The usual PCB design current will not exceed 10A, or even 5A. Especially in household and consumer electronics, the continuous working current on the PCB usually does not exceed 2 A. However, some products require a continuous current of about 80A. Considering the instantaneous current and leaving a margin for the entire system, the continuous current of the power trace should be able to withstand more than 100A. Next, Grande will introduce the PCB design method that the PCB can withstand 100A current.
PCB design method that can withstand 100A current
Method 1: Trace on PCB
To figure out the over current capability of the PCB, we first start with the PCB structure. Taking double-layer PCB as an example, this kind of circuit board is usually a three-layer structure: copper sheet, plate, and copper sheet. The copper sheet is also the path through which the current and signal in the PCB pass. It can be known that the resistance of an object is related to the material, cross-sectional area and length. Since our current is going on the copper, 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, 1 OZ copper thickness is converted to 35 um, 2 OZ is 70 um, and so on. Then it can be easily concluded that when a large current is to be passed on the PCB：the wiring must be short and thick, and the thicker the copper thickness of the PCB, the better.
In fact, in engineering, there is no strict standard for the length of wiring. Engineering usually uses: copper thickness / temperature rise / wire diameter, these three indicators to measure the current carrying capacity of the PCB board.
A 100 mil (2.5 mm) width wire can carry 4.5 A at a 10° temperature rise on a 1 OZ copper thick board. And as the width increases, the current carrying capacity of the PCB does not increase strictly linearly, but gradually decreases, which is also consistent with the actual engineering situation. If the temperature rise is increased, the current carrying capacity of the wire can also be improved.
Through the above summary, 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 run 100 A of current, I can choose 4 OZ copper thickness, set the trace width to 15 mm, double-sided trace, and increase the heat sink to reduce the temperature rise of the PCB and improve the stability.
Method 2: Binding Posts
In addition to routing on the PCB, you can also use binding posts for routing.
Fix several terminals that can withstand 100 A on the PCB or product shell, such as surface mount nuts, PCB terminals, copper posts, etc. Then use terminals such as copper noses to connect wires that can withstand 100 A to the binding posts. This allows large currents to travel through the wires.
Method 3: Customize the copper bar
Here also can use copper bars. It is a common practice in the industry to use copper bars to carry large currents. For example, applications such as transformers and server cabinets use copper bars to carry large currents.
Method 4: Special process
In addition, there are some more special PCB processes. Infineon has a PCB that uses 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 for power layout. Stream 100 A or more.