The rapid implementation of new technologies (including lead-free alloys and miniaturization) challenges assembly facilities to improve yields and reduce costly defects. Cleaning wet solder paste from stencils and misprinted circuit boards are not typically thought to cause downstream soldering defects, but these cleaning processes can and do. If stencils are not properly cleaned (be free of solder paste within the aperture walls), there is the potential of insufficient solder paste deposits and inconsistent wetting when populating the board with fine pitch components.
Additionally, cleaning of misprinted circuit boards can lead to soldering defects, such as: solder balls, solder bridging and insufficient or poor wetting. Another issue that can contribute to soldering defects is the board surface finish. A majority of circuit board finishes being used today have an OSP (Organic Solderability Preservative) finish. These OSP coatings are consumed from the board by the solder paste, cleaning agents and rinse water, and this can lead to downstream soldering problems in both the SMT and wave processes.
Finally, if the flux residues are to be removed from the assembly, complete removal is critical to ensure acceptable reliability of the circuit assembly, especially when utilizing new technology, low profile components (with component-to-board gaps of less than 1 mil). Therefore, the circuit assembly cleaning process must be carefully examined and optimized to obtain maximum performance for removing the flux residues. The presentation reviewed the cleaning process from beginning (stencil and misprinted paste boards) to the end (flux residue cleaning process) and showed where the potential problems are and how to resolve them.
Richard Brooks holds degrees in both Chemistry and Chemical Engineering from the University of Florida, and he has worked in the electronics industry for over 20 years. He began his employment at Motorola in 1988 and was a part of the Advanced Manufacturing Technology Group. In 2009, Rich joined the Kyzen team as the Southwestern Regional Manager. Rich holds three US patents and is a recipient of the Six Sigma Statistical Black Belt Certification.
Kyzen is a leading supplier of precision cleaning chemistries to the worldwide electronics, metal finishing, medical, semiconductor, and optical industries. Founded in 1990, Kyzen offers superior cleaning chemistries, technical support, application and analytical services throughout the world. Kyzen has won numerous industry awards for their exceptional products and all products are RoHS compliant. For more information, visit http://www.kyzen.com.