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December 2008

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Subject:
From:
Douglas Pauls <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Thu, 18 Dec 2008 07:46:59 -0600
Content-Type:
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Well, this Rockwell guy talks about it a lot but I don't think we have 
released a paper on it.  We did present the view at the recent cleaning 
conference in Chicago.
I have consistently told our people internally that alcohol sucks 
(technical term) as a cleaner.  It gets used because it is cheap, 
plentiful and dries fast.

Many erroneously assume that "like dissolves like" and that since 
isopropanol is used as a carrier solvent for rosin flux, it must also 
dissolve rosin flux.  As others have pointed out, alcohol does not clean 
off the rosin salts and polymerized rosin remaining after the soldering 
operation, so that "like" rule does not apply.

Doug Pauls
Rockwell Collins



Guy Ramsey <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
12/17/2008 10:47 AM
Please respond to
[log in to unmask]


To
[log in to unmask]
cc

Subject
Re: [TN] flux and board cleaning issues






I am not a chemist. But, yes alcohol dissolves rosin. But, see Brian's
comments. He is absolutely right. The by products of the soldering process
may not dissolve. And they can be released by a feeble attempt at 
cleaning.
Improper cleaning can be worse than no-cleaning. 
 
Conventional wisdom says alcohol, while commonly used, is cheap but not 
very
effective. However, Curt Alexander offered this contradictory report to 
the
Assembly Community.

http://circuitsassembly.com/cms/content/view/3851/95

It is possible to clean using the other materials mentioned earlier in 
this
thread but it is still a process of diluting and rinsing, only much more
expensive and potentially hazardous. 

Didn't the guys at Rockwell release a paper on this subject recently? 

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden
Sent: Wednesday, December 17, 2008 9:17 AM
To: [log in to unmask]
Subject: Re: [TN] flux and board cleaning issues

"Alcohol will dissolve the flux..."


Is that accurate?  I am under the impression that alcohol is a solvent 
that
will assist in loosening RMA residues, but it will not dissolve them....at
least that is how I understand it....
 

Kevin Glidden
Manufacturing Engineer
Luminescent Systems Inc.

-----Original Message-----
From: Guy Ramsey [mailto:[log in to unmask]]
Sent: Tuesday, December 16, 2008 10:48 PM
To: [log in to unmask]
Subject: Re: [TN] flux and board cleaning issues

Alcohol will dissolve the flux. Compressed air will move the mixture. 
One must wonder where it goes. Compressed air can be present an electric
potential to the board.
It may work fine . . . Or not. Your instructor was probably taught about 
the
potential problems with this cleaning method. The brush is probably not as
effective as the compressed air. 

Are there any ESDS devices on the board? 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wilson, Bob
Sent: Tuesday, December 16, 2008 7:12 PM
To: [log in to unmask]
Subject: Re: [TN] flux and board cleaning issues

Rosin Mildly Activated

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
Sent: Tuesday, December 16, 2008 4:04 PM
To: [log in to unmask]
Subject: Re: [TN] flux and board cleaning issues

Bob:  Why not advise on the type of flux you are using.

Rudy Sedlak
RD Chemical Company

--- On Tue, 12/16/08, Wilson, Bob <[log in to unmask]> wrote:
From: Wilson, Bob <[log in to unmask]>
Subject: [TN] flux and board cleaning issues
To: [log in to unmask]
Date: Tuesday, December 16, 2008, 3:55 PM

Hi,

I have a lead who is an IPC J-STD-001 certified trainer and she is very
good.  We are using a board assembly that has a nut plate under a
high-density 26-pin DSUB.

The girls were soaking the assemblies in an alcohol bath and the lead
assembler said she didn't want the boards soaked in alcohol because it 
isn't
100% guaranteed to remove all the flux from under the connector or nut
plate.

She has the girls trying to get a brush under there to get the flux out.

Am I nuts or have I been under the wrong impression that alcohol and
compressed air is the best way to clean a fluxed board?  I hate the idea 
of
me saying something like, "But...but that's the way we've always done it!"

(I don't have J-STD-001 here on the design side).

Thanks a bunch.

Bob Wilson

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