Sintering of Printed Ag on Ceramic Substrates with the Use of Formic Acid

This paper deals with joints creation on ceramic substrates with conductive patterns made by thick film technology from silver. Sintering on the thick film printed patterns is extremely specific because of porous structure, big grains, and glass phase present also on the surface of the metal film. Joints are created using pressureless sintering technology with silver-based nanoparticle paste and its sintering occurred in various atmosphere settings, using the air, formic acid or with the combination of both. Sintering is the most promising die-attach technique for power electronic devices. Presented paper deals with the process of sintering on the printed patterns, including deposition of the sintering paste, selecting, and defining correct temperature profiles. Different pre-process cleaning procedures were also applied. For evaluation, shear test showing mechanical strength and also x-ray images for advanced analysis of internal structure were used. Using suitable sintering profiles, it is possible to create high quality joints on ceramic substrates with printed patterns. Using formic acid solution is effective pre-sintering cleaning process. By combining formic acid vapours with nitrogen as an active atmosphere during the sintering process has shown to be an effective way for oxidation regulation and prevention.