What are the PCB heat dissipation methods?
For electronic equipment, a certain amount of heat is generated during operation, so that the internal temperature of the equipment rises rapidly. If the heat is not dissipated in time, the equipment will continue to heat up, and the device will fail due to overheating. The reliability of the electronic equipment Performance will decrease.
Therefore, it is very important to conduct a good heat dissipation treatment on the circuit board. The heat dissipation of the PCB circuit board is a very important link, so what is the heat dissipation technique of the printed circuit board.
The heat is dissipated through the PCB board itself. At present, the widely used PCB boards are copper clad, epoxy glass cloth substrate, phenolic resin glass cloth substrate, and a small amount of paper-based copper clad board. 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-mounted 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, and conduct or emit through the PCB board.
High heat-generating components plus radiators and heat-conducting plates. When a few components in the PCB generate a large amount of heat (less than 3), a radiator or heat pipe can be added to the heat-generating components. When the temperature cannot be lowered, a radiator with a fan can be used to enhance the heat dissipation effect.
When the number of heating devices is large (more than 3), a large heat dissipation cover (board) can be used, which is a special heat sink customized according to the position and height of the heating device on the PCB. Or cut out different component height positions on a large flat radiator. 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, the heat 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 the heat dissipation effect.
For equipment that adopts free convection air cooling, it is best to arrange integrated circuits (or other devices) vertically or horizontally.
Use reasonable wiring design to realize heat dissipation. Because the resin in the plate has poor thermal conductivity, and the copper foil lines and holes are good conductors of heat, increasing the residual rate of the copper foil and increasing the heat conduction holes are the main means of heat dissipation.
The components on the same printed circuit board should be arranged as far as possible according to their calorific value and degree of heat dissipation. Devices with low calorific value or poor heat resistance (such as small signal transistors, small-scale integrated circuits, electrolytic capacitors, etc.) are placed at the top of the cooling airflow (entry); devices with large calories or good heat resistance (such as power transistors) , Large-scale integrated circuits, etc.) placed at the most downstream of the cooling air flow.
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 placed as close as possible to the top of the printed circuit board to reduce the impact of these devices on the temperature of other devices when they work.
The heat dissipation of the printed board in the equipment mainly relies on air flow, so the air flow path should be studied during the design, and the device or printed circuit board should be reasonably configured.
When air flows, it always tends to flow in places with low resistance, so when configuring devices on a printed circuit board, avoid leaving a large airspace in a certain area. The configuration of multiple printed circuit boards in the whole machine should also pay attention to the same problem.
Temperature-sensitive devices 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 arrange multiple devices in a staggered horizontal plane.
Place the devices with the highest power consumption and heat generation near the best position for heat dissipation. Do not place high-heating devices on the corners and peripheral edges of the printed board, 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 printed board.
Avoid the concentration of hot spots on the PCB, distribute the power evenly on the PCB board 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 efficiency of the printed circuit. For example, the thermal efficiency index analysis software module added in some professional Rigid flex PCB design software can help designers optimize the circuit design.