JPH05259612A - Production of printed wiring board - Google Patents

Abstract

PURPOSE:To provide the production of a printed wiring board by full-additive method so as to permit high insulation resistance before and after the electrocorrosion test and ensure even a fine wiring pattern. CONSTITUTION:The production includes the following processes: 1) a process of forming pattern-shaped resist, which can be peeled off by alkali solution, on an insulating board, 2) a process of applying a catalyst which becomes the core of electroless copper plating, 3) a process of peeling off the resist by the alkali solution, 4) a process of forming resist for electroless copper plating and 5) a process of forming a wiring pattern by electroless copper plating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board in which a wiring pattern is formed on an insulating substrate by electroless copper plating.

[0002]

2. Description of the Related Art Conventionally, an insulating substrate having a metal thin film on its surface, that is, a copper-clad laminate has been used in the manufacture of printed wiring boards, which is mainly paper or cloth impregnated with epoxy resin, phenol resin or the like. And a copper foil coated with an adhesive are superposed on each other and laminated by heat and pressure to manufacture.
The printed wiring board is an insulator substrate (laminated board) by etching away the copper foil other than the wiring pattern part on the copper-clad laminated board.
A wiring pattern is formed on the top.

Therefore, in this method using a copper-clad laminate, most of the copper foil on the substrate is removed by etching, which is wasteful, and the holes (through holes) formed by drilling are metal-coated. Not drilled, after drilling,
Furthermore, through-hole plating is required.

On the other hand, in contrast to this method, a full-additive method of forming a wiring pattern by directly performing electroless copper plating on the insulating substrate and on the hole walls in the through holes is emphasized. This full-additive method is applied to an insulating substrate manufactured by hot-pressing and laminating a predetermined amount of paper or cloth impregnated mainly with epoxy resin, phenol resin, etc.
A base adhesive for electroless plating described in Japanese Patent Publication No. 9843 is formed. After that, holes are drilled, and a catalyst for electroless plating containing Pd as a main component is provided on the substrate surface and in the holes,
Further, after forming a resist for electroless copper plating on the portion excluding the wiring pattern, the wiring pattern is formed by electroless copper plating. Further, a full additive method in which a catalyst for electroless plating containing Pd as a main component is mixed in an insulating substrate and an adhesive, an electroless plating resist is formed on the substrate, and a wiring pattern is formed by electroless copper plating. There is also a law.

In either method, since the resolution of the electroless copper plating resist is generated in the wiring pattern, it is possible to manufacture a high density printed wiring board. However, since conductive Pd exists on the surface or inside of the insulating substrate and the adhesive, there is a problem that the insulation resistance is low and the insulation resistance is inferior in the electrolytic corrosion test in which a voltage is applied under high temperature and high humidity. .. In particular, as the density of printed wiring boards has increased in recent years, electrolytic corrosion has become a serious problem.

[0006]

As described above, in the production of a printed wiring board by the full additive method, if the wiring pattern becomes fine, the insulation resistance and the insulation resistance in the electrolytic corrosion test decrease. there were. Therefore, an object of the present invention is to provide a method for manufacturing a printed wiring board by a full additive method, which has high insulation resistance and insulation resistance in an electrolytic corrosion test and can secure even a fine wiring pattern.

[0007]

According to the present invention, a resist that can be stripped with an alkaline aqueous solution is formed in advance on an insulating substrate, and then a catalyst that serves as a core of electroless copper plating is applied so that only a portion to be plated is left uncoated. The above object is achieved by the presence of the electrolytic copper plating catalyst.

That is, according to the present invention, in a method for manufacturing a printed wiring board in which a wiring pattern is formed by electroless copper plating, a step of forming a patterned resist that can be peeled with an alkaline aqueous solution on an insulating substrate, A printed wiring characterized by including a step of applying a catalyst as a core, a step of peeling a resist with an alkaline aqueous solution, a step of forming a resist for electroless copper plating, and a step of forming a wiring pattern by electroless copper plating. The present invention relates to a method for manufacturing a plate.

Next, the method for manufacturing the printed wiring board of the present invention will be described in detail. In the present invention, the insulating substrate is not particularly limited and various ones may be used, for example, a paper phenol plate laminated with paper impregnated with phenol resin, a glass epoxy plate laminated with epoxy resin impregnated glass cloth, and the like. Can be mentioned. More specific examples of these substrates include those that do not contain a catalyst for electroless copper plating, and are available as products such as product names LP-461F and LE-67N manufactured by Hitachi Chemical Co., Ltd. is there.

Further, a base adhesive layer for electroless copper plating may be formed on the surface of the substrate. This adhesive layer is obtained by applying a liquid adhesive composed of rubber, phenol, epoxy resin or the like by a dip coating method, a curtain coating method, etc., dried and cured, or applying the adhesive in advance on a support film. The adhesive film, which has been dried and formed into a film, is laminated (thermocompression bonded) on a substrate and cured. Lamination can be performed using a laminator well known in the field of printed wiring board manufacturing. That is,
When the adhesive film does not have a protective film such as polyethylene, it is as it is, and when there is a protective film, the protective film is peeled or the adhesive side is the substrate side while peeling, and heat and pressure lamination is performed on both sides or one side of the substrate. To do.

After that, when the adhesive layer is provided, the surface can be roughened by using a chemical roughening liquid such as a mixed liquid of chromic acid and sulfuric acid.

In the process of the present invention, in order to form a resist that can be peeled off with an alkaline aqueous solution on an insulating substrate, a film commercially available as a photosensitive film for printed wiring boards is laminated to form a photosensitive layer on the substrate. Alternatively, a liquid photosensitizer is applied on the substrate by a dipping method or the like and dried to form a photosensitive layer. The photosensitive layer material is not particularly limited as long as it can form a resist that can be peeled with an alkaline aqueous solution. The former film is, for example, a product name of Fotec (registered trademark) manufactured by Hitachi Chemical Co., Ltd.
Some are available as HF240, H-S433, etc. Lamination of these films on the substrate can be similarly carried out using a laminator well known in the field of printed wiring board production, as in the case of laminating the adhesive film.

After the photosensitive layer is formed on the substrate as described above, it is imagewise exposed by using an exposure device having a light source such as an ultra-high pressure mercury lamp or a metal halide lamp (in this case, the negative film is coated with a plating resist). (The same pattern as the above pattern is used), the support film such as the polyester film is removed, and then the resist film is developed with an alkaline aqueous solution to form a patterned resist. Here, the alkaline aqueous solution is not particularly limited and various ones can be used. Examples thereof include an aqueous solution of salt.
An aqueous solution of sodium carbonate is particularly preferable.

The step in the method of the present invention is a step of applying a catalyst which becomes a nucleus of electroless copper plating. here,
The catalyst may be any catalyst used in electroless copper plating, for example, a catalyst liquid containing a palladium compound such as palladium chloride, a rhodium compound such as rhodium chloride, for example, Hitachi Chemical Co., Ltd. Product name made by HS
101B and the like. The step of applying the catalyst can be carried out by immersing the substrate on which the resist has been formed in the step in the above-mentioned catalyst solution and then washing with water. After that, activation treatment can be further performed using oxalic acid or the like.

The next step is a step of stripping the resist with an alkaline aqueous solution, which can be performed using a resist stripping machine well known in the field of printed wiring board manufacturing. The alkaline aqueous solution used for stripping the resist is, for example, an aqueous solution of an alkali metal hydroxide such as potassium hydroxide or sodium hydroxide, or a solution obtained by further containing alcohol or the like.

Next, a step of forming a resist for electroless copper plating is performed. This step can be performed in the same manner as the above-mentioned step of forming a resist that can be stripped with an alkaline aqueous solution. That is, the resist for electroless copper plating is not particularly limited, and a liquid resist or a photosensitive film can be used. When a liquid resist is used, the liquid resist is applied on the substrate by various methods such as a dip coating method and a curtain coating method, and dried. Also,
When a photosensitive film is used, it is laminated using a known laminator.

After that, imagewise exposure is performed by using an exposure device having a light source such as an ultra-high pressure mercury lamp or a metal halide lamp. In this case, the negative film used when exposing the resist capable of peeling with an alkaline aqueous solution is used. Next, when a photosensitive film is used, after peeling the support film such as a polyester film, the resist is formed by developing with an organic solvent such as trichloroethane or an alkaline aqueous solution such as a 1 wt% sodium carbonate aqueous solution. .. Further, curing may be performed by irradiation with ultraviolet rays or heat at about 150 ° C.

Finally, as a step, a step of forming a wiring pattern by electroless copper plating is performed. This step can be performed by a conventional method by immersing the substrate in various electroless copper plating solutions containing copper sulfate, formaldehyde, etc. as a main component. Here, activation treatment of the plating catalyst may be performed before electroless copper plating.

A liquid resist or a dry film type solder resist may be formed on the substrate on which the electroless copper plating has been completed.

The printed wiring board of the full-additive method manufactured by the method of the present invention has no plating catalyst under the plating resist, so that the insulation resistance and the insulation resistance in the electrolytic corrosion test are improved, and a fine wiring pattern is formed. A printed wiring board can be manufactured.

[0021]

EXAMPLES Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the invention.

Example 1 An adhesive film (manufactured by Hitachi Chemical Co., Ltd., trade name: Fotec (registered trademark) AP-1530) was used as a glass epoxy plate (manufactured by Hitachi Chemical Co., Ltd., trade name LE67N, thickness 0.8 mm, Hot roll laminator (Hitachi Chemical Co., Ltd., trade name HL) on both surfaces of 500 mm x 300 mm
M-1500) using a hot roll temperature of 150 ° C,
Hot roll pressure 4kgf / cm ² , laminating speed 1.0
The polyethylene film was peeled off and laminated under the condition of m / min, and the adhesive film was cut into a substrate size.

Next, a high-pressure mercury lamp 2 of 80 W / cm having a parallel light irradiation type reflection plate which simultaneously emits ultraviolet rays and infrared rays.
Using a UV irradiator having a book (manufactured by Oak Manufacturing Co., Ltd., trade name HMW-514 type), 1.2 J / cm ² of UV light was irradiated with a 365 nm sensor. Next, the polyester film was peeled off and heated for 30 minutes in a curing oven having an ambient temperature of 150 ° C. Next, holes for aligning the negative film were opened.

The hardened adhesive layer on the substrate was treated with a chemical roughening solution consisting of chromic anhydride 65 g / l and concentrated sulfuric acid 250 ml / l at 50 ° C. for 7 minutes, washed with water and then washed with hot water at 50 ° C. It went for 10 minutes. Next, it was treated with a 6 g / l sodium hydroxide aqueous solution at 50 ° C. for about 10 minutes to remove the roughening residue on the surface of the adhesive, and further washed with water.

In order to form a resist which can be peeled off with an alkaline aqueous solution on the substrate thus roughened, a photosensitive film (PHITECH-887AF-25, trade name, Photec (registered trademark), manufactured by Hitachi Chemical Co., Ltd.) is used on both surfaces of the substrate. While peeling off the polyethylene film, hot roll laminator, hot roll temperature 100 ℃, hot roll pressure 3
Lamination was carried out under the conditions of kgf / cm ² and laminating speed of 1.5 m / min, and the photosensitive film was cut into a substrate size.

Next, as a negative film, a copper foil peeling strength measuring pattern having a rectangular pattern having a width of 1 cm and a length of 10 cm as a light-shielding portion, and a side of 2.5.
260 ° C solder heat resistance measurement pattern having a square cm pattern as a light-shielding portion, and the electrode portion has a width of 100 μm ×
Use the insulation resistance measurement pattern of the electrolytic corrosion test, which has comb-shaped patterns with the comb teeth of 10 cm in length, which are combined so as to line up at intervals of 100 μm when the + electrode side and the − electrode side are combined, as the light-shielding portion. Align with the reference hole,
Ultra-high pressure mercury lamp (Oak Seisakusho Co., Ltd., trade name HMW
-201B) at an exposure dose of 60 mJ / cm ² . Next, after removing the polyester film of the support of the photosensitive film by peeling,
After spray developing for 30 seconds (liquid temperature 30 ° C.), washing with water and drying at 80 ° C. for 10 minutes, a patterned resist was obtained.

Next, a catalyst solution containing Pd which serves as a catalyst for electroless copper plating (manufactured by Hitachi Chemical Co., Ltd., trade name HS
The substrate on which the resist was formed was immersed in 101B) for 2 minutes to apply a catalyst. After washing with water, 1g / l oxalic acid and 36wt%
Dip for 5 minutes in an activation solution consisting of 10 ml / l of hydrochloric acid,
Further washed with water.

A resist which can be stripped with an alkaline aqueous solution on the substrate thus provided with the catalyst for electroless copper plating is sprayed with a 3 wt% sodium hydroxide aqueous solution (liquid temperature 45 ° C.) for 30 seconds, stripped, and washed with water, It was dried at 120 ° C. for 10 minutes.

Then, in order to form a resist for electroless copper plating on the surface of the substrate which has been peeled off, a photosensitive film (manufactured by Hitachi Chemical Co., Ltd., trade name Photec SR-3200-35). Is laminated on both surfaces of the substrate with a hot laminator while peeling off the polyethylene film (hot roll temperature 100 ° C., laminating pressure 3 kgf / cm ² , laminating speed 1.2 m / min),
The photosensitive film was cut into a substrate size.

Next, using the negative film used for forming the resist which can be peeled off with an alkaline aqueous solution, the reference film is used for alignment (so that the same pattern remains at the same position).
Ultra high pressure mercury lamp (Oak Seisakusho Co., Ltd., trade name H
MW-590) at an exposure dose of 200 mJ / cm ² .
Next, after peeling off the polyester film of the support of the photosensitive film, spray development with 1,1,1-trichloroethane (liquid temperature 15 ° C.) for 50 seconds, washing with water, and then at 80 ° C.
And dried for 10 minutes.

The substrate thus obtained was treated with copper sulfate / pentahydrate 15 g / l, ethylenediaminetetraacetic acid 30 g / l, 37
% HCHO aqueous solution 10 ml / l and sodium cyanide 2
An electroless copper plating solution containing 5 mg / l and adjusted to pH 12.5 with sodium hydroxide was immersed at 70 ° C. for 15 hours to form a copper plating film having a thickness of about 30 μm on each wiring pattern forming portion. Next, it was washed with water and dried at 150 ° C. for 30 minutes.

Thereafter, a thermosetting solder resist (Taiyo Ink Mfg. Co., Ltd., trade name S-222MJ6) was screen-printed on a portion other than the both electrodes with a comb pattern for an electrolytic corrosion test, and heated at 150 ° C. for 30 minutes. Cured.

With respect to the substrate having the obtained wiring pattern, peel strength and solder heat resistance were measured according to JIS-C6481 method. For the electrolytic corrosion test pattern, solder the lead wires to both electrodes and apply DC voltage 50
After applying 0 V for 1 minute and measuring the initial insulation resistance, the sample was placed in a thermo-hygrostat at 85 ° C. and a humidity of 85% while applying a DC voltage of 100 V, taken out after 240 hours, and the application was stopped. Then, a DC voltage of 500 V was applied for 1 minute, and the insulation resistance after the electrolytic corrosion test was measured. The measurement results are shown in Table 1.

COMPARATIVE EXAMPLE 1 A substrate having a wiring pattern of electroless copper plating was carried out in the same manner as in Example 1 except that the step of forming a resist that can be peeled off with an alkaline aqueous solution and the step of peeling it off were not performed. It was created. Further, peel strength, solder heat resistance and electrolytic corrosion tests were conducted in the same manner as in Example 1, and the results are shown in Table 1.

[0035]

[Table 1]

As is clear from the above results, the printed wiring boards obtained in the examples of the present invention have good peel strength and solder heat resistance, and further, since there is no plating catalyst below the plating resist, The initial insulation resistance was remarkably high, and the insulation resistance after the electrolytic corrosion test was 10 ¹² Ω or more, showing excellent characteristics. On the other hand, in the comparative example, although the peel strength and the solder heat resistance were good, the insulation resistance after the electrolytic corrosion test was a low value of 10 ¹⁰ Ω.

[0035]

According to the method of the present invention, the full additive method is excellent in peel strength and solder heat resistance, and
It is possible to obtain a printed wiring board having excellent insulation resistance such as insulation resistance after the electrolytic corrosion test.

Claims (2)

[Claims] 1. A method of manufacturing a printed wiring board in which a wiring pattern is formed by electroless copper plating, a step of forming a patterned resist that can be stripped with an alkaline aqueous solution on an insulating substrate, and a catalyst serving as a core of electroless copper plating. And a step of peeling the resist with an alkaline aqueous solution, a step of forming a resist for electroless copper plating, and a step of forming a wiring pattern by electroless copper plating. .. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the insulating substrate has an adhesive layer on its surface.