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This study compares the creep behavior of joint-scale Sn1.0Ag0.5Cu (SAC105) and Sn3.0Ag0.5Cu (SAC305) solder samples under shear loading. The basis of the comparison is experimentally derived Anand viscoplastic constitutive models for the alloys. A series of monotonic constant shear stress and constant shear strain rate tests was conducted at temperatures of 20°C, 50°C, 75°C and 100°C for SAC105 in order to provide data to extract the constitutive model parameters. The predictions of the Anand model are compared graphically with the experimental data for SAC105 in order to illustrate goodness-of-fit. The Anand parameters are shown to capture the creep performance of the SAC105 solder under shear loading very well, with the experimental data being tightly bound to the Anand predictions. For comparison, model parameters for SAC305 are taken from previously published work at the authors' institution. In terms of practical usage, SAC105 is noted to be preferable for applications which may experience high strain rate stimuli (portable electronic devices) as the alloy undergoes plastic flow at lower stress levels than SAC305, minimizing the risk of interfacial failures. Conversely, SAC305 is superior for applications which feature thermo-mechanical fatigue (desktop computers, for example, or servers) as it accumulates less strain than SAC105.
Date of Conference: 16-18 April 2012