When it comes to PCB design, the limitation created by the current capacity of PCB wiring is critical.

The current capacity of the wiring on the PCB is determined by such parameters as the width of the wiring, the thickness of the wiring, the maximum temperature rise required, whether the wiring is inner or outer, and whether it is covered with flux resistance.

In this article, we will discuss the following:

one What is PCB line width?

PCB wiring or the copper conductor on the PCB, can conduct the signal on the PCB surface. The etching leaves a narrow section of copper foil, and the current flowing through the copper wire generates a lot of heat. Correctly calibrated PCB wiring widths and thicknesses help minimize heat build-up on the board. The wider the line width, the lower the resistance to current, and the less heat accumulation. PCB wiring width is the horizontal dimension and thickness is the vertical dimension.

PCB design always starts with the default line width. However, this default line width is not always appropriate for the desired PCB. This is because you need to consider the current carrying capacity of the wiring to determine the wiring width.

When determining the correct line width, consider several factors:

1. Copper thickness — Copper thickness is the actual wiring thickness on the PCB. The default copper thickness for high-current PCBS is 1 ounce (35 micron) to 2 ounce (70 micron).

2. Cross-sectional area of conductor — To have higher power of PCB, it is necessary to have a larger cross-sectional area of the conductor, which is proportional to the width of the conductor.

3. Location of trace – bottom or top or inner layer.

two How to design high current PCB?

Digital circuits, RF circuits and power circuits mainly process or transmit low power signals. The copper in these circuits weighs 1-2Oz and carries a current of 1A or 2A. In some applications, such as motor control, a current of up to 50A is required, which will require more copper on the PCB and more wire width.

The design method for high current requirements is to widen copper wiring and increase the thickness of wiring to 2OZ. This will increase the space on the board or increase the number of layers on the PCB.

3. High current PCB layout criteria:

Reduce the length of high-current cabling

Longer wires have higher resistance and carry higher current, resulting in higher power losses. Because power losses generate heat, circuit board life is shortened.

Calculate the wiring width when appropriate temperature rises and falls are made

The line width is a function of variables such as resistance and the current flowing through it and the allowable temperature. Generally, a temperature rise of 10℃ is allowed at ambient temperatures above 25℃. If the material and design of the plate allow, even a temperature rise of 20°C can be allowed.

Isolate sensitive components from high temperature environments

Certain electronic components, such as voltage references, analog-to-digital converters and operational amplifiers, are sensitive to temperature changes. When these components are heated, their signal changes.

High current plates are known to generate heat, so the components need to be kept at a distance from high temperature environments. You can do this by making holes in the board and providing heat dissipation.

Remove solder resistance layer

To increase the current flow capacity of the wire, the solder barrier layer can be removed and the copper underneath exposed. Additional solder can then be added to the wire, which will increase the wire thickness and reduce the resistance value. This will allow more current to flow through the wire without increasing the wire width or adding additional copper thickness.

The inner layer is used for high-current wiring

If the outer layer of the PCB does not have enough space for thicker wiring, wiring can be filled in the inner layer of the PCB. Next, you can use the through-hole connection to the outer high-current device.

Add copper strips for higher current

For electric vehicles and high-power inverters with current exceeding 100A, copper wiring may not be the best way to transmit power and signals. In this case, you can use copper bars that can be soldered to the PCB pad. The copper bar is much thicker than the wire and can carry large currents as required without any heating problems.

Use through-hole sutures to carry multiple wires over multiple layers of high current

When cabling cannot carry the desired current in a single layer, cabling can be routed over multiple layers and treated by stitching the layers together. In the case of the same thickness of the two layers, this will increase the current-carrying capacity.

conclusion

There are many complicated factors in determining the wiring current capacity. However, PCB designers can rely on the reliability of line thickness calculators to help design their boards efficiently. When designing reliable and high-performance PCBS, the correct setting of line width and current-carrying capacity can go a long way.