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July 22, 2009

Staging time between wave soldering and cleaning

What is the maximum staging time permissible for PCBA's between wave soldering and cleaning? I am aware that ideally it should be ASAP in order to reduce white residues and stain formation, but in many cases our manufacturing processes are not robust enough for immediate turn around. Some PCBA's are staged for up to 24 hours prior to cleaning. Is there an industry standard specification?

J. T.

Expert Panel Responses

I am not aware of a specific industry standard, but we do have clients that clean their boards with our defluxing chemistries right away after soldering or sometime within 24 hour time frame. here are also processes that we support where the chemistry is still capable of cleaning up to 72-hour old flux residues. There was also this one unique situation with one of our aerospace defense contractor clients where he stated: "…The CCAs that I had showed you with the flux residue that had been on the CCAs with coating for almost a year came clean with 2 passes through the cleaner. Very impressive…" So there are cases where you can clean up to 1-year old flux residue.

Umut Tosun
Application Technology Manager
Zestron America
Mr. Tosun has published numerous technical articles. As an active member of the SMTA and IPC organizations, Mr. Tosun has presented a variety of papers and studies on topics such as "Lead-Free Cleaning" and "Climatic Reliability".