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I want to practice reballing of IC on iPhone logic boards. I bough several iPhone 4S boards ver cheaply, but I have run into trouble: the components are covered with brown coating that prohibits access to the individual elements.
The coating is very hard and so far I have failed to remove it with my precision knife. What is the trick?
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@lacek that stuff is the underfill. A PITA to remove. I use some heat ~120deg C and a dental pick when I have to remove it. Check on something like this for an idea.
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this one actually peels off. Mine is almost rock-solid. I have also seen this one:
https://www.youtube.com/watch?v=FUKJaf02...
and again it seems more rubbery. I Did before an iPhone 5S and there it was way easier too. Does this underfill harden after a few years?
On iPhone 5S when I try to pierce that with say tweezers, they actually penetrate the underfill even if it is cold. Here I have to use excessive force just to leave a mark.
@lacek post some images of what you are working on right now. Use this guide Adding images to an existing question for that. Underfill is pretty rock solid and like I mentioned before I use heat and a dental pick to remove it. Not an easy task and it does take plenty of time....
I do not have a camera compatible with the microscope. I will continue this thread, but I have to get the camera first.
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