Low-pressure Cu-Cu bonding using in-situ surface-modified microscale Cu particles for power device packaging

摘要

Since Pb-containing solders are currently being used for die-attach bonding in power device packaging, a number of investigations are targeted towards finding suitable Pb-free high temperature bonding. An oxidation-reduction bonding (ORB) was applied to achieve Cu-Cu bonding with microscale Cu particle paste. During sintering at 300 °C, Cu_2O nanoparticles were homogeneously formed on the surface of the microscale Cu particles through a thermal oxidation, and were subsequently reduced to Cu nanotextured surface in formic acid atmosphere. This in-situ surface modification significantly enhances the sinterability of the microscale Cu particles, leading to a well-sintered microstructure and a three times higher bonding strength than that of the bonding joints prepared with non-oxidation bonding (NOB).