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October 2004

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Subject:
From:
David Douthit <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, David Douthit <[log in to unmask]>
Date:
Wed, 27 Oct 2004 18:46:53 -0700
Content-Type:
text/plain
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text/plain (135 lines)
Ken,

The simplest method of dealing with "no-clean" flux that has not been
activated during rework is to bake the board (run them through the
reflow oven again) or find out from the flux manufacturer what the
activation temperature is and cook them.

Do not try to clean them. All you will do is "smear" the contamination
over larger areas!

David A. Douthit
Manager
LoCan LLC

Ken Patel wrote:

>Sara,
>For hand soldering and touch-up operation, flux will not be exposed to
>higher temperature like that reflow soldering. Will that be an issue and if
>so how one should resolve it? Is the hand soldering flux made to take care
>of the ionic contamination?
>
>Looks like it's s big issue to many of us.
>
>Re,
>Ken Patel
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Sara Gorcos
>Sent: Wednesday, October 27, 2004 9:29 AM
>To: [log in to unmask]
>Subject: Re: [TN] No Clean
>
>Hi Ted & TN Listserv,
>We have found that by doing general board extractions for ion chromatography
>analysis limits our understanding of the pockets of contamination that occur
>around specific components and in comparative areas such as the bottom of
>the board vs. the top.  By combining Ion Chromatography with a new localized
>extraction technology is giving us a greater understanding of these pockets
>of contamination.  No clean flux processes deposit different levels of flux
>activator in different areas of the board.  Touch-up and repair adds to
>these areas.  We have found more failures due to stray voltage in these
>areas of thick or heavier fluxes that do not get full heat activation
>through using a localized extraction approach.
>Here is a link to an article we recently published in our column for
>Circuitnet that might give you a better understanding of how to guage
>cleanliness in a no clean process, and what issues are encountered by
>contaminants being left on boards.  It also outlines some recommended limits
>for various contaminant types in determining cleanliness
>http://www.residues.com/pdf/FailureOfACircuit.pdf
>
>Sara Gorcos
>Foresite, Inc.
>1982 S. Elizabeth St.
>Kokomo, IN 46902
>(765)457-8095
>www.residues.com
>
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Ted Kong
>Sent: Monday, October 25, 2004 4:48 PM
>To: [log in to unmask]
>Subject: [TN] No Clean
>
>
>Hi All,
>
>What is the best method to measure the cleaningness of
>a board that use no-clean process?
>
>Thanks all in advance.
>
>Ted Kong
>
>
>
>
>__________________________________
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