JPS59114893A - Method of forming insulating film of metal core printed 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 relates to a method for forming an insulating film on a metal core printed circuit board.
In particular, a two-stage drill is used to drill a through hole in the board, the edges of the hole are rounded at the same time, and then an insulating film of uniform thickness is formed on the inner wall of the through hole using electrostatic coating or electrodeposition coating. Regarding a method for forming an insulating film on a metal-core printed circuit board, metal-core printed circuit boards are generally provided with through-holes in order to facilitate the wiring between three layers and the attachment of components, and to connect a large number of components at the same time. This through hole is made by drilling a straight hole in a material plate of copper, aluminum, iron, etc. with a drill or press punch, and then chamfering the entrance and exit sides of the hole with a 90 degree conical drill! After that, an insulating film is formed on the inner wall of the through hole and the surface of the material plate by electrostatic coating or electrodeposition coating. FIG. 1 shows a vertical cross section of a through hole manufactured in this way.A straight through hole 2 is bored in a printed circuit board 1, and the edges of the through hole 2 on the entrance and exit sides. Chamfered part 3
is formed, and an insulating film 4 is formed on the front and back surfaces of the printed circuit board 1 including the chamfered portion 3.0 In this method of forming an insulating film on a through hole formed by a conventional manufacturing method, As is clear from a careful look at FIG. 1, there was a problem in that the insulating film at the edge portions on the inlet and outlet sides of the chamfered portion 3 became thinner. As a result, electrical insulation properties deteriorate, causing a reduction in product reliability.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for forming an insulating film on a metal-core printed circuit board, which makes it possible to form an insulating film with a uniform thickness including the inner wall surface of a through hole drilled in a printed circuit board. be.

In order to achieve the above object, the present invention simultaneously forms a straight through hole and a rounded part at the edge of the through hole on a printed circuit board, and forms an insulating film of uniform thickness on the inner wall of the hole. It is characterized by the fact that it is made to do so.

Embodiments of the method for forming an insulating film on a metal-core printed circuit board according to the present invention will be described below with reference to FIGS. 2 and 3.

Figures 2(a) and 2(c) show the process of simultaneously forming the through hole 2 and the chamfered part 3 on the printed circuit board 1. Part 3
is formed using a two-stage drill 5. This two-stage drill 5 is a type of general drill, and is composed of a drilling drill 6 for drilling the through hole 2 and a chamfering tool 7 for forming the chamfered portion 3. The drilling drill 6 is a drill whose diameter is equal to the diameter of the pilot hole of the through hole 2, and has two twisted grooves formed in its body and a pair of cutting edges at its tip. The length of the body of the drill 6 may be slightly longer than the thickness of the printed circuit board 1 to be drilled. Further, the chamfering tool 7 has a diameter nearly twice the diameter of the above-mentioned drilling drill 6, and the boundary between the drilling drill 6 and the chamfering tool 7 is a tool end face 8 that is perpendicular to the axis.

A chamfered portion 9 is formed between this tool end face 8 and the root of the drilling drill 6, and this chamfered portion 9 is formed in advance to be equal to the radius r of the roundness of the chamfered portion. has been done.

To perform processing using the two-stage drill 5 configured as described above, the center of the drill is aligned with the location of the printed circuit board 1 to be drilled (see FIG. 2(a)). Next, as shown in FIG.
After penetrating the hole, when the drilling drill 6 is sent forward, the chamfering section 9 finally chamfers the edge of the previously drilled through hole 2. As a result of this chamfering, the through hole A rounded chamfered portion is formed on the hole edge.

After that, after pulling the two-stage drill 5 upward and pulling it out from the through hole, the printed circuit board 1 is turned over, and the drilling drill 6 is introduced from the opposite side of the through hole 2 that was previously drilled, and the surface is A recess 3 is formed. In this way, rounded chamfered portions 3 are formed on the hole edges on both the entrance and exit sides of the through hole 2.Next, the front and back surfaces of the printed circuit board 1 configured in this way are formed. An insulating film 4 made of, for example, polyester resin is formed on the inner wall surface of the through hole 2. The insulating film 4 may be formed by electrostatic coating or electrodeposition coating.

FIG. 3 shows a cross-section including the through-holes of the product obtained in this way. A rounded chamfered portion 3.3 is formed, and an insulating film having a uniform thickness is formed on the chamfered portions 3,3.

As described above, according to the present invention, a two-stage drill with a rounded chamfered portion at the boundary is produced by combining a drilling drill with a diameter equal to the diameter of the through hole to be drilled and a chamfering tool. Since the through-hole and rounded chamfer are processed at the same time using this method, it is possible to form an insulating film with a uniform thickness on the edge of the through-hole, improving the reliability of electrical insulation. can. Additionally, since through-hole drilling and chamfering can be performed simultaneously, the work process can be shortened and manufacturing costs can be reduced.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view showing the through holes and insulating film of a conventional printed circuit board, and Figures 2 (a), (b), and (c) are process diagrams showing the processing steps for through holes and chamfered parts on the printed circuit board. , FIG. 3 is a longitudinal sectional view showing through holes and an insulating film of a printed circuit board manufactured according to the present invention. 1... Printed circuit board, 2... Through hole, 3...
・Chamfered part

Claims (1)

[Claims] 1. A through-hole that is straight to the printed circuit board and a rounded chamfered portion on the edge of the through-hole are formed at the same time, and an insulating film of uniform thickness is formed on the inner wall of the hole. 1. A method for forming an insulating film on a metal-core printed circuit board. 2. In the method for forming an insulating film on a metal-core printed circuit board as set forth in claim 1, the insulating film is formed by electrostatic coating. Method 03, as set forth in claim 1. Method 0 of forming an insulating film on a metal-core printed circuit board, characterized in that the insulating film is formed by electrodeposition coating.