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 > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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