JPH10145032A - Printed circuit board for mounting electronic components - Google Patents

Abstract

(57) Abstract: When a large peeling stress is applied to an electronic component fixed to a printed circuit board for mounting an electronic component by soldering, the metal thin film pattern is peeled off from the supporting substrate. Make sure you don't have to. A metal thin film pattern is formed on a support substrate, and a peripheral edge of the pattern is covered with a solder resist film. By preventing the metal from reaching the periphery, even if a large peeling stress is applied to the electronic component fixed by soldering, only a small peeling stress is applied to the periphery of the pattern, whereby the metal The peeling of the thin film pattern 2 from the support substrate 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board for mounting electronic components used in electronic equipment, and more particularly, to a printed circuit board.
It is intended to improve a joint between an electronic component and a printed circuit board.

[0002]

2. Description of the Related Art Soldering is generally used as a joining means between an electronic component and a printed circuit board on which the electronic component is mounted. During this soldering operation, the molten solder reaches the periphery of the metal thin film pattern because the surface of the metal thin film forming the printed circuit has good wettability with respect to the solder. When a large peeling stress is applied to an electronic component soldered in this way by an improper operation, the electronic component peels with a thin metal film. As described above, the reason why the metal thin film is peeled off from the supporting substrate is that the peeling stress also reaches the peripheral portion of the metal thin film pattern, and that the adhesive force between the supporting substrate and the metal thin film causes the bonding between the metal thin film and solder. Weaker than the adhesive force between them. That is, the peeling stress is also applied to the peripheral edge of the metal thin film pattern via the solder, and as a result, the peripheral edge of the metal thin film pattern peels off from the supporting substrate, which is an opportunity. As a result, the entire soldered portion of the metal thin film is separated from the support substrate.

[0003]

As described above, when the metal thin film pattern is separated from the supporting substrate, the entire printed circuit board to which the electronic components are soldered becomes defective.
In order to exchange this for a good product, the cost of materials and man-hours for another vehicle are required.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic component mounting printing device having a structure in which even when a large peeling stress is applied to a soldered electronic component, the metal thin film pattern does not peel off from the supporting substrate. To provide a circuit board.

[0005]

In order to solve the above-mentioned problems, according to the present invention, a part or the whole of a peripheral portion of a metal thin film pattern is covered with a solder-resist film. Do not reach the edge of the metal thin film pattern. Thereby, the peeling stress applied to the periphery of the metal thin film pattern is significantly reduced, and as a result, the periphery of the metal thin film pattern does not peel off from the supporting substrate. Unless the peripheral edge of the metal thin film pattern is separated from the support substrate, the entire soldered portion of the metal thin film does not separate from the support substrate. Thus, the separation of the metal thin film from the support substrate is prevented. be able to.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.

FIGS. 1 (a) and 1 (b) are a plan view and a sectional view, respectively, of a portion of a printed circuit board for mounting electronic components according to an embodiment of the present invention where soldering is to be performed.
Shown in

The present invention does not differ from the prior art in that a metal thin film pattern and a solder resist film pattern are formed on a supporting substrate. A feature of the present invention different from the conventional one (see FIG. 3) is that the solder resist film 3 covers the periphery of the metal thin film pattern 2. The surface portion of the metal thin film pattern 2 which is not covered with the solder resist film 3 (the inside of the smallest square in FIG. 1A) is an area where soldering is to be performed. In the soldering process, the molten solder does not reach the periphery of the metal thin film pattern 2 due to the obstacle of the solder resist film because the resist film 3 surrounds the resist film 3.

The printed circuit board for mounting electronic parts according to the present invention shown in FIG. 1 can be used as it is by the conventional manufacturing process only by changing the design dimensions of the metal thin film pattern and the solder resist film pattern. , Can be manufactured.

FIG. 2A shows a state in which the electronic component 4 is fixed to the printed circuit board shown in FIG. 1 by solder 5, and FIG. 2B shows that the electronic component 4 has a large peeling stress. As a result, the electronic component 4 has been peeled off from the printed circuit board together with the solder 5. In this case, since the peripheral edge of the metal thin film pattern is away from the soldering area, it does not receive a large peeling stress and is reinforced by the solder resist film 3, so that the metal thin film pattern is reinforced. Does not create an opportunity to separate from the supporting substrate (peripheral separation from the supporting substrate). Since the peeling stress is applied to the periphery of the soldering area, if peeling occurs, it occurs between the metal thin film and the solder, as shown in FIG. 2 (b). Even if such peeling occurs, the printed circuit board is not damaged,
Complete repair is possible only by re-soldering.

FIGS. 3 (a) and 3 (b) are a plan view and a cross-sectional view, respectively, of a portion of a printed circuit board for mounting electronic components, which is one embodiment of the conventional method, where soldering is to be performed.
Shown in In this case, the periphery of the metal thin film pattern 2 is
Since it is not covered by the solder-resist film 3,
In the soldering process, the molten solder is
It reaches the periphery of ン 2.

FIG. 4A shows a state in which the electronic component 4 is fixed to the printed circuit board shown in FIG.
FIG. 4B shows a state in which a large peeling stress is applied to the electronic component 4 so that the electronic component 4 is peeled off from the printed circuit board together with the solder 5 and the metal thin film pattern 2. Is shown. As described above, in the soldering step, as shown in FIG. 4 (a), the molten solder removes the metal thin film pattern 2 without any obstacle due to the solder resist film.
Reaches the periphery of When a large peeling stress is applied to the electronic component 4 fixed to the printed circuit board in such a state, the peeling stress is also applied to the peripheral edge of the metal thin film pattern 2 via the solder 5, and as a result, As shown in FIG. 4 (b), the metal thin film on the periphery of the printed circuit board is peeled off from the supporting substrate, and the electronic component 4 is soldered together with the metal thin film pattern 2 as shown in FIG. Peel off from the board. Such damage to the printed circuit board is irreparable from a practical standpoint.

The adhesive strength between the support substrate and the metal thin film is
Since the bonding strength between the metal thin film and the solder is inferior, the peeling shown in FIG. 4B is the same as the peeling shown in FIG. Caused by smaller stresses. In other words, the implementation of the present invention increases the mechanical strength against peeling of the bond between the electronic component and the printed circuit board.

In the embodiment of the present invention illustrated in FIG. 1, the solder resist film 3 covers the entire periphery of the metal thin film pattern 2, which is essential for the effect of the present invention to appear. Not a condition. For example, only a peeling stress that is biased in one direction is applied to a small electronic component that is surrounded on three sides by a relatively large electronic component. In such a case, if only one side of the periphery (dotted square) of the metal thin film pattern shown in FIG. 1 is covered with the solder resist film, the effect of the present invention is sufficiently exhibited. .

The metal thin film pattern of the printed circuit board has a portion that only plays a role of conducting current, and it is not necessary to implement the present invention in that portion. However, in order to prevent corrosion of the metal thin film and save solder. In addition, it is desirable that the part including the edge part is covered with a solder resist.

[0016]

As described above, the present invention solves the above-mentioned problem of peeling of the metal thin film pattern of the printed circuit board for mounting electronic components, drastically reduces the number of repair steps, and reduces the material cost of component replacement. And at the same time, it is possible to supply a stable soldering pattern, secure an appropriate amount of solder supply, and secure a high soldering strength.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating the present invention.

FIG. 2 is a cross-sectional view illustrating an effect of the present invention.

FIG. 3 is a cross-sectional view illustrating a conventional technique.

FIG. 4 is a diagram for explaining a problem of the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Support substrate, 2 ... Metal thin film pattern, 3 ... Solder resist film, 4 ... Electronic components, 5 ... Solder, V ... Position of vertical cross section.

Claims (2)

[Claims] A metal thin film pattern formed on a supporting substrate;
A printed circuit board for mounting electronic components, wherein at least a part of a peripheral edge of the metal thin film pattern surrounding an area to be soldered on the metal thin film pattern is covered with a solder resist film. 2. The printed circuit board according to claim 1, wherein said metal thin film is a copper thin film.