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Epoxy Covered PCBAs Means to prevent hacking?



Epoxy Covered PCBAs Means to prevent hacking? | 22 September, 2003

Help Please!

A friend of mine works for this company (a novice in the hardware world), they are thinking about covering their PCBAs with Epoxy (don't know what) so to prevent hackers from damaging their PCBAs - they claim it is costing them too much as these PCBAs are slipping through retail chain under warranty. My questions are: 1- What kind of Epxoy that would prevent an intent hacker from damaging a board? 2- The PCBAs are being reworked today at service locations worldwide, when Epoxy is heated, wouldn't this present a safety problem for the rework technicians (inhaling toxic fumes)? 3- What type of rework equipment would be used, assuming that this Epoxy is similar to conformal coating in marine PCBAs?

Any information is highly appreciated. Thanks, Joe

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Epoxy Covered PCBAs Means to prevent hacking? | 22 September, 2003

I did some potting encapsulation as you mention for a customer. They supplied a two-part material custom designed. If you go this route, there are likey to be no board repair options. The epoxy cured hard as a rock. Too much damage to access devices on the PCBA.

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Epoxy Covered PCBAs Means to prevent hacking? | 22 September, 2003

There are some flexible epoxies which will not cause mechanical damage during thermal expansion and contraction but as noted above, you can not get them off to do re-work. Find one you can get off, please let me know.

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Epoxy Covered PCBAs Means to prevent hacking? | 22 September, 2003

Questions: 1. Is this a retail product sold as PCB only? Or is this in a finished chassis / case (like an external modem)?

2. Are the customers damaging only the BGA devices? Like prying them up with a screw driver? What?

You can dam and fill the bga device, but rework is messy. How about placing a emi (tin) shield over the bga device (tamper indicating)? Break it now suckers!

The shield could even fit around the device perimeter as long as it is taller than the device....make sense?

Just some ideas.

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Epoxy Covered PCBAs Means to prevent hacking? | 22 September, 2003

By "hacking" do you mean altering the performance of the board or something else?

This reminds me of something I saw a while back. Better termed counterfeiting than hacking, it may have some relevance to what your friend is trying to do.

The problem was that a large automotive electronics remanufacturer was being taken to the cleaners with a large quantity of bogus field returns. It turned out that this was the byproduct of warranty work being performed by their dealers. The dealers were taking subassemblies and components from certified replacement assemblies to trouble shoot and fix the more expensive entire modules. Then to avoid paying for the cannibalized assemblies they replaced the missing components with the switched faulty ones and claimed that when the units were installed they never worked. Apparently many unscrupulous dealers were taking part in this practice and the cost to them was enormous.

They had tried all kinds of pot molding and encapsulation techniques to thwart this practice over the years, but found that in the long run this was only hurting themselves as they often had to rework these encapsulated boards themselves for various reasons. It was apparent that the cure was worse than the disease as many parts were scrapped in the process.

The best solution turned out to be getting rid of encapsulation and to place a direct part mark using a laser to etch a tiny 2D matrix code that corresponded to an encrypted code for each unique board and a corresponding code for each of it's mission critical components. The mark could only be read with a hand-held 2D reader once product was returned and the code referenced the original sequence in a confidential look-up table.

If a component was found to have been uncoded "switched" or it was proven that the core was altered with other non-conforming parts they could catch the culprit red handed and null their guarantee under a fraud clause in the dealers contract.

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Michel Moninger


Epoxy Covered PCBAs Means to prevent hacking? | 24 September, 2003

Loctite makes a version too, if I recall. Designed to be tamper evident, but yes, rework is a bear. We had similar results using one of Lord Chemical's urethane potting compounds. It was a filled black fire-retardent material and if you tried to get it off, it would tear chunks of the substrate (board or component) off before the adhesion broke down.

You can also Google FIPS 140-2, since this type of security on a physical level is discussed.


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