A withstand (hipot) test is judged on two numbers: the test voltage and the time it is held. Most engineers set the voltage carefully and treat the dwell as a fixed pause before reading the pass lamp. That pause is where a surprising number of field failures are actually decided.
In the first seconds after voltage is applied, the device under test is still settling. Capacitive charging current flows, surfaces polarise, and any marginal insulation is stressed but not yet broken down. A short dwell can pass a sample that would arc if it were held for the full minute.
Standards settled on 60 s because it is long enough for transient charging to settle and for thermal runaway in a weak spot to begin. A shorter hold catches hard shorts but misses the slow breakdown; a much longer one mainly heats the sample without finding new faults.
Production lines often run 1-2 s screenings to keep throughput. Those catch a dead short, not the gradual failure that appears after a minute. A unit that passes a 2 s line test can still fail a 60 s compliance test - and the customer's lab will run the longer one.
A stable leakage current that climbs slowly toward the limit is a warning the pass lamp hides. Record the current at the end of the dwell, not only the binary result. A unit sitting at 80% of the limit at 60 s is not the same as one at 20%.
Ramp the voltage rather than switching it on, hold for the standard dwell, and log the final leakage. If throughput forces a short screen, keep a sampled 60 s verification on the line so the slow faults are still caught somewhere.
