DE102007037169A1 - Pressure sensor for use in pressure transducer, has cap that is mechanically fastened to ceramic decoupling structure and attached to primary signal path by galvanic contact, and ceramic measuring diaphragm - Google Patents

Abstract

The sensor (1) has a ceramic measuring diaphragm (3), which is pressure-tightly connected to a ceramic base (2). A transducer changes pressure-dependent deformation of the diaphragm into an electrical primary signal. A primary signal path extends from the transducer to a base rear side (11), where the rear side is turned away from the diaphragm. A signal preprocessing device is attached to the path. A ceramic decoupling structure (20) has a contact surface overlying on the base. A cap (18) is mechanically fastened to the decoupling structure and attached to the path by a galvanic contact (16). An independent claim is also included for a pressure transducer.

Description

The The present invention relates to a pressure sensor, in particular a Pressure sensor with a ceramic base body and a ceramic measuring membrane, as well as a pressure transducer with a metallic Sensor housing and such a ceramic pressure sensor, which is clamped in the sensor housing.

pressure sensors As used herein, absolute pressure sensors and relative pressure sensors include which the absolute pressure of a medium against vacuum or the Difference between the pressure in a medium and the current atmospheric pressure measure up. Furthermore, the pressure sensors according to the invention include Differential pressure sensors, which the pressure difference between a capture first and second media print.

One generic pressure sensor comprises a ceramic Main body and at least one ceramic measuring membrane, forming a measuring chamber with the main body pressure-tight, and a transducer for converting a pressure-dependent Deformation of the measuring diaphragm into a primary electrical signal, and a primary signal path extending through the body extends. The converter may, for example, be a capacitive or to be a resistive transducer. The primary signal path comprises usually at least one electrical feedthrough through the main body. To the primary signal path a signal pre-processing device is connected, the analog and may include digital circuit elements. The signal preprocessing device is preferably tightly sealed to the circuit elements To protect moisture. The capsule can, for example a housing body and a lid made of metal or ceramic include.

A pressure sensor with such an encapsulated signal preprocessing device is for example in the published patent application DE 103 26 975 disclosed. Although the solution described there is fundamentally viable, problems still have to be identified. For example, the connection of the contact wires of the signal preprocessing device to the primary signal path is possible only in the manual soldering method.

Farther Here is a conflict of objectives regarding the length of the Connection wires given. In the sense of a mechanical decoupling between the main body and the capsule should be the wires on the one hand, be long and winding. On the other hand, growing the moisture sensitivity of the pressure sensor with increasing length the wires. A mechanical decoupling is desirable because For example, an adhesive with which the capsule on the body is glued, swells under water absorption and insofar too mechanical Tension between the body and the capsule lead can. These mechanical stresses can be repercussions have on the measuring signal of the pressure sensor.

In that regard, as the pressure sensors usually in a metallic Sensor housing are axially clamped, it is advantageous if between the main body of the pressure sensor and a acting on the back of the sensor facing away from the diaphragm metallic clamping screw a ceramic decoupling body is intended to particular influences of mechanical Tensions due to the different thermal expansion coefficients to eliminate the measurement signal. This decoupling ring has in With regard to an optimized decoupling, such a material thickness, that he uses the space required by the capsule of the signal preprocessing device collided.

The publication DE 102 00 780 A1 discloses a ceramic relative pressure sensor in which a ceramic Entkopplungskörper is designed as a pot, and the otherwise unencapsulated signal pre-processing device, which is arranged on the back of the body to protect. Some limitations of this solution are in the DE 103 26 975 named. Above all, mechanical stresses between the base body and the decoupling body are to be expected, since the latter has to be glued or soldered to the base body along the circumference in order to protect the signal pre-processing device from moisture.

It Therefore, the object of the present invention, an improved To provide pressure sensor and a pressure transducer with such a pressure sensor.

The The object is achieved by the pressure sensor according to the independent claim 1 and the pressure transducer according to the independent Patent claim 8.

The pressure sensor according to the invention comprises a ceramic base body and at least one ceramic measuring membrane, which is pressure-tightly connected to the base body to form a measuring chamber; a transducer for converting a pressure-dependent deformation of the measuring diaphragm into a primary electrical signal; a primary signal path extending from the transducer through the body to a backside of the body remote from the gauge diaphragm; a signal preprocessing means disposed in a capsule, the input of which is connected to the primary signal path; and
a ceramic decoupling body with a Bearing surface, for resting on the back of the body; characterized in that the capsule is mechanically fastened to the decoupling body, and is connectable or connected to the primary signal path by means of at least one galvanic contact.

The Measuring diaphragm and the main body are preferably with a Active brazing material along a circumferential first joint together.

The Measuring diaphragm, the main body and the decoupling body have - apart from functional designs - preferably an axisymmetric basic structure.

Of the At least one galvanic contact may be presently preferred Embodiment of the invention comprise a connector coupling. in this connection are basically connector couplings with spring contacts or suitable with cutting contacts, those with spring contacts currently preferred.

A Connector coupling has a main body side connector element and a capsule-side connector element, wherein the connector elements preferably gold plated.

The Connector elements are preferably aligned so that a galvanic plug contact of a connector coupling is closed, by the decoupling body with its bearing surface aligned with the back of the main body and mounted aligned parallel to this on the body becomes.

In a presently preferred embodiment of the invention, the Entkopplungskörper an annular bearing surface and a stiffening plate axially spaced from the support surface and runs substantially parallel to this.

In a development of this embodiment of the invention, the Stiffening plate on a breakthrough, with the capsule through extends the breakthrough. The extension of the capsule in axial Direction of the pressure sensor is more than the third root of the capsule volume, preferably more than 1.5 times the third Root of the capsule volume, and more preferably more than double the third root of the capsule volume.

The Capsule is preferably by soldering to the decoupling body mechanically fixed. This can be, for example, in the area of the breakthrough respectively.

In In another embodiment of the invention, the decoupling body comprises a flat cylindrical ceramic disc with a breakthrough, in which the capsule is fixed. In this case, the back side points of the main body along its circumference a circumferential Stiffening ring on which protrudes axially, and on which the decoupling body rests with a support surface.

Of the Primary signal path is in a preferred Embodiment of the invention of the converter in a section through an opening through the body with the opening is closed by a metallic body, the has a substantially planar surface facing the measuring chamber is, and by means of an opening enclosing second joint by means of an active brazing pressure-tight is joined to the main body.

Preferably, the second joint has the same active brazing material as the first joint. Presently preferred are ternary active braids having a Zr / Ni alloy and Ti and in EP 0 490 807 B1 are described.

In a development of the invention, the metallic body a surface facing away from the measuring chamber, by means of a soft solder is contactable. For this purpose, the remote from the measuring chamber Surface of the metallic body possibly one have metallic coating, for example a Ni layer, which may be gold plated for protection against oxidation. The metallic one Coating or the Ni layer has, for example, a thickness of not less than 0.5 μm, preferably not less than 1 μm. In a currently preferred embodiment the layer thickness about 2 microns. The gold layer can have some 10 nm, for example 20 nm.

Of the Metal body may be, for example, tungsten or an alloy comprising molybdenum and copper or molybdenum, Contains titanium and zirconium. When choosing the material is on it to pay attention that the thermal expansion coefficient to the the basic body material or the active brazing fits, wherein a complete match of the coefficients of thermal expansion is not mandatory. It is enough if the different thermal expansion does not lead to failure of the solder joint. Currently preferred is a Mo-Ti-Zr alloy, which under the name TZM is available from the companies Goodfellow and Plansee.

Of the Metal body, for example, circular disk-shaped be formed, and in a matching recess in a surface the body are inserted, the opening in the recess opens.

The electrical conductor can, for example a metal pin, in particular a Ta pin extending from the transducer through the opening to the second joint. In another embodiment, the electrical conductor comprises a coating of the opening wall containing glass and at least one noble metal element. Irrespective of the choice of material of the electrical conductor, a sufficient contacting of the second joint is to be ensured, since the primary signal path extends over the second joint and the metallic body.

On the transducer facing away from the surface of the metallic Body is a first connector element of the connector coupling fastened, for example by soldering, in particular by Soldering under inert gas. The complementary connector element is suitably fixed to the capsule.

Of the Pressure sensor according to the invention thus offers the Possibility for modular production, since the assembly the actual measuring cell, consisting of the main body, the measuring diaphragm and the transducer, practically for the final assembly of the pressure transducer can be done by simply placing a prefabricated module.

Of the Pressure transducer according to the invention comprises a metallic Housing with a sensor chamber containing a media port and a pressure sensor according to the invention, which is axially clamped in the housing, wherein the measuring membrane via the media opening can be acted upon by a pressure to be measured is.

The Axial clamping takes place for example by means of a clamping ring, which is screwed into the housing and indirectly or rests directly on the decoupling body. Between the media opening and the measuring membrane is preferably one clamped annular seal assembly. To the axial Contains compensation for thermal expansion differences the pressure transducer preferably an at least axially elastic Element. This can for example by an elastic seal assembly be realized or by a spring between the clamping ring and the decoupling body is clamped. Between each adjacent, axially clamped elements can provide sliding layers be, for example in the form of PTFE films.

The The invention will now be described with reference to an embodiment shown in the drawing explained. It shows.

1 : a longitudinal section through a pressure sensor according to the invention.

The in 1 illustrated pressure sensor 1 includes a cylindrical body 2 , and a circular disk-shaped measuring diaphragm 3 , both of which have corundum as the material. The main body 2 and the measuring membrane 3 are by means of a circumferential joint 4 pressure-tightly joined together, passing through the joint 4 comprising an active hard solder, the distance between the measuring diaphragm and the base body is defined.

Between the measuring membrane 3 and the body 2 is a measuring chamber formed in which, depending on the objective of the pressure sensor, a different back pressure prevails to a force acting on the outside of the measuring diaphragm pressure. In a relative pressure sensor, the back pressure is the atmospheric pressure in the vicinity of the sensor, which is introduced into the measuring chamber via a channel, not shown here. In an absolute pressure sensor, the back pressure should be negligible, the measuring chamber is evacuated accordingly.

The pressure sensor 1 includes a capacitive transducer. The capacitive converter comprises a measuring electrode 5 on the measuring chamber side surface of the measuring diaphragm 3 that over the joint 4 is contacted, and at least one counter electrode 6 on the measuring chamber side end face of the body 2 which is contacted via an electrical conductor extending through an opening 7 extending from the measuring chamber substantially in the axial direction through the main body 2 runs.

The electrical conductor comprises a conductive layer containing glass and at least one noble metal element, for example gold and / or platinum. The layer material is in the opening as a paste 7 introduced and baked. The measuring electrode and the counter electrode may have substantially the same material as the electrical conductor.

The opening 7 is with one by means of a Aktivhartlotplättchens 8th joined, circular disk-shaped metal plates 9 closed, which has a thickness of about 200 microns and a diameter of about 4 mm. The metal plate 9 includes a Mo-Ti-Zr alloy.

To the positioning of the Aktivhartlotplättchens 8th , and the metal plate 9 To facilitate, is in the back face 11 of the basic body 2 a recess 10 provided in which the opening 7 empties.

The metal plate 9 has as soft solder contact point on its the opening 7 opposite surface of a 2 micron thick Ni layer 12 protected against oxidation by a 10 nm Au layer. Before applying the Ni layer wur de pretreated the surface by means of plasma etching. At the thus prepared contact point 12 is a first connector element of a connector coupling 16 soldered. The complementary second connector element is on a hermetically sealed ceramic capsule 18 attached and to the entrance of one in the capsule 18 arranged signal preprocessing connected. The capsule 18 extends through a breakthrough in a disk-shaped, ceramic decoupling body 20 , and is by means of soldering points in the region of the breakdown at the decoupling body 20 attached. The decoupling body 20 lies with its annular bearing surface loose on a stiffening ring 14 on top of the back of the main body 2 protrudes in the axial direction.

To connect the signal preprocessing circuit in the capsule 18 So only the appropriately populated decoupling ring 20 be placed on the back of the body, whereby the at least one or more connector couplings close a contact between the primary signal path and the input of the signal preprocessing device.

From the signal preprocessor lines extend 22 to a higher-level unit, for example, the main electronics of a transmitter in which the preprocessed measurement signals are further processed and conditioned, for example, for communication via a fieldbus or a current loop.

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 10326975 A [0004]
• - DE 10200780 A1 [0007]
• - DE 10326975 [0007]
• EP 0490807 B1 [0021]

Claims (16)

Pressure sensor ( 1 ), comprising: a ceramic base body ( 2 ) and at least one ceramic measuring membrane ( 3 ), which is connected pressure-tight with the base body to form a measuring chamber; a transducer for converting a pressure-dependent deformation of the measuring diaphragm into a primary electrical signal; a primary signal path extending from the transducer through the body to a backside of the body remote from the gauge diaphragm; one in a capsule ( 18 ) arranged Signalvorverarbeitungseinrichtung whose input is connected to the primary signal path; and a ceramic decoupling body with a bearing surface, for resting on the back ( 11 ) of the basic body ( 2 ); characterized in that the capsule ( 18 ) on the decoupling body ( 20 ) and to the primary signal path by means of at least one galvanic contact ( 16 ) is connected or connected. Pressure sensor according to claim 1, wherein the measuring diaphragm and the base body with an active braze along a circumferential first joint are joined. Pressure sensor according to claim 1 or 2, wherein the at least a galvanic contact comprises a connector coupling. A pressure sensor according to claim 3, wherein the connector coupling a main body side connector element and a capsule side Having connector element. Pressure sensor according to one of the preceding claims, wherein the decoupling body is an annular Support surface and a stiffening plate, the axially spaced from the support surface and parallel to it runs. A pressure sensor according to claim 5, wherein the stiffening plate has a breakthrough, and the capsule through the breakthrough extends. Pressure sensor according to one of claims 1 to 4, wherein the decoupling body is a flat cylindrical ceramic disk with a breakthrough in which the capsule is fixed, further wherein the back of the body along its periphery has a circumferential stiffening ring, the axial protrudes, and on which the decoupling body with a Bearing surface rests. Pressure sensor according to claim 6 or 7, wherein the extension the capsule in the axial direction of the pressure sensor more than the third Root of the capsule volume, preferably more than 1.5 times the third Root of the capsule volume, and more preferably more than double the third root of the capsule volume is. Pressure sensor according to one of the preceding claims, the capsule being soldered to the decoupling body mechanically fixed. Pressure sensor according to one of the preceding claims, the primary signal path from the converter in a section passing through an opening through the body, wherein the opening by means of a metallic body is closed, which is a substantially flat surface has, which faces the measuring chamber, and by means of a the opening enclosing second joint joined by means of an active brazing pressure-tight with the body is. Pressure sensor according to claim 10, wherein the metallic Body facing away from the measuring chamber surface having a metallic coating, for example a Ni layer to allow a soft soldering contact. Pressure sensor according to claim 10 or 11, wherein the Metal body tungsten or have an alloy, the Molybdenum and copper or molybdenum, titanium and zirconium contains. Pressure sensor according to one of claims 10 to 12, wherein the electrical conductor is a coating of the opening wall comprising glass and at least one noble metal element. Pressure sensor according to one of claims 10 to 13, wherein on the surface facing away from the transducer of the Metallic body, a first connector element of Connector coupling is attached. Pressure transducer, comprising: a metallic one Housing, with a sensor chamber containing a media port and a pressure sensor according to one of the preceding claims, the is axially clamped in the housing, wherein the measuring membrane via the media opening can be acted upon with a pressure to be measured is. Pressure transducer according to claim 15, wherein the axial Clamping is done by means of a clamping ring, which in the housing is screwed and rests directly or indirectly on the decoupling body.