Hmm
I think I would like to know what their wiping procedure is and what they
are hoping to achieve by doing it before making any firm comment. 
Naturally nothing has changed in your place or theirs, but something has if
this has just started to appear. 
I would start from the premise that the boards can be no cleaner than the
last thing that touched them.
Unless the acetone is being allowed to flush off the board the probability
is that they are making the boards dirtier. If there is anything in the
acetone or on the board and it dries in place then the board will be no
cleaner than it was before (the soil might be redistributed slightly) and
anything in the acetone or on operators gloves will be left on board. If
they are applying the acetone to the wipe by holding it against the bottle
then anything in the wipes will gradually accumulate in the bottle.
Quite likely they are just seeing a surface effect as you would get on any
shiny surface wiped over like this. Think of cleaning a mirror. So it could
be technique or the acetone is dissolving something from the wipe or
softening the resist slightly. OR your boards are contaminated from
packaging say and they are seeing partial removal. In this respect the
boards could be ionically clean as measured by zero ion tester, but
theoretically could have non ionic contamination. 
So a lot of what ifs and maybes at this point.


Regards 
 
Mike 
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert DeQuattro
Sent: Thursday, February 20, 2014 5:00 PM
To: [log in to unmask]
Subject: [TN] Acetone as a cleaning agent for PCBA's

I have a customer that uses acetone to wipe down their PCBA's upon receipt.
The assemblies we make for them are cleaned using a closed loop aqueous
board washer then sampled for cleanliness with our zero-ion tester per
J-std-001E guidelines.
Recently this customer commented that boards appeared dirty upon cleaning
with the acetone.  Does anyone have any thoughts on this acetone cleaning
process.
Thanks,

Bob

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