You should not clean "no clean".  Use no clean core solder, instead of flux all over!  for your re-work (kester has no clean core solder wire).  excess no clean flux on the board without sufficient heat plus wash = trouble!  You can find it out yourself by doing pressure cooker bias test...(may be not.... you possibly got even more trouble = what about the board you already shipped?....yak...no body want to know ;-(
                                                                              jk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Genny Gibbard
Sent: Thursday, October 10, 2002 6:25 PM
To: [log in to unmask]
Subject: [TN] no clean flux as a board cleaner?

Consider a hand rework situation. 
We had a revelation from our production floor that occasionally a certain product is cleaned using a no-clean flux pen.  We have a product that the customer is very stringent that if we use no-clean solder on their product, we must not clean any residue off the board with our standard board wash.
However, if a component is removed and replaced during a rework situation, often there is a lot of excess flux residue left on the board.  It came to light that in order to make this look better, they were applying a small amount of no-clean flux to the area with a flux pen, and then scrubbing the area with a brush.
 
There were several horrified expressions around the table when this came to light. 
 
What would be the dangers of doing this?  The board is not heated like a reflow situation, or anything like that, after the 'cleaning' operation, so does this mean the flux may not be 'inert'?  I thought that it is no-clean flux used in the rework in the first place - why do they need to clean it off?  They said that it looked awful, and the inspectors wouldn't let the product thru if it wasn't cleaned up.
 
Thoughts, suggestions?  Should we be horrified, or just let them continue?

Genny Gibbard (mailto:[log in to unmask])

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