Reliability figures of merit for surface-soldered leadless chip carriers compared to lead packages

Solder attachment reliability figures of merit (FMs) have been developed that account for the primary factors determining long-term interconnection integrity. 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. These design phases include 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