Loop height assessment for automotive package

Loop height of a wire is one of the most critical aspects of wire bonding as it affects both performance and reliability of the device. The wire loop cannot be too high, since excessively high wire loops can result in exposed wire, wire sweep and/or wire to wire shorting causing electrical yield loss. On top of that, long wires can also limit and degrade the electrical performance due to higher resistance across the whole wire span. On the other hand, wire loop height also cannot be too low, as it indicates that the wire had been excessively pulled down by the bonding tool from ball bond to the second bond. This makes the wire too tight putting an enormous stress on the wire neck or wire heel, leading to package reliability problems. In order to move towards a higher level of quality performance for automotive packages, key aspects such as machine looping parameters were revisited to obtain the optimum loop height. DMAIC approach had been utilized in this study focusing on target parameters such as the wire loop height settings and arc end pos with fixed, slow 1st reverse mode. From the feasibility results; ∼57% improvement of loop height performance can be achieved. The new optimized parameters also showed no abnormalities on wire pull test, neck stress, and looping formation.