DE102018130291A1 - Method for producing a separating membrane of a pressure sensor and pressure sensor - Google Patents

Abstract

Method for producing a multilayer separating membrane for a pressure measuring sensor with at least the following steps: - providing a separating membrane (S100); - coating a first membrane side of the separating membrane with a layer that diffuses hydrogen diffusion, in particular a diffusion-inhibiting gold layer (S200); - coating at least the diffusion-inhibiting layer with a diamond-like carbon layer (S300).

Description

The invention relates to a method for producing a multilayer separating membrane for a pressure measuring sensor and a pressure measuring sensor with such a separating membrane.

To detect pressures of a process medium, diaphragm seals are often used, which have a housing body to which a separating membrane is attached in a pressure-tight manner, forming a hydraulic chamber assembly between the housing body and the separating membrane filled with a pressure transmission liquid, a hydraulic path extending through the housing body in order to transfer the pressure of a process medium at the separation membrane.

The pressure transmission liquid enclosed in the hydraulic chamber assembly, which usually comprises an oil, has the effect that a pressure which is present on the side of the separating membrane facing the process medium is passed to a pressure sensor element for detecting a pressure measurement value. In order to ensure optimal operation of the diaphragm seal over a long service life from a few years to a few decades, it is important to ensure that the volume within the diaphragm seal should not change significantly, otherwise the pressure to be transmitted and thus the measured pressure value may be falsified would be done.

To the extent that such a falsification is caused by hydrogen forming inside or diffusing in from the outside, for example in the form of hydrogen molecules, hydrogen atoms and / or hydrogen ions, it is known that measures are taken to reduce such falsification .

For example, the DE 10 2013 110 968 A1 a hydrogen absorption material which is placed in the enclosed pressure transmission liquid so that hydrogen atoms are absorbed.

It is also known that in order to limit diffusion, the membrane is additionally coated. Usually these are galvanically deposited gold layers. Galvanic layer thicknesses of up to 40 µm (micrometers) gold are necessary for an efficient reduction of diffusion. However, the disadvantages of this variant are the relatively high costs due to a relatively thick gold layer, a possible negative change in the mechanical properties of the original separating membrane due to the relatively thick gold layer and the risk of mechanical wear of the gold layer.

It is therefore the object of the present invention to remedy this. The object is achieved according to the invention by the method according to patent claim 1 and the pressure sensor according to patent claim 7.

• - Bereitstellen einer Trennmembran;
• - Beschichten einer ersten Membranseite der Trennmembran mit einer gegenüber Wasserstoffionen diffusionshemmenden Schicht, insbesondere einer diffusionshemmenden Goldschicht;
• - Beschichten zumindest der diffusionshemmenden Schicht mit einer diamantartigen Kohlenstoffschicht.

The method according to the invention for producing a multi-layer separation membrane for a pressure measuring transducer comprises at least the following steps:

• - Providing a separation membrane;
• Coating a first membrane side of the separating membrane with a layer which diffusion inhibits hydrogen ions, in particular a diffusion-inhibiting gold layer;
• Coating at least the diffusion-inhibiting layer with a diamond-like carbon layer.

According to the invention, a new layer system is proposed that has the function of a diffusion barrier against hydrogen, but does not have the disadvantages mentioned above. The layer system consists of two functional layers: first, a high-quality thin layer, preferably a few tenths of a nanometer (nm), preferably made of gold, because of its suitability as a diffusion barrier against hydrogen, and second, a thicker protective layer.

An advantageous embodiment of the invention provides that the diffusion-inhibiting layer is applied / deposited by means of an atomic layer deposition. The layer, preferably the gold layer, is thus deposited on the membrane surface by means of atomic layer deposition, in short: ALD ) deposited. In this deposition process, monolayers of very high quality, i.e. a small number of defects and voids, are separated from the gas phase. In this way, the hydrogen diffusion can be greatly reduced even with layer thicknesses in the nm range.

A further advantageous embodiment of the invention provides that the diamond-like carbon layer is applied / deposited by means of a vapor deposition, preferably a chemical vapor deposition. After the first layer, there is the second functional layer, serving as a protective layer, made of diamond-like carbon (DLC) of 1 to 2 µm (micrometers), in order to protect the thin first layer (preferably gold layer) from mechanical damage. DLC is a diamond-like / diamond-like carbon layer and is characterized by a high chemical resistance, a very high abrasion resistance and a very low coefficient of friction. All three properties serve to protect the first layer (gold layer).

A further advantageous embodiment of the invention provides that the diffusion-inhibiting layer is applied in such a way that the diffusion-inhibiting layer has a thickness of a few tenths of a nanometer, preferably of 20 to 40 nanometers.

Yet another advantageous embodiment provides that the diamond-like carbon layer is applied in such a way that the carbon layer has a thickness in the micrometer range, preferably a few micrometers, particularly preferably approximately 1 to 2 micrometers.

• - Beschichten einer der ersten Membranseite gegenüberliegenden zweiten Membranseite der Trennmembran mit einer diamantartigen Kohlenstoffschicht.

A last advantageous embodiment also provides for the following step:

• Coating a second membrane side of the separating membrane opposite the first membrane side with a diamond-like carbon layer.

• einen im Wesentlichen metallischen Gehäusekörper; und
• eine Trennmembran, welche unter Bildung einer Druckkammer zwischen einer Oberfläche des Gehäusekörpers und der Trennmembran druckdicht an den Gehäusekörper befestigt ist,
• wobei von der Druckkammer ein hydraulischer Pfad sich durch den Gehäusekörper erstreckt, wobei die Trennmembran einen metallischen Werkstoff, insbesondere Edelstahl oder eine Nickelbasislegierung wie Hastelloy, aufweist, wobei
• die Trennmembran auf einer dem Gehäusekörper abgewandten ersten Membranseite einen Schichtaufbau aufweist, welcher zumindest eine gegenüber Wasserstoffionen diffusionshemmende Schicht, insbesondere eine diffusionshemmende Goldschicht und eine diamantartige Kohlenstoffschicht umfasst, wobei die diffusionshemmende Schicht auf der ersten Membranseite und die diamantartige Kohlenstoffschicht auf der diffusionshemmenden Schicht aufgebracht ist.

The invention further relates to a pressure transducer comprising:

• an essentially metallic housing body; and
• a separating membrane which is attached to the housing body in a pressure-tight manner to form a pressure chamber between a surface of the housing body and the separating membrane,
• wherein a hydraulic path extends from the pressure chamber through the housing body, the separating membrane having a metallic material, in particular stainless steel or a nickel-based alloy such as Hastelloy, wherein
• the separating membrane has a layer structure on a first membrane side facing away from the housing body, which layer comprises at least one layer that inhibits diffusion against hydrogen ions, in particular a diffusion-inhibiting gold layer and a diamond-like carbon layer, the diffusion-inhibiting layer being applied to the first membrane side and the diamond-like carbon layer being applied to the diffusion-inhibiting layer.

An advantageous embodiment of the pressure transducer according to the invention further provides that a further diamond-like carbon layer is applied to a second membrane side of the separating membrane facing the membrane bed and opposite.

A further advantageous embodiment of the pressure transducer according to the invention further comprises a further separating membrane which is arranged in the pressure chamber between the separating membrane and an outlet of the hydraulic path and is preferably also coated with at least one diamond-like carbon layer.

• 1: einen Längsschnitt durch ein Ausführungsbeispiel eines erfindungsgemäßen Druckmessaufnehmers, und
• 2: eine Ausgestaltung des erfindungsgemäßen Verfahrens sowie einen entsprechenden Schichtaufbau der Trennmembran.

The invention is illustrated by the following drawings. It shows:

• 1 : a longitudinal section through an embodiment of a pressure transducer according to the invention, and
• 2nd : an embodiment of the method according to the invention and a corresponding layer structure of the separating membrane.

1 shows an example of a longitudinal section through a pressure transducer designed according to the invention. The in 1 The pressure sensor shown has a metallic diaphragm body 10th and a separation membrane 20th which along an edge area 22 is welded pressure-tight with a circumferential weld seam to an end face of the diaphragm seal body, so that between the end face of the diaphragm seal body 10th and the separation membrane 20th a pressure chamber 12 is formed, which via a channel 14 that differs from the separation membrane 20th facing end face of the diaphragm seal body 10th through the diaphragm seal body to one of the separating membranes 20th facing rear end face of the diaphragm seal extends around the in the pressure chamber 12 prevailing pressure to transmit.

The separation membrane 20th has an embossed contour 24a on, for example, on a corresponding contour serving as a membrane bed 16 on the front surface of the diaphragm seal after joining the separating membrane 20th with the diaphragm seal body 10th can be embossed, or that before joining the separating membrane 20th with the diaphragm seal body 10th can be shaped otherwise. The diaphragm seal body 10th has a cylindrical shape at least in sections, the separating membrane 20th is circular disk-shaped. The (uncoated) separation membrane usually has a thickness of a few tens of micrometers, for example approximately 35 μm.

The separating membrane is according to the invention 20th formed as a layer structure. A separation membrane as described and designed above serves as the basis 20th as is also known in the prior art. The separation membrane 20th has in particular stainless steel or a nickel-based alloy, such as, for example, Hastelloy, Inconel or Monel. On the separating membrane 20th is through the in 2nd The inventive method shown applied a two-layer structure, initially a first Diffusion-inhibiting layer serving as a diffusion barrier 20a is applied, to which a second diamond-like carbon layer (English: "diamond-like carbon") then serves as a protective layer 20b is applied.

The first layer 20a is about an atomic layer deposition (English: "atomic layer deposition", short ALD ) applied to a first membrane side of the separating membrane, so that the first layer 20a has a thickness of only a few tens of nanometers. The first layer preferably has 20a Gold on. Alternatively, the first layer 20a but also have silver, titanium nitride or chromium oxide. In that the first layer 20a is applied by means of an atomic layer deposition process, the number of defects and voids in the layer is reduced in comparison to other deposition processes, such as, for example, galvanic deposition or PVD (English abbreviation for: "physical vapor deposition") process so that hydrogen diffusion can be significantly reduced with layer thicknesses in the nm range. The first layer deposited in this way 20a has a layer thickness of a few tenths of a nanometer.

The second layer 20b is a chemical vapor deposition (English: chemical vapor deposition, short CVD ) on the first layer 20a upset. The deposition is preferably carried out in such a way that the second layer 20b has a layer thickness of approximately 1 to 2 micrometers in the deposited state. By applying the second layer 20b becomes the first layer 20a protected from mechanical damage.

An unwanted friction between the separating membrane 20th and the membrane bed 16 to reduce, can optionally also a second the membrane bed 16 facing and the first opposite side of the membrane membrane with a diamond-like carbon layer 20c be provided.

The in 1 The pressure sensor shown communicates via a hydraulic path 14 of the diaphragm seal 1b with a converter unit 2nd , which provides a pressure-dependent electrical primary signal that is generated by an electronic unit 3rd processed and output. The hydraulic path includes a capillary 18th , which is between the diaphragm seal body 10th and a converter chamber 32 extends in which a piezoresistive pressure transducer 32 is arranged, in the present case the back of a measuring membrane of the piezoresistive pressure transducer 34 is subjected to atmospheric pressure, so that the present pressure sensor is a relative pressure sensor. The electronics unit 3rd contains a processing circuit in a housing 36 which is the primary signal of the piezoresistive pressure transducer 34 processed and converted into a signal suitable for output, which can be, for example, a digital signal or an analog signal, in particular 4 ... 20 mA. 1 Although it shows a relative pressure sensor, the invention is not restricted to such a sensor, but is equally applicable to an absolute pressure sensor and / or a differential pressure sensor. Furthermore, the invention is also not a pressure transducer with a diaphragm seal, as in 1 is limited, but is also transferable to pressure transducers without diaphragm seals, in which the pressure is communicated via an internal hydraulic path of the pressure transducer.

In addition, the pressure sensor can have another separating membrane 40 include which in the pressure chamber between the separation membrane 20th and an outlet of the hydraulic path 14 is arranged. The further separation membrane 40 can furthermore optionally also be coated with a diamond-like carbon layer at least on a first side facing the separating membrane. Furthermore, the further separation membrane 40 can also be coated with a diamond-like carbon layer on a second side opposite the first side.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included 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.

Patent literature cited

• DE 102013110968 A1 [0005]

Claims (9)

Method for producing a multi-layer separation membrane for a pressure sensor with at least the following steps: - Providing a separation membrane (S100); - Coating a first membrane side of the separating membrane with a layer which diffusion inhibits hydrogen ions, in particular a gold layer (S200) which inhibits diffusion; - Coating at least the diffusion-inhibiting layer with a diamond-like carbon layer (S300). Procedure according to Claim 1 , the diffusion-inhibiting layer being applied / deposited by means of an atomic layer deposition. Procedure according to Claim 1 or 2nd , wherein the diamond-like carbon layer is applied / deposited by means of a vapor deposition, preferably a chemical vapor deposition. Method according to at least one of the preceding claims, wherein the diffusion-inhibiting layer is applied in such a way that the diffusion-inhibiting layer has a thickness of a few tenths of a nanometer, preferably of 20 to 40 nanometers. Method according to at least one of the preceding claims, wherein the diamond-like carbon layer is applied in such a way that the carbon layer has a thickness in the micrometer range, preferably of a few micrometers, particularly preferably of approximately 1 to 2 micrometers. Method according to at least one of the preceding claims, further comprising the following step: - Coating a second membrane side of the separating membrane opposite the first membrane side with a diamond-like carbon layer (S400). Pressure sensor, comprising: an essentially metallic housing body (1a, 1b, 1c); and a separating membrane (20) which is attached to the housing body in a pressure-tight manner to form a pressure chamber (12) between a surface of the housing body and the separating membrane, a hydraulic path (14) extending from the pressure chamber through the housing body (10), the separating membrane (20) having a metallic material, in particular stainless steel or a nickel-based alloy such as Hastelloy, wherein the separating membrane has a layer structure on a first membrane side facing away from the housing body, which layer comprises at least one layer (20a) which is diffusion-inhibiting against hydrogen ions, in particular a diffusion-inhibiting gold layer and a diamond-like carbon layer (20b), the diffusion-inhibiting layer on the first membrane side and the diamond-like carbon layer the diffusion-inhibiting layer is applied. Pressure sensor according to the preceding claim, wherein a further diamond-like carbon layer (20c) is further applied to a second membrane side (16) facing the membrane bed and the first opposite membrane side of the separating membrane. Pressure sensor according to the preceding claim, further comprising a further separation membrane (40) which is arranged in the pressure chamber between the separation membrane and an outlet of the hydraulic path and is preferably also coated with at least one diamond-like carbon layer.

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