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Old 14th January 2007, 10:56 AM   #21
SY is offline SY  United States
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My guess is that if there were an easy way like that to do the bonding, companies that make these boards commercially would use them. The fact that they use much more hazardous and expensive methods speaks volumes.

I have direct experience with air plasma as a surface treatment. It's like slapping Mike Tyson with a hankie. It might work ok for PET, but you need the big guns for PTFE.
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Old 14th January 2007, 02:01 PM   #22
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Default bonding to ptfe

I doubt if you can uniformly etch the copper down to much less than 1/2 micron or less w/o producing bare spots and hillocks. Might give it a try though.

Whether or not the substrate would still be active for metal bonding after a total strip is a matter of try and see (though I doubt it, from sort-of similar "cheats" I've tried in the past). I always look for the cheap and easy way first...

I'd have to agree with Sy re: if it were easy to do reproducibly, everyone would be doing it...lets not re-invent the wheel here.

Air plasma's probably not gonna do much activating, since it's relatively non discriminating wrt surface composition.

Still not sure why the NIH / gotta do this myself method is so important when you might be able to bamboozle a few test samples for free or low cost from those who do this routinely ....

personally, I don't think silver vs. copper will have any affect on whatever you're making if it has to do with audio in some way. I just don't buy the alledged benefits of silver vs. copper arguments made all over the net. They don't pass the smell test...

John L.
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Old 14th January 2007, 02:35 PM   #23
Nixie is offline Nixie  Canada
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Default Re: bonding to ptfe

Quote:
Originally posted by auplater
personally, I don't think silver vs. copper will have any affect on whatever you're making if it has to do with audio in some way. I just don't buy the alledged benefits of silver vs. copper arguments made all over the net. They don't pass the smell test...
Of course I don't expect it to make a difference in sound. That's not the point.
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Old 14th January 2007, 04:33 PM   #24
KBK is offline KBK  Canada
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The only way to prove wether there is a sonic difference or not, is to do two identical ones, copper ans silver. There is a difference, in my experience. The real trick is understanding how the ear works. If you do the search, you will find several postings by me that underscore the importance of this little known -but 100% critical to audio design- aspect.

God luck with the whole thing, Nixie. I'll check in again if I have anything useful to contribute, or to see if anyone came up with anything useful. It may be possible to shock the surface of the teflon into going into a liquid state in the momentary (Kaboom!) sense, but not practical to do on a planar surface. Heating and pressing the silver sheet might to be the way to go, with a solvent bit as a side order. Tall recipe for DIY. Commercially, though, an explosive pressure melt may be workable, depending on the board size. Either blast it with compressed air, or slap it silly. Micro breakage of the silver may become an issue but then electroplating can be enacted after the inital app of a starting surface. Who knows. Both methods suffer from the potential for uniformity issues, compared to what is in standard use.
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Old 15th January 2007, 04:19 AM   #25
Nixie is offline Nixie  Canada
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Well guess what: I've done the test. I built these with both silver and copper as the wire (bare wire in both cases, wound spirally around a thin-walled hollow PTFE tube, wrapped with PTFE tape). The cable geometry is good and with an LCR meter the capacitance was the lowest of any cable I measured. I even had pretty much the same turn density on each cable. The XLR connectors had bare silver pins (but new so no oxide); gold plating XLR is not good in my opinion as XLR are self-cleaning and the gold plating tends to wear down and build up gunk if you plug and unplug them frequently; rhodium plating is very hard but expensive and I haven't looked into DIYing it.

Cables were both about 130 cm long. One was listener, the other doing the switching (man would be nice to have a computerized switchbox...), and could switch in about six seconds.
We took turns and had about ten trials each, the listener of course not being able to see the person switching the cables. Neither could pick out a difference.
HD-580 headphones driven by two-stage triode OTL amp, source was 24 bit 96 kHz uncompressed (Ravel stuff) with outboard DAC and ASRC. My friend was a non-audiophile so maybe he has tin ears, but I think mine are pretty good.

Still, I kept the silver interconnects. Again, it's not about the sound. XD
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Old 17th January 2007, 12:49 AM   #26
KBK is offline KBK  Canada
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Tetra-Etch, apparently, is used to prep teflon for gluing.

warning..extreme health hazards!

A variety of answers to this question of teflon and gluing:

"Back in the dark ages, US Plastics sold a metalic sodium solution for prepping the surfaces of teflon so glue would hold. It was not fresh when I got around to using it, and did not work very well. IE, it stuck some, but not very well."

"Teflon has very low coefficient of friction and it will not adhere properly. But you try some perfluorinated kerosines to dissolve Teflon and try to bond with metal. An epoxy adhesive may be tried but adhesion cannot be ensured. If you can adopt sintering technique, you may get some good bonding."

"Normal Teflon sheet cannot be pasted using an adhesive. You get special Teflon sheets with one side etched. Only these sheets can be pasted properly. Contact your Teflon sheet supplier for that."

"You may need to etch the Teflon first with a product such as this: http://www.actontech.com/fluor1.htm I believe W. L. Gore & Assoc used to make a similar product called Tet-Etch (or something to that effect)."

"Dear sir, treat the surface to be bonded, with Metallic sodium in ammonia. Then use an epoxy to bond the surface with the substrate. "
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Old 17th January 2007, 01:16 AM   #27
Nixie is offline Nixie  Canada
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The US Plastics solution you mention may be the same as in the link I posted above. But I wonder what the cement itself is in that kit. It's not cyanoacrylate glue since it's in two tubes to be mixed.

Any more info on the sintering method? I thought all molded PTFE is already sintered at ~370*C for strength. I'm guessing the quote you posted is for bonding PTFE to PTFE by pressing the parts and sintering them together.
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Old 17th January 2007, 03:36 AM   #28
KBK is offline KBK  Canada
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My understanding from the small bit I read, was that one would use the metallic sodium mixture to etch the teflon, and then use the glue which is now bonded to the roughed up teflon surface - to create the metal bonding surface. The metal is bonded to the glue surface. The same technique, sans metal, is used to bond two surfaces together. That's about all I know from what I read on the subject.

Funny..I'm in almost the same boat. Due to what I am doing right now..out of the blue..I have need of such. Teflon is my primary option. Other materials are a long and far away secondary choice. This has to specifically to do with the mechanical and electrical properties of teflon. I very much suspect that teflon circuit boards are quite fragile when soldering/desoldering.

I will be doing considerably more research on the subject, in the immediate future. I will be contacting suppliers, like Gore, 3M and Dupont, directly. Luckily, of the three companies, I know..someone at two of them. One a department head and another a former department head. I may not have to glue/bond for my purposes, but it would be a good thing to have.

What I seem to be coming away with in this case, is that teflon is a total PITA, period, when it comes to bonding. Best to create a lock of some sort within the aspects of being a mechanical lock. This is what is essentially being done with the etch and glue. Up to the research I've come across, which is dated mid 2005 at the newest, nothing has been found that will bond teflon, except for the etch-lock.

An adjunct may be some of the teflon/mica boards. Not the best dielectric/mechanical substrate at that point, anymore.
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Old 20th January 2007, 07:05 PM   #29
gerhard is offline gerhard  Germany
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Quote:
Originally posted by SY
My guess is that if there were an easy way like that to do the bonding, companies that make these boards commercially would use them. The fact that they use much more hazardous and expensive methods speaks volumes.
And even then the bonding stregth of PTFE boards leaves much to be desired. It's much to easy to peel the copper away.

regards, Gerhard
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Old 20th January 2007, 09:54 PM   #30
tvi is offline tvi  Australia
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Process for bonding teflon sheet to prepared surfaces US2984599

TECHNIQUE FOR BONDING TETRAFLUOROETHYLENE SHEET TO METAL SUBSTRATE us3799832&CY=ep&PGS=10&ST=number&LG=en

Hope these help

Regards
James
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