I understand the military does exactly that - encapsulates super secret circuits in a material that reacts if it is exposed to air, and destroys the circuit in side. Any mitilary contractors out there? -- Lawrence ----- Original Message ----- From: "Roman Black" To: Sent: Friday, July 13, 2001 9:47 AM Subject: Re: [OT]: removing numbers from chips > > >I would like to hear what other PIClisters use to protect their designs. > > > One technique that appeals to me is encapsulation > in a plastic resin or epoxy; > > * pot the whole product, good for small devices > especially automotive ones. > > * pot a critical circuit or even just a PIC and > it's crystal, etc in a tiny metal can, with just > a pin header coming out. These tiny cans are cheap > and can be board mounted, you see them in many > devices now. All the user sees is the main board > with the easy stuff, the 'smart" bit is in a little > can with its own part number. Plastic cans are > available too, they look like those square > capacitors. "PIC in a can"? > > * mount the smt chip(s) direct on the board, with a > big blob of epoxy over it. > > I liked the nitrocellulose comment re the > decapsulation with nitric acid, maybe you could > pot your product with a small capsule of some > reactive agent enclosed. Then if someone tries > nitric acid they get a nasty "boom" to discourage > them, or maybe it just reacts and eats the metal > in the chips as well as the plastic... > Any chemists here? ;o) > -Roman > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.