Multi-piece wiring substrate, wiring substrate, and method for manufacturing multi-piece wiring substrate

A wiring substrate, comprising:

• a substrate including a first principal face and a second principal face opposite to the first principal face and having a rectangular shape in a plan view thereof,
• the substrate including
• first side surfaces which are located along a set of opposite first sides of the first principal face,
• second side surfaces which are located along a set of opposite second sides of the first principal face,
• third side surfaces which are located along a set of opposite first sides of the second principal face,
• fourth side surface which are located along a set of opposite second sides of the second principal face,
• first fracture parts for connecting together the first side surfaces and the third side surfaces, respectively, and
• second fracture parts for connecting together the second side surfaces and the fourth side surfaces, respectively,
• in a thickness direction of the substrate, lengths of the first side surfaces and lengths of the third side surfaces being set to be greater than lengths of the second side surfaces and lengths of the fourth side surfaces,
• first curved parts being provided so that the lengths of the second side surfaces gradually increase as going toward respective corners of the substrate, and second curved parts being provided so that the lengths of the fourth side surfaces gradually increase as going toward the respective corners of the substrate.

A method for manufacturing a multi-piece wiring substrate, comprising:

• a step of preparing a matrix substrate including a monolayer or multi-layer ceramic insulating layer, the matrix substrate including a first principal face and a second principal face opposite to the first principal face and forming a plurality of wiring substrate regions provided in the matrix substrate;
• a step of, by laser processing, forming first dividing grooves on a first principal face side of the matrix substrate along respective first sides of the wiring substrate regions and forming, on the first principal face side along respective second sides of the wiring substrate regions, the third dividing grooves, depths of which are smaller than depths of the first dividing grooves and gradually increase as going toward respective corners of the wiring substrate regions, and thereby forming the first curved parts;
• and
• a step of, by laser processing, forming the second dividing grooves on a second principal face side of the matrix substrate along the respective first sides of the wiring substrate regions and forming, on the second principal face side along the respective second sides of the wiring substrate regions, the fourth dividing grooves, depths of which are smaller than depths of the second dividing grooves and gradually increase as going toward the respective corners of the wiring substrate regions, and thereby forming the second curved parts.