Optimization of TLPS Bonding Process and Joint Property using Ni-Sn Paste for High Temperature Power Module Applications

Abstract

Recently, as interest in eco-friendly vehicles such as electric and hybrid vehicles increases, the demand for power semiconductors, a key component, is also increasing. Power semiconductors convert, distribute, and control power and operate in harsh environments such as high temperature and high pressure. In order to ensure stable reliability in such harsh environments, research on a technology that can stably form joints even at high temperatures is essential. Transitional liquid phase (TLP) bonding was proposed as a high-temperature power semiconductor chip bonding technology, which has the advantage of forming an intermetallic compound (IMC) phase with a high melting point at the joint. However, it takes a long time to convert the joint into full IMC phase. Therefore, in this study, in order to shorten the process time, a paste was manufactured by mixing high-melting point Ni metal powder and low-melting point Sn metal power, and a joint was formed through a TLPS (Transition liquid phase sintering) bonding using the paste. Pastes of different compositions were prepared by adjusting the ratio of Ni and Sn powders. The chip and substrate were bonded through a thermocompression (TC) bonding process, and the highest shear strength was obtained at a bonding temperature of 250 ℃ for 10 min. Heat treatment was performed at 200 ℃ for up to 500 h to evaluate the high temperature long-term reliability of the joints. The Ni-Sn TLPS bonded joints remained reliable joints after a long-term aging test at a high temperature of 200 ℃.