4 ms·
How do these tests work? I can imagine a test where you connect up all the peripherals flash test firmware and observe the results, but presumably that doesn’t
by willyt 4y ago
How do these tests work? I can imagine a test where you connect up all the peripherals flash test firmware and observe the results, but presumably that doesn’t test parts of the board that aren’t between io pins and the processor. How do they test every single component on a board that costs ~$40? Presumably it’s not cost effective to do this manually. Do they robotically place sensor probes into the circuit around every component?
- Gibbon1 4y agoThere is a bunch of technology for this stuff. You have machine vision inspection systems. There are bed of nails systems that can measure impedance of nodes on the board and run functional tests. Really high reliably stuff gets x-rayed. If you're doing true mass production you perform inspections/tests at each step of the process.
- londons_explore 4y agoIt isn't unusual for a big circuit board to have 1000+ test points on it. A big machine will connect to all the test points and measure all the impedances at high frequency - this allows you to easily detect signal reflections from a short or open circuit somewhere it shouldn't be, and also detect if a chip has a loose pin. The machines are expensive, but the whole test can be done inside 1 second or so, which makes the process pretty cheap. Famously, those same test points are what made installing modchips in early xboxes and playstations so easy - you just have pins touch a few of the same test points that were used for the factory test to override some signals to get your code running during bootup.