Any a walk line on the PCB Board in the case of by high frequency signal to the signal caused by time delay, Serpentine alignment is the main purpose of “the same group of related” delay smaller part of the signal lines, these parts are often not or less than other signals by other processing logic;The most typical is the clock line, which is usually not processed by any other logic, so its delay is less than other related signals.
Line length is such as high-speed digital PCB for keep delay difference of each signal in a range, to ensure the effectiveness of the read data in the system in the same period (delay less than one clock cycle wrong when they read the data of the next cycle), the general requirements delay difference is not more than a quarter of the clock cycle, the unit length line delay difference is fixed, delay with the line width, line length, copper thickness, plate layer structure, but the line is too long will increase the distribution of distributed capacitance and inductance, make the signal quality inspection, so the clock IC pins are general RC termination, but Serpentine alignment, not the inductance of the role, on the contrary, The inductance causes the higher harmonic in the rising phase of the signal to phase shift,make signal quality deterioration of scale, so the requirement serpentine is at least twice the line width, line spacing, the less the rise time of a signal is examining the influence of the distribution by the distributed capacitance and inductance.
Because the applications of different with different function, if serpentine line appeared in the PC board, its main play the role of a filter inductance, improve the anti-interference capacity of circuit, and the serpentine line in computer motherboard.
Mainly used in some clock signals, such as CIClk, AGPClk, which has two functions:
1. Impedance matching;
2. Filter inductance.
For some important signals, such as the HUBLink in the INTEL HUB architecture, there are 13 roots, running 233MHz, and the requirements must be kept strictly for long, to eliminate the hidden dangers caused by the delay, and the winding is the only solution.Generally speaking, the line spacing of the coil of the snake is twice as wide as >= 2.The snake line on the PCI board is required to adapt to the line length of PCI 33MHzClock.In normal PCB board Manufacturing, it is an LC filter with distributed parameters, and it can also be used as the inductor coil of radio antennae, and the short and narrow snake line can be used to make fuses, etc.