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May 2014 • SMT Magazine 33 mECHaNICaL RELIaBILITy continues feATuRe Table 1: basic test setting of mobile devices standard & JeDeC JeSD22-b111. face finish (phosphorus content of nickel phos- phorous layer: MP = 6–9wt% P; HP = 9–12wt% P) was observed. For each DOE group nine cards were dropped and the response was statistically analyzed by Weibull method. The failure mode was optically determined by cross sectioning and optical microscopy. The drop events were continually moni- tored (online) until an event detector recorded electrical failures of any of the four middle com- ponents or until 5000 drops were exceeded. The four middle components were chosen because electrical defects happen first at the center posi- tions of the board due to the highest tension/ compression in this area (Figures 1 and 2). Test results The influence of drop shock performance caused by the phosphorus content in the nickel layer was in both cases, with and without un-