Solving Overheating: PCB Heat Dissipation Techniques

Why PCB Overheating is a Major Concern in Electronics

The continual development of cutting-edge modern electronics has taken their size and capability to unprecedented levels which introduces new issues such as heat management for components crowded together. Overheating in Printed Circuit Boards (PCBs) is more than an inconvenience; it is a harrowing problem that affects the devices’ performance, dependability, and durability. All electronics designers and manufacturers must know the basics of thermal management and highly refined strategies for heat management if they want to make sure devices continue functioning under extreme heat conditions. Properly managing heat is essential so that devices are not left permanently damaged.

Fundamentals of Thermal Management in PCBs

In simple terms, thermal management in PCBs is the ideal transfer of heat from heat-generating components. like voltage regulators. Electronic components, in carrying out their tasks, constantly use up energy in electrical resistance to generate heat. No matter how little, heat will always be created as a result of power being used. For example, average microcontrollers will dissipate about two to three milliwatts of energy to a couple of watts while high-power components and processors, power LEDs, and transistors are so powerful that they can generate heat in the order of dozens to hundreds of watts.

The PCB serves a dual purpose, including that of a thermal conductor. However, this function is not uniformly performed and depends greatly on the materials and the design chosen. Heat produced by the components needs to be relocated through the PCB with the appropriate heat distribution across its layers and then dissipated into the environment. The two modes of thermal transfer are conduction from the leads, convection transfer to the surrounding fluid or air, and radiation emission of waves that discharge much heat. Effective control and management of thermal energy seeks to improve the efficiency of this routing of thermal energy in the components so that the temperature of the components remains within their limits during operation. For commercial applications, this is between 0°C and 70 °C, but is usually much stricter for high reliability or specialized electronics.

Consequences of Inadequate Heat Dissipation: Performance, Reliability, and Lifespan

Lack of attention towards ‘heat dissipation’ for PCBs can have numerous, far-reaching negative impacts on an electronic device.

• Performance Issues: With an increase in temperature of a semiconductor device, the electrical characteristics also tend to change. This means that the switching speed of transistors can decrease, which would lead to increased processing time and reduced system performance. In the case of analog circuits, the temperature increase can lead to noise and drift signals that decrease the integrity of the signal. A processor designed to operate at 3 GHz will experience a decline between 10% to 15% for every 10°C increase in optimum temperature.
• Lowered Reliability: High heat can increase the rate of almost all chemical reactions in a device, thus leading to precocious aging and an increased rate of failures. Studies indicate that an estimated two-fold failure rate occurs for many electronic components for every 10°C increase in temperature. The Arrhenius equation depicts the relationship between temperature and component lifespan best; in practice, such components often fail. An electrolytic capacitor could be rated at 10,000 hours at 85°C, but at a constant heat of 105°C, it could reach the point of failure much faster.
• Shortened Lifespan: We can observe the term cumulative impairment, which refers to an abrasion of an electronic device’s performance, reliability, and service life. It can be said that devices always have a limited service life. Components that are exposed to high temperatures for extended periods of time have a high probability of failure. Once this happens, the device is useless. This scenario not only brings up higher warranty repair costs and lower customer satisfaction rates, but it is also a big challenge to many sectors where the useful life of a device is critical, like the aerospace, medical, and industrial control systems.
• Increased Energy Consumption: When the device overheats, it invariably uses more energy. This excessive heat has to be managed, and the cooling systems have to work overtime. This is the case in most rechargeable devices that depend on batteries for their power supply because the management of heat has a direct consequence on battery life.
• Safety Concerns: Unless active steps are taken, overheating can become a danger, and in extreme cases, result in thermal runaway or fires in materials that are flammable.

The above suggests that the design of any PCB must incorporate effective heat dissipation techniques. Such techniques must, at a minimum, ensure that the electronic products maintain the required functionality, durability, and safety.

Advanced Heat Dissipation Methods

To solve the problem of PCB overheating, many sophisticated, advanced heat dissipation methods have been developed and are commonly used in the electronic design process. These methods can be grouped into two categories: those that incorporate enhanced heat conduction from the components and those that include radiation and convection of heat to the ambient space. An overall thermal design usually employs several heat control techniques simultaneously.

Implementation of Heat Sinks

Heat sinks, in contrast, are passive devices that operate in a more advanced fashion. Sinks are a thermal management device whose objective is to elevate the surface area available for the transfer of heat to the surrounding air. They are almost always constructed from materials that have high conductivity, like aluminum or copper, and they have different shapes and sizes, usually having fins to increase surface area.

All emissive electronic components that disperse power experience an increase in temperature during operation. In the case of heat generation, a heat sink is used to receive energy from a device and augment the amount of energy dissipated into the surrounding medium. These devices maximize contact surface through the use of finned surfaces and support the flow of cooling air that can be forced through or naturally circulate around the heat sink. Its efficiency depends on the materials, the surface area, the configuration of fins, and the thermal resistance of the interface between the component and heat sink. The use of thermal interface materials – TIMs, such as thermal paste and pads – suitably attaches the interface and reduces interface thermal resistance for proper heat transfer. For example, an aluminum heat sink with a larger surface area of 50 cm² can passively cool several watts of heat through natural convection, which is significantly more than a hot part without a heat sink. In high-power applications, larger and more finely divided heat sinks are needed.

Utilizing Thermal Vias for Enhanced Heat Flow

Thermal vias consist of a plated through hole filled with a thermally conductive material, most often copper, which serves as a via for heat transfer in a vertical direction from one layer of the PCB to another. When employed in multilayer PCBs, they are critical in relocating heat from surface-mounted devices to the inner copper planes, which would then spread the heat further around the board.

To maximize the performance of thermal vias, they should be strategically placed under the heat-generating components. The number of thermal vias necessary depends on the PCB material’s thermal conductivity and the amount of heat that is being dissipated. For instance, a dense array of thermal vias, say 10-20 in number, with a diameter of 0.3mm, can drastically lower the thermal resistance value between a surface component and an inner copper plane. Effective thermal management policies must focus on optimizing the quantity and configuration of these thermal vias.

Optimizing Copper Traces and Planes for Heat Conduction

In a PCB structure, copper is the best thermal conductor and, due to its high thermal conductivity, can be employed strategically to enhance the rate of heat dissipation, providing the best heat dissipation in high-power applications. Besides the reduction of electrical resistance, an increase in the width and thickness of copper traces carrying high currents improves both the copper trace’s resistance and its ability to dissipate the heat from the components. Additionally, large area copper planes also have the ability to spread heat, especially ground and power planes, as they are directly over the PCB and can heat the plane constituents over a wide area.

Reserving whole layers or large portions of layers for copper planes on high-power applications can greatly aid in thermal management. The thermal conductance of copper is almost 400 W/m·K, which is much greater than that of common FR-4, which is around 0.2 W/m·K due to its low thermal conductivity rating. This difference underscores the need to utilize copper for heat dissipation and should be considered as part of your thermal design strategy. For example, increasing the thickness of the copper trace twofold from one side will reduce the thermal resistance by roughly 50 percent.

Heat Pipe Technology and Its Application in PCBs

The principle of a heat pipe is based upon the transfer of heat through the sequential process of evaporation and condensation of the working fluid in a sealed tube. A heat pipe is defined as a device that transfers heat with minimal temperature loss over considerable distances. In the past, the uses were rather limited, for example, the cooling of laptops, the spread of heat pipes installed in PCBs that require significant power is becoming more common as heat pipes are easily integrated and are one of the best thermal management strategies available in modern electronics.

Active cooling of Printed Circuit Boards (PCBs) can include integration of heat pipes into the PCB, direct attachment to PCB components, or application of miniaturized heat pipes. Heat pipes are extremely effective at moving concentrated fluxes of heat out of a hot spot to a designed area where the heat can be dissipated. This is made possible by the miniaturized construction of the pipe, which results in considerably higher thermal conductivity than solid copper.

As an example, the efficient thermal conductivity of small heat pipes can be several orders higher than that of solid copper. So, small heat pipes are ideally suited for any kind of electronic device with high levels of concentrated heat generation.

Utilizing Cooling Fans for Forced Air Convection

Cooling fans function as active thermal management devices that dynamically move air across the PCB and heat sinks, improving convective heat transfer. They are particularly effective in applications where passive cooling methods are insufficient to maintain component temperatures within acceptable limits, and are one of the most widely used strategies to manage heat in various devices in the electronics industry.

The fan’s configuration is determined by the volume of heat to be expelled, the space available for the fan, the airflow required, and the allowable noise level. Airflow and pressure characteristics differ in various fans: axial fans and blower fans, each providing different types of airflow and pressure.

Radial fans, also known as blower fans, are often applied if there is a need to direct airflow across a specific spot or through a confined volume, in contrast to axial fans, which are better at providing general airflow across the PCB. As an example, the capacity of a heat sink to dissipate heat can increase by 50-100% when the velocity of air flowing over the heat sink is increased from 1m/s to 3m/s.

Component Placement Strategies for Enhanced Thermal Management

Strategic placement of components on the PCB with regard to cooling systems is an area that requires innovation. Designers can enhance the dissipation of heat by thoughtfully examining the thermal properties of various systems, their positions within the system, and the cooling methods available.

• Separate High-Power Components: Heat-producing components should be located at a distance from each other to avoid elevated localized temperature spots and reduce thermal coupling.
• Orient Components for Airflow: For forced air-cooled systems, components should be positioned in a way that allows unidirectional air cooling for the majority of screened surfaces. An example is orienting finned heat sinks parallel to the direction of cooling airflow.
• Heat-Sensitive Components: Cooling sensitive components should be positioned off the powerful component areas and within cooled regions.
• Use of Board Edges: High-power components can be mounted at the edges of the PCB so that heat can be moved into the chassis or enclosure.
• Thermal Symmetry: Trying to balance the distribution of heat-producing devices on a PCB may help with lowering the temperature of localized areas on a PCB due to fewer hot spots and improving the air temperature standard on the PCB.

Best Practices for Implementing PCB Heat Dissipation Techniques

Depending on the stage of the design process, managing heat on printed circuit boards(PCBs) must be done systematically, starting from problem identification all the way to resolving the heat management challenges.

Early-Stage Thermal Analysis and Simulation

In the early stages of the design cycle, an assessment as well as a simulation should take place to mitigate any overheating risks and test the efficiency of other heat control techniques before any physical prototypes are constructed. Programs that employ processes like Finite Element Analysis (FEA), which simulate how a printed circuit board generates heat and how heat is transmitted within it, allow engineers to improve the positioning of components, cooling sections, or cooling fans. Being able to correct these problems before the product goes through the later stage of development saves a lot of resources and time.

Considerations for Different Application Environments

The operating conditions of an electronic device greatly impact the thermal management strategies that need to be adopted. Devices that function within high temperatures or within closed spaces that limit airflow, will need more complex cooling solutions as compared to devices that function in low temperatures, well-ventilated environments.

Moreover, altitude, humidity, and the presence of dust and other contaminants can also impact the thermal performance of devices. These stay factors have to be balanced when choosing and designing PCB heat dissipation methods. For instance, a device meant for outdoor usage in warm climates may need more powerful cooling fans and larger heat sinks when compared to the same device used in air-controlled indoor conditions.

Combining Multiple Techniques for Maximum Efficiency

In most cases, the best approach to achieve effective thermal management is through the adoption of several techniques. For example, a combination of a heat sink on a high-power component, as well as a strategically placed heat spreader and thermal vias, along with forced air cooling on a high-power component, will cool the device much more efficiently compared to the use of a single technique.

The actual cooling method or techniques that will be used will depend on the unique parameters of the application, such as the heat produced, the area available, the cost in terms of investment, and the reliability needed.

ACDCFAN Tips: When should you consider using a cooling fan in PCB designs?

For the most part, using a fan with a PCB design is a tradeoff between the function, cost, noise, and reliability of the system. Here are some important signs that might suggest the need for active fan cooling:

• High Power Dissipation: In case one or more components mounted on the board dissipate lots of power (for example, >10W), utilizing passive cooling such as heat sinks alone will not guarantee safe operating temperatures, particularly if the environment is compact.
• High Ambient Temperatures: When it is a requirement for the device to function in regions with high ambient temperatures (for example, >40°C), the temperature difference that drives passive heat transfer is lower than necessary, thus, active cooling is required.
• Limited Natural Convection: These encapsulated systems with poor ventilation and restricted airflow can lead to the accumulation of heat which may necessitate forced air cooling that is provided by a fan.
• Stringent Performance Requirements: If the application in question requires certain processors or GPUs to be consistently operational at peak performance, active cooling can assist in ensuring optimal operating temperatures and avoiding the consequences of thermal throttling.
• High Component Density: PCBs with dense mounting can have large amounts of heat built up in them, which makes it difficult for passive cooling methods to control the temperature.
• Reliability Issues: Active cooling can help important components last longer by reducing operational temperature. As a result, it is ideal for applications needing long-term reliability.

Passive vs. Active Cooling Techniques

The heat management strategies employed for PCBs can be divided into passive and active methods, with each one contributing differently to the overall thermal management of advanced electronics devices:

In passive cooling, heat is extracted without any external energy. Examples include heat sinks, thermal vias, copper layer optimization, and PCB material selection. Such techniques are usually less complicated, have higher reliability because they do not have moving parts, and do not require extra energy. On the flip side, their cooling potential is limited due to the passive method of heat extraction. The strategic placement of active components in a PCB may also qualify as a passive cooling technique, whereby component placement is done in such a way as to minimize thermal interference between neighboring components.

Active techniques for cooling are those that utilize an external energy powered device that works to relocate heat away from the PCB. The most widely used type of these methods involves the use of cooling fans to force air over the heatsinks and the surface of the PCB. Other examples of active methods that can be employed are liquid cooling systems, which have a higher capacity for cooling but tend to be more intricate and costly. While both active and passive methods have their own unique advantages, active cooling methods allow for dramatically improved dissipation of heat, which makes them far more beneficial for applications utilizing power electronics or in areas where there is little to no natural convection. Yet, these active solutions pose some disadvantages, such as introducing unwanted sound, drawing additional energy, and having a limited lifetime based on the reliability of their active parts.

ACDC FAN: Your Partner in Effective PCB Cooling

Global cooling solution manufacturer ACDCFAN specializes in the production of AC & radial, BLDC & radial, and axial EC fans, all necessary for optimal PCB thermoregulation. Our fans are uniquely designed to be highly dependable and durable, with lifespans of up to 70,000 hours at 40°C and limitless customizability for temperatures up to 120°C. This guarantees a reduction in long-term device stability and performance maintenance issues.

Knowing the different application needs, our fans have multi-level speeds ranging from 1000 to 30,000 RPM, which enables ease of airflow and pressure control for specific PCB confines and operational cooling environment. In addition, we provide fan size and shape customization along with design and functions to enhance system integration and address various thermal issues.

As an ISO certified company (ISO9001, ISO14001), ACDCFAN adheres to the highest quality and environmental standards. Our cooling fans are RoH compliant guaranteeing product safety and meeting international safety standards such as UL, CE, TUV, along Iso restrictions, confirming no pollutants are used.

For PCB layouts with elevated power dissipation, compact component arrangement, or difficult thermal conditions, ACDCFAN offers dependable cooling systems that can be tailored to your needs and guarantee optimal performance. This results in increased reliability and the lifetime of your electronics products. Join hands with us to solve your urgent PCB cooling requirements.

Conclusion

Dissipation techniques for PCB heat are no longer optional considerations. They have become indispensable in enhancing the reliability and super performance of electronic devices. The risks that cause overheating and erosion of the product can be solved by having a solid understanding of thermal management and implementing sophisticated cooling methods, optimizing component arrangement, and following best practices.

Whether your preference is for passive cooling solutions or the more aggressive active cooling solutions that fans offer, having a coherent thermal management approach is key. While designing electronics, do not forget that cooperation with experienced cooling solutions suppliers, such as ACDCFAN will equip and assist you in dealing with your PCB heat dissipation issues.