In some reference materials of ipcb, the effect of PCB snake routing is as follows:
Any trace on the PCB will cause a time delay to the signal as it passes through it. The main role of the serpentine routing is to compensate for the less delayed parts of the "group related" signal lines, which usually have no or less logic processing than other signals; typically clock lines, which usually do not require any other logic processing and therefore do not require any Other logic processing, delay time is smaller than other related signals.
High-speed digital PCB and other long line boards are designed to keep the delay difference of each signal within a range and ensure the validity of the system reading data in the same cycle (if the delay difference exceeds one clock cycle, the data in the next cycle will read incorrectly). Generally, the delay difference does not exceed 1/4 clock cycle, and the line delay difference per unit length is also fixed. Delay is related to line width, line length and copper thickness, and to the structure of the board, but line length will increase distributed capacitance and inductance, resulting in signal quality. Therefore, the clock IC pin is generally connected to the RC terminal. However, the serpentine wiring does not act as an inductor. Conversely, inductance causes higher harmonic phase shifts in the rising portion of the signal, resulting in reduced signal quality. Therefore, the distance between serpentine lines should be less than twice the line width. The smaller the rise time of the signal, the more susceptible it is to distributed capacitance and inductance.
Because the applications are different, they have different functions. If a serpentine line appears on the computer board, it mainly functions as a filter inductor to improve the anti-interference ability of the circuit. The serpentine traces in the main computer board are mainly used for some clock signals, such as pciclk and agpclk. It has two functions:
1. Impedance matching
2. Filter inductor.
For some important signals, such as hublinks in the Intel hub architecture, there are 13 hublinks running at 233MHz, and they must be strictly equal in length to eliminate hidden dangers caused by delay. Windings are the solution. Generally speaking, the line spacing of serpentine traces is greater than or equal to twice the line width. The serpentine lines on the PCI board are to meet the line length requirements of the PCI 33MHz clock. If it is a distributed parameter LC filter in an ordinary PCB board, it can also be used as an inductor coil for a radio antenna, and a short and narrow snake line can be used as a fuse, etc.