SMTA International Conference Proceedings


Authors: Jeff Bradford, Joe Felty, and Bill Russell
Company: Raytheon Company
Date Published: 9/25/2005   Conference: SMTA International

Abstract: Combined environments testing was conducted for the Joint Council on Aging Aircraft/Joint Group on Pollution Prevention Lead-Free Solder project. The purpose of the project was to validate and demonstrate lead-free solders as potential replacements for conventional tin-lead solders used on circuit card assemblies against the requirements of the aerospace and military electronics community.

The solder alloys tested include: Sn3.9Ag0.6Cu, Sn3.4Ag1.0Cu3.3Bi, Sn0.7Cu0.05Ni and Sn37Pb. These solder alloys were used to assemble various components on three different printed wiring board test vehicles: manufacture, rework and hybrid. The test vehicles were subjected to a combined environments test consisting of thermal cycling from -55 to +125 degrees Celsius at a ramp rate of 20 degrees Celsius per minute, dwell at the temperature extremes for 15 minutes and pseudorandom vibration of 10 grms for the last 10 minutes of the dwell periods. After every 50 cycles, the vibration level was increased by 5 grms until a maximum of 55 grms was reached. The test vehicles were electrically monitored using event detectors.

The solder joint failure data of a given component type, component finish and solder alloy were evaluated using Weibull analysis. The reliability of the lead-free solder alloys was compared to the baseline tin-lead (Sn37Pb) solder alloy.

Keywords: Thermal cycle, vibration, lead-free

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