OFweek Electronic Engineering Network News: For electronic devices, a certain amount of heat is generated during operation, causing the internal temperature of the device to rise rapidly. If this heat is not dissipated in time, the device will continue to heat up, and the components will fail due to overheating, resulting in a decrease in the reliability of electronic devices. Therefore, it is very important to perform good heat dissipation treatment on the circuit board. The heat dissipation of PCB circuit boards is a very important link, so what are the heat dissipation techniques for PCB circuit boards? Let's discuss them together below.

1. The widely used PCB boards for heat dissipation through the PCB board itself are copper-clad/epoxy glass cloth substrates or phenolic resin glass cloth substrates, as well as a small amount of paper-based copper-clad boards. Although these substrates have excellent electrical and processing properties, their heat dissipation is poor. As a heat dissipation pathway for high heat generating components, it is almost impossible to rely on the resin of the PCB itself to conduct heat, but rather dissipate heat from the surface of the component to the surrounding air. But as electronic products have entered the era of component miniaturization, high-density installation, and high heat generation assembly, relying solely on the surface area of components to dissipate heat is not enough. 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 transferred to the PCB board. Therefore, the best way to solve heat dissipation is to improve the heat dissipation ability of the PCB itself, which is in direct contact with the heating elements, and to export or dissipate it through the PCB board.

2. When there are a few devices in the PCB with high heat generation (less than 3), heat sinks or heat pipes can be added to the heat generating devices. When the temperature cannot be lowered, a heat sink with a fan can be used to enhance the heat dissipation effect. When there are more than three heating elements, a large heat dissipation cover (board) can be used, which is a specialized heat sink customized according to the position and height of the heating elements on the PCB board, or different element height positions can be cut out from a large flat heat sink. Attach the heat dissipation cover as a whole onto the surface of the component and make contact with each component to dissipate heat. However, due to poor consistency in the soldering of components, the heat dissipation effect is not good. Soft thermal phase change pads are usually added on the surface of electronic components to improve heat dissipation.

3. For equipment that uses free convection air cooling, it is best to arrange integrated circuits (or other devices) in a longitudinal or transverse manner.

4. The use of reasonable wiring design to achieve heat dissipation is due to the poor thermal conductivity of the resin in the board, while copper foil lines and holes are good conductors of heat. Therefore, increasing the copper foil residual rate and adding thermal conductivity holes are the main means of heat dissipation. To evaluate the heat dissipation capability of PCB, it is necessary to calculate the equivalent thermal conductivity (nine eq) of the insulation substrate used for PCB, which is a composite material composed of various materials with different thermal conductivity coefficients.

5. Devices on the same printed circuit board should be arranged in zones according to their heat generation and heat dissipation degree as much as possible. Devices with low heat generation or poor heat resistance (such as small signal transistors, small-scale integrated circuits, electrolytic capacitors, etc.) should be placed at the upstream (inlet) of the cooling airflow, while devices with high heat generation or good heat resistance (such as power transistors, large-scale integrated circuits, etc.) should be placed at the downstream of the cooling airflow.

6. In the horizontal direction, high-power devices should be arranged as close as possible to the edge of the printed board to shorten the heat transfer path; In the vertical direction, high-power devices should be arranged as close as possible to the top of the printed circuit board to reduce their impact on the temperature of other devices during operation.

7. The heat dissipation of the printed circuit board inside the equipment mainly relies on air flow, so it is necessary to study the air flow path and reasonably configure the components or printed circuit board during design. When air flows, it tends to flow in areas with low resistance, so when configuring components on printed circuit boards, it is important to avoid leaving a large airspace in a certain area. The configuration of multiple printed circuit boards in the entire machine should also pay attention to the same issue.

8. Devices that are sensitive to temperature are best placed in the lowest temperature area (such as the bottom of the equipment), and should not be placed directly above the heating device. Multiple devices are best arranged in a staggered manner on a horizontal plane.

9. Arrange the devices with the highest power consumption and heat generation near the optimal heat dissipation location. Do not place devices with high heat generation in the corners and edges of the printed board unless there are heat dissipation devices arranged nearby. When designing power resistors, try to choose larger components as much as possible, and ensure sufficient heat dissipation space when adjusting the layout of the printed circuit board.

10. Avoid the concentration of hotspots on the PCB, distribute power evenly on the PCB board as much as possible, and maintain the uniformity and consistency of the surface temperature performance of the PCB. It is often difficult to achieve strict uniform distribution during the design process, but it is important to avoid areas with high power density to prevent overheating from affecting the normal operation of the entire circuit. If conditions permit, it is necessary to conduct thermal efficiency analysis of printed circuits. For example, the thermal efficiency index analysis software module added to some professional PCB design software can help designers optimize circuit design.