A Simple and Non-Destructive Method to Measure Per-Terminal Baseplate Coupling of Power Modules

The high edge rates of wide bandgap semiconductors can produce common-mode currents that flow through the baseplates of multi-chip power modules. These currents increase the electromagnetic signature of these devices and force designers to reduce edge rates or add additional filters in order to meet compliance standards. Parasitic baseplate capacitances that exist within power module packaging are known to be a primary path for the flow of these common-mode currents. Unfortunately, the measurement techniques currently available to characterize these capacitances are either challenging to perform or require the internal interconnects to be removed. This paper proposes a simple and non-destructive measurement technique to characterize the baseplate capacitances of multi-chip power modules on a per- terminal basis. The technique can be performed with an impedance analyzer and does not require any special fixturing or alterations to the module. The measurement technique is applied to three fully populated commercial module and is validated by comparisons to the standard destructive measurement technique.