Repairing mylar cable?

Cable was damaged by melting several (6) traces worth of conductors. It's part of an expensive controller assembly for which no individual replacement
parts such as this are available. Terminated end is under membrane switch panel which is affixed to the front of the controller. Disassembly to reach the other end of the cable would be near-destructive.
So I'm resolved to fix it. The best approach I can think of is to scrape away the light protective coating over the conductors (which aren't copper PC, but some painted-on conductive substance) but not scrape too deeply (I've found by experimenting that this is Not Good )c: ) and affix 30 ga wires via conductive epoxy, bridging the damage.
I dread this approach because of the fine pitch of the conductors, and not knowing until I've finished each patch whether 1) there remains enough conductor to patch and 2) the epoxy "took".
There is about 1 inch undamaged conductor on either side of the damage to effect a connection, so if any one attempt at bridging a conductor fails I can attempt another, if need be.
It's going to be rough going, I fear.
Any other suggestions? Maybe find source for this type of cable and graft it to the existing one?
Sources for these cables?
Thanks,
--
John English


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What is the pitch of the conductors?
Printed circuit manufacturers make flexible printed cables - flexies - which are patterns of copper on a variety of substrates. They are usually supplied with an insulating layer on both sides of the conducting traces.
You define where you want the copper with "Gerber plots" in the same way that you describe a rigid printed circuit board you want manufactured.
Tell us where you are, and someone may be able to suggest the name of a supplier in your area.
-- Bill Sloman, Nijmegen
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20 conductor, 1 mm pitch, "painted" conductor (not copper strip).
[...]

SF bay area, N. California, USA.

Thanks for your suggestions, Bill.
On further examination the "flexie" seems to be contiguous with the membrane switch backplane; it's one piece, so a replacement doesn't sound likely.
Now, if a means exists for easily (!) and reliably grafting another 20-conductor flexie to the good stub, I'm all ears!
Or... other ideas?
Thanks again,
--
John English


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3M makes connectors that pierce such flexprint conductors, with spikes that fold over and make good contact.
John
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I wonder if they make a splice connector that would simply connect two flexies. Man, that would just save my bucket.
Other possibility with such connectors: crimp on a female flexie connector and use another flexie to bridge the gap.
Can you recall a trade name? P/N, by chance or by prayer? Source? (c:
Thanks for your assistance, John. It's a glimmer in the dark...
--
John English


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replacement
reach
away
but
found
it
Bare back to conductors , cover whole area with silver loaded paint and when cured score lines with ruler and scalpel , pairs of close lines and scrape off the areas between lines with a slightly blunt needle against ruler. You need a magnifier lamp and check with a DVM before and after the process.
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net /
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Not quite clear to me... does this involve any new flexie material? Or just paint? Is paint expected to bridge a gap in the flexie?
This seems a good way to repair breaks in conductive traces, but a damaged flexie...?
If you could explain in a bit more detail...
Thanks,
--
John English


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when
scrape
process.
just
does it flex in use or just to assemble/disassemble ?
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No movement in use. It is just a means of getting membrane switch inputs to the PCB.
Thanks,
--
John English


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wrote:

See my post to seb.
--
JF

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On Tue, 10 Apr 2007 15:06:10 -0500, John Fields

--
Which one? ;)


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John,
I've done repairs such as you describe. A PITA, but it worked when I was done. I figured it would last a few months and that was maybe four years ago. It still works, and sees service in a rugged environment with lot's of abuse!
In my case I used a technique such as your initial idea of the conductive epoxy and 30 gauge wires...
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Thanks, Peter. If I can't find a connector-cable-connector solution to my problem, it's nice to know that someone has blazed this particular trail with these particular tools before.
Thanks again,
--
John English


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if there's a gap glue a bridge behind it (you'll have to find an adhesive that sticks to it and goes hard, )
--

Bye.
Jasen
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I can't quite visualize your cable, but can you cut it at the bad spot, and clamp it between two pieces of PC board, where one or both PC boards have traces on them that line up with your conductors? The connection would be made by compression.
Tam
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It's just a single-sided, translucent mylar flex cable with 20 "printed" conductors on 1 mm centers.

The success of this would depend on how well I could scrape away the protective layer above the "painted" conductors without removing the conductive material. I'm not so confident to be able to do that 40 times reliably such that the resultant bare conductors would all line up nicely with the PC traces.
--
John English


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