Partial thermal impedance measurement for die interconnection characterization by a microsecond “pulsed heating curve technique”

Due to new applicative domains like embedded systems, power electronic converters are getting more and more compact, increasing their power densities and working in extreme environments with higher lifetime requirements in accordance with design to cost optimization. Power components packaging is thus involved in many research considerations such as thermal management, electromagnetic interference reduction and reliability. The thermal characterization of the die assembly is becoming a challenge in a power module due to the inaccessibility of the semiconductor parts in the module. This paper describes an innovative experimental method used to evaluate power chip interconnection solutions with the help of a transient thermal response of a power component. The experimental setup is designed to derive the thermal impedance of a power device in the microsecond scale in order to evaluate the thermal behaviour of the physical layers close to the chip. The method is then carried out with power diodes in order to compare the thermal impedance of two power modules having different solder voids repartitions. The results show that this method has a very good sensibility that can be used to compare the quality of the thermal behaviour of different die attaches.