Figures of merit (FMs) for solder attachment reliability that account for the primary factors determining long-term interconnection integrity are discussed. The FMs provide relative measures of the reliability impact of a component or device/substrate assembly, and serve as a GO/NO-GO decision tool for package, physical, and circuit designers. The FMs are an integral part of the design-for-reliability process at key product development stages: component design and/or selection, component/substrate assembly design, and system design including thermal environment, product service life, and attachment-reliability target. The use of FMs for attachment-reliability evaluation is discussed through examples based on the solder-joint-fatigue performance of thermally cycled leaded and leadless surface mounted devices.
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