Toward Partial Discharge Reduction by Corner Correction in Power Module Layouts

As spacing between traces in power modules is reduced to meet increasing power density requirements, partial discharge (PD) starts becoming a threat that can cause insulation breakdown, if not checked. For high voltage applications, PD awareness is particularly important, and this paper describes how various trace shapes play a critical role in the electrical reliability of modules with regard to electrical breakdown. Sharp corners of traces must be avoided, as is generally done for mechanical stability reasons, by filleting the corners. High voltage experiments were performed to confirm the detrimental electrical effects of sharp corners. The degree of improvement by completely avoiding sharp corners was quantified for various trace gaps. Simulations were performed to predict the improvement in terms of E-field concentration with respect to the radius of fillets. Preliminary fillets were implemented in a stand-alone in-house tool called PowerSynth, which is used for electrical and thermal optimization.