Bonding process without pressure using a chestnut-burr-like particle paste for power electronics

High-lead-containing solder has been pushed to the limit of high-temperature stability and eco-friendly technology for next-generation power electronic devices. Silver is an attractive material as alternative of high-lead solder due to its high melting point and good electrical and thermal properties. However, silver nanoparticle paste is high cost, and contains a number of organic materials such as solvent and dispersants. These tend to produce unexpected large voids in the sintered layer after heating, and this affects the properties and reliability of devices. In this study, silver pastes composed only micro-sized particles were used for joints and a bonding without applied pressure was tried. Chestnut-burr-like silver particles was prepared for bonding without pressure and the effect of addition of small and spherical silver particles on bondability was investigated. The addition of spherical particles in chestnut-burr-like particle paste was promoted the sintering behavior. The joint using mixed silver particle with the weight ration of 5∶5 showed the shear strength of 18.6 MPa, which was comparable to those of silver nanoparticle pastes by pressureless process.