Most electronics companies are transferring or have transferred to lead-free electronics, both to comply with government legislations and to increase market share through product differentiation. Considering that lead-based electronics have been in use for over 40 years, the adoption of lead-free technology represents a dramatic change. Key issues that are being addressed by academia and industry include lead-free solder alloy selection, characterization of lead-free solder alloy properties and behavior under various stress loading conditions, lead-free manufacturing, logistics and intellectual property issues, and lead-free assembly reliability assessment.

Although abundant data exist on the short-term reliability (i.e. less than 5 years) of lead-free solder joints under single loading conditions, long-term reliability is still unknown. Lead-free electronics are expected to be deployed in many products that require greater than 5 years of reliability, often in environments exhibiting extremes in temperature, vibration and contaminants.

The study involves the design, manufacture, test and analysis of printed circuit board assemblies with the objective of obtaining critical information related to the long-term (5-15 years) reliability of lead-free assemblies. The test conditions include long-term high temperature and low temperature aging, vibration after aging treatment, long-term temperature cycling, and combined thermal-mechanical loading. The key results expected from this long-term reliability studies include: (1) extent of the growth of intermetallics in the solder joints as a function of commercially available PCB pad finishes and component finishes, (2) assessment of any yet-unknown risks, such as tin pest of high tin solders joints after long-term exposure to low temperature, (3) impact of PCB degradation due to high temperature lead-free soldering in causing corrosion failures and degradation in insulation resistance between solder interconnects, (4) vibration fatigue life and failure modes of lead-free solder joints with thicker intermetallics, and possibly with tin pest, (5) Failure mechanisms, mode in solder joint failures in the combined temperature cycling + vibration tests, (6) Long-term life of lead-free assembly in comparison with the eutectic tin-lead solder.

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