When the wavelength of the signal is of the order of the length of the connection, such connections become components with relevant electrical properties (capacitance, inductance, characteristic impedance, and delay characteristics). The line length and the terminating resistor become important. The properties also depend on the mechanical structure and the material. In this range, it is even possible to build filters with only lines. A piece of wire can thus become a resonant circuit - which sometimes disturbs, or is intended to be so . Antennas, for example, also work in this way.
Designing circuit boards for such frequency ranges is a very challenging task.