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TPS22950: Inquiry about the cause of failure of TPS22950

Grady Lee
Genius 3165 points
Part Number: TPS22950

Hi, TI expert.

There is an inquiry about the cause analysis of the failure that occurs during the development stage by applying the TPS22950 by the customer.

The circuit configuration is as above, and TPS22950 is enabled with 1.8V level input through A1 pin.

The side that goes out to the right through the B2 pin is connected with a USB type C connector.

In the product development stage using this device, the B1 and B2 pins of the TPS22950 failed due to a short circuit. (2ea out of 100ea, 2% chance)

In the broken sample, there was no current consumption enough to cause the TPS22950 to overheat, and only data communication was performed by connecting to a notebook PC through the USB C connector.

When the USB type A to C cable is connected to the laptop on the USB C connector side, there are cases where the laptop output 5V power is connected to the VOUT part of the TPS22950 device.

In this case, we would like to ask for your help in figuring out what factors may cause the TPS22950 to fail as above.

  • +1
    TI__Genius 15550 points

    Hello, 

    Firstly, I do not see any issues with your schematic.

    Because of this device's small package and fragility, any sort of rough handling conditions while being placed onto the board could cause damage that would cause unexpected functionality, therefore manufacturing and handling is going to be very critical for this device.

    Unexpected shorting from the input to the output, could likely be due to a soldering/ handling issue or a limitation with your PCB manufacturing process.


    Foremost, we recommend to the manufacturer to reduce the nozzle pick and place force.

    Another possibility is an issue with the solder mask opening: The solder mask width needs to be 0.1mm; however, some PCB fabrication houses reduce the solder mask opening to create space for the solder mask strip. So ensure that they are capable of maintaining the 0.1mm solder mask width requirement. Also ensure that reflow profiles are specified for TI parts.

    The packaging on this device is fragile, so small chips during the manufacturing process can cause a device to fail. Double check the soldering profile as well (common reason for failure on these devices is improper soldering).

    In general, here are some resources in regard to WCSP handling:

    https://training.ti.com/troubleshooting-tips-ic-wcsp-handling?keyMatch=WCSP

    https://www.ti.com/support-quality/faqs/wafer-level-chip-scale-package-faqs.html

    Best Regards, 

    Elizabeth 

  • 0
    Prodigy 20 points

    Hello,

    At first I doubted short circuit due to poor soldering as you mentioned. However I found that the TPS22950 itself was shorted inside of it after detaching the IC from the issued PCB.

    I would like to ask if there's some reason of shorting the TPS22950 itself?

    I also found that voltage on B1 and B2 were partially transferred to A1 pin and it outputs 2.5V.

    Regards,

    Johnny

  • 0 in reply to Johnny Kim
    TI__Genius 15550 points

    Hi Johnny, 

    Could you clarify how you were able to see if the IC was shorted inside of it? Did you decap the package and look at the metal layers? 

    If this was discovered by testing continuity across pins off of the board, then that could occur because of soldering or rough handling conditions. If the IC is put under pressure, it could cause the device to show a short whether it is on the board or not. 

    Best Regards, 

    Elizabeth 

  • 0 in reply to Elizabeth Higgins
    Prodigy 20 points

    Hi Elizabeth,

    I didn't do decapsulation of the IC. I just test the deattached IC with multimeter right on solder balls on bottom of the package.

    How about short period of high voltage such as 9V? or inrush current from the output port side? Could these damage TPS22950? I found that TPS22950 allow 900mA reverse current when output voltage is higher than input voltage and the IC is enabled.

    Regards,

    Johnny

  • 0 in reply to Johnny Kim
    TI__Genius 15550 points

    Hi Johnny, 

    Yes these conditions could harm the device. 

    Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. We would recommend that the customer replace those units with fresh units.

    We do not guarantee the working of our device in any condition over the abs max rating.

    Best Regards, 

    Elizabeth