Summary for conductivity of plated steel vs stainless springs Discussion
conductivity of plated steel vs stainless springs is the core question here: Alan Kirkpatrick asked whether bright nickel plated music wire or passivated 302 stainless would be more conductive for tiny springs used as electrical contacts between a nickel-plated stamped contact and a gold-plated PCB pad. James Watts answered that the steel spring is superior to 302 stainless in conductivity, while noting that 0.010" wire carries very little current. Alan then asked whether nickel plating or stainless passivation would affect contact resistance. Watts replied that it depends on the environment, but in non-aggressive conditions there is no problem with either material and both should work well; he said the environment must be specified if it is aggressive. The thread does not report a definitive measured contact-resistance comparison, only practical guidance that both options are likely acceptable for low-current use.
Q. I’m looking at using bright nickel plated music wire vs passivated 302 stainless steel for some small springs used for electrical contacts. The spring wire is about 0.010″ in diameter, and the springs are used to make an electrical connection between a bright nickel plated stamped contact and a gold plated pad on a circuit board. Which spring material will be more conductive?
Alan Kirkpatrick
mechanical design engineer – Shelburne, Vermont
September 30, 2009
 | A. The music wire will be more conductive. But the application sounds like a very low-current situation, so even though the stainless would be less conductive than the unalloyed steel, it might well be that the stainless at the same time has a more than adequate conductivity. You don’t necessarily need the best available conductivity – you need the lowest-cost adequate conductivity.
A. So that you believe it, take a look at a conductivity chart for both metals. You will find that the steel one is superior to the 302 one as far as conductivity goes. It says nothing about corrosion or other factors. 0.010 wire does not carry much current. James Watts |
Q. Yes, the current levels are very low, so any resistance is important. The music wire spring is bright nickel plated.Is there an oxide that forms? Will the nickel plating affect the resistance between the parts?
Likewise, will passivation of the 302 stainless spring make a difference in contact resistance?
Alan Kirkpatrick [returning]
– Shelburne, Vermont, USA
October 8, 2009
| A. With very low current levels, resistance is less important – low current gives low voltage drop across whatever the resistance is.
A. It all depends on the environment. Under non aggressive environments, there is no problem with either. You need to specify the environment if it is aggressive. James Watts |