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What is the state of a diode while failure?

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muthukumar_ece2004

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Hi,

If a diode fails due to over-voltage or over-current or irregular temperature effect whatever it may be, but what is the state of the diode after fails. Either it is in open or short?
 

aquakeerthi

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physically the diode is in open condition if get affected in forward bias if it is correct me pls
 

kak111

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With long praxis in electronics I can say
diode fails caused by over-heating or over-voltage spike causes short circuit in diode.
if circuit leaves high current trough component it burns as open circuit or
can even explode.

Generally i can say that over 90% of diodes after fails are shorted (full or partly).

Regards KAK
 
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ckshivaram

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voltage transients tend to cause the wire effect.
Overcurrent tends to cause an open, like blown fuse.
On rare occasions you can get states between these extreams.

What happens depends failure mode and on what its being used for.

Sometimes a failed diode may not exhibit a complete short circuit (0 V) but may appear as a resistive diode, in which case the meter reads the same resistance in both directions..

If used a power supply part then, A shorted diode appears as a jumper between the points of the connection, as it conducts the current in both directions. The shortened diode exhibits zero resistance in both directions and it appears for the circuit as if it is simply forward-biased.
 

siilviu

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well it happened once to sweep a voltage on a IC pin which had a protection diode and forgot to clamp the current to a resonable limit. guess what? the exponential I-V characteristic of the diode turned into a liniar I-V characteristic which behave like a resistence.
so i guess by damaging a diode its state is a short circuit with a specific resistance.
 

thannara123

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It may short or open .
the diode's conduction will increase ( at reverse breakdown ) finally act as conduction wire ,it create more heat and the current will maximum .at last it will burn out
 
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muthukumar_ece2004

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It may short or open .
the diode's conduction will increase ( at reverse breakdown ) finally act as conduction wire ,it create more heat and the current will maximum .at last it will burn out
Finally burn-out means its open, right?

---------- Post added at 11:28 ---------- Previous post was at 11:25 ----------

well it happened once to sweep a voltage on a IC pin which had a protection diode and forgot to clamp the current to a resonable limit. guess what? the exponential I-V characteristic of the diode turned into a liniar I-V characteristic which behave like a resistence.
so i guess by damaging a diode its state is a short circuit with a specific resistance.
Correct, according to I-V characteristics, beyond certain level diode conduct more current. But manufacturer given maximum rating, a diode after reaching its maximum rating it automatically burn-out(infinite impedance). So it will be open!

Do you have any advise on this manufacturer recommendation concept? It will open or Short?
 

keith1200rs

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My experience is that diodes usually blow to a short circuit but that cannot be relied on.

Keith
 
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FvM

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In a fair range of energy overloading the diode, short circuit failure will be the expectable result. Typically, the semiconductor material will partially melt, transforming the pn juntion to a good conducting block of material. The likelihood of failure to open circuit in the medium energy range mainly depends on the involved package technology. Diodes with a certain risk of failing open circuit under "regular" thermal wear may possibly achieve the same in case of fatal overload.

Above a certain energy level, bond wires and ribbons, lead frame metal or even the chip itself will actually "blow" respectively evaporate. This can clearly cause open circuit. Those power electronics designer, who are required to wear ear protection at work, will know about.
 
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muthukumar_ece2004

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I thought also, may diode Open Circuited during its failure. Otherwise it damages whole circuit operation even single diode fails. Its very risky component if it behave as short during failure!

What about thinking in the view of Risky component if it fails, Diode!
 

keith1200rs

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My experience, as I have already stated, is that they usually go short circuit. That often results in several other components blowing if the fuse doesn't blow first, in the case of a power diode.

Keith
 
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FvM

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Otherwise it damages whole circuit operation even single diode fails.
We usually call this wishfull thinking. You can't derive the behaviour of a diode from what you want it to do. Some devices can be designed for a particular fail safe behaviour, e.g. fusible resistors. This is hardly possible with diodes.

There's no doubt, that short circuit failure happens in most cases, with some exceptions. I can also confirm cases of resistive behaviour as stated by ckshivaram, and as said, open circuit can occur. For a detailed analysis, the diode type and kind of overload should be considered.
 

andre_teprom

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Maybe a rasonable understanding is that, depending up of magnitude of foward biased current, a diode fails as short-circuiting, and after some time, device overheats due semiconductor resistence, and so open in consequence of real fusing.

+++
 

keith1200rs

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... or, the diode fails short circuit and because the resistance is very low, power dissipation in the diode is also low and it remains a short circuit.

Keith
 

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