Hi TechNetters!

We face a problem with flux residues on the bottom (solder) side of the PCB
after wave-soldering. We have tried to clean only the bottom side since
(usually) we do not clean the PCB after assembling, but it is very hard and
nearly impossible task! The PWB is FR4 substrate and the flux we use is
alcohol based no-clean for foam. I cannot specify the solder mask as type,
but what is obvious is the shining smooth surface. I have a strong feeling
that for better performance in solder wave process the mask should have math
surface. What should I specify to the PWB manufacturer as solder mask type?
And yet could we optimize the process in some way to reduce or even avoid
such problems? We try to follow the flux manufacturer's instruction about
application, preheat and etc.

Best regards,
Yordan Venev

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