6 ms·
Author here for all your CT scanning questions :-)
by kens 1y ago
Author here for all your CT scanning questions :-)
- OptionOfT 1y agoWhat is your CPU's yearly deductible?
- loa_in_ 1y agoIs the CPU destroyed by the process or did you reassemble this particular specimen?
- kens 1y agoI took the metal lid off the chip to improve the scan quality. If I had left the chip intact, it would probably be fine. (I assume the X-ray levels are low enough to avoid damage, but I haven't confirmed that.)
- wkat4242 1y agoAlso 386s are very resistant to radiation, I believe they still use them on the ISS for that reason (a radiation-hardened version but still)
- deleted 1y ago[deleted]
- johnklos 1y agoThis isn't about CT scanning, but about the chip itself. Since the bond wires are just hanging out in air, does this mean that a chip like this could be ruined by dropping it which might cause the bond wires to move enough to short something? Thanks for all your hard work!
- userbinator 1y agoI'm not an expert in this area but I'd expect that the bond wires' mass is low enough relative to their stiffness that any shock sufficient to bend them would also shatter the ceramic package.
- generuso 1y agoIf the chip is subjected to a few thousand g's of shock the wires can bend and short. This failure mode is quite low on the list among others, but it is something that people did investigate. For example: "Swing Touch Risk Assessment of Bonding Wires in High-Density Package Under Mechanical Shock Condition" https://asmedigitalcollection.asme.org/electronicpackaging/article-abstract/141/1/011004/367403/Swing-Touch-Risk-Assessment-of-Bonding-Wires-in https://asmedigitalcollection.asme.org/electronicpackaging/a...
- besserwisser 1y agoYes, that can be a problem. Story from one of my professors who worked on instrumentation and telemetry for a defense lab. They built a data recorder for artillery shells. In the early "flight" tests, the recorders failed and nobody could figure out why. They worked before and after. Then someone realized the high acceleration bent some of the bond wires in the chips, causing them to touch and short. The fix was surprisingly simple: make sure all chips face top down.
- imoverclocked 1y agoDoes it look like the almost connected pins could have been purposely severed during production? ie: could they have been connected and then using a calculated pulse of power, disconnected?
- kens 1y agoIf they installed wire bonds and removed them, there would be visible remnants on the die, which aren't there.
- TZubiri 1y agoWhat CT scanner was used? The images are surprisingly detailed for something so small, while we are used to coarser scales of human anatomy.
- kens 1y agoIt's a Lumafield scanner, but I don't know the specific model.
- deleted 1y ago[deleted]
- bunabhucan 1y agoWhat is the last node/cpu that had the smallest features visible at optical microscope scales?
- rts_cts 1y agoWith a good scope we could inspect 0.35um chips just fine. I honestly didn't look at die photos much after that until we started getting SEM images of 32nm and smaller chips
- s1110 1y agoGenuine question: the website doesn't work in Russia. Did you restrict the access or is it my ISP doing that? Someone tries to prevent me from studying of very niche info on ancient Intel CPUs. Thanks! P.S. Big fan of your work!
- vardump 1y ago[flagged]
- userbinator 1y agoI'm against war but it just says nothing more than stupid virtue-signaling when you do stuff like this. What's ironic is that the ones doing this crap are usually the first to cry about internet censorship.
- vardump 1y agoThis has nothing to do with "virtue-signaling". Russia's actions have been extremely evil, so it's only natural it generates dislike, even hate. That's how we humans are. Same happened to the Germans during and after World War II.
- userbinator 1y agoWhat the government and its leadership does is very different from civilians (which may not even have the power to change anything).
- tom_ 1y agoIf the people providing the information want to block you from reading it, that does rather feel like their prerogative.
- xpe 1y ago> ... nothing more than stupid virtue-signaling ... The commenter don't know this with certainty. It is a rather uncharitable assumption. It is hard to know what is inside the head of another person.
- rylando 1y agoWhat kVp/mAs do you use for this? How are you avoiding the artifacts seen from medical imaging? Curious, in school for CT in the medical field.
- kens 1y agoLumafield does all the work; I just get the images :-) The data says 130 kV, 123µA. The whole scan took 21 hours: 1200 projections of 60 seconds each. I assume that they avoid artifacts by using a whole lot more radiation than medical imaging would permit.
- rylando 1y agoI’m assuming each image was taken with 123 microamperes? Or is that total dosage over the 21 hours? If it’s total that’s much less than medical dosage, but if it’s per image that’s a lot more! Thanks for the info, how interesting! (for those who don’t know, mAs = mA • seconds = milliampere seconds. It’s how Radiographers measure how much x-ray photos are being produced by the tungsten filament in an X-ray tube. kVp is kiloVoltage potential and it’s how we measure the speed and thus the penetration power of the X-rays. 130kvp is slightly more than the 120kvp used for an avg human chest radiograph)
- fecal_henge 1y agoAny rational argument to use mAs instead of mC?
- kens 1y agoI asked Jon Bruner at Lumafield for details: The scan was performed on our Neptune Microfocus scanner, configured with a 130 kV source. Current varies on this source depending on scan settings; in this case 123 µA. Each voxel in this scan is 12.8 microns; for smaller parts that we're able to move even closer to the X-ray source we can achieve 3-6 micron voxels. Compared to medical CT scans, this is much higher resolution--medical CT scans have voxels on the order of 0.5 to 1 mm! This is possible because we're able to apply much higher X-ray doses in industrial scans. Medical CT scans are typically on the order of 120 kV, at higher current but for much less time--perhaps a few seconds compared with minutes to hours for an industrial CT scan.