Electronic equipment plays an increasingly integral role in day-to-day life, both in residential and industrial applications. Portable, personal electronic devices such as mobile phones, for instance, are now used for everything from socializing to scheduling work. No matter what the specific device, all electronic circuits operate using components that have non-zero resistance, therefore Joule heating creates thermal energy that needs to be managed.
The failure rate of semiconductor devices increases exponentially with temperature, and heat can place significant stress on the solder joints of electronic devices, further increasing the chance of failure. Plus, with the rise of device miniaturization, the amount of heat generated per unit volume of devices has increased dramatically. These developments in miniaturization, along with the increased dependency on electronic devices in general, have made the cooling of such systems a matter of critical importance.
The Challenges of Cooling Electronics Devices
Over time, electronic devices have grown thinner and more compact, which reduces the available heat transfer potential by decreasing the surface area and volume over which thermal energy can be dissipated. Additionally, the printed circuit boards (PCBs) used in devices have grown denser, featuring multiple processors operating in the GHz range. While this density can make electronic devices more cost-effective, it compounds the cooling problem by adding more sources of heat into a smaller envelope, potentially impacting the reliability of the overall device unless proper cooling mechanisms are provided.
In addition to higher-density PCBs, the integrated circuits (ICs) themselves have also increased in density over the years. The heat generated within these IC chips can cause degradation of the internal connections, weaken solder joints, and accelerate processes that shorten the life of components or degrade their electrical performance. And as consumers increasingly demand small, compact electronic devices that provide easy portability, density continues to rise necessitating more innovative methods of cooling both circuit boards and the ICs mounted on them. Given the stringent space constraints of modern-day electronics, designers and engineers must put a great deal of thought into providing adequate cooling capabilities for these components to limit junction temperatures of integrated circuits to levels consistent with reliable performance.
Solutions for Cooling Electronics Devices
Today, a variety of approaches are available for heat dissipation and conduction. Within integrated circuit devices, solutions may include the use of carbon nanotubes or synthetic diamonds, for example. Synthetic chemical-vapor-deposition (CVD) diamonds whose thermal conductivity is on the order of 2,000 W/mK (Watts per meter-Kelvin) are finding increasing application in the thermal management of semiconductors that are pushed into higher operating frequencies and temperatures.
At the circuit board level, the most common cooling techniques include utilizing a metal heat sink within the circuit board, incorporating miniature heat pipes into the design, and, the most popular method, employing forced air cooling using small fans. These methods involve heat-pipe integration, in which tiny tubes of conductive material — such as copper or aluminum — are filled with two-phase fluids to transfer heat from the device. The heated vapor carries heat out of the system and dissipates it elsewhere, cooling the electronic device.
Alternatively, PCBs can be designed to provide pathways for heat transfer, in turn improving heat-dissipation rates. Another approach involves using thermal interface materials, such as thermal grease, to fill the empty spaces within the device, thus improving overall heat dissipation. Finally, the most common method involves employing a fan for active forced air cooling. This method is still widely employed despite the challenges associated with fan size and power consumption.
Cooling electronic devices is a complex process and often involves multiple engineering challenges. But technological advancements and innovations, the ongoing miniaturization of electronic devices, and increased consumer demand for compact personal electronics make proper device cooling imperative for optimal product longevity, safety, and affordability.
Combined with the proper implementation of traditional active and passive cooling techniques, developments in material science and industrial design are now allowing manufacturers to provide the best possible heat dissipation for today’s various electronic devices.
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