Microscale mechanical properties dependent on the strain rate and temperature of cured isotropic conductive adhesive

Abstract

In this research, the microscale strain rate sensitivity and high-temperature mechanical properties of cured isotropic conductive adhesive (ICA) were investigated using microindentation. The indentation modulus and hardness of cured ICA with high silver content are relatively large. The slopes of contact stiffness–depth curve, modulus and hardness increase with increasing loading strain rate. The elastic modulus, hardness and creep behaviour at high temperature were characterised on the basis of the “rapid loading–holding–rapid unloading” loading mode and the semiempirical method from the generalised Kelvin model. With increasing temperature, the elastic modulus and hardness of cured ICA decrease from 3000–7000 and 100–300 MPa in the glassy state to 6–200 and 1–10 MPa, respectively, in the rubbery state. Creep compliance, which is relatively high in the rubbery state, increases with increasing holding time. On the retardation spectrum, the widened retardation peaks reflect different retardation processes with increasing retardation time.