Primary mode of transistor failure

Bama Slamma · 27th October 2006, 02:26 AM

I'm sure many people in pursuit of audio ecstasy (spelling?) have accidentally "let the smoke out" of transistors. I've read the primary failure mode of bipolar devices is "second breakdown" where the transistor die overheats and shorts out, putting that driver-killing DC on the speaker outputs. When mosfets let go, how do they do it. Do they fail short or open?

wrenchone · 27th October 2006, 02:50 AM

Semis fail short for the most part - they open when there's nothing left to conduct (vaporizing the bond wires does it quite nicely). Opens are far more rare - an open or intermitttent bond wire would be a plausible failure mode in this case. Diodes in the "copper slug sandwich package" (like the 1N4148 signal diode) can fail open if there's insufficient pressure between the two slugs to maintain contact with the die between them.

27th October 2006, 02:26 AM	#1
Bama Slamma diyAudio Member Join Date: Oct 2006	Primary mode of transistor failure I'm sure many people in pursuit of audio ecstasy (spelling?) have accidentally "let the smoke out" of transistors. I've read the primary failure mode of bipolar devices is "second breakdown" where the transistor die overheats and shorts out, putting that driver-killing DC on the speaker outputs. When mosfets let go, how do they do it. Do they fail short or open?

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27th October 2006, 02:50 AM	#2
wrenchone diyAudio Member Join Date: Feb 2004 Location: Silicon Valley	Semis fail short for the most part - they open when there's nothing left to conduct (vaporizing the bond wires does it quite nicely). Opens are far more rare - an open or intermitttent bond wire would be a plausible failure mode in this case. Diodes in the "copper slug sandwich package" (like the 1N4148 signal diode) can fail open if there's insufficient pressure between the two slugs to maintain contact with the die between them.

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