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May 2013

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Brian Ellis <[log in to unmask]>
Date:
Wed, 8 May 2013 15:12:25 +0300
Content-Type:
text/plain
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text/plain (148 lines)
If my aged brainbox is right, ZEVA in Germany made a flux with citric 
acid activator for their drag soldering machines, going back 40-50 
years. It is interesting as being a common tricarboxylic acid, therefore 
quite a powerful reducing agent. It is also quite a good chelating 
agent, so can "capture" difficult-to-dissolve heavy metal salts, 
including both lead and tin ones, so it has a double-whammy effect. It 
works best as an additive (say 20-30%) to conventional dicarboxylic acid 
(e.g. adipic), rather than by itself.

Brian

On 08.05.2013 14:57, Mike Fenner wrote:
> HI
> The difficulty of explaining chemistry to non chemists is not to over
> explain it. This just confuses. I usually talk of strong and weak acids,
> weak being natural acids - those found in life usually with quite big
> formulas, and strong or mineral acids which are usually quite simple. Using
> a scale (logarithmic) to illustrate where on the scale these things go and
> where fluxes would be. Also add in things from daily life which people are
> familiar with Fruit juices, vinegar, cola.
> Citric acid is naturally found in citrus fruits - oranges lemons - has a
> place on the scale, but is not much used in fluxes, it can have wash off
> problems.
>
> Best Wishes
>
>
>
> Mike
>
> -----Original Message-----
> From: Sue Powers-Hartman [mailto:[log in to unmask]]
> Sent: Tuesday, April 30, 2013 6:21 PM
> To: [log in to unmask]
> Subject: RE: [TN] Flux classification question
>
> Mike,
>
> I like what you wrote.  While teaching J-Std001 class, I try to define the
> different Fluxes.  Would you further define organic and inorganic?  It is
> difficult to find what they are made of, tho I have been told that organic
> fluxes are citrus based.
>
> Thanks
>
>
> Sue Powers-Hartman
> Certified IPC Trainer: J-STD-001E, J-STD-001ES,
> IPC-A 600H, IPC-A-610E, IPC/WHMA-A-620A,
> IPC 7711-7721B,
> Killdeer Mountain Manufacturing
> 233 Rodeo Drive
> Killdeer ND    58640
> 701-764-5651 ext 128
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Mike Fenner
> Sent: Tuesday, April 30, 2013 10:45 AM
> To: [log in to unmask]
> Subject: Re: [TN] Flux classification question
>
> The term "Resin" describes a group of chemicals which includes natural
> materials such as shellac from beetles and synthetic materials such as
> epoxies. The natural material we are most familiar with in soldering is
> rosin - aka colophony - which is extracted from pine trees in much the same
> way as rubber is tapped. Some of the first soldering fluxes were made from
> rosin which has nearly all the attributes needed for electronic soldering.
> It does not have quite the oxide removal properties to be totally
> satisfactory and so more active chemicals are blended with it, these are
> known as activators. The amount and type added is controlled to avoid too
> much activity which can lead to corrosion. This gave us the old style R
> (pure rosin) RMA (mildly activated and RA (fully activated) designations.
> You can tell the military was involved in these because mildly activated
> rosin would more naturally be abbreviated MAR rather than RMA. :) .
> These old style specs were based on composition, basically they said if you
> use these materials in these proportions and they meet compositional tests
> (e.g. less than a certain amount of activator or leachable acid then they
> were considered safe. In other words pragmatic based on a few decades of
> finding out what worked and what didn't.
> Modern no clean technology requires more than just chemical and electrical
> properties, clear light residues for example and these are more easily met
> by using other resins. If you look at current specifications you will see
> that the no clean classification is the same for rosin or resin containing
> materials. Whether or not a flux meets modern specs is not so much concerned
> with what is in the flux as supplied, but what the residues do after reflow.
> So the test criteria are surface insulation resistance (SIR) of reflowed
> test pieces and so on. The post solder tests for no cleans were based on how
> RMA fluxes behaved. The RE and RO in flux designations is really now for
> information only and help provide continuity from the previous spec regime
> and flux types to the ones we use now. [Also for those still doing legacy
> work for those requiring MIL spec fluxes.] This explanation is somewhat
> oversimplified for clarity. Hope it helps.
>
> Regards
>
> Mike Fenner
> Bonding Services & Products
> M: +44 [0] 7810 526 317
> T: +44 [0] 1865 522 663
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
> Sent: Tuesday, April 30, 2013 2:13 PM
> To: [log in to unmask]
> Subject: [TN] Flux classification question
>
> Flux gurus, can you tell me the difference between ROLO and RELO fluxes?
>
> (Dewey, I know - the second letter is different, that isn't helpful!)
>
> Is a RELO more active or less?  Or does the E mean something else?
>
> --
> regards,
>
> Graham Collins
> Senior Process Engineer
> Sunsel Systems
> (902) 444-7867 ext 211
>
>
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