Yield improvement in SMT production by integrated process monitoring and testing

Almost 30-50% of fabrication costs in electronics production are caused by testing and repair operations. A strategy for yield improvement requires strong dedication to causal relationships and specification of process and product quality. Critical process parameters and their causal effects on product quality must be analyzed. Once critical process parameters are addressed, control strategies can be developed to assure high first pass yields. An overview of ongoing work that has been performed to establish a surface mount technology (SMT) production line with closed loop quality control via direct process monitoring capabilities and integrated inspection operations is given. For different inspection tasks, 3-D laser and X-ray inspection is applied. Process parameter as well as test and inspection results are gathered online. Thus, interrelationships between process steps beginning from material inspection, solder paste application, components placement, reflow soldering and final inspection can be analyzed