Abstract:

The isothermal mechanical durability properties hypoeutectic SnAgCu is characterized at two aging levels, one without room temperature aging and one subject to 3000 hours (~ 4 months) of room temperature aging. Cyclic mechanical tests are performed at room temperature and high strain rate at various load levels, using a custom-built thermo-mechanical-microscale (TMM) test system. Work-based and ISR-based power law fatigue durability constants are derived and compared for both levels of aging. The isothermal mechanical durability of the hypoeutectic SnAgCu solder is compared relative to the near-eutectic SnAgCu and SnPb under similar test conditions. The durability of the hypoeutectic SnAgCu solder reduced on aging, with the drop being more significant for damage curves based on cyclic work dissipation, than on cyclic inelastic strain range. The hypoeutectic Sn3.0Ag0.5Cu SAC solder is found to be less durable than the near-eutectic Sn3.9Ag0.6Cu solder, but more durable than eutectic Sn37Pb. The observed trends match with thermal cycling and mechanical cycling data in the literature. Possible reasons for the observed trends are given based on post-failure analysis of the test specimens and microstructural differences reported as a function of the SnAgCu composition in literature.

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