Capacitor and method for producing the same

Abstract

Capacitor (1) comprising a dielectric layer (2) which is uniform, wherein the dielectric layer (2) contains polyamideimide with polyamideimide main chains which comprise the amide and imide groups of the polyamideimide, a first electrode (3) and a second electrode (4) are arranged directly adjacent to the dielectric layer (2), and the polyamideimide main chains in the dielectric layer (2) have urethane bridges as chemical crosslinks between the polyamideimide main chains.

Description

[0001] The invention relates to an electrical capacitor.

[0002] Polymer dielectrics are widely used in power electronics applications, particularly in passive components such as electrical capacitors.

[0003] For example, polyimide-containing dielectric films have already been proposed as capacitor dielectrics, such as polyetherimides from US 2007 / 0 258 190 A1.

[0004] Polyamideimides are primarily known for their use as temperature-resistant coatings for enamelled wires or similar.

[0005] They have so far been proposed for capacitor applications primarily in conjunction with inorganic components as dielectric layers.

[0006] Japanese patent application JP 2000-338 667 A discloses that polyamideimide can be a component of a matrix for inorganic particles in a capacitor dielectric.

[0007] US 2010 / 0 259 865 A1 discloses that polyamideimide can be used in a capacitor with a non-homogeneous dielectric layer consisting of an organic polymer material as a first dielectric layer and an inorganic material as a second dielectric layer.

[0008] Furthermore, US 2017 / 0 162 325 A1 and JP 2006-019621 A each describe other non-homogeneous dielectric layers in which nanomaterials or ceramic materials are present in polyamideimide.

[0009] The two publications US 2011 / 0 032 656 A1 and US 2012 / 0 033 342 A1 describe the production of dielectric multilayer components and in particular wound structures with a polyamideimide film produced by vapor deposition.

[0010] The publications JP 2009-038 088 A, DE31 00 181 A1 and DE 10 2017 216 109 A1 describe various processes for the deposition or production of polymer films.

[0011] However, no use of polyamideimide as a capacitor material with outstanding temperature stability and simultaneous high or tailored permittivity is known to date.

[0012] According to a first aspect, a capacitor is provided comprising a uniform dielectric layer. The dielectric layer comprises polyamide-imide, and a first electrode and a second electrode are arranged directly adjacent to the dielectric layer.

[0013] Such a uniform dielectric layer can, for example, be a homogeneous dielectric layer comprising polyamide-imide. Since electrodes are arranged directly adjacent to the uniform dielectric layer, there are no additional layers different from the uniform dielectric layer between the uniform dielectric layer and the electrodes.

[0014] A uniform polyamide-imide dielectric layer offers the advantage over other polymer-based dielectric layers in that it exhibits temperature stability up to almost 300°C. Furthermore, a polyamide-imide dielectric layer can exhibit high permittivity over a wide input frequency range. A high breakdown voltage is typically also maintained.

[0015] Thus, polyamideimide as a polymeric material for dielectric layers in capacitor applications can meet conflicting requirements for high temperature stability while simultaneously providing tailored or stable dielectric properties.

[0016] For example, a uniform dielectric comprising polyamideimide can replace biaxially oriented polypropylene (BOPP), one of the most widely used materials for capacitor dielectrics. This can be advantageous because BOPP, with a typical operating temperature of up to 105°C and a low permittivity in the range of 2.2, has reached its performance limits in terms of current developments, particularly with regard to temperature stability while maintaining electrical and electronic parameters.

[0017] Thus, a polyamide-imide dielectric layer according to the invention can exhibit a higher temperature stability of up to 150°C. Furthermore, a permittivity almost twice as high as that of BOPP can be achieved even at elevated temperatures.

[0018] This means that requirements for future applications, for example in aerospace technology, can be met, where operating temperatures of over 150°C and possibly over 200°C could 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 the uniform dielectric layer can ensure that the excellent dielectric properties of the polyamideimide prevail over other possible optional components.

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

[0022] The inventors have recognized that polyamide-imide is easily chemically functionalizable. Its properties can therefore be flexibly tailored, for example, with exclusively organic components, to the outstanding electrical or electronic properties required for a specific application. Therefore, the capacitor is preferably manufactured such that the dielectric layer, which is usually a uniform dielectric layer, is free of solid inorganic materials.

[0023] A dielectric layer free of inorganic materials may be easier to fabricate than a mixed layer made of an inorganic-organic hybrid material.

[0024] Furthermore, the dielectric layer of the capacitor has polyamideimide main chains, which comprise the amide and imide groups of the polyamideimide.

[0025] This means that, in particular, the main chains of the polyamide-imide polymer are formed exclusively via amide or imide bonds. This does not preclude the possibility of additional chemical functions being attached to or within the main chains.

[0026] Polyamideimide compounds or the chemical bonds they contain are stable at high temperatures, which is an advantage for dielectric layers that are used under high-temperature conditions.

[0027] In addition, the polyamideimide main chains contained in the dielectric layer are chemically cross-linked. This means that the polyamideimide main chains exhibit cross-links.

[0028] By tailoring the number of crosslinks, the mechanical and electronic properties of the polyamideimide, and especially its temperature properties, can be specifically adjusted. Typically, the number of crosslinks is selected to form a thermoplastic polyamideimide.

[0029] In particular, these can be covalent chemical compounds.

[0030] The chemical crosslinks are urethane bridges.

[0031] These urethane bridges can usually be formed via isocyanate groups located on the main chain, which react with a hydroxy group on another main chain to form a urethane bond.

[0032] Lactams can also be present as functional groups in the starting material, as they serve as a protecting group to control a reaction between an isocyanate group and a hydroxyl group. Such a lactam can, for example, be opened by exposure to temperature, forming an isocyanate group, which in turn then reacts with a hydroxyl group, for example, in another main chain. This means that isocyanate groups and / or lactam functional groups can be present in a starting material. However, the starting material preferably contains exclusively lactams, as this allows for longer shelf life at room temperature. Furthermore, the applicable dripping time during production of the dielectric layer can be extended.

[0033] An example of such a starting material is commercially available RESISTHERN® AI 336 L.

[0034] An example of such a starting material is polyamideimide resin solutions, which can be used, among other things, for insulating coatings on wires or electrodes. One example of such a polyamideimide resin solution is the commercially available RESISTHERN® AI 336 L.

[0035] As a further preferred aspect of the uniform dielectric layer of the capacitor, the dielectric layer may be formed such that the polyamideimide main chains are partially aromatic.

[0036] Partially aromatic polyamideimide backbones, in particular, contribute to a balanced relationship between flexibility and temperature stability. Fully aromatic polyamideimide backbones can be too rigid. However, partial aromaticity, for example, aromaticity in the imide component, can achieve the necessary temperature stability while maintaining flexibility.

[0037] According to a preferred aspect, the polyamideimide may have phenylene groups and / or furan groups as functional groups.

[0038] The introduction of phenylene groups, for example, in the polyamideimide main chain can be relevant for maintaining the necessary flexibility of the main chain. Depending on the choice, the length of the repeat unit and its flexibility can be adjusted by one or more different phenylene groups in the main chain. For example, biphenyl, di- and triphenylmethane, ortho- and paradibenzylbenzene, or tribenzylbenzene can be used as possible phenylene groups. In principle, several different types of these or other phenylene groups can be present in a polyamideimide main chain. This means that it is possible for different phenylene groups to occur in a polyamideimide main chain. However, often only one type of phenylene group is present in a main chain.

[0039] Since furans themselves have a high polarity, the polarity of the dielectric layer can be adjusted by selecting different furans. Benzofuran, dibenzofuran, furanones, or hydroxyfuranones are used for this purpose. For example, the hydroxyfuranones or other furan derivatives can contain one or more hydroxy groups, which are required as reactants for crosslinking via isocyanate groups, which can be formed, for example, from lactam groups, to form a urethane bridge.

[0040] According to a further preferred aspect, the polyamideimide may have a structure according to the chemical formula 1, where R 1 a lactam or a urethane bridge. Preferably, R 1 a urethane bridge. R 2 can be a phenylene group and R 3 a furan.

[0041] Basically, as already described above, lactams are preferred groups, which can be terminally positioned as R 1 are attached to a polymer chain in a starting material. Via the isocyanate groups formed from the lactam, bridges, for example in the form of urethane bridges, can in principle be formed to another polyamideimide main chain. The lactam can, for example, be a β, γ, δ, or ε lactam. Of these, δ and ε lactams are particularly preferred.

[0042] Urethane bridges can be formed from terminal lactams and terminal furans with hydroxy groups in the starting material, connecting the main chains in series and thus extending them. Through this reaction, the main chains can be crosslinked in such a way that the resulting polyamide-imide layer exhibits thermoplastic properties. The number of crosslinks is adjusted so that the dielectric layer of the capacitor does not become too rigid and brittle.

[0043] In a preferred embodiment of the capacitor, a plurality of first electrode layers are stacked alternately with second electrode layers. A dielectric layer is arranged between each two adjacent electrode layers.

[0044] This means that the capacitor can be a multilayer capacitor.

[0045] According to a further preferred aspect, all first electrode layers can be electrically conductively connected to a first external contact and all second electrode layers can be electrically conductively connected to a second external contact.

[0046] A multilayer capacitor with appropriate external contacts allows use in various technical applications.

[0047] According to a further embodiment, a substrate may be arranged on a side surface of the capacitor which is parallel to the plane of the electrode layers.

[0048] As described above, such a substrate can be conductive, i.e. it can also fulfill electrode functions, but it can also have an insulating effect and remain on the component after the manufacturing process.

[0049] In particular, a capacitor as described above can be a surface mounted device (SMD).

[0050] Furthermore, the capacitor, as described above, can also be a through-hole capacitor, meaning it has wires for through-hole mounting. These wires allow the capacitor to be attached to external contact points both electrically and mechanically.

[0051] The capacitor can also be a wound capacitor.

[0052] As a further aspect of the invention, a method for producing a capacitor is provided, comprising the production of a dielectric layer. The dielectric layer is produced by applying a prepolymer polyamideimide solution to a deposition surface, subsequently drying the prepolymer polyamideimide solution on the deposition surface, and annealing the dried prepolymer polyamideimide solution.

[0053] 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 the finished capacitor or simply an intermediate carrier from which the applied and optionally cross-linked polyamideimide film is removed.

[0054] By this method, a capacitor as described above can be manufactured.

[0055] This also allows a uniform dielectric layer to be produced. The prepolymer polyamideimide solution can, in particular, be a solution of a resin that is also suitable as an insulating coating, for example, RESISTHERN® AI 336 L dissolved in an organic solvent.

[0056] Polyamideimides are generally soluble in a wide range of solvents and can be applied in a variety of concentrations to form continuous layers or films. This makes them suitable for the flexible use of a wide variety of deposition methods or different layer thicknesses, as discussed in more detail below.

[0057] When drying the prepolymer polyamideimide solution, most or all of the solvent can be removed.

[0058] When the dried prepolymer polyamideimide solution is annealed, the material becomes denser and cross-linking, for example via lactams, can begin in the layer thus formed.

[0059] The rate of the cross-linking reaction can be determined by the annealing temperature.

[0060] Typically, the degree of crosslinking is determined by the number of linker groups (e.g., via the isocyanate groups and hydroxy groups protected as lactams) on the polyamide-imide main chains in the prepolymer-polyamide-imide solution, and the annealing temperature is chosen so that all linker groups form crosslinks.

[0061] As a further aspect, the method as described above may be modified such that the deposition surface is a surface of a substrate, the dielectric layer is detached from the deposition surface after its formation to produce a dielectric film, the dielectric film is metallized, and finally the metallized dielectric film is wound.

[0062] Thus, the method described above can be used to manufacture a wound capacitor. This has the advantage that the resulting dielectric layer or foil, which is provided with the first and second electrodes by metallization, can also be processed prior to metallization. For example, methods such as foil drawing or similar can be used to optimize the material properties.

[0063] According to a further aspect, the production of a capacitor can comprise the following points: An electrically conductive substrate is used, or alternatively, a substrate on whose surface a first electrode layer is produced. The deposition surface can thus be the surface of the electrically conductive substrate or of a first electrode layer. After applying the dielectric layer to the deposition surface, a second electrode layer can be produced on the dielectric layer, and a further dielectric layer can be produced on this second electrode layer by applying the prepolymer polyamideimide solution to the second electrode layer, drying it, and then annealing it.

[0064] In the case of an electrically conductive substrate, this substrate can serve as an electrode, for example, as the first electrode. A second electrode layer can be applied above this. In this case, of course, another dielectric layer can be applied on top of the second electrode layer, followed by a first electrode layer to create a multilayer capacitor.

[0065] Alternatively, as described, the substrate can be non-conductive, i.e., electrically insulating. In this case, an electrode layer is applied first before additional layers are applied or arranged above the substrate. In both cases, however, this is a process for constructing a stacked multilayer capacitor as opposed to a wound capacitor.

[0066] The prepolymer polyamideimide solution of the above-described process contains polyamideimide main chains on which isocyanate groups or isocyanate groups protected as lactam groups are arranged. Of these, the lactam groups are preferred.

[0067] These have the advantages described above.

[0068] Preferably, the process can be carried out in such a way that the prepolymer polyamideimide solution is applied by doctor blade coating, spin coating, slot die coating or spray coating.

[0069] The invention is described in more detail below using exemplary embodiments. These exemplary embodiments are illustrated in the following figures, which are not to scale. Lengths and relative and absolute dimensions cannot therefore be determined from the figures. The invention is also not limited to the following illustrations. Fig. 1 shows a first embodiment of a capacitor in schematic cross section. Fig. Figure 2a shows the mass loss of a polyamideimide layer in a thermogravimetric analysis. Fig. Figure 2b shows the loss factor of a capacitor. Fig. 3 shows a first multilayer capacitor as a second embodiment of a capacitor in schematic cross section. Fig. 4 shows a second multilayer capacitor as a third embodiment of a capacitor in schematic cross section. Fig. 5 shows a third multilayer capacitor as a fourth embodiment of a capacitor in schematic cross section. Fig. 6 shows a multilayer capacitor suitable for through-hole mounting as a fifth embodiment of a capacitor in schematic cross section. Fig. 7 shows a wound capacitor as a sixth embodiment of a capacitor in schematic cross section.

[0070] Fig. Figure 1 shows a first embodiment of a capacitor 1 in schematic cross-section. The capacitor 1 has an organic dielectric layer 2. The dielectric layer 2 is a uniform layer. This means that it consists of a single material and does not contain any separable volume regions. It is therefore not a composite material. The dielectric layer 2 consists of at least 50 wt.% polyamide-imide. Preferably, the polyamide-imide content is higher, for example, over 90%. Even more preferably, the dielectric layer 2 consists exclusively of polyamide-imide.

[0071] The polyamideimide can be any polyamideimide, in particular it can be a partially aromatic polyamideimide. A polyamideimide according to structural formula 1 is particularly preferred.

[0072] The polyamideimide according to structural formula 1 has a polyamideimide main chain and can have several functional groups. For example, in the polyamideimide main chain, R 2 The structural formula 1 may contain phenylene groups. The phenylene groups can be used to adjust the flexibility of the polyamideimide main chain. For example, a biphenyl, a di- or triphenylmethane, ortho- or paradibenzylbenzene, or tribenzylbenzene can be used.

[0073] Furthermore, furans can be terminally bound, for example as R 3 be arranged on the polyamideimide main chain. Their polarity can thus be used to adjust the polarity of the dielectric layer.

[0074] For example, benzofurans, dibenzofurans, furanones or hydroxyfuranones can be used as furans.

[0075] Furthermore, cross-links usually exist between the different polyamideimide main chains in the dielectric layer 2.

[0076] Typically, the polyamideimide main chains are linked via urethane bridges. These urethane bridges can, for example, be located terminally at the position of the residue R 1 in the structural formula 1. Alternatively, unbridged groups in R 1 -position, such as lactams or isocyanates.

[0077] Preferably, the dielectric layer 2 was made from a polyamideimide resin mixture suitable for coating wires, e.g. a RESISTHERN® AI 336 L solution.

[0078] A first electrode 3 and a second electrode 4 are arranged above and below the dielectric layer 2. Both the first electrode 3, the dielectric layer 2, and the second electrode 4 can be flat.

[0079] A typical stacking occurs over the largest areas of the flat layers.

[0080] The layer thickness of the electrodes can be, for example, 10 to 50 nm, preferably 20 nm. Depending on the manufacturing process, the layer thickness of the dielectric layer 2 can be set in the range between 500 nm and 10 µm.

[0081] 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, chromium / nickel / aluminum, or chromium / nickel / silver. In addition to the elements shown here, a protective layer of hydrocarbon compounds, such as parylenes or fluorine-based hydrocarbons, may be applied to the sides of the capacitor that do not contain the electrodes (not shown).

[0082] The Fig. The first embodiment of a capacitor shown in Figure 1 can be manufactured by any method. Preferably, it is manufactured by solvent-based processes. For example, the first electrode 3 can first be 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 a surface of the substrate by physical vapor deposition (PVD), such as sputtering or thermal evaporation.

[0083] The dielectric layer 2 made of a prepolymer polyamideimide solution can now be applied to the surface of the electrodes 3 as the deposition surface. The prepolymer polyamideimide solution typically contains a largely crosslink-free polyamideimide.

[0084] The prepolymer polyamideimide solution is prepared from a commercially available polyamideimide resin mixture (e.g. RESISTHERN® AI 336) by additional dilution with solvents.

[0085] The polyamideimide resin mixture contains approximately 36% non-volatiles (mainly polyamideimide backbones) in a solution of N-methylpyrolidone (NMP) and xylene. It has an initial viscosity of 4750 ± 1750 mPa s. Furthermore, it has a density of approximately 1.1 g / ml.

[0086] The resulting polyamideimide solution is adjusted with xylene or N-methylpyrolidone to a concentration of 20% or less of the original polyamideimide concentration. For example, a polyamideimide concentration of 19% or 15% by mass relative to the original polyamideimide resin mixture is prepared in xylene.

[0087] The concentration used depends on the layer thickness to be achieved or on the deposition method.

[0088] The resulting prepolymer polyamideimide solution can then be applied to the surfaces of the first electrode 3 as the deposition surface. Application can be carried out by doctor blade coating, stencil printing, spin coating, or spray coating. The coating method depends on the desired thickness of the dielectric layer 2. Thus, thicker layers in the range between 500 nm and 5 µm can be applied by spin coating or spray coating, or thicker layers in the range, for example, from 1 µm to 10 µm can be applied by doctor blade coating or stencil printing.

[0089] The applied solution is dried at a temperature between 60 and 100°C, preferably at 80°C. The dried film is then annealed at temperatures above 200°C, preferably at 250°C.

[0090] During drying, most of the solvent is removed. Further volatile components are removed by annealing. In addition, cross-linking between the main chains can begin during annealing. At a temperature of 250°C, almost complete cross-linking can be achieved in 5-10 minutes. This activates isocyanate groups, usually protected as lactams, which then react with existing hydroxyl groups, for example, those found on furan residues.

[0091] After cooling, the second electrode 4 can be applied again by PVD to the dielectric layer prepared in this way.

[0092] At the end of the process, the substrate can be removed to remove the object from Fig. 1. In principle, however, it can also remain on the capacitor.

[0093] Fig. Figure 2A shows a thermogravimetric analysis (TGA) of the polyamideimide resin mixture used. The temperature ramp is constant at 10 K / min. As the graph of Fig. As Figure 2A shows, no mass loss occurs up to a temperature of about 275°C. Only at a temperature above about 300°C does a mass loss of less than 5% occur. Only above 400°C does the mass loss exceed 5%.

[0094] This demonstrates the extremely high temperature stability of polyamideimide as a dielectric. In particular, continuous temperature stability of over 200°C can be expected for future applications.

[0095] This allows, in particular, the installation of the finished capacitor, for example by soldering, without any degeneration of the component or the dielectric layer being expected.

[0096] Further advantageous properties of polyamideimide as a dielectric for a capacitor are shown in the following Tables 1 and 2 as well as in the graph of the Fig. 2B.

[0097] Table 1 shows the dielectric loss factor (tan δ) of a polyamideimide plate capacitor, similar to the structure shown in Fig. 1. The dielectric layer measured here was made from the polyamideimide resin mixture described above, which was diluted to a mass fraction of 15%, based on the original mixture, with xylene as a solvent (squeegee speed 50 mm / s). The layer thickness was 3 µm, and the capacitor area was 50 mm 2 The measurement was performed using a Keysight E4990A with a PHECOS cooling / heating system from Novocontrol. [Table 1] tanδ Temperatur Frequenzen 1 kHz 10 kHz 100 kHz 1 MHz Raumtemp. 0, 009 0,016 0,019 0,014 100°C 0,009 0,009 0,010 0,017 150°C 0,015 0,013 0,012 0, 014

[0098] As shown in Table 1, the dissipation factor is consistently below 2% in the investigated frequency and temperature range. Remarkably, the dissipation factor even improves slightly with increasing temperature. This demonstrates that polyamide-imide offers excellent dielectric properties as a dielectric.

[0099] This is confirmed by the Fig. 2B, which shows the loss factor of the dielectric layer described in Table 1 at a constant temperature of 150°C as a function of frequency. It can be observed that the loss factor can be considered constant in the investigated frequency range between 1 kHz and 1 MHz, to a first approximation.

[0100] This constant behavior allows a wide application of polyamideimide capacitors in general and a high flexibility of the individual polyamideimide capacitor in particular.

[0101] Table 2 shows the dependence of the permittivity (ε r ) of a polyamideimide plate capacitor according to the structure according to Fig. 1 of temperature and field frequency. The dielectric layer used here was prepared with a 19 wt% solution based on the originally used polyamideimide resin mixture. The layer thickness was 5 µm and the capacitor area was 50 mm. 2 The measurement was performed using a Keysight E4990A with a PHECOS cooling / heating system from Novocontrol. [Table 2] e r Temperatur Frequenzen 1 kHz 10 kHz 100 kHz 1 MHz Raumtemp. 4,0 4,0 3,8 3,6 100°C 4,6 4,4 4,3 4,1 150°C 5,0 4,7 4,5 4,3

[0102] Table 2 shows that there is only a moderate variation in permittivity with respect to temperature and frequency.

[0103] Although a decrease in permittivity with increasing frequency and an increase in permittivity with increasing temperature can generally be observed, the polyamideimide, with an average permittivity of 4, has a permittivity almost twice as high as that of the standard material BOPP.

[0104] This high permittivity is attributed to the partially aromatic nature of the polyamideimide, as well as to the polar groups, such as furan groups, of the polyamideimide. Furthermore, it is fundamentally possible to adjust the polyamideimide to optimize the dielectric losses or other properties in a specific frequency range. This can be achieved by composing a prepolymer polyamideimide solution from various polyamideimides, or by specifically selecting the functional groups on the main chains.

[0105] For the parallel-plate capacitor 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).

[0106] This shows that the polyamideimide used has excellent permittivity combined with high breakdown voltage and ohmic insulation resistance.

[0107] Fig. Figure 3 shows a second embodiment of a capacitor 1 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 flat electrodes.

[0108] Between the first electrodes 3 and the second electrodes 4, i.e. between two adjacent electrodes, there is always a dielectric layer 2 arranged, which corresponds to the dielectric layer 2 from the first embodiment in Fig. 1 corresponds.

[0109] The first electrodes 3 and the second electrodes 4 have the character of internal electrodes.

[0110] The second embodiment of a capacitor 1 is therefore a multilayer capacitor.

[0111] First external contacts 5 and second external contacts 6 are arranged on opposite side surfaces of the multilayer capacitor.

[0112] The first electrodes 3 are electrically connected to the first external contact 5. The second electrodes 4 are electrically connected to the second external contact 6.

[0113] The capacitor assembled in this way can be a surface-mounted device (SMD), which is very well suited for soldering due to its temperature-stable dielectric layer 2. To make the capacitor 1 even more advantageous for use as an SMD capacitor, the external contacts 5 and 6 can be designed in a clamp-like manner. This means that the external contacts 5 and 6 can extend partially onto both sides in the stacking direction.

[0114] The capacitor can, for example, be cuboid-shaped and comprise a total of 1000 repeating units consisting of 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. The individual dielectric layer 2 can have a thickness of 500 nm to 5 µm, preferably between 500 nm and 2 µm. The internal electrodes have a thickness of 10 to 50 nm and preferably 20 nm.

[0115] However, the dimensions of the finished capacitor may differ from those specified here. Length, width, height, and layer thicknesses can be adapted to different technical requirements or to meet different technical tasks.

[0116] A manufacturing process can be similar to the manufacturing process of the first embodiment. For example, a first electrode layer 3 can be applied to a substrate using PVD. Subsequently, a dielectric layer 2 can be applied from solution, followed by a second electrode layer 4, again using PVD. A dielectric layer 2 is then applied to this second electrode layer 4, again using solution. This process can be repeated to achieve a desired number of layers or a specific capacitor capacitance.

[0117] In principle, the internal electrodes can be structured using this process. This can be done either during deposition or after the physical vapor deposition process.

[0118] After stacking, the substrate can be removed.

[0119] Optionally, a protective layer (not shown) similar to that of the first embodiment can then be applied to the side surfaces which remain free of external contacts by means of a vapor deposition process and solvent-based processes or coating methods.

[0120] The external contacts 5 and 6 are mounted on the fully stacked capacitor 1. These can be made of brass, copper, tin, aluminum, silver, or similar materials, for example, and can be applied using physical vapor deposition or other processes, such as solvent-based processes.

[0121] Fig. 4 shows a schematic cross-section of a third embodiment of a capacitor 1, which is also a multilayer capacitor.

[0122] The capacitor 1 in Fig. 4 corresponds in many respects to the capacitor as it is shown in Fig. 3 and described previously. In the Fig. However, in the example shown in Figure 4, the original substrate, which here is substrate 7, is still present on the component.

[0123] The substrate 7, in the case of Fig. 4, is insulating and can be, for example, a glass substrate, a semiconductor wafer or a flexible substrate such as polyimide films or a release tape.

[0124] The manufacturing process for the third embodiment in Fig. 4 corresponds to that of the second embodiment in Fig. 3, except for removing the substrate.

[0125] In Fig. Figure 5 shows a fourth embodiment of a capacitor 1 (here a multilayer capacitor) in schematic cross-section. Fig. The fourth embodiment shown in Figure 5 is largely similar to that of Fig. 4.

[0126] However, here, the substrate 7 is a metallic, conductive substrate, for example, made of aluminum, copper, or similar materials. It is present, for example, as a foil. Due to its conductive nature, it is not necessary to apply a conductive layer as the first electrode 3 to the substrate. The substrate 7 itself can serve as a replacement for one of the first electrodes 3. The dielectric layer 2 is then applied directly to it.

[0127] Since the substrate usually extends over the entire width and length of the capacitor, care must be taken to ensure that the second external contact 5 does not make electrical contact with the substrate.

[0128] The procedure is also similar to that in Fig. 4 described embodiment.

[0129] The fifth embodiment, which is Fig. 6 is shown in schematic cross-section, is similar in almost all aspects to the second embodiment of a capacitor 1. It is therefore also a multilayer capacitor. However, this multilayer capacitor has wires 8 and 9 on its external contacts 5 and 6, which enable through-hole installation in an application. It is therefore a through-hole capacitor. The wires 8 and 9 create an electrical and usually a mechanical contact with connection points in an application. The wires 8 and 9 can be attached to the capacitor 1 by any desired method, such as bonding.

[0130] Fig. Figure 7 shows a schematic cross-section of a sixth embodiment of a capacitor 1. This is a wound capacitor. In its structure, the wound capacitor is similar to the first embodiment, i.e., a dielectric layer 2 is sandwiched between a first electrode 3 and a second electrode 4. The corresponding sandwich-like structure is rolled up into a wound capacitor.

[0131] However, the manufacturing process used differs from the manufacturing process according to Fig. 1. This is usually done on a substrate with the Fig.Using the deposition process described in Figure 1, the dielectric film 2 is first produced. This film can then be removed from the substrate. It can then be post-processed using any method. The resulting film can then be metallized on one side or, in this case, both sides using PVD. The metallized film thus obtained can be wound into a wound capacitor. Typical layer thicknesses for wound capacitor films with polyamide-imide are in the range between 1 µm and 10 µm, preferably between 2 µm and 5 µm. List of reference symbols 1 capacitor 2 dielectric layer 3 first electrode 4 second electrode 5 first external contact 6 second external contact 7 Substrat 8 first wire 9 second wire

Claims

[1] Capacitor (1) comprising a dielectric layer (2) which is uniform, wherein the dielectric layer (2) contains polyamideimide with polyamideimide main chains which comprise the amide and imide groups of the polyamideimide, a first electrode (3) and a second electrode (4) are arranged directly adjacent to the dielectric layer (2), and the polyamideimide main chains in the dielectric layer (2) have urethane bridges as chemical crosslinks between the polyamideimide main chains. [2] The capacitor (1) according to claim 1, wherein the dielectric layer (2) consists of 50 wt% or more of polyamideimide. [3] Capacitor (1) according to one of claims 1 and 2, wherein the dielectric layer (2) is free of solid inorganic materials. [4] Capacitor (1) according to one of claims 1 to 3, wherein the polyamideimide main chains are partially aromatic. [5] Capacitor (1) according to one of claims 1 to 4, wherein the polyamideimide has phenylene groups and / or furan groups as functional groups. [6] Capacitor (1) according to claim 5, wherein the polyamideimide has a structure according to chemical formula 1, wherein - R 1 a lactam or a urethane bridge, - R 2 is a phenylene group, and - R 3 is a furan. [7] Capacitor (1) according to one of claims 1 to 6, wherein a plurality of first electrode layers (3) are stacked alternately with second electrode layers (4), and the dielectric layer (2) is arranged between each two adjacent electrode layers (3, 4). [8] Capacitor (1) according to one of claims 1 to 7, wherein all first electrode layers (3) are electrically conductively connected to a first external contact (5), and all second electrode layers (4) are electrically conductively connected to a second external contact (6). [9] Capacitor (1) according to one of claims 1 to 8, wherein a substrate (7) is arranged on a side surface of the capacitor which is parallel to the plane of the electrode layers (3, 4). [10] Capacitor (1) according to one of claims 7 to 9, wherein the capacitor (1) is a surface mounted device (SMD). [11] Capacitor (1) according to one of claims 7 to 9, wherein the capacitor has wires (8, 9) for through-hole mounting. [12] Capacitor (1) according to one of claims 7 and 8, wherein the capacitor (1) is a wound capacitor. [13] Method for producing a capacitor (1) comprising the production of a dielectric layer (2) by Applying a prepolymer polyamideimide solution containing polyamideimide main chains on which isocyanate groups and / or lactam groups are arranged on polyamideimide main chains, to a deposition surface, drying the prepolymer polyamideimide solution on the deposition surface, Annealing the dried prepolymer polyamideimide solution. [14] A method for producing a capacitor (1) according to claim 13, wherein the deposition surface is a surface of a substrate (7), the dielectric layer (2) is detached from the deposition surface after its production in order to produce a dielectric film, the dielectric foil is metallized, and the metallized dielectric foil is wound. [15] A method for producing a capacitor (1) according to claim 13, wherein an electrically conductive substrate (7) is used or a substrate (7) on the surface of which a first electrode layer (3) is produced, the deposition surface is the surface of the electrically conductive substrate (7) or the first electrode layer (3), after applying the dielectric layer (2) to the deposition surface, a second electrode layer (4) is produced on the dielectric layer (2), and a further dielectric layer (2) is produced on the second electrode layer (4) by applying the prepolymer polyamideimide solution to the second electrode layer (4), Drying of the prepolymer polyamideimide solution on the second electrode layer (4), Annealing the dried prepolymer polyamideimide solution. [16] A method for producing a capacitor (1) according to any one of claims 13 to 15, wherein the prepolymer polyamideimide solution is applied by doctor blade coating, die coating, stencil printing, spin coating or spray coating.

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