Thanks!
For me, there's no such thing as no-residue flux. It's a myth, an urban 
legend. Let's imagine the activator is, say, succinic acid which will 
react with, say, copper or tin oxide. Where does the copper or tin 
succinate go? Into thin air? Of course not! Around the solder joint? 
Why, yes, and if that's not a residue, please tell me what it is. And 
that's assuming it all is heated to a sufficient time and temperature to 
ensure 100% sublimation.

So, Miss, myth it is: your choice, Joyce!

Brian

On 27/04/2012 12:23, Joyce Koo wrote:
> Happy birthday.
> Can you comment on no residue flux? Not easy to use due to lack of any tacky ness. Many thx.
> --------------------------
> Sent using BlackBerry
>
>
> ----- Original Message -----
> From: Brian Ellis [mailto:[log in to unmask]]
> Sent: Friday, April 27, 2012 02:54 AM
> To: [log in to unmask]<[log in to unmask]>
> Subject: Re: [TN] 4 Questions: No Clean vs flux Deactivation. Possible Hogwash ???
>
> Mike
>
> It seems that the threads here have got out of hand, but let me make one
> clarification. We seem to have some confusion in the minds of some of us
> as to what different flux types are and do. I offer below thoughts about
> a few of them:
>
> 1. Pure rosin: is rarely used in practice but is the prototypical
> "no-clean" flux. It is a mix of mainly tricyclic mono-carboxylic acids
> and is modified little by heating. It is non-conductive and
> non-corrosive before and after heating and does not sublimate. It is not
> easy to clean off.
>
> 2. Halide-activated rosin: is rosin with an addition of a small quantity
> of organic activators with a hydrochloride or hydrobromide group tagged
> on. The theory is that heat decomposes the activator completely and
> leaves pure rosin compounds; the practice is that some will always
> remain. Those with small quantities of activator (RMA) may be considered
> by some as "no-clean". In reality, the more active types (RA) are almost
> no worse. The activators may be different and frequently RA types were
> paradoxically safer and easier to clean to safe levels than RMA.
>
> 3. Organic acid-activated rosin: Originally developed in Germany to DIN
> standards with the designation F-SW 32, they had large quantities of
> generally alkane mono-carboxlic acids dissolved in the rosin. They did
> not decompose much in heating and the "stronger" types left potentially
> corrosive residues. They were absolute hell to clean and usually left
> the activators on the board as the rosin was removed. Later versions
> used smaller quantities of di- and tri-carboxylic acids but were little
> better. Uncleaned, the milder versions were reasonably safe for
> non-critical applications in reasonable environments but they were never
> as good as halide-activated ones.
>
> All the above were used at 15-30% solids for wave soldering.
>
> 4. Low residue, no-clean flux: These were typically ~5% solids
> di-carboxylic acids for wave soldering with no rosin but small
> quantities of alkane derivatives (e.g. glycol ethers) as vehicles to
> blanket the solder joint in formation. These are the prototypical
> "no-clean" fluxes and theoretically most of the acids sublime at
> soldering temperature and the vehicles evaporate. As a rule, they are
> difficult to sheer hell to clean to safe levels and it is safer to not
> try to clean them.
>
> 5. Water-soluble fluxes: originally, these were organic halides in a
> glycol vehicle, typically 15-20% for wave soldering. These were the most
> active fluxes for electronics soldering and the residues were designed
> for easy cleaning in water. With the process properly controlled, thes
> gave the best soldering AND best cleaning, but woe betide he whose
> process was not properly controlled as improperly cleaned residues were
> conductive and corrosive. Later versions used other activators but were
> not as successful.
>
> These 5 prototype fluxes have since been much modified (not always for
> the better!) but the principles generally remain similar. Border-lines
> have become less clear. So far, I have not mentioned pastes which have
> rheological and other additives and higher vehicles/lower solvents, all
> of which modify cleaning and "no-cleaning" behaviour.
>
> What has always alarmed me - and still does - is that many solderers
> think they know better than the manufacturers how to handle their
> processes, often with inadequate cleaning equipment/products which often
> does a worse job than not cleaning at all or which are totally
> incompatible. When I was working, in a long-distant past life, I made
> expensive cleaning machines and ionic contamination testers. I had a
> pretty good idea of the physics/chemistry/metallurgy/cleaning of
> soldering processes and, without boasting, I wrote a book on all the
> problems around cleaning and contamination which was and is, even today,
> a best-seller. The whole subject is a Pandora's can of worms, if you
> allow me to mix my metaphors. If you have no or little knowledge of what
> you are doing, don't do it; follow makers' instructions to the letter
> and listen to the advice of guys like Doug Pauls, Terry Munson who,
> today, know more than I ever did. But we old-timers also know a wee
> bittie on the subject and we often have a wider experience, having grown
> up in the pioneering days, and we still see the same mistakes made today
> that we saw 50 years ago (I'll be 80 in a few weeks, DV)!
>
> Hope this helps!
>
> Brian
>
> On 26/04/2012 21:51, Mike Fenner wrote:
>> I started to answer your questions but the predicates and assumptions
>> surrounding them are candidly a little wrong, [if all flux manufacturers
>> make untrue claims about their no clean products then>90% of the world's
>> electronics industry is in trouble. Clearly that is not the case. Equally
>> candidly I don't have the time to write a treatise on flux chemistry.
>> So here are some facts about fluxes which you can apply to your assumptions
>> and questions. Hopefully this response will enhance your understanding.
>>
>> Fluxes have 3 functions
>> De-oxidise surfaces to be soldered
>> Keep them deoxidized at soldering temperatures
>> Help the solder to spread and wet.
>>
>> So the flux has some mechanical functions as well as the simple chemical
>> stuff you are addressing in your questions/statements
>>
>> After soldering to be considered safe flux residues have to be
>> Non conductive
>> Non corrosive
>> Non hydroscopic
>>
>> There are various ways to do this, simple chemical means, like breaking down
>> in to inert volatiles and disappearing up the chimney. Or mechanical,
>> encapsulating active residues in an insulating mass. Or only being active
>> when heated and so on. How significant the residues are depends very much on
>> the application - plumbing fluxes don't need to be washed off pipes but will
>> kill an electronics assembly.
>>
>> Alternatively the user can elect to clean the residues away.
>>
>>
>> So if you apply the above to your questions and statements I think you will
>> get some answers. The rest you will have to read on line or in a text book.
>>
>>
>>
>> Regards
>>
>> Mike
>>
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
>> Sent: Thursday, April 26, 2012 3:44 PM
>> 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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