The design current of PCB will not exceed 10A or even 5a, especially in household and consumer electronics, the continuous working current on PCB will not exceed 2A. But recently, we have to design power lines for our products, and the DC current can reach about 80 a. Considering the instantaneous current and leaving room for the whole system, the DC current of power line should be able to withstand the current of more than 100A.
So the question is, which PCB can withstand 100A of current?
01 method 1: PCB on line
In order to find out the over current capacity of PCB, we start with the structure of PCB. Take double layer printed circuit board as an example. This type of circuit board usually has three layers of structure: Copper cortex, plate and copper cortex. Copper sheet is the path through which current and signal pass through PCB. According to the physics knowledge of high school, we can know that the resistance of an object is related to the material, cross-sectional area and length. Because our current flows over the copper sheet, the resistivity is fixed. The cross-sectional area can be considered as the thickness of the copper skin, which is the thickness of copper in PCB processing options. Generally, the thickness of copper is represented by Oz, the thickness of 1oz is 35um, and that of 2oz is 70UM, and so on. It can be easily concluded that when the high current is to flow through PCB, the wiring should be short and thick, and the thicker the copper of PCB is, the better.
In fact, in engineering, there is no strict standard of wiring length. Usually used in Engineering: thickness / temperature rise of copper / diameter of conductor, which are used to measure current load capacity of PCB board.
You can refer to the following two tables:
From the table, we can roughly know that when the temperature rises by 10, the circuit board with a copper thickness of 1oz can pass through a current of 4.5a, with a width of 100mil (2.5mm). With the increase of width, the current carrying capacity of PCB is not strictly linear, but decreases gradually, which is consistent with the actual engineering. If the temperature increases, the load capacity of the cable can also be increased.
Through these two tables, the PCB wiring experience can be obtained: increasing the thickness of copper, expanding the diameter of the wire and improving the thermal dissipation of PCB can improve the current carrying capacity of PCB.
Therefore, if 100A current is to be operated, the thickness of 4oz copper can be selected, the width of the wire routing can be set to 15mm, double-sided routing can be used, and a radiator is added to reduce the temperature rise of PCB and improve stability.
02 method 2: terminal
In addition to wiring on PCB, terminal blocks can be used.
Connect various terminals that can withstand 100A current on PCB or product shell, such as surface mounting nut, PCB terminal, copper post, etc. Then, wires that can withstand 100A current are connected to terminals using terminals such as copper terminals. In this way, a large current can pass through the cable.
03 method 3: custom copper bar
Even copper bars can be customized. Copper bars are usually used in industry to carry large current. For example, transformers, server cabinets, and other applications use copper bars to carry large currents.
The copper bar load flow chart is attached:
04 method 4: special process
In addition, there are also some special PCB processes that you may not be able to find in China. The PCB of Infineon has three layers of copper layer design. The upper and lower layers are signal wiring layers, and the middle layer is 1.5mm thick copper layer, which is specially used for organizing power supply. This type of PCB is easy to reach more than 100A. (from electronics world)