RusTec has developed a process of manufacturing of thermoelectric material dices on the basis of bismuth telluride; the method does not include the step when slices are cut into dices which previously resulted in a significant loss of thermoelectric material due to the cut width and additional manhours spent on waxing/dewaxing of slices. The so-called Rod Technology is based on the following: first, rods of the required diameter are produced through melting or extrusion; then the lateral surface of a rod is coated with the specifically designed epoxy-based chemical compound which permits to coat dice ends with metal diffusion barriers after the coated rods are sliced into dices of the required height.
The advantages of the technology:
- Easiness of placement of dices with round shape;
- Feasibility of using circular-section dices in cases where the use of rectangular-section dices would have made it difficult to properly position cube-shaped dices;
- Protection (by coating) of dice lateral surface which precludes the adverse events such as electrical bridges, penetration of solder in semiconductor due to lateral surface solder acceptance during module soldering.
- Dice diameter: 1.4 – 10 mm.
- Dice height: 0.2 – 10 mm.
- Lateral surface protection: galvanic deposited epoxy composition, 10-30 micron, operating temperature: -50...+280 °C.
- Diffusion barrier: chemical deposition of nickel-based alloys; 7±2 micron thick; adhesion of not less than 1 kg/mm2.
- Solderable layer: 5 micron Sn (+1 % Bi) or 0.1-0.2 micron gold flashing.