Compression Stress/Strain Response of the 95.5Sn-3.5Ag-0.6Cu Solder[1]
P. Vianco and J. Rejent
Sandia National Laboratories
Albuquerque, NM
ABSTRACT
Constitutive-based, computational models can provide high-fidelity predictions of solder interconnect degradation, particularly under cyclic loading conditions.� However, the development of these predictive codes requires the availability of both time independent and time dependent mechanical properties for the solder composition.� Such a data base is being compiled in an effort to develop a constitutive model for the 95.5Sn-3.9Ag-0.6Cu (wt.%) Pb-free solder.� Compression testing was used to assess the time independent properties of the solder in the as-cast condition as well as after a stabilization treatment (125�C, 24 hours).� Yield stresses were measured over the temperatures of �25�C to 160�C, using strain rates of 4.2 x 10-5 s-1 and 8.3 x 10-4 s-1.� The yield stress values ranged from approximately 40 MPa at �25�C to 10 MPa at 160�C for tests performed at 4.2 x 10-5 s-1.� The values were not significantly affected by the aging treatment nor a change in strain rate. The true stress/true strain curves suggested the simultaneous occurrence of dynamic recovery and dynamic recrystallization processes.� Aging the sample prior to testing, as well as a faster strain rate, mitigated both phenomena.� The complication to constitutive model development resulting from recovery and recrystallization mechanisms will be discussed.
[1] Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the US Dept. of Energy under contract DE-AC04-94AL85000.