[jpstewart]

I recently bought some RAM off of ebay and the seller made a point of telling me that he lined the package with aluminum foil "in case it gets x-rayed".  I'm curious as to why that might be necessary.  I don't think x-rays will harm a couple of DIMMs in a box, but I don't really know.  So do any of the electronics experts here think there's any point to that? 

I know I've heard plenty about x-ray inspection systems being used in the manufacturing process.  I doubt they'd do that if x-rays were harmful to the chips. 

And does a thin piece of aluminum foil provide much protection, if the x-rays are harmful?

It's even stranger (at least to me) since the memory is being sent domestically.  I've only ever heard of packages being x-rayed by customs when they enter the country.

I kind of figure that if the package does get x-rayed and the foil blocks them from seeing inside the package, the authorities would assume it contains contraband of some sort.  Which might not be the best way to ensure the product arrives here!

Anyway, if anybody has any thoughts on protecting RAM from x-rays with aluminum foil I'd like to hear them.  It's definitely not my area of expertise but certainly doesn't seem like a worthwhile thing to do.  Or does that seller know something I don't?

[callahan]

Pointless.

First, aluminum is a low atomic number element that is mostly transparent to x-rays. So it won't actually do anything.

Second, radiation can cause bits to flip in both RAM and magnetic storage. But this is only a concern when the ram is in use.

An extremely large dose of radiation can damage anything (it even degrades concrete and steel in nuclear reactors and other facilities with very high dose rates), but this won't be a factor for any normal mail inspection system.

Some US mail is exposed to high-dose electron beam radiation to sanitize potential biological agents, but unless you are a VIP in Washington DC this probably won't happen for you. I don't know if this will damage ram in normal use, but if it gets stuck in the machine it definitely can. Also, aluminum will "help" stop electron beams (unlike x-rays), but it will create secondary radiation in the process that could be more damaging than the initial e-beam.

[Lady Serena Kitty]

If you want to shield something from roentgenography systems, you need to use Pb, 6mm thick (at least), on all sides. A thin strip of aluminum would only shield against casual radio systems, like the daystar or your favorite FM radio transmitter. X-ray photons are way more powerful (they're above visible light in terms of frequency).

Still, it is perfectly okay to send electronics through the mail without any shielding, even internationally. The roentgenography systems they use aren't powerful enough to do any harm to electronics. I have received computers and hard drives through the mail with no ill effect (data still intact both on disk and in firmware).

[jpstewart]

Thanks for the info folks. Your posts confirmed what I thought and explained the science behind it.