TECHNICAL FIELD

The present invention relates to a coil winding structure of a flyback transformer. and more particularly, to a flexible coil winding structure having a planar shape and a manufacturing process thereof.

BACKGROUND ART

Generally, a flyback transformer (hereinafter, referred to as "FBT") is employed as a device for generating high voltage in TV receivers, oscilloscopes and CRTs, etc. This FBT basically includes a primary- coil winding and a secondary coil winding, which are electromagnetically interconnected by a magnetizable core. The value of the generated voltage depends on the ratio of the number of turns of the secondary winding to that of the primary winding. In case of the conventional FBT for generating higher voltages, a greater number of turns of the secondary winding has been required, which has resulted in an increase in the volume thereof, and consequently lead to poor efficiency and also poor high voltage regulation.

To solve the above problems, U.S. Pat. No. 5,392,020 issued on Feb. 21, 1995 to Kern K.N. Chang describes a flexible transformer apparatus as illustrated in FIGS. IA to ID, which will be explained below.

FIG. IA is a perspective view schematically

illustrating the configuration of the flexible transformer apparatus. As illustrated in the figure, the flexible transformer apparatus includes a pair of planar sheets 10, 20 and a magnetizable sheet 30 interposed between them. The planar sheets 10, 20 consist of respectively an insulator sheet and a plurality of conductor lines 12, 14 and 22, 24 vapor-deposited thereon. The conductor lines 12, 14 and 22, 24 are connected with each other in a zigzag formation to form a secondary coil winding. FIGS. IB and IC are plan views illustrating the planar sheets 10, 20 of FIG. IA. As shown in the figures, the first planar sheet 10 and the second planar sheet 20 include the parallel conductor lines 12, 14 and 22, 24 respectively. The parallel conductor lines 12, 24 and 22, 24 are inclined at a predetermined angle and arranged at longitudinally interspaced distances . These configured parallel conductor lines are interconnected so as to form the flexible transformer apparatus, as illustrated in FIG. IA. The parallel conductive lines 12, 14 and 22, 24 may be formed on the surface of the insulator sheet by conventional vapor deposition techniques, RF sputtering techniques, etc., using photolithographic procedures. The materials used for the conductor lines are noble metals such as platinum, gold, silver, copper, aluminum and their alloys.

FIG. ID is a transverse sectional view of the flexible transformer apparatus of FIG. IA, which illustrates the electrically connected configuration of the conductor lines 12, 14 and 22, 24 on the planar sheets 10, 20. With regard to the electrical connection of the conductor lines, the patent describes as follows: Each of the conductor lines is provided with apertures 12a, 12b,

14a, 14b and 22a, 22b, 24a, 24b formed at both ends thereof, and connecting rods 40 are inserted into the apertures to thereby provide the electrical connection between the conductor lines of the first planar sheet and those of the second one.

In the above-described flexible transformer apparatus, however, it is understood that the secondary windings require about 4,000 turns of coil winding, and the conductor lines have a width of from 40 to 125 microns. Therefore, it is not possible actually to form the apertures at both ends of those very fine conductor lines, and also insert mechanically the connecting rod into these fine apertures one by one for achieving the electrical connection between the conductor lines. Furthermore, this mechanical connection practice is not adaptable for substantial production, especially mass production of the above flexible transformer apparatus.

DISCLOSURE OF INVENTION

Accordingly it is an ob ect of the invention to provide a new flexible coil winding structure of a flyback transformer for achieving a greater number of turns of coil winding.

It is another object of the invention to provide a manufacturing process which is readily adaptable for the mass production of the flexible coil winding structure.

To achieve the objects of the invention, there is provided a process for manufacturing a flexible coil winding structure of a flyback transformer, which comprises the steps of: a) forming a thin conductive layer on a thin

insulator sheet to obtain a flexible laminated sheet member; b) removing partly the conductive layer from the flexible laminated sheet member to obtain a conductor line pattern sheet member including a conductor line pattern, the conductor line pattern having a plurality of parallel conductor lines which are inclined at a predetermined angle; c) connecting the upper portions and the lower portions of the conductor lines with each other to obtain a coil pattern laminated sheet member including a coiled circuit pattern, whereby the coiled circuit pattern is formed by the conductor lines; and d) inserting a magnetizable core into the coil pattern laminated sheet member.

Preferably, the insulator sheet has a thickness of less than about 35 microns, and the conductive layer has a thickness of from several to about 100 microns, even more preferably of from about 25 to about 75 microns. The flexible laminated sheet member may be provided by applying an adhesive to the surface of the insulator sheet made from polyimide or polyester, etc., followed by adhering a copper or aluminum film over the adhesive. The flexible laminated sheet member may be also prepared by forming a seed layer of a conductive material such as chromium or nickel on the insulator sheet using RF sputtering technique, etc., and then forming the conductive layer of copper or aluminum over the seed layer using electroplating, electroless plating, vapor deposition or RF sputtering techniques, etc.

Preferably, the conductor line pattern sheet member includes a pair of conductor line terminals for inflow or outflow of electric current to or from the coiled circuit

pattern, and the conductor line terminals are integrally formed with the right end and the left end conductor line respectively.

The conductor line pattern sheet member may include an align mark for correctly aligning the upper and lower portions of the parallel conductor lines in the connecting step of c) . The insulator sheet may be provided with a pair of holes at either the longitudinal right or left end margin, or a plurality of holes in the transverse upper and lower end margin, or various characters and symbols such as a (+) sign, thereby employing those as the align mark.

The connecting step of c) may comprise the steps of adhering longitudinally an insulating strip for insulating the center portions of the conductor lines except for the upper and lower portions of them, folding the conductor line pattern sheet member in half lengthwise, and electrically connecting the upper and lower portions of the conductor lines with each other so that the conductor line pattern forms the coiled circuit pattern.

The electrically connecting step may be carried out by solder-plating the upper and lower portions of the conductor lines, dipping them into a molten solder, or printing a solder cream or paste on the upper and lower portions of the conductor lines, and then hot-pressing for soldering the upper and lower portions of the conductor lines. It is preferable that the hot-pressing is carried out at a temperature of from about 200 to about 280 degrees Celsius. The electrically connecting step may be also carried out by adhering longitudinally a Z-axis film on the upper and lower portion of the conductor line pattern, and hot- pressing the upper and lower portion of the conductor line

pattern. It is preferable that the hot-pressing includes carrying out a preliminary hot-pressing at a temperature of from 85 to 100 degrees Celsius for from 3 to 5 seconds followed by finishing the hot-pressing at a temperature of from 170 to 190 degrees Celsius for about 20 seconds.

Furthermore, the step of electrically connecting may be also carried out by hot-pressing the upper and lower portions of the conductor line pattern for welding the portions of the insulator sheets which correspond to the area between the individual conductor lines. It is preferable that the hot-pressing is carried out at a temperature of from about 300 to about 450 degrees Celsius for about 10 to 30 seconds.

By carrying out the above several steps of the process of the invention, there is provided a flexible coil winding structure, which comprises a magnetizable core inserted at the center portion, a conductor line pattern around the magnetizable core, and a flexible insulator sheet around the conductor line pattern for substantially insulating the overall coil winding structure and protecting it from its surroundings while in service. The conductor line pattern is arranged so as to provide a coiled circuit pattern. An insulating strip is provided between the magnetizable core and the conductor line pattern. Also, the coil winding structure includes an electrical connection for connecting the upper portions and the lower portions of the conductor lines so that the conductor line pattern provide the coiled circuit pattern. The electrical connection may be provided according to and characterized by various connecting methods of the process as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, other features and advantages of the invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the following drawings in which: FIG. IA is a perspective view showing schematically the configuration of a conventional flexible transformer apparatus;

FIG. IB is a plan view showing a first planar sheet of FIG. 1; FIG. IC is a plan view showing a second planar sheet of FIG. 1;

FIG. ID is a transverse sectional view illustrating the electrically connected configuraion of conductor lines; FIG. 2 is a sectional side view showing the layered configuration of a flexible laminated sheet member according to the first step of the invention;

FIG. 3 is a plan view showing the overall configuration of a conductor line pattern sheet member according to the second step of the invention process;

FIG. 4 is an enlarged plan view of the right and left end portions of the conductor line pattern sheet member in FIG. 3;

FIG. 5 is a plan view showing the interior configuration of a coil pattern laminated sheet member according to the third step of the invention;

FIG. 6 is a cross-sectional view taken on line A-A of FIG. 5, showing the first example for the third step of the invention; FIG. 7 is a cross-sectional view taken on line A-A of FIG. 5, showing the second example for the third step of the invention;

FIG. 8 is a cross-sectional view taken on line A-A of

FIG. 5, showing the third example for the third step of the invention; and

FIG. 9 is a transverse sectional view showing the configuration of a flexible coil winding structure according to the invention.

BEST MODE FOR CARRYING OUT OF THE INVENTION

Hereinafter, the invention will be described in further detail by way of several preferred embodiments with reference to the accompanying drawings.

<The first step of the process of the invention _>

In the first step of the process, a flexible laminated sheet member is provided by forming a thin conductive layer on the surface of a thin insulator shee .

FIG. 2 is a sectional side view illustrating the layered configuration of the flexible laminated sheet member 100, which consists of two layers. In this figure, reference numerals 110 and 120 denote respectively the thin insulator sheet and the thin conductive layer formed on the surface of the insulator sheet .

Preferably, the insulator sheet 110 is made from an insulating substance such as polyimide or polyester, etc., which has good characteristics in heat-resistance and electric insulation. The insulator sheet 110 is preferred to be sufficiently thin enough to preserve its flexibility, and more preferably has a thickness of less than about 35 microns.

The conductive layer 120 may be made from a metallic material such as copper or aluminum, which has good characteristics in electric conductivity and

adhesiveness to the insulator sheet 110. Metallic materials such as copper or aluminum do not have a very good adhesiveness to the polyimide or polyester of the insulator sheet 110. Therefore, as one preferred embodiment for easily forming the copper or aluminum layer on the surface of the polyimide or polyester sheet, a seed layer with a thickness of about 50 microns may be formed on the surface of the sheet 110 by using RF sputtering technique, etc., and then the uniform conductive layer 120 may be formed over the seed layer.

Nickel or chromium, etc., may be preferably used as materials for the seed layer. Also the conductive layer of copper or aluminum may be formed by using electroplating, electroless plating, vapor deposition or RF sputtering techniques, etc., on a case by case basis.

Another preferred embodiment for forming the conductive layer 120 of copper or aluminum on the insulator sheet 110 may be carried out by coating or layering an adhesive with a thickness of about 35 microns on the surface of the insulator sheet 100 followed by adhering copper or aluminum foil over the adhesive layer.

Preferably, the conductive layer 120 has a thickness of from several to about 100 microns, more preferably of from about 25 to 75 microns for preserving the electric conductivity thereof and also the flexibility of the overall laminated sheet member 100.

<The second step of the process of the invention> The second step of the process of the invention will be described in details below. In the second step of the process, a conductor line pattern sheet member is prepared by removing partly the conductive layer 120 from the flexible laminated sheet member 100. The second conductor line pattern sheet member

includes a conductor line pattern, which has a plurality of parallel conductor lines inclined at a predetermined angle.

FIGS. 3 and 4 are plan views of the conductor line pattern sheet member 200 manufactured by the second step of the invention. FIG. 3 illustrates the whole outline of the conductor line pattern sheet member 200, and FIG. 4 is an enlarged plan view of the longitudinally right and left end portions in FIG. 3. As illustrated in FIG. 4, the conductor line pattern sheet member 200 includes a conductor line pattern 210 having a plurality of parallel conductor lines 212, 214, 216, which are arranged at longitudinal interspaced distances in the insulator sheet 110 and inclined at the predetermined angle. Preferably, the conductor line pattern 210 includes a pair of conductor line terminals 210c integrally formed near the upper end of the right end conductor line and near the lower end of the left end conductor line respectively for being used as an input or output terminal of electric current.

The above-configured conductor line pattern sheet member 200 may be manufactured by using a conventional method such as photolithographic techniques and screen printing techniques, etc., which are usually applied to the formation of fine circuits on a printed circuit board, etc. For instance, the manufacturing procedure may be carried out by printing the patterns of conductor lines of FIG. 3 and some other patterns required or helpful to the subsequent steps of process on the surface of the conductive layer 120 of the flexible laminated sheet member 100 in FIG. 2, and removing selectively the non- printed portions from the conductive layer 120, for example by using an aqueous solution of ferric oxide which

is able to etch selectively the copper layer but not the insulator sheet 110.

As can be seen in subsequent descriptions about the third step of the invention, the conductor lines 212, 214, 216 should be adjusted in the angle of inclination, width and interdistance thereof so that the conductor line pattern 210 can constitute the coiled circuit pattern 310 of FIG. 5, when the conductor line pattern sheet member 200 is folded in half. Any skilled persons in the art could determine the angle of inclination, width and interdistance of the conductor lines, depending on the overall size of the conductor line pattern sheet member 200 and/or the conductor line pattern 210.

In order to facilitate the easy handling of the sheet member over the whole process of the invention, the conductor line pattern 210 may be smaller in width than the insulator sheet 110 so that the conductor line pattern sheet member 200 includes some margin at the transverse upper and lower end portions and the longitudinal right and left end portions, as illustrated in FIG. 3. Furthermore, in order to facilitate the correct aligning of the parallel conductor lines when they are folded, the conductor line pattern sheet member 200 includes several align marks 240 in the margins. As the align mark, the conductor line pattern sheet member 200 may include a pair of marking holes 240 in the right and left margins as illustrated in FIGS. 3 and 4, or several holes in the transverse upper and lower margins, which holes are not illustrated in figures. Also the align mark may comprises various characters and symbols such as a (+) sign.

One conductor line pattern sheet member 200 is illustrated in FIGS. 3 and 4, but any persons skilled in the art could conceive a possible mass production process

as follows : preparing a broader rectangular laminated sheet member 100, and printing and etching a plurality of conductor line patterns 210 at once.

<The third step of the process of the invention> The third step of the process of the invention will be described in details below with reference to FIG. 5.

In the third step of the process, a coil pattern laminated sheet member is provided by electrically connecting the upper and lower portions of the conductor lines with each other. The coil pattern laminated sheet member includes a coiled circuit pattern which is formed by the parallel conductor lines. FIG. 5 illustrates a plan view of the coil pattern laminated sheet member 300 provided by the third step of the process of the invention. In FIG. 5, reference numeral 300 generally denotes the coil pattern laminated sheet member provided by the third step.

In this embodiment, the coil pattern laminated sheet member 300 may be prepared by insulating the center portion of the conductor line pattern 210 except for the upper portion 210a and lower portion 210b thereof, folding the conductor line pattern sheet member 200 in half lengthwise, and electrically connecting the upper portions 212a, 214a, 216a and lower portions 212b, 214b, 216b of the parallel conductor lines 212, 214, 216 so that the conductor line pattern 210 provides the coiled circuit pattern 310, as illustrated in FIG. 5.

The third step will be described below in greater details with reference to FIGS. 4 and 5. In the figures, reference numeral 230 denotes an insulating strip for insulating the center portion of the conductor line pattern 210 except for the upper portion 210 and lower portion 210b thereof. The insulating strip

230 preferably may be attached longitudinally across the parallel conductor lines 212, 214, 216 except for the upper and lower portions of them. An electric insulation tape of polyimide and polyester, etc., may be employed as the insulating strip 230,

As illustrated in FIG. 5, the upper and lower portions of the half-folded conductor line pattern 210 have to be correctly aligned so as to form the coiled circuit pattern 310 by the electrical connection between the upper and lower portions of the conductor lines 212, 214, 216. In this regard, when the half-folded conductor line pattern 210 is aligned in the way in which the lower portion of the nth conductor line faces to the upper portion of the (n+Dth conductor line, they are made to form the coiled circuit pattern 310. Also the conductor line terminals 210c are made to locate respectively at the right and left end of the coil pattern laminated sheet member 300, that is, the coiled circuit pattern 310. Therefore, when electric current is applied to one of the conductor line terminals 210c of the coiled circuit pattern 310, the current will flow through the parallel conductor lines 212, 214, 216 in a zigzag pattern to the other conductor line terminal 210c.

The above alignment of the parallel conductor lines may be easily achieved by aligning the marking holes 240 of the conductor line pattern sheet member 200 when it is folded in half, because the inclination angle, width and interdistance of the conductor lines are adjusted in that way, as described above. It could be well known to skilled persons in the art that a plurality of the coil pattern laminated sheet members 300 could be longitudinally connected in series by electrical connection between the conductor line terminals

210c in the coiled circuit pattern 310, namely, that the coil pattern laminated sheet member 300 could be lengthened as required, depending on the desired number of turns of coil windings. (The first example on the electrical connection)

FIG. 6 is a cross-sectional view taken on line A-A of FIG. 5, illustrating the first example for carrying out the electrical connection of the upper and lower portions of the conductor lines in the third step of the invention for preparing the coil pattern laminated sheet member.

In the first example, the coiled circuit pattern 310 may be provided by soldering the upper and lower portions of the conductor lines. That is, as illustrated in FIG. 6, the first example may be carried out by applying a solder 320 to the upper portions 212a, 214a, 216a and the lower portions 212b, 214b, 216b of the conductor lines which are exposed by the insulating strip 230, thereafter, folding in half lengthwise the conductor line pattern member 200 so that the conductor line pattern 210 forms the coiled circuit pattern 310 as described above, and finally hot- pressing appropriately the solder-applied portions for soldering the upper and lower portions of the conductor lines.

Preferably, various methods may be employed for applying the solder 320 to the desired place, for instance, solder-plating the upper and lower portions of the conductor lines, or dipping them into a molten solder bath, or printing a solder cream or paste on the upper and lower portions of the parallel conductor lines. It is preferable that the hot-pressing is carried out at a temperature of from about 200 to about 280 degrees Celsius. Below that temperature range results in a defective soldered joint and/or poor bonding strength,

consequently leading to a failure of the soldered joint in service. Above that temperature range is also unpreferable because it causes the solder materials to evaporate during the hot-pressing. Besides the first example, there are provided two other examples, for which a description will follow that of the fourth step of the process of the invention just below.

<The fourth step of the process of the invention _> The fourth step of the process of the invention will be described in details below.

In the fourth step of the process, a flexible coil winding structure is completed by inserting a magnetizable core into the coil pattern laminated sheet member. FIG. 9 illustrates the transverse cross-section of the completed flexible coil winding structure, which is denoted by reference numeral 400.

As illustrated in the FIG. 9, the coil pattern laminated sheet member 300, which is manufactured through the above several steps of the process, comes to include a longitudinal flexible slit formed by and between the insulating strip 230. The flexible coil winding structure 400 is obtained by inserting the magnetizable core 410 into the longitudinal flexible slit. Preferably, the magnetizable core has a shape of an elongated strip, for example, like amorphous magnetizable ribbons which may be manufactured by conventional melt spinning technique, etc. It is preferable that the magnetizable core 410 is made from Fe-base or Co-base amorphous magnetic alloys, and has a thickness of from 10 to 25 microns. This embodiment employs Matglass (a registered trademark of Allied Signal in U.S.) having a thickness of about 17 microns.

FIG. 9 illustrates the transverse cross-section of the flexible coil winding structure, which may be manufactured by the above-described process of the invention. As described above and also shown in the figure, the flexible coil winding structure 400 includes the magnetizable core 410 at the center portion, the conductor line pattern 210 around the magnetizable core 410, and the flexible insulator sheet 110 around the conductor line pattern 210 for substantially insulating the overall coil winding structure and protecting it from its surroundings while in service. The conductor line pattern 210 is arranged so as to provide the coiled circuit pattern 310 as illustrated in FIG. 5. The insulating strip 230 is further provided between the magnetizable core 410 and the conductor line pattern 210. Also, the coil winding structure 400 includes an electrical connection 420 for connecting both end portions of the conductor lines so that the conductor line pattern 210 provides the coiled circuit pattern 310. The electrical connection 420 may be provided according to various examples of the process as described in this specification.

In respect of carrying out the electrical connection of the upper and lower portions of the conductor lines, two other examples besides the first one of FIG. 6 will be described in details below.

(The second example on the electrical connection)

FIG. 7 is a cross-sectional view taken on line A-A of

FIG. 5, illustrating the second example for carrying out the electrical connection of the upper and lower portions of the conductor lines in the third step of the invention for preparing the coil pattern laminated sheet member.

In this example as illustrated in FIG. 7, the

electrical connection may be carried out by adhering longitudinally a Z-axis film 330 on the upper and lower portions 210a, 210b of the conductor line pattern 210 (i.e., adhering on both the conductor lines and the insulator sheet therebetween) , folding the conductor line pattern 210 in half as shown in FIG. 5, and hot-pressing the portions of the conductor line patterns attached by the Z-axis film 330.

The Z-axis film denotes an adhesive substance of film type mixed up with copper, nickel or gold particles of from 6 to 15 microns in diameter without any interparticle contacts. The Z-axis film has no electric conductivity as it is, but it may be caused to have conductivity by pressing it to make the metallic particles to contact. Therefore, as illustrated in FIG. 7, by hot-pressing the film-attached portions the dispersed metallic particles are inter-contacted together with the surface of the conductor lines, but not in the portion of the film which is attached to the insulator sheets, thereby electrically connecting the upper and lower portions of the conductor lines.

Preferably, the hot-pressing may be achieved by carrying out a preliminary hot-pressing at a temperature of from 85 to 100 degrees Celsius for from 3 to 5 seconds followed by finishing it at a temperature of from 170 to 190 degrees Celsius for 20 seconds to thereby obtain better electrical contact and also desired adhesive strength. The hot-pressing may be carried out in various ways depending on the characteristics of Z-axis film as employed.

(The third example on the electrical connection) FIG. 8 is a cross-sectional view taken on line A-A of FIG. 5, illustrating the third example for carrying out

the electrical connection of the upper and lower portions of the conductor lines in the third step of the invention for preparing the coil pattern laminated sheet member.

In this example as illustrated in FIG. 8, the electrical connection may be carried out by folding the conductor line pattern 210 so as to form the coiled circuit pattern 310 as shown in FIG. 5, and then heating the upper and lower portions of the conductor line pattern 210 sufficiently enough to form a welded layer 340 in the portions of the insulator sheets 110 which correspond to the area between the individual conductor lines. Therefore, the conductor lines remain in tight contact by and between the welded layers 340 to thereby maintain the electrical connection. The heating may be carried out by the hot-pressing, similarly to the first and second examples of FIGS. 6 and 7. The heating temperature and time are preferably predetermined so that the insulator sheets are welded in the surface thereof, but not melted away. In this example, it is most preferable that the hot-pressing is carried out at a temperature of from about 300 to about 350 degrees Celsius for about 10 to 30 seconds.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the spirit and scope of the invention as defined by the appended claims.