8

I disassembled an iPod Nano 2 yesterday and was surprised to find a round brass-coloured plate glued to the back. I didn't find any mention of it at the teardown over at ifixit.com, as they didn't cut the case in half. The back of the logic board has two contacts pressed against this plate.

Since it just seems to be a piece of metal connected to the case and is quite discoloured, I'm reminded of galvanic anodes attached to chips to protect them from corroding. Does anyone know why this plate is there?

I'm a physics teacher and this seems like an opportunity to teach my students something.

eugen_e
  • 83
  • 4

2 Answers2

15

It's a naked piezoelectric buzzer.

Some piezoelectric crystal grown on a metal circle are the active part and the bottom contact glued on the back cover.

The top is then metallised to get the second contact.

Wires could be soldered to the contacts and/or the device could be cased in some plastic box but, since space is a premium here, it's used as is without case and the two spring loaded contacts on the PCB drive the buzzer.

Wasabi
  • 13,167
  • 8
  • 39
  • 62
carloc
  • 295
  • 3
  • 6
2

To enlarge upon carloc's answer, you can actually see the contact studs for making connection to the piezo disc in the lower image. they are the gold-plated spring doots in the little green PC board.

niels nielsen
  • 15,513
  • 1
  • 15
  • 33