"Too much also means a better chance that not all of it will be heat-activated." Especially, under rework condition - heat may not be applied uniformly.  

Joyce Koo
Materials Researcher - Materials Interconnect Lab
Research In Motion Limited
Office: (519) 888-7465 79945
Mobile: (226) 220-4760

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, November 06, 2012 9:15 AM
To: [log in to unmask]
Subject: Re: [TN] Limits on flux residue

Dave, I could not agree with you more. Excellent posting, and excellent philosophy.

Too many times I hear someone say "who cares, its no-clean, perfectly safe" only to find the hard way that is not true.
Not only that, but most no-clean fluxes are very effective when applied as a very, very thin sheen or veneer (less than 1 mil thick) over the BGA pads. You DON'T need gobs, more flux does not mean better wetting. Too much also means a better chance that not all of it will be heat-activated.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Tuesday, November 06, 2012 7:27 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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