Pressure sensor having a ceramic platform

Patent metadata

Field	Value
Publication number	US-9863830-B2
Application number	US-201415303241-A
Country	US
Kind code	B2
Filing date	Dec 18, 2014
Priority date	Apr 23, 2014
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

Abstract

A pressure sensor, including a platform of ceramic, a measuring membrane arranged on the platform, a pressure measuring chamber enclosed in the platform under the measuring membrane, and at least one metal body connected with the platform via a pressure-tight, preferably elastomer free, mechanical connection. Thermomechanical stresses arising from the connection are reduced by features including that the pressure-tight, mechanical connection occurs via an adapting body arranged between the platform and the metal body. The adapting body has a thermal expansion coefficient, which rises in direction (z) extending from the platform to the metal body from a coefficient of expansion corresponding to a thermal coefficient of expansion of the ceramic of the platform to a coefficient of expansion corresponding to the thermal coefficient of expansion of the metal body, and the adapting body is connected by a first joint with the platform and by a second joint with the metal body.

First claim

The invention claimed is:

1. A pressure sensor, comprising:
a platform of ceramic;
a measuring membrane arranged on said platform;
a pressure measuring chamber enclosed in said platform under said measuring membrane; and
at least one metal body connected with said platform via a pressure-tight, mechanical connection, wherein:
said pressure-tight mechanical connection includes an adapting body arranged between said platform and said metal body;
said adapting body has a thermal expansion coefficient, which rises along said adapting body in a direction extending from said platform to said metal body from a coefficient of expansion corresponding to a thermal coefficient of expansion of the ceramic of said platform to a coefficient of expansion corresponding to the thermal coefficient of expansion of said metal body; and
said adapting body is connected by a first joint with said platform and by a second joint with said metal body.

2. The pressure sensor as claimed in claim 1 , wherein:
said adapting body has layers of different composition arranged on top of one another, and applied on top of one another by laser sintering of powder layers containing metal and/or ceramic fractions; and
said layers have a ceramic fraction, which is greater than or equal to 0% and less than or equal to 100%, and a metal fraction, which is greater than or equal to 0% and less than or equal to 100%;
the ceramic fraction decreases from layer to layer in a direction extending from said platform to said metal body; and
the metal fraction rises from layer to layer in the direction extending from said platform to said metal body.

3. The pressure sensor as claimed in claim 1 , wherein:
said adapting body is a sintered body constructed of layers, and the first joint is a joint formed by sintering, especially by laser sintering, to said platform an outermost layer of said adapting body facing said platform, or
the first joint is an active hard soldered or brazed joint, especially an active hard soldered or brazed joint formed by means of a ternary active hard solder or braze having a Zr—Ni alloy and titanium; or
the first joint is a glass soldered joint.

4. The pressure sensor as claimed in claim 1 , wherein:
the second joint is a welded joint or a glass soldered joint.

5. The pressure sensor as claimed in claim 1 , wherein:
said measuring membrane is composed of metal and is one of the metal bodies; and
an outer edge of an end of said platform facing said, measuring membrane is connected via the first joint, said adapting body and the second joint with an outer edge of the side of said measuring membrane facing said platform.

6. The pressure sensor as claimed in claim 5 , wherein:
said adapting body is an annular adapting body of rectangular cross section; or
an end of said platform facing said measuring membrane includes a region formed as a membrane bed; and
said adapting body includes an inner contour, which externally surrounds said pressure measuring chamber and by which the membrane bed is outwardly continued.

7. The pressure sensor as claimed in claim 1 , wherein:
a traversing bore is provided in said platform, opening into said pressure measuring chamber;
a pressure supply line is provided connected to said traversing bore;
a pressure supply line has on its end facing said platform a metal termination having a passageway and forming one of the metal bodies,
said platform is connected via said first joint, said adapting body and said second joint with said termination; and
said adapting body has an interior, through which an interior of said bore is connected via the passageway in said noted termination with an interior of said pressure supply line.

8. The pressure sensor as claimed in claim 1 , wherein:
said platform is arranged in a housing,
the housing includes a housing segment externally enclosing said platform and spaced from said platform, and a shoulder connected with said housing segment, extending radially inwardly, and forming one of the metal bodies of metal, and
an inner edge of said shoulder is connected via said pressure-tight connection with an outer edge of said platform facing said shoulder;
an end of said adapting body facing said platform is connected via said first joint with an outer edge of the end of said platform facing said shoulder; and
an end of said adapting body facing said shoulder is connected via said second joint with a side of an inner edge of said shoulder, which side faces into said housing.

9. The pressure sensor as claimed in claim 8 , wherein:
said measuring membrane is composed of ceramic;
an outer edge of said measuring membrane is connected via a pressure-tight connection with a side of the inner edge of said shoulder, which side faces away from said platform;
said pressure-tight connection occurs via an additional adapting body, especially an additional adapting body formed identically to said adapting body arranged between said platform and said shoulder;
said additional adapting body has a thermal expansion coefficient, which in direction extending from said measuring membrane to said shoulder rises from a coefficient of expansion corresponding to a thermal coefficient of expansion (α M ) of the ceramic of the measuring membrane to a coefficient of expansion corresponding to the thermal coefficient of expansion (α M ) of the metal of the shoulder; and
said additional adapting body has an end facing said measuring membrane and connected with said measuring membrane by an additional first joint, and an end facing said shoulder and connected with said shoulder by an additional second joint.

10. The pressure sensor as claimed in claim 8 , wherein:
said shoulder is elastic in a direction extending parallel or perpendicular to the surface normal to said measuring membrane.

11. The pressure sensor as claimed in claim 1 , wherein:
said adapting body is an adapting body constructed of layers;
a number (N) of said layers is greater than or equal to a difference between the thermal coefficient of expansion of said metal body and the thermal coefficient of expansion of said ceramic platform divided by 2 ppm/K.

12. The pressure sensor as claimed in claim 1 , wherein:
said adapting body is an adapting body constructed of layers; and
said layers have a layer thickness of not less than 10 μm, especially not less than 20 μm.

13. The pressure sensor as claimed in claim 1 , wherein:
said adapting body has in a direction extending from said platform to said metal body a height, and perpendicular thereto a width;
a product of a ratio of said width of said adapting body to said height of said adapting body and the magnitude of the difference between the thermal coefficients of expansion of the ceramic of said platform and the metal of said metal body is less than a constant (ξ) of units 1/K, wherein
said constant (ξ) is less than 0.1%/K; and/or
said constant (ξ) equals a quotient of a dimensionless deformation parameter and a temperature difference between a maximum and a minimum temperature, for which the pressure sensor is to be applied, and the deformation parameter is less than 4%.

14. The pressure sensor as claimed in claim 1 , wherein:
said adapting body is an adapting body constructed of layers arranged on top of one another;
said individual layers, in each case, have a layer thickness extending parallel to the surface normal of the layer and a width extending perpendicular to the surface normal of the layer; and
the product of the ratio of the width of the respective layer to its layer thickness and the magnitude of the difference between the thermal coeffi

Assignees

• Endress Hauser Gmbh Co Kg

Inventors

• Drewes Ulfert
• Schmidt Elke
• Uehlin Thomas
• Berlinger Andrea

Classifications

• C04B2237/122

  based on refractory metals · CPC title

• C04B2237/343

  Alumina or aluminates · CPC title

• G01L19/0046

  using isolation membranes (G01L13/026 and G01L19/0645 take precedence) · CPC title

• C04B37/025 Primary

  consisting of glass or ceramic material · CPC title

• C04B2235/665

  Local sintering, e.g. laser sintering · CPC title