1. High heat generating device with heat sink and heat conducting plate
When there are a few devices in the PCB that generate a large amount of heat (less than 3), a heat sink or a heat pipe can be added to the heat generating device. When the temperature cannot be lowered, a heat sink with a fan can be used to enhance heat dissipation. effect. When the amount of heat generating devices is large (more than 3), a large heat sink (board) can be used, which is a dedicated heat sink customized according to the position and height of the heat generating device on the PCB board or a large flat plate radiator. The upper and lower parts of the different components are placed. The heat shield is integrally fastened to the component surface, and is in contact with each component to dissipate heat. However, due to the poor consistency of the components during welding, the heat dissipation effect is not good. A soft thermal phase change thermal pad is usually added to the component surface to improve heat dissipation.
2. Cooling through the PCB board itself
Currently widely used PCB sheets are copper-clad/epoxy glass cloth substrates or phenolic resin glass cloth substrates, and a small amount of paper-based copper-clad sheets are used. Although these substrates have excellent electrical properties and processing properties, they have poor heat dissipation properties. As a heat dissipation path for high-heat-generating components, it is hardly expected to conduct heat from the resin of the PCB itself, but to dissipate heat from the surface of the component to the surrounding air. However, as electronic products have entered the era of miniaturization, high-density mounting, and high-heating assembly, it is not enough to dissipate heat from the surface of a component with a very small surface area. At the same time, due to the large number of surface mount components such as QFP and BGA, the heat generated by the components is transferred to the PCB in a large amount. Therefore, the best way to solve the heat dissipation is to improve the heat dissipation capability of the PCB itself in direct contact with the heat generating components. Conducted out or emitted.
3. Use a reasonable wiring design to achieve heat dissipation
Since the resin in the sheet has poor thermal conductivity, and the copper foil line and the hole are good conductors of heat, increasing the copper foil residual ratio and increasing the heat conducting hole are the main means of heat dissipation.
To evaluate the heat dissipation capability of the PCB, it is necessary to calculate the equivalent thermal conductivity (nine eq) of the composite material composed of various materials having different thermal conductivity.
4. For devices that use free convection air cooling, it is best to arrange the integrated circuits (or other devices) in a vertically long manner or in a horizontally long manner.
5. Devices on the same PCB should be arranged as far as possible according to their heat generation and heat dissipation. Devices with low heat generation or poor heat resistance (such as small signal transistors, small scale integrated circuits, electrolytic capacitors, etc.) should be placed in the cooling airflow. The uppermost (inlet), heat-generating or heat-resistant devices (such as power transistors, large-scale integrated circuits, etc.) are placed at the most downstream of the cooling airflow.