10 Methods for PCB Heat Dissipation| 26 October, 2020
The heat generated by electronic equipment causes the internal temperature to rise rapidly. If the heat is not dissipated in time, the equipment will continue to heat up and the components will overheat and fail, resulting in a decrease in the reliability of electronic equipment. Therefore, PCB heat dissipation is a very important part. So how to design PCB heat dissipation?
1. Dissipate heat to the surrounding air through the surface of the PCB itself. However, with the miniaturization, high-density mounting, and high-heating assembly of electronic products, 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 massive use of surface mount components such as QFP and BGA, a large amount of heat generated by the components is transferred to the PCB. Therefore, the best way to solve the problem of heat dissipation is to improve the heat dissipation capacity of the PCB itself that is in direct contact with the heating element, and conduct it through the PCB board. Or send it out.
2. Install heat sinks and heat conduction plates for high heat generating devices. When there are a few components in the PCB, a heat sink or heat pipe can be added to the heating component. When the temperature cannot be lowered, a heat sink with a fan can be used to enhance the heat dissipation effect. The heat dissipation cover is integrally buckled on the surface of the element, and it is in contact with each element to dissipate heat. However, due to the poor heat dissipation effect during assembly and welding of components, a soft thermal phase change thermal pad is usually added on the surface of the components to improve the heat dissipation effect.
3. For equipment that adopts free convection air cooling, it is best to arrange integrated circuits (or other devices) vertically or horizontally.
4. Reasonable wiring design is used to realize heat dissipation. Because the resin in the plate has poor thermal conductivity, and the copper foil lines and holes are good heat conductors, increasing the remaining rate of copper foil and increasing the thermal 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 of a composite material composed of various materials with different thermal conductivity-an insulating substrate for PCB.
5. The devices on the same PCB should be arranged as far as possible according to their calorific value and heat dissipation degree. Devices with small calorific value 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 flow (at the entrance), the devices with large heat or 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, high-power devices are placed as close as possible to the edge of the PCB to shorten the heat transfer path; in the vertical direction, high-power devices are placed as close as possible to the top of the PCB to reduce the impact of these devices on the temperature of other devices. In the horizontal direction, high-power devices are placed as close as possible to the edge of the PCB to shorten the heat transfer path; in the vertical direction, high-power devices are placed as close as possible to the top of the PCB to reduce the impact of these devices on the temperature of other devices.
7. The heat dissipation of the PCB in the equipment mainly relies on air flow, so the air flow path should be studied during the design, and the device or PCB should be reasonably configured. When air flows, it always tends to flow in places with low resistance, so when configuring devices on a PCB, avoid leaving a large airspace in a certain area. The same problem should be paid attention to in the configuration of multiple PCB in the whole machine.
8. The temperature-sensitive device is best placed in the lowest temperature area (such as the bottom of the device). Never place it directly above the heating device. It is best to stagger multiple devices on the horizontal plane.
9. Place the devices with the highest power consumption and the highest heat generation near the best position for heat dissipation. Do not place high-heating devices on the corners and peripheral edges of the PCB, unless a heat sink is arranged near it. When designing the power resistor, choose a larger device as much as possible, and make it have enough space for heat dissipation when adjusting the layout of the PCB.
10. Avoid the concentration of hot spots on the PCB, distribute the power evenly on the PCB as much as possible, and keep the PCB surface temperature performance uniform and consistent. It is often difficult to achieve strict uniform distribution during the design process, but areas with too high power density must be avoided to prevent hot spots from affecting the normal operation of the entire circuit. If possible, it is necessary to analyze the thermal performance of the printed circuit. For example, the thermal performance index analysis software module added in some professional PCB design software can help designers optimize the circuit design.