Effect of polyol synthesis on sintering of microsized Ag particles

Abstract This study focuses on improving the sintering performance of microsized Ag pastes via in situ chemical synthesis. Ag particles of three different average sizes, 1.5, 2, and 5 μm, were used as the Ag fillers. Two kinds of Ag pastes were prepared: conventional Ag pastes and new Ag pastes via polyol synthesis by mixing ethylene glycol (EG) and AgNO3. The effect of the polyol synthesis on sintering was evaluated with respect to the microstructure and material properties, such as the electrical resistivity and shear strength. The conventional pastes showed a low sintering performance and poor necking, leading to low shear strengths of 8.8, 9.2, and 6.8 MPa at 300 °C for the 1.5, 2, and 5 μm Ag particles, respectively. The new pastes exhibited decreased electrical resistivity and shear strengths of 11.8, 15, and 13.0 MPa with a substantial coalescence of the Ag particles and thick necking. Moreover, the XRD and TG-DTA results indicated that the method can be applied to achieve pure metallic bonding with increased sintering performance. The increased sintering performance of the new pastes could be due to the membrane-like morphology from the synthesis process, which connects the Ag particles and may provide a diffusion layer between the Ag particles. The thermal aging test of the new paste with the 2.5 μm fillers indicated a high reliability, and the shear strength of the Ag joint was maintained.