Effect of oxygen on pressureless silver sintering in a nitrogen atmosphere

To withstand the high working temperatures of next-generation power devices, bonding technologies have evolved from soldering with low melting point materials to sintering with high melting point materials. To date, silver has been widely used as a sintering material due to its high melting point, high thermal conductivity, and low electrical resistance. Since sintering methods require low temperature and pressure to minimize internal damage to the power device, we herein achieved pressureless sintering by controlling the initial vacuum pressure in a nitrogen atmosphere. The residual oxygen present during sintering decreased with lower initial vacuum pressures, which affected the sintered Ag microstructure. Thermogravimetric analysis showed that the weight loss of the Ag sintering paste was slightly faster in air than in nitrogen atmosphere. In air atmosphere, the Ag particles aggregated to a greater degree than under vacuum. In addition, sound bonding with high die-shear strength > 40 MPa was achieved in nitrogen atmosphere when an initial vacuum pressure of > 6.7 kPa was employed, due to the higher residual oxygen content present during sintering. We therefore expect that the proposed method could be promising for the production of alternative interconnects for next-generation power devices.