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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