nasıl kullanılır? PCB for IC package heat dissipation?

The first aspect of PCB design that can improve thermal performance is the PCB device layout. Whenever possible, high-power components on the PCB should be separated from each other. This physical separation between high-power components maximizes the PCB area around each high-power component, thereby helping to achieve better heat conduction. Care should be taken to isolate temperature-sensitive components on the PCB from high-power components. Whenever possible, the installation location of high-power components should be far away from the corners of the PCB. A more central PCB location can maximize the board area around high-power components, thereby helping to dissipate heat. Figure 2 shows two identical semiconductor devices: component A and component B. Component A is located at the corner of the PCB and has a die junction temperature that is 5% higher than component B because component B is located closer to the middle. Since the board area around the component for heat dissipation is smaller, the heat dissipation at the corner of component A is limited.

How to use PCB for IC package heat dissipation?

The second aspect is the structure of the PCB, which has the most decisive influence on the thermal performance of the PCB design. The general principle is: the more copper in the PCB, the higher the thermal performance of the system components. The ideal heat dissipation situation for semiconductor devices is that the chip is mounted on a large piece of liquid-cooled copper. For most applications, this mounting method is impractical, so we can only make some other changes to the PCB to improve the heat dissipation performance. For most applications today, the total volume of the system continues to shrink, which has an adverse effect on heat dissipation performance. The larger the PCB, the larger the area that can be used for heat conduction, and it also has greater flexibility, allowing enough space between the high-power components.

Whenever possible, maximize the number and thickness of PCB copper ground planes. The weight of the ground layer copper is generally relatively large, and it is an excellent thermal path for the entire PCB to dissipate heat. The arrangement of wiring for each layer will also increase the total proportion of copper used for heat conduction. However, this wiring is usually electrically and thermally isolated, which limits its role as a potential heat dissipation layer. The wiring of the device ground plane should be as electrical as possible with many ground planes, so as to help maximize heat conduction. The heat dissipation vias on the PCB under the semiconductor device help heat to enter the buried layers of the PCB and conduct to the back of the circuit board.

To improve the heat dissipation performance, the top and bottom layers of the PCB are “golden locations”. Use wider wires and route them away from high-power devices to provide a thermal path for heat dissipation. The dedicated thermal board is an excellent method for PCB heat dissipation. The thermal board is generally located on the top or back of the PCB, and is thermally connected to the device through direct copper connections or thermal vias. In the case of inline package (packages with leads on both sides), this kind of heat conduction board can be located on the top of the PCB and shaped like a “dog bone” (the middle is as narrow as the package, and the area away from the package is relatively small. Large, small in the middle and large at the ends). In the case of a four-side package (there are leads on all four sides), the heat-conducting plate must be located on the back of the PCB or enter the PCB.

How to use PCB for IC package heat dissipation?

Increasing the size of the thermal board is an excellent way to improve the thermal performance of the PowerPAD package. Different heat conduction plate sizes have a great influence on thermal performance. The product data sheet provided in the form of a table generally lists these size information. However, it is difficult to quantify the impact of the added copper of custom PCBs. Using some online calculators, users can select a device and then change the size of the copper pad to estimate its impact on the heat dissipation performance of non-JEDEC PCBs. These calculation tools highlight the impact of PCB design on thermal performance. For a four-side package, the area of ​​the top pad is just smaller than the area of ​​the exposed pad of the device. In this case, the buried or back layer is the first way to achieve better cooling. For dual in-line packages, we can use a “dog bone” pad style to dissipate heat.

Finally, systems with larger PCBs can also be used for cooling. In the case that the screws are connected to the heat-conducting plate and ground plane for heat dissipation, some screws used to mount the PCB can also become effective heat paths to the system base. Considering the heat conduction effect and cost, the number of screws should be the maximum value that reaches the point of diminishing returns. After being connected to the thermal conductive plate, the metal PCB reinforcement plate has more cooling area. For some applications where the PCB is covered with a shell, the type controlled welding repair material has a higher thermal performance than the air-cooled shell. Cooling solutions, such as fans and heat sinks, are also common methods for system cooling, but they usually require more space or need to modify the design to optimize the cooling effect.

To design a system with higher thermal performance, it is not enough to choose a good IC device and closed solution. The heat dissipation performance of the IC depends on the PCB and the ability of the heat dissipation system to quickly cool the IC devices. By using the above passive cooling method, the heat dissipation performance of the system can be greatly improved.