Comparative study of the electrical, thermal, and reliability behavior of pressure contact technology on SiC chips

Die-attach technologies are essential for the reliability of power devices and therefore the lifetime of power modules. This article explores and compares the electrical, thermal characteristics and reliability of pressure contacts with a molybdenum plate (PCMo) with that of pressure sintered Cu (PSCu), adopted for the high-temperature operation of silicon-carbide (SiC) chips. Samples with these packaging technologies have been manufactured and compared with commercial TO220 counterparts containing the same bare SiC chips. The results of the experimental tests indicate that the pressure contact interfaces exhibit the highest electrical and thermal resistance values (35.3 mΩand 0.54 K/W respectively) due to additional contact resistances, while the sintered layer presents the lowest electrical (20 mΩ) and thermal resistance (0.022 K/W). Under power cycling tests with a junction temperature swing from 50 °C to 200 °C, PCMo samples experience a maximum thermal stress up to 54.1 MPa, which is 13 times higher than that of PSCu. However, PCMo samples present 2 times higher power cycles (∼6000 cycles) than PSCu since cracks and delamination are avoided. The PSCu contact fails due to delamination between the sintered Cu and Ag metallization of the chip. In the TO220 reference samples, cracks initiate from the voids and then propagate outward resulting in failure after ∼3000 cycles. The manufactured PCMo and PSCu samples all survive more cycles than the TO220 samples, indicating the advancements in these emerging die-attach technologies compared to conventional methods.