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Comment by basicplus2 | Hacker News Reader

I cannot count the number of circuit boards i have photocopied the backof photographed the front from all angles and created my own schematics..

Gets pretty hard with multilayer boards and smd components

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I don't remember where exactly I saw this, but some boards even stack components, so that e.g. a tiny SMD part sits under a bigger component that has some empty volume under it (e.g. an SMD resistor under a socket or capacitor). Good luck finding that without taking the board apart completely.

To be honest, I think layouts like this are done for practical reasons like space constraints rather than to annoy reverse engineers. If you are serious and can disassemble a board, you will find these components immediately.

I stuck 01005 caps between BGA balls on a Spartan 3, but that was in attempt to solve an EMI issue, rather than a specific design goal.

Interesting! Did you run into any manufacturing issues with that? I'd be worried about that.

Yes. It took two attempts. The second attempt worked, electrically, but didn’t have a measurable effect on the noise reduction, so did not end up doing it.

An x-ray machine will also easily reveal such hidden features. It's not something everyone has, but then again, as I noted in another comment here, there are entire companies specialising in this sort of RE work.

Parts can also be submerged inside the PCB.

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