Inductor devices – Coil or coil turn supports or spacers – Printed circuit-type coil
Reexamination Certificate
1995-12-08
2001-02-13
Gellner, Michael L. (Department: 2832)
Inductor devices
Coil or coil turn supports or spacers
Printed circuit-type coil
C336S206000, C336S232000
Reexamination Certificate
active
06188305
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to transformers, and deals more particularly with a transformer formed in conjunction with a printed circuit board.
Transformers are widely used today for power supplies, power converters and other circuits where electrical/ground isolation, impedance matching or voltage transformation are required. Known transformers comprise a ferrite core and primary and secondary windings wrapped around the core. Typically the core is toroidal in shape, either round or square. The primary and secondary windings are wrapped around the sidewalls of the core and either interlaced with each other or wrapped around separate sections of the core. There are various known techniques to form the windings. For example, the windings can be simple copper wires wound around the core with the free ends joined and soldered to other circuitry as required by the application.
U.S. Pat. No. 4,847,986 discloses another transformer which is formed with a printed circuit board. The core is mounted onto a printed circuit board. Underneath the core, elongated printed conductors form segments of respective windings. Metallic wires are contoured over the top and two sides of the core, and are wire bonded to ends of respective printed conductors to form continuous strings of primary and secondary windings which surround the core. While this technique has the advantages of low profile and conjunction with a printed circuit board, further improvements are desirable to lower the cost of construction.
European patent application #91309527.9 also discloses a core mounted onto a printed circuit board. Underneath the core, elongated printed conductors form segments of respective windings. Metallic strips are contoured over the top and two sides of the core, and are surface bonded to ends of respective printed conductors to form continuous strings of primary and secondary windings which surround the core. While this technique has the advantages of low profile and conjunction with a printed circuit board, further improvements are desirable to lower the cost of construction.
Accordingly, an object of the present invention is to provide a transformer (or inductor) formed in conjunction with a printed circuit board but with lower cost of construction than and comparable electrical and thermal performance as the foregoing prior art.
SUMMARY OF THE INVENTION
The invention resides in an electromagnetic device comprising a printed circuit board having elongated conductors printed thereon, a ferrite core having a bottom mounted onto the printed circuit board and a flex circuit. The flex circuit comprises a dielectric sheet and elongated conductors printed on the sheet. The flex circuit is contoured around a top and sides of the core. The conductors of the flex circuit are surface bonded to respective conductors of the printed circuit board to form a series of windings around the core. Provision of the upper portions of the windings by means of the flex circuit is more economical than by the discrete conductor portions of the foregoing prior art.
According to one embodiment of the present invention, the flex circuit comprises primary winding portions printed on one side of the sheet and secondary winding portions printed on the other side of said sheet.
REFERENCES:
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patent: 4249229 (1981-02-01), Hester
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patent: 4547961 (1985-10-01), Bokil et al.
patent: 4847986 (1989-07-01), Meinel
patent: 4975671 (1990-12-01), Dinks
patent: 5027255 (1991-06-01), Zeitlin et al.
patent: 5134770 (1992-08-01), Yerman et al.
patent: 5155648 (1992-10-01), Gauthier
patent: 5283707 (1994-02-01), Conners et al.
patent: 5291173 (1994-03-01), Yerman et al.
patent: 5321380 (1994-06-01), Godek et al.
patent: 0481755 (1992-04-01), None
patent: 2-10705 (1990-01-01), None
IBM Technical Disclosure Bulletin vol. 38, No. 2, Feb. 1995, ‘Printed Circuit Board Wire And Device Add Process’, by Boyko et al.
IBM Technical Disclosure Bulletin vol. 16, No. 9, Feb. 1994, ‘Flexible Circuit Solenoid’, by Gonnella et al.
Chang Chi Shih
Johnson Michael Joseph
Johnston Craig Neal
Lauffer John Matthew
Gellner Michael L.
International Business Machines - Corporation
Samodovitz Arthur J.
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