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Old 3rd April 2003, 12:25 PM   #1
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Default Expanded PTFE PCB substrate?

Production of PCB's

I have read an article on expanded PTFE substrates which are supposed to be relatively inexpensive (comparable to FR4). I would like to get more information on where such things can be ordered. Goal is to etch single or double sided PCB's in the normal manner or have production PCB's made.

Where do I get more information on pricing etc?

Petter
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Old 3rd April 2003, 02:20 PM   #2
SY is offline SY  United States
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PTFE will definitely NOT be more inexpensive than FR4. It's already a pretty soft material, so expanding it will have some serious impact on board rigidity, unless it's reinforced (more $$$) or thicker (more $$$).

Relative material costs (roughly):

PE $1
PC $2
PVC $1.50
PP $1
Ultem $15
Epoxy $5
PTFE $20
PI (Kapton) $20
PEEK $75
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Old 4th April 2003, 01:58 AM   #3
jcarr is offline jcarr  United States
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Petter: First of all, any of the teflon-family circuit boards are quite expensive compared to FR-4, unless you luck into surplus stock.

Also, you should think carefully whether you want to use teflon or not. Electrically, it is fine, but mechanically, it has a number of umm, "quirks". It is soft enough to require reinforcement unless you want bowed boards, it deforms fairly easily under pressure, and once it deforms, it will not return to its original shape.

But what really makes it tricky to use is the low strength of the adhesive bonds between the copper layers and teflon substrate. If you are capable and careful, it is not too hard to build circuits into teflon boards - the first time around. But should you ever have to repair one of the boards, you may regret having chosen teflon. If you don't go quite so far as expressing regrets, I am almost certain that you will be swearing more frequently than normal. I sincerely suggest that during the board layout phase, you set your pad sizes larger than normal.

OTOH, teflon boards have been used by a number of audio manufacturers in production - Accuphase, CAW, Curl, Denon, Mark Levinson, and Theta, to name a few. So it can be done, if you like adventure.

jonathan carr
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Old 4th April 2003, 12:59 PM   #4
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Thanks for your replies:

Expanded teflon boards come in many variants, some of which are loaded with resin, others reinforced with whatever they use these days.

I am aware of what jcarr so diplomatically calls "low strenght of adhesive bonds"

I also have some Rogers Duroid stuff which I plan to use for my own kit, but the goal here was to make something commercial, and hence cost not overly excessive above FR4 would be nice.

Petter
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Old 4th April 2003, 01:34 PM   #5
jcarr is offline jcarr  United States
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Petter: If your production process is completely automated, if you have access to low-temperature solders (like bismuth alloys), and if you don't intend to ever repair any of the boards, have you looked at the Noryl-based pcb materials by Sheldahl?

http://www.sheldahl.com/Product/TMComClad.htm

regards, jonathan carr
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