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Porosity control for TLP sintering paste for high-temperature thermoelectric modules
Kyeongho Lee, Soonil Lee, Kyu-Mann Lee and Soon-Mok Choi

Thermoelectric (TE) modules operating above 400°C require thermally stable bonding materials, as conventional Sn-based soldering joints degrade rapidly. Although sintered joint provides high-temperature stability, pressure-assisted processes can damage TE legs and limit complex device architectures. In this study, the role of organic content in porosity formation is systematically investigated for pressure-less Ni-Sn transient liquid phase sintering paste and process. Deviations from the well-established linear relationship between solid content and porosity are attributed to powder oxidation, poor dispersibility and rapid volatilization of excessive organics. Precise control of the organic content of the paste, along with regulation of volatilization of organic content restores linear relationship between solid content and porosity. This study provides practical guidelines for the control of organic content in pressure-less TLPS bonding.

Keywords: high-temperature thermoelectric module, transient liquid phase sintering, porosity control, solid content, intermetallic compound, Ni electrode