Re: Erasing OTP's and EPROMS by heat?


They have no windows? Wasn't there a theory that X-Rays would erase them?

I investigated this many years ago when I was using a lot of 63701
microcontrollers. I thought of designing a low-cost x-ray source for
erasing one-time programmable devices.

To test the idea I set up a number of eproms in an x-ray machine and
checked the contents regularly as I increased the dose. After a while
the contents were erased. It was even possible to reprogram the chips.

Unfortunately, the memory cells had become permanently leaky, so the
data leaked away after a minute or two.

So yes, it is possible to erase such devices with x-rays, but they may
not be much use afterwards.

I used the lowest energy the x-ray set would deliver, which was 30keV,
and the lowest dose which cleared all memory locations. Ideally, I
would have used an energy of no more than 15keV, just high enough to
get through the package filler material. So it is possible that very
low energy x-rays might work without damaging the devices, but I am not
optimistic.

John

.

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