Low Profile Inductors For High Density Circuit Boards

• US 20110018669A1
• Filed: 07/22/2009
• Published: 01/27/2011
• Est. Priority Date: 07/22/2009
• Status: Active Grant

• Current Assignee: Volterra Semiconductor Corporation (Analog Devices, Inc.)
• Original Assignee: Volterra Semiconductor Corporation (Analog Devices, Inc.)
• Inventors: Ikriannikov, Alexandr
• Granted Patent: US 8,040,212 B2
• Time in Patent Office: Days
• US Class Current: 336/192
• CPC Class Codes: H01F 17/06 with core substantially closed in itself, e.g. toroid
• CPC Class Codes: H01F 27/2847 Sheets; Strips H01F27/2866 takes precedence
• CPC Class Codes: H01F 27/292 Surface mounted devices
• CPC Class Codes: H05K 1/181 associated with surface mounted components
• CPC Class Codes: H05K 2201/1003 Non-printed inductor
• CPC Class Codes: H05K 2201/10659 Different types of terminals for the same component, e.g. solder balls combined with leads
• CPC Class Codes: H05K 3/3426 characterised by the leads
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

An inductor includes a core formed of a magnetic material and a foil winding wound at least partially around or through at least a portion of the core. A first end of the winding extends away from the core to form an extended output tongue configured and arranged to supplement or serve as a substitute for a printed circuit board foil trace. A second end of the winding forms a solder tab. At least a portion of the extended output tongue and the solder tab are formed at a same height relative to a bottom surface of the core. Another inductor includes a core formed of a magnetic material, a winding wound at least partially around or through at least a portion of the core, and a ground return conductor attached to the core. The core does not form a magnetic path loop around the ground return conductor.

Claims

1. An inductor for assembly on a printed circuit board, comprising:

a core formed of a magnetic material; and

a first foil winding wound at least partially around or through at least a portion of the core, a first end of the first winding extending away from the core to form a first extended output tongue, a second end of the first winding forming a solder tab,

the solder tab and at least a portion of the first extended output tongue formed at a same height relative to a bottom surface of the core for surface mount attachment to the printed circuit board, and

the first extended output tongue configured and arranged to supplement or serve as a substitute for a first foil trace disposed on a surface of the printed circuit board.

2. The inductor of claim 1, the first extended output tongue having a length of at least about one centimeter.

3. The inductor of claim 2, the first winding comprising a single turn winding wound through an opening in the core.

4. The inductor of claim 3, the first extended output tongue having a width of at least about one millimeter.

5. The inductor of claim 4, the width of the first extended output tongue being equal to a width of the first winding.

6. The inductor of claim 4, the width of the first extended output tongue being greater than a width of the first winding.

7. The inductor of claim 2, further comprising a second winding wound at least partially around or through at least a portion of the core, a first end of the second winding extending away from the core to form a second extended output tongue configured and arranged to supplement or serve as a substitute for a second foil trace disposed on the surface of the printed circuit board.

8. An inductor for assembly on a printed circuit board, comprising:

a core formed of a magnetic material; and

a first foil winding wound at least partially around or through at least a portion of the core, a first end of the first winding extending away from the core to form a first extended output tongue, a second end of the first winding extending away from the core to form a first extended input tongue,

at least respective portions of the first extended output tongue and the first extended input tongue formed at a same height relative to a bottom surface of the core for surface mount attachment to the printed circuit board,

the first extended output tongue configured and arranged to supplement or serve as a substitute for a first foil trace disposed on a surface of the printed circuit board, and

the first extended input tongue configured and arranged to supplement or serve as a substitute for a second foil trace disposed on the surface of the printed circuit board.

9. The inductor of claim 8, the first extended output tongue having a length of at least about one centimeter.

10. The inductor of claim 9, further comprising a second winding wound at least partially around or through at least a portion of the core, a first end of the second winding extending away from the core to form a second extended output tongue, a second end of the second winding extending away from the core to form a second extended input tongue, each of the second extended output tongue and the second extended input tongue configured and arranged to supplement or serve as a substitute for a respective foil trace disposed on the surface of the printed circuit board.

11. An inductor for assembly on a printed circuit board, comprising:

a core formed of a magnetic material;

a first winding wound at least partially around or through at least a portion of the core; and

a first ground return conductor attached to the core,

the first winding and the first ground return conductor configured and arranged such that inductance of the first ground return conductor is not significantly increased by presence of the core, while inductance of the first winding is significantly increased by presence of the core, relative to an otherwise identical inductor without the core.

12. The inductor of claim 11, the first winding being a foil winding, a first end of the first winding extending away from the core to form an extended output tongue, at least respective portions of the extended output tongue and the first ground return conductor formed at a same height relative to a bottom surface of the core for surface mount attachment to the printed circuit board, the extended output tongue configured and arranged to supplement or serve as a substitute for a first foil trace disposed on a surface of the printed circuit board.

13. The inductor of claim 12, a second end of the first winding extending away from the core to form an extended input tongue, at least respective portions of the extended input tongue, the extended output tongue, and the first ground return conductor formed at a same height relative to the bottom surface of the core, the extended input tongue configured and arranged to supplement or serve as a substitute for a second foil trace disposed on the surface of the printed circuit board.

14. The inductor of claim 12, the first ground return conductor extending along at least a portion of the extended output tongue.

15. The inductor of claim 14, further comprising a second ground return conductor attached to the core and extending along at least a portion of the extended output tongue, the second ground return conductor configured and arranged such that inductance of the second ground return conductor is not significantly increased by presence of the core, relative to an otherwise identical inductor without the core.

16. The inductor of claim 15, further comprising a second winding wound at least partially around or through at least a portion of the core.

17. The inductor of claim 14, further comprising an isolator connecting the extended output tongue and the first ground return conductor.

18. The inductor of claim 17, the extended output tongue being vertically displaced from the first ground return conductor external to the core to magnetically couple together the extended output tongue and the first ground return conductor.

19. The inductor of claim 18, the isolator being formed of a magnetic material that contributes to leakage inductance of the first winding.

20. The inductor of claim 11, wherein:

each end of the first winding has a respective solder tab electrically coupled thereto;

each end of the first ground return conductor has a respective solder tab electrically coupled thereto; and

each solder tab is formed at a same height relative to a bottom surface of the core for surface mount attachment to the printed circuit board.

21. The inductor of claim 20, the inductor being a drop-in inductor, and each of the solder tabs being displaced from the bottom surface of the core.

22. The inductor of claim 21, further comprising a second ground return conductor attached to the core, the second ground return conductor configured and arranged such that inductance of the second ground return conductor is not significantly increased by presence of the core, relative to an otherwise identical inductor without the core.

23. The inductor of claim 22, each of the first and second ground return conductors comprising a clamp for fastening the ground return conductor to the core.

24. The inductor of claim 21, further comprising a second winding wound at least partially around or through at least a portion of the core.

25. The inductor of claim 21, each of the solder tabs electrically coupled to the first winding being an extension of the first winding.

26. The inductor of claim 21, the first winding being a foil winding passing through a channel formed by the core.

27. The inductor of claim 11, further comprising a second winding wound at least partially around or through at least a portion of the core, the first ground return conductor comprising a ground return structure attached to one of a top surface and a bottom surface of the core, the ground return structure being separated from the first and second winding via an insulating layer.

28. The inductor of claim 27, the ground return structure comprising a plurality solder tabs.

29. The inductor of claim 11, the core comprising a plurality of magnetic sections attached to the first ground return conductor, the first winding wound through a respective channel in each of the plurality of magnetic sections.

30. The inductor of claim 29, further comprising a second ground return conductor attached to the plurality of magnetic sections, the second ground return conductor configured and arranged such that inductance of the second ground return conductor is not significantly increased by presence of the core, relative to an otherwise identical inductor without the core.

31. An inductor for assembly on a printed circuit board, comprising:

an elongated ground return conductor forming at least one solder tab at each end of the conductor;

at least two spacer elements disposed on the ground return conductor; and

an elongated foil winding forming at least one solder tab at each end of the winding, the winding disposed on the spacer elements such that the spacer elements separate the ground return conductor from the winding to create a channel between the ground return conductor and the winding.

32. The inductor of claim 31, the ground return conductor being disposed parallel to the winding throughout the channel.

33. The inductor of claim 31, the spacer elements being formed of a magnetic material to increase inductance of the inductor.

34. A printed circuit board assembly including a drop-in inductor attached to a printed circuit board, the drop-in inductor, comprising:

a first foil winding wound through an opening in a magnetic core; and

a first ground return conductor attached to the core; and

wherein the first foil winding and the first ground return conductor are configured and arranged such that inductance of the first ground return conductor is not significantly increased by presence of the core, while inductance of the first foil winding is significantly increased by presence of the core, relative to an otherwise identical inductor without the core;

wherein the first foil winding and the first ground return conductor have ends formed as solder tabs for attachment to the printed circuit board, and wherein the tabs of the first foil winding and the first ground return conductor are formed at a same height relative to a bottom surface of the core;

wherein the tabs of the first foil winding, and the tabs of the first ground return conductor are attached to foil of the same layer of the printed circuit board; and

wherein the printed circuit board forms an aperture, the core of the inductor extending into the aperture.

35. The printed circuit board assembly of claim 34, further comprising a second foil winding wound through an opening in the core, and wherein the first and second foil windings are magnetically coupled, and wherein the inductor forms an output inductor of a buck-type DC-to-DC converter.

36. A printed circuit board assembly, comprising:

a printed circuit board;

at least one switching device attached to the printed circuit board; and

an inductor attached to the printed circuit board, the inductor including;

a core formed of a magnetic material; and

a foil winding wound at least partially around or through at least a portion of the core,

a first end of the winding extending away from the core to form an extended input tongue, at least a portion of the extended input tongue soldered to and supplementing a first foil trace disposed on an outer surface of the printed circuit board, the first foil trace electrically coupling the at least one switching device to the first end of the winding.

37. The printed circuit board assembly of claim 36, a second end of the winding extending away from the core to form an extended output tongue, at least a portion of the extended output tongue soldered to and supplementing a second foil trace disposed on the outer surface of the printed circuit board.

38. The printed circuit board assembly of claim 36, the inductor being a buck converter output inductor, the second foil trace electrically coupling a second end of the winding to a load.

39. The printed circuit board assembly of claim 36, the winding being a single turn winding wound through an opening in the core.

40. The printed circuit board assembly of claim 36, further comprising a ground return conductor attached to the core, the winding and the ground return conductor configured and arranged such that inductance of the ground return conductor is not significantly increased by presence of the core, while inductance of the winding is significantly increased by presence of the core, relative to an otherwise identical inductor without the core, the ground return conductor supplementing a ground return trace of the printed circuit board.

41. A printed circuit board assembly, comprising:

a printed circuit board;

at least one switching device attached to the printed circuit board; and

an inductor attached to the printed circuit board, the inductor including;

a core formed of a magnetic material; and

a foil winding wound at least partially around or through at least a portion of the core,

a first end of the winding electrically coupled to the at least one switching device, a second end of the winding extending away from the core to form an extended output tongue, at least a portion of the extended output tongue soldered to and supplementing a first foil trace disposed on an outer surface of the printed circuit board.

42. The printed circuit board assembly of claim 41, the inductor being a buck converter output inductor, the first foil trace electrically coupling the second end of the winding to a load.

43. The printed circuit board assembly of claim 41, the winding being a single turn winding wound through an opening in the core.

44. The printed circuit board assembly of claim 41, further comprising a ground return conductor attached to the core, the winding and the ground return conductor configured and arranged such that inductance of the ground return conductor is not significantly increased by presence of the core, while inductance of the winding is significantly increased by presence of the core, relative to an otherwise identical inductor without the core, the ground return conductor supplementing a ground return trace of the printed circuit board.