Winding core, method for manufacturing the same, and winding core aggregate

A method for manufacturing winding cores, each of the winding cores includes

• a core portion that is located at a central portion in a longitudinal direction and around which a winding wire is to be wound, and
• a first and second flanges that are respectively connected to first and second end portions that are opposite each other in the longitudinal direction of the core portion,
• each core portion having a core portion bottom surface that is to be directed to a mounting substrate side during mounting, a core portion upper surface that is opposite the core portion bottom surface, and first and second core portion side surfaces that connect the core portion bottom surface and the core portion upper surface to each other and that face away from each other,
• each of the first and second flanges having a flange bottom surface that is to be directed to the mounting substrate side and that is to be nearer than the core portion bottom surface to the mounting substrate during mounting, a flange upper surface that is opposite the flange bottom surface, first and second flange side surfaces that are to be perpendicular to the mounting substrate during mounting, that connect the flange bottom surface and the flange upper surface to each other, and that face away from each other, an inner end surface that faces the core portion and on which an end portion of the core portion is disposed, and an outer end surface that is opposite the inner end surface and that faces outward,
• the method comprising:
• preparing a mother substrate that is composed of a nonconductive material and that enables the winding cores to be obtained in a manner in which the mother substrate is divided along x-direction division lines and y-direction division lines that are perpendicular to each other;
• forming x-direction division grooves along the x-direction division lines on a first main surface of the mother substrate;
• forming y-direction division grooves along the y-direction division lines on the first main surface of the mother substrate;
• forming bottom surface exposure grooves, for exposing surfaces each of which is to be the core portion bottom surface, on the first main surface of the mother substrate such that the bottom surface exposure grooves are shallower than the x-direction division grooves and the y-direction division grooves;
• and
• dividing the mother substrate by performing a flattening process on a second main surface of the mother substrate that is opposite the first main surface until the second main surface reaches the x-direction division grooves and the y-direction division grooves to obtain the winding cores that are separated from each other.