CIRCUIT BOARD AND MANUFACTURING METHOD THEREFOR

An electrochemical device includes: an electricity storage device that includes positive and negative electrodes stacked via a separator and wound, and lead plates electrically connected to the positive or negative electrode; a connection plate having a first surface on an electricity storage device side and a second surface opposite to the first surface, the lead plates being stacked and welded to the first surface; and a rupture disc connected to the second surface, the lead plates being welded to the connection plate at first and second welding portions on the first surface separated from each other, a lead plate on a connection plate side being welded to the connection plate at the first and second welding portions, a lead plate on a side opposite to the connection plate being welded to the connection plate at the first welding portion and unwelded to the connection plate at the second welding portion.