22 Jan
2003
22 Jan
'03
2:04 a.m.
Hello everybody, this is something I've been wondering about for some time
now. Perhaps here is the place to ask, since it's about one of the "inner
secrets of silicon":
Tony Duell wrote:
The 8751 is the EPROM version of the 8051
microcontroller. It's otherwise
identical to it.
If it's in a ceramic package with a quartz window, then you can erase it
like any other EPROM and reprogram it. If it's in the plastic package,
then it's the OTP version.
If in fact the same die was used in both components, then it's only the
plastic (which is impenetrable to the commonly-used ultra-violet light) that
prevents the OTP variant from being erased and reprogrammed.
However, there are kinds of radiation similar to light which *will*
penetrate the plastic housing...you see where this goes? Will the memory be erased
when you, say, X-ray the OTP component, will it stay unaffected, or is the
thing just going to die?
(just outta curiosity)
Arno Kletzander
--
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22 Jan
22 Jan
8:02 a.m.
On Wednesday, January 22, 2003, at 08:07 AM, Arno Kletzander wrote:
If in fact the same die was used in both components,
then it's only the
plastic (which is impenetrable to the commonly-used ultra-violet
light) that
prevents the OTP variant from being erased and reprogrammed.
However, there are kinds of radiation similar to light which *will*
penetrate the plastic housing...you see where this goes? Will the
memory be erased
when you, say, X-ray the OTP component, will it stay unaffected, or is
the
thing just going to die?
According to this:
http://www.jmargolin.com/patents/eprom.htm
it should be possible to erase an EPROM using X-rays, but there's a
possibility of the crystalline structure of the silicon being disrupted
in the process. It's an interesting read.
-Dave
--
Dave McGuire "Wear whatever you want...Just don't be surprised
St. Petersburg, FL if you wind up with a blow-gun dart in your
prosthetic boobies." -Kurt Huhn
12:08 p.m.
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.
Arno Kletzander wrote:
Hello everybody, this is something I've been
wondering about for some time
now. Perhaps here is the place to ask, since it's about one of the "inner
secrets of silicon":
Tony Duell wrote:
The 8751 is the EPROM version of the 8051
microcontroller. It's otherwise
identical to it.
If it's in a ceramic package with a quartz window, then you can erase it
like any other EPROM and reprogram it. If it's in the plastic package,
then it's the OTP version.
If in fact the same die was used in both components, then it's only the
plastic (which is impenetrable to the commonly-used ultra-violet light) that
prevents the OTP variant from being erased and reprogrammed.
However, there are kinds of radiation similar to light which *will*
penetrate the plastic housing...you see where this goes? Will the memory be erased
when you, say, X-ray the OTP component, will it stay unaffected, or is the
thing just going to die?
(just outta curiosity)
Arno Kletzander
12:35 p.m.
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
12:50 p.m.
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
6:26 p.m.
On Wed, 22 Jan 2003, Bob Shannon wrote:
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.
How long did it take?
- don
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
2:31 p.m.
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ard＠p850ug1.demon.co.uk -
Arno_1983＠gmx.de -
bshannon＠tiac.net -
donm＠cts.com -
eric＠brouhaha.com -
mcguire＠neurotica.com