Why Use 45-Degree Routing in PCB? Why Is Right-Angle Routing Prohibited in PCB?

In PCB design, why should we route circuits with 45-degree inclined traces? There are several reasons to be discussed here.

The first is Electromagnetic Compatibility (EMC). In PCB design, EMI (Electromagnetic Interference) will be generated between numerous signal lines and power lines. During PCB layout, to minimize EMI as much as possible, attention must be paid to avoiding right-angle connections. Right-angle connections will create extremely intense charge edges in the electric field of signal lines and power lines. This will cause electrons to accumulate at the edges and form a high-energy state, thereby generating electron flow. Such electron flow will lead to high-frequency leakage, which in turn causes EMI. In contrast, 45-degree angle connections make the charge distribution at the edges more uniform and the electron flow smoother, thus effectively reducing the interference level of EMI.

The second is conductivity and reliability. At right-angle connections, the tiny gaps between circuit traces will cause signal reflection and impedance changes, which will result in signal loss and instability. 45-degree angle connections can reduce such reflection and variation to a certain extent, thereby improving the conductivity and reliability of the circuit.

The last is the visual effect. The use of 45-degree angle connections can make the PCB routing look neater and more aesthetically pleasing, which is particularly important for products for commercial applications.

Although right-angle connections can reduce the complexity of PCB design, they also bring about many problems. Here are some common issues:

The first is the EMI problem. As mentioned above, right-angle connections will cause electrons to accumulate at the edges, thereby leading to high-frequency leakage and generating EMI.

The second is the problem of conductivity and reliability. Right-angle connections will cause impedance changes on the circuit traces, which in turn lead to signal reflection and signal loss.

The last is the manufacturing difficulty. Right-angle connections require a large number of corner cutting, corner turning and adjustment, which makes circuit board manufacturing more difficult and expensive. In addition, for PCBs with advanced manufacturing processes (such as high-density surface mount), right-angle connections will also increase the difficulty of wiring.

Therefore, although right-angle connections may improve the maintainability and readability of the circuit board in some cases, they have been generally regarded as a bad practice in modern PCB design.

The method of adopting 45-degree angle connections in PCB layout is usually very simple. Here are some basic practices:

First, use 45-degree angle connections as the default setting for circuit board layout. When designing a circuit schematic, right-angle connections should be avoided as much as possible, and the use of 45-degree angle connections is encouraged to reduce EMI, and improve conductivity and reliability.

Second, use the 45-degree angle connection tools provided in the PCB software. When routing, PCB software usually provides hotkeys or shortcut keys for 45-degree angle connections, which enables faster routing and reduces errors.

Finally, the overall arrangement of the routing should be considered rationally during the wiring process. In a large number of circuit routing, the wiring needs to be optimized according to factors such as the importance of the connections and the crossover between different layers. This can effectively reduce EMI, and improve conductivity and reliability.

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