CA1173123A

CA1173123A - Capacitor and method for making the same

Info

Publication number: CA1173123A
Application number: CA000390235A
Authority: CA
Inventors: Charles C. Rayburn
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 1981-02-27
Filing date: 1981-11-17
Publication date: 1984-08-21
Also published as: PT74140A; NO820598L; JPH0612749B2; DE8227050U1; FI78795B; FR2500953B1; AT386296B; IT8219860A0; NL191547C; BE892259A; CH645748A5; FI78795C; ES8303811A1; IT1149778B; BR8108082A; ATA30282A; GB2143087B; MX150745A; SE454630B; DK85482A

Abstract

ABSTRACT

Disclosed is a method of and apparatus for making capacitors, the capacitors each comprising a plurality of layers having opposed edges, each layer comprising a dielectric substrate and a metallic film, the metallic film extending from one edge toward the other edge. Each layer includes a zone free of the metallic film, the zone being adjacent to but spaced from the other edge to leave a narrow marginal metal film band at the other edge which is spaced by the zone from the remainder of the metallc film. The layers are disposed with the metal film of one layer being separated by dielectric material from the metal film of the adjacent layer, the layers being offset such that at one side of the capacitor the edges of a first group of layers lie outwardly beyond the other edges of a second group of layers. At the opposite side of the capacitor the edges of the second group of layers lie outwardly beyond the other edges of the first group of layers. The layers in the first group alternate with the layers of the second group and the outwardly lying edges of the layers in each group are coated with electrically conductive material to connect electri-cally the metal film layers of each group.

Description

Case 3788 ! l 73123 CAPACITOR AND METE~OD FOR MAKING TEIE SAME
.

Back round of the lnvention g ~
~his invention relates to layer or stack wound capacitors ànd to methods and apparatus for making of the same.

One such method and apparatus is shown and described in S U.S. Patent No. 3, 670, 378, In that patent the process for the production of the capacitors comprises first forming capacitor bodies by winding alternate metallic and dlelectric film~ l)n a drum, contemporaneously winding separating layers between the capacitor bodies to form a parent winding having alternate layers of capacitor bodies and Reparating layers, then applying a metallic spray coating to the edges of the parent winding to connect metallic Eilms, and thereafter severing the parent winding perpendicular to the separating layers to form the lndividual capacitor bodies. ~hese resultant capacitor bodies have interwoven metallic layers which are separated by dielectric layers. ~he layers of one group comprislng dielectrlc substrates and metallic films project outwardly from one side of the capacitor body whne another group of substrates and fil~ project from the other slde of the capacitor body. ~he metallic coating is applied such that lt connect~ electrically together the metalllc films on the outwardly projected group of layers. ~hus, there is provided two electrodes or sets of capacitor "plates"
which are dielectrically isolated from one another but which are interwoven.
In the foregoing arrangement it sometimes happens that during the winding process the being-wound layers will weave or depart from their intended paths resulting in one or ,.~ ..
I, - 1 - ~

l 173~23 more layers being improperly located wlth respect to the adjacent layers. If the separation between the groups of layers is not sufficient, the capacitor may be short~circuited or it may have a lower than intended dielectric strength at one or more regions. If the separation is excessive the re-sulting capacitance of the capacitor is reduced.
Moreover, although the foregoing arrangement provides economical manufacture of capacitors as compared with certain other manufacturing approaches, such as wound capacitors, there lC is nevertheless a demand for further economies in capacitor manufacture. This demand for further economies in capacitor manufacture is all the more immediate in view of the economic realities of the present-day capacitor marketplace where such devices have almost come to be regarded as commodities so that price is often the single basis upon which buying decisions are predicated. With such pressures existing with respect to selling price, the need to reduce cost of manufacture without degrading product quality is particularly strong.

SUMMARY OF THE INVENTION
This invention seeks to provide a high quality commercial capacitor of the general type stated, but which is different in structure and wherein the manufacturing process is considerably lower in cost.
This invention further seeks to provide an arrange-ment of the type stated which materially reduces the possibility of short-circuiting of the being-wound capacitor as a result of improper disposition of the metallic and dielectric films.
This invention also seeks to provide an arrangement of the type stated in which the production of capacitors is much faster than it is possible with the presently available equipment.
This invention still further seeks to provide apparatus ! ~73123 of the type st~.lt~d which functions -to apply the layers ~orm-ing the capacitor to a drum or transfer wheel directly from laminating or lay-oll rol]ers. Such an arrangement prevents the supply ma-terial from traveling unsupported in space, there-by reducing weave and consequent misalignment of the capacitor layers.
In accordance with the foregoing, the invention in one aspect pertains to a capasitive structure comprising a plurality of layers having opposed edges, with each layer comprising a dielectric substrate and a metallic film, the metallic film extending from one edge toward the other edge.
Each layer includes a zone free of the metailic film~ the zone being adjacent to but spaced from the other edge to leave a narrow marginal film band at the other edge which lS is spaced by the zone from the remainder of the metallic film. The layers are disposed with the metal film of one layer being separated by dielectric material from the metal film of the adjacent layer, the layers being offset such that at one side of the capacitor the edges of a first group of layers lie outwardly beyond the o-ther edges of a second group of layers, and at an opposite side of the capacitor the edges of the second group of layers lie outwardly beyond the other edges of the first group of layers. The layers in the first group alternate with the layers of the second group and the outwardly lying edges in each group are coated with electrically conductive material to connect electrically the metal film layers of each group, the narrow marginal metallic film band thereby separating the adjacent coating material from the metal-free zone.
The invention also comprehends a method of making the capacitor structure including providing first and second webs of material each having a dielectric substrate, a metallic film coating, and narrow parallel longitudinal ~'"1 1,, .

' ~73123 metal-free ~ones, slitting the webs along parallel lines that are offset from the metal-free zones to form ribbons, each of which has a narrow marginal metal film band extending inwardly from a longitudinal edge of the ribbon to the metal-free zone. The ribbons from the first and second webs arealternately wound on a drum and in the winding, the ribbons of one web are offset from the ribbons of the other web to form a plurality of adjacent interleaved rinqs of capacitive structure each having alternately disposed metal and di-electric layers and with there being in each structure thelayers of the ribbons of each web respectively projecting laterally outwardly from the marginal metal film band of the ribbons of the other web. The method further includes coating the laterally projected parts of each structure with a metal substance to connect electrically the metal films of the resp-ective webs of the structure, and severing the structure trans-versely of the rlbbons to form capacitive structures or ropes.
The apparatus of this invention includes first and second supply rolls of webs with each web having a dielectric substrate with a metallic film coating, a rotatable drum spaced from the supply rolls, and first and second laminator rollers, the rollers being circumferentially spaced with respect to the periphery of the drum. A tension sensing roller is assoc-iated with each laminator roller and in spaced parallel relation thereto to constitute with its associated laminator roller a roller pair, one web being strained and tensioned over each roller pair. Means are provided for slitting the web into ribbons prior to winding the ribbons on the drum to provide alternate layers of metallic and dielectric material, the laminating rollers being sufficiently close to the drum and the slitting means being sufficiently close to the laminating rollers such that the ribbons are supported over substantially their full length prior to winding onto the drum.

~;~

! ~73123 Preferably, the roller pairs are oEEset from one another such that, in winding the ribbons upon the drum, there are formed upon the drum a plurality of adjacent interleaved rings of capacitance each having alternately disposed metal and dielectric layers and with there being in each structure the layers of the ribbons of each web respectively projecting laterally outwardly from the edges of the ribbons of the other web.
The invention may also include the application to one of the webs of a thin film of adhesive in at least a portion of the electric field regions of a capacitor, but the adhesive is not applied in the region of slitting of the web or in the laterally projected parts of the structure where a spray contact is made with the metallic coating. The purpose of the adhesive is, to the extent needed, to lock the lamination so that the wound capacitor structure can be handled without delamination.
In another aspect of the invention the webs can be passed through a station where a number of laser beams can burn off the metal to form precisely spaced demetalized zones.
These demetalized zones may be made much narrower by laser beam burn-off than would be obtainable by material commercial-ly available with conventional demetalized zones, which are much wider than is necessary for capacitors with low voltage ratings.

(~ase 378~

~ 173123 Brief Description of the Figures Fig. 1 is a diagrammatic view of apparatus constructed in accordance with and for carrying out the method of the present invention, - Fig. 2 is a fragmentary sectional view taken along line

2-2 of Fig. 1;

Fig. 3 is a fragmentary top-plan view on an enlarged scale, of the structure of Fig. 2;

Fig. 4 is an enlarged fragmentary sectional view taken along line 4-4 of Fig. 3;

Fig. 5 is an enlarged diagrammatic view partially in sec-tion taken along line 5-5 of Fig. 1;

Fig. 6 is a much enlarged fragmentary sectional view of parts of the capacitor according to the invention;

Fig. 7 is an enlarged fragmentary portion of Fig. 2 and showing structure for applying adhesive to the web, appearing with Figs. S and 8; and Fig. 8 is a diagrammatic showing of the laser burn-o~f station which forms the demetalized zones as the web is withdrawn from its supply roll, appearing witl~ Figt;. 5 alld 7.

Case 3788 t 173123 Detaile_Des cription Referring now in more detail to the drawing Fig. l there is shown a pair of supply rolls 2, 4 from which webs A and B
are withdrawn. Each of the webs A, B comprises a dielectric substrate 6 and a metallic film 8. The substrate 6 may be of a suitable plastic such as the resin sold under the trademark "Mylar".
~he film 8 may be a vapor deposited aluminum, and both the substrate 6 and metallic film 8 are exceedingly thin. By way of example but not of limitation, the substrate 6 may be of the order of . 001 inches or less in thickness while the thickness of the metalized film 8 may be of the order of 500 angstrom units. Each web A, B has a plurality of parallel demetalized or metal-free zones 10, as best seen in Figs. 3 and 4 with respect to the web B. It is understood, however, that a like series of demetalized zones are provided on the web A. The webs A, B may have the demetalized zones 10 preformed thereon, or they may be formed by a laser burn-off method as will later be described. In any case the webs pass over a series of rollers respectively for slitting into ribbons and interleaved or alternate winding onto a large diameter drum or transfer wheel 20 In particular, the web A passes over an idler roll 12a, the axis of rotation of which is shiMable to control weave of the web A. The idler roll 12a moves in and out as a unit with the supply roll 2 under the control of a conventional edge guide sensor Case 3788 ' ~73123 (not shown) to control the weave. From the idler roll 12a, the web passes by the aforementioned edge guide sensor to a tension sensing idler 14a. The tension sensing idler sends a signal to a variable drag clutch (not shown) on which supply roll 2 is mounted. This closed loop control maintains the tension at any preset value. ~he apparatus also includes a laminating or lay-on roller 16a. Between the rollers 14a, 16a is a web-slitting station at which the web A is slit into a plurality of ribbons prior to passage around the lay-on roller 16a and wrapping onto the drum or transfer wheel 20. Similarly, the web B passes over a shifting idler 12b and from there to a tension sensing idler 14b past the slitting station onto the laminating or lay-on roller 16b, where the idler 12b responds to a second edge guide sensor (not shown) to control the weave of web B while the tension sensing idler 14b again sense a signal to a variable drag clutch (not shown) on which the supply roll 4 is mounted to maintain the tension at a preset value.

~he slitting station for the web B comprises a plurality of space parallel cutters such as razor blades 21b which cooperate with a polished web support bar 22b over which the web B passes.
Likewise, for the web A the slitting comprises space~l parallel razor blades 21a (Fig. 7) which cooperate with web support bar 22a.
For each web the slitting station forms a plurality of ribbons which immediately p~ss onto the rollers 16a or 16b, as the case may be, and then onto the drum 20. ~he result is that the ribbons are ,~

Case 3788 ! ~ 7 3 1 2 3 supported substantially throughout their full lengths prior to wirlding onto drum 20. Because the ribbons do not travel unsupported in space, weave is eliminated and the ribbons can be accurately deposited onto the drurn 20, ~his is in contrast to prior art arrange-5 ments which rely upon edge guides, sometimes unsatisfactorily,to prevent weave of the web.

~ he laminating or lay-on rollzrs press against the drum or transfer wheel 20 and the razor blades may operate directly in narrow slits on the rollers 16a, 16b. In any event, the arrangement 10 for slitting the webs provides smooth cuts by the razor blades without causing the web material to wrinkle. ~his is particularly important as it is difficult to obtain smooth cuts without wrinkling in web material as thin as that being utilized in the present invention.
In the present apparatus, the rollers 16a, 16b may be located either 90 apart as shown in Fig. 1, or 180 apart.

l~he web B is slit into the plurality of ribbons 18b, as seen in Figs. 2-4. ~he web A is also slit to provide ribbons 1 8a which, like the ribbons 18b, ultimately will become capacitor layers, as seen in Fig. 6. The slit lines for the web B are offset from the 20 dernetalized zones 10 so as to form marginal metal films bands 24 at one edge of each ribbon 18b. A like slitting takes place for the web A except, however, at the slit line for each blade 21a is offset from that as compared to Fig. 3 to form like marginal film Case 37 ! ~73123 bands 24 on the ribbons 18a. ~hus, if the blade 21b is located to the left of the demetalized zone 10 in cutting the web B (reference to Fig. 3) then for the web A the blade 21a will be to the right of the adjacent demetalized zone, as indicated by arrows 21aa in 5 Fig. 3.

'rhe ribbons are disposed simultaneously upon the drum 20 to produce the layered pattern shown in Fig. 5. ~here are formed a plurality of hoops or rings 30 of capacitor StruGture from which individual capacitors may be formed. In Fig. 5 only one c>f the 10 rings 30 i9 shown in cross section for purposes of clarity of illustration.
Moreover, the sources of the various ribbons, namely from the supply web A or B, is indicated on one of the structures 30 in Fig. 5. It will also be apparent that the ribbons are not illustI.ated to scale, but rather are considerably foreshortened. In any case, 15 there is an initial winding of A layers adjacent to the drum 20, as shown by the lower five such layers designated in Fig. 5.
~hereafter, the ribbons are interleaved and offs~t from each other as they are simultaneously wound onto the drum 20 to form the pattern indicated by the A and B alternate layers 1n Fig. 5.
20 ~hereafter, another group of A layers are wound over the group of A and B alternate layers. l~he inner and outer A layers serve as reinforcement while the interweaved A and B layers or ribbons provide the active portion of the capacitor structure.

Each of the separate rings 30 may be removed from the ~ase 3788 ! 173123 drum 20 and the sides 32, 34 thereof coated in a conventional manner with a metallic spray coating 40 (Fig. 6). ~he ring 30 may then be cut perpendicular to the edges 32, 34 to form a length of capacitor structure. ~hat length can then be cut again transversely 5 to form individual capacitor units.

Fig. 6 shows an enlarged sectional view through several interleaved layers of the capacitor. It will be seen that at one side of the capacitor metalized films 8a and the substrate 6a project laterally outwardly of the adjacent edges 36 of the layers 18b.
10 ~he metalized spray coating 40 electrically connects the metalized films 8a to form a set of capacitor electrodes or plates, this being made possible by the space between the layers or ribbons 18a.
~he space between the left-hand metallic coating 40 of the top portion of Fig. 6 and the metalized layer 8b of the ribbon 18b 15 is at least the width of the metalized zone 10 plus the. width of the marginal metal film band 24. ~hus, in effect, the band 24 is a "floating" electrode. By providing for the floating electrode formed by the band 24 the full width of the demetalized zone 10 is utilized for dielectric separation along the surfaces of the layers, thereby 20 reducing the possibility of short-circuiting or changing the capacitance of the capacitor from its prescribed value.

On the other side of the capacitor, as shown by the lower portion of Fig. 6, the layers 1 8b project outwardly from the ma rgin -Case 378~

1 1731~3 37 of the layers 18a for receiving the right-hand metal spray coating 40, shc~vn in the bottorn portion of Fig. 6. l~he marginal rnetal film band 24 in the lower portion of Fig. 6 and located on the layer 18a likewise serves as a "floating" electrode so that full advantage is taken of the demetalized zones 10, as previously des cribed .

In a modified form of the invention shown in Fig. 7 any suitable thin adhesive may be deposited on the web A by an applicator 50 p(Y3itioned just before the slitting operation occurs.
Epoxy resin is one type of adhesive that may be used, but the invention is not limited thereto. ~he adhesive is not applied in the region of slitting or in the extension areas o~ the web where the metallic spray is to be applied. The purpose of the adhesive, if needed, is to lock the lamination together after being wound onto the drum 20 so that the structures 30 can be handled without delamination. ~he adhesive can be deposited and spread in a film thickness substantially less than one micron, and the adhesive may thus be used without materially reducing an efficient capacitance-to-volume ratio.

~he web material used in the present invention may be purchased with the demetaliæed zones. However, these demetalized zones are usually somewhat larger than is necessary for low voltage capacitors. Accordingly, as shown in Fig. 8, it is possible to form the demetallized zones 10 as the web A or B is being withdrawn from ~e ~ / d~:;

the supply roll. ~his Inay be accompllshed by running the web through a laser burn off ~tatlon 52 at which laser beams 53 may be utilized to burn off the deposlted metal and form an extremely narrow demetalized zone 10, much narrower thsn is provided on commercially available webs. Con~equently, material cost is reduced a long with the size of the capacitor. ~he tension sensing and edge guide control ~ystems employed in the present in~ention are ava.ilable from Advanced Web Systems, Inc., 4793 Colt Road, P.O. Box 6025, Rockford, Illino~ 61125.
It is to be understood that, while the detailed drawings and specific examples given describe the preferred embodiments of -the invention, they are for the purpose of illustration only, that the invention is not limited to the precise details and conditions disclosed and that various changes may be made therein without departing from the spirit of the invention which is defined by the following claims.

SUPPLEMENTAR~ DISCLOSURE
_ As noted on Page 11, the ring 30 may be cut perpendicular to the edges 32, 34 to form a length of capacitor structure which length in turn may be cut trans-versely to form individual capacitor units.
The invention herein also contemplates the provision of an intermediate length of capacitive structure which is sufficiently rugged to withstand the rigors of shipping to remote locations for further processing into individual capacitors.
Accordingly, the capacit~e structures formed by cut--ting perpendicular to the edges 32, 34 may be subjected to pres-sure and heat to create a substantially rigid capacitive stick.

That capacitive stick can then be cut transversely to form individual capacitor units.
An alternative or complementary approach to the locking of the lamination together after being wound onto the drum 20, as referred to on Page 12, is by the application of heat to the ribbons as they are wound upon the drum. Such application of heat would be sufficiently frequent and sufficiently warm to tack adjacent layers of ribbons together as they are wound upon the drum. The laminations thereby become locked and the wound capacitor structure can be handled without delamination.

Claims

The embodiments of the invention in which an ex-clusive property or privilege is claimed are defined as follows:

1. A capacitive structure comprising a length of a plurality of layers, each said layer having opposed edges; each said layer comprising a dielectric substrate and a metallic film, said metallic film extending from a first one of said edges toward a second one of said edges, each of said layers including a zone free of metallic film, said zone being spaced from said second edge leaving a narrow marginal metal film band at said second edge which is spaced by said zone from the remainder of said metallic film, said layers being disposed with said metallic film of each layer being separated by dielectric material from said metallic film of the adjacent layer, said layers being offset such that at a first side of the capacitive structure said first edges of a first group of layers lie outwardly beyond said second edges of a second group of layers, and at a second side of the capacitive structure said first edges of said second group of layers lie outwardly beyond said second edges of said first group of layers, said layers of said first group alternating with said layers of said second group, and the outwardly lying edges of said layers of each group being coated with electrically conductive material to electrically connect said metallic film of each layer of each respective group.

2. A capacitive structure as recited in claim 1, wherein said capacitive structure further comprises elect-rical connection means bonded to said electrically conductive material to facilitate electrical connection of said capacitive structure in electrical circuitry.

3. A capacitive structure as recited in claim 2, wherein said capacitive structure further comprises protective enveloping means applied to encapsulate said capacitive structure in a manner providing electrical insulation and moisture resistance for said capacitive structure while permitting electrical connection to said electrical connection means.

4. A capacitor comprising a plurality of layers, each of said layers comprising a dielectric substrate and a metallic film upon said substrate, said metallic film covering substantially all of a first side of said substrate of each of said layers, said metallic film being interrupted by a metal-free zone, said metal-free zone extending substantially parallel to a first of two opposing edges of said substrate and spaced therefrom thereby defining two metallized regions upon said substrate extending respectively from said first edge and a second edge of said substrate to said metal-free zone; said layers being disposed in two groups, layers of a first group of said two groups alternating with layers of a second group of said two groups, said metallic film of each layer lying adjacent the substrate of an adjacent layer, said two groups of layers being offset so that said first edges of said first group of layers extend beyond said second edges of said second group of layers and said first edges of said second group of layers extend beyond said second edges of said first group of layers, said extending first edges of said first and second groups of layers being respectively coated with electrically conduct-ing material to electrically connect said metallized regions adjacent said first edges of each group.

5. A capacitor as claimed in claim 4, wherein said capacitor further comprises electrical connection means bonded to said electrically conductive material to facilitate electrical connection of said capacitor in electrical circuitry.

6. A capacitor as claimed in claim 5, wherein said capacitor further comprises protective enveloping means applied to encapsulate said capacitor in a manner providing electrical insulation and moisture resistance for said capacitor while permitting electrical connection to said electrical connection means.

7. A method of making capacitive structures comprising: providing first and second webs of material, each having a dielectric substrate, a metallic film coating, and narrow parallel longitudinal metal-free zones; slitting said webs along parallel lines that are offset from said metal-free zones to form ribbons, each of which has a narrow marginal metal film band extending inwardly from one longitudinal edge of the ribbon to said metal-free zones; winding said ribbons from said first and second webs alternately on at least one drum and in said winding offsetting the ribbons of one web from the ribbons of the other web to form on each of said at least one drum a plurality of adjacent interleaved rings of capacitive structure, each having alternately disposed metal and dielectric layers and with there being in each structure the layers from the ribbons of each web respectively projecting laterally outwardly from said marginal metal film bands of the ribbons of the other web; separating said interleaved rings of capacitive structure and coating the laterally projecting parts of each of said rings of capacitive structure with a metal substance to electric-ally connect the metal film of the respective webs of each of said rings of capacitive structure; and severing each ring of capacitive structure transversely of the ribbons to form lengths of capacitive structure.

8. A method of making capacitive structures as recited in claim 7, wherein said at least one drum is one drum.

9. A method of making capacitive structures as recited in claim 7, wherein said method further comprises interposing adhesive between said ribbons before winding of said ribbons upon said at least one drum.

10. A method of making capacitive structures comprising: providing first and second webs of material each having a dielectric substrate, a metallic film coating, and narrow parallel longitudinal metal-free zones; slitting said webs along parallel lines that are offset from said metal-free zones to form ribbons each of which has a narrow marginal metal film band extending inwardly from one longitudinal edge of the ribbon to said metal-free zone, winding said ribbons from said first and second webs alternately on a single drum and in said winding offsetting the ribbons of one web from the ribbons of the other web to form a plurality of adjacent rings of capacitive structure on said drum each having alternately disposed metal and dielectric layers and with there being in each ring of capacitive structure the layers from the ribbons of each web respectively projecting laterally outwardly from said marginal metal film bands of the ribbons of the other web, separating said interleaved rings of capacitive structure and coating the laterally projected parts of each ring of capacitive structure with a metal substance to connect electrically the metal films of the respective webs of each ring of capacitive structure, and severing each ring of capacitive structure transversely of the ribbons to form lengths of capacitive structure.

11. A method of making capacitive structures as recited in claim 10 wherein said method further comprises interposing adhesive between said ribbons before winding of said ribbons upon said one drum.

CLAIMS SUPPORTED BY THE SUPPLEMENTAL DISCLOSURE

12. A method of making capacitive structures as recited in claim 7, wherein said method further comprises pressing and heating said lengths of capacitive structure to form substantially rigid capacitive sticks.

13. A method of making capacitive structures as recited in claim 12 wherein said method further comprises transversely severing said capacitive sticks to form capacitor chips wherein said capacitor chips are suitably valued and dimensioned for generally accepted electronics applications.

14. A method of making capacitive structures as recited in claim 7, wherein said method further comprises application of heat to said ribbons as said ribbons are wound upon said at least one drum, said application of heat being sufficiently frequent and sufficiently warm to effect tacking of adjacent layers of ribbons as said ribbons are wound upon said at least one drum.

15. A method of making capacitive structures as recited in claim 10 wherein said method further comprises pressing and heating said lengths of capacitive structure to form substantially rigid capacitive sticks.

16. A method of making capacitive structures as recited in claim 15 wherein said method further comprises transversely severing said capacitive sticks to form capacitor chips wherein said capacitor chips are suitably valued and dimensioned for generally accepted electronic applications.

21 .

17. A method of making capacitive structures as recited in claim 16, wherein said method further comprises interposing adhesive between said ribbons before winding of said ribbons upon said at least one drum.

18. A method of making capacitive structures as recited in claim 10, wherein said method further comprises application of heat to said ribbons as said ribbons are wound upon said one drum, said application of heat being sufficiently frequent and sufficiently warm to effect tacking of adjacent layers of ribbons as said ribbons are wound upon said one drum.