Forming method of magnetic body, magnetic body, and printed circuit board

摘要

A method of forming a magnetic body, alternative to a ferrite core, on a printed circuit board is provided. A printed circuit board is set in a mold and injection molding is conducted. The mold comprises a fixed plate, an intermediate plate and a movable plate. A cavity in the intermediate plate is filled with a melted material (i.e., mixture of resin and magnetic filler) supplied via a sprue and a runner. A cavity in the movable plate is also filled with the material supplied to the cavity in the intermediate plate through a hole in the printed circuit board. When a magnetic body for noise control is directly injection molded onto the printed circuit board in such a way, no gap appears between the magnetic body and the printed circuit board. As a result, the magnetic body functions well as desired.