JP2009182029A - Stacked solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stacked solid-state electrolytic capacitor which is much more improved in reduction effect of ESR. <P>SOLUTION: The stacked solid-state electrolytic capacitor with a multi-terminal structure is constituted by stacking a plurality of single-plate capacitor elements each having an anode portion on one side of valve-acting metal and a cathode portion on a surface of the other such that anode portions are stacked alternately to the right and left while cathode portions are placed in the center. In the respective single-plate capacitor elements stacked, an upper element and an under element have different lateral sizes to form steps on side end surfaces of the stack, and the side end surface portions are additionally coated with conductive paste. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multilayer solid electrolytic capacitor having a multi-terminal structure in which a plurality of single plate capacitor elements are stacked.

  A solid electrolytic capacitor has a valve action metal foil such as aluminum, tantalum, or niobium or a sintered body thereof as an anode, an oxide film layer formed thereon as a dielectric, and a solid electrolyte layer formed thereon to form a cathode. Is configured. As this solid electrolyte layer, manganese dioxide, a TCNQ complex, a conductive polymer, and the like are known.

In recent years, the current flowing through the capacitor has increased dramatically with the lowering of the voltage and speed of the CPU of the computer. Therefore, if the ESR / ESL of the capacitor is high, the amount of heat generated is large, which causes a failure of the capacitor. . Therefore, a capacitor corresponding to this type of needs is required to have a low ESR / ESL.

  As one form corresponding to this reduction in ESR / ESL, a multilayer solid electrolytic capacitor in which a plurality of single plate capacitor elements are stacked one above the other is widely used. This multilayer solid electrolytic capacitor generally includes an anode portion in which an oxide film layer is provided on the surface of a porous body obtained by etching the surface of a valve action metal foil or molding and sintering a valve action metal powder. A single plate capacitor element composed of a cathode portion formed by sequentially forming a solid electrolyte layer, a carbon layer, and a silver layer on a coating layer is laminated by a conductive adhesive.

FIG. 1 shows the structure of this general multilayer solid electrolytic capacitor. P is an anode part, C is a cathode part, K is a carbon film layer, and M is a masking layer that insulates between the cathode and anode. The anode parts are joined to each other and connected to an anode terminal PL indicated by a dotted line, the cathode parts are joined to each other via a conductive adhesive R, and the lowermost surface is electrically joined to the cathode terminal CL with the same adhesive. The entire laminated body element is molded with an exterior resin to obtain a finished product.
Functionally, the whole valve action metal plate (or a sintered plate made of valve action metal powder) is an anode, but in this specification, for convenience of explanation, a solid electrolyte layer formed on the right surface of the metal plate The carbon layer / silver layer portion is indicated as a cathode portion C, and the left anode metal plate exposed portion is indicated as an anode portion P.

In this case, as can be seen in the figure, the cathode portion C is formed with a solid electrolyte layer, a carbon layer, and a silver layer, and the thickness is slightly larger than the anode portion. In the case of pressure welding, there is a tendency that the interlayer of the cathode part slightly spreads, and the conductivity between the cathodes deteriorates.
In order to solve this problem, usually in this type of multilayer capacitor, the entire end face of the cathode portion of the laminate is additionally covered with a conductive paste such as silver to reduce the connection resistance between the cathode portions. It is. (See Patent Document 1)
The additional coating with the conductive paste is performed in the laminated body as shown in FIG. 1 after laminating each single plate capacitor element and before joining the anode part P and cathode part C to the terminals PL and CL. A method is adopted in which the anode part of the body is suspended from above and only the cathode part is immersed in a bath of conductive paste in which silver or the like is dissolved, and the paste is applied to the entire peripheral surface of the cathode.

As a result, a conductive paste is additionally formed in the laminated cathode portion, and at the same time, the paste penetrates between the cathode layers. As a whole, the conductivity between the cathode layers is greatly improved and the ESR is lowered.
In this case, since the anode part needs to be completely insulated from the cathode, it is natural that the anode part is not immersed in the paste bath so that the conductive paste does not adhere.

  Furthermore, in recent years, in this type of multilayer capacitor, when laminating each single plate capacitor element in order to achieve lower ESR and ESL, the anode part is laminated so that the left and right sides are centered around the cathode part, and the anode potential is increased. A solid electrolytic capacitor having a multi-terminal structure that can be taken out from both the left and right sides has been developed and put into practical use. (See Patent Document 2)

In this multi-terminal structure, as described above, the anode potential is taken out from both the left and right sides, and the cathode potential is taken out from the center. In addition, the anode part of the single plate capacitor element is shifted by 90 degrees about the cathode part. A five-terminal structure in which the anode branches in the front, rear, left and right directions is also known.
By adopting the multi-terminal structure in this way, even if the number of stacked layers increases corresponding to the increase in capacity, the ESR / ESL value can be further improved by the magnetic field canceling effect.

  However, in this multi-terminal structure laminate, the anode is on both sides or front and back, so the additional coating layer on the circumference of the laminate is submerged only in the cathode circumference into the paste tank as described above. It is difficult to form. Therefore, the additional coating in such a case is usually applied by spraying a conductive paste with a syringe having an air dispenser connected to the side edge of each cathode.

2 and 3 show an outline of a conventional multilayer capacitor having such a multi-terminal structure. FIG. 2 is a perspective view showing an example of a multilayer element of a three-terminal solid electrolytic capacitor. FIG. It is the figure which expanded and displayed so that each coating layer could understand the YY 'cross section of a laminated element.
In FIG. 2, P1, P2, P3, and P4 are anode exposed portions, C1, C2, C3, and C4 are cathode portions formed on the anode substrate, K is a carbon layer, and M is an insulator between the negative and anode. A masking layer is shown.
In FIG. 3, 1 is a valve metal substrate, 2 is an oxide film layer, 3 is a solid electrolyte layer, 4 is a carbon layer, 5 is a silver layer for extracting a cathode potential, and 6 is electrically connected to each cathode layer simultaneously. These are conductive adhesives for ensuring conduction, and these are formed on each single plate in the process of manufacturing each single plate capacitor element, and are common to each single plate.
7 is a conductive coating layer additionally formed on the cathode portion side end face of the laminate element after laminating a plurality of each single plate, and using the syringe as described above, the conductive paste is applied from the direction of the arrow. It is formed by spraying and coating.

However, according to the inventor's experiment, when the conductive paste is sprayed on the cathode end face when the number of stacked layers is large, the paste flows from the end face before the conductive paste penetrates between the layers of each single plate element. It has been found that the amount of paste entering between the cathode layers becomes insufficient, the conductivity between the cathode layers cannot be sufficiently improved, and an effective ESR reduction cannot be expected.
That is, as can be seen from FIG. 3, it is desirable that the conductive paste 7 enters as much as possible into the gap g between the cathode layers, but in most cases, only a small portion such as 7 'enters.
For this reason, even if a conductive coating layer is additionally formed by taking man-hours, the expected effect as described above cannot be obtained.
JP 2004-281515 A JP 2007-1116064 A

  In view of the above problems, the present invention provides a novel cathode element structure for further improving the conductivity between stacked cathode layers in a multi-terminal multilayer solid electrolytic capacitor, and further improves ESR. The purpose is to make possible declines.

In order to solve the above-mentioned problems, the present invention is formed on the oxide film layer by using one side of the valve metal as an anode portion and using an oxide film layer formed on the other surface of the valve metal as a dielectric. In a multilayer solid electrolytic capacitor having a multi-terminal structure in which a plurality of single-plate capacitor elements each having a solid electrolyte layer as a cathode portion are laminated so that the anode portion branches right and left around the cathode portion,
The width of the cathode part of the single-plate capacitor element constituting the multilayer element is made different between the upper layer and the lower layer to form a step on the cathode side part of the laminate, and a conductive paste is applied to the cathode side part on which the step is formed. By applying it, the connection resistance between the laminated cathodes is reduced, and as a result, the ESR of the laminated solid electrolytic capacitor can be reduced.

  According to a second aspect of the present invention, in the multilayer solid electrolytic capacitor having the multi-terminal structure, the lateral width of the cathode portion of each single plate capacitor element is configured to be narrower as the element is stacked on top, and the cathode side end face portion of the multilayer body is stepped. The multilayer solid electrolytic capacitor as described above, wherein the multilayer solid electrolytic capacitor is formed in a shape.

  Since the multilayer solid electrolytic capacitor of the present invention has steps on the side portions on both sides of the multilayer element, additional coating with the conductive paste becomes more reliable, and this conductive paste easily enters between the multilayer elements. The connection resistance between the cathode layers can be extremely reduced. Therefore, low ESR can be realized for the entire multilayer capacitor.

〔Example〕
4, 5, and 6 are explanatory views of a structure of a four-layered solid electrolytic capacitor having a three-terminal structure according to an embodiment of the present invention. FIG. 4 is a perspective view showing only a laminated element, and FIG. The YY ′ cross-sectional view of FIG. 2 is enlarged to explain the details of the cathode structure. FIG. 6 is a perspective view showing a completed electrolytic capacitor in which each electrode of the multilayer element is bonded to a terminal plate (lead frame) and sheathed with an exterior resin.

4, 5 and 6, the properties of the coating layer of each single plate element are the same as those of the conventional example shown in FIGS.
That is, four single-plate capacitor elements that are provided with an anode part P on one side and a cathode part C on the other side of the valve-acting metal subjected to the etching process (in this embodiment, aluminum foil) and separated and insulated by the masking layer M, Laminate so that the anode part is symmetrical. In this embodiment, in this case, the respective valve action metal foils are prepared so that the lateral width sizes thereof are slightly different, and the cathode layer is formed thereon. As can be seen from FIG. 4, the element plate C1 having the widest width is formed on the lowermost layer, the sheet C2 having a slightly narrower size is formed thereon, the narrower one C3 is finally stacked, and the narrowest cathode portion C4 is finally stacked. Laminate.
This will be described in more detail based on the YY ′ cross-sectional view of FIG. 5. Each single-plate capacitor element includes an anode portion in which an oxide film layer 2 is formed on an aluminum foil 1 and a solid formed thereon. The cathode layer is composed of an electrolyte layer 3, a carbon layer 4, and a silver layer 5, and each cathode layer is bonded and laminated via a conductive adhesive 6. In this case, since the widths w are different from each other as described above, by stacking the element plates symmetrically with respect to the center line N, a step S is formed on the end surface on the side of the stacked body as can be seen in the figure. As a result, the shape of the side end face is stepped.

In this embodiment, the lateral width w of each single plate capacitor element is w1 = 4.5 mm, w2 = 4.0 mm, w3 = 3.5 mm, where w1 is the lowest one and w4 is the uppermost one. , W4 = 3.0 mm.
In addition, the vertical length l including the anode portion of each element plate was 4.5 mm, and the thickness d of each single plate element was 0.2 mm.

Next, by discharging and applying silver conductive paste from the double arrow direction to the side end face of the cathode portion of the laminated element formed in a stepped manner in this manner with a syringe connected with an air dispenser, the cathode laminated portion is cured. An additional coating layer 8 of silver was formed on both end faces of the film.
In this case, since the step S is provided at the side of the laminate in this embodiment, the discharged paste temporarily stays at this step, and the gap between the layers as indicated by 8 'in the meantime. It will go deeper into. Therefore, the conductivity of the gap is greatly improved. In addition, the adhesiveness of the paste to the side end surface itself is further improved because there is no risk of flowing down as in the case of a conventional side end surface.

Further, in this type of multi-terminal laminated element, the upper and lower anode parts protrude from the rear end face of the cathode (the end face opposite to the anode part), so that an additional coating layer is formed directly on this rear end face. Although difficult, as described above, the conductive paste penetrates deeply into the gaps between the cathode layers, and as a result, this wraps around to the rear end face of the cathode plate, and this part also adds more than the conventional method. A coating layer is formed.
Due to the above synergistic effect, the multilayer capacitor of this example has achieved a significant reduction in ESR.

  FIG. 6 shows resistances of the left and right anode terminals (anode potential extraction terminal plates) PL and PL ′ to the anode parts P1, P3 and P2, P4 on both sides of the laminated element in which the additional covering layer is formed on the cathode part as described above. After electrically connecting by welding or the like, and connecting the cathode terminal (cathode potential extraction terminal plate) CL to the lowermost cathode portion C1 via a conductive adhesive, the entire laminate is packaged with an exterior resin (epoxy resin) 9 FIG. 2 is a perspective view of a finished product of the multilayer solid electrolytic capacitor of the embodiment of the present invention, which is a three-terminal laminated solid electrolytic capacitor having a rated voltage of 2.5 V and a rated capacity of 220 μF.

Table 1 below shows the production of 100 solid electrolytic capacitors of the above-mentioned example, the ESR performance was actually measured for these, and the average value of each data was shown in comparison with the conventional example.
In order to align the conditions of the comparison data, the conventional example is a four-layered solid electrolytic capacitor having a three-terminal structure illustrated in FIGS. Using the same length of 4.5 mm and only the width w of all 4.5 mm, an additional covering layer is formed by discharging and applying the conductive silver paste to the side end face of the laminate as in the example. After connecting each anode / cathode to the respective terminal, the entire product is packaged with the same exterior resin as in the examples.
The data illustrated in Table 1 is an average value of the results of actually measuring ESR values for the 100 conventional products.

As can be seen from Table 1, the ESR value of the multilayer solid electrolytic capacitor of the example is significantly improved over the conventional multilayer solid electrolytic capacitor of the same rating, and the multilayer type having a very low ESR according to the present invention. It was proved that a solid electrolytic capacitor was obtained.
This reduction in ESR is because the both sides of the laminate are stepped, preventing unnecessary flow of the conductive paste when forming the additional coating layer, and the conductive additional coating layer on the side edge of the multilayer element is effective. This is because the conductive paste can easily enter between the elements and the connection resistance between the laminated cathode layers is reduced.

In the above embodiment, aluminum (Al) is used for the valve action metal, but an element in which tantalum (Ta), niobium (Nb), titanium (Ti), etc. are formed in a sheet shape, or these metal powders as a sheet. The same effect can be obtained when using an element that has been compression-molded and sintered.
The conductive coating layer has a conductive filler made of silver (Ag), gold (Au), copper (Cu), carbon, etc., epoxy resin, acrylic resin, rubber resin so as to have a desired conductivity. A combination of a binder resin composed of, etc. can be used.
In addition, a conductive polymer such as polypyrrole or polyaniline may be used for the solid electrolyte serving as the cathode layer, and the same effect can be obtained with the manganese dioxide layer.

  The above embodiment is an example in which the anode parts P of the single plate capacitor elements are laminated so as to be alternately left and right with the cathode part N as the center, that is, each single plate capacitor element is laminated by shifting the phase by 180 degrees. However, when the number of stacked layers increases, the layers may be stacked by shifting the phase by 90 degrees, that is, the anode portions may be alternately stacked back and forth and right and left around the cathode portion.

  In the above embodiment, for the sake of production, an example in which the width of the entire single plate capacitor element including the anode portion is made uniform from the lower layer to the upper layer in a uniform state has been described, but the side end face of the anode portion is additionally coated. Since it is not formed, there is no need to provide a step on the side surface. Therefore, when processing or casting the valve action metal plate, it is possible to produce one in which only the width of the part where the cathode part is formed is changed in order, and the anode part and the cathode part may be formed thereon and laminated. However, naturally the same effect as the embodiment can be expected.

(Modification)
FIG. 7 is a cross-sectional view of a multi-terminal laminated body in which each single-plate capacitor element has two different widths, and these are alternately laminated. As in the case of FIG. In this example, layers 8 and 8 ′ are formed. The other code | symbol part shows the same part as FIG. Also in this case, since the step S is formed on the side end face of the laminated body, the additional covering layer can be formed effectively as in the case of the embodiment by appropriately discharging and spraying the conductive paste from the side.
In this case, it is a matter of course that the same effect can be obtained even if the lateral widths of the elements are made large, medium, and small and stacked in an appropriate order.

The perspective view which shows the general example of a multilayer type solid electrolytic capacitor. The perspective view which shows the structure of the laminated element of the conventional 3 terminal structure. The expanded sectional view of the Y-Y 'cross section of the laminated body of the said prior art example. The perspective view which shows the laminated element of this invention Example. FIG. 5 is a cross-sectional view taken along line Y-Y ′ of FIG. 4. FIG. 6 is a perspective view of a multilayer solid electrolytic capacitor embodiment including the multilayer element of FIGS. 4 and 5. Sectional drawing of the laminated element of the modified example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Valve action metal foil 2 Oxide film layer 3 Solid electrolyte layer 4 Carbon layer 5 Silver layer 6 Conductive adhesives 7 and 8 Additional coating layer 9 by electrically conductive paste Exterior resin P, P1, P2, P3, P4 Anode part C, C1, C2, C3, C4, cathode part K carbon layer M masking layer for insulation g gap between stacked cathodes

Claims (3)

  After forming an anode part on one side of the valve metal plate and an oxide film layer on the other side, a plurality of single plate capacitor elements having a cathode part comprising a solid electrolyte layer and a cathode lead layer, the anode part being a cathode In a multi-terminal multilayer capacitor that is laminated so that it is staggered left and right around the center, by making the horizontal width (w) of the stacked upper and lower single plate capacitor elements different from each other, a step is formed on the cathode side end face of the multilayer element A multilayer solid electrolytic capacitor formed and coated with a conductive paste on the cathode side end face portion.   The width (w) of a plurality of single-plate capacitor elements to be stacked is sequentially narrowed from the lower layer to the upper layer, and the cathode portion side end surface of the stacked element is formed in a step shape. Multilayer solid electrolytic capacitor.   3. The multilayer solid electrolytic capacitor according to claim 1, wherein the width of only the cathode portions of the laminated single plate capacitor elements is made different between the upper layer and the lower layer. 4.

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