“The usual PCB design current does not exceed 10 A, or even 5 A. Especially in household and consumer electronics, usually the continuous working current on the PCB does not exceed 2 A. However, it is necessary to design power wiring for the company’s products recently. The continuous current can reach about 80 A. Considering the instantaneous current and leaving a margin for the entire system, the continuous current of the power wiring should be able to withstand more than 100 A.
The usual PCB design current does not exceed 10 A, or even 5 A. Especially in household and consumer electronics, usually the continuous working current on the PCB does not exceed 2 A. However, it is necessary to design power wiring for the company’s products recently. The continuous current can reach about 80 A. Considering the instantaneous current and leaving a margin for the entire system, the continuous current of the power wiring should be able to withstand more than 100 A.
So the question is, what kind of PCB can withstand a current of 100 A?
01. Method 1: Layout on PCB
To figure out the over-current capability of the PCB, we first start with the PCB structure. Taking a double-layer PCB as an example, this circuit board usually has a three-layer structure: copper skin, plate, and copper skin. The copper skin is the path through which the current and signals in the PCB pass. According to the knowledge of physics in middle school, the resistance of an object is related to the material, cross-sectional area, and length. Since our current runs on the copper skin, the resistivity is fixed. The cross-sectional area can be regarded as the thickness of the copper skin, which is the copper thickness in the PCB processing options. Usually copper thickness is expressed in OZ. The copper thickness of 1 OZ is 35 um, 2 OZ is 70 um, and so on. Then it is easy to draw a conclusion: when a large current is to be passed on the PCB, the wiring should be short and thick, and the thicker the copper thickness of the PCB, the better.
Actually, in engineering, there is no strict standard for the length of wiring. Usually used in engineering: copper thickness / temperature rise / wire diameter, these three indicators to measure the current carrying capacity of the PCB board.
You can refer to the following two tables:
From the table, we can roughly know that a 1 OZ copper-thick circuit board can pass a current of 4.5 A with a 100 mil (2.5 mm) width wire at a temperature rise of 10°. And as the width increases, the current-carrying capacity of the PCB does not strictly increase linearly, but the increase gradually decreases, which is also consistent with the actual project. If the temperature rise is increased, the current-carrying capacity of the wire can also be improved.
Through these two tables, the PCB wiring experience that can be obtained is: increasing the copper thickness, widening the wire diameter, and improving the PCB heat dissipation can enhance the current-carrying capacity of the PCB.
So if I want to take 100 A electricity
For flow, I can choose a copper thickness of 4 OZ, set the trace width to 15 mm, double-sided traces, and add a heat sink to reduce the temperature rise of the PCB and improve stability.
02. Method two: terminal
In addition to wiring on the PCB, wiring posts can also be used.
Fix several terminals that can withstand 100 A on the PCB or product shell, such as surface mount nuts, PCB terminals, copper columns, etc. Then use terminals such as copper lugs to connect wires that can withstand 100 A to the terminal. In this way, large currents can pass through the wires.
03. Method 3: Customize copper bars
Even copper bars can be customized. It is a common practice in the industry to use copper bars to carry large currents. For example, transformers, server cabinets and other applications use copper bars to carry large currents.
Attached copper row current carrying capacity table:
04. Method 4: Special process
In addition, there are some more special PCB processes, and you may not be able to find a manufacturer in China for processing. Infineon has a PCB with a 3-layer copper layer design. The top and bottom layers are signal wiring layers, and the middle layer is a copper layer with a thickness of 1.5 mm, which is specially used to arrange power supplies. This kind of PCB can easily be small in size. Flow above 100 A.