Abstract
Two kinds of alumina with 99.5% and 91.0% purity were ultrasonically bonded to aluminum. The effect of thermal conductivity, hardness and the content of SiO2 in the alumina on the strength of a joint were examined. Results obtained are summarized as follows. Under the condition of bonding pressure of 882 N and applying time of ultrasonic vibration for 1.0 s, an excellent joint is stably achieved in both alumina. The strength of the Al–91% alumina joint is higher than that of the Al–99.5% alumina joint. It seems that the effect of the thermal conductivity of the alumina on the strength of the joint is small, however, the temperature at the interface between Al and 91% alumina with lower thermal conductivity is higher by about 15°C than that between Al and 99.5% alumina. Although 99.5% alumina harder than 91% alumina tends to facilitate the breakup of Al surface oxide film and exposure of clean surface at the interface, the effect of the difference in hardness of the alumina on the strength of the joint is small.
