Epoxying over chip numbers?

Electric eraser with "ink" type insert... very quick.

...Jim Thompson

You're wasting your time. Anyone that would be interested in figuring it out will anyway, and those that aren't won't anyway.

IMO, DLC

: We have several prototypes being built over the next few weeks and : wanted to hide the chip numbers of some of the glue logic. We've : sanded them off up to now, but that's an awful and time consuming way : to do it. A search of the sci.electronics groups came up : empty....amazingly.

: Does anyone have any recommendations for covering up the numbers on : plastic and ceramic DIP packages? Loctite's black Prism 410 adhesive : looks good, but we're not sure if it will stick well enough or if it : can be pried off like a "pancake".

: Or is sanding still the best option for doing this?

: Thanks!

: John Muchow : -- remove SPAMMENOT for e-mail responses --

On Fri, 02 Jul 2004 21:48:58 GMT, John Muchow put finger to keyboard and composed:

It doesn't amaze me at all. If I knew how to do it, I wouldn't tell you. It's an abhorrent practice.

Please don't do it. I've spent hours reverse engineering products such as alarm panels and electric wheelchairs (for repair reasons), only to discover that they use garden variety ICs costing around $1.

- Franc Zabkar

Unless the device is trivial and the buyers have trivial skills.

Or if the device is 'magic' - golden ear audio comes to mind. Audio reviewers do not have great technical skills usually. Hmm... reminds me of a product that had the 'advantage' of no resistors in the signal path... great invention.

Thomas

Hi!

Don't bother for standard LS/4xxx logic - anyone interested would desolder it and chuck it in a digital chip tester, and it will come back what the chip number is.

If you've got some flip flops in there, put a chip or two of those into a GAL and secure it - that will stop all but the most hardened design theives. Even better, put as much of the logic as possible into a CPLD, again securing it.

Yours, Mark.

John Muchow wrote:

How are you doing the sanding? Try using different tools in a dremel.

Epoxy can be removed one way or another. I've seen some chips whose number was hidden under black marks (permanet marker) but it can be cleaned off with some effort. Sanding is still a foolproof option.

If you have dremmel, try using that. It can sand off number in a pinch but don't overdo or the chip might get too hot or worse, you might sand the case clean off and expose the chip.

Does that work on laser scribed devices also?

Al

I haven't done it in years... I was last "hands-on-discrete" in 1987, but I'd think so, the "ink" type insert is actually abrasive.

...Jim Thompson

For an interesting "golden ear" story relevant to this issue, see:

For my nickel: Any manufacturer who grinds chips (and therefore makes it impossible for me to service the device, whatever it might be, but replacing chips that die (they do that eventually, yknow) is a manufacturer who will never again receive any money from me.

acetone

John Muchow wrote:

On 03 Jul 2004 05:30:27 GMT, Dennis Clark put finger to keyboard and composed:

Exactly. In the case of one alarm panel, it took me only a few hours to determine that all the ICs were 4000 series CMOS. For someone intending to steal the design, these few hours could easily be amortised over a large production run. However, for a repairer such as myself, this labour cost must be passed on to the customer. The only thing the manufacturer has achieved in this case is to generate animosity towards his brand.

- Franc Zabkar

On 3 Jul 2004 13:38:11 -0500, Don Bruder put finger to keyboard and composed:

I also despise the practice of relabelling chips with obscure in-house numbers. HP and Ford Motor Company are two bad examples that come to mind. I also recall junking a swimming pool solar heater controller because the manufacturer refused to supply a replacement field-programmable pre-programmed CPU. Instead I was offered an uneconomically priced replacement module. What hurt even more was that the original faulty CPU's code would have been retrievable had its security bit not been set.

- Franc Zabkar

Abrasion does the trick: sanding, milling, laser. However, anyone can still find out what chips you used, so why bother? No other company i know of does something as infantile as hiding part numbers.

Nope; hasn't worked since the mid 1980s...

That's a great idea! Too much like using a Dremel (with the rubberized wheel) though...what we're doing now. I was hoping to just put a drop of epoxy on the chip and go. After thinking about it, I'm pretty sure it won't stick well enough to the ceramic packages. But, it would be nice if it could work with PDIPs.

John Muchow

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You're probably right, but we're just trying to keep things in our pocket until the prototype testing is done.

John Muchow

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