JPS63160297A - Laser soldering - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a laser soldering method suitable for assembling electronic components such as an R network and a C network in which a large number of terminals are connected to a single board. Regarding improvements to the attachment method.

When manufacturing electronic components in which multiple terminals were soldered to a single board, the conventional method was to apply each paste solder in advance to each location using a soldering iron. I was soldering it while melting it.

However, as electronic components become smaller and lighter (and the tip of the soldering iron is large, it becomes difficult to work with the contact-type soldering iron mentioned above.) As a result, a method has been adopted in which soldering is performed by using the irradiation energy to sequentially melt paste solder that has been applied to the soldering location from the end.

This conventional laser soldering method has excellent advantages such as non-contact heating and fine work, energy transmission through optical fibers, and irradiation through glass.

However, the boards of electronic components to which soldering is performed often use alumina, which has a small heat capacity and relatively high thermal conductivity, and are also small, so adjacent soldering points are very close to each other. The situation is as follows. Therefore, when soldering is performed at one soldering point, the heat is transferred to the adjacent soldering point and is stored, and the adjacent soldering points are already heated up before soldering. , the paste solder melts at the soldering point before the laser energy reaches a predetermined intensity. However, since the laser irradiates all soldering points with the same energy, the temperature of the soldering points that are soldered late will rise abnormally, causing electrode holes and solder spatter, resulting in poor soldering. There are some problems that have not been addressed properly.

On the other hand, in order to obtain good soldering, it is necessary to change the laser irradiation energy for each soldering point, and as the types of electronic components become more diverse, different types of parts must be soldered at the same time. cannot be easily handled, and such control is difficult.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a laser soldering method that can perform uniform and good soldering using a laser.

Plate a! , G' old friend t , a ? , = y 朕杕E , = y 朕杕E , In order to achieve the above object, the laser soldering method of the present invention involves bringing a terminal into contact with a plurality of electrodes formed on a substrate, and applying paste solder to each electrode. Then, a laser beam having energy that does not melt the paste solder in one irradiation is scanned over the paste solder at all soldering locations, and this is repeated multiple times in a short period of time to melt the paste solder and solder it. It is characterized by the fact that it is attached.

χ-shi-kan An embodiment of the present invention will be described below.

FIG. 1 is a schematic diagram of an apparatus for scanning and irradiating a laser beam as an embodiment of the present invention.

In the figure, ■ is a YAG laser for irradiating the laser beam α, 2 is a polygon mirror provided for scanning the laser beam α, and 3 is soldered using the laser soldering method according to the present invention. An example of an electronic component that performs this is a network resistor.

FIG. 2 (al and bl are respectively a front view and a side view of the network resistor. The network resistor 3 has a plurality of resistance patterns 6 made of carbon formed on one surface of a substrate 4 by printing, and On one side of pattern 6,
Individual electrodes 7 are connected to each, and a common electrode 8 is connected to the opposite side. Lead terminals 9 are attached to the lead-out ends 8a of the individual electrodes 7 and the common electrode 8, and
Paste solder 58-51 is attached. Note that the ends 9a of the lead terminals 9 are shown connected by a lead frame during manufacture.

Next, the procedure of the soldering method using YAG laser-1, which is the subject of this embodiment, will be explained. First, one tip 9b of the lead wire 9 and the lead-out end 8 of the individual electrode 7 and common 1ffi electrode 8 are connected.
With the solder pastes 5a to 51 adhered to the solder parts 58 to 51, a laser beam α emitted from the YAG laser 1 is irradiated via the polygon mirror 2 to each soldering location 58 to 51. At this time, the laser beam α is
Use a low-energy material that does not melt the solder paste in one scan. The laser beam α is irradiated by rotating the polygon mirror 2 in the direction of arrow X to scan the solder at all the soldering locations 58 to 51 from one end to the other for a short period of time. For example, this is done by repeating the process several times while the heat from the previous irradiation is still accumulated.

If the scanning direction for the soldering points 58-51 is Y, then the relationship between the irradiation value ay of the laser beam α and the time t for the soldering points 53-51 is expressed as shown in FIG.

Further, the temperature rise caused by irradiating a certain soldering point, for example 5b, with the laser beam α is schematically shown in FIG. 4. Here, H is the temperature at which the paste solder melts, and point A is the temperature that rises after being irradiated with the first laser beam α, which is lower than the temperature at which the paste solder melts, and points 4 to 1 are , adjacent soldering points 5a and 5c when the laser beam α is not irradiated.
The temperature rises due to the heat transferred from the point L to H, and the temperature rises due to the irradiation of the laser beam α. The temperature is the optimum temperature at which the solder paste melts and the solder blends with the area to be bonded, resulting in good soldering. However, the above-described scanning of the laser beam α is repeated until the temperature of all the soldering points 58 to 51 reaches zero, and when the irradiation is finished, the paste solder cools and solidifies, and the soldering points 58 to 51 touch the board. Electrical connection between the lead terminals 9 and the lead terminals 8a of the individual electric bridges 7 and the common electrodes 8 of No. 4 is completed.

As described above, in this embodiment, by providing the polygon mirror 2, which is a simple equipment, the laser beam α emitted from the YAG laser 1 is scanned and a plurality of soldering points 5a are scanned.
Since all the temperatures of 1 to 51 can be raised uniformly, uniform and good soldering can be performed.

Note that the laser is not limited to YAG laser, gas laser such as Coz laser can also be used, and laser α
The scanning method is not limited to the polygon mirror 2;
Well-known mirrors such as mirrors with coils can be used.

Furthermore, the terminals that can be attached to one board are not limited to lead terminals as in the above-mentioned embodiments, but may also be chip electrode terminals without lead wires.In short, multiple terminals can be soldered to one board. The present invention can be applied to any electronic component that can be attached using the following methods.

As described above, according to the method of the present invention, paste solder at multiple soldering locations can be melted simultaneously and under approximately the same conditions, so that soldering is uniform at all soldering locations. And it works well.

In particular, even if there are multiple soldering points on a board with a small heat capacity of 1 or a board with good thermal conductivity such as a metal plate, laser soldering can be performed successfully at all soldering points. .

Furthermore, since there is no need to change the intensity of the laser beam emitted from the laser, an increase in equipment costs is prevented without requiring a complicated control circuit.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an apparatus capable of scanning and irradiating a laser beam as an embodiment of the present invention, and Fig. 2 fa) and crest) are respectively a front view and a network resistor as an electronic component. A side view, Figure 3 is a graph showing the relationship between the irradiation position and time by laser beam scanning, Figure 4
The figure is a graph showing the relationship between the temperature rise of solder at a soldering point and time. DESCRIPTION OF SYMBOLS 1... YAG laser, 3... Network resistor, 4... Board, 5a-51... Soldering point, α... Laser beam. Patent Applicant 2 Murata Manufacturing Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 FI + Interval

Claims (1)

[Claims] (1) Bringing the terminal into contact with multiple electrodes formed on the substrate,
With the paste solder attached to each electrode, a laser beam with energy that does not melt the paste solder in one irradiation is scanned over the paste solder at all soldering points, and this is repeated multiple times in a short period of time. A laser soldering method characterized in that the paste solder is melted and soldered by repeating the soldering process.