| Summary: | 碩士 === 國立臺灣師範大學 === 機電科技學系 === 102 === Thermoelectric materials featuring the advantage of energy interconvertibility between heat and electrical energy shows a great potential on the application of waste heat recovery. However, the element inter-diffusion between thermoelectric materials and electrode during bonding process is a major challenge for module production. In this study, Ni diffusion barrier was deposited by electroplating on intermediate-temperature PbTe and PbAgTe thermoelectric materials to prevent the element diffusion. The bonding process for SnAgTi filler and copper electrode was carried out at 400℃ for 20 minutes under vacuum with a pressure of 2×10-2 torr. On the other hand, the high-temperature AgCuTi filler was also used for the investigation of solid-state diffusion bonding at a high temperature of 580℃for 1 hour under vacuum. Finally, the bonding samples were evaluated by short-time aging test and electrical measurement over the temperature range from 300℃ to 550℃. The cross-sectional structure was observed by scanning electron microscope.
The experimental results demonstrate that the stack of PbTe/Ni/SnAgTi/Cu and PbAgTe/Ni/SnAgTi/Cu can be successfully bonded below 450℃. These samples with appropriated bonding conditions also maintain good bonding stability at an ageing temperature of 300℃ for 30 minutes. Another bonding stack of PbTe/Ni/AgCuTi/Cu even obtained a well-bonded interface with increasing aging temperature up to 500℃ for 30 minutes. Besides, it is worth to note that the interface resistance for the bonding structure of PbTe/Ni/SnAgTi/Cu and PbAgTe/Ni/SnAgTi/Cu raised with increasing aging temperature. On the contrary, the PbTe/Ni/AgCuTi/Cu structure based on diffusion bonding approach shows a reverse trend that was evident in a lowered interface resistance with relevant increase in aging temperature.
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