High Reliability Al Bonding Wire for Power Devices

Abstract:
Heavy Al wire bonding is one of the weakest links in reliability testing, often causing the entire power device to fail. Due to the difference in coefficient of thermal expansion (CTE) between Al wire and Si die material, the interface for standard Al wires degrades rapidly during temperature cycling, resulting in cracking at the interface. Thermal fatigue performances of the Al wire bonds were examined using temperature cycle tests (TCT), rapid temperature cycle tests (rapid-TCT), and active power cycle test (APC). A high reliability Al bonding wire LX1 has been developed for SiC power devices. It is a highly alloyed Al wire and has quite advantageous performances compared to the standard Al wires; (1)high thermal bond reliability, (2)lower CTE, (3)high shear force. In particular, LX1 wire produced significantly longer lifetime at the bonds on Al metallization in TCT tests. LX1 can suppress crack propagation at the bond interface. The lifetime of LX1 in APC testing was much prolonged rather than the standard Al wire. Enhanced thermal reliability for high reliability Al wire bonded to Al metallization can preferably meet the demands for the high power electronics.