Complications in life prediction estimates at elevated temperatures in lead/tin solders during accelerated cycling

It was reported previously that cyclically tested Pb/Sn solders of different compositions exhibited a complicating anelastic effect. The storage and recovery of anelastic strains suppress damaging creep strain from being stored, thus causing nonconservative life prediction estimates, and result in complications with respect to accelerated testing. These complications were at that time believed to be characteristic of only eutectic solders at near ambient temperatures. It is now found that these complications exist for high-end Pb solders and at higher temperatures. Experiments done on 90/10 Pb/Sn solder indicate that the anelastic strains are not due to an interaction between the lead and tin phases. This leads to the conclusion that grain morphology would play an important role in determining anelastic responses in solder. The effect of grain size on accelerated cycling is also discussed