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New for November 2023. Particle impact noise detection (PIND) has been used for decades to screen hybrid modules for applications where reliability is critical, especially for space systems. PIND is used to determine how much foreign object debris FOD is floating around inside a module, and FOD can lead to failures. Typical FOD inside a module could be chunks of solder or epoxy, gold wire left over from wire-bonding, or even hardware such as screws and nuts. The English language re-uses a lot of words, we mean metal, threaded nuts, not the kind that squirrels eat...
PIND is an easy test to perform and requires just a small investment in test equipment. It's a non-destruct test, so what's not to like? The PIND test set-up has three components, the controller, the shaker, and the oscilloscope. The controller commands the shaker to shake the unit, and the oscilloscope displays the noise generated by the loose particles. Typical systems can detect particles with masses of 1 micro-grams and diameters of less than 1 mil (0.001 inch) at accelerations as low as 2 Gs and 40 hertz.
The image of the PIND setup is courtesy of NASA's Goddard Space Flight Center.
The test is defined as part of MIL-STD-883 Method 2020. Here is a copy of that section of this huge document. A word of caution, when you reference MIL standards, be sure to look for the latest revision (sorry to say, the links we provide might be out of date).
https://q-tech.com/wp-content/uploads/STD-883-2020.pdf
Here is a summary report on PIND from 1981, found on Defense Technical Information Center. If you pay taxes in the US, this is site just one of the many benefits! If you live outside the US, you're welcome to take a peak too. If you are a terrorist, you might want to consider what keywords you search for on a US government website,
https://apps.dtic.mil/sti/tr/pdf/ADA111347.pdf
Below we present a very short video of an actual PIND test, featuring Michael Lin of VPT Tech. VPT is in the business of high-rel DC-DC converters, in this case they are sealed hybrid modules that are screened for very high reliability (MIL-STD-883 Method 2020 Condition A, Class K, intended for spaceborne applications). The unit is first shocked at 1000 Gs to stir things up, then it is tested four times for three seconds. Mike tests a good unit and then a bad one so you can see the difference in response. You can even hear the difference in noise levels. Bravo!
PIND testing DC-DC converter with Michael Lin