High current bond design rules based on bond pad degradaton and fusing of the wire

摘要

In this paper design rules for maximum current handling capability of gold bond wires are derived based on two failure mechanisms:(1) fusing of the wire; and (2) degradation of the interface between gold bond balls and the aluminum bond pads under high current/high temperature stress. For determination of hte fuse current as a funciton of the length an analyticla model is used to caluclte the temperautre and power distribution in the wire as a function of the position. The current level at which the melt temperature of gold is reached is the fuse current. The degradation mechanism under high current stress (up to 2.5 A) was studied by in-situ monitoring of the gold bond ball-aluminum interconnect contact resistance under high current stress at varios temperatures adn stress currents. The cumulative failure distributions were used to fit a modle for lifetime as a funcito of current and temperautre that shows an order of magnitude difference in lifetime between positive and negative current stress. Finally, fuse current and the lifetime modle result in data-driven high current design rules for bond pad and wire.