Contact Resistance Of A Probe

Many test engineers focus on the Contact Resistance is to keep the test line stable and fast transmitting.

What will contribute to the Contact Resistance of a test probe?

As former probe definition essay said, a probe is composed of plungers, barrel and spring.

Let's have a detailed concept of the resistance of a contact probe.

We always confound the contact resistance with mechanical resistance, even with impedance.


What is mechanical resistance?

It namely equals to probe resistance itself, only based on materials, length, cross-area etc. 

But Contact Resistance is not a mechanical resistance but included, furthermore, it is not the original resistance, let see the contact resistance for a double-ended probe and ICT probe.

semiconductor probe resistance
ICT probe resistance

So, we should focus on more about a probe making, a good process will help a lot to reduce the resistance.

  1. A good tube can keep R2 and R3 as low as possible,
  2. Elaborate electroplating increases electric conductivity of plungers,
  3. Even we never want current goes from the plunger to spring, but a plating treatment for spring will be better. Nobody can work like a god, neither does a probe.( Spring is always made of steel, and steel is a low electric conductivity material with high spring and lifespan )

Sometimes contact resistance is a key to test, like high speed.

Focus more, keep you flux off.

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