PCB design should avoid right-angle traces, and most PCB engineers know this requirement. So, must the PCB design trace not run at a 90-degree right angle? To answer this question, we must first understand the impact of the 90-degree right-angle trace on the signal. The impact of 90° right-angle routing on the signal is mainly reflected in three aspects:
1. The right angle can be equivalent to a capacitive load on the transmission line, slowing down the rise time;
2. Impedance discontinuity will cause signal reflection;
3. EMI generated by the right-angle tip.
The reason why 90° right-angle traces cause signal integrity problems is that the width of the copper foil at the right-angle corner of the transmission line is wider than that of the straight trace, which will cause a sudden change in the characteristic impedance at the right-angle bend; Ordinary signal routing will not cause problems, but for high-speed transmission lines, it will cause signal reflections, and serious reflections will cause signal integrity problems. Therefore, when designing a high-speed circuit board, routing through a 45° corner pattern instead of a 90° pattern can reduce signal reflections caused by changes in wiring width and signal rise delays caused by this additional discrete capacitance change.
In addition, many people think that the right-angle tip is easy to emit or receive electromagnetic waves, which will generate EMI, which is also one of the reasons why many people think that right-angle routing cannot be done.
In general, it is recommended that you prohibit right angles when performing PCB layout. Whether it is ordinary signal lines, high-speed digital signal transmission lines, or RF transmission lines, including copper-clad copper skins, they are all designed to be obtuse angles.
