Critical review of size effects on microstructure and mechanical properties of solder joints for electronic packaging

With the miniaturization of electronic packaging and devices, the size of solder joints in electronics is also decreasing from bulk solder joints to micro-bumps. Both the microstructure and mechanical properties of the solder joints are also evolving with the decreasing size, which brings great concern for the reliability of different sizes of solder interconnections. In this paper, the effect of solder size on the microstructure (i.e., interfacial intermetallic compound (IMC) growth, precipitation in the solder matrix, dendrite arms, and undercooling) and mechanical properties (i.e., tensile property, shear and compression strength, fracture toughness, and creep deformation) are reviewed from the mechanical point of view. In addition, some areas for further researches about size effects on solder joints are discussed.