Electronics Cooling Methods for PCB Thermal Management
Learn why it is important to use the right electronics cooling method.
Explore the different ways to cool down electronic components.
Find out if you need to use active or passive cooling methods.
When the summer heat leaves you drenched in sweat, you might be tempted to take some drastic measures to cool yourself down. Personally, I have tried such methods as soaking in an ice cube-filled bathtub, indulging in countless scoops of gelato, and turning the air conditioner on full-blast. While all these measures provide some sort of relief for me, it’s a different story with electronics products. Unfortunately, most electronics products do not have the luxury of an air-conditioner, and soaking a PCB in ice cubes is a very bad idea.
In all seriousness, cooling off electronic components is not as easy as getting yourself cooled on a hot day. You will need strategic planning to incorporate the right thermal management solutions to cool your device. In this article, we will discuss the various electronic cooling methods available to you, but, first, let’s explore how heat impacts electronic components to understand why these methods are needed in the first place.
How Does Heat Impact Electronic Components?
To a certain extent, all electronic components dissipate heat. The question is: how hot do these components get and how does the temperature affect the finished product? If you do not take thermal management seriously in your design, you can end up with overheated products and costly recalls.
Choosing the right thermal management technique is vital if you are using components that dissipate a large amount of heat. For example, FGPAs, graphic processors, power transistors, voltage regulators, and high-power LEDs are common culprits of overheating. These components tend to produce more heat than their less power-hungry counterparts. When a design consists of such components, it can get scalding hot. It is not surprising for parts, such as a microprocessor, to hit 100°C. Luckily, you can usually estimate how hot a component will get by referring to the thermal coefficient chart in its datasheet.
To make matters worse, designs are getting smaller in size, which means that components have less breathing space. When placed in an enclosure without proper cooling techniques, trapped heat negatively affects these other components by derating their performance and lifespan. Fortunately, there are a few methods designers can use to mitigate these issues.
Choosing an Electronics Cooling Method
A heatsink over an electronic component
Hardware designers face the dilemma of choosing which electronics cooling method to use in their design. Such a decision is influenced by cost, design space, power consumption, type of components, and the nature of the application.
Generally, electronics cooling methods are divided into two broad categories--active and passive cooling methods.
Active Cooling Methods
Active cooling methods include using cooling fans, proper component spacing, and liquid condensation with heat pipes. Active methods are often used for microprocessors or high-power output designs. They are generally more efficient in heat reduction through conduction and convection mechanisms, but require a power source to operate.
Add a Cooling Fan and Space Components Properly
Adding a cooling fan goes a long way to keeping temperatures down. The cooling fan moves heated air away from the components to a ventilation outlet. It is important to plan the ventilation path when using a cooling fan. This means determining the air inlet, outlet, and projecting the direction of the airflow.
And, if you have ample space to work on, maintain some distance between components. An example of a component that uses this strategy is a power MOSFET with adjacent parts. This design allows part of the heat to be ventilated instead of being conducted into adjacent components.
Use Heat Pipes
Heat pipes are cylindrical copper pipes used to transfer heat away from high-temperature components. Sometimes, heat pipes may contain liquids, such as water, to remove heat via a condenser. One recent innovation is miniature heat pipes, which conduct heat more efficiently and are small enough to be embedded into a PCB.
Passive Cooling Methods
Heatsinks and thermal vias are types of passive cooling techniques. These techniques offer limited heat dissipation efficiency, but they do not require a power source. They are suitable for designs that do not give off substantial heat. An example of a passive cooling technique is the use of a temperature data logger, which does not have any high-current components.
Use a Heatsink
Heatsinks are commonly used for components like power transistors and microprocessors. They feature fin-like surfaces, which maximize the heat transfer to the air. Often, the heat transfer compound is applied between the component and heatsink to improve heat conduction efficiency.
Use Thermal Vias
Thermal vias are padded holes drilled into the thermal dissipation pads on a PCB. They are great for quickly channeling heat away from power dissipating components. Thermal vias are usually arranged in a grid to maximize dissipating efficiency. These vias are often included in the grounding pad of footprints, such as for QFN components.
Effective thermal management requires strategic planning, design placement, and simulation to ensure the chosen electronic cooling methods are efficient enough to channel heat away and keep components within the optimum temperature range. The best way to determine if the electronics cooling method you have chosen is sufficient for your design is to run a thermal simulation with Cadence’s Celsius Thermal Solver (featured in the video below).
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