Apparent Fracture Toughness of Pressureless Sintered Silver Interconnects
This study uses three-point flexural testing to estimate the room-temperature apparent fracture toughness ( K Ic_app ) of a pressureless sintered-silver interconnect - a candidate material for use in power electronic devices. The K Ic_app estimation occurs via work-of-fracture measurement of a chevron-shaped sintered-silver joint centrally located in an “interconnect bend test specimen”. The chevron-shape was stencil-printed on a silver (Ag)-plated direct bonded copper (DBC) substrate, mated to an Ag-plated DBC substrate, and then sintered. The chevron-shape, used for decades in fracture mechanics examinations and in standardized tests of monolithic materials, enables controlled stable crack initiation and propagation that are prerequisites for valid K Ic_app estimation. The employed combination of an interconnect bend test specimen and bend test method is robust and simple, enables a means for interpreting the resistance to crack growth and delamination in an interconnect, provides a dependable way to judge the efficacies of sintered-silver processing conditions, and ultimately supports process optimization of sintered-silver interconnects.