Brian, once again I did not give a satisfactory reply to a serious question. You are correct about the rinse of course. I should have given more info than just the tool. So to partially make amends, rinse, rinse and rinse again. Last summer when we bought the sprayer I did ionic testing of many boards. I know the limitations of this but it was helpful in showing that as you say the rinse is critical. We have since then switched to a no clean for most BGA rework and to a water washable paste for most of our SMT build. I was only trying to help with a solution and should have suggested prevention.
Charles Caswell
The Big Kahuna
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Sunday, April 27, 2003 2:09 AM
To: [log in to unmask]
Subject: Re: [TN] cleaning under BGAs
Big problem! IPA is not a good solvent for flux residues and is
flammable and must be used, especially if spraying, in a
flameproof/explosion-proof zone. Whatever mechanical method is used with
whatever liquid, you need to establish a cleaning protocol (method, time
and temperature + safety margin).
Remember that, if you apply, e.g., a saponifier or an alcohol, the
residual liquid is a dangerous, ionic, chemical and has to be thoroughly
removed by several successive rinses. This is more difficult than the
initial cleaning, as each rinse must displace the liquid which is firmly
lodged there by capillary forces. It is absolutely no use just passing
it through a cleaning machine unless you can be sure that every
microgram of liquid is eliminated and replaced by clean water. For
example, if you use a "water-pik" or similar, you should have another,
more powerful one, with pure DI water, just to displace the contaminated
liquid. If the cleaning takes 5 minutes, for example, the rinsing may
take as much as 15 minutes before you have a satisfactory level of
cleanliness in the middle of a large BGA.
Much better and cheaper would be to use a "no-clean" flux and not to
attempt to clean, at all. Remember the old adage, dating back 40-odd
years, "Poor cleaning is far worse than not cleaning".
Brian
Macko, Joe @ IEC wrote:
> Fellow Technets,
>
> Periodically, BGAs are reflowed using our AIR-VAC hot air rework station.
> RMA liquid flux is 1st flowed under the BGA prior to reflow and then clean
> afterwards starting with IPA spray followed by an in-line cleaner wash.
> Occasionally, flux residue remains which requires additional cleaning.
>
> I am in need of a creative and operator safe way to either spray/flow warm
> IPA or a mixture of hot saponifier/DI water (from our in-line cleaner) under
> BGAs to expedite cleaning. I do not know of any equipment on the market
> that can be used for this application.
>
> Welcome ALL suggestions and proven methods. thanks
>
> joe
>
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