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Polygon thermal relief

mairomaster , 06-03-2016, 10:09 AM
Hi guys.

I couldn't find much useful information on the topic. I have a board that is purely SMD. On the top and bottom layers I have some polygons that connect different components. I know that thermal relief connection is used when dealing with TH components, since it makes the soldering a lot easier. However in my case, since I only have SMD components and the board is reflow soldered, I feel there is no need to use thermal relief.

Do you think there might still be some benefit of using thermal relief? I read about a problem called tombstoning, which might occur because of unequal heating of the 2 pads of a component, because of one of them being connected to a big plane for example. What happens is the component lifts on its side during the reflow soldering. They say that thermal relief might help in such cases.

Any thoughts on the topic?
robertferanec , 06-06-2016, 12:43 AM
Hi @mairomaster. I read same/similar articles and in past I have seen some components lifted or moved.

However, due density of the boards which we normally do, we do not really have many options to connect the pads of SMD components, so we just do it the way which is possible ... and everything is ok. Maybe the technology is now different, but I have not seen problems cause by connecting pads "not the most recommended way". So, for SMD components, we do not use thermal relief (we use direct connections).
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