In this paper, the authors propose a highly conductive die attach material based on Ag@Sn powder for power devices operating at high temperatures or in other harsh environments. The preform can be reflowed at 250 °C (18 °C above the Tm of Sn, 232 °C), but the resulting bondline can sustain high temperatures up to 400 °C with a high shear strength due to the high re‐melting temperature of the formed Ag3Sn (Tm = 480 °C) after the complete consumption of the outer Sn layers. In addition, the formed bondline exhibits excellent electrical and thermal conductivities due to the embedded Ag particles in the interconnections. The interconnections also exhibit excellent reliability under thermal shock cycling from −55 to 200 °C because of the increased bondline thickness and inherent ductility of the Ag particles embedded in the Ag3Sn. Ag@Sn Core‐shell Powder Preforms is successfully prepared, the preforms required only a short time (5 min) reflow processing at 250 °C, but the resulting interconnections can withstand a high temperature up to 480 °C and exhibit excellent electrical and thermal conductivities due to the high density and the embedded Ag particles in the interconnections.