How to improve the thermal reliability of PCB

///How to improve the thermal reliability of PCB

In general, the copper foil distribution on PCB board is very complicated, and it is difficult to model accurately. Therefore, it is necessary to simplify the shape of wiring and make the electronic components on the board of ANSYS model, which are close to the actual circuit board, to be simulated by simplified modeling, such as MOS tube, integrated circuit block and so on.

Thermal analysis

Thermal analysis in the mounting process assists the designer in determining the electrical properties of the components on the pcb board and helps the designer determine if the component or board burns out due to high temperatures. A simple thermal analysis only calculates the average temperature of the circuit board. If it is complicated, a transient model must be established for the electronic equipment containing multiple circuit boards. The accuracy of thermal analysis ultimately depends on the accuracy of the component power consumption provided by the board designer.

Weight and physical size are very important in many applications, and if the actual power consumption of the component is very small, it may result in the design safety factor being too high. Therefore, the design of the circuit board is based on the thermal analysis, which is not in accordance with the actual or too conservative component power value. The opposite (and more serious) is that the thermal safety factor is designed to be too low, that is, the temperature at which the component is actually operating is higher than the analyst predicted. Such problems are usually solved by cooling the circuit board by adding a radiator or fan. These add-on accessories increase the cost, prolong the manufacturing time. Adding fans to the design will bring instability to reliability, so the PCB board mainly uses active cooling rather than passive cooling (such as natural convection, conduction and radiation to dissipate heat).

Simplified modeling of PCB

Before modeling, the main heating devices in the circuit board should be analyzed such as MOS transistors and integrated circuit blocks which convert most of the lost power into heat. Therefore, these devices should be considered when modeling.

In addition, we should consider the copper foil coated as a wire on a circuit board substrate. They not only play a conductive role in the design, but also conduct heat. Their thermal conductivity and heat transfer area are relatively large. Circuit boards are an indispensable part of electronic circuits, whose structure consists of epoxy resin substrate and copper foil coated as conductor. The thickness of epoxy resin substrate is 4 mm and copper foil is 0.1 mm. The thermal conductivity of copper is 400 W / m ℃, while that of epoxy resin is only 0.276 W / m ℃. Although the added copper foil is thin and thin, it has a strong guiding effect on heat and can not be ignored in modeling.

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