The power button on my old iPhone 4s (ok, I suppose I should retire this phone for something a bit more modern, but the obvious Apple upgrade in near $1000! so I am looking at China androids. Anyway) stopped working.
The Internet says it is the surface mount cable strip under the button that is likely to go wrong. I ordered one that included tools for about $5 from ebay. I ordered a new battery for another $7 at the same time as I was going to be opening up the device.
It was an exceptionally tricky repair. Much harder than replacing a laptop screen or anything except maybe when I tried to surface mount solder some RAM chips to a Palm Pilot back in 1998 (I failed, and wasted $50 worth or chips back then).
Luckily, I was a bit better this time, but the internal design is pretty close to impossible to repair, as if Steve Jobs said make it hard so it can’t be repaired, just replace.
If you are brave, there are directions to fix it here: