EP4204781A1

EP4204781A1 - Temperature sensor and method for producing a temperature sensor of this kind

Info

Publication number: EP4204781A1
Application number: EP21762446.9A
Authority: EP
Inventors: Karlheinz Wienand; Tim Asmus; Christoph Nick
Original assignee: Yageo Nexensos GmbH
Current assignee: Yageo Nexensos GmbH
Priority date: 2020-08-27
Filing date: 2021-08-12
Publication date: 2023-07-05
Also published as: US20230360825A1; WO2022043084A1; CN116097072A; EP3961170A1; KR20230029955A; JP2023535769A

Abstract

The invention relates to a temperature sensor (10) comprising: - a substrate (15), formed from a metal element, in particular a metal foil, wherein the substrate (15) has a front side (16) and a rear side (17), - an insulation layer (20), which covers the front side (16) of the substrate (15) only in some portions, in such a way that an insulation-layer-free portion (25) is formed on the front side (16) of the substrate (15), and - a sensor structure (30), in particular a resistive sensor structure, which is formed on the insulation layer (20) and on the insulation-layer-free portion (25) of the front side (16) of the substrate (15), wherein the sensor structure (30) has at least two electrical contacting portions (31, 32), and a first contacting portion (31) is connected to the insulation-layer-free portion (25) of the front side (16) of the substrate (15), and a second contacting portion (32) is a first contact path (41) or is connected to a first contact path (41), wherein the first contact path (41) is preferably arranged on the insulation layer (20).

Description

DESCRIPTION

Temperature sensor and method for manufacturing such a temperature sensor

The invention relates to a temperature sensor and a method for producing such a temperature sensor.

It is known from the prior art to make temperature sensors as small or miniaturized as possible. In EP 1 692 476 B1, for example, a temperature sensor based on a platinum thin-film sensor is proposed. The contact areas of the thin-film sensor are arranged on opposite sides of a substrate. The sensor structure is contacted with the aid of what is known as a feedthrough, which electrically connects a first contact pad on the upper side to the metallization on the underside of the substrate. However, the production of such a sensor is relatively expensive. A feedthrough is to be made in an insulating substrate, and this feedthrough must be filled with an electrically conductive material.

In contrast, US Pat. No. 6,151,771 A discloses an SMD temperature sensor based on a platinum thin-film structure. In this case, the contacts are routed from an upper side to an underside of the substrate, in that two side surfaces of the substrate are metallized. In order to ensure a reliable electrical connection between the two contact sections on the top and bottom of the substrate, additional soldering connections are formed which enclose the side surfaces. A disadvantage of such a design of a temperature sensor is again the complexity of the production. The side surfaces described must be metalized in a work step that is necessary for this. Furthermore, it is necessary to form an additional soldered connection in order to enable the connection between the two contact sections.

Furthermore, it is known to implement small temperature sensors in the form of NTCs. For this purpose, a semiconductor material is provided in the form of a cuboid and metallized on two opposite side faces. The metallized side surfaces in turn serve as contacts for the electrical leads. Although this design allows small dimensions of a temperature sensor, however, such temperature sensors have the disadvantage of only limited accuracy.

Proceeding from the aforesaid, it is the object of the present invention to provide such a temperature sensor which on the one hand can have small dimensions, on the other hand has high measuring accuracy and is also easy to manufacture.

A further object of the invention consists in specifying a corresponding method for producing a temperature sensor according to the invention.

According to the invention, this object is achieved with regard to a temperature sensor by the subject matter of claim 1 and with regard to a method for producing a temperature sensor by the subject matter of patent claim 11.

The invention is based on the idea of specifying a temperature sensor which comprises: a substrate formed from a metal element, in particular a metal foil, the substrate having a front side and a rear side, an insulating layer which covers the front side of the substrate only in sections, such that an insulating layer-free section is formed on the front side of the substrate, and a sensor structure, in particular a resistive sensor structure, which is formed on the insulating layer and on the insulating layer-free section of the front side of the substrate, the sensor structure having at least two electrical contacting sections, and a first contacting section is connected to the insulating layer-free portion of the front side of the substrate and a second contacting portion is a first contact pad or is connected to a first contact pad, the first contact pad preferably being on the insulation layer is arranged.

A sensor structure is to be understood in particular as a coherent structure. In other words, the sensor structure is preferably formed in one piece. When the sensor structure is designed as a continuous or one-piece structure, the first and the at least second contacting section are each formed by a section of a continuous or one-piece sensor structure.

A sensor structure is understood to be a coherent structure that does not consist of a number of structurally separate components.

In particular, the first and the at least second contacting section are not structurally separate components.

An electrical contacting section is to be understood in particular as a section that brings about electrical contact with another component or another layer.

The sensor structure preferably has a meandering structure at least in sections, with the at least two contacting sections being different sections of the meandering structure.

According to the invention, the first contacting section is formed from the section of the sensor structure that is formed on the section without an insulating layer.

In other words, a temperature sensor is specified which has a substrate, an insulation layer and a sensor structure, the insulation layer not being applied and/or applied over the full area on a front side of the substrate. An insulating film bare portion is formed on the substrate. The sensor structure is in turn formed at least in sections on this section without an insulation layer.

The sensor structure is formed on the section free of the insulation layer in such a way that at least one contacting section of the sensor structure is connected, in particular electrically connected, to the section of the front side of the substrate which is free of the insulation layer. The underlying object is thus achieved according to the invention in that a sensor structure can be applied to a substrate, which can have relatively small dimensions, the electrical contacting on the insulating layer being made by connection to a contact pad and on the other hand by contacting the substrate due to the formation of the Sensor structure takes place on the insulating layer-free section. The first contact pad can be arranged directly or indirectly on the insulation layer or can be connected to the insulation layer. It is possible for the first contact pad to be indirectly connected to the insulation layer via the second contacting section.

The front and back of a substrate are two opposite sides of the substrate. These are the opposite sides of the substrate that are larger in terms of surface area. The front and back of a substrate are preferably not to be understood as meaning the sides of the substrate that are formed by the layer thickness or component thickness of the substrate. If both the front side and the back side are made of the same material or have the same coating, both sides can function as the front side and/or the back side.

In a particularly preferred embodiment of the invention, the substrate is an electrically conductive substrate.

The front side of the substrate is preferably understood to mean the side of the substrate on which an insulating layer is formed directly or indirectly. The insulating layer does not completely or incompletely cover the substrate.

In a preferred embodiment of the invention, the insulating layer-free portion is formed at an edge portion of the front side of the substrate. An edge section is to be understood in particular as such a section of the front side which adjoins at least one side edge of the front side of the substrate. Preferably, the edge portion of the front side is the edge portion of the front side formed by a shorter side of the substrate.

The temperature sensor has supply lines for making electrical contact with it. The temperature sensor preferably has two electrical supply lines. It is possible for the temperature sensor to have a first electrical lead, which is connected to the rear side of the substrate, and has at least a second electrical lead, which is connected to the first contact pad. The electrical contacting of the temperature sensor thus takes place on the one hand on the rear side of the substrate and on the other hand on the opposite side of the temperature sensor, namely on the first contact pad.

Because of such an electrical contact, it is possible to use a temperature sensor to be made available with particularly small dimensions. The small dimensions are achieved, among other things, by the contacting of the temperature sensor taking place on the opposite sides of the temperature sensor and not, as is usual with sensor structures, next to one another on one side of the temperature sensor or the substrate.

In a further embodiment of the invention, a passivation layer can be formed at least in sections on the side of the sensor structure pointing away from the substrate.

It is possible for the passivation layer to be formed from glass frits or to have glass frits. It is also possible, for example, for layers made of aluminum oxide (Al2O3) to be formed as passivation layers.

In a further embodiment of the invention, the sensor structure is completely covered with a passivation layer. It is possible for the first contact pad of the temperature sensor to be covered, at least in sections, by a passivation layer.

Furthermore, it is possible for the first contact pad to be arranged in such a way that it rests in sections on the side of the passivation layer facing away from the sensor structure and is at the same time electrically connected to the sensor structure. In such an embodiment of the invention, a further reduction in the sensor area is brought about. Such an embodiment is realized by applying the contact pad simultaneously to the passivation layer and the uncovered area of the sensor structure after the application of the passivation layer, for example by screen printing a paste containing noble metal.

The metal element, in particular the metal foil, from which a substrate is formed, preferably has one of the following elements: aluminum (Al) and/or steel, in particular ferritic steel, and/or titanium (Ti) and/or niobium (Nb) and /or tantalum (Ta) and/or nickel (Ni) and/or copper (Cu).

In a particularly preferred embodiment, the metal element, in particular the metal foil, is formed from one of the following elements: aluminum (Al) and/or steel, in particular ferritic steel, and/or titanium (Ti) and/or niobium (Nb) and/or tantalum (Ta) and/or nickel (Ni) and/or copper (Cu).

In particular, it is possible for the metal foil to be preferably formed from materials that form dense metal oxide layers with high electrical insulation during anionic oxidation. This serves to produce a corresponding insulation layer.

The steel, in particular the ferritic steel, is preferably an FeCrAI alloy, in particular X8CRAI20-5 or FeCr25AI5. When using metal alloys as a component of the substrate, these should preferably be selected in such a way that their resistance remains as constant as possible over its lifetime. In addition, the resistance of the carrier substrate according to the geometry of the sensor can be taken into account in a possible trim adjustment of the sensor.

In another embodiment, a roll clad or clad metal substrate or sheet with a metallic surface coating such as electroplating may be provided.

The substrate preferably has a substrate thickness of from 10 μm to 1 mm, in particular from 0.02 mm to 0.5 mm, particularly preferably from 0.05 mm to 0.3 mm. If the substrate is formed from a metal foil with a substrate thickness of less than 300 μm, the substrate has particularly good mechanical flexibility.

Depending on the choice of material in connection with the sensor structure, a special choice can be made with regard to the material of the substrate. If, for example, the sensor structure is made of platinum and/or a platinum alloy, the thermal expansion coefficient of the substrate should be in the range of 6*10′ ⁶ K′ ¹ to 15*10′ ⁶ K′ ¹ . The selection of the material of the substrate with such a coefficient of expansion prevents a sensor structure applied thereon, which is made of platinum and/or a platinum alloy, from flaking off. If a sensor structure is formed from platinum, ferritic steels or titanium or tantalum are particularly suitable with regard to the substrate material.

Furthermore, it is possible that the substrate is particularly preferably on at least one side, particularly preferably both on the front and on the back completely, is coated with a nickel protective layer and/or a gold protective layer. Such a nickel protective layer preferably has a thickness of about 3 μm.

A protective gold layer preferably has a layer thickness of 0.1 μm, in particular approximately 0.1 μm.

Electrically insulating layers that electrically isolate the electrically conductive substrate from the heating structure are particularly suitable as insulating layers. In general, layers with a specific resistance of > 10E10 Q * cm are suitable for this.

The insulation layer includes, for example, a metal oxide layer, in particular an anodized metal oxide layer, or a metal nitride layer or a metal oxynitride layer. In a particularly preferred embodiment of the invention, the insulation layer is a metal oxide layer, in particular an anodized metal oxide layer, or a metal nitride layer or a metal oxynitride layer.

The advantage of an insulation layer that is or has a metal oxide layer, a metal nitride layer or a metal oxynitride layer is that such insulation layers have both good insulating properties and can be made as thin as possible, preferably as thin as possible and mechanically flexible.

Some metals, such as aluminum or FeCrAI alloys, form particularly stable metal oxide layers, so that the insulation layer does not flake off or cracks form in the insulation layer, even in the event of rapid temperature changes.

Furthermore, it is possible that the insulation layer has the following components or consists of the following components:

Aluminum oxide (AI2O3) and/or aluminum titanate (AhTiOs) and/or titanium dioxide (TiÜ2) and/or silicon dioxide (SiÜ2) and/or silicon oxide (SiO) and/or magnesium oxide (MgO) and/or magnesium titanate (MgTiOs) and/or a binary zirconia alloy and/or a ternary zirconia alloy and/or boron nitride (BN) and/or aluminum nitride (AIN) and/or silicon nitride (SisN^.

In a particularly preferred embodiment of the invention, the insulation layer is produced by means of an ADM process (aerosol deposition method). With the help of one Method ceramic or glass-like insulation layers can be produced. These layers have a particularly high level of electrical insulation and can also have a thin layer thickness. If the insulation layer is produced using the ADM process, the thickness of the insulation layer can be 0.2 μm - 10 μm.

In addition to the ADM method, other known deposition methods such as CVD (chemical vapor deposition), CSD (chemical solution deposition) or PVD (physical vapor deposition) are also possible for applying an insulating layer to a metal foil.

It is possible that the insulation layer is a metal oxide layer, in particular an anodized metal oxide layer or a metal nitride layer or a metal oxynitride layer, or is formed from a composite layer, or a vitreous or glass-ceramic layer formed from a slip or a paste containing metal oxides, in particular Aluminum oxide particles (AI2O3) and/or magnesium oxide particles (MgO), or is formed from a layered composite, wherein at least one layer has a polymer layer.

It is possible to adapt the choice of material for the insulating layer to the choice of material for the metal element, in particular for the metal foil.

The use of a metal foil for the production or the provision of a substrate, in particular the use of an aluminum foil, has the advantage that warping of the metal foil is prevented when the temperature sensor to be produced is subjected to higher temperatures.

The use of a metal foil to form an electrically conductive substrate also has the advantage that, for example, in contrast to the use of polymeric substrates, the insulation layer can be applied using variable methods. Since the metal foil can be exposed to high temperatures, the insulation layer can also be applied by means of such methods that involve exposure to high temperatures. This is the case, for example, when applying metal-containing pastes. Such pastes or layers of sintering paste are regularly to be sintered at high temperatures of, for example, 1,000.degree. Due to the use of a metal foil as a substrate, such thermal stresses can be applied without further ado.

An anodized metal oxide layer differs from an atmospheric metal oxide layer in having higher electrical insulation. An anodized metal oxide layer can be produced, for example, by anodizing a metal surface. In other words, an insulating layer that is an anodized metal oxide layer can be produced by anodizing the metal surface of the substrate. Due to electrolytic oxidation, the surface of the metal foil is converted into a metal oxide layer.

An anodizing process is a surface technology method for producing an oxidic protective layer through anodic oxidation. In contrast to galvanic coating processes, the protective layer is not deposited on the workpiece, but rather an oxide or hydroxide is formed by converting the top metal layer. A 5 pm - 25 pm thin layer is formed, which protects and insulates the underlying layers or elements, namely the substrate.

Another way to produce a metal oxide layer is a hard anodizing process. As in the anodizing process, the metal foil is immersed in an electrolyte and connected as an anode. The surface of the metal foil is oxidized in the process, so that a metal oxide layer is formed. In this case, the volume of the metal foil increases.

By appropriately selecting the material of the electrically conductive substrate, an appropriate selection can be made with regard to the insulation layer to be formed thereon.

When using a steel foil made of an FeCrAl alloy, oxidation of this layer in air at elevated temperatures can also produce a metal oxide layer.

When using an FeCrAl alloy with an aluminum content of 6%, for example, in an oxygen-containing atmosphere in a furnace at oxidation temperatures of 1,000 °C up to 1,100° C. an electrically insulating insulation layer, in particular an electrically insulating aluminum oxide layer, of up to 5 μm can be produced.

In another embodiment of the invention, it is also possible to use steel materials with a low CrAl content, provided that such a steel material is aluminated on at least one surface or on at least one side. An alitizing process provides that a layer containing aluminum is applied to the substrate material, with this layer containing aluminum then being annealed at temperatures of 800 °C to 1,200 °C. This results in dense AhOs layers with a thickness of > 20 pm. The AhOs layer is in the a phase. Due to this process, an insulating layer is formed on at least one side of the substrate. Such an insulation layer is an electrically insulating metal oxide layer.

Furthermore, the insulating layer can be made of a vitreous compound. Glass slips containing various finely ground metal oxides, in particular aluminum oxide particles and/or magnesium oxide particles and/or titanium oxide particles, are used for this purpose.

It is also possible for the insulation layer to be formed from a layered composite. In other words, the insulation layer can have a multilayer structure. Such a layered composite or a multilayer structure has the advantage that pinholes or other disruptions and/or defects in a first layer of the layered composite are covered by the application of further layers and as a result the probability of a short circuit between the sensor structure and the conductive substrate decreases.

If the temperature sensor according to the invention is to be used at temperatures of less than 260° C., the layered composite can also have the combination of inorganic layers with polymer layers. If the insulation layer is formed from a layer composite with a polymer layer, such polymer layers can be formed in particular that have materials that can be deposited from solution. For example, the polymer layer is a layer made of polyimide and/or teflon and/or polycarbonate.

In a particularly preferred embodiment of the invention, the layered composite can be formed from three layers. A first layer is an aluminum oxide (Al2O3) layer. This layer is preferably produced using the ADM method. The second layer can be a polyimide layer. The third layer is preferably in turn an aluminum oxide (Al20s) layer, which is particularly preferably produced by means of ADM processes. Such a layered composite provides an insulating layer that is particularly resistant to short circuits.

Irrespective of the embodiment of the insulating layer, the insulating layer covers the substrate, in particular the electrically conductive substrate, only in sections. In other words, the substrate, in particular the electrically conductive substrate, is not covered with the insulation layer in at least one section and can therefore be electrically contacted in this section which is free of the insulation layer.

In a further embodiment of the invention it is possible for the temperature sensor to have a second contact pad which is formed in particular on the insulation layer. The second contact pad is preferably electronically connected to the first contact pad, with the second contact pad preferably forming a further tap of a resistance network.

The first contact pad and/or the second contact pad form(s) the connection of the sensor structure to a contacting section of the sensor structure, in particular to the second contacting section of the sensor structure. If the temperature sensor according to the invention has a complex resistance network, it is necessary to form more than two contact pads on the side of the sensor structure. The contact pads serve both as a contacting section for electrical leads and for corresponding taps.

In one embodiment of the invention, two contact pads that are bridged with one another can be formed, so that the contribution of the electrical supply line to the overall resistance of the sensor structure can be detected.

The first contact pad and/or the second contact pad can be a bonding pad, for example. The at least one contact pad preferably has a sinterable material or consists of such a sinterable material. The sinterable material can contain or consist of metal. The metal can preferably be formed from the group consisting of noble metals and non-noble metals. Noble metals can be selected from the group consisting of gold, silver, platinum, palladium or iridium.

Base metals can be selected from the group consisting of aluminum, copper or nickel.

The metal may include or consist of an elemental metal or an alloy.

In a preferred embodiment, the metal is an alloy. The alloy may contain a noble metal selected from the group consisting of gold, silver, platinum, palladium or iridium. The alloy preferably contains two or more noble metals. For example, the alloy can be a silver alloy or a silver-platinum alloy. In another embodiment, the alloy may include at least one precious metal and at least one non-precious metal. Optionally, the alloy can include both precious metal and non-precious metal. Furthermore, it is possible for the alloy to include non-metals.

The area of the at least one contact pad is not further restricted according to the invention. In a preferred embodiment, the first contact pad and/or the second contact pad has a dimension of not more than 1 mm, in particular not more than 200 μm, and very particularly preferably not more than 50 μm, in a first direction, which runs in particular parallel to the substrate surface. on.

In a further embodiment, the first contact pad and/or the second contact pad has a dimension of not more than 300 μm, in particular not more than 100 μm, in particular not more than 5 mm, and most preferably not more than 50 pm.

The shape of the first contact pad and/or the second contact pad is not further restricted. For example, the first contact pad and/or the second contact pad can be round or angular, in particular rectangular.

The sensor structure, in particular the resistive sensor structure, can in particular be formed from a metal. Preferably, the sensor structure, in particular the resistive Sensor structure consist of a pure metal or a metal alloy. In particular, the sensor structure has a metal or a metal alloy that has a temperature coefficient >3E-3/K.

In a particularly preferred embodiment of the invention, the sensor structure has platinum and/or aluminum and/or nickel. In a particularly preferred embodiment of the invention, the sensor structure, in particular the resistive sensor structure, is formed from platinum and/or a platinum alloy. The at least one sensor structure is preferably applied in sections directly to the insulation layer. In other words, the sensor structure is applied, at least in sections, directly to the side of the insulation layer pointing away from the substrate. In such an embodiment of the invention, no further layers are formed between the sensor structure and the side of the insulating layer pointing away from the substrate.

However, embodiments are also possible in which adhesion promoter layers, such as those made of the materials titanium/titanium oxide, tantalum/tantalum oxide or titanium nitride, lie between the insulation layer and the sensor structure.

The sensor structure describes such a structured element, which is preferably made of metal, which actually detects the temperature.

The sensor structure, which is made in particular from a Meta II structure, can have any shape. For example, it is possible to form a sensor structure in a square shape. It is also possible to form a sensor structure with an essentially straight line structure.

The sensor structure particularly preferably has a meandering shape. Such a meandering shape can be formed, for example, from a coherent, interwoven and/or nested and/or interlocking line structure. The individual sections, in particular the individual line sections, can be made relatively thin.

The sensor structure, which is present in particular in a meandering form, can cover a relatively large area of the temperature sensor due to the structure formed. This enables the temperature to be detected to be recorded quickly. The sensor structure can be formed from a structured metal foil. If such an embodiment with regard to the sensor structure is present, the sensor structure can be produced in a separate process and then applied to the insulation layer.

Furthermore, it is possible for the sensor structure to be produced from a metal-containing paste and/or a metal-containing ink. Such a metal-containing paste and/or ink can be applied to the insulation layer and to the section of the front side of the substrate that is free of the insulation layer by means of printing, in particular by means of a screen printing process.

In a particularly preferred embodiment of the invention, the sensor structure is formed from a paste containing noble metal. In particular, the noble metals can be platinum and/or silver and/or gold.

In a further embodiment of the invention, the sensor structure is a Meta II structure produced by means of thin-film metal deposition.

Due to the configuration of the temperature sensor according to the invention with the layers configured according to the invention and the arrangement of the sensor structure, an improved temperature sensor with a reduced area can be made available in comparison to the prior art.

The area of the temperature sensor is preferably smaller than 10 mm ² , particularly preferably smaller than 3 mm ² , particularly preferably smaller than 2 mm ² , very particularly preferably smaller than 1 mm ² . The surface of the temperature sensor can be seen in particular when the temperature sensor is viewed from above.

In a further embodiment of the invention, the sensor structure can have a trimming distance. The trimming distance is used to set a preferred desired resistance value for the sensor structure.

In a further embodiment of the invention it is possible for a three-dimensional sensor structure to be arranged on the substrate. A three-dimensional sensor structure is to be understood as meaning a sensor structure of this type that has at least two stacked at least partially spaced metal layers. An insulation layer is formed at least in sections between the metal layers. In addition, the two metal layers touch at least in sections. The at least two metal layers preferably touch in a region of the first contacting section.

With the aid of the temperature sensor according to the invention, a temperature sensor is made available which is characterized by a high level of accuracy with a very small size. Due to the small design of the temperature sensor, the mass of the temperature sensor is also reduced, so that the response time of the temperature sensor is correspondingly reduced. In other words, the temperature sensor responds more quickly to temperature changes.

The advantages of a temperature sensor according to the structure according to the invention, in particular with a sensor structure made of Pt, compared to an NTC sensor are the linear characteristic over a wide temperature range, the long-term stability and the high accuracy according to DIN IEC 60751.

A further aspect of the invention relates to a method for producing a temperature sensor according to the invention. With regard to individual aspects of the method, reference is also made to the explanations in connection with the temperature sensor according to the invention. Individual aspects relating to the production of the temperature sensor are already contained in the preceding part of the description.

The method according to the invention for producing a temperature sensor comprises the steps: a) providing a substrate which is formed from a metal element and has a front side and a rear side, b) forming at least one insulation layer on the front side of the substrate in such a way that a section of the Substrate is formed. c) application of a sensor structure, in particular a resistive sensor structure, to the insulation layer and to the insulation-free section of the front side of the substrate, d) application of at least one contact pad.

In step b), the insulating layer is applied to the front side of the substrate, for example over the entire surface, and in a further method step at least in sections removed such that the insulating layer free portion of the substrate is formed. It is possible to remove an insulation layer applied to the front side of the substrate again, for example by means of laser ablation and/or lift-off and/or by means of chemical etching and/or by means of plasma etching and/or abrasive removal. With some removal methods, in addition to removing the insulation layer, part of the underlying substrate material can optionally be removed and its thickness reduced locally.

The actual formation of the insulating layer-free section or the actual method to be used for producing an insulating layer-free section depends, for example, on the composition of the insulating layer and on the method by which the insulating layer is/was applied to the front side of the substrate.

In a further embodiment of the invention, it is possible for the insulation layer to be applied to the front of the Substrate is applied.

If the insulation layer is already applied in a structured manner, as is made possible, for example, by means of a printing process, in particular by means of a screen printing process, no subsequent process step for removing the insulation layer in sections is required.

The use of shading masks also allows the insulating layer to be applied in a structured manner on the front side of the substrate.

In step c), in order to apply the sensor structure, a thick film can be applied to the insulation layer and to the section free of the insulation layer by screen printing, for example.

In a further embodiment of the invention, in step c) the sensor structure can first be applied as a homogeneous metal layer, preferably over the entire surface, by means of PVD processes. The metal layer can then be structured using a laser structuring method or photolithographically. Furthermore, it is possible for a lift-off process to be carried out in order to produce the structure. For this purpose, a photoresist is applied to the insulation layer and to the section free of the insulation layer. The photoresist is then dried and exposed and then developed. A conductive layer is then applied to the photoresist structure produced in this way. The conductive layer is then structured by dissolving the photoresist structure with the aid of a solvent. Here, the metallization on the photoresist is removed and the film remaining on the surface again corresponds to the negative of the original photoresist structure.

In one embodiment of the invention, the contact pad to be applied in step d) can be applied to the insulation layer. Furthermore, it is possible that the at least one contact pad is applied at least indirectly to the insulation layer or is at least indirectly connected to the insulation layer.

A further embodiment of the method according to the invention provides for a passivation layer to be applied at least in sections to the sensor structure.

A passivation layer is preferably applied to the entire upper side of the sensor structure. The at least one contact pad is provided with a passivation layer at least in sections. Furthermore, it is possible for the contact pad or contact pads to be formed completely without a passivation layer. This makes it possible to make electrical contact with the contact pads in a correspondingly simple manner.

The method according to the invention for producing a temperature sensor according to the invention is characterized by a particularly simple method and a cost-effective implementation.

In a further embodiment of the invention, steps a) to d) are carried out on a substrate strip and/or a substrate carrier. In other words, steps a) to d) are carried out in such a way that a large number of temperature sensors are produced together on a substrate strip and/or a substrate carrier and are then separated.

The molds of individual substrates are placed on the substrate strip and/or the substrate carrier. For this purpose, the substrates are separated from the substrate strip and/or the substrate carrier at the sides. At corners and/or individual side sections the substrates are not detached or separated from the substrate belt and/or the substrate carrier, so that the individual substrates continue to be connected to the substrate belt and/or the substrate carrier. The individual substrates can then be processed further in this form, so that steps b) to d) can be carried out in common method steps.

Finally, the individual substrates are separated from the substrate band and/or the substrate carrier.

In a further embodiment of the invention, a first lead of the temperature sensor is connected to the rear side of the substrate and a second lead of the temperature sensor is connected to the at least one contact pad, which is preferably formed on the front side.

Various temperature sensors according to the invention and various methods for producing such temperature sensors are specified below according to embodiments 1 to 3.

Embodiment 1:

The substrate is formed from a nickel sheet, the substrate having a front side and a back side. The substrate is gold-plated on both sides and has a length of 0.8 mm, a width of 0.8 mm and a height of 100 μm. An insulating layer is applied to the front of the substrate. For this purpose, an aluminum oxide (Al20s) layer is applied using the ADM process. The layer thickness of the insulation layer is 2 μm. Then a section of the insulation layer, i. H. a section of the AhCh layer is removed again by laser ablation, leaving, for example, a 0.1 mm x 0.8 mm strip of the underlying gold-coated substrate, i. H. of the gold-coated nickel sheet, is exposed.

A platinum layer is then applied to the insulation layer and to the section free of the insulation layer. This is done using the PVD process. A platinum layer with a layer thickness of 200 nm is applied. A sensor structure is worked out of the platinum layer by laser ablation. The trench created with the laser can also penetrate into the AhCh layer and/or into the area of the exposed nickel sheet. The sensor structure consists of a first contacting section on the is formed insulation layer-free portion of the front side of the substrate, a meander, a trimming distance and a second contacting portion. The second contacting section is connected to a contact pad. The meander of the sensor structure is dimensioned as follows:

The distance between the meander webs is 20 pm. The web width is 20 μm. The web length is 500 pm. With a total meander length of 3.81 mm, the total resistance of the meander is about 100 Ω. The meander covers an area of about 0.3 mm x 0.5 mm.

The trimming distance, which is also worked out of the platinum layer by laser ablation, has a similar dimension. The total area of the sensor structure is 0.5mm*0.6mm.

The sensor structure is then set to the desired resistance value by removing individual segments of the trimming distance with a laser.

Then a glass slip is applied to the entire sensor structure with the exception of the second contacting section and baked.

A first contact pad, which is electrically connected to the second contacting section, is then applied to the passivation layer.

A first electrical lead is applied, which is connected to the rear side of the substrate. The first electrical supply line is preferably connected to the underside by means of soldering. The second electrical lead is provided in the form of a gold bonding wire. This gold wire is connected to the first contact pad.

Embodiment 2:

The substrate is formed from a copper sheet. An A^Os insulation layer is applied to the front of the copper sheet. The A^Os layer is deposited using ADM processes. The thickness of the insulation layer is 20 μm. The copper sheet is then exposed to air in a furnace at 500°C for one hour. No additional copper oxidation is observed under the AhOs insulation layer after aging.

Embodiment 3:

In contrast to embodiment 2, a glass slip layer is applied to the cleaned copper sheet and baked. The layer thickness is also about 20 μm. The copper sheet is then exposed to air in a furnace at 500°C for one hour.

In embodiment 3, under the same aging conditions as those used in embodiment 2, circular oxidation areas are formed on the copper foil in the masked area. Such circular oxidation areas indicate pin holes in the glass cover.

In a comparison of embodiments 2 and 3, the improved insulation properties of an insulation layer produced using the ADM method compared to a glass slip layer become visible.

Embodiment 4:

The substrate is formed from a nickel sheet, the substrate having a front side and a back side. Both of these sides are simultaneously coated over their entire surface by dip coating using the Chemical Solution Deposition process, each with 200 nm thick layers of lanthanum zirconate (La2Zr2O?). To protect the substrate from unwanted oxidation during heat treatment, this step is carried out in a forming gas atmosphere. With the Chemical Solution Deposition method, the back is inevitably coated as well, unless specific countermeasures are taken to prevent such a coating. In this case, the positive side effect is that the back is also covered with the same insulating layer and the substrate can be protected against unintentional oxidation in the further metallization steps.

This is followed by three metallization steps with platinum and two more deposition steps of a screen-printed aluminum oxide layer (AI2O3) to form a three-dimensional structure with a total resistance of approx. 300 ohms. In the first platinum metallization step, a 0.25 mm ² contact pad and a meander structure with a web width of 20 μm and a web length of 3.81 mm and a layer thickness of 200 nm are applied to the lanthanum zirconate layer in such a way that there is still a sufficiently large area next to it for subsequent contacting of the still area to be exposed remains unused. In addition, the meander is to be designed in such a way that the last 0.4 mm of the meander length is close to the contact pad that has already been deposited. A laser ablation process is used to structure the meander.

In the second deposition step of the insulation layer, 90% of the meander structure is covered with another insulation layer consisting of aluminum oxide deposited by screen printing. In this case, at least the one contact pad that has already been applied is left out of the coating.

In the deposition step of the platinum layer structure, a further meander structure with a length of 3.81 mm and a width of 20 μm is printed predominantly on the second insulation layer, starting at the end of the conductor track that is not covered with aluminum oxide. The first and the second meander structure touch in the area that is not covered by the second insulation layer.

In the third deposition step of an insulation layer, 90% of the second platinum layer structure of the second deposition step is again covered.

At least one area of the substrate that is not covered with platinum has all covering insulating layers removed by means of laser ablation in order to expose the underlying metal substrate. The future electrical contact area to the substrate has a length of 0.5 mm and a width of 20 μm. This corresponds to an area of only 0.01 mm ² .

In the third deposition of the meandering platinum structure, this contacts the second platinum structure with its first end area. The metal substrate exposed by laser ablation is contacted with its second end area.

In the final step, a 0.30 mm ² area of the lanthanum zirconate layer is exposed as a contact pad to the nickel substrate on the back of the substrate using laser ablation. After that, optionally the front side of the substrate including the 0.01 mm ² small contact area to the nickel substrate, but excluding the first deposited platinum contact pad, can be coated with a passivation layer.

The electrical contacting of the entire three-dimensional meander takes place via the platinum contact pad deposited in the first metallization step and the metallic nickel area exposed on the back of the substrate.

Those skilled in the art will recognize that the dimensions specified in connection with exemplary embodiment 4 are exemplary values. The three-dimensional structure presented in exemplary embodiment 4 can also be produced with other materials and/or with other dimensions.

The invention is explained in more detail below using exemplary embodiments with reference to the accompanying drawings.

In these show:

1a - 1d different views and intermediate production products of a first temperature sensor according to the invention;

2a and 2b show a further temperature sensor according to the invention; and

3 shows a further embodiment of a temperature sensor according to the invention.

In the following, the same reference numbers are used for the same components and those with the same effect.

1a shows an intermediate stage of a temperature sensor 10 to be produced in a plan view. An insulating layer 20 is applied to the front side 16 of a substrate 15, which is formed, for example, from a metal foil.

As shown in the side view of FIG. 1b, the insulating layer 20 does not cover the front side 16 of the substrate 15 completely. Rather is an isolation layer free Section 25 formed. The insulating layer-free section 25 is formed on an edge section 18 of the front side 16 of the substrate 15 .

An edge section 18 is to be understood as such a section of the front side 16 of the substrate 15 which is attached to at least one of the illustrated side edges 19 or 19' of the substrate

15 adjacent. The side edges 19 are the long side edges of the substrate 15. The side edges 19', on the other hand, are the short side edges of the rectangular substrate 15.

The insulation layer-free section 25 is produced, for example, by already structuring the insulation layer 20, i. H. in the final shape to be achieved on the front

16 of the substrate 15 is applied. In a further embodiment of the invention, it is possible first to coat the entire front side 16 with an insulation layer 20 and then to produce the insulation-layer-free section by removing a corresponding insulation-layer section.

A sensor structure 30 can also be seen. The sensor structure 30 has a meander section 36 . The sensor structure 30 also includes a first contacting section 31 and a second contacting section 32. The first contacting section 31 is connected to the section 25 of the front side 16 of the substrate 15 which is free of an insulating layer. In contrast, the second contacting section 32 is connected to the first contact pad 41 . The contact pad 41 is in turn arranged on the insulation layer 20 .

The sensor structure 30 is arranged with a first side 34 on the first side 21 of the insulation layer 20 and on the front side 16 of the substrate 15 . The insulation layer 20 is in turn arranged with the second side 22 directly on the substrate 15 or on the front side 16 of the substrate 15 .

As can be seen from FIG. 1c, the second side 35 of the sensor structure 30 or the side 35 of the sensor structure 30 which points away from the substrate 15 can be coated with a passivation layer 60. This relates both to the part of the sensor structure 30 which includes the first contacting section 31 and to the section of the sensor structure 30 which has the second contacting section 32 . The first contact pad 41 is also coated by the passivation layer 60 at least in sections. The passivation layer 60 essentially has a first side 61 and a second side 62 . The first side 61 of the passivation layer 60 is the side facing away from the sensor structure 30 . The second side 62 of the passivation layer is the side of the passivation layer that rests on the section 25 that is free of the insulating layer and on the insulating layer 20, among other things.

The supply lines 51 and 52 of the temperature sensor 10 are shown in FIG. 1d.

Accordingly, the temperature sensor 10 has a first electrical supply line 51 which is connected to the rear side 17 of the substrate 15 . A second electrical supply line 52 is connected to the first contact pad 41 .

The electrical contacting of the temperature sensor 10 is thus made on the one hand via the first contact pad 41 and on the other hand via the rear side 17 of the substrate 15. A contacting of the rear side 17 of the substrate 15 is possible by the sensor structure 30 in the first contacting section 31 in the insulation layer-free section 25 is electrically connected to the front side 16 of the substrate 15.

The sensor structure 30 is preferably a platinum structure. This sensor structure 30 is used for temperature detection. A temperature sensor 10 as shown in FIGS. 1a to 1d has a high degree of accuracy, among other things due to a platinum sensor structure. The small dimensions of the temperature sensor 10 can be realized by the electrical contacts of the temperature sensor 10 on the opposite sides of the temperature sensor, i. H. take place on the back 17 of the substrate 15 and on the side of the contact pad 41.

It is possible for the temperature sensor 10, as shown in FIG. 1d, to be immersed in a glass slip and fired together with the supply lines 51, 52, so that the temperature sensor 10 is completely encapsulated.

The area A of the temperature sensor 10 is preferably smaller than 10 mm ² , particularly preferably smaller than 1 mm ² . The area A of the temperature sensor 10 is formed due to the long side edge 19 and the short side edge 19' of the substrate 15 (see FIG. 1a). A further embodiment of a temperature sensor 10 according to the invention is shown in FIGS. 2a and 2b. Such an embodiment allows a further reduction in the sensor area. The structure essentially corresponds to the structure of FIGS. 1a to 1d.

In contrast to the embodiment according to FIGS. 1a to 1d, the first contact pad 41 is arranged in such a way that this contact pad 41 rests at least partially on the side 61 of the passivation layer 60 facing away from the sensor structure 30 and at the same time with the second contacting section 32, which does not of the passivation layer 60 is electrically connected. Due to such an arrangement, the space of the substrate 15, which is associated with the extension of the first contact pad 41 in FIG. 1a, is additionally saved. With the embodiment shown in FIG. 2a, the area of the temperature sensor is further reduced.

The feed lines 51 and 52 are again shown in FIG. 2b. The first lead 51 is in turn connected to the rear side 17 of the substrate 15 . The second electrical supply line 52 is connected to the first contact pad 41 .

A further embodiment of a temperature sensor 10 is shown in FIG. 3 . The structure essentially corresponds to the structure of a temperature sensor shown in FIG. 1a.

In addition, a second contact pad 42 is formed. The sensor structure 30 or the second contacting section 32 of the sensor structure is indirectly connected to the first contact pad 41 . The second contact pad 42 and the first contact pad 41 are connected to each other. The second contact pad 42 can be used as a center tap for a resistance network, for example to tap off a potential without current. Reference List

10 temperature sensor

15 substrate

16 front side substrate

17 backside substrate

18 edge section

19, 19' side edge

20 insulation layer

21 first side insulation layer

22 second side insulation layer

25 insulation layer free section

30 sensor structure

31 first contacting section

32 second contacting section

34 first page sensor structure

35 second side sensor structure

36 meander section

41 first contact pad

42 second contact pad

51 first electrical lead

52 second electrical lead

60 passivation layer

61 first side passivation layer

62 second side passivation layer

A surface temperature sensor

Claims

27 CLAIMS

A temperature sensor (10) comprising:

- a substrate (15) formed from a metal element, in particular a metal foil, the substrate (15) having a front side (16) and a back side (17),

- an insulation layer (20) which covers the front side (16) of the substrate (15) only in sections, such that an insulation layer-free section (25) is formed on the front side (16) of the substrate (15), and

- A sensor structure (30), in particular a resistive sensor structure, which is formed on the insulating layer (20) and on the insulating layer-free section (25) of the front side (16) of the substrate (15), the sensor structure (30) having at least two electrical contacting sections (31, 32), and a first contacting section (31) is connected to the insulating layer-free section (25) of the front side (16) of the substrate (15) and a second contacting section (32) is a first contact pad (41) or with a first contact pad (41) is connected, wherein the first contact pad (41) is preferably arranged on the insulating layer (20).

2. Temperature sensor (10) according to claim 1, characterized in that the insulating layer-free section (25) is formed on an edge section (18) of the front side (16) of the substrate (15).

3. Temperature sensor (10) according to claim 1 or 2, characterized in that the temperature sensor (10) has a first electrical lead (51) which is connected to the back (17) of the substrate (15) and at least one second electrical lead (52) which is connected to the first contact pad (41).

4. Temperature sensor (10) according to any one of the preceding claims, characterized in that on the side facing away from the substrate (35) of the sensor structure (30) at least a passivation layer (60) is formed in sections.

5. Temperature sensor (10) according to claim 4, characterized in that the first contact pad (41) is arranged in such a way, in particular is bent in such a way, that it is partially on the side (61) of the passivation layer (60) pointing away from the sensor structure (30). rests.

6. Temperature sensor (10) according to one of the preceding claims, characterized in that the metal element, in particular the metal foil, is made of aluminum (Al) and/or steel, in particular ferritic steel, and/or titanium (Ti) and/or niobium (Nb ) and/or tantalum (Ta) and/or nickel (Ni) and/or copper (Cu).

7. Temperature sensor (10) according to one of the preceding claims, characterized in that the insulating layer (20) is aluminum oxide (Al2O3) and/or aluminum titanate (A^TiOs) and/or titanium dioxide (TiC>2) and/or silicon dioxide (SiC> 2) and/or silicon oxide (SiO) and/or magnesium oxide (MgO) and/or magnesium titanate (MgTiCh) and/or a binary zirconia alloy and/or a ternary zirconia alloy and/or boron nitride (BN) and/or aluminum nitride (AlN) and/or silicon nitride (SisN^.

8. Temperature sensor (10) according to any one of the preceding claims, characterized in that the insulating layer (20)

- a metal oxide layer, in particular an anodized metal oxide layer or a metal nitride layer or a metal oxynitride layer, or

- is formed from a layered composite, or

- a vitreous or glass-ceramic layer formed from a slip or a paste containing metal oxides, in particular aluminum oxide particles (AI2O3) and/or magnesium oxide particles (MgO), or - Is formed from a layered composite, wherein at least one layer has a polymer layer.

9. Temperature sensor (10) according to one of the preceding claims, characterized by a second contact pad (42) which is formed in particular on the insulating layer (20), the second contact pad (42) being electronically connected to the first contact pad (41), wherein the second contact pad (42) preferably forms a further tap of a resistance network.

10. Temperature sensor (10) according to one of the preceding claims, characterized in that the area (A) of the temperature sensor (10) is smaller than 10 mm ² , preferably smaller than 3 mm ² , particularly preferably smaller than 2 mm ² , is very particularly preferably smaller than 1 mm ² .

11. A method for manufacturing a temperature sensor (10) according to any one of claims 1 to 10, comprising the steps of: a) providing a substrate (15) which is formed of a metal member and has a front side (16) and a back side (17). , b) forming at least one insulation layer (20) on the front side (16) of the substrate (15) in such a way that a section (25) of the substrate (15) without an insulation layer is formed, c) applying a sensor structure (30), in particular one resistive sensor structure, on the insulation layer (20) and on the insulation-free section (25) of the front side (16) of the substrate (15), d) applying at least one contact pad (41, 42).

12. The method according to claim 11, characterized in that in step b) the insulating layer (20) is applied to the front side (16) of the substrate (15) over the entire surface and is removed at least in sections in a further method step, such that the insulating layer-free section ( 25) of the substrate (15) is formed.

13. The method according to claim 11 or 12, characterized in that in step b) the insulating layer (20) is applied by means of a gas deposition method, a printing method, an immersion method or a spraying method, in particular by means of an ADM method (aerosol deposition method). .

14. The method according to any one of claims 11 to 13, characterized in that steps a) - d) are carried out such that a plurality of temperature sensors (10) are produced together on a substrate strip and / or a substrate carrier and then separated.

15. The method according to any one of claims 11 to 14, characterized in that a first supply line (51) is connected to the rear side (17) of the substrate (15) and a second supply line (52) is connected to the at least one contact pad (41, 42 )is connected.