Can not pick up wi-fi signal

I have been piddling with replacing iPhone digitizers and have run across several that will not pick up on any wi-fi signal right net to a known good one that will get a signal . On 2 of these there was corrosion on the wi-fi chip on the back of the board which i sprayed with contact cleaner and hit with a toothbrush pretty good with no resolve. I have scoured the net to the best of my ability and hoped that one of the pros here could give me some better ideas. It must be pretty common because i have seen several this way

-thanks in advance