![]() The setup was designed so that the pogo pins only compress to approximately half of their 100 mil travel. The difference is that I'm using two parallel PCB boards to position the pins instead of 3D printed parts. This setup is similar to the one described by Hacker Noon. During the test the DUT is securely fixed onto the pins using a clamp, centering pins and a frame. The mechanical parts have been removed in the photograph above, but you can get an idea of how they look from the CAD render below. The pin bodies are directly soldered to the test jig PCB. P75 pogo pins seem to use exposed steel for the head and plunger (they are slightly magnetic) and only have the gold plating on the bottom body part. There was not enough PCB space on the DUT for all the required test pads so I used cupped head pins to mate with the underside of THT connector pins. The whole bed has 21 pins and uses a combination of needle heads (P75-B1) and cupped heads (P75-A1). It uses P75-type pogo pins - a widely available, cheap variant of uncertain origin. It seems that reliability is not a common problem people have with pogo pins, once initial mechanical problems have been ironed out. Thom wrote that they didn't have many issues with contacts on their test jig. The Big Mess o' Wires blog says that their test board only worked reliably after three iterations of the design. Hacker Noon mentions that getting the fine mechanical details correct can be tricky. There are quite a few blog posts and basic tutorials around about the pogo pin test jigs. I was surprised at this outcome, since I've never heard about bad contacts being such a problem with pogo pins. ![]() All evidence, like the fact that detected defect types appear completely random and that most test failures disappear when re-seating the DUT, firmly points towards the pogo pins as the cause. Such test repetitions obviously cause a lot of frustration, decrease the confidence in the testing procedure and significantly lengthen a test that would otherwise take only a few moments. In many cases, the operator must remove, re-seat the DUT and restart the test several times before the test will signal a pass. Even after a lot of fussing around with various adjustments, the procedure still has an abysmal false error rate compared to the actual rate of manufacturing defects. However one problem that has been constantly troubling this setup since the beginning is its unreliability. This setup has now made thousands of cycles and the device proved itself to be capable of detecting a large variety of defects, without doubt preventing many expensive debugging sessions. ![]() While I'm not new to electronic test fixtures, this was the first time I've used the bed-of-nails approach: the test jig has a number of spring-loaded pogo pins that make contact with various test pads on the device-under-test (DUT). A bit over a year ago I designed and built a device for testing assembled printed circuit boards as they come off the assembly line.
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