DE102008043567A1 - Pressure sensor e.g. absolute pressure sensor, for industrial measurement technique, has metal pin inserted into cylindrical opening and comprising pin end, which lies opposite to closing head and is alignably locked with end of opening - Google Patents

Abstract

The sensor has a circular disk shaped measuring membrane (5) connected with a base body (1) in a pressure-tight manner under formation of a measuring chamber (3) by a joint patch (7). A metal pin (15) is inserted into a cylindrical opening (13) and is made of tantalum. The pin has a pin end (21), which lies opposite to a closing head (19) and is alignably locked with an end (25) of the opening, where the opening end is turned away from the membrane. The base body and the membrane are made of ceramic or corundum. A metallic body is made of molybdenum-titanium-zirconium alloy. An independent claim is also included for a method for producing a pressure sensor.

Description

The The invention relates to a pressure sensor with a base body, one with the main body to form a measuring chamber pressure-tight connected by a joint measuring membrane, an electromechanical transducer that serves to provide a pressure dependent Deformation of the measuring diaphragm into an electrical primary signal to transform, and one leading through the body Primary signal path through which the converter electrically is connectable.

pressure sensors As used herein, absolute pressure sensors include the measure the absolute pressure of a measuring medium against vacuum, relative pressure sensors, which is the difference between the pressure in a measuring medium and the measure current atmospheric pressure, as well as differential pressure sensors, the one pressure difference between a first and a second Capture media print.

she find today widely used application in almost all Areas of industrial metrology.

Appropriate Pressure sensors are named by the Applicant under the name Cerabar manufactured and placed on the market.

These Pressure sensors preferably have ceramic base body and Membranes on, as ceramic for use in pressure measurement particularly advantageous thermal, chemical and mechanical properties has, inter alia, a high long-term stability the achievable measurement results and within a wide temperature ranges relatively stress-free installation of the Sensors in corresponding usually metallic sensor housing and / or allow process connections.

there the electrical connection of the converter typically takes place via a applied on the membrane-facing side of the body Electrode of the transducer and one in a cylindrical, through the Body through leading opening inserted metal pin. The electrical connection between metal pin and electrode is thereby effected, for example, that the cylindrical opening at the membrane-facing end a widening in a funnel shape in a membrane-facing direction Section has. The electrode of the transducer extends over the inner surface of this funnel. The electric Contact is made by fitting the metal pin accurately into the Basic body used and against a on the membrane-facing away Side of the body pressed abutment pressed becomes. This will be the opposite of the abutment End of the metal pin against the on the lateral surface of the Funnel applied electrode pressed. This cold welding causes a reliable electrical contact.

additionally becomes one between the metal pin and the cylindrical opening existing annular gap on the messmembran-opposite side of the body sealed by means of an active solder. To the electrical contact the over the metal pin extending primary signal path on the side facing away from the diaphragm by means of a soft solder connection To enable this, an active solder is used, the compatible with the subsequent soldering process is. For example, Ag-Cu active solders are suitable for this purpose. These solders However, they have a much lower soldering temperature as the active hard solder, which is preferred for joining the measuring membrane be used with the ceramic body. this leads to in addition to that when joining measuring diaphragm and body in a high vacuum soldering process until the soldering temperature is reached of the active braze used for this purpose components of the messmembran-facing side of the body applied Aktivlots different due to their different vapor pressure values evaporate strongly. As a result, on the one hand, the composition of Aktivlots adversely affect. For another, this can contamination of the active brazing solder or the brazier to be soldered Surfaces on the messmembran-facing side of the body respectively. It therefore remains only a narrow window of process parameters, where the production of these pressure sensors in the high vacuum soldering at all can be done.

A solution to this problem is in the filed on 07/07/2007 German patent application with the file number 10 2007 030 910.6 the applicant described. In this case, a recess adjacent to the cylindrical opening recess is provided in the base body on the side facing away from the diaphragm, which is closed by means of a metallic body. This metallic body has a flat surface facing the measuring chamber, which is mechanically connected to the main body and electrically conductively connected to the metal pin by means of a, an active braze having, the opening pressure-tight closing joint. The Weichlötfähigkeit this contact point is now given over the material of the metallic body or a corresponding coating thereof. Accordingly, the active solder for joining the metallic body and the base body no longer needs to be selected depending on the subsequent soldering process. It can now be used an active brazing, in which the above problems no longer occur. This is accomplished through the use of an active braze that has a brazing temperature that is no longer than 50 ° C, preferably not more than 25 ° C lower than that of the active brazing material, which is used for the addition of measuring membrane and body. Preferably, the same active brazing material is used for the two joints. Presently preferred are ternary active hard solders comprising a Zr-Ni alloy and titanium, as described for example in the EP 0 490 807 B1 are described.

Around Insert the metal pin precisely into the base body to be able to and a reliable electrical connection to be able to produce the electrode is here, however a relatively precise production of the basic body required. It must be ensured in particular be that the metal pin in no case protrudes into the measuring chamber. Since the distance between the base body and measuring diaphragm in Dependent on the measured membrane acting on the measuring membrane Pressure can be very low, this could possibly happen to an impairment of the pressure-dependent Deflection of the measuring membrane lead. For capacitive pressure sensors located on the base body facing inside the measuring membrane has a counter electrode, which together with the on the Base body applied measuring electrode a capacitor forms, whose pressure-dependent capacity is the actual Measuring signal of the converter forms. In this case, one could in the measuring chamber protruding metal pin at a sufficient large diaphragm displacement lead to a short circuit, which makes the pressure sensor useless.

ceramic Basic bodies are made today from a granulate, that is filled in a prefabricated form. Subsequently the granules are pressed, in which a correspondingly shaped press die is pressed into the mold precisely and it is the pressed Granules sintered.

On this way, the cylindrical, through the main body leading opening and an adjacent recess produce with very low manufacturing tolerances. It will be the cylindrical opening and the recess through the prefabricated Mold kept free of granules, and the punch has a flat Pressing surface on. By pressing any resulting inhomogeneities concentrate thereby usually on the the punch facing Top of the ceramic and can be retrofitted be removed by grinding. In order to also small tolerances of Thickness of the body is to be able to the reduction in thickness caused by the grinding appropriate grinding allowance taken into account.

Tries however, to make a body in the same way which has a cylindrical opening, one end of which widened funnel-shaped and at the other end a recess provided for the metallic body is, so occur significantly larger manufacturing tolerances on. Inhomogeneities, located at the two opposite Training body surfaces can Although these are also ground down, this leads to it to that the height of the recording of the metal pin inside the main body available standing interior, by the height of the cylindrical opening and the subsequent funnel-shaped Range is predetermined, can change. Accordingly each base body would have to be measured individually and the length of the metal pin to be adjusted accordingly. Alternatively, the main body without the recess be made for the metallic body and this recess subsequently while maintaining very low Manufacturing tolerances milled into the body become. Both methods are expensive and expensive and esp. For a series production in large numbers too cumbersome and too time consuming.

This Problem not only with ceramic bodies, but of course also with all other basic bodies, for cost reasons and / or production engineering Reasons not to produce high precision with very low manufacturing tolerances are.

It is an object of the invention, a pressure sensor of the aforementioned Specify type, in which the primary signal path also on time efficient cost effective way over a guided into the body inserted metal pin can be when the body manufacturing tolerances having.

• – einem Grundkörper,
• – einer mit dem Grundkörper unter Bildung einer Messkammer druckdicht mittels einer ersten Fügestelle verbundenen Messmembran, und
• – einem elektromechanischen Wandler, der dazu dient, eine druckabhängige Verformung der Messmembran in ein elektrisches Primärsignal umzuwandeln, bei dem
• – im Grundkörper eine zylindrische durch den Grundkörper führende Öffnung vorgesehen ist,
• – auf einer der Messmembran zugewandten Seite des Grundkörpers eine topfförmige, in die Öffnung mündende erste Ausnehmung vorgesehen ist, deren Innenfläche mit einer Elektrode des Wandlers ausgekleidet ist, und
• – ein Metallstift in die Öffnung eingesetzt ist,
• – der ein vollständig in der ersten Ausnehmung angeordnetes, zu einem Schließkopf verformtes Stiftende aufweist, das flächig auf der die Ausnehmung auskleidenden Elektrode aufliegt, und
• – dessen dem Schließkopf gegenüberliegendes Ende bündig mit einem von der Messmembran abgewandten Ende der Öffnung abschließt. Gemäß einer Weiterbildung
• – umfasst die erste Fügestelle ein Aktivhartlot,
• – ist auf einer von der Messmembran abgewandten Seite des Grundkörpers eine an die Öffnung angrenzende zweite Ausnehmung vorgesehen, und
• – ist die zweite Ausnehmung mittels eines metallischen Körpers verschlossen, der eine ebene, der Messkammer zugewandte Fläche aufweist, die mittels einer zweiten, ein Aktivhartlot aufweisenden, die Öffnung druckdicht verschließenden Fügestelle mechanisch mit dem Grundkörper und elektrisch leitend mit dem Metallstift verbunden ist.

For this purpose, the invention consists in a pressure sensor

• A basic body,
• - One with the main body to form a measuring chamber pressure-tight connected by a first joint measuring membrane, and
• An electromechanical transducer which serves to convert a pressure-dependent deformation of the measuring diaphragm into a primary electrical signal, in which
• A cylindrical opening leading through the main body is provided in the main body,
• A pot-shaped first opening opening into the opening is provided on a side of the base body facing the measuring diaphragm, the inner surface of which is lined with an electrode of the transducer, and
• A metal pin is inserted in the opening,
• - Which has a completely arranged in the first recess, deformed to a closing head pin end, the area on the Ausneh mung lining electrode rests, and
• - The opposite end of the closing head is flush with an end remote from the measuring diaphragm end of the opening. According to a development
• The first joint comprises an active hard solder,
• - Is provided on a side facing away from the measuring membrane side of the base body adjacent to the opening a second recess, and
• - The second recess is closed by means of a metallic body having a planar, the measuring chamber facing surface which is mechanically connected by means of a second, an active braze, the opening pressure-tight closing joint mechanically connected to the base body and electrically conductive to the metal pin.

According to one preferred embodiment, the metal pin made of tantalum.

According to one Another preferred embodiment is the metallic body made of a Mo-Ti-Zr alloy, and the first and second joints include a ternary active hard solder, esp. a Zr-Ni Alloy and Ti exhibiting active brazing alloy.

According to one Another embodiment, the main body and the Measuring diaphragm made of ceramic, especially of corundum.

• – ein Widerlager am Grundkörper angesetzt wird, dass bündig mit dem von der topfförmigen Ausnehmung abgewandten Ende der Öffnung abschließt,
• – ein Metallstift derart in die Öffnung eingesetzt wird, dass er auf dem Widerlager aufsitzt und in die topfförmige Ausnehmung hinein ragt, und
• – der Metallstift mittels eines Pressstempels derart gegen das Widerlager gepresst wird, dass dessen in die topfförmige Ausnehmung hinein ragendes Stiftende derart verformt wird, dass es den Schließkopf bildet, der flächig auf der die Ausnehmung auskleidenden Elektrode aufliegt.

Furthermore, the invention comprises a method for producing a pressure sensor according to the invention, in which

• - An abutment is attached to the base body that is flush with the end remote from the pot-shaped recess end of the opening,
• - A metal pin is inserted into the opening such that it rests on the abutment and protrudes into the cup-shaped recess, and
• - The metal pin is pressed by means of a ram against the abutment such that its protruding into the cup-shaped recess pin end is deformed such that it forms the closing head, which rests flat on the recess lining the electrode.

The Invention and its advantages will now be described with reference to the figures of the drawing, in which an embodiment is shown, closer explained. The same elements are in the figures with the provided the same reference numerals.

1 shows a section through a pressure sensor according to the invention;
and

2 shows the main body of the pressure sensor of 1 together with an abutment and a metal pin inserted against the abutment in the body.

1 shows a section through a pressure sensor according to the invention with a substantially cylindrical body 1 and one with the main body 1 forming a measuring chamber 3 pressure-tight connected circular disk-shaped measuring diaphragm 5 , Depending on the objective of the pressure sensor prevails in the measuring chamber 3 another back pressure to one on the outside of the measuring diaphragm 5 acting pressure p. In a relative pressure sensor, the back pressure is the atmospheric pressure in the vicinity of the sensor, which via a reference pressure not shown here in the measuring chamber 3 is initiated. For an absolute pressure sensor, the measuring chamber is 3 evacuated accordingly. body 1 and measuring membrane 5 are preferably made of ceramic, esp. Of corundum. The measuring membrane 5 and the main body 1 are at the edge by means of a joint 7 pressure-tight and gastight connected. This defines the joint 7 the distance between the measuring membrane 5 and the body 1 , For this joint 7 Preferably, an active brazing material is used. Particularly preferred are the ternary active hard solders mentioned at the beginning which have a Zr-Ni alloy and titanium.

The measuring membrane 5 is pressure-sensitive, ie a pressure p acting on it causes a deflection of the measuring diaphragm 5 from their rest position. The pressure sensor has an electromechanical transducer, which serves for a pressure-dependent deformation of the measuring diaphragm 5 to convert into a primary electrical signal. Capacitive or resistive converters are suitable for this purpose, for example. In the illustrated embodiment of a capacitive pressure sensor, the transducer comprises one on one of the measuring membrane 5 facing side of the body 1 applied electrode 9 and one on the inside of the measuring membrane 5 arranged counter electrode 11 , electrode 9 and counter electrode 11 form a capacitor whose capacity depends on the pressure-induced deflection of the measuring diaphragm 5 changes. The pressure-dependent capacity or its change is via a to the electrode 9 and the counter electrode 11 connected, not shown here measuring circuit detected and converted into a pressure-dependent measurement signal that is then available for display, for further processing and / or evaluation.

The electrode 9 gets over one through the main body 1 electrically outwardly guided primary signal path. This is in the main body 1 a cylindrical through the main body 1 through the opening 13 provided, in the one metal pin 15 is used. The metal pin 15 is preferably made of the same material as the electrode 9 , preferably tantalum.

On the measuring membrane 5 facing side of the body 1 is a cup-shaped recess 17 provided in the opening 13 opens and their inner surface with the electrode 9 of the converter is lined. The metal pin 15 has a completely in the cup-shaped recess 17 arranged to a closing head 19 deformed pin end, the surface on the recess 17 lining electrode 9 rests, and its the closing head 19 opposite end of the pencil 21 flush with one of the measuring membrane 5 opposite end 25 the opening 13 concludes.

In the production of these pressure sensors according to the invention is thereby moved such that an abutment 23 at the base body 1 is set flush with that of the cup-shaped recess 17 opposite end 25 the opening 13 concludes. This is in 2 shown. The abutment 23 closes the opening 13 flush. Subsequently, the metal pin 15 so in the opening 13 used that one of a pen end 21 on the abutment 23 seated and the other end of the pen 27 in the cup-shaped recess 17 protrudes into it. The supported in this way metal pin 15 is now using a press stamp 29 so against the abutment 23 pressed that in the cup-shaped recess 17 protruding pin end 27 is deformed such that it, as in a rivet, the closing head 19 forms, which then flat on the recess 17 lining electrode 9 rests. The pressing of the closing head 19 causes cold welding between the electrode 9 facing, the opening mouth radially enclosing bottom of the closing head 19 which provides a reliable electrical connection to the electrode 9 arises.

Due to the cup-shaped recess 17 and the deformation of the pin end 27 in the closing head 19 It is possible, quite considerable tolerances of the dimensions of the body 1 compensate. This advantage naturally applies first and foremost to tolerances in the height of the opening 13 and the height of the cup-shaped recess 17 , On the one hand is through the abutment 23 made sure the pen end 21 precisely flush with the opening 13 concludes. On the other hand, by the cup-shaped recess 17 and the deformation of the pin end 27 in the closing head 19 made sure the metal pin 15 Even with strong deviations of the basic body dimensions of the predetermined nominal dimensions enough space for receiving the possibly excess metal pin length is available. This will ensure that the metal pin 15 does not survive and thus never with the measuring diaphragm 5 come into contact. This makes it possible, in series production for all sensors, metal pins 15 to use a predetermined length. A precise measurement of the actual basic body dimensions and / or an adjustment of the pin length is not required.

Of course, this advantage of tolerance compatibility also applies with regard to the diameter of the opening 13 , The diameter only has to be the insertion of the metal pin 15 but he does not have to fit the diameter of the metal pin 15 Be tuned, as the electrical contact does not exceed the cylindrical portion of the metal pin 15 takes place, but over the automatically through the press in the form adapted closing head 19 , In this case, by the pressure of the final shape of the closing head 19 also unevenness of the bottom surface of the cup-shaped recess 17 , which inevitably leads to bumps of the electrode 9 take into account in this area.

Another advantage of the cup-shaped recess 17 is that the electrode 9 can be easily applied by sputtering.

For the reasons explained in the introduction, the invention can be used particularly advantageously in conjunction with a pressure sensor in which the measuring diaphragm is used 5 opposite side of the body 1 one to the opening 17 adjacent second recess 31 is provided, by means of a metallic body 33 is closed. The metallic body 33 has a plane of the measuring chamber 3 facing surface, by means of a second having a Aktivhartlot the opening 13 pressure tight closing joint 35 mechanically with the main body 1 and electrically conductive with the metal pin 15 connected is. Preferably, for this joint 35 the same active brazing used that also for the joint 7 between the measuring membrane 5 and the body 1 is used. The metallic body 33 is preferably a circular disc-shaped metal plate, for. B. a metal plate with a thickness of about 200 microns and a diameter of about 4 mm, and serves as a soft solder contact point. For this purpose, it consists either of a material which is suitable as such for a soft soldering, or it has a corresponding coating. For example, tungsten or an alloy containing molybdenum and copper or molybdenum, titanium and zirconium is suitable for this purpose. Preferably, a metallic body 33 used in a Mo-Ti-Zr alloy, on its outwardly facing surface of a 2 micron thick Ni layer is applied, which is protected with a 10 nm thick Au layer against oxidation. Before applying the Ni layer, the surface was pretreated by sputter etching. About this soft solder contact point further circuits can be connected to the electromechanical transducer be sen. The production of these soft solder contacts can also be done in automated processes. Under protective gas can be dispensed with flux here if necessary.

1

body

3

measuring chamber

5

measuring membrane

7

first joint

9

electrode

11

counter electrode

13

opening

15

metal pin

17

cup-shaped recess

19

closing head

21

the Closing head opposite pin end

23

abutment

25

The End the opening

27

in the recess protruding pin end

29

press die

31

recess

33

metallic body

35

second joint

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102007030910 [0008]
• - EP 0490807 B1 [0008]

Claims (6)

Pressure sensor with - a basic body ( 1 ), - one with the main body ( 1 ) to form a measuring chamber ( 3 ) pressure-tight by means of a first joint ( 7 ) connected measuring membrane ( 5 ), and - an electromechanical transducer, which serves, a pressure-dependent deformation of the measuring diaphragm ( 5 ) into an electrical primary signal, in which - in the main body ( 1 ) a cylindrical through the body ( 1 ) leading opening ( 13 ), - on one of the measuring diaphragms ( 5 ) facing side of the body ( 1 ) a pot-shaped, in the opening ( 13 ) opening first recess ( 17 ) is provided, the inner surface with an electrode ( 9 ) of the transducer is lined, and - a metal pin ( 15 ) in the opening ( 13 ) is inserted, - the one completely in the first recess ( 17 ), to a closing head ( 19 ) deformed pin end ( 27 ), which is flat on the recess ( 17 ) lining electrode ( 9 ) rests, and - whose the closing head ( 19 ) opposite end of the pen ( 21 ) flush with one of the measuring membrane ( 5 ) facing away from the end ( 25 ) of the opening ( 13 ) completes. Pressure sensor according to claim 1, in which - the first joint ( 7 ) comprises an active brazing material, - on one of the measuring membrane ( 5 ) facing away from the body ( 1 ) one to the opening ( 13 ) adjacent second recess ( 31 ), and - the second recess ( 31 ) by means of a metallic body ( 33 ), which is a flat, the measuring chamber ( 3 ) facing surface, which by means of a second, an active braze having, the opening ( 13 ) pressure-tight closing joint ( 35 ) mechanically with the main body ( 1 ) and electrically conductive with the metal pin ( 15 ) connected is. Pressure sensor according to claim 1, wherein the metal pin ( 15 ) consists of tantalum. Pressure sensor according to claim 1, in which the metallic body ( 33 ) consists of a Mo-Ti-Zr alloy, and the first and the second joint ( 7 . 35 ) comprises a ternary active brazing material, in particular an active brazing material comprising a Zr-Ni alloy and Ti. Pressure sensor according to Claim 1, in which the basic body ( 1 ) and the measuring membrane ( 5 ) made of ceramic, esp. Made of corundum exist. Method for producing a pressure sensor according to one of the preceding claims, in which - an abutment ( 23 ) on the base body ( 1 ) is assumed to be flush with that of the cup-shaped recess ( 17 ) facing away from the end ( 25 ) of the opening ( 13 ), - a metal pin ( 15 ) in the opening ( 13 ) is inserted on the abutment ( 23 ) and in the cup-shaped recess ( 17 ), and - the metal pin ( 15 ) by means of a press ram ( 29 ) so against the abutment ( 23 ) is pressed, that in the cup-shaped recess ( 17 ) end of the pin ( 27 ) is deformed such that it is the closing head ( 19 ), which flat on the recess ( 17 ) lining electrode ( 9 ) rests.