Failure analysis of assembly defect with IR-OBIRCH from backside

In our failure analysis, there were some dual die product which included one control die and power die, and there was no passivation on power die so as to radiate heat conveniently. We may occasionally meet some cases, which revealed simple leakage failure on external pins, such as OUTPUT-GND leakage. However, when we decapped the fail unit from front-side, failure disappeared and then we could do nothing on this unit, even we well knew the failure on power die. In these cases, IR-OBIRCH could not capture hotspot successfully even with general backside analysis. So, in this paper we proposed one defect localization method with backside & IR-OBIRCH technology. This method was employed to find out assembly defect location between power die and compound. We had some successful cases for assembly defect, for example particle defect, metal scratch, wire bond defect and die crack.