Improvement of Bondability by Addition of Carboxylic Acid to the Sinter-Bonding Paste Containing Bimodal-Sized Cu Particles and Rapid Bonding in Air

Die attachment by pressure (2 MPa)-assisted sinter bonding in air at 300 °C was rapidly achieved using bimodal-sized (1.86 µm and 340 nm) Cu particles, yielding a joint sustainable even at high temperature for wide-band-gap semiconductor-based power devices. Adding carboxylic acid (succinic acid and ascorbic acid) to a used reducing solvent enhanced in situ reducibility during the bonding, which considerably shortened the bonding time required for achieving shear strengths exceeding 15 MPa. The dies bonded for 1 min exhibited shear strengths of 16.0–17.5 MPa, while 5-min-long bonding yielded a nearly full dense bondline structure. The addition of these carboxylic acids delayed the oxidation of Cu particles and reduced the intrinsic oxide layers on the Cu particles more effectively to rapidly form the dense bondline and increase the joint strength.