DCV010512D: DCV010512DP-U Isolation failure after climatic test

Hi Angel,

Can you provide more information on the test prior to the climatic? What exactly are the test conditions?

Can you clarify the following:

Angel Hurtado said:

isoaltion of your dc/dc works correctly, but after the climatic test, the dc/dc start to fail,

Is the isolation failing? Or the DC/DC converter is failing? We need details of the test they are performing where the module is failing.

If the company is temperature cycling the device three times with three hours of 60°C followed by three hours of 0°C, it is possible that the final 0°C cycle is condensing and absorbing moisture. Moisture degrades the isolation of these modules. Simplest fix would be to reverse the sequence of the cycles so that the final cycle is three hour bake at 60°C. This might be a solution to the test problem.

Thanks,
Alejandro

Hi Alejando,

Thanks for your reply.

I clarify that the isolation is what is failling. We try the isolation of the application by injecting 1000V between the pins 1, 2, 14 against pins 5, 6, 8.

At this tension there must not be consumtion but it is at 50V when a failing isolator starts to consume.

I have baked some failling parts at 60ºC for 3 hours and they are still failing. However I will bake them at 60ºC until tomorrow and try again the isolation test.

Best regards,

Ángel

Hi Angel,

What is the time duration of the 1kV? Has the manufacture company been using the modules for a long time and just started seeing them behave differently, or they just started using the devices?

Please note, that a continuous voltage of 42.5Vrms or 60Vdc can be applied across the part. The modules ought to pass a 1kV 1second flash test when they are new. See further information in Section 8.3.1.
Repeated high-voltage isolation testing of a barrier component can degrade the isolation capability, depending on materials, construction, and environment. Therefore, strictly limit the number of high-voltage tests and repeated high-voltage isolation testing. However, if it is absolutely required, reduce the voltage by 20% from specified test voltage with a duration limit of one second per test. See section 8.3.1.5 for further info.

Regards,
Alejandro

Hi Alejandro,

The duration of the test is 1 second and the test is done just once. The issue appears just at the moment of testing, when applying 100V-200V for less than a second consumption is noted.

Our way of testing is by means of a wheel. We increase from 0 to 1KV and if consumption is not noted then the the dc/dc passes the test.

But with the failing dc/dcs we do not reach the 1KV because, as I said, at 100V-200V consumption is noted. 

On the other hand, I have baked some failing parts at 60ºC for almost 24h and they are still failing. Could it be that these parts are broken since the first test in manufacturing (after the climatic test)?

As I told you on a previuous answer we test the relays on cicles of 3h @ 60º and 3h @ 0º. Maybe if we revert this procedure (this was your suggestion) the moisture in the dc/dc is considerably reduced before testing the isolation.

Best regards,

Ángel

Hi Angel,

Understood, thanks for the information. It could be that the parts were damaged after the climatic test. I would recommend to revert the procedure on working devices and capture the results. This might be the solution to the problem.

Kind regards,
Alejandro

Hi Alejandro,

We are going to try that but we do not really believe that is going to work honestly. Anyway we will try and I will come back to you with the result.

Best regards,

Ángel

Okay, please provide us with an update as soon as you get results.

Thanks,
Alejandro