The Anand parameters for SAC solders after extreme aging

The mechanical behavior of lead free solder materials is often represented using the Anand viscoplastic constitutive model. This nine parameter model is built into popular commercial finite element codes, and is widely used in the electronic packaging industry. Reliability prediction results are often highly sensitive to the specified Anand parameters, and there are great variations in the available literature values for common solder alloys. In this work, we have explored the range of Anand parameters possible for four common SAC (Sn-Ag-Cu) alloys by testing samples with a wide range of microstructures. The lead free solder materials tested include 98.5Sn1.0Ag0.5Cu (SAC105), 97.5Sn2.0Ag0.5Cu (SAC205), 96.5Sn3.0Ag0.5Cu (SAC305), 95.5Sn4.0Ag0.5Cu (SAC405). These SACN05 solders have various Ag contents from N = 1.0 to 4.0%, and all contain 0.5% Cu.