In this paper we present the finite element modelling and analysis of the wirebond structure and sintered silver joint structure of power electronic module in reliability based design optimisation context. The emphasis is on the optimal design for reliability based on computational approach that composed of high fidelity analysis, surrogate modelling, and reliability based optimisation. In particular, the reliability of the power module related to the thermal mechanical fatigue material degradation of wirebond structure and sintered silver joint were the focus of this study. The surrogate modelling was based on interpolation techniques using Kriging and wavelet radial basis functions. A reliability based design optimisation was demonstrated using Particle Swarm Optimisation algorithm and Latin hypercube sampling for constraint optimisation task in wirebond and sintered silver structures. Additionally optimising the clamping pressure of press pack diode structure was demonstrated.