A STUDY ON RELIABILITY OF NI PLATING IN A HIGH TEMPERATURE POWER DEVICE

Recently, the SiC chip for power devices had been developed to downsize the cooling system, because the operative temperature of SiC chip can be increase to over 300 degrees C. However it is necessary to realize low temperature mounting and high reliability in high temperature. The author's group has proposed a new method using Ag-Nano material to mount the SiC chip on a Al board. The Ag-Nano can be mounted firmly on Al board with about 300 degrees C, the stress relaxation facility can be given to the pure aluminum substrate side. In addition Ni plating was used as the final finish. As a result, Ni plating becomes as a new weak point. In this study, the authors proposed a new experimental method for investigating the reliability issues of the Ni plating in the Ag-Nano joint. Three point bending test is performed to evaluate the mechanical properties of Ni plating. A test specimen with Ni plating and a test specimen without plating in same size are prepared for a bend test, properties of Ni plating are calculated by comparing difference of those bend tests. And the fatigue strength was investigated by cyclic bending tests.