Effect of Thermal Residual Stress on the Measurement of the Adhesion Between Polyimide and Underfill Using an Asymmetric Double Cantilever Beam Specimen

Abstract

Abstract An asymmetric double cantilever beam (ADCB) technique was used to measure the interfacial adhesion of polyimide passivation to underfill materials. A thin layer of polyimide was coated on a standard diglycidyl ether of bisphenol-A (DGEBA) epoxy plate as one of the beams and an underfill epoxy was flowed over the polyimide film and cured to form the second beam. Due to the large difference in the coefficients of thermal expansion (CTE) between the two beams, a new term in critical strain energy release rate GT caused by the thermal residual stress becomes significant. This fact has been demonstrated experimentally by varying the thickness ratio of the two beams. The interfacial fracture energies of different underfill materials with polyimide were also measured. The results indicate that the effect of thermal residual stress must be taken into account in the calculation of critical strain energy release rate to achieve the realistic interfacial fracture energy Gc*.