Ramon,
I agree with what you have said here, but (you knew there was a "but"
coming) I have a teeny tiny issue with the alcohol being used to wash
the dust bunnies out from under parts. Every time I have attempted a
cleaning process like this I have ended up with soggy dust clods stuck
on any sharp corner or looped around through hole component leads.
I wish there was a magic wand that could magically remove the dust and
particulates without having to go through all sorts of manual steps to
get a used board clean.
Phil
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
Sent: Friday, November 04, 2005 8:38 AM
To: [log in to unmask]
Subject: Re: [TN] compressed air
The recommendation to clean a lot better than just blowing the
dust bunnies of the board with alcohol is not going to redistribute the
dust from one area to another. These boards should not have any flux
since they were already cleaned at manufacturing. The alcohol will
remove dust from under connectors and any low parts. If they are really
dirty it can be cleaned using rough soak and brush clean bath, followed
by two more rinses in fresh alcohol baths. By experimentation it can be
determined how many boards can be processed through the baths before the
alcohol must be changed. Of course, a DI rinse after an alcohol wash,
cleans any substance that "might" be left by the alcohol impurities.
A lot fancier and controlled use a Mega II alcohol cleaner as a
rinser and monitor the resistivity of the alcohol after each batch
clean. This cleaner has a deionizing tank that cleans the impurities
after a filter. The beauty of alcohol is that you do not have to worry
about concentration being too low and the boards not coming out clean,
or corrosion of the lines and pumps and having leaks all over the floor.
Evacuating personnel because of leaks and so on. In the previous life we
had an alcohol inline cleaner that was never down and cleaned very well.
It was made of teflon and it had double wall and a water spray between
walls to prevent fires.
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard
Sent: Thursday, November 03, 2005 4:24 PM
To: [log in to unmask]
Subject: Re: [TN] compressed air
I don't think isopropanol has any ionic elements by itself, at 99%
purity or higher, to speak of. But when directly applied to any surface,
if there are elements such as oils, flux hydrochlorides, bromides, or
other reagents and solids present it will suspend them throughout itself
while still liquid, and then as it evaporates quickly it leaves these
solids (both ionic and non-ionic residues) distributed over the area
that it originally covered prior to evaporating. It takes concentrated
amounts of flux and spreads them all over, in other words. If attempts
are made to use alcohol to clean, there should be a means of getting rid
of the suspended solids, such as a de-ionized water rinse immediately
following the alcohol bath. In fact, the reason liquid isopropanol is
used for ROSE testing is because of this ability to "cut and lift" the
flux residues entrapped under components and other tight spots and bring
them out for measurement. When cleaning with alcohol, the old batch
cleaners condensed distilled (pure) alcohol onto the boards suspended
above the sump, and the residues dripped off into the "dirty" liquid
alcohol in the bottom of the tank.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Nutting
Sent: Thursday, November 03, 2005 2:39 PM
To: [log in to unmask]
Subject: Re: [TN] compressed air
Hmmm... Bev and Brian do you want to weigh in on this?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Russeau
Sent: Thursday, November 03, 2005 3:08 PM
To: [log in to unmask]
Subject: Re: [TN] compressed air
Phil,
What ionic element does alcohol leave on the board surface? I'm not
sure that I would agree with that statement, especially since alcohol
(isopropyl to be exact) is defined in many of the IPC specifications for
cleanliness testing such as: IC (2.3.28); ROSE (2.3.25) and Mod-ROSE
(2.3.25.1). I agree that alcohol is not a good solvent in all cases.
Keep in mind that the old chemistry premise is that "like dissolves
like". In some instances it may be okay if used on alcohol based
materials. The point being that you need to match materials and make
darn sure you're getting them completely rinsed off.
Best Regards,
Joe Russeau
Process Analyst
Precision Analytical Laboratory, Inc.
4106 Cartwright Dr. Ste. A
Kokomo, IN 46902
P: 765-455-1993
F: 765-455-1996
E: [log in to unmask]
----- Original Message -----
From: "Phil Nutting" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, November 03, 2005 2:44 PM
Subject: Re: [TN] compressed air
> But Ramon, all the experts in this forum have repeatedly stated that
> alcohol is a poor cleaning agent. It desolves any oil, greases or
> fluxes and then redeposits a thin layer everywhere as the alcohol
> evaporates. Oh, and it also leaves an ionic element on the board
> surface.
> The DI water wash is a better solution IMHO.
>
> Phil
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
> Sent: Thursday, November 03, 2005 2:32 PM
> To: [log in to unmask]
> Subject: Re: [TN] compressed air
>
> It would be better in a exhaust hood. To get very clean air, use
> an in line air refrigerant system. They cost around $ 800.00 and are
low
> maintenance. Hook an ESD air gun to blow and you are ready to remove
> those bunnies. I would clean them in alcohol bath with a brush
> afterwards to make sure they are all clean.
> Ramon
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Bloomquist, Ken
> Sent: Thursday, November 03, 2005 11:20 AM
> To: [log in to unmask]
> Subject: Re: [TN] compressed air
>
> Hi Barb,
>
> We do this all the time and depending on how bad it is we either
gently
> blow with an ionized air gun in the return and repair area or if it's
> worse we'll actually take it out on the loading dock and give it a
good
> blast again using an ionized air gun.
>
> If you are not sure about where it's been or what sort of "dust
bunnies"
> are on it you might want to wear a dust mask.
>
> KennyB
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Barbara J. Rich
> Sent: Thursday, November 03, 2005 8:00 AM
> To: [log in to unmask]
> Subject: [TN] compressed air
>
>
>
> I am looking for any information on using compressed air to blow off
> "dust bunnies" on circuit boards coming from the field.
>
>
>
> Barb Rich
>
> Admin. Support Mfg.
>
> Sanmina-Sci
>
> 321 S. Taylor Ave.
>
> 303-264-2009
>
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