Take a Dremel with a round rubber drum sanding attachment of about 1/2" diameter.
Grind off all the ID marks on the chips.
Then, pot it in "Stycast".
No, epoxy is what you need. Most anything else can be removed one way or another too easily.
There are high adhesion polyurethane potting compounds, but they are far more costly.
An alternative to fully potting it, would be to do the chip grind thing, and then 'paint' the epoxy over those chip-top locations. You could also 'paint' over the traces until the build up is high enough to hide them, but they can be traced via continuity tests usually.
You could also build a small trace array that you selectively cut and bridge to complete uniquely "keyed" circuits ala Dongle Key technology.
You could make each circuit unique, yet the same, yet harder to copy.
In addition to adhesion, the potting has to resist solvent/chemical baths that pirates may use.
Maybe I could do some micro wire jumpers running through the epoxy. If tools are used to remove the epoxy, the pirates might buzz through the wires by accident.
This might be ironic. It's possible the first people to tear into the epoxy potting will not be Asian copy cats but instead US patent owners who suspect their patent is being used without permission.
Hmm... I wonder if you can be made to reveal your design schematics/software/etc. if a patent holder is able to convince a judge that there's a very good change you're infringing on their patent, yet you have made it effectively impossible for an outside party to determine as much?
The stuff I am thinking of is a tough rubbery thing that can stop a knife point or a bullet, much less most solvents that you worry about that would melt polycarbonate, but not this. It is used by NASA. It is the ONLY encapsulant they have approved for HV space applications.
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