A multi-layer printed circuit board comprises: at least two insulation layers, respectively having glass fiber cloth and cured resin covering thereon, the insulation layers being stacked on each other; an internal trace layer formed between two neighboring insulation layers; and an external trace layer formed on an outer surface of the outermost insulation layer; wherein the insulation layers have a dielectric constant of 3.4 or less, and the internal and external trace layers have a trace width between 40 and 75 micrometers, such that the multi-layer printed circuit board has a characteristic impedance between 45 and 55Ω in single-ended signaling and between 90 and 110Ω in differential signaling.