Wednesday, December 31, 2014

Trr Testing in High Voltage Diodes - to Mil Specs

During the research phase of a project I was working on, I came across a public domain Mil-Std method for testing reverse recovery time(Trr) in high voltage diodes.

What was interesting was the number of conditions the test looked for, including jitter, soft knee(rounded transition), slope, drift, double break, double trace, discontinuity, and snap-back.

Of particular interest to me was, years ago, I would occasionally see the Vbr of a DUT snap back. That usually meant a junction arced.  You could see it on the oscilloscope.  Usually the remaining junctions could withstand the same applied voltage because the reverse current was limited, thus limiting the heat dissipation.  Otherwise, the diode would have gone into thermal runaway.

Anyway, below are a few generic graphs illustrating some of the more interesting reverse voltage breakdown failure modes.

During Trr testing, VMI tests for all of the above conditions, and more.  100% of VMI diodes are Trr tested.  It is not a sample test.  It's part of our total commitment to quality,  

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