A novel method combining laser ablation and chemical etch to expose packaged silicon backside for electrical fault isolation

The evolution of packaging requirements and innovations drives the constant need for improvement in package level failure analysis. For silicon backside dynamic electrical fault isolation, partial decapsulation is done to remove signal blocking materials and assess the silicon backside of the chip, while maintaining the electrical components and connections of the package. The control of such selective backside opening technique is an intricate process. Any damage can easily be induced to the package connections and silicon substrate without proper control. In this paper, we introduce a novel method with the combination of laser ablation and chemical etch to selectively open die in QFN packages where the package backside is a metallic Cu heatsink.