Development of low-temperature sintered nano-silver pastes using MO technology and resin reinforcing technology

Traditional thick film technology is widely used in various electronics products. With that technology, there are two types of pastes: a high-temperature sintering type and a low-temperature processing type. The high-temperature sintering type contains glass and requires over 400 °C for adhesion. It provides high electrical and thermal performance. The low-temperature processing type, on the other hand, requires 150-300°C which is the same curing condition as silver epoxy. For the low-temperature processing, nano-silver technology has made great progress in the last decade. This paper will discuss the fundamental study on nanosilver pastes newly developed with an unique approach using MO (Metallo-organic) technology and resin reinforcing technology. Nano-silver pastes contain several types of dispersants as surface coating to prevent agglomeration of the particles. Various coating techniques have been reported to optimize sintering performance and stability. Our coating techniques in MO technology provide a low-temperature sintering capability by minimizing the coating materials. The nanosilver pastes show high electrical and thermal performance. However, degradation of die shear strength had been found by thermal cycling test due to the fragility of porous sintered structure. To improve the mechanical property, resin reinforcing technology has been developed. Adding special resin to the pastes fills the porous area and reinforces the sintered structure. Degradation of die shear strength have not found by 1000 cycles of thermal cycling test. Additionally, adding different types of special resins to the pastes decreases the elastic modulus. These techniques will expand the applicable die size range even though C.T.E difference between die and substrate is large. Nano-silver pastes using MO technology and resin reinforcing technology will meet various requirements for many different types of thick film applications.