PCB manufacturing circuit board heat dissipation method introduction
1. High thermal generating device with heat sink and heat conducting board
If 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. If the temperature cannot be lowered during pcb manufacturing, a heat sink with a fan can be used to enhance heat dissipation effect. When the amount of heat-generating devices is more (over 3), a large heat-dissipating cover (plate) can be used, which is a dedicated heat sink customized according to the position and height of the heat-generating device on the PCB or large flat-plate heat sink. The upper and lower parts of the different components are placed during pcb manufacturing. The heat shield is integrally fixed to the component surface, and is in contact with each component to dissipate heat. However, due to the poor consistency of components during soldering, the heat dissipation effect is poor. A soft phase change thermal pad is usually added to the component surface to improve heat dissipation during pcb manufacturing.
2.Cooling through the PCB board itself
Currently widely used PCB substrate 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 and processing properties, they have poor heat dissipation. As 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 during pcb manufacturing. However,because electronic products have entered miniaturization era, high-density mounting, and high-heat 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-scale use of surface mount components such as QFP and BGA, the heat generated by the components is transmitted to the PCB in a large amount. Therefore, the heat dissipation method is to improve the heat dissipation capability of the PCB itself in direct contact with the heat generating component, and conduct it through the PCB board or Dissipated during pcb manufacturing.
3.Usinga reasonablelayout design to achieve heat dissipation
Since the resin in the substrate has poor thermal conductivity, and the copper foil line and the hole are good heat conductors, increasing the copper foil residual ratio and the heat conductivity hole are the main means of heat dissipation during pcb manufacturing.
To evaluate the heat dissipation capability of a PCB, it is necessary to calculate the equivalent thermal conductivity of a composite material composed of various materials which have different thermal conductivity coefficients during pcb manufacturing.
4.For devices that use free convection air cooling, arrange the integrated circuits (or other devices) in a vertically long manner or in a horizontally long manner.
5.Devices on the same printed board should be placed as far as possible according to their heat generation and heat dissipation. Devices with low heat or poor heat resistance (such as small signal transistors, small scale integrated circuits, electrolytic capacitors, etc.) should be placedat theuppermost flow (at the inlet) of the cooling airflow, the device that generates a large amount of heat or heat (such as a power transistor, a large-scale integrated circuit, etc.) is placed at the most downstream of the cooling airflow during pcb manufacturing.
6.In the horizontal direction, the large-power devices are placed as close as possible to the edges of the printed board to shorten the heat transfer path; in the vertical direction, high-power devices are placed close to the top of the printed boardas far as possibleto reduce the temperature of other devices while operation.
7.Temperature-sensitive devices should be placed in the lowest temperature area (such as the bottom of the device). Do not place it above the heat-generating devicedirectly. Multiple devices are staggered on a horizontal planeduring pcb manufacturing.
8.The heat dissipation of the printed circuit board in the device mainly depends on the air flow, so the air flow path should be studied during the design, and the device or printed circuit board should be properly configured. When the air flows, it tends to flow in the direction of smallresistance. Therefore, when configuring the device on the printed circuit board, avoid leaving a large air space in a certain area. The same problem should be noted in the configuration of multiple printed circuit boards in the whole machineduring pcb manufacturing.
9.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 a strict uniform distribution during the design process, but it is necessary to avoid areas where the power density is too high, so as to avoid the hot spots affecting the normal operation of the entire circuit. If it’s permitted, it is necessary to perform thermal performance analysis of printed circuits. For example, the thermal performance index analysis software modules are added in some professional PCB design software can help designers optimize circuit designduring pcb manufacturing.
10. Place the highest power and heat generating components near the heat sink location. Do not place a device with a higher heat on the corners and peripheral edges of the printed board unless a heat sink is placed near it. Choosinga larger device as much as possiblewhen designing the power resistor, and leaving enough space for heat dissipation while adjusting the layout of the printed board during pcb manufacturing.
11.For high heat dissipation devices should minimize the thermal resistance between them when they are connected to the substrate. In order to better meet the thermal characteristics requirements, some thermal conductive materials (such as a layer of thermal silica gel) can be used on the bottom surface of the chip, and a certain contact area is maintained for the device to dissipate heatduring pcb manufacturing.
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