Name this part

Question

I have recently purchased a Raspberry Pi 4 (4GB). Upon close inspection of the board, I've noticed one of the parts has fallen off in the package.

It is a very small part and I am at the limits of available magnification. Is there anyone that can help me identify this part?

Fred27 · Answer

I'd agree with Shabaz that it's a decoupling capacitor. I suspect the Pi will work fine without it, but if you feel like practicing your soldering... The component on the other side is a rectangular 16 pin QFN package marked "uK RX", but I'm not sure what it is.

shabaz · Answer

Hi Trent,

I have a Pi 4 near me, and you're right, that part is tiny! : )

I *think* it's a capacitor but not 100% sure. It measures approx 1.3 kohm in one direction, and 1.5 kohm in the other, in-circuit (since I didn't want to desolder it - it is dust sized : )

Anyway, it's likely a capacitor, because continuity testing on each end of it shows that one end is connected to pin 1 of the 40-way GPIO header, and the other end is connected to pin 9. These are the +3.3V and GND pins respectively, so it's possible it is a capacitor across the supply rail. The reason why it appears in the middle of nowhere, is because on the other side of the PCB there is some IC there, but I don't know what it does. The IC is next to 4 resistors and nothing else, It could be some glue logic maybe. It doesn't seem to be a voltage regulator or anything.

If you cannot solder it back on, if the Pi is still working, then I wouldn't worry about it, but worth holding on to that part and measuring it at some point if you can, to confirm it is a capacitor. To do that, just measure with the ohms setting, and if the resistance is very high (not measurable) in both directions, then it is a capacitor.

Fred27 · Answer

Unless you have a microscope, it's likely to be frustrating. Also, shorting out those pads could cause problems. If your Pi is running ok then count yourself lucky that you dislodged a non-critical component. How did you do it, by the way?