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Display Your Know How: Thermal Relief

PCBTech

Can you think of any design methods to enable the removal of thermal reliefs, such as shown in the following scenario?

Thermal relief traces

 Thermal reliefs are widely used to improve assembly soldering. However, after soldering is complete these copper features generally do not favour the electrical or thermal performance of the circuit. So what if we could remove them?

Simply suggest any ideas how we could do this in the comments below. Any alternatives and opinions are welcome!

  • in reply to PCBTech

    Also for repair: is pin is full contact on all layer you have to heat up too much in order to remove solder and replace component: this can destroy the area.

  • in reply to PCBTech

    A full contact on several layers brings to heat up too much pcb in order to remove/replace a component and bring to pcb destruction localy

  • in reply to excellon1

    Thanks for your input excellon1. These insights are greatly appreciated!

    In the image above used for this question, we show two different pin types: through-hole and surface. Focusing on the surface pins: do you see any other layout solution that would enable us to use full contact on the surface pins while encouraging good soldering? ( hint: imbalance)

    One key point we would like to highlight is that thermal reliefs on surface pins vs those on through-holes combat slightly different problems. The reason for their use is not exactly the same for each technology. Kudos goes to anyone that can think of what that difference is...   

  • You could change the narrow trace to a bigger shape and change both to full contact. This way both sides would have similar thermal properties and the risk of tombstoning would be reduced.

    Bonus note: If the component is a DFN type, the risk of tombstoning is not so big, because of reduced leverage on the terminals. Agree?

  • in reply to PCBTech

    Hi PCBTech.

    Good questions. Looking at that particular design I would go with direct for both the smd and surface pins. From the soldering
    perspective you are looking at a really small copper surface area so soldering wont be any problem for even a budget rated IR oven.

    Basically because the copper surface area is tiny IR Ramp up will be fine.

    Best regards.

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