Multi-piece-array and method of manufacturing the same

A multi-piece-array that is formed by laminating a plurality of ceramic layers and has a front surface and a back surface, the multi-piece-array comprising:

• a product region where a plurality of wiring board portions having a rectangular shape in plan view and including cavities are arranged in matrix;
• an edge portion that is positioned along a periphery of the product region;
• and
• dividing grooves that are formed on at least one of the front surface and the back surface along a boundary between the wiring board portions and a boundary between the wiring board portion and the edge portion,
• wherein a deepest portion of the dividing groove has an arc shape and the dividing groove includes a middle portion between the deepest portion and a groove inlet on a cross-section orthogonal to an extending direction of the dividing groove, and
• wherein a width of the deepest portion is greater than a width of the groove inlet and a width of the middle portion is equal to or less than the width of the groove inlet.