A Guide to PCB Heat Dissipation Techniques

Much like forest fires, when the heat rises within your PCB, the entire ecosystem could be potentially damaged by the rise in temperature. Companies that don’t take a proactive approach to heat management within PCB design may face long-standing product performance issues. So, to help further your understanding of proactive heat management in PCB design, our Toronto PCB assemblers will explore the best heat dissipation techniques to adopt for your next design.

The Challenges of Heat Management With PCBs

Boards running at high current levels with components that have high power demands have a higher potential for overheating. Thermal problems within these boards may lead to issues such as:

• Breakdown of dielectric materials
• Burn through of metal traces
• Detachment of soldering

Thermal issues can also occur during the manufacturing of the PCB. If the product doesn’t have the required heat dissipation, the system may not withstand the high temperatures generated during the soldering process. And so, from the early stages of development, teams must retain a clear focus on heat dissipation and its long-term value for their PCB operation.

The Steps to Dissipate Heat in PCBs

So, we’ve explored the importance of thermal management within PCB design processes. Now let’s review the steps your team can take to control the flow of heat.

Identify Thermal Hotspots

Identifying the thermal hotspots within the design is a crucial first step. Your team can use thermal modelling or thermal simulation techniques to run tests that help pinpoint potential areas of high temperatures within the PCB.

Once you’ve identified areas generating high heat levels, the design team must route high current traces away from thermally sensitive components such as sensors.

Consider Trace Width

The width of the copper pad and traces used within the PCB design also plays a decisive role in channelling heat within the design. When the current encounters resistance within a thinner copper trace, it generates high heat levels that can cause power loss.

A thicker copper trace allows for a lower impedance path for the current passing through it.

Use Thermal Vias

Thermal vias conduct heat via copper barrels between the upper and lower areas of the board. They are often used to transfer heat away from surface-mounted devices because of their high levels of thermal heat conduction.

As a channel between the upper and lower layer of the board, the vias transfer heat to the heat sink, which then passes the heat energy to a cooling medium.

Review Pad Design

The design of pads within the PCB is also a critical factor in heat management. The heat dissipates toward the top copper layer of the pad. So the padded section must have an adequate thickness to spread the heat across a larger surface area.

Mounting heat sinks within the PCB design is a tangible step towards effective dissipation. The heat sinks can be mounted to the bottom layer of the copper pad, thereby ensuring the pad sections have sufficient coverage for streamlined heat transfer to the sink.

Another priority consideration when evaluating pad design is the amount of solder.

The use of solder paste should be minimal to help prevent components from floating on molten solder during the reflow. Too much paste can cause movement within the component package, causing significant issues for your manufacturing team.

Ensure Careful Placement of High-Power Components

Ensure the team evaluates local high-temperature areas within the PCB board design at the earliest design stages.

High-powered components are often the source of overheating, so they must be placed towards the centre of the board so that heat flows evenly throughout the circuit.

When placed too close to the edge of the board, the components can cause high levels of heat in localized areas which can damage other parts and prevent optimal flow across the board.

High power components should also be placed evenly across the board to ensure that each area has a similar level of heat generation.

Use a Heat Sink

A heat sink may be the best solution for teams with challenging PCB design requirements and high heat loads. The heat sink transfers the heat from the PCB components to another cooling medium.

They operate via conduction, in which heat transfers from an area of high thermal resistance to a location of low thermal resistance. The heat sink draws heat away from the PCB, toward specific fins with a larger surface area for heat dissipation.

Try to choose a heat sink for your specific PCB design based on factors such as the thermal resistance of the materials, the velocity of the cooling liquid inside the heat sink, the thermal interface used and the mounting technique required.

Integrate Cooling Fans

In some cases, exchanging heat through induction is not enough to manage high heat levels within the PCB. So you may be required to integrate cooling fans within your PCB design. Cooling fans operate through convective heat transfer which is considered a more efficient mode of transferring heat away from sensitive components.

The ability of the fan to move air is the prime factor when evaluating choices for your design work. But there are other factors for you to review. When considering cooling fans for your PCB design, you should take into consideration the following:

• Fan friction
• Fan size
• Operational cost
• Power demands

Analyze Solder Thickness

Perhaps one of the simplest methods to manage heat during the design and manufacturing of PCB boards is to ensure uniform solder thickness. Soldering within the device joints should be even to reduce the levels of heat accumulation of component leads.

Another key soldering consideration is vias. Complete the soldering near the vias carefully to avoid creating bumps on the board that interrupt the connection between the board and the heat sink.

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To learn more about heat dissipation techniques in PCBs, call Circuits Central at 1(888) 602-7264 or contact us here.