Interfacial science in metal–ceramic joining for thermoelectric module

Abstract

Achieving high reliable metal–ceramic joint is dependent on both interfacial bond strength and favorable stress gradient in the interface. The work is based on comparative study of the various metal–ceramic combinations: copper with aluminum nitride and nickel with nitride to identify the best for the required operating temperature of thermoelectric module. The use of CuSil ABA alloy in paste form and a brazing alloy was prepared in-house with the same composition as that of CuSil ABA alloy was separately used for bonding metal interconnect and ceramic substrate. The microstructural analysis and study of thermal loss of the bonded substrate were studied. The comparisons of microstructures of different combinations suggest that the bonding of Cu with alumina is more effective when compared to AlN, since the interface forms a continuous TiOX reaction layer over the ceramic surface. The microstructure of post-thermal gradient tested sample is evaluated for the presence of flaws when the hot side temperature is 300 °C, which is significant suggesting the quality of the interface needs further improvement.