Room-temperature microjoining using ultrasonic bonding of compliant bump

Ultrasonic bonding was applied to cone-shaped microbump made of Au on a Si chip to perform bonding at room temperature. Array of cone-shaped microbump having 10 μm in diameter and 20μm in pitch was formed on Si using photolithography and electroplating. The counter electrode was a planar electrode which was also made by using electroplating of Au. Bonding was carried out at room temperature under conventional air circumstances. It has been found that bump array whose number is over 10,000 can be electrically connected. Die share tests have revealed that bonding strength can be increased to the strength that bonding at 150°C provides.