Patent Application
20060109071
1. Technical Field
This invention relates generally to electronic assemblies, and more specifically to an inductor formed integrally with a printed circuit board.
2. Background Art
Contactless, or inductive, electrical connections are well known in the field of portable electrical devices. For example, portable, motorized toothbrushes typically contain a rechargeable battery which is charged by an inductive connection. Similarly, portable wireless communication devices, such as two-way RF radios, cellular phones, paging devices, and wireless communicators, sometimes utilize a rechargeable battery that in certain applications is recharged by contactless, induction charging.
Most all contactless chargers charge batteries by induction. Current, passed through a coil, creates a magnetic flux in accordance with Ampere's law. When a second coil is placed in close proximity to such a current-driven coil, the flux couples to the second coil, thereby “inducing” a current in the second coil. Such an induction circuit is illustrated in
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The problem with traditional contactless charging schemes is that electronic devices, like cellular telephones, are getting smaller every day. For instance, the RAZR™ V3 phone, manufactured by Motorola, Inc., is less than a quarter of an inch thick. Traditional secondary coils used in contactless charging systems are made by wrapping wire about an iron core. These cores often measure a half inch or more in thickness. Consequently, thin devices like the RAZR™ V3 are not able to accommodate contactless charging systems due to the fact that the physical size of the secondary coil is larger than the form factor of the phone.
There is thus a need for an improved, smaller secondary coil that may be used in contactless charging systems.
A preferred embodiment of the invention is now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.”
This invention is an inductive component that can be manufactured integrally with a circuit substrate like a printed circuit board. A magnetic core material, like an amorphous metal ribbon, is laminated between the layers of an electronic circuit substrate, like a printed wiring board (PWB) or flexible substrate. The finished assembly then has the magnetic core material fixed within in the center of a multi-layered PWB or flexible substrate. The top and bottom layers have conductive traces disposed thereon, wherein the conductive trace patterns each resemble one half of a wire winding that would be on a traditional iron core. The conductive traces on the top and bottom layers are connected about the magnetic core material with conductive vias, which are metallized holes running through the layers of the PWB or flexible substrate. The combined substrate, magnetic core material, traces and connecting vias create a thin, easy to manufacture electronic assembly that may be used as an inductor, transformer, primary coil for contactless charging or secondary coil for contactless charging.
In other embodiments of the invention, the PWB or flexible substrate may be made larger than the magnetic material such that electronic circuits, traces and components may be populated on the outer surfaces of the substrate. In these embodiments, complete circuit assemblies, including circuitry, contact blocks and integral magnetic components can be manufactured on a single printed circuit board (PCB). (A PCB differs from a PWB in that the printed circuit board includes populated electronic components, while the printed wiring board is the substrate itself.)
In alternate embodiments, one or more additional layers may be added to the three-layer core assembly. The outer layers of the final assembly are then suitable for population with electronic components and circuitry. When outer layers are used, the traces about the magnetic material may be disposed upon inner layers of the assembly, thereby leaving more space for components on the outer layer. One example of such an assembly might be where the plastic housing of the device has a curved form factor rather than the typical flat housing. In such applications, an air gap results between the PCB and the plastic housing. The surface mount components may then be placed on the outer layers of the substrate within the air gap.
This invention is ideally suited for use as a secondary coil in inductive charging systems, but other devices can be accommodated as well. For example, the integrated magnetic circuit assembly may be constructed as a transformer where the primary coil, the secondary coil, primary winding and secondary winding are integrally formed within single, multi-layer substrate. As such, the invention facilitates a very thin, low profile transformer. By adding electronic circuitry and components on the outer layers, one may construct complete power supply on a single PCB assembly.
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Conductive electrical traces 206 are disposed on the first layer 201. In the embodiment of
A third, or center layer 202 has an aperture 205 therein. A piece of magnetic material 203, which is comparably shaped with the aperture 205 in the third layer 202 is disposed within the aperture 205. The magnetic material 203 preferably has a Curie temperature that is higher than the temperatures experienced in the substrate lamination process, which are around 150 degrees centigrade. Suitable examples of materials for the magnetic component are amorphous metal ribbon as is known in the art, ferrite material in a suitable binder or magnetic steel lamination material.
The magnetic material 203 is secured within the aperture 205, and the third layer 202 is laminated between the first layer 201 and the second layer 204 such that the first major surface 212 of the third layer 202 is attached to the second major surface 209 of the first layer 201, and the second major surface 213 of the third layer 202 is attached to the first major surface 210 of the second layer 204.
Metallized, conductive vias 214 may be used to couple the traces 206 on the first layer 201 with the traces on the second layer 204. Conductive vias 214 are drilled holes that tunnel through the layers 201,202,204 which have been plated with a conductive, metal material like aluminum or copper. It will be clear to those of ordinary skill in the art having the benefits of this disclosure that other devices, like rivets, may be substituted for plated vias. In either event, by coupling the top traces 206 with the bottom traces 207 with vias 214 about the magnetic material 203, a circumfluent, conductive path that equates to the “windings” about an inductor may be made integrally with the PWB assembly 200.
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In the embodiment of
It will be clear to those of ordinary skill in the art having the benefit of this disclosure that various combinations of outer layers and core assembly layers may be attached together. Turning now to
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Additionally, rather than using a single set of traces 606,607 to create a single “winding”, multiple sets of interleaved, bifilar windings may also be “wrapped” about the magnetic component 603 to create a transformer. It will be clear to those of ordinary skill in the art having the benefit of this disclosure that tri-filar, quadrafilar, or n-filar windings could additionally be used to form transformers with 3, 4 or n windings, respectively.
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In the transformer assembly 700, a first set of top traces 706 and a second set of top traces 726 are disposed on the top layer 701. The first set of top traces 706 and a second set of top traces 726 are electrically disconnected so as to provide the isolation associated with a transformer. Similarly, a first set of bottom traces 707 and a second set of bottom traces 727 are disposed on the bottom layer 704.
The first set of top traces 706 and the first set of bottom traces 707 are coupled with a first set of conductive vias 714 about one leg of the magnetic component 703. Similarly, the second set of top traces 726 and the second set of bottom traces 727 are coupled with a second set of conductive vias 724 about another leg of the magnetic material 703. In so doing, a transformer assembly 700 is created with the magnetic component serving as the magnetic flux conduit. The first set of top traces 706, first set of bottom traces 707 and first set of conductive vias 714 form one winding of the transformer, and the second set of top traces 726, second set of bottom traces 727, and second set of conductive vias 724 form the second winding.
To summarize, the invention includes electronic assembly having a substrate assembly, wherein the substrate assembly has at least three layers of substrate material. Each layer of the substrate assembly has a first and a second major surface. The three layers include a first layer that has conductive traces disposed on the first major surface. The second layer has conductive traces disposed on the second major surface. The third layer has an aperture, and the first major surface of the third layer is attached to the second major surface of the first layer. The second major surface of the third layer is attached to the first major surface of the second layer.
A magnetic material, like an amorphous metal ribbon component, has a shape that is comparable with the aperture in the third layer. During manufacture, the magnetic material is first disposed within the aperture of the third layer. This magnetic component/third layer assembly is then laminated between the first and second layers. The traces on the first and second layers are then coupled with metallized, conductive vias that run through the multi-layered assembly. The result is a PWB that includes an integral magnetic component suitable for use as an inductor, transformer, or contactless charging primary or secondary coil.
While the preferred embodiments of the invention have been illustrated and described, it is clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the following claims. For example, while one application for this invention is contactless charging, numerous other applications, including EMI suppression, power conversion, electrical isolation and filtering are equally suitable for the invention.
