As the trace width (W) increases, the impedance decreases, while the signal propagation delay remains unchanged, and vice-versa. Any adjustments in width should include adjustments in spacing (S) to maintain immunity to crosstalk effects. Spacing factors are roughly 1.0X to 3X depending on the particular type of memory and signal. The associations in Table: Relationship of Trace Width to Impedance, Required Spacing, and Propagation Delay show the effect of width on impedance, spacing, and propagation delay.