Pressureless transient liquid phase bonding using SAC305 with hybrid Ag particles and its reliability under high-temperature storage test

Abstract

Transient liquid phase (TLP) bonding has attracted much attention as a high-temperature interconnection method. TLP is a bonding method that converts entire joints into heat endurable intermetallic compounds (IMCs) by solid–liquid interdiffusion between high-melting-point (high-MP) parent metals and low-MP bonding metals. However, conventional TLP bonding requires high bonding pressure and long process time because IMC reactions occur only at the interfaces between the high-MP parent metals and the low-MP bonding metals.We fabricated TLP paste using SAC305 with 10 wt% Ag particles to induce IMC reactions to take place across an entire joint simultaneously. A TLP bonding process was performed at 300 °C for 2 h in air without added pressure. SAC residue was found in the SAC305 joint, while the whole SAC305–10 wt% Ag joint was converted into Cu–Sn and Ag–Sn IMCs. The SAC305–10 wt% Ag joint also demonstrated 2.5 times higher maximum shear strength compared with the SAC305 joint. In addition, the bonding reliability was evaluated by high-temperature storage test at 200 °C for 1000 h. The SAC305–10 wt% Ag joint maintained its bonding strength, while the SAC305 joint mechanically deteriorated.