copper-graphite connections

Hi,
Does anyone have experience of making very low resistance
copper-graphite fixed connections ? Is there anything I should use to
coat the interface to minimise the resistance ? I am just using "naked"
graphite and OFHC copper, with screws to clamp a copper washer on top of
the sandwich. At 350A, I am dropping around 300mV, which is around 1
milliOhm, with a contact area of around 2 sq inch (~1300 mm^2)
Is one milliohm good ?
Thanks for suggestions.
Steve
Reply to
Steve
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Not for 2sq" Try putting some conductive silver paste between, and see what you get.
Reply to
Michael Gray
Hi Michael, Do you mean something like a conductive "ink" like they use to repair PCB tracks and window de-misters ? I have some of that,
Thanks
Steve
Reply to
steve
The "ink" would probably be my last choice, as it has laquers in it that won't flex when dry. My first choice would be a very thin layer of conductive grease. Although if you have some, it probably wouldn't hurt to try a bit. The thinnest layer that you can get, such that a piece of plate glass over either surface is just wetted completely.
RS Components have what I was contemplating:
Grease:
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Epoxy:
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Paint:
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(This is the Australian website, in $AU)
Reply to
Michael Gray
The paint we have is from RS - never realised they did a grease too. Thanks for that. You don't think the grease will cause problems as it migrates into the graphite do you ? The graphite gets up to 100 degrees C or so in use.
Thanks for your help, it is much appreciated.
Steve
Reply to
Steve
:
The Data Sheet says, (in part): "Remains stable in a wide temperature range; -57 to 252 C"
And I would judge that migration into the graphite would actually enhance the conductivity, rather than reduce it, as the aliphatic components of the grease would migrate preferentially into the graphite, rather than the conductive silver suspension, leaving more conductive silver colloid in the junction area. Expect a slight odour, mind you, as the organic compounds degrade.
This is just an informed guess/judgement, mind you, never having used the stuff in this situation before.
Reply to
Michael Gray
That's alright - its an approach I hadn't thought of. We tried an aluminium foil gasket, but I doubt we could get a decent clamping force. Your method is elegant !
Thanks for your help. I'll let you know what happens.
Steve
Reply to
Steve Taylor
That's alright - its an approach I hadn't thought of. We tried an aluminium foil gasket, but I doubt we could get a decent clamping force. Your method is elegant !
Thanks for your help. I'll let you know what happens.
Steve
Reply to
Steve

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