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Testing 1N4007 with a megger
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taydin:
So I did another test, but now using a lower voltage BAW27 diode (rated reverse voltage is 60V). The worst case leakage current is specified to be 50 uA (rated voltage, 100 degrees celsius temperature).

I used my 2450 SMU to source 60V and measured the leakage current. I waited until the current settled at about 20 nA. Then I configured a 50 uA current limit and started to increase the reverse voltage. The leakage current increased to about 100 nA at 100V. And finally at 110V, the current hit the 50 uA limit.

Then I reduced the voltage back to 60V, and indeed, the leakage current returned back to 20 nA.

So the conclusion is that an avalanche is not harmful to the diode if the current stays below the worst case leakage current specification.
zitt:
Wonders to self; how this breakdown "knee" is temperature related.... If running at 120C; is the breakdown voltage higher or lower. what about -40 C?
taydin:

--- Quote from: zitt on March 06, 2020, 08:11:25 pm ---Wonders to self; how this breakdown "knee" is temperature related.... If running at 120C; is the breakdown voltage higher or lower. what about -40 C?

--- End quote ---

Don't know. But the reverse leakage is temperature dependent. For the BAW27, the reverse leakage current is 100 nA at 25 degrees and 50 uA at 100 degrees.
mikerj:

--- Quote from: taydin on November 01, 2019, 12:08:41 pm ---After the above  test, I did another ramp, this time 5 kV. But the test stopped at 4.8 kV, because either the resistor broke down or the diode. Not sure which, will find out

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--- Quote from: taydin on November 01, 2019, 12:11:05 pm ---I measured the resistor, it is still 10 MOhms. And just to make sure the diode is OK, I ramped it up to like 800V and it didn't breakdown. So I suppse the resistor arced internally, but the megger shut off the voltage before the diode would get killed. The resistor is 1/4W metalfilm.

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--- Quote from: taydin on November 01, 2019, 12:12:32 pm ---So can we conclude that limiting the current prevents the junction from sustaining permanent damage under avalanche?

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--- Quote from: taydin on November 01, 2019, 12:18:30 pm ---Nope, we can't ...

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If the resistor broke down then you didn't limit the diode avalanche current to the expected value.
taydin:

--- Quote from: mikerj on March 06, 2020, 10:29:02 pm ---If the resistor broke down then you didn't limit the diode avalanche current to the expected value.

--- End quote ---

The resistor broke down at 4.8 kV, which is way past the 2 kV point where the diode avalanched.
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