Electronic transformer/inductor devices and methods for making same

Abstract

The present invention relates to the methods of construction for inductive components of, preferably, ferromagnetic materials such as inductors, chokes, and transformers when used as an integral part of the fabrication of PCB's or FLEX's. In one preferred embodiment, holes are formed through a ferromagnetic substrate and plated with conductive material. The arrangement of these holes, and the subsequent design that ensues, will form the inductive components within the plane of the media in which the device is formed; using the substrate for a magnetic core. By using this approach, the inductive components can be miniaturized to physical sizes compatible with the requirements of modem surface mount technology (SMT) for integrated circuitry (IC). This process also allows these components to be fabricated using mass production techniques, thereby avoiding the need to handle discrete devices during the manufacturing process. In another preferred embodiment, a series of thin, concentric high permeability rings are etched on a substrate to provide high permeability transformers and inductors having minimal eddy current effects.

1 . (canceled)  
   
   
       2 . A miniature inductor/transformer having minimal eddy current effects comprising: 
 a stack of a plurality of substantially identical thin concentric ferromagnetic rings respectively separated by their dielectric layers;    a first printed circuit and a second printed circuit on opposite sides of said stack of the concentric ferromagnetic rings; and    conductive via holes through said stack in electrical contact with said printed circuits, the axis of said via holes being substantially parallel to the center axis of said concentric rings.    
   
   
       3 . A miniature inductor/transformer comprising: 
 a thin layer of ferromagnetic ferrite material on a substrate; and    a plurality of plated vias through said ferrite material, said vias providing electrical windings of said inductor/transformer.    
   
   
       4 . A method for making a miniature inductor/transformer comprising: 
 forming a thin layer of ferromagnetic on a thin sheet of insulating material;    laminating said sheet having said layer of ferromagnetic material between first and second thin sheets;    forming through holes through said laminated sheets;    plating electrically conductive material within said through holes, forming a printed electrical circuit on said first and second thin sheets in electrical contact with said conductive through holes, said printed circuitry providing a portion of an electrical winding of the inductor/transformer.    
   
   
       5 . The method of  claim 4 , wherein said sheets are printed circuit boards.  
   
   
       6 . The method of  claim 4 , wherein said sheets are flex circuits.  
   
   
       7 . The method of making a plurality of miniature inductor/transformers comprising: 
 laminating a plurality of spaced ferromagnetic cores with top and bottom layers of circuitry.    
   
   
       8 . The method of  claim 7 , wherein said top and bottom layers are sheets of flex circuits.  
   
   
       9 . The method of  claim 7 , wherein said top and bottom layers are printed circuit boards.  
   
   
       10 . The method of  claim 7 , wherein vias are formed in said ferromagnetic cores during fabrication of said cores from ferrite material.  
   
   
       11 . The method of  claim 7 , wherein vias are formed by drilling through said ferromagnetic cores after fabrication of said cores.  
   
   
       12 . The method of  claim 7 , wherein said cores are formed within through holes, and using a conducive ink process to form, circuitry on the top and bottom of said cures and through said holes.  
   
   
       13 . A method for making a miniature inductor/transformer comprising: 
 forming a first thin sheet having a printed electrical circuit thereon,;    forming a second thin sheet having a printed circuit thereon;    laminating said sheet having said layer of ferromagnetic material between said first and second thin sheets;    forming through holes through said laminated sheets; and    plating electrically conductive material within said through holes in electrical contact with said printed circuitry on said first and second thin sheets, said conductive through holes providing a portion of an electrical winding of the inductor/transformer.    
   
   
       14 . The method of  claim 13 , wherein said sheets are printed circuit boards.  
   
   
       15 . The method of  claim 13 , wherein said sheets are flex circuits.  
   
   
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       25 . (canceled)  
   
   
       26 . A method for making devices for use in printed circuit board design comprising; 
 printing a circuit pattern onto said circuit board;    forming holes which go through said circuit board;    filling said holes with a conductive material; and    using the connections and said pattern such that a device is created which uses said circuit board as a magnetic core.    
   
   
       27 . The method of  claim 26  further comprising the introduction of a ferromagnetic substrate into said printed circuit board, and the formation of said holes through said substrate.  
   
   
       28 . An inductor or transformer comprising: 
 a slab of magnetic material having a series of spaced holes therethrough;    an electrically conductor material within said holes, and    electrical printed circuits located on the top and bottom surfaces of said slab respectively in electrical contact with said conductive material.    
   
   
       29 . A method for making a miniature inductor/transformer having minimal eddy current effects comprising: 
 etching a thin sheet of ferromagnetic metal to form a plural array of ten or more concentric narrow continuous rings of said ferromagnetic metal;    stacking four or more of said arrays separated by a dielectric material to form a plurality of cores, said cores so constructed having a very small cross-sectional area defined by the thickness of the sheet of ferromagnetic material and the width of said concentric narrow rings so as to minimize the eddy current effect;    laminating said stack of arrays between copper sheets;    forming said copper sheets into printed circuits;    forming vias through said printed circuits proximate said laminated ferromagnetic arrays; and    plating said vias in electrical contact with said printed circuitry to form electrical windings.    
   
   
       30 . A method for making a miniature inductor/transformer comprising: 
 forming a thin layer of a ferromagnetic on a thin sheet of insulating material;    etching said thin layer to form ten or more thin discrete continuous ferromagnetic members;    forming a first thin sheet having a printed electrical circuit thereon    forming a second thin sheet having a printed circuit thereon;    stacking four or more of said sheets having said etched ferromagnetic material members between said first and second thin sheets;    forming through holes through said laminated sheets; and plating electrically conductive material within said through holes in electrical contact with said printed circuitry on said first and second thin sheets, said conductive through holes providing a portion of an electrical winding of the inductor/transformer.