Pressure sensor having a joint of active braze

Patent metadata

Field	Value
Publication number	US-10908044-B2
Application number	US-201615573959-A
Country	US
Kind code	B2
Filing date	May 10, 2016
Priority date	Jun 8, 2015
Publication date	Feb 2, 2021
Grant date	Feb 2, 2021

Abstract

A pressure sensor comprising two parts connected with one another via an active braze joint manufactured by active hard soldering, or brazing, with an active hard solder, or braze, especially a pressure contactable, pressure-dependently elastically deformable, measuring membrane, especially a ceramic measuring membrane, and a platform, especially a ceramic platform, which are connected by an active braze joint connecting an outer edge of the measuring membrane (which covers a pressure chamber with an outer edge of an end of the platform facing the measuring membrane, whose measuring characteristics are improved in that the active braze joint has a coefficient of thermal expansion dependent on the dimensions of the active braze joint and on the materials of the parts and matched to a coefficient of thermal expansion of at least one of the parts, especially the measuring membrane.

First claim

The invention claimed is:

1. A pressure sensor, comprising:
two parts connected with one another via an active braze joint manufactured by active hard soldering, or brazing, with an active hard solder, or braze, wherein one of the two parts is a pressure contactable, pressure-dependently elastically deformable, measuring membrane, and the other one of the two parts is a base body, wherein the membrane and the base body are connected by the active braze joint connecting an outer edge of said measuring membrane with an outer edge of an end of said base body facing said measuring membrane, thereby creating a pressure chamber, wherein:
said active braze joint has a coefficient of thermal expansion dependent on the dimensions of said active braze joint and on the materials of said two parts and said coefficient of thermal expansion of said active braze joint is matched to a coefficient of thermal expansion of said measuring membrane;
wherein the matching is performed based on the dimensions of the active braze joing such that a difference between the coefficient of thermal expansion of said active braze joint and a coefficient of thermal expansion of said measuring membrane, has an absolute value smaller than a difference between a coefficient of thermal expansion of said active hard solder, or braze, and the coefficient of thermal expansion of said measuring membrane.

2. The pressure sensor claimed in claim 1 , wherein:
at least one of said measuring membrane and said base body, is composed of an oxide ceramic, and said active hard solder, or braze, contains zirconium, nickel and titanium.

3. The pressure sensor as claimed in claim 2 , wherein:
said active hard solder, or braze, contains copper and/or aluminum.

4. The pressure sensor as claimed in claim 1 , wherein:
said active braze joint is produced from an active hard solder, or braze, which has the composition, Zr 63 Ni 22 Ti 15 , Zr 60 Ni 8 Ti 2 Cu 20 Al 10 , Zr 54.5 Ni 8 Ti 7.5 Cu 20 Al 10 , Zr 47 Ni 35 Ti 18 , Zr 58 Ni 23 Ti 9 Cu 10 , Zr 52.5 Ni 14.6 Ti 5 Cu 17.9 Al 10 , Zr 43 Ni 33 Ti 24 , or Zr 11 Ni 8 Ti 34 Cu 47 .

5. An apparatus configured to measure a coefficient of thermal expansion of the active braze joint of a pressure sensor as claimed in claim 1 , comprising:
two measuring bodies, said two measuring bodies being connected with one another via a second active braze joint, which is produced from the same active hard solder, or braze, from which also the active braze joint having the expansion coefficient to be measured is produced, and has the same dimensions as such active braze joint, and having electrodes on mutually facing ends, said electrodes form a capacitor having a capacitance dependent on their electrode separation dependent on a temperature dependent height of the second active braze joint;
a heating apparatus; and
a measuring circuit connected to the electrodes, which measures capacitance of said capacitor at at least two different temperatures of the second active braze joint, and based on its dependence on the height of the second active braze joint, determines the coefficient of thermal expansion of the second active braze joint.

6. The apparatus as claimed in claim 5 , wherein:
the electrodes are of equal construction and circular disk shaped;
the temperature dependence of the electrode areas of the electrodes is taken into consideration based on a temperature dependent diameter of said electrodes, which rises with temperature approximately linearly with an electrode expansion coefficient.

7. The apparatus as claimed in claim 5 , wherein:
the electrodes are disk shaped and have in comparison to the height of the second active braze joint a disk thickness, which is smaller in the order of magnitude of two powers of ten than the height of the second active braze joint.

8. The pressure sensor as claimed in claim 1 , wherein the measuring membrane is a ceramic measuring membrane and/or the base body is a ceramic base body.

9. The pressure sensor as claimed in claim 2 , wherein at least the measuring membrane or the measuring membrane and the base body platform, is/are composed of aluminum oxide.

10. A method for manufacturing a pressure sensor, the pressure sensor comprising: two parts connected with one another via an active braze joint manufactured by active hard soldering, or brazing, with an active hard solder, or braze, wherein one of the two parts is a pressure contactable, pressure-dependently elastically deformable, measuring membrane, and the other one of the two parts is a base body, wherein the membrane and the base body are connected by an active braze joint connecting an outer edge of said measuring membrane with an outer edge of an end of said base body facing said measuring membrane, thereby creating a pressure chamber,
wherein the method comprises the steps of:
determining the active hard solder, or braze, for manufacturing the active braze joint of the pressure sensor, based on the dimensions of the active braze joint, such, that said active braze joint has a coefficient of thermal expansion dependent on the dimensions of said active braze joint and on the materials of said two parts and said coefficient of thermal expansion of said active braze joint is matched to a coefficient of thermal expansion of said measuring membrane wherein the matching is performed such that a difference between the coefficient of thermal expansion of said active braze joint and a coefficient of thermal expansion of said measuring membrane has an absolute value smaller than a difference between a coefficient of thermal expansion of said active hard solder, or braze, and the coefficient of thermal expansion of said measuring membrane,
and wherein the determination of the active hard solder, or braze, comprises steps of:
performing at least one measurement; wherein
a thermal expansion coefficient of a second active braze joint made with an active hard solder, or braze, is determined, wherein:
the dimensions of the second active braze joint equal the dimensions of the active braze joint of the pressure sensor; and
wherein two measuring bodies are connected with one another by the second active braze joint, and
wherein a thickness of each of the two measuring bodies is larger than a thickness of the membrane of the pressure sensor.

11. The method as claimed in claim 10 , wherein:
the measuring bodies have electrodes on mutually facing ends and the electrodes form a capacitor having a capacitance dependent on their electrode separation dependent on a temperature dependent height of the second active braze joint;
and wherein said at least one measurement comprises the step of:
measuring the capacitance of the capacitor at at least two different temperatures of the second active braze joint and, based on a dependence of the capacitance on the height of the second active braze joint the thermal expansion coefficient of the second active braze joint is determined.

12. The method as claimed in claim 11 , wherein:
the electrodes are of equal construction and circular disk shaped; and
the temperature dependence of the electrode areas of the electrodes is taken into consideration based on a temperature dependent diameter of the electrodes, which rises approximately linearly with temperature in accordance with an electrode expansion coefficient.

13. The method as claimed in claim 10 , wherein:
the active hard solder, or braze, from which the active braze joint of the pressure sensor is produced, is ascertained by:
ascertaining, for active brazing of the two parts of the pressure sensor, suitable test hard solders, or brazes, of different compositions, containing componen

Assignees

• Endress Hauser Gmbh Co Kg
• Endress Hauser Se Co Kg

Inventors

• Rossberg Andreas
• Schmidt Elke
• Rettenmayr Markus
• Siegmund Peter
• Kuhn Uta
• Pauly Simon
• Ponath Nils

Classifications

• G01L9/0075 Primary

  using a ceramic diaphragm, e.g. alumina, fused quartz, glass · CPC title

• G01L19/145 Primary

  with stress relieving means · CPC title

• G01L19/143

  Two part housings · CPC title