Sinter-attach of Peltier dice for cooling of deep-drilling electronics

We evaluate Ag particle sintering as a highly reliable die attach technology for the assembly of thermoelectric modules. Bismuth telluride (Bi₂Te₃)-based Peltier coolers are realized using Ag sintering and tested for high-temperature applications (e.g. Measurement-While-Drilling, MWD). Bonding takes place at a pressure of 6 N/mm² and a temperature of 250°C for 2 min. Shear tests are performed for evaluating the adhesion according the American military standard for chip-substrate contacts (MIL-STD- 883H, method 2019.8). Sintered layers are analyzed for porosity, Young´s modulus, electrical conductivity, and thermal conductivity. It is shown that due to specific additives (i.e. micro-diamond particles) the coefficient of thermal expansion (CTE) of sintered Ag layers can be reduced to meet the requirements of Bi₂Te₃ as well as next-generation thermoelectric materials (e.g. skutterudites) for minimized thermally induced stress during drilling.