Printed circuit board capable of preventing electromagnetic interference.

摘要

A printed circuit board (10) includes a first electric conductive layer (11) formed on an insulating base plate (12) to form signal patterns (14) and a ground pattern (16). An insulation layer (26) covering the signal patterns and a second electric conductive layer (28) connected to the ground pattern are sequentially formed on the plate. A large area ground land (20ae) formed in the vicinity of a ground terminal (32) of a digital IC by the first electric conductive layer (11), to be connected to the ground terminal, the land being directly surface-connected to the second electric conductive layer (28) so that a ground impedance of the ground terminal can be reduced. A large area power source land (20av) connected to a power source terminal (30) of the digital IC is formed in the vicinity of the power source terminal by the first electric conductive layer (11), which sandwiches the insulation layer (26) in cooperation with the second conductive layer (28) 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.