Monitoring Power Module Solder Degradation From Heat Dissipation in Two Opposite Directions

Solder degradation is still a main failure mechanism for power semiconductor modules. This study proposes a monitoring method to detect the relative change in heat dissipation from a module in two opposing directions, affected by the degradation—upward via the silicone gel and downward via the solder layer to the heatsink. The method is based on external module package measurements, and a condition indicator
$\gamma $
is defined as the ratio of heat transfer rates in the two directions. The expected response of
$\gamma $
to the level of degradation is analyzed for different module operating points and external environment conditions. The method is demonstrated by experiment.