Deformations of a simplified flip chip structure under thermal testing inspected using a real-time Moiré technique

Zhong, Z.W., Wong, K.W. and Shi, X.Q. (2006) Deformations of a simplified flip chip structure under thermal testing inspected using a real-time Moiré technique. International Journal of Advanced Manufacturing Technology, 27 (7/8). pp. 708-714.

Abstract

Deformations of a Si-epoxy-FR4 (simplified flip chip) structure under thermal testing were inspected with a real-time Moiré technique. Specimens without cracks and specimens with a crack at the silicon-epoxy interface were prepared. The measurement results showed that the maximum deformation appeared at the edge. When the specimen was cooled to 20 °C, there was residual plastic deformation in the specimen. The creep effect was more dominant in the FR4-epoxy interface. Upon cooling to 20 °C, the specimen experienced partial strain recovery. To characterize the behavior of the interfacial crack, stress intensity factors KI and K II, and the strain energy release rate G in the vicinity of the crack tip were calculated using the measured deformations to conduct a quantitative study. It was observed that a sharp strain gradient occurred at the crack tip. KI and KII were dependent on temperature, and G was dominated by KI for the interfacial crack in the specimen.