JPH04105578U - printed wiring board - Google Patents

Abstract

(57) [Summary] [Structure] The exposed portions of the conductive metal foil circuit patterns 3 and 4 provided on the front and back layers of the copper-clad wiring board 1 and the hole surfaces 5 of these exposed portions are selectively formed by the metal 6 that cannot be soldered. It is plated on. [Effect] Since the reinforcing copper foil pattern 3 and the grounding copper foil pattern 4 are plated with metals 6 and 6a that cannot be soldered, even if electronic components are mounted and flow soldering is performed, the grounding copper foil pattern 4 Solder icicles can be completely prevented from forming in the screw holes, eliminating the need to apply heat-resistant tape.
In addition, since nickel has higher hardness than copper, it can suppress the deformation of the copper foil when screwed, and by plating the inside of the hole, it also improves resistance to compressive force when screwed. . Furthermore, the surface of the copper foil is completely covered with a solder resist mask or a non-solderable metal 6a, so that it can be protected from corrosion.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to printed wiring boards, and in particular, mechanically fixes each electronic component to a housing. It relates to a printed wiring board that also functions as a chassis.

0002

[Conventional technology]

A conventional printed wiring board with a pattern that can be grounded by screwing it to the housing is shown in Figure 3. As shown in (a) to (c), the diameter is 2.8 to 4 m on the base material 1 of the printed wiring board. An opening with a diameter of 8 to 15 mm is provided around the screw hole 5 of A girder solder resist mask 2 and a grounding copper foil pattern 4 provided on the back side of the base material 1 and a reinforcing copper foil pattern 3 provided so that the head of the screw touches the top surface of the board 1. (Conventional Example 1)

0003 In addition, as shown in FIGS. 4(a) to 4(c), as a grounding copper foil pattern 4a, There is a conventional example 2 in which a non-copper foil portion of 0.2 to 0.5 mm is provided around the same hole 5. This servant The reason why the 0.2 to 0.5 mm non-copper foil part is provided in Example 2 is because it is for grounding across the screw hole 5. By keeping the distance between the copper foil patterns, the weight of the solder can prevent solder icicles. Aiming for results.

0004 When these printed wiring boards are mounted, the mounting portion will be as shown in FIG. 5. this In order to ground the printed wiring board to the housing 11, a washer 9 and a spring washer 8 were passed through the screw 7. After that, pass the screw 7 from the reinforcing copper foil pattern 3 side to the grounding copper foil pattern 4, 4a side. Then, install the protruding thread on the metal part on the side of the housing 11 and screw it into the female screw 10. . Here, the spring washer 8 may be omitted.

[0005]

[Problem that the idea aims to solve]

The grounding copper foil patterns 4, 4a of the printed wiring board described above have screw holes 5 connected to the printed wiring board. Since it also serves as a screw fastener, it becomes a soldering surface for mounting electronic components on printed wiring boards. Afterwards, the terminal leads will be flow soldered. In this case, firstly, copper Depending on the solder wetting characteristics, solder icicles 12 are created in the screw holes 5 as shown in Figure 6. There is a problem that the screws cannot be inserted. Also, secondly, this soldering Place heat-resistant tape over the holes, including the grounding copper foil patterns 4 and 4a, to prevent It is necessary to prevent the solder from touching the copper foil, which results in losses in terms of man-hours and costs. Become. Thirdly, a non-copper foil part of 0.2 to 0.5 mm is provided around the screw hole 5. Even if an attempt was made to improve by moving the ground copper foil patterns 4 and 4a away, experiments showed that It will not be completely soldered unless there is a non-copper foil part of 2 to 5 mm or more around the 4 mm diameter hole. It was not a countermeasure because it could not prevent icicles.

[0006] The purpose of this invention is to solve these problems and to provide printed wiring that can prevent solder icicles. The purpose is to provide a board.

[0007]

[Means to solve the problem]

The structure of the present invention consists of conductive metal foil circuit patterns provided on the front and back layers of a copper-clad wiring board. The exposed portion of the connector and the hole surface of this exposed portion may be selectively removed due to non-solderable metal. It is characterized by being plated with.

[0008]

【Example】

Figures 1(a), (b), and (c) are a partial top view, a sectional view, and a partial top view of an embodiment of the present invention. It is a bottom view. Around the screw hole 5 with a diameter of about 2.8 to 4.0 mm provided on the base material 1 Directly connect the reinforcing copper foil pattern 3 and the grounding copper foil pattern 4 as shown in the top and bottom views. Provided in a rectangular size with a diameter of 7 to 12 mm or a side of 7 to 12 mm, top view As shown in the bottom view, cover the parts you do not want to expose with solder resist mask 2. There is. Furthermore, as shown in the figure, there is a metal 6 that cannot be soldered on the exposed part. Electroless plating or electrolytic plating of nickel with a thickness of about 0.2 to 5 μm I'm going to do something. The thickness of this plating increases as the strength increases, but according to experiments. A thickness of about 2 μm is sufficient to prevent solder from getting wet, and a thickness of 5 μm or more is excessive. It is.

[0009] FIGS. 2(a), (b), and (c) are partial top views, sectional views, and cross-sectional views of the second embodiment of the present invention. and a bottom view. The difference in this embodiment compared to FIG. 1 is in the cross-sectional view. It is possible to solder up to the sides of the reinforcing copper foil pattern 3 and the grounding copper foil pattern 4. This point is covered with metal 6a.

0010

[Effect of the idea]

As explained above, the present invention has the following advantages: First, the reinforcement copper foil is made of metal that cannot be soldered. Because the pattern and grounding copper foil pattern are plated, it is possible to install electronic components on the floor. - Completely remove solder icicles from the screw holes of the grounding copper foil pattern even after soldering. This eliminates the need to apply heat-resistant tape. Also, compared to copper, nickel Because it has higher hardness, it can suppress the deformation of the copper foil when screwed. Also, by plating the inside of the hole, resistance to compressive force when screwed is improved. . Furthermore, the copper foil surface cannot be soldered using a solder resist mask or is completely metal. It is fully covered and can be protected from corrosion.

[Brief explanation of drawings]

FIG. 1 shows a top view, a sectional view, and a bottom view of an embodiment of the present invention.

FIG. 2 shows a top view, a sectional view, and a bottom view of a second embodiment of the present invention.

FIG. 3 is a top view, a sectional view, and a bottom view of a conventional printed wiring board.

FIG. 4 is a top view, a sectional view, and a bottom view of another conventional printed wiring board.

FIG. 5 is a cross-sectional view illustrating how a conventional reinforcing copper foil pattern and a grounding copper foil pattern are used.

FIG. 6 is a cross-sectional view of an example of a conventional solder icicle.

[Explanation of symbols]

1 Base material 2 Solder resist mask 3 Reinforcing copper foil pattern 4, 4a Grounding copper foil pattern 5 Screw holes 6, 6a Metal that cannot be soldered (on the grounding copper foil pattern) 7 Screw 8 Spring washer 9 Washer 10 Female thread 11 Housing 12 Solder icicles

Claims (1)

[Scope of utility model registration request] [Claim 1] The exposed portions of each conductive metal foil circuit pattern provided on the front and back layers of a copper-clad wiring board and the hole surfaces of these exposed portions are selectively plated with a metal that cannot be soldered. Characteristic printed wiring board.