Patent ID: 7112967
Filing Date: 2006-09-26
Classification: G01R

Abstract:
1. A circuit board testing apparatus for testing a plurality of wirings of a circuit board, each wiring including a terminal formed on a surface of the circuit board and an electric conductor, which is formed on at least one of the surface of the circuit board and inside of the circuit board, and the electric conductor electrically connected to the terminal formed on the surface, the apparatus comprising: an electromagnetic wave irradiator which irradiates an electromagnetic wave onto a terminal of a selected wiring which is formed on the surface, to discharge electrons from the irradiated terminal by photoelectric effect; a first electrode disposed to trap the electrons discharged from the irradiated terminal; a second electrode capacitively coupled to conductors of the plurality of wirings; a DC power source connected between the first electrode and the second electrode to cause a difference of an electric potential in such a manner that the first electrode has a higher potential than that of the second electrode, wherein the first electrode, the DC power source, the second electrode and at least one of the conductors of the wirings form a closed loop circuit; a current detector provided in the closed loop circuit to detect an electric current that passes through the closed loop circuit; and a judger which judges whether the electric conductor of the selected wiring is continuous, based on a current value detected by the current detector when the first terminal is irradiated by the electromagnetic wave and another current value detected by the current detector when another terminal is irradiated by the electromagnetic wave; wherein the closed loop circuit is arranged such that the electric current, due to electrons discharged by the photoelectric effect and trapped by the first electrode, flows through the closed loop circuit including the DC power source, the second electrode and the capacitive coupling, and returns to at least one of the plurality of wirings.