EP0435999B1 - Temperature sensor and process for producing the same - Google Patents
Temperature sensor and process for producing the same Download PDFInfo
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- EP0435999B1 EP0435999B1 EP90911276A EP90911276A EP0435999B1 EP 0435999 B1 EP0435999 B1 EP 0435999B1 EP 90911276 A EP90911276 A EP 90911276A EP 90911276 A EP90911276 A EP 90911276A EP 0435999 B1 EP0435999 B1 EP 0435999B1
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- temperature
- oxide
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/04—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having negative temperature coefficient
- H01C7/041—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having negative temperature coefficient formed as one or more layers or coatings
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/30—Apparatus or processes specially adapted for manufacturing resistors adapted for baking
Definitions
- the invention relates to a temperature sensor according to the preamble of the main claim.
- Temperate sensors with platinum made of a temperature-sensitive element are known, which are manufactured using thin-film technology, in which platinum is thus diffused onto a carrier substrate in a few atomic layers. If a corresponding geometric structure, such as a meandering shape, is maintained, a sufficiently high basic resistance can be achieved with sufficiently thin layers by means of a few atomic layers, which for such a temperature sensor must be in the range of 100 ohms.
- These thin-film sensors can only be used at lower temperatures in the range up to 400 degrees C, in any case below 600 degrees C, since platinum evaporates at higher temperatures and, due to the thickness of the layer of only a few atomic layers, this alone makes it non-negligible The resistance is changed so that reproducible measurements are no longer possible.
- Platinum wires have also been used as temperature sensors. In order to achieve the sufficiently large basic resistance, the wire had to have a considerable length, which, even in the case of winding in coil form, only led to a sensor with considerable external dimensions, which cannot be used in many areas where miniaturization is important.
- Platinum-containing thick-film pastes are also known which contain organic binders and solvents as further constituents. These are used as thick film heating elements, where they reach their sufficient resistance due to the length of the heating element and are used for heating the usual pressure point temperatures. Apart from the low specific resistance, which would also only lead to very large sensor elements, these could not be used for temperatures higher than 600 degrees C, since reproducibility would no longer be ensured here. In both cases, moreover, platinum becomes red-hot from approx. 800 degrees C and can then still be used as a radiator, but no longer as a temperature sensor.
- a temperature sensor is known (GB-A 2 120 453) which consists of a ceramic substrate on which a temperature-sensitive film layer of an electrical resistance element is applied.
- a commercially available organometallic paste is used which does not contain any ceramic or purely metallic components. This can consist of platinum or a platinum-containing ceramic material. No further information on the composition is disclosed.
- thermometer according to the preamble of the main claim (GB-A 2 006 521), the temperature-sensitive element of which consists of platinum-containing ceramic bodies.
- the platinum content is over 90% and the sintering takes place over a period of two hours at a temperature of 1200 ° C.
- a high-temperature stable thermometer cannot be obtained.
- the invention is therefore based on the object of providing a sensitive, time-stable, high-temperature sensor in a miniaturized design which can be used in a variety of ways.
- the stated object is achieved according to the invention in a generic temperature sensor according to the preamble of the main claim by its characterizing features.
- a method is proposed according to the invention, which is characterized in that platinum powder, oxides and binders are mixed with one another and, after the layer has been applied to the carrier substrate, are heat-treated with the latter.
- the temperature-sensitive layer of the temperature sensor according to the invention has metallic platinum between 60 and 90% by weight and is preferably characterized in that it contains metallic platinum in a proportion of approximately 70 to 85% by weight.
- a mixture of silicon, aluminum and alkaline earth oxide, in particular calcium oxide, is used as the oxide component, the aluminum oxide component resulting from the fact that the carrier substrate is generally aluminum oxide.
- the carrier substrate consists of a different oxide
- the aluminum oxide could also be replaced by the material of the corresponding carrier substrate. Due to the tempering, silicon oxide produces quartz or the glass-like character and forms an inert material that is particularly suitable for the desired high-temperature applications.
- Calcium oxide is the preferred alkaline earth oxide; strontium and barium oxides can also be used instead, but calcium oxide has proven to be more stable.
- the oxide mixture forms a eutectic, the melting point of which can be adjusted and in particular reduced by the addition of the alkaline earth oxide, while a mixture of aluminum oxide and silicon oxide gives a relatively high melting point which is above the evaporation point of platinum, so that no heating up to this point could take place .
- the melting point of the eutectic mixture is reduced below the evaporation point of platinum, so that annealing can take place up to the desired melting point of the oxide mixture, at which the desired quartz-like or glass-like compact consistency of the material is achieved.
- the temperature sensitive Layer of the temperature sensor preferably has a composition such that silicon oxide is present in the oxide mixture in a range from 40 to 55% by weight, aluminum oxide to 25 to 40% by weight and the remainder is alkaline earth oxide, while silicon oxide with 45 to 50% by weight is extremely preferred.
- silicon oxide with 30 to 35% by weight, rest of alkaline earth oxide is given, in particular the oxide mixture containing 18 to 20% by weight of alkaline earth oxide and the rest of silicon oxide and aluminum oxide.
- the invention accordingly provides that the temperature-sensitive layer is baked on the carrier substrate, the temperature-sensitive layer in particular having a compact, glass-like morphology.
- platinum paste with 65 to 70% by weight, oil and thinner each with 5 to 10% by weight and the rest of oxide are mixed with one another, the platinum content of the paste itself preferably being 75% by weight.
- a preferred specific overall composition of the thick-film printing compound used according to the invention can also be found in the description of the figures.
- the maximum temperature of the tempering should remain below the evaporation temperature of platinum and is preferably below 1400 degrees, a preferred embodiment provides a maximum temperature of 1300 to 1350 degrees.
- a holding time for the complete combustion of organic binder portions of the layer is maintained in the range from 300 to 400 degrees C.
- the holding time serves to generate the desired compact, glass-like consistency of the temperature-sensitive layer of the temperature sensor to be created.
- the maximum holding time is not critical per se, but must not be unduly excessive, since in addition to the desired morphological changes leading to the compact, glass-like consistency, changes in the platinum base structure due to sintering effects, which lead to undesired larger structures or plaster formation, and possibly also to oxidation and lead to a breakdown of the platinum surfaces.
- a holding time of 20 to 40 minutes is therefore preferred, a time of 25 minutes having proven to be an optimal value.
- a platinum paste containing in particular organic binders - which are generally cellulose derivatives - is used, it is advantageous in the region of the temperature rise at 300 to 400 degrees C, especially at 350 degrees C, also to provide a holding time during which the temperature is held at a fixed value over a predetermined time. While the maximum duration of the holding time is ultimately only limited by economic requirements, the holding time should not be too short, in particular not less than five minutes, in order to achieve a perfect result. About ten minutes turned out to be the ideal value. If such a holding time is used, the tempered layer has a typical light quartz / ceramic color, while if the holding time is too short in the area mentioned, the color darkens until it becomes black. This is because the orange binder burns only slowly and does not completely burn to CO2 if the holding time is not sufficient in the temperature range mentioned, but rather carbon portions remain, which can also have a negative effect on the temperature-sensitive properties of the layer.
- the invention creates a miniaturized temperature sensor, which can preferably be used at temperatures of over 600 degrees C to 1200 degrees C.
- the temperature sensor according to the invention is inexpensive to manufacture and can in particular also be applied simultaneously and together with other functional elements, such as oxygen sensors, which are produced using the same technology, and heat conductors can be applied to a common substrate.
- a preferred embodiment provides that an oxygen sensor and a heating conductor regulated by the temperature-sensitive layer are applied to the carrier substrate, and in a further development that the heating conductor is applied to the surface of the carrier substrate which carries the oxygen sensor and the temperature-sensitive layer.
- the manufacture of the sensor according to the invention is cheaper than thin-film technology, apart from the fact that no sensors of this type that can withstand high temperatures can be produced as a result. No vacuum and no complex equipment are necessary. Furthermore, the effect of the temperature measurement result is also not to complicated specifications, such as environmental sensors, which are required for measurements using thermal voltage or additional electronics. Rather, the sensor output can be used directly to control, for example, a heating conductor.
- the above combination is used in particular for raw oxygen measurement, for example in gas power plants or in process control technology in the chemical industry, if the residual oxygen content is to be measured there with regard to inerting.
- the lambda value measurement takes place on the basis of a solid-state effect with reduction or oxidation depending on the oxygen content of the ambient gas, this solid-state effect only occurring at higher temperatures, in particular temperatures above 600 degrees C., so that the temperature sensor must be heated to this temperature and to the desired one Specification temperature must be kept with high accuracy, for which the temperature sensor according to the invention can be used in an ideal manner.
- Other areas of application concern high-temperature furnaces, sintering furnaces etc.
- Oxygen sensors for lambda measurement such as gas power plants, process technology, etc., show their highest sensitivity, which is based on an oxidation-reduction-solid-state effect corresponding to the available oxygen, at higher temperatures. They must therefore be heated to higher temperatures and, since the effect changes depending on the temperature, stabilized at a predetermined temperature.
- the oxygen or gas sensor 2 which is known per se, can be applied to a substrate or carrier 1, such as made of aluminum oxide.
- a temperature sensor 7 is applied near the oxygen sensor 2 on the surface 3 of the carrier 1 in the manner described below.
- the temperature sensor 7 is guided in a meandering shape and has, for example, an overall length of 10 mm, a width of 3 mm, a total "wire length" of 60 to 70 mm and a layer thickness of 10 to 15 micrometers and a width of 250 micrometers in the composition specified below on.
- the temperature sensor 7 consists of a ceramic - which is preferably largely "glazed" due to the tempering process - of oxide and pure metal platinum dispersed in this with a proportion of 80% by weight.
- the oxide composition is 50% by weight of silicon oxide, 30% by weight of aluminum oxide and 20% by weight of calcium oxide.
- the basic resistance of the temperature sensor 7 described in this way is approximately 100 ohms.
- the temperature sensor 7 is produced on the carrier substrate 1 in the following way:
- platinum powder and oxide are mixed with the desired final proportions of 80% by weight and 20% by weight.
- a paste is then produced from 65% by weight of platinum and oxide powder and 35% by weight of vehicle.
- the vehicle consists of 70% by weight of an organic binder, such as methyl cellulose, and 30% by weight of an organic solvent, such as dibutyl carbitol acetate.
- the paste obtained in this way is then printed on the carrier substrate 1 made of aluminum oxide in the desired geometric shape, such as the meandering shape shown, using screen printing and thus thick film technology.
- An annealing is then carried out, with the support 1 and the printed-on temperature sensor substrate being heated to about 350 degrees C. in a tempering furnace, starting from ambient temperature (20 degrees) with a differential temperature increase of about 13 degrees C. per minute. Solvents, thinners and oil evaporate above their evaporation temperature. From about 100 degrees C, the previously viscous printing mass is an almost solid mass, since the liquid components are largely burned. Furthermore, the organic binder, which is a cellulose derivative, begins to burn. Since the organic binder burns slowly, the temperature is kept constant at about 350 degrees for about 10 minutes to allow complete combustion (conversion to CO2) of the organic binder.
- the oxide ceramic obtained was black or dark due to an incompletely burned binder, with no or insufficient holding time, while if a sufficient holding time was observed in the temperature range mentioned, the ceramic ultimately obtained had the typical light color due to the complete combustion of the binder. Binder that is not completely burned could also impair the properties of the temperature sensor.
- the holding time shown in FIG. 2 at a temperature of 350 ° C., there is a further temperature increase with the same temperature coefficient up to the desired final or maximum stoving temperature of approx. 1330 ° C. It has been shown that the temperature rise is a critical variable is. With a steeper temperature rise, cracks occur in the sensor layer. A flat rise in temperature is quite possible, but this means longer production times and thus higher production costs and higher costs. In this respect, the specified temperature control provides an optimization while ensuring a flawless result represents.
- the specified baking temperature of 1330 degrees C is maintained for a certain time, which was 25 minutes in the illustrated embodiment. This is necessary in order to cause the layer to flow into one another and thus to change the morphology (while maintaining the structure) and overall to achieve a glass-like, more compact layer which ensures uniform conductivity. It should be noted that the baking temperature should not be maintained too long, since internal structural changes then take place, in particular platinum bridges are apparently broken and the continuous electrical contact is damaged, be it due to typical sintering effects in the form of larger structures or plaster formation , be it due to oxidation of plate particles.
- the mentioned holding time at the stoving temperature can hardly be shortened, a certain lengthening is not critical since the above-mentioned disadvantageous effects only occur when the stoving temperature is excessively long.
- an optimization is carried out in such a way that the holding time of the baking temperature was chosen to be as short as possible, it being ensured that the desired compact, glass-like structure is achieved.
- the temperature is then reduced using the same temperature coefficient on the heating element, ie the same temperature control. Due to the furnace's own cooling behavior, the temperature in the furnace cools more slowly, as shown. It is essential to cool the temperature with the temperature coefficient mentioned to approximately 1100 ° C., which should not be chosen more, since otherwise the structure obtained could also be damaged by bus.
- thermosensor with a sufficiently high basic resistance in the specified range, which is resistant to high temperatures and in particular with Temperatures of over 600 to well over 1000 degrees C can be used for temperature measurement and thus for temperature control of the heater 6 in the exemplary embodiment shown in FIG. 1.
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Abstract
Description
Die Erfindung betrifft einen Temperatursensor gemäß dem Oberbegriff des Hauptanspruchs.The invention relates to a temperature sensor according to the preamble of the main claim.
Es sind Temperatusensoren mit Platin aus temperaturempfindlichem Element bekannt, die in Dünnfilm-Technik hergestellt sind, bei denen also auf einem Trägersubstrat Platin in wenigen Atomlagen aufdiffundiert wird. Bei Einhaltung einer entsprechenden geometrischen Struktur, wie Mäanderform, kann bei hinreichend dünnen Schichten durch wenige Atomlagen ein ausreichend hoher Grundwiderstand erreicht werden, der für einen derartigen Temperatursensor im Bereich von 100 Ohm liegen muß. Diese Dünnfilm-Sensoren können nur bei niedrigeren Temperaturen im Bereich bis zu 400 Grad C, auf jeden Fall unterhalb von 600 Grad C eingesetzt werden, da bei höheren Temperaturen Platin verdampft und aufgrund der Dicke der Schicht von nur wenigen Atomlagen alleine hierdurch eine nicht vernachlässigbare Änderung des Widerstandes erfolgt, so daß keine reproduzierbaren Messungen mehr möglich sind.Temperate sensors with platinum made of a temperature-sensitive element are known, which are manufactured using thin-film technology, in which platinum is thus diffused onto a carrier substrate in a few atomic layers. If a corresponding geometric structure, such as a meandering shape, is maintained, a sufficiently high basic resistance can be achieved with sufficiently thin layers by means of a few atomic layers, which for such a temperature sensor must be in the range of 100 ohms. These thin-film sensors can only be used at lower temperatures in the range up to 400 degrees C, in any case below 600 degrees C, since platinum evaporates at higher temperatures and, due to the thickness of the layer of only a few atomic layers, this alone makes it non-negligible The resistance is changed so that reproducible measurements are no longer possible.
Es wurden weiterhin schon Platindrähte als Temperatursensoren eingesetzt. Zur Erreichung des hinreichend großen Grundwiderstandes mußte der Draht eine erhebliche Länge aufweisen, die auch bei Wicklung in Spulenform nur zu einem Sensor mit erheblichen Außenabmessungen führte, der in vielen Bereichen, dort, wo es auf die Miniaturisierung ankommt, nicht eingesetzt werden kann. Ferner sind Platin enthaltende Dickschichtpasten bekannt, die als weitere Bestandteile organische Binder und Lösungsmittel aufweisen. Diese werden als Dickfilm-Heizelemente eingesetzt, wobei sie ihren hinreichenden Widerstand aufgrund der Länge des Heizelements erreichen und für Beheizungen üblicher Druckstellentemperaturen eingesetzt werden. Abgesehen von dem niedrigen spezifischen Widerstand, der ebenfalls lediglich zu sehr großen Fühlerelementen führen würde, könnten diese nicht für höhere Temperaturen als 600 Grad C eingesetzt werden, da hier die Reproduzierbarkeit nicht mehr gegeben wäre. In beiden Fällen gilt im übrigen, daß Platin ab ca. 800 Grad C rotglühend wird und dann zwar noch als Heizkörper eingesetzt werden kann, aber nicht mehr als Temperatursensor.Platinum wires have also been used as temperature sensors. In order to achieve the sufficiently large basic resistance, the wire had to have a considerable length, which, even in the case of winding in coil form, only led to a sensor with considerable external dimensions, which cannot be used in many areas where miniaturization is important. Platinum-containing thick-film pastes are also known which contain organic binders and solvents as further constituents. These are used as thick film heating elements, where they reach their sufficient resistance due to the length of the heating element and are used for heating the usual pressure point temperatures. Apart from the low specific resistance, which would also only lead to very large sensor elements, these could not be used for temperatures higher than 600 degrees C, since reproducibility would no longer be ensured here. In both cases, moreover, platinum becomes red-hot from approx. 800 degrees C and can then still be used as a radiator, but no longer as a temperature sensor.
Es hat Sich herausgestellt, daß für Hochtemperaturanwendungen keine miniaturisierten Temperatursensoren bekannt sind. Es werden Thermoelemente, die mit Thermospannungen arbeiten, eingesetzt. Nachteil ist, daß hier eine definierte Umgebungstemperatur als Referenztemperatur oder ein Mikroprozessor eingesetzt werden muß. Derartige Temperaturfühler sind teuer.It has been found that no miniaturized temperature sensors are known for high temperature applications. Thermocouples that work with thermal voltages are used. The disadvantage is that a defined ambient temperature must be used as the reference temperature or a microprocessor. Such temperature sensors are expensive.
Es ist ein Temperatursensor bekannt (GB-A 2 120 453), der aus einem keramischen Substrat besteht, auf dem eine temperaturempfindliche Filmschicht eines elektrischen Widerstandselements aufgebracht ist. Dabei wird eine kommerziell erhältliche organo-metallische Paste verwendet, die aber keine keramischen oder rein metallischen Bestandteile enthält. Dieses kann aus Platin oder einem platinhaltigen Keramikmaterial bestehen. Weitere Angaben über die Zusammensetzung sind nicht offenbart.A temperature sensor is known (GB-A 2 120 453) which consists of a ceramic substrate on which a temperature-sensitive film layer of an electrical resistance element is applied. A commercially available organometallic paste is used which does not contain any ceramic or purely metallic components. This can consist of platinum or a platinum-containing ceramic material. No further information on the composition is disclosed.
Es ist ferner ein gattungsgemäßes Widerstandsthermometer nach dem Oberbegriff des Hauptanspruchs bekannt (GB-A 2 006 521), dessen temperaturempfindliches Element aus platinhaltigen Keramikkörpern besteht. Der Gehalt an Platin liegt über 90 %, und die Sinterung erfolgt über einen Zeitraum von zwei Stunden bei einer Temperatur von 1200°C. Hierdurch kann aber ein hochtemperaturstabiles Thermometer nicht erhalten werden.There is also known a generic resistance thermometer according to the preamble of the main claim (GB-A 2 006 521), the temperature-sensitive element of which consists of platinum-containing ceramic bodies. The platinum content is over 90% and the sintering takes place over a period of two hours at a temperature of 1200 ° C. As a result, however, a high-temperature stable thermometer cannot be obtained.
Der Erfindung liegt daher die Aufgabe zugrunde, einen empfindlichen, zeitstabilen Hochtemperatursensor in miniaturisierter Ausführung zu schaffen, der in vielfältiger Weise einsetzbar ist.The invention is therefore based on the object of providing a sensitive, time-stable, high-temperature sensor in a miniaturized design which can be used in a variety of ways.
Erfindungsgemäß wird die genannte Aufgabe bei einem gattungsgemäßen Temperatursensor nach dem Oberbegriff des Hauptanspruchs erfindungsgemäß durch dessen kennzeichnende Merkmale gelöst. Zur Herstellung eines derartigen Temperatursensors wird erfindungsgemäß ein Verfahren vorgeschlagen, das dadurch gekennzeichnet ist, daß Platin-Pulver, Oxide und Bindemittel miteinander vermischt und nach dem Auftragen der Schicht auf dem Trägersubstrat mit diesen getempert werden.According to the invention, the stated object is achieved according to the invention in a generic temperature sensor according to the preamble of the main claim by its characterizing features. To produce such a temperature sensor, a method is proposed according to the invention, which is characterized in that platinum powder, oxides and binders are mixed with one another and, after the layer has been applied to the carrier substrate, are heat-treated with the latter.
Die temperaturempfindliche Schicht des erfindungsgemäßen Temperatursensors weist metallisches Platin zwischen 60 und 90 Gew.-% auf und ist vorzugsweise dadurch gekennzeichnet, daß sie metallisches Platin mit einem Anteil etwa von 70 bis 85 Gew.-% enthält. Als Oxidanteil wird ein Gemisch aus Silizium-, Aluminium- und Erdalkalioxid, insbesondere Kalziumoxid, eingesetzt, wobei der Aluminiumoxidanteil sich dadurch ergibt, daß in der Regel das Trägersubstrat Aluminiumoxid ist. In dem Falle, daß das Trägersubstrat aus einem anderen Oxid besteht, könnte auch das Aluminiumoxid durch das Material des entsprechenden Trägersubstrats ersetzt werden. Siliziumoxid ergibt aufgrund der Temperung Quarz, bzw. den glasartigen Charakter und bildet ein inertes Material, das für die gewünschten Hochtemperaturanwendungen besonders geeignet ist. Als Erdalkalioxid kommt vorzugsweise Kalziumoxid in Frage, stattdessen können auch Strontium und Bariumoxide eingesetzt werden, Kalziumoxid hat sich aber als stabiler erwiesen. Die Oxidmischung bildet ein Eutektikum, deren Schmelzpunkt durch die Zugabe des Erdalkalioxids eingestellt und insbesondere reduziert werden kann, während eine Mischung aus Aluminiumoxid und Siliziumoxid einen relativ hohen Schmelzpunkt ergibt der über dem Verdampfungspunkt von Platin liegt, so daß keine Erhitzung bis zu diesem Punkt erfolgen könnte. Durch die Zugabe von Kalziumoxid wird der Schmelzpunkt der eutektischen Mischung unter den Verdampfungspunkt von Platin reduziert, so daß eine Temperung bis zum gewünschten Schmelzpunkt der Oxidmischung, an dem die gewünschte quarzartige bzw. glasartige kompakte Konsistenz des Materials erreicht wird, erfolgen kann. Demgemäß hat die temperaturempfindliche Schicht des Temperatursensors vorzugsweise eine Zusammensetzung derart, daß im Oxidgemisch Siliziumoxid in einem Bereich von 40 bis 55 Gew.-%, Aluminiumoxid zu 25 bis 40 Gew.-% und als Rest Erdalkalioxid vorliegt, während äußerst vorzugsweise Siliziumoxid mit 45 bis 50 Gew.-%, Aluminiumoxid mit 30 bis 35 Gew.-%, Rest Erdalkalioxid gegeben ist, wobei insbesondere das Oxidgemisch 18 bis 20 Gew.-% Erdalkalioxid sowie Rest Siliziumoxid und Aluminiumoxid enthält. Um eine möglichst weitgehende Reduzierung des Schmelzpunktes der eutektischen Oxidmischung zu erreichen, sieht die Erfindung demgemäß vor, daß die temperaturempfindliche Schicht auf dem Trägersubstrat aufgebrannt ist, wobei insbesondere die temperaturempfindliche Schicht eine kompakte, glasartige Morphologie aufweist. Ein ideales Oxidgemisch ist in der nachfolgenden Figurenbeschreibung erläutert. Durch das Verhältnis von Platin und Oxidanteil in der temperaturempfindlichen Schicht wird deren spezifischer elektrischer Widerstand festgelegt. Es ist dabei darauf zu achten, daß der Platinanteil nicht so weit reduziert wird, daß die erforderlichen Leitfähigkeitsbrücken vollständig unterbrochen werden oder leicht beim Einsatz unterbrechbar sind. Insofern hat sich als vorteilhaft herausgestellt, daß Platin einen Anteil an der temperaturempfindlichen Schicht von 80 Gew.-%, bezogen auf die Gesamtmischung selbst zwischen 60 und 80 Gew.-%, aufweisen sollte. Demgemäß wird verfahrensmäßig das Oxidgemisch mit einem Anteil von 14 bis 20 Gew.-% am Gesamtgemisch aus Platinpaste, Öl und Verdünner eingesetzt. In bevorzugter Ausgestaltung ist vorgesehen, daß Platinpaste mit 65 bis 70 Gew.-%, Öl und Verdünner mit jeweils 5 bis 10 Gew.-% und Rest Oxid miteinander vermischt werden, wobei der Platinanteil der Paste selbst vorzugsweise 75 Gew.-% beträgt. Auch eine bevorzugte konkrete Gesamtzusammensetzung der erfindungsgemäß eingesetzten Dickschicht-Druckmasse ist der Figurenbeschreibung zu entnehmen.The temperature-sensitive layer of the temperature sensor according to the invention has metallic platinum between 60 and 90% by weight and is preferably characterized in that it contains metallic platinum in a proportion of approximately 70 to 85% by weight. A mixture of silicon, aluminum and alkaline earth oxide, in particular calcium oxide, is used as the oxide component, the aluminum oxide component resulting from the fact that the carrier substrate is generally aluminum oxide. In the event that the carrier substrate consists of a different oxide, the aluminum oxide could also be replaced by the material of the corresponding carrier substrate. Due to the tempering, silicon oxide produces quartz or the glass-like character and forms an inert material that is particularly suitable for the desired high-temperature applications. Calcium oxide is the preferred alkaline earth oxide; strontium and barium oxides can also be used instead, but calcium oxide has proven to be more stable. The oxide mixture forms a eutectic, the melting point of which can be adjusted and in particular reduced by the addition of the alkaline earth oxide, while a mixture of aluminum oxide and silicon oxide gives a relatively high melting point which is above the evaporation point of platinum, so that no heating up to this point could take place . By adding calcium oxide, the melting point of the eutectic mixture is reduced below the evaporation point of platinum, so that annealing can take place up to the desired melting point of the oxide mixture, at which the desired quartz-like or glass-like compact consistency of the material is achieved. Accordingly, the temperature sensitive Layer of the temperature sensor preferably has a composition such that silicon oxide is present in the oxide mixture in a range from 40 to 55% by weight, aluminum oxide to 25 to 40% by weight and the remainder is alkaline earth oxide, while silicon oxide with 45 to 50% by weight is extremely preferred. %, Aluminum oxide with 30 to 35% by weight, rest of alkaline earth oxide is given, in particular the oxide mixture containing 18 to 20% by weight of alkaline earth oxide and the rest of silicon oxide and aluminum oxide. In order to achieve the greatest possible reduction in the melting point of the eutectic oxide mixture, the invention accordingly provides that the temperature-sensitive layer is baked on the carrier substrate, the temperature-sensitive layer in particular having a compact, glass-like morphology. An ideal oxide mixture is explained in the following description of the figures. The specific electrical resistance is determined by the ratio of platinum and oxide content in the temperature-sensitive layer. Care must be taken to ensure that the proportion of platinum is not reduced to such an extent that the required conductivity bridges are completely interrupted or are easily interrupted during use. In this respect, it has been found to be advantageous that platinum should have a proportion of 80% by weight in the temperature-sensitive layer, based on the total mixture itself, between 60 and 80% by weight. Accordingly, the process uses the oxide mixture with a share of 14 to 20 wt .-% of the total mixture of platinum paste, oil and thinner. In a preferred embodiment, it is provided that platinum paste with 65 to 70% by weight, oil and thinner each with 5 to 10% by weight and the rest of oxide are mixed with one another, the platinum content of the paste itself preferably being 75% by weight. A preferred specific overall composition of the thick-film printing compound used according to the invention can also be found in the description of the figures.
Während die Maximaltemperatur der Temperung unterhalb der Verdampfungstemperatur von Platin bleiben sollte und vorzugsweise unter 1400 Grad liegt, sieht eine bevorzugte Ausgestaltung eine maximale Temperatur von 1300 bis 1350 Grad vor.While the maximum temperature of the tempering should remain below the evaporation temperature of platinum and is preferably below 1400 degrees, a preferred embodiment provides a maximum temperature of 1300 to 1350 degrees.
In weiterer Ausbildung ist vorgesehen, daß im Bereich von 300 bis 400 Grad C eine Haltezeit zur vollständigen Verbrennung organischer Binderanteile der Schicht eingehalten wird. Die Haltezeit dient zur Erzeugung der gewünschten kompakten, glasartigen Konsistenz der zu schoffenden temperaturempfindlichen Schicht des Temperatursensors. Die maximale Haltezeit ist an sich unkritisch, darf aber nicht unmäßig überzogen werden, da hierdurch, neben den gewünschten zu der kompakten, glasartigen Konsistenz führenden morphologischen Veränderungen, Veränderungen der Platingrundstruktur aufgrund von Sintereffekten, die zu unerwünschten größeren Strukturen oder Pflasterbildung, möglicherweise auch zu Oxidationen und insgesamt zu einem Aufbrechen der Platinflächen führen, eintreten können. Es wird daher vorzugsweise eine Haltezeit von 20 bis 40 Minuten angestrebt, wobei sich als ein optimaler Wert eine Zeit von 25 Minuten herausgestellt hat.In a further development it is provided that a holding time for the complete combustion of organic binder portions of the layer is maintained in the range from 300 to 400 degrees C. The holding time serves to generate the desired compact, glass-like consistency of the temperature-sensitive layer of the temperature sensor to be created. The maximum holding time is not critical per se, but must not be unduly excessive, since in addition to the desired morphological changes leading to the compact, glass-like consistency, changes in the platinum base structure due to sintering effects, which lead to undesired larger structures or plaster formation, and possibly also to oxidation and lead to a breakdown of the platinum surfaces. A holding time of 20 to 40 minutes is therefore preferred, a time of 25 minutes having proven to be an optimal value.
Der gleichmäßig, nicht zu steile Temperaturanstieg und -abfall ist im Hinblick darauf erforderlich, daß die temperaturempfindliche Schicht beim Tempervorgang keinem Temperatursprung ausgesetzt werden darf, da dies zu Beschädigungen, wie Versprödung und Rissen führen könnte. Es hat sich demgemäß eine Temperatursteuerung mit einem Temperaturkoeffizienten von 10 bis 15 Grad C pro Minute und insbesondere von 13 Grad C pro Minute für den Temperaturanstieg und -abfall, letzteres insbesondere über etwa 1100 Grad C, herausgestellt. Während dies hinsichtlich des Abfalls die Temperaturführung am Heizelement des Sinterofens betrifft, kann der Ofen aufgrund seiner Ausgestaltung einen insgesamt langsameren Temperaturabfall zeigen.The steady, not too steep temperature rise and fall is necessary in view of the fact that the temperature-sensitive layer must not be exposed to a temperature jump during the tempering process, since this could lead to damage such as embrittlement and cracks. Accordingly, a temperature control with a temperature coefficient of 10 to 15 degrees C per minute and in particular of 13 degrees C per minute for the temperature rise and drop, the latter in particular above about 1100 degrees C, has been found. While this relates to the temperature control on the heating element of the sintering furnace in terms of the drop, the design of the furnace can cause an overall slower drop in temperature.
Wenn eine insbesondere organische Binder - die in der Regel Cellulosederivate sind - enthaltende Platin-Paste eingesetzt wird, so ist es vorteilhaft, im Bereich des Temperaturanstiegs bei 300 bis 400 Grad C, insbesondere bei 350 Grad C, ebenfalls eine Haltezeit vorzusehen, bei der die Temperatur über eine vorgegebene Zeit auf einen festen Wert gehalten wird. Während die maximale Dauer der Haltezeit letztendlich lediglich durch ökonomische Forderungen begrenzt ist, sollte die Haltezeit, um ein einwandfreies Ergebnis zu erzielen, nicht zu kurz, insbesondere nicht unter fünf Minuten, gewählt werden. Als idealer Wert haben sich etwa zehn Minuten herausgestellt. Wenn eine solche Haltezeit eingesetzt wird, so hat die ausgetemperte Schicht eine typische helle Quarz-/Keramikfarbe, während bei zu kurzer Haltezeit in dem genannten Bereich eine Verdunklung der Farbe bis zu einer Schwärzung bedingt. Dies liegt daran, daß der oranische Binder nur langsam verbrennt und bei nicht ausreichender Haltezeit in dem genannten Temperaturbereich nicht vollständig zu CO₂ verbrennt, sondern vielmehr Kohlenstoffanteile zurückbleiben, die sich darüberhinaus negativ auf die temperatursensitiven Eigenschaften der Schicht auswirken können.If a platinum paste containing in particular organic binders - which are generally cellulose derivatives - is used, it is advantageous in the region of the temperature rise at 300 to 400 degrees C, especially at 350 degrees C, also to provide a holding time during which the temperature is held at a fixed value over a predetermined time. While the maximum duration of the holding time is ultimately only limited by economic requirements, the holding time should not be too short, in particular not less than five minutes, in order to achieve a perfect result. About ten minutes turned out to be the ideal value. If such a holding time is used, the tempered layer has a typical light quartz / ceramic color, while if the holding time is too short in the area mentioned, the color darkens until it becomes black. This is because the orange binder burns only slowly and does not completely burn to CO₂ if the holding time is not sufficient in the temperature range mentioned, but rather carbon portions remain, which can also have a negative effect on the temperature-sensitive properties of the layer.
Insgesamt wird durch die Erfindung ein miniaturisierter Temperatursensor geschaffen, der vorzugsweise bei Temperaturen von über 600 Grad C bis zu 1200 Grad C einsetzbar ist. Der erfindungsgemäße Temperatursensor ist preiswert herstellbar und kann insbesondere auch gleichzeitig und zusammen mit anderen Funktionselementen, wie Sauerstoffsensoren, die in gleicher Technik hergestellt werden sowie Heizleitern auf einem gemeinsamen Substrat aufgebracht werden. So sieht eine bevorzugte Ausgestaltung vor, daß auf dem Trägersubstrat ein Sauerstoffsensor sowie ein durch die temperaturempfindliche Schicht geregelter Heizleiter aufgebracht sind und in Weiterbildung, daß der Heizleiter auf der den Sauerstoffsensor und die temperaturempfindliche Schicht tragenden Fläche des Trägersubstrats aufgebracht ist. Insbesondere ist die Herstellung des erfindungsgemäßen Sensors billiger als die Dünnfilmtechnik, abgesehen davon, daß hierdurch keine derartigen hochtemperaturbelastbaren Sensoren herstellbar sind. Es sind kein Vakuum und keine aufwendige Apparatur notwendig. Weiterhin ist auch die Auswirkung des Temperaturmeßergebnisses nicht an komplizierte Vorgaben, wie Umgebungsmeßfühlern, die bei Messungen mittels Thermospannung erforderlich sind oder zusätzliche Elektroniken, erforderlich. Vielmehr kann der Sensorausgang unmittelbar zur Regelung beispielsweise eines Heizleiters verwendet werden.Overall, the invention creates a miniaturized temperature sensor, which can preferably be used at temperatures of over 600 degrees C to 1200 degrees C. The temperature sensor according to the invention is inexpensive to manufacture and can in particular also be applied simultaneously and together with other functional elements, such as oxygen sensors, which are produced using the same technology, and heat conductors can be applied to a common substrate. Thus, a preferred embodiment provides that an oxygen sensor and a heating conductor regulated by the temperature-sensitive layer are applied to the carrier substrate, and in a further development that the heating conductor is applied to the surface of the carrier substrate which carries the oxygen sensor and the temperature-sensitive layer. In particular, the manufacture of the sensor according to the invention is cheaper than thin-film technology, apart from the fact that no sensors of this type that can withstand high temperatures can be produced as a result. No vacuum and no complex equipment are necessary. Furthermore, the effect of the temperature measurement result is also not to complicated specifications, such as environmental sensors, which are required for measurements using thermal voltage or additional electronics. Rather, the sensor output can be used directly to control, for example, a heating conductor.
Die vorstehende Kombination wird insbesondere zur Rohsauerstoffmessung beispielsweise in Gaskraftwerken oder in der Prozeßleittechnik in der chemischen Industrie eingesetzt, wenn dort im Hinblick auf Inertisierungen der Restsauerstoffgehalt zu messen ist. Die Lambdawertmessung erfolgt aufgrund eines Festkörpereffekts mit Reduktion bzw. Oxidation in Abhängigkeit von dem Sauerstoffgehalt des Umgebungsgases, wobei dieser Festkörpereffekt erst bei höheren Temperaturen, insbesondere Temperaturen über 600 Grad C, einsetzt, so daß der Temperatursensor auf diese Temperatur aufgeheizt werden muß und auf der gewünschten Vorgabetemperatur mit hoher Genauigkeit gehalten werden muß, wozu der erfindungsgemäße Temperatursensor in idealer Weise einsetzbar ist. Weitere Einsatzgebiete betreffen Hochtemperaturöfen, Sinteröfen etc.The above combination is used in particular for raw oxygen measurement, for example in gas power plants or in process control technology in the chemical industry, if the residual oxygen content is to be measured there with regard to inerting. The lambda value measurement takes place on the basis of a solid-state effect with reduction or oxidation depending on the oxygen content of the ambient gas, this solid-state effect only occurring at higher temperatures, in particular temperatures above 600 degrees C., so that the temperature sensor must be heated to this temperature and to the desired one Specification temperature must be kept with high accuracy, for which the temperature sensor according to the invention can be used in an ideal manner. Other areas of application concern high-temperature furnaces, sintering furnaces etc.
Weitere Vorteile und Merkmale der Erfindung ergeben sich aus den Ansprüchen und aus der nachfolgenden Beschreibung, in der ein Ausführungsbeispiel der Erfindung unter Bezugnahme auf die Zeichnung im einzelnen erläutert ist. Dabei zeigt:
- Figur 1
- Eine bevorzugte Ausgestaltung eines erfindungsgemäßen Temperatursensors;
- Figur 2
- eine bevorzugte Temperaturführung beim Tempervorgang zur Herstellung des Temperatursensors.
- Figure 1
- A preferred embodiment of a temperature sensor according to the invention;
- Figure 2
- a preferred temperature control during the tempering process for producing the temperature sensor.
Sauerstoffsensoren zur Lambda-Messung, wie beispielsweise den Gaskraftwerken, der Prozeßtechnik etc., zeigen ihre höchste Empfindlichkeit, die auf einem Oxidations-Reduktions-Festkörper-Effekt entsprechend dem vorhandenen Sauerstoff beruht, bei höheren Temperaturen. Sie müssen daher auf höhere Temperaturen aufgeheizt werden und, da der Effekt sich temperaturabhängig ändert, auf einer vorgegebenen Temperatur stabilisiert werden. Hierzu kann auf einem Substrat oder Träger 1, wie aus Aluminiumoxid, der Sauerstoff- oder Gassensor 2, der an sich bekannt ist, aufgebracht sein. Auf der der den Sauerstoffsensor 2 tragenden Fläche 3 des Trägers 1 entgegengesetzten Fläche 4 ist ein Heizleiter 6 aufgebracht, der beispielsweise ein Heizleiter auf keramischer Basis sein kann. Weiterhin ist nahe dem Sauerstoffsensor 2 ein Temperatursensor 7 auf der Fläche 3 des Trägers 1 in der weiter unten beschriebenen Weise aufgebracht. Der Temperatursensor 7 ist mäanderförmig geführt und weist beispielsweise bei der unten angegebenen Zusammensetzung eine Gesamtlänge von 10 mm, eine Breite von 3 mm, eine gesamte "Drahtlänge" von 60 bis 70 mm sowie eine Schichtdicke von 10 bis 15 Mikrometer und eine Breite von 250 Mikrometer auf.Oxygen sensors for lambda measurement, such as gas power plants, process technology, etc., show their highest sensitivity, which is based on an oxidation-reduction-solid-state effect corresponding to the available oxygen, at higher temperatures. They must therefore be heated to higher temperatures and, since the effect changes depending on the temperature, stabilized at a predetermined temperature. For this purpose, the oxygen or gas sensor 2, which is known per se, can be applied to a substrate or carrier 1, such as made of aluminum oxide. A heating conductor 6, which can be, for example, a heating conductor on a ceramic basis, is applied to the surface 4 of the carrier 1 opposite the oxygen sensor 2. Furthermore, a
Der Temperatursensor 7 besteht aus einer Keramik - die vorzugsweise aufgrund des Temperungsvorganges weitgehendst "verglast" ist - aus Oxid und in diesem dispergierten reinmetallischen Platin mit einem Anteil von 80 Gew.-%. Die Oxidzusammensetzung ist gemäß einer bevorzugten Ausgestaltung 50 Gew.-% Siliziumoxid, 30 Gew.-% Aluminiumoxid und 20 Gew.-% Kalziumoxid. Der Grundwiderstand des derart beschriebenen Temperatursensors 7 liegt bei etwa 100 Ohm.The
Der Temperatursensor 7 wird auf dem Trägersubstrat 1 in der folgenden Weise hergestellt:The
Zunächst werden Platin-Pulver und Oxid mit den gewünschten Endanteilen von 80 Gew.-% und 20 Gew.-% vermischt. Anschliessend wird eine Paste aus 65 Gew.-% Platin und Oxid-Pulver und 35 Gew.-% Vehikel hergestellt. Das Vehikel besteht zu 70 Gew.-% aus einem organischen Binder, wie Methylcellulose, und zu 30 Gew.-% aus einem organischen Lösungsmittel, wie Dibutylcarbitolacetat. Anschließend wird die hierdurch erhaltende Paste in Siebdruck- und damit Dickfilmtechnik auf dem Trägersubstrat 1 aus Aluminiumoxid in der gewünschten geometrischen Form, wie der dargestellten Mäanderform, aufgedruckt.First, platinum powder and oxide are mixed with the desired final proportions of 80% by weight and 20% by weight. A paste is then produced from 65% by weight of platinum and oxide powder and 35% by weight of vehicle. The vehicle consists of 70% by weight of an organic binder, such as methyl cellulose, and 30% by weight of an organic solvent, such as dibutyl carbitol acetate. The paste obtained in this way is then printed on the carrier substrate 1 made of aluminum oxide in the desired geometric shape, such as the meandering shape shown, using screen printing and thus thick film technology.
Sodann wird eine Temperung vorgenommen, wobei Träger 1 und aufgedrucktes Temperatursensor-Substrat in einem Temperofen, ausgehend von Umgebungstemberatur (20 Grad) mit einem differentiellen Temperaturenstieg von ca. 13 Grad C pro Minute, bis auf ca. 350 Grad C erhitzt wurden. Oberhalb ihrer Verdampfungstemperatur verdampfen Lösungsmittel, Verdünner und Öl. Ab etwa 100 Grad C ist die vorher zähflüssige Druckmasse eine nahezu feste Masse, da die flüssigen Anteile weitgehend verbrannt sind. Weiterhin beginnt der organische Binder, der ein Cellulosederivat ist, zu verbrennen. Da der organische Binder langsam verbrennt, wird bei ca. 350 Grad die Temperatur über etwa 10 Minuten konstant gehalten, um eine vollständige Verbrennung (Umwandlung in CO₂) des organischen Binders zu ermöglichen. Es wurde festgestellt, daß ohne oder bei nicht ausreichender Haltezeit die erhaltene Oxidkeramik aufgrund nicht vollständig verbranntem Binder schwarz bzw. dunkel ist, während bei Einhaltung einer ausreichenden Haltezeit im genannten Temperaturbereich aufgrund der vollständigen Verbrennung des Binders die letztendlich erhaltene Keramik die typische helle Farbe aufwies. Nicht vollständig verbrannter Binder könnte auch die Eigenschaften des Temperatursensors beeinträchtigen. Nach der aus der Figur 2 ersichtlichen Haltezeit bei einer Temperatur von 350 Grad C erfolgt eine weitere Temperaturerhöhung mit dem gleichen Temperaturkoeffizienten bis zu der gewünschten End- oder maximalen Einbrenntemperatur von ca. 1330 Grad C. Es hat sich gezeigt, daß der Temperaturanstieg eine kritische Größe ist. Bei steilerem Temperaturanstieg ergeben sich Risse in der Sensorschicht. Ein flacher Temperaturanstieg ist durchaus möglich, bedingt damit aber längere Herstellungszeiten und damit einen höheren Herstellungsaufwand und höhere Kosten. Die angegebene Temperaturführung stellt insofern eine Optimierung unter Sicherstellung eines einwandfreien Ergebnisses dar.An annealing is then carried out, with the support 1 and the printed-on temperature sensor substrate being heated to about 350 degrees C. in a tempering furnace, starting from ambient temperature (20 degrees) with a differential temperature increase of about 13 degrees C. per minute. Solvents, thinners and oil evaporate above their evaporation temperature. From about 100 degrees C, the previously viscous printing mass is an almost solid mass, since the liquid components are largely burned. Furthermore, the organic binder, which is a cellulose derivative, begins to burn. Since the organic binder burns slowly, the temperature is kept constant at about 350 degrees for about 10 minutes to allow complete combustion (conversion to CO₂) of the organic binder. It was found that the oxide ceramic obtained was black or dark due to an incompletely burned binder, with no or insufficient holding time, while if a sufficient holding time was observed in the temperature range mentioned, the ceramic ultimately obtained had the typical light color due to the complete combustion of the binder. Binder that is not completely burned could also impair the properties of the temperature sensor. After the holding time shown in FIG. 2 at a temperature of 350 ° C., there is a further temperature increase with the same temperature coefficient up to the desired final or maximum stoving temperature of approx. 1330 ° C. It has been shown that the temperature rise is a critical variable is. With a steeper temperature rise, cracks occur in the sensor layer. A flat rise in temperature is quite possible, but this means longer production times and thus higher production costs and higher costs. In this respect, the specified temperature control provides an optimization while ensuring a flawless result represents.
Die angegebene Einbrenntemperatur von 1330 Grad C wird über eine gewisse Zeit aufrechterhalten, die im erläuterten Ausführungsbeispiel bei 25 Minuten lag. Dies ist erforderlich, um ein Insichverfließen der Schicht, und damit eine Änderung der Morphologie (bei Beibehaltung der Struktur) und insgesamt eine glasartige, kompaktere Schicht zu erreichen, die eine gleichmäßige Leitfähigkeit gewährleistet. Es ist dabei zu beachten, daß die Einbrenntemperatur auch nicht zu lange aufrechterhalten werden darf, da hier dann innere Strukturänderungen erfolgen, insbesondere werden offenbar Platinbrücken aufgebrochen und damit der durchgehende elektrische Kontakt geschädigt, sei es aufgrund typischer Sintereffekte in Form von Bildung größerer Strukturen oder Pflasterbildung, sei es aufgrund von Oxidationen von Plattenteilchen. Während im Hinblick auf die erwünschte kompakte glasartige Konsistenz die genannte Haltezeit bei Einbrenntemperatur kaum verkürzt werden kann, ist eine gewisse Verlängerung unkritisch, da die vorstehend erwähnten nachteiligen Auswirkungen erst bei übermäßig langer Einbrenntemperatur auftreten. Auch insofern erfolgt eine Optimierung dahingehend, daß die Haltezeit der Einbrenntemperatur möglichst kurz gewählt wurde, wobei sichergestellt wurde, daß die gewünschte kompaktartige glasartige Struktur erreicht wird. Anschließend erfolgt eine Temperaturreduzierung mit dem gleichen Temperaturkoeffizienten am Heizelement, also der gleichen Temperaturführung. Aufgrund des ofeneigenen Abkühlverhaltens kühlt die Temperatur im Ofen, wie dargestellt, langsamer ab. Wesentlich ist ein Abkühlen der Temperatur mit dem genannten Temperaturkoeffizienten bis etwa auf 1100 Grad C, das nicht stärker gewählt werden darf, da ansonsten ebenfalls Buschädigungen der erhaltenen Struktur eintreten könnten.The specified baking temperature of 1330 degrees C is maintained for a certain time, which was 25 minutes in the illustrated embodiment. This is necessary in order to cause the layer to flow into one another and thus to change the morphology (while maintaining the structure) and overall to achieve a glass-like, more compact layer which ensures uniform conductivity. It should be noted that the baking temperature should not be maintained too long, since internal structural changes then take place, in particular platinum bridges are apparently broken and the continuous electrical contact is damaged, be it due to typical sintering effects in the form of larger structures or plaster formation , be it due to oxidation of plate particles. While with regard to the desired compact glass-like consistency the mentioned holding time at the stoving temperature can hardly be shortened, a certain lengthening is not critical since the above-mentioned disadvantageous effects only occur when the stoving temperature is excessively long. In this respect, too, an optimization is carried out in such a way that the holding time of the baking temperature was chosen to be as short as possible, it being ensured that the desired compact, glass-like structure is achieved. The temperature is then reduced using the same temperature coefficient on the heating element, ie the same temperature control. Due to the furnace's own cooling behavior, the temperature in the furnace cools more slowly, as shown. It is essential to cool the temperature with the temperature coefficient mentioned to approximately 1100 ° C., which should not be chosen more, since otherwise the structure obtained could also be damaged by bus.
Insgesamt ist erfindungsgemäß ein Temperatursensor mit einem hinreichend großen Grundwiderstand im angegebenen Bereich gegeben, der hochtemperaturbeständig ist und insbesondere bei Temperaturen von über 600 bis weit über 1000 Grad C zur Temperaturmessung und damit im dargestellten Ausführungsbeispiel der Figur 1 zur Temperatursteuerung des Heizers 6 eingesetzt werden kann.Overall, according to the invention there is a temperature sensor with a sufficiently high basic resistance in the specified range, which is resistant to high temperatures and in particular with Temperatures of over 600 to well over 1000 degrees C can be used for temperature measurement and thus for temperature control of the heater 6 in the exemplary embodiment shown in FIG. 1.
Claims (18)
- Temperature sensor with a temperature-sensitive layer deposited on a carrier substrate and containing platinum, said layer containing metallic platinum finely distributed in oxide ceramic, in which the layer contains metallic platinum in a content of 60 to 90% by wt, and the oxidic portion of the temperature-sensitive layer (7) is an oxidic mixture of silicon, aluminium and alkaline earth oxides, in particular calcium oxide, characterised in that silicon oxide is present in the oxidic mixture in a range of 40 to 55% by wt, aluminium oxide in a range of 25 to 40% by wt and the balance is alkaline earth oxide.
- Sensor according to claim 1, characterised in that the oxidic mixture contains 18 to 20% alkaline earth oxide and the balance is silicon oxide and aluminium oxide.
- Sensor according to any one of the preceding claims, characterised in that the temperature-sensitive layer (7) is burnt onto the carrier substrate (1).
- Sensor according to any one of the preceding claims, characterised in that the temperature-sensitive layer (7) exhibits a compact, glass-like morphology.
- Sensor according to any one of the preceding claims, characterised in that on the carrier substrate (1) there is deposited an oxygen sensor (2) together with a heating conductor (6) which is controlled by the temperature-sensitive layer (7).
- Sensor according to claim 5, characterised in that the heating conductor (6) is deposited on the surface (4) of the carrier substrate (1) facing away from the surface (3) bearing the oxygen sensor (2) and the temperature-sensitive layer (7).
- Method for manufacturing a temperature sensor according to any one of claims 1 to 6, in which a platinum-containing layer is deposited on a carrier substrate, characterised in that platinum powder, oxides and binder are mixed with one another and after the application of the layer to the carrier substrate are tempered therewith.
- Method according to claim 7, characterised in that at least one oil is used as binder.
- Method according to claim 7 or 8, characterised in that platinum-powder mixed with organic binder and solvent is used as a paste.
- Method according to any one of claims 7 to 9, characterised in that a thinner is also incorporated for adjusting the consistency.
- Method according to any one of claims 7 to 10, characterised in that the oxidic portion is used as a silicon, aluminium or alkaline earth oxide mixture.
- Method according to claim 11, characterised in that an oxidic mixture containing silicon oxide in a range of 45 to 50% by wt, aluminium oxide 30 to 35% by wt and the balance alkaline earth oxide, in particular calcium oxide, (calculated on the total oxide weight) is used.
- Method according to claim 11 or 12, characterised in that an oxidic mixture with an oxidic content of 18 to 20% alkaline earth oxide and the balance silicon oxide and aluminium oxide (calculated on the total oxide weight) is used.
- Method according to any one of claims 7 to 13, characterised in that oxide in a proportion of 14 to 20% by wt of the total mixture weight is used.
- Method according to any one of claims 7 to 14, characterised in that platinum paste in 65 to 70% by wt, oil and thinner in respectively 5 to 10% by wt and the balance oxide are mixed with one another.
- Method according to any one of claims 7 to 15, characterised in that the tempering takes place at a temperature of between 1300 and 1350 °C.
- Method according to any one of claims 7 to 16, characterised in that the heating temperature control curve ascends uniformly in the main and descends in the same manner with a final holding time at the maximum tempering temperature.
- Method according to any one of claims 7 to 17, characterised in that in the range of 300 to 400 °C a holding time is observed for the complete incineration of organic binder components of the layer.
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AT9090911276T ATE105100T1 (en) | 1989-07-25 | 1990-07-13 | TEMPERATURE SENSOR AND METHOD FOR ITS MANUFACTURE. |
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DE3924518A DE3924518A1 (en) | 1989-07-25 | 1989-07-25 | TEMPERATURE SENSOR AND METHOD FOR THE PRODUCTION THEREOF |
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PCT/DE1990/000527 WO1991001561A1 (en) | 1989-07-25 | 1990-07-13 | Temperature sensor and process for producing the same |
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GB201216861D0 (en) * | 2012-09-20 | 2012-11-07 | Univ Southampton | Apparatus for sensing at least one parameter in water |
DE102014104219B4 (en) | 2014-03-26 | 2019-09-12 | Heraeus Nexensos Gmbh | Ceramic carrier and sensor element, heating element and sensor module each with a ceramic carrier and method for producing a ceramic carrier |
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-
1989
- 1989-07-25 DE DE3924518A patent/DE3924518A1/en not_active Withdrawn
-
1990
- 1990-07-13 US US07/671,920 patent/US5202665A/en not_active Expired - Fee Related
- 1990-07-13 JP JP2510485A patent/JP2676564B2/en not_active Expired - Fee Related
- 1990-07-13 ES ES90911276T patent/ES2053200T3/en not_active Expired - Lifetime
- 1990-07-13 EP EP90911276A patent/EP0435999B1/en not_active Expired - Lifetime
- 1990-07-13 WO PCT/DE1990/000527 patent/WO1991001561A1/en active IP Right Grant
- 1990-07-13 DE DE59005531T patent/DE59005531D1/en not_active Expired - Fee Related
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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DE19545590A1 (en) * | 1995-12-07 | 1997-06-12 | Bosch Gmbh Robert | Co-sintered cermet layer containing glass |
DE19545590C2 (en) * | 1995-12-07 | 1999-10-21 | Bosch Gmbh Robert | Co-sintered cermet layer on a ceramic body and a process for its production |
Also Published As
Publication number | Publication date |
---|---|
WO1991001561A1 (en) | 1991-02-07 |
DE3924518A1 (en) | 1991-01-31 |
EP0435999A1 (en) | 1991-07-10 |
DE59005531D1 (en) | 1994-06-01 |
US5202665A (en) | 1993-04-13 |
JP2676564B2 (en) | 1997-11-17 |
JPH04502966A (en) | 1992-05-28 |
ES2053200T3 (en) | 1994-07-16 |
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