Joe,
From my perspective, there is an apparent conflict in the standard between
4.2 b and 4.2c. Jack Crawford, this should be discussed in the upcoming
meetings in Austin.
4.2 b reads:
When other activity levels or flux materials are used,
data demonstrating compliance with testing of Appendix
B shall7 be available for review.
Note: Flux or solder paste soldering process combinations
previously tested or qualified in accordance with
other specifications do not require additional testing.
To me, this says you can use any kind of flux you want, regardless of
activity level, provided you have objective data to show that your cleaning
process adequately addresses the harmful residues. You apparently have
done this.
4.2c is a hold over from MIL-STD-2000, pure and simple. I know Class 3
manufacturers who routinely manufacture with type M and H fluxes and do it
very well. I know other manufacturers that use ROL0 fluxes and could not
find their rumps with both hands and a flashlight.
In my opinion, 4.2b takes precedence over 4.2c, so I agree with your
position.
From a philosophical standpoint, the current Appendix B was written as a
path for a manufacturer to generate objective evidence that they can use
their preferred combination of materials with some expectation of success.
It shows you have done at least a rudimentary amount of homework. From
what you describe, I don't think you need do more. Having a certain
"familiarity" with Appendix B (and the "Son of Sam" version I am working on
for Rev D), I can tell you that the testing was developed with higher
activity fluxes in mind. Earlier versions of J-STD-001 said that if you
were using an ROL0 or ROL1 or ORM0 flux, you did not have to do Appendix B
testing. The materials were assumed to be benign (materials yes, assembly
process no) as they were.
Rockwell Collins used to have one water soluble flux (before my time here),
but we are now completely low residue. I could not provide you references
of Class 3 avionics manufacturers using high activity fluxes.
Doug Pauls
"Kane, Joseph E"
<joseph.kane@BAES To: [log in to unmask]
YSTEMS.COM> cc:
Sent by: TechNet Subject: [TN] Water Soluble Flux For Class 3
<[log in to unmask]>
04/23/2004 01:06
PM
Please respond to
"TechNet E-Mail
Forum."; Please
respond to "Kane,
Joseph E"
We're trying to qualify a water soluble flux, Alpha 3355 HB, for
wave soldering our military product. We've installed an ultrasonic
spray fluxer for our wave solder machine, and an in-line aqueous
cleaner with Vigon A200 in the wash section.
We've performed SIR testing in accordance with J-STD-001C
Appendix B. We've also done ion chromatography on some
production boards, some testing with our Omega Meter, and for
good measure, we conformal coated some samples and ran them
through ten-day humidity. Everything looks good.
We're not making this change lightly. We think we've done our
homework, and we've got good equipment and process controls.
But before we implement, we're reviewing with some of our
customers, and we're having trouble with one.
Their Objection #1 is that J-STD-001 doesn't permit water soluble
flux for Class 3. Obviously, that's not how we read it, because
para. 4.2.b says:
When other activity levels or flux materials are used, data
demonstrating compliance with testing of Appendix B shall 7
be available for review.
They get hung up on 4.2.c:
Type H or M fluxes may be used only for tinning of terminals, solid
wire and sealed components when performed as part of an integrated
fluxing, soldering, cleaning, and cleanliness test system.
They see "may be used only for tinning..." and stop there. We
see "may be used only for tinning...when performed as part of..."
In other words, we think that subparagraph b allows you to qualify
for soldering per Appendix B, subparagraph c says that if you
pretin, you must also clean and test.
Their Objection #2 is that nobody else is out there using water
soluble flux to solder flight-qualified military hardware. We know
for a fact that this is not true, because we have a sister plant that
does this, as does one of our competitors just down the road.
First question, a plea really, does anyone have an opinion about
the intent of J-STD-001C paragraph 4.2?
Second question - who else out there is using water soluble flux
for Class 3 military? Can you say which flux? Which military
programs?
I won't use anyone's company name without permission, but I
need to let our our customer know that we're not trying something
crazy and without precedent. If we can get beyond that, I think we
can have meaningful discussion with them about our equipment,
testing, and process controls.
Joe Kane
BAE SYSTEMS Controls
Johnson City, NY
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