JPH05308179A - Mounting method for surface mounting component - Google Patents

Abstract

PURPOSE:To enhance the soldering connection strength of a surface mounting component and to restrain an irregularity in the title mounting method. CONSTITUTION:A surface mounting component (SMD) recessed part 4A is formed in one part of a bonding face which is faced with a copper foil pattern 2 for an SMD 4; a solder film thickness 3A is decided by the depth of the SMD recessed part 4A. It is known that the solder film thickness (amount) 3A has a tendency indicating a certain critical value in which its connection strength indicates a maximum value. The depth of the SMD recessed part can be selected variously so that the proper strength of the title mounting method can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of mounting surface mount components, and more particularly to a method of mounting surface mount components for improving soldering strength.

[0002]

2. Description of the Related Art FIG. 3 is a cross-sectional view of an essential part showing an example of a mounting portion by a conventional mounting component mounting method.

As a mounting method, as shown in FIG. 3, first, an appropriate amount of solder 3 is applied onto a copper foil pattern 2 formed on a printed circuit board 1. The solder 3 is supplied onto the copper foil pattern 2 by screen printing, a dispenser method or the like in the form of a cream or a paste that is well mixed with the flux. Next, a surface mount device (surface mount device) (hereinafter, referred to as SMD) 4 is grasped by a collet of an automatic mounter or the like and pressed down from above the solder 3. Next, the SMD soldering mounting work is completed by heating and melting the solder 3 according to an appropriate temperature profile in a reflow furnace or the like.

[0004]

However, such a soldering method has the following problems.

That is, there is a large variation in the connection strength value in the solder connection strength test for evaluating the adhesive force between the SMD 4 and the printed circuit board 1. As a result of investigating the cause of such a variation in connection strength, the cause of the variation was a large variation in the coating layer of the solder 3. In general, it is known that the connection strength tends to have a maximum value with respect to the amount or thickness of the solder 3. As shown in FIG.
It is shown that the connection strength becomes small when the solder film thickness 3A is small or large. In the conventional mounting method of FIG. 3, it is very difficult to accurately control the solder film thickness 3A of the solder 3 after pressing the SMD 4. Rather, the solder rising part of solder 3 (generally called fillet) 3B
As a result of the survey, it was revealed that the connection strength was maintained to some extent.

An object of the present invention is to have a high solder connection strength,
It is to provide a mounting method of SMD without variation.

[0007]

The present invention provides a method of mounting a surface mount component on a copper foil pattern formed on a printed circuit board by soldering, wherein the copper of the surface mount component is A recess is provided in a part of the bonding surface facing the foil pattern, the recess is mounted so as to be in contact with the copper foil pattern via solder, and the thickness of the solder is controlled by the depth of the recess.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

1 (a) and 1 (b) are a fragmentary sectional view of a mounting portion according to a first embodiment of the present invention and a partially enlarged sectional view of an SMD recess thereof.

In the first embodiment, as shown in FIGS. 1A and 1B, an SMD 4 having an SMD recess 4A formed on a copper foil pattern 2 formed on a printed circuit board 1 is mounted. The SMD recess 4A is in contact with the copper foil pattern 2 via the solder 3 at a depth of 250 μm.

The mounting method is basically the same as the conventional SMD.
There is no difference from the implementation method of. First, an appropriate amount of solder 3 is applied to a predetermined position on the copper foil pattern 2 by a screen printing method or the like. Next, the SMD 4 is gripped by the collet and pressed down from above the solder 3. Copper foil pattern 2 pressed down with SMD4
The solder 3 applied on top is thinly stretched, but the solder film thickness 3A determined by the depth of the SMD concave portion 4A is maintained at a little over 250 μm. In such an SMD mounting method, the solder film thickness 3A can be partially thickened, and the connection strength can be controlled in the vicinity of the maximum value shown in FIG.

This is because the contribution ratio to the connection strength is SMD.
This is because the connection portion of the solder film thickness 3A formed by the concave portion 4A is the main part and the rising portion 3B is the subordinate part, and as a result, a great effect is brought about in improving the connection strength and suppressing variations.

FIG. 2 is a sectional view of a main portion of a mounting portion according to the second embodiment of the present invention.

In the second embodiment, as shown in FIG.
The SMD recessed portion 4B is characterized in that a plurality of D recessed portions 4B are provided, and the SMD recessed portion 4B is formed with a depth of 350 μm.

[0015]

As described above, according to the present invention, in order to accurately control the solder film thickness for soldering the SMD, the SMD concave portion is provided on the joint surface facing the copper foil pattern of the SMD, and the depth of the SMD concave portion is increased. The connection strength is maintained by the solder film thickness determined by the thickness. This SMD
Since the recesses can be accurately controlled at the stage of manufacturing the parts, it becomes possible to select the depth of the SMD recesses to a value at which the connection strength has a maximum value. In the conventional method, it is difficult to control the solder film thickness after pressing the SMD, and as a result, the solder connection strength varies.
According to the present invention, the addition of the SMD concave portion capable of controlling the solder film thickness has an effect that a surface mounting method capable of simultaneously improving the solder connection strength and suppressing variations can be obtained.

Although the present embodiment has been described assuming a chip resistor, a chip capacitor, etc., the metal IC of the flat IC is partially provided with a concave portion by the half etching technique so that the same as in the present embodiment. It can be easily analogized that the effect can be obtained, and the application range is wide.

[Brief description of drawings]

FIG. 1 is a fragmentary cross-sectional view of a mounting portion according to a first embodiment of the present invention and a partially enlarged cross-sectional view of an SMD concave portion thereof.

FIG. 2 is a sectional view of an essential part of a mounting portion according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of an essential part showing an example of a mounting portion by a conventional mounting component mounting method.

FIG. 4 is a characteristic diagram showing the relationship between solder film thickness and connection strength.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed circuit board 2 Copper foil pattern 3 Solder 3A Solder film thickness 3B Solder rising part 4 SMD 4A, 4B SMD recess

Claims (1)

[Claims] 1. A method of mounting a surface mount component, comprising mounting a surface mount component on a copper foil pattern formed on a printed circuit board by soldering, the method comprising: A surface-mounted component characterized in that a recess is provided in a part, the recess is mounted so as to be in contact with the copper foil pattern via solder, and the thickness of the solder is controlled by the depth of the recess. How to implement.