A substrate includes a first plate member; a plurality of first electrodes provided on the major surface of the first plate member, the first electrodes including at least one electrode for circuit connection and at least one monitor electrode separate from the electrode for circuit connection; a second plate member; a plurality of second electrodes provided on the major surface of the second plate member; a plurality of solder members provided between the first electrodes and the second electrodes for electrical connection therebetween, repeatedly; and a detector for detecting an electrical disconnection between at least one of the monitor electrode and the second electrode.