Tin Whisker Test Standardization

A National Electronics Manufacturing Initiative (NEMI) Committee, Whisker Test Method Standardization, was formed in 2001 to evaluate and identify environmental test conditions that are useful in predicting the propensity for tin whisker growth. The objective of the committee is to develop standardized whisker testing methods to provide to the electronics industry for characterizing and qualifying tin-based finishes. The team completed two evaluation phases and has identified three test methods effective in inducing whisker growth, two isothermal storage methods and one temperature cycle method. A Phase 3 evaluation was initiated in mid 2003 to confirm the consistency of these testing methods, determine effectiveness for different Sn-based finishes, and possibly define test end points by determining the longest duration for whisker growth saturation for different Sn-based finishes. Results thus far confirm that temperature cycling and 60C/93 RH isothermal storage are effective in producing whiskers. An additional evaluation, Phase 4, has been initiated to look at the effect of electrical bias on accelerating whisker growth. A Phase 5 Evaluation is in the design stage. The objectives of the Phase 5 Evaluation are still being discussed. A brief review of the Phase 1 and 2 Evaluations results which led to NEMI's test method recommendations will be provided. In addition, the latest results for the Phase 3 Evaluation and status of the Phase 4 and 5 Evaluations will also be shared.