Embedded toroidal transformers in ceramic substrates

• US 20050212642A1
• Filed: 03/26/2004
• Published: 09/29/2005
• Est. Priority Date: 03/26/2004
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Thomson, Andrew John, Pleskach, Michael David
• Granted Patent: US 7,196,607 B2
• Time in Patent Office: Days
• US Class Current: 336/200
• CPC Class Codes: H01F 17/0033 with the coil helically wound around a magnetic core
• CPC Class Codes: H01F 41/046 structurally combined with ferromagnetic material
• CPC Class Codes: H01L 23/49822 Multilayer substrates multilayer metallisation on monolayer substrate H01L23/498
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor

Abstract

Method for forming a transformer (118) in a ceramic substrate. The method can include the steps of forming at least one conductive coil (119a, 119b) comprising a plurality of turns about an unfired ceramic toroidal core region (120a, 120b) defined within an unfired ceramic substrate (100). The method can also include the step of co-firing the unfired ceramic toroidal core region (120a, 120b), the unfired ceramic substrate (100), and the conductive coil (119a, 119b) to form an integral ceramic substrate structure with the conductive coil at least partially embedded therein.

Claims

1. A transformer embedded in an LTCC substrate, comprising:

a ceramic substrate;

a ceramic toroidal core embedded within said ceramic substrate; and

at least one conductive coil comprising a plurality of turns about said ceramic toroidal core, wherein said ceramic toroidal core is integrally formed with said ceramic substrate in a co-firing process.

2. The transformer according to claim 1 wherein said plurality of turns are contained within said ceramic substrate at all points.

3. The transformer according to claim 1 wherein said ceramic toroidal core is comprised of a ceramic material that has a permeability greater than a second ceramic material comprising at least one other portion of said ceramic substrate.

4. The transformer according to claim 1 further comprising at least one conductive metal ground plane layer disposed within said ceramic substrate.

5. The transformer according to claim 4 wherein said ground plane layer is interposed between said conductive coil and at least one surface mount component disposed on a surface of said ceramic substrate.

6. The transformer according to claim 1 further comprising a second conductive coil including a plurality of turns disposed about said ceramic toroidal core and having a coil radius different from said first conductive coil.

7. The transformer according to claim 1 further comprising a second conductive coil formed of a plurality of turns disposed about a radial portion of said ceramic toroidal core exclusive of a second radial portion of said ceramic toroidal core where said first conductive coil is disposed.

8. The transformer according to claim 1 wherein said transformer is an autotransformer.

9. The transformer according to claim 1 wherein at least a portion of said ceramic toroidal core region has a permeability greater than one.

10. A method for forming a transformer in a ceramic substrate, comprising the steps of:

forming at least one conductive coil comprising a plurality of turns about an unfired ceramic toroidal core region defined within an unfired ceramic substrate; and

co-firing said unfired ceramic toroidal core region, said unfired ceramic substrate, and said conductive coil to form an integral ceramic substrate structure with said conductive coil at least partially embedded therein.

11. The method according to claim 10, further comprising the step of forming at least a portion of said ceramic toroidal core region of a ceramic material having a permeability greater than one.

12. The method according to claim 10 further comprising the step of disposing a conductive ground plane layer between said conductive coil and an outer surface of said ceramic substrate.

13. The method according to claim 12 further comprising the step of disposing said ground plane layer between said conductive coil and at least one surface mount component disposed on a surface of said ceramic substrate.

14. The method according to claim 10 further comprising the step of forming a second conductive coil including a plurality of turns disposed about said ceramic toroidal core.

15. The method according to claim 14 further comprising the step of selecting a coil radius of said second conductive coil to be different from a coil radius of said first conductive coil.

16. The method according to claim 10 further comprising the step of forming a second conductive coil of a plurality of turns disposed about a radial portion of said ceramic toroidal core exclusive of said radial portion of said ceramic toroidal core where said first conductive coil is disposed.

17. The method according to claim 10 further comprising the step of providing at least one tap along a length of said conductive coil to form an autotransformer.

18. A method for forming a transformer in a ceramic substrate, comprising the steps of:

forming a plurality of vias and traces in an unfired ceramic substrate to define least one conductive coil comprising a plurality of turns about an unfired ceramic toroidal core region defined within said; and

co-firing said unfired ceramic toroidal core region, said unfired ceramic substrate, and said conductive coil to form an integral ceramic substrate structure with said conductive coil at least partially embedded therein.

19. The method according to claim 18 further comprising the step of forming said vias from a conductive metal paste.

20. The method according to claim 18, further comprising the step of forming at least a portion of said ceramic toroidal core region of a ceramic material having a permeability greater than one.

21. The method according to claim 18 further comprising the step of disposing a conductive ground plane layer between said conductive coil and an outer surface of said ceramic substrate.

22. The method according to claim 21 further comprising the step of disposing said ground plane layer between said conductive coil and at least one surface mount component disposed on a surface of said ceramic substrate.

23. The method according to claim 18 further comprising the step of forming a second conductive coil from a plurality of conductive vias and conductive traces to define a plurality of turns disposed about said ceramic toroidal core.

24. The method according to claim 23 further comprising the step of selecting a coil radius of said second conductive coil to be different from a coil radius of said first conductive coil.

25. The method according to claim 18 further comprising the step of forming a second conductive coil of a plurality of turns disposed about a radial portion of said ceramic toroidal core exclusive of said radial portion of said ceramic toroidal core where said first conductive coil is disposed.

26. The method according to claim 18 further comprising the step of providing at least one tap along a length of said conductive coil to form an autotransformer.