Synergistic size and shape effect of dendritic silver nanostructures for low-temperature sintering of paste as die attach materials

Electrically conductive epoxy adhesive, which combines with Ag sintering materials rather than traditional Pb-based solder materials, attracts wide research interest in modern die attach technology for power electronic packaging owing to its advantages of low processing temperature and high working temperature. In this work, Cu foil and AgNO3 were used as raw materials to synthesize dendritic silver nanostructure with a central trunk of 5-10 mu m along with many primary branches of 200 nm. Subsequently, the sintering behavior of the obtained dendritic Ag nanostructures, as low-temperature interconnect material, was systematically investigated under different sintering conditions. Remarkably, the shear strength of the interconnect joints formed from dendritic Ag nanostructures could reach around 21 MPa after sintering for 30 min at 250 degrees C under a pressure of 10 MPa, whereas the shear strengths of the interconnect joints, which formed from Ag microspheres and microflakes under similar conditions, were only 9 MPa and 11 MPa. We think that the dramatic increment in the shear strength may result from the higher contact area of nanoscale primary branches of the synthesized dendritic structures than Ag microstructures and the low-temperature sintering of their nanoscale primary branches. In addition, the interconnect joint formed from dendritic Ag nanostructures also exhibited high reliability, and it still maintained a high shear strength of 27 +/- 2 MPa even after 1000 cycles thermal quenching between - 55 and 125 degrees C. The thermal resistance and electrical conductivity of these interconnect joints were about 78.89 Wm(-1) K-1 and 9.85 x 10(-6) omega cm, respectively, which makes its further interconnect applications feasible. This means that the synthesized special dendritic Ag nanostructure has an excellent potential as a high-performance die attach material for high- and low-temperature power device.