A way to erase OTP components? - test-drb@ccmp.vtda.org

22 Jan 2003

A UV LED?????

(Drops his project planning tools, and kind of wishes he was at the
technical coal face once more)

I was aware that we have White, and blue (Through Phospor, and funky
doping), but these UV devices are new to me...

regards

Doug Jackson
Director, Managed Security Services
Citadel Securix

+61 (0)2  6290 9011 (Ph)
+61 (0)2  6262 6152 (Fax)
+61 (0)414 986 878 (Mobile)

Web: <www.citadel.com.au>   
Offices in Melbourne, Sydney, Canberra, Hong Kong, Boston

-----Original Message-----
From: Bob Shannon [mailto:bshannon@tiac.net]
Sent: Thursday, January 23, 2003 10:58 AM
To: cctalk(a)classiccmp.org
Subject: Re: A way to erase OTP components?

I currently work for a company that makes the X-Ray supplies 
for airport 
scanners.  We have the full X-Ray
emitter heads at test loads for the -180KV, 15ma supplies in-house.

These scanners place the high voltage under computer control, 
they don't 
run at any one preset level.  I gather
that the operating point shifts as the tubes age, and perhaps also with 
the material being examined under software
control.

But crank one of these babies up to full power, and the X-rays will 
generate very high charge levels in the die and
cook the part.  

The question now becomes, does the date go away before the 
transistors do?

On a related note, I recently erased a (windowed) 27C512 using 
a UV led. 
 I did'nt think it would work, but it did.

Eric Smith wrote:

...
 Bob Shannon wrote:

 X-rays will erase the part at high energy levels,
but this will also
degrade the part to the point where it
will fail soon, or die during erasure.

A friend had a large quantity of programmed 27C512 OTP EPROMs, with
contents of no use to him.  He tried to erase them using a commerical
X-ray machine, of the type used for inspecting assembled circuit boards
(to check solder joints on BGA packages) and was unable to produce any
noticable change to the part.

This subject has been discussed on sci.electronics multiple  times in the
...
 past, and the consensus was that the frequency of Xrays
is such that
they have no direct effect on the stored data.  But at very high
exposures it is definitely possible to damage the part.

Note that the exposure levels used for baggage inspection at airports
is far too low to cause any measurable effect on EPROMs.  They are
generally set to substantially lower levels than medical X-rays
equipment.

The normal erasure procedure for EPROMs is to use short-wave UV light,
nominally at a wavelength of 2537 angstroms (about 254 nm).  Unlike the
more common long-wave UV (black lights), this *is* dangerous  to your eyes;
...
 never look into the light.  The light bulbs and the
window on the EPROM
are made from quartz rather than glass, because glass blocks  most of the
...
 short-wave UV.  Suitable bulbs are commonly sold for
germicidal use.

In the mid-1980s, at least one Japanese semiconductor company offered
plastic windowed EPROMs.  The package was a normal epoxy DIP package,
except that a square area in the center was molded from a different
plastic.  The window was translucent (not transparent) to  visible light.
...
 These were less expensive than the usual ceramic
windowed parts, but
more expensive than OTP parts.  However, they could only be erased a
small number of times because the plastic window becomes opaque to the
shortwave UV with prolonged exposure.

I'd heard of these plastic windowed packages at the time, but never
actually saw one until I purchased a coin-op video game board at an
auction.

Eric

CAUTION - The information in this message may be of a privileged or confidential nature
intended only for the use of the addressee or someone authorised to receive the
addressee's e-mail. If you are not the intended recipient, you are hereby notified
that any dissemination, distribution or copying of this e-mail is strictly prohibited.  If
you have received this email in error please notify postmaster(a)citadel.com.au. Any views
expressed in this message are those of the individual 
sender and may not necessarily reflect the views of Citadel Securix.
Feel free to visit the Citadel Securix website! Click below.
http://www.citadel.com.au