PCB circuit board how to design heat

For electronic equipment, the work will produce a certain amount of heat, so that the internal temperature of the device increased rapidly, if not the heat will be released in time, the device will continue to heat up, the device will be due to overheating and failure , The reliability of electronic equipment will decline. Therefore, the circuit board for a good heat treatment is very important. PCB circuit board cooling is a very important part, then what is the PCB circuit board cooling skills, the following we discuss together.

1、through the PCB board itself is widely used in the current PCB board 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.

2、high fever devices with heat sink, thermal conductivity board When a small number of devices in the PCB heat when the larger (less than 3), the heating device can be added to the radiator or heat pipe, when the temperature can not come down, Can be used with a fan of the radiator to enhance the cooling 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.

3、for the use of free convection air cooling equipment, it is best to integrated circuits (or other devices) arranged in a vertical way, or arranged in a horizontal manner.

4、the use of reasonable alignment design to achieve heat dissipation due to poor thermal conductivity of the plate, and copper wire and the hole is a good heat conductor, so to improve the copper foil residual rate and increase the thermal hole is the main means of heat. In order to evaluate the heat dissipation capacity of the PCB, it is necessary to calculate the equivalent thermal conductivity (Nine eq) of the composite substrate consisting of various materials with different thermal conductivity.

5、the same piece of printed circuit board devices should be as far as possible the size of their heat and heat degree of partition arrangement, heat or heat resistance of poor devices (such as small signal transistors, small scale integrated circuits, electrolytic capacitors, etc.) on The most upstream (inlet) of the cooling air stream, heat-generating or heat-resistant devices (such as power transistors, large scale integrated circuits, etc.) are placed at the most downstream of the cooling airflow.

6、in the horizontal direction, high-power devices as close as possible to the edge of the printed circuit board layout in order to shorten the heat transfer path; in the vertical direction, high-power devices as close as possible to the top of the printed circuit board in order to reduce these devices work on other device temperature Impact.

7、the equipment within the printed circuit board heat mainly rely on air flow, so in the design to study the air flow path, a reasonable configuration device or printed circuit board. Air flow always tends to flow where the resistance is small, so when configuring the device on a printed circuit board, avoid having a larger airspace in a certain area. Machine in the multi-block printed circuit board configuration should also pay attention to the same problem.

8、the temperature sensitive devices are best placed in the lowest temperature areas (such as the bottom of the device), do not put it directly above the heating device, multiple devices are best in the horizontal plane staggered layout.

9、the highest power consumption and heat the largest device arranged in the vicinity of the best heat dissipation. Do not place higher heaters on the corners of the printed circuit board and the surrounding edges unless a heat sink is arranged near it. In the design of power resistors as much as possible to choose a large number of devices, and adjust the layout of the printed circuit board to have enough room for cooling.

10、to avoid the concentration of hot spots on the PCB, as far as possible the power evenly distributed in the PCB board to maintain the PCB surface temperature performance uniformity and consistency. Often in the design process to achieve a strict uniform distribution is more difficult, but must avoid the power density is too high in the area, so as to avoid overheating the normal operation of the entire circuit. If conditions permit, the thermal performance analysis of the printed circuit is necessary, such as some of the professional PCB design software to increase the thermal performance index analysis software module, you can help designers optimize the circuit design.