Low stress silver-glass die attach material

The sintering characteristics of a silver-filled lead borate glass composite were studied since it influences die stresses. This is especially true for very-large-area die attachments. The kinetics of silver particle sintering in the presence of liquid-phase glass was examined by dilatometry and electron microscopy. During heat treatment, the sintering rate is significantly increased after the glass becomes liquid. This can cause excessive die stresses, resulting in cracks, typically at the die-bond interface, and/or poor adhesion. The sintering process is influenced by material parameters such as silver flake surface area, glass transition temperature, and additives, and by process profiles such as temperature ramp rate and dwell time. It was found that, by adding a small amount of appropriate additives, it is possible to either increase or decrease the sintering rate significantly. Thus, stress relief in large-area dice can be achieved by using additives in silver-glass to control the sintering rate