brian@ucsd.EDU (Brian Kantor) (02/10/88)
Easy to do. Go to a LARGE industrial electrical, restaurant, laundry, or hospital/sickroom supply house and buy an ultraviolet GERMICIDAL LAMP. This will be a small clear fluorescent-style lamp tube. They are typically available in either 15 or 25 watt sizes. You will also need the two SOCKETS that it mounts in, and the BALLAST that must be wired in series with it, a starting pushbutton (any normally-open pushbutton rated for 115VAC will do fine - there's very little current here), and a safety interlock switch. I haven't priced this stuff recently, but I'd guess that it's on the order of $20 or so. Find a box that it will fit in that is OPAQUE and has an easily removable lid. I used an 8-track cartridge storage box from my local K-mart. Install the lamp, sockets, ballast, an AC mains power cord, and for safety, a switch which disconnects power when you open the lid. See the crude circuit below. Put some conductive foam in the bottom of the box so you can put the EPROMS into the foam within a few inches of the lamp. It should erase the bits in about 1/2 hour exposure to the ultraviolet light the germicidal lamp gives out. Be careful. Don't fry your eyes, and be sure to insulate everything well so you don't zap yourself. - Brian / safety interlock ballast AC -------./ o---------------------()()()()-| | ________________________ | AC ---------==|=\ /=|==---| | } lamp { | |-==|=/ \=|==---| | ------------------------- | | ___ | |--------o o----------------------| norm-open starting pushbutton
bobc%wings@Sun.COM (Bob Clark) (02/10/88)
In article <12@ucsd.EDU> brian@ucsd.edu (Brian Kantor) writes: >Easy to do. Go to a LARGE industrial electrical, restaurant, >laundry, or hospital/sickroom supply house and buy an ultraviolet >GERMICIDAL LAMP. This will be a small clear fluorescent-style lamp >tube. They are typically available in either 15 or 25 watt sizes. > All good stuff, especially the interlock. UV is dangerous - please exercise a great deal of caution. A few details: Most EPROMs have a sensititity to a specific wavelength, e.g. 253.7 nanometers for the TI TMS2732A. Erase time is a function of total exposure dose, which is the product of the intensity * time. To quote from TI (I just grabbed the TMS2732A spec at random): "The recommended minimum exposure dose (UV intensity x exposure time) is fifteen watt-seconds per square centimeter." The exposure time will vary from device type to device type. Bob Clark Sun Microsystems
spike@bu-cs.BU.EDU (Spike) (02/11/88)
In article <12@ucsd.EDU> brian@ucsd.edu (Brian Kantor) writes: > >Find a box that it will fit in that is OPAQUE and has an easily >removable lid. I used an 8-track cartridge storage box from my local >K-mart. We found that a bread pan worked well. The light was mounted in the pan and this was placed over a board with two pegs in it that matched two holes in the handles of the pan. ---------------------------------------- / \ <------Bread Pan / \ / \ [] / \ [] <----Peg ===[]==/ \==[]=== [][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][] <-- Board [][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][] >Be careful. Don't fry your eyes, and be sure to insulate everything >well so you don't zap yourself. > - Brian "Last night I had that dream again. I dreamt I had to take a test, in a Dairy Queen, on another planet." UUCP: ...!harvard!bu-cs!bu-it!spike ARPANET: spike@bu-it.bu.edu CSNET: spike@bu-it BITNET: engemnc@bostonu "VPS sucks" -- ->Spike
gwu@clyde.ATT.COM (George Wu) (02/11/88)
A shown in an earlier post, a pretty inexpensive and cheap UV eraser can be built. But why not use a huge piece of expensive equipment; commonly referred to as an oven. It can double to roast your Thanksgiving turkey, and lots more. Anyways, the reasoning goes something like this: the UV light is just some extra energy you're giving to release trapped electrons. So why not use some other form of energy, like heat? This has actually been successfully done, although I can't remember the temperature or time. I think it was half an hour at 300 degrees. Start at a low temperature and work up to it by trial and error. One extra note, this works only for ceramic packages. Plastic ones would probably melt and be difficult to plug back into the sockets. George J Wu rutgers!clyde!gwu
dbraun@cadev4.intel.com (Doug Braun ~) (02/12/88)
In article <41487@sun.uucp> bobc@sun.UUCP (Bob Clark) writes: >In article <12@ucsd.EDU> brian@ucsd.edu (Brian Kantor) writes: >>Easy to do. Go to a LARGE industrial electrical, restaurant, >>laundry, or hospital/sickroom supply house and buy an ultraviolet >>GERMICIDAL LAMP. This will be a small clear fluorescent-style lamp >>tube. They are typically available in either 15 or 25 watt sizes. >> An even better idea: Go to Goodwill or Salvation Army, or a garage sale, and buy one of those old, cheap suntan lamps. These usually have a bulb about 1 1/2" long. Just mount the chips 2-3" in front of the bulb, and run it for 1/2 hour. This has worked fine for years for me. These suckers are BRIGHT. I put it in the bathroom, and close the door until it is done. Don't look at the lamp without goggles. The lamps also give off lots of heat, so you might want to make a little aluminum-foil shield, with holes in front of the EPROM windows. Total cost: ~$3.00 While you wait, you can get a tan! (actually, these cheap lamps are very bad for you. The UV is not filtered at all) Doug Braun Intel Corp CAD 408 496-5939 / decwrl \ | hplabs | -| oliveb |- !intelca!mipos3!cadev4!dbraun | amd | \ qantel /
koko@uthub.toronto.edu (M. Kokodyniak) (02/12/88)
In article <21651@clyde.ATT.COM>, gwu@clyde.ATT.COM (George Wu) writes: > ... > Anyways, the reasoning goes something like this: the UV light is just > some extra energy you're giving to release trapped electrons. So why not use > some other form of energy, like heat? > > This has actually been successfully done, although I can't remember the > temperature or time. I think it was half an hour at 300 degrees. ... I would not want to try this, or at least not to often, since the heat may destroy the device. Components in the silicon wafer are formed during the manufacturing process by controlled diffusion of impurities into selected areas in the wafer. Further heating might cause further diffusion which would make these components gradually disappear. Why else would all data sheets for silicon integrated circuits specify a maximum ambient temperature? Another potential problem is cracking -- this might not even be visible -- because of non-uniform heating or cooling.
andy@rbdc.UUCP (Andy Pitts) (02/15/88)
Take them to your dentist, and have him place them under his x-ray machine. That'll erase them, and you don't even have to clean the lid. Or you could ship them to your self in a box labeled "Bomb". :-) :-) :-) Andy Pitts {gladys, bakerst}!rbdc!andy
straka@ihlpf.ATT.COM (Straka) (02/17/88)
In article <41487@sun.uucp> bobc@sun.UUCP (Bob Clark) writes: >In article <12@ucsd.EDU> brian@ucsd.edu (Brian Kantor) writes: >A few details: > Most EPROMs have a sensititity to a specific wavelength, > e.g. 253.7 nanometers for the TI TMS2732A. Not really true. 253.7 nanometers just happens to be the primary wavelength of the short-wave UV emitted by the typical lamps used for this application. What this spec really means is that you can't use long-wave UV lamps (like black lights, or mercury-vapor sun lamps) to do the job. It also means that you can't put ordinary glass or plastic in the light path either. Only special materials, such as fused quartz or some boro-silicate glasses have the necessary transmissivity at that particular wavelength. As for protection from light as to the erasing of your data, unless the EPROM is marginal, the danger from typical light sources is grossly exaggerated by most people. When I was MAKING EPROMS back about 10 years ago (w/ Nat'l Semi), once we put a THIN coating of polyimide on the chip as a contamination barrier. You could NEVER erase the data. Same thing with Nitride passivation. -- Rich Straka ihnp4!ihlpf!straka Advice for the day: "MSDOS - just say no."
straka@ihlpf.ATT.COM (Straka) (02/17/88)
In article <698@uthub.toronto.edu> koko@uthub.toronto.edu (M. Kokodyniak) writes: >In article <21651@clyde.ATT.COM>, gwu@clyde.ATT.COM (George Wu) writes: >> ... >> Anyways, the reasoning goes something like this: the UV light is just >> some extra energy you're giving to release trapped electrons. So why not use >> some other form of energy, like heat? >> >> This has actually been successfully done, although I can't remember the >> temperature or time. I think it was half an hour at 300 degrees. ... WAIT A MINUTE!!! All of the above is WAY off base! Let's get back to physics! ***************************************************************************** Let me preface my remarks by stating that 10 years ago, my job was to provide test strategies and reliability for the first N-channel EPROMs, the 2708 and 2716. The chips have gotten better over the years, but the physics remains the same. Summary: Heat alone won't do it. A combination of heat and short wave UV may or may not be significantly better than short wave UV alone. The electrons are stuck up in a floating gate structure in the EPROM. To get them off, they have to "tunnel" across the bandgap represented by the oxide layer to the surrounding layer(s). There is a specific threshold energy that must be exceeded (which can vary as a result of processing parameters) in order to tunnel. The number of electrons which can tunnel is based on the distribution of energy that the subject electrons posess. This is, of course, some sort of (probably) normal distribution given a base ambient temperature. Raising the temperature raises the proportion of electrons that exceed that tunneling threshold and can tunnel across the oxide barrier. The degree to which the device is sensitive to temperature is known as its activation energy, which is measured in units of electron volts. This activation energy is empirically determined, and typically is in the range of 0.7 to 0.8 ev. A very small change in activation energy has a tremendous effect on the acceleration factor, as the relationship is exponential with the ratio of the two temperatures (with regard to absolute zero). See some basic college physics (or chemistry?) text for more details. This phenomenon is basic, and not just related to EPROMs. Manufacturers routinely subject EPROMs to long bakes at elevated temperatures (usually SUBSTANTIALLY higher than the above mentioned 300 degrees F) to ensure proper data retention of each individual part. The object is to simulate worst case high temperature operation for a number of years. Any EPROM worth its salt (so to speak :-)) will in actuality last at least 10 times the standard 5-year specification. Good ones are quite bullet-proof. The reason that short wave (and not long wave) UV light does the trick, whereas heat doesn't is that the UV adds quite a kick to those electrons, yes, enough to get them over that tunneling barrier. That is why long wave, which is of lower energy, doesn't work too well (if at all). It doesn't add enough energy to kick the electrons over the threshold. Heat might add a little bit, perhaps enough to make a bit of difference. I don't know. Sorry for getting a little bit long, but the non-semiconductor-device-physics people need to get some solid information on this one. PS: > >I would not want to try this, or at least not to often, since the heat may >destroy the device. Components in the silicon wafer are formed during the >manufacturing process by controlled diffusion of impurities into selected >areas in the wafer. Further heating might cause further diffusion which >would make these components gradually disappear. Diffusion is not an issue below 900 degrees C. Alloying of the aliminum contacts into the silicon and shorting out junctions is an issue at anything above about 425-450 degrees C. If you have gold-aluminum junctions in the packaging, the temperatures get even lower (but most manufacturers have fixed this particular problem (purple plague)). -- Rich Straka ihnp4!ihlpf!straka Advice for the day: "MSDOS - just say no."
artm@phred.UUCP (Curmudgeon) (02/17/88)
In article <21651@clyde.ATT.COM> gwu@clyde.UUCP (George Wu) writes: > > A shown in an earlier post, a pretty inexpensive and cheap UV eraser >can be built. But why not use a huge piece of expensive equipment; commonly >referred to as an oven. > > > This has actually been successfully done, although I can't remember the >temperature or time. I think it was half an hour at 300 degrees. >... Plastic ones would probably melt and be >difficult to plug back into the sockets. > Not a very good idea. Even if you use ceramic packages, this high a temperature will severely weaken the wire bonds to the die pads. You might get a few devices that still work, but you wouldn't have any idea for how long. Better to buy a cheap sunlamp. OR...I wonder how many thousand of the little critters would fit into a tanning bed. Get together with all your friends and buy an hour session at the local electric beach....;-) ;-) ///////////////////////////////////////////////////////////////////////////// My employers only take responsibility for those of my opinions for which I am paid. ///////////////////////////////////////////////////////////////////////////// Art Marriott ...uw-beaver!tikal!phred!artm
przemek@gondor.cs.psu.edu (Przemyslaw Klosowski) (02/18/88)
This is written in response to the long and basically correct article about the physics of the EPROM. It explained th phenomenon correctly, but omitted the quantitative expression for the process: one expression is worth 1000 words :^) The physics of this process is simply of a dynamically activated system: the probability of the electron passing the barrier (and consequently the current, and the time to discharge the gate) is proportioonal to E-E 0 where e=2.7182818... - ----- E - electron energy kT k is Boltzman const e T is temperature E is activation energy 0 So: ypu can either raise the energy of the electrons ( by bombarding with UV light quanta) or raise the temperature. But you better raise it enough! UV has energy of ~3eV. Room temp kT is 25 meV; or in other words you have to raise temp to 120 * 300 K or 36000K to get the same discharge speed, if I got my numbers right. This is impractical :^) przemek@psuvaxg.bitnet psuvax1!gondor!przemek
krc@cs.purdue.EDU (Kenny "RoboBrother" Crudup) (02/19/88)
In article <3711@ihlpf.ATT.COM>, straka@ihlpf.ATT.COM (Straka) writes: > Any EPROM worth its salt (so to speak :-)) will in actuality last at least > 10 times the standard 5-year specification. Good ones are quite bullet-proof. > Rich Straka ihnp4!ihlpf!straka I thought the *lower* limit was at least 100 yrs!! Does this mean in say, 25 years for some of the more marginal products, the application in question will develop a senility complex? I'll be driving my classic '88 Ford Mustang GT (with a souped up EFI chip, of course) along at 30 mph in 2013 and all of a sudden, hyperspeed, or fried engine? > Advice for the day: "MSDOS - just say no." Works for me! -- Kenny "_R_o_b_o_B_r_o_t_h_e_r" Crudup krc@arthur.cs.purdue.edu Purdue University CS Dept. W. Lafayette, IN 47907 1-31-88. A great day for football, +1 317 494 7842 and Black Americans. Yo Dougie!
sfaber@ihlpg.ATT.COM (Faber) (02/20/88)
> Not really true. 253.7 nanometers just happens to be the primary wavelength > of the short-wave UV emitted by the typical lamps used for this application. > > What this spec really means is that you can't use long-wave UV lamps (like > black lights, or mercury-vapor sun lamps) to do the job. It also means that > you can't put ordinary glass or plastic in the light path either. Only > special materials, such as fused quartz or some boro-silicate glasses have > the necessary transmissivity at that particular wavelength. I bought an old sunlamp at a garage sale that had a quartz tube with a drop of Hg and no electrodes. It was excited by rf from a tube oscillator in the base of the lamp. These work great as EPROM erasers. Mine erases a row of EPROMS the length of the tube (~7") in about 10 minutes. These lamps were made in Chicago and sold in the 1940s or 50s I think. The inner quartz tubes from broken mercury vapor street lights or newer sunlamps will also work (these contain electrodes) and may be excited with a fluorescent light ballast. In general if you can smell ozone from your lamp, you probably have a good source of short wavelength UV. Steve N9FYX
markz@ssc.UUCP (Markz Zenier) (02/22/88)
There are three types of flourescent lights that produce enough UV to zap EPROMS. The Black Light and Black Light Blue Phosphor peaks at 350 nanometers and will take 3 1/2 days (Back in my starving student days I was patient) These bulbs are typed FnnTn/BL or FnnTn/BLB. The first number is the wattage, the second the Tube diameter in 1/8ths of and inch, and the phosphor is the Alphanumeric code at the end. The BL produces visible light. The BLB is the good old poster light with a purple filter. The Sunlamp Phosphor peaks at 300 nanometers, and should take less time to erase the PROMS. Germicidal Lights are just the raw mercury plasma in a quartz tube and take 3 to 6 minutes to erase a prom sitting on the tube. They are numbered G??T?? and plug in to the same fixture as the equivalent F numbered flourescent tube. They peak at the 250 nanometer wavelength. Recomendation: Buy the Heathkit, the cost of the parts is about the same. A germicidal lamp at a speciality lamp house will run $30 to $50. A lot for a flourescent lamp with half the stuff left out.
markz@ssc.UUCP (Markz Zenier) (02/22/88)
Safety warning: Germicidal Lamps will rot your eyeballs and cause skin cancer. There is a reason for the interlock switches on EPROM erasers.
jimc@iscuva.ISCS.COM (Jim Cathey) (02/23/88)
In article <4878@ihlpg.ATT.COM> sfaber@ihlpg.ATT.COM (Faber) writes: >I bought an old sunlamp at a garage sale that had a quartz tube with >a drop of Hg and no electrodes. It was excited by rf from a tube >oscillator in the base of the lamp. These work great as EPROM >erasers. Mine erases a row of EPROMS the length of the tube (~7") >in about 10 minutes. These lamps were made in Chicago and sold in >the 1940s or 50s I think. > The inner quartz tubes from broken mercury vapor street lights >or newer sunlamps will also work (these contain electrodes) and may >be excited with a fluorescent light ballast. In general if you can >smell ozone from your lamp, you probably have a good source of short >wavelength UV. It's hard to beat a $10 germicidal lamp from your local electrical supply house. An old flourescent ballast and starter and you're in business. I built mine into an old wooden box. +----------------+ ! II CCCCCC ! Jim Cathey ! II SSSSCC ! ISC Systems Corp. ! II CC ! TAF-C8; Spokane, WA 99220 ! IISSSS CC ! UUCP: uunet!iscuva!jimc ! II CCCCCC ! (509) 927-5757 +----------------+ "With excitement like this, who is needing enemas?"