D. Ho’s research while affiliated with Santa Clara University and other places

As device feature dimensions get ever smaller, the industry trend is to shrink the die size for higher throughput and yield. Smaller pad size at finer pitch presents many difficulties and are unachievable with the current generation of bonders. This paper presents the highlights of a Sematech-funded effort to identify barriers to fine pitch wirebonding, and develop the necessary capabilities to achieve 70 μm in-line wirebonding on fine pitch leadframes. The program addressed the tooling, software, and hardware needed to enhance the performance of a wirebonder. The ESEC 3006 F/X wirebonder was selected for the case study. Feasibility was shown in a lab environment, and manufacturability was demonstrated under a high volume production environment

Twenty different epoxy compound formulations were evaluated to assess the moldability and the resulting wire sweep propensity in a manual gang-pot molding machine. Effects such as filler content, filler shape and size, hardener viscosity, catalyst level, resin type, and thixotropic index were considered. Results obtained on a 160-lead PQFP with wire lengths up to 160 mils helped reduce the selection down to 5 formulations, which were then tested in a fully automated gang-pot system in a production environment. Aside from wire sweep, effects on die pad shift was also considered. This paper will discuss the relationship between the compound formulations, moldability, wire sweep, and pad shift. Although results were obtained on a test die with 100 μm pad pitch, the information garnered should be extendible down to finer pitch