Epoxying over chip numbers?

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
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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 --

 

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.

 

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

 

You're wasting your time. Anyone that would be interested in figuring

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

http://groups.google.com/groups?selm=

 

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

 

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.

 

*EXACTLY* !!

 

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

 

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

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 wasting your time. Anyone that would be interested in figuring

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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Don't bother for standard LS/4xxx logic - anyone interested would

Forgot about those things. ;-)

Good ideas, thanks!


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

We're currently using a Dremel with the rubberized wheels and they
work great. But, it takes a while to do and it's easy to damage a
chip. We'd love to place a drop of epoxy on the plastic packages and
be done with it.


John Muchow
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For my nickel:

I'm stunned that you've never, ever purchased a product that uses a
microprocessor. The manufacturers don't post the source code and
that's no different IMHO than hiding chip numbers.


John Muchow
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