Components themselves exhibit characteristic impedance so the impedance of the PCB traces must be chosen to match the characteristic impedance of the logic family in use.
If the impedance of the PCB traces does not match the device characteristic impedance multiple reflections will occur on the line before the device can settle. This can result in increased switching times or random errors in high-speed digital systems. The value and tolerance of impedance will be specified by the circuit design engineer and the PCB designer, however, it will often be left to the PCB manufacturer to conform to the designer's specification and verify that the finished boards meet the specification.