JPH07147479A - Printed wiring board conductive foil - Google Patents

Abstract

PURPOSE:To prevent solder bridges from being produced by a method wherein a conductive foil provided onto a printed wiring board to solder the leads of an electronic part is formed into a teardrop shape, and the teardrop-shaped conductive foils are alternately arranged changing the position. CONSTITUTION:A conductive foil 1 used for soldering the leads of an electronic part is formed into a teardrop shape which has two opposed sides, a wide side 5A and a narrow side 5B, and the teardrop-shaped conductor foils 1 are alternately arranged on a printed wiring board changing position. The leads of an electronic part are soldered to the conductive foil 1 through a soldering gun method, a reflow process, or a flow process. As mentioned above, teardrop- shaped conductor foils are alternately arranged on a printed wiring board changing positions so that the wide side of the conductive foil where molten solder is concentrated is set distant from an adjacent conductive foil, and consequently a solder bridge can be prevented from being produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board,
In particular, it relates to a conductive foil provided for soldering leads of electronic components on the substrate.

[0002]

2. Description of the Related Art FIG. 7 is a plan view showing a conventional conductive foil. Conventionally, a conductive foil for soldering a lead of an electronic component having a plurality of protruding electrodes (hereinafter referred to as leads) has a width W1 and a width W2 at both ends which are equal (W1 = W2) as shown in FIG. It has a shape (hereinafter referred to as a straight shape). FIG. 8 shows a state in which the leads 2 of the electronic component having the leads 2 in the shape of gull wing are soldered to the straight conductive foil 1 without any problem.

[0003]

However, in the above conventional straight-shaped conductive foil, a bridge 4 in which the solder 3 crosses between the leads 2 is likely to occur as shown in FIG. 9, and especially the lead pitch (conductive foil pitch) is large. There is a problem that the narrower it is, the more likely it is to occur.

[0004]

In order to solve the above-mentioned problems, the conductive foil of the present invention has a conductive foil 1 attached to solder a lead 2 of an electronic component on a printed wiring board in a tear drop shape. The tear-drop shaped conductive foils 1 are alternately arranged.

[0005]

[Operation] When soldering the leads 2 of the electronic component to the conductive foil 1 having a teardrop shape, the solder 3 tries to move to the wider side of the conductive foil 1 due to the effect of surface tension. Therefore, by arranging the tear-drop-shaped conductive foils 1 in a staggered manner, a wide portion where the solder 2 is concentrated becomes far between the adjacent conductive foils 1, so that the occurrence of a bridge can be prevented and the reliability of soldering can be improved. Can be improved and the production cost can be reduced.

[0006]

1 is a plan view showing a first embodiment of the conductive foil of the present invention. In the first embodiment, the conductive foil 1 for soldering the leads 2 of the electronic component has a tear drop shape in which the width gradually narrows from one wide end 5A to the other narrow end 5B. The teardrop-shaped conductive foils 1 are alternately arranged on the printed wiring board. The operation will be described in the first embodiment having the above configuration. FIG. 2 is a plan view for explaining the operation of the first embodiment. When soldering to the conductive foil 1 having a teardrop shape, the solder 3 is a surface of the conductive foil 1 having a wider width, in this case, the wide end 5A.
Try to move in the direction of. This action has a width Wa at the wide end.
And the width Wb at the narrow end is larger, the larger the difference is. In the first place, one of the factors that causes the bridge is that the solder 3 is likely to concentrate on a certain part of the conductive foil 1. In the worst case,
The bridge is to occur. When the conductive foil has a straight shape, the solder is likely to concentrate on a part, and thus a bridge is likely to occur. By arranging the teardrop-shaped conductive foils 1 in an alternating manner as in the first embodiment, the conductive foils 1 adjacent to the wide end 5A side on which the solder 2 concentrates.
Since it is far from each other in the mutual diagram, the occurrence of the bridge can be prevented.

FIG. 3 is a plan view showing the second embodiment. This
In the second embodiment, the conductive foil 1 has one end 5A. ₁From the other end 5B₁Well
With a teardrop shape that gradually narrows at
It FIG. 4 is a plan view showing the third embodiment. This third real
In the example, the conductive foil 1 is gradually moved from the wide portion 5Aa to the narrow end 5B.
This is the case when the teardrop shape becomes narrower.
FIG. 5 is a plan view showing the fourth embodiment. This fourth embodiment
Is the conductive foil 1 with a step between the wide portion 5Aa and the narrow portion 5Bb.
This is the case when the teardrop shapes are connected. Figure 6
It is a top view showing a 5th example. This fifth embodiment is
The foil 1 is gradually narrowed from the wide end 5A, and the narrow portion 5 is formed.
This is a case where the teardrop shape is formed so as to be connected to Bb.
In any of the second to fifth embodiments, teardrop
By arranging the up-shaped conductive foils 1 alternately,
The operation is similar to that of the first embodiment.
And a method of soldering the leads 2 of the electronic component to the conductive foil 1.
Then, the soldering iron method, reflow method
Supply solder to electric foil, mount components, heat and solder
Method) and flow method (using molten solder liquid
For example, there is a method of contacting the soldered parts and soldering.
However, the present invention is effective in any case.

[0008]

As described above, according to the present invention, the conductive foil 1 attached on the printed wiring board for soldering the leads 2 of the electronic component has a tear-drop shape, and the conductive foil 1 has a tear-drop shape. Since the conductive foils 1 are alternately arranged, the occurrence of bridges can be prevented, the reliability of soldering can be improved, and the production cost can be reduced.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of a conductive foil of the present invention.

FIG. 2 is a plan view for explaining the operation of the first embodiment.

FIG. 3 is a plan view showing a second embodiment.

FIG. 4 is a plan view showing a third embodiment.

FIG. 5 is a plan view showing a fourth embodiment.

FIG. 6 is a plan view showing a fifth embodiment.

FIG. 7 is a plan view showing a conventional conductive foil.

8 is a perspective view showing a state in which leads of an electronic component are soldered to the conventional conductive foil shown in FIG. 7 without any problem.

FIG. 9 is a perspective view showing a case where a bridge is generated between the leads in FIG.

[Explanation of symbols]

1 Conductive Foil 2 Lead 3 Solder 4 Bridge 5A Wide End 5B Narrow End 5A ₁ One End 5B ₁ Other End 5Aa Wide Part 5Bb Narrow Part

Claims (1)

[Claims] 1. A printed wiring characterized in that a conductive foil attached to solder a lead of an electronic component on a printed wiring board has a teardrop shape, and the teardrop-shaped conductive foils are arranged alternately. Conductive foil for substrates.