In today's article we would like to bring you closer to another, very important topic from a designer's perspective – the cooling of electronic systems. In the article you will learn why it is important to control the operating temperature of components and how it can be achieved. We introduce you to different ways in which the cooling function can be realized. We also discuss various design practices and methods of improving heat dissipation.
As you are probably well aware, there are no processes with 100% efficiency. Every transformation of energy is accompanied by some loss, most often in the form of heat – this follows directly from the principles of thermodynamics. Electronic circuits are no exception – components, tracks and wires heat up during operation.
Many modern electronic components have a relatively narrow operating temperature range. Excessively high temperatures can interfere with their operation, cause performance degradation or even lead to their failure. That is why it is important to take care of proper heat dissipation in order to keep system temperature under control.
A heatsink is one of the most frequently used devices for cooling electronic components. It is a passive heat exchanger designed to increase the surface of heat dissipation to the environment. The energy flows from the base of the heat sink to its fins, from where it is then transferred to the surrounding air. In passive cooling systems the air is exchanged by convection. For this reason, fins of the heat sink should be oriented vertically. It is also important to ensure a constant flow of air – for example by using vents in the case. To further increase the effectiveness of the heat sink, the air flow can be forced by a fan – then we talk about active cooling.
Heat sinks are constructed of metals with high thermal conductivity – usually aluminum or copper. Aluminum heat sinks are the most popular solution, because despite the slightly lower thermal conductivity of the metal they are lighter and cheaper to make. Speaking of making, there are many methods for manufacturing heat sinks – these include milling, extruding or die forging. It is also possible to integrate a heat sink directly into a device's casing – this solution is used, among others, in modular power supplies and other devices that do not require high cooling capacity.
In order for a cooling system to do its job effectively, sufficient heat transfer must be ensured between the cooled element and the heatsink. Most frequently thermally conductive pastes are used for this purpose. Those compounds are made on the basis of substances with high thermal conductivity – such as metals, silicone or ceramic materials. Their task is to fill microscopic irregularities of the element surface, which increases the contact area. The layer of paste should be as thin as possible to ensure the best possible exchange of heat energy.
The basic parameter characterizing a thermally conductive paste is, of course, its thermal conductivity. This parameter defines the maximum power of heat dissipation at a given contact surface, thickness and temperature difference. When selecting a paste, you should also consider its resistance to drying out. Thanks to it, the paste will maintain its parameters for a longer time and will be able to effectively perform its task without the need for frequent replacements.
To give you a closer look, here is an example of our IE-HAY-410 thermal compound. It is a general purpose silicone thermal conductive paste with a thermal conductivity of 1.42W/(m*K). Its noteworthy feature is an especially wide operating temperature range, ranging from -30°C to 280°C. This makes it suitable for a wide range of applications, starting from simple bimetallic sensors, all the way to advanced thermoelectric cooling systems. Get acquainted with the offer of InterElcom thermoconductive compounds!
| Symbol | IE-HAY-410 |
| Type | Thermally conductive silicone paste |
| Thermal conductivity | 1.42 W / (m ᛫ K) |
| Working temperature range | -30 ÷ 280 ° C |
| Packages available | Sachet (0.5g), syringe (20g), jar (100g) |
Apart from thermal pastes, there are also other solutions performing a similar function. These include, among others, thermally conductive pads. These are especially useful in cases, where strict control of the distance between the cooled elements is not possible. You can also choose from special thermal self-adhesive tapes and glues. Some types of components also allow for the use of silicone sleeves and pads, enabling easier mounting to the heatsink with screws.
On the surface, it may seem that commonly used PCBs are not suitable for use as cooling elements. However, it turns out that a significant group of components rely on the PCB design to dissipate excess heat and thus ensure optimal working conditions. These primarily include components such as microcontrollers, high-brightness LEDs, transistors, converters and amplifier ICs. For this purpose, they use the so-called thermal pad – a specially adapted lead, which by connecting to the board enables effective transfer of heat out from the package. The function of a heat sink is performed by a uniform area of copper, the size and shape of which should correspond to the needs of a given component. Additionally, the efficiency of this type of cooling can be further increased by using special heatsinks mounted directly to PCB.
Another option is to use aluminum substrate PCBs. These allow for even more efficient heat dissipation, as well as easy integration with other cooling systems. They are primarily used in LED lighting, where a large amount of heat is released, while uncomplicated circuits do not require the use of multiple PCB layers.
Read also: LED – a summary of the most important parameters
It is the PCB designer's responsibility to consider the heat generated by the components and its dissipation. Failure to do so can lead to shortened component life or lead to their premature failure. This is especially true for components that are sensitive to overheating, such as high power LEDs. To make sure that a given component is provided with optimal cooling, it is worth following the solutions suggested by the manufacturer in the data sheet. In the case of more complex systems, computer simulations can be helpful.
A good strategy for avoiding overheating problems is to reduce heat generation in the first place. To do this, it is a good idea to use modern solutions and technologies that are created with higher operating efficiency in mind. An excellent example is the use of a voltage converter instead of a linear regulator, or replacing the mains transformer with an efficient switching power supply. It is also important to ensure that components are not running at maximum power for long periods of time, as this usually generates more heat. This makes it easier to control the temperature of the systems, and thus ensures long and trouble-free operation.
Designing and building a reliable device can be quite a challenge, so it is best to entrust this task to professionals. InterElcom specializes in designing and manufacturing electronic circuits as well as distributing a wide range of components. Our qualified and experienced engineers make every effort to ensure that our products always meet even the most stringent customer requirements. Our solutions can be found not only in the lighting industry, but also in many industrial sectors, where they have been reliably fulfilling their tasks for years. Become one of our satisfied customers – contact us today!
