Is it a Relief to Use Thermal Relief?
What is a Thermal Relief and why do some PCB Designers incorporate it in their design? Can you guess which one above uses Thermal Relief? Does it present a trade-off?
Step 1: Is it a Relief to Use Thermal Relief?
Question:
What is a Thermal Relief and why do some PCB Designers incorporate it in their design? Can you guess which one above uses Thermal Relief? Does it present a trade-off?
Answer:
First of all, we take a look at 2 kinds of pads immersed in a copper pour. In Figure A, we can see a normal pad that is connected to a copper pour in all directions. In Figure B, the pad is connected to the copper pour through only 4 traces or spokes. Which of the two do you think is a thermal relief pad?
We know that copper has high thermal conductivity, so is a copper pour. Let’s say we want to solder a lead having a normal pad (Fig. A). Since the copper pour conducts heat easily, the heat that is used to melt the solder is distributed easily to the pour. You may have to keep the iron on the pad longer in order to properly solder the component but in doing so, you could damage the component.
The solution is to use thermal relief pads (Fig. B). Since we only have 4 copper connections to the pour, we minimize the amount of heat that is transferred to the plane, making it easier focus heat and solder components.
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