

How to Fix iPhone 4S Wi-Fi Grayed Out – With a Roofing Nail and a Blow Torch - martin_drapeau
http://martindrapeau.tumblr.com/post/116344427765/how-to-fix-iphone-4s-wi-fi-grayed-out-with-a

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mukyu
People use methods like towels, hair dryers, heatguns, and ovens to do the
same sort of repairs on PS3s and xbox360s so this doesn't surprise me too
much.

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PebblesHD
Thats an amazing trick, but my question is why does a significant thermal
shock affect it in this way?

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femto
I'd guess that the problem is solder joints under (in?) the chip cracking. The
solder joints attach the chip to the circuit board, and also provide the
electrical connectivity to the chip. A cracked joint means the electricity
does not flow and so things don't work.

The "in the fridge" temporary fix is causing thermal expansion/contraction,
which is providing enough mechanical movement to close gaps in the solder
joints, thus getting the electricity flowing again, and making the WiFi work.
The fix stops working when everything gets back to room temperature, meaning
the cracks in the joint open up again.

The permanent fix is heating the chip until the solder joints melt, so the
solder can flow back together, repairing the cracks in the joints. Hence the
use of a bit of solder on the nail to monitor the temperature, so one can stop
when it reaches the melting point of solder.

It's worth noting that such extended duration heating would be a no-no in
production, where high yields are important, but in a case like this, do
whatever works.

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PebblesHD
great explanation, thanks!

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JohnLen
Amazing

