JP2010040959A - Electric double-layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an outer packaging structure for an electric double-layer capacitor, which can improve the thermal resistance and reliability by preventing an insulating rubber for sealing from being peeled off in soldering reflow process for a basic cell inside the electric double-layer capacitor. <P>SOLUTION: The electric double-layer capacitor comprises: a pair of polarizing electrodes impregnated with an electrolytic solution; a separator sandwiched between the pair of polarizing electrodes; a conductive current collector; an element with a plurality of base cells 1 laminated in series, wherein the base cell 1 has a structure made of an insulating rubber placed so as to perform sealing at the side surface of the outer periphery of the conductive current collector; a first lead terminal 13 and second lead terminal 14 for leading out electrode; an insulating case 12 for holding the element; and an outer packaging metal case 11 which are placed so as to cover the insulating case 12, and an opening of which is sealed with the outer part of the insulating case 12. The electric double-layer capacitor has a metal reinforcement plate 16 which has a concave portion at the center part of the inside-bottom-part inside of the outer packaging metal case 11 and has a concave portion at the center part of the bottom-part-side inside of the insulating case 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric double layer capacitor, and more particularly to a structure for preventing electrolyte leakage and capacitor burst against an increase in internal pressure during solder reflow.

  In an electric double layer capacitor, an element comprising a polarizable electrode impregnated with a pair of electrolytes arranged so as to sandwich a separator that transmits ions in the electrolyte is contained in an outer metal case. The polarity electrode is in contact with the upper case in the outer metal case on one side, the other side is in contact with the lower case in the outer metal case, and the upper case and lower case are insulated by a gasket. Some are caulked and sealed.

  In order to mount such an electric double layer capacitor on a printed circuit board, solder reflow at 200 ° C. or higher is usually used. In such surface mounting by solder reflow, leakage or rupture of the electrolyte has occurred due to an increase in pressure accompanying a temperature rise in the case or deformation / melting of the gasket at a high temperature.

  In order to solve such a problem, a gasket having high heat resistance has been proposed. For example, there is one described in Patent Document 1.

  The gasket for an electric double layer capacitor described in Patent Document 1 is a polyether ether ketone or an alloy material thereof, which has been subjected to annealing treatment in the range of 170 ° C. to 230 ° C. to promote crystallization, or an alloy thereof. It is composed of a composite material with another member, has excellent heat resistance characteristics, and does not cause deformation or melting when mounted on the surface of a printed wiring board of an electric double layer capacitor by solder reflow at about 200 ° C. Since sealing can be performed without causing cracking due to caulking mechanical stress when sealing the gasket, there is an effect that the electrolytic solution of the electric double layer capacitor is hardly vaporized or leaked.

JP-A-11-251202

  An electric double layer capacitor is a capacitor that utilizes an interfacial conductivity phenomenon in which positive and negative charges are charged relative to a very short distance at an interface where two layers of solid and liquid are in contact with each other, and the technology on which the present invention is based will be described. An example of the structure of the basic cell 31 of the electric double layer capacitor is shown in FIG.

  In the basic cell 31 shown in FIG. 3, for example, powdered activated carbon impregnated with an electrolytic solution is used as the pair of polarizable electrodes 32 and polarizable electrodes 33. The pair of polarizable electrodes are arranged so as to be opposed to each other with a separator 34 that transmits ions in the electrolytic solution therebetween, preventing short-circuit between the polarizable electrodes. A conductive current collector 35 and a conductive current collector 36 are respectively disposed on the back surfaces of the polar electrode 33 that are not on the separator 34 side so as to be in electrical contact with the polarizable electrodes. Yes.

  The conductive current collectors 35 and 36 have a structure to which a voltage can be applied. In addition, polarizable electrodes 32 and 33 made of powdered activated carbon are impregnated with dilute sulfuric acid as an electrolytic solution, and ions in the dilute sulfuric acid pass through the separator 34 and can freely go back and forth. A large amount of dilute sulfuric acid is impregnated in the central portions of the polarizable electrodes 32 and 33.

  In order to insulate the sealing of the electrolytic solution from the respective conductive materials, an insulating rubber 37 for sealing is disposed on the outer peripheral side surfaces of the conductive current collectors 35 and 36. The basic cell 31 is hard at the central polarizable electrodes 32 and 33 impregnated with the electrolytic solution, and softer than the sealing insulating rubber 37 at the outer peripheral portion. Further, in order to ensure that the sealing insulating rubber 37 is in close contact with the conductive current collectors 35 and 36, the outer peripheral portion has a slightly recessed shape as compared with the central portion.

  In general, an electric double layer capacitor is formed by stacking a required number of basic cells 31 in series according to the voltage to be used, and the electricity between basic cells, between polarizable electrodes, or between a polarizable electrode and a conductive current collector. In order to stabilize the connection resistance, a constant pressure is applied inside.

  FIG. 4 shows the exterior structure of the electric double layer capacitor that is the basis of the present invention. The exterior metal case 43 including the bottom, the opening, and the side surface is built in so as to be in contact with one conductive current collector surface of the element 42 formed by laminating a plurality of basic cells 41 similar to FIG. 3 at the bottom surface. ing.

  The insulating case 44 has a bottom, an opening, and a side surface. The opening of the outer metal case 43 is sealed on the bottom side of the insulating case 44, and the side surface of the insulating case 44 is connected to the side surface of the outer metal case 43. Contact with the side surface of the element 42 and short circuit are prevented.

  The insulating case 44 can be taken out outside while preventing contact and short-circuit between the pair of first lead terminals 45 and second lead terminals 46 that are in electrical contact with the conductive current collector surfaces on both sides of the element 42. It has a structure. Engineering plastics such as polyacetal, polyphenylene sulfide (PPS), and liquid crystal polymer (LCP) are used for the insulating case 44, and the external metal case 43 is mechanically caulked to keep the internal pressure constant. Have been to. The seat plate 47 holds the first lead terminal 45 and the second lead terminal 46 and serves as a capacitor stage for surface mounting. Polyacetal is a kind of polymer, specifically known as DuPont's trade name Delrin.

  Under a high temperature environment such as a solder reflow condition when mounting an electric double layer capacitor on a printed circuit board, heat in the atmosphere at the time of solder reflow is transferred to the internal element 42, and the heat causes dilute sulfuric acid as an electrolytic solution. As a result of vaporization, the internal pressure of the basic cell 31 constituting the element 42 is increased, and the outer metal case 43 and the insulating case 44 are firmly held from above and below, so that the vertical deformation is suppressed and the strength is weak. The insulating rubber 37 for sealing at the outer peripheral portion that is easily deformed breaks without being able to withstand the increase in internal pressure, or the sealing performance is impaired due to deformation due to heat, and the electrolyte in the basic cell 31 leaks. May arise.

  The present invention has been made in order to solve the above-mentioned problems, and the deformation of the insulating rubber for sealing due to the increase in the basic cell internal pressure accompanying the thermal expansion during the solder reflow of the basic cell inside the electric double layer capacitor An object of the present invention is to provide an exterior structure of an electric double layer capacitor that can suppress peeling and improve heat resistance and reliability.

  In order to solve the above-mentioned problems, the present invention prevents a short circuit between a pair of polarizable electrodes impregnated with an electrolyte and disposed between the pair of polarizable electrodes and the pair of polarizable electrodes. A separator that transmits ions in the electrolyte and a back surface of the pair of polarizable electrodes that are not separated from each other so as to be in electrical contact with the polarizable electrode and sandwiching the polarizable electrode therebetween. A basic cell having a structure comprising a pair of conductive current collectors and an insulating rubber disposed on an outer periphery of the pair of conductive current collectors for sealing and electrically insulating the electrolyte solution And a first lead terminal and a second lead terminal for taking out an electrode from the element, and one of the first and second lead terminals. Hold it on the other bottom side and disconnect between the lead terminals. And an insulating case for holding the element, and having an opening, a bottom part, and a side part, arranged so as to cover the insulating case and one of the outermost conductive current collectors of the element The second lead terminal is electrically contacted with a body surface and electrically contacted with the first lead terminal, and the opening has an exterior metal case sealed outside on the bottom side of the insulating case. Is an electric double layer capacitor having a structure in electrical contact with the outermost conductive collector surface of the outermost part of the element, and has a recess at the center inside the bottom of the outer metal case, and the insulating case The electric double layer capacitor is characterized by having a metal reinforcing plate having a recess at the center inside the bottom side.

  Further, the present invention is an electric double layer capacitor in which the metal reinforcing plate on the bottom side of the insulating case is a part of the second lead terminal.

  The material of the exterior metal case is preferably SUS or iron, and SUS is more preferable from the viewpoint of mechanically caulking and sealing. The outer diameter of the capacitor is assumed to be about 4 mm to 20 mm, and the thickness of the outer metal case is 0.2 mm or more. The depth of the recess at the center of the bottom of the outer metal case is preferably about 0.1 mm or more and less than 0.2 mm, although it depends on the wall thickness.

  The material of the insulating case can withstand mechanical caulking with the outer metal case and solder reflow temperature. For example, Aalen (trade name of polyamide-based engineering plastic manufactured by Mitsui Chemicals), Genesta (polyamide-based manufactured by Kuraray) Engineering plastic product name), LCP (liquid crystal polymer as described above) and the like are preferable.

  As the metal reinforcing plate, SUS is preferable as in the case of the exterior metal case, the thickness is about 0.1 mm to 0.4 mm, and the depth of the recess is 0.05 mm to 0.00 mm within a range not exceeding the thickness. About 2 mm is preferable.

  As the lead terminal, SUS, iron, copper or the like can be used, but strength is required, and iron plated with solder is preferable.

  According to the present invention, the central portion of the bottom portion of the outer metal case is recessed, and the thickness of the other portion of the case is made slightly thicker than that of the conventional case, and further, the metal reinforcement having a recess in the central portion on the bottom side of the insulating case. By inserting a plate, it is possible to maintain the pressure in the sealed outer metal case at the outer periphery of the basic cell against the expansion of the basic cell due to the evaporation of the electrolyte due to the temperature rise during solder reflow. In addition, since deformation at the outer periphery of the basic cell can be suppressed, it is possible to prevent peeling of the insulating rubber for sealing due to thermal expansion during solder reflow of the basic cell inside the electric double layer capacitor, and leakage of the electrolyte It is possible to provide an exterior structure of an electric double layer capacitor that can improve heat resistance and reliability without causing or explosion.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an exterior structure of an electric double layer capacitor according to an embodiment of the present invention. In the electric double layer capacitor of the present invention, an element 2 formed by laminating a plurality of basic cells 1 in an outer metal case 11 is inserted, and an opening of the outer metal case 11 having a concave bottom central portion (in FIG. 1, The first lead terminal 13, the second lead terminal 14, the first lead terminal 13, and the second lead terminal for taking out the electrodes are drawn in such a manner that the bottom of the outer metal case is on the top and the opening is on the bottom. An insulating case 12 for preventing contact and short-circuit between the lead terminals 14 and a metal reinforcing plate 16 having a recess at the center are arranged, and the exterior metal case 11 is mechanically moved outside the bottom side of the insulating case. By sealing and sealing, the element 2 is held under pressure.

  FIG. 2 is an exploded configuration diagram of the electric double layer capacitor according to the embodiment of the present invention. The electric double layer capacitor of the present invention can be manufactured, for example, as shown below.

  The basic cell 1 is basically the same as that shown in FIG. 3, powdered activated carbon is used for the polarizable electrodes 32 and 33, and dilute sulfuric acid is used for the electrolytic solution impregnated into the polarizable electrodes. A PTFE microporous membrane is used for the separator 34, butyl rubber is used for the sealing insulating rubber 37, and conductive rubber is used for the conductive current collectors 35 and 36. In the present invention, an element 2 that connects four such basic cells 1 in series is used. Of course, how many basic cells 1 are used can be selected according to the purpose and application.

  Regarding the exterior parts of the electric double layer capacitor, for example, SUS430 is used for the exterior metal case 11 and the metal reinforcing plate 16, and polyamide resin is used for the insulation case 12, and the first lead terminal 13 and the second lead terminal are used. 14 may be made of SUS430 plated with Sn.

  As an assembling procedure, first, the element 2 is inserted into the exterior metal case 11, then the metal reinforcing plate 16 is placed from the opening side of the exterior metal case 11, and further insulated from the first lead terminal 13 and the second lead terminal 14. The case 12 is covered, and then the exterior metal case 11 is mechanically caulked and sealed on the opening side while applying a certain pressure. Finally, the electric double layer capacitor of the present invention is completed by bending the other side of the seat plate 15 through the first lead terminal 13 and the second lead terminal 14 from one side of the seat plate 15. The thickness of the exterior metal case 11 is, for example, 0.2 mm, which is the same as the thickness of the conventionally used exterior metal case 43 for the recess, and 0.3 mm for the other portions, and the depth of the recess. It is sufficient to use a material having a thickness of 0.1 mm. Further, the thickness of the concave portion may be about 0.15 mm, and the thickness of other portions may be about 0.2 mm or more.

  Regarding the shape of the metal reinforcing plate 16, it is necessary to cover the side where the concave portion is located on the element 2 side. However, in order to improve workability, the metal reinforcing plate having the concave portion at the center on both side surfaces in FIG. 17 can also be used. The thickness of the metal reinforcing plate 16 or 17 other than the recess is about 0.1 mm to 0.4 mm, and the depth of the recess may be about 0.05 mm to 0.2 mm within a range not exceeding the thickness. .

(Comparative example)
As a comparative example for the present invention, the conventional electric double layer capacitor that is the basis of the present invention shown in FIG. 4 is made of the same material as the embodiment of the present invention, and the outer metal case 43 has a thickness of 0.2 mm. Used to assemble and produce.

  Regarding the heat resistance of the electric double layer capacitor thus obtained, the peak temperature of the solder reflow temperature was changed in the range of 230 ° C to 260 ° C, and the number of device failures (liquid leakage) occurring with respect to the solder reflow temperature was investigated. did. Table 1 shows the results for 100 p samples for each level.

  As shown in Table 1, the electric double layer capacitor having an exterior structure according to the present invention has a strength increase due to a slight increase in the thickness of the exterior metal case 11 having a recess at the bottom center, and the center of the element 2 with the recess. The outer peripheral portion of the element 2 is held by the thick bottom portion of the peripheral portion so that the pressure is uniform, and the same effect as the outer metal case 11 has a concave portion at the center portion. By adding the metal reinforcing plate 16 exhibiting the above, the expansion of the internal element 2, particularly the expansion of the insulating rubber 37 for sealing at the outer peripheral portion of the basic cell 1 can be suppressed, and the element can be prevented from bursting. The heat resistance of the capacitor can be improved.

  As described above, according to the present invention, the expansion of the element 2 due to heat is suppressed by increasing the pressure applied to the sealing insulating rubber 37 and improving the strength of the exterior structure, and the sealing insulating rubber 37 is sealed. As a result, the heat resistance of the electric double layer capacitor can be improved.

Sectional drawing which shows the exterior structure of the electrical double layer capacitor which concerns on embodiment of this invention. The disassembled block diagram of the electric double layer capacitor which concerns on embodiment of this invention. The figure which shows the structural example of the basic cell of the electric double layer capacitor for demonstrating the technique used as the basis of this invention. The figure which shows the exterior structure of the electric double layer capacitor used as the basis of this invention.

Explanation of symbols

1, 31, 41 Basic cell 2, 42 Element 11, 43 Exterior metal case 12, 44 Insulating case 13, 45 First lead terminal 14, 46 Second lead terminal 15, 47 Seat plate 16, 17 Metal reinforcing plate 32 , 33 Polarized electrode 34 Separator 35, 36 Conductive current collector 37 Insulating rubber for sealing

Claims (3)

A pair of polarizable electrodes impregnated with an electrolyte and arranged to face each other;
A separator that is sandwiched between the pair of polarizable electrodes, prevents a short circuit between the polarized electrodes, and transmits ions in the electrolyte solution;
A pair of conductive current collectors disposed so as to be opposed to each other in electrical contact with the polarizable electrodes on the back side of the pair of polarizable electrodes that are not separators; and
An element in which a plurality of basic cells having a structure composed of an insulating rubber disposed on the outer periphery of the pair of conductive current collectors for sealing and electrically insulating the electrolyte solution are stacked in series; ,
A first lead terminal and a second lead terminal for extracting an electrode from the element;
An insulating case for holding the first and second lead terminals on the other bottom side, insulating the lead terminals and taking them out to the outside, and holding the element;
An opening portion, a bottom portion, and a side surface portion are disposed so as to cover the insulating case, and are in electrical contact with one of the outermost conductive current collector surfaces of the element and in electrical contact with the first lead terminal. And the opening has an exterior metal case sealed outside on the bottom side of the insulating case,
The second lead terminal is an electric double layer capacitor having a structure in electrical contact with the other outermost conductive current collector surface of the element,
Having a recess in the center inside the bottom of the exterior metal case,
An electric double layer capacitor comprising a metal reinforcing plate having a recess at a central portion inside a bottom side of the insulating case.   2. The electric double layer capacitor according to claim 1, wherein the metal reinforcing plate on the bottom side of the insulating case is a part of the second lead terminal. The thickness other than the concave portion of the central portion of the bottom of the outer metal case is 0.2 mm or more, and the depth of the concave portion of the outer metal case is 0.1 mm or more and less than 0.2 mm,
The thickness of the metal reinforcing plate other than the central concave portion is 0.1 mm to 0.4 mm, and the depth of the concave portion of the metal reinforcing plate is 0.05 mm to 0.2 mm within a range not exceeding the thickness.
The electric double layer capacitor according to claim 1, wherein:

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