Internal pressure distributions of press-pack IGBT modules under two contact methods

Pressure contact methods of press-pack IGBT include rigid contact and compliant contact. The rigid contact structure is supported by rigid copper electrode for each chip module, and the compliant contact structure is supported by disc spring assemble for each chip module. In this paper, the finite element mechanical models of IGBT sub-modules in rigid and compliant contact were established, and the pressure distribution rules of the chips under different height tolerances and uneven forces on the modules were analyzed. The experimental tests on IGBT samples using two kinds of contact methods were carried out by mechanical press and FUJI prescale films, and the correctness of the FEM simulation results was verified. By comparison, it is found that the use of disc springs will compensate for the displacement deviations caused by the machining errors, thereby automatically adjusting the pressure distributions on surfaces of chips. The parameters of the disc springs are more easily controlled than the machining errors of the various components, thus the requirements for the packaging process can be reduced.