Study of Multi Principal Element Solders with Low Melting Point for 3D Electronic Packaging

Currently, three-dimensional packaging (3D packaging) is used as the most feasible technological way to break Moore's law. In 3D packaging, three different sizes of solder joints must work together to achieve highly integrated vertical interconnects. This architecture needs to be realized by multiple reflow in industrial production. Therefore, it is necessary to choose three solders with different melting points. In order to further extend the reflow temperature range and increase the flexibility of 3D integration, the development of low melting point solders is required. SnBi solder joints often suffer from brittle fracture due to the inherent brittleness of Bi, and SnIn solder joints is limited in its low tensile strength. Therefore, a series of SnBiIn alloys with different ratios were prepared. During the composition design, orthogonal experimental method was used to determine composition ratios. The effects of different composition on the micro-morphology as well as the mechanical properties of SnBiIn alloys were investigated. Samples were prepared using a vacuum induction furnace and the microstructure of the samples was analyzed. The mechanical properties of the alloys with different compositions were measured by tensile test. The results of this study provide a research basis for the design of low melting point solder.