The MX-850 has what looks like a membrane circuiyt layer between the pcb and the rubber buttons. This thin layer appears to have 2 to 3 contact points near the bottom of the remote. How is this layer attached to the pcb? Is it a conductive glue or solder paste? Does the pad in the middle get connected? Are there any other contact points joining membrane to the pcb. I am calling it a membrane layer, but it appears to be a circuit layer. Pink on top and silver on bottom. I assume new stock on the MX-850 doesn't exist anymore, so I need to repair several units.

You haven't stated your symptom.

Most likely fail is wear on the buttons, not solder issues. There are no reliable fixes for wear.

Thanks for the reply. I'm looking for someone with rework experience. The symptom is, top layer of the printed circuit assembly is detached from the PCB. I'm referring to the pink layer just below the rubberized keys, sitting on top of the PCB. Pink on top side, silver on bottom side. It is attached to the PCB near the bottom of the keyboard assembly. By what appears to be conductive glue, solder paste or conductive tape. Can someone confirm the attachment material? How, where, and how many points exist.

I don't believe you are gonna find much information. As you know, those don't even get repaired when they go back to URC – for the repair cost, they just send a brand new one in the box. There was a period of time where you could buy buttons for the MX-900 that fixed that one model. None avail for the 850 that I know of.

At one time you could buy a conductive paint of sorts that you could paint on the circuitboard pads when they started getting flaky, but that was an incredibly temporary fix. I am not much help, I am sorry to say, just not expecting that what you are trying to do gets done by people on this board.

FWIW I may have a few new 850s still.

That pink layer is for the backlighting, has nothing to do with conductivity of buttons working or not.