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November 2002

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From:
David Douthit <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 18 Nov 2002 13:10:04 -0700
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Brian,

Once again you have provided valuable information and insight for these 2 threads.

These threads do bring up a growing concern I have with the subject of "high reliability" electronic equipment.
I am aware that this type of hardware represents <1% of the total electronic market BUT this equipment
is increasingly being used to support critical infrastructure for national and international interests
( defense, command and control, telecommunications, transportation, security, banking, etc...).

My concern is that the concept of "best commercial practices"  seems to be growing as the
accepted method for manufacturing high reliability hardware (as those 2 threads indicated).
Commercial electronics are making dramatic performance advances almost daily BUT
there is a price. It is the reduction in reliability and durability that comes with commercial/consumer equipment
which makes "best commercial practices" incompatible with high reliability electronic hardware.

Unfortunately the test equipment and testing protocols needed to "prove" long term wearout mechanisms
in "harsh environments" don't exist. As long as both parties agree to the terms of a contract it does not matter if
the terms can be met because more than likely the parties signing them will not be there when failures occur.
Contractual arrangements for high reliability system are being made
with concerns focused on the "short term" bottom line and not on the ability to verify the particulars.

This results in the technical competent and experienced people being placed in difficult
positions concerning their employment status.

David A. Douthit
Manager
LoCan LLC
Brian Ellis wrote:

> Juan
>
> The answers to your question are largely treated in the thread 'To wash
> or not to wash (again)' started by George Carroll on 16.11.02.
>
> I don't know anything about ROLO or ORLO (for me ROLO is a chocolate
> covered toffee :-) ) so I can't make specific comments. However mixing
> flux types is NEVER a good idea. It just adds to the composition of the
> porridge I talk about in the above thread.
>
> What shocks me, though, is that you talk about cleaning in Forane
> (CFC-113). This has not been manufactured since 1995 and is a controlled
> substance under the Montreal Protocol. If you have pure CFC-113 from a
> stockpile, which is legal if against the spirit of the Protocol, you may
> get away with it, although it is a terribly poor defluxing solvent. If
> you have a blended CFC solvent, made for defluxing, it is well past its
> sell-by and best-before dates. It will certainly not be what you think
> it is and will quite likely cause far more harm than good to your
> assemblies. If you purchased it after 01.01.96, you have probably
> committed an illegal act. I'm not sure, but I believe the USE of
> ozone-depleting solvents may also be banned in the EU. I would seriously
> suggest you contact immediately the Spanish ozone office and ask for
> advice as to how to dispose of it legally. And **please** do not
> contribute any more to ozone depletion.
>
> Oh! and all fluxes used for electronics soldering are organic :-)
>
> Brian
>
> Juan T. Marugán wrote:
> > Hi technetters !
> >
> > Although I’ve read some messages about this matter, let me ask you some
> > additional information.
> >
> > For our class 3 boards (avionics & military), we used rosin fluxes (ROL0).
> > Now, we are thinking about to subcontract the assembly of some type of
> > boards. One of the possible subcontractors uses no-clean organic flux
> > (ORL0) for wave soldering. No post-solder cleaning is performed.
> >
> > After this assembly, we have to solder some components/wires to these
> > boards so we will use our rosin flux. And, at the end, boards will
> > conformal coated with Humiseal (acrylic).
> >
> > My questions are:
> >
> > 1.- Can the use of an organic flux (residues) to produce some effect in the
> > solder joints performed later using rosin flux?
> > 2.- What happen when these boards are cleaned with CFC solvents (Forane)?
> > 3.- Have no-clean flux residues some effect in the quality (adherence, ...)
> > of conformal coating?
> >
> > Thank you from Spain for your help.
> >
> >
> > Juan T. Marugán López
> > Production Quality Assurance
> >
> > INDRA EWS, Sociedad Anónima
> > C/ Joaquín Rodrigo 11
> > 28300 Aranjuez - Madrid (SPAIN)
> > [log in to unmask]
> > www.indra.es
> >
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> >
> >
> >
> >
>
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