Heat Dissipation Methods in PCBs, Discussed by Keven Coates
In the ever-evolving world of electronics, understanding heat management and signal integrity is becoming increasingly important for engineers and designers working on Printed Circuit Board (PCB) designs. Keven Coates, a senior electrical engineer in avionics and a decade-long speaker at PCB West, strongly advocates for this knowledge as a means to enhance skills, elevate value in the industry, and boost careers.
Best practices for heat management in PCB designs, particularly focusing on processors, power MOSFETs, and LEDs, involve a combination of layout optimization, material selection, and cooling techniques tailored to each component's thermal profile.
For processors such as CPUs and GPUs, thermal vias are extensively used beneath the processor to conduct heat from the top layers to internal copper planes or bottom layers, thereby spreading and dissipating heat effectively. Heavy copper planes (minimum 2 oz or about 70 µm thickness) are employed for efficient heat spreading, and heat sinks are attached directly on the processor packages to increase surface area for convective cooling.
In the case of power MOSFETs, heavy copper layers with dense via arrays (via stitching) beneath the MOSFET exposed pads facilitate heat transfer through multiple board layers. Connecting thermal vias to large copper planes for heat spreading and selecting appropriate via sizes and spacing to optimize thermal conductivity without compromising structural integrity are also crucial.
For LEDs, thermal vias underneath LED pads, connecting to internal or bottom copper planes, aid heat dissipation from the LED junction. Attaching LEDs to thermally conductive PCB materials and considering adding heat sinks or heat spreaders if the LEDs operate at high power levels or high duty cycles complete the thermal management strategy for LEDs.
General thermal management practices include using four-layer (or more) PCB stack-ups to effectively separate signal and power layers while providing dedicated thermal planes, utilising thermal simulation tools to identify hot spots and optimise thermal paths early in the design phase, implementing active cooling (fans, blowers) oriented to direct airflow over critical heat-generating components, and considering preheating and controlled cooling processes in PCB assembly.
Keven Coates emphasises the importance of understanding heat management and signal integrity for PCB designers and engineers. He is offering a webinar on heat management and high-speed boards for those interested in learning more. In high-power applications, managing heat and mitigating radiated emissions are key challenges. Spreading components across the entire board is an efficient circuit board component placement technique, while using thermal interface materials such as thermal pads and heat sinks on power MOSFETs and LEDs helps dissipate heat effectively.
When designing processors, employ methods to handle heat by identifying the source of heat generation and applying thermal interface material. For a five-by-five MOSFET, using the thickest copper available is suggested to maximise heat dispersion. Incorporating thermal vias adjacent to the MOSFET can help facilitate heat transfer to the opposite side. Positioning heat-dissipating elements at the centre of the board for effective PCB heat management is also recommended. An additional heat sink on the opposite side of the board can be attached for effective thermal dissipation. Preferably, select materials that are readily available and don't cost extra for optimising heat dissipation in circuit boards.
By implementing these strategies, designers can balance the electrical and thermal requirements to protect sensitive components, maintain performance, and prolong PCB lifespan in power-dense applications.
Technology plays a crucial role in the effective management of heat in Printed Circuit Board (PCB) designs, particularly in high-power applications. For instance, thermal vias are extensively used to conduct heat from processors, power MOSFETs, and LEDs to internal copper planes or bottom layers, thereby facilitating heat dissipation. Additionally, the use of heat sinks and thermal interface materials such as thermal pads can significantly aid in heat management for components like power MOSFETs and LEDs.
