Tensile Behaviors and Ratcheting Effects of Partially Sintered Chip-Attachment Films of a Nanoscale Silver Paste
The mechanical behaviors of partially sintered thick films of a nanoscale silver paste used for attaching semiconductor chips are studied. The films, about 150 μm thick, were made by repeatedly stencil-printing the paste on a ceramic substrate and sintering by a recommended heating profile suitable for device attachment. The partially sintered films were lifted off the substrate, and their tensile behaviors, i.e., stress–strain curves, were measured at temperatures between −60°C and 300°C using a dynamic mechanical analyzer (DMA). The elastic modulus and tensile strength of the sintered silver films decreased with increasing temperature. Ratcheting behaviors of the films under cyclic tension at 150°C were also tested by using the DMA by examining the effects of loading rate, mean stress, and stress amplitude. The ratcheting strain grew with increasing mean stress or stress amplitude and with decreasing loading rate.