JPS5952559B2 - Printed wiring board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a printed wiring board (hereinafter simply referred to as a board) that can create a complete printed wiring circuit board without soldering defects or short-circuit accidents between circuits, and in particular, a method for manufacturing a printed wiring board (hereinafter simply referred to as a board) using a solder resist. It relates to the method used.

FIG. 1 shows a conventional board 1, in which a copper foil 3 etched in a predetermined pattern is adhered to the surface of an insulating plate 2.

This predetermined pattern is formed of lands 4, which are portions for connecting conductor portions and component terminals provided for interconnection of electronic components and circuits.

A hole 5 is provided in the center of the land 4 for passing terminals of electronic components, lead wires for electrical connection, and the like. A lead wire, a leg 6 of an electronic component, etc. is inserted into the hole 5 of the substrate 1, and is fixed to the land 4 of the substrate 1 with molten solder for electrical connection.

However, when soldering is performed with dense patterns on the same plane, solder bridges 8 may occasionally form locally between adjacent conductors, resulting in a short circuit between circuits.

In addition, in order to prevent the above-mentioned accident, as well as to prevent the insulation between the circuits from deteriorating due to the adhesion of dust and moisture, and the corrosion of the copper foil 3, as shown in FIG. Leaving only the land 12 of the board 11 to be soldered,
A method is adopted in which the entire surface is covered with a solder resist film 13 and then immersed in molten solder.

Since this solder resist film 13 is required to be thick for its purpose, it has conventionally been formed by silk screen printing.

However, with the silk screen printing method, the image is distorted due to the expansion and contraction of the gauze used, and the printing position accuracy is poor.
As shown in the figure, the window hole 14 that should expose the land 12 in the solder resist film 13 is shifted from the land 12, resulting in defective soldering of components, or the gauze is clogged, causing the window hole 14 that should expose the land 12 to be removed from the board 1θ1. As shown in Figure 4, due to the nature of the solder resist paint, missing parts 15 may occur at the corners of the conductor where the filler cannot be completely filled, or air bubbles may occur during soldering. The solder resist may be torn due to the heat, leaving soldering marks! 5 became extremely unsightly.

The present invention relates to a method of manufacturing a substrate that eliminates the above-mentioned drawbacks, and will be specifically described below with reference to FIGS. 5 to 8.

FIG. 5 shows a substrate 21 etched in the same pattern as the substrate 1, in which 22 is an insulating plate, 23 is a copper foil,
24 is a land.

At the center of this land 24, a paint that repels the solder resist paint as a coating film and whose solvent is different from that of the solder resist paint (hereinafter referred to as an oil-repellent paint) is applied and dried to form an oil-repellent coating. A film 25 is formed.

As the oil-repellent paint, for example, linseed oil-based paint 85
% and 15% silicone oil can be used.

After application, by drying at 100°C for about 10 minutes,
An oil-repellent coating film 25 is formed. This method is preferably applied to a general offset printing method, which is different from the conventional screen printing for forming a solder resist film, and is preferably applied in Japanese Patent Application No. 54-157315 (Japanese Unexamined Patent Application Publication No. 56-119) filed by the present applicant.
No. 1 Intaglio printing plate and printing method", it is possible to easily print on the land 24 with good positional accuracy.

Next, when a solder resist paint is applied to the entire surface of the substrate 21 using a roll coater or the like and dried, the substrate 21 is coated with a solder resist film 26 as shown in FIG. 6, but it is not oil repellent. Only a portion of the coating film 25 is repelled to form a window hole 27. Thereafter, the mounting portion 24 is temporarily immersed in a solvent such as unleaded gasoline that does not dissolve the solder resist film 26 but dissolves the oil-repellent coating 25, and removes the oil-repellent coating 25 with a brush or the like. By drilling the mounting hole 28 in the center of the board, the window hole 27 is correctly positioned on the land 24 and the board 21 covered with the solder resist film 26 is obtained, as shown in FIGS. 7 and 8. .

As described above, in the method of the present invention, the easy-to-print oil-repellent coating film 25 is used to once cover the central part of the land 24 to form the window hole 27, so the printing position accuracy is good and the conventional Unlike the window hole 14 formed by silk screen printing, it does not shift from the land 12.

Furthermore, since the solder resist paint can be applied by roll coating or dip coating, no missing portions 15 or uneven coating as shown in FIG. 4 will occur.

Therefore, by using the board 21 manufactured by the method of the present invention, it is possible to create a high-quality printed wiring circuit board that is always free from accidents such as poor soldering and short circuits between circuits.

[Brief explanation of drawings]

Figure 1 is an enlarged plan view of the main parts of a conventional printed wiring board.
FIG. 2 is a sectional view taken along the line A-A in FIG. Figure 3 is a sectional view taken along the line B-B, and Figures 5 to 8 are for explaining the method of the present invention. An enlarged plan view, Fig. 6 is a sectional view corresponding to the line C-C in Fig. 5 of the printed wiring board coated with solder resist paint, and Fig. 7 shows the oleophobic coating removed and mounting holes drilled. FIG. 8, which corresponds to FIG. 6, is also a plan view. 1... Printed wiring board, 2... Insulating board, 3... Copper foil, 4... Land, 5...
...hole, 6 ... leg, 7 ... solder, 8 ... solder bridge, 11 ... board, ]2 ... ... Land, 13 ... Solder resist film, 14 ... Window hole, 15 ...
Missing part, 21... Board, 22... Insulating plate, 23... Copper foil, 24... Land,
25...Oil repellent coating film, 26...Solder resist film, 27...Window hole, 28...
- Hole.

Claims (1)

[Scope of Claims] 1. A coating film is formed by applying an oil-repellent coating film that repels the solder resist paint and in which the solvent of the coating film is different from the solvent of the solder resist paint to the land of a printed wiring board and drying it. Then, a solder resist paint is applied to the entire surface and dried, and after forming a window hole in the oil-repellent paint film, a solvent that dissolves only the oil-repellent paint film is applied. A method for manufacturing a printed wiring board, comprising the step of removing the coating film. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the oil-repellent paint comprises linseed oil-based oil-based ink and silicone oil.