How to use design to improve thermal issues
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. Performance will degrade. Therefore, it is very important to perform a good heat dissipation process on the circuit board.
1. Add heat dissipation copper foil and copper foil with large area power supply.
The larger the area connected to the copper skin, the lower the junction temperature.
2. Thermal vias
Thermal vias can effectively reduce the junction temperature of the device, improve the temperature uniformity in the thickness direction of the board, and provide the possibility to adopt other heat dissipation methods on the back of the PCB. Through simulation, it is found that compared with no thermal vias, thermal vias with a device thermal power consumption of 2.5W, a pitch of 1mm, and a center design of 6x6 can reduce the junction temperature by about 4.8 ° C, and the temperature difference between the top and bottom surfaces of the PCB Reduced from 21 ° C to 5 ° C. After the thermal via array is changed to 4x4, the junction temperature of the device is 2.2 ° C higher than that of 6x6, which is worthy of attention.
3. Copper is exposed on the back of the IC to reduce the thermal resistance between the copper skin and the air
Requirements for high-power, thermal-sensitive devices.
a. The heat sensitive device is placed in the cold wind area.
b. The temperature detection device is placed in the hottest position.
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. At the top of the cooling airflow (at the entrance), devices with high heat generation or heat resistance (such as power transistors, large-scale integrated circuits, etc.) are placed at the most downstream of the cooling airflow.
d. In the horizontal direction, the 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, the 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 studied during 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 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.
f. The 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. Multiple devices are preferably staggered on the horizontal plane.
g. Place the device with the highest power consumption and heat generation near the best position for heat dissipation. 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.