.
Heat and pressurize at 150-180°C for 30-120 minutes,
The prepreg is cured to uniformly and integrally form the adhesive layer to produce a laminate for additive processing.

Next, the aluminum foil is mechanically peeled off.

Next, a printed circuit board is obtained through a conventional additive process.

That is, the surface of the above-described additive recessed printed circuit board is chemically etched using, for example, a chromic acid-sulfuric acid mixture to make the surface hydrophilic.

Next, electroless plating is applied to the surface of the laminate through a normal electroless plating process, such as electroless copper plating or electroless nickel plating process.

The obtained object to be plated is heated, for example, at 100 to 150°C for 20
Heat treatment for ~60 minutes to strengthen the adhesion of the plating film.

Next, the object to be plated (a mask is printed leaving the necessary circuit shape, electrolytic copper plating is applied to the non-printed parts, and finally a printed resist film and an electroless plating film are applied to the mask-printed parts). is removed to obtain a printed circuit board.

One of the features of the present invention is the use of resol resin.

The reason for this is that it has good compatibility with nitrile rubber and can undergo a single condensation reaction without a curing agent, resulting in a uniform adhesive layer.

In this case, the resol resin is preferably a solid resol resin.

Furthermore, the blending ratio of nitrile rubber and solid resol resin in the adhesive layer is preferably 1 part ioo of nitrile rubber to 150 to 200 parts of solid resol resin.

If the amount of solid resol resin is greater than the above blending ratio, it is difficult to obtain sufficient adhesive strength.

On the other hand, when the solid resol resin is small, that is, when the nitrile rubber content is large, the solvent resistance of the obtained additive process printed circuit board is poor, and the printed circuit board obtained through the above-mentioned plating process is heated to 260°C. If the solder resin properties are insufficient, the conductor circuit may peel off from the board during component mounting.

The nitrile rubber used in the present invention is preferably a high nitrile rubber with an acrylonitrile content of 35 to 50%.

When the acrylonyl-IJ content is low and the butadiene content is high, the compatibility with the solid resol resin decreases, and the adhesive strength, solvent resistance, and soldering heat resistance are insufficient.

By using the high nitrile rubber, it is completely cured with the solid resol resin, so it has good solvent resistance, and the adhesive strength can be improved by processing at high temperature (150°C) (30 days). It is stable even when subjected to soldering heat resistance test (260℃
, 10 seconds) without blistering or peeling.

The thickness of the adhesive layer is preferably 12 to 20 microns.

When the film thickness is thin, sufficient adhesion strength can be obtained. There is no problem when using special E, but when using glass cloth base epoxy resin impregnated prepreg, the surface of the printed circuit board becomes colored with the color of the solid resol resin of the adhesive layer, and the original color is lost. The commercial value of epoxy glass printed circuit boards is damaged.

Another feature of the present invention is that lecithin is coated on the surface of the aluminum foil in advance.

When applying adhesive directly to the surface of aluminum foil, stacking the adhesive layer so that it is in contact with the surface of the thermosetting resin-impregnated prepreg, and heating and pressing one part of the aluminum foil, the aluminum foil is mechanically (It is difficult to peel off and must be removed by chemical dissolution.

On the other hand, after applying a mold release agent such as silicone, vaseline, or stearic acid to one surface of the aluminum foil in advance, apply an adhesive, and then connect the adhesive layer to the surface of the thermosetting resin-impregnated prepreg. When they are stacked so that they touch each other and heated and pressure molded into one piece, the above-mentioned mold release agent migrates to the adhesive layer, resulting in uneven hydrophilicity during the plating process and the chemical etching described above. , or the electroless plating film is unevenly deposited 1
As a result, the adhesive strength between the conductor circuit and the substrate of the final printed circuit board obtained was not sufficient.

In order to solve these problems, the present invention has been developed by applying lecithin to the surface of the aluminum foil in advance, then applying an adhesive, and bringing the adhesive layer into contact with the surface of the thermosetting resin-impregnated prepreg. Stack them together and heat and press them into one piece.

In this case, the lecithin serves as a mold release agent and can easily (mechanically) peel off the aluminum foil after hot-press molding.

Furthermore, even if the lecithin transfers to the adhesive layer, it will not have any adverse effects during the plating process.

In other words, it is made uniformly hydrophilic through chemical etching, and a plating film is uniformly deposited through the electroless plating process, and the final printed circuit board has excellent heat resistance and extremely good adhesion of conductor circuits. .

In addition, when using a through-hole plated printed circuit board,
Pre-drill holes at the required locations on the additive process printed circuit board (thus, the purpose can be easily achieved).

Next, the present invention will be explained in detail.

Example 1 After thoroughly mixing 200 parts of alkylphenol and 100 parts of high nitrile rubber (35% tolyl content), 700 parts of methyl ethyl ketone was added to prepare a varnish.

Surface 1 of aluminum foil coated with lecithin in advance with this varnish
This was applied, air-dried, and then heat-treated at 130°C for 10 minutes.

A thin adhesive film is formed on the surface of the aluminum foil.

Next, 10 sheets of paper-based phenolic resin-impregnated prepreg were stacked, this adhesive film was laminated on one surface, and the inside (
This is heated and pressurized to obtain a laminate.

Next, the aluminum foil on the surface of this laminate was mechanically peeled off to obtain a printed circuit board.

The circuit board is chemically roughened using a trowel with a chromic acid-sulfuric acid mixture.

Next, electroless plating is performed. The obtained plated object is 1
Heat treatment was performed at 00°C for 230 minutes to more firmly adhere the plating film to the substrate.

Next, resist printing was carried out on one surface of the object to be plated, electrolytic plating was applied on one part without resist, and finally unnecessary parts of the resist and electroless plated film were removed to obtain an additive process printed circuit board.

The performance of this printed circuit board is shown in Table 1.

Example 2 An adhesive film is formed in the same manner as in Example 1.

Next, the paper-based epoxy resin-impregnated prepreg was stacked, and this adhesive film was laminated on one surface of the prepreg, and after heating and pressurizing the whole body (the aluminum foil was removed, the additive process was carried out through the same steps as in Example 1). A printed circuit board was obtained.

The performance of this circuit board is shown in Table 1.

Example 3 Solid resol resin (Sumitomo Durez PR-175) 150
Part, high nitrile rubber (Nippon Zeon, Hi-Riki 1001) 1
After sufficiently kneading 00 parts, 750 parts of methyl ethyl ketone were added to prepare a varnish.

This varnish is applied to the surface of aluminum foil that has been previously coated with lecithin (
This coating is followed by heat treatment at 150° C. for 5 minutes.

A thin adhesive film is formed on the surface of the aluminum foil.

Next, eight sheets of glass cloth base epoxy resin-impregnated prepreg are stacked, this adhesive film is laminated on both surfaces thereof, and the laminate is heated and pressurized to obtain a laminate.

Next, the aluminum foil on the surface of this laminate was mechanically peeled off to obtain a printed circuit board.

Place the above circuit board in the specified position (after drilling the holes)
The substrate surface is treated with a chromic acid-sulfuric acid mixture.

Thereafter, through the same steps as in Example 1, an additive process through-hole plating printed circuit board was obtained.

The performance of this circuit board is shown in Table 1. Comparative Example 1 Solid resol resin (Sumitomo Durez, PR-175) 15
0 parts, low nitrile rubber (Japan Synthetic Rubber, JSR2408
) After thoroughly kneading 100 parts of the mixture, 750 parts of methyl ethyl ketone was added to prepare a varnish.

Following the same steps as in Example 1, an additive process printed circuit board was obtained.

The performance of this circuit board is shown in Table 1.

As is clear from Table 1, the printed circuit board produced by the method of the present invention has improved plating film adhesion, heat resistance, and electrical properties compared to conventional additive process printed circuit boards.
Compared to this, it has very superior quality.

Claims (1)

[Scope of Claims] 1. A layer of thermosetting resin-impregnated prepreg and a layer of adhesive made of resol resin and Nidol rubber coated on the surface of aluminum foil coated with Lentin in advance. The adhesive layer covers at least one layer of the prepreg.
A method for manufacturing an additive process printed circuit board, which comprises stacking two surfaces so that they are in contact with each other, integrally forming the aluminum foil under heat and pressure, and then removing the aluminum foil. 2. The method for manufacturing a printed circuit board according to claim 1, wherein the resol resin is a solid resol resin. 3. The method for manufacturing a printed circuit board according to claim 1, wherein the nitrile rubber is a high nitrile rubber having an acrylonitrile content of 35% by weight or more. 4. The method for manufacturing a printed circuit board according to claim 1, wherein the thermosetting resin-impregnated prepreg is a paper-based phenolic resin-impregnated prepreg. 5. The method for manufacturing a printed circuit board according to claim 1, wherein the thermosetting resin-impregnated prepreg is a paper-based epoxy resin prepreg. 6. The method for manufacturing a printed circuit board according to claim 1, wherein the thermosetting resin-impregnated prepreg is a glass cloth base epoxy resin-impregnated prepreg. 7 The layer of adhesive is
3. The method of manufacturing a printed circuit board according to claim 2, wherein the solid resol resin is made from 150 to 200 parts. 8. The method for manufacturing a printed circuit board according to claim 1 or 7, wherein the adhesive layer has a thickness of 12 to 20 μm.