Abstract
In this study, we tried to solder directly heat treatable aluminum alloy to oxygen free copper without metallizing of solder, and investigated the effects of flux and the application of ultrasonic vibration on the strength of soldered joints and the soldered layer structure. The following results were obtained. Aluminum can be soldered to copper by applying ultrasonic vibration and using flux. However, in this case, many voids of 30~35 volume % are formed in the soldered layer. At the interface between Cu and soldered layer, AlCu intermetallic compound phase is formed and it grows with the duration of the ultrasonic vibration. When the thickness of the intermetallic phase is over about 760nm, the strength of the joint decreases. Only by applying ultrasonic vibration aluminum can be also soldered to copper without flux. The soldered layer includes few voids, however, the strength of the joint is lower than that of the joint soldered using flux. In this case, the AlCu intermetallic compound phase is also formed at the interface between Cu and soldered layer, and it grows with the duration of the ultrasonic vibration. However, the intermetallic phase does not grow uniformly and continuously along the overall interface, resulting in the low strength of the joint.
