On 12/14/2015 7:14 PM, Dave McGuire via vcf-midatlantic wrote:
On 12/14/2015 07:11 PM, Jonathan Gevaryahu via vcf-midatlantic wrote:
Yeah 300F was completely wrong, I was mixing baking floppies up with baking EPROMS after x-ray (not UV!) based erasure (which really does need 300F). Can you tell me more about this? Does baking somehow address the problem of surface state creation during X-ray erasure?
(I type this with a glance at a stack of trays containing several thousand non-windowed EPROM-based microcontrollers, and another glance over at my X-ray machine..)
-Dave
All I can tell you about this is what I read from wikipedia's "EPROM" article and some articles on history of EPROM/intel 1702 stuff: " Erasure can also be accomplished with X-rays <https://en.wikipedia.org/wiki/X-ray>: Erasure, however, has to be accomplished by non-electrical methods, since the gate electrode is not accessible electrically. Shining ultraviolet light on any part of an unpackaged device causes a photocurrent to flow from the floating gate back to the silicon substrate, thereby discharging the gate to its initial, uncharged condition (photoelectric effect <https://en.wikipedia.org/wiki/Photoelectric_effect>). This method of erasure allows complete testing and correction of a complex memory array before the package is finally sealed. Once the package is sealed, information can still be erased by exposing it to X radiation in excess of 5*10^4 rads <https://en.wikipedia.org/wiki/Rad_%28unit%29>,^[a] <https://en.wikipedia.org/wiki/EPROM#cite_note-6> a dose which is easily attained with commercial X-ray generators.^[6] <https://en.wikipedia.org/wiki/EPROM#cite_note-7> In other words, to erase your EPROM, you would first have to X-ray it and then put it in an oven at about 600 degrees Celsius (to anneal semiconductor alterations caused by the X-rays). The effects of this process on the reliability of the part would have required extensive testing so they decided on the window instead.^[7] <https://en.wikipedia.org/wiki/EPROM#cite_note-jmargolin_com-eprom-8> " Also, 600C(1100F) is a fair bit higher than what I remembered from last time I read this. Maybe try it with one less-desirable microcontroller and the X-ray generator? And bake it at various temperatures and see if it 'recovers'? -- Jonathan Gevaryahu jgevaryahu@gmail.com jgevaryahu@hotmail.com