Electronic – How to choose a spacer/stand-off to maintain electrical contact


I have a situation where I want a stand-off to maintain electrical contact between the PCB and the chassis it's attached to.

My question is, what's the best material and finish for this application?

I see RAF has options of aluminum (unfinished), aluminum (clear iridite), stainless steel (unfinished), and stainless steel (chrome/nickel finish), which I would expect all are conductive surfaces.

Which one will have the best reliability?

Are there any material compatibility issues with any of these choices (like causing corrosion when in contact with the PCB)?

Are there better options I haven't mentioned?

Additional information: This system will have to pass rigorous environmental qualification including (IIRC) a few hundred hours in 85 C / 85% RH. It won't have to pass salt spray or any other corrosive chemical stresses.

Best Answer

Not sure if your application is more sensitive than the computer motherboard, brass standoffs like these are commonly used in computer chassis. They connect motherboard ground to the chassis.

  • Available - These standoffs and screws are easy to get.
  • Reliable - I haven't seen one with corrosion yet in 20 years. (Reliable)
  • Monolithic - Less parts. As you don't want to provide special training to your assembly & manufacturing crew, this option has the least parts count and is straightforward.

According to wikipedia, certain brasses are used where there is a risk of corrosion from factors like chlorides, soft water, etc.


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