SMTA International Conference Proceedings

On The Fatigue Life Of Microelectronic Interconnects In Cycling With Varying Amplitudes

Authors: Y. Jaradat, J. E. Owens, A. Qasaimeh, B. Arfaei, L. Yin, M. Anselm, and P. Borgesen
Company: Binghamton University and Universal Instruments Corporation
Date Published: 10/14/2012   Conference: SMTA International

Abstract: The fatigue and failure of interconnects under realistic service conditions are almost never well approximated by cycling with fixed amplitude, or in fact by a single loading condition. However, results of tests with varying amplitudes, not to mention tests combining vibration and thermal cycling, are not easily generalized.

We and others have reported on the breakdown of common damage accumulation rules in cycling of SnAgCu solder joints. A general trend is emerging for isothermal cycling where the remaining life, after a step-down in amplitude, is consistently shorter than predicted by Miner’s rule, while a step-up tends to have the opposite effect. The effect of the latter is often minor and temporary. Each set of cycles with a given amplitude does, however, lead to a permanent increase in the rate of damage accumulation in subsequent cycling with a lower amplitude. Reductions in overall life therefore continue to increase with repeated alternations in amplitude. We show this to be consistent with the measured evolution in the associated solder properties. Similar trends were found for annealed Cu, possibly offering clues as to the underlying mechanisms.

We propose a first practical approach to the assessment of life of SnAgCu solder joints under any combination of amplitudes.

Key Words: 

Reliability, damage accumulation rules, service conditions, life in service, Pb-free

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