JPH0329831B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder-containing electrodeposition coating composition suitable for forming an insulating layer on the surface of a metal core in the production of a printed wiring board with a metal core.

A printed wiring board with a metal core has the surface of the metal core insulated to form a predetermined circuit.
It is characterized by mechanical strength and heat dissipation.

Various methods have been proposed for insulating the surface of a metal core, one of which is an electrodeposited insulating coating method.

Electrodeposition insulation coating has been widely used as a corrosion-resistant base coating for automobile bodies, and we have also proposed a new manufacturing technology for metal-core printed wiring boards by using this technology to insulate plate-shaped metal substrates with holes. (Special Publication No. 56-39076, Special Publication No. 55-24716, Japanese Patent Publication No. 54-13968, No. 53-111471, No. 53-111470, Special Publication No. 1984-8494). However, since these technologies are based on consideration of insulating metal parts, they are not compatible with other properties required for printed wiring boards, such as solder heat resistance and adhesion between conductors and insulating coatings. Appropriate solutions are not proposed for defective phenomena such as inferiority and blistering.

In order to provide adhesion between the insulating layer of the metal core and the circuit conductor, in conventional technology, after electrodeposition coating,
It was necessary to apply a nitrile rubber adhesive. Therefore, this method not only has the disadvantages of manufacturing costs and work environment due to the adhesive application process, but also has the disadvantage of making the hole diameter as large as about 1.2 mm, since it is extremely difficult to paint the hole to prevent it from clogging. I had no choice.

The present invention has been made in view of these points, and provides a powder-containing electrodeposition coating composition suitable for forming an insulating layer on the surface of a metal core of a printed wiring board with a metal core. It is something to do.

The powder-containing electrodeposition coating composition of the present invention consists of: A: a cationic synthetic resin that has been given water dilutability by partially neutralizing a basic resin containing nitrogen in its molecules with an acidic compound; B: at room temperature: It is characterized by containing C rubber, a synthetic resin fine powder that is solid and melts and hardens when heated.

Examples of basic resins containing nitrogen in the molecule include amino group-added epoxy resins obtained by addition-reacting organic amino compounds to epoxy groups in epoxy resins or epoxy-modified resins, acrylic esters and methacrylic esters having amino groups. , amino group-containing acrylic acid esters obtained from copolymers of nitrogen-containing acrylic or vinyl compounds such as vinylpyridines and vinylimidazole, and vinyl compounds having no free acid groups; Polymers, polyamide resins, etc. are used.

As acidic compounds that neutralize basic resins, hydrochloric acid, phosphoric acid, formic acid, acetic acid, propionic acid, citric acid, malic acid, tartaric acid, acrylic acid, etc. are useful, but other inorganic acids and organic acids can also be used. obtain.

Adding acidic compounds to the amino groups of basic resins
By adding 0.2 equivalents to 3 equivalents, preferably 0.5 equivalents to 1.5 equivalents and mixing thoroughly, a cationic synthetic resin imparted with water diluting performance can be obtained.

As the cationic synthetic resin, for example, an epoxy resin with an epoxy equivalent of 200 to 2400 and a primary or secondary
An adduct of a grade amine made water-soluble with an acidic compound is used.

Synthetic resins that are solid at room temperature and melt and harden when heated include epoxy resins, polyester resins, and acrylic resins. Powder particle size is 1~
20 μm is preferred. A synthetic resin fine powder that is solid at room temperature and melts and hardens when heated, with a particle size of 3 to 50 parts by weight, consisting of an epoxy resin with an epoxy equivalent of 400 to 2,400, a color vehicle consisting of 50 to 80 parts by weight of a hardening agent, and 50 to 20 parts by weight of a pigment. 15 μm is used.

The weight ratio of fine powder to cationic resin is 0.5 to 20:
1 is preferred.

As the rubber, styrene-butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR) are used.

The styrene-butadiene rubber preferably contains 20 to 40% by weight of a styrene component, and the acrylonitrile-butadiene rubber preferably contains 18 to 14% by weight of acrylonitrile groups.

The rubber is preferably added in an amount of 0.5 to 50 parts by weight when the total weight of the cationic synthetic resin and the synthetic resin fine powder is 100. The amount is preferably 1 to 10 parts by weight. If the amount of rubber added is less than 0.5 parts by weight, a sufficiently roughened surface will not be obtained when the electrodeposited coating is chemically roughened.
Furthermore, if the amount of rubber added exceeds 50 parts by weight, the thickness of the electrodeposited coating film obtained will be extremely thin, less than 10 μm.
Addition of ~10 parts by weight is optimal as a method for obtaining a coating thickness of around 100 μm.

The rubber is preferably added in the form of a latex to the cationic synthetic resin, synthetic resin fine powder, or aqueous dispersion thereof. It can also be kneaded into synthetic resin fine powder.

Powder-containing electrodeposition paint has a solid content of 5 to 20% by weight in water.
It is used in a distributed manner.

The metal core is a flat plate made of iron, aluminum, etc. that has a large number of through holes as necessary, and both sides of these metal plates are insulated in advance by a method such as laminating prepreg, and the ends of the flat plate are Metal is exposed only on the inner wall of the hole (if it has a through hole), or copper foil is laminated on the outside of the pre-formed surface insulation layer. . Preferably, the insulating layer previously formed on the metal substrate contains a component that can be chemically roughened by a strongly oxidizing treatment liquid such as CrO ₃ /H ₂ SO ₄ .

The electrodeposition conditions are preferably such that the cell voltage is 1 to 25V.

After forming an insulating layer of an electrocoating film on a metal core using the powder-containing electrocoating composition of the present invention,
After curing for 30 to 90 minutes, CrO ₃ /H ₂ SO ₄ mixture,
After chemical roughening with a mixture of Na ₂ Cr ₂ O ₃ /NaF/H ₂ SO ₄ , etc.
Circuit processing is performed by electroless plating or a combination of electroless plating and electroplating. In this case, circuit processing was easy, and the adhesion between the conductor and the electrodeposited insulating layer by electroless plating was excellent.

Further, the electrodeposition coating film made from the powder-containing electrodeposition coating composition according to the present invention has excellent flexibility and flexibility, and is resistant to cracking, and is suitable for coating metal surfaces subject to strong vibrations, such as automobiles, agricultural machinery, etc. Painting of metal surfaces with large heat shrinkage, such as guardrails, air conditioners, etc.
Furthermore, it is widely used in undercoating and intermediate coating to alleviate distortion caused by the difference in thermal shrinkage between the upper and lower coatings.

Example The following paints for forming an insulating film on a metal substrate were tested. (Parts are parts by weight) (1) Powder particles Epoxy resin Epicoat 1007 (Ciel Chemical) 400 parts Isocyanate curing agent EH-118-2 (Asahi Denka) 360 parts Pigment-1 Titanium R-80 (Ishihara Sangyo) 210 parts Pigment -2 0.5 part of Carbon MA-100 (Mitsubishi Kasei) was melted and kneaded using an extruder using a normal powder manufacturing method, and the average particle size was reduced using an impact crusher.
12.5μ powder coating particles were obtained.

(2) Water-dilutable cationic resin Epicote 1001 488 parts diethanolamine 105 parts isopropyl alcohol 250 parts were reacted under reflux at 80°C for 3 hours to obtain a liquid resin.

(3) NBR latex, 1562 (Nippon Zeon, medium nitrile), was added to water containing 1% by weight of Emulgen 920 (Kao Sekiken, nonionic surfactant) with stirring to make a 10% by weight aqueous solution of latex. I made it.

Add 38 parts of glacial acetic acid and 5105 parts of deionized water to 857 parts of the above cationic resin, stir thoroughly with a dissolver, then add 5400 parts of the above powder coating particles,
After mixing and dispersing for 30 minutes using a high-speed rotating homogenizer, the mixture was diluted with deionized water to a solid content of 20% to prepare 30,000 parts of a powder electrodeposition coating solution.

Further, 6000 parts of the latex solution (3) above was added to the above coating solution to prepare an electrodeposition coating.

The above paint was transferred to an electrodeposition tank, and a phosphoric acid-treated iron substrate (250 x 280 x 0.8 mm) with many holes of 1 mm in diameter was immersed as a deposit, with the Pt-Ti net serving as the cathode and the metal substrate serving as the anode. Electrodeposition was performed for about 30 seconds.

Electrodeposition conditions: Bath temperature: 22°C; electrode ratio: -○/+○=1/1; electrode spacing: 15cm; voltage: 20V; time: 30 seconds. After electrodeposition, the electrodeposition was washed with clean water, and then baked. Baking conditions are 80℃ x 10 minutes, then 200℃ from 80℃
The temperature was raised to ℃ over 15 minutes, and baking was further performed at 200℃ for 15 minutes. The resulting coating film had a uniform and beautiful appearance and a film thickness of 120 μm.

The withstand voltage is over 2.5kV, and CrO ₃ (100g),
When roughened for 15 minutes with a chemical roughening solution of H ₂ SO ₄ (300 g) at 50°C, a well-roughened surface was obtained. In addition, when electroless copper plating was applied to 1 μm and electrolytic copper plating was applied to 35 μm according to the conventional method, the conductor beer strength was 2.0 on the flat surface.
Kg/cm or more, and no blistering occurred after processing at 260°C for 60 seconds.

Claims (1)

[Scope of Claims] 1 A: A cationic synthetic resin that has water-dilutable properties by partially neutralizing a basic resin containing nitrogen in its molecules with an acidic compound; B: A solid at room temperature and melts when heated. A powder-containing electrodeposition coating composition containing a hardening synthetic resin fine powder and C rubber, wherein the rubber is 0.5 to 50 parts by weight based on 100 parts of the total weight of the cationic synthetic resin and the synthetic resin fine powder. 2. The powder-containing electrodeposition coating composition according to claim 1, wherein the rubber is in the form of latex. 3. The powder-containing electrodeposition coating composition according to claim 1 or 2, wherein the rubber is styrene-butadiene rubber or acrylonitrile-butadiene rubber.