I have had success using complexing acids for removing tin and lead oxides (namely citric). Additionally, urea sulfate, 43% liquid diluted in water was successfully used to remove stannic oxide from polyimide. The latter has some unique properties if the substrate can withstand exposure to acids.
Ted Stern
HAWKINS, INC.
direct: 612-617-8539
cell: 612-702-1871
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of R Sedlak
Sent: Thursday, December 18, 2008 10:30 AM
To: [log in to unmask]
Subject: Re: [TN] flux and board cleaning issues
Bob: You are correct. The only way to dissolve rosin metal salts is
in a chelated aqueous cleaner, probably needing to be applied hot, and
for some time.
Rudy Sedlak
RD Chemical Company
--- On Thu, 12/18/08, Robert Kondner <[log in to unmask]> wrote:
From: Robert Kondner <[log in to unmask]>
Subject: RE: [TN] flux and board cleaning issues
To: "'TechNet E-Mail Forum'" <[log in to unmask]>, "'R Sedlak'" <[log in to unmask]>
Date: Thursday, December 18, 2008, 7:01 AM
Hi,
In addition, if you overheat during reflow and allow those salts to form
on a PCB surface they will not be removed. At least not in any solvent I
know. They look like white residue on the PCB around joints.
Bob Kondner
PS: AI would appreciate anyone chiming in here. I am not a chemist.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
Sent: Wednesday, December 17, 2008 12:21 PM
To: [log in to unmask]
Subject: Re: [TN] flux and board cleaning issues
Kevin & others:
The purpose of flux is to remove oxide from the metal surface. A rosin acid
flux does this by forming rosin salts with the oxides, and dissolving these
salts into the un-used rosin acid remaining on the surface.
Alcohols do a reasonable job of dissolving the unused rosin acids, but are
virtually useless on the rosin acid salts formed with the metal oxides.
It could be argued that the remaining rosin acid metal salts are harmless,
but that is another whole discussion.
Rudy Sedlak
RD Chemical Company
--- On Wed, 12/17/08, Kevin Glidden <[log in to unmask]> wrote:
From: Kevin Glidden <[log in to unmask]>
Subject: Re: [TN] flux and board cleaning issues
To: [log in to unmask]
Date: Wednesday, December 17, 2008, 6:16 AM
"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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