Degradation behavior of Al wire bonding strength in thermal shock test

The degradation of Al wire bonding strength in MOSFET devices under thermal shock test was investigated. In the thermal shock test,two kinds of Al wires（ 250 μm/380 μm） with different packaging were studied. Degradation behaviors of the Al wire bonds during thermal shock tests were evaluated by measuring tensile stresses and comparing these values with those of the original Al wire bonds. The bonding strength degradation was compared under the different aging test. Metallographic microscope and scan electron microscope（ SEM） were used to evaluate Au-Al bonding interface. The influences of the thickness and impurity of the plated gold film on the bonding reliability were investigated under the shock test. Two kinds of Al wires bonding strength were degenerated after the thermal shock test,the degradation of thick gold pad bonding strength was not obvious,some bonded lift-off phenomena occurred in the thin gold pad,which shows poor resistance to the thermal shock.