Ultrasonic vibration aided soldering of aluminum with various kinds of filler metals

Soldering of aluminum with the aid of ultrasonic vibration (4th Report)

Abstract

We attemted to solder aluminum with the aid of ultrasonic vibration using solder of Zn, Ag, Cu, Mg, Si and Sn as a filler metal, and examined the tensile strength of the soldered joints. From the observation of the interface reaction, the mechanism by which the aluminum oxide film is broken and removed out of the interface was discussed.
The mechanism of removing the oxide film was suggested as follows : First, the oxide film on the convex of faying surface is broken by the friction due to the ultrasonic vibration. Secondly, the interdiffusion through the fresh surface between the aluminum and the filler metal occurs, resulting in the formation of liquid by the eutectic reaction at the interface.
The eutectic liquid, of which the amount is dependent on the erosion of the aluminum, aggresively promotes to remove the oxide film at the concave of faying surface.
The metals other than zinc are also available as a filler metal, if they form low melting point liquid by the eutectic reaction with the aluminum, and several filler metals prove to provide the soldered joints with sufficient strength.