JPS58205675A - Method for soldering with laser - Google Patents

Abstract

PURPOSE:To perform soldering which is free from soldering defects and high in reliability, by irradiating laser light transmitted from optical fibers whose exit side ends are bundled together upon a soldering part through a condenser lens. CONSTITUTION:Laser light 11 is split by a composite lens 13 and each split laser light 12 is transmitted through an optical fiber 10. Ends of the optical fibers 10 are bundled together so as to face to a condenser lens 9 and the transmitted laser light 12 is irradiated upon a soldering part through the condenser lens 9. At this time, a wire solder placed on the soldering part is instantaneously melted and drawn to a direction expressed by a lead wire 14 and a solder fillet 16 is formed. When the irradiation of the laser light 12 is stopped, the fillet 16 is cooled and solidified, and thus, the lead wire 14 is soldered to a terminal 15. When this method is applied, high quality soldering which is free from soldering defects, such as pinhole is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a laser soldering method, and more particularly to a method for preventing soldering defects due to non-uniformity of laser energy density.

[Technical background of the invention and its problems (Recently, as shown in FIG. The terminal (2) close to this lead wire 13) is fixed in contact with the
), place a piece of solder wire inside (4) on the top surface of (
After placing the condenser lens (5), as shown in Figure 2,
), the thread solder pieces (4) are melted to form a solder fillet (7), and the lead wire (3
) to the terminal (2).

However, the energy density in the cross section of the laser beam emitted from the condenser lens (5) is a Gaussian distribution with an extremely higher energy interval in the center than in the periphery, as shown by curve (8) in Figure 3. The situation is as follows. Therefore, only the center of the laser spot becomes high temperature, resulting in poor soldering, such as burning and carbonization of the FLA7/cus contained in the soldering thread, pinholes, and not properly formed solder fillets. This caused a significant loss in soldering reliability.

However, although various methods have been developed to make the laser energy density distribution uniform, all of them have the disadvantage of complicating and expensive equipment.

[Purpose of the Invention] The present invention has been made in consideration of the above circumstances, and provides a method for laser soldering that is highly reliable and does not cause defects using a relatively simple device. The purpose is to provide.

[Summary of the Invention] Laser beams transmitted by a plurality of optical fibers transmitted at the light output side end are irradiated onto the soldering area through a condensing lens, and a laser spot is focused on the soldering area. This is designed to flatten the energy density distribution.

[Embodiment of the Invention] Hereinafter, the present invention will be described in detail based on one embodiment with reference to the drawings.

4 to 6 show an embodiment of the present invention, in which two optical fibers (one end of 1■, ('1■ These two optical fibers αOf, (101 are arranged at one end thereof, so that their outer peripheral surfaces are in close contact with each other, and their end faces face the condenser lens (9). The other ends of the optical fibers fIl and tll divide and condense one laser beam 0υ into two laser beams α3 and +13, respectively, as shown in FIG. The laser beams nz and (tz) are arranged on the end faces of the light-emitting compound lens f13 at the condensing position on the light output side thereof. A laser source (not shown) is provided to irradiate the light.Furthermore, on the light output side of the condenser lens (9), a copper lead wire α4 to be laser soldered is connected to a terminal α9 also made of steel. and is fixed in contact with the surface.

Furthermore, although not shown, similar to FIG.
(within the laser spot area), a plurality of solder threads are placed.

In such a configuration, the laser beam (11!) emitted from the laser source is divided into two laser beams α3. 1 and z are optical fibers 0I and α[
transmitted inside. Thus, the laser beams 1'2 . na is the condenser lens (9
) through 4), the soldering area is irradiated. Then, the solder wire instantaneously heats up to a high temperature and melts into contact with the lead wire 11.
The surface tension of the smear draws the lead wire in the side direction, forming a solder fillet [L[j].
is fixed to terminal a9 by soldering. At this time, the energy density curve of the soldering part irradiated with the laser beam (see Figure 6) shows that the energy density curve (see Figure 6) shows an extreme value at the center (no high peak value exists and becomes flat), and the energy density curve at the center of the laser spot Energy concentration is alleviated. Therefore,
At the center of the laser spot, the temperature does not rise excessively, and the temperature distribution becomes uniform over the entire laser spot. As a result, the flux contained in the solder wire will not be carbonized and solder defects such as pinholes will not occur, making it possible to achieve highly reliable soldering. Although the number of optical fibers shown in FIG. 7 is two, the number may be increased as necessary, for example, as three optical fibers are bundled in FIG. 7.

Furthermore, in the above embodiment, two optical fibers l'
The ends facing the condensing lens of lI, 01 are tied together so that their outer peripheral surfaces are in close contact, but in order to obtain a uniform energy density distribution, a large number of soldered parts are separated by an appropriate amount. It can also be applied to sequential laser irradiation.

[Effects of the Invention] The present invention irradiates the soldering area with laser light transmitted by a plurality of optical fibers bundled at the light output side end through a condensing lens. The energy density distribution of the laser spot is made uniform, which eliminates carbonization of flux, solder defects such as pinholes, and improper formation of solder fillets, resulting in high reliability. This has the remarkable effect that laser soldering can be easily performed.

[Brief explanation of the drawing]

Figure 1 is a plan view showing the target of laser soldering, Figure 2 is a diagram showing conventional laser soldering, and Figure 3 is Figure 2K.
A diagram showing the energy density distribution of the soldering part,
4 and 5 are diagrams showing laser soldering in one embodiment of the present invention, FIG. 6 is a diagram showing the energy density distribution of the soldering portion in FIG. 4, and FIG. 7 is a diagram showing laser soldering in an embodiment of the present invention. It is a figure showing the bundling state of the optical fiber in the example. (2), α9 terminal, (3+, (141... lead wire (soldered body), +51, (91... condenser lens, (6), flol... optical fiber agent patent attorney rules Kensuke Chika (and 1 other person)

Claims (1)

[Claims] For soldering, the body is fixed to a surface, and for K soldering, solder and flux are placed close to the part, and for the above soldering, the part is irradiated with a laser beam, and for the above soldering, the body is fixed to the soldering part. Laser soldering is a method in which the light output side ends of a plurality of optical fibers are bundled together to face the light input side of a condenser lens, and a method in which the ends of the light output side of a plurality of optical fibers are soldered to the condenser lens. A method for laser soldering, characterized in that the method comprises: irradiating the soldering part with a laser beam;