Thermal deformation measurement of flip-chip substrate using digital image correlation method

Abstract

With the accelerated development of electronic products, flip-chip packaging has become one of the most prominently used and efficient designs in the integrated circuit (IC) industry. In daily application, the IC chip will be subjected to a temperature increase when it is in operation. With the rise in temperature, the chip is liable to a series of deformations which lead to possible malfunction of the IC unit. Therefore, the investigation of thermal deformation of flip-chip substrates is important. In this study, the thermal deformation of flip-chip substrates is measured with dual-camera digital image correlation technology, and with the measured data, a basis is established to predict the warpage conditions and strain tendencies of substrates due to thermal effect. Experiments were carried out with the substrates heated from room temperature to 200°C in a specialized vacuum-sealed oven. The topographic surface profile at higher temperatures can be obtained by adding the measured deformation to the surface profile of the substrates at room temperature. Experimental results show that the center area of the specimen had been warped up around 90 µm from the initial condition and the warpage effect of the substrate is obvious when the temperature increases to 200°C. The related maximum normal and shear strains are also discussed.

Keywords:

• flip-chip packaging
• substrate
• warpage
• digital image correlation