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Power Supply Regular - Thermal pad via filling

Dhamodharan Nagarajan
Prodigy 60 points
Other Parts Discussed in Thread: TPS54620, TPS73801

 

Hi,

We are using following Power Regulator ICs in our design.

  1. TPS54620 Switching Regulator –  8V with max 4A load current used in our board
  2. TPS73801 LDO –  5V with max 1.5A load current used in our board
  3. TPS7A4501 LDO –  5V with max 1.5 A load current used in our board

In these Regulators datasheets, Thermal pad vias are recommended.

1. TPS54620 - QFP package 4- Thermal vias are recommended underon the IC Thermal pad

2. LDOs - Thermal vias around the Ground pad are recommended.

Please tell whether these Thermal Via holes need to be filled with any material for better Theremal dissipation or can be left unfilled? In QFN package layout guidelines, Soldermask plugging/tenting is given. But our PCB Fabrication vendor is not supporting via filling. So, please confirm whether these vias canbe left unfilled. If it needs to be filled then please tell the material that can be used for filling this vias.

Thank you.

 

  • 0
    TI__Guru**** 191445 points

    The intent is for them to not be filled.  In general, the via holes will wick solder out from under the area of the exposed thermal pad, decreasing the surface solder contact and hence reducing thermal performance.  Keeping the via hole diameter small limits the solder wicking during the assembly process.  see SLMA002 for more information:

    http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slma002&fileType=pdf&track=no