There are actually ten ways to dissipate heat from PCB boards! The heat dissipation of PCB circuit boards is a very important link, so what are the heat dissipation techniques of PCB circuit boards?
1. Dissipate heat through the PCB board itself.
At present, the widely used PCB boards are copper-clad/epoxy glass cloth substrates or phenolic resin glass cloth substrates, and there are also a small amount of paper-based copper-clad boards. Although these circuit board substrates have excellent electrical properties and processing properties, they have poor heat dissipation. As a heat dissipation path for high-heating components, heat can hardly be expected to be conducted by the resin of the PCB itself; instead, heat is dissipated from the surface of the electronic components to the surrounding air.
However, as electronic products have entered the era of component miniaturization, high-density installation, and high-heating assembly, it is not enough to rely on the surface of components with a very small surface area to dissipate heat. At the same time, due to the extensive use of surface mount components such as QFP and BGA, a large amount of heat generated by the components is transmitted to the PCB board. To transmit or radiate.
2. For equipment cooled by free convection air, it is best to arrange integrated circuits (or other devices) in a vertical or horizontal manner.
3. Use reasonable wiring design to realize heat dissipation.
Since the resin in the circuit board has poor thermal conductivity, and the copper foil lines and holes are good conductors of heat, increasing the remaining rate of copper foil and increasing the heat conduction holes are the main means of heat dissipation. To evaluate the heat dissipation capacity of PCB, it is necessary to calculate the equivalent thermal conductivity of the insulating substrate for PCB, which is a composite material composed of various materials with different thermal conductivity.
4. Add radiators and heat conduction plates to high-heating devices.
When there are a few devices in the PCB with large heating stars (less than 3), radiators or heat pipes can be added to the heating devices. When the temperature cannot drop, A radiator with a fan can be used to enhance the cooling effect. When there are many heating components (more than 3), a large heat dissipation cover (board) can be used, which is a special radiator customized according to the position and height of the heating components on the PCB or a large flat radiator Cut out the height and position of different components. Buckle the cooling cover on the component surface as a whole, and contact each component to dissipate heat. However, due to the poor consistency of the components when they are assembled and soldered, the heat dissipation effect is not good. Usually, a soft thermal phase change thermal pad is added on the surface of the component to improve the heat dissipation effect.
5. Devices on the same printed circuit board should be arranged according to their calorific value and heat dissipation degree as much as possible. Devices with small calorific value or poor heat resistance (such as small signal transistors, small-scale integrated circuits, electrolytic capacitors, etc.) At the uppermost flow (inlet) of the cooling airflow, devices with high heat generation or good heat resistance (such as power transistors, large-scale integrated circuits, etc.) are placed at the most downstream of the cooling airflow.
6. In the horizontal direction, arrange high-power devices as close to the edge of the printed circuit board as possible to shorten the heat transfer path; in the vertical direction, arrange high-power devices as close as possible to the top of the printed circuit board to reduce the temperature of other devices when these devices are working. Impact.
7. The heat dissipation of the printed PCB board in the equipment mainly depends on air flow, so the air flow path should be studied during design; reasonable configuration of devices or printed circuit boards. When air flows, it always tends to flow in places with less resistance, so when configuring devices on a printed circuit board, avoid leaving a large airspace in a certain area. The configuration of multiple printed circuit boards in the whole machine should also pay attention to the same problem.
8. Devices that are sensitive to temperature are best placed in the lowest temperature area (such as the bottom of the device), and never place it directly above the heating device; multiple devices are best arranged staggered on the horizontal plane.
9. Arrange the components with the highest power consumption and heat generation near the best heat dissipation position. Do not place devices with high heat generation on the corners and edges of the printed circuit board unless there is a heat sink near it. When designing the power resistor, choose a larger device as much as possible, and make it have enough heat dissipation space when adjusting the layout of the printed board.
