How to reconnect to potential of ripped off solder pad without visible circuit traces

Question

I am trying to get a data backup from a broken LG/Google Nexus 5 smartphone. It was repeating in a boot loop, because the on-switch was stuck at always on. I dismantled the mainboard. Here is a overview:

After desoldering the little push button (from the sport marked with the arrow) I soldered two wires to the contacts the switch was shorting, to make a provisory switch. Then I reassembled the phone partially, to get it started.

While doing so I unfortunately pulled to much on one wire and ripped it off the PCB with the solder pad. Annoyingly it was not one of the four pads which are connected to the ground plane, but the "signal contact" which probably only has a narrow connection path to some controller pin.

As I can see on this microscope images, there is no conductive track leaving my broken signal pad on the top layer of the PCB. It is isolated all-around against the ground plane. So it must be connected by a "via in pad". Is that correct?

I already tried to cover the broken pad with tin by making a solder bridge between the neighboring ground pads, without success. But after the heating it gave me a better view on the underground of the broken pad.

There seems to be an outer and an inner conductive plane, the inner one with an little golden point in it. Is that the via-in-pad?

I also tried to short the connection by a wire with an alligator clamp on ground on the one side and a multimeter probe on the other side. With the probe I tried to touch the via. I had no success in switching on the phone by this method.

Is the inner circular area with the golden point my target potential which I have to pull on ground?

1. With what technique can I expose that area? Scratching?
2. Are there some other spots on the PCB where I could search for my target potential?
3. Is there an other way to get a data backup of the flash memory?

Thank you in advance!

Edit: You can find some close up photographies of the switch here: http://runawaybrainz.blogspot.com/2015/05/google-nexus-5-power-button-woes.html

Answer 1

The ripped pad was not connected to the ground plane, so don’t try connecting it there anymore. The pad is connected to an internal signal trace, or perhaps a trace on the other side of the board, via a plugged via. That’s the little bit of metal inside of the darker ring under the pad. The darker ring is an isolated area to separate the via from the plane immediately under the top side of the board. There may be more of those deeper into the board, but it’s hard to tell.

Answer 2

You could replate it, or find the other end of the via by testing with the multimeter on "bip mode" so you can find where the trace goes, and then solder a small transformer wire to the other end.

Answer 3

You could try to buy a pen with conductive ink if the reason you couldnt solder the via was surface tension. Just put a spot of ink on the pad and it should work, if the via still connects to the top layer.