Làm thế nào để bảng mạch PCB cải thiện hiệu quả tản nhiệt2020-03-20
Làm thế nào để bảng mạch PCB cải thiện hiệu quả tản nhiệt
Double-Sided Boards. This type of circuit board has wiring on both sides, but to use the wires on both sides, you must have a proper circuit connection between the two sides.
2. Multi-Layer Boards. In order to increase the wiring area, multi-layer boards use more single- or double-sided wiring boards.
For electronic equipment, a certain amount of heat is generated during work, which causes the internal temperature of the equipment to rise rapidly. If the heat is not released in time, the equipment will continue to heat up and the device will fail due to overheating. The reliability of the electronic equipment Performance will degrade. Therefore, it is very important to perform a good heat dissipation process on the circuit board. The heat dissipation of PCB circuit board is a very important link.
So what is the heat dissipation technique of PCB circuit board, let’s discuss it together.
1. Heat dissipation through the PCB board itself:
Currently widely used PCB boards are copper-clad / epoxy glass cloth substrate or phenolic resin glass cloth substrate, and there are a few paper-based copper-clad boards used. Although these substrates have excellent electrical properties and processing properties, they have poor heat dissipation properties. As a heat dissipation method for highly heat-generating components, it is almost impossible to rely on the PCB resin to conduct heat, but to dissipate heat from the surface of the components to the surrounding air. However, as electronic products have entered the era of component miniaturization, high-density installation, and high-heat assembly, it is not enough to dissipate heat only on the surface of components with a very small surface area. At the same time, due to the large use of surface mount components such as QFP and BGA, the heat generated by the components is transferred to the PCB board. Therefore, a better way to solve the heat dissipation is to improve the heat dissipation capability of the PCB itself that is in direct contact with the heating element. Conducted or emitted.
2. Heat dissipation through layout:
a. The heat sensitive device is placed in the cold wind area.
b. The temperature detection device is placed in a relatively hot location.
c. The devices on the same printed board should be arranged as much as possible according to the amount of heat generated and the degree of heat dissipation. Devices with low heat generation or poor heat resistance (such as small signal transistors, small-scale integrated circuits, electrolytic capacitors, etc.) should be placed. The cooling airflow is quite upstream (at the entrance). Devices with high heat generation or good heat resistance (such as power transistors, large-scale integrated circuits, etc.) are placed quite downstream of the cooling airflow.
d. In the horizontal direction, high-power devices should be arranged as close to the edge of the printed board as possible to shorten the heat transfer path; in the vertical direction, high-power devices should be arranged as close to the top of the printed board as possible to reduce the temperature of these devices when they are working. Impact.
e. The heat dissipation of the printed board in the device mainly depends on the air flow, so the air flow path should be researched in the design, and the device or printed circuit board should be reasonably configured. When air flows, it tends to flow in a place with low resistance, so when configuring the device on the printed circuit board, avoid leaving a large airspace in a certain area. The configuration of multiple printed circuit boards in the whole machine should also pay attention to the same problem.
f. The temperature-sensitive devices are better placed in areas with lower temperatures (such as the bottom of the device). Do not place them directly above the heating device. Multiple devices are better arranged on a horizontal plane.
g. Place devices with high power consumption and high heat generation near good heat dissipation locations. Do not place devices with high heat generation at the corners and peripheral edges of the printed board, unless a heat sink is arranged near it. When designing the power resistor, select a larger device as much as possible, and make sure that there is enough space for heat dissipation when adjusting the layout of the printed board.
2、High heat-generating device plus heat sink and heat-conducting board When a few devices in the PCB have a large amount of heat (less than 3), a heat sink or heat-conducting tube can be added to the heat-generating device. When the temperature cannot be lowered, it can be used Radiator with fan to enhance heat dissipation.
When there are many heating devices (more than 3), a large heat shield (board) can be used. It is a dedicated heat sink customized according to the position and height of the heating device on the PCB board or a large flat heat sink. Cut out different component height positions.
The heat sink is integrally buckled on the surface of the component, and contacts each component to dissipate heat. However, the heat dissipation effect is not good due to the poor consistency of the components when mounting and welding. Generally, a soft thermal phase change thermal pad is added on the component surface to improve the heat dissipation effect.
3、For equipment using free convection air cooling, it is better to arrange integrated circuits (or other devices) in a lengthwise manner, or in a horizontal lengthwise manner.
4.Adopt reasonable wiring design to achieve heat dissipation. Due to the poor thermal conductivity of the resin in the plate, and copper foil lines and holes are good conductors of heat, increasing the copper foil residual rate and increasing the heat conduction holes are the main means of heat dissipation. To evaluate the heat dissipation capability of a PCB, it is necessary to calculate the equivalent thermal conductivity (nine eq) of a composite material composed of various materials with different thermal conductivity, one by one, for an insulating substrate for a PCB.
5 、 Các thiết bị trên cùng một bảng in nên được sắp xếp càng nhiều càng tốt theo lượng nhiệt tỏa ra và mức độ tản nhiệt. Các thiết bị sinh nhiệt thấp hoặc chịu nhiệt kém (như bóng bán dẫn tín hiệu nhỏ, mạch tích hợp quy mô nhỏ, tụ điện, v.v.) được đặt trong luồng không khí làm mát. Tương đối cao (ở cửa ra vào), và các thiết bị sinh nhiệt lớn hoặc chịu nhiệt tốt (chẳng hạn như bóng bán dẫn nguồn, mạch tích hợp quy mô lớn, v.v.) được đặt tương đối xuôi dòng khí làm mát.
6 、 Theo chiều ngang, các thiết bị công suất cao được bố trí càng gần mép bảng in càng tốt để rút ngắn đường truyền nhiệt; theo hướng thẳng đứng, các thiết bị công suất lớn được bố trí càng gần bảng in càng tốt để giảm tác động của các thiết bị này đến nhiệt độ của các thiết bị khác trong quá trình hoạt động.
7 、 Sự tản nhiệt của bảng in trong thiết bị chủ yếu phụ thuộc vào luồng không khí, do đó cần nghiên cứu đường dẫn luồng không khí trong thiết kế và thiết bị hoặc bảng mạch in phải được cấu hình hợp lý.
Khi không khí lưu thông, nó có xu hướng chảy ở nơi có điện trở thấp, vì vậy khi cấu hình thiết bị trên bảng mạch in, tránh để một vùng trời rộng lớn trong một khu vực nhất định. Cấu hình nhiều bảng mạch in trong cả máy cũng cần chú ý đến vấn đề tương tự.
8、Temperature-sensitive devices are better placed in areas where the temperature is relatively low (such as the bottom of the device). Do not place it directly above the heat-generating device. It is better to arrange multiple devices on a horizontal plane.
9、Place devices with high power consumption and high heat generation near good heat dissipation locations. Do not place devices with high heat generation at the corners and peripheral edges of the printed board, unless a heat sink is arranged near it.
When designing the power resistor, select a larger device as much as possible, and make sure that there is enough space for heat dissipation when adjusting the layout of the printed board.
10、Avoid the concentration of hot spots on the PCB, and distribute the power as evenly as possible on the PCB to maintain uniform and consistent temperature performance on the PCB surface.
It is often difficult to achieve strict uniform distribution during the design process, but it is necessary to avoid areas with too high power density to avoid excessive hot spots that affect the normal operation of the entire circuit