JPS6314516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for insulating holes in a printed wiring board using a metallic substrate whose surface layer is insulated to form a conductor pattern, and its purpose is to insulate the holes in the printed wiring board. To efficiently insulate the wall surface of a through hole provided in a plate.

In general, a metallic substrate with an insulating surface layer is called a metal core, and a conductive pattern is formed on the insulating surface layer to be used as a printed wiring board. By the way, when using the metal core described above as a printed wiring board, it is necessary to form through-holes for forming through-hole connections and through-holes for mounting parts into which lead wires of electrical parts are inserted. Since metal is exposed on the wall of the through hole, the wall surface of the through hole must be insulated. Known techniques for insulating the walls of such through holes include electrophoresis, powder resin stamping, and the like. However, in the conventional method described above, the amount of the insulating resin layer attached to the wall surface of the through hole is not constant, and the insulating resin layer becomes thin, especially at the edges of the through hole, and the underlying metallic substrate is exposed. There were many problems, and it was difficult to achieve reliable insulation.

The present invention solves these conventional drawbacks, and the present invention will be described below with reference to drawings of embodiments.

Example 1 First, as shown in FIG.
metal substrate 5 with through holes 7 formed at appropriate locations.
was prepared as a printed wiring board 8, and a printing mask 2 in which stepped holes 1 were formed at locations corresponding to the through holes 7 of the printed wiring board 8 was prepared. Then, the printing mask 2 is opposed to one surface of the printed wiring board 8, and the insulating paint 4 placed on the surface of the printing mask 2 is moved with the squeegee 3 in the direction of the arrow A shown in FIG. As shown, the insulating paint 4 was embedded and applied in the through holes 7 of the printed wiring board 8 in a stopper shape. Next, the above-mentioned printed wiring board 8 is formed by curing the grommet-shaped insulating paint 4 embedded in a heating furnace.
pin 9 in the uncured state as shown in Figure 3.
A through hole 10 is formed by poking it with a hand. In this way, as shown in FIG. 4, the embedded insulating paint 4 is formed in a grommet shape from the through hole 7 of the printed wiring board 8 to the front and back surfaces of the printed wiring board 8, and the through hole The hole wall surface and edge portion of No. 7 can be effectively insulated. Here, as insulation paint 4, No. 810 manufactured by Shell Co., Ltd., to which tertiary amine was added as a hardening agent, and the viscosity was adjusted to 130 centipoise with butyl acetate, was used. Further, as the printing mask 2, a copper plate having a thickness of 0.2 mm and having a step of 0.1 mm was used, and the diameters of the stepped holes were 2.5 mm and 1.4 mm, respectively. Also,
Thickness when both front and back layers are insulated as printed wiring board 8
A 0.5 mm aluminum plate with a through hole 7 of 0.8 mm in diameter was used. Then, the printed wiring board 8
The distance between the mask 2 and the printing mask 2 was 0.25 mm, the angle of the squeegee 3 was 60 degrees, and printing was performed at a speed of 15 cm per second. In printing under such conditions, the insulating paint 4 is simultaneously formed on the insulating surface 6 of the printed wiring board 8 and the through-holes 7, and the insulating paint 4 in the through-holes 7 has its own wettability. Then, it spreads to the insulating back surface 6 of the printed wiring board 8, and as a result, the through hole 7 is closed and embedded in the shape of an eyelet. Thereafter, the insulating paint 4 was air-dried, a hole was formed by piercing with a pin having a diameter of 0.4 mm, and the paint was cured at 150° C. for 30 minutes.

Example 2 Insulating paint 4 was made of glass powder (2 to 10 percent), phenolic resin, and solvent (butyl carbitol acetate) and had a viscosity of 140 centipoise, and was printed using the same printing procedure as in Example 1 to a thickness of 0.2 centipoise. Embedded printing was done on a printed wiring board using mm steel plate. After printing, it was burned in an oven at 500°C for 30 minutes. Note that at this time, the resin component of the insulating paint 4 scatters and disappears.

The material for the mask may be metal, wood, resin/rubber plates, paper, film, etc., but iron, stainless steel, copper, etc. can be etched from both sides using the photo-etching method to form stepped holes. It is also possible to make the steps sloped rather than at right angles. It is also possible to use the mask as a flat printing mask for general resist-in 7.

Insulating surfaces of printed wiring boards are also available such as paper-based phenolic resin laminates, paper-based epoxy resin laminates, glass cloth-based epoxy resin laminates, glass matt epoxy resin laminates, glass matt unsaturated polyester resin laminates, Resin-impregnated multilayer board of glass cloth or paper,
Glass plates, alumina porcelain plates, forsterite porcelain plates, mullite porcelain plates, etc. may be pasted.
Of course, polyimide can be used as a plastic film board.
Polyester, polyimide amide, polysulfonimidazole, etc. may be used, and silicone rubber, polybutadiene rubber, acrylonitrile rubber, etc. may be used as the rubber plate. especially,
It is effective for insulating holes in metal plates and metal films made of materials such as iron, aluminum, copper, nickel, stainless steel, and zinc.

The resin paint used consists of inorganic or organic solids and some solvent. Resin-based ones
It cures and adheres to printed wiring boards at temperatures below 350℃.
Glass powder, a typical inorganic type, is baked and bonded to an inorganic wiring board at temperatures above 350°C, and if resin is mixed with glass powder, the resin will burn and scatter. It is important to volatilize the solvent before curing or baking the insulating paint to prevent voids and pinholes from forming and to stabilize the shape, and butyl acetate, butyl carbitol acetate, etc. are often used. . It is also possible to use a solvent-free gel-like resin, and it is also possible to measure adhesion by photocuring using a photocurable resin.

As described above, the present invention can insulate the through-hole portion of a metallic substrate whose surface layer is made into an insulating surface by one printing and curing process.

[Brief explanation of the drawing]

The drawings show an embodiment of the hole insulating method of the present invention, FIGS. 1 and 2 are diagrams for explaining the insulating paint application process in the method, and FIG. 3 shows the through hole formation in the same method. Diagrams to explain the process,
FIG. 4 is an enlarged view of the main part. 1...Stepped hole, 2...Printing mask, 3...Squeegee, 4...Insulating paint, 5...Metallic substrate, 6...Insulating surface, 7...Through hole, 8...Printed wiring board , 9... pin, 10... through hole.

Claims (1)

[Claims] 1. A printing mask with stepped holes is placed opposite a printed wiring board with through holes formed on a metallic substrate whose surface layer is an insulating surface, and the insulating paint placed on the surface of the printing mask is printed once with a squeegee. Then, the insulating paint is cured and a through hole is formed before curing, so that the wall surface of the through hole is printed in a grommet shape with a through hole. A method for insulating holes in printed wiring boards, which is characterized by insulating them with insulating paint.