Humidity Operation of the CAS300M17BM2

Fertmann

Hi,

I wanted to ask about the Humidity Operation of the CAS300M17BM2.

How long could this module withstand 85% humidity at 60°C?

Thanks!

TBhatia

Hello, thank you for your message. A member of our technical team is looking into your questions and we will respond shortly. 

Bdeboi

Hi Fertmann,

First, you may find reading our application note on humidity helpful in understanding the failure mechanisms associated with moisture:

https://assets.wolfspeed.com/uploads/2022/08/environmental-considerations-for-power-electronics-systems.pdf

To answer your question succinctly, the CAS300M17BM2 module is not formally qualified for high-temperature, high-humidity operation and we cannot provide a lifetime rating under those conditions. However, you may be interested in the WAS310M17BM3 power module, which passes THB-80 qualification (85C, 85%, 1360V, 1000 hours). It is the direct replacement of the CAS300M17BM2 power module and features several improvements over the older device.

More generally, the lifetime of your module will depend on your conditions of operation. For example, module degradation due to moisture will occur more quickly in the presence of strong electric fields caused by higher bus voltages. If you plan on cooling the module below 60C, the relative humidity of the module may increase above 85% (it is very important that you do not allow condensation to form). If the module is actively switching, it may reach temperatures above 60C, which will reduce the relative humidity in the module. Thus, it is important to consider the conditions of your overall system when determining the lifetime degradation, not just the conditions of the surrounding air.

Another thing to consider is that the encapsulating gel within the power module does not respond instantly to environmental moisture conditions. Consider the below figure, where a power module was placed in an environmental humidity chamber (this is not for the CAS300M12BM2 module). Humidity and temperature sensors were placed within the encapsulating gel by the die. On the left subfigure, you can see that it takes tens of hours for the humidity of the encapsulation to reach the humidity of the surrounding air. (Note: the only difference between (a) and (b) is that the module in (b) was placed on a 25C hot plate).

In summary, I apologize that I cannot provide a minimum lifetime for your conditions for this device. However, you can minimize the risk of failures by reducing the bus voltage and minimizing the duration of exposure to these high-humidity conditions, and by not allowing condensation to form on the module by cooling below the dew point.

I hope this helps. Please let me know if you have any further questions.

Brian