PCB carries 100A current? High current path setting tips

Home News Industry News PCB carries 100A current? High current path setting tips

2022-03-16 240

The usual PCB design current will not exceed 10 A, or even 5 A. Especially in household and consumer electronics, usually the continuous operating current on the PCB does not exceed 2 A. However, recently we have to design power wiring for the company's products, and 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.

Then the problem comes,What kind of PCB can withstand 100 A current?

Method 1: Routing on PCB

To figure out the overcurrent capability of PCB, we first start with the PCB structure. byTake double-layer PCB as an example. This kind of circuit board usually has a three-layer structure: copper, plate, and copper.Copper is the path through which current and signals pass in the PCB. According to middle school physics knowledge, we can know that the resistance of an object is related to the material, cross-sectional area, and length. due to ourThe current flows through the copper, so the resistivity is fixed.The cross-sectional area can be seen as the thickness of the copper sheet, which is the copper thickness in the PCB processing option. Usually the copper thickness is expressed in OZ. The converted copper thickness of 1 OZ is 35 um, 2 OZ is 70 um, and so on. Then we can easily draw the conclusion:When a large current needs to pass through the PCB, the wiring must be short and thick. At the same time, the thicker the copper thickness of the PCB, the better.

In actual engineering, there is no strict standard for the length of wiring. Usually used in engineering:Copper thickness/temperature rise/wire diameter, these three indicators are used to measure the current carrying capacity of the PCB board.

The following two tables can be referenced:

From the table, we can roughly know that for a 1 OZ copper-thick circuit board, a 100 mil (2.5 mm) wide wire can carry a current of 4.5 A at a 10° temperature rise. And as the width increases, the PCB current carrying capacity does not increase strictly linearly, but the increase slowly decreases, which is consistent with the situation in actual engineering.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 copper thickness, widening wire diameter, and improving PCB heat dissipation can enhance the current carrying capacity of PCB.

So if I want to carry a current of 100 A, 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.

Method 2: Binding post

In addition to routing wires on the PCB, you can also use binding postsWay to route.

Fix several terminal posts that can withstand 100 A on the PCB or product shell, such as surface mount nuts, PCB terminal blocks, copper posts, etc. Then use terminal blocks such as copper noses to connect wires that can withstand 100 A to the terminals. This allows large currents to flow through the wires.

Method 3: Customized copper rows

Even custom-made copper busbars can be made.It is a common practice in industry to use copper bars to carry large currents. For example, transformers, server cabinets and other applications all use copper bars to carry large currents.

Attached is the copper bank current-carrying capacity table:

Method 4: Special process

In addition, there are some special PCB processes that may not be processed by domestic manufacturers.Infineon has a PCB that uses 3Layer copper layer design, the top and bottom layers are signal wiring layers, and the middle layer is 1.5 thickmm copper layer is specially used for power supply layout. This PCB can easily achieve an overcurrent of 100 in a small volume.A or above.

EMC message：With the development of the times, more and more electronic and electrical equipment or system products need to be inspected and tested.Among them, EMC testing is one of the necessary inspection and testing indicators. However, EMC testing projects are relatively expensive, EMC laboratories are expensive to build, and most measurement equipment requires imported equipment. As a result, few inspection and testing institutions have the ability to build EMC laboratories. The EMC performance of the product is given during the design stage. If EMC factors are not considered during the design of general electronic products, it will easily lead to failure of the EMC test and fail to pass the testing or certification of relevant EMC regulations. For example, product design and R&D engineers design effective filter circuits according to needs and place them in the preamplifier of the product's I/O (input/output) interface, which can eliminate the interference noise that enters the system due to conduction at the entrance of the circuit system; design isolation circuits (such as transformer isolation and photoelectric isolation, etc.) Solve the conduction interference entering the circuit through power lines, signal lines and ground wires, while preventing interference caused by public impedance and long-term transmission; design energy absorption loops to reduce the noise energy absorbed by circuits and devices; reduce the impact of interference by selecting components and rationally arranging circuit systems.

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