Thanks Dave for this information.  I have been preaching this to my
company and EMS' for a number of years with no effect.  One of the worst
areas of leaving flux behind in from wave solder pallets where flux has
built up on the edges of the pallet and gets transferred to the PWB but
is not heated enough to deactivate during the wave because of the
additional mass of the pallet and the protection it gives to the PWB.

Mark

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Tuesday, November 06, 2012 6:27 AM
To: [log in to unmask]
Subject: Re: [TN] Limits on flux residue

Hi Wayne - no, the JSTD-001 committee has not addressed that aspect of
No 
Clean processing because there are a number of product use environment 
influences and process parameters that come into play on what is 
acceptable and unacceptable. Your description would lead me to believe 
that someone has taken extreme liberty in calling something a "no clean"

process. One of the things that we have found most interesting in the 
implementation of a no clean process for a couple of our products is
that 
many folks believe "no clean" is a sloppy process and you can leave flux

residue anywhere on the assembly in uncontrolled quantities. But the 
reality is that "no clean" solder processing requires very careful
control 
of what/how much/where you allow flux residues to exist. In my view, a
"no 
clean" process actually is a much tighter controlled process than a 
process that utilizes cleaning to insure that product functionality is
not 
impacted.

Dave Hillman
Rockwell Collins
[log in to unmask]



From:   "Thayer, Wayne - IS" <[log in to unmask]>
To:     <[log in to unmask]>
Date:   11/05/2012 05:52 PM
Subject:        [TN] Limits on flux residue
Sent by:        TechNet <[log in to unmask]>



Is there a spec somewhere which limits the amount of residue allowed for

no clean processing?  I just saw a board where a BGA was about 70% 
"underfilled" by flux residue.  No, this was not a flux/underfill
product! 
 A quick look at JSTD-001 Section 8 didn't seem to have specific
guidance 
on this condition.

Wayne Thayer

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