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March 2005

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Subject:
From:
Leo Higgins <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Leo Higgins <[log in to unmask]>
Date:
Thu, 17 Mar 2005 17:18:51 -0800
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text/plain (210 lines)
It is also often important to remove as much water from the surface as is
possible (air knife, etc.).  It has been demonstrated that airborne
impurities can dissolve into standing DI water droplets remaining on the
surface of a cleaned assembly.  This can result in otherwise unexplainable
"water stains" that form when the water ultimately evaporates and deposits
the previously airborne materials.  This is likely a second order issue, but
if the assembly facility is in a heavily industrialized/polluted area, and
the air quality in the assembly area is not cleaned up in any way, this can
be an issue.


Best regards,
Leo

Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas     78704

ph     512-383-4593
fx      512-383-1590
[log in to unmask]
www.asat.com


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-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Thursday, March 17, 2005 11:35 AM
To: [log in to unmask]
Subject: Re: [TN] DI Water


... and one of the most important factors, far more than the water
quality, is how you dry.

If you have comparatively dirty water that is mechanically removed, you
may get far less residual contamination than with excellent water which
is contaminated with residues from under the components and simply
allowed to evaporate.

Been there, done that.

Brian

Douglas O. Pauls wrote:
> I would agree with Joe.  I would use at least 2 megohm-cm (0.5 uS/cm)
> resistivity water.  I would not go higher than 10 megohm-cm because the
> water starts to get too "hungry" can can start to attack stainless steel.
>
> I do not know of any IPC specifications on water quality, but we will be
> starting on revisions to the J-STD-001 Handbook and perhaps we can fold
> that in.  Keep in mind that cleaning is a solubility equation.  It is not
> just water quality that is important but temperatures, pressure, flow
> rates, etc.
>
> Doug Pauls
>
>
>
>
>              Joe Russeau
>              <jrusseau@PRECISI
>              ONANALYSTS.COM>                                            To
>              Sent by: TechNet          [log in to unmask]
>              <[log in to unmask]>                                          cc
>
>                                                                    Subject
>              03/17/2005 09:39          Re: [TN] DI Water
>              AM
>
>
>              Please respond to
>               TechNet E-Mail
>                    Forum
>              <[log in to unmask]>
>              ; Please respond
>                     to
>                 Joe Russeau
>              <jrusseau@PRECISI
>               ONANALYSTS.COM>
>
>
>
>
>
>
> Hello,
>
> Obviously the higher the resistivity of the DI water the more effective
the
> cleaning.  Using water in the 2-10 Megohm-cm range is usually sufficient
> for
> water purity.  We usually recommend leaning towards the higher end of that
> range for better cleaning, but it depends on your water system and set-up
> as
> to the level of quality that can be reached.
>
> As far as specs, I am not aware of any industry specs or guidelines for DI
> water quality, but that does not mean that none exist.  Some of the other
> Tech guru's may have more information on that front.
>
> Best Regards,
>
> Joe Russeau
> Process Analyst
>
> Precision Analytical Laboratory
>
>
>
> ----- Original Message -----
> From: "SUBSCRIBE TechNet Doug" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, March 17, 2005 9:26 AM
> Subject: [TN] DI Water
>
>
>
>>How "clean" does my DI water need to be for cleaning water soluble flux
>>from PWB assemblies? Is there an industry minimum guideline?
>>
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