SNVA853C December   2019  – March 2024 LMZ10500 , LMZ10501 , LMZ20501 , LMZ20502 , LMZ21700 , LMZ21701 , LMZ30604 , LMZ31506 , LMZ31520 , LMZ31530 , LMZ31704 , LMZ31707 , LMZ31710 , LMZ34202 , LMZ35003 , LMZ36002 , LMZM23600 , LMZM23601 , LMZM33602 , LMZM33603 , LMZM33604 , LMZM33606 , TLVM13610 , TLVM13630 , TLVM13640 , TLVM13660 , TLVM23615 , TLVM23625 , TPS82085 , TPS82130 , TPSM265R1 , TPSM33615 , TPSM33625 , TPSM365R3 , TPSM365R6 , TPSM53604 , TPSM5601R5 , TPSM5601R5H , TPSM5601R5HE , TPSM560R6 , TPSM63603 , TPSM63604 , TPSM63606 , TPSM63608 , TPSM63610 , TPSM84424 , TPSM84624 , TPSM846C23 , TPSM846C24 , TPSM84824

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Package Types
    1. 2.1 MicroSiP
    2. 2.2 QFN Overmolded
    3. 2.3 QFN Open Frame
    4. 2.4 Leaded
    5. 2.5 QFN-FCMOD
  6. 3Package CAD/CAE Symbols and Footprints
  7. 4Soldering
    1. 4.1 MSL Ratings
    2. 4.2 Reflow Profile
    3. 4.3 Back Side PCB Mounting Considerations
      1. 4.3.1 Method 1 - Solder Surface Perimeter
      2. 4.3.2 Method 2 - Solder Surface Area
      3. 4.3.3 Back Side PCB Mounting Evaluation of TI Modules
      4. 4.3.4 Reflow Fixture
  8. 5Rework During Prototyping
  9. 6References
  10. 7Revision History

4.3 Back Side PCB Mounting Considerations

Will the part fall off or stay on the board after a second reflow upside-down?

Some high density applications can require mounting the power module on the back side of the PCB. Normally, the PCB side with heavy components would be reflowed last. However, in some cases, there can be heavy components on both sides of the board. In such applications, the power module package can go through a second reflow while the component is upside-down. The feasibility of the component staying attached to the board during the second reflow depends on the component mass, component pad sizes, and the solder alloy surface tension. There are at least two empirical models in the industry to evaluate the back side mounting feasibility.