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|Mixed Metals Impact on Reliability|
|Keywords: Reliability, RoHS, Lead Free Solders|
|With the adoption of RoHS and implementation of Lead Free solders a major concern is how this will impact reliability. Both commercial and military hardware are impacted by this change even though military hardware is considered exempt from the requirements of RoHS. As the supply chain has moved to the new lead free alloys both markets are being forced to understand these impacts and form risk mitigation strategies to deal with the change. This paper will be investigating the mixing of Leaded and Lead Free alloys on BGA devices and how this impacts reliability. Three of the most common pitch BGA packages will be included in the study to determine if the risk is the same as pitches decrease. Metallurgical analysis will be performed utilizing cross-sections and SEM to study the alloying of tin/lead and tin/silver/copper both separately and combined. MIL-STD-883 Method 1010.8 Temperature Cycling will be used to accelerate fatigue life of the samples and testing of those samples will be performed at regular intervals. Elevated Soldering temperatures as well as under-filling of assembled BGA's will be studied as risk mitigation strategies.|
|Rick Gunn, Director of Engineering