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Thermal reliefs for vias used in SMD pads

CADmaniac

Hi all I am doing a design with via in pad for the first time and was wondering if there are any known soldering issues if you don't thermally relive the via on a plane? Normally we never put thermals on a via but have never put the via through a solderable pad before.

 

Thanks in advance to any and all answers.

  • girish
    Hi,
    Thermal Relief is not required for the VIP technique , But via filling is must to avoid issue during soldering
    I hope below link & attached document will help you in understanding better on this aspect

     

    Best Regards,
    GK
    screaming_5myths.pdf
  • David Yackman

     I've added vias to pads mainly on power components that needed to be attached to a copper plane for heat sinking purposes.  I didn't use any thermal reliefs because that would've reduced heat transfer.  I made the via connect directly to the pad and the copper plane to maximize the heat sinking effect.  I have done this successfully on components that had a large pad underneath the chip without filling and plating over the via holes.  I make sure to follow the component manufacturer's recommendations for placement and size of the vias. 

     I've seen a couple of designs where the guy that did the layout was a little overzealous with the number and size of the vias he added to the ground slug thinking that this help keep the part cool(er), but what ended up happening is that the solder paste gets wicked into the vias causing a poor solder joint at the ground slug. We had to rework those boards by hand by heating up the vias on the back side of the chip and adding solder.  Of course, filling and plating over the vias would have eliminated the possibility of this happening. 

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