>As a first line of defence against code copying, I'd like
>to remove the markings on ICs; logo, number, etc. Can
>anybody suggest a chemical that can dissolve the printing
>and not damage the IC package?

The other part that people forget to do is remove the part number that
sometimes exists on the bottom of the chip. I have an HP plotter that no-one
wanted as it had died, and HP wanted an arm and a leg to repair it. There
was another identical plotter around and someone swapped chips between the
two until they identified the faulty chip. The plotter eventually fell into
my "rubbish bin" as no-one wanted it, and I removed the chip, looked on the
bottom, and found 6805 stamped there. Sure enough, changing the chip for a
6805 micro out of some other equipment in the workshop ensured a working
plotter again.

>An interesting variant is to design the board with the chip
>upside down, then bend the leads backwards.  Don't laugh
>too hard - I once reverse-engineered a board that used this
>trick.  Its also way more effective if you do this with only
>the obscure chips on the board.

It is also a trick fraught with other potential problems. A colleague had
dealings with doing this as a PCB had been designed back to front because
someone forgot the pinout was viewed from the top of the chip, and not the
bottom. They fitted chips by reverse bending the leads, but they would fail
regularly. eventually he came up with some arrangement that meant the chips
did not need the leads reverse bent (IIRC it was not possible to just mount
the chip on the other side of the PCB) and the failures stopped. He surmised
that the action of reverse bending the leads damaged the seal between the
leads and the body, allowing ingress of moisture (it was a sub tropical
environment) leading to eventual failure of the chip.

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