Printed circuit board capable of preventing electromagnetic interference

摘要

A printed circuit board includes a first electric conductive layer formed on an insulating base plate to form signal patterns and a ground pattern. An insulation layer covering the signal patterns and a second electric conductive layer connected to the ground pattern are sequentially formed on the plate. A large area ground land is formed in the vicinity of a ground terminal of a digital IC by the first electric conductive layer to be connected to the ground terminal, which is directly surface-connected to the second electric conductive layer so that a ground impedance of the ground terminal can be reduced. A large area power source land connected to a power source terminal of the digital IC is formed in the vicinity of the power source terminal by the first electric conductive layer, which sandwiches the insulation layer in cooperation with the second electrostatic conductive layer so that an electrostatic capacitance larger than a line-to-line distribution capacitance formed by the signal patterns can be formed between the power source land and the second electric conductive layer.