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From:
"Black, Paul" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Black, Paul
Date:
Wed, 8 Sep 2004 07:50:49 -0400
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I would like to thank everyone for their responses. After listening to what you had to say, I decided that using a chemistry was with a DI rinse would be the best way to go. My solder paste manufacturer said that isopropyl would work fine on stencils and bare boards but my real concern is boards that already have components on them. As for my current "sink" setup, to those who were concerned that I might be putting effluent down the drain, I just didn't explain that very well. It is a closed loop, filtered system.

Thanks again, 
Paul Black 
Manufacturing Engineer 
Kronos 
E-mail: [log in to unmask] 
Voice: (978) 947-1520 



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Douglas O. Pauls
Sent: Wednesday, September 01, 2004 12:23 PM
To: [log in to unmask]
Subject: Re: [TN] Cleaning populated boards with Isopropyl


Grand Wazoo?  <snort>  Kinda gives "out tha wazoo" a whole new perspective.

As to your recommendation for cleaning machines, I would agree.  Both
companies make some good cleaners.

Let's dissect Paul's situation:

I currently clean SMT stencils in a sink with hot deionized water.

**So you are putting lead down the drain?.  Might be some local effluent
laws waiting to bite you.  Might want to check on that with your local POTW
or EPA folks.

I would like to automate this process (and eliminate the DI water) and have
been looking at cleaners that can do the job.

**Automation is good.  Automation is consistent.  And DI water is your
friend, not your enemy. Tap water is the Darth Vader of materials.
Remember that.

One of them uses Isopropyl Alcohol with no rinsing.

**Which means you have a cloud of flammable vapor inside the machine.  Is
it explosion-proof?  What does your local fire marshall have to say?  Does
the machine empty the workspace of fumes before you open it.  Having spent
the last 20 years cleaning the insides of humidity chambers with
isopropanol, I can say you get some wonderful hallucinations from the
fumes, but not something you want to do on a regular basis.  Also, the use
of IPA may also affect your VOC emissions for EPA compliance.  In terms of
the material, does your paste manufacturer indicate that pure IPA will
remove all of the paste residues?  Does the machine capture the lead in a
trap somewhere?  If yes, does it get recycled?  If not, you have a
hazardous waste situation.  DI water is cheaper than isopropanol,
especially when you start counting the cost of handling flammable
materials, storage, fire suppressions, Aunt Gladys going home with fume
headaches each day....

This should work fine for the stencils but occasionally I also have to
clean misprinted boards that may already be populated on one side, using
no-clean solder paste. If I were to use this Isopropyl process on the
misprints, would I be risking reliability of the board?

**Arrghhhhhhhhhhhhhhhhh! Burn the Heretic!!!!!  Ummm, not a practice you
want to use.  First, IPA is a lousy cleaner of flux residue, reflowed or
not.  DI water alone is not much better.  One advantage  with either is
that paste residues that are not reflowed are easier to clean, but you
would have to get used to seeing a white haze on your boards.  The only
advantage I see from IPA only is that the stencil comes out dry.  What I
suggest is that you use DI water, with a small amount of a cleaning agent
that works with your paste.  We use a lot of Kyzen products at Rockwell and
I have found their technical staff to be very good in matching the right
material to the right soil.  Many products can go to drain as long as you
capture the lead.  In the products we use, the micro-critters at the waste
treatment site love the Aquanox chemical.  To them, Rockwell is Delmonico.

In terms of reliability, I would never take the chance with our products of
getting those iddy biddy spheres of solder somewhere they don't belong or
places where you cannot remove them.  They will see reflow conditions
before they see another mass cleaning.  So relays, connectors, under fine
pitch devices, BGAs, air wound coils and transformers, etc., all become
compromised if those solder balls reflow in place.  Bare boards,
maaaaaaaybe, but assemblies, no way.

OK, beaming back up to the mother ship.

Doug Pauls




                      Phil Nutting
                      <PNutting@KAISERS        To:       [log in to unmask]
                      YSTEMS.COM>              cc:
                      Sent by: TechNet         Subject:  Re: [TN] Cleaning populated boards with Isopropyl
                      <[log in to unmask]>


                      09/01/2004 10:17
                      AM
                      Please respond to
                      TechNet E-Mail
                      Forum; Please
                      respond to Phil
                      Nutting






I'm interested in what the "Grand Wazoo" Doug Pauls and Brian Ellis have to
say about this.  If I've read their musings correctly alcohol does a nice
job of spreading the ionic schmootz where DI water cleans it very well.

If my research is correct, there are several automated DI water stencil
cleaning systems readily available on the market (www.aqueoustech.com
www.aat-corp.com to name just two) and these suppliers also make batch
style board cleaners.  Austin American (aat-corp) has a new unit on the
market for under $10k.

Oops, was that too close to a sales pitch?

Why would you want to "eliminate DI water"?

Phil

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Black, Paul
Sent: Wednesday, September 01, 2004 10:58 AM
To: [log in to unmask]
Subject: [TN] Cleaning populated boards with Isopropyl


Hi Everyone,

I currently clean SMT stencils in a sink with hot deionized water. I would
like to automate this process (and eliminate the DI water) and have been
looking at cleaners that can do the job. One of them uses Isopropyl Alcohol
with no rinsing. This should work fine for the stencils but occasionally I
also have to clean misprinted boards that may already be populated on one
side, using no-clean solder paste. If I were to use this Isopropyl process
on the misprints, would I be risking reliability of the board?

Any help would be appreciated.

Thank you,
Paul Black
Manufacturing Engineer
Kronos
E-mail: [log in to unmask]
Voice: (978) 947-1520


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