JP2531466B2 - Method for manufacturing printed wiring board - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a printed wiring board, and more particularly to a method of manufacturing a printed wiring board using an additive method.

[0002]

2. Description of the Related Art Generally, a printed wiring board is panel-plated with a copper clad laminate as a base, and then a desired pattern is printed on the surface of the substrate by using a photoresist or an ink resist, and then cured. After forming the acid-resistant resin layer by etching, the exposed copper foil portion is removed by etching using an aqueous solution of ferric chloride or an aqueous solution of cupric chloride to form a desired pattern. However, in this method, copper parts other than the desired circuit are removed by etching, which is a waste of resources, and there is a problem that it is difficult to form a fine pattern because the circuit is thinned due to side etching. . Due to such problems, the additive method is drawing attention in order to solve these drawbacks. The additive method includes a full additive method in which a circuit is formed only by electroless copper plating and a semi-additive method in which electroplating is used in combination, but the present invention particularly relates to improvement of the former full additive method.

The general manufacturing process of the full additive method is as follows. A roughening treatment is applied to a substrate coated with an adhesive for promoting adhesion of plating, and then a catalytic treatment is performed to attach plating catalyst nuclei to the substrate surface. Next, the area excluding the necessary circuit portion is covered with a resist having a plating solution resistance (this resist remains as an insulating layer in the substrate as it is and is called a permanent mask). After that, the entire substrate is immersed in an electroless copper plating solution to deposit plated copper on a portion not covered with the permanent mask, that is, a necessary circuit portion. However, in the above-mentioned method, since the permanent mask, the adhesive, and the catalyst exist near the interface, there is a possibility that insulation deterioration may occur during humidification. In recent years, in particular, high density wiring has been demanded in response to downsizing and high performance of equipment, but the wiring board produced by the above-mentioned manufacturing method cannot reduce the wiring density due to insulation deterioration, resulting in low cost and low cost. It was put to practical use by limiting to density products. In order to overcome this problem, a method for selectively attaching a catalyst is disclosed in Japanese Patent Laid-Open No. 58-1.
It is proposed in Japanese Patent Publication No. 99. FIG. 3 shows a cross-sectional view for explaining the manufacturing method of the publication. First, as shown in FIG. 3A, the adhesive 2 is applied onto the substrate 1. Then, as shown in FIG. 3B, the holes 3 are provided by a method such as punching or dring.
Next, as shown in FIG. 3C, an acid resistant resist 7 is formed on a portion other than the necessary circuit portion. Next, as shown in FIG. 3D, the entire substrate is immersed in the catalyst treatment liquid to form a palladium catalyst 5 on the entire surface of the substrate.
After applying the acid resist 7 as shown in FIG.
Peel off. At this time, the palladium catalyst 5 attached on the acid-resistant resist 7 is also removed at the same time and remains only in the necessary circuit portion. Next, as shown in FIG. 3F, a permanent mask 4 is formed by a photo method at a portion other than the necessary circuit portion, that is, at the same position as the acid resistant resist 7. As a result, the palladium catalyst 5 is attached to the surface other than the permanent mask 4. Then, as shown in FIG. 3 (g), the whole substrate was immersed in an electroless plating solution to manufacture a wiring board having a desired circuit in which plated copper 6 was deposited on the inner surface of the hole and the necessary circuit portion.

[0004]

This conventional method for manufacturing a printed wiring board has a drawback that the manufacturing cost is higher than that of the above-mentioned manufacturing method because the steps of forming an acid resistant resist and peeling are added.

Secondly, in the prior art, it is necessary to form the permanent mask 4 at the same position as the acid resistant resist 7, but in reality, a slight deviation occurs. This is caused by a film misalignment when the photo method is used, which causes a misalignment amount of 0 to 0.1 mm, and when a screen printing method is used, the screen misalignment is caused by 0 to 0.1 mm.
A shift amount of 4 mm is generated. Therefore, at the boundary between the catalyst and the permanent mask 4, the catalyst is covered with a permanent mask or a gap is formed between the catalyst and the permanent mask. As a result, in particular, in the case of a thin pattern such as a circuit, a plated copper deposition defect may occur, which may cause a circuit disconnection. Therefore, it is difficult to form a circuit having a circuit width and a circuit gap of 0.1 mm in the photo method and 0.4 mm or less in the screen printing method. Therefore, it has been difficult to manufacture a high-density printed wiring board.

[0006]

A method of manufacturing a printed wiring board according to the present invention comprises a step of roughening a substrate having an adhesive for plating on the surface, and a permanent mask having a smooth surface other than a portion where a circuit is to be formed on the substrate. And a step of applying a plating treatment by applying a catalyst treatment to the entire surface of the substrate,
The method includes the steps of immersing the substrate in an oxidizing agent to remove the catalyst deposited on the smooth surface of the permanent mask, and forming a chemical plating metal layer on a portion where a circuit is to be formed.

[0007]

The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view for explaining one embodiment of the present invention. First, as shown in FIG. 1 (a), a glass epoxy insulating plate having a thickness of 1.6 mm is used as a base material, and a dry film type adhesive 2 having a thickness of 50 μm is attached by a laminator, and then ultraviolet rays having a peak wavelength of about 400 nm are 3 J / cm
^After being exposed and cured at ² , it was heated at 120 to 140 ° C. for 1 to 2 hours to be completely cured.

Next, as shown in FIG. 1B, a hole 3 having a diameter of 1.0 mm is formed by drilling, and then the adhesive 2 is roughened. Here, as the roughening solution, the most suitable one is selected for the adhesive 2, and there are an aqueous solution of permanganate, an aqueous solution of chromic acid, concentrated sulfuric acid and the like, but in the present embodiment, 75 g of chromic anhydride, 98% sulfuric acid of 3%.
A chromium-sulfuric acid aqueous solution of 00 ml and 700 nl of water was used. After soaking in this aqueous solution for 7 minutes at 50 ° C., a neutralizing solution such as 5-20% sodium sulfite aqueous solution is added at room temperature for 2 minutes.
The chromic acid residue remaining on the substrate surface is neutralized and removed by immersing for ~ 5 minutes to remove the maximum roughness (Rma) on the surface of the adhesive 2.
x) formed a roughened surface of 2 to 5 μm. Then Fig. 1
After laminating a dry film type permanent mask of acrylic resin as shown in (c), 200 to 300 m
A circuit pattern having a circuit width / circuit interval (L / S) of 100 μm was formed on the substrate by performing spray development after exposure to ultraviolet rays of J / cm ² . 1000-2000mJ /
The permanent mask 4 was cured by irradiating it with ultraviolet rays of cm ² . Then, the whole substrate was subjected to catalytic treatment. The catalyst used here is copper / catalyst, and 10 g of gelatin, 5 g of polyethylene gurul and 15 ml of 60% sulfuric acid are added to about 700
After dissolving in ml of water, the pH was adjusted to about 2 with NaOH, 25 g of copper pentahydrate was dissolved, and finally 120 ml of dimethylamine borane having a concentration of 100 g / l was gradually added to prepare a colloidal catalyst having metallic copper as a nucleus. . By immersing the substrate 1 in this catalyst solution at room temperature for 2 minutes, the copper catalyst 5 was attached to the entire surface of the substrate. (This state is shown in FIG. 1 (d))
Then, the substrate is immersed in an aqueous solution of potassium permanganate 5 g / l and sodium hydroxide 5 g / l at room temperature for 1 to 2 minutes to remove the copper catalyst 5 attached to the permanent mask 4 as shown in FIG. 1 (e). Remove. At this time, the copper catalyst 5 attached to the surface of the permanent mask 4 is easily removed by the permanganate treatment because the surface of the permanent mask 4 is smooth, but part of the copper catalyst 5 attached to the adhesive 2 is coarse. It is trapped and remains in the minute holes on the surface. The surface of a normal permanent mask is smooth unless special treatment such as roughening treatment is performed, so that almost any known permanent mask can be used in the present invention.
Further, the wall surface of the hole 3 is rough due to the cut surface of the glass cloth, and like the roughened surface, part of the catalyst remains.

The concentration of potassium permanganate in the aqueous potassium permanganate solution of this example was 5 g / l, but 1 to 20 g / l is suitable as the permanganate ion. This is because when the permanganate ion concentration is less than 1 g / l, the removal of the catalyst becomes insufficient, while when it exceeds 20 g / l, the removal of the catalyst increases and the copper catalyst attached to the adhesive 2 becomes less likely to remain. This is because. Further, when the copper catalyst 5 is similarly carried out by using a commonly used palladium catalyst, the adhesion is too strong, and the catalyst on the permanent mask 4 is not completely removed but remains partially, resulting in a short circuit. Occurs.

On the other hand, since the adhesion force of the copper catalyst is weak, the patterning of the catalyst becomes possible due to the difference in the orientation. Next, electroless copper plating was performed to deposit plated copper 6 using the catalyst 5 trapped in the adhesive 2 as a nucleus to form a circuit having a thickness of 40 μm.

At this time, plated copper 6 is also deposited on the wall surface of the hole 3 to form a through hole. By carrying out as described above, a printed wiring board having a desired through hole was obtained.

When the circuit of this printed wiring board was inspected, there was no bridge between the circuits, and the cross-sectional shape of the circuit was rectangular as shown in FIG. 1 (f).

Further, a humidification test was conducted while applying a voltage between the circuits of this printed wiring board, but no short circuit occurred between the circuits.

FIG. 2 is a sectional view for explaining the second embodiment of the present invention.

First, as shown in FIG. 2 (a), a glass epoxy insulating plate having a thickness of 1.6 mm is used as a base material 1 and a dry film type adhesive agent 2 having a thickness of 50 μm is bonded by a laminator, and then an ultraviolet ray having a peak wavelength of about 400 nm is applied. 1-3 J / cm ²
After exposure and curing at 120 ° C., it was completely cured by heating at 120 to 140 ° C. for 1 to 2 hours.

Next, as shown in FIG. 1B, a hole 3 having a diameter of 1.0 mm is formed by drilling, and then the adhesive 2 is roughened. Here, as the roughening liquid, the most suitable one for the adhesive 2 is selected, and an aqueous solution of permanganate, an aqueous solution of chromic acid, concentrated sulfuric acid or the like is used. In this embodiment, 75 g of chromic anhydride and 300 m of sulfuric acid are used.
1, an aqueous solution of 700 ml of chromium sulphate was used. After being immersed in this aqueous solution at 50 ° C. for 7 minutes, it is immersed in a neutralizing solution such as a 5-20% aqueous solution of sodium sulfite for 2 to 5 minutes at room temperature to neutralize and remove the chromic acid residue remaining on the substrate surface. To form a roughened surface with Rmax = 2 to 5 μm on the surface of the adhesive 2.

Then, after laminating a dry film type permanent mask as shown in FIG.
After exposure to ultraviolet light of 00 mJ / cm ² , sprue development was performed to form a circuit pattern of L / S = 100 μm on the substrate. Further, the permanent mask 4 was cured by irradiating with an ultraviolet ray of 1000 to 2000 mJ / cm ² . Then, the whole substrate was subjected to catalytic treatment. The catalyst used here is a copper catalyst, 10 g of gelatin and 5 of polyethylene glycol.
g and 60 ml of 60% sulfuric acid are dissolved in about 700 ml of water, then adjusted to about pH 2 with NaOH, and 25 g of pentahydrated copper sulfate is added.
After the dissolution, finally 120 ml of dimethyl P-minborane having a concentration of 100 g / l was gradually added to prepare a colloid catalyst having metallic copper as a nucleus. The copper catalyst 5 was attached to the entire substrate by immersing the substrate 1 in this catalyst solution at room temperature for 2 minutes.
(This state is shown in FIG. 1 (d)) Then, the substrate is immersed in an aqueous solution of potassium permanganate 5 g / l and sodium hydroxide 5 g / l at room temperature for 1 to 2 minutes to obtain the substrate shown in FIG.
As shown in (e), the copper catalyst 5 attached to the permanent mask 4 is removed.

Then, as shown in FIG. 2 (f), 0.1 to 0.5 g / l of palladium chloride is immersed in an aqueous solution whose pH is adjusted to about 0.5 to 2 with hydrochloric acid at room temperature for 1 to 2 minutes to form Cu + Pd. The reaction of ²⁺ → Cu ²⁺ + Pd occurs and the copper catalyst is replaced with metallic palladium to become a catalyst nucleus. The copper catalyst has a short catalyst treatment life because the core metal copper is easily oxidized by oxygen dissolved in the liquid, but a palladium catalyst can be substituted for a longer life to form a practical process. Further, since the copper catalyst has a weak adhesive force, it falls off due to contact when handling the substrate, but by replacing it with a palladium catalyst, it is possible to prevent the catalyst from falling off and maintain a high yield.

Next, as shown in FIG. 2 (g), electroless copper plating is performed to form plated copper 6 by using the palladium catalyst 5 adhering to the roughened surface of the adhesive 2 as a nucleus to form a circuit having a thickness of 40 μm. did.

At this time, plated copper 6 is projected on the wall surface of the hole 3 to form a sley hole. By carrying out as described above, a printed wiring board having a desired through hole was obtained. When the circuit of this printed wiring board was inspected, there was no bridge between the circuits, and the sectional shape of the circuit was rectangular as shown in FIG. 2 (g). Furthermore, a humidification test was conducted while applying a voltage between the circuits of this printed wiring board, but no short circuit occurred between the circuits.

[0022]

As described above, according to the method of manufacturing a printed wiring board of the present invention, there is no problem of deterioration of insulation resistance in the conventional manufacturing method, and the manufacturing method described in JP-A-58-199. Unlike the method, the step of forming an acid-resistant resist is unnecessary, and the method can be carried out only by adding a permanganate treatment step to the conventional step. Therefore, the manufacturing process is simple and an inexpensive printed wiring board can be manufactured.

Furthermore, since circuit opening or short circuit due to misalignment of the acid resistant resist permanent mask, which is a problem in the manufacturing method described in the above publication, does not occur, it is possible to increase the circuit density.

The material of the permanent mask is not limited to that of the embodiment, and may be a normally used permanent mask having a smooth surface unless special treatment such as roughening treatment is performed. Needless to say.

[Brief description of drawings]

FIG. 1 is a sectional view illustrating a manufacturing process according to a first embodiment of the present invention.

FIG. 2 is a sectional view illustrating a manufacturing process according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a manufacturing process of a conventional printed wiring board.

[Explanation of symbols]

 1 Base Material 2 Adhesive 3 Hole 4 Permanent Mask 5 Copper Catalyst 6 Plated Copper 7 Acid Resistant 8 Palladium Catalyst

Claims (4)

(57) [Claims] 1. A step of roughening a substrate having an adhesive for plating on the surface thereof , and a step of applying a permanent mask having a smooth surface other than a portion where a circuit is to be formed on the substrate .
As a plating catalyst is subjected to catalytic treatment to the entire surface of the substrate
A step of a copper catalyst depositing in the which immersed the substrate to an oxidizing agent was applied to the smooth surface of the permanent mask
A method of manufacturing a printed wiring board, comprising: a step of removing a copper catalyst; and a step of forming a chemical plating metal layer on a portion where a circuit is to be formed. 2. After and before the step of removing the copper catalyst
Before the step of forming the chemical plating metal layer, the copper catalyst
2. The method for manufacturing a printed wiring board according to claim 1, further comprising the step of substituting palladium catalyst for palladium . 3. The method for manufacturing a printed wiring board according to claim 1, wherein an alkaline permanganate aqueous solution is used as the oxidizing agent. 4. The method for manufacturing a printed wiring board according to claim 3, wherein the alkaline permanganate aqueous solution has a permanganate ion concentration of 1 to 20 g / l.