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We just received back 3 pieces of equipment that may have been inadvertently put through a Gamma radiation sterilisation process. The equipment is a low-power embedded device consisting of a 16 bit microcontroller with peripheral FLASH memory and SRAM backed up by a lithium battery. The equipment appears completely dead.

What possible effects would Gamma radiation have on embedded devices? FLASH memory corruption? Circuit degradation? Component failure?

More info:

The equipment is three nephelometer instruments that we make, which use a quite expensive COTS logger as the brains. The instruments were sent back to us from overseas along with some sediment samples. Customs / quarantine decided that they wanted to sterilise the sediment samples, and I think they must have put the instruments through as well.

geometrikal
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  • I can't see gamma radiation being good for flash *at all*... – Ignacio Vazquez-Abrams Aug 07 '14 at 01:42
  • Yea its looks that way. Arrgh overzealous Australian customs. – geometrikal Aug 07 '14 at 01:45
  • I guess that'll teach you to stick to [FRAM](http://www.ti.com/lsds/ti/microcontrollers_16-bit_32-bit/msp/ultra-low_power/msp430frxx_fram/overview.page?DCMP=FRAM&HQS=FRAM) ;) – Ignacio Vazquez-Abrams Aug 07 '14 at 01:46
  • Wow, that series just keep getting better and better. – geometrikal Aug 07 '14 at 01:57
  • Space based electronics used in satellite has radiation specification. Traditional design (decades ago to now) commercial sat, with design life of 4 to 8 years, use special chip that are designed to be 'radiation harden'. Recent years, small experimental small/micro/nano satellite, some funded by non Government organization, some has shorter design life (experimental), seem to be using off-the-shelf components successfully. Not sure how they do it. May be cover in lead box or modern chip are already more tolerance to radiation than those decades ago? – EEd Aug 07 '14 at 02:32
  • High enough energy radiation permanently changed silicon structure, effectively destroy the device. Lower level, causes error, but not permanent damage. Different silicon device have different 'kill dosage'. Wiki on hardening http://en.wikipedia.org/wiki/Radiation_hardening – EEd Aug 07 '14 at 02:38
  • Try reload software to see if it recovers. If radiation is medium, it erases some memory (flash, eeprom or battery backed RAM) but the chip is ok. of course, high rad level permanently kills. – EEd Aug 07 '14 at 03:04
  • From OP new edit, COTS logger may need be reload/repair at logger factory, instead of single board computer as used in many edu settings. Email factory see if they approve this. Try remove battery, wait 24 hours to ensure cap discharged and this erase SRAM (make sure factory says ok before doing and they do not save important data, like calibration on sram) – EEd Aug 07 '14 at 04:11
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    I guess they were trying to get the bugs out of the code! – Enemy Of the State Machine Aug 07 '14 at 05:54
  • I sent a temperature logger NZ-Taiwan-USA-NZ. The object was to log the sea journey temperature profile Taiwan-US to see if it was causing problems from extreme temperatures. NZ-Taiwan and US-NZ were by air. When I downloaded the complete record most was as expected. BUT on arrival in NZ for about 12 hours it dipped to about -30C (or was that 0-40C). Somebody had put it in a VERY cool coolstore overnight. For interest I rang the courier and asked why this had been done and they swore utterly, even in the face of the record, that nothing ever got put into coolstore :-). – Russell McMahon Aug 07 '14 at 06:13
  • @EEdeveloper : From a practical perspective, electonics are more susceptible to radiation nowadays than before because of lower power devices and smaller semiconductor feature sizes. We use commercial junk in nanosatellites for two reasons : (a) they're dirt cheap, and the cost of mission failure is lower than the cost of radiation hardened electronics, and (b) radiation damage is actually pretty rare in low orbit. The reason it's scary is that one unfortunately placed random event can muck up the works, and not because radiation damage is overly common. – Chintalagiri Shashank Aug 07 '14 at 08:54

1 Answers1

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The prognosis is probably not too flash [groan].

Depending on energy of radiation, device death ranges from possible to essentially certain.

You can potentially expect all the effects you described.
Even if apparently still operating you may get increased leakage currents and 'general unhappiness'.

What was the gamma source? what energy?, what distance? Why?

Radiation Damage in Electronic Memory Devices PDF
HTML
Says:

... Obtained results show that gamma radiation causes decrease in threshold voltage, being proportional to the absorbed dose of radiation.

EPROM & EEPROM: ... Gamma radiation causes generation of electron-hole pairs in SiO2 insulator of the gate. The number of generated pairs is directly proportional to the energy deposited in material, depending on the total absorbed dose of radiation [8, 14]. ...

Conclusion

... Based on analysis of data gathered from performed experiments, the exposure of semiconductor memories to gamma radiation causes three effects: holes being captured in trapping sites of an oxide, injection of holes from oxide into FG, and emission of electrons through FG-oxide interface.

The generation of electron-hole pairs leads to trapping of positive-charged carriers (holes) in insulator, causing negative shift in characteristics. Namely, positive-charged carriers induced by gamma radiation require the increase of negative gate voltage to compensate the positive charge. It means that gamma radiation causes decrease in threshold voltage, being proportional to the absorbed dose of radiation.

NASA - Chips in space

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Russell McMahon
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    If the board only got medium rad and recovers after reload, if "decrease in threshold voltage" may lead to still work but reduced temperature, supply tolerance then still it could 'still be used' in lab, good temperature, education purposes. Not reliable enough if the board controls heavy motor, or similar dangerous stuff. – EEd Aug 07 '14 at 03:28
  • See update to the question for more info on what happened. In Australia strict quarantine often results in things getting sterilised. Don't bring in any cuban cigars! – geometrikal Aug 07 '14 at 03:54
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    I don't know the protocols involved in sterilization, but to be honest, I would be surprised if a standard customs sterilization process will have enough gamma intensity to reach the kill level of radiation for semiconductors. That sort of sterilization would likely needs it's own heavy lead containers and so forth to protect the customs folk. Most likely, the levels are those needed to kill bacteria and such, which is much, much lower than what silicon can tolerate. Reprogram all flash and EEPROM, and you should be fine. If you have EPROM in there, then you're out of luck if that got hit. – Chintalagiri Shashank Aug 07 '14 at 09:03