10 Simple and Practical Methods for PCB Heat Dissipation

Have you ever worried about the heat dissipation of the PCB due to the excessive load of the equipment?
For electronic equipment, a certain amount of heat will be generated during work, which will cause the internal temperature of the equipment to rise 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 electronic equipment Performance will drop.
Therefore, it is very important to conduct a good heat dissipation treatment on the circuit board. The heat dissipation of PCB circuit board is a very important link, so what are the heat dissipation skills of PCB circuit board, let's discuss together below.

01
Heat dissipation through the PCB board itself is currently widely used as a copper-clad/epoxy glass cloth substrate or a phenolic resin glass cloth substrate, and a small amount of paper-based copper-clad board is used.
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 the heat to be conducted by the resin of the PCB itself, but to dissipate heat from the surface of the component to the surrounding air.
However, as electronic products have entered the era of component miniaturization, high-density installation, and high-heating assembly, it is not enough to rely solely on the surface of components with a very small surface area to dissipate heat.
At the same time, due to the extensive use of surface mount components such as QFP and BGA, a large amount of heat generated by the components is transmitted to the PCB board. To transmit or radiate.

PCB layout
Thermally sensitive devices are placed in a cool air area.
The temperature detection device is placed in the hottest position.

The devices on the same printed board should be arranged according to their calorific value and heat dissipation degree as much as possible. 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 high heat generation or good heat resistance (such as power transistors, large-scale integrated circuits, etc.) are placed at the most downstream of the cooling airflow.

In the horizontal direction, the 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, the high-power devices are arranged as close as possible to the top of the printed board in order to reduce the influence of these devices on the temperature of other devices.

The heat dissipation of printed boards in the equipment mainly depends on air flow, so the air flow path should be studied during design, and the components or printed circuit boards should be reasonably configured.

When the air flows, it always tends to flow where the resistance is small, so when configuring devices on the 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.

Devices that are sensitive to temperature are best placed in the lowest temperature area (such as the bottom of the device). Never place it directly above the heat-generating device. It is best to arrange multiple devices staggered on the horizontal plane.

Place the components that dissipate the most power and generate the most heat near the best locations for heat dissipation. Do not place devices with high heat generation on the corners and edges of the printed board unless there is a heat sink near it.

When designing the power resistor, choose a larger device as much as possible, and make it have enough heat dissipation space when adjusting the layout of the printed board.

02
Add radiators and heat conduction plates to high-heating devices. When there are a few devices in the PCB that generate large amounts of heat (less than 3), you can add radiators or heat pipes to the heating devices. When the temperature cannot drop, you can use Radiator with fan for enhanced heat dissipation.

When there are many heating components (more than 3), a large heat dissipation cover (board) can be used, which is a special radiator customized according to the position and height of the heating components on the PCB or a large flat radiator Cut out the height and position of different components. Buckle the cooling cover on the component surface as a whole, and contact each component to dissipate heat.

However, due to the poor consistency of the components when they are assembled and soldered, the heat dissipation effect is not good. Usually, a soft thermal phase change thermal pad is added on the surface of the component to improve the heat dissipation effect.

03
For equipment cooled by free convection air, it is best to arrange the integrated circuits (or other devices) either vertically or horizontally.

04
Use reasonable wiring design to realize heat dissipation. Because the resin in the board has poor thermal conductivity, and copper foil lines and holes are good conductors of heat, increasing the remaining copper foil and increasing heat conduction holes are the main means of heat dissipation. To evaluate the heat dissipation capability of PCB, it is necessary to calculate the equivalent thermal conductivity (nine eq) of the insulating substrate for PCB, which is a composite material composed of various materials with different thermal conductivity.

05
The devices on the same printed board should be arranged according to their calorific value and heat dissipation degree as much as possible. 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 most upstream (at the entrance), the devices with high heat generation or good heat resistance (such as power transistors, large-scale integrated circuits, etc.) are placed at the most downstream of the cooling airflow.

06
In the horizontal direction, the high-power devices are arranged as close as possible to the edge of the printed board in order to shorten the heat transfer path; in the vertical direction, the high-power devices are arranged as close as possible to the top of the printed board in order to reduce the influence of these devices on the temperature of other devices. .

07
The heat dissipation of printed boards in the equipment mainly depends on air flow, so the air flow path should be studied during design, and the components or printed circuit boards should be reasonably configured. When the air flows, it always tends to flow where the resistance is small, so when configuring devices on the 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.

08
Devices that are sensitive to temperature are best placed in the area with the lowest temperature (such as the bottom of the device). Never place it directly above the heat-generating device. It is best to arrange multiple devices staggered on the horizontal plane.

09
Place the components that dissipate the most power and generate the most heat near the best locations for heat dissipation. Do not place devices with high heat generation on the corners and edges of the printed board unless there is a heat sink near it. When designing the power resistor, choose a larger device as much as possible, and make it have enough heat dissipation space when adjusting the layout of the printed board.

10
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 strict uniform distribution during the design process, but it is necessary to avoid areas with too high power density to avoid hot spots that affect the normal operation of the entire circuit.

If conditions permit, it is necessary to conduct thermal performance analysis of printed circuits. For example, the thermal performance index analysis software module added to some professional PCB design software can help designers optimize circuit design.