This study examines the effect of unidirectional porous copper (lotus Cu) on the reliability of Ag-sintered interfaces between Si and Cu during thermal cycling. In high-performance wide-bandgap semiconductor power modules, the large coefficient of thermal expansion (CTE) mismatch generates significant thermomechanical stresses, leading to interfacial degradation. Lotus Cu, with high vertical thermal conductivity and a low elastic modulus was proposed as an alternative joint material. Si/sintered Ag/lotus Cu and Si/sintered Ag/bulk Cu joints were fabricated via Ag particle paste and evaluated through thermal cycling tests (−55 °C to 150 °C). After 500 cycles, bulk Cu joints exhibited extensive delamination, whereas lotus Cu joints maintained bonding area with only localized interfacial damage. These results suggest that the unique pore structure of lotus Cu can redistribute thermal stress, provide more complex crack propagation paths, and potentially improve the reliability of the Si/Cu joint. • Thermal reliability of Ag-sintered Si/lotus Cu joints was evaluated. • Lotus Cu joints mitigated delamination versus bulk Cu joints. • Porous structure and heterogeneous layer redistribute thermal stress. • Failure mode shifted from Si/Ag to Cu/Ag interface in lotus Cu.
Kim et al. (2026) studied this question.