Evaluation of Shear Properties of Indium Solder Alloys for Cryogenic Applications

In this work, different indium solder alloys were developed and characterized for their shear properties to find out their suitability for cryogenic applications. Microstructures were investigated by backscattered scanning electron microscopy; phases were identified by energy dispersive x-ray spectroscopy and confirmed by x-ray diffraction. Solder joints were prepared using copper substrates, and shear strength of substrate/solder/substrate joints was measured at room temperature (+27 °C), cryogenic temperature (–196 °C) and after 10 thermal cycles. Highest shear strength of 47.2 and 32.5 MPa was obtained in Cu/In-32Bi-20Sn/Cu joint at room temperature as well as after thermal cycling, respectively, but at cryogenic temperature, the shear strength (67.5 MPa) of Cu/In-3Ag/Cu joint was found to be the highest.