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Thermal Issues of PCB Boards

Understanding PCB boards

For electronic devices, they generate heat as they work, which causes the internal temperature of the device to quickly rise. If this heat is not dissipated in a timely manner, the device will continue to heat up, causing components to fail due to overheating and reducing the reliability of electronic devices. Therefore, it is very important to handle the heat dissipation of circuit boards well. The heat dissipation of printed circuit board is a very important part of thermal design. In thermal design, PCB is the most important heat source carrier, and its sources of heat mainly come from three aspects: the heat generated by electronic components, the heat generated by the PCB itself, and the heat transmitted from other parts.

Currently, widely used PCB board materials for thermal dissipation are copper-clad/epoxy glass cloth substrate or phenolic resin glass cloth substrate, and a small amount of paper-based copper-clad board materials. Although these substrates have excellent electrical properties and processing properties, they have poor heat dissipation performance. As a high-heat-generating element, it is almost impossible to expect the PCB resin itself to conduct heat, but rather to dissipate heat from the surface of the component to the surrounding air.

Understanding heat dissipation issues of PCB boards

However, with electronic products entering the era of component miniaturization, high-density installation, and high thermal assembly, relying only on the small surface area of the component surface to dissipate heat is insufficient. At the same time, with the widespread use of surface-mounted elements such as QFP and BGA, a large amount of heat generated by components is transmitted to PCB boards. Therefore, the best solution to solving heat dissipation is to improve the heat dissipation capacity of PCB itself that is in direct contact with the heating component, and dissipate or emit heat through the PCB board.

Heat dissipation treatment in PCB layout design

Layout is an important part of the entire PCB heat dissipation design, and plays a crucial role in PCB heat dissipation. As a designer, when designing a PCB layout, you need to consider the following:

  • Consider designing and installing high heat-generating, high radiation components on another PCB board, and perform separate centralized ventilation cooling to avoid interference with the motherboard.

  • Distribute the heat capacity of the board printed circuit evenly, and do not place high-power-consuming devices in a concentrated area. If it is unavoidable, place the shorter components in the upstream airflow and ensure that enough cooling air flows through the heat concentration area.

  • Make the heat transfer path as short as possible and maximize the cross-sectional area of heat transfer.

  • The layout of components should consider the impact on the thermal radiation of surrounding parts. Parts and components (including semiconductor devices) that are sensitive to heat should be kept away from the heat source or isolated.

  • Pay attention to the consistency of forced ventilation and natural ventilation directions. Additional sub-boards, component air ducts, and ventilation directions should be consistent.

  • Do not place components that generate large amounts of heat or current in the corners and edges of the printed circuit board. Install heat sinks as much as possible and keep them away from other components, and ensure unobstructed heat dissipation channels.

  • Place temperature detection components in the hottest position.

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