Development of high-strength and superior thermal shock-resistant GaN/DBA die attach structure with Ag sinter joining by thick Ni metallization

Abstract

With the advent of wide band-gap (WBG) semiconductors like silicon carbide (SiC) and gallium nitride (GaN), the operation temperature of WBG power modules are expected to be over 250 °C. High temperature die-attach materials that can withstand these harsh conditions are emerging as one of the main issues of the reliability of power electronic applications. In this study, high-strength and superior thermal shock-resistant GaN/DBA die attach structures with Ag sinter joining by thick Ni metallization (7 μm) were developed and compared to conventional Pb5Sn soldering die attach. A thermal shock test was conducted at a temperature range of −50/250 °C, holding 30 min at each extreme temperature up to 500 cycles. Consequently, the shear strength of the Ag sinter joining structure was sustained above the initial strength after 500 cycles, which showed durable sinter necks and non-deformed interfaces due to the thick Ni metallization. On the other hand, the Pb5Sn solder joined structure showed a 50% reduction in shear strength after 500 cycles compared to the initial state. Some disadvantages of these solder joints occurred such as an intermetallic compound and interface degradation. Thus, with the new design and evaluation reported in this study, Ag sinter joining can be expected as an environment-friendly replacement die material for the long-term reliability of WBG semiconductor module packaging.