CA1136232A

CA1136232A - Sealed flat electrolytic capacitor and method

Info

Publication number: CA1136232A
Application number: CA000346900A
Authority: CA
Inventors: Joseph A. Moresi, Jr.
Original assignee: Sprague Electric Co
Current assignee: Sprague Electric Co
Priority date: 1979-04-02
Filing date: 1980-03-04
Publication date: 1982-11-23
Also published as: US4267566A; JPS55133531A; GB2046019B; GB2046019A

Abstract

SEALED FLAT ELECTROLYTIC
CAPACITOR AND METHOD
Abstract of the Disclosure A flat capacitor is manufactured by placing an abide foil within a fold of spacer that is within a folded cathode foil, impregnating the assembly with electrolyte, and then heat-sealing the assembly between layers of polymer. The foils have electrode tabs attached thereto that are spaced laterally from each other and extend beyond the same edges of the polymer.

Description

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SEALED FLAT ELRCTROLYTIC
CAPACITOR AND METHOD
This invention relates to a flat electrolytic capacitor and to the manufacture thereof. More parti-cularly it relates to a method of making such a capaci-tor which can be automated and which produces a rela- -tively low-cost product.
There is an increasinv demand for electro- ~;-lytic capacitors with a low CV (Capacitance multiplied by Voltage) value. This demand has been met by a variety of capacitors: subminiature wound aluminum electroly-tics; solid electrolytics; and some plastic film, paper, and ceramic capacitors. Ea~h type embodies advantages in terms of cost, size, form factor, electrical charac-teristics, etc. No one type, however, offers all or a majority of the advantages or required characteristics.
A feature of this invention is the provision of a method for making an electroly~ic capacitor in such a size and ~orm as to give maximum component packaging density when used with circuit boards. Another feature i5 the provision of automatic assembly of such units, thus reducing costs.

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- 2 -In accordance with this invention a flat elec-trolytic capacitor has an anode within spacer material that is within a cathode that is within a polymer with anode and cathode tabs extending therefrom.
In a drawing which illustrates embodiments of the invention, Figure 1 is a series of steps in one of the methods of making the capacitors of the present inven-tion 7 and Figure 2 shows another embodiment of the invention .
In general, the flat capacitors of this inven-tion may be assembled on a continuous plastic strip that becomes one side of the final package, or the units may be assembled continuously and placed on the plastic strip just before final sealing. In either case, the result is a flat electrolytic capacitor encased in a heat-sealable plastic with leads spaced for automatic insertion into circuit boards.
In the method shown in Figure 1, a plastic film strip 11 having a laminar heat-sensitive adhes-ive layer ls first provided with a sheet of spacer paper 12. Over spacer 12 is placed etched cathode foil 13 with attached electrode tab 14. On top of foil 13, a second sheet of spacer paper 15 is placed, followed by etched anodized anode foil 16 with attached elec-trode tab 17. In the embodiment shown, the anode foil 16 is approximately one-half the length of cathode foil 13 and spacer 15. The excess cathode foil 13 and spacer 15 are folded back ovPr anode foil 16. A third paper spacer 18 is placed over the assembly, and electrolyte (not shown) is applied to the foil and spacer assembly.
A plastic film cover sheet 19 is placed over all, and the assembly is heat-sealed at least around the peri-phery thereof. Cathode and anode leads (not shown) areattached by known means to cathode electrode tab 1 and anode electrode tab 17, respectively.
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The assembly scheme lends itself to automa-tion by using a continuous plastic film strip that is moved along the line from station to station for super-position of each succeeding layer at each succeeding station.
In another embodiment, ~he anode foil is approximately one-half the length of the cathode foil and second spacer. Before adding the third spacer, excess cathode foil and second spacer is folded over the anode foil. The process is completed as before.
Similarly, the first paper may be the length of the cathode foil and second spacer, and all may be folded over the anode, doing away with the third spacer paper. Also, the plastic strip may be twice the final width and it may be folded over the unit instead of using a second plastic strip prior to heat-sealing, thus eliminating the second strip and a seam on one side of the unit. Another permutation is to space the units farther apart, cut them apart after impregnation, fold the plastic over from the side, and heat-seal.
Another way of automatically assembling the units is to preassemble the capacitors and then deposit them on adhesive coated portions of the plastic strip and finally heat-sealing the units in plastic. This may be achieved using paper spacer wider than the cathode foil, a continuous strip of etched cathode foil with electrode tabs attached and a continuous strip of etched and anodized anode foil with electrode tabs attached.
In the method shown in Figure 2, as paper spacer 12 is unwound from a roll it is folded in half lengthwise. Etched cathode foil 13 with attached elec-trode tabs 14 is likewise unwound from a roll, folded in half lengthwise, and positioned inside folded paper spacer 12. Another paper spacer 15 is unwound from its supply roll, folded in half lengthwise, and positioned inside folded cathode foil 13. Another foil 16 with attached electrode tabs 17 is positioned inside Eolded .lt paper spacer 15. Subsequently, the assembly is flatted .. . ,, . ~ . . . , :
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and cut into individual capacitors before or after impregnation with an electrolyte. The individual units may be placed on a plastic strip which may be folded over to form an envelope or a second cover strip may be used. The units are then heat sealed as above, and leads are attached.
Alternately, the continuous anode foil strip might be inserted into folded paper spacer strip, in turn inserted into folded cathode foil strip that in turn is inserted into an outer folded paper strip and crimped, impregnated, separated into individual uni~s, and heat sealed in plastic as above.
If more rigidity is desired, plastic grids, e.g. 10-20 mils (0.25-0.51 mm) thick, may be placed on the plastic strip, and the pods placed in them. Other permutations will be obvious to ~hose skilled in the art.
The plastic strip is of thermoplastic material;
suitable commercially available thermoplastics include polyolefins, e.g. polyethylene or polypropylene, perfluoroethylene, polyvinylchloride, or polyester.
While not restricted to the following sizes, the above methods are suitable for making capacitors of 0.5 to 1.5 inches (12.7 to 38.1 mm) by 0.75 to 1.5 inches (19.05 to 38.1 mm) by 0.1 inch (2.54 mm). Lead wire spacing on the smallest of the above is 0.2 inch (5.0 mm) with increments of 0.1 inch (2.54 mm) for the larger sizes.
A light weight capacitor is thus produced that takes up a minimum of board area and provides maximum component packaging density per board and for automatic insertion with conventional equipment.
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Claims

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

1. A process of manufacturing a sealed flat electrolytic capacitor comprising locating an etched and anodized anode foil within a folded first spacer that is located within a folded etched cathode foil that in turn is located within a folded second spacer, said anode and cathode foils having electrode tabs attached thereto, impregnating said first and said second spacers with electrolyte so as to contact both sides of said anode and both sides of said cathode with electrolyte, encas-ing in a heat-sealable polymer with said electrode tabs extending beyond edges of said polymer, and heat-sealing around at least the periphery of the unit.

2. A process according to claim 1 wherein said anode foil is approximately one-half the length of said cathode foil and said first and said second spacers, and excess cathode foil and spacers are folded over said anode foil to provide said locating of said anode foil within said folded first spacer located within said folded cathode foil within said folded second spacer.

3. A process according to claim 1 wherein said electrode tabs extend beyond the same edges of said polymer.

4. A process according to claim 3 wherein said edges are opposite said fold of said cathode foil and said spacer.

5. A process according to claim 1 wherein said second spacer placed between said foils and said poly-mer before said heat-sealing is a paper spacer.

6. A flat electrolytic capacitor comprising an etched and anodized foil anode bearing an electrode tab, an etched foil cathode bearing an electrode tab, said anode foil being of substantially the same width and approximately one-half the length of said cathode foil, said anode foil being within a fold of a first spacer, said cathode foil being folded once to overlie both sides of said anode and said first spacer and to cover both sides of said anode, said folded cathode being within a fold of a second spacer, said first and said second spacers being impregnated with an electrolyte, thereby providing said electrolyte in contact with both sides of said anode and both sides of said cathode, said tabs being laterally spaced from each other and extending beyond the edges of said spacers; said foils, said spacers, and a portion of said tabs being heat-sealed between layers of polymer.

7. A capacitor according to claim 6 wherein, said electrode tabs extend beyond said polymer layers, lead attachment to said tabs being external to the edges of said polymer layers and said heat-seal.

8. A capacitor according to claim 6 wherein said spacer is a paper spacer.