The problem here is the protective cover, the traces aren't exposed there, and you'd have to get under it.
It looks like the break is right on the transition. I've had this happen and what I did was jam a very thin wire (a strand from a multistrand wire) under the cover and extending out a little, then taping it down. Not my proudest fix, but did work.
what do you mean by protective cover??
actually I think I am not quit getting your idea
I think he's saying that there are multiple layers of plastic and the traces themselves are not exposed, but sandwiched between. This is typical with membrane traces. They're only exposed where they connect to the controller.
I have seen traces that look like that that work perfectly fine (I deal with student Chromebooks, so I see one heck of a lot of damage that should literally never happen). I have seen traces that are even partially burnt up from liquid damage that still have continuity and work fine. Kind of hard to test with a multimeter if the damaged parts of the traces aren't exposed unless you can follow them back to another point they are exposed on the membrane and test from where they connect to the controller, or if the protective layer can be lifted enough nondestructively.
I haven't used conductive ink, etc. I have read of problems with getting a proper electrical connection with them, excessive resistance (maybe not a problem here) and their being relatively fragile. It may not hold up well in places the membrane flexes. I haven't used it, but I have ordered some of this
MG Chemicals conductive epoxy because my research suggested that it was more resilient and less resistive than other alternatives. They're a trusted brand in soldering supplies as well. I was going to try to use it to replace the factory LEDs on a Mini M membrane but I haven't gotten around to hacking it up.
E TwentyNine's use of thin wire sounds the least destructive. Definitely worth trying to narrow down the problem to that specific place if a continuity tester/multimeter won't work as easily.
