When a MOSFET fails, which terminal of the MOSFET is open or shorted?

[mssong]

When a MOSFET fails, which terminal of the MOSFET is shorted or open?

I know that when a MOSFET fails, it is either SHORT or OPEN. (Is this correct?)

Then I am wondering if the GATE and SOURCE are shorted or open or the DRAIN and SOURCE are shorted or open when it fails.

Also, if the problem is between gate and source, I wonder if it is due to overvoltage on the VGS or if it could be a problem between other terminals.

 

[G4BCH]

It depends on the failure mechanism. All terminals could be shorted together or all open or any combination.

 

[KlausST]

Hi,

First: what is the reason for failure?
* V_GS overvoltage?
* V_DS overvoltage?
* Short term overcurrent?
* Overheat?

In most cases there will be "unintentional" increased current. It may lead to increased heat ... or a short circuit condition.
Now in case of a short circuit condition ... if the input current is limited .. nothing much more will happen.
But When the input current is able to go very high, then one might expect an explosion.

Klaus

 

[danadakk]

Google "mosfet reliability and failure pdf", lots of docs.

Also in browser look at images form the search. You can see see scans of
failures.

Most vendors have a reliability handbook, with extensive information on the topic.


Regards, Dana.

 

[dick_freebird]

There's MOSFETs and there's MOSFETs. Your planar IC ones are way different construction than power vertical MOSFETs. And within each group are detail variants that affect ruggedness and reliability and likeliest failure modes. A threat-mode may also deliver different electrical and physical signatures (gate ox rupture could be short, resistive or low level leakage or even a blown bond wire depending on the harshness of abuse).

In cases where the part comes back from the field, busted, the FA lab might take the pics and data, and then set about trying to find the abuse conditions that produce a matching signature.

 

[Vbase]

When a MOSFET fails, which terminal of the MOSFET is shorted or open?

I know that when a MOSFET fails, it is either SHORT or OPEN. (Is this correct?)

Then I am wondering if the GATE and SOURCE are shorted or open or the DRAIN and SOURCE are shorted or open when it fails.

Also, if the problem is between gate and source, I wonder if it is due to overvoltage on the VGS or if it could be a problem between other terminals.

Often in over voltage drain is shorted to gate and source is open, in over current drain and source are short circuit.

 

[dick_freebird]

You can have cascades of failure. For example a burnout
event (from excess dV/dt, snapback or a heavy ion) might
begin with thermal runaway (which if you cut the power
promptly, might recover), proceed into a hard D-{S+B} short
(which slightly less prompt removal might deliver to measure)
then that short allows the bond wires to blow domino-style
and you end up measuring an open (all source wires
gone, presuming this is all about a discrete power device;
good luck blowing out the drain die attach without some
extra special help).

A good experienced F/A tech will recognize all the common
signatures that've been observed in their technology's
development, qual and field returns. Then they'll perhaps
start smart with the replication-of-damage effort
on virgin parts if damage is too gross or of a style that
"goes through some things" like above, and the task is
to declare a cause and recommend an action. Which
could and often will include "none".