Influence of Thermal Field Distribution on the Sintering Performance of Ag Micron-flakes

Ag paste is widely regarded as one of the most promising die-attach materials to replace conventional Sn-based solders for the packaging of wide band gap (WBG) power devices. In order to form robust sintered Ag joints, the influence of various sintering parameters should be carefully considered. In this work, we investigated the effect of thermal field distribution and uniformity on the formation of sintered Ag joints by adjusting the heating temperatures of the upper and the lower heating plate separately. Strong sintered Ag joints (42.07 MPa) were formed when the temperatures of both the upper and the lower heating plate were set to 250 °C. However, if there is a big temperature difference between the upper and the lower heating plate, this temperature difference will heavily affect the sintering of Ag micron-flakes (MFs) and lead to the formation of weak sintered Ag joints (2.67 MPa). In addition, an finite element analysis was used to simulate the thermal field between the upper and the lower heating plate to reveal the effect of the distribution and uniformity of thermal field on the sintering of Ag MFs. Both experiment results and finite element simulation indicate that a uniform thermal field tends to result in robust sintered Ag joints. Therefore, we think that the uniformity of thermal field is a very important factor that affects the sintering of silver and the precise modulation of thermal field is an effective way to improve the sintering performance of silver.