Can I go 100A on a PCB design? Tips for setting up a high current path

The usual PCB design current will not exceed 10A, or even 5A, especially in the home, consumer electronics, usually PCB continuous current will not exceed 2A. but recently for a product design power line, the continuous current can reach 80A or so, taking into account the transient current as well as for the whole system to leave a margin, the power line should be able to withstand more than 100A of continuous current.

Then the question arises, how the PCB can withstand 100A of current?

Method 1: PCB alignment
To figure out the overcurrent capacity of the PCB, we first start with the PCB structure. Double-layer PCB, for example, this circuit board is usually a three-layer structure: copper skin, plate, copper skin. Copper skin is the PCB current, signal to pass through the path. According to secondary school physics knowledge can know the resistance of an object with the material, cross-sectional area, length.

Since our current is traveling on the copper skin, the resistivity is fixed. The cross-sectional area can be seen as the thickness of the copper skin, which is the copper thickness in the PCB processing option. Usually copper thickness is expressed in OZ, 1OZ of copper thickness converted to 35um, 2OZ is 70um, and so on. Then it can be easily concluded: in the PCB to pass large currents, the wiring should be short and thick, while the copper thickness of the PCB the thicker the better.

In practice, in the project, for the length of the wiring does not have a strict standard. Engineering is usually used: copper thickness / temperature rise / wire diameter, the three indicators to measure the current-carrying capacity of the PCB board.

The following two tables can be referred to:

From the table can be approximately know 1OZ copper thickness of the board, in 10 ° temperature rise, 100 mil (2.5mm) width of the wire can pass 4.5A current. And as the width increases, the PCB current-carrying capacity is not strictly linear increase, but the increase slowly decreases, which is also consistent with the actual engineering situation. If you increase the temperature rise, the current-carrying capacity of the wire can also be improved.

Through these two tables, can get the PCB wiring experience is: increase copper thickness, widen the wire diameter, improve PCB heat dissipation can enhance the current-carrying capacity of the PCB.

So if I want to go 100 A current, I can choose 4 OZ of copper thickness, set the alignment width of 15 mm, double-sided alignment, and increase the heat sink to reduce the temperature rise of the PCB, improve stability.

Method 2: Terminals
In addition to routing on the PCB, you can also use the terminal block method of routing. In the PCB or product shell on the fixed several can withstand 100A terminal such as: table sticker nut, PCB terminals, copper columns and so on. Then use the copper nose and other terminals will be able to withstand 100A wire to the terminal. So that the large current can go through the wire.

Method 3: Customized copper row
Even, it is possible to customize the copper row. It is a common practice in industry to use copper bushing to carry high currents, for example, transformers, server cabinets and other applications are using copper bushing to carry high currents.

A table of current-carrying capacity of copper rows is attached:

Method 4: Special Processes
There are also some special PCB process, such as the use of 3-layer copper layer design, the top and bottom layer is the signal wiring layer, the middle layer is a thickness of 1.5mm copper layer, specifically for the layout of the power supply, this PCB can be easily done in a small volume of overcurrent of 100A or more.