Monitoring through-life thermal path degradation using real time thermal models

Consideration of health management and reliability form an integral part of the design and development cycle of electronic products. In this paper real-time compact thermal models are employed as an efficient tool to monitor thermal path degradation at particular locations within the module such as interfaces between the base-plate and heatsink. The compact real-tine thermal model is used to predict the temperatures of the active device junctions and inaccessible locations such as solder layers within the power module. The resulting estimated temperatures are compared with measured data from the in-service real-tine environment to provide an indication of changes in the thermal characteristics of the thermal path. It is thus possible to track the degradation of the thermal path at critical bonded and bolted interfaces through observing the difference between the real-time temperature estimates and measurements of the modulepsilas layers. This technique provides direct diagnostic information about developing faults and thus provides a versatile real-time health management tool for monitoring selected wear out mechanisms within the power module thermal path, for example propagation of cracks in soldered joints, and substrate delamination.