Re: Erasing OTP's and EPROMS by heat?

I chose 60 kV since the die and die attach material were visible on film. I placed the UVEPROMs on the top shelf, about 12 inches from the target. I chose 60 - 90 minutes since that was > 10 times the exposure needed to produce a good quality result on Polaroid type 55 film.

I also used a black light (blue ray) UV source with the windows about 8 inches from the source (in the most intense spot). About 20 minutes the data was unreadable. The EPROM would not take a new program. It took only 4 minutes inside the commercial eraser. The EPROM could then be programmed.

I am not sure if the long wave UV completely erased all cells and prevented a rewrite. All of the devices that went through the near and far UV could be reprogrammed (if none of the traces were blown during initial programming or in the system).

I used to have a lot of these devices to work with. The main problem was that project used two or more of these devices in a system. After programming the wrong label was applied. People on project did not know how to read out the check sum (or that there was such a thing).

Another problem: the home brew programmer often applied +15 or more to the enable pin during programming. It was easy to diagnose since the blown bond wires and traces were visible through he window.

The populated PC boards went through a bed-of-nails test called a "fault finder" (I never saw the beast). The program often caused good parts to go bad. On one occasion it actually wrote data into the '2716' (we only use the lower 8k for data). It was a real suprise when I saw data on the upper 8k. The 'fault finder' also used to blow traces on the some of the CMOS parts (it would drive the inputs negative with respect to GND to check for opens). The RCA parts at the time could take >>>100 mA in this direction, the competition could only take about 100 mA. The 'fault finder' was programmed to only put out 10 mA but just before it was scrapped a defect was found that caused it to sometimes produce 1A pulses.

jrwalliker@xxxxxxxxx wrote:
nermal wrote:

Interesting: I tried zapping a bunch (with windows) at 60 KV @ 10 mA for
about 60 minutes but with no effect. These were '2716' series.


How far from the target? I had mine a few cm away in a microfocal
system and I think it took around 20 or 30 minutes to erase/destroy
them. I can't remember the exact details as this was around 20 years
ago - although I may still have my lab notebook from then.

It may be that at 60keV there is much less interaction with the silicon
- the x-rays don't do much if they are passing straight through.

John

.

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