PCB News - PCB circuit board heat dissipation

PCB circuit board heat dissipation

When electronic equipment is working, the heat generated 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, the device will fail due to overheating, and the reliability of the electronic equipment will decrease. Therefore, it is very important to conduct heat dissipation treatment on the PCB board of the PCB circuit board manufacturer.

1. Analysis of temperature rise factors of printed circuit boards
The direct cause of the temperature rise of the PCB board is due to the existence of the circuit power consumption devices, and the electronic devices all have power consumption to varying degrees, and the heating intensity varies with the size of the power consumption.
Two phenomena of temperature rise in printed circuit boards:
(1) Local temperature rise or large area temperature rise;
(2) Short-term temperature rise or long-term temperature rise.
When analyzing the thermal power consumption of the PCB, it is generally analyzed from the following aspects.

1. Electrical power consumption
(1) Analyze the power consumption per unit area;
(2) Analyze the distribution of power consumption on the PCB.
2. The structure of the printed circuit board
(1) The size of the printed circuit board;
(2) Materials for printed circuit boards.
3. Installation method of printed circuit board
(1) Installation method (such as vertical installation, horizontal installation);
(2) The sealing condition and the distance from the casing.
4. Heat conduction
(1) Install the radiator;
(2) Conduction of other installation structural parts.
5. Thermal radiation
(1) The radiation coefficient on the surface of the printed circuit board;
(2) The temperature difference between the printed circuit board and adjacent surfaces and their absolute temperature;
6. Thermal convection
(1) Natural convection;
(2) Forced cooling convection.
The analysis of the above factors from the PCB circuit board proofing manufacturers is an effective way to solve the temperature rise of the printed board. These factors are often related and dependent on each other in a product and system. Most of the factors should be analyzed according to the actual situation. According to a specific actual situation, parameters such as temperature rise and power consumption can be more accurately calculated or estimated.

2. Circuit board heat dissipation method
1. High heat-generating device plus radiator and heat conduction plate
When a small number of components in the PCB circuit board 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), large
The heat dissipation cover (board), which is a special radiator customized according to the position and height of the heating device on the PCB, or different component height positions are cut out on a large flat radiator. The heat dissipation cover is integrally buckled on the surface of the component, and it is in contact with each component to dissipate heat. But because of the components
The consistency of height during welding is poor, and 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.
2. Use reasonable wiring design to realize heat dissipation
Because the resin in the plate has poor thermal conductivity, and the copper foil lines and holes are good conductors of heat, increasing the residual rate of the copper foil and increasing the heat conduction holes are the main means of heat dissipation.
To evaluate the heat dissipation capacity of the PCB circuit board, it is necessary to calculate the equivalent thermal conductivity (nine eq) of the composite material composed of various materials with different thermal conductivity-the insulating substrate for the PCB circuit board.

3. Heat dissipation through the PCB circuit board itself
At present, the widely used PCB circuit boards are copper clad/epoxy glass cloth substrates or phenolic resin glass cloth substrates, and a small amount of paper-based copper clad plates are used. Although these substrates have excellent electrical properties and processing properties, they have poor heat dissipation. As a way to dissipate heat for high heating elements,
It is almost impossible to expect 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 miniaturization of components, high-density mounting, and high-heating assembly, it is not enough to rely on the surface of the component with a very small surface area to dissipate heat.
of. 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 transferred to the PCB circuit board in a large amount. Therefore, the best way to solve the heat dissipation is to improve the heat dissipation capacity of the PCB itself that is in direct contact with the heating element. The board conducts or radiates.
4. Arrange the devices with the highest power consumption and 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 power resistors, choose larger devices as much as possible, and
When adjusting the printed board layout, make it have enough space for heat dissipation.
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 small calorific value or poor heat resistance (such as small signal transistors, small-scale integrated circuits, electrolytic capacitors, etc.) should be placed The uppermost flow (at the entrance) of the cooling airflow, which generates a large amount of heat or
Devices with good heat resistance (such as power transistors, large-scale integrated circuits, etc.) are placed at the most downstream of the cooling airflow.
6. The temperature-sensitive device is best placed in the lowest temperature area (such as the bottom of the device). Never place it directly above the heating device. It is best to stagger multiple devices on the horizontal plane.

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