Solid Electrolytic Capacitors

Abstract

This solid electrolytic capacitor 1 having a self-stop valve action comprises: a capacitor element 90 having a valve action metal substrate 10, which has a positive electrode terminal region and a negative electrode formation region, a dielectric layer 20 formed on the negative electrode formation region, a solid electrolyte layer 40 formed on the dielectric layer 20, and a conductive layer 50 formed on the solid electrolyte layer 40; a sealing material that seals the capacitor element 90 to form a sealed body 60; and a vent structure 110 embedded in the sealing material so that a portion thereof is exposed from the outer surface of the sealed body 60, wherein the vent structure 110 becomes a melted body at a reflow mounting temperature and receives the pressure of vaporized components generated inside the sealed body 60, whereby a portion of the melted body is cut off so that holes 150 communicating from the inside through the outer surface of the sealed body 60 are formed and the vaporized components are discharged, and the melted body, when cooled from the reflow mounting temperature, flows and then solidifies so that the holes 150 are blocked.

Description

[Technical field]

[0001] The present invention relates to a solid electrolytic capacitor. [Background technology]

[0002] A solid electrolytic capacitor is known which includes a solid electrolytic capacitor element and a resin sealing material that seals the solid electrolytic capacitor element, with a cathode terminal and an anode terminal extending from the solid electrolytic capacitor element to the outside of the sealing material, and each terminal functioning as an external electrode. Moisture inevitably penetrates into solid electrolytic capacitor elements, and the moisture vaporizes during reflow mounting, causing an internal pressure rise. This internal pressure rise can cause electrical failures and cracks. In addition, when the vaporized moisture inside the capacitor suddenly escapes, it can cause the tombstone phenomenon and positional misalignment.

[0003] To address this phenomenon, the following measures are being considered: In Patent Document 1, grooves are dug in the anode and cathode terminals to increase the path for water to move from the external environment at the bonding surface between the terminals and the exterior body to the element, thereby attempting to suppress the intrusion of water. In Patent Documents 2 and 3, fine holes are provided in the exterior body from the end faces to the vicinity of the element and the anode and cathode terminals, thereby reducing the internal pressure by allowing the vaporized water to escape during reflow mounting, and by controlling the outflow direction of the vaporized water to reduce defects such as the tombstone phenomenon. In Patent Document 4, an attempt is made to suppress an increase in internal pressure by providing and arranging a material with high water vapor permeability in an exterior body so as to serve as an air vent from the inside to the outside. In Patent Document 5, a material with a lower melting point than the temperature during reflow mounting is placed in the part of the anode / cathode terminal that is bonded to the exterior member, and the material is melted during reflow mounting, allowing vaporized moisture to be released from the melted part, thereby reducing the increase in internal pressure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 061535 [Patent Document 2] Patent No. 3413591 [Patent Document 3] JP 2018-142668 A [Patent Document 4] JP 2001-057321 A [Patent Document 5] JP 2008-270253 A Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 attempts to lengthen the path through which water moves to prevent moisture from entering, but because water enters from the entire surface of the exterior body, it is not possible to sufficiently prevent moisture from entering. In addition, lengthening the path through which water moves also lengthens the path through which water is released, which is expected to promote an increase in internal pressure during reflow mounting. In Patent Documents 2, 3, and 4, the vaporized moisture is released by providing pores, a material with high water vapor permeability, and a material that melts during reflow mounting, and the internal pressure during reflow mounting is attempted to be reduced. However, if the exterior body has holes or a material with high water vapor permeability at the stage when the electronic component functions on the circuit after mounting, those parts become paths that facilitate the intrusion of moisture and oxygen into the interior. If moisture or oxygen intrudes into the exterior body at the stage when the component functions on the circuit, the element will deteriorate, leading to a shortened lifespan as a capacitor. In Patent Document 5, a material that melts during reflow mounting is provided, but since the material is placed over the entire path from the inside to the outside, holes that serve as release ports do not appear until the internal pressure has begun to increase.

[0006] As described above, none of the techniques disclosed in the prior art has been able to adequately solve the problems caused by the evaporation of moisture present in the solid electrolytic capacitor element during reflow mounting. The present invention has been made to solve the above problems, and has an object to provide a solid electrolytic capacitor in which defects caused by evaporation of moisture present in the solid electrolytic capacitor element during reflow mounting are prevented. [Means for solving the problem]

[0007] A solid electrolytic capacitor according to a first aspect of the present invention comprises a valve action metal base having an anode terminal region and a cathode formation region, a capacitor element having a dielectric layer formed on the cathode formation region, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer, a sealing material that seals the capacitor element to form a sealing body, and a vent structure embedded in the sealing material so that a part of the vent structure is exposed from an outer surface of the sealing body, the vent structure becoming a molten body at a reflow mounting temperature, and by receiving pressure from a vaporized component generated inside the sealing body and causing a part of the molten body to break, the vaporized component is released by generating a hole communicating from the inside of the sealing body to the outer surface, and when cooled from the temperature, the molten body flows so as to close the hole and then solidifies, thereby having a self-stopping valve action.

[0008] A solid electrolytic capacitor according to a second aspect of the present invention comprises: a valve action metal base having an anode terminal region and a cathode formation region; a capacitor element having a dielectric layer formed on the cathode formation region, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer; a sealing material that seals the capacitor element to form a sealing body; and a vent structure embedded in the sealing material so that a part of it is exposed from an outer surface of the sealing body, the vent structure being made of a material whose melting point is 240° C. or less and having a thin-walled portion that is partially shorter in dimension in a direction from the inside of the sealing body toward the outer surface when viewed from above. Effect of the Invention

[0009] According to the present invention, it is possible to provide a solid electrolytic capacitor in which defects caused by evaporation of moisture present in the solid electrolytic capacitor element during reflow mounting are prevented. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view illustrating an example of a solid electrolytic capacitor according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 1 taken along line AA. [Diagram 3] FIG. 3 is a top view that typically illustrates the surface of the vent structure of the solid electrolytic capacitor illustrated in FIG. 2, as viewed from above along line BB. [Figure 4] 4A, 4B, 4C, and 4D are top views that diagrammatically show the self-stopping valve action of the vent structure. [Diagram 5] 5A, 5B, 5C, 5D, 5E, and 5F are top views each showing a schematic example of a shape of the vent structure. [Figure 6] 6A, 6B, and 6C are top views each showing a schematic example of another example of the shape of the vent structure. [Figure 7] FIG. 7 is a perspective view illustrating an example of the solid electrolytic capacitor according to the second embodiment. [Figure 8] FIG. 8 is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 7 taken along line CC. [Figure 9] FIG. 9 is a top view that typically illustrates the surface of the vent structure of the solid electrolytic capacitor illustrated in FIG. 8, as viewed from above along line DD. [Figure 10] FIG. 10 is a cross-sectional view illustrating a schematic diagram of another example of the solid electrolytic capacitor according to the second embodiment. [Figure 11] FIG. 11 is a top view that typically illustrates the surface of the vent structure of the solid electrolytic capacitor illustrated in FIG. 10, as viewed from above along the line EE. [Figure 12] FIG. 12 is a cross-sectional view illustrating a schematic diagram of another example of the solid electrolytic capacitor according to the second embodiment. [Figure 13] FIG. 13 is a cross-sectional side view that typically illustrates the surface of the vent structure of the solid electrolytic capacitor illustrated in FIG. 12, as viewed from the side along line FF. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The solid electrolytic capacitor of the present invention will now be described. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that the present invention also includes a combination of two or more of the individual preferable configurations of the present invention described below.

[0012] A solid electrolytic capacitor according to a first aspect of the present invention comprises a valve action metal base having an anode terminal region and a cathode formation region, a capacitor element having a dielectric layer formed on the cathode formation region, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer, a sealing material that seals the capacitor element to form a sealing body, and a vent structure embedded in the sealing material so that a part of the vent structure is exposed from an outer surface of the sealing body, the vent structure becoming a molten body at a reflow mounting temperature, and by receiving pressure from a vaporized component generated inside the sealing body and causing a part of the molten body to break, the vaporized component is released by generating a hole communicating from the inside of the sealing body to the outer surface, and when cooled from the temperature, the molten body flows so as to close the hole and then solidifies, thereby having a self-stopping valve action. Furthermore, a solid electrolytic capacitor according to a second aspect of the present invention comprises: a valve action metal base having an anode terminal region and a cathode formation region; a capacitor element having a dielectric layer formed on the cathode formation region, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer; a sealing material that seals the capacitor element to form a sealing body; and a vent structure embedded in the sealing material so that a part of it is exposed from an outer surface of the sealing body, wherein the vent structure is made of a material whose melting point is 240° C. or less and has a thin-walled portion that is partially shorter in dimension in a direction from the inside of the sealing body toward the outer surface when viewed from above. The solid electrolytic capacitor according to the first aspect of the present invention and the solid electrolytic capacitor according to the second aspect of the present invention will be described below together. In the following description, when there is no need to distinguish between the solid electrolytic capacitor according to the first aspect of the present invention and the solid electrolytic capacitor according to the second aspect of the present invention, they will simply be referred to as the solid electrolytic capacitor of the present invention.

[0013] [First embodiment] The solid electrolytic capacitor of the first embodiment includes a lead frame connected to the anode terminal area or the cathode formation area. The lead frame is extended outside the encapsulant. The vent structure is provided on the surface of the lead frame.

[0014] FIG. 1 is a perspective view illustrating an example of a solid electrolytic capacitor according to a first embodiment. The solid electrolytic capacitor 1 shown in FIG. 1 has a sealing body 60 formed by sealing a plurality of solid electrolytic capacitor elements 90 with a sealing material, and includes a lead frame 70 connected to the anode terminal region and a lead frame 80 connected to the cathode formation region. A vent structure 110 is provided on the surface of the lead frame 70, and a vent structure 111 is provided on the surface of the lead frame 80, and the vent structures 110 and 111 are exposed on the surface of the sealing material. The vent structures 110 and 111 are embedded in the sealing material such that a portion of each of them is exposed from the outer surface of the sealing body 60.

[0015] FIG. 1 shows the longitudinal direction (L direction), width direction (W direction), and thickness direction (T direction) of the solid electrolytic capacitor. The longitudinal direction (L direction) of the solid electrolytic capacitor is also the longitudinal direction of the lead frame.

[0016] FIG. 2 is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 1 taken along line AA. The solid electrolytic capacitor 1 shown in FIG. 2 includes a plurality of solid electrolytic capacitor elements 90 (hereinafter also simply referred to as capacitor elements 90), a lead frame 70 connected to the anode terminal region, a lead frame 80 connected to the cathode formation region, and a sealing body 60 formed from a sealing material.

[0017] The sealing body 60 (sealing material) seals the capacitor element 90 . Sealing body 60 is formed so as to cover the entire capacitor element 90, a part of lead frame 70, and a part of lead frame 80. Sealing body 60 (sealing material) may be made of a material such as epoxy resin, for example.

[0018] Capacitor element 90 comprises a valve metal substrate 10 having an anode terminal region (region indicated by double arrow a in FIG. 2) and a cathode formation region (region indicated by double arrow b in FIG. 2), a dielectric layer 20 formed on the anode terminal region a and the cathode formation region b, a solid electrolyte layer 40 formed on dielectric layer 20, and a conductive layer 50 formed on solid electrolyte layer 40. On the anode terminal region a, a masking region made of a masking member 30 is formed to separate the anode terminal region a from the cathode forming region b and to insulate the valve metal base 10 from the counter electrode. The masking region may not be formed on the capacitor element.

[0019] The valve metal substrate is made of a valve metal that exhibits a so-called valve action. Examples of the valve metal include simple metals such as aluminum, tantalum, niobium, titanium, and zirconium, and alloys containing these metals. Among these, aluminum or an aluminum alloy is preferred.

[0020] The shape of the valve metal substrate is preferably a flat plate, more preferably a foil. In addition, a porous layer such as an etching layer is preferably provided on the surface of the valve metal substrate. By providing the porous layer on the valve metal substrate, the surface area of ​​the valve metal substrate serving as the anode increases, thereby increasing the capacitance of the capacitor.

[0021] The dielectric layer is formed on the cathode forming region of the valve metal substrate, and is preferably made of an oxide film of the valve metal. For example, when an aluminum foil is used as the valve metal substrate, the oxide film can be formed by oxidizing the aluminum foil in an aqueous solution containing boric acid, phosphoric acid, adipic acid, or their sodium salts, ammonium salts, or the like. The dielectric layer may be formed on the anode terminal region of the valve metal substrate, or may not be formed on the anode terminal region.

[0022] A solid electrolyte layer is formed on the dielectric layer on the cathode forming region. When the valve metal substrate has a porous layer, the solid electrolyte layer is preferably composed of an inner layer impregnated in the porous layer of the valve metal and an outer layer covering the inner layer. The inner layer and the outer layer may have the same composition or different compositions.

[0023] Examples of materials constituting the solid electrolyte layer include conductive polymers having a skeleton of pyrroles, thiophenes, anilines, etc. Examples of conductive polymers having a skeleton of thiophenes include PEDOT [poly(3,4-ethylenedioxythiophene)], which may be PEDOT:PSS complexed with polystyrene sulfonic acid (PSS) as a dopant.

[0024] The conductive layer is formed on the solid electrolyte layer. The conductive layer is preferably a carbon layer, a graphene layer, or a silver layer formed by applying a conductive paste such as a carbon paste, a graphene paste, or a silver paste. The conductive layer may also be a composite layer in which a silver layer is provided on a carbon layer or a graphene layer, or a mixed layer in which a carbon paste or a graphene paste is mixed with a silver paste. Specifically, it is preferable that the silver layer is formed on a carbon layer as a base, but it may be formed of only a carbon layer or only a silver layer.

[0025] Examples of materials for the masking member include insulating resins such as polyphenylsulfone resin, polyethersulfone resin, cyanate ester resin, fluororesin (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, etc.), polyimide resin, polyamideimide resin, and derivatives or precursors thereof.

[0026] On the anode terminal area side, the valve metal substrates 10 of the capacitor elements 90 are held together by a lead frame 70 and are extended outside the sealing material (sealant 60). A vent structure 110 is provided on the surface of the lead frame 70 on the anode side, and a part of the vent structure 110 is exposed from the outer surface of the encapsulant 60 .

[0027] On the cathode formation region side, the conductive layers 50 of the capacitor elements 90 are electrically connected, and further electrically connected to the lead frame 80, and are led out of the sealing material (sealant 60). A vent structure 111 is provided on the surface of the lead frame 80 on the cathode side, and a part of the vent structure 111 is exposed from the outer surface of the sealing body 60 . Below, the configuration and action of a vent structure that is provided on the surface of a lead frame and embedded in the sealing material so that a portion of it is exposed from the outer surface of the sealing body will be described using a vent structure provided on the surface of the lead frame on the anode side as an example.

[0028] The vent structure of the solid electrolytic capacitor according to the first aspect of the present invention becomes a molten body at the reflow mounting temperature, and a part of the molten body is cut off by the pressure of the vaporized components generated inside the sealing body, generating a hole connecting the inside of the sealing body to the outer surface to release the vaporized components, and when cooled from the reflow mounting temperature, the molten body flows so as to close the hole and then solidifies, thus acting as a self-sealing valve. In this way, the vent structure may have a self-sealing valve action in which the molten body melts at the reflow mounting temperature, generates a hole connecting the inside to the outside by the pressure of the vaporized moisture, and closes the hole after the vaporized moisture is released. The vent structure of the solid electrolytic capacitor according to the second aspect of the present invention is made of a material having a melting point of 240° C. or less, and has a thin-walled portion that is partially shorter in dimension from the inside of the sealing body to the outer surface when viewed from above. In this way, the vent structure may be made of a material having a melting point of 240° C. or less, and have a thin-walled portion that is partially shorter in dimension from the inside of the solid electrolytic capacitor to the outside when viewed from above. A vent structure having both the characteristic features of the vent structure for a solid electrolytic capacitor according to the first aspect and the characteristic features of the vent structure for a solid electrolytic capacitor according to the second aspect will be described below.

[0029] FIG. 3 is a top view that typically illustrates the surface of the vent structure of the solid electrolytic capacitor illustrated in FIG. 2, as viewed from above along line BB. The vent structure 110 is provided on the surface of the lead frame 70. A part of the vent structure 110 is exposed from the outer surface 60a of the encapsulant 60. The vent structure 110 has a thin-walled portion 130 in a top view. The thin-walled portion 130 is a portion that is partially shorter in dimension in a direction from the inside of the sealing body 60 toward the outer surface thereof in a top view. In the vent structure 110 shown in FIG. 3, the direction from the inside of the sealing body 60 toward the outer surface is defined as the longitudinal direction (L direction) of the solid electrolytic capacitor in a top view. Then, by comparing the dimension of the part of the vent structure that has the shorter dimension in the L direction (the dimension indicated by the double-headed arrow L1 in FIG. 3) with the dimension of the other part of the vent structure that has the longest dimension in the L direction (the dimension indicated by the double-headed arrow L2 in FIG. 3), the part of the vent structure that has the shorter dimension in the L direction is determined to be the thin-walled part.

[0030] The vent structure is made of a material whose melting point is equal to or lower than 240° C. A material whose melting point is equal to or lower than 240° C. melts at the reflow mounting temperature (for example, equal to or higher than 240° C. and equal to or lower than 260° C.). The melting point of the material having the vent structure can be measured by DSC (differential scanning calorimetry).

[0031] The vent structure becomes a molten material at the reflow mounting temperature, and when pressure from the vaporized components generated inside the sealing body is applied, part of the molten material is cut off, creating a hole that connects the inside of the sealing body to the outer surface, thereby releasing the vaporized components.When cooled from the reflow mounting temperature, the molten material flows to close the hole and then solidifies, providing a self-stop valve action. This action will be explained with reference to the drawings. 4A, 4B, 4C, and 4D are top views that diagrammatically show the self-stopping valve action of the vent structure. FIG. 4A shows the vent structure 110 before reflow mounting. 4B shows the vent structure 110 during reflow mounting. When the solid electrolytic capacitor is heated during reflow mounting, the material constituting the vent structure melts and becomes a molten mass. At the same time, the internal pressure in the solid electrolytic capacitor, i.e., the pressure of the vaporized components generated inside the sealing body, increases. Due to the pressure of the vaporized components, a part of the molten mass, specifically, the thin-walled portion 130 of the vent structure, breaks, forming a hole 150 that communicates from the inside of the sealing body to the outer surface, and vaporized moisture G is released from the hole 150. 4C and 4D show the vent structure 110 after the evaporated moisture G has been released. FIG. 4C shows a state where the release of evaporated water G from holes 150 has been completed. After the vaporized moisture G is released from the hole 150, when the solid electrolytic capacitor is cooled from the reflow mounting temperature, the vent structure 110 is still a molten body and exists in a molten state around the hole 150. As shown in Fig. 4D, the molten body flows and spreads due to surface tension, and can block the hole 150. After the hole 150 is blocked, the molten body is cooled to a temperature below its melting point and solidifies.

[0032] In this way, the vent structure becomes a molten material at the reflow mounting temperature, and when pressure from the vaporized components generated inside the sealing body is applied, part of the molten material is cut off, creating a hole that connects the inside of the sealing body to the outer surface, thereby releasing the vaporized components, and when cooled from the reflow mounting temperature, the molten material flows to close the hole and then solidifies, thereby acting as a self-stop valve. The thin-walled portion is a portion that is intentionally provided so that a hole that communicates from the inside of the sealing body to the outer surface is formed by cutting off a part of the molten material under the pressure of the vaporized components generated inside the sealing body. During reflow mounting, it is possible to prevent an increase in internal pressure due to vaporized moisture. Furthermore, since the holes in the vent structure are blocked after the vaporized moisture is released, it is possible to prevent a path for moisture or oxygen to enter through the holes after reflow mounting. From the above, it is possible to provide a solid electrolytic capacitor in which defects caused by evaporation of moisture present in the solid electrolytic capacitor element during reflow mounting are prevented.

[0033] The material constituting the vent structure may be a thermoplastic resin having a melting point of 150°C or more and 240°C or less, or a mixture containing a thermoplastic resin having a melting point of 150°C or more and 240°C or less. As the thermoplastic resin having a melting point of 150° C. or more and 240° C. or less, at least one resin selected from the group consisting of polyamide, polypropylene, polyvinylidene fluoride, and polysulfone can be suitably used. Also, metals and alloys having melting points of 180° C. or higher and 240° C. or lower can be used. As the metal or alloy having a melting point of 180° C. or more and 240° C. or less, tin, tin-based alloys, etc. can be suitably used.

[0034] In the direction from the inside of the sealing body to the outer surface (from the inside to the outside of the solid electrolytic capacitor), the dimension of the thin portion is preferably ½ or less of the dimension of the longest portion of the vent structure. If the dimensions of the thin-walled portion are set in this way, the pressure of vaporized water is likely to cause holes that connect the inside of the sealing body to the outer surface, and the holes in the vent structure are likely to become clogged after the vaporized water is released. If the dimension of the thin-walled portion is more than half the dimension of the longest part of the vent structure, the dimension of the thin-walled portion is not so short that it may be difficult for the pressure of evaporated moisture to create a hole connecting the inside of the sealing body to the outer surface. In addition, it is preferable that the dimension of the thin-walled portion in the direction from the inside of the encapsulant to the outer surface (from the inside to the outside of the solid electrolytic capacitor) is 1 / 20 or more of the dimension of the longest part of the vent structure. If the dimension of the thin-walled portion is too short, holes may appear in the thin-walled portion before reflow mounting, which may become a path for moisture and oxygen to enter.

[0035] The dimension of the thin portion in the direction from the inside of the sealing body to the outer surface (from the inside to the outside of the solid electrolytic capacitor) is preferably 0.8 mm or less, and more preferably 0.02 mm or more. If the dimension of the thin portion is 0.02 mm or more and 0.8 mm or less, the pressure of vaporized water is likely to cause holes that connect the inside of the sealed body to the outer surface, and the holes in the vent structure are likely to become clogged after the vaporized water is released.

[0036] The thickness of the vent structure is preferably 10 μm or more and 1 mm or less. If the thickness of the vent structure is set in this way, holes that communicate from the inside of the sealed body to the outer surface are likely to be generated by the pressure of vaporized moisture. In addition, the holes of the vent structure are likely to be blocked after the vaporized moisture is released.

[0037] It is preferable that the width dimension of the vent structure 110 (the dimension indicated by the double-headed arrow W1 in FIG. 3) is shorter than the width dimension of the lead frame 70 (the dimension perpendicular to the longitudinal direction of the lead frame, and indicated by the double-headed arrow W2 in FIG. 3). Moreover, the dimension in the width direction of the vent structure 110 is preferably the same as the dimension in the width direction of the valve metal substrate 10 (the dimension indicated by the double-headed arrow W3 in FIG. 3). Furthermore, the width of the lead frame 70 may be longer or shorter than the width of the valve metal base 10 .

[0038] A portion of the vent structure 110 is exposed from the outer surface of the sealing body 60, but as shown in Fig. 3, an end 110a of the vent structure 110 may protrude slightly outward from the outer surface 60a of the sealing body 60. Protruding the end of the vent structure outward from the outer surface of the sealing body can prevent the sealing material from blocking the surface of the vent structure when sealing is performed with the sealing material.

[0039] Although FIG. 2 shows an example in which the vent structure is provided on only one surface of the lead frame, the vent structure may be provided on both surfaces of the lead frame.

[0040] The vent structure provided on the surface of the lead frame on the cathode side may have the same configuration as the vent structure provided on the surface of the lead frame on the anode side. The vent structure provided on the surface of the lead frame on the cathode side has the same effect as the vent structure provided on the surface of the lead frame on the anode side. The vent structure may be provided on both the surface of the lead frame on the anode side and the surface of the lead frame on the cathode side, or on only one of them.

[0041] The shape of the vent structure when viewed from above can be, for example, a rectangle cut into a triangle with one side of the rectangle as its base, as shown in FIG. 3, but other shapes are also possible.

[0042] 5A, 5B, 5C, 5D, 5E, and 5F are top views each showing a schematic example of a shape of the vent structure. In these examples, a thin-walled portion having a short dimension in the direction from the inside of the sealing body toward the outer surface is located near the center of the width of the vent structure, and a long portion is located on both sides of the thin-walled portion (above and below the thin-walled portion in the drawings).

[0043] The vent structure 112 shown in FIG. 5A has a rectangular shape cut out with a semicircle having a diameter equal to a portion of one side of the rectangle, and has a thin-walled portion 132. 5B shows a vent structure 113 having two triangular shapes formed by cutting out a rectangle with one side of the rectangle as the base. This vent structure 113 has two thin portions 133a and 133b. In other words, this is an example of a vent structure having multiple thin portions. The vent structure 114 shown in FIG. 5C has a shape obtained by cutting out a part of an ellipse with one side of the rectangle being the minor axis, and has a thin portion . The vent structure 115 shown in FIG. 5D has a shape in which a rectangle is cut out into a triangle with one side of the rectangle as its base, as shown in FIG. 3, and the apex of the triangle, which is the end of the thin-walled portion, is replaced with part of an ellipse, and has a thin-walled portion 135. The vent structure 116 shown in FIG. 5E has a shape in which part of a rectangle is cut out in an L-shape (the shape shown in FIG. 5E is an L-shape reversed from side to side), and has a thin-walled portion 136. The vent structure 117 shown in FIG. 5F has a shape in which a part of a rectangle is cut out with a part of an ellipse that is oblique to a side of the rectangle, and has a thin portion 137.

[0044] 6A, 6B, and 6C are top views each showing a schematic example of another example of the shape of the vent structure. The vent structure 118 shown in FIG. 6A is trapezoidal in shape, with the shorter sides being thin-walled portions 138. As shown in FIG. The vent structure 119 shown in FIG. 6B is triangular in shape, with a thin-walled portion 139 near one of its vertices. The vent structure 120 shown in FIG. 6C is L-shaped, with one side (the long side in FIG. 6C) of the L shape being a thin portion 140 that extends in the width direction of the solid electrolytic capacitor.

[0045] Each of the vent structures shown in the above drawings has a thin wall portion. Therefore, at the reflow mounting temperature, it becomes molten, and when pressure from the vaporized components generated inside the sealing body is applied, part of the molten body is cut off, creating a hole that connects the inside of the sealing body to the outer surface, thereby releasing the vaporized components.When cooled from the reflow mounting temperature, the molten body flows so as to close the hole and then solidifies, thus acting as a self-stop valve.

[0046] In the process of manufacturing a solid electrolytic capacitor, the method of providing a vent structure on the surface of a lead frame is not particularly limited. For example, the vent structure can be provided by screen printing, dispenser coating, plating, or the like on the surface of the lead frame to form a layer of material that will be the vent structure in a predetermined pattern having thin portions. Alternatively, a vent structure can be formed on the surface of a lead frame by producing a resin film or the like shaped to form a vent structure by molding (cutting) it into a predetermined pattern having a thin-walled portion and attaching this to the surface of the lead frame.

[0047] Also, after the lead frame is welded to the capacitor element, a vent structure may be provided on the surface of the lead frame, or a vent structure may be provided on the surface of the lead frame and then the lead frame may be welded to the capacitor element.

[0048] It is preferable to provide the vent structure on the surface of the lead frame because the bond between the vent structure and the lead frame can be strengthened. Since the lead frame has a stronger structure than the material constituting the surface of the capacitor element, the vent structure and the lead frame can be strongly bonded to each other. Furthermore, providing a vent structure on the lead frame makes it easier to add a process for providing the vent structure compared to providing the vent structure in another location, so it is preferable to provide the vent structure on the surface of the lead frame.

[0049] [Second embodiment] The solid electrolytic capacitor of the second embodiment includes an anode external electrode connected to the anode terminal region, and a cathode external electrode electrically connected to the conductive layer in the cathode formation region. The vent structure is provided in a portion where neither the anode external electrode nor the cathode external electrode is provided.

[0050] FIG. 7 is a perspective view illustrating an example of the solid electrolytic capacitor according to the second embodiment. FIG. 7 shows resin molded body 209 which constitutes solid electrolytic capacitor 2. The shape of the resin molded body is not particularly limited, and any three-dimensional shape can be adopted. The shape of the resin molded body is preferably a rectangular parallelepiped. In addition, the rectangular parallelepiped does not necessarily mean a perfect rectangular parallelepiped, and the surface forming the resin molded body may be tapered and not perpendicular to other surfaces, and the corners may be chamfered.

[0051] FIG. 7 shows a rectangular parallelepiped resin molded body 209, which has a length direction (L direction), a width direction (W direction), and a thickness direction (T direction). The resin molded body 209 has, as its outer surfaces, a first end face 209a and a second end face 209b facing each other in the longitudinal direction. An anode external electrode 221 is formed on the first end face 209a, and a cathode external electrode 223 is formed on the second end face 209b. The resin molded body 209 has, as its outer surfaces, a bottom surface 209c and a top surface 209d which face each other in the thickness direction. Moreover, the resin molded body 209 has, as its outer surfaces, a first side surface 209e and a second side surface 209f that face each other in the width direction. The vent structure 210 is exposed on a first side surface 209 e , which is the outer surface of the sealing body 208 , in the vicinity of the anode external electrode 221 . Although not shown in FIG. 7, the vent structure 210 is also exposed on the second side surface 209f, which is the outer surface of the sealant 208, in the vicinity of the anode external electrode 221.

[0052] FIG. 8 is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 7 taken along line CC. The capacitor element 220 includes an anode 203 having a dielectric layer 205 on a surface thereof, and a cathode 207 facing the anode 203 . A plurality of capacitor elements 220 are laminated to form laminate 260 , and the periphery of laminate 260 is sealed with a sealing material to form sealing body 208 , thereby forming resin molded body 209 . In the laminate 260, the laminated capacitor elements 220 may be bonded to each other via a conductive adhesive (not shown). The number of capacitor elements 220 included in the laminate 260 may be one.

[0053] An anode external electrode 221 is formed on a first end surface 209a of the resin molded body 209, and the anode external electrode 221 is electrically connected to the anode 203 exposed from the first end surface 209a. A cathode external electrode 223 is formed on a second end surface 209b of the resin molded body 209, and the cathode external electrode 223 is electrically connected to the cathode 207 exposed from the second end surface 209b. Valve metal substrate 204 constituting capacitor element 220 has an anode terminal region (region indicated by double arrow a in FIG. 8) and a cathode forming region (region indicated by double arrow b in FIG. 8). Dielectric layer 205 is formed on anode terminal region a and cathode forming region b.

[0054] At the end of the valve metal substrate 204 on the second end face 209b side, the valve metal substrate 204 is not in direct contact with the solid electrolyte layer 207a or the conductive layer 207b. On the other hand, when the end of the valve metal substrate 204 on the second end face 209b side is insulated by being covered with the dielectric layer 205, for example, the end of the valve metal substrate 204 on the second end face 209b side may be covered with the solid electrolyte layer 207a and the conductive layer 207b.

[0055] Cathode 207 constituting capacitor element 220 is formed by laminating a solid electrolyte layer 207a formed on dielectric layer 205, a conductive layer 207b formed on solid electrolyte layer 207a, and a conductive layer 207c formed on conductive layer 207b.

[0056] Furthermore, conductive layer 207c of each capacitor element 220 is gathered into cathode lead portion 207d in the vicinity of second end face 209b and exposed at second end face 209b. The conductive layer 207b, the conductive layer 207c and the cathode lead portion 207d can be formed of a conductive paste such as a carbon paste, a graphene paste, an Ag paste, a copper paste, or a Ni paste. Furthermore, the conductive pastes constituting the conductive layer 207b, the conductive layer 207c, and the cathode lead portion 207d may each have a different composition.

[0057] The preferred configurations of the valve metal substrate, dielectric layer, solid electrolyte layer, conductive layer, and sealing material may be similar to those of the solid electrolytic capacitor of the first embodiment.

[0058] The vent structure of the solid electrolytic capacitor according to the second embodiment will be described below. FIG. 9 is a top view that typically illustrates the surface of the vent structure of the solid electrolytic capacitor illustrated in FIG. 8, as viewed from above along line DD. A vent structure 210e and a vent structure 210f are provided on the dielectric layer 205. The vent structure 210e is provided so as to be exposed from the encapsulant 208 at a first side 209e, and the vent structure 210f is provided so as to be exposed from the encapsulant 208 at a second side 209f.

[0059] The vent structure 210e has a thin portion 230e in a top view, and the vent structure 210f has a thin portion 230f in a top view. This vent structure, like the vent structure described in the first embodiment, becomes molten at the reflow mounting temperature, and part of the molten material is cut off by the pressure of the vaporized components generated inside the sealing body, creating a hole that connects the inside of the sealing body to the outer surface, thereby releasing the vaporized components, and when cooled from the reflow mounting temperature, the molten material flows to close the hole and then solidifies, providing a self-stop valve action. In the vent structure 210 shown in FIG. 9, the direction from the inside of the sealant 208 toward the outer surface is the width direction (W direction) of the solid electrolytic capacitor in the top view.

[0060] In the solid electrolytic capacitors shown in Figures 7, 8, and 9, the capacitor elements constituting the laminate have a vent structure on the surface of the uppermost capacitor element and the surface of the lowermost capacitor element. By providing the vent structure at this position, it is possible to sufficiently suppress an increase in internal pressure caused by the pressure of evaporated moisture, but the position of the vent structure is not limited to this position. All of the capacitor elements constituting the laminate may be provided with a vent structure, or only one of the capacitor elements may be provided with a vent structure. Also, while FIG. 9 shows an example in which two vent structures are provided for one capacitor element, the number of vent structures for one capacitor element may be one.

[0061] Fig. 10 is a cross-sectional view showing a schematic diagram of another example of the solid electrolytic capacitor according to the second embodiment. The solid electrolytic capacitor 3 shown in Fig. 10 has a masking member 250 in the anode terminal region. A vent structure 211 is provided on the masking member 250.

[0062] FIG. 11 is a top view that typically illustrates the surface of the vent structure of the solid electrolytic capacitor illustrated in FIG. 10, as viewed from above along the line EE. A vent structure 211e and a vent structure 211f are provided on the masking member 250. The vent structure 211e is provided so as to be exposed from the encapsulant 208 at a first side surface 209e, and the vent structure 211f is provided so as to be exposed from the encapsulant 208 at a second side surface 209f.

[0063] The vent structure 211e has a thin portion 231e in a top view, and the vent structure 211f has a thin portion 231f in a top view. This vent structure, like the vent structure described in the first embodiment, becomes molten at the reflow mounting temperature, and part of the molten material is cut off by the pressure of the vaporized components generated inside the sealing body, creating a hole that connects the inside of the sealing body to the outer surface, thereby releasing the vaporized components, and when cooled from the reflow mounting temperature, the molten material flows to close the hole and then solidifies, providing a self-stop valve action. In FIG. 10, the masking member 250 is depicted as being provided on the surface of the valve metal substrate 10, but the masking member 250 may be provided on the dielectric layer 205.

[0064] Fig. 12 is a cross-sectional view showing a schematic diagram of another example of the solid electrolytic capacitor according to the second embodiment. The solid electrolytic capacitor 4 shown in Fig. 12 has a vent structure 212 exposed from the cathode formation region to each of the bottom surface 209c and the top surface 209d of the resin molded body 209.

[0065] FIG. 13 is a cross-sectional side view that typically illustrates the surface of the vent structure of the solid electrolytic capacitor illustrated in FIG. 12, as viewed from the side along line FF. The vent structure 212c is provided so as to be exposed from the encapsulant 208 at the bottom surface 209c, and the vent structure 212d is provided so as to be exposed from the encapsulant 208 at the top surface 209d.

[0066] Vent structure 212c has a thinned portion 232c, and vent structure 212d has a thinned portion 232d. In the vent structure 212 shown in FIG. 13, the direction from the inside of the sealing body 208 toward the outer surface is the thickness direction (T direction) of the solid electrolytic capacitor. In the explanation so far, the thin-walled portion of the vent structure has been defined based on "the dimension in the direction from the inside of the sealing body to the outer surface when viewed from above." However, when the direction from the inside of the sealing body to the outer surface is the thickness direction of the solid electrolytic capacitor as shown in FIG. 13, the dimension based on the dimension when viewed from the side instead of the top shall be interpreted as the dimension when viewed from the top. This vent structure, like the vent structure described in the first embodiment, becomes molten at the reflow mounting temperature, and part of the molten material is cut off by the pressure of the vaporized components generated inside the sealing body, creating a hole that connects the inside of the sealing body to the outer surface, thereby releasing the vaporized components, and when cooled from the reflow mounting temperature, the molten material flows to close the hole and then solidifies, providing a self-stop valve action. [Explanation of symbols]

[0067] 1, 2, 3, 4 Solid electrolytic capacitor 10, 204 Valve metal substrate 20, 205 Dielectric layer 30, 250 Masking material 40, 207a solid electrolyte layer 50, 207b, 207c conductive layer 60, 208 Sealing body 60a Outer surface of encapsulant 70 Lead frame (anode side) 80 Lead frame (cathode side) 90, 220 Solid electrolytic capacitor element (capacitor element) 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 210, 210e, 210f, 211, 211e, 211f, 212, 212c, 212d Vent structure 110a End of vent structure 130, 132, 133a, 133b, 134, 135, 136, 137, 138, 139, 140, 230e, 230f, 231e, 231f, 232c, 232d Thin section 150 holes 203 Anode 207 Cathode 207d Cathode lead-out section 209 Resin Molding 209a: First end surface of resin molded body (outer surface of resin molded body) 209b Second end surface of resin molded body (outer surface of resin molded body) 209c Bottom surface of resin molded body (outer surface of resin molded body) 209d Upper surface of resin molded body (outer surface of resin molded body) 209e First side surface of resin molded body (outer surface of resin molded body) 209f Second side of resin molded body (outer surface of resin molded body) 221 Anode external electrode 223 Cathode external electrode 260 Laminate

Claims

1. a capacitor element including a valve metal base having an anode terminal region and a cathode formation region, a dielectric layer formed on the cathode formation region, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer; a sealing material for sealing the capacitor element to form a sealing body; a vent structure embedded in the sealing material such that a portion of the vent structure is exposed from an outer surface of the sealing body; The vent structure becomes a molten material at a temperature for reflow mounting, and a part of the molten material is cut off by pressure of a vaporized component generated inside the sealing body, thereby generating a hole communicating from the inside of the sealing body to the outer surface, thereby releasing the vaporized component, and when cooled from the temperature, the molten material flows so as to close the hole and then solidifies, thus providing a self-stop valve action; The vent structure is provided between the sealing body and an anode lead portion that is led from the inside of the sealing body to an outer surface of the sealing body.

2. a capacitor element including a valve metal base having an anode terminal region and a cathode formation region, a dielectric layer formed on the cathode formation region, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer; a sealing material for sealing the capacitor element to form a sealing body; a vent structure embedded in the sealing material such that a portion of the vent structure is exposed from an outer surface of the sealing body; the vent structure is made of a material having a melting point of 240° C. or less, and has a thin-walled portion having a dimension that is partially short in a direction from the inside of the sealing body toward an outer surface thereof when viewed from above, The vent structure is provided between the sealing body and an anode lead portion that is led from the inside of the sealing body to an outer surface of the sealing body.

3. 3. The solid electrolytic capacitor according to claim 2, wherein the dimension of the thin portion in the direction from the inside of the sealing body toward the outer surface is equal to or less than half the dimension of the longest portion of the vent structure.

4. 4. The solid electrolytic capacitor according to claim 1, wherein the vent structure has a thickness of 10 μm or more and 1 mm or less.

5. a lead frame connected to the anode terminal region or the cathode formation region and extending to the outside of the sealing material; 5. The solid electrolytic capacitor according to claim 1, wherein the vent structure is provided on a surface of the lead frame.

6. an anode external electrode connected to the anode terminal region and a cathode external electrode electrically connected to a conductive layer in the cathode formation region are provided on an outer surface of the sealing body; 5. The solid electrolytic capacitor according to claim 1, wherein the vent structure is provided in a portion where neither the anode external electrode nor the cathode external electrode is provided.

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