Planar grooved power inductor structure and method

• US 7,971,340 B2
• Filed: 01/14/2011
• Issued: 07/05/2011
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: Alpha & Omega Semiconductor, Ltd.
• Original Assignee: Alpha & Omega Semiconductor, Ltd.
• Inventors: Hébert, François, Feng, Tao, Lu, Jun
• Primary Examiner(s): NGUYEN, TUYEN T
• Application Number:
  US13/007,551
• Publication Number:
  US 20110107589A1
• Time in Patent Office: 172 Days
• Field of Search: 336/65, 336/192, 336/200, 336232-234, 296/021, 2960316- 18, 295/30
• US Class Current: 29/602.1
• CPC Class Codes: H01F 1/344 Ferrites, e.g. having a cubic spinel structure (X2+O)(Y23+O3), e.g. magnetite Fe3O4
• CPC Class Codes: H01F 17/0033 with the coil helically wound around a magnetic core
• CPC Class Codes: H01F 2017/002 Details of via holes for interconnecting the layers
• CPC Class Codes: H01F 41/046 structurally combined with ferromagnetic material
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor

Abstract

An inductor may include a planar ferrite core. A first group of one or more grooves is formed in a first side of the ferrite core. A second group of two or more grooves is formed in a second side of the ferrite core. The grooves in the first and second groups are oriented such that each groove in the first group overlaps with two corresponding grooves in the second group. A first plurality of vias communicates through the ferrite core between the first and second sides of the ferrite core. Each via is located where a groove in the first group overlaps with a groove in the second group. A conductive material is disposed in the first and second groups of grooves and in the vias to form an inductor coil.

Claims

1. A method for manufacturing an inductor comprising:

a) forming a first group of one or more grooves formed on a first side of a planar ferrite core;

b) forming a second group of two or more parallel grooves formed on a second side of the ferrite core, wherein the grooves in the first and second groups are oriented such that each groove in the first group overlaps with one or two corresponding grooves in the second group;

c) forming one or more vias communicating through the ferrite core between the first and second sides of the ferrite core, wherein each of via is located where a groove in the first group overlaps with a grooves in the second group; and

d) disposing a conductive material in the first and second groups of grooves and the vias.

2. The method of claim 1, wherein a) includes etching the first side of the ferrite core.

3. The inductor of claim 1, wherein b) includes etching the second side of the ferrite core.

4. The method of claim 1, further comprising forming one or more additional vias communicating between the first side and the second side.

5. The method of claim 1 wherein d) includes filling the grooves and vias with the conductive material.

6. The method of claim 1 wherein d) includes lining a bottom and sidewalls of the grooves and sidewalls of the vias with the conductive material.

7. The method of claim 1 wherein a) or b) includes cutting the grooves across a surface of the ferrite core.

8. The method of claim 7 wherein cutting the grooves across a surface of the ferrite core includes cutting the grooves with a saw.

9. The method of claim 1 wherein a) includes forming the first group of grooves in a surface of a first ferrite layer and wherein b) includes forming the second group of grooves in a surface of a second ferrite layer, the method further comprising attaching the first and second ferrite layers to each other back to back such that the first and second sides are disposed on outside surfaces of the ferrite core.

10. The method of claim 1, further comprising passivating the first or second side of the ferrite core with a dielectric layer.

11. The method of claim 1 wherein a)-d) are performed on a plurality of die on a ferrite sheet, the method further comprising singulating the ferrite sheet into individual inductor chips after d).