Failure Modes in Gold-Aluminum Thermocompression Bonds

Electrical opens and mechanical fracture have been reported as two distinct failure modes in gold-aluminum thermocompression ball bonds. It is found that the thickness of the aluminum film to which the gold wires are bonded and the temperature at which the bonds are held during aging determine which failure mode will be observed. The electrical failure mode predominates when bonds made to aluminum films 5000Å or more in thickness are aged at temperatures above 200°C but at 200°C both failure modes are observed. Mechanical fracture is expected to be the dominant failure mode when ball bonds to these 5000-10000-Å films are aged at temperatures below 200°C. Bonds to thinner aluminum films (500-3000 Å) exhibited only the electrical failure mode.