Thermal Management in PCBs

Thermal vias are a critical element of proper thermal management for high power and tightly packed PCBs to avoid excessive component temperatures that lead to premature failure. They provide a means of conducting heat efficiently from the PCB surface layers to inner planes and to external cooling devices such as heat sinks attached to the board, preventing circuit stability issues and thermomechanical failures. Thermal via placement, size, and positioning are important considerations when designing a PCB to take full advantage of their thermal performance benefits.

Vias are plated through-holes (PTHs) on a pcb that transfer heat between the surface and internal layers of the board through metal conduction. When filled with thermal epoxies or solder, they become solid metal poles that span the layers of the board. Thermal vias are generally sized larger than signal vias, and they may be positioned closer to the heat source to increase their efficiency in conducting heat.

A key design feature when working with thermal vias is to ensure that the copper surface they are terminating on has a large area. This will help the vias transfer the heat to a wider copper surface that can dissipate it more effectively and quickly. In addition to reducing thermal resistance, this will also prevent soldering problems during assembly.

Thermal Vias Enhance Thermal Management in PCBs

Another design consideration for thermal vias is that the tracks they are routing through need to be wide enough to allow adequate current to flow without exceeding recommended track width limits. If the tracks are too narrow, they will limit the amount of current that can be carried, causing a potential failure or degrading the performance of some components.

Using a substrate material with high thermal conductivity is also useful in aiding heat dissipation from the board, such as ceramics or metal core PCBs, to speed up the transfer of heat away from the active components on the surface. This is particularly important when using high current traces, as the heat they generate can rapidly raise the temperature of adjacent copper surfaces.

A well-designed PCB will include both thermal vias and thicker power/ground planes to dissipate heat from the active components more efficiently. The thermal vias conduct the heat from the hot pads directly to the power/ground plane and spread it across multiple layers of copper, while the thicker planes disperse it into the surrounding air through convection.

This helps stabilize the temperature of the pad and reduces internal stress on the component during operation, improving reliability. In addition, it will improve the overall thermal expansion of the PCB so that it has a more uniform equilibrium temperature. This will help reduce internal stress due to asymmetrical thermal expansion between different copper conductors, preventing the occurrence of acoustic resonance or stress cracks. This is particularly important in high-speed or high-frequency designs where acoustic resonance can cause instability and failure.