Mechanism Study of the Cu Foam Reinforced Sandwich Structure of Cu Sintered Joints

In this paper, the Cu foam layer is incorporated into the sintered structure, and the traditional sandwich structure is transformed into a composite sintered structure consisting of dummy chip/Cu paste/Cu foam/Cu paste/substrate. The traditional sintered joints and composite sintered joints are compared through microstructure observation and shear strength tests. The results show that incorporating Cu foam results in more connection interfaces and increased connection area for the sintered layer. The shear strength of the sintered joints without Cu foam was approximately 42.4 MPa at 250°C, 20 MPa, 5 min in air, while the average strength of the composite structure joints increased to 67.7 MPa under the same conditions. Compared with the traditional sintering structure, the shear fracture location of the composite sintering structure changes from the interface of sintered Cu particles/Cu substrate to the middle of the sintered layer. These findings provide a new method for achieving reliable Cu-sintered joints with high mechanical properties.