PCB Heat Sinks
There are no specific PCB area specifications cast on stone or works outside the box. However, there are design guidelines that address this concern: PCB heat sinks. PCB power components generate heat from themselves. This happens when the current is passing through components that happen to have some resistance. This can be understood through the equation P = I2×R. The heat generated via this equation must be dissipated away from the PCB. Without a proper PCB Design mechanism, the components would get heated until they get destroyed.
When designing a professional PCB, it is important to understand how the generated heat is distributed. When the PCB prototype is powered and is in operation, thermal imaging can visualize how the heat is distributed in the PCB. This can then be helpful when doing a final design since one will choose better locations for different components to ensure uniform heat distribution.
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 before prototyping. Software programs such as HyperLynx can even generate a 3D PCB Model that will consider changes of component height and airflow on the PCB heat dissipation.
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 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.