Soldermask developers are notoriously difficult to clean, and to keep clean, and that is likely to be the cause of the problem.   This operation and the Tin stripper are the most difficult modules in a PCB shop to keep clean.

The conventional approach to cleaning using either caustic soda, or acid, or even a combination will not effectively clean a soldermask developer, and usually a proprietary cleaner is required.

If you need specific recommendations, contact me off-Technet.

Rudy Sedlak
RD Chemical Company

Saint Jerky <[log in to unmask]> wrote: I received some PWB photo from my customer which they claim the present
of "Solder Resist(Clear Color)" on the Solder Pad thus preventing the
solder from wetting. In your opinion, what's that clear color layer of
substance that is preventing it from wetting? Is it really solder resist?
Picture:
http://img115.imageshack.us/img115/6089/untitled3or.jpg
http://img126.imageshack.us/my.php?image=untitled16ut.jpg

This PWB is coated with Green Color Solder resist,if it is really solder
resist, shouldn't it be Green color instead of Clear? I am puzzle why the
resist turn clear instead of Green when adhere to the solder pad. Can
someone teach me?

Sorry if you feel this is a noob question as I am new.

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