Viscoplastic Behavior of Hypo-Eutectic Sn3.0Ag0.5Cu Pb-Free Alloy Under Creep Loading Conditions

The time-dependent viscoplastic behavior of hypoeutectic Sn3.0Ag0.5Cu (SAC305) solder is presented. Mechanical shear tests are conducted at room and high temperatures, using a custom-built thermo-mechanical-microscale (TMM) test system. This test system uses a modified Iosipescu shear specimen with a 180 microns wide solder joint. Creep deformation is measured at constant stress levels between 3 MPa to 20 MPa, at different temperatures. The creep results are fit using Garofalo’s secondary creep model and a generalized exponential primary creep model. Secondary creep measurements from the current work are higher than those reported in literature. Discrepancies in the curve fits based on the chosen continuum creep models are discussed. Possible sources of the discrepancies are discussed. In future work the primary and secondary creep constants measured from this work will be used in viscoplastic finite element models to compare with stress relaxation behavior measured earlier on the TMM specimens at various temperatures and strain levels [1].Copyright © 2007 by ASME