High-Temperature Reliability of Sintered Silver-Tin Alloy Paste for Die Attach Applications

The growing demands for high power density in inverters for electric vehicles have led to an increase in the operating temperature of power devices. Die attachments with high-temperature reliability in high-power device packaging are thus under improvement. In this study, a Ag10Sn alloy paste is developed. The Ag10Sn alloy powders are prepared by mechanical alloying of Ag and Sn powders with a series of milling speeds for 2, 4, and 10 h to determine the optimal milling parameters. Characterization of the powders is carried out by XRD and SEM. The die bonding process is accomplished between Ag-metalized Cu substrates. The structural integrity of the Ag10Sn bond line is investigated by thermal aging at 300°C. The bond line is comprised of homogenous Ag solid solution with limited pore coarsening during aging. The high shear strength of the Ag10Sn bond line is obtained at 53 MPa after 1000 h of aging. The results show that bond lines of the Ag10Sn solid solution phase possess good mechanical properties and low porosity under high temperatures. In addition, the bond line could prevent Cu substrate from forming Cu
2
O layer. Consequently, Ag10Sn alloy paste possesses high thermal reliability and is thus a promising die attachment for high-power device packaging.