Peter, Duncan and other Technnetters,
This thread ties in quite well with the one recently started by Doug Pauls
and answered by Brian Ellis. Generally speaking any organic,
plastic-producing material that has been allowed to polymerize is going to
be extremely difficult, if not impossible, to actually dissolve. As has
been pointed out below, the OS-2 is not actually dissolving the set RTV
material (room temperature vulcanizable)(and unless there is a licensing
agreement in place it is a Dow Corning material, not a 3M material).
Anyway, polymerized silicones are particularly robust (and thus their use!),
but can be degraded by things like, concentrated mineral acids, boiling
molten sodium hydroxide, good sized electric arcs and plasmas - none of
which I would like to subject a circuit pack to for which I had developed
any emotional attachment. :) Note I said "broken down". I wouldn't even
guarantee that these would actually dissolve the stuff.
regards,
Bev Christian
Research in Motion
-----Original Message-----
From: Gary Camac [mailto:[log in to unmask]]
Sent: March 21, 2001 11:51 AM
To: [log in to unmask]
Subject: Re: [TN] Solvent for RTV738
Pete,
Before you try the Dow "OS-2", let me tell a little story. This material
works by causing the
silicone to expand, to the point where is looses its grip.
I had an engineering prototype of a small sensor assembly that the design
guys wanted stripped
of coating for some reason or another. So, I let the assembly sit submerged
in some OS-2 for
5-10 minutes. I then removed the assembly and brushed off the loose coating.
After repeated
the process a couple of times I had removed the vast majority of the visible
coating, but
there was still some coating under the components. I figured I would just
let the assembly
sit in the OS-2 overnight. When I pulled the assembly out the following
morning, the silicone
had expanded enough that it popped every SO-8 and SO-14 right off the board.
The silicone had
developed enough force under the parts to pull the legs right out of the
solder fillet.
Gary Camac
"" wrote:
> Hi, TechNetters,
>
> I am trying to find a solvent for removing 3M's RTV 738 that has been used
> for bonding components to a number of boards, or to each other. Any
> suggestions?
>
> I have tried 3M themselves and they have no solvent of their own apart
from
> "Citrus Base Adhesive Remover" that 'may soften' it enough to peel it off,
> but this seems pretty indefinite.
>
> Thanks in hope
>
> Pete Duncan
> Asst Principal Engineer
> Singapore Technologies Aerospace
>
>
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