Abstract

Chip access for flip-chip packages in high-performance microprocessors is performed by removing the lid then by extraction of the die from the package substrate. Residual stresses built in temperature cycled (TC) units result in a low success rate using conventional delidding techniques. A need has developed in failure analysis for stress-free removal of the materials surrounding a flip-chip device. This paper discusses a novel, cost effective, wet chemical process that has been developed for thin die and lid removal of flip-chip packaged units. The process uses n-methy-2-pyrrolidone (NMP) for epoxy-based lid attach and underfill materials. A reflux unit is designed to reduce the risk of fire and explosion when the sample is heated in the solvent to the desired temperature. The method of heating reduces the chance of thermal shock, which could fracture the sample due to rapid heating or cooling.

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