Electronics > Projects, Designs, and Technical Stuff
BSP100 mosfet blows open, not short
Circlotron:
Using a BSP100 mosfet and several times because of equipment installation errors the mosfet drain get +12V battery applied and so when it switches to ground it dies. The thing is, gate is shorted to drain but drain-source is open circuit. I thought that’s a bit unusual. Seen it happen several times. Bonding wire failure?
fourtytwo42:
I used to use these a lot and had trouble with failures on some prototypes, eventually turned out to be ESD damage during assembly!
Miyuki:
As most today low Rds MOSFETs datasheet have line with: "current rating limited by package"
Bond wires are weak link, they can blow even sooner than chip is busted, but their melting will kill it as it produce hot spot
T3sl4co1l:
Step 1. Die overheats.
Step 2. Die melts, becomes 3-way short. Gate oxide is disturbed, junctions are melted together.
Step 3. Fault current ensues. Melt spot becomes vaporization spot; die surface and bondwires evaporate into plasma.
Step 4. Supersonic plasma ball builds pressure until the package is fractured, releasing a sharp "CRACK" into the surrounding air.
It would seem your example went through at least steps 1-3, and had little gate current to vaporize that bondwire, leaving a 2-way short.
Drain will almost never become open, because it's the tab the die backside is glued onto. source bondwires will vaporize instead. Gate may become disconnected due to the cracked package if step 4 is reached, or remain connected after all.
Note that during steps 3 and 4, the transistor becomes an all-way short, exposing gate and source circuits to some fraction of drain circuit voltage. This can destroy e.g. gate drivers, even behind a coupling transformer, even if the device ends up a three-way open. Transients are not to be underestimated!
I've seen a lot of "silent" deaths in my work. Steps 1-3 are followed, but there isn't enough energy available (or the device doesn't fail in a low enough resistance mode) to blow open the resulting short. A bit annoying for fault finding, but, it doesn't leave shrapnel which is nice, right?
Tim
TheHolyHorse:
--- Quote from: T3sl4co1l on September 19, 2019, 06:05:15 pm ---I've seen a lot of "silent" deaths in my work. Steps 1-3 are followed, but there isn't enough energy available (or the device doesn't fail in a low enough resistance mode) to blow open the resulting short. A bit annoying for fault finding, but, it doesn't leave shrapnel which is nice, right?
--- End quote ---
I think I prefer the shrapnel over more complicated debugging ;D
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