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Author Topic: Vanished pbc tracks (just want to share failure pictures)  (Read 1172 times)

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Offline Miyuki

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Vanished pbc tracks (just want to share failure pictures)
« on: July 17, 2017, 08:44:58 PM »
Hi
I'm experimenting with design of welding inverter, full bridge topology
Yesterday I have spectacular failure, it was really BIG BANG
It use huge capacitor 4700uF at ~400V with datasheet ESR just 40mOhm so it have lot of pretty fast energy (I buy them cheap as old stock)

It was huge bright flash and stunning bang. When I turn everything off there was no visible damage at first but at second look, just see on your own eyes:
« Last Edit: July 17, 2017, 09:29:57 PM by Miyuki »
 

Offline alm

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Re: Vanished pbc tracks (just want to share failure pictures)
« Reply #1 on: July 17, 2017, 08:57:21 PM »
Is this a case where you should cover tracks in solder for increased current handling capacity? ;)

It was huge bright flash and stunning bang. When I turn everything off there was no visible damage at first but at second look, just see on your eyes:
Eye protection indeed sounds like a good idea.
 

Online capt bullshot

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Re: Vanished pbc tracks (just want to share failure pictures)
« Reply #2 on: July 17, 2017, 09:15:45 PM »
Been there, done that long time ago ...

But your results looks really clean and surgical, congratulations!
Safety devices hinder evolution
 

Offline Miyuki

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Re: Vanished pbc tracks (just want to share failure pictures)
« Reply #3 on: July 17, 2017, 09:27:58 PM »
Is this a case where you should cover tracks in solder for increased current handling capacity? ;)

In this case tracks worked as a good fuse, must measure transistors, they are not shorted (maybe opened will see), rectifier with PFC boost is intact and continue to work fine
 

Offline alm

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Re: Vanished pbc tracks (just want to share failure pictures)
« Reply #4 on: July 17, 2017, 09:43:38 PM »
If the transistors survived, then you are lucky. Failures in these kind of circuits tend to take a whole bunch of expensive power semiconductors with them.
 

Offline MK

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Re: Vanished pbc tracks (just want to share failure pictures)
« Reply #5 on: July 18, 2017, 04:25:59 AM »
usually expensive power transistors lay down their life protecting the fuse...
 

Online hermit

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Offline DBecker

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Re: Vanished pbc tracks (just want to share failure pictures)
« Reply #7 on: July 18, 2017, 05:08:17 AM »
Not bullet proof, but a good place to start:

http://www.circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/

That's probably not useful here.  These traces didn't overheat from a minor error in design calculations.  They delaminated so quickly that not even a scorch mark was left.
 

Online ConKbot

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Re: Vanished pbc tracks (just want to share failure pictures)
« Reply #8 on: July 18, 2017, 05:59:02 AM »
Impressive that there isn't any vapor deposited copper/copper oxide left either. I've put 30awg wire across a photoflash cap bank switched by a chunky SCR (intended for powering a disk launcher) and it left a nice copper colored coating on the binding posts. Perhaps the pcb glue (holding down the copper) vapor cloud pushed the copper vapor cloud away.
 

Offline marshallh

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Re: Vanished pbc tracks (just want to share failure pictures)
« Reply #9 on: July 18, 2017, 02:59:31 PM »
Very impressive, top marks not even a single burn mark!
Verilog tips
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11:37 <@ktemkin> c4757p: marshall has transcended communications media
11:37 <@ktemkin> He speaks protocols directly.
 

Offline alm

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Re: Vanished pbc tracks (just want to share failure pictures)
« Reply #10 on: July 18, 2017, 03:06:10 PM »
Just nature's suggestion for a change in PCB layout I guess ;).
 


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