Abstract
Wire bonding technology is being applied to narrower pad piches and longer spans in LSI packages with the increase in number of input-output pins and shrinkage in chip size. This makes adjoining wires liable to touch during the molding process. To solve fundamentally this problem, the authors have been developing bonding technologies, using coated gold wires which do not suffer from short circuit failures even if the wire touch occurs.
In this study, various coated wires were evaluated to select the optimum coating film with improved resistance to the wire touch at high tempratures and improved bonding continuity. Packages were then assembled with the selected wires, and various reliability tests were conducted.
The best properties were obtained with the coating film of 0.4 μm thick heat-resistant formal, which showed high insulation reliability in a high temperature wire-crossing test and enabled continual bonding for more than one hundred thousand wire connections. It was confirmed that the assembled packages have sufficient insulation reliability between touching wires and that no failures occurred in various reliability tests including temperature cycling and high temperature high humidity bias tests.
