Rich,
Can you specify which formula? I am sure all the flux from different vendor are not made as per your claim "equal". Especially, it is not std requirements outlined as such: not reflowed flux shall pass SIR. I am looking forward to learn from you. Many thanks.
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 Robert Kondner
Sent: Monday, April 30, 2012 2:02 PM
To: [log in to unmask]
Subject: Re: [TN] 4 Questions: No Clean vs flux Deactivation. Possible Hogwash ???
Hi,
If I read Rich correctly he is saying that flux formulated as No Clean is
designed to pass the conditions specified on the data sheets without being
"Thermally Deactivated".
If that is correct it might be a "Big Time Wow" for a lot of folks on this
list.
Rich, Did I correctly summarize what you were saying?
Thanks,
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Garcia, Rigo
(GSFC-300.0)[MANTECH SRS TECHNOLOGIES]
Sent: Monday, April 30, 2012 8:17 AM
To: [log in to unmask]
Subject: Re: [TN] 4 Questions: No Clean vs flux Deactivation. Possible
Hogwash ???
Interesting input Rich.
Are you then saying that in reality the activators don't ever get completely
deactivated by the soldering process? Do we have to then, either rely on the
encapsulating characteristics of the rosin/resin fluxes or rely on the
cleaning process to get rid of them?
Thanks for the feedback.
Rigo
Sr. Quality Assurance Engineer
Workmanship Standards, Code 300
NASA, Goddard Space Flight Center
Greenbelt, MD 20771
Phone. (301) 286-6129
Fax. (301) 286-6576
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Richard Kraszewski
Sent: Friday, April 27, 2012 5:18 PM
To: [log in to unmask]
Subject: Re: [TN] 4 Questions: No Clean vs flux Deactivation. Possible
Hogwash ???
As a former flux formulator, we would never expect to rely on heat to
deactivate (neuter) any flux activators. Reduce risk, sure. Eliminate, no.
It was always part of good marketing and sales tool kit however, because it
sounds plausible (& desirable).
This kind of thinking related to thermal deactivation is not uncommon. Good
example is the old Battelle Institute glutamic acid hydrochloride & urea
concept. Heat releases the HCl for activity and the later & higher peak heat
releases the urea activity to neutralize the free HCL. Was touted as ~a
No-clean water soluble flux at one time. Actually worked rather well, but
not enough to always count on the residues being harmless.
Rich Kraszewski/PLEXUS
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Thursday, April 26, 2012 9:45 AM
To: [log in to unmask]
Subject: [TN] 4 Questions: No Clean vs flux Deactivation. Possible Hogwash
???
Hi,
4 Questions (Please respond by number and elaborate if possible.)
I have been listening to this thread about no clean fluxes and "Possible"
problems with flux residues that have not been "De-Activated" through
complete heating during a soldering process.
First, I understand that a flux is "Activated", ie becomes chemically
active, by heat. An example is ammonium chloride that when heated releases
HCl (hydrochloric acid) which is a strong agent for cleaning a surface for
good solderability. Below the temperature where a flux becomes "Activated"
the flux in not active. IE: "All Cold Fluxes are De-Activated".
Question 1: Are fluxes "Active" when they are cold? Is a RMA active when
it is cold?
If the above is true what is all the stuff about "Active Flux" remaining
on a PCB surface? Hogwash?
Further, I know from experience that reflow temperatures that are too high
or too long "Burn Off" the flux and provide very poor surface finishes. If
so this implies a significant portion of un-used flux will remain on the PCB
after the reflow cycle. Flux will not be "Activated" once the PCB cools but
it will remain active during the liquid solder phases.
Question 2: Is it true that we want flux active throughout the entire
liquid solder phase and does this imply there should be un-altered flux
remaining on the PCB surface after the reflow period? (Me Thinks Yes?)
A good example is an RMA flux. From experience I know RMA fluxes have a
very wide processing window, You can "Touch Up" a joint covered with RMA
without additional flux because of RMA robustness. It simply leaves a
"Messy" board finish.
Also, it has been my understanding that leaving an RMA flux on a PCB was a
"Cosmetic Issue" but I do find that hard to believe. There must be "Bad
Stuff" in all that gunk left behind. But wire solder and RMA flux has been
used for decades and is considered "OK" to remain on a PCB, I think.
Question 3: Are any flux chemistries acceptable to be left on a PCB and not
cleaned and would such PCBs pass an ionic contamination test?
Question 4: Do all the companies that make "No Clean" Flux lie when they
call them "No-Clean"?
Thanks,
Bob K.
> I have an issue with one of the assembly houses we use. They are
> using a No-clean flux that contains adipit and succinic acids (per the
> MSDS) in an alcohol base.
>
> Is it allowed to leave flux on the PWB that HAS NOT BEEN DEACTIVATED
> BY HIGH TEMPERATURES OF SOLDERING?
>
> I am not talking about the flux used in the solder paste or wave
> soldered flus. I am talking about the flux used at rework and
> touch-up of the PWB.
>
>
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