Capacitor

Abstract

To provide an electrical capacitor that uses polyamideimide as a capacitor material having excellent temperature stability as well as a high or customized dielectric constant.SOLUTION: A capacitor (1) has a single dielectric layer (2) that is free of solid inorganic materials, the dielectric layer (2) includes polyamideimide, and a first electrode (3) disposed directly adjacent to the dielectric layer (2).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electric capacitor.

Background Art

[0002] Polymer dielectrics are applied to various uses in power electronics applications, particularly in passive elements such as electric capacitors, for example.

[0003] As a capacitor dielectric, for example, a dielectric film containing polyimide, such as the polyetherimide of Patent Document 1, has already been proposed.

[0004] Polyamideimide has hitherto been known particularly through use as a heat-resistant coating for enameled wires and the like.

[0005] Regarding capacitor applications, they have hitherto been proposed first in relation to inorganic components as dielectric layers.

[0006] Patent Document 2 discloses that polyamideimide can be a component of a matrix for inorganic particles in a capacitor dielectric.

[0007] Patent Document 3 discloses that polyamideimide can be used in a capacitor having a non-uniform dielectric layer composed of an organic polymer material as a first dielectric layer and an inorganic material as a second dielectric layer.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] However, it has not been known heretofore to use polyamideimide as a capacitor material having excellent temperature stability and at the same time a high or customized dielectric constant.

MEANS FOR SOLVING THE PROBLEMS

[0010] According to a first aspect, a capacitor having a single dielectric layer is presented. In this case, the dielectric layer contains polyamideimide, and at least one first electrode is disposed directly adjacent to the dielectric layer.

[0011] The directly adjacent electrode can be placed on the layer. Preferably, the direct contact exists at the molecular level so that it can be achieved by the coating method described below.

[0012] The second electrode is preferably also part of the capacitor. Optionally or according to technical requirements, it is also preferred that the second electrode is disposed directly adjacent to the dielectric layer. In this case, the dielectric layer is sandwiched by the first and second electrodes.

[0013] The single dielectric layer can be, for example, homogeneous and contain polyamideimide. Homogeneous here can particularly mean that the dielectric layer does not contain additives that would make the layer inhomogeneous. In particular, it is preferred that no micro materials or nano materials or additional other solids are contained in the dielectric layer. The dielectric layer preferably does not contain a hybrid material. Since the electrodes are disposed directly adjacent to the single dielectric layer, there is no further layer, for example, different from the single dielectric layer, between the single dielectric layer and the electrodes.

[0014] A single dielectric layer containing polyamideimide has the advantage of having temperature stability up to approximately 300 °C compared to other polymer-based dielectric layers. Furthermore, a dielectric layer containing polyamideimide can have a high dielectric constant over a wide input frequency range. In that case, preferably, a high breakdown voltage is also maintained.

[0015] Therefore, polyamideimide as a polymer material for a dielectric layer in capacitor applications can simultaneously satisfy two conflicting requirements: high temperature stability and customized or stable dielectric properties.

[0016] Therefore, a single dielectric containing polyamideimide can be a substitute for biaxially oriented polypropylene (BOPP), one of the most widely used materials for capacitor dielectrics. This can be advantageous because BOPP, which has a normal operating temperature of up to 105 °C and a low dielectric constant in the region of 2.2, has reached its performance limits for current development, particularly with regard to temperature stability while simultaneously maintaining electrical or electronic parameters.

[0017] Therefore, a polyamideimide-containing dielectric layer according to the present invention can have higher temperature stability up to 150 °C. Furthermore, a dielectric constant almost twice that of BOPP can be achieved even at higher temperatures.

[0018] Therefore, it may even meet the requirements for future applications such as those in aerospace engineering, in which case operating temperatures exceeding 150 °C and, in some cases, exceeding 200 °C may be achieved.

[0019] According to a preferred embodiment of the capacitor, the dielectric layer consists of at least 50% by weight of polyamideimide.

[0020] Such a high polyamideimide content in a single dielectric layer can ensure that the excellent dielectric properties of polyamideimide prevail over any other possible components.

[0021] Preferably, the dielectric layer has a weight ratio of polyamideimide of 90% or more, and more preferably, the dielectric layer consists only of polyamideimide.

[0022] The inventors recognized that polyamideimide can be easily chemically functionalized. Therefore, it can be flexibly customized in its properties to excellent electrical or electronic properties that should be satisfied according to the application by, for example, only organic components. Therefore, the capacitor is preferably manufactured such that the dielectric layer, which is preferably a single dielectric layer, does not contain additional materials of solids such as inorganic materials. The dielectric layer is preferably not a hybrid material.

[0023] A dielectric layer that does not contain inorganic materials may be easier to manufacture than a mixed layer composed of an inorganic-organic hybrid material.

[0024] Preferably, the dielectric layer of the capacitor contains a polyamideimide main chain containing amide groups and imide groups of polyamideimide.

[0025] This means, in particular, that the main chain of the polyamideimide polymer is formed only via amide bonds or imide bonds. This does not exclude that further chemical functional groups can be bonded to the main chain or within the main chain.

[0026] The polyamideimide compound or the chemical bonds contained therein are stable at high temperatures, which is an advantage for the dielectric layer used under high temperature conditions.

[0027] As a more preferred embodiment, the polyamideimide main chains contained in the dielectric layer can be chemically crosslinked to each other, that is, they can have crosslinks.

[0028] By a customized number of crosslinks, the mechanical and electronic properties of polyamideimide, and in particular the temperature properties, can be adjusted as desired.

[0029] In principle, the term "crosslink" in the context of this application includes any kind of covalent chemical bond existing between polyamide-imide main chains or between different points on a polyamide-imide main chain. A crosslink is a chemical bond formed in addition to the chemical bond between repeating units of the polyamide-imide main chain. In this case, preferably, the number of crosslinks is selected such that a thermoplastic polyamide-imide is formed.

[0030] Preferably, the crosslink includes a linear bond that connects the terminal units of one polyamide-imide main chain to the terminal units of another polyamide-imide main chain, thereby generating a chain connection in series. Preferably, the linear bond between the main chains is different from the bond type inside the polyamide-imide main chain. That is, the crosslink preferably does not have an amide-imide motif. However, the crosslink can be an amide bond or an imide bond. In that case, such a bond can interrupt the repeating motif of the polyamide-imide motif repeated within the polyamide-imide main chain. A plurality of polyamide-imide main chains can be linearly connected in series.

[0031] The number of crosslinks can be controlled by the annealing temperature. The higher this is, the more polyamide-imide main chains are connected to each other in series. Thus, the polymer chains become longer as the annealing temperature rises. Thereby, the mechanical stability of the dielectric layer can be enhanced. Furthermore, the dissipation factor can be reduced. This method of controlling the degree of crosslinking by temperature is particularly preferable for linear bonds.

[0032] Preferably, the chemical crosslink is formed via a urethane crosslink.

[0033] The urethane crosslink can preferably be formed via isocyanate groups on the main chain, and the isocyanate groups react with hydroxyl groups on other main chains to form urethane bonds.

[0034] The lactam can also be present as a functional group in the starting material. This is because the lactam functions as a protecting group for controlling the reaction between the isocyanate group and the hydroxyl group. Such a lactam is ring-opened, for example, by the action of temperature to form an isocyanate group, and then this isocyanate group reacts with, for example, the hydroxyl group of another main chain. That is, in the starting material, an isocyanate group and / or a lactam functional group may be present. However, preferably, only lactam is present in the starting material. This is because very long durability can be achieved even at room temperature. Furthermore, for example, the applicable dropping time during the production of the dielectric layer can also be extended.

[0035] Instead of or in addition to other crosslinks such as urethane crosslinks, preferably, imide crosslinks can be formed between the polyamideimide main chains.

[0036] The imide crosslink can be formed by reacting, for example, an anhydride group with a suitable group such as an amine on another polyamideimide main chain to form an imide so as to form an imide crosslink as a crosslink between two polyamideimide main chains. Preferably, the anhydride group is a phthalic anhydride group. By such a reaction, a bond can also be formed between different points of the polyamideimide main chain.

[0037] Both urethane crosslinks and imide crosslinks are particularly suitable for the technically simple formation of linear bonds. Furthermore, the degree of the linear bond with these groups can be adjusted particularly accurately by controlling the annealing temperature.

[0038] Furthermore, crosslinking can also be formed via urea crosslinking. This can be formed under the involvement of amine groups on the polyamideimide main chain. When a three-dimensional crosslinking is formed thereby, that is, when a linear bond is formed not exclusively but by this bonding motif, it is particularly preferred. Even more preferably, only such crosslinking that is not a linear bond can be formed via urea crosslinking. Particularly preferably, these can coexist with linear bonds. For example, a three-dimensionally crosslinked polymer material via urea crosslinking, or a polymer material linearly crosslinked via imide crosslinking or urethane crosslinking, can be formed or can be formed for the dielectric layer.

[0039] In principle, urethane crosslinking can exist in addition to imide crosslinking. However, it is preferred that there is only one linear bonding motif. This is because it facilitates process control.

[0040] Examples of suitable starting materials are, for example, the commercially available RESISTHERN® AI 336 L.

[0041] As an example of such a starting material, a polyamideimide resin solution can be used, which can also be used, inter alia, for the insulating coating of wires or electrodes. An example of such a polyamideimide resin solution is, for example, the commercially available RESISTHERN® AI 336 L.

[0042] As a further preferred embodiment of a single dielectric layer of a capacitor, the dielectric layer can be formed such that the polyamideimide main chain is partially aromatic.

[0043] The partially aromatic polyamideimide main chain particularly contributes to a well-balanced relationship between flexibility and temperature stability. Thus, a fully aromatic polyamideimide main chain may be too hard. However, partial aromaticity, that is, for example, the aromaticity of the imide component, can provide the necessary temperature stability simultaneously with flexibility.

[0044] According to a preferred embodiment, the polyamideimide can contain a phenylene group and / or a furan group as a functional group.

[0045] For example, the introduction of a phenylene group in the polyamideimide main chain can be related to obtaining the necessary flexibility of the main chain. For example, depending on the selection from one or more different phenylene groups within the main chain, the length and flexibility of the repeating unit are adapted. For example, biphenyl, diphenylmethane and triphenylmethane, orthodibenzylbenzene and paradibenzylbenzene or tribenzylbenzene can be used as possible phenylene groups. In principle, within the polyamideimide main chain, a plurality of different ones of these or other phenylene groups can be present. That is, it is possible for various phenylene groups to be present within the polyamideimide main chain. However, in many cases, only one type of phenylene group is present within the main chain.

[0046] Since furan itself has a high polarity, by selecting different furans, the polarity of the dielectric layer can be adjusted. For example, for this purpose, benzofuran, dibenzofuran, furanone or hydroxyfuranone are used. For example, hydroxyfuranone or other furan derivatives can have one or more hydroxyl groups required as a reaction partner for forming a urethane crosslink via an isocyanate group that can be formed from, for example, a lactam group for crosslinking.

[0047] According to another preferred embodiment, the polyamideimide can have a structure according to Chemical Formula (Chemical Formula 1), where R 1 is an unreacted group such as a lactam, anhydride or amine, or a urethane crosslink or an imide crosslink. Preferably, R 1 is a urethane crosslink or an imide crosslink. Here, R 2 is a phenylene group, and R 3 can be furan. Alternatively, R 3can be a urethane crosslink or an imide crosslink. In this case, the polyamide-imide main chain is bonded to two other polyamide-imide main chains at both ends.

[0048] [Chemical formula]

[0049] In principle, lactam is, as already described above, for example, a preferred group bonded to the end as R in the polymer chain in the starting material. Through the isocyanate group formed from lactam, in principle, crosslinking to other polyamide-imide main chains, for example, in the form of a urethane crosslink, can be formed. Lactam can be, for example, β, γ, δ or ε lactam. Among these, the preferred ones are particularly δ and ε lactam. 1

[0050] The urethane crosslink can be formed with the hydroxyl group from the lactam at the end and the furan at the end in the starting material, whereby the main chains are connected in series and thus extended. By this reaction, the main chain can be crosslinked so that the formed polyamide-imide layer has thermoplastic properties. In that case, the number of crosslinks is adjusted so that the dielectric layer of the capacitor does not become too hard and brittle.

[0051] As described above, the linearly bonded imide crosslink can be formed via an anhydride such as phthalic anhydride that reacts with an amine. Alternatively, the isocyanate group reacts with the anhydride group to form an imide, with CO2 being separated in the process.

[0052] In the starting material, that is, before the crosslink containing a linear bond is generated, the functional groups suitable for the corresponding bond are at the position of R 3 or R 1 in the chemical formula (Chemical formula 1).

[0053] In a preferred embodiment of the capacitor, a number of first electrode layers are alternately laminated with a second electrode layer. A dielectric layer is disposed between each two adjacent electrode layers.

[0054] That is, the capacitor can be a multilayer capacitor.

[0055] Alternatively, the multilayer capacitor can be cut from, for example, a coil. In this case, a conductive or preferably metallic structured layer can be used as the electrode, and the layer has at least two electrically separated regions and thus functions as a capacitor electrode.

[0056] According to a further preferred aspect, all of the first electrode layers can be conductively connected to a first external contact, and all of the second electrode layers can be conductively connected to a second external contact.

[0057] The external contacts can be applied by flame spraying, a PVD process or other methods.

[0058] A multilayer capacitor having corresponding external contacts enables use in various technical applications.

[0059] According to a further embodiment, the substrate can be disposed on a side surface of the capacitor that is parallel to the plane of the electrode layer.

[0060] As described above, such a substrate can be conductive, that is, it can also perform an electrode function, but it can also have an insulating effect and remain on the component after the manufacturing process.

[0061] In particular, the capacitor as described above can be a surface mount device (SMD).

[0062] Furthermore, the capacitor can also be a through-hole capacitor (Durchsteckkondensator), i.e., it has wires for through-hole mounting. Using these wires, the capacitor can be attached to the external contacts both electrically and mechanically.

[0063] The capacitor may also be a wound capacitor. In particular, in this case, the capacitor can have only a single metallization as the electrode in direct contact with the dielectric layer. A structure having two electrodes in direct contact with the dielectric layer is also possible.

[0064] As a further aspect of the present invention, a method for manufacturing a capacitor is presented, including the manufacture of the dielectric layer. The dielectric layer is manufactured by applying a prepolymer-polyamideimide solution onto the deposition surface, subsequently drying the prepolymer-polyamideimide solution on the deposition surface, and annealing the dried prepolymer-polyamideimide solution.

[0065] The deposition surface can be the surface of an electrode or an electrode layer. The deposition surface may also be the surface of a substrate. The substrate may be the substrate of the completed capacitor, or it may be just an intermediate carrier from which the applied and optionally crosslinked polyamideimide film is peeled off again.

[0066] By this method, the above-described capacitor can be manufactured.

[0067] In this way, a single dielectric layer can also be manufactured. The prepolymer-polyamideimide solution can in particular be a solution of RESISTHERN® AI 336 L dissolved in a resin, for example, which is also suitable as an insulating coating, in an organic solvent.

[0068] Polyamideimides are basically soluble in many solvents and can be applied in various concentrations to form closed layers or films. Therefore, they are particularly suitable for the flexible use of a variety of deposition methods or various layer thicknesses, as will be described in more detail below.

[0069] When the prepolymer polyamideimide solution is dried, most or all of the solvent can be removed.

[0070] When the dried prepolymer polyamideimide solution is annealed, the material becomes denser, and crosslinking via, for example, lactam can be used within the layer thus formed.

[0071] The rate of the crosslinking reaction can be determined by the annealing temperature.

[0072] Preferably, the degree of crosslinking is determined by the number of linker groups (e.g., isocyanate groups protected by lactam) on the polyamideimide backbone in the prepolymer polyamideimide solution, and the annealing temperature is selected such that all linker groups form crosslinks.

[0073] In a preferred case, the linker groups are arranged at the ends of the polyamideimide backbone. Basically, however, especially in this case, the degree of crosslinking can be affected or adjusted by the annealing temperature. The higher the annealing temperature selected, the more crosslinks are formed within a given time. Thereby, more polyamideimide backbones can be bonded together.

[0074] As a further aspect, the method can be modified as described above, where the deposition surface is the surface of the substrate, the dielectric layer is peeled off from the deposition surface after its manufacture to produce a dielectric film, the dielectric film is metallized, and finally the metallized dielectric film is wound.

[0075] Therefore, the method described above can be used to manufacture a wound capacitor. This has the advantage that the dielectric layer or film thus formed, which is provided with the first and second electrodes by metallization, can be further processed even before metallization. For example, methods such as foil stretching can be applied to optimize the material properties.

[0076] According to a further aspect, the manufacture of the capacitor can include the following: a conductive substrate, or alternatively a substrate on which a first electrode layer is formed, is used. Thus, the deposition surface can be the surface of the conductive substrate or the first electrode layer. After applying the dielectric layer on the deposition surface, a second electrode layer can be formed on the dielectric layer, and a prepolymer polyamide-imide solution can be applied on the second electrode layer, dried, and subsequently annealed to form a further dielectric layer on this second electrode layer.

[0077] In the case of a conductive substrate, this substrate can function as an electrode, for example as the first electrode. A second electrode layer can be applied above this. In this case, of course, in order to obtain a multilayer capacitor, a further dielectric layer and subsequently a first electrode layer can be applied again on the second electrode layer.

[0078] Alternatively, as described above, the substrate can be, for example, non-conductive, i.e., electrically insulating. In that case, an electrode layer is first applied before further layers are applied or arranged above the substrate. In either case, it is a method for constructing a stacked multilayer capacitor from a solution, in contrast to a wound capacitor or a multilayer capacitor cut out from a wound body.

[0079] It is preferred for the above-described method that the prepolymer polyamide-imide solution contains a polyamide-imide main chain in which isocyanate groups and / or more preferably isocyanate groups protected as lactam groups are arranged in the polyamide-imide main chain.

[0080] These have the advantages described above.

[0081] Preferably, the method can be carried out such that the prepolymer polyamide-imide solution is applied by doctor blade, spin coating, nozzle coating (slot die coating) or spray coating.

[0082] In the following, the present invention will be described in detail with respect to exemplary embodiments. These exemplary embodiments are shown in the following drawings, which are not to scale. Therefore, lengths and relative and absolute dimensions cannot be read from the drawings. The present invention is also not limited to the following description.

Brief Description of the Drawings

[0083]

Figure 1

Figure 2a

Figure 2b

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0084] Figure 1 shows a first embodiment of a capacitor in a schematic cross-sectional view. The capacitor 1 comprises an organic dielectric layer 2. The dielectric layer 2 is a single layer. This means that it consists of a single material and does not contain any volume regions separable from one another. It is therefore not a composite material. The dielectric layer 2 consists of at least 50% by weight of polyamideimide. Preferably, the polyamideimide content is higher, for example more than 90%. More preferably, the dielectric layer 2 consists exclusively of polyamideimide.

[0085] The polyamideimide can be any polyamideimide, in particular a partially aromatic polyamideimide, with polyamideimides conforming to the structural formula (Formula 2) being particularly preferred.

[0086] [ka]

[0087] The polyamideimide according to the structural formula (Chemical Formula 2) has a polyamideimide main chain and can have multiple functional groups. For example, the polyamideimide main chain can have R 2 The phenylene group may be included as the aryl group. The flexibility of the polyamideimide main chain can be adjusted by the phenylene group. For example, biphenyl, diphenylmethane, triphenylmethane, ortho-dibenzylbenzene, para-dibenzylbenzene, or tribenzylbenzene may be used.

[0088] Furthermore, furans can be used, especially at the terminal end, e.g., R 3 As such, it can be arranged on the polyamideimide main chain. Therefore, the polarity of the dielectric layer can be adjusted by its polarity. For example, benzofuran, dibenzofuran, furanone, or hydroxyfuranone can be used as the furan.

[0089] Alternatively, the anhydride can be 3 It can be used as.

[0090] Furthermore, preferably, crosslinking exists between various polyamideimide main chains in the dielectric layer 2.

[0091] Preferably, the polyamideimide main chains are bonded to each other via urethane crosslinking and / or imides. These bonds can be present at the ends, for example, at the positions of the R residues in Structural Formula (Chemical Formula 2). Instead, uncrosslinked groups, such as lactam isocyanates or anhydrides, can also be present at the R positions. 1 As an alternative, instead of this, uncrosslinked groups, such as lactam isocyanates or anhydrides, can also be present at the R positions. 1 positions.

[0092] Preferably, the dielectric layer 2 is produced from a polyamideimide resin mixture suitable for coating wires, for example, from the RESISTHERN® AI 336 L solution.

[0093] Above and below the dielectric layer 2, a first electrode 3 and a second electrode 4 are arranged. The first electrode 3, the dielectric layer 2, and the second electrode 4 can all be formed flat.

[0094] The preferred lamination is carried out over the largest surface of the flatly formed layer.

[0095] The layer thickness of the electrode can be, for example, 10 to 50 nm, preferably 20 nm. Depending on the manufacturing method, the layer thickness of the dielectric layer 2 can be set in the range of 500 nm to 10 μm.

[0096] The electrode can be made of aluminum or silver, or preferably of an aluminum - zinc alloy. Alternatively, the electrode can be a multilayer electrode made of chromium / aluminum, chromium / silver, or chromium / nickel / aluminum, or chromium / nickel / silver. In addition to the elements shown here, a protective layer made of a hydrocarbon compound, such as parylene or fluorinated hydrocarbons, may be applied on the side surface of the capacitor without an electrode (not shown).

[0097] As an alternative example not shown, only one electrode may be in contact with the dielectric layer.

[0098] The first embodiment of the capacitor shown in FIG. 1 can be manufactured by any arbitrary method. Preferably, it is manufactured by a solvent-based process. For example, first, the first electrode 3 can be formed on a substrate. The substrate can be a rigid substrate such as, for example, a glass or semiconductor wafer. It can be a metal film such as, for example, aluminum or copper, or a flexible polymer film such as, for example, polyimide or a release tape. On the surface of the substrate, the first electrode is applied by physical vapor deposition (physical vapor growth, PVD) such as, for example, sputtering or thermal evaporation.

[0099] Here, on the surface of the electrode 3 as the deposition surface, a dielectric layer 2 made of a prepolymer-polyamideimide solution can be applied. The prepolymer-polyamideimide solution preferably contains polyamideimide that is mostly uncrosslinked.

[0100] The prepolymer-polyamideimide solution is prepared by further diluting a commercially available polyamideimide resin mixture (for example, RESISTHERN® AI 336) with a solvent.

[0101] The polyamideimide resin mixture contains about 36% non-volatile substances (mainly polyamideimide main chain) in a solution of N-methylpyrrolidone (NMP) and xylene. It has an initial viscosity of 4750 ± 1750 mPa·s. Further, it has a density of about 1.1 g / ml.

[0102] The polyamideimide solution thus provided is adjusted to a concentration of 20% or less of the initial polyamideimide concentration using xylene or N-methylpyrrolidone. For example, a polyamideimide concentration of 19% by mass or 15% by mass is produced for the initial polyamideimide resin mixture in xylene.

[0103] The concentration used depends on the layer thickness to be achieved or the type of deposition method used.

[0104] Here, the prepolymer-polyamideimide solution thus produced is applied onto the surface of the first electrode 3 as the deposition surface. The application can be carried out by doctor blade, screen printing, spin coating or spray coating. The coating method depends on the thickness of the dielectric layer 2 to be achieved. For example, a relatively thick layer in the range of particularly 500 nm to 5 μm can be applied by spin coating or spray coating, or a relatively thick layer in the range of, for example, 1 μm to 10 μm can be applied by doctor blade or screen printing, respectively.

[0105] The solution thus applied is dried at a temperature of 60 to 100°C, preferably 80°C. Subsequently, the dried film is annealed at a temperature exceeding 200°C, preferably 250°C.

[0106] During drying, most of the solvent is removed. The other part of the volatile substances is removed by annealing. Furthermore, crosslinking between the main chains can be used during annealing. At a temperature of 250°C, almost complete crosslinking can be achieved in 5 to 10 minutes. Here, preferably, the isocyanate groups protected as lactam are activated, which subsequently react with existing hydroxyl groups or anhydrides present, for example, on furan residues.

[0107] After cooling, the second electrode 4 can be applied again by PVD onto the dielectric layer thus prepared.

[0108] Finally, the substrate can be removed to obtain the article of FIG. 1. However, basically, it can also remain on the capacitor.

[0109] Figure 2a shows the thermogravimetric analysis (TGA) of the polyamide-imide resin mixture used. The temperature gradient is constant at 10 K / min. As shown by the graph in Figure 2a, no mass loss occurs up to a temperature of about 275°C. Only at temperatures above about 300°C does a mass loss of less than 5% occur for the first time. Only when the temperature exceeds 400°C does the mass loss exceed 5%.

[0110] This demonstrates the extremely high temperature stability of polyamide-imide as a dielectric. In particular, long-term temperature stability above 200°C can be expected for future applications.

[0111] This allows, in particular, the finished capacitor to be mounted, for example by soldering, without assuming degradation of the components or the dielectric layer.

[0112] Further advantageous properties of polyamide-imide as a dielectric for capacitors are shown in Tables 1 and 2 below and the graph in Figure 2b.

[0113] Table 1 shows the dissipation factor (tanδ) of a polyamide-imide flat capacitor similar to the structure described in Figure 1. The dielectric layer measured here was measured from the above polyamide-imide resin mixture diluted to a mass fraction of 15% with respect to an initial mixture with xylene as a solvent (squeegee speed 50 mm / s). The layer thickness was 3 μm and the area of the capacitor was 50 mm 2 . The measurements were carried out using a Keysight E4990A with a PHECOS cooling / heating system from Novocontrol.

[0114]

Table 1

[0115] As shown in Table 1, the dissipation factor is always less than 2% in the tested frequency range and temperature range. Notably, the dissipation factor even improves slightly with increasing temperature. This indicates that polyamide-imide as a dielectric has excellent dielectric properties.

[0116] This can also be confirmed from the graph shown in FIG. 2b, which shows the dissipation factor of the dielectric layer described with reference to Table 1 at a constant temperature of 150° C. as a function of frequency. Therefore, it can be seen that the dissipation factor in the tested frequency range of 1 kHz to 1 MHz can be regarded as constant in a first approximation.

[0117] This constant behavior generally enables the wide use of polyamideimide capacitors and in particular enables the high flexibility of individual polyamideimide capacitors.

[0118] Table 2 shows the dependence of the dielectric constant (ε r ) of a polyamideimide flat capacitor corresponding to the structure according to FIG. 1 on temperature and electrical frequency. The dielectric layer used here was manufactured using a 19 wt % solution with respect to the initially used polyamideimide resin mixture. The layer thickness was 5 μm and the capacitor area was 50 mm 2 . The measurements were carried out using a Keysight E4990A with a Novocontrol PHECOS cooling / heating system.

[0119]

Table 2

[0120] Table 2 shows that there are only slight variations in the dielectric constant with respect to temperature and frequency. Basically, a decrease in the dielectric constant with increasing frequency or an increase in the dielectric constant with increasing temperature can be seen, but polyamideimide with an average dielectric constant of 4 has a dielectric constant almost twice that of the standard material BOPP.

[0121] This high dielectric constant is due to the semi-aromatic character of the polyamide-imide and polar groups such as, for example, furan groups. Furthermore, it is basically possible to adjust the polyamide-imide so that the dielectric loss or other properties are optimized in a specific frequency range. This can be done either by the composition of the prepolymer-polyamide-imide solution consisting of various polyamide-imides or by a special selection of the functional groups on the main chain.

[0122] In the flat capacitor described in Table 2, the breakdown voltage at room temperature is 300 - 550 V / μm depending on the frequency (measured with Sefelec S50). The insulation resistance at room temperature always exceeds 3 TΩ (measured with Novocontrol system Alpha A).

[0123] This shows that the polyamide-imide used has excellent dielectric constant along with high breakdown voltage and ohmic insulation resistance.

[0124] Figure 3 shows a second embodiment of capacitor 1 in a schematic cross-sectional view. Capacitor 1 has a number of first electrodes 3 laminated alternately with a second electrode 4. The two electrodes are flat electrodes.

[0125] Between the first electrode 3 and the second electrode 4, that is, between two adjacent electrodes respectively, there is always one dielectric layer 2 arranged, which corresponds to the dielectric layer 2 of the first embodiment in FIG. 1 respectively.

[0126] The first electrode 3 and the second electrode 4 have the nature of internal electrodes.

[0127] Therefore, the second embodiment of capacitor 1 is a multilayer capacitor.

[0128] On the opposite sides of the multilayer capacitor, a first external contact 5 and a second external contact 6 are arranged.

[0129] The first electrode 3 is conductively connected to the first external contact 5. The second electrode 4 is conductively connected to the second external contact 6.

[0130] The capacitor assembled in this way can be a surface mount device (SMD), which is very suitable for soldering because of its temperature-stable dielectric layer 2. In order to make the capacitor 1 more advantageously usable as an SMD capacitor, the external contacts 5 and 6 can be configured in a clamp shape. That is, the external contacts 5 and 6 can extend slightly in the stacking direction on both sides.

[0131] The capacitor can be, for example, cuboid-shaped and can have a total of 1000 or more repeating units, including the first electrode, the dielectric layer, the second electrode, and a further dielectric layer. It can have a length of 3 to 4 mm, a width of 2 to 3 mm, and a height of 1 to 2 mm. Each dielectric layer 2 can here have a thickness of 500 nm to 5 μm, preferably 500 nm to 2 μm. The internal electrodes have a thickness of 10 to 50 nm, preferably 20 nm.

[0132] However, the dimensions of the completed capacitor may be different from those presented here. The length, width, height, and layer thickness can be adapted to various technical requirements or various technical tasks.

[0133] The manufacturing method can be the same as the manufacturing method of the first embodiment. For example, on a substrate, for example, the first electrode layer 3 can be applied by PVD. Subsequently, the dielectric layer 2 can be applied from a solution, and subsequently, the second electrode layer 4 can be applied again by PVD. On this, the dielectric layer 2 is again applied from a solution. This can be repeated to achieve the desired number of layers or a specific capacitance of the capacitor.

[0134] In principle, in the method, the internal electrodes can be structured. This can be done already during deposition or after physical vapor deposition.

[0135] After lamination, the substrate can be removed.

[0136] Optionally, subsequently, a protective layer (not shown) similar to that of the first embodiment can be applied on the side where there are no external contacts by a vapor deposition process and a solvent-based process, or a coating process.

[0137] External contacts 5 and 6 are attached onto the completed capacitor 1. These can be made of, for example, brass, copper, tin, aluminum, silver, etc., and can be applied by either a physical vapor deposition process or other, for example, solvent-based processes.

[0138] FIG. 4 is a schematic cross-sectional view showing a third embodiment of capacitor 1, which is also a multilayer capacitor.

[0139] Capacitor 1 in FIG. 4 mostly corresponds to the capacitor shown and described in FIG. 3. However, in the example shown in FIG. 4, the original substrate, which is substrate 7 here, still exists on the component.

[0140] Substrate 7 is insulating in the case of FIG. 4 and can be, for example, a glass substrate, a semiconductor wafer, or a flexible substrate such as a polyimide film or a release tape.

[0141] The manufacturing method of the third embodiment in FIG. 4 corresponds to the manufacturing method of the second embodiment in FIG. 3, except for the removal of the substrate.

[0142] FIG. 5 shows a fourth embodiment of capacitor 1 (here a multilayer capacitor) in a schematic cross-sectional view. The fourth embodiment shown in FIG. 5 is mostly similar to that of FIG. 4.

[0143] However, here, the substrate 7 is a conductive substrate made of a metal such as aluminum, copper, or a similar material. It exists, for example, as a film. Due to its conductivity, there is no need to provide a conductive layer as the first electrode 3 on the substrate. The substrate 7 itself can function as an alternative to one of the first electrodes 3. On this, the dielectric layer 2 is then directly applied.

[0144] Since the substrate preferably extends across the entire width and length of the capacitor, care must be taken so that the second external contact 5 does not come into electrical contact with the substrate.

[0145] The method is also similar to the embodiment described in FIG. 4.

[0146] The fifth embodiment schematically shown in cross-section in FIG. 6 is similar to the second embodiment of the capacitor 1 in almost all respects. That is, it is also a multilayer capacitor. However, this multilayer capacitor has wires 8 and 9 at its external contacts 5 and 6, which, in one application, enable attachment in a through-hole mounting. That is, it is a through-hole capacitor. The wires 8 and 9 create electrical and in most cases mechanical contact with the connection site in one application. The wires 8 and 9 can be fixed to the capacitor 1 by any method such as bonding, for example.

[0147] FIG. 7 shows, in a schematic cross-section, a sixth embodiment of the capacitor 1. Here, it is a wound capacitor. In its structure, the wound capacitor is similar to the first embodiment, that is, the dielectric layer 2 is sandwiched by the first electrode 3 and the second electrode 4. The corresponding sandwich-like structure is wound to form the wound capacitor.

[0148] However, the manufacturing method used is different from the manufacturing method corresponding to FIG. 1. Therefore, preferably, on the substrate, the dielectric film 2 is first formed by the deposition method described with respect to FIG. 1. This can then be peeled off from the substrate. It can then be post-processed by any method. Subsequently, the film thus obtained can be metallized by PVD on one side or, in this case, on both sides. The metallized film thus obtained can be wound into a wound capacitor. The preferred layer thickness of the wound capacitor film having polyamideimide is in the range of 1 μm to 10 μm, preferably 2 μm to 5 μm.

[0149] As an additional or alternative method for manufacturing various structures, first, the formation of a polyamideimide film for dielectrics in a roll-to-roll process from a solution is carried out by a doctor blade of a prepolymer-polyamideimide solution onto a substrate previously provided with a release agent. Subsequently, drying and, simultaneously, annealing at temperatures above 200 °C, preferably above 220 °C, and optimally at 250 °C are carried out. Thereafter, peeling of the dried and crosslinked polyamideimide film from the substrate and its winding follow. Optionally, an intermediate film as protection can be wound together. Subsequently, the application of the electrodes is carried out. This is preferably also carried out in a roll-to-roll process. The electrode layer can here be applied on one side or on both sides, depending on the technical requirements. The electrodes may or may not be structured. The thickness of the electrodes towards the edges can be adapted or can be adapted. Subsequently, the segmentation of the roll follows, with any subsequent pressing into flat coils. Subsequently, the external contacts are applied by flame spraying, PVD (e.g., sputtering, thermal evaporation), or by an electrical process. By the latter, SMD components can be manufactured. In the case of flat coils, similarly, the application of side contacts and, in addition thereto, the attachment of wires, followed by the injection of a temperature-stable water-repellent grout, follow. In the case of SMD capacitors, as already described above, a protective layer or a barrier layer can be applied.

[0150] However, further processing of the film produced as described above can also be carried out by a sheet-to-sheet method. Here, the film pieces are cut into defined sizes, such as DIN A5 or DIN A4 size, for example. These film pieces are subsequently coated with electrodes. This corresponds to the production of a mother stack. The electrode coating is carried out on both sides and structured by a PVD process. Subsequently, the individual film pieces are stacked and pressed, and then the individual capacitors are cut out of the mother stack, and side contacts are provided, for example, by flame spraying, electroplating, etc. Subsequently, grout injection or stabilization with a protective layer or barrier layer is carried out.

Explanation of reference signs

[0151] 1 Capacitor 2 Dielectric layer 3 First electrode 4 Second electrode 5 First external contact 6 Second external contact 7 Substrate 8 First wire 9 Second wire

Claims

1. 1. A capacitor (1) having a single dielectric layer (2) free of solid inorganic materials, the dielectric layer (2) comprising polyamideimide, a first electrode (3) disposed directly adjacent to the dielectric layer (2), the dielectric layer (2) comprising a polyamideimide backbone including amide and imide groups of the polyamideimide, and chemical crosslinks formed within the dielectric layer (2) between the polyamideimide backbones or within the polymer backbone.

2. 2. The capacitor (1) of claim 1, wherein a second electrode (4) is also disposed directly adjacent to the dielectric layer (2).

3. The capacitor (1) according to claim 1 or 2, wherein the dielectric layer (2) is made of at least 50% by weight of polyamideimide.

4. The capacitor (1) of claim 1, wherein the crosslinks linearly link the polyamideimide backbones to one another.

5. The capacitor (1) according to claim 1 or 4, wherein the chemical crosslinks are selected from urethane crosslinks, imide crosslinks and urea crosslinks.

6. 5. The capacitor (1) according to claim 4, wherein the linear bonds are formed via imide or urethane bridges.

7. The capacitor (1) according to claim 4, in which in addition to linear bonds, three-dimensional cross-links are formed via urea cross-links.

8. The capacitor (1) according to any one of claims 1 to 7, wherein the polyamideimide backbone is partially aromatic.

9. The capacitor (1) according to any one of the preceding claims, wherein the polyamideimide contains, as functional groups, phenylene groups, anhydride and / or furan groups.

10. 6. The capacitor (1) of claim 5, wherein the polyamide-imide has a structure according to the chemical formula (Chemical Formula 1): 【Chemistry 1】 Where: R 1 is a lactam, anhydride, urethane or imide bridge, R 2 is a phenylene group, R 3 is a furan, amine, anhydride, urethane or imide crosslink; Capacitor (1).

11. The capacitor (1) according to any one of claims 1 to 10, wherein a number of first electrodes (3) are stacked alternately with second electrodes (4), and one dielectric layer (2) is disposed between each two adjacent electrodes (3, 4).

12. A capacitor (1) according to any one of claims 1 to 11, wherein all of the first electrodes (3) are conductively connected to a first external contact (5) and all of the second electrodes (4) are conductively connected to a second external contact (6).

13. Capacitor (1) according to any one of the preceding claims, wherein a substrate (7) is arranged on a side of the capacitor lying parallel to the plane of the first electrode (3).

14. The capacitor (1) according to any one of claims 11 to 13, wherein the capacitor (1) is a surface mounted device (SMD).

15. Capacitor (1) according to any one of claims 11 to 13, wherein the capacitor has wires (8, 9) for through-hole mounting.

16. The capacitor (1) according to claim 11 or 12, wherein the capacitor (1) is a wound capacitor.

17. A capacitor (1) having a single dielectric layer (2) free of solid inorganic materials, said dielectric layer (2) comprising polyamideimide, a first electrode (3) disposed directly adjacent said dielectric layer (2), The polyamideimide comprises an anhydride functional group.

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