DE102017114299A1 - Method for producing a pressure measuring device - Google Patents

Abstract

It is a method for producing a pressure measuring device, comprising a pressure sensor (1) having a measuring membrane (9) which can be acted upon by a pressure to be measured (p) to form a pressure chamber (7) with a ceramic base body (5) and a capacitive sensor , electromechanical transducer with a measuring capacitor with one of a on the measuring membrane (9) acting pressure (p) dependent deflection of the measuring membrane (9) dependent capacity comprises, and a measuring electronics (3), the pressure to be measured (p) based on a determined by the measuring capacitance of the measuring capacitor dependent auxiliary variable (C), in which the transducer is connected to the measuring electronics (3), wherein for one or more components of the converter in each case a connection (21, 23, 25) on a membrane-facing away End face of the base body (5) and provided thereon via a lead-free soft soldering (35) with a connected to the measuring electronics (3) connection line (37) is connected. In order to achieve the highest possible measuring accuracy, in particular the lowest possible temperature-dependent hysteresis, a temperature-dependent hysteresis (H) of the auxiliary variable (C) reducing and / or minimizing position on the membrane-remote end face of the main body is provided in advance for at least one of the soft solderings (35) (5) and each of these Weichlötungen (35) in the subsequent production of the pressure measuring device in each case at the position determined for them on the associated at this position applied terminal (21, 23, 25) generated.

Description

• - einem Drucksensor, der eine unter Bildung einer Druckkammer mit einem keramischen Grundkörper druckdicht verbundene, mit einem zu messenden Druck beaufschlagbare Messmembran und einen kapazitiven, elektromechanischen Wandler umfasst, wobei der Wandler einen oder mehrere Kondensatoren umfasst, von denen mindestens einer ein Messkondensator mit einer von einer vom auf die Messmembran einwirkenden Druck abhängigen Durchbiegung der Messmembran abhängigen Kapazität ist, und
• - einer Messelektronik, die derart ausgebildet ist, dass sie den zu messenden Druck anhand einer von der Messkapazität des Messkondensators abhängigen Hilfsgröße bestimmt,
• - bei dem der Wandler an die Messelektronik angeschlossen wird, wobei für eine oder mehrere Komponenten des Wandlers, jeweils ein eine weichlötfähige Oberfläche aufweisender, elektrisch leitend mit der jeweiligen Komponente verbundener Anschluss auf einer membran-abgewandten Stirnseite des Grundkörpers vorgesehen und über eine darauf aufgebrachte bleifreie Weichlötung mit einer an die Messelektronik angeschlossenen Anschlussleitung verbunden wird,

sowie eine mittels dieses Verfahrens hergestellte Druckmesseinrichtung.The invention relates to a method for producing a pressure measuring device with

• a pressure sensor which comprises a measuring diaphragm which is pressure-tightly connected to a ceramic base body to form a pressure chamber and a capacitive electromechanical transducer, the transducer comprising one or more capacitors at least one of which has a measuring capacitor with one of is a dependent of the force acting on the measuring membrane pressure dependent deflection of the measuring membrane dependent capacity, and
• a measuring electronics which is designed such that it determines the pressure to be measured on the basis of an auxiliary variable dependent on the measuring capacitance of the measuring capacitor,
• - In which the transducer is connected to the measuring electronics, being provided for one or more components of the transducer, each having a weichlötfähige surface exhibiting, electrically connected to the respective component connection on a membrane-remote end face of the body and a lead-free applied thereto Soft soldering is connected to a connecting cable connected to the measuring electronics,

and a pressure measuring device produced by this method.

Pressure measuring devices are used in industrial measurement technology for measuring pressures.

One of the features mentioned above pressure measuring device is eg in the DE 10 2013 101 315 A1 described. In the pressure measuring device described therein, the connection lines are formed as columnar, the measuring electronics supporting elements, which are soldered in each case by means of a soft soldering at a designated connection location on a soft solderable coating applied to the body. Solderable coatings have very good wetting properties with regard to soft solders, with the solder solidifying in the entire wetting area after the brazing process. As a result, unevenness on the surface of the coating may also occur outside of the connection locations, which may result in the areas affected by this being subsequently unable or only to a limited extent to be used. Due to such unevenness, it is not possible, for example, to support any sensor surround, clamping or mounting on these surfaces.

This problem is in the in the DE 10 2013 101 315 A1 pressure measuring devices described by the fact that in the base body, the respective connection locations are at least partially provided on the outside surrounding grooves, which cause a limitation of the wetted surface during soldering.

Apart from the consideration of the space on the side facing away from the membrane, if necessary, the positioning of the soft soldering and the dimensioning of their dimensions is customary today on the basis of manufacturing technology, their connection to the respective component of the converter and their application facilitating aspects. In that regard, large base areas of the soft soldering facilitate the dispensing of the soft solder, the positioning of the connecting lines, and, if necessary, also manual soldering. Correspondingly, soft soldering used today in conjunction with pressure measuring devices of the type mentioned at the beginning has circular disk-shaped base surfaces with diameters of greater than or equal to 2.5 mm.

In pressure measuring devices of the type mentioned above, the construction and connection technology chosen for the connection of the transducer to the measuring electronics has an admittedly very slight but nevertheless noticeably disadvantageous influence on the measuring accuracy achievable with the pressure measuring device. Investigations by the applicant have found that, inter alia, the selection of the solder used also plays a role. This result is surprising insofar as arranged on the membrane-remote end face of the base body solder joints are relatively small and are spaced from the measuring membrane and the capacitors of the capacitive transducer by the thickness of the base body. Both factors seem to justify the assumption that the choice of soft solder should not affect the accuracy of the measurement. Investigations by the Applicant have shown, however, that the pressure-measuring devices with lead-free soldering mentioned at the beginning have regularly poorer measuring properties than otherwise identical pressure-measuring devices which have lead-containing solder joints in place of the lead-free solder joints. In that regard, it has been found in particular that these pressure measuring devices have a greater temperature-dependent hysteresis.

However, the use of lead-containing soft solders, which are more suitable with regard to the measurement accuracy, is opposed by lead Hazardous substance whose use and placing on the market is to be avoided.

It is an object of the invention to provide a method for producing a lead-free soft soldering having pressure measuring device of the type mentioned, can be generated with the pressure measuring devices with the highest possible accuracy, esp. The lowest possible temperature-dependent hysteresis.

• - einem Drucksensor, der eine unter Bildung einer Druckkammer mit einem keramischen Grundkörper druckdicht verbundene, mit einem zu messenden Druck beaufschlagbare Messmembran und einen kapazitiven, elektromechanischen Wandler umfasst, wobei der Wandler einen oder mehrere Kondensatoren umfasst, von denen mindestens einer ein Messkondensator mit einer von einer vom auf die Messmembran einwirkenden Druck abhängigen Durchbiegung der Messmembran abhängigen Kapazität ist, und
• - einer Messelektronik, die derart ausgebildet ist, dass sie den zu messenden Druck anhand einer von der Messkapazität des Messkondensators abhängigen Hilfsgröße bestimmt,
• - bei dem der Wandler an die Messelektronik angeschlossen wird, wobei für eine oder mehrere Komponenten des Wandlers jeweils ein eine Weichlötfähige Oberfläche aufweisender, elektrisch leitend mit der jeweiligen Komponente verbundener Anschluss auf einer membran-abgewandten Stirnseite des Grundkörpers vorgesehen und über eine darauf aufgebrachte bleifreie Weichlötung mit einer an die Messelektronik angeschlossenen Anschlussleitung verbunden wird,

das sich dadurch auszeichnet, dass

• - vorab für mindestens eine der Weichlötungen eine eine temperaturabhängige Hysterese der Hilfsgröße reduzierende und/oder minimierende Position auf der membran-abgewandten Stirnseite des Grundkörpers bestimmt wird, und
• - jede dieser Weichlötungen bei der nachfolgenden Herstellung der Druckmesseinrichtung jeweils an der für sie bestimmten Position auf dem zugehörigen an dieser Position aufgebrachten Anschluss erzeugt wird.

For this purpose, the invention comprises a method for producing a pressure measuring device, with

• a pressure sensor which comprises a measuring diaphragm which is pressure-tightly connected to a ceramic base body to form a pressure chamber and a capacitive electromechanical transducer, the transducer comprising one or more capacitors at least one of which has a measuring capacitor with one of is a dependent of the force acting on the measuring membrane pressure dependent deflection of the measuring membrane dependent capacity, and
• a measuring electronics which is designed such that it determines the pressure to be measured on the basis of an auxiliary variable dependent on the measuring capacitance of the measuring capacitor,
• - In which the transducer is connected to the measuring electronics, wherein for one or more components of the converter each having a Weichlötfähige surface, electrically connected to the respective component connection provided on a membrane-remote end face of the body and a lead-free soft soldering applied thereto is connected to a connecting cable connected to the measuring electronics,

which is characterized by the fact that

• - Before for at least one of the soft soldering a temperature-dependent hysteresis of the auxiliary size reducing and / or minimizing position on the membrane-remote end face of the body is determined, and
• - Each of these Weichlötungen is produced in the subsequent production of the pressure measuring device respectively at the position determined for them on the associated applied at this position connection.

The positioning of the soft soldering according to the invention offers the advantage that pressure measuring devices can thereby be produced with which high measurement accuracies can be achieved despite the use of lead-free soft soldering in a comparatively large temperature range.

A first variant is characterized in that the positions of the soft solderings are determined in such a way that they are each arranged in a region of the membrane-remote end face of the base body, on the membrane-facing end side of the base body an electrode-free region of the membrane-facing end face of the main body opposite.

A second variant is characterized in that the auxiliary quantity is an auxiliary variable dependent on the capacitances of at least two capacitors of the converter, and the positions of the soft solderings are determined such that their temperature-dependent influences on the individual capacitors within the auxiliary variable at least partially compensate each other.

A first development is characterized in that for at least one predetermined pressure, in particular a zero point pressure corresponding to a zero point of the pressure measuring range of the pressure sensor, a nominal pressure corresponding to a measuring range upper limit of the pressure measuring range and / or at least one further pressure within the measuring range of the pressure sensor, in each case an optimization method is carried out in which the positions of the soft soldering are determined in such a way that they reduce and / or minimize the magnitude of a maximum difference between two auxiliary times determined at different times at the same reference temperature auxiliary quantities, which at a time-invariable pressurization of the pressure sensor with the the respective predetermined pressure occurs when the pressure sensor undergoes a predetermined temperature range, esp. A temperature range of -10 ° C to + 70 ° C or from -40 ° C to + 125 ° C, covering the temperature cycle.

• - die Abmessungen der Weichlötungen festgelegt werden,
• - in einem ersten Verfahrensschritt Startpositionen für alle vorzusehenden Weichlötungen vorgegeben werden, und
• - in einem zweiten Verfahrensschritt durch Variation der Position nur einer der Weichlötungen eine die Hysterese reduzierende und/oder minimierende Soll-Position für die jeweilige Weichlötung ermittelt wird, während alle anderen Weichlötungen auf deren Startposition verbleiben.

A second development is characterized by the fact that

• - the dimensions of the solder joints are determined
• in a first method step, starting positions are specified for all soft soldering to be provided, and
• - In a second process step by varying the position of only one of the soft soldering a hysteresis reducing and / or minimizing target position for the respective soft soldering is determined, while all other soft soldering remain on their starting position.

• - in einem dritten Verfahrensschritt zusätzlich eine Soll-Position für mindestens eine weitere Weichlötung bestimmt wird, indem der erste und der zweite Verfahrensschritt wiederholt werden, wobei als Startposition für jeden der Anschlüsse für den zuvor bereits eine Soll-Position ermittelt wurde, die jeweilige Soll-Position angesetzt wird,
• - wobei insb. derart Verfahren wird, dass der erste und der zweite oder alle drei Verfahrensschritte mindestens einmal wiederholt werden, wobei im ersten Verfahrensschritt jeweils die zuletzt bestimmten Soll-Positionen als Startpositionen für die jeweiligen Weichlötungen verwendet werden.

A development of the second development is characterized by the fact that

• - In a third method step, additionally a desired position for at least one further soft soldering is determined by repeating the first and the second method step, wherein the starting position for each of the connections for which a desired position has already been determined is the respective desired position is set
• - In particular esb. Such method is that the first and the second or all three process steps are repeated at least once, in the first process step in each case the last determined target positions are used as starting positions for the respective soft soldering.

• - die Anschlüsse einen Messelektroden-Anschluss, einen Referenzelektroden-Anschluss und einen Gegenelektroden-Anschluss umfassen,
• - der Messelektroden-Anschluss elektrisch leitend mit einer auf einer membran-zugewandten Stirnseite des Grundkörpers angeordnete Messelektrode, insb. einer kreisscheibenförmigen Messelektrode, verbunden ist, die zusammen mit einer auf einer dem Grundkörper zugewandten Innenseite der Messmembran angeordneten mit dem Gegenelektroden-Anschluss verbundenen Gegenelektrode den Messkondensator bildet,
• - der Referenzelektroden-Anschluss elektrisch leitend mit einer auf der membran-zugewandten Stirnseite des Grundkörpers angeordneten Referenzelektrode, insb. einer kreisringförmigen oder kreisringsegmentförmigen, die Messelektrode außenseitlich umgebenden Referenzelektrode verbunden ist, die zusammen mit der auf der dem Grundkörper zugewandten Innenseite der Messmembran angeordneten Gegenelektrode einen Referenzkondensator bildet,
• - die Hilfsgröße eine von der Messkapazität des Messkondensators und einer Referenzkapazität des Referenzkondensators abhängige Hilfsgröße ist,
• - bei der erstmaligen Ausführung des ersten Verfahrensschritts drei von der Sensormitte ausgehende Strahlen definiert werden, zwischen denen jeweils ein vorgegebener Winkel, insb. ein Winkel in der Größenordnung von 120°, eingeschlossen ist, und die Startpositionen des mit der Messelektrode verbundenen Anschlusses, des mit der Referenzelektrode verbundenen Anschlusses und des mit der Gegenelektrode verbundenen Anschlusses derart vorgeben werden, dass jeder der Anschlüsse jeweils auf einem der drei Strahlen in einem dessen Startposition festlegenden Abstand zur Sensormitte angeordnet wird, und
• - bei jeder Ausführung des zweiten Verfahrensschritts jeweils die zu variierende Position der jeweiligen Weichlötung entlang des jeweiligen Strahls variiert wird, indem deren Abstand zur Sensormitte verändert wird.

A development of the second development is characterized by the fact that

• the connections comprise a measuring electrode connection, a reference electrode connection and a counterelectrode connection,
• - The measuring electrode terminal is electrically conductively connected to a arranged on a membrane-facing end face of the base body measuring electrode, esp. A circular disk-shaped measuring electrode, which together with a arranged on one of the base body inside of the measuring membrane arranged counter electrode connected to the counter electrode Measuring capacitor forms,
• - The reference electrode terminal electrically conductively connected to a arranged on the membrane-facing end side of the base body reference electrode, esp. An annular or annular segment-shaped, the measuring electrode outside the surrounding reference electrode is connected, which arranged together with the on the main body facing the inside of the measuring membrane disposed counter electrode Forms reference capacitor,
• the auxiliary variable is an auxiliary variable dependent on the measuring capacitance of the measuring capacitor and a reference capacitance of the reference capacitor,
• in the first execution of the first method step, three beams emanating from the center of the sensor are defined, between each of which a predetermined angle, in particular an angle in the order of magnitude of 120 °, is included, and the starting positions of the terminal connected to the measuring electrode the reference electrode connected terminal and connected to the counter electrode terminal are predetermined such that each of the terminals is arranged in each case on one of the three beams in a starting position defining the distance to the sensor center, and
• - In each execution of the second process step in each case the position of the respective soldering to be varied along the respective beam is varied by the distance to the sensor center is changed.

A third development is characterized in that the soft solderings are produced such that they each have a base area of less than or equal to 2.1 mm ² , in particular a circular disk-shaped base area with a diameter of less than or equal to 1.6 mm, and / or are formed as substantially disc-shaped Weichlötungen whose disc thickness is less than or equal to 2 times a diameter of the connecting lines, wherein the thickness of the disc in particular greater than or equal to a 1.5 times the diameter of the connecting lines.

Furthermore, the invention comprises a pressure measuring device produced by the method according to the invention, which is characterized in that the pressure measuring device in a predetermined temperature range, esp. A temperature range from -10 ° C to + 70 ° C or from - 40 ° C to + 125 ° C, at least one of the predetermined pressures, in particular the zero-point pressure, or in the entire measuring range, a hysteresis normalized to a measuring span of less than or equal to 0.04%, in particular less than or equal to 0.02%, in particular less than or equal to 0.01 % having.

• - eine außenseitlich im Wesentlichen allseitig von einer keramische Oberfläche des Grundkörpers umgebene Grundfläche aufweist, die im Wesentlichen gleich der Grundfläche der darauf erzeugten Weichlötung ist,
• - am Endes einer auf den Grundkörper aufgebrachten Leitung oder eines leitungsförmigen Fortsatzes einer auf den Grundkörper aufgebrachten Beschichtung angeordnet ist, wo er abgesehen von dessen an die Leitung bzw. den Fortsatz angrenzenden Bereich außenseitlich, allseitig von der keramischen Oberfläche des Grundkörpers umgeben ist, oder
• - außenseitlich von einer Lötstoppschicht oder einer im Grundkörper vorgesehenen Nut umgeben ist.

A first development of the pressure measuring device is characterized in that at least one of the connections

• an outer surface substantially surrounded on all sides by a ceramic surface of the base body, which is substantially equal to the base of the soft soldering produced thereon,
• - Is arranged at the end of a line applied to the body or a line-shaped extension of a coating applied to the body coating, where it is outside of its adjacent to the line or the extension area outside, on all sides surrounded by the ceramic surface of the body, or
• - Is surrounded on the outside by a Lötstoppschicht or provided in the main body groove.

• - einen oder mehrere unter Verwendung eines Hartlots, insb. eines weichlötfähigen Kupfer, Silber und Titan umfassenden Hartlots, auf den Grundkörper aufgebracht Anschlüsse umfassen, und/oder
• - einen oder mehrere Anschlüsse umfassen, die jeweils eine auf den Grundkörper aufgebrachte Hartlötung umfassen, auf der eine oder mehrere aufeinander angeordnete Schichten angeordnet sind, wobei die Schichten insb. eine als Haftvermittler dienende Primärschicht, insb. eine Chrom enthaltende Primärschicht, eine oder mehrere weitere Schichten, insb. eine oder mehrere Nickel und/oder Vanadium enthaltende weitere Schichten, und/oder eine als Oxidationsschutz ausgebildete weichlötfähige Oberschicht, insb. eine Gold umfassende Oberschicht, umfassen, und/oder
• - mindestens einen Anschluss umfassen, der als Teilbereich einer auf den Drucksensor aufgebrachten leitfähigen, weichlötfähigen Beschichtung ausgebildet ist oder auf einem Teilbereich einer auf den Drucksensor aufgebrachten leitfähigen Beschichtung angeordnet ist.

A second development of the pressure measuring device is characterized in that the connections

• - comprising one or more brazing alloys comprising a brazing alloy, in particular a soft solderable copper, silver and titanium, connections applied to the base body, and / or
• - comprise one or more terminals, each comprising a brazing applied to the base body, on which one or more layers arranged on one another are arranged, wherein the layers esp. Serving as primer primary layer, esp. A chromium-containing primary layer, one or more further Layers, in particular one or more nickel and / or vanadium-containing further layers, and / or a soft solderable upper layer designed as an oxidation protection, in particular a gold-comprising upper layer, comprise, and / or
• comprise at least one terminal which is formed as a portion of a conductive, weichlötfähigen coating applied to the pressure sensor or disposed on a portion of a conductive coating applied to the pressure sensor.

A third development of the pressure measuring device is characterized in that at least one of the connections via a line applied to the membrane-facing end face of the body, a coating applied to the body coating and / or passing through the body through-hole with the associated component of the transducer connected is.

• - die Hilfsgröße eine von der Messkapazität des Messkondensators und der Referenzkapazität des Referenzkondensators abhängige Hilfsgröße, insb. eine von einer auf die Messkapazität des Messkondensators bezogenen Differenz von Messkapazität und Referenzkapazität abhängige Hilfsgröße, ist, und
• - die Anschlüsse, nämlich der Messelektroden-Anschluss, der Gegenelektroden-Anschluss und der Referenzelektroden-Anschluss, in einem Dreieck angeordnet sind,
• - wobei der mit der Gegenelektrode verbundene Anschluss und der mit der Referenzelektrode verbundene Anschluss jeweils auf einem Bereich der membran-abgewandten Stirnseite des Grundkörpers angeordnet sind, der einen der Messelektrode gegenüberliegenden Bereich der membran-abgewandten Stirnseite des Grundkörpers außenseitlich umgibt, und
• - wobei der mit der Messelektrode verbundene Anschluss in einem äußeren Randbereich des der Messelektrode gegenüberliegenden Bereichs der membran-abgewandten Stirnseite des Grundkörpers angeordnet ist.

A fourth development of the pressure measuring device is characterized in that

• the auxiliary variable is an auxiliary variable dependent on the measuring capacitance of the measuring capacitor and the reference capacitance of the reference capacitor, in particular an auxiliary variable dependent on a difference between measuring capacitance and reference capacitance related to the measuring capacitance of the measuring capacitor
• the terminals, namely the measuring electrode terminal, the counterelectrode terminal and the reference electrode terminal, are arranged in a triangle,
• - Wherein the connection connected to the counter electrode and the connection connected to the reference electrode are each arranged on a region of the membrane-remote end face of the base body, which surrounds a measuring electrode opposite the region of the membrane-remote end face of the body outside, and
• - Wherein the connected to the measuring electrode terminal is arranged in an outer edge region of the measuring electrode opposite region of the membrane-remote end face of the base body.

• - der mit der Referenzelektrode verbundene Anschluss in einem der Referenzelektrode gegenüberliegenden Bereich der membran-abgewandten Stirnseite des Grundkörpers angeordnet ist, und
• - der mit der Gegenelektrode verbundene Anschluss einen innerhalb und einen außerhalb des der Referenzelektrode gegenüberliegenden Bereichs der membran-abgewandten Stirnseite des Grundkörpers angeordneten Teilbereich umfasst.

A development of the latter training is characterized by the fact that

• - The connected to the reference electrode terminal is disposed in an opposite region of the reference electrode of the membrane-remote end face of the base body, and
• - The connected to the counter electrode terminal comprises a within and outside of the reference electrode opposite portion of the membrane-remote end face of the body arranged portion.

• - die Anschlussleitungen Drähte, insb. versilberte oder verzinnte Kupferdrähte, sind, die einen Drahtdurchmesser in der Größenordnung von einem oder wenigen Zehntelmillimetern, insb. einen Drahtdurchmesser von kleiner gleich 0,3 mm, aufweisen,
• - der Grundkörper einen Durchmesser von größer gleich 1,5 cm, insb. von 1,5 cm bis 3,5 cm und/oder eine Dicke in der Größenordnung größer gleich mehreren Millimetern, insb. von 0,4 cm bis 0,5 cm, aufweist,
• - die Messmembran eine Membranstärke von größer gleich einem oder mehreren Zehntelmillimetern aufweist,
• - die Anschlüsse innerhalb eines außenseitlich allseitig von einem äußeren Sensor-Rand umgebenen Bereichs der membran-abgewandten Stirnseite des Grundkörpers angeordnet sind,
• - eine Halterung vorgesehen ist, auf der die Messelektronik vom Drucksensor beabstandet angeordnet ist, und/oder
• - das bleifreie Weichlot ein Zinn-Silber-Kupfer Lot, ein Zinn-Silber Lot, ein Zinn-Kupfer Lot, ein Nickel und Germanium enthaltendes Lot, insb. Nickel und Germanium enthaltendes Zinn-Silber-Lot, oder ein Indium- und/oder Wismut-haltiges Lot, insb. ein Indium- und/oder Wismut-haltigen Zinn-Silber-Lot ist.

Preferred embodiments of the pressure measuring device are characterized in that

• - the connecting leads are wires, in particular silver-plated or tin-plated copper wires, which have a wire diameter of the order of one or a few tenths of a millimeter, in particular a wire diameter of less than or equal to 0.3 mm,
• - The body has a diameter of greater than or equal to 1.5 cm, esp. From 1.5 cm to 3.5 cm and / or a thickness in the order of magnitude equal to several millimeters, esp. From 0.4 cm to 0.5 cm , having,
• the membrane has a membrane thickness greater than or equal to one tenth of a millimeter,
• the connections are arranged within a region of the membrane-remote end face of the main body which is surrounded on all sides by an outer sensor edge,
• - A holder is provided, on which the measuring electronics is arranged spaced from the pressure sensor, and / or
• the lead-free soft solder is a tin-silver-copper solder, a tin-silver solder, a tin-copper solder, a nickel and germanium-containing solder, especially nickel and germanium-containing tin-silver solder, or an indium and / or Bismuth-containing solder, in particular an indium and / or bismuth-containing tin-silver solder.

• 1, 4 und 7 zeigen jeweils ein Ausführungsbeispiel einer erfindungsgemäßen Druckmesseinrichtung;
• 2 zeigt: eine Ansicht der membran-zugewandten Stirnseite des Grundkörpers von 1;
• 3 zeigt: eine Ansicht der Innenseite der Messmembran von 1.
• 5 zeigt eine Ansicht der membran-abgewandten Stirnseite und 6 eine Ansicht der membran-zugewandten Stirnseite des Grundkörpers von 4;
• 8 zeigt: eine Ansicht der membran-abgewandten Stirnseite einer alternativen Ausführungsform des Drucksensors von 1; und
• 9 zeigt: eine Ansicht der membran-abgewandten Stirnseite des Drucksensors von 7.

The invention and its advantages will now be explained in more detail with reference to the figures of the drawing, in which three embodiments are shown. Identical elements are provided in the figures with the same reference numerals. Around To be able to represent elements of very different dimensions, a non-scale representation was chosen.

• 1 . 4 and 7 each show an embodiment of a pressure measuring device according to the invention;
• 2 shows: a view of the membrane-facing end face of the main body of 1 ;
• 3 shows: a view of the inside of the measuring membrane of 1 ,
• 5 shows a view of the membrane-facing end face and 6 a view of the membrane-facing end face of the main body of 4 ;
• 8th shows a view of the membrane-facing end side of an alternative embodiment of the pressure sensor of 1 ; and
• 9 shows: a view of the membrane-facing end face of the pressure sensor of 7 ,

The invention comprises a method for producing a pressure measuring device with a pressure sensor 1 and one to a capacitive, electromechanical transducer of the pressure sensor 1 connected measuring electronics 3 , 1 . 4 and 7 each show an embodiment of a pressure measuring device produced by the method according to the invention, the pressure sensor 1 a basic body 5 and one to form a pressure chamber 7 with the main body 5 pressure-tight connected, with a pressure to be measured p loadable diaphragm 9 includes. The main body 5 consists of ceramic, eg alumina. Optionally, the measuring diaphragm 9 made of ceramic, eg made of aluminum oxide.

body 5 and measuring membrane 9 are preferably by means of an outer edge of the measuring membrane 9 with an outer edge of the main body 5 connecting, the pressure chamber 7 outside on all sides surrounding joining 11 connected with each other. As a coincidence 11 esp. Is a metallic joint, which can be produced for example by means of an active brazing.

body 5 and measuring membrane 9 each have a function of a pressure measuring range of the pressure sensor 1 given dimensions. In that regard, the body can 5 Depending on the pressure measuring range, for example, a diameter of the order of magnitude greater than or equal to 1.5 cm, in particular of 1.5 cm to 3.5 cm, and a thickness in the order of greater than or equal to several millimeters, esp. From 0.4 cm to 0.5 cm. The measuring membrane 9 preferably has a membrane thickness greater than or equal to one tenth of a millimeter. To measure very high pressures can with appropriate increase in the thickness of the body 5 Membrane thicknesses of up to several millimeters can be used.

The pressure sensor shown here as an example 1 For example, it can be designed as an absolute pressure sensor, which points to an outside of the measuring diaphragm 9 acting pressure p metrologically recorded. In that case it is under the measuring membrane 9 enclosed pressure chamber 7 evacuated. Alternatively, the pressure sensor 1 be formed as a relative pressure sensor, the one on the outside of the measuring diaphragm 9 acting pressure p relative to one of the pressure chamber 7 about one through the main body 5 passing through, in 1 as an alternative dashed line pressure supply 13 supplied reference pressure p _ref detected. However, the invention can also be used analogously in conjunction with pressure measuring devices which comprise a capacitive, ceramic differential pressure sensor.

The pressure sensor 1 comprises a capacitive electromechanical transducer, which serves a from the on the measuring diaphragm 9 acting pressure p dependent deflection of the measuring membrane 9 to convert to an electrical size. The converter comprises one or more capacitors, of which at least one as a measuring capacitor with one of the pressure-dependent deflection of the measuring diaphragm 9 dependent measuring capacity C _p , is trained. The measuring capacitor shown here as an example comprises one on a membrane-facing end face of the main body 5 applied measuring electrode 15 and one on one of the main body 5 facing inside of the measuring diaphragm 9 arranged counter electrode 17 ,

Optionally, the converter may comprise at least one further capacitor. An example of this is an in 1 and 4 optional reference capacitor. This comprises in the illustrated embodiment, one on the membrane-facing end face of the main body 5 applied reference electrode 19 , which together with the counter electrode 17 forms the reference capacitor. The reference capacitor is preferably designed such that its reference capacitance C _R preferably no or only a very small dependence on the pressure-dependent deflection of the measuring membrane 9 having. This is achieved in the illustrated embodiment in that the reference electrode 19 is designed as an annular disk-shaped or ring segment disc-shaped electrode, which is the circular disk-shaped measuring electrode 15 surrounds the outside.

The measuring electronics 3 is designed to be the pressure to be measured p based on one of the measuring capacity C _P dependent auxiliary size C _V certainly. For example, this can only be done by the by means of the measuring electronics 3 recorded measuring capacity C _P be dependent auxiliary size. Preferably, however, one by means of the measuring electronics 3 to be determined by the measuring capacity C _P and the reference capacity C _R dependent auxiliary size C _V used. As auxiliary size C _V Insofar it is particularly suitable for this purpose from one to the measuring capacity C _p related difference of measuring capacity C _P and reference capacity C _R , dependent auxiliary size C _V, such as C _V = (C _P -C _R ) / C _P. Alternatively, however, another of the measuring capacity C _P and the reference capacity C _R dependent auxiliary size can be used.

In the manufacture of the pressure measuring device, the converter is connected to the measuring electronics 3 connected. In this case, for one or more components of the converter in each case on a membrane-remote end face of the base body 5 a connection electrically connected to the respective component 21 . 23 . 25 provided, which has a weichlötfähige surface. Subsequently these connections become 21 . 23 . 25 each with a lead-free soft soldering applied thereto 35 with one to the measuring electronics 3 connected connection cable 37 connected.

The connections 21 . 23 . 25 For example, you can use the measuring electrode 15 connected measuring electrode connection, one with the reference electrode 19 connected reference electrode terminal and / or one with the counter electrode 17 connected counter-electrode connection.

In the in 1 illustrated embodiment are serving as a measuring electrode connection terminal 21 and the terminal serving as a reference electrode terminal 23 each directly over a through the body 5 through through hole 27 connected to the associated electrode. The connection serving as counter-electrode connection 25 is about one through the main body 5 through through hole 27 with an on the membrane-facing end face of the body 5 applied electrically conductive connection 29 with the here necessarily electrically conductive joining 11 connected, in turn, in electrically conductive contact with the counter electrode 17 stands. As vias 27 are suitable for example in the main body 5 used metal pins, such as tantalum pins.

2 shows a view of the membrane-facing end face of the body 5 on the the measuring electrode 15 , the reference electrode 19 and the conductive connection 29 are applied. There are the positions of the vias 27 through points and in the pressure sensor 1 about the coincidence 11 with the measuring membrane 9 connected edge 31 the front side of the body 5 indicated by a dashed circle. 3 shows a view of the body 5 facing inside of the measuring diaphragm 9 on the the counter electrode 17 is applied, the outside to the over the Fufgung 11 with the main body 5 connected edge 33 the measuring membrane 9 borders.

The connections 21 . 23 . 25 For example, you can have one or more ports 21 . 23 . 35 each one using a Hartlots such. As a copper, silver and titanium soft solderable brazing alloy, on the body 5 having applied brazing. For this purpose, the brazing material can be applied, for example in the form of a paste, by means of a dispenser and brazed in a brazing process. In the illustrated embodiment, the braze offers the advantage that the electrically conductive connection to the through-holes formed here as a metal pin by brazing 27 and a pressure-tight seal of the vias 27 is achieved.

Alternatively or additionally, the connections 21 . 23 . 25 one or more connections 21 . 23 . 25 each include one using a braze on the base body 5 have applied brazing, in which on the brazing layers arranged on one another are provided. In that case, it suffices to obtain the soft solderable surface of the terminals 21 . 23 . 25 already out, if the uppermost layer has a weichlötfähige surface. These layers can, for example, by sputtering on the membrane-remote end face of the body 5 be applied. In that case, the layers of the respective terminal comprise 21 . 23 and or 25 Preferably, in each case serving as a primer primary layer, in particular a chromium-containing primary layer, one or more further layers, esp., One or more nickel and / or vanadium-containing further layers, and / or designed as oxidation protection weichlötfähige upper layer, especially a gold comprehensive upper class.

Alternatively or additionally, the connections 21 . 23 . 25 at least one connection 25 include, as part of one on the pressure sensor 5 applied coating 39 is formed, or on a partial area of the pressure sensor 5 applied conductive coating is arranged. 4 shows as an example, a pressure measuring device, which differs from the in 1 shown measuring device distinguished by the fact that the counter electrode 17 via the electrically conductive joint 11 electrically conductive with a on an outer circumferential surface of the pressure sensor 1 applied, electrically conductive coating 39 is connected, which differs from the coincidence 11 up to that on the membrane-remote end face of the body 5 arranged, serving as a counter-electrode connection terminal 25 extends. 5 shows a plan view of the membrane-remote end face of the body 5 from 4 , 6 shows a view of the membrane-facing end face of the body 5 from 4 in which the positions of the on the opposite, membrane-remote end face of the body 5 arranged connections 21 . 23 . 25 are marked by dots. In this embodiment, the coating 39 preferably a line-shaped extension 41 at the end of which here as part of the coating 39 trained connection 25 is arranged.

The coating 39 can eg - as shown here - as a relatively large-scale coating 39 be formed, which at the same time a shield of the pressure sensor 1 causes electromagnetic interference. At the in 4 illustrated embodiment, the coating extends 39 via an outer side outer surface of the pressure sensor 1 and an outer edge of the membrane-remote end face of the body 5 , The coating 39 For example, it may comprise a plurality of layers applied to one another, preferably a primary layer serving as adhesion promoter, in particular a chromium-containing primary layer, one or more further layers, in particular one or more nickel and / or vanadium-containing further layers, and / or one designed as oxidation protection soft solderable upper layer, in particular a gold-comprising upper layer, include. Alternatively, the coating 39 as a metallization on the body 5 applied, for example, sputtered coating 39 be educated. In this respect, the metallization is, in particular, a metallization of gold, a copper alloy, nickel or a nickel alloy. Alternatively, the coating 39 also be applied as a metallic paint, for example as a carbon or silver conductive paint.

If such a coating via one of the previously described, metal pins having vias 27 is to be connected to one of the components of the transducer is between via 27 and coating is preferably provided in each case a brazing, via which the electrically conductive connection to the via 27 takes place and at the same time a pressure-tight seal of the feedthrough 27 causes.

As a lead-free soft solder, for example, a tin-silver-copper solder, a tin-silver solder, a tin-copper solder, a nickel and germanium-containing solder, esp. A nickel and germanium-containing tin-silver solder, or indium and or bismuth-containing solder, in particular an indium and / or bismuth-containing tin-silver solder can be used.

The lead-free soft soldering 35 For example, can be generated manually or by means of a soldering robot by soft solder is supplied via a wire or a hollow wire and the respective connecting cable 37 is used in the molten solder. This creates soft soldering 35 with a substantially hemispherical shape. Alternatively, lead-free solder in the form of a solder paste can be dispensed onto the terminals by means of a dispenser 21 . 23 . 25 be applied, where it is then melted in a soldering process, such as reflow soldering. In this variant, the connecting cables 37 for example, by means of a placement machine on the associated connections 21 . 23 . 25 placed and by the melting of the soft solder with the respective connection 21 . 23 . 25 get connected. This creates soft soldering 35 with a substantially disc-shaped shape.

The lead-free soft soldering 35 differ from lead-containing soft soldering in particular by their creep strength, their thermal expansion coefficient, their elastic properties, as well as by having a higher melting temperature. By investigations of the applicant it could be shown that the lead-free soft soldering 35 Deformations of the per se planar surface of the membrane-facing end face cause when the measuring device to higher temperatures, such as temperatures of up to 70 ° C or even 125 ° C, heated. These temperature-dependent deformations occur in limited spatial areas of the membrane-facing end face of the body 5 on, which arranged on the membrane-facing end side soft soldering 35 are opposite. These deformations lead to temperature-dependent changes in the electrode spacing in the affected areas of the measuring capacitor, and if necessary. Also of the reference capacitor. Although the maximum amplitudes of these spatially limited deformations in parallel to the surface normal to the measuring membrane 9 extending direction are low, they can esp. When used in a wide temperature range, such as in a temperature range from - 10 ° C to + 70 ° C or from - 40 ° C to + 125 ° C, pressure measuring devices to a temperature-dependent hysteresis H perform the pressure measurements carried out with the measuring device, which is significantly greater than with identical, lead-containing soft soldering having pressure measuring devices.

This problem is inventively countered that in advance for at least one of the Weichlötungen 35 a temperature-dependent hysteresis H the auxiliary size C _V reducing and / or minimizing position on the membrane-remote end face of the body 5 certainly is, and each of these Weichlötungen 35 in the subsequent production of the pressure measuring device in each case at the position determined for them on the associated connection applied to this position 21 . 23 . 25 is produced.

The advantageous in this regard positions of the soft soldering 35 can be determined deductively, numerically, eg by simulation calculations, and / or experimentally. It offers by the appropriate positioning of Weichlötungen 35 achieved reduction and / or minimization of the temperature-dependent hysteresis H the pressure measuring device has the advantage that hysteresis-related and thus dependent on both the temperature and the time course of the temperature at the site and therefore not readily compensated measurement errors are correspondingly small. This leads to a significant improvement in the achievable measurement accuracy.

For pressure measuring devices, their measuring electronics 3 the pressure to be measured p based on a dependent of the capacities of at least two capacitors auxiliary size C _V determines the positions of the soft soldering 35 For this purpose, preferably determined such that their temperature-dependent influences on the individual capacities within the auxiliary size C _V at least partially compensate.

Regardless of the number of capacitors of the converter, the hysteresis H the auxiliary size C _V reducing and / or minimizing positions of the soft soldering 35 preferably determined by for at least one predetermined pressure p _i each carried out an optimization process in which the positions 35 the soft soldering 35 be determined to be the amount of a maximum difference ΔC _v (p _i ) between two at different times t1 and t2 at the same reference temperature T _ref certain auxiliary sizes C _V reduce and / or minimize, with a time-invariable pressurization of the pressure sensor 1 with the given pressure p _i occurs when the pressure sensor 1 a predetermined temperature range, eg a temperature range of -10 ° C to + 70 ° C or from - 40 ° C to + 125 ° C, covering temperature cycle passes. This maximum difference ΔC _v (p _i ) can be used for each to find the hysteresis H Positioning the soft soldering to be tested for reducing and / or minimizing positioning 35 eg determined experimentally. For this purpose, the pressure sensor 1 with a time-invariable pressurization with the respective predetermined pressure p _i at least once starting from a temperature corresponding to the temperature upper limit of the temperature range to a below the reference temperature T _ref lying temperature and cooled at least once, starting from one of the lower temperature limit of the temperature range corresponding temperature to one above the reference temperature T _ref heated temperature heats. During cooling, the reference temperature is reached at the time t1 of reaching T _ref the auxiliary quantity C _v (t1, p _i , T _ref ) and in the heating at time t2 of reaching the reference temperature T _ref the auxiliary quantity C _v (t 2, p _i, T _ref ) and then determines the maximum difference ΔCv (p _i ) as the amount of the difference of these two auxiliary quantities according to: ΔCv (p _i ) = IC _v (t 2, p _i , T _ref ) - C _v (t1, p _i , T _ref ) I determined.

The about the corresponding positioning of the soft soldering 35 achieved reduction and / or minimization of each of these maximum differences .DELTA.C _v (p _i ) causes a corresponding reduction and / or minimization of the hysteresis H (p _i ) of the pressure measuring device at the respective predetermined pressure p _i These hystereses H (p _i ) can be calculated, for example, as hystereses H (p _i ) normalized to the measuring span according to: H (p _i ): = ΔCv (p _i ) / min [IC _V (p _max , T _ref ) -C _V ( p ₀ , T _ref ) I]. Where Cv (p _max , T _ref ) one at a constant, a measuring range upper limit of the pressure measuring range corresponding to the pressure sensor 1 acting nominal pressure p _max specific value of the auxiliary quantity Cv. Analogously, C _V (p ₀ , T _ref ) designates a pressure sensor corresponding to a constant, a zero point of the pressure measuring range 1 acting zero point pressure p ₀ specific value of the auxiliary quantity Cv. Both values are preferably at the reference temperature T _ref certainly. Since the particular for determining the normalization factor values Cv (p _max, T _ref), C _V (p _0, T _ref) of the auxiliary variable Cv are respectively subject to hysteresis, in order to obtain an unambiguous definition is preferably the minimum for the given temperature range difference Min [ IC _V (p _max , T _ref ) - C _V (p ₀ , T _ref ) I used as normalization factor.

The one or more preset pressures p _i lie respectively within the measuring range of the pressure sensor 1 and preferably include the zero point pressure p ₀ , A pressurization of relative pressure sensors with the zero-point pressure p ₀ is always present when on the outside of the measuring diaphragm 9 the same pressure p ₀ which also acts in the pressure chamber 7 prevails. This offers the advantage that the optimization method at the zero point pressure p ₀ can be performed without the measuring diaphragm 9 is deflected from the initial position, and without the pressure sensor 1 with a pressure port for pressurizing and a pressure sensor 1 must be equipped in its position fixing bracket. The maximum difference ΔCv (p ₀ ) thus provides a measure of the influence of the positions of the soft soldering 35 on the hysteresis H not by other influences, such as the holder, on the pressure sensor 1 exerted forces is distorted.

In contrast, when pressure is applied to absolute pressure sensors with the zero point pressure p ₀ a vacuum pressure is applied to that in the evacuated pressure chamber 7 corresponds to prevailing pressure. To the result not by pressure-related, if necessary. Temperature-dependent voltages in the range of the measuring diaphragm 9 to falsify that can for the zero-point pressure p ₀ to be executed in absolute pressure sensors optionally also on the basis of the absolute pressure sensor identical sensors in which the pressure chamber 7 about one through the main body 5 passing through pressure supply line 13 with the outside of the measuring membrane 9 acting pressure p ₀ is charged.

Alternatively or additionally, the optimization method for at least one further predetermined pressure p _i , eg the nominal pressure p _max and / or further distributed over the pressure measuring range arranged pressures p _i be executed. If two or more for different preset pressures p _i executed optimization methods result in different positioning, is determined on the basis of these different positioning preferably in a subsequent further optimization step that positioning, with the lowest hysteresis in the entire measuring range H can be achieved.

To find the hysteresis H or the respective maximum difference ΔCv (p _i ) reducing and / or minimizing positions 35 the soft soldering 35 For example, the position determination method described below can be used. First, the dimensions of the soft soldering 35 established. Subsequently, in a first method step, start positions for all are in each case on one of the connections 21 . 23 . 25 to be applied soft soldering 35 specified. Subsequently, in a second method step, by varying the position, only one of the soft solderings is produced 35 one the hysteresis H reducing, preferably the hysteresis H Minimizing nominal position for this soft soldering 35 determined while all other soft soldering 35 remain on their starting position.

Optionally, in a third method step, additionally a desired position for at least one further soft soldering 35 be determined by repeating the first and the second process step, wherein as starting position for each of the soft soldering 35 for which a target position has already been determined, the respective target position is set. Optionally, in this case, iterative methods can be repeated by repeating the first and the second or all three method steps at least once, wherein in the first method step, respectively, the last determined desired positions as starting positions for the respective soft soldering 35 be used.

In conjunction with pressure measuring devices, their measuring electronics 3 the pressure to be measured p on the basis of the measuring capacity C _p and the reference capacity C _ref dependent auxiliary size C _v determined, the starting positions are preferably set such that the with the measuring electrode 15 connected connection 21 that with the measuring electrode 15 outside surrounding reference electrode 19 connected connection 23 and the one with the counter electrode 17 connected connection 25 arranged in a triangle. For this purpose, preferably three outgoing from the sensor center rays are defined, between each of which a predetermined angle, preferably an angle in the order of 120 °, is included. Subsequently, the starting positions are specified such that each of the three connections 21 . 23 . 25 is arranged in each case on one of the three beams in a starting position defining the distance to the sensor center. Subsequently, each time the second method step is executed, the position of the respective connection is determined 21 . 23 , respectively. 25 along the respective beam varies by the distance to the sensor center is changed.

For these pressure measuring devices, the in 2 and 5 shown positions of the connections 21 . 23 . 25 applied soft soldering 35 proved to be particularly advantageous. There are the with the counter electrode 17 connected connection 25 and the one with the reference electrode 19 connected connection 23 in each case on a substantially annular disk-shaped region of the membrane-remote end face of the main body 5 arranged, that of the measuring electrode 15 opposite region of the membrane-remote end face of the body 5 surrounds the outside. In addition, the one with the measuring electrode 15 connected connection 21 in an outer edge region of the measuring electrode 15 opposite region of the membrane-remote end face of the body 5 arranged. In this embodiment, the one with the reference electrode 19 connected connection 23 preferably in one of the reference electrode 19 opposite region of the membrane-remote end face of the body 5 arranged and the one with the counter electrode 17 connected connection 25 Preferably, it is arranged to have one inside and one outside of the reference electrode 19 opposite region of the membrane-remote end face of the body 5 arranged sub-area includes.

To the positions of the soft soldering 35 corresponding positions of the connections 21 . 23 . 25 during the optimization process, the position determination method and / or in the subsequent production of the pressure measuring device as free as possible, esp. Regardless of the positions of the bushings 27 To be able to vary, for example, they can each have an end face of the main body facing away from the membrane 5 applied wire 43 be connected to the associated component of the converter. 9 shows a view of the membrane-remote end of the pressure sensor 1 a modification of the pressure measuring device of 1 , There are the connections 21 . 23 . 25 each via a line 43 with the spaced therefrom, here along a diagonal of the circular disk-shaped body 5 juxtaposed vias 27 whose position is below the respective line 43 in 8th indicated by a dot. These lines 43 can, for example, analogous to those in 5 illustrated extension 41 with the end adjacent thereto connection 25 and / or applied as a coating and / or as a metallization in the manner described above.

Alternatively or in addition to process components of the optimization and / or positioning methods described above, in the production of pressure measuring devices according to the invention, however, it is also possible to proceed in such a way that the soft solderings 35 each in an area of the membrane-remote end face of the body 5 are arranged, on the membrane-facing front side of the body 5 an electrode-free region of the membrane-facing end face of the body 5 opposite.

7 shows a pressure measuring device that differs from the pressure measuring devices described above in that the capacitive transducer of the pressure sensor 1 includes only the measuring capacitor and the one with the measuring electrode 15 connected connection 21 and the one with the counter electrode 17 connected connection 25 each in a partial region of the membrane-remote end face of the main body 5 are arranged outside of the measuring electrode 15 opposite portion of the membrane-facing end face is located. 9 shows a plan view of the membrane-remote end face of the body 5 from 7 , In this embodiment, the measuring electrode 15 with the associated connection 21 over through the main body 5 through through hole 27 and a via 27 with the connection 21 connecting, on the membrane-remote end face of the body 5 applied wire 43 connected. Here is the line 43 preferably via a braze 42 with the via 27 connected. The brazing 42 can eg, as in 7 shown in the main body 5 be used.

With regard to the dimensions of soft soldering 35 are preferably soft soldering 35 used, each having a footprint of less than or equal to 2.1 mm ² . Here, the shape of the base is within essentially by the shape of the connecting cable 37 predetermined limits freely selectable. With regard to the desired minimization of the base area, the soft soldering 35 preferably a circular disk-shaped base with a diameter of less than or equal to 1, 6 mm. About this limitation of the base area of the lead-free soft soldering 35 and the necessarily associated volume reduction is both a limitation of the surface of the temperature-dependent deforming portions, as well as a limitation of the amplitudes of the deformations in parallel to the surface normal to the measuring membrane 9 running direction causes.

By numerical analyzes carried out by the applicant using finite element models, it has been possible to show that the limitation of the base area of the soft soldering according to the invention can be demonstrated 35 the amplitudes of the deformations particularly relevant for the capacitive pressure measurement in parallel to the surface normal to the measuring diaphragm 9 extending direction compared to identical pressure measuring devices with hemispherical Weichlötungen used today with conventional manner circular disk-shaped base surfaces with diameters greater than or equal to 2.5 mm can be reduced by a power of ten. The analyzes were performed in conjunction with capacitive pressure sensors 1 with ceramic bodies 5 with the previously mentioned commonly used dimensions that the maximum, in parallel to the surface normal to the measuring diaphragm 9 extending direction occurring amplitudes of the deformations by the above limitation of the base of the soft soldering 35 in a temperature range of - 40 ° C to + 125 ° C can be limited to values smaller than several 10 ^-6 mm. In comparison, the analyzes for otherwise identically constructed pressure measuring devices with hemispherical, lead-free soft soldering with a circular disk-shaped base area with a diameter of 2.6 mm in the same temperature range in parallel to the surface normal to the measuring membrane 9 extending direction occurring maximum amplitudes of the deformation in the order of up to several 10 ^-5 mm.

Considering these results compared to the electrode spacing between the measuring electrode 15 and counter electrode 17 of the measuring capacitor, as well as between the reference electrode 19 and counter electrode 17 , the usual way in the Order of magnitude 25 μm to 30 microns, and the electrode spacing of the measuring electrode 15 and counter electrode 17 depending on the on the measuring membrane 9 acting pressure p changing membrane stroke, depending on the pressure measuring range, membrane thickness and pressure-dependent deformable membrane surface of the pressure sensor 1 is within a range of less than or equal to 10 microns, it is clear that this limitation of the base area of the soft soldering 35 a further reduction of the temperature-dependent hysteresis H is achieved.

Both the limitation of the maximum amplitude of the deformations and the boundary surface of the deforming portions is the more pronounced, the smaller the base areas of the soft soldering 35 are. In this respect, the soft soldering 35 preferably a base area which is greater than or equal to, preferably substantially equal to, depending on the dimensions of the connection lines 37 predetermined, to achieve an electrically conductive, mechanically stable connection of the respective connecting cable 37 with the respective connection 21 . 23 . 25 required minimum area. With regard to the desired minimization of the base areas of the soft soldering 35 be used as connecting cables 37 preferably wires, such as silvered or tinned copper wires, used with a wire diameter in the order of one or a few tenths of a millimeter. Particularly preferred for this purpose wires are used with a wire diameter of less than or equal to 0, 3 mm. In connection with wires having a circular disk-shaped cross-sectional area, in view of the desired minimization of the base area of the solder joints 35 preferably soft soldering 35 used with circular disk-shaped base.

In addition, wires have a higher flexibility than rigid, e.g. column-shaped connecting lines, whereby an additional reduction of possibly caused by the construction and connection technology influences on the measurement accuracy is effected.

Weichlötungen 35 with a correspondingly small footprint are preferably generated by the fact that the connections 21 . 23 . 25 on which they are applied, each having a base area which is substantially equal to the base area of the soft soldering to be produced thereon 35 is. In that case, it serves the respective connection 21 . 23 . 25 Outer surrounding ceramic surface of the body 5 as a solder stop, which is a flow of liquid solder over the edge of the respective connection 21 . 23 . 25 prevented. In this case, as part of a conductive coating 39 trained connections 25 with terminals applied to a portion of a conductive coating 25 , as well as over one of the lines 43 connected to the associated component of the converter terminals 21 . 23 . 25 preferably such procedure that these connections at the end of the line 43 or at the end of the line-shaped extension 41 be arranged where the the respective connection 21 . 23 . 25 apart from that to the line 43 or the extension 41 adjacent area here on the outside, on all sides surrounding ceramic surface of the body 5 serves as a soldering stop. Alternatively, a solder stop layer can be applied to a region of the coating surrounding the respective connection on the outside or in the main body 5 a connection surrounding the outside of the groove is provided, which is a flow of the molten solder through the edge of the terminal 25 prevented.

A further improvement can optionally be achieved by additionally including the volume of the soft soldering 35 is minimized. For this purpose, the soft soldering 35 preferably as substantially disk-shaped soft soldering 35 formed, whose disc thickness is less than or equal to a 2 times the diameter of the connecting cables 37 is, where the thickness of the disc in particular greater than or equal to 1.5 times the diameter of the connecting cables 37 is.

With the method according to the invention, by means of the inventive positioning of the soft soldering 35 or alternatively by means of the positioning according to the invention and the dimensions of the dimensions described above, pressure measuring devices are produced which despite the use of lead-free soft solders in a predetermined temperature range, esp. A temperature range of - 10 ° C to + 70 ° C, preferably even from - 40 ° C to + 125 ° C, at least one of the predetermined pressures p _i , eg the zero point pressure p ₀ , or even in the entire pressure measuring range standardized on its span hysteresis H (p) of less than or equal to 0.04%, preferably less than or equal to 0.02%, more preferably even less than or equal to 0.01%.

In pressure measuring devices according to the invention are the soft soldering 35 preferably within an outside on all sides of an outer sensor edge 45 surrounded area of the membrane-remote end face of the body 5 arranged. That offers the advantage of being on the sensor edge 45 a sensor enclosure, clamping or mounting can be supported. 4 shows a housing as a possible embodiment 47 in which the sensor edge 45 with the interposition of a seal 49 between a paragraph 51 of the housing 47 and a counter bearing 53 , such as a pressure ring, in parallel to the surface normal on the measuring membrane 9 running direction is clamped. The housing 47 has front one, outside on all sides of the paragraph 51 surrounded opening 55 on, over which the measuring diaphragm 9 of the pressure sensor 1 with the pressure to be measured p can be acted upon.

In addition, pressure measuring devices according to the invention preferably include an in 4 only schematically illustrated holder 55 on which the measuring electronics 3 from the pressure sensor 1 is mounted spaced.

LIST OF REFERENCE NUMBERS

1

pressure sensor

3

measuring electronics

5

body

7

pressure chamber

9

measuring membrane

11

coincidence

13

pressure supply line

15

measuring electrode

17

counter electrode

19

reference electrode

21

connection

23

connection

25

connection

27

via

29

conductive connection

31

edge

33

edge

35

soft soldered

37

connecting cable

39

coating

41

extension

42

brazing

43

management

45

Sensor Edge

47

casing

49

poetry

51

paragraph

53

thrust bearing

55

bracket

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• DE 102013101315 A1 [0003, 0004]

Claims (15)

Method for producing a pressure measuring device, having - a pressure sensor (1) which has a measuring membrane (9) pressure-tightly connected to form a pressure chamber (7) with a ceramic base body (5) and a pressure to be measured (p) and a capacitive, comprises electromechanical transducer, wherein the transducer comprises one or more capacitors, of which at least one is a measuring capacitor with a dependent of one of the measuring diaphragm (9) pressure (p) dependent deflection of the measuring diaphragm (9) dependent capacity, and - a measuring electronics (3), which is designed such that it determines the pressure to be measured (p) on the basis of one of the measuring capacitance of the measuring capacitor dependent auxiliary size (C _V ), - in which the transducer is connected to the measuring electronics (3), wherein for a or a plurality of components of the transducer, each one having a weichlötfähige surface, electrically connected to the respective component composite ener connection (21, 23, 25) provided on a membrane-remote end face of the base body (5) and connected thereto via a lead-free soldering (35) with a connected to the measuring electronics (3) connecting line (37), characterized in that a temperature-dependent hysteresis (H) of the auxiliary variable (C _V ) reducing and / or minimizing position on the membrane-remote end face of the main body (5) is determined in advance for at least one of the soft solderings (35), and -any of these soft solderings ( 35) is generated in the subsequent production of the pressure measuring device in each case at the position determined for them on the associated at this position applied connection (21, 23, 25). Method according to Claim 1 , characterized in that the positions of the Weichlötungen (35) are determined such that they are each arranged in a region of the membrane-facing end side of the base body (5), on the membrane-facing end side of the base body (5) an electrode-free area the membrane-facing end face of the base body (5) opposite. Method according to Claim 1 Characterized in that - the auxiliary variable (C _V) being dependent on the capacity of at least two capacitors of the converter auxiliary variable (C _V), and - the positions of the Weichlötungen (35) are determined so that their temperature-dependent influences on the individual capacitances within the auxiliary variable (C _V ) at least partially compensate. Method according to Claim 1 or 3 , characterized in that for at least one predetermined pressure (p _i ), esp. A zero point of the pressure measuring range of the pressure sensor (1) corresponding zero-point pressure (p ₀ ), one of a measuring range upper limit of the pressure measuring range corresponding nominal pressure (p _max ) and / or at least one further within the measuring range of the pressure sensor (1) lying pressure (p _i ), in each case an optimization method is carried out in which the positions of the Weichlötungen (35) are determined such that they the amount of a maximum difference (.DELTA.C _v (p _i )) between two at different times (t1, t2) at the same reference temperature (T _ref ) certain auxiliary quantities (C _V ) reduce and / or minimize the at a fixed time pressure of the pressure sensor (1) with the respective predetermined pressure (p _i ) occurs when the pressure sensor (1) a a predetermined temperature range, esp. A temperature range of -10 ° C to + 70 ° C or vo n -40 ° C to + 125 ° C, passing through the covering temperature cycle. Method according to Claim 1 or 3 to 4 characterized in that: - the dimensions of the soft solderings (35) are determined, - in a first method step starting positions for all soft soldering (35) to be provided are specified, and - in a second method step by varying the position of only one of the soft solderings (35) the hysteresis (H) reducing and / or minimizing desired position for the respective soft soldering (35) is determined, while all other soft soldering (35) remain at their starting position. Method according to Claim 5 , characterized in that - in a third method step additionally a desired position for at least one further soft soldering (35) is determined by repeating the first and the second method step, wherein as starting position for each of the terminals (21, 23, 25) for which previously a desired position has already been determined, the respective desired position is set, - in particular such a procedure that the first and the second or all three process steps are repeated at least once, wherein in the first process step in each case the last determined Target positions are used as start positions for the respective Weichlötungen (35). Method according to Claim 5 to 6 , characterized in that - the connections (21, 23, 25) comprise a measuring electrode connection, a reference electrode connection and a counter-electrode connection, - the measuring electrode connection is electrically conductive with a measuring electrode (15) arranged on a membrane-facing end side of the basic body (5) , in particular a circular disk-shaped measuring electrode (15), which forms the measuring capacitor together with a counterelectrode (17) arranged on an inner side of the measuring diaphragm (9) facing the main body (5) and connected to the counterelectrode terminal. Connection electrically conductive with a on the membrane-facing end side of the base body (5) arranged reference electrode (19), esp. An annular or annular segment-shaped, the measuring electrode (15) outside surrounding the reference electrode (19) is connected to the on the Base body (5) facing the inside of the measuring diaphragm (9) arranged Gegenelektr ode (17) forms a reference capacitor, - the auxiliary variable (C _V) is one of the measuring capacitance (C _p) of the measuring capacitor and a reference capacitance (C _ref) of the reference capacitor dependent auxiliary variable (C _V), - at the first-time execution of the first process step three defined by the sensor center rays are defined, between each of which a predetermined angle, esp. An angle in the order of 120 °, is included, and the starting positions of the measuring electrode (15) connected to the terminal (21), with the reference electrode (19) connected terminal (23) and connected to the counter electrode (17) terminal (25) are predetermined such that each of the terminals (21, 23, 25) each on one of the three beams in a starting position defining the distance to the sensor center is arranged, and - in each execution of the second method step respectively the position to be varied of the respective soft soldering (35) entla ng of the respective beam is varied by their distance to the sensor center is changed. Method according to Claim 1 to 7 , characterized in that the soft soldering (35) are produced such that they each - have a base area of less than or equal to 2.1 mm ² , esp. A circular disk-shaped base area with a diameter of less than or equal to 1.6 mm, and / or - Are designed as a substantially disc-shaped Weichlötungen (35) whose disc thickness is less than or equal to 2 times a diameter of the connecting lines (37), wherein the thickness of the disc is esp. greater than or equal to 1.5 times the diameter of the connecting lines (37) , With a method according to Claim 1 to 8th manufactured pressure measuring device, characterized in that the pressure measuring device in a predetermined temperature range, esp. A temperature range of -10 ° C to + 70 ° C or from - 40 ° C to + 125 ° C, at least one of the predetermined pressures (p _i ) , in particular the zero-point pressure (p ₀ ), or in the entire measuring range a hysteresis (H (p)) normalized to one measuring span of less than or equal to 0.04%, in particular less than or equal to 0.02%, in particular less than or equal to 0 , 01%. Pressure measuring device according to Claim 9 , characterized in that at least one of the terminals (21, 23, 25) - has a base surface which is externally substantially surrounded on all sides by a ceramic surface of the base body (5), which is substantially equal to the base area of the soft soldering (35) produced thereon, - At the end of a on the base body (5) applied line (43) or a line-shaped extension (41) of a on the base body (5) applied coating (39) is arranged, where he apart from the to the line (43) or the extension (41) adjacent area on the outside, on all sides by the ceramic surface of the base body (5) is surrounded, or - outside of a solder stop layer or in the base body (5) provided groove is surrounded. Pressure measuring device according to Claim 9 to 10 , characterized in that the terminals (21, 23, 25) - one or more hard solder, esp. Of a brazing copper, silver and titanium brazing, applied to the base body (5) terminals (21, 23, 25) comprise, and / or - one or more terminals (21, 23, 25), each comprising a on the base body (5) applied brazing, on which one or more layers arranged on each other are arranged, wherein the layers esp Adhesion promoter serving primary layer, in particular a chromium-containing primary layer, one or more further layers, esp., One or more nickel and / or vanadium-containing further layers, and / or formed as an oxidation protective weichlötfähige upper layer, esp. and / or - at least one connection (25), which as part of a region of the pressure sensor (1) applied conductive, solderable Bes is formed (39) or arranged on a portion of a pressure applied to the pressure sensor (1) conductive coating. Pressure measuring device according to Claim 9 to 11 , characterized in that at least one of the connections (21, 23, 25) via a line (43) applied to the end face of the base body (5) remote from the membrane, a coating (39) applied to the base body (5) and / or a coating (39) applied through the base body (5) ) through passage (27) is connected to the associated component of the transducer. Pressure measuring device according to Claim 9 to 12 , characterized in that - the auxiliary variable (C _V ) one of the measuring capacitance (C _P ) of the measuring capacitor and the reference capacitance (C _ref ) of the reference capacitor dependent auxiliary size (C _V ), in particular a one on the measuring capacity (C _P ) the difference between the measuring capacitance (C _P ) and the reference capacitance (C _ref ) dependent auxiliary variable (C _V ), and - the terminals (21, 23, 25), namely the measuring electrode terminal, the counterelectrode terminal and the reference electrodes Are arranged in a triangle, - wherein the connected to the counter electrode (17) terminal (25) and connected to the reference electrode (19) connection (23) each on a region of the membrane-remote end face of the base body (5) are arranged, which surrounds one of the measuring electrode (15) opposite region of the membrane-remote end face of the base body (5) on the outside, and - wherein the connected to the measuring electrode (15) Ans Closure (21) in an outer edge region of the measuring electrode (15) opposite region of the membrane-remote end face of the base body (5) is arranged. Pressure measuring device according to Claim 13 , characterized in that - the connection (23) connected to the reference electrode (19) is arranged in a region of the membrane-remote end face of the base body (5) opposite the reference electrode (19), and - connected to the counter electrode (17) Terminal (25) comprises a within and outside of the reference electrode (19) opposite region of the membrane-remote end face of the base body (5) arranged portion. Pressure measuring device according to Claim 9 to 14 , characterized in that - the connecting leads (37) are wires, in particular silvered or tinned copper wires, which have a wire diameter of the order of one or a few tenths of a millimeter, in particular a wire diameter of less than or equal to 0.3 mm, - Base body (5) has a diameter of greater than or equal to 1.5 cm, in particular of 1.5 cm to 3.5 cm and / or a thickness in the order of magnitude greater than several millimeters, esp. From 0.4 cm to 0.5 cm, -, the measuring membrane (9) has a membrane thickness of greater than or equal to one tenth of a millimeter, - the terminals (21, 23, 25) within a outside of all sides of an outer sensor edge (45) surrounded region of the membrane-facing away - a holder (55) is provided, on which the measuring electronics (3) from the pressure sensor (1) is arranged spaced, and / or - the lead-free solder a tin-silver-copper solder, a Zi nn-silver solder, a tin-copper solder, a nickel and germanium-containing solder, esp. Nickel and germanium-containing tin-silver solder, or an indium and / or bismuth-containing solder, especially an indium and / or Bismuth-containing tin-silver solder is.

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