JPS6281268A - Soldering method - 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 [Field of Industrial Application] The present invention relates to a fluxless soldering method that is particularly suitable for efficiently soldering a wide range of joint surfaces in a void-free manner.

[Background and Objectives of the Invention] As is well known, soldering is a widely used method for joining metal materials at relatively low humidity.

There is not much problem with this kind of soldering, when connecting the tops of wires with a small joint area, or when connecting the ends of thin plates, etc., but when soldering is used to join the opposing surfaces of two wide copper strips. It is necessary to apply solder in a layer over a wide area, and as a result, solid flux may remain inside the solder layer, or scum generated during air entrainment or heating may be trapped inside. Therefore, it is inevitable that these cannot escape from within the solder layer and cause internal defects such as voids.

The occurrence of such voids and residual flux not only have an adverse effect on the mechanical bonding strength, but also deteriorate the conduction characteristics of heat and electricity, causing generation of Joule heat and apparent current density failure. This results in many problems such as uniformity and poor corrosion resistance. In particular,
If the material is used in electrical circuits, the presence of such internal defects may be fatal, and therefore improvements have been strongly desired.

In view of these circumstances, the present invention aims to provide an innovative soldering method that does not leave behind the aforementioned flux or generate voids even when metal materials are joined over a wide area by the soldering method. -It's something.

[Summary of the Invention] That is, the gist of the present invention is to form a preliminary coating layer on the surfaces to be joined in advance by ion blasting or vacuum evaporation, coat it as it is, or add solder, and then apply it in a vacuum without using any flux. The present invention is a method of soldering using a method of soldering, thereby preventing the flux from remaining and the generation of voids.

[Example] The present invention will be explained below based on Examples.

FIG. 1 is an explanatory diagram showing how a preliminary coating layer 3 is formed by vacuum deposition on a copper plate 4 having a width of 3 Q mm and a length of 200 mm.
Alloy 2 was added and heated in a vacuum to form a preliminary coating layer 3 of about 25 μm thick on the copper plate 4 made of the alloy. The pre-coated surfaces 3 and 3 of the pre-coated copper plates thus formed were brought together and vacuum soldering was performed for 350'C x 5 minutes without adding any solder.

When the results were evaluated using the voidless rate of the following formula, rB
=99.5%, an outstanding result of 1q. It was found that the solder layer at that time had a very uniform thickness of 50μ±3μ.

FIG. 2 shows the same copper plate 4 with 5n-A (1
This shows an example of forming a pre-coating layer 3 made of an alloy. In the case of Fig. 1, an alloy having the same composition as the alloy to be pre-coated is put into the tungsten heater 1, whereas in the case of Fig. 2, The first tungsten heater 1a contains Sn, the second heater 1b contains Ag, and a preliminary coating layer 3 made of an alloy of both is formed. As a result of heating in a vacuum in the state shown in FIG. 2, it was possible to form a preliminary coating layer 3 made of Sn--Ag alloy with a uniform thickness of about 25 .mu.m in this case as well. The coated surfaces 3 and 3 of the copper plates on which the preliminary coating layer had been formed in this way were brought together and heated at 350° C. for 5 minutes in a vacuum without adding any solder. In this case, the thickness of the solder layer was 50μ±2μ, and the voidless ratio rB was 99.9%.

FIG. 3 shows an example in which the preliminary coating layer is formed using an ion blating method instead of the vacuum evaporation method described above. The same composition as in Figure 1 requires 5n-
A 3.5% ACI alloy 2 was heated with an electron gun 7 to form a preliminary coating layer 3 on the copper plate 4 by ion blating. In this case as well, it was possible to form the preliminary coating layer 3 on the copper plate 4 with a uniform thickness of about 25 μm. Thus copper plate 4
The preliminary coating layers 3 and 3 were combined and heated at 350°C for 5 minutes in a vacuum without adding any solder, resulting in uniform solder with a void-free rate of 99.6% and a solder layer thickness of 50μ±3μ. layer could be formed.

In addition, in FIG. 4, the materials to be heated by the electron gun 7 are not based on alloys, but as in FIG. The pre-coating layer 3 made of Sn-Ag alloy is formed by heating.The pre-coating layer 3 in this case also has a thickness of about 25μ, and the pre-coating layers 3.3 of the copper plate 4 thus formed are combined and soldered. Heating was carried out at 350'C for 5 minutes in vacuum without adding any additional heat.

As a result, the void-free rate was 99.9%, and the thickness was 50μ±1μ.
We were able to form an extremely uniform and excellent solder layer.

Table 1 shows the results of a salt spray test to compare the corrosion resistance performance of the soldering method according to the present invention and the conventional soldering method using flux. In Table 1, Example 1 indicates the above-mentioned example shown in FIG. 1, and the examples described below with respect to FIGS. 2 to 4 correspond to Examples 2 to 4, respectively. Moreover, the conventional example is one in which soldering is performed in the atmosphere using a conventional flux.

Table 1 clearly shows the remarkable corrosion resistance improvement effect brought about by the fluxless feature of the present invention.

Table 1 * × There is a change between the solder part and the copper plate. ○ None The above embodiments have been described using soldering to a copper plate as an example, but the method according to the present invention can also be applied to semiconductors etc. that require extremely high reliability. Needless to say, it can also be applied to the joining of materials, and has a remarkable effect.

Further, if necessary, pressure may be applied during soldering during heating, and further integrity can be expected by this.

As described above, according to the soldering method according to the present invention, soldering with an extremely good void-free rate can be performed without using any hooks, and corrosion resistance can be greatly and reliably improved, and reliability can be improved. As something that can be clearly secured, its significance to this industry is enormous.

[Brief explanation of drawings]

1 to 4 are explanatory diagrams showing respective embodiments of a preliminary drawing method for soldering according to the present invention. Agent Patent Attorney Adversary Fujio Hajime 2-(G)

Claims (2)

[Claims] (1) Form a preliminary coating layer that can be a solder composition on the joining surfaces of the members to be joined by vacuum evaporation or ion blating, and either bring the joining surfaces into direct contact with each other, or add solder between them and use flux. A soldering method that heats up in a vacuum without any heat. (2) The soldering method according to claim 1, wherein a pressurizing force for joining is applied during heating in a vacuum for soldering.