Fail to open or Fail to short - short circuit

littlemoon

Hello,

Thanks in advance for any help.

Hope I can find the answer to the question about the short-circuit of SiC module.

It is found in "SiC MOSFET Short Circuit Application Note" as follows:

"This kind of heating is typically adiabatic, and the resulting temperatures can trigger a failure within a
few microseconds." I have a silly question: will the SiC module be left as fail-to-open or fail-to-short?

I guess a burn out may happen, but if the circuit is left short, then it will need more effort to deal with this short circuit situation.

It is said that it may fail to open in the end. I am wondering if there is a general answer, will the SiC will be open finally? And how long the short circuit can last until it burned to open?

"Depending on the currents and bus voltage, the heat generated by a thermal-runaway-induced short-circuit
could be intense enough to burn out the wire bonds and die attach, which could result in the physical
destruction of the discrete package or module. It is worth pointing out that although the chip might fail short,
it is possible that the discrete package or module terminals fail open due to wire-bond burnout as shown in
Figure 19."

Looking forward to hearing any answers. Thanks.

Forum_Moderator

Thank you for your post, it has been approved and we will respond as soon as possible.

FelixF

Thank you for reaching out. The MOSFET will be destroyed once the critical energy for the particular product is exceeded. Therefore, the short circuit time until it fails is strongly dependent on many parameters like the bus voltage, current reached or temperature and cannot be generalized for all conditions.

Failures with and without fail-to-open are very close together in terms of short circuit duration (under same conditions). It can occur that the metallization begins to melt due to high temperatures and therefore a leakage path between source and gate builds up. Yet, you may still be able to turn off the device. If the short-circuit event would last slightly longer (talking about 10s or 100s of nanoseconds) the energy can be sufficient to melt the topside metallization so that the bond wires detach, and your device fails to open.

Therefore, we recommend usage of a suitable gate driver with a DESAT protection that will detect the short and turn the device off in time before it can be damaged. In the SiC MOSFET Short Application Note, Figure 17 shows the turn-off through DESAT protection in about 1/10th of the maximum short circuit withstand time for given conditions and module. Feel free to reach out for further questions.

littlemoon

Thanks very much for the response.

TBhatia

Hi, I hope that this answered your question. I will close this discussion for now but if you have a follow up question, please "Start a New Discussion" and we would be glad to support you further.