Electronic – Surface mount bead core

emcferrite-bead

I am experimenting with surface mount components for a project. All the other components seem to be OK and I have deduced that it is the surface mount bead core that is the problem. When I remove the surface mount bead core and replace it with the through hole, things work again. When I swap it out again for the surface mount, things don't work. I tried it many times so it seems like this component is the problem.

Previously, I was using this component:

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and I replaced it with this component:

enter image description here

When I measure the ohms of the through hole component, I at first get around 50 ohms then it decreases to about 30 ohms. Which is about what I would expect.

However, when I measure the resistance of the surface mount component I basically get that it has infinite resistance. For this component, I am putting the probes on the two silver parts of the component. I did this for 4 different SMD so I don't think it is a faulty device.

Are these two components not "interchangeable"? Why is the resistance of the SMD infinite?

Best Answer

It sounds like you either have a broken bead, haven't got a good contact with your probes, or you have a capacitor rather than a bead (they can look very similar)
Where did the SMD bead come from?
It's not unknown for big vendors to ship the wrong parts in the right packaging or vice versa. It's happened to us about 5 times in the past 6 months - on one occasion they got it wrong 3 times in the same fashion for the same part (well we have a load of spare capacitors now...)

The surface mount bead should have a low DC resistance (100mOhm according to the product page)

To figure out whether it's actually a cap, if you have a LCR tester, try it on the part and see what you get. If you don't have one, you will have to get a bit more inventive (e.g. scope + signal generator)
A multimeter on high resistance range (e.g. 1 Megaohm or higher) can give a good idea - if the resistance starts out low(ish) and quickly rises to infinity then it's probably a capacitor. Swap testing leads to reverse the charge to test more than once.

First, try another couple of parts from the package to make sure it's not just a broken part.

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