I didn't take the board out, just the battery and metal shield and sticker over the wifi chip... also didnt replace the chip...
i finally upgraded my 4S to IOS 8.3, and after a few weeks the wifi dies...
So i pulled the back off, took out a few screws and a sticker off of the wifi chip to expose the metal top of the chip. heated it with a soldering iron (a few seconds) until it was very hot to the touch...
Put it back together and it works again... thanks internet community!