Papers by Keyword: Diffusion Soldering

Abstract: One of the environment protection’s main aims is working out soldering materials able to replace the Sn-Pb solders commonly used so far. The joint obtained using diffusion soldering fulfills these conditions and takes up 6 times less space than in the case of conventional soldering. Moreover, it can work at the temperatures higher than 350 [°C] and it often shows mechanical and thermal stability at temperatures 2-3 times higher than the joining temperature. This paper presents the morphology and chemical composition Ag/In/Ag joint diffusion-soldered at 193 [°C] for 1.5 and 2 hours. Two intermetallic phases, namely AgIn₂ and Ag₂In were identified within the joint using an energy dispersive X-ray microanalysis and selected area electron diffraction techniques. Most probably the AgIn₂ phase was formed during cooling of the joints from the soldering temperature because its melting point is 166 [°C]. On the other hand, the Ag₂In phase is desired as its thermal stability is over 300 [°C]. This phase grows into the solder material (In) relatively fast. The exponential factor n determined from the appropriate kinetic equation was found to be 0.41, which suggests some contribution of the grain boundary diffusion process in addition to the volume diffusion (n=0.5).

Abstract: SiC power devices have reached a high market penetration, especially for high-voltage applications like switch mode power supplies. In the past, however, the superior material properties like, e.g., good thermal conductivity, have often not been put to full use due to the limitations of current packaging techniques. Especially the inferior thermal conductivity of current die attach materials have been an obstacle to realise the full potential of SiC technologies. In this paper, we describe in detail the use of diffusion solder for the die attach of SiC chips. Replacing the conventional solder layer by a thin metal stack for diffusion soldering, the thermal conductivity of the device is significantly improved. In addition, we show the positive impact of diffusion soldering on the assembly process and on the device reliability. These results are interesting for, both, SiC diodes and switches.

Abstract: Paper describes solid state phenomena occurring during the formation of interconnections intended to the electronic industry. Diffusion soldering technology is an undemanding and functional tool to use when the growth of intermetallic phase(s) is desired and controlled in order to obtain the joint consisted solely of an intermetallic phase. Scanning and transmission electron microscopy investigations of the microstructure and sequence of appearance of the intermetallics within the joined area are discussed. The diffusion path describing the chemical composition changes across the interconnection was found to correlate with microstructure transformations. The growth kinetics of the δ′[Cu41(Sn,In)11] phase was determined in the temperature range of 300 – 350 °C.