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As someone who knows nothing about this stuff, can someone explain to me how soaking the CPU in sulfuric acid removes the packaging material, but does no harm t
by rockdiesel 13y ago
As someone who knows nothing about this stuff, can someone explain to me how soaking the CPU in sulfuric acid removes the packaging material, but does no harm to the chip inside?
- samatman 13y agoSulphuric acid is powerful enough to react with polymers, but not to dissolve silicon. "does no harm" might be an exaggeration here. It's doubtful you'd have a functional chip. But the fine structure remains, clearly. Toss some nitric acid in there, forming aqua regia, and you'll dissolve the whole chip including any gold.
- azonenberg 13y ago> It's doubtful you'd have a functional chip I have a couple of fully functional examples on my desk that say otherwise. If you actually want to keep the device usable to the point that you can still solder it to a board, then you normally preserve most of the package, bond wires, and leadframe which requires more care during decap. For this particular specimen we didn't bother because we just wanted the ROM. Here's an example of a fully functional decapped device soldered back to a board: http://i.imgur.com/UebB3FO.jpg http://i.imgur.com/UebB3FO.jpg My lecture notes at http://security.cs.rpi.edu/courses/hwre-spring2014/Lecture3_Depackaging.pdf http://security.cs.rpi.edu/courses/hwre-spring2014/Lecture3_... go into more detail on various methods, chemical and otherwise, for decapping with and without preserving the leadframe.
- rockdiesel 13y agoInteresting stuff. Thank you for taking the time to explain.