Thermal management in PCBs is a crucial design aspect, especially in high-power designs where components and conductors generate significant heat during operation. Excessive temperature can increase electrical resistance, accelerate component aging, create localized hotspots, and reduce the service life of the board.
Circuit board designers can improve thermal performance by selecting suitable dielectric materials, creating efficient paths to heat sinks, using thermal vias, maintaining adequate trace width, monitoring component temperatures, and validating the design through thermal simulation.
The infographic above highlights six practical thermal management guidelines that PCB designers can apply to improve heat dissipation.
1. Select dielectric materials with high thermal conductivity
Choose laminates with thermal conductivity greater than 0.5 W/m·K when your application requires improved heat dissipation through the substrate.
Standard FR4 materials generally have relatively low thermal conductivity, which can limit heat transfer through the board. High-thermal-conductivity dielectrics can improve heat spreading from components into copper layers and other thermal structures.
This approach is useful for applications such as power electronics, motor drives, LED systems, and other designs with concentrated heat sources. Material selection should also consider dielectric strength, glass-transition temperature (Tg), mechanical properties, fabrication requirements, and cost.
The required thermal conductivity depends on the application’s power density and overall thermal path. Selecting a material with higher conductivity alone does not guarantee lower component temperatures. Designers should evaluate the complete path from the heat source to the final heat sink or cooling environment.
2. Integrate heat sinks using TECA and TIMs
Use thermally and electrically conductive adhesive (TECA) and thermal interface material (TIM) to create a low-thermal-resistance path between high-power components and heat sinks.
Heat sinks can remove heat from power components, but the interface between the component and heat sink can introduce significant thermal resistance. TECA provides both mechanical attachment and thermal conduction, making it useful when a conventional mechanical mounting method is impractical.
TIMs fill microscopic surface irregularities between mating surfaces and reduce thermal contact resistance. Materials such as Fujipoly’s Sarcon® 30-YR can be used for thermal interface applications, depending on the required thermal performance and mechanical conditions.
When selecting a TECA or TIM, consider thermal conductivity, thickness, compressibility, operating temperature, electrical insulation requirements, and mechanical reliability. The interface material should form a consistent thermal path without introducing excessive thickness or contact resistance.
3. Place thermal vias beneath high-power components
Incorporate thermal vias under high-power parts to provide a direct, low-resistance vertical thermal path into internal or backside copper structures.
These holes transfer heat from component pads into copper planes or heat-spreading structures on other layers. They are particularly useful beneath parts with exposed thermal pads, such as power ICs and other high-power packages.
Designers should also consider the PCB manufacturer’s fabrication capabilities and the component manufacturer’s recommended land pattern.
For exposed-pad components, uncontrolled vias can allow solder to flow into the holes during assembly. Designers may need filled, capped, or otherwise controlled vias depending on the package and assembly process. The thermal-via design should therefore be evaluated for both heat transfer and soldering requirements.
4. Increase the power trace width beyond the calculated minimum
Provide additional line width beyond the calculated minimum to reduce electrical resistance, I²R heating, and voltage drop.
A wider copper trace has lower electrical resistance for a given copper thickness and length. Since resistive power loss follows P = I²R, reducing resistance also lowers the heat generated by current flow.
For example, a designer may provide approximately 10 mil of additional trace width for 2 oz copper when the layout permits it. This additional width provides thermal margin beyond the minimum calculated conductor dimension.
The actual conductor width should be determined from current requirements, copper thickness, allowable temperature rise, length, and applicable design standard such as IPC-2152. Designers should also consider fabrication tolerances and available board space before increasing dimensions.
5. Place temperature sensors near critical components
Incorporate temperature sensors close to heat-generating parts, such as CPUs, GPUs, and power devices, to provide real-time thermal monitoring.
These devices can detect rising temperatures near critical components and provide feedback to the system controller. The system can use this information to activate cooling fans or take other thermal-management actions when temperatures approach defined limits.
Sensor placement is important. A sensor located too far from the heat source may not accurately represent the part’s actual operating temperature. Designers should position sensors close enough to capture meaningful temperature changes without interfering with routing, assembly, or component placement.
Thermal monitoring is particularly useful in systems with active cooling, variable power loads, or strict operating-temperature limits.
6. Run thermal simulations for high-power designs
Perform thermal simulations for high-load or thermally constrained designs to identify hotspots and potential thermal issues before fabrication.
This process can help designers evaluate temperature distribution, heat flow, and potential hotspots under expected operating conditions. It can also reveal areas that may require changes to copper distribution, thermal vias, component placement, heat sinks, or other thermal structures.
Simulation becomes particularly valuable when multiple heat sources interact or when the available PCB area limits heat spreading. Designers can use simulation results to compare different thermal strategies before committing to hardware.
The simulation model should represent relevant conditions such as component power dissipation, copper thickness, material thermal properties, ambient temperature, and cooling conditions. Designers should validate important simulation results with physical temperature measurements during prototype testing.
Effective PCB thermal management requires a combination of material selection, heat-transfer paths, copper design, thermal monitoring, and design validation. High-thermal-conductivity dielectrics can improve heat spreading, TECA and TIMs can reduce thermal resistance to heat sinks, and thermal vias can transfer heat into internal or backside copper structures. Wider power traces reduce resistive heating, temperature sensors provide real-time feedback, and thermal simulations help identify problems before fabrication.
Applying these six guidelines early in the PCB design process can help designers control operating temperatures, reduce thermal hotspots, and improve overall board reliability.