CPLD erase from Airport X-ray scanners - Page 1
Forum section: electronics / projects

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 02, 2020, 11:49:16 am
content: Has anybody experienced a complete erasure of a CPLD logic when it passed through an airport X-ray machine? Or may be some other scanner used in the airport?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 02, 2020, 04:38:26 pm
content: FYI, I've passed my laptop through, in standby, with no apparent change in operation when later opened. (That would be a target size of, less than 1GB I think, of active, in use, RAM. Data that I would expect might cause a crash if it gets corrupted.) I would expect DRAM to be more vulnerable to EEPROM cells, or some Flash. (I wouldn't thinkCPLDsare using the latest, highest density Flash processes, no?)AFAIK, erasing EEPROMs is possible with x-rays, but only with extreme levels, levels that cause rapid and permanent damage to the chip. Whereas electronic erase cycles might be 10^5, or UV cycles might be 10^3, x-ray cycles are like... 10^1 if that. Or something.Also AFAIK, most programmable devices are rated for assembly inspection x-raying, which are probably around the same level?? I can't remember actually reading such a rating actually, but it must exist? There are plenty of no-lead packaged devices out there, that would need to be x-rayed, that can be supplied pre-programmed. Which means they need to retain their programming through soldering cycles, too.Tim

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 02, 2020, 04:48:18 pm
content: Quote from: T3sl4co1l on February 02, 2020, 04:38:26 pmI've done that many times too and never experienced any issue. Even when left in standby.Quote from: T3sl4co1l on February 02, 2020, 04:38:26 pmI'll say yes and yes.And I'd say typical inspection x-ray machines have significantly higher level.

author: magic
author_rank: Super Contributor
timestamp: February 02, 2020, 07:07:34 pm
content: There is also a whole bunch of actual EEPROMs and Flash in computers and other consumer electronics which go through those scanners.

author: filssavi
author_rank: Frequent Contributor
timestamp: February 02, 2020, 07:39:30 pm
content: I fly fairly often, so I have USB keys, sata SSDs (MLC), laptops and tablets go through x ray scanners 5/10 times a year and I have never had any problems. I expect CPLDs to be much less susceptible as they are usually manufactured on very old nodes (the older the node, the larger the feature size, the higher the energy needed to flip a bit)Also I think complete erasure is basically impossible, unless you exposed the memory to extreme levels of radiations (nuclear reactor type levels), I would expect more of an erratic behaviour due to single bit flips (I seriously doubt CPLDs do crac checks on startup)Anyway airport scanners are allegedly designed to be film (as in photographic film under ISO800 sensitivity) safe, and I expect that to be quite more sensitive than flash

author: LaserSteve
author_rank: Super Contributor
timestamp: February 02, 2020, 08:15:47 pm
content: I've worked for two employers where medical/safety of life grade boards were hand inspect no-xray , when shipped. This wss for good reason.The cargo grade machines are upwards of 260 KV at a LOT of maS, rated to see through 70 mm of steel. I'vr had older PICs and some modern FPGAs , as well as 80 ISO panchromatic film trashed by cargo x-ray in a past life. We carried JTAG programmers in our toolkits for a reason.Really fun fact. Our packaged film, used for laser beam analysis, came in custom cardboard boxes with the company logo on them. The metal oxides in the logo colors interacted with the x-rays and I'd open the film packs to find five or so plates with a dark latent print of the logo showing without development.Steve

author: ebastler
author_rank: Super Contributor
timestamp: February 02, 2020, 08:29:16 pm
content: Quote from: EEEnthusiast on February 02, 2020, 11:49:16 amYour questions makes me curious. I assume you are asking since you did experience difficulties with an erased CPLD? Could you describe the affected device and the circumstances, and whether you are sure that is was damaged due to handling at the airport?

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 03, 2020, 03:02:32 am
content: Well, in this case it was an Altera CPLD which was erased/corrupted. This was about couple of years ago when some boards were shipped to the USA from India. These were recovered after re-flashing the CPLD. I cannot be 100% sure if it was the airport handling which caused it or it was not programmed to begin with for which the chance was very small. There was no other event which could erase the code and hence the airport scanner was the primary suspect. I was wondering if the high enough radiation power can displace the electrons and cause some bits to change which could modify the logic programmed. Especially if the exposure time is long enough.There are some reports available which shows that flash memory could be corrupted with high dose X-rays. But I could not find any info on CPLD.https://www.cypress.com/file/202521/download

author: David Hess
author_rank: Super Contributor
timestamp: February 03, 2020, 04:46:39 am
content: Like T3sl4co1l says, x-rays will erase floating gate memory but it takes quite a dose. An awful lot of consumer electronics goes through airport x-ray machines and multilevel NAND Flash is a lot more sensitive than a floating gate programmed CPLD.Maybe someone left the package in the x-ray machine for an extended inspection?

author: LaserSteve
author_rank: Super Contributor
timestamp: February 03, 2020, 05:59:20 am
content: Boards from the US warehouse which was in plant were blank to begin with. Boards from the Indian logistics warehouse were the ones with glitches. India seems to be a great place for overnight emergency shipping of medical parts to the US for some reason.Edit: The. Boards stored overseas were flashed and verifed before leaving the US. Stored in exquisite ASTAT packing and packed in boxes with world class shock proof padding. Not a chance of mishandling. Multiple FPGA in the programming chain would read corrupted when the checksum was computed.The film exposures were in the US.So were the PICs.Steve

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 03, 2020, 09:45:12 am
content: Quote from: LaserSteve on February 03, 2020, 05:59:20 amThat explains some of it. I have had 2 instances of the boards getting corrupted and both of the time, it originated in India and destination was the USA. It might just happen that all the shipments to the USA are scrutinised more and so they spend more time in the X-ray machine at high power levels. Any time the guys at the customs see an electronic part, which they cannot recognise, they suspect it to be some kind of a bomb set to explode on the flight.

author: Psi
author_rank: Super Contributor
timestamp: February 03, 2020, 10:02:34 am
content: Quote from: David Hess on February 03, 2020, 04:46:39 amAbout 12 years ago I was contracted to write a small report into the safety of consumer electronics going through airport xrays.The airport staff wanted some factual data/evidence when dealing with customers who insisted the xray machine had damaged their device or data.For the first test I put a hard disk, a floppy disk and USB drive through the machine 5 times and checksum'ed them before/after to confirm data integrity.Then i sat them on the xray window inside the tunnel with the conveyor off but xrays forced on. They were in the xray beam continuously for a time that equaled around 9000 cycles through the machine normally. They still all checksum'ed correctly.

author: LaserSteve
author_rank: Super Contributor
timestamp: February 03, 2020, 10:31:59 am
content: Did you run that test as cargo or checked/carry-on?My glitches are ALL cargo.Steve

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 03, 2020, 12:26:35 pm
content: Quote from: LaserSteve on February 03, 2020, 10:31:59 amIt was all cargo mode...

author: Psi
author_rank: Super Contributor
timestamp: February 03, 2020, 06:26:54 pm
content: Quote from: LaserSteve on February 03, 2020, 10:31:59 amMy tests were using the carry-on baggage xrays

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 04, 2020, 03:51:44 am
content: I guess the cargo X-rays are much stronger than the carry on ones. The cargo X-ray machines are larger as they scan through larger consignments and it makes sense to make the X-rays stronger for them to see through metal sheets.

author: texaspyro
author_rank: Super Contributor
timestamp: February 04, 2020, 05:10:28 am
content: There is a company (can't recall who) that makes a line of precision voltage reference chips that use the charge in a floating gate to set the voltage. They have a report on how x-rays affect the voltage. Also saw some independent tests. I seem to remember the results said the technology was not all that precision.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 04, 2020, 05:15:30 am
content: Next time I will put a 2 inch solid lead block over my CPLD....Oh...wait a minute... that will violate LEAD free rules... I'm screwed now..

author: texaspyro
author_rank: Super Contributor
timestamp: February 04, 2020, 05:23:40 am
content: Quote from: EEEnthusiast on February 04, 2020, 05:15:30 amTungsten or tantalum works better that lead

author: BravoV
author_rank: Super Contributor
timestamp: February 04, 2020, 05:38:58 am
content: Quote from: texaspyro on February 04, 2020, 05:10:28 amFormer Intersil (now Renesas), their product line of voltage references that use Floating Gate Array is affected by X-Ray.->AN1533: X-Ray Effects on Intersil FGA ReferencesInteresting quote :"Shielding and PC board solutions. The FGA package leadframe plus two planes of copper provide an excellent shield for radiation from one direction as shown in Table 5 on page 4. Protection for the device side of the board must also be considered. A shield of zinc foil or sheet, 250µm minimum can be placed inside the enclosure above the FGA which effectively filters the most damaging energy. An alternative to consider is a thick aluminum sheet, 10mm or greater, placed over the device side of the PC board."

author: filssavi
author_rank: Frequent Contributor
timestamp: February 04, 2020, 05:49:46 am
content: Quote from: texaspyro on February 04, 2020, 05:23:40 amYes that will succeed 100% of the times in getting your baggage stopped and opened by TSA or whoever in order to check that the lump of metal is not a battery bank or something

author: filssavi
author_rank: Frequent Contributor
timestamp: February 04, 2020, 05:54:14 am
content: If you really need the CPLD to withstand strong x-rays you can get the space rated ones, they shoul be able to shrug off anything an airport throws at them with ease.It won’t be neither cheap nor easy to get

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 04, 2020, 05:58:33 am
content: Based on the inputs, it looks like an aluminum heat sink over the CPLD may be the cheapest solution for the problem. They are easy to buy and install..Not sure of Zinc sheets, will check if they are available online.

author: BravoV
author_rank: Super Contributor
timestamp: February 04, 2020, 06:08:57 am
content: Quote from: EEEnthusiast on February 04, 2020, 05:58:33 amNot sure if this can be used, long time ago when I did DIY Zinc electro plating, I bought big chunk of Zinc block, that usually used for sacrificial anode for sea water vessels like ship, they're dirt cheap and easily sourced, especially near shipping dock/yard area as they're consumable.Random image from Google

author: ebastler
author_rank: Super Contributor
timestamp: February 04, 2020, 06:40:07 am
content: Quote from: EEEnthusiast on February 04, 2020, 05:58:33 amHow would that protect against x-rays coming from other directions? I understand that cargo is often screened in CT-type x-ray scanners.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 04, 2020, 08:55:53 am
content: I can minimize the impact in one direction. that the best which can be done..

author: David Hess
author_rank: Super Contributor
timestamp: February 04, 2020, 04:20:59 pm
content: Quote from: Psi on February 03, 2020, 10:02:34 amMultilevel Flash memory with a low retention time is what would fail first and it was neither as common nor as sensitive 12 years ago. I would not expect magnetic media or drives to be affected at all. NOR Flash and EPROM are relatively insensitive but they can be erased by x-rays eventually just like UVEPROMs.Quote from: texaspyro on February 04, 2020, 05:10:28 amThat was Xicor purchased by Intersil in 2004.Advanced Linear Devicesalso uses floating gate technology in analog applications.

author: ejeffrey
author_rank: Super Contributor
timestamp: February 04, 2020, 05:15:08 pm
content: Quote from: EEEnthusiast on February 04, 2020, 05:58:33 amOne of those tin plated steel EMI cans may be better than an aluminum heat sink depending on the relative thickness. And as that intersil appnote listed above suggests copper ground planes on the PCB side helps a lot.Basically, x-rays come out of the source in an energy spectrum. X-rays are efficiently stopped by materials that have ionization transitions comparable to the xray energy. The bigger the atomic number, the higher energy the innermost electrons ionization energy and the higher total absorption cross section for lower energy x-rays. You mostly only care about the xrays that will be absorbed by silicon (Z=14) or other elements inside your chip -- higher energy xrays will just go right through with little fuss. Aluminum (Z=13) is only marginally effective at stopping the x-ray energies that you care about. Iron (Z=26), copper (Z=29) and tin (Z=50) are going to be much more effective even if they are substantially thinner.