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TPSM846C23: TPSM846C23 fell off on second reflow

Part Number: TPSM846C23

Hi,

The inductor on the power modules falls off after second reflow. Hence i would like to know more about the reflow profile of this device & does the reflow applies to the onboard inductor as well?

  • Is there any recommended process to mount this part? Please share document as reference
  • Are there limits of times a device can undergo reflow?
  • Any recommendation/advise to resolve this issue?

Regards,

Leo

  • Hi Leo,

    Yes, the reflow applies to the onboard inductor. I'm interested to know if the module is primary or backside mounted?

    I've attached an Application Report indicating peak reflow classifications. Also, Section 10.5 in the datasheet recommends mounting and thermal profiles. To your question in regards to if there are limits to reflow: We have tested the module with a peak temperature of 260°C, 3x reflow and peak temp +5°C tolerance.

    Regards,

    Alejandro
  • Hi Alejandro,
    can you elaborate on primary or backside mounted? Customer had this device mounted with inductor facing upwards. The inductor on the TOP side of the module then falls off during the secondary reflow where the part was hanging upside down. Hope this description helps.

    Regards,
    Leo
  • Hi Leo,

    During the secondary reflow, if the inductor is facing downwards, the weight of the inductor may be heavy enough to overcome the tensile force of the solder and case the inductor to fall off. My recommendation is to change the reflow sequence such that the side with the heavy components is reflowed last. This way the inductor will be facing upwards during the reflow and not fall off the board.

    In the case where you have heavy components on both sides of the board, normal practice is to mount the component on the bottom side first, reflow, then put the board on a fixture with partial block to protect the heavy components already reflowed, flip the board, then mount component on top side and run second reflow.  


    Regards,
    Jimmy