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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