Abstract:

While the majority of consumer based electronics has converted to lead-free materials, a portion of the industry that provides electronics for critical applications, such as aerospace and defense, has resisted this change due to uncertainty in reliability. For these equipment manufacturers, limited availability of tin-lead parts has resulted in the potential use of lead-free parts in a tin-lead assembly process. However, reliability concerns remain with lead-free parts assembled with tin-lead solder (mixed solder interconnects). While some studies have examined the reliability of mixed solder interconnects under temperature cycling, very little data is present on the mixed solder interconnect reliability under vibration loading. This study presents the results of a random vibration test applied to mixed solder joint assemblies. A test assembly with a common layout was used which included surface mount components: 256 IO PBGAs, 100 IO TQFPs, 2512 and 1210 resistors. Lead-free board finishes examined included Organic Solderability Preservative (OSP) , (Electroless Ni over Immersion Gold (ENIG), Immersion Silver (ImAg) and Immersion Tin (ImSn). TQFP lead finishes included Sn, Sn0.7Cu and Sn2Bi. Test assemblies were subjected to step-stress tests for a total of thirty six hours and a peak vibration input of 14 Grms at room temperature.

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