Interfacial reaction and joint reliability of (1 1 1)-oriented nanotwinned Ag film and Sn solder

Nanotwinned materials (Ag/Cu) are increasingly promising for transient liquid phase (TLP) bonding materials in next-generation power chip packaging. This work proposes using (1 1 1)-oriented nanotwinned Ag (Nt-Ag) with coherent twin boundaries to replace polycrystalline Ag (Poly-Ag) for TLP bonding. The correlations between the wettability, interfacial reaction, microstructure, and performance of Nt-Ag-Sn joints were systematically studied. Results demonstrate that Sn achieves superior wettability on Nt-Ag with a wetting angle of 19.8° than Poly-Ag. During bonding, Ag₃Sn is the sole phase formed at the interface with a specific orientation relationship (OR): (0 0 0 1)_Ag3Sn//(1 1 1)_Ag. As temperature increases, the morphology of Ag₃Sn evolves from ridge-shaped to coarse needle-shaped. The Ag₃Sn grains orientation shifts gradually from (0 0 0 1) preferred orientation to a random distribution due to the increased random nucleation energy. Notably, Nt-Ag maintains high microstructural stability even 250–300 °C. A full-Ag₃Sn joint was successfully fabricated at 250 °C for 5–10 min, achieving a shear strength of 62.6 MPa. Here, a mixed brittle-ductile fracture occurs in Ag₃Sn. After aging at 200 °C for 336 h, the shear strength of joints declines only ∼7.7 %. High reliability stem from the high-quality bonding interface and high microstructural stability of Nt-Ag. The findings offer novel insights for the process development of Nt-Ag-Sn as packaging materials.