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LP2985: LP2985-33DBVR

SHAWN FONG
Intellectual 490 points
Part Number: LP2985

Hello experts,

Customer observed that the dropout-voltage was out of specs. They did a SEM n saw cracks at the DIE level. 
1. Would this be the primary cause of the issue? 

2. What would be the cause of the cracks? Customer observed that these were not caused by chemical decaps. 

 /resized-image/__size/320x240/__key/communityserver-discussions-components-files/196/SEM-INSPECTION-DC2134.png

Some information are confidential and I am not at liberty to share in a public forum. If this discussion can be brought off-line, please advise an email I can reach.

Thank you.

Regards

Shawn

  • 0
    TI__Genius 12511 points

    Hi Shawn,

    1. Without looking at the part ourselves we would be unable to comment on root cause of the out of spec operation.

    2. There are many possible causes for cracking on the die of a chip, however this many cracks on the part would most likely be caught in final test. These cracks would have only occurred after the fact from esd discharge or mishandling of the part.

    I will talk with a quality engineer to see if there is anything else that we can do.

    Regards,

    John

  • 0 in reply to John Schneider
    Intellectual 490 points

    Hi John,

    Thanks. 

    The date code of the part which is showing an issue is DC: 2134.

    Here's the summary of the problem and table of findings attached.

    a. 2 out of 4 pcs of the DC: 2134 part showed circuit damage after chemical decap. No abormaly observed on control sample DC: 2124.

    b. From inspection, passivation layer was damaged. Suspected damage possibly happened at factory and manufacture level. 

    c. Electrical test showed the parts fall out of specs on the DROP OUT Voltage.

    /resized-image/__size/320x240/__key/communityserver-discussions-components-files/196/COMPARISON-TABLE.png

    Regards

    Shawn

  • 0 in reply to SHAWN FONG
    TI__Genius 12511 points

    Hi Shawn,

    There are a few things to convey from our quality team:

    Firstly we are confident that there is no systemic risk to the device mentioned in your post as over 70+ million units have shipped with no customer issue reports on fabrication in the last 3 years

    The next thing is we would like to know the application of the device. Including input voltage, and load conditions etc.

    Finally what is the total unit failure count, out of how many units deployed, not just from those that you have decap'd.

    Regards,

    John

  • 0 in reply to John Schneider
    Intellectual 490 points

    Hi John,

    Thanks for the info.

    Customer was going to use them on POWER ADAPTERS. The application was presumingly irrelevant because the decap n C-SEM was conducted at IQC. These were unused parts. They were not mounted on any boards. They took 4 pieces for sampling from a reel of 3000pcs and 2 pieces exhibited the cracks as shown. At this moment, customer is not proceeding with any more checks.

    Regards

    Shawn

  • 0 in reply to SHAWN FONG
    TI__Genius 12511 points

    Hi Shawn,

    At this point, we believe the failure would have been detected at our fabrication site before being shipped out, a VDO spec failing is part of the testing each part must pass before being shipped. At this point I can point to you returns, to contact your certified distributer, as we need to determine the chain of possession that the parts went through. Either the customer inadvertently damaged it or somewhere in handling it was damaged.

    https://www.ti.com/support-quality/additional-information/customer-returns.html

    Linked above is our return page detailing how the process should begin. The FA process would begin with documenting the failure of the device, and that is required anyway for returns through the authorized distributer. If the distributer is unable to account for the cracking you see, then we would move forward from there to determine the root cause of the parts failure mode.

    Regards,
    John