Improvement of Bondability by Depressing the Inhomogeneous Distribution of Nanoparticles in a Sintering Bonding Process with Silver Nanoparticles

Low-temperature bonding by sintering of Ag nanoparticles (NPs) is a promising lead-free bonding technique used in the electronic packaging industry. In this work, we prepare Ag nanoparticle (NP) paste using both an aqueous method and a polyol method. Sintering bonding trials were then conducted using different forms of Ag NPs. The results showed that use of the aqueous-based Ag NP paste led to inhomogeneous distribution of NPs, known as the “coffee-ring effect.” This led to low strength of fabricated joints. We investigated the influence of the coffee-ring effect and ways to depress it by changing the bonding material composition. Our results show that, when using polyol-based Ag NP paste as the bonding material, the coffee-ring effect was successfully depressed due to increased Marangoni flow. The corresponding shear strength of joints was increased significantly to 50 MPa at bonding temperature of 250°C.