JPS5884495A - Method of producing metal core printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has excellent economic efficiency, mechanical strength, high temperature durability,
The present invention relates to a method for manufacturing a printed wiring board with good adhesion.

Conventionally, commonly used printed wiring boards are insulating laminates made of composites of organic base materials such as phenol resins and epoxy resins and glass fibers. However, with the recent development of electronic devices, the printed wiring boards used are also required to have higher density, mechanical strength, and lower cost. For this reason, various methods of manufacturing printed wiring boards have been developed, ranging from the conventional method of manufacturing using copper-clad laminates to forming an organic insulating layer of epoxy or polyester on an inexpensive iron plate. Attempts have been made to form conductive circuits thereon. However, printed wiring boards in which conductive circuits are formed by direct electroless plating or electrolytic plating on an epoxy or polyester organic insulating layer have poor adhesion between the organic insulating layer and the conductive circuit, so it is difficult to assemble electronic devices during the electronic device assembly process. The molten soldering method has serious drawbacks such as poor high-temperature durability and an extremely high rate of defective products when connecting parts, so it is hardly ever put into practical use.

The adhesive strength of circuits on printed wiring boards is 1.2 to 1.4 Kg/cm, as specified in the Japanese Industrial Standards.
Although the above is said to be durable for practical use, the adhesion strength of conductor circuits that are directly electroless plated or electrolytically plated on conventional organic insulating layers such as epoxy resin or polyester resin is 0.1 to 0.
．． 3 Kg/cm, which is a technical limitation that makes it impossible to put it into practical use. Therefore, as an organic insulating material, the metal that is formed as a conductor circuit by electroless plating and electrolytic plating must be tightly adhered. To maintain adhesive strength without deteriorating itself at the high temperature of 260°C in the molten soldering method. Properties such as good plating properties are required.

Therefore, the present inventor coated a metal plate with an organic powder made of nitrile rubber and phenol resin as an insulating material to insulate the metal plate, and then formed a conductive circuit on it to improve adhesive strength and solderability. We have developed a metal core printed wiring board with excellent heat resistance.

The method of the present invention will be explained in detail with reference to the drawings below.
Figure 6 is a cross-sectional view of the manufacturing process of a metal-core printed wiring board. After opening a through hole 2 in the metal plate 1, as shown in Figure 2, the surface of the metal plate 1 is made of nitrile rubber and phenolic resin. An insulating layer 3 was formed by coating the powder, and the metal plate was used as an electrical insulating plate. In order to coat a metal plate with an organic substance made of nitrile rubber and phenolic resin and use it as an insulating material, the following conditions must be met to some extent.

Thick film coating is possible. Good adhesion to metal plates (iron, aluminum). The coating must be in good condition. Therefore, since it would be difficult to form an insulating layer by coating with a thickness of 100 microns or more using a solution type, the nitrile rubber and phenol resin were powdered and then electrostatic powder coating was performed to insulate.

As a nitrile rubber, it has a low acrylonitrile content.
All nitrile rubbers from so-called low nitrile rubber to high nitrile rubber can be used.

The phenol resin is a resol type or novolak type phenol resin obtained by the reaction of phenols such as P-phenol, phenylphenol, butylphenol, and formaldehyde.

To obtain the nitrile rubber-phenol resin powder, nitrile rubber is kneaded using cold rolls, and 130 parts of the phenol resin and 10 parts of fine sandstone powder are added to 70 parts of the nitrile rubber and thoroughly kneaded. The thus-produced mixed material is cooled in a freon gas cooling device, and then ground to a fine powder, and further 10 parts of phenol resin powder is added to prevent blocking.

The film thickness in electrostatic powder coating of the above powder varies depending on the discharge amount, spraying time, and voltage, but in general, a thickness of 100 to 200μ is easy, and a thickness of 300 to 40μ is possible by preheating the metal plate.
A coating film of 00μ is obtained.

Therefore, no preheating is required for a coating thickness of 100 microns.

Next, to prevent pinholes, after preheating at 80℃ for 10 minutes,
Baking is performed at 0°C for 20 minutes.

After baking, several micrometers of electroless plating 4 is applied to the surface of this insulating layer 3.
After forming, anti-corrosion ink 5 is applied as a coating material to prevent electroplating from depositing on areas other than the areas where conductor circuits are to be formed.

Next, as shown in FIG. 5, a circuit pattern 6 is formed by electrolytic plating, and then, as shown in FIG. This is a method for manufacturing a metal-core printed wiring board. This will be explained below using examples.

After degreasing, acrylonitrile content 35 tinonitrile rubber 70 parts, phenol 4ttJ] 140 parts 2) IJ rubber - phenol resin powder was electrostatically powder coated to form a 100μ insulating layer. An electrical insulation board was obtained. Next, the surface of the insulating layer was etched with a chromium-sulfuric acid solution, washed with water, sensitized with an aqueous solution of di-7-zoochloride-hydrochloric acid, activated with an aqueous palladium chloride-hydrochloric acid solution, and washed with water. Next, a plating layer with a thickness of about 0.3μ is formed by electroless nickel plating, and after washing and drying, the parts other than those that will become conductors are coated with anti-corrosion ink.
Then in a solution of 100 f/l silver pyrophosphate at 50°C2
A/drr? , electrolytic plating was carried out for 60 minutes,
A copper circuit pattern with a film thickness of 40 μm was formed. Next, the anti-corrosion ink was dissolved and removed using an organic solvent, and the electroless nickel plating film other than the circuit pattern area was removed using a phosphoric acid-hydrogen peroxide etching agent, resulting in an adhesive strength of 1.6 kg.
/cm, a metal core printed wiring board with high temperature durability of 260°C IO seconds or more and arc resistance of 135 seconds was obtained.

As described above in the Examples, the metal core printed wiring board manufactured by the present invention has high mechanical strength, excellent adhesive strength, and excellent heat resistance.

[Brief explanation of the drawing]

FIGS. 1 to 6 are cross-sectional views of the manufacturing process of the metal core printed wiring board of the present invention. 1......Metal plate 2...Through hole 3...
...Insulating layer 4... Electroless plating film 5...
・・・・・・・・・Corrosion-resistant ink 6・・・・・・・・・・
・・Electrolytic plating film size 1 Figure R-

Claims (1)

[Claims] A perforated metal plate is electrostatically powder coated with powder mainly composed of nitrile rubber and phenolic resin to create an electrically insulating plate, and then thick electroless plating or electroless plating is applied directly onto the plate. Is it possible to form a conductor circuit using electrolytic plating? : Characteristic manufacturing method of metal core printed wiring board