JPH01124286A - Manufacture of printed-circuit board - Google Patents

Abstract

PURPOSE:To manufacture a printed-circuit board whose thermal resistance and insulating characteristic are excellent and whose adhesion force with reference to a plated metal is high by a method wherein a nickel thin layer formed on a rough face of a metal-foil support body is laminated on an insulating organic material, the metal-foil support body is etched selectively, the nickel thin layer is left on the insulating organic material and a conductive metal is plated on this surface. CONSTITUTION:A nickel layer formed on the surface of a metal-foil support body such as copper foil or the like having a rough face of a microscopic uneven shape is formed with a uniform film thicknests along the rough face shape if the metal-foil support body. The metal-foil support body where the nickel layer has been formed and a resin are laminated; after that, a nickel thin layer together with the uneven shape of the metal-foil support body is transcribed onto the surface of a substrate where only the metal-foil support body has been etched and removed. A metal layer of a desired thickness is plated on this nickel thin layer and a circuit is formed; as a result, a printed-circuit board whose adhesion force with reference to a plated metal is high can be obtained.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method of manufacturing a printed wiring board.

(Prior art) The main conventional method for imparting adhesive strength between an organic substrate for printed wiring boards and plated metal is to physically or chemically treat the surface of the organic substrate to make it hydrophilic and rough. This is a way to make it more visible. The most commonly used method among these methods is to use an adhesive layer on the surface of the substrate, which can be made hydrophilic by treatment with a chemical roughening solution, resulting in a roughened surface with fine irregularities. This method uses an attached board.

(Problems to be Solved by the Invention) In this conventional method, a roughening liquid must be used to roughen the surface of the substrate with an adhesive layer, and most of the roughening liquids that can be used contain an oxidizing agent. and is highly toxic. As a result, the working environment is poor and special waste liquid treatment is required. In addition, components soluble in the roughening solution generally have poor electrical insulation properties.

For example, moisture-resistant insulation properties and insulation properties deteriorate at high temperatures. Furthermore, since the adhesive layer has low heat resistance and a high rate of change in one dimension, there is a limit to its application to multilayer printed wiring boards that require good dimensional accuracy and through-hole connection reliability.

The present invention provides a method for manufacturing single circuit metal and adhesive printed wiring.

(Means for Solving the Problem) The present invention involves forming nickel filti on the rough surface of a metal foil support such as copper foil, which has a rough surface with fine irregularities, and first insulating this surface. The support metal is removed from the substrate material by contacting it with an etching solution that selectively etches the support metal, leaving a thin layer of nickel on the substrate, and electroless plating is applied to this surface. Alternatively, manufacturing printed wiring boards that involves circuit processing that involves plating a conductive metal to a desired thickness by electroplating, or plating a conductive metal to a desired thickness by using a combination of electroless plating and electroplating. It is the law.

There are various methods for forming a thin layer of nickel on the surface of supporting metal foil such as copper foil used in the present invention, including dry methods such as vapor deposition and sputtering, and wet methods such as electroplating and electroless plating. It can be formed with a uniform thickness along the surface shape of supporting metal foil such as copper foil. ■Can be processed continuously. ■Electroless nickel plating is particularly desirable because of its low cost. Furthermore, it is easy to use a type of electroless nickel plating that is deposited on steel without catalytic treatment.

As for the thickness of the thin nickel layer on the metal foil support, it is deposited along the rough surface shape of the metal foil support, and in order to cover most of this, a minimum thickness of about 0.1 μm is required. . If the film thickness is less than this, and if only the copper foil is etched after lamination using pressure and heat, the nickel layer remaining on the insulating resin substrate will have many defects, which means that the nickel layer remaining on the entire board will remain under pressure and heat. Since the area of the nickel adhesion part during lamination is small, sufficient adhesion strength of the metal layer cannot be obtained even if a metal layer is formed by plating on the nickel layer.

On the other hand, when a nickel layer with a thickness of 8 μm or more is formed on a metal foil support, the initial uneven shape on the metal foil support becomes flattened, resulting in a shape that does not have a casting effect, or the stress of the nickel layer It tends to be difficult to obtain adhesion to the insulating substrate because of the large thickness of the substrate.

For the above reasons, the thickness of the nickel layer on the metal foil support should be such that: ■ it should cover most of the rough surface shape on the metal foil support, ■ it could maintain the rough surface shape of the metal foil support, and ■ it should be able to withstand stress. It is important that the condition of 1st class is satisfied, that is small.

For this purpose, a thickness of about 0.1 to 7 μm is good.

In particular, about 1 to 2 μm is desirable.

The thickness of the metal foil support used is not limited from a technical standpoint, but from the viewpoint of handling and price, it is 18 to 70 mm.
μm is good.

In order to enhance the adhesion between the insulating resin surface and the metal layer of the metal thin layered laminate produced according to the present invention, the surface of the metal foil support used is roughened in advance so as to have fine irregularities. Methods for roughening the surface include polishing, honing, etching, and electrolytic or electroless deposition. Good one
An example is steel foil for tRffi-strung laminates.

No particular pretreatment is required for forming the nickel layer, but in order to ensure that the nickel layer is formed uniformly, the metal foil support should be degreased, washed, or treated with an aqueous hydrochloric acid solution or an aqueous sulfuric acid solution before use. is desirable. After forming a nickel layer on the surface of the metal foil support, the insulating organic materials that are laminated are phenol, epoxy, and modified polyimide.

Thermosetting resins such as polyimide are used.

These resins are also used in the form of prepreg attached to paper base materials or glass fiber cloth materials. Also used are thermoplastic materials such as polyethylene, Teflon, polyethersulfone, polyetherimide, and the like. After the metal foil support on which the nickel layer has been formed and the insulating organic material are laminated under pressure and heat, in order to remove only the metal foil support from the substrate, a selective etching solution that etches only the metal foil support is used. used. An example of such an etching solution is:

If the metal foil support is copper, use an alkaline etching solution commonly used in the solder etching method (a method of etching copper using solder as an etching resist to form two circuits), which is one of the methods for manufacturing printed wiring boards. (The main ingredient is ammonia, and NaC is used as an oxidizing agent.)
120t, which contains NH4HCCh etc. as a pH buffering agent).

An insulating resin substrate with a thin nickel layer made by etching only the metal foil support can be used as it is as a laminate with an ultra-thin metal foil.

The metal foil can also be made into a desired thickness by electroless plating or electroplating. This surface does not require any special pretreatment for electroless plating or electroplating;
Reduction of the oxide layer to metal by immersion in a reducing solution facilitates subsequent metal deposition by electroless plating or electroplating.

Moreover, stronger adhesion between the nickel layer and the plating metal can be obtained.

Electroless plating is electroless nickel plating.

Electroless copper plating is used. Generally, electroless copper plating is used. Regarding electroplating, electrolytic copper plating is also generally used.

Note that if heat treatment is performed at 160° C. for about 90 minutes after plating, the adhesion between the nickel layer and the plating metal will be strengthened, and a decrease in the peel strength of the plating metal due to peeling at this interface can be prevented.

(Function) A nickel layer formed by electroless nickel plating on the surface of a metal foil support such as W4 foil, which has a rough surface with fine irregularities, forms a uniform film along the rough surface shape of the metal foil support. Formed in thickness. Therefore, after laminating the metal foil support on which the nickel layer has been formed and the resin, only the metal foil support is etched away, and a thin layer of nickel is transferred onto the surface of the substrate at the same time as the uneven shape of the metal foil support. . In addition,
This thin nickel layer is the part where the resin and metal come into close contact during pressure and heating lamination, and it is important to leave this part when etching the metal foil support. The reason for this is that this thin layer of nickel not only serves as a catalyst nucleus for the subsequent steps (1) electroless plating, (2) a base metal layer for electroplating, but also (2).

This is because the close contact between the metal layer formed by plating and the resin as in (2) acts as a kind of adhesive layer that provides a strength comparable to that during heat-pressure lamination.

Therefore, if a circuit is formed by plating a metal layer to a desired thickness on this thin nickel layer by electroless plating, electroplating, or a combination thereof, a printed wiring board with high adhesion to the plated metal can be obtained.

Example Using 18 μm w4 foil for copper foil-clad laminates made by Nippon Denki,
A nickel layer was formed on the surface of the copper foil. The nickel layer forming treatment conditions are as follows.

Electroless nickel plating solution: Schumer 5B-55-1 manufactured by Nippon Kanigen Bath temperature: 80 to 85°C Time: 10 minutes (approximately 1 μm) for nickel layer formation As a pretreatment, the copper foil was immersed in Neutral Clean, a degreasing liquid manufactured by Sisoplay Co., Ltd., for 5 minutes, rinsed with running water, further immersed in 10% sulfuric acid water for 2 minutes, and rinsed with running water. After forming the nickel layer, it was washed with running water and dried at 80° C. for 30 minutes. Next, it was laminated with a glass-containing epoxy prepreg (Prepreg E-67 manufactured by Hitachi Chemical Co., Ltd.) under pressure and heat. The lamination conditions are a molding pressure of 80 kg/aa and a temperature of 177°C.
It is a minute.

Next, only the copper was removed by etching using an alkaline etching solution.

The etching conditions are as follows.

Alkaline etching liquid: Polyvalent ammonium type Liquid temperature...R,T.

Time: After washing with water for 20 to 30 minutes, the oxide layer on the nickel surface was reduced under the following conditions in order to easily start the electroless plating reaction.

DMAB ・・・・・・5g/β NaOH-5g/l Liquid temperature: 55℃ Time: 2 minutes Next, electroless copper plating was performed using the following composition and conditions.

Cu5Oa・5Hz○−=40g/ItEDTA・4
Na...--40g#p)l
・・・・・・12.337%CH2O・・・・・・3
/1 Plating solution additive: Small amount Plating solution temperature: 70°C Plating was carried out until the electroless copper plating had a film thickness of 35 μm. Further, electrolytic copper plating was also performed to a thickness of 35 μm.

After this, heat treatment was performed at 160℃ for 90 minutes, and w4 was applied before and after that.
As a result of examining the foil peel strength, it was 1.5 k before heat treatment.
g/cm, but after heat treatment it decreased to 2.3 kg/cm.
The stripping width of the copper foil was 10 cm, and the stripping speed was 50 fins/min.

The reason why there is a difference in peel strength of copper foil is that the one before heat treatment peels off at the interface between the nickel layer and the plated copper, while the one after heat treatment peels off.

This is because the nickel layer and resin peel off at the interface. That is, this is because the heat treatment strengthened the adhesion between the hoxin nickel layer and the plated copper.

Comparative Example The copper foil manufactured by Nippon Denki Co., Ltd. used in the example was laminated using the prepreg used in the example under the same lamination conditions as in the example. The plating film thickness was 35 μm using an electroless copper plating solution with the same composition as in the example.
Plating was performed until . In this case, due to the low adhesive strength, the plated copper foil peeled off from the substrate during the plating time, making it impossible to measure the 9w4 foil peel strength.

(Effect of the invention) According to the present invention, it is heat resistant and has excellent insulation properties.

Printed wiring boards with high adhesion to plated metal can be manufactured.

Agent Patent Attorney Akira Hirose ingredient

Claims (1)

[Claims] 1. By forming a thin nickel layer on the rough surface of a metal foil support having a rough surface, integrating the nickel thin layer surface with an insulating organic material, and bringing it into contact with an etching solution that selectively etches the metal foil support. removing the metal foil support leaving a thin layer of nickel on the insulating organic material;
A method for manufacturing a printed wiring board, characterized by performing circuit processing including a step of plating conductive metal on the surface to a desired thickness.