sorry for the late answer . thermal pad did the job. chip was overheating and thermal throttling. saddly the poor design couldnt keep the device cool , so with the addition of regular thermal pads and graphite thermal pad , iphone work as it should be. to be honest , expect your phone to be slightly warmer on the case , because now you dissipate the board’s heat into the aluminium case ! :) i tested this , on some iphone7 and 7plus. all works fine after the mod
i think thermal paste , wont do anything unless you have some kind of heatsink in contact with chips(that’s what oldturkey said above). is impossible in other words. personally , i am waiting for some thermal pads to arrive (just ordered some), so i can use them between the small gap of the board and the back of my phone (iphone 7 plus) i am getting so much thermal throttle , even in some light games.antutu report 120.000 points without any modification, if i cool the device with some fresh water on the back or some ice + water on my hand i get 195.000++ points , thats crazy. i have cleaned the phone from inside , with ultrasonic cleaner filled with isopropyl alchocol (case - board) but still no better results. i will try to fit those pads (0.2 and 0.3mm thickness) into that phone and i ll report back in some days.