In one exemplary embodiment, an electrical connector includes a D-subminiature connector assembly including a base, a D-subminiature connector mounted to the base, and a terminal block mounted to the base and spaced from the D-subminiature connector. Thus, a fine treatment agent which makes fine treatment on a multilayer film, including a tungsten film and a silicon oxide film, possible by controlling the etching rate and a fine treatment method using the same can be provided. The testing unit includes a headform upon which a protective mask to be tested is mounted. Impurities are introduced by a self-aligning process. As a result, the manufacturing cost of the control unit can be reduced.