Capacitor

Abstract

To provide an electric capacitor that uses polyamideimide as a capacitor material.SOLUTION: A capacitor (1) includes a single dielectric layer (2) that is free of solid inorganic materials, the dielectric layer (2) includes polyamideimide, and a first electrode (3) and a second electrode (4) are disposed immediately adjacent to the dielectric layer. The dielectric layer includes a polyamideimide backbone that contains amide and imide groups and is linked through various crosslinks.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to electrical capacitors. [Background technology]

[0002] Polymer dielectrics find diverse application in power electronics applications, particularly in passive components such as electrical capacitors.

[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] Polyamideimides have been known for some time now, inter alia, through their use as heat resistant coatings for enameled wire and the like.

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

[0006] US Pat. No. 5,399,633 discloses that polyamideimide can be a component of a matrix for inorganic particles in a capacitor dielectric.

[0007] US Patent No. 5,399,633 discloses that polyamideimide can be used in a capacitor having a non-uniform dielectric layer consisting 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] US Patent Application Publication No. 2007 / 0258190 [Patent Document 2] JP 2000-338667 A [Patent Document 3] US Patent Application Publication No. 2010 / 0259865 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the use of polyamideimides as capacitor materials with excellent temperature stability and simultaneously high or customized dielectric constants has not been previously known. [Means for solving the problem]

[0010] According to a first aspect, a capacitor is presented having a single dielectric layer, where the dielectric layer comprises polyamideimide and at least one first electrode is disposed immediately adjacent to the dielectric layer.

[0011] Directly adjacent electrodes can be placed on top of the layers. Preferably, the direct contact is at the molecular level, as can be achieved by the coating methods described below.

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

[0013] The single dielectric layer may be homogeneous and may comprise polyamideimide, for example. Homogeneous here may in particular mean that the dielectric layer does not comprise additives that would make the layer inhomogeneous. In particular, it is preferred if no micro- or nano-materials or additional other solids are included in the dielectric layer. The dielectric layer preferably does not comprise hybrid materials. Since the electrodes are arranged directly adjacent to the single dielectric layer, there are also no further layers between the single dielectric layer and the electrodes, for example different from the single dielectric layer.

[0014] A single dielectric layer comprising polyamideimide has the advantage over other polymer-based dielectric layers of being temperature stable up to approximately 300° C. Furthermore, a dielectric layer comprising polyamideimide can have a high dielectric constant over a wide input frequency range, where a high breakdown voltage is preferably also maintained.

[0015] Therefore, polyamideimide as a polymeric material for dielectric layers in capacitor applications can simultaneously meet the conflicting requirements of high temperature stability and customized or stable dielectric properties.

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

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

[0018] Thus, even the requirements for future applications, such as those in aerospace engineering, may be met, where operating temperatures of more than 150° C., possibly even more than 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 superior dielectric properties of polyamideimide outweigh 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 solely of polyamideimide.

[0022] The inventors have recognized that polyamideimide can be easily chemically functionalized. It can therefore be flexibly customized in its properties, for example with outstanding electrical or electronic properties to be met depending on the application by only organic components. Thus, the capacitor is preferably fabricated such that the dielectric layer, which is preferably a single dielectric layer, does not contain solid additional materials such as inorganic materials. The dielectric layer is preferably not a hybrid material.

[0023] Dielectric layers that do not contain inorganic materials may be easier to manufacture than mixed layers made of inorganic-organic hybrid materials.

[0024] Preferably, the dielectric layer of the capacitor comprises a polyamideimide backbone that includes the amide and imide groups of the polyamideimide.

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

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

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

[0028] Through a customized number of crosslinks, the mechanical and electronic properties, and especially the temperature properties, of polyamideimides can be targeted.

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

[0030] Preferably, the crosslinks include linear bonds linking terminal units of a polyamideimide backbone to terminal units of other polyamideimide backbones, thereby producing a series of chain links. Preferably, the linear bonds between the backbones are different from the bond type within the polyamideimide backbone. That is, the crosslinks preferably do not have an amide-imide motif. However, the crosslinks can be amide or imide bonds. In that case, such bonds can interrupt the repeating motif of the polyamideimide motif that is repeated within the polyamideimide backbone. Multiple polyamideimide backbones can be linearly linked in series.

[0031] The number of crosslinks can be controlled by the annealing temperature. The higher it is, the more polyamideimide backbones are connected in series with each other. Thus, the polymer chains become longer as the annealing temperature increases. This can increase the mechanical stability of the dielectric layer. Furthermore, the dissipation factor can be reduced. This method of controlling the degree of crosslinking by temperature is especially favorable for linear bonds.

[0032] Preferably, the chemical crosslinks are formed via urethane crosslinks.

[0033] Urethane crosslinks can be preferably formed through isocyanate groups on the backbone, which react with hydroxyl groups on other backbones to form urethane bonds.

[0034] Lactams can also be present as functional groups in the starting material, since they act as protective groups to control the reaction between isocyanate groups and hydroxyl groups. Such lactams are ring-opened, for example by the action of temperature, to form isocyanate groups, which then react, for example, with hydroxyl groups of other main chains. That is to say, isocyanate groups and / or lactam functional groups can be present in the starting material. However, preferably, only lactams are present in the starting material, since very long durability can be achieved even at room temperature. Furthermore, the applicable drop times, for example, during the production of the dielectric layer, can be extended.

[0035] Preferably, imide crosslinks may be formed between the polyamideimide backbones instead of or in addition to other crosslinks such as urethane crosslinks.

[0036] Imide crosslinks can be formed by, for example, reacting an anhydride group with a suitable group, such as an amine, on another polyamideimide backbone to form an imide crosslink as a crosslink between two polyamideimide backbones. Preferably, the anhydride group is a phthalic anhydride group. Such reactions can also form bonds between different points on the polyamideimide backbone.

[0037] Both urethane and imide crosslinks are particularly suitable for the technically convenient formation of linear bonds. Moreover, the degree of linear bonding with these groups can be adjusted particularly precisely by controlling the annealing temperature.

[0038] Furthermore, crosslinks can also be formed via urea crosslinks. This can be formed with the participation of amine groups on the polyamideimide backbone. It is particularly preferred that three-dimensional crosslinks are formed thereby, i.e. linear bonds are formed not exclusively by this binding motif. Even more preferably, only such crosslinks can be formed via urea crosslinks, but not linear bonds. Particularly preferably, these can coexist with linear bonds. For example, polymer materials that are three-dimensionally crosslinked via urea crosslinks, as well as linearly crosslinked via imide or urethane crosslinks, have been formed or can be formed for the dielectric layer.

[0039] In principle, urethane bridges can be present in addition to imide bridges, however it is preferred that only one linear bonding motif is present, as this facilitates process control.

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

[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, commercially available RESISTERN® AI 336 L.

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

[0043] The partially aromatic polyamideimide backbone in particular contributes to a balanced relationship between flexibility and temperature stability. A fully aromatic polyamideimide backbone may therefore be too rigid. However, the partial aromaticity, i.e. the aromaticity of, for example, the imide component, allows the necessary temperature stability to be obtained at the same time as flexibility.

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

[0045] For example, the introduction of phenylene groups in the polyamideimide backbone may be related to the acquisition of the necessary flexibility of the backbone. For example, the length of the repeating unit and its flexibility are adapted depending on the selection from among one or more different phenylene groups in the backbone. For example, biphenyl, diphenylmethane and triphenylmethane, ortho- and para-dibenzylbenzene or tribenzylbenzene can be used as possible phenylene groups. In principle, several different ones of these or other phenylene groups can be present in the polyamideimide backbone. That is, it is possible for various phenylene groups to be present in the polyamideimide backbone. However, in many cases, only one type of phenylene group is present in the backbone.

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

[0047] According to another preferred embodiment, the polyamideimide can have a structure according to the formula (Formula 1), where R 1 is an unreacted group such as a lactam, an anhydride or an amine, or a urethane or imide bridge. 1 is a urethane crosslink or an imide crosslink. 2 is a phenylene group, R 3 Alternatively, R can be furan. 3can be a urethane or imide crosslink, in which case the polyamideimide backbone is attached at both ends to two other polyamideimide backbones.

[0048] [ka]

[0049] In principle, lactams can be prepared as already mentioned above, for example by reacting R 1 is a preferred group which is terminally bonded as a carboxylate. Via the isocyanate groups formed from the lactams, in principle, crosslinks, for example in the form of urethane crosslinks, can be formed to other polyamideimide backbones. The lactams can be, for example, β, γ, δ or ε lactams. Of these, in particular δ and ε lactams are preferred.

[0050] Urethane crosslinks can be formed from the lactam terminal and furan terminal in the starting material with hydroxyl groups, which connects the main chain in series and thus extends it. Through this reaction, the main chain can be crosslinked so that the formed polyamideimide layer has thermoplastic properties. In this case, the number of crosslinks is adjusted so that the dielectric layer of the capacitor is not too hard and brittle.

[0051] As explained above, linearly linked imide crosslinks can be formed via anhydrides, such as phthalic anhydride, reacting with amines. Alternatively, isocyanate groups can react with anhydride groups to give imides, with CO2 being liberated.

[0052] In the starting material, i.e. before the crosslinks containing linear bonds are generated, the functional groups suitable for the corresponding bonds are represented by R 3 or R 1 It is in position.

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

[0054] That is, the capacitor can be a multi-layer capacitor.

[0055] Alternatively, a multilayer capacitor can be cut, for example from a coil, in which case a conductive or preferably metallic structured layer can be used as an electrode, which layer has at least two electrically isolated areas and thus functions as a capacitor electrode.

[0056] According to a further preferred embodiment, 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 may be applied by flame spray, PVD process or other methods.

[0058] Multilayer capacitors with corresponding external contacts allow for use in a variety of technological applications.

[0059] According to a further embodiment, the substrate may be arranged on a side of the capacitor that lies parallel to the plane of the electrode layer.

[0060] As mentioned above, such a substrate can be conductive, i.e. perform an electrode function, but 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 mounted device (SMD).

[0062] Furthermore, the capacitors can be through-hole capacitors (Durchsteck condensers), as mentioned above, i.e. have wires for through-hole mounting, with which the capacitors can be both conductively and mechanically attached to external contacts.

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

[0064] In a further aspect of the present invention, a method for manufacturing a capacitor is provided, including the preparation of a dielectric layer by applying a prepolymer-polyamideimide solution onto a deposition surface, followed by 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 electrode layer. The deposition surface can also be the surface of a substrate. The substrate can be that of a finished capacitor or it can simply be an intermediate carrier from which the applied and possibly crosslinked polyamideimide film is peeled off again.

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

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

[0068] Polyamideimides are essentially soluble in many solvents and can be applied in a wide variety of concentrations to form closed layers or films, and therefore are suitable for the flexible use of a wide variety of deposition methods or different layer thicknesses, as will be explained in more detail below.

[0069] Upon drying of the prepolymer-polyamideimide solution, the solvent may be largely or completely removed.

[0070] Upon annealing of the dried prepolymer-polyamideimide solution, the material becomes denser and crosslinking, for example via lactams, can be used within the layers 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., lactam-protected isocyanate groups) on the polyamideimide backbone in the prepolymer polyamideimide solution, and the annealing temperature is selected such that all linker groups form crosslinks.

[0073] In the preferred case, the linker group is located at the end of the polyamideimide backbone.Basically, but especially in this case, the degree of crosslinking can be influenced or adjusted by the annealing temperature. The higher the annealing temperature is selected, the more crosslinks are formed in a given time. This allows more polyamideimide backbones to be bonded together.

[0074] In a further aspect, the method can be modified such that the deposition surface is a surface of a substrate as described above, the dielectric layer is stripped from the deposition surface after its fabrication to produce a dielectric film, the dielectric film is metallized, and finally the metallized dielectric film is rolled.

[0075] The method described above can therefore be used to manufacture wound capacitors. This has the advantage that the dielectric layer or film thus formed, which is applied to the first and second electrodes by metallization, can be further processed even before metallization. By way of example, methods such as foil drawing can be applied in order 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 whose surface a first electrode layer is produced, is used. Thus, the deposition surface can be the conductive substrate or the surface of the first electrode layer. After applying a dielectric layer onto 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 a prepolymer polyamideimide solution onto the second electrode layer, drying it and subsequently annealing it.

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

[0078] Alternatively, as discussed above, the substrate can be, for example, non-conductive, i.e., electrically insulating. In that case, an electrode layer is applied first before further layers are applied or disposed over the substrate. In either case, it is a method for constructing a laminated multilayer capacitor from solution, as opposed to a wound capacitor or a multilayer capacitor cut from a winding.

[0079] It is preferred for the above described process if the prepolymer polyamideimide solution comprises a polyamideimide backbone having isocyanate groups and / or more preferably isocyanate groups protected as lactam groups disposed on the polyamideimide backbone.

[0080] These have the advantages mentioned above.

[0081] Preferably, the method may be carried out such that the prepolymer polyamideimide 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 reference to exemplary embodiments. These exemplary embodiments are illustrated in the following drawings, which are not to scale. Therefore, lengths as well as 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] 1 shows a first embodiment of a capacitor in a schematic cross-sectional view. [Figure 2a] 1 shows the mass loss of a polyamideimide layer in a thermogravimetric analysis. [Figure 2b] The transition of the dissipation factor of the capacitor is shown. [Diagram 3] 2 shows a first multilayer capacitor as a second embodiment of a capacitor in a schematic cross-sectional view. [Figure 4] 2 shows a second multilayer capacitor as a third embodiment of a capacitor in a schematic cross-sectional view. [Diagram 5] 2 shows a third multilayer capacitor as a fourth embodiment of a capacitor in a schematic cross-sectional view. [Figure 6] 1 shows in schematic cross-section a fifth embodiment of a capacitor, a multilayer capacitor suitable for through-hole mounting. [Figure 7] 1 shows a schematic cross-sectional view of a wound capacitor as a sixth embodiment of a capacitor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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, crosslinks preferably exist between the various polyamideimide backbones in the dielectric layer 2 .

[0091] Preferably, the polyamideimide backbones are bonded to one another via urethane bridges and / or imides. These bonds are, for example, represented by R 1 Alternatively, non-bridging groups such as lactam isocyanates or anhydrides may also be present in R 1 It may be in position.

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

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

[0094] The preferred lamination is performed across the largest surface area of ​​the flat 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 electrodes can be made of aluminum or silver, or preferably an aluminum zinc alloy. Alternatively, the electrodes can be multi-layer electrodes 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 a fluorinated hydrocarbon, may be applied on the side of the capacitor that does not have an electrode (not shown).

[0097] As an alternative, not shown, there may be only one electrode 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 a first electrode 3 can be produced on a substrate. The substrate can be a rigid substrate, for example glass or a semiconductor wafer. It can be a metal film, for example aluminum or copper, or a flexible polymer film, for example polyimide, or a release tape. On the surface of the substrate, the first electrode is applied, for example by physical vapor deposition (physical vapor deposition, PVD), for example sputtering or thermal evaporation.

[0099] Now, on the surface of the electrode 3 as the deposition surface, a dielectric layer 2 consisting of a prepolymer polyamideimide solution can be applied. The prepolymer polyamideimide solution preferably contains a large proportion of non-crosslinked polyamideimide.

[0100] Prepolymer polyamideimide solutions are prepared from commercially available polyamideimide resin mixtures (e.g., RESISHERN® AI 336) by further dilution with a solvent.

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

[0102] The polyamideimide solution thus provided is adjusted with xylene or N-methylpyrrolidone to a concentration of 20% or less of the initial polyamideimide concentration. In one example, a polyamideimide concentration of 19% or 15% by weight is produced based on the initial polyamideimide resin mixture in xylene.

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

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

[0105] The solution thus applied is dried at a temperature between 60 and 100° C., preferably at 80° C. The dried film is subsequently annealed at a temperature above 200° C., preferably at 250° C.

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

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

[0108] At the end of the method, the substrate can be removed to obtain the article of Figure 1. In principle, however, it can also remain on the capacitor.

[0109] Figure 2a shows the thermogravimetric analysis (TGA) of the polyamideimide resin mixture used. The temperature gradient is constant at 10 K / min. As the graph in Figure 2a shows, 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. Only above 400°C does the mass loss exceed 5%.

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

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

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

[0113] Table 1 shows the dissipation factor (tan δ) of a polyamideimide flat capacitor similar to the structure described in Figure 1. The dielectric layers measured here were measured from the above polyamideimide resin mixture diluted to a mass fraction of 15% with respect to the initial mixture with xylene as the 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 performed using a Keysight E4990A with a Novocontrol PHECOS cooling / heating system.

[0114] [Table 1]

[0115] As shown in Table 1, the dissipation factor is always less than 2% in the tested frequency and temperature ranges. Notably, the dissipation factor even improves slightly with increasing temperature, indicating that polyamideimide as a dielectric has outstanding dielectric properties.

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

[0117] This consistent behavior allows for a wide range of uses for polyamide-imide capacitors in general, and for high flexibility for individual polyamide-imide capacitors in particular.

[0118] Table 2 shows the dielectric constant (ε r The dependence of the dielectric layer on temperature and electrical frequency is shown. The dielectric layer used here was produced using a 19% by weight solution of 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 Novocontrol PHECOS cooling / heating system.

[0119] [Table 2]

[0120] Table 2 shows that there is only a small variation in the dielectric constant with respect to temperature and frequency. Essentially, one can see a decrease in dielectric constant with increasing frequency or an increase in dielectric constant with increasing temperature, however, polyamideimide with an average dielectric constant of 4 has almost twice the dielectric constant of the standard material BOPP.

[0121] This high dielectric constant is due to the partially aromatic character of polyamideimides and to polar groups, such as furan groups. Moreover, it is fundamentally possible to tailor polyamideimides so that their dielectric losses or other properties are optimized in a particular frequency range. This can be done both by the composition of prepolymer polyamideimide solutions consisting of different polyamideimides and by the special selection of functional groups on the backbone.

[0122] For the flat capacitors listed 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 is always above 3 TΩ (measured with Novocontrolsystem Alpha A).

[0123] This indicates that the polyamideimide used has an excellent dielectric constant as well as a high breakdown voltage and ohmic insulation resistance.

[0124] 3 shows in a schematic cross-sectional view a second embodiment of a capacitor 1. The capacitor 1 comprises a number of first electrodes 3 stacked alternating with second electrodes 4. The two electrodes are flat electrodes.

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

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

[0127] The second embodiment of the capacitor 1 is therefore a multilayer capacitor.

[0128] On the opposite side 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 a first external contact 5. The second electrode 4 is conductively connected to a second external contact 6.

[0130] The capacitor thus assembled can be a surface mounted 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 clamp-like manner, i.e. they can extend slightly in the stacking direction on both side surfaces.

[0131] The capacitor can be, for example, rectangular and can have a total of more than 1000 repeat units, including the first electrode, the dielectric layer, the second electrode and the further dielectric layer. It can have a length of 3-4 mm, a width of 2-3 mm and a height of 1-2 mm. The individual dielectric layers 2 here can 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 finished capacitor may differ from those presented here: length, width, height and layer thicknesses can be adapted to different technical requirements or for different technical tasks.

[0133] The manufacturing method can be similar to that of the first embodiment. For example, on a substrate, for example a first electrode layer 3 can be applied by PVD. Then, from solution, a dielectric layer 2 can be applied, followed by a second electrode layer 4, again by PVD. On top of this, again from solution, a dielectric layer 2 is applied. This can be repeated to achieve the desired number of layers of the capacitor or a certain capacitance.

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

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

[0136] Optionally, a protective layer (not shown) similar to that of the first embodiment can then be applied on the sides that remain free of external contacts by a deposition process, a solvent-based process, or a coating process.

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

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

[0139] The capacitor 1 of Figure 4 corresponds in large part to the capacitor shown in Figure 3 and described above. However, in the example shown in Figure 4, the original substrate, here substrate 7, is still present on the component.

[0140] The substrate 7 in FIG. 4 is insulating 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] 5 shows a fourth embodiment of the capacitor 1, here a multilayer capacitor, in a schematic cross-sectional view. The fourth embodiment shown in FIG. 5 is similar to that of FIG.

[0143] Here, however, the substrate 7 is a metallic conductive substrate, for example made of aluminum, copper or a similar material. It is present, for example, as a film. Due to its electrical conductivity, it is not necessary to provide a conductive layer on the substrate as the first electrodes 3. The substrate 7 itself can serve as a substitute for one of the first electrodes 3. Onto this, the dielectric layer 2 is then applied directly.

[0144] Since the substrate preferably extends across the entire width and length of the capacitor, care must be taken to ensure 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.

[0146] The fifth embodiment shown in schematic cross section in FIG. 6 is in almost all respects similar to the second embodiment of the capacitor 1, i.e. 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 allow mounting in a through-hole mounting, i.e. it is a through-hole capacitor. The wires 8 and 9 in one application create an electrical and mostly mechanical contact with the connection sites. The wires 8 and 9 can be fixed to the capacitor 1 by any method, for example by bonding.

[0147] 7 shows in a schematic cross-sectional view 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, i.e. a dielectric layer 2 is surrounded in a sandwich-like manner by a first electrode 3 and a second electrode 4. The corresponding sandwich-like structure is rolled to form the wound capacitor.

[0148] However, the manufacturing method used differs from the one corresponding to FIG. 1. Thus, preferably on a substrate, a dielectric film 2 is first produced by the deposition method described with reference to FIG. 1. This can then be peeled off from the substrate. It can then be post-treated by any method. The film thus obtained can then be metallized by PVD on one side or in this case on both sides. The metallized film thus obtained can be rolled into a wound capacitor. The preferred layer thickness of the wound capacitor film with 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 producing the various structures, first the formation of a polyamideimide film for the dielectric in a roll-to-roll process from solution is carried out by doctor blade of a prepolymer polyamideimide solution onto a substrate previously provided with a release agent. This is followed by drying and simultaneously annealing at above 200 ° C, preferably above 220 ° C, best at 250 ° C. This is followed by peeling of the dried and crosslinked polyamideimide film from the substrate and its rolling. Optionally, an intermediate film as a protection can be rolled together. This is followed by application of the electrodes. This is preferably also carried out in a roll-to-roll process. The electrode layers here can be applied on one side or on both sides, depending on the technical requirements. The electrodes can be structured or unstructured. The thickness of the electrodes towards the edges can be adapted or can be adapted. This is followed by segmentation of the roll with an optional subsequent pressing into a flat coil. The external contacts are then applied by flame spraying, PVD (e.g. sputtering, thermal evaporation) or by electrical processes. By the latter, SMD components can be produced. In the case of flat coils, the application of the side contacts and, in addition, the attachment of the wires is likewise followed by the injection of a temperature-stable, water-repellent grout. In the case of SMD capacitors, the application of a protective or barrier layer can take place, as already mentioned above.

[0150] However, further processing of the membranes produced as described above can also take place in a sheet-to-sheet process. Here, membrane pieces are cut to defined sizes, for example DIN A5 or DIN A4 size. These membrane pieces are subsequently coated with electrodes. This corresponds to the production of a motherstack. The electrode coating is carried out on both sides and structured by a PVD process. The individual membrane pieces are then stacked and pressed, after which the individual capacitors are cut out of the motherstack and provided with side contacts, for example by flame spraying, electroplating, etc., followed by grouting or stabilization with protective or barrier layers. [Explanation of symbols]

[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, said dielectric layer (2) comprising polyamideimide, a first electrode (3) disposed directly adjacent said dielectric layer (2), said polyamideimide comprising biphenyl, triphenylmethane, orthodibenzylbenzene, paradibenzylbenzene, tribenzylbenzene, benzofuran, dibenzofuran, furanone, or hydroxyfuranone as a functional group.

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) according to any one of claims 1 to 3, wherein the dielectric layer (2) comprises a polyamideimide backbone containing amide and imide groups of the polyamideimide.

5. 5. The capacitor (1) of claim 4, wherein chemical crosslinks are formed within the dielectric layer (2) between the polyamideimide backbones or within the polymer backbone.

6. The capacitor (1) of claim 5, wherein the crosslinks linearly link the polyamideimide backbones to one another.

7. The capacitor (1) according to claim 5 or 6, wherein the chemical crosslinks are selected from urethane crosslinks, imide crosslinks and urea crosslinks.

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

9. The capacitor (1) according to claim 6, in which in addition to linear bonds, three-dimensional cross-links are formed via urea cross-links.

10. The capacitor (1) according to any one of claims 4 to 9, wherein the polyamideimide backbone is partially aromatic.

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

12. 8. The capacitor (1) of claim 7, 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).

13. The capacitor (1) according to any one of claims 1 to 12, 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).

14. A capacitor (1) according to any one of claims 1 to 13, 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).

15. 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).

16. The capacitor (1) according to any one of claims 13 to 15, wherein the capacitor (1) is a surface mounted device (SMD).

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

18. The capacitor (1) according to claim 13 or 14, wherein the capacitor (1) is a wound capacitor.

19. A method for producing a capacitor (1) according to claim 1, comprising the steps of: A prepolymer polyamide-imide solution is applied onto the deposition surface, drying the prepolymer-polyamideimide solution on the deposition surface; annealing the dried prepolymer-polyamideimide solution; 23. A method for producing a capacitor (1), comprising producing a solid inorganic-free dielectric layer (2) by:

20. the deposition surface being a surface of a substrate (7); After its formation, the dielectric layer (2) is stripped from the deposition surface to form a dielectric film; The dielectric film is metallized; The metallized dielectric film is rolled. A method for manufacturing a capacitor (1) according to claim 19.

21. An electrically conductive substrate (7) or a substrate (7) on whose surface a first electrode (3) is produced is used, the deposition surface is a surface of the conductive substrate (7) or the first electrode (3); After application of the dielectric layer (2) onto the deposition surface, a second electrode (4) on the dielectric layer (2) is produced, A further dielectric layer (2) on said second electrode (4), A prepolymer polyamideimide solution is applied onto the second electrode (4), drying the prepolymer polyamideimide solution on the second electrode (4); annealing the dried prepolymer-polyamideimide solution; This results in A method for manufacturing a capacitor (1) according to claim 19.

22. The method for producing a capacitor (1) according to any one of claims 19 to 21, wherein the prepolymer polyamideimide solution contains a polyamideimide main chain, and an isocyanate group, a lactam group, and / or anhydride group are disposed on the polyamideimide main chain.

23. 23. The method for producing a capacitor (1) according to claim 22, wherein the isocyanate group, lactam group and / or anhydride group are located at the end of a polyamideimide main chain.

24. The method for manufacturing a capacitor (1) according to any one of claims 19 to 23, wherein the prepolymer polyamideimide solution is applied by doctor blading, nozzle coating, stencil printing, spin coating or spray coating.

Images