PCB cooling method
1. Heat dissipation through the PCB board itself: the currently widely used PCB sheet is copper-clad/epoxy glass cloth substrate or phenolic resin glass cloth substrate, and a small amount of paper-based copper-clad sheet is used. Although these substrates have excellent electrical performance and processing performance, they have poor heat dissipation. As a heat dissipation route for high heat-generating components, the PCB itself can hardly be expected to conduct heat from the resin of the PCB, but to dissipate heat from the surface of the component to the surrounding air. However, as electronic products have entered the era of miniaturization of components, high-density installation, and high-heat assembly, it is not enough to rely on the surface of components with very small surface area to dissipate heat. At the same time, due to the heavy use of surface-mounted components such as QFP and BGA, the heat generated by the components is transferred to the PCB board in large quantities. Therefore, the best way to solve the heat dissipation is to improve the heat dissipation capacity of the PCB itself in direct contact with the heating element. Conduct or emit.
2. Adopt reasonable wiring design to achieve heat dissipation: due to the poor thermal conductivity of the resin in the plate, and the copper foil lines and holes are good conductors of heat, improving the copper foil residual rate and increasing the heat conduction holes are the main means of heat dissipation.
To evaluate the heat dissipation capacity of the PCB, it is necessary to calculate the equivalent thermal conductivity (nine eq) of the composite material composed of various materials with different thermal conductivity coefficients—the insulating substrate for PCB.
3. The heat dissipation of the printed board in the equipment mainly depends on the air flow, so the air flow path should be studied during the design, and the device or the printed circuit board should be reasonably configured. When the air flows, it always tends to flow where the resistance is small, so when configuring devices on the printed circuit board, it is necessary to avoid leaving a large air space in a certain area. The configuration of multiple printed circuit boards in the whole machine should also pay attention to the same problem.
4. Avoid the concentration of hot spots on the PCB, distribute the power evenly on the PCB as much as possible, and keep the temperature performance of the PCB surface uniform and consistent. It is often difficult to achieve strict uniform distribution in the design process, but it is necessary to avoid areas with too high power density to avoid hot spots that affect the normal operation of the entire circuit. If conditions permit, thermal efficiency analysis of printed circuits is necessary. For example, thermal efficiency index analysis software modules added in some professional PCB design software can help designers optimize circuit design.
5. Arrange the device with the highest power consumption and the largest heat generation near the optimal heat dissipation position. Do not place devices with high heat generation at the corners and surrounding edges of the printed board unless heat dissipation devices are arranged near it. When designing the power resistor, choose a larger device as much as possible, and adjust the layout of the printed circuit board to make it have sufficient heat dissipation space.
6. High heat dissipation devices should minimize the thermal resistance between them when connected to the substrate. In order to better meet the thermal characteristics requirements, some thermal conductive materials (such as a layer of thermally conductive silica gel) can be used on the bottom surface of the chip, and maintain a certain contact area for the device to dissipate heat.