Drying and Densification Kinetics of a Low-temperature Sinterable Nanosilver Die-attach Paste
To provide fundamental understanding on the sintering behavior of the nanosilver paste for its die-attach application, the drying and densification kinetics of the die-attach material were studied. An optical setup was used to measure the shrinkage profiles of the paste in the die-attach assembly as the material underwent solvent evaporation, binder-burnout, and densification stages of the die-attach process. The measured shrinkage kinetics were found in good agreement with the weight-loss kinetics of the paste measured by thermogravitational analysis (TGA), and the comparison offered direct evidence of shrinkage contributed by the late-stage densification of silver nanoparticles. When observing the microstructure evolution of sintered joint, it is found that densification mostly happened after the removal of organics from since binders systems prevent the silver particles coming into contact. Drying of the paste tends to arise pushing up of the chip and further cracking of the sintered joint for large sintered joint in die-attached structure.