Most electronic components dissipate heat whenever a current flows through them. The amount of heat depends on the power, device characteristics, and circuit design. Besides the components, the resistance of the electrical connections, copper traces, and vias contribute to some heat, and power losses.

To avoid failures or circuit malfunctions, designers should aim at producing PCBs that operate and remain within safe temperature limits. While some circuits will work without additional cooling, there are situations where adding heat sinks, cooling fans, or a combination of several mechanisms is inevitable.

There are several techniques that designers can use to remove heat from components and PCBs. The common mechanisms include heat sinks, cooling fans, heat pipes, and thick copper. Most often, circuits generating more heat require more than one technology. For example, cooling a laptop processor and display chips requires a heat sink, heat pipe, and a fan.

Heat Sinks and Cooling Fans
A heat sink is a thermally conductive metallic part with a large surface area, usually attached to components such as power transistors and switching devices. A heat sink allows the component to dissipate its heat over a larger area and transfer that heat to the surroundings. In some cases, such as high current power supplies, adding a cooling fan aids in faster and better heat removal.

Heat Pipes
Heat pipes are suitable for compact devices with limited space. The pipes provide a reliable and cost-effective passive heat transfer. Benefits include a vibration-free operation, good thermal conductivity, low maintenance, and quiet operation since they have no moving parts.

A typical pipe contains small amounts of nitrogen, water, acetone, or Ammonia. These fluids help to absorb the heat, upon which they release a vapor that travels along the pipe. The pipe has a condenser where, as the vapor passes through, it condenses back to its liquid form and the cycle begins again.

Thermal Via Arrays
Thermal vias increase the mass and area of the copper, reducing the thermal resistance and improving heat dissipation from the critical components through conduction. As such, better performance is achieved when the vias are placed closer to the heat source.

In some applications, heat from a device, such as a thermally optimized IC, is conducted away through the combination of a thermal via array and pad. This eliminates the need for a heat sink while improving the heat dissipation through the PCB.

Thick Copper Traces
Using more copper provides a larger surface area that helps in heat distribution and dissipation. Such PCBs are suitable for high power applications.

Conclusion
PCB thermal management techniques depend on a number of factors including the amount of heat the components and circuit dissipate, the environment, the overall design, and the enclosure. If heat generation is low, the circuit can work without additional cooling. However, if the circuit generates higher amounts of heat, there should be a cooling mechanism to take away the heat.

To provide thermally optimized PCBs, designers should consider everything that influences temperature right from the concept stage and throughout the design and manufacturing stages.