We used sand filled epoxy to pot modules for military applications. We routinely used a "soda Blaster" to remove potting for failure analysis.
Hi Justin,
You sound as a reverse engineer :-)
Thanks for the enjoying reading material. It is helpful.
Best regards,
Enrico Migchels
It is reasonable, however:
1) We just x-ray stuff. Its cheap, easy, and very obvious where all the tracks are.
2) Depolymerization agent. The potting compound, if not designed to prevent this sort of attack (i.e. just an off the shelf one) will fall apart under this attack.
3) Heat. Most epoxy resins curl up thier toes after a few jhours of baking. Follow that with a microscope and a set of dental probes....
4) Microtome. Yup, just cool her down and slice her up.
So that is the bad news.
The good news is you can:
1) Get potting componds with metalic salts (barium, strontium come to mind) that are radio-opaque
2) Get componds that resist chemical and heat attack (again, they are designed for this)
3) You can, and it works well as a cheap foil, run a few wires from vias into a birds nest over the board. That defeats all but the most patient x-ray, and
makes microtoming tedious in the extreme.
4) Re-etch the componets on the board, or at least grind off all identification.
P.S., a microcontroller is not much of a defense - you have to get to the encrypted ones to be any good against more than a mosest attack.
In reality, is it worth anyone's time to reverse enginbeer your product? Make them good, make them affordable and get brand loyalty. Concentrate on moving forward, and jsut stay one step ahead....
:-)
I read that decades ago worked for a company that used printed circuit boards made on a glass substrate. (Not fiberglass, real glass, like in windows.) The board was mounted in an enclosure that had a spring-loaded weight that would shatter the board if you opened the box.
A trap might be an even better solution.
C
Hi Cabe,
Been reading your post on potting. Of the various potting material available, epoxy potting is preferable in view of heat dissipation.
Jay,
Electro-plating? Genius idea.
You are right; anything can be reversed. But, I want to stop the casual, average, hapless engineer from easily deducing the design.
The solution is potting. So, What is the toughest potting compound I can get?
Cabe
Enrico,
Thank you, those are good suggestions. Some designs I have are not microcontroller based, so I was looking for a way to protect that too.
A determined person will break any security. I just want to make it harder to do and stop the casual thief.
Cabe