Assessment of mechanical reliability of surface mounted capacitor by an accelerated shear fatigue test technique

In this study mechanical reliability of Sn3.5Ag0.75Cu solder joints in SMD capacitors has been investigated. Tensile response of the solder joint with respect to thicknesses and aging conditions was studied by using Cu/SnAgCu/Cu model samples. Isothermal lifetime curves of SMD devices subjected to high strain vibrational loading were obtained by using an ultrasonic fatigue testing set-up. Mechanical reliability and the failure modes of solder joints in the SMD capacitors were found to be highly dependent on the microstructure of the solder and the intermetallic compound layer and the testing temperature. Testing at elevated temperature resulted in a clear change of crack path and fracture mode of the solder joints.