Toward next generation interconnection technology: Ag/Cu sinter joining and their innovative application

With the rapid development of high-power electronic devices, there is an increasing demand for lead-free technology with high thermal conductivity and thermal reliability. Wide band gap semiconductors have entered the market, and there is growing interest in interconnection technologies for these devices that can operate at temperatures above 200 °C. Sinter joining technology has emerged as a promising solution due to its exceptional thermal and electrical conductivity and thermal reliability. However, there are advantages and disadvantages to both Ag sinter joining and Cu sinter joining, along with their potential applications and scientific challenges that need to be addressed to realize their practical use. Ag sinter joining is a novel interconnection process that has shown unique benefits in SiC device packages. Ag particles can be sintered at low temperatures, even below 200°C, and can operate over 250°C. Sintered Ag layers exhibit high electric and thermal conductivity, high melting points, and strong bonding. Ag sintering can also be applied to various metallization such as Ag, Al, and Au, making it a promising process. However, the use of Ag as a die-attach material still faces challenges such as high cost, poor chemical migration properties, and corrosion. Cu sinter joining provides a cost-effective alternative with similar thermal and electrical conductivity as Ag, and higher resistance to chemical/gas corrosion, making it applicable in a wider range. Yet, sintering Cu demands serious conditions due to its low self-diffusion coefficient and intrinsic oxidation tendency, requiring the application of high pressure, temperature or reductive protecting gas. Cu particle sinter joining technology is highly regarded for its cost-performance ratio in interconnecting power devices. However, several issues must be resolved to make Cu sinter joining a practical alternative.This paper highlights the need for further research and development to overcome the challenges associated with each technology and realize their practical application in high-power electronic devices. Firstly, some Ag sinter joining cases were proposed to discuss the sinter behavior, and the recently emerged novel application of sinter process, such as large area bonding for substrate attachment. Secondly, the mechanism of Cu sinter joining was discussed, and efforts to realize Cu sinter joint at mild sintering conditions were released. Finally, the newest development in each technology was suggested, and the scientific challenges to fill in these gaps are presented as well.