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Can anyone help me in identifying this SMD part?

Dimensions 6mm x 2.5mm x 2mm.


2 Answers 2


It looks like an SMD fuse from Littelfuse.

If so, it will be rated for 12A since it is marked "X":

enter image description here

It should test as a complete short circuit if you use an ohmmeter on it.

How I found it:

  1. It looks like a resistor, but it isn't marked like a resistor. SMD resistors typically have numeric markings (when they are marked at all.)
  2. It appears to be too thick to be a standard resistor.
  3. Since it isn't a resistor, it must be a fuse. SMD fuses look somewhat like resistors, though they are thicker and look more "glassy."
  4. Search for: SMD fuse marked X
  5. Found the Littlefuse datasheet, opened it, verified the size and shape as well as the marking.

Mostly it is just recognizing what type of part it could be then finding a datasheet that verifies it.

Finding the datasheets for SMD parts is something of a crapshoot. The parts have very little space, and there are only so many letters and numbers you can put on them. Since there are more different parts than there are usable letter and number combinations, most combinations are used by different manufacturers for different things.

You have to have some idea what the part might be, then search for that type of part with the marking you have.

Another thing that helps is to look at the markings on the PCB.

The designations are somewhat standardized. Your fuse probably has an "F" with a number somewhere near it. The "F" means "fuse."

A few common designations:

  • U = complex integrated circuit
  • Q = transistor
  • R = resistor
  • L = inductor
  • C = capacitor
  • D = diode
  • Z = Zener diode

The number after the letter doesn't tell you much unless you have a schematic diagram or a parts list for the circuit. If you have a parts list then you can look up the part and find the correct type or value.

  • 1
    \$\begingroup\$ Thanks ! Can you please guide me on how you were able to find it. I have done google search in many ways but never got this result. Just want to know how to search for other SMD parts I have and not identified. \$\endgroup\$ Dec 30, 2021 at 17:45
  • \$\begingroup\$ A large part of identifying components is just experience, when you've been looking at components for years you can recognize most just by sight. If you can recognize the basic type of component it narrows down what you need to search for. \$\endgroup\$
    – GodJihyo
    Dec 30, 2021 at 17:54
  • 1
    \$\begingroup\$ For me, the trigger was the castellated ends that seems to be common on smd polyfuses. \$\endgroup\$
    – Kartman
    Dec 30, 2021 at 18:17

Judging by the brownish color it looks like a fuse.
Bourns makes ones marked X = 12A, Y = 15A, Z = 20A so that's a possibility.
If it's a fuse it should measure as a very low resistance.

Look up Bourns SF-2410FA-W series.

  • \$\begingroup\$ Thanks for your quick answer; yes it is confirmed a 12A fuse. \$\endgroup\$ Dec 30, 2021 at 17:49

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