Numerical and Experimental Evaluation of the Microsecond Pulsed Heating Curve Technique Dedicated to Die Interconnection Characterization

This paper describes and qualifies a partial thermal impedance measurement technique to evaluate the thermal behavior of the physical layers close to the die in power electronic assemblies. The measurement approach is derived from the pulsed heating curve method; nonetheless, the experimental setup proposed here is fitted for a higher sensitivity analysis of die interconnections due to the extraction of the transient thermal impedance at very high current levels and short heating times. Another advantage of this method is that the cooling efficiency of the system has no impact on the sensitivity of the measurements, which makes it particularly suitable for aging monitoring or in-line manufacturing process control. The method is then implemented with power diodes in order to compare the thermal impedance of two power modules with different solder void repartitions. Experimental results and finite-element simulations show that this method has a very good sensitivity and can, therefore, be used to compare the quality of different die attaches without requiring an efficient power module cooling system.