Device for detecting the temperature of a medium or for heating the medium and manufacturing method

Abstract

The invention comprises a device (V) for detecting the temperature of a medium or for heating the medium, comprising: - A layer system comprising a first green film layer (S1), a second green film layer (S2) and a third layer (S3); - A resistance layer comprising a resistance structure, which resistance structure is applied to the first green film layer (S1) and is covered by the second green film layer (S2), a trim structure with a multitude of conductor tracks (LB, LB'), which trim structure is applied to the second green film layer (S2) and is covered by the third green film layer (S3), and a plurality of first vias (DK11, ..., DK16) which electrically connect the resistor structure and the trim structure by each of the conductor tracks (LB, LB') electrically contacting two of the first vias (DK11, ..., DK16), and a method for manufacturing such a device (V).

Description

[0001] The invention relates to a method for producing a device for detecting the temperature of a medium or for heating the medium. Furthermore, the invention comprises a device for detecting the temperature of a medium or for heating the medium.

[0002] Temperature sensor designs are described in detail in the prior art. These typically comprise an active surface, in particular a metallic resistance layer that serves as a thermistor. The thermistor's electrical resistance changes as a result of a temperature change. Knowing the material and characteristic curve (electrical resistance over temperature ranges) of a thermistor allows the current temperature of the thermistor to be determined by measuring the electrical resistance. For example, such temperature sensors are manufactured using thin-film technology and have a functional layer, such as platinum, as the thermistor.

[0003] By supplying electrical power to the thermistor, it heats up and emits heat. This allows such a temperature sensor to be used as a heating element for heating a medium.

[0004] Temperature sensors are often less stable when used in applications with high temperatures or in chemically aggressive media than when used in less stressful applications. In today's commercially available temperature sensors, the active surfaces are protected with a glass layer or a layer consisting of a compound of glass and metal oxides - with or without additional covers. Examples of this are disclosed in DE 20 2019 002 164 U1, DE 10 2012 110 210 A1, and DE 10 2007 046 900 A1. If the sensor element is used at temperatures greater than 1200°C, for example, the glass or the glass-metal oxide compound becomes soft and the protection of the active surface can no longer be guaranteed. Furthermore, glass or glass components can be chemically reduced in an oxygen-poor environment at high temperatures, which can lead to degeneration of the active element.

[0005] Laser trimming is typically used to precisely adjust the resistance of the temperature sensors described above. An example of such a process is disclosed in DE 11 2015 004 513 T5. It is also known to produce high-temperature sensors from multilayer ceramics (see, for example, temperature sensors manufactured by Fraunhofer IKTS). For this purpose, ceramic green sheets are printed, pressed, and densely sintered. Since the active element in such structures is covered with ceramic, subsequent trimming of the structures is not possible. This leads to temperature sensors manufactured using this process exhibiting a large variation in resistance.

[0006] Based on this problem, the invention is based on the object of presenting a device for detecting the temperature of a medium or for heating the medium, which device is designed to be thermally and chemically resistant and whose electrical resistance can be adjusted with high accuracy.

[0007] The object is achieved by a method according to claim 1 and by a device according to claim 11.

[0008] With regard to the method, it is provided that the method serves to produce a device for detecting the temperature of a medium or for heating the medium, the method comprising: - Providing a first green film layer made of a ceramic material; - applying a first metallic layer to the first green film layer, which first metallic layer is structured such that a resistance structure is formed; - applying a second green film layer made of a ceramic material, which second green film layer has a plurality of first vias, wherein the second green film layer is aligned with respect to the first green film layer such that the second green film layer, after application, covers the first metallic layer and at least a portion of the first green film layer and that the first vias electrically contact the resistor structure, wherein: a) A second metallic layer is initially applied to the second green film layer; or b) In the event that no second metallic layer is initially applied to the second green film layer, the second metallic layer is applied to the second green film layer after the step of applying the second green film layer; wherein the second metallic layer is structured in such a way that a trimming structure with a plurality of conductor tracks is formed, wherein the second metallic layer is applied in such a way and / or the second green film layer is aligned with respect to the first green film layer in such a way that each conductor track electrically contacts two of the first vias, wherein the resistance structure, the first vias and the trimming structure form a resistance element; - Pressing and sintering the first green film layer with the second green film layer applied on top; - trimming the resistance element, whereby one or more of the conductor tracks are severed during the trimming process; - applying a third layer, wherein the third layer is aligned with respect to the second green film layer such that the third layer, after application, covers the second metallic layer and at least a partial area of ​​the second green film layer.

[0009] The invention combines the advantages of both types of temperature sensors described above. The use of ceramic green sheets, which are joined by sintering, achieves good thermal and chemical resistance of the resulting device. A key feature of the invention is that the trimming step can be performed before the final third layer is applied to the layer system as a protective layer. This allows the resistance of the device to be precisely adjusted without reducing the resistance after completion of production.

[0010] A green film is a film consisting of a material with a solid ceramic component and a binder. The initial properties of the material are soft and flexible. This makes the film relatively easy to process, particularly cutting and pressing. Metal layers can also be applied to such a green film, or several green layers can be combined to form a layer system. By sintering the green film at sintering temperature for a predetermined period of time, the material hardens, so that after sintering is complete, a ceramic layer or a solid ceramic layer system is present. A large number of different types of green films are commercially available. A person skilled in the art would select the sintering temperature and the predetermined period of time depending on the specific type or composition of the green film. For example, sintering temperatures in the range of approx.1500 °C is used, with the predetermined period being in the low hour range.

[0011] According to a first variant of the method, the third layer is a green film layer made of a ceramic material. The third layer is pressed after application, and the first green film layer and the second green film layer are sintered with the third green film layer applied thereon. Such a device is thermally and chemically more stable than known temperature sensors because it no longer uses glass as a cover layer, which may have a low glass transition point.

[0012] According to an embodiment of the first variant of the method, it is provided that the third layer has a plurality of second vias, wherein the third layer is aligned with respect to the second green film layer such that the second vias are brought into contact with at least a subset of the first vias.

[0013] According to a second variant of the method, the third layer is made of glass. Depending on the application of the device, it may nevertheless be advantageous to use glass as the top layer. Glass can be particularly advantageous in applications that do not involve an aggressive medium and the device is not exposed to high temperatures. For example, there is no need to operate at additional high temperatures. The largest part of the resistance layer is already protected by the ceramic (first and second green film layers), so the influence of the glass is significantly lower. The starting material for the glass layer can be a glass paste with added ceramic or a crystallizing glass system, which in each case forms a glass-ceramic after the firing step.

[0014] One embodiment of the method provides for the first metallic layer and / or the second metallic layer to be applied using a thin-film process. Typical layer deposition processes known from MEMS and microelectronics manufacturing, such as CVD and PVD processes, can be used as thin-film processes. The resulting layer thicknesses of such metallic layers are in the nanometer to low micrometer range.

[0015] An alternative embodiment of the method provides for the first metallic layer and the second metallic layer to be applied using a thick-film process, in particular screen printing. The resulting layer thicknesses of such metallic layers are in the mid-µm range.

[0016] Materials that can be considered are metals with a defined temperature curve and / or a defined temperature coefficient of resistance (TCR), e.g. platinum, nickel, titanium or a suitable alloy.

[0017] According to one embodiment of the method, a metallic contact pad is applied to each of the second vias before or after the pressing and sintering step. The metallic contact pads are used to connect the device to an external device. The external device supplies the device with electrical energy, which is used, for example, for heating, and / or determines the current electrical resistance of the device to determine the temperature.

[0018] One embodiment of the method provides that the first vias are formed by inserting one hole per first via into the second green film layer and filling the holes introduced into the second green film layer with metallic material. Similarly, the second vias can be formed by inserting one hole per second via into the third green film layer and filling the holes introduced into the third green film layer with metallic material. In particular, it is provided that the material of the first metallic layer and / or the second metallic layer is used as the metallic material here.

[0019] According to one embodiment of the method, the trimming step comprises: - Detecting an electrical resistance value of the resistance structure, - comparing the resistance value with a target value, and - Adjusting the resistance value to the target value by cutting one or more of the conductor tracks in the event of a deviation of the resistance value from the target value by at least a predetermined factor.

[0020] The conductor tracks can be cut using a laser or a similar heat process, or mechanically, e.g. using a blade.

[0021] With regard to the device, it is provided that the device serves to detect the temperature of a medium or to heat the medium, the device comprising: - A layer system of ceramic green film comprising a first green film layer, a second green film layer and a third layer; - A resistance layer comprising a resistance structure, which resistance layer is applied to the first green film layer and is covered by the second green film layer, a trimming structure having a plurality of conductor tracks, which trimming structure is applied to the second green film layer and is covered by the third green film layer, and a plurality of first vias which electrically connect the resistance structure and the trimming structure, in that each of the conductor tracks electrically contacts two of the first vias, wherein the third green film layer has a plurality of second vias, which second vias are brought into contact with a subset of the first vias.

[0022] The device according to the invention exhibits high chemical and thermal resistance. The resistance structure as a whole forms a thermistor when used as a temperature sensor. Measurements demonstrate a further advantage of the device according to the invention: the characteristic curve of a platinum resistance layer, compared to a regular thin-film temperature sensor, follows the standard characteristic curve for platinum over larger temperature ranges.

[0023] One embodiment of the device provides that the device comprises a metallic contact pad for each second via, with one of the contact pads being applied to each of the second vias. The metallic contact pads are used to connect the device to an external device. The external device supplies the device with electrical energy, which is used, for example, for heating, and / or determines the current electrical resistance of the device to determine the temperature.

[0024] According to one embodiment, the trimming structure is provided to be a digital trimming structure. A digital trimming structure is a resistor structure with a plurality of conductor tracks, which conductor tracks are designed in particular in a meandering shape. By severing individual conductor tracks, the total length of the resistor structure is successively reduced or increased - depending on the specific embodiment - thereby changing the resistance. In particular, it is provided that the conductor tracks have different lengths than one another - and therefore each have a different resistance value. In particular, it is provided that a first conductor track has a first resistance, or a first length. With each subsequent conductor track, the length, or the resistance, doubles.This allows the resistance to be adjusted very precisely, so that the trimming process can be carried out very efficiently, while at the same time the number of conductor tracks is reduced compared to a design with conductor tracks of the same length.

[0025] One embodiment of the device provides for the third layer to be a green film layer made of a ceramic material or glass. Using a green film layer as the third layer makes the device more thermally and chemically stable than known temperature sensors, as glass, which may have a low glass transition point, is no longer used as the cover layer. Depending on the device's application, it may still be advantageous to use glass as the top layer. Glass can be particularly advantageous in applications that do not involve an aggressive medium and the device is not exposed to high temperatures.

[0026] The invention is explained in more detail with reference to the following figures. Fig. 1: a first method step of an embodiment of the manufacturing method according to the invention; Fig. 2: a second process step; Fig. 3: a third procedural step; and Fig. 4 a final fourth method step of an embodiment of the manufacturing method according to the invention.

[0027] In Fig. Figure 1 shows a first method step for producing a device V according to the invention, which device can be used as a temperature sensor or as a heating element. A first ceramic green film layer S1 is provided. Fig. Figure 1 (a) shows a top view of the first green film layer S1. The first green film layer is cut from a commercially available green film consisting of a material with a solid ceramic component and a binder. The specific configuration of the material components depends on the type of green film, which the person skilled in the art selects depending on the desired properties. A first metallic layer MS1 is applied to the first green film layer S1 using a screen printing process. This first metallic layer MS1 is structured in such a way that a resistor structure, in particular a meandering one, is formed. In particular, platinum is used as the material of the first metallic layer MS1.

[0028] Likewise, a second green film layer MS2 is provided, the material of which corresponds to the material of the first green film layer S1. Fig. 1 (b) shows a top view of the second green film layer S2. Fig. Figure 1 (c) shows a cross-section through the first green film layer S1 and the second green film layer S2. This second green film layer S2 essentially corresponds in dimensions to the first green film layer S1, but can also be smaller. However, the dimensions of the second green film layer S2 are selected to be large enough that the first metallic layer MS1 can be completely covered by the second green film layer S2.

[0029] The second green film layer S2 has a plurality of first vias DK11, ..., DK16. These first vias DK11, ..., DK16 are formed by holes punched into the second green film layer S2 and by filling them with metallic material, in particular a metallic paste. Furthermore, a second metallic layer MS2 is applied to the second green film layer S2. The second metallic layer MS2 is applied to the second green film layer MS2 in a manner analogous to the application method of the first metallic layer MS1. The second metallic layer MS2 is structured such that a plurality of conductor tracks LB, LB' are formed as trimming structures, each of which connects two of the first vias DK11, ..., DK16. In the present case, the conductor track LB connects the first vias DK12 and DK13, with the conductor track LB' connecting the first vias DK14 and DK14.It can be provided that the first metallic layer MS1, the second metallic layer MS2, and the first vias DK11, ..., DK16 consist of the same material.

[0030] The second green foil layer S2 is then connected to the first green foil layer S1. For this purpose, the second green foil layer S2 is placed on the first green foil layer S1 and arranged such that the first vias DK11, ..., DK16 touch the structures of the first metal layer MS1. In this case, the trimming structures shorten the effective length of the resistor structure.

[0031] After the second green film layer S2 is applied to the first green film layer S1, the layered composite is pressed together in a next process step and heated to a sintering temperature for a predetermined period of time. It can also be provided that the second metallic layer MS2 is applied to the second green film layer S2 only after the second green film layer S2 has been applied to the first green film layer S2.

[0032] Fig. 2 shows the sintered layer composite, which now consists of a hard ceramic. Fig. Figure 2 (a) shows a top view of the laminate. Fig. Figure 2 (b) shows a cross-section through the layered composite. In the next process step, the resistor structure is subjected to a trimming process to set a desired resistance value. For this purpose, the resistance value of the resistor track is first measured and compared with a reference value. Subsequently, one of the conductor tracks is severed, e.g., using a laser. This enlarges the resistor structure, so that the resistance value of the resistor structure is increased. If the resistance value still deviates from the desired value, the process is repeated with additional conductor tracks. It should be noted that in the figures Fig. 1 to Fig. 4 For reasons of clarity, only two conductor tracks LB, LB' are shown. A real device has a plurality of additional conductor tracks LB, LB', or more windings in the first metallic layer MS1.

[0033] After the successful trimming process, a third layer S3 is applied to the layer composite. In the illustrated embodiment, the third layer S3 is another green film layer, the material of which corresponds to the material of the first green film layer S1 and the second green film layer. This third layer S3 essentially corresponds in size to the dimensions of the second green film layer S2, but can also be selected to be smaller. However, the dimensions of the third layer S3 are selected to be large enough that the second metallic layer MS2 can be completely covered by the third layer S3. Fig. 3 (a) shows a top view of the sintered layer composite consisting of first green film layer S1 and second green film layer S2. Fig. 3 (b) shows a top view of the third layer S3. Fig. Figure 3 (c) shows a cross-section through the sintered layer composite and through the third layer S3.

[0034] The third layer S3 has two second vias DK21, DK22. These second vias DK21, DK22 are formed by holes punched into the third layer S3 and filled with metallic material, in particular a metallic paste. Furthermore, two contact pads KP1, KP2 are applied as a metallic layer over the vias DK21, DK22. These can be made of the same material as the first metallic layer MS1 or the second metallic layer and can be applied using the same process.

[0035] The third layer S3 is then connected to the layered composite. For this purpose, the third layer is placed on top of the second layer and positioned such that the second via DK21 contacts the first via DK11, and the second via DK21 contacts the first via DK16. The contact pads therefore offer the possibility of electrically contacting the resistor structure at both end areas and, for example, measuring its resistance value using an external unit.

[0036] After the third layer S3 has been placed on the second green film layer S2, the layer composite is pressed together in a next process step and heated to a sintering temperature for a predetermined period of time. Fig. 4 shows the resulting sintered layer composite, which now consists of a hard ceramic and which represents the final device V. Fig. Figure 4 (a) shows a top view of the laminate. Fig. Figure 4 (b) shows a cross section through the composite layer.

[0037] Alternatively, a glass layer can be provided as the third layer S3 instead of another green sintered film. This can be applied, for example, as a glass paste using a screen printing process and then baked. In this case, second vias are not necessarily required. List of reference symbols DK11, ..., DK16 first vias DK21, DK22 second vias KP1, KP2 contact pads LB, LB' Conductor tracks of the trimming structure MS1 first metallic layer MS2 second metallic layer S1 first green film layer S2 second green film layer S3 third layer V device QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 20 2019 002 164 U1

[0004] DE 10 2012 110 210 A1

[0004] DE 10 2007 046 900 A1

[0004] DE 11 2015 004 513 T5

[0005]

Claims

[1] Method for producing a device (V) for detecting the temperature of a medium or for heating the medium, comprising: - Providing a first green film layer (S1) made of a ceramic material; - applying a first metallic layer (MS1) to the first green film layer (S1), which first metallic layer (MS1) is structured such that a resistance structure is formed; - applying a second green film layer (S2) made of a ceramic material, which second green film layer (S2) has a plurality of first vias (DK11, ..., DK16), wherein the second green film layer (S2) is aligned with respect to the first green film layer (S1) such that the second green film layer (S2) covers the first metallic layer (MS1) and at least a partial area of ​​the first green film layer (S1) after application and that the first vias (DK11, ..., DK16) electrically contact the resistance structure, where a) A second metallic layer (MS2) is initially applied to the second green film layer (S2); or b) In case that initially no second metallic layer (MS2) is applied to the second green film layer (S2), the second metallic layer (MS2) is applied to the second green film layer (S2) after the step of applying the second green film layer (S2); wherein the second metallic layer (MS2) is structured in such a way that a trimming structure with a plurality of conductor tracks (LB, LB') is formed, wherein the second metallic layer (MS2) is applied in such a way and / or the second green film layer (S2) is aligned with respect to the first green film layer (S1) in such a way that each of the conductor tracks (LB, LB') electrically contacts two of the first vias (DK11, ..., DK16), wherein the resistance structure, the first vias (DK11, ..., DK16) and the trimming structure form a resistance element; - pressing and sintering the first green film layer (S1) with the second green film layer applied thereon; - trimming the resistance element, wherein one or more of the conductor tracks (LB, LB') are severed during the trimming; - applying a third layer (S3), wherein the third layer (S3) is aligned with respect to the second green film layer (S2) such that the third layer (S3) covers the second metallic layer (MS2) and at least a partial area of ​​the second green film layer (S2) after application. [2] Method according to claim 1, wherein the third layer (S3) is a green film layer made of a ceramic material, wherein the third layer (S3) is pressed after application and the first green film layer (S1) and the second green film layer (S1) are sintered with the third layer (S3) applied thereon. [3] Method according to claim 2, wherein the third layer (S3) has a plurality of second vias (DK21, DK22), wherein the third layer (S3) is aligned with respect to the second green film layer (S2) such that the second vias are brought into contact with at least a subset of the first vias (DK11, ..., DK16). [4] The method according to claim 1, wherein the third layer (S3) consists of a glass. [5] Method according to one of the preceding claims, wherein the first metallic layer (MS1) and / or the second metallic layer (MS2) are applied by means of a thin-film process. [6] Method according to one of the preceding claims, wherein the first metallic layer (MS1) and the second metallic layer (MS2) are applied by means of a thick-film process, in particular by means of screen printing. [7] Method according to one of the preceding claims, wherein a metallic contact pad (KP1, KP2) is applied to each of the second vias (DK21, DK22) before or after the pressing and sintering step. [8] Method according to one of the preceding claims, wherein the first vias (DK11, ..., DK16) are formed by introducing one hole per first via (DK11, ..., DK16) into the second green film layer (S2) and filling the holes introduced into the second green film layer (S2) with metallic material. [9] Method according to one of the preceding claims, wherein the second vias (DK21, DK22) are formed by introducing one hole per second via (DK21, DK22) into the third layer (S3) and filling the holes introduced into the third layer (S3) with metallic material. [10] A method according to any one of the preceding claims, wherein the trimming step comprises: - Detecting an electrical resistance value of the resistance structure, - comparing the resistance value with a target value, and - adjusting the resistance value to the target value by severing one or more of the conductor tracks (LB, LB') in the event of a deviation of the resistance value from the target value by at least a predetermined factor. [11] Device (V) for detecting the temperature of a medium or for heating the medium, comprising: - A layer system comprising a first green film layer (S1), a second green film layer (S2) and a third layer (S3); - A resistance layer comprising a resistance structure, which resistance structure is applied to the first green film layer (S1) and is covered by the second green film layer (S2), a trimming structure with a plurality of conductor tracks (LB, LB'), which trimming structure is applied to the second green film layer (S2) and is covered by the third green film layer (S3), and a plurality of first vias (DK11, ..., DK16) which electrically connect the resistance structure and the trimming structure, in that each of the conductor tracks (LB, LB') electrically contacts two of the first vias (DK11, ..., DK16), wherein the third green film layer (S3) has in particular a plurality of second vias (DK21, DK22), which second vias (DK21, DK22) are brought into contact with a subset of the first vias (DK11, ..., DK16). [12] Device according to claim 11, comprising one metallic contact pad (KP1, KP2) per second via (DK21, DK22), wherein one of the contact pads (KP1, KP2) is applied to one of the second vias (DK21, DK22). [13] The apparatus of claim 11 or 12, wherein the trimming structure is a digital trimming structure. [14] Device according to one of claims 11 to 13, wherein the third layer (S3) is a green film layer made of a ceramic material or consists of a glass.

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