PCB News - The principle of heat dissipation on the surface of the circuit board

Circuit boards are mainly used on electronic components and have a strong conductivefunction. Due to long-term conduction, it will inevitably generate high heat, especially for some electronic products with relatively large power. How can it be better at this time? The heat dissipation is a more important knowledge point. Here are some things I need to know about circuit boardheat dissipation:

1. High heat-generating device plus radiator and heat conduction plate
   When a small number of components in the PCBgenerate a large amount of heat (less than 3), a heat sink or heat pipe can be added to the heating device. When the temperature cannot be lowered, a heat sink with a fan can be used to enhance heat dissipation Effect. When the number of heating devices is large (more than 3), a large heat sink (board) can be used, which is a special radiator customized according to the position and height of the heating device on the circuit board or a large flat radiator Cut out different component height positions. The heat dissipation cover is integrally buckled on the surface of the component, and it is in contact with each component to dissipate heat. However, theheat dissipation effect is not good due to the poor consistency of height during assembly and welding of components. Usually, a soft thermal phase change thermal pad is added on the surface of the component to improve theheat dissipation effect.

2. Heat dissipation through the PCB board itself
The currently widely used circuit boards are copper clad/epoxy glass cloth substrates or phenolic resin glass cloth substrates, and a small amount of paper-based copper clad boards are used. Although these substrates have excellent electrical properties and processing properties, they have poor heat dissipation. As a heat dissipation path for high-heating components, it is almost impossible to expect heat from the resin of the PCB itself to conduct heat, 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 mounting, and high-heating assembly, it is not enough to rely on the surface of a component 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 transferred to the PCB board. Therefore, the best way to solve the problem of heat dissipation is to improve the heat dissipation capacity of the PCB itself, which is in direct contact with the heating element, through the PCB board. To be transmitted or emitted.

3. Use reasonable wiring design to realize heat dissipation
Because the resin in the sheet 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 a PCB, it is necessary to calculate the equivalent thermal conductivity (nine eq) of a composite material composed of various materials with different thermal conductivity-an insulating substrate for PCB.

4. For equipment that adopts free convection air cooling, it is best to arrange the integrated circuits (or other devices) vertically or horizontally.

5. The devices on the same printed board should be arranged as far as possible according to their calorific value and degree of heat dissipation. Devices with small calorific value or poor heat resistance (such as small signal transistors, small-scale integrated circuits, electrolytic capacitors, etc.) should be placed The uppermost flow of the cooling airflow (at the entrance), and the devices with large heat generation or goodheat resistance ( such as power transistors, large-scaleintegrated circuits, etc.) are placed at the lowermost part of the cooling airflow.

6. In the horizontal direction, high-power devices are arranged as close to the edge of the printed board as possible to shorten the heat transfer path; in the vertical direction, high-power devices are arranged as close as possible to the top of the printed board to reduce the temperature of other devices when these devices work. Impact.

7. Devices that are more sensitive to temperature are best placed in the lowest temperature area (such as the bottom of the device). Do not place it directly above the heating device. It is best to stagger multiple devices on the horizontal plane.

The above is the principle of heat dissipation on the surface of the circuit board. ipcb also provides PCB manufacturing and printing,PCB board design technology, etc.