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HMC637LP5E solder void % on exposed ground paddle


I've encountered 4 failed cases with HMC637LP5E in recent NPI. With all biasing and sequencing and input/output impedance matching confirmed to be fine. Only two things to look at are;

1. Effects of solder void on thermal dissipation on the exposed ground paddle. Is 30% void spec sufficient for good thermal dissipation?

2. Higher failure rate on HMC637LP5E compared to HMC637ALP5E? Any reliability issue related to HMC637LP5E?

Best Regards,


  • Hi.

    I moved your question about HMC637LP5E to Hittite Microwave Products from ADI community. Someone here should be able to assist you.



  • Hi Eric,

    This is a PA with 1+W Pout; hence high power dissipation. 30 percent void will increase thermal resistance, which may cause problems.

    I replied your email on this matter, the issue can also be bias sequence related.



  • Thanks Kagan.

    The Thermal Resistance of LFCSP/QFN packaged HMC637LP5E marginally changed below 50% void, according to the info from Hittite's web. I do not know whether the info is correct. Bias sequencing has been reviewed and followed the recommendation from the datasheet. Not sure whether it was tested thru IPC-9701 compare to JESD22 standard on reliability for QFN packaged components. Else, what are the changes in manufacturing process and internal circuits between the 'A' and without the A parts? We had no issue with the 'A' parts.

  • The article suggests that testing is performed to verify the results. But results can vary device to device. Maybe that minor change is causing some problems.

    Anyway, for this case. I think we can agree that the bias sequencing followed was not correct at the beginning. Let us wait and see, if the problem will persist with the updated sequencing or not.

    As for the difference between HMC637LP5 and HMC637ALP5, the foundry used during the die fabrication is changed.



  • This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin