Is HTS Redundant with 85C/85%RH Test?

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Some reliability tests that subject the reliability samples to the same accelerating factors can appear to be redundant with each other. A case in point is the 85 deg C High Temperature Storage (HTS) Test and the 85 deg C/85% RH Soak Test. The archived forum thread below discusses this, with the thread starter asking if there are failure mechanisms accelerated by the former test that the latter test can't accelerate. After all, aren't both tests subjecting the parts to the same temperature (85 deg C) for the same duration (500 H in the given example)?

The answer is simple - adding moisture as an accelerating factor to accelerate failure mechanisms that can be accelerated by temperature only might cause moisture-related failure mechanisms to appear, making the failure analysis of the rel failures more difficult. Thus, it is not advisable to use the 85/85 soak test to accelerate failure mechanisms for which the HTS was designed.

Posted by Paula: Sat Jun 07, 2008 11:07 am Post subject: rel tests

I came across a reliability test requirements for cards.

It requires (among other reliability test):
1. 85°C temperature storage
2. 85°C and 85%RH temperature humidity storage:

What is the difference between the two?
Is 85°C temperature storage a redundant test?

Posted by Logan218142: Tue Jun 17, 2008 10:55 pm Post subject:

Hi Paula, 85 constant temperature bake and with/without humidity control humidity have different targeted failure mechanism. You are right we do this for cards/COB - TH as well as elevated temperature storage, typically we choose higher temperature ie 125degC

Posted by Paula: Tue Jun 24, 2008 9:38 am Post subject:

Can you pls share the targeted failure mechanism for the ff tests:
1. 85°C temperature storage , 500 hours
2. 85°C and 85%RH temperature humidity storage, 500 hours

Thanks a lot.

Posted by Logan218142: Tue Jun 24, 2008 4:35 pm Post subject:

Hi Paula, Failure mechanism is not associated with stress duration, which typically we term it 'Qualification'. The stress duration can be useful for FIT calculation and Acc model. For temperature humidity stress tests, they are primarily related to material degradation. They can fall into three major area - corrosion, metal migration and delamination of material interfaces. However, for temperature storage test, we are looking for intermetallic bond reliability, mobile ion for some of specific application.

Posted by Paula: Fri Jun 27, 2008 10:02 am Post subject:

I put the duration for emphasis. Going back to my original questions, do you see any redundancy in the 2 tests?

Can test item 2 be use to accelerate Au-Al IMC growth? or even data retention test?

Posted by Logan218142: Fri Jun 27, 2008 5:54 pm Post subject:

Paula, I will run both tests if I do not have any baseline data to understand responses for each test. TH test can acc Au-Al IMC as this is temperature driven and similarly for bake retention. Perhaps with the presence of control humidity level, some other failure mechanism will show up and make the analysis more tricky at later stage.

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