Journal of SMT Article

Vibration Testing of Lead-Free Alloys for High Reliability

Authors: Suthakaran Subramaniam, Polina Snugovsky, Jeffrey Kennedy, Eva Kosiba, Zohreh Bagheri, and Marianne Romansky
Company: Celestica Inc.
Date Published: 10/1/2014   Volume: 27-4

Abstract: This paper discusses the lead (Pb) free alloy qualification through mechanical vibration testing. With the RoHS directives prohibiting the use of hazardous substances, electronics manufacturers are moving away from alloys containing Pb. Environments in the aerospace industry are particularly harsh and the products must withstand those conditions and perform with high reliability. Through collaboration with the high reliability customers, a wealth of knowledge in reliability compliance testing was gained. A sound methodology has been developed to carry out reliability comparisons of different Pb-free alloys.

This paper discusses the methodology for evaluating solder alloy performance for high reliability products and gives a detailed description of the technique for vibration testing using 2 and 5 G harmonic dwells. Industry standards, test protocol, test vehicle design, and measurements techniques are reviewed. The results of vibration testing and some preliminary data analysis of three Bi-containing alloys: Sn3.4Ag4.8Bi (Paul) and two reduced Ag content variations, with and without Cu, Sn2.25Ag0.5Cu6Bi (Violet) and Sn2Ag7Bi (Orchid), in comparison with SAC305 and SnPb are discussed. The vibration failure results are based on one million cycles and show failure modes that might give an indication of what material combinations fail early. Both 2G and 5G vibration levels showed a similar failure progression of the number of failures based on resistance measurements. The lowest failure rate found was for Violet followed by Paul and Orchid at the 2 G level. Violet and Paul showed the lowest rate of failure at the 5G level, followed by SnPb and Orchid. The SAC305 had the highest failure rate.

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