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 Thermal reliefs for vias used in SMD pads 

Last post Wed, Jun 19 2013 1:36 PM by David Yackman. 2 replies.
Started by CADmaniac 06 Jun 2013 08:59 AM. Topic has 2 replies and 1250 views
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  • Thu, Jun 6 2013 8:59 AM

    • CADmaniac
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    • Joined on Thu, Jun 6 2013
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    • Points 35
    Thermal reliefs for vias used in SMD pads Reply

    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.

    • Post Points: 35
  • Thu, Jun 13 2013 10:45 PM

    • girish
    • Top 25 Contributor
    • Joined on Wed, Jul 16 2008
    • Bangalore, Karnataka
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    Re: Thermal reliefs for vias used in SMD pads Reply
    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
    • Post Points: 5
  • Wed, Jun 19 2013 1:36 PM

    • David Yackman
    • Top 150 Contributor
    • Joined on Wed, Jan 18 2012
    • Lawrenceville, GA
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    Re: Thermal reliefs for vias used in SMD pads Reply

     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. 

    • Post Points: 5
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Started by CADmaniac at 06 Jun 2013 08:59 AM. Topic has 2 replies.