Die punch test study and relationship to delta VBE

Experimental data to correlate the die punch test and the delta VBE (DVBE) are presented. Power transistors on a wafer with a multilayer backing of Al/Ti/Ni/Ag were used. These two methods were used to the test die attach quality, and therefore, good heat transfer from die to frame. The test samples were assembled at three different locations using standard processes at each place, and three different types of cases were used. Scanning electron microscope (SEM) analysis was used to determine if any contamination was present in the frames of the punched samples, but no oxidizing agent or corrosive material was found on any of the samples analyzed. Materials that could produce a lack of adherence were sought, but none were found. The spread in delta VBE values was observed after thermal aging, but no clear relationship was found between the two tests