Shape Dependency of Fatigue Life in Solder Joints of Chip Resistors

This study is attempted to correlate between solder joint shape and fatigue life in experimental and numerical approaches. The test assemblies consisting of R1005 (1.0 × 0.5 mm) and R0402 (0.4 × 0.2 mm) soldered with SAC 305 solder material are subjected to thermal shock loading (-55 °C to 150 °C, dwell time 3 min, 6 cycles per hour). In an effort to analyze the effect of solder joint shape on fatigue life, the test assemblies are printed with different solder paste volume which induces variations in solder joint shape. The variations observed on the solder volumes generated are categorized as concave, straight, tiny convex, and convex symmetrically which are essentially achieved using stencils with different opening sizes. Another variation that is induced artificially is having unsymmetrical solder paste volume on two copper pads of a single component. Group of passive components which induces variations in solder joint shape symmetry or asymmetry are monitored to measure the resistances during thermal shock test.