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          How to heat the circuit board?

          2021-07-17 273

            1. After the heat dissipation of PCB board, the widely used PCB board is copper-clad / epoxy glass cloth or phenolic resin glass cloth, and a small amount of paper-based copper-clad board. Although these circuit board substrates have excellent electrical and processing functions, they have poor heat dissipation. As the heat dissipation way of high heating elements, they can hardly hope to transfer heat from the resin of PCB itself, but dissipate heat from the appearance of electronic components to the surrounding air.

            However, as electronic products have entered the era of miniaturization of components, high-density equipment and high heat generation, it is not enough to rely only on the appearance of very small components to dissipate heat. At the same time, due to the use of QFP, BGA and other external equipment components, a lot of heat generated by the components is transferred to the PCB board. Therefore, the way to deal with the heat dissipation is to advance the heat dissipation ability of the PCB itself, which is in direct contact with the heating elements, and transmit or emit it through the PCB board.

            2. On the selection of leisure convection air cooling equipment, is the integrated circuit (or other devices) according to the longitudinal method of placement, or according to the transverse method of placement.

            3. Because of the poor thermal conductivity of the resin in the circuit board, and the copper foil lines and holes are good conductors of heat, the first method of heat dissipation is to advance the copper foil residual rate and increase the heat conduction holes. To comment on the heat dissipation ability of PCB, it is necessary to calculate the equivalent thermal conductivity of the composite material composed of various materials with different thermal conductivity.

            4. When there are a small number of devices in PCB with large heating capacity (less than 3), heat sink or heat pipe can be added on the heating device. When the temperature can not be lowered, the radiator with electric fan can be selected to enhance the heat dissipation effect. When there are more heating elements (more than 3), you can choose a large radiator cover (board), which is customized according to the orientation and concave convex of the heating elements on the PCB board, or cut out different concave convex orientation of the elements on a large flat radiator. All the heat hoods are buckled on the surface of the components, and contact with each component to dissipate heat. However, due to the poor consistency of concave and convex in the assembly and welding of components, the heat dissipation effect is not good. Soft thermal phase change thermal pad is usually added on the surface of components to improve the heat dissipation effect.


            5. The devices on the same printed circuit board should be placed in different areas according to their calorific value and heat dissipation degree. The devices with small calorific value or poor heat resistance (such as small signal transistors, small-scale integrated circuits, electrolytic capacitors, etc.) should be placed above the cooling air flow (entrance). The devices with large calorific value or good heat resistance (such as power transistors, small-scale integrated circuits, electrolytic capacitors, etc.) should be placed above the cooling air flow (entrance) Large scale integrated circuits, etc.) are placed downstream of the cooling air stream.

            6. In the horizontal direction, the high-power devices are arranged close to the edge of the printed circuit board to shorten the heat transfer path; In the straight direction, the high-power devices are arranged close to the top of the printed circuit board as far as possible, so as to reduce the influence of these devices on the temperature of other devices.

            7. The heat dissipation of PCB in the equipment mainly depends on the air activity, so the air activity way should be studied in the planning, and the devices or PCB should be equipped reasonably. Air activities tend to be local activities with low resistance, so when the devices are equipped on the printed circuit board, large airspace should be avoided in a certain area. The same problem should also be paid attention to when equipping multiple printed circuit boards in the whole machine.

            8. The temperature sensitive devices should be arranged in the low temperature area (such as the bottom of the equipment). Do not place it directly above the heating device. Multiple devices are arranged in a horizontal plane.

            9. The devices with high power consumption and high heat dissipation are arranged near the location with good heat dissipation. Do not place the components with high heat on the corners and edges of the printed circuit board, unless there are heat dissipation devices nearby. In the planning of power resistance, the larger devices should be selected as much as possible, and the layout of printed circuit board should be adjusted to provide satisfactory heat dissipation space.

                The article comes from:http://www.marysbrideandformals.com


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