I agree with @DeepSea
Though you could drill a hole in the cover, when you have taken it off.
Through a hole in the cover of the phone lots of dust, dirt and debris will find it’s way inside and most likely cause more damage than you can gain heatwise.
Even more important - all just from my personal unprofessional reasoning - there are 2 big points against that solution:
- There is virtually no room left inside the Fairphone shell to insert a copper sheet. When you take off the back-cover of the phone, you can see a rectangular rubber rim and two plastic pins. They are pressing the battery and the SIM-cards in place. So, there is no space available.
- When you place the copper sheet inside the phone, the copper is transferring the heat from the processor to the plastic cover; and that is rather storing it tha passing it on. So you would still need some copper on the outside of the cover to take the heat away from the phone and “into thin air”.
Or do you mean to replace parts of the plastic cover by copper.
If you are a real craftsman, have the neccessary tool and know what you do; go ahead. You sure will get a very unique phone and a show-stopper as well.
Please post some pictures on this thread, if you have done so; I will be curious as hell. (Honestly!)
My - less sophisticated - solution would be to put a copper plate/sheet in the cradle where you place the phone and maybe the plate/sheet can be a bit larger, so it is sticking out of the cradle. How to do it and if it is possible at all, depends on the kind of phone holder you have.