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So when do you know that the heat sinks are sufficient?
One way of telling that the heat sink is sufficient is by ensuring that the PCB heat profile is similar throughout. A PCB thermal image can reveal how the heat is distributed in the whole system. A PCB is an anisotropic system. Naturally, heat would not be distributed uniformly. Another way is to generate a heat profile using the software right after designing the PCB and prototyping. Software programs such as HyperLynx can even generate a 3D PCB Model that will consider changes in component height and airflow on the PCB heat dissipation.
Solution of PCB heat to be uniformly distributed
First, you want your PCB heat to be uniformly distributed for the good health of the PCB and to facilitate uniform heat sinking. The heat-generating components must be positioned evenly throughout the board. Generally, to dissipate 1 watt of power, you need to have around a 15cm2 board area for about 35◦C board temperature rise. To improve heat sinking on the board, thicker traces or copper pours can be used. PCB Assemblies such as Graphics cards and Motor Drivers need to dissipate lots of heat from one component. In this case, a heat sink is attached directly to the component.
In some cases, a Fan is also installed together with the heat sink to facilitate the flow of heat away from the PCB. Other techniques include using several screws with washers and also connecting the PCB with the chassis. Still, adding multiple vias when designing the PCB greatly improves the board’s heat dissipation and distribution.
