How many times have you heard about someone burning a transistor because of overtemperature? Why do IC manufacturers put larger thermal pads for switching ICs and power ICs? Have you noticed your laptop's thermal management system? Do you know that all these systems with large heatsinks, fans, and radiators are used to cool just a single or two tiny chips, which are the CPU and GPU? And did you think about the reason for the power supply case design and why the power supply volume is large in comparison to its board design, just a rectifier with capacitors?
All these questions pushed us to talk about a very insightful topic in the PCB design world. It’s PCB Thermal Management. Effective PCB thermal management ensures reliability, efficiency, and longevity of electronic systems. Keep reading, you will learn a lot about this topic.
What Is Thermal Management in PCB Design?
PCB thermal management is the optimization and control of the temperature of the board, including traces, layers, and components.
This process is done properly by collaborating with system engineers who determine the requirements and limitations of the project, including thermal ones, moving to senior hardware engineers who select components with a matrix of high temperature standability and good layout structure, reaching PCB layout engineers who keep in mind large width traces, thermal pads and vias, placement of high temperature components distribution on the board and much more aspects that we will talk about later.
Why Thermal Management Matters in PCBs
PCB thermal management is crucial for all electronic systems because it can cause full or partial damage to the system; in the best case, it will lead to degradation of system performance.
Excessive heat may affect the stability of the system. Many ICs, like microcontrollers or power MOSFETs, are temperature-dependent; their performance is reduced with the increase of temperature.
For example, the following chart from the onsemi MOSFET datasheet shows that when temperature rises, the on resistance value of mosfet also increases, which is considered a degradation as power loss increases!
Also, for safety purposes, overheating can cause fire in high-power applications, battery management systems designs. Temperature management is a very crucial aspect while choosing charging and discharging MOSFETs, placing components on the board, distributing high-temperature sources all over the board, and designing suitable heat sinks for processors, LDOs, and switching elements.
Thermal Management Techniques in PCB Design
There are a lot of techniques that are used to manage the temperature of components and substrates of the intended PCB. Designers should be aware of these techniques, best practices in design, and common mistakes to avoid. We will discuss many of them as follows:
Copper Pour
It also called a copper fill, usually done by creating a polygon for ground or power nets instead of routing traces, this causes many benefits like great heat dissipation, as the area of flat conducting surface increases, also reducing traces resistance as it’s very wide, this reducing power loss in these nets which is lost in a form of heat.
Thermal Vias Arrays
They are vias connected to planes and placed in contact with thermal pads of components to dissipate the components' heat. These vias are filled with copper or epoxy, or not filled; the best of these solutions is copper-filled because it’s a very thermal conductive material, but also it’s very expensive to fill and plate vias with copper, so most of designs use non filled vias and use large number of them to dissipate heat easily.
Trace Width & Copper Thickness
When copper traces and copper vias carry high current densities, the resistance will generate a large amount of heat. The thickness of the copper trace should meet the condition of providing a low-impedance path for the current passing through it. Only sufficient trace width and thickness can reduce heat generation. While routing a power trace, you should avoid sharp bends to avoid hot spots, also use wide traces to reduce overall resistance, and try to use copper pours as much as possible, as mentioned before.
Component Placement & Layout
When a designer chooses the placement of board components, he should keep high power components away from each other, and also away from sensitive components like oscillators and sensors, because high temperature changes the characteristics of elements' resistances, inductances, and capacitances, and as a consequence, these parameters can vary the frequency of the oscillator, consisting a huge delay or ticking mismatch in the system in both software wise and hardware wise.
Also, you can group high-power components for a single reason: it’s to use one huge heatsink for your system. If this heatsink is not applied properly, this advantage will turn into a disadvantage in your design, so be careful while placing your components.
If you can change the stack-up materials, it’s recommended for very high temperature loads like LEDs to use aluminum core PCBs to act as a heatsink.
Heat Sinks, Heat Pipes & Cooling Fans
Most systems use a combined system of heat pipes and heat sinks, like laptops or servers. This is the optimum solution for PCB cooling, also, you should be aware of the type of thermal paste that is used in the contact between the heat pipe/sink and the surface of the IC. Using a heatsink only is cost-effective, while using heatsinks and heat pipes provides high thermal management performance. Also, using cooling fans with thermal pipes and heatsinks is important, and it’s determined from thermal analysis of the system.
Predictive Thermal Modelling
Thermal simulation or thermal modelling techniques are software-based, allowing PCB designers to simulate heat dissipation along the board and let them know hotspots before manufacturing to avoid them in their designs. Designers can use software like Ansys, Cadence or Altium with SimLab to predict heat distribution before manufacturing. This reduces redesign costs, improving cooling efficiency in all parts of boards, and being confident about designs.
Thermal Design Mistakes & How to Avoid Them?
|
Thermal Design Mistake |
Potential Issue |
Thermal Management Solution |
|---|---|---|
|
Unassigned copper pour |
Acts as an antenna, increasing EMI and signal integrity issues. |
Always assign copper pours to a reference net (e.g., GND or power). |
|
Missing thermal relief in pads |
Difficult soldering due to heat dissipation into the copper plane. |
Use thermal relief connections in polygon pours for pads. |
|
No thermal interface materials (TIMs) |
Poor heat transfer, leading to component failure (e.g., MOSFETs, IGBTs). |
Include thermal pads/paste in high-power component footprints. |
|
Thin traces for high-current paths |
Excessive heat due to resistive (I²R) losses, risking trace damage. |
Follow IPC-2152 standards for trace width based on current requirements. |
|
Neglecting cooling systems |
Inadequate heat dissipation in enclosed systems (e.g., CPUs, GPUs). |
Use forced airflow (fans) alongside heatsinks and low-resistance thermal paste. |
|
Skipping thermal simulations |
Costly redesigns in power systems (e.g., inverters, motor drivers). |
Run thermal simulations early to identify hotspots and optimize layout. |
Key Takeaways:
- Copper pours must be properly connected to avoid EMI.
- Thermal reliefs ensure manufacturability and soldering reliability.
- TIMs (thermal pads/paste) are critical for power components.
- Adequate trace width prevents overheating in high-current paths.
- Active/passive cooling (fans, heatsinks) must be considered.
- Simulations reduce long-term costs by catching thermal issues early.
Conclusion
Proper PCB thermal management system is important to ensure the reliability and performance of the circuit board. By avoiding the common mistakes while designing PCBs, the reliability of the PCB can be improved. If you are looking for high-quality PCB manufacturing, then FC PCBA ensure that your board are not just manufactured but also designed for real-world applications. Get in touch with FC PCBA for your optimized thermal designs.
FAQs on PCB Thermal Management
Q1: What is the best material for high-temperature PCBs?
Metal-core PCBs (MCPCBs) or ceramics like aluminum nitride (AlN) offer excellent thermal conductivity.
Q2: How do I identify overheating components on a PCB?
Use thermal imaging cameras, infrared thermometers, or temperature sensors to detect hotspots.
Q3: Are thermal vias better than heat sinks?
They serve different purposes—thermal vias help conduct heat internally, while heat sinks dissipate it externally. Often, both are used together.
Q4: What are the types of thermal interface materials?
There are many types of TIMs, like thermal paste, silicon pads, liquid metal and much more.
The most famous is thermal pads, because it has high performance and are also not expensive. The best is metal liquid, it is used for extreme cooling, but it’s very expensive and has a possibility of short circuit because it’s conductive.
Q5: When to decide to use a heatsink with your LDO?
Calculate the dissipated power. If it’s more than 1 Watt, it’s recommended to use a heatsink, This is the power loss equation:
