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Category: Datasheet/Specs
Product Number: HMC1121

I am looking for MTTF data for HMC1121 based off of channel temperature. I assume the listed max temperature in the data sheet refers to the 1 million hour point, but I would also like to see how this degrades if the temperature goes higher than the max rated value.

Is this documented anywhere (aside from the data sheet of course)

  • I am not a fan of the terminology "max channel temperature to ensure 1000000 hours of MTTF". It suggests that the devices' MTTF is 1000000 hours if you operate it at 175 degC. In reality at 175, the MTTF will be some number other than this.  Also, when we calculate MTTF, we calculate a cumulative number for multiple devices manufactured on that process. In the attached reliability report, the MTTF calculations are performed based on High Temp Operating Life Test (HTOL) based on data from HMC1121 and  HMC7357. MTTF is calculated based on a die temp of 85 degC. You can re-run these equations for a different temperature, e.g. 175 degC and you will see a reduced MTTF. - Eamon


  • Enash, thanks for the reply. My goal here is to predict based on PCB thermal resistance(C/W) vs the thetaJC of 4.4(C/W) of HMC1121 what happens to reliability at various housing baseplate temps. For that I need to safley predict MTTF at different die temps.

    With that being said, I've read through the attached Reliability Report. When you state I can re-run the equations, I assume for the acceleration factor, I would change Tuse to the desired temp and keep Tstress at the HTOL temperature. Is this correct? Also, can you advise what value for k is being used? It is not defined in the document, and the JESD85 value of 8.6e-5 eV/K doesn't seem to work with the reports calculated values.

    I appreciate the response

  • Please disregard my question on k value. I found my error

  • That is correct. Tstress is fixed. That is the temperature at which the HTOL test was performed. MTTF was calculated based on a Tuse of 85 degC. So you need to figure out your new die operating temperature based on your baseplate temp and your thermal resistance. Once you have that temp, you can re-calculate MTTF. 

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