A NEW APPROACH FOR EVALUATION OF FATIGUE LIFE OF Al WIRE BONDS IN POWER ELECTRONICS

摘要

Ultrasonically bonded Al wire bonds on Al metallization pads arewidely used in power semiconductors. The required long timereliability of the devices is highly dependent on the interfacialquality of Al wire and the bond pad. Reliability of wire bonds iscommonly assessed by thermal and power cycling tests.Accelerated mechanical fatigue testing can be used as analternative to these time consuming procedures. In the presentstudy, lifetime of thick Al wedge bonds on Si substrates wasinvestigated using a novel mechanical fatigue testing techniqueoperating at high frequencies and elevated temperatures. Theinfluence of microstructure, testing temperature and frequency onlifetime of Al wire bonds was investigated. Finite elementanalysis was applied to calculate the stress distribution at theinterfacial region and to establish life time prediction curves. Theresults of mechanical isothermal fatigue curves were comparedand correlated with thermal cycling data of Al wire bonds.