PCB circuit board cooling tips
PCB circuit board cooling tips. Edit Date:2006.4.8
The heat generated during the operation of electronic equipment, so that the internal temperature of the device quickly rise, if the heat is not distributed in time, the device will continue to heat up, the device will fail due to overheating, the reliability of electronic equipment will decline. Therefore, it is very important to dispose the circuit board.
I. Analysis of Temperature Rise of Printed Circuit Boards
The direct cause of PCB temperature rise is due to the existence of circuit power devices, electronic devices have varying degrees of power consumption, heat intensity varies with the size of power consumption.
Two phenomena of temperature rise in printed board:
(1) local temperature rise or large area temperature rise;
(2) Short-term temperature rise or long-term temperature rise.
In the analysis of PCB thermal power consumption, the general analysis from the following aspects.
Electric power consumption
(1) Analyze power consumption per unit area;
(2) Analyze the distribution of power consumption on the PCB board.
2. The structure of the printed board
(1) The size of the printed board;
(2) The material of the printed board.
3. How to install the printed board
(1) Installation method (such as vertical installation, horizontal installation);
(2) Sealing conditions and distance from the casing.
4. Thermal radiation
(1) The emissivity of the printed board surface;
(2) The temperature difference between the printed board and the adjacent surface and their absolute temperature;
5. Heat conduction
(1) Install a radiator;
(2) Conduction of other mounting structures.
6. Heat convection
(1) natural convection;
(2) Forced cooling convection.
The analysis of the above factors from the PCB is an effective way to solve the temperature rise of the PCB. Often these factors are related and dependent on one product and system. Most of the factors should be analyzed according to the actual situation, only for a specific The actual situation can be calculated or estimated more correctly temperature rise and power consumption and other parameters.
Second, the circuit board cooling method
1. High heat-generating device plus heat sink and heat conducting plate
When a small number of devices in the PCB generate a large amount of heat (less than 3), a heat sink or a heat pipe can be added to the heat-generating device. When the temperature cannot be lowered, a fan-equipped heat sink can be used to enhance heat dissipation. effect. When there are a large number of heat generating devices (more than 3), a large heat dissipation cover (board) can be used, which is a dedicated heat sink customized according to the position and height of the heat generating device on the PCB or a large flat heat sink. Pull up different component heights. The entire heat dissipation cover is fastened on the surface of the component and comes into contact with each component to dissipate heat. However, due to the low level of consistency in component mounting and welding, the heat dissipation effect is not good. Soft thermal phase change thermal pads are usually added on the component surface to improve heat dissipation.
2. Heat dissipation through the PCB itself
Currently widely used PCB materials 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 and processing properties, they have poor heat dissipation. As a heat dissipation path for high-heating components, it is almost impossible to expect that the heat is transferred from the surface of the component to the surrounding air by the resin itself. However, as electronic products have entered the era of component miniaturization, 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 mount components such as QFP and BGA, the heat generated by the components is transmitted to the PCB in large quantities. Therefore, the best way to solve the problem of heat dissipation is to improve the heat dissipation capability of the PCB itself that is in direct contact with the heat-generating components. Conducted or emitted.