Capacitor

Abstract

Capacitor and method for producing a capacitor, having a uniform dielectric layer, in which the dielectric layer (2) contains a polyamideimide, and a first electrode (3) is arranged directly adjacent to the dielectric layer (2).

Description

[0001] This application is a divisional application of the invention patent application with application number 202180005644.8 (PCT / EP2021 / 075666) and application date September 17, 2021. Technical Field

[0002] The present invention relates to a capacitor. Background Art

[0003] Polymer dielectrics are widely used in power electronics applications, especially in passive components such as capacitors.

[0004] For example, dielectric films containing polyimide, such as polyetherimide from US 2007 / 0258190 A1, have been proposed as capacitor dielectrics.

[0005] Polyamide-imides have hitherto been known primarily through their use as temperature-resistant coatings for enameled wires or the like.

[0006] To date, they have been proposed primarily in combination with inorganic components as dielectric layers for capacitor applications.

[0007] Japanese patent application JP 2000-338667 discloses that polyamideimide can be a matrix component for inorganic particles in capacitor dielectrics.

[0008] US 2010 / 0259865 A1 discloses that polyamideimide can be used in a capacitor having a heterogeneous dielectric layer consisting of an organic polymer material as a first dielectric layer and an inorganic material as a second dielectric layer.

[0009] However, there has hitherto been no known use of polyamideimides as capacitor materials having outstanding temperature stability and at the same time a high or tailored dielectric constant. Summary of the invention

[0010] According to a first aspect, a capacitor having a homogeneous dielectric layer is provided, wherein the dielectric layer comprises polyamide-imide and at least one first electrode is arranged directly adjacent to the dielectric layer.

[0011] Directly adjacent electrodes can be placed on this layer. Preferably, direct contact is made at the molecular level, as can be achieved, for example, by the coating method described below.

[0012] The second electrode is also preferably part of a capacitor. Optionally or according to technical requirements, it is preferred that the second electrode is also arranged directly adjacent to the dielectric layer. In this case, the dielectric layer is surrounded by the first and second electrodes in a sandwich-like manner.

[0013] The homogeneous dielectric layer can be homogeneous and contain polyamide-imide, for example. Homogeneous can mean in particular that the dielectric layer contains no additives that would make the layer inhomogeneous. It is particularly preferred that the dielectric layer contains no micro- or nano-materials or additional other solids. The dielectric layer preferably contains no mixed materials. Since the electrode is arranged directly adjacent to the homogeneous dielectric layer, no other layers besides the homogeneous dielectric layer are present between the homogeneous dielectric layer and the electrode.

[0014] Compared to other polymer-based dielectric layers, uniform dielectric layers with polyamideimide have the advantage that they have a temperature stability up to approximately 300° C. In addition, dielectric layers containing polyamideimide can have a high dielectric constant over a wide input frequency range. In this case, it is preferred to also maintain a high breakdown voltage.

[0015] Thus, the use of polyamideimide as polymer material for the dielectric layer in capacitor applications can satisfy the conflicting requirements for high temperature stability with simultaneously tailored or stabilized dielectric properties.

[0016] Thus, a homogeneous dielectric with polyamide-imide can replace biaxially oriented polypropylene (BOPP), which is one of the most widely used materials for capacitor dielectrics. This can be an advantage, since BOPP with a typical use temperature of up to 105°C and a low dielectric constant in the range of 2.2 has reached its performance limit relative to current developments, especially in terms of temperature stability while maintaining electrical and electronic parameters.

[0017] Dielectric layers with the polyamideimide according to the invention can therefore have a higher temperature stability of up to 150° C. Furthermore, a dielectric constant which is almost twice that of BOPP can also be achieved at elevated temperatures.

[0018] Thus, even requirements for future applications, for example in aerospace technology, can be met, in which operating temperatures of more than 150° C., possibly more than 200° C., can be achieved.

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

[0020] Such a high proportion of polyamideimide in the uniform dielectric layer ensures the superior dielectric properties of polyamideimide over other possible optional components.

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

[0022] The inventors have recognized that polyamide-imide can be easily functionalized chemically. Therefore, it can be flexibly customized in its properties, for example with only organic components, according to the excellent electrical or electronic properties that should be met according to the application. Therefore, the capacitor is preferably manufactured so that the dielectric layer, which is preferably a uniform dielectric layer, does not contain solid additional materials such as inorganic materials. The dielectric layer is preferably not a mixed material.

[0023] A dielectric layer containing no inorganic material may be easier to manufacture than a hybrid layer made of an inorganic-organic hybrid material.

[0024] Preferably, the dielectric layer of the capacitor has a polyamideimide backbone comprising amide groups and imide groups of polyamideimide.

[0025] This means that, in particular, the backbone of the polyamideimide polymer is formed exclusively via amide or imide bonds. This does not exclude that further chemical functional groups can be attached to or into the backbone.

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

[0027] As a more preferred aspect, the polyamideimide main chains contained in the dielectric layer may be chemically cross-linked with each other, ie, they may have cross-links.

[0028] The mechanical and electronic properties of polyamide-imides, in particular the temperature properties, can be adjusted in a targeted manner by tailoring the number of crosslinks.

[0029] In principle, the term "crosslinking" in the sense of the present application includes any type of covalent chemical bonds present between the polyamideimide backbones or between different points of a polyamideimide backbone. Crosslinks are chemical bonds formed in addition to the chemical bonds between the repeating units of the polyamideimide backbone. In this case, the number of crosslinks is preferably selected so that a thermoplastic polyamideimide is formed.

[0030] Preferably, crosslinking comprises a linear link connecting the end unit of one polyamideimide backbone to the end unit of another polyamideimide backbone, thereby forming a chain connection in series. Preferably, the linear link between the backbones is different from the connection type in the polyamideimide backbone. Therefore, the crosslinking preferably does not have an amideimide motif. However, the crosslinking can be an amide bond or an imide bond. Such a bond can break through the repeating motif of the polyamideimide motif repeated in the polyamideimide backbone. It can linearly connect multiple polyamideimide backbones in series.

[0031] The number of crosslinks can be controlled by the annealing temperature. The higher the temperature, the more polyamide-imide main chains are linked in series. As a result, the polymer chains become longer with increasing annealing temperature. As a result, the mechanical stability of the dielectric layer can be increased. In addition, the loss factor can be reduced. This way of controlling the degree of crosslinking by temperature is particularly preferred for linear links.

[0032] The chemical crosslinks are preferably formed via urethane bridges.

[0033] The urethane bridges can preferably be formed via isocyanate groups located on one backbone, which react with hydroxyl groups on the other backbone to form urethane bonds.

[0034] Lactams can also be present in the starting material as functional groups, because they are used as protective groups to control the reaction between isocyanate groups and hydroxyl groups. Such lactams can be opened, for example, by the action of temperature, thereby forming isocyanate groups, which then react with hydroxyl groups, for example hydroxyl groups of another main chain. This means that isocyanate groups and / or lactam functional groups can be present in the starting material. However, preferably, only lactams are present in the starting material, because this allows longer durability at room temperature. In addition, this can also extend the usable drop time during the manufacture of the dielectric layer.

[0035] Instead of or in addition to other crosslinks such as urethane bridges, it may be preferred to form imide bridges between the polyamideimide backbone chains.

[0036] For example, the imide bridge can react to form an imide by reacting an anhydride group with a suitable group (e.g., amine) on another polyamideimide backbone to form an imide bridge as a crosslink between two polyamideimide backbones. Preferably, the anhydride group is a phthalic anhydride group. Links can also be formed between different points of a polyamideimide backbone by such a reaction.

[0037] Both urethane bridges and imide bridges are particularly well suited for the technically simple formation of linear linkages. Furthermore, the degree of linear linkage with these groups can be adjusted particularly precisely by controlling the annealing temperature.

[0038] In addition, crosslinking can also be formed by urea bridges. This can be formed on the polyamide-imide main chain with the participation of amide groups. Particularly preferably, three-dimensional crosslinking is formed by it, that is, not only linear links are formed by means of this bond motif. Still more preferably, only such crosslinking is formed by urea bridges, and this crosslinking is a non-linear link. Particularly preferably, these can also be present in addition to linear links. For example, it can be formed by a polymer material that is three-dimensionally crosslinked by a urea bridge and linearly crosslinked by an imide bridge or a carbamate bridge for a dielectric layer, or a polymer material that is three-dimensionally crosslinked by a urea bridge and linearly crosslinked by an imide or carbamate bridge can be formed for a dielectric layer.

[0039] In principle, urethane bridges can be present in addition to imide bridges. However, it is preferred that only one linear linkage motif is present, since this makes process control simpler.

[0040] An example of a suitable starting material is commercially available, for example AI 336L.

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

[0042] As another preferred aspect of the uniform dielectric layer of the capacitor, the dielectric layer can be formed such that the polyamideimide backbone is partially aromatic.

[0043] Partially aromatic polyamide-imide backbones contribute in particular to a balanced ratio of flexibility and temperature stability. Thus, fully aromatic polyamide-imide backbones may be too rigid. However, by partial aromaticity, i.e., aromaticity on the imide component, for example, the necessary temperature stability and flexibility can be obtained simultaneously.

[0044] According to a preferred aspect, the polyamideimide may have a phenylene group and / or a furyl group as a functional group.

[0045] For example, the introduction of phenylene groups in the polyamide-imide backbone may be relevant to obtaining the necessary flexibility of the backbone. Therefore, according to the selection, the length of the repeating unit and its flexibility are adjusted by one or more different phenylene groups in the backbone. Therefore, for example, biphenyl, diphenylmethane and triphenylmethane, o- and p-dibenzylbenzene or tribenzylbenzene can be used as possible phenylene groups. In principle, a plurality of different these phenylene groups or other phenylene groups may also be present in a polyamide-imide backbone. That is, different phenylene groups may be present in a polyamide-imide backbone. However, usually only one type of phenylene group is present in a backbone.

[0046] Since the furan group itself has a high polarity, the polarity of the dielectric layer can be adjusted by selecting different furan groups. For example, benzofurans, dibenzofurans, furanones or hydroxyfuranones are used for this purpose. For example, hydroxyfuranones or other furan derivatives can have one or more hydroxyl groups, which are required for crosslinking via isocyanate groups as reaction partners to form urethane bridges, which can be formed, for example, from lactam groups.

[0047] According to another preferred aspect, the polyamideimide may have a structure according to Chemical Formula 1, wherein R 1 These are unreacted groups such as lactams, anhydrides or amines or urethane bridges or imide bridges. 1 is a carbamate bridge or an imide bridge. 2 Here, phenylene may be present and R 3 is furan. Alternatively, R 3 Urethane bridges or imide bridges are also possible. In this case, the polyamide-imide backbone is linked to two other polyamide-imide backbones at both ends.

[0048]

Chemical formula 1

[0049]

[0050] In principle, as already described above, lactams are preferred groups, for example as R 1 In the polymer chain connected to the starting material at the end. Through the isocyanate group formed by the lactam, a bridge to another polyamide-imide main chain can be formed in principle, for example in the form of a urethane bridge. The lactam can be, for example, a β, γ, δ or ε lactam. Among them, δ and ε lactams are particularly preferred.

[0051] Urethane bridges can be formed from terminal lactams and terminal furans with hydroxyl groups in the starting materials, thereby connecting the main chain in series and thus extending it. This reaction can crosslink the main chain so that the polyamide-imide layer formed has thermoplastic properties. The number of crosslinks is adjusted in this way so that the dielectric layer of the capacitor does not become too rigid and brittle.

[0052] As mentioned above, linearly linked imide bridges can be formed by anhydrides such as phthalic anhydride, which react with amines. Alternatively, isocyanate groups can react with anhydride groups to form imides, thereby dissociating CO2.

[0053] In the starting material, i.e. before preparing the crosslinking including the linear linkage, the functional group suitable for the corresponding linkage is located at R in the chemical formula 1 3 or R 1 In position.

[0054] In a preferred embodiment of the capacitor, a plurality of first electrode layers and second electrode layers are stacked alternately, and a dielectric layer is arranged between every two adjacent electrode layers.

[0055] That is, the capacitor may be a multilayer capacitor.

[0056] Alternatively, for example, a multilayer capacitor can be cut from a coil. In this case, an electrically conductive or preferably metal-containing structured layer can be used as an electrode, which has at least two electrically isolated regions and thus serves as a capacitor electrode.

[0057] According to another preferred aspect, all first electrode layers can be electrically conductively connected to the first external contact, and all second electrode layers can be electrically conductively connected to the second external contact.

[0058] The outer contacts may be applied by flame spraying, PVD process or other methods.

[0059] Multilayer capacitors with corresponding external contacts can be used in a wide variety of technical applications.

[0060] According to another embodiment, the substrate may be arranged on a side of the capacitor parallel to the plane of the electrode layer.

[0061] As mentioned above, such a substrate can be electrically conductive, ie can also fulfil the function of an electrode, but it can also have an insulating function and remain on the component after the production process.

[0062] In particular, the capacitor as described above may be a surface mounted device (SMD).

[0063] Furthermore, the capacitors described above can also be through-hole capacitors, ie they have leads for through-hole mounting. With these leads, the capacitors can be electrically and mechanically connected to external contact points.

[0064] The capacitor can also be a wound capacitor. In particular, in this case, the capacitor can have only one metallization as electrode, which is in direct contact with the dielectric layer. A configuration with two electrodes in direct contact with the dielectric layer is also possible.

[0065] As another aspect of the present invention, a method for manufacturing a capacitor is provided, comprising manufacturing a dielectric layer. The dielectric layer is prepared by applying a prepolymer-polyamideimide solution to a deposition surface, drying the prepolymer-polyamideimide solution on the deposition surface, and annealing the dried prepolymer-polyamideimide solution.

[0066] The deposition surface can be the surface of an electrode or an electrode layer. The deposition surface can also be the surface of a substrate. The substrate can be the substrate of a finished capacitor or can also be just an intermediate carrier from which the applied and optionally crosslinked polyamideimide film is separated.

[0067] By this method, a capacitor as described above can be manufactured.

[0068] In this way, uniform dielectric layers can also be produced. The prepolymer-polyamide-imide solution can be, in particular, a solution of a resin which is also suitable as an insulating coating, for example dissolved in an organic solvent. AI 336L.

[0069] Polyamideimides are in principle soluble in a wide variety of solvents and can be applied in a wide variety of concentrations to form closed layers or films. They are therefore suitable for flexible use with a wide variety of deposition methods or different layer thicknesses, as will be explained in more detail below.

[0070] When drying the prepolymer-polyamideimide solution, most or all of the solvent may be removed.

[0071] When the dried prepolymer-polyamideimide solution is annealed, the material thickens and crosslinking can begin in the layer thus formed, for example via the lactam.

[0072] The speed of the cross-linking reaction can be determined by the annealing temperature.

[0073] The degree of crosslinking is preferably determined by the number of linking groups on the polyamideimide backbone in the prepolymer-polyamideimide solution (eg, via isocyanate groups protected as lactams), and the annealing temperature is selected so that all linking groups form crosslinks.

[0074] In a preferred case, the linking group is arranged at the end of the polyamideimide main chain. In principle, but especially in this case, the degree of crosslinking can be influenced or adjusted by the annealing temperature. The higher the selected annealing temperature, the more crosslinks are formed in a given time. In this way, more polyamideimide main chains can be linked to each other.

[0075] As another aspect, as described above, the method can be modified so that the deposition surface is the surface of the substrate, the dielectric layer is separated 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.

[0076] Thus, the above method can be used for producing wound capacitors. This has the advantage that the dielectric layer or film thus formed, which is provided with the first and second electrodes by metallization, can also be processed before metallization. For example, methods such as film drawing can be used to optimize the material properties.

[0077] According to another aspect, the manufacture of a capacitor may include the following: Using a conductive substrate or alternatively giving a substrate a first electrode layer on its surface. The deposition surface may thus be the surface of the conductive substrate or the first electrode layer. After applying the dielectric layer to the deposition surface, a second electrode layer may be manufactured on the dielectric layer, and another dielectric layer may be manufactured on the second electrode layer by applying a prepolymer-polyamideimide solution to the second electrode layer, drying it and then annealing it.

[0078] In the case of a conductive substrate, the substrate can be used as an electrode, for example as a first electrode. A second electrode layer can be applied above it. In this case, of course, a further dielectric layer can be applied on the second electrode layer and then subsequently the first electrode layer to obtain a multilayer capacitor.

[0079] Alternatively, the substrate can be non-conductive, i.e. electrically insulating, as described. In this case, the electrode layer is applied first and then the further layers are applied or arranged above the substrate. In both cases, this is a method for building a stacked multilayer capacitor from a solution, rather than a wound capacitor or a multilayer capacitor cut from a coil.

[0080] It is preferred for the above-described process that the prepolymer-polyamideimide solution comprises a polyamideimide backbone on which isocyanate groups and / or isocyanate groups which are still more preferably protected as lactam groups are arranged.

[0081] These have the advantages mentioned above.

[0082] The process can preferably be carried out in such a way that the prepolymer-polyamideimide solution is applied by knife coating, spin coating, nozzle coating or spray coating.

[0083] The present invention is described in more detail below using exemplary embodiments. These exemplary embodiments are presented in the following drawings, which are not drawn to scale. Therefore, lengths and relative and absolute dimensions cannot be obtained from the drawings. The present invention is also not limited to the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 A first embodiment of a capacitor is shown in schematic cross section.

[0085] Figure 2a shows the mass loss of the polyamideimide layer in thermogravimetric analysis. Figure 2b shows a graph of the loss factor of the capacitor.

[0086] Figure 3A first multilayer capacitor is shown in schematic cross section as a second exemplary embodiment of a capacitor.

[0087] Figure 4 A second multilayer capacitor is shown in schematic cross section as a third exemplary embodiment of a capacitor.

[0088] Figure 5 A third multilayer capacitor is shown in schematic cross section as a fourth exemplary embodiment of a capacitor.

[0089] Figure 6 A multilayer capacitor suitable for through-mounting is shown in schematic cross section as a fifth exemplary embodiment of a capacitor.

[0090] Figure 7 A wound capacitor is shown in schematic cross section as a sixth embodiment of a capacitor. DETAILED DESCRIPTION

[0091] Figure 1 A first embodiment of a capacitor 1 is shown in schematic cross section. The capacitor 1 has an organic dielectric layer 2. The dielectric layer 2 is a homogeneous layer. This means that it consists of a single material and does not contain mutually separable volume regions. It is therefore also not a composite material. At least 50% by weight of the dielectric layer 2 consists of polyamideimide. Preferably, the polyamideimide proportion is high, for example more than 90%. Still more preferably, the dielectric layer 2 consists only of polyamideimide.

[0092] The polyamideimide may be any polyamideimide, in particular it may be a partially aromatic polyamideimide. The polyamideimide according to formula 1 is particularly preferred.

[0093]

Structural formula 1

[0094]

[0095] The polyamideimide according to Structural Formula 1 has a polyamideimide main chain and may have a plurality of functional groups. For example, a phenylene group may be included as R of Structural Formula 1 in the polyamideimide main chain. 2 The flexibility of the polyamideimide backbone can be adjusted by the phenylene group. For example, biphenyl, diphenylmethane or triphenylmethane, o- or p-dibenzylbenzene or tribenzylbenzene can be used.

[0096] Furthermore, furanic groups can be arranged, in particular, at the ends of the polyamideimide main chain, for example as R 3 Therefore, the polarity of the dielectric layer can be adjusted by its polarity. For example, benzofurans, dibenzofurans, furanones or hydroxyfuranones can be used as the furan group.

[0097] Alternatively, anhydrides can be used as R3 .

[0098] Furthermore, there are preferably crosslinks between different polyamideimide backbones in the dielectric layer 2 .

[0099] The polyamideimide main chains are preferably linked to each other via urethane bridges and / or imides. For example, these links can be located at the end of the group R in formula 1 1 Alternatively, the unbridged groups may be present in R 1 position, such as, for example, a lactam isocyanate or an anhydride.

[0100] The dielectric layer 2 is preferably made of a polyamide-imide resin mixture suitable for coating conductive wires, such as AI 336L solution.

[0101] The first electrode 3 and the second electrode 4 are arranged above and below the dielectric layer 2. The first electrode 3, the dielectric layer 2 and the second electrode 4 may all be formed in a planar manner.

[0102] Preferably, stacking takes place on the largest surface of the planarly shaped layer.

[0103] The layer thickness of the electrode can be, for example, 10 to 50 nm, preferably 20 nm. Depending on the production method, the layer thickness of the dielectric layer 2 can be set at 500 nm to 10 μm.

[0104] The electrodes may be made of aluminum or silver, or preferably of an aluminum-zinc alloy. Alternatively, the electrodes may be multilayer electrodes made of chromium / aluminum, chromium / silver or chromium / nickel / aluminum or chromium / nickel / silver. In addition to the elements shown here, a hydrocarbon protective layer, such as polyparaxylene or a fluorocarbon, may be placed on the side of the capacitor that does not have an electrode (not shown).

[0105] As an alternative, not shown in the figures, only one electrode may be in contact with the dielectric layer.

[0106] Figure 1 The first embodiment of the capacitor shown in can be manufactured by any arbitrary method. It is preferably manufactured by a solvent-based process. For example, the first electrode 3 can be first manufactured on a substrate. The substrate can be a rigid substrate, such as glass or a semiconductor wafer. It can be a metal foil, such as aluminum or copper, or a flexible polymer film, such as polyimide or a release tape. The first electrode is applied to the substrate surface by physical vapor deposition (physical vapor deposition, PVD), such as sputtering or thermal evaporation.

[0107] The dielectric layer 2 can now be applied from the prepolymer polyamideimide solution to the surface of the electrode 3 as deposition surface. The prepolymer polyamideimide solution preferably contains a largely non-crosslinked polyamideimide.

[0108] The prepolymer-polyamideimide solution is prepared from a commercially available polyamideimide resin mixture (e.g. AI 336) is produced by additional dilution with a solvent.

[0109] The polyamide-imide resin mixture contains about 36% of non-volatile matter (mainly polyamide-imide backbone) in a solution of N-methylpyrrolidone (NMP) and xylene. Its initial viscosity is 4750±1750 mPa s. In addition, its density is about 1.1 g / ml.

[0110] The concentration of the polyamideimide solution thus provided is adjusted to 20% or less of the initial polyamideimide concentration with xylene or N-methylpyrrolidone, for example, to produce a polyamideimide concentration of 19% or 15% by mass relative to the initial polyamideimide resin mixture in xylene.

[0111] The concentration used depends on the layer thickness to be achieved or on the type of deposition method used.

[0112] On the surface of the first electrode 3 as deposition surface, the prepolymer-polyamide-imide solution prepared in this way can now be applied. The application can be done by blade coating, template printing, spin coating or spray coating. The coating method depends on the thickness of the dielectric layer 2 to be achieved. Thus, thicker layers of 500 nm to 5 μm can be applied, in particular, by spin coating or spray coating, or even thicker layers of, for example, 1 μm to 10 μm can be applied by blade coating or template printing.

[0113] The solution thus applied is dried at a temperature of 60 to 100° C., preferably at 80° C. The dried film is then annealed at a temperature of more than 200° C., preferably at 250° C.

[0114] During drying, most of the solvent is removed. Further volatile components are removed by annealing. In addition, crosslinking between the main chains can be initiated during annealing. At a temperature of 250° C., almost complete crosslinking is achieved within 5-10 minutes. In this case, the isocyanate groups protected as lactams are preferably activated and then reacted with existing hydroxyl groups, which are present, for example, on furan residues, or with anhydrides.

[0115] After cooling, the second electrode 4 can again be applied by PVD to the dielectric layer produced in this way.

[0116] At the end of the process, the substrate can be removed to obtain Figure 1 However, in principle it could also remain on the capacitor.

[0117] Figure 2A Thermogravimetric analysis (TGA) of the polyamide-imide resin mixture used is shown. The temperature ramp is constant at 10 K / min. Figure 2A As shown in the graph of , no mass loss occurs up to a temperature of approximately 275° C. A mass loss of less than 5% occurs only at temperatures above approximately 300° C. A mass loss of more than 5% occurs only at temperatures above 400° C.

[0118] This demonstrates the extremely high temperature stability of polyamide-imide as a dielectric. In particular, long-term temperature stability of more than 200°C can be expected for future applications.

[0119] In particular, this allows the finished capacitor to be mounted, for example by soldering, without expecting degradation of the components or the dielectric layers.

[0120] Other favorable properties of polyamideimide as a dielectric for capacitors are shown in Tables 1 and 2 below and in Figure 2B in the curve graph.

[0121] Table 1 shows a similar Figure 1 The dielectric loss factor (tan δ) of the polyamide-imide flat capacitor of the construction described in the figure is measured here from the above polyamide-imide resin mixture (scraper speed 50 mm / s), which is diluted to a mass ratio of 15% with xylene as solvent relative to the initial mixture. The layer thickness is 3 μm and the capacitor area is 50 mm 2 The measurements were performed using a Keysight E4990A with a cooling / heating system PHECOS from Novocontrol.

[0122] [Table 1]

[0123]

[0124] As shown in Table 1, the loss factor is always below 2% in the examined frequency- and temperature range. It is noteworthy that the loss factor even improves slightly with increasing temperature. This indicates that polyamide-imide as a dielectric brings excellent dielectric properties.

[0125] This is also Figure 2B This is confirmed in the graph shown in , which shows the frequency dependence of the loss factor for the dielectric layers described in Table 1 at a constant temperature of 150° C. It can be observed from this that the loss factor in the examined frequency range between 1 kHz and 1 MHz can be regarded as a constant in a first approximation.

[0126] This constant performance allows for widespread use of polyamideimide capacitors in general and for high flexibility of individual polyamideimide capacitors in particular.

[0127] Table 2 shows the corresponding Figure 1 The dielectric constant (ε) of the polyamide-imide flat plate capacitor constructed r ) on temperature and electrical frequency. The dielectric layer used here was produced from a 19 wt. % solution relative to the polyamide-imide resin mixture initially used. The layer thickness was 5 μm and the capacitor area was 50 mm 2 The measurements were performed using a Keysight E4990A with a cooling / heating system PHECOS from Novocontrol.

[0128] [Table 2]

[0129]

[0130] Table 2 shows that the dielectric constant has only moderate variations with respect to temperature and frequency. Although in principle one can observe a decrease in the dielectric constant with increasing frequency or an increase in the dielectric constant with increasing temperature, the dielectric constant of polyamide-imide with an average dielectric constant of 4 is almost twice that of the standard material BOPP.

[0131] The high dielectric constant is due to the partially aromatic character of the polyamide-imide and to polar groups, such as furan groups. In addition, the polyamide-imide can in principle be adjusted so that the dielectric loss or other properties are optimized in a specific frequency range. This can be achieved by composing the prepolymer-polyamide-imide solution from different polyamide-imides and by a specific selection of the functional groups on the main chain.

[0132] For the plate capacitors described in Table 2, the breakdown voltage at room temperature is between 300 and 550 V / μm, depending on the frequency (measured with Sefelec S50). The insulation resistance at room temperature is always above 3 TΩ (measured with Novocontrolsystem Alpha A).

[0133] This shows that the polyamide-imide used has an excellent dielectric constant and simultaneously high breakdown voltage and ohmic insulation resistance.

[0134] Figure 3 A second embodiment of a capacitor 1 is shown in schematic cross section. The capacitor 1 has a plurality of first electrodes 3 which are stacked alternately with second electrodes 4. Both electrodes are planar electrodes.

[0135] The dielectric layer 2 is always arranged between the first electrode 3 and the second electrode 4, that is, always between two adjacent electrodes, and the dielectric layer 2 always corresponds to Figure 1 The dielectric layer 2 of the first embodiment.

[0136] The first electrode 3 and the second electrode 4 have the characteristics of inner electrodes.

[0137] The second embodiment of the capacitor 1 is therefore a multilayer capacitor.

[0138] The first external contact 5 and the second external contact 6 are arranged on opposite sides of the multilayer capacitor.

[0139] The first electrode 3 is electrically conductively connected to a first external contact 5 , and the second electrode 4 is electrically conductively connected to a second external contact 6 .

[0140] The capacitor thus composed can be a surface mount device (SMD), which is very suitable for soldering due to its temperature-stable dielectric layer 2. In order to be able to use the capacitor 1 more advantageously as an SMD capacitor, the external contacts 5 and 6 can be configured in a clip-like manner. That is, the external contacts 5 and 6 can extend to a certain extent on both sides in the stacking direction.

[0141] For example, the capacitor can be a rectangular flat hexahedron and can have a total of 1000 or more repeating units, which include a first electrode, a dielectric layer, a second electrode and another 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. Here, a single dielectric layer 2 can have a thickness of 500 nm to 5 μm, preferably 500 nm to 2 μm. The thickness of the inner electrode is 10 to 50 nm, preferably 20 nm.

[0142] However, the dimensions of the finished capacitor may also differ from those given here. The length, width, height and layer thickness may be adapted based on different technical prerequisites or different technical tasks.

[0143] The manufacturing method can be similar to the manufacturing method of the first embodiment. For example, the first electrode layer 3 can be applied on the substrate by PVD. Then the dielectric layer 2 can be applied from a solution, and then the second electrode layer 4 can be applied by PVD. On top of it, the dielectric layer 2 is applied from a solution. This can be repeated to achieve the desired number of layers or a specific capacitance of the capacitor.

[0144] In principle, the inner electrode can be structured during the process. This can be done already during deposition or after the physical vapor deposition process.

[0145] After stacking, the substrate may be removed.

[0146] Optionally, a protective layer (not shown) similar to the first exemplary embodiment can then be applied on the side remaining free of external contacts by means of a vapor deposition process and a solvent-based process or coating method.

[0147] The outer contacts 5 and 6 are mounted on the finished stack capacitor 1. They may consist, for example, of brass, copper, tin, aluminum, silver, etc. and may be applied by means of physical vapor deposition methods or other, for example, solvent-based processes.

[0148] Figure 4 A third exemplary embodiment of a capacitor 1 is shown in schematic cross section, which capacitor 1 is also a multilayer capacitor.

[0149] Figure 4 The capacitor 1 in the Figure 3 The capacitor shown in and as previously described. However, in Figure 4 In the embodiment shown in , the original substrate, here the substrate 7 , is still present on the component.

[0150] exist Figure 4 In the case of FIG. 5 , the substrate 7 is insulating and may be, for example, a glass substrate, a semiconductor wafer, or a flexible substrate such as a polyimide film or a release tape.

[0151] Figure 4 The manufacturing method of the third embodiment corresponds to Figure 3 The manufacturing method of the second embodiment is as follows, except that the substrate is removed.

[0152] Figure 5 A fourth exemplary embodiment of a capacitor 1 , here a multilayer capacitor, is shown in schematic cross section. Figure 5 The fourth embodiment shown in Figure 4 The one shown in is mostly similar.

[0153] However, here, the substrate 7 is a metal-containing conductive substrate, for example made of aluminum, copper or similar materials. It is present, for example, as a film. Due to its conductive characteristics, it is not necessary to arrange a conductive layer on the substrate as the first electrode 3. The substrate 7 itself can be used as a substitute for one of the first electrodes 3. The dielectric layer 2 is then applied directly thereto.

[0154] Since the substrate preferably extends over the entire width and length of the capacitor, care must be taken that the second external contact 5 does not make electrical contact with the substrate.

[0155] This method is also similar to Figure 4 The embodiments described in .

[0156] exist Figure 6The fifth embodiment shown in a schematic cross section in FIG. 1 is similar in almost all respects to the second embodiment of the capacitor 1. It is therefore also a multilayer capacitor. However, it has conductors 8 and 9 on its external contacts 5 and 6, which can be mounted in a through-hole mounting in the application. It is therefore a through-hole capacitor. The conductors 8 and 9 make the electrical and most mechanical contact with the connection point in the application. The conductors 8 and 9 can be fixed to the capacitor 1 by any method, such as crimping / welding.

[0157] Figure 7 A sixth exemplary embodiment of a capacitor 1 is shown in schematic cross section. This is a wound capacitor. The wound capacitor is similar in design to the first exemplary embodiment, i.e. the dielectric layer 2 is sandwiched by the first electrode 3 and the second electrode 4. The corresponding sandwich-like structure is wound into a wound capacitor.

[0158] However, the manufacturing method used is different from that corresponding to Figure 1 For example, it is preferred to use a pair of Figure 1 The deposition method described first produces a dielectric film 2. This can then be separated from the substrate. This can then be post-processed by any method. The film thus obtained can then be metallized on one side or, in the present case, on both sides by PVD. The metallized film thus obtained can be wound up to form a wound capacitor. Preferred layer thicknesses of wound capacitor films with polyamide-imide are 1 μm to 10 μm, preferably 2 μm to 5 μm.

[0159] As an additional or alternative method for producing different structural types, the formation of polyamide-imide films for dielectrics can first be carried out in a roll-to-roll method from a solution by coating a prepolymer-polyamide-imide solution onto a substrate previously provided with a release agent. Subsequently, drying and simultaneous annealing are carried out at more than 200° C., preferably more than 220° C., and most preferably at 250° C. The dried and cross-linked polyamide-imide film is then layered or peeled off from the substrate and wound up. Optionally, an intermediate film can be wound together as protection. Then the electrodes are applied. This is also preferably carried out in a roll-to-roll method. Here, depending on the technical requirements, one or more electrode layers can be applied on one or both sides. The electrodes can be structured or remain unstructured. The thickness of the electrode to the edge can be adjusted or the thickness of the electrode to the edge can be adjusted. The coil is then divided with optional subsequent pressing to form a flat coil. External contacts are then applied by means of flame spraying, PVD (e.g., sputtering, thermal evaporation) or by electroplating methods. With the latter, SMD components can be manufactured. In the case of flat coils, side contacts are also applied and conductors are additionally arranged thereon and then cast with a temperature-stable, waterproof casting material. In the case of SMD capacitors, a protective layer or barrier layer can be applied, as already described above.

[0160] However, further processing of the film produced as above can also be carried out using a sheet-to-sheet method. Here, the film sheets are cut to a given size, for example to a size of about DIN A5 or DIN A4. These film sheets are then coated with electrodes, which corresponds to the production of a mother stack. Both sides of the electrodes are coated and structured by means of a PVD method. The individual film sheets are then stacked and pressed, and then the individual capacitors are cut from the mother stack, provided with side contacts, for example by means of flame spraying, electroplating or other means, and then stabilized by means of casting or a protective layer or barrier layer.

[0161] Reference numerals list

[0162] 1 Capacitor

[0163] 2 Dielectric layer

[0164] 3. First electrode

[0165] 4 Second electrode

[0166] 5 First external contact

[0167] 6 Second external contact

[0168] 7 substrate

[0169] 8 First conductor

[0170] 9 Second wire.

Claims

1. A capacitor (1) comprising a homogeneous dielectric layer (2), wherein the dielectric layer (2) comprises polyamideimide and a first electrode layer (3) is arranged directly adjacent to the dielectric layer (2), and the dielectric layer (2) comprises a polyamideimide backbone chain, the polyamideimide backbone chain comprises amide groups and imide groups of the polyamideimide, chemical crosslinks are formed in the dielectric layer (2) between the polyamideimide backbone chains or within the polymer backbone, and the chemical crosslinks are selected from urethane bridges, imide bridges and urea bridges.

2. A capacitor (1) comprising a uniform dielectric layer (2), wherein the dielectric layer (2) comprises polyamideimide and a first electrode layer (3) is arranged directly adjacent to the dielectric layer (2), the dielectric layer (2) comprises a polyamideimide backbone chain, the polyamideimide backbone chain comprises amide groups and imide groups of the polyamideimide, chemical crosslinks are formed in the dielectric layer (2) between the polyamideimide backbone chains or within the polymer backbone chain, and the crosslinks linearly link the polyamideimide backbone chains to each other.

3. A capacitor (1) comprising one or more than one dielectric layer (2) and a first electrode layer (3) arranged directly adjacent to the dielectric layer (2), wherein all dielectric layers (2) present are homogeneous and contain polyamideimide.

4. A wound capacitor (1) comprising a dielectric layer (2) and at least one first electrode (3) arranged directly adjacent to the dielectric layer (2), wherein the dielectric layer (2) is homogeneous and contains polyamideimide.

5. A multilayer capacitor (1) comprising a plurality of first electrode layers (3) and second electrode layers (4), wherein the first electrode layers (3) and the second electrode layers (4) are stacked alternately, and a uniform dielectric layer (2) is arranged between each two adjacent electrode layers (3, 4), wherein all dielectric layers (2) contain polyamideimide.

6. A capacitor (1) comprising a homogeneous dielectric layer (2), wherein the dielectric layer (2) comprises polyamideimide and a first electrode layer (3) is arranged directly adjacent to the dielectric layer (2), and the polyamideimide has phenylene, anhydride and / or furan groups as functional groups.

7. A capacitor (1) comprising a homogeneous dielectric layer (2), wherein the dielectric layer (2) comprises polyamideimide and a first electrode layer (3) is arranged directly adjacent to the dielectric layer (2), and the dielectric layer (2) comprises a polyamideimide backbone chain comprising amide groups and imide groups of the polyamideimide.

8. The capacitor (1) according to claim 7, wherein a second electrode layer (4) is also arranged directly adjacent to the dielectric layer (2).

9. The capacitor (1) according to claim 7 or 8, wherein 50% by weight or more of the dielectric layer (2) consists of polyamideimide.

10. The capacitor (1) according to claim 7 or 8, wherein the dielectric layer (2) is free of solid inorganic material.

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