PLANAR TRANSFORMER

• US 20140167901A1
• Filed: 12/19/2012
• Published: 06/19/2014
• Est. Priority Date: 12/19/2012
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Persson, Oscar, Karlsson, Magnus
• Granted Patent: US 9,576,717 B2
• Time in Patent Office: Days
• US Class Current: 336/200
• CPC Class Codes: H01F 27/2804 Printed windings
• CPC Class Codes: H01F 27/323 Insulation between winding turns, between winding layers
• CPC Class Codes: H01F 41/041 Printed circuit coils apparatus or processes for manufacturing printed circuits in general H05K3/00
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor

Abstract

A multi-layered printed circuit board, PCB, includes first windings for a first side of a planar magnetic transformer and second windings for a second side of the planar magnetic transformer. The PCB further includes conductive layers configured as the first windings, conductive layers configured as the second windings, and layers of an isolation material. Each layer of the isolation material is arranged between two conductive layers to provide electrical isolation between the two conductive layers. A group of two or more adjacent conductive layers are all conductive layers of the first windings and are all arranged between two conductive layers of the second windings. The thickness of the isolation material between the group of adjacent conductive layers of the first windings is less than the thickness of the isolation material between a conductive layer of the second windings and a conductive layer of the first windings.

Claims

1. A multi-layered printed circuit board, PCB, for providing first windings for a first side of a planar magnetic transformer and second windings for a second side of the planar magnetic transformer, the multi-layered PCB comprising:

a plurality of conductive layers configured to provide the first windings;

a plurality of conductive layers configured to provide the second windings; and

a plurality of layers of an isolation material;

wherein;

each layer of the isolation material is arranged between an adjacent pair of the conductive layers to provide electrical isolation between said adjacent pair of the conductive layers; and

a group of two or more adjacent conductive layers are all conductive layers of the first windings and are all arranged between conductive layers of the second windings, wherein the thickness of the isolation material between at least one of the adjacent pairs of the conductive layers in the group of layers of the first windings is less than the thickness of the isolation material between a conductive layer of the second windings and a conductive layer of the first windings.

2. The multi-layered PCB according to claim 1, wherein:

a group of two or more adjacent conductive layers are all conductive layers of the second windings and are all arranged between conductive layers of the first windings; and

the thickness of the isolation material between at least a pair of adjacent conductive layers in the group of layers of the second windings is less than the thickness of the isolation material between a conductive layer of the first windings and a conductive layer of the second windings.

3. The multi-layered PCB according to claim 2, the multi-layered PCB wherein the plurality of conductive layers are arranged in at least four groups such that:

a first group of two or more adjacent conductive layers are all conductive layers of the first windings and are all arranged between conductive layers of the second windings, wherein the thickness of the isolation material between at least a pair of adjacent conductive layers in the first group of layers of the first windings is less than the thickness of the isolation material between a conductive layer of the second windings and a conductive layer of the first windings;

a second group of two or more adjacent conductive layers, that does not comprise a layer in the first group of two or more adjacent conductive layers, are all conductive layers of the first windings and are all arranged between conductive layers of the second windings, wherein the thickness of the isolation material between at least a pair of adjacent conductive layers in the second group of layers of the first windings is less than the thickness of the isolation material between a conductive layer of the second windings and a conductive layer of the first windings;

a third group of two or more adjacent conductive layers are all conductive layers of the second windings and are all arranged between conductive layers of the first windings, wherein the thickness of the isolation material between at least a pair of adjacent conductive layers in the third group of layers of the second windings is less than the thickness of the isolation material between a conductive layer of the first windings and a conductive layer of the second windings; and

a fourth group of two or more adjacent conductive layers, that does not comprise a layer in the third group of two or more adjacent conductive layers, are all conductive layers of the second windings and are all arranged between conductive layers of the first windings, wherein the thickness of the isolation material between at least a pair of adjacent conductive layers in the fourth group of layers of the second windings is less than the thickness of the isolation material between a conductive layer of the first windings and a conductive layer of the second windings.

4. The multi-layered PCB according to claim 1, further comprising:

a substrate that is between an adjacent pair of the conductive layers of the first windings and that is the isolation material, wherein the adjacent pair of the conductive layers are on opposite sides of the substrate.

5. The multi-layered PCB according to claim 2, further comprising:

a substrate that is between an adjacent pair of the conductive layers of the second windings and that is the isolation material, wherein the adjacent pair of the conductive layers are on opposite sides of the substrate.

6. The multi-layered PCB according to claim 5, wherein:

the isolation material between a conductive layer of the first windings and a conductive layer of the second windings is pre-preg.

7. The multi-layered PCB according to claim 6, wherein:

the thickness of the substrate has a value in the range of 90 μ

m to 110 μ

m; and

the thickness of the pre-preg has a value in the range of 157.5 μ

m to 192.5 μ

m.

8. The multi-layered PCB according to claim 1 wherein the first windings are the windings of the primary side of a transformer and the second windings are the windings of the secondary side of the transformer;

or

the first windings are the windings of the secondary side of a transformer and the second windings are the windings of the primary side of the transformer.

9. A method of manufacturing a multi-layered printed circuit board, PCB, comprising a plurality of layers for providing the first windings of a first side of a planar magnetic transformer and second windings of a second side of the planar magnetic transformer, the method comprising:

forming a group of at least two conductive layers, wherein adjacent conductive layers of the group are separated from each other by a layer of an isolation material;

forming at least one conductive layer above the group of conductive layers, wherein the at least one conductive layer is separated from a conductive layer of the group by a layer of isolation material;

forming at least one further conductive layer below the group of conductive layers, wherein the at least one further conductive layer is separated from a conductive layer of the group by a layer of isolation material;

connecting all of the conductive layers in the group of conductive layers so that all of the conductive layers provide first windings; and

connecting said at least one conductive layer and said at least one further conductive layer to provide second windings;

wherein the thickness of the isolation material between at least a pair of adjacent conductive layers in the group of conductive layers of the first windings is less than the thickness of the isolation material between a conductive layer of the second windings and a conductive layer of the first windings.

10. The method of manufacturing a multi-layered PCB according to claim 9, wherein forming the group of at least two conductive layers comprises:

forming two adjacent conductive layers of the group of conductive layers on the upper and lower surfaces of a substrate, wherein the substrate provides the isolation material between the adjacent conductive layers and the thickness of the substrate is less than the thickness of the isolation material between a conductive layer of the second windings and an adjacent conductive layer of the first windings.

11. The method of manufacturing a multi-layered PCB according to claim 10, wherein forming the group of at least two conductive layers further comprises:

forming two adjacent conductive layers of the group of conductive layers on the upper and lower surfaces of a second substrate, wherein the second substrate provides the isolation material between the two conductive layers; and

bonding a conductive layer of the second substrate to a conductive layer of the other substrate so that the conductive layers are separated by a layer of isolation material, wherein the isolation material between the conductive layers of the group is thicker than the substrates and is less than the thickness of the isolation material between a conductive layer of the second windings and an adjacent conductive layer of the first windings.

12. The method of manufacturing a multi-layered PCB according to claim 10, further comprising:

bonding a further conductive layer to a conductive layer of the two adjacent conductive layers of the first windings to form a group of three adjacent conductive layers of the first windings with a layer of isolation material separating all adjacent conductive layers, wherein the isolation material between the further conductive layer and said two adjacent conductive layers is thicker than the substrate and less thick than the isolation material between a conductive layer of the second windings and an adjacent conductive layer of the first windings.

13. The method of manufacturing a multi-layered PCB according to claim 10, wherein:

the bonding of conductive layers is performed using a pre-preg process and provides pre-preg as the isolation material between the bonded layers;

the thickness of the substrate has a value in the range of 90 μ

m to 110 μ

m;

the thickness of the pre-preg between adjacent conductive layers of the group has a value in the range of 135 μ

m to 165 μ

m; and

the thickness of the pre-preg between a conductive layer of the first windings and an adjacent conductive layer of the second windings has a value in the range of 157.5 μ

m to 192.5 μ

m.

14. The method of manufacturing a multi-layered PCB according to claim 9 wherein the first windings are the windings of the primary side of a transformer and the second windings are the windings of the secondary side of the transformer;

or

the first windings are the windings of the secondary side of a transformer and the second windings are the windings of the primary side of the transformer.