Quasi-ambient Bonding Semiconductor Components for Power Electronics Integration

Multiple components stacking is a key technology to enable power electronics integration wherein components are stacked through planar bonding. The commonly used reflow soldering present drawback of needing high bonding temperatures, thus excursions of heat and intervention between each bonding steps, and potentially causing serious reliability problems of the entire structure, such as warpage and premature failure due to the inevitable coefficient of thermal expansion (CTE) mismatch among different materials of components. Bonding method based on self-propagating exothermic reactions (SPER) is a promising technology to overcome this challenge. The SPER- based bonding process can be performed under a benign environment without needing for high temperature, thanks to localized heating by the highly reactive alternative nanoscale multilayers. In this study, SPER-based bonding was utilized to bond stacks using Sn-3.0Ag-0.5Cu solder sheets as bonding interlayer in a sandwich structure with Al-Ni reactive multilayers. The effect of surface metallization layer on the bonding quality was investigated. The thermal distribution during the reactive bonding process was simulated. The bonds show relative high shear strength about 20 MPa when bonding with etched Cu and Ni-P coatings. The simulation results show that the excursions of heat and intervention between each bonding steps were reduced significantly. Therefore, SPER-based bonding for multiple components stacking with minimum heating affect are promising to enable heterogeneous integration of future hybrid/power electronics.