Mechanical properties of cured isotropic conductive adhesive (ICA) under hygrothermal aging investigated by micro-indentation

Cured isotropic conductive adhesive (ICA) with different conductive fillers (micro silver flakes) contents were prepared. Based on the loading mode of “rapid loading-holding-rapid unloading” and semi-empirical method from the generalized Kelvin model, micro-indentation tests were carried out to investigate the effect of hygrothermal aging on the mechanical properties of cured ICA. On the whole, the elastic modulus and hardness of cured ICA with high silver content are relatively larger. As the hygrothermal aging time increases, both elastic modulus and hardness decrease at first and then stabilize, and the creep deformation is more evident. Indentation creep displacement-time curves for cured ICA were characterized by the generalized Kelvin model. During the holding stage, creep compliance increases slowly at first and then increases quickly with modulus loss. With the aggravated aging creep compliance increases, and creep compliance of cured ICA with high silver content increases faster at the later stage of hygrothermal aging. The widened retardation peaks with increasing retardation time reflect the different retardation processes during the holding stage. With increasing aging time, the creep rate sensitivity exponent increases and creep resistance reduces accordingly.