David
Fluxes are used for essentially 2 purposes: one to remove surface oxides and
to facilitate good wetting and second as a heat transfer medium.
You then ask: "do they burn off...during the soldering process" - to quote
my good friend Doug Pauls: "It depends".
It depends on the type of flux being used. If it is a no-clean flux, then it
is the flux manufacturers intention that the residues - and ALL fluxes leave
residues - shall be volatilised off the surface by the correct amount of
heat relative to residue volume. Of course, if you have areas (i.e. topside
in wave soldering) that do not see the correct temperature for the desired
time, then they will remain behind and might cause you some reliability
issues when in the field.
Some other rosin based, dare I say classic, fluxes, are sometimes designed
to be left on the surface, or at least may be left behind in the knowledge
and comfort (well, on a wing and a prayer sometimes!) that they will be
cleaned off afterwards.
VOC's:
As defined by ³Council Directive 1999/13/EC of 11th March 1999:
17. volatile organic compound (VOC) shall mean any organic compound having
at 293.15 K a vapour pressure of 0.01kPa or more, or having a corresponding
volatility under the particular conditions of use
As defined by ³Council Directive 1999/13/EC of 11th March 1999:
Organic compound shall mean any compound containing Carbon and at least one
or more of hydrogen, halogens, oxygen, sulphur, phosphorous silicon or
nitrogen
As defined by ³Council Directive 1999/13/EC of 11th March 1999:
9. Šemission shall mean any discharge of volatile organic compounds from an
installation into the environment. Šinto air, soil and water as well as
solvents contained in any products. They include uncaptured emissions
released to the outside environment via windows, doors, vents and similar
openings.
VOC Controls:
USA = Tax on solvents BUT Tax-Free solvents on EPA list
EU = Anything with a vapour pressure that is >0.01kPa @293.15K
This includes Whisky, Gin, Brandy, VodkaŠbut not beer and wine!
I hope this helps
--
Regards Graham Naisbitt
[log in to unmask]
Concoat Limited - Engineering Reliability in Electronics
A British Manufacturer
NEW WEB SITE: www.concoat.co.uk :NEW WEB SITE
Golf Quote of the week: Golf is Golf. You hit the ball, you go find it. Then
you hit it again.
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> From: David Tremmel <[log in to unmask]>
> Reply-To: TechNet E-Mail Forum <[log in to unmask]>, David Tremmel
> <[log in to unmask]>
> Date: Tue, 30 Nov 2004 14:50:32 -0600
> To: <[log in to unmask]>
> Subject: [TN] VOCs
>
> Dear Technetters,
>
> VOCs (Volatile Organic Compounds) are part of many fluxes, but how do they
> affect the wetting process, or do they burn off for the most part during the
> soldering process?
>
> TIA
>
> David
>
> _________________________________________________________________
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