Bonding silver foil to PTFE - diyAudio
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Old 11th January 2007, 04:37 AM   #1
Nixie is offline Nixie  Canada
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Default Bonding silver foil to PTFE

How to do it?
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Old 11th January 2007, 04:43 AM   #2
Apogee is online now Apogee  United States
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I'd try silicone or contact cement...

Just a couple of guesses.

PTFE - Could you have possible chosen a material more difficult to bond to????

The only other thought that comes to mind would be to contact 3m (maker or PTFE) and see if they recommend any specific glues.
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Old 11th January 2007, 04:53 AM   #3
Nixie is offline Nixie  Canada
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I want to make my own silver/PTFE boards. Blank PTFE boards I've found are only copper-clad.

If I dissolve away the copper I'm not sure if the PTFE surface will need to be re-etched for bonding something else. Usually etchant is sodium in a carrier such as tetrahydrofuran. The THF I can distill from PVC bonding fluid, but I don't have a source of sodium (electrolysis of molten table salt is beyond my current capabilities). But if on the other hand the removed copper cladding leaves a bondable surface, then this may be an easy process. Silverplating would be an option if I could leave a small uniform thickness of the original copper cladding, but there's no way to etch that evenly.
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Old 11th January 2007, 08:23 AM   #4
Elvee is online now Elvee  Belgium
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Hi

I would coat one side of the silver sheet with a teflon solution (see some examples here: http://www2.dupont.com/Teflon_Indust.../coatings.html), dry it at 110C to remove any trace of solvent. The teflon and silver sheet should then be put in a press and heated at the recommended temperature to cure the teflon coating; hopefully, the coating will also bond to the teflon sheet. The silver sheet might have to be treated in order to promote adhesion, but this might involve highly dangerous chemicals, such as PFOA. I recommend you get more information on a specialized forum, such as finishing.com or groupsrv/science/materials.
LV
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Old 11th January 2007, 11:25 AM   #5
SY is offline SY  United States
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This is definitely NOT a diy operation. What needs to happen is a pretreatment of the PTFE surface with sodium naphthalide (or something similar) in THF. This solution can only be made and handled under strict anaerobic conditions (e.g., vacuum line and high quality glove box). Then the surface can accept cladding, which is usually done by coating the foil with a tie layer resin, then applying it to the PTFE using heat and pressure.

Nixie, what you're thinking of is the pretreat solution. VERY dry THF has naphthalene dissolved in it, then metallic sodium added. The naphthalide anion, a strong free radical, forms spontaneously and is a brilliant green color. It's also deadly toxic, corrosive, and in the presence of air or water, potentially explosive.
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Old 12th January 2007, 12:25 AM   #6
Nixie is offline Nixie  Canada
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Quote:
Originally posted by SY
This is definitely NOT a diy operation.
Tetra-Etch is sold in the exact same types of cans that PVC cement is sold in.
Click the image to open in full size.
Clearly intended to DIY. Instead of THF it uses 1,2-dimethoxyethane as the base and there's nothing about anhydrous conditions being necessary.
The reason I asked for DIY alternatives is because I didn't find a Canadian source yet for this.
I actually have all the hardware and vacuum, it's that I don't have a source of metallic sodium. It's available on eBay but importing is a problem.
Any ideas how to find a consumer source of etchant in my country?

Quote:
tie layer resin
What is it? I never heard of this before. Unless the material is extremely thin, wouldn't this counteract the benefits of teflon's dielectric properties?
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Old 12th January 2007, 01:00 AM   #7
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Quote:
Originally posted by Nixie

Tetra-Etch is sold in the exact same types of cans that PVC cement is sold in.
Click the image to open in full size.
Clearly intended to DIY. Instead of THF it uses 1,2-dimethoxyethane as the base and there's nothing about anhydrous conditions being necessary.
The reason I asked for DIY alternatives is because I didn't find a Canadian source yet for this.
I actually have all the hardware and vacuum, it's that I don't have a source of metallic sodium. It's available on eBay but importing is a problem.
Any ideas how to find a consumer source of etchant in my country?


What is it? I never heard of this before. Unless the material is extremely thin, wouldn't this counteract the benefits of teflon's dielectric properties?
Instead of screwing around with stuff that could cause permanent personal damage ( packaging doesn't determine DIY-ness,btw) why not request a quote from a firm such as
this, (sometimes you can get free samples)

http://www.gsassociates.com/

and leave the nasty hazardous stuff to those with extensive experience dealing with such (I've messed with this and LOTS of other hazardous mat'ls, perchloric/permanganic/chromic mixes, pertechnetic acid, cyanides, RDX/PETN, HF/HNO3/Perchloric, you name it) and it's REAL EASY to get hurt. Take Sy's advise. Don't DIY with this stuff.

Good luck

John L.
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Old 12th January 2007, 01:26 AM   #8
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Nixie, I deleted your post. Behave.
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Old 12th January 2007, 01:27 AM   #9
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Default patronizing..naw

no one is patronizing anyone... sorry if you feel that way. Nothing in your post indicates your extensive experience.. just trying to help.. and packaging doesn't imply diy as you indicated above... which doesn't re-inforce perceptions of competence

trying to prevent some disasters if others are reading this.. sheesh... what a short fuze...

forget it.
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Old 12th January 2007, 01:29 AM   #10
Nixie is offline Nixie  Canada
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The point is I came here with pretty specific questions, not seeking "let someone else do it, don't DIY" comments.

As for indicating my experience, I didn't do it because it comes off exactly the way your post did -- as bragging. It's not that my fuse is short, it's that after a lot of people set fire to it, it gets burned down eventually.

I still don't know what that "tie layer resin" is. What I found on the web is nothing related to PTFE.
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