DE102008034350A1 - Sensor membrane for pressure sensor, has two surfaces comprising profiles which are formed by corroding, where surfaces face each other and run parallel to each other and profiles are formed in form of concentric circles around center point - Google Patents

Abstract

The membrane (1) has two surfaces (10, 20) comprising fine profiles which are formed by corroding, where the surfaces face each other and run parallel to each other. The fine profiles are formed in the form of concentric circles around a center point which is present on the respective surfaces. The membrane is installed in a sensor housing that is made of metal. The distance (30) between the surfaces is in the range of 10-150 micrometers. The membrane is made of raw material such as metal. Independent claims are also included for the following: (1) a method for manufacturing a sensor membrane (2) a method for manufacturing a pressure sensor.

Description

The The invention relates to a sensor membrane, in particular the sensor membrane for one Pressure sensor, a pressure sensor with a sensor membrane according to the invention, a manufacturing method of a sensor membrane, in particular the Sensor membrane for a pressure sensor, and a method of manufacturing a pressure sensor with a sensor membrane according to the invention.

A Sensor membrane, in particular the sensor membrane of a pressure sensor, usually indicates as starting material a metal foil. The thickness of the metal foil is between 15 and 150 μm and the surfaces the metal foil are flat.

to Generation of the sensor membrane is in a step of manufacture a desired one Shape of the sensor membrane punched out of the metal foil. Usually is the mold for sensor membranes, which are used in a pressure sensor to make a circular shape. In a further step, a profile training then takes place Pulling and / or embossing the metal foil. The two process steps can be in any order accomplished become.

at the profile formed on the sensor membrane is it is, for example, a wave structure. The wave structure is therefore formed because of the linear region a pressure-stroke characteristic of the sensor diaphragm increases. This in turn leads to better measurement results.

One Disadvantage of this conventional method is that during the Form process internal stresses are built up in the sensor membrane. These have a negative effect on the elasticity of the sensor membrane and thus negative for the result achieved. That's why in a last step, a thermal treatment of the sensor membrane instead of. However, this thermal treatment represents another, additional Burden for The starting material of the sensor membrane. Therefore, the finished Sensor membrane no longer the original elasticity of the starting material on. This is another disadvantage.

Farther It is disadvantageous that the processing of metal foils with a Thickness <15 μm with these Procedural steps is only conditionally possible. This depends together, that with the same starting material a thinner sensor membrane the registration of smaller pressure changes due to the higher elasticity allowed.

at Pressure sensors for designed for use at high temperatures or for measuring high pressures are, the sensor membrane provides an interface between a to be measured medium and a pressure-sensitive silicon chip. A space between the sensor membrane and the silicon chip is, for example with silicone oil filled. The pressure to be measured is over the separation membrane on the silicone oil and thereby transferred to the pressure-sensitive silicon chip. This structure is also suitable if the pressure sensor is the pressure to record aggressive chemicals.

One Disadvantage of these pressure sensors is that a thermal expansion coefficient of silicone oil and the sensor membrane are not matched. This leads Temperature changes to a negative influence on the measurement.

It is therefore the object of the present invention, a comparison to the prior art optimized sensor membrane, especially for use in a pressure sensor, and a method of making this sensor membrane provide.

The The above object is achieved by a sensor membrane according to claim 1, a pressure sensor according to claim 6, a manufacturing method according to claim 7 and a method for producing a pressure sensor according to claim 14 solved. Further advantageous embodiments From the description, the drawings and the dependent claims.

• – mindestens eine erste Oberfläche mit einem ersten Profil, während das erste Profil mittels Ätzen hergestellt ist.

The sensor membrane according to the invention, in particular the sensor membrane for a pressure sensor, has the following features:

• - At least a first surface having a first profile, while the first profile is made by etching.

A Forming a first profile on a first surface of a Starting material for a Sensor membrane is made by etching. An advantage of the sensor membrane according to the invention is any profile formation on a surface of the membrane. Conventional sensor membranes exhibit due to the process steps Pulling and / or embossing on both surfaces always the same structure up.

Farther are, compared to drawing and / or embossing, by etching finer profiles in the surface of the Sensor diaphragm generated. These finer structures increase the flexibility the sensor membrane. The flexibility in turn influences the reaction the sensor membrane to pressure changes such that even smaller pressure changes can be detected.

Another advantage is that a wide variety of materials for the production of the sensor membrane can be used. Thus, the sensor membrane can be adapted to individual properties of a medium to be measured. If the sensor membrane is used, for example, in a pressure sensor, a spring steel with a higher strength can be used instead of a conventional metal foil. In addition, eliminates the need for a thermal aftertreatment. These points are advantageous in that a linear range of a pressure-stroke characteristic of the sensor membrane is increased as compared with a conventionally manufactured sensor membrane.

In an advantageous embodiment the sensor membrane according to the invention is an additional one second profile etched in a second surface. The second surface is across from the first surface arranged. Characterized in that on both sides of the sensor membrane a etched Profile is present, the linear range of the pressure-stroke characteristic of the Sensor membrane can be expanded specifically. In addition, two different profiles are formed. An optimal adaptation to a respective measurement environment and a medium to be measured is so realizable.

In In another advantageous embodiment, the profiles are on the two surfaces the sensor membrane formed in the form of concentric circles. These are, for example, around a center, which is located on the each associated surface is located, arranged. This has a particularly advantageous effect on the flexibility of the sensor membrane out. This in turn becomes the measuring range in which the sensor membrane can be used, enlarged.

Farther advantageous, as mentioned above, the Use of a metal for the manufacture of the sensor membrane, in particular if the first and second surface in opposite Areas without profile have a distance between 10 and 150 microns. By using metal, the sensor membrane can affect the properties be adapted to the medium to be measured. Furthermore, a selection of the metal due to its thermal expansion coefficient respectively. This is just in terms of contact with one Silicone oil, which transfers the pressure to a silicon chip makes sense. This will be disturbing temperature influences largely eliminated.

One inventive pressure sensor has a sensor membrane described above. By use the sensor membrane according to the invention Within a pressure sensor, the pressure sensor also points out all described advantages. This allows the use of such Pressure sensors in a broader range of applications in comparison to the state of the art. Because the sensor membrane made of different materials can be made, the pressure sensor can optimally to the respective Be adapted to the operating environment. This leads to more accurate measurements.

The Production method according to the invention a sensor membrane, in particular the sensor membrane for a Pressure sensor, includes the following steps: Providing a Starting material suitable for the production of the sensor membrane with at least a first surface, Covering areas of the starting material with a covering agent, not etched to be, etching a profile in the at least one surface of the starting material, that is predetermined by the uncovered areas of the at least one surface is, removing the etchant and removing the cover means.

The inventive method etches predetermined Structures in a material that are suitable for use as a sensor membrane suitable. After a suitable starting material has been selected, all areas that should not be covered are covered. To the Covering is a covering means, for example a lacquer, used, not later by an etchant, For example, a chloride is attacked. Now the etching of the given by the covering means structure. In a penultimate and last step will be both the etchant and the masking agent away.

Especially advantageous in this manufacturing process is that depending the contact time of material and etchant structures different Deep etching to let.

Thereby can Furthermore the structures to be etched be specified exactly. These are then finer and more accurate than the structures by embossing and / or pulling are feasible.

advantageously, it is the starting material is a metal band. This can be particularly advantageous for the production of sensor membranes in be used in a continuous process. Through this process will a consistent quality realized the finished parts.

Around the dissolution the etched To facilitate sensor membrane from the metal strip are preferred Predetermined breaking points around the membrane introduced into the metal strip. This can be done in particular by etching happen. It is also advantageous if these predetermined breaking points at regular intervals Edge of the membrane are attached.

Furthermore, it is advantageous, in addition to etching a profile in the first surface, to etch a profile into a second surface of the membrane. This second surface faces the first surface. The etching of the profile in the second surface additionally reduces rigidity of the membrane. Since the structure to be etched is given by the covering means, different structures of different depths can be etched into the two surfaces. This is another advantage.

• – Bereitstellen eines Sensorsgehäuses,
• – Installieren der Sensormembran in dem Sensorgehäuse.

The inventive method for producing a pressure sensor with the sensor membrane described above according to one of claims 1 to 5 comprises the following steps:

• Providing a sensor housing,
• - Installing the sensor membrane in the sensor housing.

By installing the sensor membrane according to the invention in the sensor housing, transmitted the advantages of the sensor membrane according to the invention on the complete Pressure sensor.

in the Below, the present invention will be described with reference to FIGS accompanying drawing based on a preferred embodiment explained. This embodiment includes a pressure sensor in which the sensor membrane is installed is. Show it:

1 a schematic sectional view of a sensor membrane before etching,

2 a schematic sectional view of the sensor membrane after the etching,

3 a plan view of the sensor membrane 2 with a concentric wave structure and

4 a flow chart of the inventive method for producing a sensor membrane.

In 1 a preferred embodiment of the sensor membrane according to the invention is shown schematically. The sensor membrane 1 is part of a pressure sensor. Furthermore, the sensor membrane according to the invention can be used wherever a pressure or a force has to be transferred from one medium to another, without the two media being in contact with each other.

The sensor membrane 1 consists of a suitable starting material, preferably a metal. This metal has a first surface 10 and a second surface 20 on. These two surfaces 10 . 20 lie opposite each other and parallel to each other. Advantageously, the distance 30 between the first and second surfaces in opposite regions without a profile between 10 and 150 μm. The areas 14 on the first surface 10 that are above a dashed line 12 were not provided with a cover during manufacture (see below). The areas 16 the first surface 10 are therefore covered and are not attacked by an etchant. The same applies to the areas 26 the second surface 20 , The areas 14 . 24 are therefore etched away or the structure shown in dashed lines was produced by etching. The same applies to the areas 24 the second surface 20 extending below a dashed line 22 are located. With these areas 14 . 24 a profile of the respective surface is given.

For clarity shows 2 the sensor membrane after the etching process. Here, along the dashed lines 12 . 22 out 1 the profile is formed. The etching of a metal is characterized by the edges created in the profile 18 . 28 , These arise in each case at the transitions from a covered area 16 . 26 to an uncovered area 14 . 24 ,

3 shows a plan view of the etched sensor membrane 2 , The sensor membrane 1 has a circular shape. The profile of the surface is in the form of concentric circles around the center 40 educated. In concentric circles, an area not covered before etching alternates 14 with an area covered before etching 16 from. In other words, a wave valley is changing 14 and a wave mountain 16 from. Advantageously, the structure on the second surface of the sensor membrane is reversed. At points where the trough is present on the first surface, there is a wave crest on the second surface. Accordingly, where there is the wave crest on the first surface, there is a wave trough on the second surface.

The Wave structure on both surfaces increases flexibility or decreases the stiffness of the sensor membrane. The finer the wave structure formed the more sensitive the sensor membrane is to pressure changes. Provided the same starting material was used. By the Use of metal allows the sensor membrane even in an environment be used with aggressive chemicals. Because the starting material thinner can be than in the conventional manufacturing process, is a linear region of a pressure-stroke characteristic of the sensor membrane greater. Also this has an advantageous effect on a pressure response of the sensor membrane out.

Preferably, the sensor membrane is used in a pressure sensor (not shown). Such pressure sensors have a sensor diaphragm ran on to transfer the pressure of a medium to another medium, such as a silicone oil. The silicone oil then transfers the pressure to a silicon chip. When using the pressure sensor in changing temperature conditions, the temperature-dependent expansion coefficient of the silicone oil must be taken into account. Experience has shown that the internal pressure additionally generated by the silicone oil must not exceed 1/10 of a measuring range of the pressure sensor. Since the etched sensor membrane can be made of different starting materials, care can be taken in selecting the starting material.

4 shows the flow chart of the method according to the invention. Starting from the sensor membrane described above, the method steps are set forth below.

In a first step A is the starting material for the production the sensor membrane provided. Thereafter, the covering takes place (step B) with a covering, such as a paint. It will be covered areas that should not be etched. Is this done, will be a profile in at least one surface of the Etched starting material (Step C). For etching For example, a chloride can be used. It will only etched in the places which are not covered. Following the etching process, the etchant removed (step D). additionally removal (step E) of the cover means.

The inventive method allows the etching a profile in just one surface. Dependent on From the scope of the sensor membrane, this proves to be advantageous. Furthermore, by varying the contact time of the starting material with the etchant In step C, a tread depth can be influenced.

In an optional step F is the starting material in the form of a Provided metal strip. Due to the metal band, the Production of the sensor membrane done in a continuous process. This is a continuous production with consistent quality the finished parts feasible.

Basically proves it is helpful in a further step G breaking points to introduce into the starting material. It is in particular makes sense to introduce these predetermined breaking points by etching. This facilitates a later one Dissolve the Sensor membrane from the starting material. Advantageously the breaking points at regular intervals on Inserted edge of the membrane.

Around the flexibility to further increase the sensor membrane, In a step H, a profile is made into a second surface of the Etched sensor membrane. These second surface is opposite the first surface arranged the sensor diaphragm. The sensor membrane produced in this way has now the advantages that were explained in the previous part.

In an advantageous step I, the leaching out of Sensor membrane from the metal strip by means of cutting, punching or Burning by laser. This can either be done directly after production the sensor membrane or at a later date.

The thus prepared sensor membrane is advantageously in a pressure sensor used. This will be first a sensor housing provided. Subsequently becomes the sensor membrane according to the invention in the sensor housing Installed.

1

sensor diaphragm

10

first surface

12

dashed line

14

Not covered area

16

covered Area

18

edge

20

second surface

22

dashed line

24

Not covered area

26

covered Area

28

edge

30

distance

40

Focus

Claims (14)

Sensor membrane, in particular the sensor membrane for a pressure sensor, which has the following features: a) at least one first surface ( 10 ) with a first profile, while b) the first profile is made by etching. A sensor membrane according to claim 1, further comprising: a) a second surface ( 20 ) having a second profile disposed opposite to the first surface, while b) the second profile is made by etching. Sensor membrane according to claim 1 or 2, further comprising: the first and / or the second profile are in the form of concentric circles around a center ( 40 ), which is located on the profile belonging to the profile ( 10 . 20 ) is formed. Sensor membrane according to a of the preceding claims, which consists of a metal. Sensor membrane according to claim 4, the first and second surfaces of which have a spacing in opposite regions without profile ( 30 ) between 10 μm and 150 μm. Pressure sensor with a sensor membrane according to a the claims 1 to 5. Manufacturing method of a sensor membrane, in particular the sensor membrane for a pressure sensor that includes the following steps: a) Provide (A) a starting material suitable for the production of the sensor membrane with at least a first surface b) covering (B) of Areas of the starting material with a covering agent that is not etched should be c) etching (C) a profile in the at least one surface of the starting material, that is predetermined by the uncovered areas of the at least one surface is d) removing (D) the etchant and e) Remove (E) the covering agent. The manufacturing method according to claim 7, wherein providing (F) of the starting material takes place in the form of a metal strip. Manufacturing method according to one of claims 7 to 8, in which the manufacture of the sensor membrane in a continuous process he follows. Manufacturing method according to one of the preceding claims 7 to 9, with the further step: - Introduction (G) of predetermined breaking points in the starting material, in particular by etching. Manufacturing method according to claim 10, in which the predetermined breaking points at regular intervals Edge of the membrane are introduced. Manufacturing method according to one of claims 7 to 11, with the further step: - Etching (H) of a profile into one second surface of the Sensor membrane, which lies opposite the first surface. Manufacturing method according to one of claims 7 to 12, which includes the further step: - Dissolve (I) the membrane from the Metal strip by means of cutting, punching or burnishing by means of laser welding. Method for producing a pressure sensor with a sensor membrane according to a the claims 1 to 5, which comprises the following steps: a) Provide a sensor housing, b) Install the sensor membrane in the sensor housing.