The reliability of AlN power hybrids using Cu thick film conductive

A power hybrid construction using AlN substrates, copper thick-film conductives, and a power chip has been evaluated. Tests included aged adhesion of the copper thick film, thermal conductivity of the substrate, thermal conductivity of the hybrid, thermal shock of the hybrid, and power cycling of the hybrid. It was found that a copper thick-film conductive can be made to adhere well to AlN. A wire-bondable copper thick-film conductive is possible, but presently needs some work. In this construction, an AlN 170 w/mk substrate will dissipate almost twice the power of a 96% Al₂O₃ substrate and maintain the same chip temperature. The AlN units are good for 10000 cycles of thermal shock; the Al₂O₃ are not. For the same construction, the AlN units can handle over four times the power cycles of the Al₂O₃ units. The solder thickness between the chip and the conductive is a major factor in power-cycle reliability