SLVAFH0 December   2023 CSD13201W10 , CSD13302W , CSD13303W1015 , CSD13306W , CSD13380F3 , CSD13381F4 , CSD13383F4 , CSD13385F5 , CSD15380F3 , CSD17381F4 , CSD17382F4 , CSD17483F4 , CSD17484F4 , CSD17585F5 , CSD18541F5 , CSD22202W15 , CSD22204W , CSD22205L , CSD22206W , CSD23202W10 , CSD23203W , CSD23280F3 , CSD23285F5 , CSD23381F4 , CSD23382F4 , CSD25202W15 , CSD25211W1015 , CSD25213W10 , CSD25304W1015 , CSD25480F3 , CSD25481F4 , CSD25483F4 , CSD25484F4 , CSD25485F5 , CSD25501F3 , CSD75207W15 , CSD75208W1015 , CSD83325L , CSD85302L , CSD86311W1723 , CSD87501L

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Solving Assembly Issues with Chip Scale Power MOSFETs
  5. 2Land Grid Array (LGA) MOSFET Packaging Technology
  6. 3Wafer Level Chip Scale Packaging Technology
  7. 4Common Issues
  8. 5Best Practices
  9. 6Considerations When There are Problems
    1. 6.1 Tilted or Misaligned Packages
    2. 6.2 Solder Balls, Poor, or no Solder
    3. 6.3 Chipped or Cracked Devices
  10. 7Summary
  11. 8References

6.2 Solder Balls, Poor, or no Solder

Assembly issues such as solder balls, poor, or no solder joints can occur during reflow soldering.

  1. Review the solder paste used. TI recommends using type 3 (25 to 45-micron particle size range) or finer, no-clean or water-soluble solder paste.
  2. Flux content of solder paste can lead to solder balls. TI’s qualification of these package used solder pastes with flux content between 10.5% and 10.8% with minimal solder balls. Other paste formulations can perform differently.
  3. Allow solder paste to warm up to room temperature per supplier recommendations.
  4. Do not exceed solder paste floor life per supplier guidelines.
  5. Solder paste needs to be stirred thoroughly before printing. Component placement and reflow must follow paste printing as soon as possible to minimize flux evaporation and moisture absorption.
  6. The PCB can absorb moisture causing solder balls. Pre-baking the PCB before assembly can drive the moisture out.
  7. Avoid applying too much pressure during component placement. Depending on the pick and place machine, this can be controlled by adding 0.05mm to measured component thickness or by setting the minimum force. Placement force must not exceed 3N.
  8. Follow the TI PCB layout and stencil pattern recommendations for best results. For LGA parts, solder mask defined (SMD) are recommended. For WLCSP FETs, non-solder mask defined (NSMD) are recommended.
  9. Check the reflow profile. TI has several recommended IR reflow profiles depending on PCB thickness and component density. Contact your TI representative for more details.