All that Contacts doesn't need to be Gold

17 October 2010
Posted by Chris Smith.

More and more of our lives is becoming dependent on electronics, and that electronics is dependent on wires and cables. A cable needs a plug and producing a good contact on a plug is quite challenging. The problem is that you want to make a connector out of a metal which is strong, conductive and resistant to wear, and of course cheap, however all the metals that fulfil these constraints, like copper, brass, etc. will oxidise in air. This wouldn't be a problem in itself, but the oxides are insulating, so you cover your nice conducting contact with an insulating layer. The standard solution to this problem is to cover the contact in a thin layer of a noble metal which doesn't oxidise like gold. The problem is of course that gold is very rare and so its expensive, and because of historical reasons it is used as a secure investment when markets are feeling insecure, so at the moment it is even more expensive than usual.

A 1Kg Gold KeyWhilst it is not possible to stop cheap base metals corroding and oxidising, Mark Aindow and colleges at the university of Connecticut have been approaching the problem from the opposite direction. They have been trying to make the oxide more conductive so it doesn't matter. They have been using a variety approaches, to do this, alloying the original metal with one that has a conductive oxide so there are some scales of conductive oxide on the surface, and they have been adding metals to the alloy which effectively dope the oxide, adding or removing electrons allowing current to flow.

The results are promising, they have increased the conductivity of copper contacts by a factor of 3 by adding lanthanum, Iron by a factor of over 200 by adding Vanadium and adding ruthenium to nickel improves it by a factor of about 300, so that the contact resistance only gets 20-30 times worse after a thousand hours in an oxidising atmosphere, rather than over 10000 times worse.

They are very encouraged by this result as they are only using a few 2 metal alloys, and expect further improvements with more work. This approach has the other advantage that there is no problem with the surface coating rubbing off, so in the future cables might not have to be gold plated - though I am not sure it will stop the HiFi cable manufacturers.

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