Your prototype radio worked fine on the bench. Then you enabled the buck converter, and the link margin dropped by 6 dB. The receiver didn’t fail. The transmitter didn’t fail. The power supply started switching, and the radio started listening to its own power rail. This is self-desense: a receiver’s sensitivity degradation caused by an …
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The Golden Board That Disagreed With the Fixture: Test Limit Correlation, Guardbanding, and GR&R at the CM
Your prototype passed. Your golden board passed. The fixture says the golden board failed. That is not a board problem. That is a measurement-system problem, and at 1k–10k unit volumes it is the kind of problem that eats a week of engineering time and produces a shipment hold that nobody can explain to the customer. …
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The Bathtub Curve That Was Actually a Cliff: Weibull Analysis of Field Returns and the Burn-In Decision
Every reliability deck has the same slide: the bathtub curve. Infant mortality on the left, a long flat useful life in the middle, wear-out on the right. It is a comforting shape. It implies that if you burn in your product long enough, you scrape off the early failures and ship the flat part. Then …
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How a Brown-Out Detector That Worked Became a Field Failure Nobody Could Diagnose
The first return came in on a Tuesday. A battery-powered environmental sensor deployed at a cold-storage facility in Jönköping had reset itself 47 times in six days. The unit passed every test we threw at it on the bench — brown-out detection, watchdog recovery, low-power sleep cycling, the works. The second return came Thursday from …
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How Fault Code NC-04 Became a Three-Week Root Cause Chase, and Why Naming Is an Engineering Decision
The field return showed up on a Tuesday. One-line complaint from the installer: device won’t boot, red LED, nothing else. The return authorization listed fault code NC-04, which our application firmware team recognized on sight — brown-out recovery failure. The Nordic nRF52840’s power management IC had dropped below the 1.7 V VDD minimum during cold-start, …
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Why You Should Test the Thing That Will Break First, Not Last
In hardware product development, the thing that will break first is rarely the thing you’re most worried about. It’s the connector that gets yanked at a bad angle, the flex cable that fatigues after 2,000 cycles, the mounting boss that cracks when someone over-torques a screw. This article is about failure analysis and design for …
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