Unit for high-temperature use

Abstract

To provide a unit for high-temperature uses, in particular for uses above 700°C.SOLUTION: A unit 1 includes a housing 100 and at least one electrical functional element 10. The electrical functional element includes at least one connection wire 14 or at least one connection pad. A first section 11 of the electrical functional element is housed within a housing, and a second section 12 of the electrical functional element is accessible from the outside. The electrical functional element also includes a third section 13 embedded in an electrically insulating material 102 of the housing, between the first section and the second section. In addition, the electrically insulating material seals off the housing from the electrical functional element. The electrically insulating material is selected from glass, glass ceramic, and a combination of a plurality of the materials, or from a composite material having, as its principal constituent, glass or glass ceramic, the insulating material being fused onto the at least one electrical functional element.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a unit for high temperature use, in particular for use above 700° C., comprising a housing and at least one electrical functional element, which may in particular be designed as a sensor element or a heating element.

[0002] The unit is particularly adapted for use in harsh environments where aggressive media such as hot gases containing corrosive and / or decomposing chemicals and / or molecules may be present as well as high temperatures above about 700° C. Examples of such harsh environments are, for example, the off-gas systems of power plants and combustion engines in vehicles such as automobiles and industrial plants.

[0003] In the prior art, units are known in which a sensor element, for example a temperature sensor element, is accommodated in a housing, for example including a protective tube. Such housings are often not hermetically sealed, especially at high temperatures, so that the sensor element is damaged, for example by corrosive gases. This leads, in particular, to drift in the measured values ​​determined by the sensor element.

[0004] EP 3301420 A1 discloses a temperature sensor arrangement with high resistance to aggressive gases, in which a measuring insert with a measuring element is housed in a protective tube to create an interspace through which a purge gas can flow. Furthermore, an absorption unit is provided in the interspace, which at least partially surrounds the measuring insert and absorbs contaminants present in the interspace with a getter material.

[0005] The construction of a hermetically sealed temperature sensor is not described in EP 3301420 A1.

[0006] EP 3559620 A1 describes a sensor device having a temperature sensor element disposed within a sensor head. The sensor head is filled with two materials: a first material that holds the temperature sensor element components in place within the sensor head, and a second material that conducts heat within the sensor head. The first material can be ceramic powder or ceramic grout.

[0007] The fixing material of the sensor device does not allow for hermetically sealed encapsulation of the temperature sensor element.

[0008] German Patent Application No. 102006015427 discloses a measuring probe for determining physical values, which comprises a tube at the end of which the measuring probe is arranged, which passes through a fixing sleeve and is held in place in the fixing sleeve by a glass packing so as to be electrically insulated.

[0009] Ordinary glass materials are not suitable for temperatures above 700°C.

[0010] WO 2020 / 094755 discloses a bonding connection between two bonding partners that includes an at least partially crystallized glass as an insulating component. The at least partially crystallized glass enables the formation of a stable microstructure that is mechanically stable even at high temperatures. The insulating component may further include a structure that extends a direct path along the surface of the insulating component between the two bonding partners.

[0011] WO 2020 / 260099 describes a sensor component having a bushing element for use at temperatures above 700° C. The bushing element includes a through opening through which a contact pin passes and is held in place by an insulating element.

[0012] To ensure continued functionality of the sensor element in high temperature applications, it is necessary to protect the sensor element from contaminants in the local environment that may impair its functionality and thereby cause distortion and drift in the measurements provided by the sensor. To this end, it is desirable to house and hermetically seal the sensor element or its active components within a sensor unit.

[0013] SUMMARY OF THE INVENTION It can therefore be seen as an object of the present invention to provide a unit for high temperature applications comprising a housing and at least one electrical functional element.

[0014] Disclosure of the Invention The proposed unit is for high-temperature use, particularly at temperatures above 700°C, and includes a housing and at least one electrical functional element. The at least one electrical functional element includes a non-conductive substrate, an electrically conductive element, and at least one connecting wire or pad. The design employs the at least one electrical functional element within a housing, whereby a first section of the electrical functional element is contained within the housing and shielded from the local environment by the housing, and a second section of the electrical functional element, including at least a portion of the at least one connecting wire or pad, is accessible from the outside. The design further includes a third section between the first and second sections embedded within an electrically insulating material of the housing, the electrically insulating material sealing the housing from the electrical functional element. The electrically insulating material is selected from glass, glass ceramic, a combination of a plurality of such materials, or a composite material having glass or glass ceramic as its main component, and the insulating material is fused onto the at least one electrical functional element, resulting in a physical and / or chemical bond at the interface therebetween.

[0015] This intimate connection between the electrically insulating material and the at least one functional element makes further sealing elements unnecessary. The at least one electrical functional element may in particular be designed as a sensor element or a heating element.

[0016] The fusion of the insulating material to the at least one electrical functional element forms a hermetically sealed bushing through which the second section of the electrical functional element exits the housing and is accessible from the outside. -5 mbar·l / s, preferably less than 1·10 -10 mbar·l / sec~1·10 -6 This is understood to mean a bushing having a helium leak rate in the range of mbar·l / s, preferably measured in accordance with DIN EN 60068-2-17 or MIL-STD-883 method 1014.9 condition A4.

[0017] A first section of the at least one electrical functional element is located inside the housing of the unit, and a hermetically sealed bushing of the at least one electrical functional element hermetically closes the housing, which means that the first section of the electrical functional element is protected from contamination by substances outside the housing.

[0018] At least one electrical functional element includes at least one non-conductive substrate, a conductive element, and at least one connecting wire or at least one connecting pad. Such connecting wire or connecting pad provides electrical contact with the electrical functional element. Here, the connecting pad may be designed as a metallized surface configured to be contacted by a conductor, such as a wire. For example, the wire may be connected to the connecting pad by soldering or welding. The connecting pad may include, in particular, a row composed of several different layers, for example, the top layer may be made of gold.

[0019] The non-conductive substrate is preferably made from a heat-resistant, non-conductive material, such as ceramic, glass, and / or glass-ceramic. Ceramics commonly used for ceramic substrates include alumina (Al2O3) and zirconia (ZrO2).

[0020] The non-conductive substrate can be designed, for example, as a flat, preferably rectangular substrate, however, cylindrical designs are also possible, for example in the form of a cylinder.

[0021] The conductive element is preferably disposed on or embedded in the substrate. The conductive element is preferably provided in the form of a thick layer, a thin layer, or a wire made of a conductive material. The material of the conductive element is preferably a metal or a metal alloy, or a material mixture containing at least one metal or metal alloy.

[0022] Thin layers can be obtained, for example, by coating processes such as vapor deposition, chemical vapor deposition, electrodeposition, or physical vapor deposition. Thin layers have thicknesses ranging, for example, from a few nanometers to a few micrometers. Thin layers are usually thinner than 1 μm. Thick layers can be obtained, for example, by applying a paste containing a conductive material and a binder, followed by heat treatment. Thick layers are typically one to two orders of magnitude thicker than thin layers.

[0023] If the electrical functional element is designed as a sensor element, in particular as a temperature sensor element, the material used for the conductive element is preferably platinum or a platinum alloy.

[0024] When the electrical functional element is designed as a heating element, it is preferable to use a metal or metal alloy with a high melting point and high electrical resistance as the conductive element.In particular, a thermal conductor alloy, such as a nickel-chromium alloy containing 80% nickel and 20% chromium, or an alloy of 55% copper, 44% nickel, and 1% manganese, such as the one available under the name Constantan, can be used as the material.When using metal, suitable examples are tungsten or platinum.However, it is also possible to use semiconductors such as silicon carbide as the conductive element.In the heating element, the conductive element is preferably designed in the form of a wire or thick layer.

[0025] When the conductive element is configured in the form of a layer, it is preferably structured, so that one or more conductor tracks can be formed. Here, this layer is preferably structured so that a single conductor track is formed, which has a meandering path on the non-conductive substrate. When the conductive element is provided in the form of a wire, it is preferably wound, and the wire can be at least partially wound around the substrate. However, it is also possible to embed the wound wire in the substrate.

[0026] If the electrical functional element is designed as a sensor element or a heating element, the meandering portion of the conductor track or the wound portion of the wire represents the active component of the electrical functional element. This active component is preferably located entirely in the first section of the electrical functional element, and a small portion of the conductor track leading to the connection can extend into the adjacent third section. If a connection pad is provided, the portion of the conductor track can extend through the adjacent third section to the connection pad in the second section, thereby connecting the connection pad with the meandering portion of the conductor track.

[0027] The connection at which the conductor track is contacted by the connecting wire is preferably located in the third section of the electrical functional element, which ensures that this connection is embedded in the electrically insulating material of the housing.

[0028] The non-conductive substrate forms the base of the conductive elements, the design of which depends on the specific embodiment of the conductive elements: thus, flat substrates are preferably used when combined with conductive elements designed as thick or thin layers, while cylindrical substrates are preferably used in combination with conductive elements designed in the form of wires.

[0029] In the case of a conductive element designed in the form of a layer, at least one connecting wire is connected to this layer as a further element at a contact point, for example by soldering or welding. If the conductive element is designed as a wire, the at least one connecting wire can be configured as an extension of the conductive element, with the part of the conductive element that protrudes beyond the non-conductive substrate serving as the connecting wire.

[0030] If an additional connecting wire is used, it is preferable to select a material that is a heat-resistant metal or alloy. Suitable materials for the connecting wire include, in particular, nickel, platinum, or a nickel / platinum alloy. The connecting wire may be coated; for example, platinum-plated nickel wire may be used.

[0031] Preferably, the conductive element and / or at least the electrical contact points between at least one connecting wire of at least one functional element and the conductive element are coated with a coating material, which is preferably different from the electrically insulating material.

[0032] The coating material may be in the form of a layer or a layer sequence. The coating material may in particular comprise a protective layer and / or a passivation layer. In particular, in the case of conductive elements designed in the form of thick or thin layers, it is preferred that at least one passivation layer is present there, which insulates the conductive element, in particular the conductive layer, and protects it from changes caused by substances in the local environment. It is also possible that multiple layers made of different materials are present there. Particularly suitable materials for the passivation layer are glass or ceramic. Additionally or alternatively, the protective layer and / or passivation layer may also cover the contact points where the connecting wire is connected to the conductive layer.

[0033] If the electrical functional element is designed as a temperature sensor element, it is in particular configured as a standard temperature measuring resistor, more particularly as a Pt100, Pt200, Pt500, Pt1000 or Pt10000 temperature measuring resistor, where the temperature measuring resistor is an electrical functional element whose electrical resistance changes characteristically with temperature.

[0034] It is possible to integrate multiple functions into an electrical functional element: for example, a flat ceramic substrate may have on a first surface a thin layer of platinum that serves as a temperature sensor, and on a second surface opposite the first surface, the ceramic substrate may have a thicker layer that serves as a heating element.

[0035] Similarly, an electrical functional element may be considered to comprise multiple substrates each having one or more conductive elements, thus combining multiple functions together into a single electrical functional element.

[0036] The electrically insulating material is preferably selected from glass or glass ceramic, or a combination of several such materials. Alternatively, the electrically insulating material may also be a composite material having glass or glass ceramic as its main component, which may further contain aggregates such as ceramic powder. Preferably, the composite material here consists of glass and / or glass ceramic to an extent of more than 70% by weight, preferably more than 80% by weight, more preferably more than 90% by weight.

[0037] To enable use in the high temperature range, the electrically insulating material is particularly selected so that its melting temperature or, in the case of glass, its glass transition temperature is preferably above 700° C. Here, the electrically insulating material is configured so that it is fused onto at least one electrical functional element, thereby achieving an intimate connection, also referred to as a joint connection or joining connection.

[0038] The electrically insulating material may in particular be a sealing glass, which is used to achieve a tight connection between the components to be joined.

[0039] The electrically insulating material is preferably designed as a molding which serves as the housing of the unit or as part of the housing of the unit.

[0040] The electrically insulating material may in particular be a glass ceramic or a partially crystallized glass. Glass ceramics and at least partially crystallized glasses can be obtained by crystallization, preferably by controllable crystallization, more preferably by controlled crystallization, in which a structure is obtained that allows for a narrow size distribution in the space of crystals or crystallites that can be assigned to the same crystalline phase and / or a preferred arrangement of the crystals or crystallites can be achieved.

[0041] Crystallization results in an at least partially crystallized glass from a crystallizable glass, i.e., a glass having a crystalline phase content of more than 0.1% by volume. Such at least partially crystallized glasses, which contain at least one crystalline phase and also a glass phase, for example, an at least partially crystallizable glass or a residual glass phase, are also referred to as glass ceramics in the context of the present invention. It is also possible for glass ceramics to exist in a fully crystallized form, in the sense that the crystallized phase accounts for more than 99% by volume, for example, up to 99.9% by volume. The proportion of the residual glass phase is preferably still sufficiently high to ensure good wetting of the joining partner, for example, in particular at least one electrical functional element. Therefore, it is advantageous if the proportion of the residual glass phase in the at least partially crystallized glass is at least 5% by volume, preferably at least 10% by volume.

[0042] A high level of crystallinity in the electrically insulating material is advantageous to avoid reactions with the material of the electrically functional elements, in particular to avoid ionic migration at high temperatures.

[0043] Partially crystallized glasses of this type are disclosed, for example, in WO 2020 / 094755. The partially crystallized glasses described there are suitable for high-temperature stable bonding connections and can also be used advantageously for bonding connections that are subjected to mechanical stress.

[0044] Preferably, the at least partially crystallized glass contains, in addition to SiO2, La2O3: more than 0.3 mol% and less than 5 mol%, preferably 4.5 mol% or less, more preferably 4 mol% or less; Nb2O50mol%~9mol%, Ta2O50mol%~7mol% Including, Σ(A2O5) 0.2mol% to 9mol% and wherein A is an element which in the oxide is normally in the oxidation state V+ and which includes or may include, for example, Nb and / or Ta or P and / or mixtures thereof.

[0045] It has been shown that strong bonded connections, for example bonded connections that are stable at high temperatures and / or resistant to mechanical stress, can be achieved by adding the oxides La2O3, Ta2O5 and / or Nb2O5, and optionally further oxides of composition A2O5, in suitable amounts, i.e. within the limits defined above.

[0046] where A denotes an element that is normally in the oxidation state V+ in the oxide. It is therefore possible that not all atoms "A" present in a crystallizable or at least partially crystallized glass are in the same oxidation state.

[0047] The oxides La2O3, Nb2O5, and Ta2O5, as well as optional further oxides A2O5, present in the glass are also referred to in the context of the present disclosure as “glass matrix-forming oxides,” a term that is understood in the context of the present disclosure to mean that such oxides initially remain in the glass matrix after heat treatment of a crystallizable glass, i.e., when the glass is present in the form of an at least partially crystallized glass. This distinguishes the term “glass matrix-forming oxides” from the more general term “glass-forming oxides.” More specifically, the oxides MgO and CaO are not glass matrix-forming oxides in the context of the present disclosure, even though CaO is a standard component of conventional glasses, such as soda-lime glass. In glasses according to embodiments of the present disclosure, oxides such as CaO and MgO are incorporated into the crystalline phase, but they do not remain in the glass matrix and are therefore not glass matrix-forming oxides.

[0048] However, it is quite possible that at least a portion of the glass matrix-forming oxides, e.g., La2O3, may be at least partially incorporated into the crystalline phase during the further course of ceramming, although small amounts of glass phase residues usually remain, which are formed in particular by the glass matrix-forming oxides.

[0049] The formation of a bonded connection according to the present disclosure using the oxides La2O3, and also Nb2O5 and / or Ta2O5, and also optionally further oxides A2O5, within the limits defined above, is advantageous because the at least partially crystallized glass is thereby particularly advantageously configured so that fusion subsequently occurs during heat treatment to form the connection. This is therefore a particularly advantageous way of forming a strong connection between the individual components of the bonded connection, in particular a strong connection of the at least partially crystallized glass to the bonded partner. However, by limiting the glass matrix-forming oxides within the limits defined above, it is advantageously ensured that the bonded connection simultaneously has high thermal stability and / or high mechanical strength.

[0050] In the context of this disclosure, the following definitions apply:

[0051] In the context of the present disclosure, crystallizable glass is understood to mean glass that undergoes crystallization, in particular, controlled or at least controllable crystallization.Here, controlled crystallization means that crystallizable glass can be converted by selective heat treatment into a state in which the glass exists in at least partially crystallized form, and the crystallographic composition and / or microstructure of the at least partially crystallized glass, i.e., the spatial and / or size configuration of the crystals and / or crystallites present in the at least partially crystallized glass, are preferably selectively set.Preferably, controlled crystallization can obtain a microstructure in which, for example, the crystallites are essentially uniform in size, for example, in the single-digit micrometer range, i.e., all crystallites have an equivalent diameter of, for example, about greater than 1 μm to 3 μm.

[0052] Of course, other microstructures, including larger or smaller crystallites, are possible.

[0053] When an at least partially crystallized glass has more than one different crystalline phase, the average crystal or crystallite size may be relatively similar within one crystalline phase, but the crystallite size may vary significantly between individual crystalline phases.

[0054] The opposite situation to the preferred controlled or controllable crystallization can be considered as the spontaneous crystallization of the glass, in which unexpected, often undesirable, crystalline phases can occur, and in particular complete devitrification can occur.

[0055] In the context of the present disclosure, a crystalline aggregate or crystal association is understood to mean an intergrowth of at least two crystals or crystallites, where the crystals or crystallites may in particular have grown together irregularly, meaning that the individual crystals or crystallites of the aggregate do not necessarily grow together along a preferred direction or along a specific crystallographic plane.

[0056] When a crystal or crystallite has a needle-like shape, this is understood to mean that the crystal or crystallite has a dimension in a direction that is at least one order of magnitude larger than the dimensions in the other two directions in space.In other words, a crystal or crystallite with a needle-like shape can be formed in a pointed or rod-like shape, or in a prism shape, and the transverse dimension of the basic shape of the prism is at least one order of magnitude smaller than the length of the crystal or crystallite.Such a crystal or crystallite is also described as being in the shape of a prism.

[0057] Crystallites may also be formed in a plate-like shape, i.e., in the shape of small plates scattered in crystallizable glass.In cross section, such shapes also have the appearance of rods, which makes it difficult to distinguish them individually.In the context of the present disclosure, plate is understood to mean a geometric form in which the lateral dimension (thickness) in one direction in the space of a Cartesian coordinate system is formed one order of magnitude smaller than the lateral dimensions (length, width) in the other two directions perpendicular to the first direction.

[0058] In the context of the present disclosure, the radial arrangement of crystals or crystallites is understood to mean that needle- or plate-shaped crystals, for example, pointed or prismatic crystals or crystallites, are arranged around a center with one end point pointing toward said point and the other end pointing radially outward in a different direction in space in each case. For example, the end pointing toward the center may be in contact with the center point. However, this is not required. Such a formation of crystal aggregates pointing radially outward from the center exists, for example, when the crystal aggregates are formed in a spherulitic form. In such a spherulitic form, the crystal aggregates may be approximately spherical or elliptical in shape and approximately circular when viewed in two dimensions. However, in reality, the intergrowth of crystals and crystal aggregates in the microstructure often results in deviations from the ideal spherical or circular shape of a spherulite. In particular, the crystals or crystallites forming a spherulite may have various lengths and / or thicknesses.

[0059] Another example of a radial arrangement is the formation of a fan shape in a two-dimensional cross section. For example, the formation of crystals or crystallites in a specific direction in space may not be possible in a microstructure. Here, the crystallites or crystals again extend outward from the center, but only within a specific angle in space.

[0060] A rod-like or plate-like interspersed arrangement is understood to mean that the individual crystals or crystallites do not extend outward from a common center in different directions in space, but are arranged irregularly, for example, without a significant preferred direction. In particular, the crystallites or crystals may be arranged interlockingly. This type of structure can also be compared, for example, to a house-of-cards structure, in which individual plates are arranged one above the other to form a stable structure (like cards in a house of cards).

[0061] In the context of the present disclosure, crystallization nuclei are understood to mean the starting points of crystallization. Crystallization nuclei promote the accretion of atoms to build a crystallization lattice, for example, thermodynamically or kinetically. More specifically, crystallization nuclei can be lattice defects and / or atomic arrangements. Often, interfaces can be or contain such starting points of crystallization.

[0062] In one embodiment of the bonded connection, at least some of the crystallites contain crystallization nuclei at the grain boundaries and / or in at least some cases, enrichments comprising lanthanum, more particularly comprising lanthanum compounds, are located at the grain boundaries of the crystallites.

[0063] Such a configuration of the bonding connection is advantageous in that it allows the formation of a particularly strong connection between the at least partially crystallized glass and the bonding partner. If at least some of the crystallites contain crystallization nuclei at the grain boundaries, this promotes the formation of a microstructure in the at least partially crystallized glass that includes crystalline aggregates with, for example, a radial arrangement or with an arrangement of scattered rod-shaped or plate-shaped crystals, for example, like a house of cards.

[0064] This is also the case when enriched portions containing lanthanum, more specifically lanthanum compounds, are located at the grain boundaries of crystallites, at least in some cases, and the inventors suspect that enriched portions of lanthanum, e.g., lanthanum compounds, can act as effective crystallization nuclei.

[0065] Further preferred glass ceramics comprise, in mol %, based on the oxides: SiO2 25 to 55, preferably 35 to 50, B2O3 0.1 to 15, preferably 5 to 15, Al2O3 0 to 15, preferably 0 to 5, more preferably 0 to less than 2, MO 20-50, preferably 30-50 wherein MO is selected, individually or in any desired combination, from the group consisting of MgO and / or CaO and / or SrO and / or BaO; SrO and / or BaO are greater than 0, and MgO is less than 12] M2O is 0 to less than 2, preferably 0 to less than 1, wherein MO is selected from the group consisting of LiO and / or NaO and / or KO, individually or in any desired combination. Contains:

[0066] This glass ceramic is described, for example, in DE 102014218983 A1 in connection with bushing elements, in particular in the range of 1.0-10 10 It has the distinctive property of specific volume resistivity exceeding Ωcm.

[0067] Another preferred glass ceramic / another at least partially crystallized glass comprises the following oxides, specified in wt. %: SiO2: 20 to 60, preferably 25 to 50 Al2O3: 0.5 to 20, preferably 0.5 to 10 CaO: 10-50 MgO: 0.5 to 50, preferably 0.5 to 10 Y2O3: 0.1 to 20, preferably 3 to 20 ZrO2: 0.1 to 25, preferably 3 to 20 B2O3: 1 to 15, preferably 3 to 12 It contains HfO2 may optionally further be present in a content of up to 0.25% by weight.

[0068] Another suitable at least partially crystallized glass or glass-ceramic is composed of the following oxides, specified in weight percent: SiO2: 36 to 54, preferably 40 to 54 Al2O3: 8 to 16, preferably 8 to 13 CaO: 0 to 35, preferably 5 to 25 MgO: 0 to 17, preferably 3 to 14 RO: 8 to 39, preferably 8 to 35 ZrO2: 0 to 25, preferably 0 to 17 B2O3: 0 to 3, preferably 0 to 2, more preferably 0 It contains The ratio RO refers to the oxides BaO, SrO, MgO, ZnO, in each case individually or in any desired mixture, Preferably, the RO, individually or in any desired mixture, in weight percent: BaO 0~36 MgO 0-22 CaO 0 is.

[0069] At least partially crystallized glasses of this type are disclosed, for example, in WO 2017 / 220700.

[0070] At least partially crystallized glasses are initially obtained in glassy form as crystallizable glasses by a melting process and only undergo at least partial crystallization in a subsequent heat treatment.

[0071] The hermetically sealed connection between the electrically insulating material and at least one electrical functional element is achieved by fusing the electrically insulating material onto the electrical functional element. For this purpose, for example, a green body containing the electrically insulating material or its precursor, such as a crystallizable glass, can be provided. The green body is then subjected to a heat treatment together with the at least one electrical functional element, so that the electrically insulating material is fused onto the electrical functional element, forming a physical and / or chemical bond and providing a hermetic seal. In the case of a crystallizable glass precursor, the crystallizable glass at least partially crystallizes during this process.

[0072] Here, crystallization can be controlled in the sense that, for example, a selective heat treatment, for example so-called nucleation, is carried out to form a precursor phase for at least one crystalline phase. However, crystallization can also occur uncontrolled during a separate process step, for example in the form that a connection providing a hermetic seal is formed between a material, for example the material of the container, and the at least partially crystallized glass, without a further process step for selective crystallization being carried out.

[0073] The housing of the unit may include a cap made of a heat-resistant material that at least partially encloses the electrically insulating material. This cap may be particularly cup-shaped, with the open side of the cup facing the second section of the at least one electrical functional element. Likewise, the protective cap is preferably shaped and positioned so that the first section of the at least one electrical functional element is located within the protective cap.

[0074] The housing of the unit may include a protective tube made of a heat-resistant material that surrounds at least a portion of the second section of the electrical functional element. This can protect, in particular, the connecting wires of at least one electrical functional element. If the housing also includes a cap, the protective tube is preferably connected to the cap of the housing. The connection can be made, for example, by laser welding or soldering.

[0075] The heat-resistant material of the protective tube and / or the heat-resistant material of the cap are preferably selected from heat-resistant steels or alloys or heat-resistant ceramics, in particular alloy 600, steel 1.4762, or Al2O3 ceramic. If the housing includes both a cap and a protective tube, these may be made of the same or different materials, depending on the embodiment variant.

[0076] The housing of the unit is preferably designed and constructed so that at least a first section of the at least one electrical functional element is shielded from the metallic portions of the housing, which may be achieved by embedding the entire first section in an electrically insulating material, by coating the first section with another non-metallic material, or by forming a cavity containing the first section and having a non-metallic wall.

[0077] Preferably, the housing of the unit comprises a protective element made of glass, glass ceramic, ceramic or a combination of several of said materials. The materials mentioned in connection with the electrically insulating material of the housing are in principle also suitable as materials for the protective element.

[0078] This protective element can, for example, be connected to an electrically insulating material or to a molding made from an electrically insulating material.

[0079] Preferably, the first section of the electrical functional element is accommodated in a cavity in the housing, which cavity is preferably evacuated or filled with an inert gas, for example nitrogen or argon.

[0080] The first section of the at least one electrical functional element is then advantageously not in direct contact with any material of the housing that could potentially interact with the electrical functional element and thereby cause distortions in the measured values, for example. In particular, aging caused by corrosion or movement is prevented or at least substantially reduced. This reduces drift over time in the measured values ​​obtained from the electrical functional element.

[0081] Here, the walls of the cavity are preferably made from the electrically insulating material of the housing. If the housing includes a protective element, this protective element may form one of the walls of the cavity.

[0082] The first section of the at least one electrical functional element is preferably entirely embedded in the electrically insulating material of the housing, whereby in particular the first two sections are seamlessly surrounded by the electrically insulating material of the housing.

[0083] In particular if the housing comprises a protective cap, this also ensures that the electrical functional elements are shielded from being affected by the material of the protective cap.

[0084] The unit may further comprise at least one holding element which may be particularly configured to support at least one connecting wire, where the holding element may for example be designed in the form of a tube through which the at least one connecting wire passes.

[0085] The at least one retaining element may be made of the same material as the electrically insulating material and may be designed as a single unit therewith. However, the retaining element may also be designed as a separate unit and connected to the electrically insulating material. Alternatively, the at least one retaining element may be made of a different material selected from glass, glass ceramic, or ceramic. In this case, the at least one retaining element is preferably partially embedded in the electrically insulating material and thereby held in place.

[0086] The thermal expansion coefficient of the electrically insulating material is preferably matched to the thermal expansion coefficient of the at least one electrical functional element, whereby the difference between these thermal expansion coefficients is preferably less than 5·10 -6 / K, particularly preferably less than 3·10 -6 / K, very particularly preferably less than 1·10 -6 / K.

[0087] Therefore, if the electrical functional element has a zirconia ceramic substrate with a platinum layer, the thermal expansion coefficient of the electrical insulating material is approximately equal to that of platinum, i.e., approximately 8.8·10 -6 / K and the thermal expansion coefficient of zirconia, i.e., approximately 10.2 10-6 / K. Therefore, it is preferable that the electrical insulating material is -6 / K~10.2·10 -6 It is preferable that the thermal expansion coefficient is in the range of 1 / K.

[0088] The thermal expansion coefficient of the insulating material is adjusted by the appropriate selection of the material, i.e., the glass or glass ceramic used. The selected material, or a mixture of one or more such materials, can be modified by the addition of aggregates. For example, the thermal expansion coefficient of the insulating material can be adjusted by the selective addition of ceramic powders such as MgO as aggregates.

[0089] In the case of functional elements with a platinum layer, the thermal expansion coefficient of the electrically insulating material preferably matches that of platinum. Alternatively, the thermal expansion coefficient may match the average of the thermal expansion coefficient of the conductive element and the expansion coefficient of the substrate of the electrical functional element. This is particularly preferred when using an alumina-based substrate.

[0090] The electrical functional element of the unit is preferably designed as a temperature sensor element, preferably comprising a ceramic substrate and a structured resistive layer disposed thereon. More preferably, the temperature sensor element is designed as a Pt100, Pt200, Pt500, Pt1000, or Pt10000 temperature sensor. Therefore, the electrical functional element is preferably a standard temperature measuring resistor in a temperature-resistant structure. This temperature measuring resistor is held in place within the housing of the unit by an electrically insulating material so that the entire active part of the temperature measuring resistor is housed within the housing. The electrically insulating material hermetically seals the housing from the part of the temperature measuring resistor that protrudes from the housing, including the connecting wire, thereby protecting the active part of the temperature measuring resistor from local environmental influences. In this way, a heat-resistant and corrosion-resistant temperature measuring unit is obtained.

[0091] The electrical functional element of the unit is preferably designed as a heating element, which results in a heat- and corrosion-resistant heating unit.

[0092] The temperature measurement unit and the heating unit can be used together to measure the flow of a fluid, e.g., a gas or a liquid. For example, the temperature measurement unit determines the current temperature, and the heating unit is controlled to aim for a constant temperature. From the energy required by the heating unit to maintain the temperature, it can then be estimated how much fluid passes through the two units.

[0093] This type of heat flow measurement can also be performed by an integrated flow measurement unit. Therefore, it is preferred that the unit designed as a heat flow meter includes at least two electrical functional elements, at least one of which is designed as a temperature sensor element and at least one of which is designed as a heating element. Naturally, it is also possible to integrate both functions into one electrical functional element. Therefore, in this case, the unit designed as a heat flow meter includes an electrical functional element designed as a combined temperature sensor element and heating element.

[0094] The proposed units can be used in particular in areas where adverse conditions exist, such as high temperatures and corrosive media. Furthermore, the proposed units are mechanically very robust, which means that they can also be used in areas of high mechanical stress, such as strong vibrations. Preferred possible uses of the proposed units include, for example, as sensors in the transport sector, in particular the automotive sector, the power plant sector, and industry, in particular the chemical industry.

[0095] A particularly preferred use of the proposed unit relates to the measurement of exhaust gases, in particular exhaust gases from power plants, internal combustion engines, power generating units or industrial plants, where the good heat resistance, resistance to corrosive media and high mechanical stability of the unit are particularly advantageous.

[0096] It is understood that the features mentioned above and those that will be further elucidated below can be used not only in the combinations indicated in each case, but also in other combinations or alone, without departing from the scope of the invention.

[0097] Preferred configurations and embodiments of the present invention are illustrated in the drawings and will be elucidated in more detail in the following description, where like reference symbols refer to identical or similar or functionally identical components or elements. [Brief explanation of the drawings]

[0098] Illustrated in schematic form below: [Figure 1] 1 shows a schematic cross-section of an electrical functional element designed as a temperature sensor element. [Figure 2] 1 shows a first embodiment of a unit with electrical functional elements for high temperature use. [Figure 3] 10 shows a second embodiment of the unit further comprising a holding element. [Figure 4] 1 shows a third embodiment of the unit. [Figure 5] 10 shows a fourth embodiment of the unit. [Figure 6] 10 shows a fifth embodiment of the unit. [Figure 7] 10 shows a sixth embodiment of the unit. [Figure 8] 10 shows a seventh embodiment of the unit. [Figure 9] 10 shows an eighth embodiment of the unit. [Figure 10] 10 shows a ninth embodiment of the unit. [Figure 11] 10 shows a tenth embodiment of the unit. [Figure 12] 11 shows an eleventh embodiment of a unit including two electrical functional elements.

[0099] 1 shows in schematic form, in a cross-sectional view from the side, an electrical functional element 10 designed as a temperature sensor element. The electrical functional element 10 comprises a non-conductive substrate 16. Arranged on one surface of the non-conductive substrate 16 is an electrically conductive element 18 in the form of a thin layer. This is in the example of a temperature sensor element structured so that a conductor track is formed which follows a meandering path on the surface of the non-conductive substrate 16. Here, this conductor track is a temperature-measuring resistor, the electrical resistance of which varies characteristically with temperature.

[0100] The conductive elements 18 and the conductor tracks formed by the structuring are in electrical contact with the contact points 20 via connecting wires 14. In the case of a temperature sensor element, for example, two or four connecting wires 14 are used to enable a two- or four-point measurement of the electrical resistance, only one of which is visible in the cross-section of FIG.

[0101] In the example shown in Figure 1, the conductive layer 18 and the contact points 20 are provided with a covering material 22 to provide protection from environmental influences. Instead of a single layer as outlined in Figure 1, the covering material 22 may also be formed as a layer sequence having several different layers.

[0102] 2 shows a first embodiment of a unit 1 for high-temperature use, including an electrical functional element 10 and a housing 100. Here, the unit 1 is shown in a cross-sectional view from the front. In this exemplary embodiment, the housing 100 includes a cap 104, which is made, for example, of a heat-resistant metal alloy. In addition to the cap 104, the housing 100 also includes an electrically insulating material 102 that closes the open side of the cap 104. The electrically insulating material 102 is, for example, a partially crystallized glass or glass ceramic.

[0103] A first section 11 of the electrical functional element 10 is entirely embedded in an electrically insulating material 102. In the case of a temperature sensor element as shown in Figure 1, this first section comprises the serpentine conductor track and therefore the active part of the temperature sensor element.

[0104] Here, the second section 12 of the electrical functional element 10, which includes a portion of the connecting wire 14, is not surrounded by the electrically insulating material 102 and is externally accessible for electrical contact. In an alternative embodiment variant, the electrical functional element 10 also includes connection pads instead of the connecting wires 14. In that case, these are located on the non-conductive substrate 16, similar to the contact points 20 shown in FIG. 1, and the second section therefore includes a portion of the substrate 16. An exemplary embodiment in which the second section 11 includes a portion of the non-conductive substrate 16 is also described below with reference to FIG. 5.

[0105] In the embodiment shown in Figure 2, the third section 13 of the electrical functional element 10, which is located between the first section 11 and the second section 12 and includes the contact point 20 shown in Figure 1, is similarly embedded within the electrically insulating material 102 so that only a portion of the connecting wire 14 protrudes from the electrically insulating material 102.

[0106] The electrically insulating material 102 is fused onto the connecting wire 14 so that a hermetically sealed connection exists. The electrically insulating material 102 is likewise fused onto the cap 104 so that a hermetically sealed connection exists here as well. As a result of this intimate connection between the electrically insulating material 102 and the at least one functional element 10 and between the electrically insulating material 102 and the cap 104, no further sealing elements are necessary, which means that the proposed unit 1 does not include any further sealing elements.

[0107] The first section 11, which includes the active part of the electrical functional element 10, is advantageously entirely enclosed in insulating material 102, which means that this first section 11 cannot interact either with the local environment or with other components of the unit 1, such as the cap 104. Thus, for example, contamination of the electrical functional element 10 by components of the cap 104 is excluded.

[0108] Figure 3 shows a second embodiment of the unit 1, which essentially corresponds to the first embodiment described with reference to Figure 2, except that it further comprises a holding element 106.

[0109] Here, the retaining element 106 is in tubular form and is held in place by the electrically insulating material 102. For this purpose, a portion of the retaining element 106 is embedded in the electrically insulating material 102. The retaining element 106 is arranged to surround the connecting wires 14 and thereby mechanically support them. The retaining element 106 can be made of ceramic, for example.

[0110] Figure 4 shows a third embodiment of the unit 1, which essentially corresponds to the second embodiment described with reference to Figure 3, except that it does not include the cap 104. Here, the housing 100 consists solely of a molding made of an electrically insulating material 102.

[0111] 5 shows a fourth embodiment of the unit 1. In this exemplary embodiment, the housing 100 comprises a cap 104, to the open end of which is connected a protective tube 108. The cap 104 and the protective tube 108 are, for example, in both cases made of a heat-resistant metal alloy and are connected to each other, for example, by welding.

[0112] The electrical functional element 10 is inserted into the protective tube 108 up to the area of ​​the protective cap 104, where it is held in place and sealed from the protective tube 108 by a plug of electrically insulating material 102, so that a closed cavity 112 exists in the area of ​​the cap 104 and at the end of the protective tube 108. A first section 11 of the electrical functional element 10 is located within the cavity 112, while a second section 12 of the electrical functional element 10, which here includes the entire connecting wire 14, is located outside the cavity and is not covered by the electrically insulating material 102, meaning that the connecting wire 14 is accessible from outside the housing 100. Instead of the connecting wire 14, the electrical functional element 10 may also have connection pads arranged within the second section 12.

[0113] The third section 13, located between the first section 11 and the second section 12, is held in place by an electrically insulating material 102, which is connected to the electrical functional element 10 by forming a hermetic seal in the third section. More specifically, the electrically insulating material 102 is fused onto the non-conductive substrate 16 and the covering material 22 (see FIG. 1 ). The electrically insulating material 102 is likewise connected to the protective tube 108 by forming a hermetic seal, so that the cavity 112 is closed by the hermetic seal.

[0114] Figure 6 shows a fifth embodiment of the unit 1, which essentially corresponds to the fourth embodiment described with reference to Figure 5. In this case, however, the third region 13 of the electrically functional element 10, which is connected to the electrically insulating material 102, further encloses a part of the connecting wire 14, which means more particularly that the contact point 20 between the conductive element 18 (see Figure 1) and the connecting wire is located within the area surrounded by the electrically insulating material 102. This provides particularly good protection for the contact point 20.

[0115] Figure 7 shows a sixth embodiment of the unit 1, which essentially corresponds to the fifth embodiment described with reference to Figure 6, except that it further comprises a holding element 106.

[0116] Here, the retaining element 106 is in tubular form and is held in place by the electrically insulating material 102. For this purpose, a portion of the retaining element 106 is embedded in the electrically insulating material 102. The retaining element 106 is arranged to surround the connecting wires 14 and thereby mechanically support them. The retaining element 106 can be made of ceramic, for example.

[0117] Figure 8 shows a seventh embodiment of the unit 1, which essentially corresponds to the fifth embodiment described with reference to Figure 6, except that the wall of the cap 104 facing the interior of the cavity 112 is lined with a non-metallic material.

[0118] In this example, the walls at the closed end of the cap 104 are lined with a protective element 110. The material of the protective element 110 is, for example, glass, ceramic, or glass-ceramic. The side walls of the cavity 112 are lined with an electrically insulating material 102, and in the exemplary embodiment shown in Figure 8, these side walls are designed as a single unit with a plug-shaped portion 112 of electrically insulating material that holds the third section 13 of the electrical functional element 10 in place.

[0119] Furthermore, in the seventh embodiment, the first section 11 of the electrical functional element 10 is selected such that it contains the conductor tracks that constitute the entire measuring resistor if the electrical functional element 10 is designed as a temperature measuring resistor. Thus, in this embodiment, the active part of the electrical functional element 10 is located entirely within the cavity 112.

[0120] Figure 9 shows an eighth embodiment of the unit 1, which essentially corresponds to the seventh embodiment described with reference to Figure 8, except that the eighth embodiment does not include the cap 104. The housing 100 therefore consists of an electrically insulating material 102 and a protective element 110.

[0121] Figure 10 shows a ninth embodiment of the unit 1. This essentially corresponds to the eighth embodiment described with reference to Figure 9, except that it further comprises a holding element 106.

[0122] Here, the retaining element 106 is in tubular form and is held in place by the electrically insulating material 102. For this purpose, a portion of the retaining element 106 is embedded in the electrically insulating material 102. The retaining element 106 is arranged to surround the connecting wires 14 and thereby mechanically support them. The retaining element 106 can be made of ceramic, for example.

[0123] Figure 11 shows a tenth embodiment of the unit 1, which essentially corresponds to the ninth embodiment described with reference to Figure 10, except that the tenth embodiment does not include the cap 104. The housing 100 therefore consists of an electrically insulating material 102 forming a cup-shaped body and a protective element 110.

[0124] Figure 12 shows, in a cross-sectional side view, an eleventh embodiment of the unit 1, which is similar in design to the first embodiment described with reference to Figure 1, but which further comprises a further electrical functional element 10', which in this example is designed as a heating element and is arranged next to the electrical functional element 10 designed as a temperature sensor element.

[0125] The unit 1 shown in Fig. 12 can be used as a heat flow sensor. In this case, the temperature determined by the electrical functional element 10, which is designed as a temperature sensor element, can be used to adjust the heating current in a further electrical functional element 10', which is designed as a heating element, so that the temperature remains constant. The more fluid flows through the unit 1, the more heat is transferred to the fluid and the larger the heating current that is required to set the temperature constant. The volume of the flowing fluid can therefore be determined from the heating current. [Explanation of symbols]

[0126] 1 unit 10 Electrical Functional Elements 10' Further electrical functional elements 11 First Division 12 Second Division 13 Third Division 14 connecting wires 16 Non-conductive substrate 18 Conductive Elements 20 contact points 22 Covering materials 100 Housing 102 Electrical insulating materials 104 Cap 106 Holding Element 108 Protection tube 110 Protection Elements 112 Cavity

Claims

**Claim 1** A unit (1) for high-temperature use, in particular for use above 700 °C, comprising a housing (100) and at least one electrical functional element (10), said at least one electrical functional element (10) comprising a non-conductive substrate (16), a conductive element (18), and at least one connection wire (14) or at least one connection pad, said at least one electrical functional element (10) being used within the housing (100), whereby a first section (11) of said electrical functional element (10) is housed within said housing (100) and shielded from the local environment by said housing (100), and a second section (12) of said electrical functional element (10) comprising at least a part of said at least one connection wire (14) or said connection pad is externally accessible, said at least one electrical functional element (10) comprising, between said first section (11) and said second section (12), a third section (13) embedded within the electrical insulating material (102) of said housing (100), in the unit (1). Said electrical insulating material (102) seals said housing (100) from said electrical functional element (10), said electrical insulating material (102) being selected from glass, glass ceramic, a combination of said materials, or a composite material having glass or glass ceramic as its main component, said insulating material (102) being fused onto said at least one electrical functional element (10), such that a physical and / or chemical bond is formed at the interface therebetween, characterized unit (1). **Claim 2** The unit (1) according to claim 1, characterized in that said housing (100) comprises a cap (104) made of a heat-resistant material at least partially surrounding said electrical insulating material (102). **Claim 3** The unit (1) according to claim 1, characterized in that said housing (100) comprises a protective tube (108) made of a heat-resistant material surrounding at least a part of said second section (12) of said electrical functional element (10), said protective tube (108) preferably being connected to the cap (104) of said housing (100) by means of laser welding or soldering in particular. **Claim 4** The heat-resistant material of the protective tube (108) and / or the heat-resistant material of the cap (104) is selected from heat-resistant steel or alloy or heat-resistant ceramic, in particular alloy 600, steel 1.4762, or Al ２ O ３ Unit (1) according to claim 2 or 3, characterized in that it is selected from ceramics. **Claim 5** The unit (1) according to claim 1 or 2, characterized in that the housing (100) comprises a protective element (110) made of glass, glass ceramic, ceramic, or a combination of said materials.

6. The unit (1) according to claim 1 or 2, characterized in that the first section (11) of the electrical functional element (10) is accommodated in a cavity (112) within the housing (100), and the cavity (112) is preferably evacuated or filled with an inert gas such as nitrogen or argon.

7. The unit (1) according to claim 6, characterized in that the wall of the cavity (112) consists of the electrical insulating material and / or one wall of the cavity (112) is formed by the protective element (110).

8. The unit (1) according to claim 1 or 2, characterized in that the conductive element (18) and / or the electrical contact points (20) between the at least one connection wire (14) of the at least one functional element (10) and the conductive element (18) are at least coated with a coating material (22), and the coating material (22) is preferably different from the electrical insulating material (102).

9. The unit (1) according to claim 1 or 2, characterized in that the entire first section (11) of the at least one electrical functional element (10) is embedded in the electrical insulating material (102) of the housing.

10. The unit (1) according to claim 1 or 2, characterized in that the electrical contact points (20) between the at least one connection wire (14) of the electrical functional element (10) and the conductive element (18) are arranged within the third section (13) and are thus embedded in the electrical insulating material (102).

11. The unit (1) according to claim 1 or 2, further characterized in that it comprises at least one holding element (106) for supporting the at least one connection wire (14).

12. The at least one holding element (106) is made of the same material as the electrical insulating material (102) and is designed as a single unit therewith, or the at least one holding element (106) consists of a different material selected from glass, glass ceramic, or ceramic, and the at least one holding element (106) is partially embedded in the electrical insulating material (102), whereby it is held in a predetermined position, the unit (1) according to claim 11.

13. The coefficient of thermal expansion of the electrical insulating material (102) matches the coefficient of thermal expansion of the at least one electrical functional element (10), and the difference between the coefficients of thermal expansion is preferably less than 5·10 －６ / K, particularly preferably less than 3·10 －６ / K, and extremely particularly preferably less than 1·10 －６ / K. The unit (1) according to claim 1 or 2, characterized in that this is the case.

14. The electrical functional element (10) is designed as a temperature sensor element, the temperature sensor element preferably comprising a ceramic substrate and a structured resistance layer arranged thereon, the temperature sensor element being more preferably designed as a Pt100, Pt200, Pt500, Pt1000, or Pt10000 temperature sensor, the unit (1) according to claim 1 or 2.

15. The electrical functional element (10) is designed as a heating element, the unit (1) according to claim 1 or 2.

16. The unit (1) comprises at least two electrical functional elements (10, 10'), the unit (1) being preferably designed as a heat flow meter having at least one temperature sensor element and at least one heating element, the unit (1) according to claim 1 or 2.

17. The electrical insulating material (102) is a glass ceramic, La ２ O ３ 0.3 mol% to less than 5 mol%, Nb ２ O ５ 0 mol% to 9 mol%, Ta ２ O ５ 0 mol% to 7 mol% comprising, Σ(A ２ O ５ ) 0.2 mol% to 9 mol% being, wherein A is an element which is normally in the oxidation state V+ in the oxide and may contain or may contain, for example, Nb and / or Ta or P and / or mixtures thereof, the unit (1) according to claim 1 or 2.

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