SJ: The soldermask if thin enough will appear clear even if it has
coloring pigmentation. 

Residual photo imageable soldermask is normally caused by under
developing after exposure. The cause can be in the developing process
itself or in upstream processes i.e. excessive coating thickness, uneven
tack dry, photo tools etc.
It is also possible that a thin layer of mask can re-deposit in the
final cure step. 

Are you sure this is soldermask? It's hard to tell from the pictures but
it could also be poor activation in the assembly process. It looks like
you are using an OSP coating. If this is not activated properly by the
flux you could see a similar result.

	
Regards
	
Michael Barmuta
	
Staff Engineer
	
Fluke Corp.
	
Everett WA
	
425-446-6076

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Saint Jerky
Sent: Thursday, April 20, 2006 8:42 AM
To: [log in to unmask]
Subject: [TN] Solder Resist Question

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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