New Quantitative Measurements of IC Stress Introduced by Plastic Packages

New strain gauge test bars have been designed forming individual and bridge structures for silicon integrated circuits. They are used to quantitatively measure internal stress introduced in IC bars during packaging. The results show that unexpectedly high levels of stress are introduced as a function of plastic material selection as well as mold and cure temperatures of the materials. The stress can be reduced, and process control can be tightened by appropriate choice of packaging conditions. The importance for IC reliability and electrical performance is discussed.