Brian,
I agree with you. Our bench cleaning procedure includes Axarel 2200 for the
reasons you state. I'm looking for alternatives. Also, contrary to most
board assembly areas I've ever seen, we don't blow off/dry the dirty
solvent, we use a pretty good sized vacuum probe to immediately remove the
dirty solvent from the surface of the cleaned area. This is done
specifically to prevent the spread of contaminants as you mentioned. It also
prevents the assembly area from smelling strongly of IPA by not turning the
liquid into an aerosol. A final, total board cleaning is performed in the
Axarel 32 batch cleaner to address the small remaining residue and items
that IPA can't.
Thanks,
Rainer
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Wednesday, February 16, 2000 3:37 AM
To: TechNet E-Mail Forum.; Blomberg, Rainer (FL51)
Subject: Re: [TN] PWB CLEANING SOLVENTS
Rainer
There is hardly a worse cleaning solvent for RMA fluxes than IPA. At the
best, it will
spread the soluble rosin over a larger area, until it is thin enough to be
invisible.
This increases the surface area so that any dangerous contaminants, such as
those
ionics that are soluble in IPA are more readily accessible to cause harm.
Furthermore,
IPA is VERY poor at dissolving the metal-organic salts formed by reaction
between the
flux and the oxides and will do so ONLY if it is virtually 100% pure:
saturation occurs
at ppm levels.
It became popular because of the erroneous belief that what is used for
formulating a
liquid flux must be good for cleaning off the residues. This hypothesis
ignores the
facts a) that certain components, including the rosin, are much modified by
heating to
over 200°C and b) there are chemical reactions occurring that modify the
residues.
Beware!
Brian
"Blomberg, Rainer (FL51)" wrote:
> Hans, Faz,
>
> I am currently in the middle of a cleaning improvement investigation and
> could share some info. Hans, I have found a spray-under-immersion batch
> cleaning machine which is getting strong consideration. It is made by
> Austin America (Mega II) and is compatible with aqueous and semi-aqueous
> cleaning solvents. It has a lot of nice features that might suit your
> needs.
>
> Faz, for your information, we use RMA flux on space quality assemblies and
> are using IPA and Axarel 2200 for hand cleaning at the bench and using
> heated Axarel 32 in our ECD spray-in-air (nitrogen) batch cleaner followed
> by hot DI water rinsing, IPA spray off and oven drying. It's a long
process
> that we are looking to shorten. Operators don't like the solvent smell
and
> use IPA/brush/vacuum probe almost exclusively with great success. IPA is
> inexpensive, relatively safe and effective for small touch-up type work.
> Complete board cleaning does indeed have many options and the type of flux
> is the biggest driver of which is "best". We are currently exploring
> long-chain alcohol like Kyzen Ionox I3330 to do the job of several
solvents.
> We have found it to clean both RMA and NC fluxes from wave and hand solder
> operations equally well in immersion type equipment. I understand it is
> also available in a bench cleaning formulation. It may well turn out to
be
> our "best" choice, but you have to judge your application independently.
In
> another application (military boards), an in-line cleaner using Bioact
EC-7
> works well, but didn't clean well enough (too much white residue) for the
> space application boards. You can't predict cleaning effectiveness
> beforehand, it's something you have to tailor to your situation. I know
> that's not much help, but equipment and chemistry suppliers can help by
> providing free cleaning evaluations with parts submitted by you.
>
> Good luck.
>
> R. G. Blomberg
> Honeywell - Space Systems
> Staff Production Engineer
> (727) 539-5534 voice
> 727-539-4469 Fax
> [log in to unmask]
>
> -----Original Message-----
> From: Hinners Hans Civ WRALC/LYPME [mailto:[log in to unmask]]
> Sent: Tuesday, February 15, 2000 9:03 AM
> To: [log in to unmask]
> Subject: Re: [TN] PWB CLEANING SOLVENTS
>
> Hi Faz,
>
> You're in luck. I'm using Kester 186 and 186-18 RMA fluxes with their
5738
> Dross Inhibiting Fluid. We do a mix of thick (150 mil) multilayer and not
> so think double sided boards and assemblies. We wave solder using an old
> (translation: museum quality) Hollis machine.
>
> First, we do a cascade wash with hand brushing in Trans LC (Trans 1,
> 2-Dichloroethlyne) which replaced Trichloroethylene (the environmentally
bad
> stuff not the less bad stuff). I'm looking for a substitute. It cleans
> great but has health & safety issues I'd like to eliminate. If we were a
> bigger outfit I'd prefer an immersion spray washer if one exists for PCBs
> (hint hint). Depending on the board a cascade rinse in isopropyl alcohol
> can do the trick or skipping it all together. I've tried some other stuff
> but haven't found it yet, some are so aggressive they'll strip the
> silkscreen printing off or change the appearance of the board. I just
hate
> when that happens.
>
> Next, we run the boards through our Tooltronics Ultra Clean II Aqueous
> Cleaner with Kyzen's Aquanox XJN chemistry at 25% strength (minimum). The
> boards get washed for 2 to 3 minutes (depends on the conveyor speed) at
~35
> psi. Lighter stuff goes in baskets with lids. A two stage DI Water rinse
> for 3 - 4 minutes. Aquanox XJN is very good at rinsing clean and it takes
a
> while to load up. We used to run Armakleen (before my time) but it never
> stayed active long enough to pay for itself. Plus it would scale the
pipes
> up something awful. What supply we have left is used in one of our dish
> washers.
>
> Depending on the assembly, we also dry with compressed air (Nitrogrn line
> coming soon!) and store in Nitrogen cabinets.
>
> We're a small shop so I'm not sure how portable this info will be.
>
> Hans
>
> ~~~~~~~~
> Hans M. Hinners
> Materials (& Process!) Engineer
> Warner Robins - Air Logistics Center/Avionics Production Division
> Manufacturing Branch (LYPME)
> 380 Second Street, Suite 104 (Building 640)
> Robins AFB, GA 31098-1638
> 912-926-1970 (Voice) 468 - 1970 (DSN) 912-926-7164 (Fax)
> mailto:[log in to unmask]
> .
>
> > -----Original Message-----
> > From: Dan Fazioli [SMTP:[log in to unmask]]
> > Sent: Thursday, February 10, 2000 02:11
> > To: [log in to unmask]
> > Subject: [TN] PWB CLEANING SOLVENTS
> >
> > Greetings, TechNetters!
> >
> > I have a question for the "guru's" of PWB cleaning, and obviously it
> > relates to
> > the new legislation (Montreal Protocol) which now bans the use of Ozone
> > depleting substances containing CFC based materials. So, with that in
> > mind...."What are the best "cleaning solutions" (chemicals) to use which
> > are
> > most effective for removing the flux residuals from PWB's that also has
> > compatibility with a wide variety of different chemicals and materials
> > such as
> > adhesives, connectors, sleeving, wire, inks, epoxies and etc.?" In
> > essence,
> > we all know that establishing a suitable substitute is no small task,
and
> > involves many trade-offs as well. However, I would appreciate anyone
> > sharing
> > their experience with regard to this endeavor.
> >
> > Best regards,
> >
> > Faz
> >
>
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--
Brian Ellis
Protonique SA
PO Box 78
CH-1032 Romanel-sur-Lausanne, Switzerland
Voice: +41 21-648 23 34 Fax: +41 21-648 24 11
E-mail: [log in to unmask]
URL: Technical and consultancy divisions:
http://www.protonique.com
Web services division:
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