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October 2013

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Subject:
From:
Phil Bavaro <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 22 Oct 2013 15:14:41 +0000
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I am going to second what Brian said almost.  The PTFE substrate surface needs to be activated and Tetra Etch® is a current fluorocarbon etchant
(mixture of sodium, naphthalene and 1,2 – dimethoxyethane).   Definitely as nasty process and I would not use it on any Printer Wiring Assembly containing components.  If you have a raw PWB, then maybe a potential method.

I disagree with Brian as far as mechanically abrading the PTFE.  In my experience this does not work as even the abraded area still does not want to bond.

My suggestion is to go overboard with a trace bonding adhesive with regard to surface area.  Simply attaching the trace bottom to the PTFE is not enough, so instead apply adhesive over the top of the repair and include enough of the traces being attached to, in order to maintain some mechanical strength.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Tuesday, October 22, 2013 7:59 AM
To: [log in to unmask]
Subject: Re: [TN] Bonding to PTFE

You need an etchant containing a strong sodium hydroxide, ammonia and tetrahydrofuran, which will remove the outer fluorine atoms, leaving an electrically charged surface that will bond to adhesives. However, this is a very toxic, caustic, really nasty stuff and your H&S guys will baulk at its use, after the first operator drops dead! In addition, I think that removing the residues after etching and before glueing will be electrically ultra-problematic.

I would suggest that mechanically abrading would really be your best compromise, hopefully providing a key to a low-viscosity solvent-free epoxy.

Brian

On 22.10.2013 17:21, Bob Landman wrote:
> Bob,
>
> McMaster Carr supplies a Teflon epoxy system which has a liquid etchant to prepare the surface for their two component epoxy. Its packaged in a circular cardboard box with a screw top lid.  We've used it to bond Teflon to aluminum for decades. Don't know if it works on epoxy/resin boards but as it can bind Teflon to Teflon (another app we have a requirement for) give them a call to see what they recommend.
>
> Bob Landman
>
> Sent from my iPhone
>
> H&L Instruments,LLC
>
> On Oct 22, 2013, at 10:09 AM, Bob Wettermann <[log in to unmask]> wrote:
>
>> Can a chemist/board SME tell me if an epoxy/resin system will bond to
>> a PTFE matrix laminate for pad/trace repair?
>>
>> Thanks!
>>
>> Bob Wettermann
>>
>>
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