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PCB Tech
10 heat dissipation techniques in PCB circuit layout
PCB Tech
10 heat dissipation techniques in PCB circuit layout

10 heat dissipation techniques in PCB circuit layout

2021-11-08
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Author:Downs

Thermal sensitive devices are placed in the cold wind area.

The temperature detection device is placed in the hottest position.

The devices on the same printed circuit board should be arranged as far as possible according to their calorific value and degree of heat dissipation. Devices with small calorific value or poor heat resistance (such as small signal transistors, small-scale integrated circuits, electrolytic capacitors, etc.) should be placed in cooling The uppermost flow (at the entrance) of the airflow, and the devices with large heat generation or good heat resistance (such as power transistors, large-scale integrated circuits, etc.) are placed at the most downstream of the cooling airflow.

In the horizontal direction, the high-power devices are arranged as close to the edge of the printed board as possible to shorten the heat transfer path; in the vertical direction, the high-power devices are arranged as close as possible to the top of the printed board to reduce the influence of these devices on the temperature of other devices. .

The heat dissipation of the printed board in the equipment mainly relies on air flow, so the air flow path should be studied during the design, and the device or printed circuit board should be reasonably configured. When air flows, it always tends to flow in places with low resistance, so when configuring devices on a 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.

pcb board

The temperature-sensitive device is best placed in the lowest temperature area (such as the bottom of the device). Never place it directly above the heating device. It is best to stagger multiple devices on the horizontal plane.

Place the devices with the highest power consumption and heat generation near the best position for heat dissipation. Do not place high-heating devices on the corners and peripheral edges of the printed board, unless a heat sink is arranged near it. When designing the power resistor, choose a larger device as much as possible, and make it have enough space for heat dissipation when adjusting the layout of the printed board.

Method Two

High heat-generating components plus radiators and heat-conducting plates When a few components in the PCB generate a large amount of heat (less than 3), a radiator or heat-conducting pipe can be added to the heat-generating components. When the temperature cannot be lowered, a radiator with a fan can be used to enhance the heat dissipation effect.

Radiator with fan

When the number of heating devices is large (more than 3), a large heat dissipation cover (board) can be used, which is a special heat sink customized according to the position and height of the heating device on the PCB. Or cut out different component height positions on a large flat radiator.

The heat dissipation cover is integrally buckled on the surface of the component, and it is in contact with each component to dissipate heat. However, the heat dissipation effect is not good due to the poor consistency of height during assembly and welding of components. Usually, a soft thermal phase change thermal pad is added on the surface of the component to improve the heat dissipation effect.

Method Three

For equipment that adopts free convection air cooling, it is best to arrange integrated circuits (or other devices) vertically or horizontally.

Method Four

Use reasonable wiring design to realize heat dissipation. Because the resin in the plate has poor thermal conductivity, and the copper foil lines and holes are good conductors of heat, increasing the residual rate of the copper foil and increasing the thermally conductive holes are the main means of heat dissipation.

To evaluate the heat dissipation capacity of the PCB, it is necessary to calculate the equivalent thermal conductivity (nine eq) of the composite material composed of various materials with different thermal conductivity-the insulating substrate for the PCB.

Method Five

The components on the same printed circuit board should be arranged as far as possible according to their calorific value and degree of heat dissipation. Devices with low calorific value or poor heat resistance (such as small signal transistors, small-scale integrated circuits, electrolytic capacitors, etc.) are placed at the top of the cooling airflow (entry); devices with large calories or good heat resistance (such as power transistors) , Large-scale integrated circuits, etc.) placed at the most downstream of the cooling air flow.

Method Six

In the horizontal direction, high-power devices are 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 are placed as close as possible to the top of the printed circuit board to reduce the impact of these devices on the temperature of other devices when they work.

Method Seven

The heat dissipation of the printed board in the equipment mainly relies on air flow, so the air flow path should be studied during the design, and the device or printed circuit board should be reasonably configured.

When air flows, it always tends to flow in places with low resistance, so when configuring devices on a 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.

Method Eight

Temperature-sensitive devices are best placed in the lowest temperature area (such as the bottom of the device). Do not place it directly above the heating device. It is best to arrange multiple devices in a staggered horizontal plane.

Method nine

Place the devices with the highest power consumption and heat generation near the best position for heat dissipation. Do not place high-heating devices on the corners and peripheral edges of the printed board, unless a heat sink is arranged near it.

When designing the power resistor, choose a larger device as much as possible, and make it have enough space for heat dissipation when adjusting the layout of the printed board.

Method ten

Avoid the concentration of hot spots on the PCB, distribute the power evenly on the PCB board as much as possible, and keep the PCB surface temperature performance uniform and consistent.

It is often difficult to achieve strict uniform distribution during the design process, but areas with too high power density must be avoided to prevent hot spots from affecting the normal operation of the entire circuit. If possible, it is necessary to analyze the thermal efficiency of the printed circuit. For example, the thermal efficiency index analysis software module added in some professional PCB design software can help designers optimize the circuit design.