Mixture for coating an electrical device, method for producing a coating layer on an electrical device, and electrical device

Abstract

A mixture for coating an electrical device is specified. According to one embodiment, the mixture comprises a fluorinated polymer powder and a fluorinated dielectric liquid. Furthermore, a method for producing a coating layer on an electrical device and an electrical device are specified.

Description

[0001] P2023,1107 WO N August 8, 2024 - 1 - Description Mixture for coating an electrical device, method for producing a coating layer on an electrical device, and electrical device A mixture for coating an electrical device, a method for producing a coating layer on an electrical device, and an electrical device are specified. It is an object to provide a mixture for efficiently coating an electrical device. It is a further object to provide a simple method to produce a coating layer on an electrical device. Additionally, it is an object to provide an electrical device with improved efficiency. A mixture for coating an electrical device, in particular for coating a sensor arrangement, is specified. A mixture is a product of mechanically blending or mixing two or more chemical substances or compounds without chemical bonding or other chemical change so that each substance or compound retains its chemical properties. Even though there are no chemical changes to the substances or compounds of the mixture, the physical properties of the mixture, such as its viscosity, may differ from those of the individual substances or compounds. In particular, the mixture is a liquid. In other words, the mixture is in liquid form such as a paste. For example, the mixture is a solution or a dispersion such as a suspension or a colloid. According to at least one embodiment, the mixture comprises a fluorinated polymer powder. Here and in the following, a fluorinated chemical compound is a chemical compound in which P2023,1107 WO N August 8, 2024 - 2 - one or more hydrogen atoms of the compound is replaced with fluorine. Here and in the following, a polymer is an organic molecule comprising or consisting of a chain or network of many repeating units formed by chemically bonding together a plurality of monomers. In other words, a fluorinated polymer is a fluoropolymer. Here and in the following, a powder is a solid comprising a multiplicity of fine particles having diameters in the micrometer range. In other words, the fluorinated polymer powder is a solid of a multiplicity of small particles of a fluorinated polymer. In particular, the particles of the fluorinated polymer have a diameter between and including 1 µm and 500 µm, for example, between and including 1 µm and 100 µm. According to at least one embodiment, the mixture comprises a fluorinated dielectric liquid. Here and in the following, a dielectric is an electrical insulator that can be polarized by an applied electric field. In other words, the fluorinated dielectric liquid is a fluorinated compound having dielectric properties that is present in the liquid state of matter. According to at least one embodiment, the mixture comprises a fluorinated polymer powder and a fluorinated dielectric liquid. It is an idea of the present application to provide a mixture for coating an electrical device that is easily processable. By using a fluorinated dielectric liquid in conjunction with a fluorinated polymer powder, the processing properties of the fluorinated polymer powder are enhanced. The mixture allows to flexibly process fluorinated polymer powders and transform them into liquid form such as into a paste. The fluorinated dielectric liquid binds the particles of the P2023,1107 WO N August 8, 2024 - 3 - fluorinated polymer powder in the mixture in order to bring the mixture to a surface that is to be coated with the fluorinated polymer powder. As a result, the mixture can be easily applied and processed. Furthermore, by using a fluorinated polymer powder and a fluorinated dielectric liquid, the mixture maintains stable properties, such as viscosity and processability, for a longer period of time. According to at least one embodiment, the fluorinated dielectric liquid has a vapor pressure of less than or equal to 100 hPa at 25 °C, in particular of less than or equal to 50 hPa at 25 °C, for example of less than or equal to 1 hPa at 25 °C. In other words, the fluorinated dielectric liquid has a low evaporation rate. In particular, the fluorinated dielectric liquid has a vapor pressure of at least 0.001 hPa at 25 °C. For example, the fluorinated dielectric liquid has a vapor pressure of 0.2667 hPa at 25 °C. A mixture comprising a fluorinated dielectric liquid with a low evaporation rate can advantageously increase the pot life of the mixture, i.e. the time that the mixture can be used before becoming unusable, by reducing the amount of fluorinated dielectric liquid evaporating during storing and processing the mixture. According to at least one embodiment, the mixture consists of the fluorinated polymer powder and the fluorinated dielectric liquid. In other words, the mixture is free of other substances, compounds, or components. A mixture consisting of the fluorinated polymer powder and the fluorinated dielectric liquid can advantageously be produced easily and cost- effective. According to at least one embodiment, the mixture is a heterogeneous mixture. In particular, the particles of the P2023,1107 WO N August 8, 2024 - 4 - fluorinated polymer powder are at least partially, in particular completely, insoluble in the fluorinated dielectric liquid. In other words, the mixture can be a dispersion, in particular a suspension. Here and in the following, a dispersion describes distributed particles of one material that are dispersed in a continuous phase of another material. Here and in the following, a suspension is a heterogeneous mixture of a liquid and a solid in which the particles of the solid do not dissolve, but get suspended throughout the bulk of the liquid. In other words, the fluorinated polymer powder particles are dispersed or suspended in the fluorinated dielectric liquid. This advantageously allows to flexibly process fluorinated polymer powders and transform them into liquid form. According to at least one embodiment, a viscosity of the mixture is a function of the proportion of the fluorinated dielectric liquid in the mixture. In other words, the amount of the fluorinated dielectric liquid in the mixture determines the viscosity of the mixture. In particular, the higher the proportion of fluorinated dielectric liquid in the mixture, the lower the viscosity of the mixture. In particular, the lower the proportion of fluorinated dielectric liquid in the mixture, the higher the viscosity of the mixture. Thus, the viscosity of the mixture can advantageously be tailored to specific applications by the proportion of the fluorinated dielectric liquid in the mixture. According to at least one embodiment, the fluorinated dielectric liquid has a similar chemical composition as the fluorinated polymer powder. Here and in the following, a similar chemical composition is to be understood in such a P2023,1107 WO N August 8, 2024 - 5 - way that the compounds having a similar chemical compositions are composed of the same chemical elements. In particular, the fluorinated dielectric liquid and the fluorinated polymer powder both comprise at least carbon atoms and fluorine atoms, for example carbon atoms, fluorine atoms, and oxygen atoms. For instance, both the fluorinated dielectric liquid and the fluorinated polymer powder are composed of carbon atoms, fluorine atoms, and oxygen atoms. Due to the similar chemical composition, the mixture can be chemically inert. In other words, the mixture is not chemically reactive. Further, due to their similar chemical composition, the fluorinated dielectric liquid and the fluorinated polymer powder can advantageously have improved mixing properties. According to at least one embodiment, the fluorinated polymer powder and / or the fluorinated dielectric liquid are perfluorinated. Here and in the following, a perfluorinated chemical compound is a chemical compound in which all hydrogen atoms of the compound are replaced with fluorine. In other words, a perfluorinated compound comprises no hydrogen atoms. Perfluorinated compounds such as perfluorinated polymers and perfluorinated dielectric liquids are advantageously chemically stable and chemically inert. According to at least one embodiment, the fluorinated polymer of the fluorinated polymer powder is at least one of a perfluoroalkoxy (PFA), an ethylene tetrafluoroethylene (ETFE), an ethylene chlorotrifluoroethylene (ECTFE), an polytetrafluoroethylene (PTFE), and a fluorinated ethylene propylene (FEP). For example, the fluorinated polymer is a perfluoroalkoxy having the following chemical formula: P2023,1107 WO N August 8, 2024 - 6 - According to at least one embodiment, the fluorinated dielectric liquid is a perfluoropolyether (PFPE). In particular, the fluorinated dielectric liquid is a polyperfluoromethylisopropyl ether. For example, the fluorinated dielectric liquid has the following chemical formula: In summary, the advantages of the mixture described herein are as follows: - high pot life due to the low evaporation rate of the fluorinated dielectric liquid; - viscosity stability can be maintained a longer time which leads to a longer processing time; - the mixture is chemically inert; - viscosity of the mixture can be determined depending on the application; - flexibility to process fluorinated polymer powders, such as PTFE, PFA, FEP, ETFE, and ECTFE, and transform them into liquid form; P2023,1107 WO N August 8, 2024 - 7 - - overcoming the humidity sensitivity of fluorinated polymer powders by mixing with the fluorinated dielectric liquid; - increasing the processing safety by eliminating solvents having a high health hazard or a high fire source hazard due to a low burning point. Furthermore, a method for producing a coating layer on an electrical device, in particular on a sensor arrangement, is specified. In particular, the mixture for coating an electrical device described herein is used in the method for producing coating layer on an electrical device. Thus, embodiments, features, and advantages described in combination with the mixture also apply to the method for producing a coating layer on an electrical device and vice versa. According to at least one embodiment, the method comprises coating an electrical device at least partially with the mixture described herein. In particular, the electrical device comprises an electrical element comprising two electrodes at a tip of the electrical device and two wires connected to the electrodes of the electrical element. For example, the electrical device is a sensor arrangement and the electrical element is a sensor element. For instance, the electrical element is a NTC chip or a PTC chip. The mixture can comprise each of the features described above in conjunction with the mixture. In particular, at least partially coating the electrical device comprises applying the mixture to at least one surface of the electrical device. For instance, the mixture is applied in direct physical contact to the at least one surface of the electrical device. For example, all surfaces of the electrical element and at least a part of the surfaces of the wires at the tip of the P2023,1107 WO N August 8, 2024 - 8 - electrical device, i.e. in the region of the electrical element, are coated with the mixture. For instance, all surfaces of the electrical element and at least the part of the wires that is not insulated by an insulating layer, for example, at the tip of the electrical device is coated with the mixture. According to at least one embodiment, the method comprises curing the mixture to form a coating layer on the electrical device. In particular, the liquid mixture is hardened or cured in order to form a solid coating layer on at least one surface of the electrical device. For example, the coating layer comprises or consists of the particles of the fluorinated polymer powder of the mixture adhering to each other, in particular being melted, sintered, vitrified, or fused together. According to at least one embodiment, the method for producing an electrical device comprises coating an electrical device at least partially with the mixture described herein and curing the mixture to form a coating layer on the electrical device. It is an idea of the present application to simply and cost- effectively produce an electrical device having a fluoropolymer-based coating layer. The mixture described herein can be easily and effectively applied to at least one surface of the electrical device and processed by curing to form a coating layer. According to at least one embodiment, coating the electrical device is performed by dip coating or roller coating. Applying the mixture to the electrical device by dip coating P2023,1107 WO N August 8, 2024 - 9 - or roller coating is in particular facilitated by the mixture being a liquid. In particular, coating the electrical device is performed by dip coating. In that instance, the electrical device is dipped into the mixture and is subsequently removed from the mixture with a specific dipping out speed. In particular, using dip coating processing methods results in a high utilization of material. According to at least one embodiment, during coating the electrical device, a thickness of the mixture on the electrical device is controlled by the viscosity of the mixture and / or the dipping out speed. In particular, a mixture having a high viscosity results in a thick layer of mixture on the electrical device. A mixture having a low viscosity can result in a thin layer of mixture on the electrical device. In particular, a high dipping out speed results in a thick layer of the mixture on the electrical device. A low dipping out speed can result in a thin layer on the electrical device. The thickness of the mixture on the electrical device can be controlled by a combination of the viscosity of the mixture and the dipping out speed. Thus, the thickness of the mixture on an electrical device can advantageously be tailored to specific applications. According to at least one embodiment, the thickness of the liquid mixture on the electrical device is at least 40 µm. in particular, the thickness of the liquid mixture on the electrical device is at most 1.035 mm. For example, the thickness of the liquid mixture on an electrical device is between and including 110 µm and 135 µm. According to at least one embodiment, during curing the mixture, the thickness of the mixture shrinks by between and P2023,1107 WO N August 8, 2024 - 10 - including 10 µm and 35 µm. In other words, the liquid mixture applied to the electrical element has a thickness greater than a thickness of the coating layer obtained after curing the mixture by between and including 10 µm and 35 µm. According to at least one embodiment, curing the mixture comprises evaporating the fluorinated dielectric liquid. In particular, the fluorinated dielectric liquid is completely evaporated during curing the mixture. In other words, the fluorinated dielectric liquid evaporates during curing and leaves the fluorinated polymer powder on the electrical device to be melted together to form the coating layer. For instance, evaporating the fluorinated dielectric liquid is performed by heating the mixture on the electrical device. In particular, after curing, the coating layer is free of residues of the fluorinated dielectric liquid. By evaporating the fluorinated dielectric liquid, the coating layer can be advantageously formed of the fluorinated polymer powder of the mixture. According to at least one embodiment, curing the mixture comprises heating the mixture on the electrical device to a curing temperature. In particular, the curing temperature is higher than the temperature during coating the electrical device with the mixture. For instance, heating the mixture on the electrical device to the curing temperature results in evaporating the fluorinated dielectric liquid and melting, sintering, vitrifying, or fusing together the particles of the fluorinated polymer powder. In particular, the curing temperature depends on the boiling point of the fluorinated dielectric liquid and the melting point or curing point of the fluorinated polymer powder. For example, the curing temperature is between and including 200°C and 450°C. For P2023,1107 WO N August 8, 2024 - 11 - instance, the fluorinated polymer is a PFA having a melting point or curing point of above 320°C. Alternatively, the fluorinated polymer is a FEP, an ETFE, or an ECTFE having a melting point or curing point below 270°C. Curing the mixture by heating to a curing temperature can be advantageous for forming the coating layer in a simple manner. According to at least one embodiment, the electrical device comprises a contact between wires and electrodes of an electrical element and the curing temperature is lower than a melting temperature of the contact. In other words, the curing temperature is chosen such that the curing temperature is lower than the melting temperature of the contact of the wires and the electrodes of the electrical element. In particular, as the curing temperature is dependent from the melting point or curing point of the fluorinated polymer powder and the boiling point of the fluorinated dielectric liquid in the mixture, the fluorinated polymer powder and / or the fluorinated dielectric liquid are chosen such that the curing temperature is lower than the melting temperature of the contact. The contact of the wires and the electrodes can be a soldered contact or a welded contact. A soldered contact comprises a solder material and the melting temperature of the soldered contact is the melting temperature of the solder material. A welded contact comprises the joint metals of the wire and electrode and the melting temperature of the welded contact is the melting temperature of the joint metal. For example, the melting temperature of a welded contact is higher than a melting temperature of a soldered contact. Thus, a welded contact advantageously allows to use fluorinated polymer powders having higher melting temperatures and thus brings more flexibility to choose the fluorinated polymer for the coating layer. P2023,1107 WO N August 8, 2024 - 12 - According to at least one embodiment, the curing temperature is below 270°C. In particular, the fluorinated polymer is a FEP, an ETFE, or an ECTFE having a melting point or curing point below 270°C. A curing temperature below 270°C can advantageously ensure that parts and components of the electrical device, such as the solder material used for contacting the wires and the electrodes of the electrical element, are not damaged during curing of the mixture. In summary, the advantages of the method for producing a coating layer on an electrical device described herein are as follows: - by using a dip coating method or a roller coating method, powder recycling is not needed, less material is needed during processing, and contamination with foreign material can be reduced; - using a dip coating processing method results in a high utilization of material; - using a dip coating processing method allows to control the coating thickness by the dipping out speed; - using the mixture described herein allows for a simple and cost-effective method; - due to the lower melting point or curing point of some fluorinated polymers, it is possible to cure the mixture without damaging the electrical device, in particular a soldered contact. Furthermore, an electrical device, in particular an electrical device for measuring a temperature, fur example a sensor arrangement for measuring a temperature, is specified. In particular, the electrical device described herein is produced by the method for producing a coating layer on an P2023,1107 WO N August 8, 2024 - 13 - electrical device. Thus, embodiments, features, and advantages described in combination with the method for producing a coating layer on an electrical device also apply to the electrical device and vice versa. According to at least one embodiment, the electrical device comprises an electrical element comprising two electrodes and two wires connected to the electrodes of the electrical element. In particular, the electrical element is arranged at a tip of the electrical device. For example, the electrical device is a sensor arrangement and the electrical element is a sensor element. For instance, the electrical element is a NTC chip or a PTC chip. According to at least one embodiment, the electrical device comprises a coating layer comprising a fluorinated polymer. In particular, the coating layer consists of the fluorinated polymer. For example, the coating layer is formed of melted, sintered, vitrified, or fused particles of a fluorinated polymer powder. According to at least one embodiment, the coating layer abuts the electrical element and at least a part of the wires. In other words, the coating layer is in direct contact to the electrical element and at least a part of the wires. In particular, the coating layer abuts the electrical element and at least the part of the wires at the tip of the electrical device. For example, the coating layer abuts at least the part of the wires that is not insulated by an insulating layer. For instance, the coating layer abuts all surfaces of the electrical element and at least a part of the wires, in particular at least a part of the wires that is not insulated by an insulating layer. P2023,1107 WO N August 8, 2024 - 14 - According to at least one embodiment, the electrical device comprises an electrical element comprising two electrodes, two wires connected to the electrodes of the electrical element, and a coating layer comprising fluorinated polymer, wherein the coating layer abuts the electrical element and at least a part of the wires. It is an idea of the present application to provide an electrical device having an improved humidity resistance due to a coating layer of a fluorinated polymer abutting the electrical element and at least a part of the wires of the electrical device. Further encapsulation materials such as epoxy or glass can thus be dispensed with. By eliminating further encapsulation materials, a geometrical miniaturization of the electrical device is facilitated. Further, this can lead to a reduction of the thickness of the coating layer, which, in turn, enables a faster response time of the electrical device. Furthermore, the fluorinated polymer material of the coating layer is transparent compared to, for example, epoxy. This gives the possibility for quality control by visual inspection and to do optical analysis. According to at least one embodiment, the coating layer has a thickness between and including 5 µm and 1 mm, in particular between and including 30 µm and 1 mm. For example, the thickness of the coating layer is 100 µm. Thin coating layer thicknesses can advantageously increase the response time of the electrical element, in particular of a sensor element. According to at least one embodiment, the wires are connected to the electrodes of the electrical element by a soldered P2023,1107 WO N August 8, 2024 - 15 - contact. The electrical element can be a soldered miniature sensor. In particular, a soldered contact comprises a solder material configured for providing the physical and electrical contact between the wires and the electrodes. For instance, the coating layer further abuts the soldered contact. For example, the coating layer comprises or consists of a FEP, an ETFE, or an ECTFE. According to at least one embodiment, the wires are connected to the electrodes of the electrical element by a welded contact. In particular, a welded contact comprises the joint metals of the wire and electrode. For instance, the wires each comprise a flat region as a contacting end that is welded to the electrodes of the electrical element. An electrical device with welded contact advantageously reduces the material interfaces with the coating layer from four interfaces (sensor element to coating layer, joining material such as paste or solder to coating layer, wire to coating layer, and wire insulation to coating layer) to two interfaces (sensor element to coating layer and wire to coating layer). In other words, this reduces thermal barriers created by the interfaces. According to at least one embodiment, the wires comprise wire extensions (wire horns) protruding beyond the electrodes of the electrical element. In particular, the wire extensions are directly adjacent to the welded contact between the wires and the electrodes. For instance, the wire extensions are adjacent to the flat region, but are not part of the flat region. Wire extensions can advantageously increase the response time of the electrical device, in particular of a sensor arrangement. This effect can be further increased by the reduction of the thickness of the coating layer. P2023,1107 WO N August 8, 2024 - 16 - According to at least one embodiment, a thermal expansion coefficient of the coating layer is between and including 12·10-5K-1and 22·10-5K-1at 20 °C. A high thermal expansion can advantageously reduce crack formation in the coating layer during operation of the electrical device in an environment with rapid temperature changes and thus improves water impermeability. In summary, the advantages of the electrical device described herein are as follows: - improved humidity resistance performance by direct contact of sensor element and wire surfaces to the coating layer; - further encapsulation material such as glass or epoxy can be dispensed with; - geometrical miniaturization is facilitated by eliminating further encapsulation materials; - the coating layer is transparent in comparison to epoxy which gives the possibility for quality control by visual inspection and to do optical analysis, in particular for miniature sensor arrangements; - improved humidity resistance performance by using a fluorinated polymer in comparison to epoxy, in particular for miniature sensor arrangements; - faster response time by reduction of the thickness of the coating layer; - in combination with a reduced thickness of the coating layer, an even faster response time can be achieved due to the wire extensions; - E-modulus and hardness of the coating layer is lower than for encapsulating layers of epoxy and glass, but the thermal expansion is higher: hence, when the electrical device is exposed to rapid temperature change environments during P2023,1107 WO N August 8, 2024 - 17 - operation, it reduces crack formation which could be penetrated by water molecules; - reduction of material interfaces with the coating layer from four interfaces (sensor element to coating layer, joining material such as past or solder to coating layer, wire to coating layer, and wire insulation to coating layer) to two interfaces (sensor element to coating layer and wire to coating layer) which reduces thermal barriers created by the interfaces. Advantageous embodiments and developments of the mixture, the method for producing a coating layer on an electrical device, and the electrical device will become apparent from the exemplary embodiments described below in conjunction with the figures. In the figures: Figures 1 to 4 each show a schematic illustration of an electrical device according to different exemplary embodiments, Figures 5 to 7 each show a schematic illustration of an electrical device having a coating layer produced by a method for producing a coating layer on an electrical device according to different exemplary embodiments. In the exemplary embodiments and figures, similar or similarly acting constituent parts are provided with the same reference signs. The elements illustrated in the figures and their size relationships among one another should not be regarded as true to scale. Rather, individual elements may be P2023,1107 WO N August 8, 2024 - 18 - represented with an exaggerated size for the sake of better representability and / or for the sake of better understanding. Figure 1 shows a schematic illustration of an electrical device 1 described herein according to an exemplary embodiment. The electrical device 1 shown in figure 1 is a sensor arrangement. The electrical device 1 comprises an electrical element 2 at the tip of the electrical device 1A. The electrical element in figure 1 is a sensor element. The electrical element 2 comprises two electrodes 21 (not shown here). Two wires 3 are connected to the electrodes 21 of the electrical element 2. A coating layer 4 abuts the electrical element 2 and a part of the wires 3, in particular the part of the wires at the tip 1A of the electrical device 1. The coating layer 4 comprises or consists of a fluorinated polymer, in particular a perfluorinated polymer powder, for example a PFA, an ETFE, an ECTFE, a FEP, or a PTFE. The coating layer 4 is produced as follows: A mixture is provided. The mixture comprises, in particular consists of, a fluorinated polymer powder and a fluorinated dielectric liquid. In particular, the fluorinated dielectric liquid has a similar chemical composition as the fluorinated polymer powder. Due to the similar chemical composition, the mixture is chemically inert. The mixture is produced by pouring the fluorinated dielectric liquid into the fluorinated polymer powder. The ratio of the mixture can be defined depending on the targeted viscosity. By using a fluorinated dielectric liquid, the processing properties of the fluorinated polymer powder are enhanced. The electrical device 1 comprising the electrical element 2 and the wires 3 is coated with the mixture by dip coating or P2023,1107 WO N August 8, 2024 - 19 - roller coating. In particular, the tip 1A of the electrical device 1 is dipped into the mixture with a specified dipping length. The thickness of the liquid mixture on the electrical device 1 is controlled by the viscosity of the mixture and the dipping out speed. After the coating process, the mixture is cured by a heat treatment comprising heating the mixture on the electrical device 1 to a curing temperature, in particular between and including 200°C and 450°C. During this curing step, the fluorinated dielectric liquid evaporates and leaves the fluorinated polymer powder to be melted, sintered, vitrified, or fused together to form the coating layer 4. Figure 2 shows a schematic illustration of a tip 1A of an electrical device 1 described herein according to an exemplary embodiment. The electrical device 1 shown in figure 2 is a sensor arrangement. The tip 1A shown in figure 2 can be the tip 1A of the electrical device 1 of the exemplary embodiment of figure 1. The exemplary embodiment shown in figure 2 comprises an electrical element 2 having two electrodes 21. The electrical element 2 in figure 2 is a sensor element. The electrical device 1 further comprises two round wires 3. The round wires 3 comprise flat regions 31 at the contacting ends of the wires 3 that are directly connected to the electrodes 21 with welded contacts. Further, the wires 3 comprise wire extensions 32 (wire horns) protruding beyond the electrodes 21 of the electrical element 2. The electrical element 2 and at least the part of the wires in region of the tip 1A including the flat regions 31 and the wire extensions 32 are covered with a coating layer 4. For example, the fluorinated polymer of the coating layer 4 is a PFA. The coating layer 4 may further comprise air bubbles due to air entrapment inside the material of the coating layer 4. P2023,1107 WO N August 8, 2024 - 20 - The coating layer 4 is substantially produced as described in conjunction with the exemplary embodiment of figure 1. However, by using welded contacts, fluorinated polymers having a high melting point or curing point can be used, since the curing temperature limit depends on the melting temperature of the joint metal. The melting temperature of the joint metal of a welded contact is in particular higher than for soldered contacts. The advantage of higher curing temperatures brings more flexibility to choose the fluorinated polymer for the coating layer 4. Figure 3 shows a schematic illustration of a tip 1A of an electrical device 1 described herein according to an exemplary embodiment. The electrical device 1 shown in figure 3 is a sensor arrangement. The exemplary embodiment of figure 3 corresponds substantially to the exemplary embodiment shown in figure 2. In contrast to the exemplary embodiment of figure 2, the wires comprise no wire extensions 32. Instead, the wires only comprise the flat region 31 on the contacting end that is protruded over by the electrode 21 or ends flush therewith. In particular, the flat region 31 is the outermost region of the wires 3 at the contacting end. The coating layer 4 on the electrical device 1 of figure 3 can be produced as described in conjunction with the exemplary embodiment of figure 2. Figure 4 shows a schematic illustration of a tip 1A of an electrical device 1 described herein according to an exemplary embodiment. The electrical device 1 shown in figure 4 is a sensor arrangement, in particular a miniature sensor. The tip 1A shown in figure 4 can be the tip 1A of the electrical device 1 of the exemplary embodiment of figure 1. P2023,1107 WO N August 8, 2024 - 21 - The exemplary embodiment shown in figure 4 comprises an electrical element 2 having two electrodes 21. The electrical element 2 in figure 2 is a sensor element. The electrical device 1 further comprises two wires 3. The wires 3 can comprise an insulation 33. At least in the region of the electrical element 2, the wires 3 are free of the insulation. The wires 3 are connected to the electrodes 21 of the electrical element 2 with soldered contacts comprising a solder material 5. A coating layer 4 covers the electrical element 2, the soldered contact and at least the part of the wires 3 without the insulation 5. To get a fully closed protection, at least a part of the insulation 33 on the side of the wires 3 facing the electrical element 2 can also be covered with the coating layer 4. For example, the fluorinated polymer of the coating layer 4 is an ETFE, an ECTFE, or a FEP. Due to the shorter chain length of the fluorinated polymer powder compared to epoxy coating materials, the coating layer 4 is chemically more resistant to water penetration, when the electrical device 1, in particular the electrical element 2, is operated in harsh environments such as environments having a high humidity. The coating layer 4 may further comprise air bubbles due to air entrapment inside the material of the coating layer 4. The coating layer 4 is substantially produced as described in conjunction with the exemplary embodiment of figure 1. However, a mixture comprising a fluorinated polymer powder having a low melting point or curing point, in particular of below 270°C, ensures that the solder material 5 used for contacting the wires 3 and the electrodes 21 of the electrical element to is not damaged during curing of the mixture on the electrical device 1. P2023,1107 WO N August 8, 2024 - 22 - Figure 5 shows a schematic illustration of an electrical device 1 having a coating layer 4 produced by a method for producing a coating layer 4 on an electrical device 1 according to an exemplary embodiment. The electrical device 1 shown in figure 5 is a sensor arrangement. The coating layer 4 of the electrical device 1 of figure 5 is substantially produced as described in conjunction with the exemplary embodiment of figure 1. In contrast to the exemplary embodiment of figure 1, the electrical device 1 of figure 5 comprises an encapsulation layer 6, in particular completely, encapsulating the electrical element 2 and a part of the wires 3, in particular including the contact between the electrodes 21 of the electrical element 2 and the wires 3. The encapsulation layer 6 is, for example, a glass encapsulation. In this instance, coating the electrical device 1 further includes coating the encapsulation layer 6. Due to the encapsulation layer 6, higher curing temperatures can be used as the electrical element 2 is protected by the encapsulation layer 6. For example, the mixture is cured by a heat treatment at a minimum temperature of 320°C. For example, the fluorinated polymer powder in the mixture is a PFA. Figures 6 and 7 each show a schematic illustration of a tip 1A of an electrical device 1 having a coating layer 4 produced by a method for producing a coating layer 4 on an electrical device 1 according to an exemplary embodiment. The electrical devices 1 shown in figures 6 and 7 are sensor arrangements. The tips 1A shown in figures 6 and 7 can be the tip 1A of the electrical device 1 of figure 5. Figure 6 shows an electrical device 1 having welded contacts and wire extensions 32 as described in conjunction with figure 2. Figure 7 shows an electrical device 1 having welded contacts P2023,1107 WO N August 8, 2024 - 23 - and no wire extensions 32 as described in conjunction with figure 3. In contrast to figures 2 and 3, figures 6 and 7 comprise an encapsulation layer 6 as described in conjunction with figure 5. The coating layers 4 on the electrical devices of figure 6 and 7 are produced as described in conjunction with figure 5. The features and exemplary embodiments described in connection with the figures can be combined with each other according to further exemplary embodiments, even if not all combinations are explicitly described. Furthermore, the exemplary embodiments described in connection with the figures may have alternative or additional features as described in the general part. The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

[0002] P2023,1107 WO N August 8, 2024 - 24 - References 1 electrical device 1A tip of the electrical device 2 electrical element 21 electrode 3 wire 31 flat region 32 wire extension 33 insulation 4 coating layer 5 solder material 6 encapsulation layer

Claims

P2023,1107 WO N August 8, 2024 - 25 - Patent claims 1. A mixture for coating an electrical device (1) comprising - a fluorinated polymer powder and - a fluorinated dielectric liquid.

2. The mixture according to the preceding claim, wherein the fluorinated dielectric liquid has a vapor pressure of less than or equal to 100 hPa at 25 °C.

3. The mixture according to one of the preceding claims, wherein the mixture consists of the fluorinated polymer powder and the fluorinated dielectric liquid.

4. The mixture according to one of the preceding claims, wherein the mixture is a heterogeneous mixture.

5. The mixture according to one of the preceding claims, wherein a viscosity of the mixture is a function of the proportion of the fluorinated dielectric liquid in the mixture.

6. The mixture according to one of the preceding claims, wherein the fluorinated dielectric liquid has a similar chemical composition as the fluorinated polymer powder.

7. The mixture according to one of the preceding claims, wherein the fluorinated polymer powder and / or the fluorinated dielectric liquid are perfluorinated.

8. The mixture according to one of the preceding claims, wherein the fluorinated polymer of the fluorinated polymer powder is at least one of a perfluororalkoxy (PFA), anP2023,1107 WO N August 8, 2024 - 26 - ethylene tetrafluoroethylene (ETFE), an ethylene chlorotrifluoroethylene (ECTFE), an polytetrafluoroethylene (PTFE), and a fluorinated ethylene propylene (FEP).

9. The mixture according to one of the preceding claims, wherein the fluorinated dielectric liquid is a perfluoropolyether (PFPE).

10. A method for producing a coating layer (4) on an electrical device (1) comprising - coating an electrical device (1) at least partially with the mixture according to claim 1, - curing the mixture to form a coating layer (4) on the electrical device (1).

11. The method according to the preceding claim, wherein coating the electrical device (1) is performed by dip coating or roller coating.

12. The method according to one of the claims 10 or 11, wherein, during coating the electrical device (1), a thickness of the mixture on the electrical device (1) is controlled by the viscosity of the mixture and / or the dipping out speed.

13. The method according to the preceding claim, wherein the thickness of liquid the mixture on the electrical device (1) is at least 40 µm.

14. The method according to one of the claims 12 or 13, wherein, during curing the mixture, the thickness of the mixture shrinks by between and including 10µm and 35µm.P2023,1107 WO N August 8, 2024 - 27 - 15. The method according to one of the claims 10 to 14, wherein curing the mixture comprises evaporating the fluorinated dielectric liquid.

16. The method according to one of the claims 10 to 15, wherein curing the mixture comprises heating the mixture on the electrical device (1) to a curing temperature.

17. The method according to the preceding claim, wherein the electrical device (1) comprises a contact between wires (3) and electrodes (21) of an electrical element (2) and wherein the curing temperature is lower than a melting temperature of the contact.

18. The method according to one of the claims 16 or 17, wherein the curing temperature is below 270 °C.

19. An electrical device (1) comprising - an electrical element (2) comprising two electrodes (21), - two wires (3) connected to the electrodes (21) of the electrical element (2), and - a coating layer (4) comprising a mixture for coating an electrical device (1) comprising a fluorinated polymer powder and a fluorinated dielectric liquid, wherein the coating layer (4) abuts the electrical element (2) and at least a part of the wires (3).

20. The electrical device (1) according to the preceding claim, wherein the coating layer (4) has a thickness between and including 5 µm and 1 mm.P2023,1107 WO N August 8, 2024 - 28 - 21. The electrical device (1) according to one of the claims 19 or 20, wherein wires (3) are connected to the electrodes (21) of the electrical element (2) by a soldered contact or a welded contact.

22. The electrical device (1) according to one of the claims 19 to 21, wherein the wires (3) comprise wire extensions (32) protruding beyond the electrodes (21) of the electrical element (2).

23. The electrical device (1) according to one of the claims 19 to 22, wherein a thermal expansion coefficient of the coating layer (4) is between and including 12·10-5K-1and 22·10-5K-1 at 20

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