PCB circuit board cooling skills

Date：

2017-01-05

Source：

The heat generated by the electronic equipment work, so that the internal temperature of the equipment increased rapidly, if not the heat in time, the device will continue to heat up, the device will be due to overheating failure, the reliability of electronic equipment will decline. Therefore, it is very important to heat the circuit board.

First, the printed circuit board temperature rise factor analysis

The direct cause of the temperature rise of the printed circuit board is due to the existence of circuit power devices, electronic devices are varying degrees of power consumption, heat intensity changes with the size of power consumption.

Print plate in the temperature rise of the two kinds of phenomena:

(1) local temperature rise or large area temperature rise;

(2) short temperature or long temperature rise.

In the analysis of PCB thermal power, the general from the following aspects to analyze.

Electrical power

(1) to analyze the power consumption per unit area;

(2) Analyze the distribution of power consumption on the PCB board.

2. The structure of the printed circuit board

(1) the size of the printed circuit board;

(2) the material of the printed board.

3. How to install the printed circuit board

(1) installation (such as vertical installation, horizontal installation);

(2) the sealing situation and the distance from the shell.

Heat radiation

(1) the radiation coefficient of the surface of the printed circuit board;

(2) the temperature difference between the printed board and the adjacent surface and their absolute temperature;

5. Heat conduction

(1) install the radiator;

(2) conduction of other mounting structures.

6. Thermal 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 printed circuit board, often in a product and system of these factors are interrelated and dependent, most factors should be based on the actual situation to analyze, only for a specific The actual situation can be more accurately calculate or estimate the temperature rise and power consumption and other parameters.

Second, the circuit board cooling method

1. High fever device plus radiator, thermal plate

When a small number of devices in the PCB heat when the larger (less than 3), the heating device can be added radiator or heat pipe, when the temperature can not be down, you can use a fan with a fan to enhance the heat effect. When the amount of heat generating device is more (more than 3), a large heat sink (plate) can be used. It is a special heat sink customized by the location and height of the heating device on the PCB board or in a large flat plate radiator On the different elements out of the high and low position. The whole heat sink on the element surface, with each component in contact with the heat. But because of the high and low consistency of components installed welding, cooling effect is not good. Usually in the component surface plus soft thermal phase change thermal pad to improve the cooling effect.

2. Heat through the PCB itself

Currently widely used PCB sheet is copper / epoxy glass cloth substrate or phenolic resin glass cloth substrate, there are a small amount of paper-based CCL. Although these substrates have excellent electrical properties and processability, they are poor in heat dissipation and can hardly be expected to heat heat from the PCB itself, but from the surface of the component to the surrounding air. But with the electronic products have entered the miniaturization of components, high-density installation, high fever assembly era, if only the surface area is very small component surface to heat is not enough. At the same time due to QFP, BGA and other surface-mounted components of the large-scale use of components generated by the heat generated by a large number of PCB board, so the best way to solve the heat is to improve the direct contact with the heating element PCB self-cooling capacity, through the PCB Pass out or emit out.