solid electrolytic capacitor

Abstract

To achieve high reliability while maintaining good electrical characteristics in a solid electrolytic capacitor.SOLUTION: A solid electrolytic capacitor 100 includes a plurality of stacked capacitor elements 1 covered with an exterior body. The capacitor element 1 includes an anode body 2, a dielectric layer 3 provided on the surface of the anode body 2 and having a plurality of voids 3a, a solid electrolyte layer 5 provided on the surface of the dielectric layer 3, a cathode body 6 provided on the surface of the solid electrolyte layer 5, and an insulating layer 4 provided on the anode side of the dielectric layer 3. An insulating resin is filled in the plurality of voids 3a included in the insulating layer 4, and an anode side electrode layer 12a is provided adjacent to the insulating layer 4 of each capacitor element 1, the anode body 2 of each capacitor element 1, and the anode part adhesive resin 17 between the capacitor elements 1. An anode terminal portion 9, which is the end of the anode body 2, is inserted into the anode side electrode layer 12a.SELECTED DRAWING: Figure 1B

Description

[Technical Field]

[0001] The present disclosure relates to solid electrolytic capacitors. [Background technology]

[0002] As electronic devices operate at higher frequencies, there is a demand for capacitors with excellent impedance characteristics in the high-frequency range. To meet this demand, various solid electrolytic capacitors that use conductive polymers with high electrical conductivity as the solid electrolyte have been investigated (see, for example, Patent Document 1).

[0003] In recent years, there has been a strong demand for smaller, larger capacitance solid electrolytic capacitors used in the CPU (Central Processing Unit) and surrounding areas of personal computers. Furthermore, there is a demand for lower ESR (Equivalent Series Resistance) to accommodate higher frequencies, and lower ESL (Equivalent Series Inductance) for superior noise reduction and transient response. Various studies are being conducted to address these demands.

[0004] The stacked solid electrolytic capacitor disclosed in Patent Document 1 will now be described with reference to Fig. 3. Fig. 3 is a side cross-sectional view of the stacked solid electrolytic capacitor disclosed in Patent Document 1.

[0005] In FIG. 3, solid electrolytic capacitor 31 includes laminate 33, exterior casing 43, anode external electrode 47, and cathode external electrode .

[0006] The laminate 33 is formed by stacking a plurality of capacitor elements 32. Each capacitor element 32 has a valve metal substrate 34 having a core 35 and a rough surface portion 36 formed along the core portion 35's surface, a dielectric coating 37 formed on the rough surface portion 36, a solid electrolyte layer 39 formed on the dielectric coating 37, and a current collector layer 40 formed on the solid electrolyte layer 39. The current collector layers 40 of the plurality of capacitor elements 32 are electrically connected to one another.

[0007] The exterior 43 has electrical insulation properties and covers the laminate 33 with one end surface 38 of the valve metal substrate 34 exposed on the first end surface 44 .

[0008] The anode-side external electrode 47 is provided on the first end face 44 of the exterior casing 43 and on parts of the upper and lower faces adjacent to the first end face 44. The anode-side external electrode 47 is electrically connected to the core 35 of the valve metal substrate 34.

[0009] The cathode side external electrode 48 is provided on a second end face 45 opposite to the first end face 44 of the exterior casing 43. The cathode side external electrode 48 is also electrically connected to the current collector layer 40.

[0010] The anode-side external electrode 47 includes a first conductive layer 49, a second conductive layer 50, and a third conductive layer 51. The first conductive layer 49 is formed so as to be in direct contact with the core 35 of the valve metal 34, and electrically connects the cores 35 of the valve metal substrates 34 of adjacent capacitor elements 32 to each other. The first conductive layer 49 is formed by a dry process such as sputtering so as to cover one end face 38 of the valve metal substrate 34 and the entire first end face 44 of the surrounding exterior 43, and to extend to parts of the upper and lower faces adjacent to the first end face 44.

[0011] The solid electrolytic capacitor 31 having the above-described configuration can prevent water from penetrating into the rough surface portion 36 of the valve metal substrate 34 and between the rough surface portion 36 and the exterior casing 43. Furthermore, since the second conductive layer 50 is formed on the first conductive layer 49, adhesion strength can be increased. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Patent No. 6233410 Summary of the Invention [Problem to be solved by the invention]

[0013] In the solid electrolytic capacitor 31 of Patent Document 1, a core 35 exposed on one end surface 38 of a valve metal substrate 34 is made of a metal foil such as Al (aluminum) foil. The surface of the metal foil is etched to form a rough surface portion 36, on which a dielectric coating 37 is formed.

[0014] Furthermore, when the first conductive layer 49 is formed on one end surface 38 of the valve metal substrate 34 by a dry process such as sputtering, the dielectric coating 37 on the rough surface portion 36 and the exterior 43 made of a resin material are merely mechanically attached using the anchor effect, rather than being bonded by a metal bond with high bonding strength.

[0015] Therefore, the bonding strength between the dielectric coating 37 and the exterior casing 43 is extremely weak, and peeling occurs when only a weak pressure is applied when the second conductive layer 50 and the third conductive layer 51 are formed.

[0016] Furthermore, at the interface between the first conductive layer 49 formed by the anchor effect and the rough surface portion 36, peeling may occur, which may allow moisture to penetrate through the porous structure of the rough surface portion 36.

[0017] Similarly, peeling at the interface between first conductive layer 49 and exterior casing 43 may also cause moisture to penetrate into capacitor element 32 as a whole.

[0018] Therefore, when mounting the solid electrolytic capacitor 31 on a printed circuit board, the moisture contained in the solid electrolytic capacitor 31 evaporates at high temperatures and expands between the capacitor elements 32, which can destroy the capacitor elements 32 and cause quality defects.

[0019] An object of one aspect of the present disclosure is to provide a solid electrolytic capacitor that has high reliability while maintaining good electrical characteristics, and a method for manufacturing the same. [Means for solving the problem]

[0020] A solid electrolytic capacitor according to one aspect of the present disclosure is a solid electrolytic capacitor in which a plurality of stacked capacitor elements are covered with an exterior body, and the capacitor elements each include an anode body and a plurality of voids provided on the surface of the anode body. Porous structure a dielectric layer; a solid electrolyte layer provided on a portion of the surface of the dielectric layer; and a cathode body provided on the surface of the solid electrolyte layer. a part of the dielectric layer on the anode side where the solid electrolyte layer is not provided is formed as an insulating layer by filling the void with an insulating resin; An anode-side electrode layer is provided adjacent to the insulating layer of each capacitor element and the anode body of each capacitor element. R . [Effects of the Invention]

[0022] According to the present disclosure, a solid electrolytic capacitor can achieve high reliability while maintaining good electrical characteristics. [Brief explanation of the drawings]

[0023] [Figure 1A] FIG. 1 is a perspective view showing a solid electrolytic capacitor according to an embodiment of the present disclosure; [Figure 1B] A-A' cross section of Figure 1A [Figure 1C] Enlarged view of area X in Figure 1B [Figure 2A] 1 is a cross-sectional view illustrating a solid electrolytic capacitor during a lamination process according to an embodiment of the present disclosure; [Figure 2B] 1 is a cross-sectional view illustrating a solid electrolytic capacitor during a sealing process according to an embodiment of the present disclosure; [Figure 2C] FIG. 1 is a cross-sectional view illustrating a solid electrolytic capacitor during an exposure step according to an embodiment of the present disclosure. [Figure 2D] FIG. 1 is a cross-sectional view illustrating a solid electrolytic capacitor during a contact layer forming step according to an embodiment of the present disclosure. [Figure 2E] FIG. 1 is a cross-sectional view illustrating a solid electrolytic capacitor during a first electrode formation step according to an embodiment of the present disclosure. [Figure 2F] FIG. 10 is a cross-sectional view illustrating the solid electrolytic capacitor during a second electrode formation step according to the embodiment of the present disclosure. [Figure 3] A cross-sectional side view showing the configuration of the solid electrolytic capacitor disclosed in Patent Document 1. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that common components in the drawings are denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0025] [Configuration of solid electrolytic capacitor 100] The configuration of solid electrolytic capacitor 100 according to an embodiment of the present disclosure will be described with reference to FIGS. 1A, 1B, and 1C. FIG. 1A is a perspective view showing solid electrolytic capacitor 100 according to the present embodiment. FIG. 1B is a cross-sectional view taken along line A-A' in FIG. 1A. FIG. 1C is an enlarged view of portion X in FIG. 1B.

[0026] As shown in FIGS. 1A to 1C, the solid electrolytic capacitor 100 includes a capacitor element 1, a support member 7, a conductive material 8, an anode terminal portion 9, an outer casing 10, a contact layer 11, an anode-side electrode layer 12a, a cathode-side electrode layer 12b, an anode-side external electrode 13a, a cathode-side external electrode 13b, and an anode part adhesive resin 17.

[0027] The contact layer 11 is formed on the surface of the anode terminal 9 .

[0028] The anode side electrode layer 12 a is formed to cover at least the contact layer 11 .

[0029] The anode side external electrode 13a and the cathode side external electrode 13b are formed on the surfaces of the anode side electrode layer 12a and the cathode side electrode layer 12b, respectively.

[0030] <Capacitor element 1> As shown in FIG. 1B, capacitor element 1 has anode body 2, dielectric layer 3, insulating layer 4, solid electrolyte layer 5, and cathode body 6.

[0031] Dielectric layer 3 is obtained by forming porous layers on both sides of the Al foil that is anode body 2 by a method such as chemical etching, and then forming a dielectric coating on the porous layers.

[0032] The anode body 2 is an Al foil core portion that remains without being made porous. The anode body 2 is surrounded by a dielectric layer 3. That is, the dielectric layer 3 is disposed on both surfaces (top and bottom surfaces) of the anode body 2.

[0033] The thickness of anode body 2 and the thickness of dielectric layer 3 are each 20 to 80 μm. The material of anode body 2 and dielectric layer 3 is not limited to Al foil, and may be, for example, Ta (tantalum), which is commonly used as a capacitor material.

[0034] An insulating layer 4 is formed in the anode-side insulating resin-filled portion 18 of the anode body 2. The insulating layer 4 electrically insulates and separates the anode end surface 14 from the cathode body 6. In other words, the anode side and the cathode side (not shown) are electrically insulated and separated.

[0035] 1C, the dielectric layer 3 has a porous structure with numerous voids 3a ranging in size from several nm to several tens of μm (upper limit: 30 μm). This porous structure is formed by a method such as chemical etching.

[0036] A portion of the dielectric layer 3 corresponding to the insulating layer 4 is impregnated with an insulating resin 16 having insulating properties. As a result, as shown in Fig. 1C, the voids 3a in the insulating layer 4 are filled with the insulating resin 16. In order to fill the voids 3a with the insulating resin 16, it is preferable that the insulating resin 16 be a resin with low viscosity.

[0037] Methods for filling the voids 3a with the insulating resin 16 include, for example, placing the dielectric layer 3 in a reduced-pressure environment or applying external pressure. While this depends on the material (e.g., viscosity) of the insulating resin 16, applying external pressure can improve the filling rate (or impregnation rate) by adjusting the applied pressure. For example, in the insulating layer 4, the insulating resin 16 is filled in order from the largest voids to the largest voids. When the filling rate reaches approximately 50% or more, voids of several tens of microns in size are filled with the insulating resin 16, while voids of several nanometers in size are left unfilled. In contrast, since the size of moisture particles is said to be several tens of microns, a filling rate of 50% or more can prevent moisture from penetrating from the outside.

[0038] Furthermore, insulating resin 16 is heat-resistant because it is thermally cured in the lamination process described below. The heating temperature during thermal curing is 150°C to 220°C, depending on the curing temperature of the conductive resin in the lamination process, etc. Therefore, it is preferable that insulating resin 16 has a glass transition temperature Tg of at least 150°C or higher.

[0039] Furthermore, it is preferable that the insulating resin 16 has the ability to absorb impact energy (details will be explained in the contact layer formation step described later) that occurs when the insulating resin 16 is impregnated into a portion of the dielectric layer 3 (the portion corresponding to the insulating layer 4) to form the contact layer 11. That is, it is preferable that the insulating resin 16 has the property of absorbing impact energy to a certain extent, remaining resilient even when deformed, and being shock-resistant. For example, in terms of resin properties, it is preferable that the insulating resin 16 is a resin having an elastic modulus of 3 GPa to 7 GPa or more.

[0040] The insulating resin 16 filled in the gap 3a is cured by heat, for example, in a high-temperature furnace, etc. If the insulating resin 16 is a UV (ultraviolet) curable resin, the insulating resin 16 filled in the gap 3a may be cured by irradiating the insulating resin 16 with ultraviolet light.

[0041] The insulating layer 4 may be formed, for example, by impregnating a portion of the porous dielectric layer 3 with the insulating resin 16 and then coating it with an insulating resin such as polyimide. Alternatively, to increase the density, a method may be used in which a compressive stress is first applied to the dielectric layer 3 to make it a dense layer, and then the porous dielectric layer 3 is partially impregnated with the insulating resin 16 to provide insulation.

[0042] 1B, anode part adhesive resin 17 is laminated between the anode elements of anode terminal 9. This fills the gaps between the anode elements of anode terminal 9.

[0043] Furthermore, since the anode part adhesive resin 17 is thermally cured in the lamination step described below, the anode part adhesive resin 17 has heat resistance. The heating temperature during thermal curing is 150°C to 220°C, although it depends on the curing temperature of the conductive resin in the lamination step. Therefore, the glass transition temperature Tg of the anode part adhesive resin 17 is preferably at least 150°C or higher.

[0044] Furthermore, it is preferable that the anode part adhesive resin 17 has the ability to absorb impact energy (details will be explained later in the contact layer formation step) generated when forming the contact layer 11. That is, it is preferable that the anode part adhesive resin 17 has the property of absorbing impact energy to a certain extent, remaining tough even when deformed, and being shock-resistant. For example, in terms of resin properties, it is preferable that the anode part adhesive resin 17 is a resin having an elastic modulus of 3 GPa to 7 GPa or more.

[0045] 1B illustrates an example in which capacitor element 1 has a single structure, but capacitor element 1 may have a composite structure made of a combination of different materials. For example, capacitor element 1 may have a laminated structure of a dense Al oxide film and a polyimide resin.

[0046] A solid electrolyte layer 5 is formed on the dielectric layer 3, which is insulated and separated by the insulating layer 4 and serves as the cathode. The solid electrolyte layer 5 is made of a conductive polymer material such as polypyrrole or polythiophene. In general, the solid electrolyte layer 5 is formed by a method such as chemical polymerization or electrolytic polymerization.

[0047] A cathode body 6 is formed on the solid electrolyte layer 5. The cathode body 6 is formed by sequentially laminating a carbon layer and an Ag (silver) paste layer by, for example, a printing method or a transfer method.

[0048] The cathode body 6 is not limited to a laminated structure of a carbon layer and an Ag paste layer. For example, the cathode body 6 may include a conductive paste using a filler other than Ag or a sintering material instead of the Ag paste. An example of the conductive paste is Cu (copper) paste.

[0049] <Support member 7, conductive material 8, exterior body 10> A plurality of capacitor elements 1 are laminated on a support member 7 made of, for example, a glass epoxy substrate, with the cathode portions sandwiching conductive material 8 and the anode portions sandwiching anode portion adhesive resin 17. The capacitor elements 1 are sealed with an exterior body 10 so as to form an anode terminal portion 9 where the end of the anode body 2 is exposed. Note that, although FIG. 1 illustrates an example in which the number of laminated layers of the capacitor element 1 is three, the number of laminated layers of the capacitor element 1 is not limited to three.

[0050] As described above, the gaps between the anode part elements are filled with the anode part adhesive resin 17. This has the effect of preventing moisture penetration due to breakage of the elements or gaps caused by pressure or the like when forming the anode side external electrode 13a and the cathode side external electrode 13b.

[0051] As the support member 7, in addition to a glass epoxy substrate, for example, a substrate with excellent heat resistance such as a BT (Bismaleimide-Triazine) resin or polyimide resin substrate, a Cu lead frame, etc. can be used. However, when using a conductive material such as a lead frame, it goes without saying that the anode side and the cathode side must be separated so as to be insulated.

[0052] For example, a conductive paste such as Ag paste is used as the conductive material 8. The conductive material 8 is electrically connected to the cathode body of the capacitor element 1.

[0053] Note that Figure 1B illustrates a case where only conductive material 8 is provided between adjacent capacitor elements 1, but in addition to the conductive material 8, a metal foil such as Al, Cu, or In (indium) may also be interposed.

[0054] <Anode terminal 9, contact layer 11> A contact layer 11 made of a metal having a lower ionization tendency than anode body 2 is formed on anode terminal 9. This contact layer 11 is not formed on exterior body 10 and insulating layer 4, which are made of a resin-based material, but is selectively formed only on the surface of anode terminal 9, which is made of a metal material.

[0055] When the anode body 2 is made of Al, it is preferable to use a metal having a lower ionization tendency than Al as the material for the contact layer 11. Examples of such metals include Zn (zinc), Ni (nickel), Sn (tin), Cu, and Ag. Such metals suppress the formation of a strong oxide film on the surface of the contact layer 11, thereby ensuring a more reliable electrical connection between the contact layer 11 and the anode-side electrode layer 12a.

[0056] Furthermore, when anode body 2 is made of Al, contact layer 11 can be made of Cu, Zn, or Ag, which have close interatomic distances, to form an alloy layer due to intermetallic bonding with Al. This can further strengthen the bonding strength between anode bodies 2. Note that contact layer 11 may be made of a single-element metal, or may be made of an alloy such as bronze or brass, or may be made by laminating Ni and Ag, Cu and Ag, or the like.

[0057] <Electrode structure> The anode end surface 14 is composed of the contact layer 11, the anode side end surface 4a of the insulating layer 4, the anode side end surface 10a of the package 10, and the anode side end surface 7a of the support member 7.

[0058] Cathode end surface 15 is composed of cathode terminal portion 8b which is the cathode side end surface of conductive material 8, cathode side end surface 10b of exterior body 10, and cathode side end surface 7b of support member 7.

[0059] The anode end surface 14 is covered with the anode-side electrode layer 12a, and the cathode end surface 15 is covered with the cathode-side electrode layer 12b. Electrical conduction between the anode terminals 9 of the stacked capacitor elements 1 is achieved mainly through the anode-side electrode layer 12a.

[0060] The anode electrode layer 12a is covered with an anode external electrode 13a, and the cathode electrode layer 12b is covered with a cathode external electrode 13b.

[0061] The material for the anode side electrode layer 12a and the cathode side electrode layer 12b is preferably a conductive paste material (conductive resin material) in which a metal filler (metal particles) such as Ag or Cu is mixed into a resin material that serves as a binder. This allows the resin to contain a binder component suitable for bonding with the materials that constitute the insulating layer 4, the exterior body 10, and the support member 7, and is expected to form bonds through chemical bonds or hydrogen bonds.

[0062] Furthermore, it is desirable to set the surface roughness Ra of each of the anode-side end face 4a of the insulating layer 4, the anode-side end face 10a and cathode-side end face 10b of the exterior body 10, and the anode-side end face 7a and cathode-side end face 7b of the support member 7 to 5 micrometers or more. This increases the contact area between each end face and the anode-side electrode layer 12a or cathode-side electrode layer 12b, and also provides additional bonding strength due to the anchor effect.

[0063] [Method of manufacturing solid electrolytic capacitor 100] Next, a method for manufacturing solid electrolytic capacitor 100 of the present embodiment will be described with reference to Figures 2A to 2F. Figures 2A to 2F are cross-sectional views of a solid electrolytic capacitor in each step of the manufacturing method (in other words, a solid electrolytic capacitor in the middle of manufacturing).

[0064] <Lamination process> The first step, the lamination step, will be described with reference to FIG. 2A.

[0065] First, a plurality of capacitor elements 1 shown in Fig. 2A are prepared. Here, an example in which three capacitor elements 1 are stacked will be described.

[0066] Next, an appropriate amount of conductive material 8 is applied to the cathode side of support member 7, and an appropriate amount of anode part adhesive resin 17 is applied to the anode side. Then, the first capacitor element 1 is precisely placed on top of conductive material 8 and anode part adhesive resin 17 applied to support member 7.

[0067] Next, an appropriate amount of conductive material 8 is applied to the cathode side of the first capacitor element 1, and an appropriate amount of anode part adhesive resin 17 is applied to the anode side. Then, the second capacitor element 1 is precisely placed on the conductive material 8 and anode part adhesive resin 17 applied to the first capacitor element 1.

[0068] Next, an appropriate amount of conductive material 8 is applied to the cathode side of the second capacitor element 1, and an appropriate amount of anode part adhesive resin 17 is applied to the anode side. Then, a third capacitor element 1 is precisely placed on the conductive material 8 and anode part adhesive resin 17 applied to the second capacitor element 1.

[0069] For example, a thermosetting Ag paste can be used as the conductive material 8. Furthermore, for example, a dispensing method, printing, an inkjet method, a dipping method, or a transfer method can be used as a method for applying the conductive material 8. Furthermore, the conductive material 8 may be in the form of an adhesive sheet instead of a paste.

[0070] For example, a thermosetting adhesive resin can be used as anode part adhesive resin 17. Furthermore, a method for applying anode part adhesive resin 17 can be, for example, a dispensing method, printing, an inkjet method, a dipping method, or a transfer method. Furthermore, anode part adhesive resin 17 may also be in the form of an adhesive sheet that can be attached, rather than in the form of a paste.

[0071] Next, the conductive material 8 and the anode part adhesive resin 17 are thermally cured using a high-temperature furnace or the like to establish electrical continuity between the cathode bodies 6 of each capacitor element 1. Note that the means for thermal curing is not limited to a high-temperature furnace, and for example, a hot plate, a reflow furnace, or the like may also be used.

[0072] Through the lamination process described above, the solid electrolytic capacitor is in the state shown in FIG. 2A.

[0073] In the above explanation, an example was given in which three capacitor elements 1 are stacked sequentially at one location on the support member 7, but this stacking may also be performed simultaneously at multiple locations on the support member 7 (for example, in a matrix of multiple columns and rows).

[0074] <Sealing process> The sealing step, which is the step following the lamination step, will be described with reference to FIG. 2B.

[0075] As shown in FIG. 2B, the three stacked capacitor elements 1 are sealed with an exterior package 10 so as to cover them.

[0076] For example, an epoxy resin containing an inorganic filler such as silica is used as the exterior body 10. The exterior body 10 also fills the gaps between the stacked capacitor elements 1 and the gap between the support member 7 and the capacitor element 1. Examples of sealing methods that can be used include transfer sealing, compression sealing, and a method in which a liquid resin is poured into a mold and then thermally cured.

[0077] <Exposure process> The exposing step, which is the step following the sealing step, will be described with reference to FIG. 2C.

[0078] In order to expose the cathode terminal 8b and the anode terminal 9, the anode end surface 14 and the cathode end surface 15 are formed.

[0079] This formation method, for example, involves cutting by rotating a dicing blade with diamond particles fixed with a bonding material at high speed. Using this method, parts (both ends in the figure) of exterior body 10 and support member 7 shown in Figure 2B are cut away, forming anode end surface 14 and cathode end surface 15 as shown in Figure 2C.

[0080] At this point, the anode end surface 14 is mainly composed of the anode terminal portion 9, the anode-side end surface 4a of the insulating layer 4, the anode-side end surface 10a of the outer casing 10, and the anode-side end surface 7a of the support member 7. The porous layer of the anode-side end surface 4a is impregnated with insulating resin 16.

[0081] At this point, the cathode end surface 15 is mainly composed of the cathode terminal portion 8b, which is the cathode side end surface of the conductive material 8, the cathode side end surface 10b of the outer casing 10, and the cathode side end surface 7b of the support member 7.

[0082] <Contact layer formation process> The contact layer forming step, which is the step following the exposure step, will be described with reference to FIG. 2D.

[0083] 2D, each end face (anode-side end face 4a of insulating layer 4, anode-side end face 10a of package 10, and anode-side end face 7a of support member 7) that constitutes anode end face 14 is roughened. Also, as shown in FIG. 2D, a contact layer 11 is formed on the surface of each anode terminal portion 9.

[0084] This contact layer 11 is formed, for example, by colliding Cu particles at high speed with the anode terminal 9. Cu particles are a metal that has a lower ionization tendency than Al, which is the material of the anode terminal 9, and has an interatomic distance that is relatively close to that of Al.

[0085] The technique for forming this contact layer 11 is called the cold spray method, which uses compressed gas such as air, nitrogen, or helium to accelerate metal particles on the order of several micrometers to several tens of micrometers to subsonic or supersonic speeds, causing them to collide with a substrate in a solid state, forming a metal coating.

[0086] Although the mechanism of metal particle adhesion in cold spraying is not fully understood, it is generally believed that the collision energy of the metal particles causes plastic deformation of the metal particles or metal substrate, exposing a new surface on the metal surface, thereby activating it.

[0087] According to the cold spray method, Cu particles colliding with the anode terminal 9 at high speed break through the oxide film on the Al surface of the anode terminal 9. This forms a metallic bond between Al and Cu. Therefore, an alloy layer of Al and Cu is formed at the interface between the contact layer 11 and the anode terminal 9. Meanwhile, a layer of Cu, a non-valve metal, is formed on the surface of the contact layer 11. Therefore, the contact layer 11 contains a metal with a lower ionization tendency than the anode terminal 9.

[0088] Furthermore, the cold spray method generally uses particles on the order of several micrometers to several tens of micrometers in size. This is because, when particles are smaller than several micrometers, the energy (collision energy) required to collide with the substrate cannot be secured even when the particles are accelerated from subsonic to supersonic speeds. If the collision energy cannot be secured, a metallic bond between Al and Cu cannot be formed, and adhesion occurs due to the anchor effect. This results in a very weak bond strength.

[0089] The contact layer 11, formed using particles with sizes on the order of several μm to several tens of μm, has a thickness of several μm to several hundred μm. In the case of an aluminum capacitor, the thickness of the contact layer 11 is preferably 5 to 100 μm. If the thickness of the contact layer 11 is less than 5 μm, the strength decreases. On the other hand, if the thickness of the contact layer 11 is more than 100 μm, the resistance increases by the amount of the electrode thickness, causing degradation of the characteristics.

[0090] Furthermore, when the above-mentioned cold spray method is performed, the Cu particles also collide with each end surface made of a non-metallic material (the anode-side end surface 4a of the insulating layer 4, the anode-side end surface 10a of the outer casing 10, and the anode-side end surface 7a of the support member 7).

[0091] When the substrate (e.g., insulating layer 4, exterior body 10, support member 7) that the metal particles collide with is a resin substrate, it is believed that the bonding between the metal particles and the resin substrate is primarily a mechanical bonding, whereby the plastically deformed metal particles bite into the irregularities on the surface of the resin substrate. Therefore, in order to form a metal film on a resin substrate, it is necessary to provide the resin substrate with sufficient hardness so that the energy of the collision is efficiently used to plastically deform the metal particles, to select a metal material and processing conditions that are likely to cause plastic deformation of the metal particles, and to ensure that the resin substrate is not easily damaged by the energy of the collision.

[0092] Here, the epoxy resin commonly used as the outer casing 10 can be made more hard when viewed macroscopically by increasing the proportion of fillers such as silica mixed in, but the proportion of the epoxy resin component that acts as a binder decreases, making the resin more brittle.

[0093] That is, there are areas where the resin substrate does not break and the metal particles cause sufficient plastic deformation to form a metal film, and areas where the resin substrate breaks down due to the impact energy of the metal particles and is scraped off.

[0094] Therefore, in order to stably form a metal film having a thickness greater than a specified value over the entire surface, it becomes necessary to extend the film formation processing time or increase the amount of metal particles sprayed, which significantly reduces productivity.

[0095] Although it is possible to form a metal film over the entire surface, the thickness of the metal film formed on the anode terminal 9, which is made of aluminum, which is easy to form a film on, and on the exterior body 10, which is made of a material such as a resin base material, which is easily scraped, will differ greatly. This will affect the accuracy of the external shape of the solid electrolytic capacitor.

[0096] Furthermore, if the Young's modulus of the metal particles is smaller than that of the components constituting the resin substrate, the metal particles tend to undergo plastic deformation upon impact, which makes it easier for the metal particles to adhere to the resin substrate when a metal film is formed on the resin substrate.

[0097] On the other hand, if the metal particles are not to be completely fixed to the resin substrate, the basic conditions are to give the resin substrate elasticity so that the collision energy is not converted into the energy of plastic deformation, to reduce the strength of the resin substrate so that the substrate breaks at an impact lower than that which would cause plastic deformation, and to select a metal material and processing conditions that are less likely to cause plastic deformation within a range that allows the contact layer 11 to be formed on the anode terminal portion 9.

[0098] That is, by making the Young's modulus of the metal particles (which may also be referred to as the contact layer 11) larger than the Young's modulus of the material that constitutes the resin base material, it is possible to create a state in which the metal particles are less likely to stick together.

[0099] For example, if a resin substrate is filled with silica having a Young's modulus of 94 GPa, it is preferable to use metal particles (e.g., Cu or Ni) that have a Young's modulus equal to or greater than that and that are easily bonded to Al. However, this is not limiting, as the state of adhesion varies depending on the shape, size, and temperature of the metal particles, as well as the size and filling rate of the silica filled in the resin material.

[0100] Furthermore, when metal particles are not fixed to the resin substrate, the effect of roughening the surface can be obtained by colliding metal particles with the resin substrate.

[0101] Note that, although Figure 2D illustrates an example in which the end faces constituting cathode end face 15 (cathode terminal portion 8b, cathode-side end face 10b, and cathode-side end face 7b) have not been subjected to roughening treatment, the end faces constituting cathode end face 15 may be roughened by sandblasting or the like.

[0102] In the above description, the contact layer 11 is formed using a cold spray method, which is an example of a dry process. However, a wet process such as plating may also be used. When a wet process such as plating is used, problems arise, such as deterioration of characteristics due to the infiltration of plating solution between elements during the formation of the contact layer 11. In this embodiment, the porous layer on the anode-side end surface 4a is impregnated with insulating resin 16 to fill the gaps. Furthermore, by laminating anode part adhesive resin 17 between the elements of the anode part, the gaps between the elements can be filled, making it possible to prevent liquid from penetrating into the elements.

[0103] Furthermore, in the cold spray method, which is a dry process, large pressure is generated when metal particles are sprayed with high-pressure gas. However, in this embodiment, since the porous layer is impregnated with insulating resin 16, which is a low-elasticity resin, and anode adhesive resin 17 adheres tightly between the anode elements, disconnection of the capacitor elements can be prevented.

[0104] In addition, in this embodiment, since the insulating resin 16, which is a low-elasticity resin, is impregnated into the porous layer and the anode part adhesive resin 17 is in close contact with the spaces between the elements of the anode part, moisture generated in the first electrode formation process (formation of the anode-side electrode layer 12a and the cathode-side electrode layer 12b) and the second electrode formation process (formation of the anode-side external electrode 13a and the cathode-side external electrode 13b) can be prevented from penetrating between the elements.

[0105] <First electrode formation process> The first electrode forming step, which is the step subsequent to the contact layer forming step, will be described with reference to FIG. 2E.

[0106] 2E, an anode-side electrode layer 12a is formed on an anode end surface 14, and a cathode-side electrode layer 12b is formed on a cathode end surface 15. As a result, the anode body 2 is electrically connected to the anode-side electrode layer 12a, and the cathode body is electrically connected to the cathode-side electrode layer 12b.

[0107] Specifically, Ag paste is applied to each end surface by a dipping method, a transfer method, a printing method, a dispensing method, or the like, and then cured at a high temperature to form the anode side electrode layer 12a and the cathode side electrode layer 12b.

[0108] As described above, the anode-side electrode layer 12a and the cathode-side electrode layer 12b are electrically connected to the anode body 2 and the cathode body 6, respectively, and the electrode thicknesses of the electrode layers 12a and 12b directly affect the characteristic values.

[0109] For example, if the thickness of the anode-side electrode layer 12a is 300 μm or more, the resistance of the electrode itself increases, resulting in a lower performance evaluation. Conversely, if the thickness of the anode-side electrode layer 12a is 20 μm or less, the resistance of the electrode itself decreases, but the interfacial strength with the contact layer 11 decreases. Therefore, the thickness of the anode-side electrode layer 12a is preferably, for example, 20 to 300 μm.

[0110] The anode-side electrode layer 12a may cover a part of a surface (e.g., the upper surface of the package 10 or the lower surface of the support member 7) that is perpendicular to the anode end-face 14. Similarly, the cathode-side electrode layer 12b may cover a part of a surface (e.g., the upper surface of the package 10 or the lower surface of the support member 7) that is perpendicular to the cathode end-face 15.

[0111] <Second electrode formation process> The second electrode forming step, which is the step subsequent to the first electrode forming step, will be described with reference to FIG. 2F.

[0112] As shown in FIG. 2F, an anode-side external electrode 13a is formed on the outer surface of the anode-side electrode layer 12a, and a cathode-side external electrode 13b is formed on the outer surface of the cathode-side electrode layer 12b.

[0113] Specifically, the anode side external electrode 13a and the cathode side external electrode 13b are formed by barrel plating, which is one of the electrolytic plating methods. The anode side external electrode 13a and the cathode side external electrode 13b have a laminated structure of Ni and Sn.

[0114] The anode side external electrode 13a and the cathode side external electrode 13b may be formed as a structure containing Ag and Sn by the above-mentioned cold spray method, or may be formed by a combination of barrel plating and solder dipping.

[0115] Alternatively, the anode-side external electrode 13a and the cathode-side external electrode 13b may be formed by adhering a cap made of a Cu material previously coated with Sn to the anode-side electrode layer 12a and the cathode-side electrode layer 12b, which are made of Ag paste (which can function as an adhesive), respectively.

[0116] In this manner, the solid electrolytic capacitor 100 shown in FIGS. 1A to 1C is manufactured.

[0117] <Effects> The solid electrolytic capacitor 100 of this embodiment includes the contact layer 11 metallurgically bonded to the anode terminal 9 made of a valve metal foil, thereby ensuring a low-resistance current path from the anode-side external electrode 13a to the cathode-side external electrode 13b, thereby maintaining good electrical characteristics.

[0118] Furthermore, the anode end surface 14 and the cathode end surface 15 are bonded to the anode-side electrode layer 12a and the cathode-side electrode layer 12b, respectively, which are made of a conductive resin paste that has excellent bonding properties with resin substrates, thereby achieving strong bonding, thereby improving the reliability of the solid electrolytic capacitor 100.

[0119] Furthermore, if the contact layer 11 is formed only in the anode terminal 9, the time required for metal film formation can be significantly reduced. This significantly reduces the amount of metal particles consumed and shortens the process time. This improves the productivity of the solid electrolytic capacitor 100.

[0120] Furthermore, by roughening the end faces constituting the anode end face 14 (the anode-side end face 4 a of the insulating layer 4, the anode-side end face 10 a of the outer casing 10, and the anode-side end face 7 a of the support member 7) simultaneously with the formation of the contact layer 11, it is possible to further improve adhesion between the anode-side electrode layer 12 a and the cathode-side electrode layer 12 b without increasing the processing time, thereby achieving extremely high reliability.

[0121] Furthermore, when the cold spray method, which is a dry process, is used, a large pressure is generated when metal particles are sprayed with high-pressure gas, but because the porous layer is impregnated with insulating resin 16, which is a low-elasticity resin, and anode part adhesive resin 17 is tightly adhered (filled) between the elements in the anode part, disconnection of the capacitor elements can be prevented. Furthermore, moisture generated in the first electrode formation process (formation of anode-side electrode layer 12a and cathode-side electrode layer 12b) and the second electrode formation process (formation of anode-side external electrode 13a and cathode-side external electrode 13b) can be prevented from penetrating between the elements.

[0122] As described above, solid electrolytic capacitor 100 of the present embodiment can achieve improved reliability and productivity while maintaining good electrical characteristics.

[0123] The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure. [Industrial Applicability]

[0124] The solid electrolytic capacitor of the present disclosure has high reliability and productivity while maintaining good electrical properties, and can therefore be used as a capacitor in a wide range of fields, including electronic devices (e.g., personal computers, mobile terminals, etc.), industrial equipment, and automotive equipment. [Explanation of symbols]

[0125] 1 Capacitor element 2 anode body 3 Dielectric Layer 4. Insulation layer 4a Anode side end surface of insulating layer 4 5 Solid electrolyte layer 6 cathode body 7 Support member 7a Anode side end surface of support member 7 7b Cathode side end surface of support member 7 8 Conductive materials 8b Cathode terminal 9 Anode terminal section 10. Exterior body 10a: Anode side end surface of the exterior body 10 10b: cathode side end surface of the exterior body 10 11 Contact layer 12a Anode side electrode layer 12b Cathode side electrode layer 13a Anode side external electrode 13b Cathode side external electrode 14 Anode end surface 15 Cathode end surface 16 Insulating resin 17 Anode adhesive resin 18 Anode side insulating resin filling part 100 Solid electrolytic capacitor

Claims

1. A solid electrolytic capacitor in which a plurality of stacked capacitor elements are covered with an exterior body, The capacitor element is an anode body; a porous dielectric layer having a plurality of voids and provided on a surface of the anode body; a solid electrolyte layer provided on a portion of the surface of the dielectric layer; a cathode body provided on a surface of the solid electrolyte layer, a portion of the dielectric layer on the anode side where the solid electrolyte layer is not provided is formed as an insulating layer by filling the void with an insulating resin; an anode-side electrode layer is provided adjacent to the insulating layer of each capacitor element and the anode body of each capacitor element; Solid electrolytic capacitor.

2. an anode terminal portion which is an end of the anode body and an end of the insulating layer are exposed from an anode-side end surface of the exterior packaging; On the anode side end surface side, a contact layer metallurgically bonded to the anode terminal; the anode-side electrode layer covering the contact layer; an anode-side external electrode provided on a surface of the anode-side electrode layer, The solid electrolytic capacitor according to claim 1 .

3. the contact layer contains a metal having a lower ionization tendency than the anode body, The thickness of the contact layer is 5 to 100 μm. The solid electrolytic capacitor according to claim 2 .

4. On the cathode side end surface of the outer casing, a cathode-side electrode layer electrically connected to the cathode body; a cathode-side external electrode provided on a surface of the cathode-side electrode layer, The solid electrolytic capacitor according to claim 1 .

5. a filling rate of the insulating resin with respect to the plurality of voids included in the insulating layer is 50% or more; The solid electrolytic capacitor according to claim 1 .

6. The insulating resin has a glass transition temperature of 150°C or higher. The solid electrolytic capacitor according to claim 1 .

7. The insulating resin has an elastic modulus of 3 GPa to 7 GPa or more. The solid electrolytic capacitor according to claim 1 .

8. the anode layer is made of a conductive resin material containing metal particles mixed in a resin material, The thickness of the anode side electrode layer is 20 to 300 μm. The solid electrolytic capacitor according to claim 2 .

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