Planar inductors and method of manufacturing thereof

• US 6,696,910 B2
• Filed: 07/12/2001
• Issued: 02/24/2004
• Est. Priority Date: 07/12/2001
• Status: Expired due to Fees

• Current Assignee: Custom One Design, Inc.
• Original Assignee: Custom One Design, Inc.
• Inventors: Kulinets, Joseph M., Popeko, Ilya E., Nuytkens, Peter R.
• Primary Examiner(s): MAI, ANH T
• Application Number:
  US09/904,014
• Publication Number:
  US 20030011458A1
• Time in Patent Office: 957 Days
• Field of Search: 336/200, 336/212, 336/223, 336/232, 296/021
• US Class Current: 336/200
• CPC Class Codes: H01F 17/0013 with stacked layers
• CPC Class Codes: H01F 17/0033 with the coil helically wound around a magnetic core
• CPC Class Codes: H01F 27/24 Magnetic cores
• CPC Class Codes: H01F 27/2804 Printed windings
• CPC Class Codes: H01F 27/36 Electric or magnetic shields or screens movable for varying inductance H01F21/10
• CPC Class Codes: H01F 27/363 made of electrically conductive material
• CPC Class Codes: H01F 41/02 for manufacturing cores, coils, or magnets H01F41/14 takes precedence; for dynamo-electric machines H02K15/00
• CPC Class Codes: H01F 41/046 structurally combined with ferromagnetic material
• CPC Class Codes: H01L 2224/04105 Bonding areas formed on an encapsulation of the semiconductor or solid-state body, e.g. bonding areas on chip-scale packages
• CPC Class Codes: H01L 2224/18 High density interconnect [HDI] connectors; Manufacturing methods related thereto
• CPC Class Codes: H01L 2224/24137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/73267 Layer and HDI connectors
• CPC Class Codes: H01L 2924/15153 the die mounting substrate comprising a recess for hosting the device
• CPC Class Codes: H05K 1/165 incorporating printed inductors
• CPC Class Codes: H05K 2201/086 for inductive purposes, e.g. printed inductor with ferrite core
• CPC Class Codes: H05K 2201/097 Alternating conductors, e.g. alternating different shaped pads, twisted pairs; Alternating components
• CPC Class Codes: H05K 2203/072 Electroless plating, e.g. finish plating or initial plating
• CPC Class Codes: H05K 3/184 using masks
• CPC Class Codes: H05K 3/381 by special treatment of the substrate
• CPC Class Codes: H05K 3/4614 : the electrical connections between the circuit boards being made during lamination
• CPC Class Codes: Y10T 29/4902 : Electromagnet, transformer or inductor
• CPC Class Codes: Y10T 29/49073 : by assembling coil and core
• CPC Class Codes: Y10T 29/49075 : including permanent magnet or core
• CPC Class Codes: Y10T 29/49124 : On flat or curved insulated base, e.g., printed circuit, etc.
• CPC Class Codes: Y10T 29/4913 : Assembling to base an electrical component, e.g., capacitor, etc.

Abstract

A printed circuit board has two layers of printed circuit board dielectric material; a core made of ferromagnetic material between the two layers; and conductive leads on the opposite side of each dielectric layer from the core connected by via holes through both dielectric layers to form a conducting coil around the core. The conductive leads can form two separate coils around the core to form a transformer. A planar conducing sheet can be placed on or between one or more of the printed circuit board'"'"'s dielectric layers to shield other circuitry on the printed circuit board from magnetic fields generated around the core. The core can be formed at least in part by electroless plating. Electroplating can be used to add a thicker layer of less conductive ferromagnetic material. Ferromagnetic inductive cores can be formed on the surface of a dielectric material by: dipping the surface of the dielectric in a solution containing catalytic metal particles having a slight dipole; and placing the dielectric in a metal salt to cause a layer containing metal to be electrolessly plated upon the dielectric. Plasma etching or other technique can be used before the dipping process to roughen the dielectric'"'"'s surface to help attract the catalytic particles. This method can be used to form an inductor core on or between one or more dielectric layers of a printed circuit board, of a multichip module, of an integrated circuit, or of a micro-electromechanical device.

Claims

1. A printed circuit board comprising:

two layers of dielectric material, each of the two dielectric layers having a pair of surfaces thereon;

a core comprised of ferromagnetic material disposed between the two dielectric layers, said ferromagnetic core being plated on at least one surface of the two dielectric layers;

a plurality of vias disposed through each of the two dielectric layers; and

a plurality of conductive leads in the form of at least one conductive lead attached to each of the two dielectric layers, said conductive leads connected through the via holes so as to form a conducting coil around the core.

2. A printed circuit board as in claim 1 wherein the conductive leads form two separate coils around the same core so that one such coil can act as a primary winding and the other can act as a secondary winding of a transformer.

3. A printed circuit board as in claim 1, further comprising:

a planar conducting sheet positioned with respect to the dielectric layers so as to shield other circuitry on the printed circuit board from magnetic fields generated around the core.

4. A printed circuit board as in claim 1, wherein the core further comprises two separate segments of ferromagnetic material, each disposed at a corresponding location on a facing surface of one of said two dielectric layers.

5. A printed circuit board as in claim 1 wherein the core has been formed at least in part by electroless plating.

6. A printed circuit board as in claim 1, wherein said core has been plated on the at least one surface of said dielectric layers by a process comprising:

dipping the at least one surface in a solution containing catalytic metal particles which have a slight electrostatic dipole moment when in the solution to deposit a layer of catalytic metal particles on the at least one surface; and

placing the at least one surface in a first metal salt solution in metastable equilibrium with a reducing agent so as to plate a layer of metallic material upon the at least one surface.

7. A printed circuit board as in claim 6, wherein the plating process further includes:

roughening the at least one surface to create peaks and valleys in the at least one surface exhibiting van der Waal forces capable of attracting the catalytic metal particles.

8. A printed circuit board as in claim 6:

wherein said layer of metallic material comprises a thin layer of relatively conductive metallic material used as a seed layer; and

the plating process further includes, after the formation of said seed layer, placing the at least one surface in a second metal salt solution in metastable equilibrium with a reducing agent which has a higher concentration of non-metal elements than said first solution so as to plate upon the seed layer a ferromagnetic material layer having a lower conductivity than the conductivity of said seed layer.

9. A printed circuit board as in claim 6:

wherein said layer of metallic material comprises a thin layer of relatively conductive metallic material used as a seed layer; and

the plating process further includes using electroplating to plate a ferromagnetic material layer onto said seed layer having a lower conductivity than the conductivity of said seed layer.

10. A printed circuit board as in claim 1, wherein the at least one surface has a sufficient roughness so as to exhibit electrostatic forces.

11. A printed circuit board as in claim 1, wherein said core further comprises:

a layer of catalytic metal particles electrostatically attracted to the at least one surface;

a relatively thin layer of conductive metallic material deposited upon the layer of catalytic metal particles; and

a layer of ferromagnetic material plated upon the thin layer of conductive metallic material and having a conductivity lower than the conductivity of the thin layer of conductive metallic material.

12. A printed circuit board as in claim 11, wherein the thin layer of conductive metallic material serves as an electrode in electroplating the less conductive layer of ferromagnetic material.

13. A printed circuit board as in claim 11, wherein the core has been formed at least in part by electroless plating.