International Brazing &Soldering Conference, San Diego, CA, February 16-19, 2003

Isothermal Mechanical Creep and Fatigue of Pb-free Solders

Q. Zhang, P. Haswell and A. Dasgupta
CALCE Electronic Products and Systems Center
University of Maryland
College Park, MD 20742


The creep resistance of Sn3.9Ag0.6Cu Pb-free solder alloy is compared to that of the baseline eutectic Sn37Pb solder at same temperature and at same homologous temperature, respectively. The homologous temperature is defined as the ratio of absolute temperature to absolute melting temperature. Sn3.9Ag0.6Cu shows larger creep resistance than Sn37Pb solder at both conditions. The isothermal mechanical durability properties of Sn3.5Ag and Sn3.9Ag0.6Cu Pbfree solder alloys are presented and compared to that of the baseline eutectic Sn37Pb solder. Cyclic mechanical tests are performed at high temperature at various strain- rates and load levels, using a thermo-mechanical-microstructural (TMM) test system developed by the authors. The data is analyzed using standard power-law durability models based on work and inelastic strain range. The durability curve of Sn3.9Ag0.6Cu Pb-free solder is found to have the largest slope, followed by the Sn3.5Ag solder and finally the baseline Sn37Pb eutectic solder, under the test conditions investigated. At a homologous temperature of 0.75, Sn3.9Ag0.6Cu shows the best durability, while Sn3.5Ag and Sn37Pb have very similar durability performance according to damage relations based on either work or inelastic strain range.

Complete article is available to CALCE Consortium Members.


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