Effective acquisition of elastoplastic and creep parameters of lead-free solder alloy from high-temperature micro-indentation eliminating the size effect

Abstract

Effective acquisition of the related mechanical properties of lead-free solder alloys through micro-indentation tests is of great significance in the research on electronic interconnection design and reliability for the multi-functionalization and high integration of electronic products. The temperature-dependent elastoplastic and creep parameters of Sn–3.0Ag–0.5Cu (SAC) solder are systematically investigated by micro-indentation with plural indenters and the “rapid loading-holding-rapid unloading” test mode. Based on the depth dependence of indentation hardness from mechanism-based strain gradient plasticity and the stress independence of creep compliance for linear viscous assumption, the complete indentation load-depth curves eliminating the indentation size effect of SAC solder under different temperature and two pyramidal indenters with different equivalent semi-cone angles are reconstructed. Combining with the temperature-dependent elastic modulus measurements from cylindrical indentation, corrected load-depth curves for pyramidal indentation, and the concept of representative stress and representative plastic strain, the elastoplastic parameters eliminating the indentation size effect under different temperature are uniquely determined through numerical simulation and inversion analysis, as well as the corresponding creep parameters. The temperature dependence of elastoplastic and creep parameters of SAC solder is analyzed, and related deformation mechanism is discussed. Results of forward and inverse analyses indicate the effectiveness of proposed characterization method.