Thermal management is necessary to keep electronic components from overheating. Overheating can damage equipment, reduce lifespan, and even lead to outages and permanent failure.
Most designers can use cooling methods and other techniques to minimize heating issues. This includes placing thermal vias in strategic locations to aid heat transfer.
Thermal Interface Materials (TIM)
Many types of TIMs are available in electronic systems, and the choice depends on the critical performance factors that must be achieved. Each type of TIM has unique characteristics, which are important for effective thermal management technologies.
The primary function of TIMs is to fill the gaps or voids between mating components with a substance that has better thermal conductivity than the air it displaces. Typical TIMs conduct heat tens to hundreds of times more effectively than the air they replace. Various TIMs, including thermal tapes, pads, and greases, are available. Unlike the other two, thermal tapes are designed to be used as a conformal cover over the interface, and their low viscosity makes them easy to apply. Thermal pads are a more traditional TIM in solid and soft versions. The choice of pad material is often determined by whether or not the interface needs to be held in place and how thick a bond line is required.
Electronic devices create electromagnetic emissions that interfere with the operation of other equipment when they are of high magnitude and certain frequencies. Most countries have regulations that limit the amount of EMI a product produces and at what frequency.
Most of this EMI energy is radiated in heat, but some may also be conducted through components such as capacitors and inductors. These non-ideal characteristics make EMI minimization essential to ensure that the components do what they’re designed to do and not pick up and emit unwanted emissions.
EMI can be reduced by separating signals, avoiding right angles (capacitance increases at angles greater than 45 degrees), and keeping return paths short. By doing so, the risk of EMI is significantly reduced.
Another way to minimize EMI is by using shielding, which is used to enclose the circuit board and keep out external interference completely. Shielding is effective but must be incorporated into the design process—not added afterward. Otherwise, shielding can have unintended consequences, such as increasing the inductance of a signal due to magnetic coupling with adjacent lines.
Cooling is a critical component in modern electronics, and there are several cooling systems to choose from. Passive thermal management uses heat sinks, heat spreaders, and thermal interface materials (TIM) to maintain optimal operating temperatures. In contrast, active cooling uses fans, blowers, or liquid cooling systems to enhance convection. In passive cooling, air or liquid cools the components via conduction, evaporation, and condensation. This is typically the best option for small and lightweight products. However, large and complex electronic devices require more sophisticated cooling technologies to prevent overheating. These systems use more energy than passive cooling but can provide higher performance and accuracy.
Thermal vias are a crucial element to consider in PCB design. These tiny holes are drilled into the circuit board and filled with silver or copper to boost their thermal conductivity. When placed close to ICs or heated components’ pads, they help reduce the pad’s temperature. As a result, they can transport heat more evenly throughout the board, eliminating hot spots.
When designing a thermal management strategy for your PCB, you must consider the size and placement of your copper areas and your power and reference planes. The best results are achieved when the top copper area is large, and the solder mask-defined thermal pad is on that surface layer of the PCB. This allows the thermal vias to transfer heat more efficiently to the board’s bottom or inner copper planes.
Surface Mount Technology (SMT)
Surface mount technology is a process where electronic components are directly mounted onto the surface of printed circuit boards or PCBs. This has replaced traditional through-hole technology, which involves inserting element leads into holes in the board. This allows for higher circuit densities, making electronics smaller and more compact.
The SMT assembly process begins with a layer of solder paste being applied to the surface of the PCB. This is followed by placing the components on top of it with the help of sophisticated robotic systems. These systems can work at very high speeds, handling different parts with varying requirements. This includes passive elements, such as resistors, capacitors, and IC, BGA, and FPGA components.
In addition to reducing the amount of space components take up on a PCB, SMT also reduces manufacturing costs and improves quality efficiency. As such, it is an increasingly popular option for manufacturers looking to streamline their production processes. However, this has challenges, including carefully selecting and designing compatible components with SMT.