Abstract: A flexible printed circuit board according to an embodiment includes a base film and a first wire. The base film has a first surface. The first wire is disposed on the first surface. The first wire has a first layer and a second layer. The first layer is disposed on the first surface directly or indirectly. The second layer covers the first layer. In the first surface, a first groove is formed next to the first layer in a plan view. The second layer on a side surface of the first layer exists on a bottom surface and a side surface of the first groove.

Abstract: A positioning mark (20) has a shape by which a position and a direction can be identified when moved together with a separator (10) along a plane. In other words, the positioning mark (20) is formed, for example, in a cross shape so that a position on the X-axis and a position on the Y-axis and the tilt in the ? direction of the positioning mark (20) can be identified. The positioning mark (20) is optically read by, for example, a sensor, and the positions on the x-axis and the Y-axis of the positioning mark (20) are calculated by, for example, image analysis processing. Based on the calculation result, positioning of the separator (10) is performed.