What are the requirements for PCB thermal design

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On the basis of comprehensive consideration of signal quality, EMC, thermal design, DFM, DFT, structure, safety requirements, the device is placed on the board reasonably. – the PCB layout.

The wiring of all component pads shall meet thermal design requirements except for special requirements. — General principles of PCB outbound.

It can be seen that in PCB design, whether layout or routing, engineers should consider and meet the requirements of thermal design.

The importance of thermal design

The electrical energy consumed by electronic equipment during work, such as RF power amplifier, FPGA chip and power products, is mostly converted into heat emission except useful work. The heat generated by electronic equipment makes the internal temperature rise rapidly. If the heat is not dissipated in time, the equipment will continue to heat up, and the components will fail due to overheating, and the reliability of electronic equipment will decline. SMT increases the installation density of electronic equipment, reduces the effective cooling area, and seriously affects the reliability of equipment temperature rise. Therefore, it is very important to study the thermal design.

PCB thermal design requirements

1) in the arrangement of components, in addition to the temperature detection device shall be temperature sensitive device in near the inlet position, and located in the large power, large calorific value of upstream components of air duct, as far as possible away from the calorific value of components, in order to avoid the effects of radiation, if not away from, also can use heat shield plate (sheet metal polishing, blackness as small as possible).

2) The device that is hot and heat resistant itself is placed near the outlet or on the top, but if it cannot withstand high temperature, it should also be placed near the inlet, and try to stagger the position with other heating devices and thermal sensitive devices in the direction of air rise.

3) High-power components should be distributed as far as possible to avoid heat source concentration; Components of different sizes are arranged as evenly as possible, so that the wind resistance is evenly distributed and the air volume is evenly distributed.

4) Try to align the vents with devices with high heat dissipation requirements.

5) The high device is placed behind the low device, and the long direction is arranged along the direction with the least wind resistance to prevent the air duct from being blocked.

6) The radiator configuration should facilitate the circulation of heat exchange air in the cabinet. When relying on natural convection heat transfer, the length direction of the heat dissipation fin should be perpendicular to the ground direction. Heat dissipation by forced air should be taken in the same direction as the airflow direction.

7) In the direction of air flow, it is not suitable to arrange multiple radiators in a longitudinal close distance, because the upstream radiator will separate the air flow, and the surface wind speed of the downstream radiator will be very low. Should be staggered, or the heat dissipation fin spacing dislocation.

8) The radiator and other components on the same circuit board should have an appropriate distance, through the calculation of thermal radiation, so as not to make it have inappropriate temperature.

9) Use PCB heat dissipation. If the heat is distributed through a large area of copper laying (open resistance welding window can be considered), or it is connected to the flat layer of PCB board through the hole, and the whole PCB board is used for heat dissipation.