Solid electrolytic capacitors
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD
- Filing Date
- 2021-11-25
- Publication Date
- 2026-07-31
Smart Images
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Abstract
Description
Technical Field
[0006] , at least one , 、 , , , and,
[0001] The present disclosure relates to a solid electrolytic capacitor.
Background Art
[0002] A solid electrolytic capacitor includes a capacitor element having a solid electrolyte layer, a lead terminal electrically connected to the capacitor element, and an exterior body that seals the capacitor element.
[0003] The exterior body suppresses oxygen and moisture in the atmosphere from reaching the capacitor element and deteriorating the capacitor element. However, if the adhesion at the interface between the lead terminal and the exterior body is low, oxygen and moisture easily penetrate from the interface, and the solid electrolytic capacitor deteriorates.
[0004] Patent Document 1 (Japanese Patent Laid-Open No. 4-253314) discloses "a solid electrolytic capacitor characterized in that an oxide film, a conductive substance layer, a conductive polymer film, and a conductor layer are sequentially formed on the surface of a valve metal to form a capacitor element, a lead frame serving as a lead terminal is connected to the valve metal portion and the conductor layer portion of the capacitor element, and a part of the capacitor element and the lead frame is encapsulated with a molding resin, and the lead frame has a copper metal layer on its surface and the surface is roughened."
Prior Art Documents
Patent Documents
[0005]
Patent Document 1
Summary of the Invention
[0006] A solid electrolytic capacitor according to one aspect of the present disclosure includes at least one capacitor element including an anode portion and a cathode portion, an anode lead terminal electrically connected to the anode portion 、 a cathode lead terminal electrically connected to the cathode portion and, the at least oneThe capacitor element includes an outer casing, and the anode lead terminal and the cathode lead terminal each include a recessed portion embedded in the outer casing and an exposed portion connected to the recessed portion and exposed from the outer casing, wherein the recessed portion of the anode lead terminal is in contact with the outer casing. 1 contact face The embedded portion of the cathode lead terminal is in contact with the outer casing. 2nd contact face Having, the above 1 contact face and the aforementioned 2nd contact face At least one of the selected contact surfaces has a rough surface with an interface development area ratio of 0.4 or more.
[0007] According to this disclosure, a solid electrolytic capacitor can be obtained that can particularly suppress degradation due to the intrusion of oxygen and other elements. [Brief explanation of the drawing]
[0008] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a solid electrolytic capacitor according to an embodiment of this disclosure. [Figure 2] Figure 2 is an example image showing the rough surface condition of capacitor C2. [Figure 3] Figure 3 is an example image showing the rough surface condition of capacitor A2. [Modes for carrying out the invention]
[0009] Before describing the embodiments, the problems of the prior art are briefly outlined below.
[0010] Currently, there is a need to further suppress degradation caused by the intrusion of oxygen and other elements. In this context, one of the objectives of this disclosure is to provide a novel solid electrolytic capacitor that can particularly suppress degradation caused by the intrusion of oxygen and other elements.
[0011] In view of the above issues, this disclosure provides an electrolytic capacitor and a paste for forming a conductive layer of an electrolytic capacitor, for providing a solid electrolytic capacitor that can particularly suppress degradation due to the intrusion of oxygen and the like.
[0012] Examples of embodiments of the present disclosure are described below. While examples of embodiments of the present disclosure are given in the following description, the present disclosure is not limited to the examples described below. Specific numerical values and materials may be given as examples in the following description, but other numerical values and materials may be applied as long as the effects of the present disclosure are achieved. In this specification, when "numerical value A to numerical value B" is used, the range includes numerical value A and numerical value B.
[0013] (Solid electrolytic capacitor) The solid electrolytic capacitor according to this embodiment includes at least one capacitor element including an anode portion and a cathode portion, and an anode lead terminal electrically connected to the anode portion. 、 Cathode lead terminals electrically connected to the cathode portion and, The aforementioned at least one The capacitor element includes an outer casing. The anode lead terminal and the cathode lead terminal each include a recessed portion embedded in the outer casing and an exposed portion connected to the recessed portion and exposed from the outer casing. The recessed portion of the anode lead terminal has a contact surface p that contacts the outer casing. (1st contact surface) It has a contact surface n that contacts the outer casing. The embedded portion of the cathode lead terminal has a contact surface n that contacts the outer casing. (2nd contact surface) The device has the following characteristics: At least one of the contact surfaces selected from contact surface p and contact surface n has a rough surface with an interface area ratio of 0.4 or more. A rough surface with an interface area ratio of 0.4 or more may be referred to as "rough surface (R)" below. The interface area ratio can be measured by the method described later.
[0014] As a method for improving the adhesion between a lead terminal and an exterior body, a method of roughening the surface of the lead terminal by a method such as the sandblast method has been conventionally used. However, as a result of investigations, the inventors of the present application newly found that sufficient effects may not be obtained even when the surface of the lead terminal is roughened by the conventional method. The present disclosure is based on this new finding. <At least one selected from the contact surface p and the contact surface n has a rough surface (R). In a preferred example, each of the contact surface p and the contact surface n has a rough surface (R).
[0020] By increasing the ratio of the rough surface (R) in the contact surface, the effect of the present disclosure can be enhanced. The ratio of the area of the rough surface (R) to the area of the contact surface p is preferably 50% or more, more preferably 80% or more (for example, 90% or more). The ratio of the area of the rough surface (R) to the area of the contact surface n is preferably 50% or more, more preferably 80% or more (for example, 90% or more). All of the contact surface p and the contact surface n may be rough surfaces (R). Here, the area is the apparent area, which is the area assuming that the surface is smooth.
[0021] In addition, the surface of the lead terminal may also have a rough surface (R) on the surface other than the contact surface that contacts the exterior body. For example, among the surfaces of the cathode lead terminal, the surface that is electrically connected to the cathode portion may be a rough surface (R) with an interface development area ratio of 0.4 or more. The ratio of the area of the rough surface (R) to the area of the surface of the embedded portion may be 50% or more, 80% or more, or 90% or more. All of the surface of the embedded portion may be a rough surface (R).
[0022] As described above, the interface development area ratio of the rough surface (R) is 0.4 or more. There is no particular upper limit to the interface development area ratio of the rough surface (R), but by setting the development area ratio to a certain value or less, the manufacture of the lead terminal can be facilitated. The interface development area ratio of the rough surface (R) may be 10.0 or less, 6.0 or less, 4.0 or less, 2.0 or less, 1.0 or less, or 0.6 or less. The interface development area ratio may be within the range defined by any of the upper limits described here and the lower limit (0.4 or more). For example, the interface development area ratio of the rough surface (R) may be in the range of 0.4 to 10.0, 0.4 to 6.0, 0.4 to 4.0, 0.4 to 2.0, 0.4 to 1.0, or 0.4 to 0.6.
[0023] A preferred example of a solid electrolytic capacitor relating to this disclosure satisfies the following conditions (1) and (2), and may further satisfy condition (3).
[0024] (1) The ratio of the area of the rough surface (R) to the area of the contact surface p and the ratio of the area of the rough surface (R) to the area of the contact surface n are 50% or more, and may be 80% or more (for example, 90% or more). The entire contact surface p and contact surface n may be rough surface (R). In this condition (1), the area of the contact surface p and the area of the contact surface n may be read as the area of the embedded portion of the anode lead terminal and the area of the embedded portion of the cathode lead terminal, respectively.
[0025] (2) The ratio of the developed area of the interface of the rough surface (R) is 0.4 or more. The ratio of the developed area of the interface may be 10.0 or less, or may be within the range of the examples above.
[0026] (3) The rough surface (R) is formed from the boundary between the embedded portion and the exposed portion to the interior of the exterior body. The rough surface (R) may be formed across the embedded portion to the exposed portion so as to be formed on at least a portion of the exposed portion as well.
[0027] At least one of the substrates selected from the anode lead terminal substrate and the cathode lead terminal substrate may be a copper substrate. In this case, at least a portion of the copper substrate in the exposed area may be coated with a copper plating layer. In a preferred example, both the anode lead terminal substrate and the cathode lead terminal substrate are copper substrates. In this case, at least a portion of both copper substrates may be coated with a copper plating layer. The entire surface of the exposed area may be coated with a copper plating layer.
[0028] A rolled copper sheet can be used as the copper base material (lead frame). However, the rolled copper sheet extends along the rolling direction. metal It has an organizational structure. When punching out rolled copper sheets to manufacture lead frames, depending on the direction in which the rolled copper sheets are punched out, the direction of the ridge line at the bending position of the lead terminal and metalThe direction in which the tissue extends can be approximately parallel. In this case, on the mountain side of the bending point, metal The spacing between microstructures can widen due to bending, potentially leading to crack formation. As a result, the plating layer formed on the copper substrate (e.g., a tin plating layer) may experience tensile stress, causing cracks to form in the plating layer and reducing the wettability of the solder.
[0029] When the surface of a copper substrate is directly coated with a tin plating layer, the heat generated during mounting causes an alloy layer of copper and tin to form between the copper substrate and the tin plating layer. Because this alloy layer is harder and less ductile than copper and tin, it cannot relieve the stress caused by cracks in the copper substrate, making it prone to cracking. As a result, cracks may also occur in the tin plating layer, potentially reducing the wettability of the solder. By forming a copper plating layer on the copper substrate, the highly ductile copper plating layer can relieve the stress caused by cracks in the copper substrate. Furthermore, the copper plating layer has good affinity with the copper substrate, which is also primarily composed of copper, and easily fills in irregularities caused by cracks in the copper substrate. This suppresses the occurrence of cracks in the copper plating layer and the plating layer covering it, thus reducing the decrease in solder wettability. Therefore, the reliability of the electrical connection between the solid electrolytic capacitor and the external substrate can be improved. Note that the copper plating layer is perpendicular to the direction of extension of the copper substrate. metal Because tissue is present, for example, microscopic observation allows for the distinction between the copper substrate and the copper plating layer covering the copper substrate, and the boundary between the copper substrate and the copper plating layer can be identified.
[0030] The thickness of the copper plating layer is preferably 2 μm or more. By making the thickness 2 μm or more, the tensile stress generated by cracks in the copper substrate can be effectively relieved, and the occurrence of cracks in the copper plating layer and the plating layer covering the copper plating layer can be effectively suppressed. As a result, the effect of suppressing the decrease in solder wettability can be enhanced. The thickness of the copper plating layer may be, for example, 10 μm or less or 15 μm or less.
[0031] The copper substrate may have a bent portion in the exposed area that bends along the outer surface of the exterior body. In this case, the outer surface of the bent portion may be covered with a copper plating layer. Since high stress is applied to the bent portion, it is preferable to cover that portion with a copper plating layer.
[0032] The solid electrolytic capacitor (more specifically, the lead terminals) according to this embodiment may further include a tin plating layer covering the copper plating layer. In this case, the solid electrolytic capacitor (more specifically, the lead terminals) may further include another layer disposed between the copper plating layer and the tin plating layer. This other layer may be a copper-tin alloy layer or a nickel plating layer. The tin plating layer can improve the wettability of the solder and improve the reliability of the electrical connection between the solid electrolytic capacitor and the external substrate. When a tin plating layer is formed on a copper plating layer, the heat generated during mounting may cause tin (Sn) in the tin plating layer to diffuse into the copper plating layer, forming a copper-tin alloy layer between the copper plating layer and the tin plating layer. A nickel plating layer may also be formed between the copper plating layer and the tin plating layer.
[0033] The solid electrolytic capacitor (more specifically, the lead terminals) according to this embodiment may further include a precious metal plating layer covering the copper plating layer. The precious metal plating layer may include at least one selected from the group consisting of gold, platinum, and palladium.
[0034] The solid electrolytic capacitor (more specifically, the lead terminals) according to this embodiment may further include a nickel plating layer disposed between the copper plating layer and the precious metal plating layer.
[0035] In the following, the layer formed on the substrate of the lead terminal (such as the plating layer mentioned above) may be referred to as the "coating layer."
[0036] (Examples of components of a capacitor element) Examples of components for a capacitor element (solid electrolytic capacitor element) are described below. Known components may be used for components other than those characteristic of this disclosure. Furthermore, there are no particular limitations on the capacitor element as long as the effects of this disclosure are achieved; other capacitor elements (e.g., known capacitor elements) other than those described below may be used.
[0037] (Anode part) The anode portion includes an anode body. The anode body may include a valve metal, an alloy containing a valve metal, and a compound containing a valve metal. These materials may be used individually or in combination of two or more. As valve metals, aluminum, tantalum, niobium, and titanium are preferably used. An anode body having a porous portion on its surface can be obtained, for example, by roughening the surface of a metal foil containing a valve metal. Roughening may be performed by electrolytic etching or the like. The entire anode body may be porous. However, from the viewpoint of strength, it is preferable that the anode body includes porous portions arranged on both main surfaces and a core portion arranged between these porous portions. The porosity of the core portion is lower than that of the porous portions. The porous portion is a region having a large number of fine pores. The core portion is, for example, a region that has not been electrolytically etched.
[0038] (Dielectric layer) A capacitor element includes a dielectric layer positioned between the anode and the cathode. The dielectric layer is an insulating layer that functions as a dielectric. The dielectric layer may be formed by anodizing the valve metal on the surface of the anode (e.g., metal foil). The dielectric layer only needs to be formed to cover at least a portion of the anode (anode portion). The dielectric layer is usually formed on the surface of the anode. Since the dielectric layer is formed on the surface of the porous portion of the anode, it is formed along the inner walls of holes and depressions (also called pits) on the surface of the anode.
[0039] A typical dielectric layer contains an oxide of the valve metal. For example, a typical dielectric layer when tantalum is used as the valve metal contains Ta2O5, and a typical dielectric layer when aluminum is used as the valve metal contains Al2O3. However, the dielectric layer is not limited to these examples; any material that functions as a dielectric is acceptable.
[0040] (Cathode part) The cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer, and may further include a cathode extraction layer covering at least a portion of the solid electrolyte layer. The solid electrolyte layer and the cathode extraction layer are described below. The theory I will reveal it.
[0041] (solid electrolyte layer) For example, a solid electrolyte layer containing a conductive polymer can be used. The solid electrolyte layer may, if necessary, contain at least one additive selected from the group consisting of dopants and other additives, in addition to the conductive polymer. Examples of dopants include, but are not limited to, p-toluenesulfonic acid, naphthalenesulfonic acid, and polystyrenesulfonic acid (PSS).
[0042] Examples of conductive polymers include π-conjugated polymers. Examples of conductive polymers include polymers based on polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene as the basic skeleton. The above polymers also include homopolymers, copolymers of two or more monomers, and derivatives thereof (such as substituted products having substituents). For example, polythiophene includes poly(3,4-ethylenedioxythiophene). However, these are merely examples, and conductive polymers are not limited to these examples.
[0043] (Cathode extraction layer) A conductive layer can be used for the cathode extraction layer. For example, the cathode extraction layer may be a layer containing conductive particles, a metal foil, etc. Examples of conductive particles include conductive carbon and metal particles. The cathode extraction layer may include a first layer and a second layer stacked sequentially from the solid electrolyte layer side. In one example, a layer containing conductive carbon is used for the first layer. Alternatively, a layer containing metal particles or a metal foil may be used as the second layer. Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.). Examples of metal particles include silver particles. The layer containing conductive particles may be formed using a composition containing conductive particles and resin (binder resin), or it may be formed using a metal paste (e.g., silver paste).
[0044] (Solid electrolytic capacitor) The solid electrolytic capacitor according to this embodiment includes at least one capacitor element. The number of capacitor elements included in the solid electrolytic capacitor may be in the range of 1 to 20 (for example, in the range of 2 to 10).
[0045] If an electrolytic capacitor includes multiple capacitor elements, these elements may be stacked. Typically, the ends of the anodes of stacked capacitor elements are electrically connected to each other. For example, the ends of these anodes may be joined by welding. Anode lead terminals may be connected to the ends of these anodes.
[0046] Typically, the cathode lead layers of stacked capacitor elements are electrically connected to each other. A cathode lead terminal may be joined to the cathode lead layer of at least one capacitor element. The cathode lead terminal may be joined to the cathode lead layer via a conductive adhesive or solder. Alternatively, the cathode lead terminal may be joined to the cathode lead layer by welding (such as resistance welding or laser welding). The conductive adhesive is, for example, a mixture of a curable resin and carbon or metal particles.
[0047] As described above, a solid electrolytic capacitor includes an outer casing that covers the capacitor element. The outer casing also covers a portion of the anode lead terminal (embedded portion) and a portion of the cathode lead terminal (embedded portion). The outer casing preferably contains a cured product of a curable resin composition, and may also contain a thermoplastic resin or a composition containing the same. The curable resin composition may contain a curable resin and a filler. A thermosetting resin is preferred as the curable resin.
[0048] The curable resin composition may include, in addition to the curable resin, fillers, curing agents, polymerization initiators, and catalysts. Examples of curable resins include epoxy resins, phenolic resins, urea resins, polyimides, polyamide-imides, polyurethanes, diallyl phthalates, and unsaturated polyesters. The curable resin composition may contain multiple curable resins.
[0049] Examples of fillers include insulating particles (inorganic particles, organic particles) and insulating fibers. Examples of insulating materials that make up the fillers include insulating compounds (oxides, etc.) such as silica and alumina, glass, and mineral materials (talc, mica, clay, etc.). The outer casing may contain only one type of filler or two or more types. The filler content in the outer casing may be in the range of 10 to 90% by mass.
[0050] Examples of thermoplastic resins that can be used include polyphenylene sulfide (PPS) and polybutylene terephthalate (PBT). The composition containing the thermoplastic resin may also contain the above-mentioned fillers in addition to the thermoplastic resin.
[0051] The solid electrolytic capacitor according to this embodiment may further include a case disposed on the outside of the outer casing (resin composition). Examples of resin materials constituting the case include thermoplastic resins or compositions containing them. Examples of metal materials constituting the case include metals such as aluminum, copper, and iron, or their alloys (including stainless steel and brass).
[0052] (Lead terminals) As described above, the anode lead terminal and the cathode lead terminal each include a recessed portion and an exposed portion. The anode lead terminal and the cathode lead terminal can be formed from known materials and by known methods, except for the roughened (R) portion. As described above, the anode lead terminal and the cathode lead terminal may each be formed by processing a metal sheet (including metal plates and metal foils) made of a metal (copper, copper alloy, etc.). That is, examples of materials for the base material of the anode lead terminal and the cathode lead terminal include copper and copper alloys.
[0053] One end of the anode lead terminal (the end of the embedded portion) is connected to the anode portion. One end of the cathode lead terminal (the end of the embedded portion) is connected to the cathode portion (e.g., the cathode lead layer). The exposed portions of the anode lead terminal and the cathode lead terminal can each function as terminals that are soldered or otherwise connected when the solid electrolytic capacitor is mounted.
[0054] (Method for manufacturing solid electrolytic capacitor elements and solid electrolytic capacitors) There are no particular limitations on the method for manufacturing solid electrolytic capacitors according to this embodiment. For their manufacturing, known manufacturing methods may be applied, except for the method for forming the rough surface (R), or a part of a known manufacturing method may be modified and applied.
[0055] An example of a method for manufacturing a solid electrolytic capacitor according to this embodiment is described below. However, the solid electrolytic capacitor according to this embodiment may be manufactured by a method other than the one described below. Since the matters described for solid electrolytic capacitors can also be applied to the manufacturing method described below, redundant explanations may be omitted. Furthermore, the matters described for the manufacturing method described below can also be applied to the solid electrolytic capacitor according to this embodiment.
[0056] First, the capacitor element, anode lead terminal, and cathode lead terminal are fabricated (step (i)). There are no particular limitations on the method of fabricating the capacitor element, and it can be formed by known methods. When manufacturing a solid electrolytic capacitor that includes multiple stacked capacitor elements, multiple capacitor elements are stacked. In that case, the anode portions of the multiple capacitor elements are connected by welding or other means as needed. Also, the cathode portions of the multiple capacitor elements are connected by conductive paste or the like as needed.
[0057] Next, the anode lead terminals are electrically connected to the anode portion of the capacitor element, and the cathode lead terminals are electrically connected to the cathode portion of the capacitor element (step (ii)). There are no particular limitations on these connection methods, and known connection methods may be applied. For example, the anode portion and the anode lead terminals may be connected by welding, etc. The cathode portion and the cathode lead terminals may be connected by conductive paste, etc.
[0058] Next, the capacitor element, the embedded portion of the anode lead terminal, and the embedded portion of the cathode lead terminal are covered with an outer casing (step (iii)). The outer casing can be formed using molding techniques such as injection molding, insert molding, or compression molding.
[0059] This manufacturing method includes a step (I) for producing lead terminals (anode lead terminals and / or cathode lead terminals) having a rough surface (R). Step (I) includes a step (a) for processing a metal sheet (substrate) into a predetermined shape by press working or the like, and a step (b) for forming a rough surface (R). Step (I) may further include a step (c) for forming a coating layer (such as a plating layer) on the substrate. Steps (a) and (b) may be performed in any order.
[0060] If step (I) includes step (c), there is no particular limit to the order of steps (a), (b), and (c), as long as a rough surface (R) is ultimately formed in the predetermined area. However, if a coating layer is formed on a surface having a rough surface (R) after the rough surface (R) has been formed, the developed area ratio of the interface of the rough surface (R) may decrease. In that case, step (b) may be performed after step (c). Alternatively, after forming the rough surface (R) in step (b), step (c) may be performed in which the coating layer is formed only in the area that does not need to be a rough surface (R). Step (c) may be performed before step (iii), in which the embedded portion of the capacitor element and lead terminals is covered with an outer casing. Alternatively, step (c) may be performed after step (iii), and the coating layer may be formed only on the exposed portion of the lead terminals.
[0061] The step (a) of processing a metal sheet (base material) into a predetermined shape by press working or the like can be carried out by known methods.
[0062] The step (b) of forming the rough surface (R) may be carried out by, for example, sandblasting, roughening plating, or roughening etching. Sandblasting is preferred because it allows for quick processing and is cost-effective. Roughening plating is preferred because it is inexpensive. Roughening etching is preferred because it produces a fine roughness with minimal unevenness. In addition, roughening plating and roughening etching have the advantage that, unlike sandblasting, no beads (blasting material) remain.
[0063] Methods for roughening the surface of lead terminals by sandblasting have been conventionally employed. However, under conventional conditions, the adhesion between the outer casing and the lead terminals was insufficient. In the method disclosed herein, surface roughening is performed under conditions such that the developed area ratio of the roughened surface interface is 0.4 or higher.
[0064] By reducing the particle size (for example, increasing the grit size), it is possible to increase the surface area ratio of the interface of the sandblasted surface. Therefore, in this method, sandblasting is usually performed using particles smaller than those conventionally used for roughening lead terminals. Increasing the number of sandblasting shots can also increase the surface area ratio of the interface of the sandblasted surface to some extent. If the particle size (abrasive material) is made too small, the surface area ratio of the interface may decrease, but the conditions under which the surface area ratio of the roughened surface interface is 0.4 or higher can be easily determined experimentally. There are no particular limitations on the particles (abrasive material) used for sandblasting; alumina particles or garnet particles may also be used.
[0065] When forming a rough surface (R) using a roughening plating method, for example, by forming needle-like or particulate plating to increase the surface area, Ratio of the developed area of the interface The Sdr can be set to 0.4 or higher. For example, the proportion of needle-shaped or particulate plating may be increased.
[0066] When forming a roughened surface (R) using a roughening etching method, for example, by utilizing the difference between the etching rate of grain boundaries and the etching rate of grains (grain boundaries have a higher etching rate), the surface area can be increased to form a roughened shape, and as a result, Ratio of the developed area of the interface Sdr can be set to 0.4 or higher. For example, the ratio of grain boundaries to grains in the metal can be changed by selecting the metal used for the lead terminals, or the difference in etching rates can be changed by changing the etching conditions.
[0067] As described above, a rough surface (R) with an interface area ratio of 0.4 or more is formed on the lead terminal. The coating layer (layer on the substrate) formed in step (c) may be formed by a known method (for example, a known plating method). In this way, a solid electrolytic capacitor can be manufactured.
[0068] Examples of embodiments relating to this disclosure will be specifically described below with reference to the drawings. The components of the examples described below can be the components described above. Furthermore, the examples described below can be modified based on the above description. Furthermore, the matters described below may be applied to the embodiments described above. In addition, in the embodiments described below, components that are not essential to the solid electrolytic capacitor of this disclosure may be omitted. The solid electrolytic capacitor described below may be manufactured by the method described above.
[0069] (Embodiment 1) Figure 1 is a schematic cross-sectional view showing a solid electrolytic capacitor according to Embodiment 1. The solid electrolytic capacitor 10 shown in Figure 1 includes a capacitor element 100, lead terminals 20, and an outer casing 30. The lead terminals 20 include an anode lead terminal 21 electrically connected to the anode portion (anode body) 111 of the capacitor element 100, and a cathode lead terminal 22 electrically connected to the cathode portion 113 of the capacitor element 100.
[0070] The capacitor element 100 includes an anode portion (anode body) 111, a dielectric layer 112 covering at least a portion of the anode portion 111, and a cathode portion 113 covering at least a portion of the dielectric layer 112. The cathode portion 113 includes a solid electrolyte layer 113a covering at least a portion of the dielectric layer 112, and a cathode extraction layer 113b covering at least a portion of the solid electrolyte layer 113a.
[0071] The anode lead terminal 21 includes a recessed portion 21a embedded in the casing 30 and an exposed portion 21b exposed from the casing 30. The cathode lead terminal 22 includes a recessed portion 22a embedded in the casing 30 and an exposed portion 22b exposed from the casing 30. Figure 1 shows the boundary 21x between the recessed portion 21a and the exposed portion 21b, and the boundary 22x between the recessed portion 22a and the exposed portion 22b.
[0072] One end of the anode portion 111 is electrically connected to the embedded portion 21a of the anode lead terminal 21 by welding or the like. The cathode portion 113 of the capacitor element 100 (specifically the cathode lead layer 113b) is electrically connected to the embedded portion 22a of the cathode lead terminal 22 by conductive paste 23.
[0073] The embedded portion 21a has a contact surface p that contacts the outer casing 30. The embedded portion 22a has a contact surface n that contacts the outer casing 30. The contact surface p and / or contact surface n have the rough surface (R) described above. The rough surface (R) portion increases the adhesion between the outer casing 30 and the lead terminal 20. Therefore, it is possible to suppress the intrusion of oxygen and other substances from the interface between the outer casing 30 and the lead terminal 20. As a result, the deterioration of the capacitor element 100 can be suppressed, and the long-term reliability of the solid electrolytic capacitor 10 can be improved.
[0074] The anode lead terminal 21 and / or cathode lead terminal 22 may include the coating layer described above. Preferably, the coating layer is formed to cover the bent portions 21d and 22d that are bent along the outer surface of the outer casing 30 in the exposed portions 21b and 22b.
[0075] An example electrolytic capacitor according to this embodiment may include a plurality of stacked capacitor elements 100. In this case, one end of the anode portion 111 of the plurality of capacitor elements 100 is joined by welding or the like, and at least one anode portion 111 is connected to an anode lead terminal 21. The cathode portions 113 of the plurality of capacitor elements 100 are connected by conductive paste or the like, and at least one cathode portion 113 is further connected to a cathode lead terminal 22 by conductive paste or the like. That is, the plurality of capacitor elements 100 are connected in parallel. In this case as well, the contact surfaces p and / or contact surfaces n have a rough surface (R). [Examples]
[0076] The solid electrolytic capacitors related to this disclosure will be described in more detail by reference to examples.
[0077] [Fabrication and evaluation of solid electrolytic capacitors] Several types of solid electrolytic capacitors were fabricated using the method described below. Each solid electrolytic capacitor contains one capacitor element. The solid electrolytic capacitor and capacitor element have a structure similar to the solid electrolytic capacitor 10 and capacitor element 100 shown in Figure 1, respectively.
[0078] First, an anode was fabricated by roughening both surfaces of an aluminum foil (thickness: 100 μm) through etching. Next, a dielectric layer (aluminum oxide layer) was formed on the anode by anodic oxidation while a portion of the anode was immersed in a chemical conversion solution.
[0079] Next, a solid electrolyte layer was formed on the dielectric layer using the following method. First, an aqueous solution containing pyrrole monomer and p-toluenesulfonic acid was prepared. The anode body with the dielectric layer formed on it and the counter electrode were immersed in the obtained aqueous solution, and electropolymerization was carried out. This electropolymerization formed the solid electrolyte layer.
[0080] Next, graphite particles and a dispersant (cellulose derivative, etc.) were wet-milled with water using a bead mill to obtain a dispersion. This dispersion was then applied to the surface of the solid electrolyte layer. Paint After weaving, the material was dried. In this way, a carbon layer was formed on the surface of the solid electrolyte layer. Next, a silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of the carbon layer, and then heated to form a metal paste layer. Through these steps, a cathode extraction layer containing the carbon layer and the metal paste layer was formed. In this way, a capacitor element was fabricated.
[0081] A copper sheet (thickness: 100 μm) was prepared to form the anode lead terminal and the cathode lead terminal. Next, the areas that would be embedded in the anode lead terminal and the areas that would be embedded in the cathode lead terminal were roughened to create a rough surface. After that, the metal sheet was processed to form the shapes of the anode lead terminal and the cathode lead terminal.
[0082] Surface roughening was performed using sandblasting, roughening plating, and roughening etching. In the sandblasting method, the average particle size of the blast beads (projection material such as alumina particles or garnet particles) was changed. Ratio of the developed area of the interface Sdr was varied. In the roughening plating method and the roughening etching method, the method described above was used. Ratio of the developed area of the interface Sdr was increased. To evaluate the roughness of the formed surface, the arithmetic mean height Sa and the interface area ratio Sdr were measured for the formed surface. Note that for capacitor C1, which was not roughened, the surface of the lead terminals was measured. rough Regarding this, the arithmetic mean height Sa and the ratio of the developed area of the interface Sdr were measured.
[0083] The interface area ratio Sdr was measured in accordance with ISO 25178. Similarly, the arithmetic mean height Sa was measured in accordance with ISO 25178.
[0084] Next, one end of the anode portion of the capacitor element was connected to the anode lead terminal. The cathode portion of the capacitor element was also connected to the cathode lead terminal using conductive paste. Then, the capacitor element, a portion of the anode lead terminal (embedded portion), and a portion of the cathode lead terminal (embedded portion) were covered by molding. In this way, an electrolytic capacitor having a structure similar to the electrolytic capacitor shown in Figure 1 was fabricated.
[0085] In this example, 100 units each of seven types of solid electrolytic capacitors (capacitors C1, C2, A1-A5) were manufactured by changing the surface roughening method. The surface roughening methods used are shown in Table 1. For sandblasting capacitors C2 and A1-A3, the ratio of the developed area of the interface was changed by varying the average particle size of the blast beads (projection material) used, as shown in Table 1 below. Specifically, the average particle size of the blast beads used in the sandblasting of capacitor C2 was used as a reference, and the ratio of the average particle size to that was changed as shown in Table 1. For example, the average particle size of the blast beads used in the sandblasting of capacitor A1 is half the average particle size of the blast beads used in the sandblasting of capacitor C2. The sandblasting conditions for capacitor C2 were the same as those used conventionally.
[0086] The fabricated capacitors were heat-treated under the same conditions as the solder reflow process (peak temperature of 260°C for 10 seconds). The airtightness failure rate of the heat-treated capacitors was then evaluated.
[0087] The airtightness failure rate was evaluated using a gross leak test. Specifically, a capacitor was placed inside a small capsule, and the minute pressure drop caused by the leakage of internal pressure from the capsule into the capacitor's casing was measured. Capacitors with large pressure changes were judged to have airtightness failure. Some of the capacitor manufacturing conditions and evaluation results are shown in Table 1.
[0088] [Table 1]
[0089] As shown in Table 1, the airtightness failure rate after heat treatment was significantly reduced by setting the interface development area ratio Sdr to 0.4 or higher. Compared to capacitor C1, the arithmetic mean height Sa of the surface of capacitor C2, which underwent sandblasting, was significantly increased, indicating that the surface was roughened by sandblasting. However, the airtightness failure rate of capacitor C2 after heat treatment remained high. Despite the arithmetic mean height Sa of the roughened surfaces of capacitors A1 to A5 being lower than that of capacitor C2, the airtightness failure rate of capacitors A1 to A5 was significantly lower than that of capacitor C2. This indicates that the conventional evaluation method was not able to provide an appropriate evaluation.
[0090] Figure 2 shows an example image illustrating the unevenness of the rough surface of capacitor C2, and Figure 3 shows that of capacitor A2. As shown in Figure 2, on the rough surface of capacitor C2, the area of one recess is large and the area of one protrusion is large, and the recesses and protrusions are unevenly distributed. On the other hand, on the rough surface of capacitor A2, fine irregularities are uniformly distributed. [Industrial applicability]
[0091] This disclosure can be used for solid electrolytic capacitor elements and solid electrolytic capacitors. [Explanation of symbols]
[0092] 10: Solid electrolytic capacitor 20: Lead terminals 21: Anode lead terminal 21a, 22a: Embedded part 21b, 22b: Exposed part 22: Cathode lead terminal 22a: Embedded part 22b:Exposed part 30: Exterior 100: Capacitor element 111: Anode section 112: Dielectric layer 113: Cathode part 113a: Solid electrolyte layer 113b: Cathode lead-out layer p, n: contact surfaces
Claims
1. A capacitor element comprising an anode portion and a cathode portion, A positive lead terminal electrically connected to the anode portion, The cathode lead terminals electrically connected to the cathode portion, Includes an outer casing that covers at least one capacitor element, The anode lead terminal and the cathode lead terminal each include a recessed portion embedded in the outer casing and an exposed portion connected to the recessed portion and exposed from the outer casing. The embedded portion of the anode lead terminal has a first contact surface that contacts the outer casing, The embedded portion of the cathode lead terminal has a second contact surface that contacts the outer casing. At least one of the contact surfaces selected from the first contact surface and the second contact surface has a rough surface with an interface development area ratio of 0.4 or more and 10 or less. At least a portion of the exposed portion of the anode lead terminal and / or at least a portion of the exposed portion of the cathode lead terminal have areas that are not roughened. A solid electrolytic capacitor in which the rough surface is formed extending from the embedded portion to the exposed portion, so as to be formed on at least a portion of the exposed portion.
2. The solid electrolytic capacitor according to claim 1, wherein each of the first contact surface and the second contact surface has the rough surface.
3. At least one of the substrates selected from the substrate of the anode lead terminal and the substrate of the cathode lead terminal is a copper substrate. The solid electrolytic capacitor according to claim 1 or 2, wherein at least a portion of the copper substrate in the exposed portion is covered with a copper plating layer.
4. The copper substrate has a bent portion in the exposed portion that is bent along the outer surface of the exterior body, The solid electrolytic capacitor according to claim 3, wherein the outer surface of the bent portion is covered with the copper plating layer.
5. The solid electrolytic capacitor according to claim 3 or 4, further comprising a tin plating layer covering the copper plating layer.
6. The present invention further includes another layer disposed between the copper plating layer and the tin plating layer, The solid electrolytic capacitor according to claim 5, wherein the other layer is a copper-tin alloy layer or a nickel-plated layer.
7. The copper plating layer further comprises a noble metal plating layer covering the copper plating layer, The solid electrolytic capacitor according to claim 3 or 4, wherein the noble metal plating layer comprises at least one selected from the group consisting of gold, platinum, and palladium.
8. The solid electrolytic capacitor according to claim 7, further comprising a nickel plating layer disposed between the copper plating layer and the precious metal plating layer.