9

I was tearing down some old CD drives and while taking a look to the PCB I found two pointy solder spots, connected to the first pin of each side of a chip which makes me think is an EEPROM.

There seems to be no trace connecting to these.

What are they used for ?

Here's a picture :

enter image description here

Other odd shaped pads in the same direction :

enter image description here

Nick Alexeev
  • 37,739
  • 17
  • 97
  • 230
GmodCake
  • 574
  • 1
  • 3
  • 16

2 Answers2

13

These are solder-thieving pads, I think.

This is indeed related to wave soldering process, as @Ignacio had mentioned, but it's not just an indication of travel direction. As the IC travels through the wave, the solder accumulates and it can short the legs towards the end of the IC that enters the wave last. Solder-thieving pads give the excess solder a place to go, which reduces the likelihood that it will build-up and create a short.

Here's a more abstract example (Source)

enter image description here

If these are solder-thieving pads, then every surface-mount IC (at least on that side of the board) should have a pair of odd-shaped pads (all pointing in the same direction).

Nick Alexeev
  • 37,739
  • 17
  • 97
  • 230
  • 1
    This does seem more likely, given both that they are on the bottom of the board and their topology. – Ignacio Vazquez-Abrams Nov 09 '14 at 05:16
  • I cannot post a photo in the comment section but, yes it makes sense because there is other odd shaped pads in the same direction which fits your explication – GmodCake Nov 09 '14 at 16:22
  • 1
    @GmodCake: Could you post a photo of the other odd shaped pads by editing your original question and appending that photo to the end? – davidcary Nov 09 '14 at 16:58
3

They are most likely used to provide indication of the direction of travel of the PCB through a wave soldering machine. This is evidenced by the buildup of solder towards the back ends of the arrows (and in fact all exposed metal on the board), with much less towards the points.

Ignacio Vazquez-Abrams
  • 48,282
  • 4
  • 73
  • 102