Reliability Improvement of Wire Bonds Subjected to Fatigue Stresses

The failure of wire bonds due to repeated flexure when semiconductor devices are operated in an on-off mode has been investigated. An accelerated fatigue testing apparatus was constructed and the major fatigue variables, aluminum alloy composition and bonding mechanism, were tested. The data showed Al-1% Mg wires to exhibit superior fatigue characteristics compared to Al-1% Cu or Al-1% Si and ultrasonic bonding to be better than thermo-compression bonding for fatigue resistance. Based on these results highly reliable devices were fabricated using Al-l% Mg wire with u1-trasonic bonding which withstood 1.2 × 105 power cycles with no failures.