Well before we decide the residue is from break down of PCB Laminate maybe
we should consider the fact that boards have passed in the past. And this
simple wipe is a pretty quick event, probably just perfect for picking up
grease, oil or other contaminates.
So after wiping the board a few times doe the wipe become cleaner or
dirtier?
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Thursday, February 20, 2014 4:02 PM
To: [log in to unmask]
Subject: Re: [TN] Acetone as a cleaning agent for PCBA's
Robert-
You need to qualify a process which results in acceptable performance for
your customer. This is the same as the automotive companies getting a match
between a no-clean assembly process and a conformal coat: Lots of variables
which can affect the outcome.
The important thing is no residue between the part and the pcb. The gap is
probably ridiculously small, and that's the reason for the device
manufacturer's recommendation. Artificially increasing that gap may screw
up the RF performance in other ways, but is one possibility. To qualify
whatever cleaning process you come up with, just remove a mounted, cleaned,
device and check for residue.
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert DeQuattro
Sent: Thursday, February 20, 2014 3:49 PM
To: [log in to unmask]
Subject: Re: [TN] Acetone as a cleaning agent for PCBA's
Of course my permission to post the picture has been granted. It is
apparent that using the acetone is not a good approach and worse, that the
residue may be from breaking down of the PCB laminate.
So next question, how can I tactfully inform the customer of this and best
direct him to a more appropriate method?
Several of you have hinted on better technologies.
Bob
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, February 20, 2014 3:35 PM
To: [log in to unmask]
Subject: Re: [TN] Acetone as a cleaning agent for PCBA's
Hi Doug and Bob,
Here's the pic:
http://cp.mcafee.com/d/k-Kr4zqb9EVjd7arPX3VKVJBUsYMzt4SOYeuohoKrpu7fc8TpdICz
CXbzRTPskf5CZDedgkpza23t9NBZendCoOwwTispvjBPqaoVNOXb_nV5Vx5NV7HTbEILEYCUqerI
9EYJt6OaaJNP_axVZicHs3jq9J4TvAm4TDNOb2pEVdTdw0WjYPUFVDu9Rl-A_R3BY6b4RmVyD2aN
4TkN3UBV_oC3gl9qT00jqdS61NI5-Aq83iS2goqnjh08m-touq8dEq8dd45z_S4E4jh1F7Ujd43J
oCy0b2gO86yuxJwsrPIz3yYdD
You're right that is some serious looking schmutz! Almost looks as bad
as the Stridex pads I used when I was a teenager. :o)
Seriously, that acetone is breaking something down and I don't think it's
anything good.
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Thursday, February 20, 2014 12:52 PM
To: [log in to unmask]
Subject: Re: [TN] Acetone as a cleaning agent for PCBA's
Bob sent me a picture of what the wipes look like after the acetone wipes.
I have forwarded it to Steve, and with Bob's permission, to put on Steves
web page.
There is some serious schmutz here. Bob, a couple of questions - is the
solder mask dark in color or is it the garden variety green? Are the legend
and marking inks dark and are they smeared or blurred after the acetone
wipe? Is it a light wiping with low pressure, done by Millie the Mouse, or
heavy cleaning by Magilla the Gorilla?
Has anyone thought to analyze the wipe cloths by FTIR to see what the
chemical signature of the schmutz is?
Doug Pauls
From: Robert DeQuattro <[log in to unmask]>
To: <[log in to unmask]>
Date: 02/20/2014 12:19 PM
Subject: Re: [TN] Acetone as a cleaning agent for PCBA's
Sent by: TechNet <[log in to unmask]>
Thanks all on the comments.
This is a picture of what the residue looks like from the acetone cleaning
process.
[cid:[log in to unmask]]
Based upon the replies at this point to this thread, it appears:
1. Using the acetone as they are seems acceptable for cleaning
2. The boards we are supplying have some type of residue on them
regardless of the results of the zero-ion testing.
Bob
-----Original Message-----
From: Mike Fenner [mailto:[log in to unmask]]
Sent: Thursday, February 20, 2014 12:56 PM
To: 'TechNet E-Mail Forum'; Robert DeQuattro
Subject: RE: [TN] Acetone as a cleaning agent for PCBA's
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]<mailto:[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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