well I'm having same problem here:
WIFI chip died without any inappropriate usage.
Basically I know the chip is hard to get and hard to weld according to my geek friends
so I thought to myself:
if it's hard to weld, that means it's welded well
and if it's welded well, all we need to make the link between logic board and the chip back online is to add something on the back on the chip, so the chip can gain some physical pressure and then the link will be assured.
And THAT WORKED!!!
all I did was add on a thin plastic piece on the back on the chip (between the chip and the back shell to be exactly)
Hope this can solve your problem:)
Solution from China (by Lupin3rd)