Design and Characterization of Micro Thermoelectric Cross-Plane Generators With Electroplated ${\rm Bi}_{2}{\rm Te}_{3}$ , ${\rm Sb}_{x}{\rm Te}_{y}$ , and Reflow Soldering

Abstract

We demonstrate and discuss the fabrication of cross-plane microthermoelectric generators with electrochemically deposited thermoelectric materials. A new process based on two layers of photoresist is presented to deposit the legs on the final substrate. The n-type Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , Cu, and p-type Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> are integrated into the generator. The deposition of antimony telluride is performed to the largest thickness reported to date. The influence of thermal annealing on the material properties is studied. A new flip-chip reflow soldering process with Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">57</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">42</sub> Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> soldering paste is presented that allows for enhanced thermal coupling of the generators. The manufactured generators are electrically and thermally fully characterized. They generate up to 1.63 μW cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , which corresponds to a maximum power density of 2434.4 μW cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> .