A novel TLP bonding based on sub-micron Ga particles

In recent years, electronic devices used in our ordinary life become powerful and multifunctional, such as virtual reality (VR), internet of things (IoT), also the electrical vehicle. 3D IC and wide bandgap (WBG) semiconductor packaging are one of the most notable technologies in electronic packaging industries [1]–[3]. However, Conventional packaging technologies are gradually unable to meet the requirements of 3D IC or high-power devices operated in extremely harsh environments. In our previous work, we proposed a novel approach based on a transient liquid phase (TLP) bonding for forming face-centered cubic solid-solution joints without the formation of intermetallic compounds. A trace amount of gallium (Ga) and nickel (Ni) in an under-bump-metallurgy (UBM) process at 300°C for 24 h with high-strength and excellent thermal stability. In this study, due to the high surface tension of liquid Ga and the long time it takes to form the bonding joints, liquid Ga was replaced with Ga-based submicron particles (SMPs) by a sonochemical process. With Ga-based paste and Ni UBM, high-strength, thermally stable, and low resistance Cu-to-Cu bonding joints can be fabricated at a relatively low temperature and short bonding time comparing to the process reported in our previous work. The industrial application of Ga-based SMPs was conclusively demonstrated by a series of evaluations of Ga-based SMPs and Cu-to-Cu bonding joints.