Circuit board embedded inductor

• US 6,996,892 B1
• Filed: 03/24/2005
• Issued: 02/14/2006
• Est. Priority Date: 03/24/2005
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Rao, Yang, Kay, Michael, Shah, Milind, Dening, David, Dorn, Steve, Jorgenson, Jon
• Primary Examiner(s): Nguyen, Tuyen T
• Application Number:
  US11/089,297
• Time in Patent Office: 327 Days
• Field of Search: 336/65, 336/83, 336/200, 336206-208, 336/232, 296/021, 296/031.3, 296/031.8, 296/09, 438/3, 438/381
• US Class Current: 29/602.1
• CPC Class Codes: H01F 17/0013 with stacked layers
• CPC Class Codes: H01F 2017/002 Details of via holes for interconnecting the layers
• CPC Class Codes: H01F 2017/048 with encapsulating core, e.g. made of resin and magnetic powder
• CPC Class Codes: H05K 1/165 incorporating printed inductors
• CPC Class Codes: H05K 2201/0187 with regions of different dielectrics in the same layer, e.g. in a printed capacitor for locally changing the dielectric properties
• CPC Class Codes: H05K 2201/0209 Inorganic, non-metallic particles
• CPC Class Codes: H05K 2201/086 for inductive purposes, e.g. printed inductor with ferrite core
• CPC Class Codes: H05K 3/4626 characterised by the insulating layers or materials H05K3/4688 takes precedence
• CPC Class Codes: H05K 3/4652 Adding a circuit layer by laminating a metal foil or a preformed metal foil pattern H05K3/4647 takes precedence
• CPC Class Codes: H05K 3/4655 by using a laminate characterized by the insulating layer general-purpose insulating materials H05K1/03, H05K3/4673
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor

Abstract

A circuit board having an embedded inductor and a process for making the circuit board is provided. In general, the process begins by providing a core structure including a dielectric core layer and a first metal layer on a top surface of the dielectric core layer. The first metal layer is etched to form first inductor windings. A material, such as an epoxy material, including magnetic filler material is deposited over the first inductor windings. Thereafter, a prepreg layer is placed over and attached to the material deposited over the first inductor windings to form the circuit board having the embedded inductor.

Claims

1. A method for manufacturing a circuit board having an embedded inductor comprising:

providing a core structure comprising a dielectric core layer and a first metal layer on a top surface of the dielectric core layer;

etching the first metal layer to form first inductor windings;

depositing a material including a magnetic filler material over the first inductor windings;

placing a first prepreg layer over the material including the magnetic filler material deposited over the first inductor windings; and

attaching the first prepreg layer to the material including the magnetic filler material deposited over the first inductor windings.

2. The method of claim 1 further comprising depositing the material including the magnetic filler material over a bottom surface of the dielectric core layer to provide a magnetic path surrounding the first inductor windings.

3. The method of claim 1 wherein the core structure further comprises a second metal layer on a bottom surface of the dielectric core layer, the method further comprising:

etching the second metal layer to form second inductor windings;

depositing the material including the magnetic filler material over the second inductor windings;

placing a second prepreg layer over the material including the magnetic filler material deposited over the second inductor windings; and

attaching the second prepreg layer to the material including the magnetic filler material deposited over the second inductor windings.

4. The method of claim 3 further comprising electrically coupling the first inductor windings to the second inductor windings such that the first and second inductor windings form an inductor.

5. The method of claim 4 wherein electrically coupling the first inductor windings to the second inductor windings comprises forming a via filled with an electrically conductive material coupling an output of the first inductor windings to an input of the second inductor windings.

6. The method of claim 4 wherein etching the second metal layer to form the second inductor windings comprises etching the second metal layer such that a spiral pattern of the second inductor windings is a continuation of a spiral pattern of the first inductor windings.

7. The method of claim 5 further comprising:

providing a third metal layer on a top surface of the first prepreg layer;

etching the third metal layer to form a first contact pad and a second contact pad;

electrically coupling the first contact pad to an input of the first inductor windings; and

electrically coupling the second contact pad to an output of the second inductor windings.

14. The method of claim 3 wherein etching the first metal layer comprises etching the first metal layer to form the first inductor windings and an exposed portion of the top surface of the dielectric core layer surrounding the first inductor windings, placing the first prepreg layer comprises placing the first prepreg layer over the material including the magnetic filler material deposited over the first inductor windings and the exposed portion of the top surface of the dielectric core layer, and attaching the first prepreg layer comprises attaching the first prepreg layer to the material including the magnetic filler material deposited over the first inductor windings and the exposed port on of the top surface of the dielectric core layer.

15. The method of claim 14 wherein etching the second metal layer comprises etching the second metal layer to form the second inductor windings and an exposed portion of the bottom surface of the dielectric core layer surrounding the second inductor windings, placing the second prepreg layer comprises placing the second prepreg layer over the material including the magnetic filler material deposited over the second inductor windings and the exposed portion of the bottom surface of the dielectric core layer, and attaching the second prepreg layer comprises attaching the second prepreg layer to the material including the magnetic filler material deposited over the second inductor windings and the exposed portion of the bottom surface of the dielectric core layer.

16. The method of claim 1 wherein attaching the first prepreg layer comprises laminating the first prepreg layer to the material including the magnetic filler material deposited over the first inductor windings.

17. The method of claim 1 wherein the material is an epoxy material.

18. The method of claim 1 wherein the magnetic filler material is a ferrite filler material.

8. The method 3 further comprising:

providing a third metal layer on a top surface of the first prepreg layer;

etching the third metal layer to form third inductor windings;

depositing the material including the magnetic filler material over the third inductor windings;

placing a third prepreg layer over the material including the magnetic filler material deposited over the third inductor windings; and

attaching the third prepreg layer to the material including the magnetic filler material deposited over the third inductor windings.

9. The method of claim 8 further comprising electrically coupling the first inductor windings, the second inductor windings, and the third inductor windings such that the first inductor windings, the second inductor windings, and the third inductor windings form an inductor.

10. The method 8 further comprising:

providing a fourth metal layer on a bottom surface of the second prepreg layer;

etching the fourth metal layer to form fourth inductor windings;

depositing the material including the magnetic filler material over the fourth inductor windings;

placing a fourth prepreg layer over the material including the magnetic filler material deposited over the fourth inductor windings; and

attaching the fourth prepreg layer to the material including the magnetic filler material deposited over the fourth inductor windings.

11. The method of claim 10 further comprising electrically coupling the first inductor windings, the second inductor windings, the third inductor windings, and the fourth inductor windings such that the first inductor windings, the second inductor windings, the third inductor windings, and the fourth inductor windings form an inductor.

12. The method of claim 11 wherein etching the second metal layer to form the second inductor windings, etching the third metal layer to form the third inductor windings, and etching the fourth metal layer to form the fourth inductor windings comprise etching the second, third, and fourth metal layers such that a spiral pattern of the second, third, and fourth inductor windings is a continuation of a spiral pattern of the first inductor windings.

13. The method of claim 11 further comprising:

providing a fifth metal layer on a top surface of the third prepreg layer;

etching the fifth metal layer to form a first contact pad and a second contact pad;

electrically coupling the first contact pad to an input of the third inductor windings; and

electrically coupling the second contact pad to an output of the fourth inductor windings.