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From: hull@hao.UUCP (Howard Hull)
Newsgroups: net.micro
Subject: Re: EPROM memory lifetime query
Message-ID: <1686@hao.UUCP>
Date: Sat, 10-Aug-85 15:58:12 EDT
Article-I.D.: hao.1686
Posted: Sat Aug 10 15:58:12 1985
Date-Received: Wed, 14-Aug-85 01:17:27 EDT
References: <562@wdl1.UUCP>
Organization: High Altitude Obs./NCAR, Boulder CO
Lines: 48

> 
>       How long do current EPROMS and EEPROMS hold their memory? 
Intel states (in their EPROM Applications Manual AFN-01648A) that you will
have 5% cell failures after only 220,000 years at 70C in storage.  This is
from tests taken at high temperatures to accelerate failures.  Assuming that
these failures are linear over time gives a cell failure rate of 0.0001%
in 4.4 years at 70 degrees C.
> The data sheets don't say.
That's because the data sheets are written by lawyers, not engineers.
> Is it temperature dependent?
Failures are accelerated at the rate of one to two orders of magnitude for
each 40 degrees C rise in temperature.  Very very strongly temperature
dependent.  Ever check out hole mobility at 3 degrees Kelvin?  
Humidity dependent?
It would be if the humidity were allowed to get into the chip!  But the
EPROMS are sealed.  Please refer to other reliability reports concerning
the package bonds and seals to get a notion about failures from this cause.
> Five years?  Ten years?  Twenty years?
The more bits you have stored in EPROM, the more likely you are to lose one
of them.  We have some that were programmed over six years ago, and they
still have the right data in them, as near as anyone running the program
can tell, anyway.  :-}))  <-- You can tell this is a MIL spec smile; it has
a double chin.
> Are some kinds better than others?  Which ones?
If you like to drop bits, use ones made before 1980.  If you like to pick
up bits use ones made after 1980.
> Is lifetime testable?
If the semi mfrs think they can test them, then so can you.
> These things have a finite lifetime; they're just capacitors.  All those
> bits out there are slowly leaking away.  How long will they last?
If you want to use five packages for every one needed and compare them
like NASA does shuttle computer decisions, they will still be around and
functioning after you are long gone...  Provided the comparators are still
ok, that is.
> 
>       I'd like to hear from some semiconductor industry people who know what
> they are talking about.
Ooops.  Sorry.  I have no way of knowing if I know what I'm talking about.
I just read the applications data the semiconductor mfrs put out and hope
that *they* know what they are talking about.  So far, it's worked...
> 
> 				John Nagle
> 				Ford Aerospace and Communications Corp.
> 				415-852-4126
								     Howard Hull
[If yet unproven concepts are outlawed in the range of discussion...
                   ...Then only the deranged will discuss yet unproven concepts]
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