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| (ultra)acoustic in circuit component level crack detector? |
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| coppercone2:
also knowledge of impedance units and values in this area will help in designing any sort of test system that is mechanical i do see merits for RF but if you want to measure like a inductor or diode or something its going to get really hairy, the mechancial method should work in circuit on anything even while powered I think correct VNA and even ohm setup (range selection) always depends on measurement impedance. the similar wave behavior of electrical and mechanical system should make this useful to know |
| rhb:
I don't think that you could get satisfactory mechanical coupling with tweezers on one side of the board. That also would not detect a solder joint crack between the board and the device. The correct electrical analogy is a transmission line. The presence of cracks will attenuate the signal transmitted through the part and the board. A significant complication is applying enough force to get good coupling, but not so much force that it closes the cracks. And when I look at the 0.15 mm thick xtals I wonder how one can mount them so they vibrate but not break them. |
| coppercone2:
maybe rubber bands? a spring should be linear too, you can add one to tweezers |
| Kleinstein:
Attaching the probes would be a big problem, as too little force would cause poor contact and possible false alarm. To much force could cause the transducers to wear out fast. With many parts on a board I am afraid individual testing with a contact sensor would be not practical as it takes a long time with manual handling and much wear on the sensors. So if at all it would be something for very high requirements where they can pay something like $10 extra per part for the test. The more practical test would likely be high resolution X-Ray. The is some kind of ultrasonic microscopy available already: https://www.ksisam.com/acousticmicroscopy-en/technology-transducer.php Depending on the circuit one could also do an electrical test under mechanical load to the board. Some cracks would show up as kind of jumps / spikes. |
| coppercone2:
hmm if i wanted to experiment further, how would i crack ceramics to make test samples? |
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