JPS6054142B2 - Ultrasonic soldering method for aluminum bars - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of soldering an aluminum bar by directly bringing an ultrasonic horn into contact with the aluminum bar to be soldered.

Aluminum materials are difficult to solder and solder due to the stable and dense oxide film that exists on their surfaces, and many methods have been studied to overcome this problem.

In particular, the method of applying ultrasonic waves is known as the most effective method for this type of work on rods, as it is in principle possible to solder without using flux.
Generally speaking, there are two methods for ultrasonic soldering. One is a method in which an aluminum rod is immersed in solder Rakunan activated by ultrasonic waves, and the solder material is coated metallically on the rod surface. The other method is to directly apply ultrasonic waves to an aluminum rod immersed in molten solder Rakunan.

In the former method, not only the aluminum bar material but also the metal constituting the solder bath undergoes cavitation and erosion caused by ultrasonic waves, causing deterioration, whereas the latter method has no fear of this and has a very long bath life.

However, when the ultrasonic horn is immersed in molten solder, the immersed part will suffer from cavitation and erosion, but if it is exposed above the hot metal surface together with the aluminum rod, this problem will be eliminated. Therefore, in practical terms, it is advantageous to place an ultrasonic horn in contact with an aluminum rod and apply ultrasonic waves directly to it for soldering. From the viewpoint of workability, it is preferable to perform this on the end face of the Hereinafter, this method will be abbreviated as the horn contact method. In the rice-horn contact method, an aluminum rod at room temperature is usually immersed in molten solder at a constant temperature, waits until it is heated to a predetermined temperature by the heat from the molten metal, and then applies ultrasonic waves for a predetermined period of time. Complete the work by lifting it out of the solder tank. However, the ultrasonic energy attenuates as it leaves the abutting part, so when viewed in the longitudinal direction, the state of solder plating decreases from the abutting end to the opposite end, or the ultrasonic energy is strong at the abutting ground. Therefore, erosion due to solder is severe and the surface condition deteriorates. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for soldering an aluminum bar using horn contact type ultrasonic waves, which eliminates the drawbacks of the prior art described above and enables uniform solder plating in the longitudinal direction.

The gist of the present invention is to perform ultrasonic soldering by giving an aluminum bar a gradient temperature distribution such that the temperature decreases in the longitudinal direction from the horn contact ground to the opposite end.

Generally, the progress of solder plating depends on the degree of diffusion reaction between the solder material and the A1 rod.

Further, the diffusion reaction is controlled by the interfacial temperature between the bath and the A1 rod, the energy of the applied ultrasonic waves, and the reaction time. Assuming that the reaction time is constant, the interfacial temperature and the ultrasonic energy have a complementary relationship with each other; even when the interfacial temperature is low, if the ultrasonic energy is large, diffusion will proceed; conversely, the ultrasonic energy Even when the temperature is small, the diffusion reaction is promoted if the interfacial temperature is high. Therefore, in the horn contact method described above, it is inevitable that the ultrasonic energy is attenuated along the longitudinal direction of the rod. It is possible to compensate for the delay in diffusion due to energy attenuation. In reality, the ultrasonic energy is gradually attenuated from the horn abutting end, so
On the contrary, it is preferred that the diffusion temperature increases gradually. On the other hand, if the rod is preheated with a separate gradient temperature distribution and the soldering process is completed in a short time so that this distribution does not substantially change, then the diffusion temperature will gradually change in the longitudinal direction. can be given. Based on the following examples,
The effects obtained by the method of the present invention will be explained.

Example 1 As shown in FIG. 1, an aluminum rod 1 having a diameter of 20φ and a length of 280mm is immersed in a solder bath 2 made of Sn, and an ultrasonic horn 3 is brought into contact with one end exposed above the bath surface to apply ultrasonic waves. Solder plating was performed while applying ultrasonic waves using a vibrator 4.

At this time, the bath temperature was set to 300°C, and the aluminum rod 1 was separately preheated so as to have a gradient temperature distribution in the longitudinal direction as shown in curve b) in Fig.
Frequency 19.5Hz 1 Horn 3 tip vibration maximum value 30μ
When ultrasonic waves were applied for 3 seconds, it was possible to obtain uniform solder plating in the longitudinal direction. Comparative Example 1 Same composition and temperature of aluminum rod 1 and solder bath 2 as in Example 1,
Under ultrasonic application conditions, the aluminum rod 1 was not given any particular gradient temperature distribution, and after preheating the entire length to 280°C as shown in curve c) in Figure 2, soldering work was performed, and the horn abutting side The surface of the rod is melted with Sn, but the opposite end is coated with S.
The n-boarding was extremely poor, and there were many exposed parts of the aluminum surface.

Comparative Example 2 Under the same composition, temperature, and ultrasonic application conditions of the aluminum rod 1 and solder bath 2 as in Example 1, the total length was as shown by curve a) in Figure 2, which gives a particularly sloped temperature distribution to the aluminum rod 1. 355℃
After preheating, when soldering work was carried out, the Sn was melted over the entire length, but the side where the horn was in contact was melted! ! 1! Erosion caused by Sn was severe and the surface condition deteriorated significantly.

Example 2 After casting a Pb layer with a thickness of 2wn on the surface of the soldered Al rod in Example 1, extrusion and wire drawing were carried out, but the Pb layer was not covered soundly until the wire diameter was 0.5. It was possible to process it in the same condition.

From the above, the horn-contact type ultrasonic soldering method also makes it possible to solder rods uniformly in the longitudinal direction, and it is also possible to solder rods efficiently and uniformly without causing horn or bath erosion. Plating becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a method of immersing an aluminum rod in a solder bath and a procedure for applying an ultrasonic horn, and FIG. 2 is a diagram showing a preheating temperature of the aluminum rod, particularly the temperature distribution in the longitudinal direction. 1... Aluminum rod, 2... Solder bath, 3.
...Ultrasonic horn, 4...Ultrasonic vibrator.

Claims (1)

[Claims] 1 An ultrasonic horn is brought into contact with the exposed end of the molten metal of an aluminum rod, one end of which is exposed above the solder bath surface and the other end of which is immersed in the solder bath, and the Al rod is soldered while applying ultrasonic energy. Ultrasonic soldering of aluminum bar material, characterized in that the method of soldering the aluminum bar material includes performing ultrasonic soldering by giving the aluminum bar a gradient temperature distribution such that the temperature gradually increases from the horn abutting end to the opposite end. How to fry.