Method of making a plated core electrical component

Feb. 23, 1971 j. c. Harris 3,564,708

METHOD OF MAKING A PLATED CORE ELECTRICAL COMPONENT Filed April 15, 1968 2 Sheets-Sheet 1 fig: i

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Feb. 23, 1971 j. _c Harris 3,564,70«

METHOD OF MAKING A PLATED CORE ELECTRICAL COMPONENT Filed April 15, 1968

Sheets-Sheet 2

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3,564,708

Patented Feb. 23, 1971

United States Patent Office

3,564,708

METHOD OF MAKING A PLATED CORE ELECTRICAL COMPONENT

John C. Harris, Durham, N.C., assignor to Technitrol, Inc., Philadelphia, Pa., a corporation of Pennsylvania Filed Apr. 15, 1968, Ser. No. 721,313

Int. Cl. HOlf 7/06

U.S. CI. 29—606 2 Claims

ABSTRACT OF THE DISCLOSURE

A method of making an electrical component including providing a torous with a raised portion including a fin which winds about the torous to form a helix. Raised members are provided between at least one pair of turns of the helix. The torous, fin and member are coated with a conductor. The conductor coated fin and member are removed so that the conductive coating remaining on the torous forms a winding on the toroidal core.

Other embodiments are disclosed which include methods for making electrical components having multi-layered windings and electrical components having a plurality of windings in which adjacent turns are in juxtaposed relationship.

This invention relates generally to a method of manufacturing an electrical component and, more particularly, pertains to a simple and economic method for making an inductive element.

The present trend toward miniaturization and microminiaturization of circuits has produced a need for correspondingly miniaturized electrical components. As a result so-called miniaturized transformers, for example, presently are produced by etching a conductor which has been deposited on a core to provide the transformer windings. However, this method inherently is costly in terms of both time and money.

Accordingly, an object of this invention is to provide a method of making an electrical component which is particularly advantageous for fabricating miniature transformers.

Another object of the present invention is to provide a simple and economic method of manufacturing an inductive element.

A further object of this invention is to provide a method of making an electrical component, such as a transformer, wherein windings are produced on a substrate core in a precise manner.

Another object of the present invention is to provide a method for producing miniature inductive elements which are reliable in operation.

Accordingly, the method of the present invention comprises providing a toroidal core with a raised portion including at least a helical fin. The toroidal core and raised portion are coated with a conductor. The raised conductor coated portion is removed to provide a helical conductor winding on said core.

Other features and advantages of the present invention will become more apparent from a consideration of the following detailed description when taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a perspective view of a toroidal core produced in accordance with the method of the present invention, prior to coating the core with a conductor;

FIG. 2 is a sectional view of a portion of the core with a conductive coating thereon;

FIG. 3 is a perspective view of the core with the winding thereon;

FIG. 4 is a sectional view of a portion of a modified embodiment of the present invention prior to removing the raised portion of a second layer; and

FIG. 5 is a perspective view of a further modified embodiment prior to coating the same with a conductive layer.

The method of the present invention includes the provision of a torous or a toroidal core 10 which may be made in any conventional manner. The torous 10 includes an upper surface 12, a lower surface 14, an outer circumferential wall 16 and an inner circumferential wall 18. By way of example, the torous 10 may be fabricated from a ferrite material. Alternatively, the torous may contain a powdered ferro- or ferri-magnetic material dispersed therethrough. To be more specific, the torous 10 may comprise a polytetrafluoroethylene material in which is dispersed particles of magnetic material such as powdered iron or powdered ferrite.

Provided on the surface of the torous 10 is a raised portion which defines windings on the torous in the manner noted below. More particularly, the raised portion includes a raised fin 20 which is provided on the surfaces of the torous 10 and which winds about the torous and closes upon itself to form a closed helix or helical fin winding. The turn 22, which is representative of the turns which make up the helical fin winding, comprises a vertical member 24 which extends outwardly from the outer circumferential wall 16 of the torous. Extending diagonally across the upper surface 12 of the toroidal core 10 and connected to the member 24 is an arm 26 of the fin 20. Projecting inwardly and downwardly along the inner circumferential wall 18 is another vertical member 28 which connects with the arm 26. Extending diagonally across the lower surface 14 of the torous is another arm (not shown) similarly to the arm 27 which connects the member 28 with a member 30 which comprises a portion of the next turn of the helical fin winding or fin 20.

The raised portion further includes a member or connecting portion 32 which extends outwardly from the circumferential wall 16 between two adjacent turns 34 and 36 of the fin 20. As shown in FIG. 1, the member 32 is spaced from the upper surface 12 and the lower surface 14 of the torous or toroidal core 10. When it is desired to make an inductor only one member 32 is provided on the core 10. However, when it is desired to provide a transformer having two windings another member 32 is provided between a different pair of adjacent turns of the fin 20. Additionally, if more than two windings on the transformer are desired, a number of members equal to the number of windings will be provided on the core 10. Additionally, it may be desirable to provide a device or component having a shorted winding. In this latter case no member 32 will be provided.

The core 10 and the raised portion which includes the fin 20 and the member or members 32 may be molded integrally utilizing any one of the known molding techniques now available. Alternatively, the torous or toroidal core 10 may be manufactured separately and the raised portions including the fin 20 and the member or members 32 may be later molded on the torous 10.

The torous and the raised portions thereon are then coated with a conductive coating by any convenient method. For example, in constructing the winding of this invention, the toroidal core including the raised fin 20 and the member or members 32 may be coated by the electroless deposition of a conducting material such as copper or silver. Thereafter, a coating of another film of conductive material may be electroplated thereon in the usual manner. Alternatively, the conductive layer of material may be deposited on the core and raised portions by the use of sputter techniques. Inasmuch as the entire structure including the core 10 and the raised portions are subjected

3,564,708 to the deposition of the conductive coating, the conductive coating 38 (FIG. 2) will cover the entire surface of the core 10, tin 20 and member 32.

Since, in practice, a ferrite material is used for the core 10, no insulation is required between the core and the conductive winding. However, in many applications the impedance of the core material may not be sufficiently high and, accordingly, there will be leakage between turns of the finished component. In order to prevent such occurrences the core 10 and, therefore, the raised fin 20 and member or members 32 may be coated with an insulating material prior to the deposition of the conductive layer thereon. For example, the device illustrated in FIG. 1 may be placed in a fluidized bed to coat the same with a layer of insulating material. Then the conductive layer 38 of copper or silver, for example, may be coated thereon.

Thereafter, the raised fin 20 and the member 32 or, when the device is utilized as a transformer-—the members 32, including their associated conductive layers 38, are removed from the torous or toroidal core 10. More specifically, the raised portions may be removed, in whole or in part, in any conventional manner as by a grinding or a tumbling process, or the like. It should be noted that the raised members need not be removed in whole, it being sufficient that the surface including the conductive layers on these portions are removed. Thus, as shown in FIG. 3, the removal of the fin 20 leaves a continuous space 40 between the layer of conducting material 38. Thus, the material 38 winds about the torous 10 in the shape of a helix thereby to define a helical winding on the torous 10. Additionally, the removal of the member 32 leaves a space 42 between the sections 38A and 38B of the conductive layer 38 to define the ends of the winding. Thereafter, leads 43 and 44 may be connected to the respective ends 38A and 38B of the winding in any conventional manner, as by soldering or welding the leads thereto, so that the inductive element may be connected easily to an external circuit. As noted hereinabove, if the device shown in FIG. 3 is to be utilized as a transformer, another member 32 would have been positioned adjacent to other turns of the fin 20 so that another space 42 would exist between sections of the conductive layer 38 to define thereby two windings on the core 10. Appropriate leads may be connected to the ends of all windings so that the primary and the secondary windings of the transformer may be utilized in an external circuit in the conventional manner.

FIG. 4 illustrate a sectional view of a modified embodiment of the invention which includes multi-layered windings. Accordingly, the embodiment of FIG. 3 is provided with an insulating coating of material 45 having raised portions thereon which include a continuous helical fin 20' and a member (not shown) between adjacent turns similarly to the member 32. This layer is then provided with a conductive coating 38' by, for example, any of the methods noted above. The fin 20' and associated members interconnecting adjacent turns of the fin 20' are removed to define a second winding on the torous 10. Appropriate leads then may be connected to the ends of the winding so defined to provide a transformer having multi-layered windings, it being understood that the leads 43 and 44 connected to the winding or layer of conductive material 38 extend through the layer of insulating material 45.

A further modified embodiment of the present invention is shown in FIG. 5 which illustrates a substrate 50 prior to the application of a conductive coating thereto. The substrate 50 includes a torous 52 which may be fabricated from any of the materials noted above relative to the torous 10. Provided on the torous are a pair of raised fins 54 and 56 which wind about the torous 52 and form a pair of closed helices in a manner similar to the raised fin 20. Thus, each turn of the helical fin 54 will be in juxtaposition to a respective turn of the helical fin 56.

A member 58 is provided on the outer circumferential wall of the torous 52 that extends from one turn of the helical fin 54, past the adjacent turn of the helical fin 56, to the next adjacent turn of the fin 54. Similarly to the member 32, the raised member 58 is spaced from the upper and lower surfaces of the torous.

The fins 54, 56 and the member 58 may be molded on the torous 52 in the manner noted above, or the elements may be molded as a unitary structure.

The substrate 50 is coated with a conductive material and thereafter the fins 54, 56 and the member 58 are removed in a manner similar to that noted above in conjunction with the embodiment of FIGS. 1-3. Accordingly the removal of the conductor coated fins 54, 56 and the member 58 define a double winding on the torous 52 wherein adjacent turns of one winding are in juxtaposition to respective turns of the other winding. Thereafter, appropriate leads may be connected to the ends of the windings so that the device may be utilized in a circuit.

Accordingly, a simple and economic method has been described for producing so-called miniature electrical components.

While preferred methods of the invention have been shown and described herein, it will become obvious that numerous omissions, changes and additions may be made in such methods without- departing from the spirit and scope of the present invention.