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 coffeering 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