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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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20th Aug 2018, 6:46 pm | #1 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
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Elastomer Strips
Never heard of this stuff before, i only learned about it after looking at the thread on repairing a Fluke Multimeter.
How many ways are there to connect electrical items together I wonder? Cheers John |
21st Aug 2018, 12:32 am | #2 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
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Re: Elastomer Strips
I had to look it up, but then realised that I know well what they are, but I've always called them Zebra strips.
You find them in digital clocks, thermometers and meters, the filling in the sandwich twixt PCB and LCD
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21st Aug 2018, 7:38 am | #3 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
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Re: Elastomer Strips
Thanks, I learn something every day!
Cheers John |
21st Aug 2018, 9:54 am | #4 |
Heptode
Join Date: Feb 2010
Location: Heysham, Lancashire, UK.
Posts: 669
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Re: Elastomer Strips
As I understand it, the elastomer strip has many fine wires running from one side to the other, much finer pitch than the two things you’re connecting together, so the “two things” must be accurately aligned to each other, but the alignment of the elastomer strip is not critical.
Stuart |
21st Aug 2018, 11:07 am | #5 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
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Re: Elastomer Strips
I'm not at all sure as to the nature of the conductive threads. It looks like something similar to carbon or graphite. Anyone know?
Alan |
21st Aug 2018, 11:27 am | #6 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
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Re: Elastomer Strips
Here you go, according to Wiki ('instant erudition for the hard of thinking'!), possibly carbon, gold or silver, depending on the application.
'Zebra Strip' isn't a colloquialism - it's a trade mark, which is perhaps why they're better known by that term. https://en.wikipedia.org/wiki/Elastomeric_connector Odd that some Fluke meters seem to be afflicted by the 'fading display' phenomenon when meters costing a tenth of the price seem to be immune to it.
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21st Aug 2018, 1:41 pm | #7 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,887
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Re: Elastomer Strips
Thank you that David.
If I may expand by asking what type of connectors are used in aviation, with there many displays etc. Cheers John |
21st Aug 2018, 4:51 pm | #8 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
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Re: Elastomer Strips
Thanks David. Now you've highlighted it I seem to remember reading somewhere that Fluke upgraded the specification to gold at some point, presumably in an attempt to resolve the display issues. My guess would be that it was originally carbon which would also explain why the pencil rubber I used when cleaning my zebra strips turned black.
Hope they would use gold for a 'plane John! Alan Last edited by ajgriff; 21st Aug 2018 at 5:01 pm. |
21st Aug 2018, 5:01 pm | #9 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,887
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Re: Elastomer Strips
Took a look at pdf of Zebra connectors, in it they say for use in Aviation and Military etc etc.
A long way from the days of me using Plessey connectors! Cheers John |
23rd Aug 2018, 8:15 am | #10 |
Heptode
Join Date: Feb 2010
Location: Heysham, Lancashire, UK.
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Re: Elastomer Strips
Whether you use carbon, silver or gold in the elastomer strip depends on the material used on the contact material it’s used with. Gold will not always be the best option.
I once had to resolve a problem where a piece of kit was very very slightly intermittent, so slightly that when the kit was brought back to the factory, it invariably worked perfectly, and resisted all attempts to make it fail. The problem was finally found (by careful examination of a faulty unit undisturbed on a customer site) to be a plug-in IC with gold plated pins in a tin plated socket. The device spec called for tin plated pins, our goods inward folk accepted gold as it was “better” than tin, so must be OK. Beware of dissimilar metals! Stuart |
23rd Aug 2018, 9:25 am | #11 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
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Re: Elastomer Strips
Thank you Stuart, Interesting how the non technical stores inward department overruled the technical specification!
I have encountered suppliers officers trying to overrule a technical officers on grounds of cost, it got very heated!! Cheers John |
23rd Aug 2018, 11:10 am | #12 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
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Re: Elastomer Strips
Interesting point about galvanic corrosion. Gold plated audiophool phono plugs anyone?
I also note that elastomeric connectors/strips (the generic description apparently) are manufactured in large quantities. They come in all sorts of shapes, sizes and styles for a variety of applications particularly in relation to modern vehicle display modules. However, there doesn't seem to be much of a retail market, although strips can be bought wholesale with minimum order lengths of 50m plus, which is not very useful for people like us. Alan |
23rd Aug 2018, 9:21 pm | #13 |
Dekatron
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
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Re: Elastomer Strips
I understand that early ICs that used Gold metallisation suffered from the "Purple Plague" , an inter-metallic gold compound that led to failure of chips that suffered from it.
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24th Aug 2018, 7:44 am | #14 | |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
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Re: Elastomer Strips
Quote:
Of course, what is commonly forgotten is that the base metal is either brass or phosphor bronze, and there is always an adhesion layer between the base metal and the gold - usually nickel or chromium. All things that audio connector manufacturers omit to mention FWIW NPL chose connectors in which the base metal is copper, and then pay to have the platings chemically stripped - so in particularly DC calibration work all connections are copper/copper. And they use Van Damme cheapo cable - again they choose a cable in which the core and screen are both high purity copper. They only use esoteric aerospace teflon insulated cable for internal wiring inside cryostats and for wiring standards immersed in warm oil, both environments being unsuitable for any other insulation. Craig |
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24th Aug 2018, 8:44 am | #15 |
Retired Dormant Member
Join Date: Dec 2007
Location: Shropshire, UK.
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Re: Elastomer Strips
The issue with combining gold-plated and base metal contacts is quite well known in relation to computer memory modules too. Logically, there's little point in using gold (whatever its perceived advantage) on only one side of a contact pair anyway.
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24th Aug 2018, 6:44 pm | #16 |
Heptode
Join Date: Feb 2010
Location: Heysham, Lancashire, UK.
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Re: Elastomer Strips
Gold inside the package, and gold outside the package are quite different things.
IIRC, some early processes used gold doping to improve switching speed. But gold killed the gain of other processes. You couldn't run both processes in the same fab without the gold from one contaminating the other. Then there was the purple plague mentioned by emeritus which was a problem with gold bond wires. But if you keep wafers away from gold until they are passivated, you can use gold for the packaging. Stuart |
24th Aug 2018, 9:55 pm | #17 |
Nonode
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
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Re: Elastomer Strips
I had never heard of "gold plague", but 55+ years ago in our "colours" lectures (Ceramic Technology) we were acquainted with the fact that colloidal gold when finely dispersed was purple, and referred to as "Purple of Cassius".
If you look carefully at a gold lined cup or saucer, you will probably see the purple if the gold is very thin at the edge. I would assume this is the same purple. Les. |
24th Aug 2018, 10:32 pm | #18 |
Heptode
Join Date: Feb 2010
Location: Heysham, Lancashire, UK.
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Re: Elastomer Strips
We've drifted a bit off topic. I'd just like to say that gold on contacts is not necessarily a good thing, and if anyone has some gold which is causing them problems, I'd be happy to take it off their hands and dispose of it safely.
Meanwhile on topic, the connections in the elastomer strip, whatever they are made of must not be rigid, as the name implies they must be elastic, they must be compressible to take up variations in the spacing between the two things they are supposed to connect together. Stuart |
25th Aug 2018, 12:44 am | #19 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
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Re: Elastomer Strips
Surely they must be a stack of conductive rubber and insulating layers all stacked together.
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25th Aug 2018, 11:36 am | #20 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
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Re: Elastomer Strips
Thank you all for your very informative and interesting answers, how about a couple of suggestions to my original post #1?
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