Reliability enhancing of heavy wire bonds through manipulation of geometry by laser

Power cycling tests of heavy wire bonds show that with increasing wire diameter the wire bond strength is significantly decreasing. The theory behind this behavior and technical options to increase reliability will be discussed. The article will describe our innovative approach for improving reliability by shaping a chute on the bonding surface. This has to happen in a way that the current ampacity is not reduced. A laser is used to cut trenches crosswise to the course of the wire and across the bonding surface. Previously the particular depth of cut has been determined by simulation. The simulations prove the theoretically predicted enhancement of the reliability true. In addition, the method can be used as "non-destructive" in-situ measurement, since the crack growth can be derived from the deformation analysis. The research work is partially carried out within the project RoBE, which is funded by BMBF. The manufacturing method and the geometric shapes are patented.