SMTA International Conference Proceedings


NASA-DoD COMBINED ENVIRONMENTS TESTING RESULTS

Author: Cynthia Garcia
Company: Raytheon Company
Date Published: 10/24/2010   Conference: SMTA International


Abstract: As part of the NASA-DoD Lead-Free Electronics project, combined environments testing was performed to validate and demonstrate lead-free solders as potential replacements for conventional tin-lead solders against aerospace and mili-tary electronics industry requirements for circuit card as-semblies.

Solder alloys Sn3.0Ag0.5Cu, Sn0.7Cu0.05Ni (=0.01Ge) and Sn37Pb were used to assemble components on two different printed wiring board test vehicles: manufactured and re-work. The rework test vehicles included BGA-225, CSP-100, PDIP-20, and TSOP-50 components that were removed and replaced.

The test vehicles were subjected to thermal cycling from -55 to 125 degrees Celsius, a ramp rate of 20 degrees Celsius per minute, and dwelling at each temperature extreme for 15 minutes in a HALT (highly accelerated life test) chamber. Pseudorandom vibration was applied continuously through-out the life test beginning at 10 grms and increased by 5 grms after 50 cycles until a maximum of 55 grms was reached. The test vehicles were electrically monitored for 650 cycles us-ing event detectors.

Solder joint failure data of a given component type, compo-nent finish and solder alloy were evaluated using 2-parameter Weibull analysis. The reliability of each lead-free solder alloy tested was compared to the baseline Sn37Pb solder alloy.

Key words: Lead-free, tin-lead, solder, reliability testing



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