Coil component, method of manufacturing the same, and electronic device
A coil component includes an air-core coil embedded in a magnetic body constituted by resin and metal magnetic grains. Both ends of the coil are exposed on the surface of the magnetic body, and the side on which both ends are exposed is polished and etched to form terminal electrodes. To be specific, an underlying layer of metal material is formed across the surface of the magnetic body and the ends by means of sputtering, and then a cover layer is formed. Where the magnetic body contacts the underlying layer, the areas where the underlying layer is in contact with the resin ensure insulation, while the contact between the underlying layer and the exposed parts of the metal magnetic grains ensures adhesion, thus increasing the adhesion strength with respect to the terminal electrodes.
1. A coil component comprising an air-core coil embedded in a magnetic body constituted by resin and metal magnetic grains, and having terminal electrodes electrically connected to both ends of the coil, wherein:
both ends of the coil are exposed on a surface of the magnetic body;
the terminal electrodes are formed across the surface of the magnetic body and ends of the coil, and constituted by an underlying layer formed with metal material and a cover layer placed on an outer side of the underlying layer; and
the underlying layer is in contact with the resin and metal parts of the metal magnetic grains where the underlying layer is in contact with the magnetic body,
wherein a magnetic body surface on a side where each terminal electrode is connected to the end of the coil contains less resin than a magnetic body surface on a side where each terminal electrode is not connected to the end of the coil.
2. A coil component according to claim 1 , wherein, where the underlying layer is in contact with the magnetic body, a ratio of areas where the underlying layer is in contact with the metal magnetic grains is greater than a ratio of areas where the underlying layer is not in contact with the metal magnetic grains.
3. A coil component according to claim 1 , wherein the metal magnetic grains of the magnetic body include two or more types of metal magnetic grains of different grain sizes.
4. A coil component according to claim 1 , wherein the metal material that forms the underlying layer contains one of Ag, Cu, Au, Al, Mg, W, Ni, Fe, Pt, Cr, and Ti.
5. A coil component according to claim 1 , wherein the metal material that forms the underlying layer contains at least Ag or Cu.
6. A coil component according to claim 1 , wherein the cover layer is formed with Ag or conductive resin containing Ag.
7. A coil component according to claim 1 , wherein a protective layer covering an outer side of the cover layer is provided.
8. A coil component according to claim 7 , wherein the protective layer is formed with Ni and Sn.
9. A coil component according to claim 1 , wherein, on a magnetic body surface where the terminal electrodes are not formed, phosphorus is contained at least in some areas of the surface.
10. A coil component according to claim 1 , wherein, on a magnetic body surface where the terminal electrodes are not formed, at least some areas of the surface are covered with resin that contains an oxide filler whose grain size is smaller than that of the metal grains.
11. An electronic device having a coil component according to claim 1 .
12. A coil component according to claim 1 , wherein surfaces of the metal parts of the metal magnetic grains, which are in contact with the underlying layer, are etched surfaces.
13. A coil component according to claim 1 , wherein the underlying layer is a sputter-formed metal layer.