Flat magnetic element and power IC package using the same
View Patent ↗A planar magnetic device 1 including a first magnetic layer 3 , a second magnetic layer 5 , and a planar coil 4 disposed between the first magnetic layer 3 and the second magnetic layer 5 , wherein magnetic particles 7 having a shape ratio S/L of 0.7 to 1 when a length of a long axis is L and a length of a short axis orthogonal to the long axis is L are filled in a gap W between coil wirings of the planar coil 4 . According to the planar magnetic device 1 , it is possible to realize a planar magnetic device such as an inductor reduced in height by using fine particles that enable to effectively obtain a large inductance value.
1. A planar magnetic device comprising:
a first magnetic layer,
a second magnetic layer, and
a planar coil disposed between the first magnetic layer and the second magnetic layer,
wherein
magnetic particles, having a shape ratio S/L of 0.7 to 1 where a length of a long axis is L and a length of a short axis orthogonal to the long axis is S, fill a gap between coil wirings of the planar coil, the gap between the coil wirings of the planar coil being W, where W is 200 μm or less;
an average particle diameter of the magnetic particles is W/2 or less;
a thickness of the planar magnetic device is 0.5 mm or less; and
a filling ratio of the magnetic particles filled in the gap between the coil wirings of the planar coil is 30 vol. % or more.
2. The planar magnetic device according to claim 1 , wherein the filling ratio of the magnetic particles filled in the gap between the coil wirings of the planar coil is 50 vol. % or more.
3. The planar magnetic device according to claim 1 , wherein the magnetic particles are made from at least one of an amorphous alloy, a crystalline soft magnetic alloy, and ferrite.
4. The planar magnetic device according to claim 1 , wherein the first magnetic layer and the second magnetic layer are made from a mixture of a magnetic powder and a resin.
5. The planar magnetic device according to claim 1 , wherein the planar coil is made from a mixture of a metal powder and a resin.
6. The planar magnetic device according to claim 1 , wherein the magnetic particles are a magnetic mixture containing 20 mass % or less of a resin binder.
7. The planar magnetic device according to claim 1 , wherein a resin binder is dried after a magnetic layer is formed by filling the magnetic particles in the gap between the coil wirings and in a state where the resin binder penetrates into the magnetic particles, and a content of the resin binder in the dried magnetic layer is 0 to 20 mass %.
8. A power source IC package using the planar magnetic device according to any one of claims 1 , 2 - 4 , 5 and 6 .
9. The power source IC package according to claim 8 , wherein the power source IC package is an IC-integrated type.
10. The planar magnetic device according to claim 1 , wherein the magnetic particles are a magnetic mixture containing 2 mass % or less of a resin binder.
11. The planar magnetic device according to claim 1 , wherein a resin binder is dried after a magnetic layer is formed by filling the magnetic particles in the gap between the coil wirings and in a state where the resin binder penetrates into the magnetic particles, and a content of the resin binder in the dried magnetic layer is 0 to 2 mass %.