High temperature degradation of palladium coated copper bond wires

摘要

High temperature storage lifetime tests of palladium coated copper bond wires (pcc-wires) beyond 1000 h@150 ℃ lead to an increased number of broken stitches during wire bond pull test. In this article we show that there is an intrinsic degradation of pcc-wires: defects in the Pd layer allow a temperature driven diffusion of Cu to the Pd surface reacting to CuO on the wire surface. Voids in the range of several microns in the Cu wire core weaken the bond wire strength to very low values. The degradation mechanism of pcc-wires is found in both cases, in molded packages and at non-molded wires from the spool. We present results after temperature storage at 150℃, 175 ℃, 200 ℃, and 250 ℃ up to 3000 h.