PCB Tech - 9 tips for PCB circuit board heat dissipation

The heat generated by the work of the circuit board causes the temperature inside the device to rise rapidly. If the heat is not released 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 deal with the heat dissipation of the circuit board.

Circuit board manufacturers

1. Analysis of temperature rise factors of printed circuit boards

The direct cause of PCB temperature rise is the existence of power dissipation devices.

The degree varies with the size of the power consumption.

Two phenomena of printed circuit board temperature rise:

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

(2) The temperature rises for a short time or for a long time.

In the analysis of PCB thermal power consumption, it is generally analyzed from the following aspects.

1. Electrical power consumption

(1) Analyze the power consumption per unit area;

(2) Analyze the power distribution on the printed circuit 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) The sealing condition and the distance from the casing.

4. Thermal radiation

(1) The emissivity of the printed board surface;

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

5. Heat conduction

(1) Install the radiator;

(2) Transmission of other installation 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 board. These factors are often mutually exclusive in a product and system.

Related and dependent, most of the factors should be analyzed according to the actual situation, only for a specific actual situation can be more correct

Calculate or estimate parameters such as temperature rise and power consumption.

2. Circuit board heat dissipation method

1. High-heat equipment, radiators and heat conducting plates

When several devices in the PCB have a large heating value (less than 3), when the temperature has not yet reached, a radiator or a heat pipe can be added to the heating device.

When it can be lowered, a radiator with a fan can be used to enhance the heat dissipation effect. It can be used when the amount of heating device is large (greater than 3).

A large heat sink (board), which is a special heat sink customized according to the position and height of the heating device on the PCB or on a large flat plate

Cut out different component height positions on the radiator. The radiator cover is integrally fixed on the surface of the components and contacts each component to dissipate heat. But due to the yuan

When the device is installed and welded, the high and low consistency is poor, and the heat dissipation effect is not good. In order to improve the heat dissipation efficiency of the component, a soft thermal phase change thermal pad is usually installed on the surface of the component.

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2. The PCB board itself dissipates heat

At present, the widely used printed circuit boards are copper clad/epoxy glass cloth or phenolic resin glass cloth, and a small amount of paper-based copper clad laminates are also used.

material. 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, almost

You cannot 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. But as electronic products have entered

In the era of miniaturization, high-density mounting, and high-heating assembly, it is not enough to dissipate heat only on the surface of a small component.

At the same time, due to the widespread use of surface mount components such as QFP and BGA, a large amount of heat generated by the components is transferred to the PCB board, which provides a solution.

The best way to dissipate heat is to increase the heat dissipation capacity of the PCB that is in direct contact with the heating element, and transmit or emit through the PCB board.

3. Reasonable linear design for heat dissipation

Due to the poor thermal conductivity of the resin in the sheet material, copper foil wires and copper foil holes are good heat conductors, increasing the residual rate of the copper foil, and increasing the heat conduction holes is the key to heat dissipation.

The main means.

In order to evaluate the heat dissipation performance of the printed circuit board, it is necessary to evaluate the equivalent electrical conductivity of the insulating substrate of the printed circuit board. This composite material is composed of materials with different thermal conductivity.

4. For equipment that adopts free convection air cooling, it is best to set the integrated circuit (or other device) to the longitudinal length or the transverse length.

5. The components on the same printed circuit board should be arranged as much as possible according to their heat generation and degree of heat dissipation, so that the heat generation is small or the heat resistance is poor.

6. In the horizontal direction, the high-power device is as close as possible to the edge of the printed circuit board in order to shorten the heat transfer path; in the vertical direction, the high-power device

These devices are as close as possible to the top of the printed circuit board to reduce the influence of these devices on the temperature of other devices.

7. Temperature sensitive equipment is best placed in the lowest temperature area (such as the bottom of the equipment). Do not put it in a heating device.

8. The heat dissipation of the printed circuit board mainly depends on the airflow, so the airflow path should be studied in the design, and the device or the printed circuit board should be reasonably configured.

Circuit board. When air flows, it always tends to flow in places with low resistance, so when configuring equipment on a printed circuit board, avoid it in a certain area.

9. Avoid hot spots concentrated on the PCB, distribute power on the PCB as evenly as possible, and maintain the uniformity of the PCB surface temperature performance.

10. Place the equipment with the highest power consumption and highest heat output near the best heat dissipation location. Do not place the heating device at the corner of the printed circuit board.