Removal of flux residues from highly dense assemblies

Abstract

Quality and reliability is a function of the manufacturing design that achieves repeatability and reproducibility. Designing advanced packages and assemblies is more difficult due to lead-free wetting and higher process temperature requirements. The associated manufacturing changes along with component miniaturization and board density increases complexity. From a cleaning perspective, many designers have poor insight into factors that assure a cleanable design. Solder paste selection, reflow conditions, component placement, component clearance (standoff), cleaning agent and cleaning equipment are important factors. Collaboration between process engineers, assembly designers, solder materials, cleaning agent and cleaning equipment experts can improve integration of the circuit design and assembly. Package design plays an important role when cleaning is required. Density of components, component layout, thermal heat requirements, and standoff height/clearance are key considerations. From a cleanability perspective, package on package, flip chip, bottom termination component (BTC) selection, solder mask definition, placement and layout influence the clearance gaps. The purpose of this research is to use a BTC test vehicle for studying factors related to the cleaning process. The designed experiment will present findings for removing flux residues under bottom termination components.