Method for manufacturing magnetic core module in magnetic head, magnetic core module in magnetic head and magnetic head

A magnetic head comprising a magnetic core module and a shield case housing the magnetic core module, the magnetic core module comprising:

• a magnetic core group disposed as an insert in a holder mold cavity of a holder, the magnetic core group comprising magnetic cores welded together with a laser beam by means of a laser beam welding technique before the magnetic core group is disposed in the holder mold cavity, and the magnetic core group being disposed at a specified position in the holder mold cavity, an optical detector having detected the magnetic core group to be at the specified position in the holder mold cavity;
• wherein the magnetic core group and the holder are formed in one piece through injection molding a plastic resin to the holder mold cavity containing the magnetic core group, a plurality of opening windows being provided on a side of the holder;
• and
• comprising a conductive retaining spring pressing both the magnetic core group and the shield case, so as to connect to ground and a nonmagnetic metal spacer between the magnetic core group and the retaining spring, the retaining spring in contact with the metal spacer and a tip of the retaining spring in contact with the shield case to ground between the magnetic core group and the shield case.