Reliability of tape automated bonding using Au-Sn alloy

When too much bonding pressure is applied in inner lead bonding, the bonding characteristic of a finger in contact with a bonding tool edge tends to degrade. When bonding pressure exceeds 21.0 kg/mm(2), the finger penetrates a bump, causing damage in the AL pad. The size of the finger is much larger than that of the solder bump. However, if the bonding condition is appropriate, the bonded section is reliable. Adhesive thermal resistance for securing Cu fingers on the TAB tape determines the upper limit of inner lead-bonding temperature. The alloy is formed during bonding operation. The alloy formation is not sufficient at 380 degrees C, but it is sufficient at 500 degrees C. In outer lead bonding, bonding pressure should be controlled to prevent the substrate surface from cracking. Increasing pad length and width and reducing the temperature difference between the bonding tool and test piece were effective in preventing cracks. In both inner lead and outer lead bonding, the damage of fingers, separation of the bump from the pad, and substrate surface cracking must be taken into account in addition to the properties of the bonded area.