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UCD90120A EXPOSED TO X-RAY RADIATION IN PRODUCTION

WhiteHorse
Genius 4430 points
Other Parts Discussed in Thread: UCD90120A

e2e,

We have a customer asking about the effects of X-ray radiation on the non-volatile memory inside the UCD90120A.  If being exposed to X-ray radiation in a production environment should the UCD90120A be reprogrammed?

Thanks for your help.

Regards,

John Wiemeyer

  • 0
    TI__Genius 9845 points
    My impression is that X-ray should not affect Flash, although I don't have enough knowledge on this topic.

    UCD90120A is checksum protected. If any bit is altered, the checksum will not match, thus the program will not run, and invalid configuration will be erased.

    Thanks,
    Zhiyuan
  • 0
    TI__Genius 9845 points
    Hi John,

    Here is what I got from expert:

    Flash stores data by storing electronic charge in floating gate memory cells. If the floating gates are hit by X-ray, the charge may leak. When the leakage exceeds a certain degree, the bit will be erased. So in theory, there is always a risk exposing flash under X-ray.

    Whether the flash will corrupt depends on the amount of radiation it receives, which is affected by exposure time, beam current and voltage potential of the X-ray machine. X-ray machines are different so it is difficult for TI to specify a safety threshold.

    However, customer can conduct a test: if the device can survive X-ray exposure for 10x longer time than real application case, the device should be OK.

    Customer should avoid inspecting or leaving the board under X-ray for extended time period.

    Also, the X-ray machine usually generates a relatively wide spectrum but only a certain frequency is used to develop the image. A technique that applies a thin Zinc film to filter output unnecessary frequencies can be used to reduce X-ray exposure of the board. Please refer to Richard C. Blish II, Susan X. Li, and David Lehtonen, Filter Optimization for X-Ray Inspection of Surface-Mounted ICs, IEEE Transactions on Device And Materials Reliability, vol.2, No.4, December 2002.

    Thanks,
    Zhiyuan