Low-temperature sintering behavior of ternary solder and copper powder for high-power device packaging

摘要

For a high-power device of hybrid electrical vehicles requiring high thermal reliability, the concept of low temperature sintering material composed of Ag coated Cu, Sn/Ag/Cu ternary solder and chemical components removing oxide on the surface of metal fillers was studied under a processing temperature of 240°C. Due to the limited thermal reliability of conventional Tin based solder systems, the high-power device applications with a good thermal performance have been hindered because these solder materials were possibly re-melted under extreme operating conditions. Isotropic conductive paste based on thermosetting resin was previously investigated. With increase of temperature during processing, the Sn/Ag/Cu ternary solder in low temperature sintering material was melted at the melting temperature (220°C) of solder, and then, Sn was reacted with the adjacent Cu particles, producing intermetallic compound such as Cu₆Sn₅or Cu₃Sn. The metallic reaction between Tin and copper increased the melting temperature of the yielded metal filler from 220°C to 360°C. Therefore, we expect the enhanced reliability and thermal stability of low temperature sintering material, compared to the solder-based conventional conductive interconnection materials, because the created metal filler product (intermetallic compound) in low temperature sintering material after processing will not be re-melted at the similar operating temperature to the processing temperature, 240°C. After sintering processing of low temperature sintering material in present research, 3.7 wt.% of the residue chemicals was detected by TGA because most of chemical components was evaporated during sintering process. In conclusion, low temperature sintering material is believed to be a good candidate material for the high-power device packaging due to the phenomena of the increased melting temperature of metal filler.