Effect of Sn element on the interfacial reinforced AlN/Cu joint brazed by Ag-Cu-Ti-(Sn<i>x</i>) filler

Abstract

The AlN substrate is anticipated to fulfill the heat dissipation requirements for SiC power modules, owing to its exceptional thermal conductivity. Nevertheless, the strength and reliability of the AlN/Cu interface join between the substrate and Cu plate is often compromised and requires significant improvement. In this study, reinforced AlN/Cu joins were successfully fabricated by incorporating Sn phase with a low melting point of 232 degrees C into the Ag-Cu-Ti brazing filler. The XRD and SEM results suggest that the Sn element facilitates the transformation of the AgCu eutectic structure into a soft Ag solid solution buffer layer, which alleviates residual thermal stress, and promotes the extension of the TiN reaction layer along the AlN grain boundary, thereby enhancing joint bonding strength. Furthermore, ultrasonic scanning results reveal that the Sn additive effectively eliminates voids to 0% at the interface due to increased fluidity of the Ag-Cu-Ti-(Sn-x) filler and also improves the wettability of the modified filler to the AlN ceramic substrate. With a Sn concentration of 0.24 mg/cm(2), the peeling strength of the join attains a maximum value of 47.53 N/mm, which is 9.14 N/mm greater than that of the counterpart without Sn additive. Significantly, this study achieves the mitigation of thermal stress and enhanced substrate reliability without the need for additional equipment or process conditions, thus holding great promise for rapid implementation in practical applications.