JPS5814759B2 - Method for coating and forming a resin layer on a metal material substrate for printed wiring boards having through holes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coating and forming a resin layer simultaneously on the through-hole portions and flat portions of a metal material substrate for a printed wiring board having through-holes without clogging the through-holes.

As the density of electronic devices increases, the physical requirements for printed wiring boards, such as heat dissipation ability and rigidity that can withstand the mounting of a large number of important components, have increased, making it possible to replace conventional organic materials as substrates. Printed wiring boards made of metal materials are not fully satisfactory, so there is a trend towards printed wiring boards based on metal materials.

However, in printed wiring boards with metal cores, forming a resin layer such as an insulating layer on the metal core is an important issue.
When forming a resin layer on a metal material substrate for a printed wiring board having through holes, it is necessary to prevent the through holes from clogging.

For this purpose, attempts have been made to apply and form a resin layer using a spray gun, but this has not been put to practical use due to poor efficiency and uneven coating.

Moreover, other than this method, no effective coating method has yet been found.

The present invention has been made in view of these points, and involves applying a resin solution having a viscosity of 100 to 1000 centipoise to the through-hole portions and flat parts of a metal material substrate for printed wiring boards having through holes, and then horizontally holding the metal material substrate. While maintaining the angle of ±30°, the through-hole and flat surface can be removed by blowing air, vacuum suction, etc., onto the clogged through-hole to remove the resin solution that has clogged the through-hole. At the same time, a resin layer is applied and formed.

A suitable method for applying a resin solution to the through-hole portions and flat portions of the metal material substrate is a curtain flow coater method.

In the curtain flow coater method, a resin solution film is dropped vertically through slits at regular intervals, and a metal material substrate is moved horizontally to pass through the falling film to apply the resin solution.

Other coating methods include a dipping method and a spraying method, which can be appropriately selected depending on the purpose.

The resin solution used has a viscosity of 100 to 1000 centipoise.

If the viscosity is higher than 1000 centipoise, it will be difficult to remove the resin solution clogging the through-hole by blowing air or suction, and it will be difficult to remove the resin solution that has clogged the through-hole by blowing air or suction. This causes the inconvenience that it cannot be formed.

On the other hand, if it is lower than 100 centipoise, not only will the required resin thickness not be obtained, but the applied resin will flow violently, making it difficult to form a resin layer with a uniform thickness, and the resin will flow back into the through holes that have been unclogged. This is not desirable as it may cause problems.

When removing the resin solution from the through-holes that are clogged with resin solution by blowing or suctioning air such as air blowing or vacuum suction, hold the metal material substrate horizontally by ±3.
The reason for maintaining the temperature at 0° is to prevent the resin solution from flowing in one direction and making the resin layer non-uniform.

In the method of the present application, if an electrically insulating resin is used as the resin solution, an insulating layer can be easily applied and formed on a metal material substrate for a printed wiring board having through holes.
It can be suitably used when an adhesive layer is further formed on the insulating layer.

In other words, with the current electroless copper plating technology, it is not yet common to form a printed circuit directly on the insulating resin layer, and it is necessary to improve the adhesion and heat resistance between the electroless copper plating circuit layer and the insulating resin layer. If it is necessary to further provide an adhesive layer on the insulating resin layer, the adhesive layer can be formed by coating using the method of the present application.

Depending on the degree of adhesion and heat resistance, insulation can be improved at the same time.
Even when a resin that acts as an adhesive to the electroless copper plating layer can be used, the resin layer can be formed on the metal material substrate by the method of the present application.

The drawing is a cross-sectional view showing a state in which a resin solution is applied and formed on a metal material substrate having through holes by the method of the present invention, and FIG. It is formed by coating.

In FIG. 2, an adhesive layer 5 is further formed thereon by the method of the present invention.

The metal material substrate used in the present invention includes iron, aluminum, and alloys mainly composed of these materials, and has a thickness of 0.5
~3 mm, and the inner diameter of the through hole is 0.8~5 mm.

As the insulating layer, epoxy resin, phenol resin, polyester resin, polyamide resin, polyamideimide resin, polyimide resin, urea resin, melamine resin, vinyl chloride resin, fluororesin, polyacrylic acid ester resin,
For the adhesive layer, one type or mixture of polymethacrylic acid ester resin, etc., can be used as synthetic rubber such as NBR, SBR1 chlorobrene, chlorosulfonated polyethylene, natural rubber,
Rubber/phenolic resin, rubber/epoxy resin, polyacetal/phenolic resin, epoxy resin, etc. are used as a resin layer that has insulation properties and also acts as an adhesive. , epoxy resin/rubber types and mixtures are used.

Note that fillers such as calcium carbonate, silica, zinc white, titanium oxide, zirconium silicate, and curcum may be mixed into the above-mentioned insulating layer, adhesive layer, and resin layer having the characteristics of both.

As the solvent, one or a mixed solvent such as methyl ethyl ketone, acetone, methyl iributyl ketone, toluene, xylene, methanol ethanol, impropanol, methyl cellosolp, ethyl cellosolp, acetic acid sorosolve, ethyl acetate, dimethylformamide, etc. is used.

Example 1 1 of polyvinyl acemer resin (Eslec BH-4, manufactured by Sekisui Chemical Co., Ltd.) was added to a 60% methyl ethyl Katone solution of epoxy resin (Ebicoat 1001 manufactured by Ciel Chemical Co., Ltd. and curing agent).
Equal weights of 0% methyl ethyl ketone solution were mixed, and the mixture was further adjusted to about 600 centipoise using cellosol acetate.

Next, using a flow coater manufactured by Bürkle, West Germany, the solution was allowed to flow down in the form of a film by setting the slit width of the discharge die to 0.5 mm.

In this fluid coating film, diameters of 1.0 mm, 1.5 mm and 20
Thickness 1.mm with 100 holes each of 3 types of Surpol.
A 2 mm iron substrate was passed through the conveyor at a conveyor speed of 60 m/min, and the resin was coated on the flat surface of the substrate and inside the through holes.

In this case, the inside of the hole is clogged with resin, so immediately hold the board horizontally with the resin-coated surface on the surface.
Using a blower from below, the wind pressure is 10 mAg and the air volume is 10 m3/
Air was blown for 1 minute to eliminate clogging in the through holes and form a resin coating.

In this case, there was no resin clogging in each through hole, and the coating thickness on the flat surface after drying was about 35 μm.

In the same manner, a resin coating film was also formed on the back surface of the substrate and on the through-hole portions.

The thickness of the coating film on the inner wall of the through hole after drying was approximately 35 μm.

After these resin insulating layers were cured by heating, the dielectric breakdown voltage was measured and was found to be 2 KV or more.

In addition, when printed wiring was formed using electroless copper plating on a board with only these insulating resin layers, sufficient adhesion of the wiring could not be obtained, so an adhesive mainly composed of acrylonitrile buddiene rubber and phenolic resin was used. Agent 2
An adhesive layer was provided inside the through hole and on the insulating layer on the flat surface using a 5-functional methyl ethyl ketone solution (viscosity 600 centipoise) in the same manner as above, and the thickness of the adhesive on the inner wall of the through hole was approximately 30μ adhesive thickness on the flat surface. When printed wiring was then created using a known electroless copper plating method, the adhesive strength of the wiring was approximately 30μ, and the peel strength was 1. 8 kg/cm or more, through-hole pull-out strength is 5 kg or more, and 26 kg/cm or more.
No abnormal changes were observed even when the sample was left on a 0°C solder bath for 30 seconds or more.

Example 2 After forming an epoxy resin electrodeposition coating film by electrophoresis on an iron substrate with a thickness of 1.2 mm and a hole with a diameter of 1.2 to 3.0 +++ m (film thickness of 100 to 200 μm implemented) Example 1
6 adhesive solution with cellosol acetate/toluene mixed solvent.
Adjust the slit width to 0.00 centipoise. The substrate was passed through this falling solution model at a conveyor speed of 60 m/min, and the adhesive was applied to the surface of the substrate and the inside of the through hole in a state where it was clogged, and the substrate was immediately removed. The surface adhesive-applied surface was kept facing up and held horizontally, and air was blown from below using a blower at a pressure of 10 mA and a flow rate of 10 m3/min to eliminate adhesive clogging inside the through holes and form an adhesive coating.

In this case, there was no adhesive clogging in each through-hole, and the surface coating film thickness after drying was about 30 μm.

In the same way, an adhesive coating was formed on the back side of the board and inside the through holes.The thickness of the coating on the inner walls of the through holes after drying was approximately 3.
In this case, the dielectric breakdown voltage was around 1KV, but the adhesive properties of electroless copper plating printed wiring had a peel strength of 1.8kg/cm and a soldering heat resistance of 260℃ for 30 seconds or more. It was something.

As explained above, according to the present invention, a resin layer such as an insulating layer or an adhesive layer is applied to the through-hole portion and flat surface of a metal material substrate for a printed wiring board having a large number of through-holes without clogging the through-holes. Can be applied and formed at the same time.

[Brief explanation of the drawing]

The drawings are cross-sectional views of a metal material substrate in which a resin layer is formed on the flat surface and through-hole portions of the metal material substrate according to the present invention. , shows the case where an adhesive layer is further formed on the insulating layer. Explanation of symbols 1...Metal material substrate, 2...Through hole part, 3...Plane part, 4...Insulating layer, 5...Adhesive layer.

Claims (1)

[Claims] 1. Apply a resin solution with a viscosity of 100 to 1000 centipoise to the through-hole portion and flat surface of a metal material substrate for printed wiring boards having through holes, and hold the metal material substrate horizontally at an angle of +30°.
A resin layer is applied and formed on a metal material substrate for a printed wiring board having through-holes, which is characterized by removing the resin solution clogging the through-holes by blowing air or suctioning the clogged through-holes in a state where the through-holes are maintained at Method.