The heat dissipation hole is the method of using the channel through the PCB board (through the hole) to conduct heat to the back to dissipate heat. The heat dissipation hole should be configured directly below or as close as possible to the heating body.
Heat dissipation holes are used to improve the heat dissipation effect of surface mount components. In the structure, the PCB board is provided with a through hole, if it is a single-layer double-sided PCB board, the PCB board surface and the back of the copper foil connection, increase the area and volume for heat dissipation, that is, reduce the thermal resistance of the method. If it is a multi-layer PCB board, the surface between the layers can be connected or the layer connected by the limited part, etc., and the theme is the same.
In order to effectively use the heat dissipation hole, it is important to configure the heat dissipation hole near the heating body, such as directly below the component. As shown in the following figure, it can be seen that it is a good method to use the heat balance effect to connect the position with a large temperature difference.
The following is an example of heat sink layout and dimensions for HSOP-J8 package with rear heat sink exposed. In order to improve the thermal conductivity of the heat dissipation hole, it is recommended to use a small aperture with an inner diameter of about 0.3mm that can be filled with electroplating. It should be noted that if the aperture is too large, the solder creep problem may occur during the reflow process.
The space between the heat dissipation holes is about 1.2mm. The heat dissipation holes are installed directly below the heat dissipation fins on the back of the package. If just below the rear heat sink is not sufficient for heat dissipation, heat dissipation holes can also be configured around the IC. The point of configuration in this case is to configure as close to the IC as possible.
Knowledge to expand the PCB cooling design requirements
1. in the layout of components, should be in addition to the temperature detection device temperature sensitive devices placed near the position of the air inlet, and located in the power, heat of the upper reaches of the components, as far as possible away from the heat of the components, to avoid the impact of radiation, if can not be far away, you can also use a heat shield plate (polished metal sheet, the blackness of the smaller the better) separated.
2. the heat and heat resistant device is placed near the position or top of the outlet, but if it can not withstand higher temperatures, it should also be placed near the inlet, and pay attention to other heating devices and thermal devices as far as possible in the direction of air rise staggered position.
3. high-power components as far as possible scattered layout, to avoid heat concentration; Components of different sizes are arranged as evenly as possible, so that the wind resistance is evenly distributed and the air volume is evenly distributed.
4. the vent as far as possible to align with high heat dissipation requirements of the device.
5. the high device is placed behind the low device, and the long direction is arranged along the direction of the smallest wind resistance to prevent the air duct obstruction.
6. The radiator configuration should facilitate the circulation of heat exchange air in the cabinet. When heat is transferred by natural convection, the length direction of the fin is perpendicular to the ground. When heat is dissipated by forced air, it should be in the same direction as the air flow.
7. in the direction of air circulation, it is not appropriate to vertically arrange multiple radiators in close distance, because the upstream radiator will separate the air flow, the downstream radiator surface wind speed will be very low. Should be staggered, or the heat fin spacing is misaligned.
8. the radiator and other components on the same circuit board should have a suitable distance, calculated by thermal radiation, in order not to make it have inappropriate warming.
9. use PCB heat dissipation. If the heat is distributed through a large area of copper (consider opening a solder window), or the ground is connected through the hole to the plane layer of the PCB board, the whole PCB board is used to dissipate heat.
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