Rfid tag substrate, rfid tag, and rfid system

An RFID tag board having a plate surface on which a semiconductor integrated circuit is to be mounted, the RFID tag board being used with the plate surface and the semiconductor integrated circuit thereon sealed with a sealing member, comprising:

• an insulating substrate one surface of which forms the plate surface;
• a first surface conductor that is disposed on the one surface of the insulating substrate;
• a second surface conductor that is disposed on a surface of the insulating substrate opposite to the one surface;
• a short-circuit part through conductor that passes through the insulating substrate in a thickness direction to electrically connect the first surface conductor and the second surface conductor;
• a capacitance conductor that is disposed in the insulating substrate and faces at least part of the first surface conductor or at least part of the second surface conductor to form a capacitance element;
• a capacitance part through conductor that is disposed in the insulating substrate to electrically connect the capacitance conductor and one of the first surface conductor and the second surface conductor not facing the capacitance conductor;
• a first electrode that is disposed on the one surface of the insulating substrate and to which, among terminals that the semiconductor integrated circuit has, a terminal from which a voltage signal relating to a transmission radio wave is output is electrically connected;
• and
• a second electrode that is disposed on the one surface of the insulating substrate and to which, among the terminals that the semiconductor integrated circuit has, a terminal serving as a reference potential is electrically connected,
• wherein a first conductor of a pair of conductors that forms the capacitance element is electrically connected to the first electrode not via the short-circuit part through conductor, and a second conductor of the pair of conductors is electrically connected to the second electrode not via the short-circuit part through conductor, and
• wherein a distance from the first electrode to the short-circuit part through conductor is shorter than a distance from the second electrode to the short-circuit part through conductor.