Planar inductor

• US 6,466,122 B1
• Filed: 11/21/2000
• Issued: 10/15/2002
• Est. Priority Date: 09/30/1988
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Sahashi, Masashi, Hasegawa, Michio
• Primary Examiner(s): MAI, ANH T
• Application Number:
  US09/716,403
• Time in Patent Office: 693 Days
• Field of Search: 336/200, 336/223, 336/232
• US Class Current: 336/200
• CPC Class Codes: H01F 1/15308 based on Fe/Ni H01F1/15325 takes precedence
• CPC Class Codes: H01F 17/0013 with stacked layers
• CPC Class Codes: H01F 41/046 structurally combined with ferromagnetic material

Abstract

A planar inductor has a spiral coil, insulating layers stacked on both surfaces of the spiral coil, and ferromagnetic layers stacked on the insulating layers, wherein each ferromagnetic layer has a saturation magnetization 4πM_s of 10 kG or more, and a thickness of 100 μm or less.

Claims

1. A planar inductor, comprising:

a planar inductance element comprising a plurality of windings, the plurality of windings all extending in the same plane; and

at least one ferromagnetic layer stacked on said planar inductance element;

wherein said at least one ferromagnetic layer comprises a plurality of ferromagnetic sub-layers which are stacked upon one another and form said ferromagnetic layer and have no electrically conductive material between them; and

wherein an effective permeability ^μ

10 k at a frequency of 10 kHz of said at least one ferromagnetic layer is not less than 1×

10⁴.

2. The planar inductor according to claim 1, wherein a saturation magnetization 4π

Mζ

of said at least one ferromagnetic layer is not less than 10 kG.

3. The planar inductor according to claim 1, wherein the thickness of each of said plurality of sub-layers is between 4 and 100 microns.

4. The planar inductor according to claim 1, wherein insulating layers and ferromagnetic layers stack on both surfaces of said planar inductance element.

5. The planar inductor according to claim 4, wherein said planar inductance element comprises a spiral coil.

6. The planar inductor according to claim 4, wherein said planar inductance element has a structure obtained by stacking a plurality of spiral coils with insulating layers interposed therebetween.

7. The planar inductor according to claim 1, further comprising:

a coating of a mold resin surrounding said planar inductor element and said at least one ferromagnetic layer; and

a relaxation layer formed on said ferromagnetic layer, for providing strain relaxation due to contraction of said coating of a mold resin when said coating of a mold resin is hardened.

8. The planar inductor according to claim 7, wherein said relaxation layer consists of an organic polymer film, said organic polymer film having a thermal deformation temperature which is higher than a hardening temperature of the mold resin.

9. The planar inductor according to claim 8, wherein said organic polymer film consists of polyphenylenesulfide.

10. The planar inductor according to claim 8, wherein the thickness of said organic polymer film is less than 20 microns.

11. A planar inductor having an inductance, comprising:

at least one ferromagnetic layer, each ferromagnetic layer having a saturation magnetization that is greater than 10 kG and a thickness of less than 100 microns; and

a coil stacked on said ferromagnetic layer and having a plurality of windings, the plurality of windings all extending in the same plane,

wherein an effective permeability at a frequency of 10 kHz of said at least one ferromagnetic layer is not less than 1×

10⁴.

12. The planar inductor according to claim 11, further comprising:

an insulating layer interposed between said coil and said ferromagnetic layer.

13. The planar inductor according to claim 11, wherein said saturation magnetization is greater than 12 kilogauss.

14. The planar inductor according to claim 11, wherein said coil comprises a plurality of stacked spiral coils, in which an insulating layer is disposed between each pair of adjacent coils.

15. The planar inductor according to claim 11, wherein said at least one ferromagnetic layer comprises a plurality of ferromagnetic layers.

16. A planar inductor, comprising:

a laminated structure including a spiral conductor coil for conducting a current, said spiral conductor coil comprises a plurality of windings, the plurality of windings all extending in the same plane, wherein said spiral conductor coil is sandwiched between ferromagnetic layer, each of said ferromagnetic layers comprising a plurality of ferromagnetic ribbons which are sandwiched together; and

wherein an effective permeability at 10 kilohertz of each ferromagnetic layer is at least 1×

10⁴.

17. A planar inductor comprising a laminated structure including a planar inductance element comprising a plurality of windings, the plurality of windings all extending in the same plane, said planar inductance element is sandwiched between ferromagnetic layers each including a plurality of ferromagnetic ribbons, each one of said plurality of ferromagnetic ribbons having a thickness of 100 microns or less,

wherein an effective permeability at a frequency of 10 kHz of said at least one ferromagnetic layer is not less than 1×

10⁴.

18. The planar inductor according to claim 17, further comprising:

insulating layers interposed between the planar inductance element and said ferromagnetic layers.

19. The planar inductor according to claim 17, wherein the thickness of each ferromagnetic ribbon is in the range between 4 and 100 microns.

20. The planar inductor according to claim 17, wherein each ferromagnetic layer has a thickness and a side length, and a ratio of the thickness to the side length of each ferromagnetic layer, composed of a plurality of ferromagnetic ribbons, falls within the range between 2×

10<sup>−

4</sup> and 1×

10<sup>−

2</sup>.

21. A planar inductor, comprising:

a planar inductance element comprising a plurality of conducting coils which are stacked upon one another and separated from one another only by an insulating non-ferromagnetic layer, each of said conducting coils comprising a plurality of windings, a first plurality of windings for a first one of the plurality of conducting coils all extending in the same plane; and

at least one ferromagnetic layer stacked on said planar inductance element;

wherein said at lest one ferromagnetic layer is formed from a plurality of ferromagnetic sub-layers that are stacked upon one another and each of the plurality of ferromagnetic sub-layers has a thickness of 100 microns or less, and

wherein an effective permeability at a frequency of 10 kHz of said at least one ferromagnetic layer is not less than 1×

10⁴.

22. The planar inductor according to claim 21, wherein a saturation magnetization of said at least one ferromagnetic layer is not less than 10 kG.

23. The planar inductor according to claim 21, wherein a thickness of each of said plurality of sub-layers is between 4 and 100 microns.

24. A planar inductor comprising a laminated structure including spiral conductor coil sandwiched between ferromagnetic layers each including a plurality of ferromagnetic ribbons, each of said ferromagnetic ribbons having a thickness of 100 microns or less,

wherein an effective permeability at a frequency of 10 kHz of said at least one ferromagnetic layer is not less than 1×

10⁴.

25. The inductor according to claim 24, wherein a saturation magnetization of each of said ferromagnetic layers is not less than 10 kilogauss.

26. The inductor according to claim 24, wherein the thickness of each of said plurality of ferromagnetic ribbons is between 4 and 100 microns.

27. The inductor according to claim 24, wherein said spiral conductor coil means comprises a plurality of coils with insulating layers interposed therebetween to form a stack of the plurality of coils and the insulating layers.