Problems regarding THT Zener diode shorts

[proksima]

Does anybody have a recent problem regarding to THT Zener Diode (They behave like short circuits)
Actually we faced with such a problem where we use 1.3W Zener diodes below their electrical ratings in our capacitive supplies(In our boards, our worst case Zener condition is 600mW ).
We observe this problem in the first function test during manufacturing or in the life test also so the failure rate doesn’t depend on the working period of the electronic board.

I do appreciated for all kinds of comments.

Best regards,

Ahmet

 

[IanP]

Re: Zener Shorts

In the event of a fault causing excessive voltage on the rail, the zener over-dissipates and fails usually to a short circuit .. and that is pretty common phenomenon ..
On the other hand, if the overload is relatively minor, the diode can partially fail to a lower voltage than Vz ..

If the fault current is high, the short circuit diode can get very hot and finally fail open-circuit ..


Regards,
IanP

 

[proksima]

Re: Zener Shorts

I do appreciated for your help,

thank you very much,

best regards,

Ahmet