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> ... high end server manufacturers like SM - use sophisticated automated tests and quality control on boards. MFG test guy here (not supermicro!) Not necessa
by crispyambulance 8y ago
> ... high end server manufacturers like SM - use sophisticated automated tests and quality control on boards.
MFG test guy here (not supermicro!)
Not necessarily. Automated production tests are there to configure and exercise the system and confirm it works as specified. Such tests are good at things like finding bad solder joints, pick-and-place mishaps, misconfiguration of firmware and weeding out product that fails functional test. That, by itself, is hard enough.
Such tests are not _really_ able to detect things which no one is expecting, or worse, things which an adversary has specifically designed to avoid detection. Sure, if something gets "discovered" during a failure analysis, a test or process can be created to specifically address THAT problem in the future.
To find "unknown unknowns", you need an audit of some kind and that is definitely different from production test.
- lovelearning 8y agoThank you for the insight. I was rather naively imagining that every board is subject to some kind of x-ray image matching with the original PCB design to find differences. Not that simple, I see.
- crispyambulance 8y agoSome manufacturers do X-ray boards. Typically this is done to check that BGA devices (https://en.wikipedia.org/wiki/Ball_grid_array https://en.wikipedia.org/wiki/Ball_grid_array) are soldered properly. Usually not done on every board, but only if there's a problem suspected. When it happens they tend to focus only on particular BGA components or suspect copper traces rather than the whole PCB.
- extrapickles 8y agoUsually you scan boards at a percentage determined by statistics (SPC can get complex). However the checks are automated, so you would have to perform the checks in a different trust zone (eg: different country).
- scoggs 8y agoI'm guessing the answer is obviously yes that this type of x-ray would easily be able to discover / distinguish something the size of what's been described? (1mm x 2mm from what I've seen thus far?)
- PeterisP 8y agoThe x-ray picture would contain information sufficient to detect that thing, but it's quite plausible that the process/procedure of analyzing that x-ray would not find it. If they're looking for extra hardware, they're going to detect it, but if they're looking for bad solder joints, they're going to detect bad solder joints but not extra harware.
- scoggs 8y agoRight. It doesn't exactly align with what a normal auditor would be looking out for, I suppose. Thanks, I appreciate it.
- avip 8y agoI've only seen X-ray as a destructive test. AOI is pretty commonplace on a per-unit base, but whether it could or could not detect some modification depends on lots of details we don't have.
- btashton 8y agoIt's not uncommon at all to do AOI on all or a percentage of the PCBs. X-ray is more useful to identify solder issues or defects in the raw PCB itself.
- avip 8y agoExactly. I've never seen x-ray used post SMT. We've used it to post-mortemly debug BGA issues.
- ksutariya 8y agoThey would be able to detect rogue component(s) if AOI, Automated Optical Inspection, was done. However, if the source files already had the component(s) on it, it would pass all tests and QC.
- csours 8y agoIn other words, most automated tests are regression tests.