Statistical analysis of the impacts of refinishing process on the reliability of microelectronics components

Tin-whisker induced failures have been one of the major concerns of using electronic components with Sn or Sn-rich lead free solder coated I/Os. In some applications, this risk can be mitigated by refinishing the lead-free finishes with conventional tin-lead coatings using a solder dipping process. However, the solder dipping process does not come without reliability risks of its own. In this paper, the impacts of a refinishing process on the reliability of microelectronics components were statistically studied by comparing the electrical test data measured from refinished samples with those of not-refinished. A hot solder dipping (HSD) process was used and all the samples (not-refinished and refinished) were subjected to environmental test conditions of 150 cycles -65/150°C thermal cycling followed by 500 hours 85%RH/85°C humidity test. Electrical testing was designed to measure the current in reverse or zero bias conditions as currents in these regimes would have a measurable increase if moisture ingress occurs. A data reduction process, in conjunction with statistical hypothesis testing, was used to analyze the electrical test data and the results showed that there was no significant difference between the measured currents of post-aged refinished samples and not-refinished ones. Therefore it was concluded that the refinishing process did not have a significant impact on the reliability performance of the tested components.