Ultra-fine-wire applications and challenges in 30um process

Wire bonding perceives greater challenges ahead as we go into the ultra-fine pitch (UFP) applications, due to continued integration and miniaturization of package. These challenges included satisfying the general bondability specifications in reliability, looping and molding on a package, using ultra-fine-wires (UFW) on 30 um bond pad pitch (BPP) process applications. Besides wire handling in manufacturing and during bonding; wire threading and contamination control with such UFWs can induce enormous stress and tension in the end-user. Efforts in all aspects, including the bonders; capillaries and wires need to be improved and better controlled to achieve optimum bonding results in 30um process applications. With UFP bonding, the use of 2N wires is necessary due to better reliability robustness. However, 2N wires gives rise to significantly higher frequency of non-concentricity in bonded balls than their 3N and 4N counterparts. Bonded ball non-concentricity poses potential threat to the stability of the reliability as these `off-centered' balls often does not have a uniform distribution of intermetallics formation beneath the ball bonds and thus allowing large voids to be built-up over the aging time. This paper investigates into the 30um process setup; optimization guidelines; bonding responses and some of their measurement methodologies; process robustness and reliability under high-temperature-storage (HTS) test at 175°C in air, using 10-13 um UFWs.