How to Dissipate Heat from Printed Circuit Boards?

We all know that the heat generated by electronic equipment during operation causes the internal temperature of the equipment to rise rapidly. If the heat is not dissipated in time, the equipment will continue to heat up, the device will fail due to overheating, and the reliability of the electronic equipment will decrease. Therefore, it is very important to dissipate heat from the circuit board.

The direct cause of the temperature rise of the printed circuit board is due to the existence of power consumption devices in the circuit, and the electronic devices all have power consumption to varying degrees, and the heating intensity varies with the size of the power consumption. PCB Quick shared the following heat dissipation methods for printed circuit boards, hoping to help everyone.

 

1. High heat-generating components plus radiator and heat-conducting plate

When a small number of components in the PCB generate a large amount of heat (less than 3), a radiator or heat pipe can be added to the heating component. 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 a large flat heat sink Cut out different component height positions.

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 to the component surface to improve the heat dissipation effect.

2. Heat dissipation through the PCB board itself

At present, the widely used PCB boards are copper-clad/epoxy glass cloth substrates or phenolic resin glass cloth substrates, as well as a small amount of paper-based copper-clad boards. 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.

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, the heat generated by the components is transferred to the PCB board in a large amount. Therefore, the best way to solve the problem of heat dissipation is to increase the heat dissipation capacity of the PCB itself, which is in direct contact with the heating element and dissipate it by itself through the PCB board.

3. Use reasonable wiring design to achieve heat dissipation

Because of the poor thermal conductivity of the resin in the board, and the copper foil lines and holes are good conductors of heat, PCB Quick believes that increasing the remaining rate of copper foil and increasing the thermal holes are the main means of heat dissipation.

To evaluate the heat dissipation capacity of a PCB, it is necessary to calculate the equivalent thermal conductivity of a composite material composed of various materials with a different thermal conductivity-an insulating substrate for PCB.

 

4. For equipment that adopts free convection air cooling, it is best to arrange integrated circuits (or other devices) vertically or horizontally.

5. The devices on the same printed 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.) should be placed The uppermost flow of the cooling airflow (at the entrance), and the devices with large heat generation or good heat resistance (such as power transistors, large-scale integrated circuits, etc.) are placed at the lowermost part of the cooling airflow.

 

6. In the horizontal direction, high-power devices are placed 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 to the top of the printed board as possible to reduce the temperature of other devices when these devices are working. Impact.

7. Devices that are more sensitive to temperature 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 stagger multiple devices on the horizontal plane.

8. The heat dissipation of the printed board in the equipment mainly relies on airflow, so the airflow 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 the printed circuit board, avoid leaving 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.

 

9. Avoid the concentration of hot spots on the PCB, distribute the powder 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 performance of the printed circuit. For example, the thermal performance index analysis software module added in some professional PCB design software can help designers optimize the circuit design.

10. Place the devices with the highest power consumption and the highest 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.

11. When connecting high heat dissipation devices to the substrate, the thermal resistance between them should be reduced as much as possible. In order to better meet the requirements of the thermal characteristics, some thermal conductive materials (such as a layer of thermally conductive silica gel) can be used on the bottom surface of the chip, and a certain contact area is maintained for the device to dissipate heat.

 

12. The connection between the device and the substrate:

 

(1) Try to shorten the lead length of the device;

(2) When selecting high-power devices, the thermal conductivity of the lead material should be considered, and the largest cross-section of the lead should be selected as far as possible;

(3) Choose a device with more pins.

13. Package selection of device:

(1) When considering thermal design, pay attention to the package description of the device and its thermal conductivity;

(2) Consider providing a good heat conduction path between the substrate and the device package;

(3) Air partitions should be avoided in the heat conduction path. If this is the case, heat-conducting materials can be used for filling.

If you want to learn more about printed circuit boards after reading the above, you can get a comprehensive solution by contacting us.

As a professional PCB product manufacturer, PCB QUICK can not only provide users with diversified choices but also formulate effective solutions. In order to control the quality of the products, we are equipped with a professional quality inspection system and a comprehensive management team, which can control the quality of the products in an all-round way. If you want to buy our products, please contact us immediately!