Process Optimization of Pressure-Assisted Rapid Ag Sintering Die Attach for 300 °C Applications

Ag sintering is a promising die-attach technique to fabricate digital and analog thick-film modules for 300°C applications. In this paper, a low-temperature, pressure-assisted rapid sintering process was developed. Process optimization decreased the sintering time to 1 min, which allowed the use of an FC150 thermocompression flip-chip/die bonder for automated die attach instead of a hydraulic press, improving the manufacturability. The porosity of the sintered Ag layer was decreased from 30% (pressureless assembly) to 15% with the application of a low pressure (7.6 MPa) during the 1-min sintering process for large die. The average shear strength for the 3 × 3-mm
²
die was 70.7 MPa, and the 8 × 8-mm
²
die could not be sheared off due to the 100-kg force limit of the shear test module. Both Ag and Au metallization (die and substrate) were studied. A new substrate metallization combination was found that was compatible with thick-film Au metallized substrates.