Core–Shell Transformation-Imprinted Solder Bumps Enabling Low-Temperature Fluidic Self-Assembly and Self-Alignment of Chips and High Melting Point Interconnects

• DOI: 10.1021/acsami.8b12390
• Publication Date: 2018-11-15T20:52:31Z
• Authors: Mahsa Kaltwasser; Udo Schmidt; Shantonu Biswas; Johannes Reiprich; Leslie Schlag; Nishchay Angel Isaac; Thomas Stauden; Heiko O. Jacobs
• Keywords: Fluidics

We demonstrate the realization of core–shell transformation-imprinted solder bumps to enable low-temperature chip assembly, while providing a route high-temperature interconnects through transformation. The reported bump uses lower melting point BiIn-based shell and higher Sn core in initial stage. fluidic self-assembly self-alignment at relatively low temperatures (60–80 °C). use high surface free energy liquid during capture freely suspended Si dies inside heated (80 °C) water bath, leading well-ordered defect-free arrays; molten wets metal contact (binding site) on chips yields self-aligned electrically connected devices. solid provides anchor substrate. After completion short reflow raises point, yielding electrical connection. diffuses into core. tuning material ratios leads tailored solders with points (160–206 final structure.