Quantitative Comparison of Electronic Component/Solder Joint Stress Relief in Encapsulated Assemblies

A quantiative comparison was made of various stress relief bends with and without sleeving in three commonly used encapsulants. Silicone rubber and heat shrinkable polyolifin sleeving were used on right angle, full loop, and hump style lead bends. Small (from 254mum to 762mum diameter) and large (762 mum to 1.27 mm diameter) wires were used to simulate small and large component leads. The component leads were encapsulated in microballoon-filled epoxy, 128 kg/m³urethane foam, and 320 kg/m³urethane foam. Ten test samples were fabricated in each configuration; five were used for tensile loading, and five were used for compressive loading.