There are several methods for implementing thermal management in PCB layout, ranging from simple cooling fans to complex shell and heat sink designs. The goal of thermal management is to lower the temperature of the device below a certain level. When the temperature exceeds this level, the device may fail or users may be exposed to extreme temperatures. In many PCB designs with loose dimensional requirements, high-temperature components are typically managed using fans or heat sinks for thermal management.

How can the heat from high-temperature components be dissipated when there is no space to install fans or heat sinks? At this point, it may be necessary to adopt a thermal management scheme, such as embedding copper blocks, in the components or inner layers of the circuit board. Most designers know that thermal conductive holes are embedded with copper blocks, but a more advanced solution is to use press fit copper blocks to provide higher thermal conductivity.

Embedded copper block

Embedded copper blocks are small or large copper blocks that can transfer heat through stacking. A heat dissipation hole is a typical embedded copper block that can transfer heat to the internal plane or heat sink (or both) on the other side of the circuit board.

Low power devices sometimes have a component that generates most of the heat in the system, and in this case, only a thermal management technique needs to be implemented for that component. In SMD integrated circuits, this is likely a set of heat dissipation holes connected to the surface heat dissipation pads. Then it can be directly soldered onto the ground pad connected to the die in the device package.

Footprint of devices with four heat dissipation holes.

Some devices have higher output power or do not have much space to install solder pads connected to the die, so other methods need to be used to dissipate heat. The typical method is to install a heat sink and fan, which is a common approach used by CPUs or GPUs. Another strategy in small devices such as smartphones is to use thermal interface materials to directly attach the processor to the casing.

Larger devices such as CPUs, FPGAs, or GPUs are packaged in BGA/LGA and cannot accommodate heat dissipation holes as they may not have solder pads connected to the die. However, embedding copper pillars (known as "copper blocks") is a feasible heat dissipation strategy. Copper pillars must be designed as compression components into the circuit board, with tolerances equal to those of the compression holes.

When the compression element is installed under the integrated circuit, it can be used as a heat transfer element.

Solder pillar

The last structure that can be used for thermal management is solder columns. A solder column is a large piece of solder material that is connected to the top layer of device packaging. During the assembly process, these solder pillars will form very strong joints with the SMD footprint in the PCB. These structures are more common in component packaging used in military aviation systems that require severe vibration, high temperature, and mechanical shock.

The following image shows an example of Microsemi's device packaging. In the figure, the solder pillar is embedded in the package and will form a strong eutectic during the assembly process. Solder pillars are typically used together with carriers to provide a highly reliable assembly platform, but the additional solder used in these solder pillars helps dissipate more heat from the package.

Example of packaging with solder pillars.

Other thermal management strategies

Effective thermal management involves multiple strategies in circuit boards that generate a large amount of heat. This includes the mixed use of pressed/embedded copper blocks, thick copper, thermal interface materials, and fans or heat sinks. Other heat dissipation strategies used in electronic assembly include:

Shell design supporting forced and convective airflow

Use alternative substrate materials with higher thermal conductivity

Apply thermal interface material to the radiator

So, how do we choose the right thermal management strategy for Busbar, which serves as the "main artery" for power transmission and distribution?

Busbar undoubtedly plays a crucial role in modern power systems and industrial facilities, whether it is the distribution system of large power plants, substations, or factory production lines, Busbar is an indispensable component! And with the surge in demand for AI data centers and HPC, Busbar's design challenges and requirements continue to grow.