Pressure sensor, especially pressure difference sensor
The pressure sensor of the invention includes at least one platform, at least one measuring membrane 30 , and a transducer, wherein the measuring membrane comprises a semiconductor material, wherein the measuring membrane, enclosing a pressure chamber, is secured on the platform, wherein the measuring membrane is contactable with at least one pressure and is elastically deformable in a pressure-dependent manner, wherein the transducer provides an electrical signal dependent on deformation of the measuring membrane, wherein the platform has a membrane bed, on which the measuring membrane lies in the case of overload, in order to support the measuring membrane, wherein the membrane bed 21 has a glass layer 20 , whose surface faces the measuring membrane and forms a wall of the pressure chamber, wherein the surface of the glass layer has a contour, which is suitable for supporting the measuring membrane 30 in the case of overload, characterized in that the contour of the membrane bed 21 is obtainable by a sagging of an unsupported region of a glass plate at increased temperature, due to the force of gravity on the unsupported region of the glass plate, and subsequent cooling of the glass plate.
1. A method for the preparation of a membrane bed of a pressure sensor, comprising the steps of:
(a) providing a planar glass layer, said glass layer having a thickness of not less than 200 μm and not more than 2000 μm;
(b) applying the glass layer on a support body, which has a surface, which supports the glass layer, wherein the surface has at least one cavity, so that the glass layer is not supported in the region of the cavity, said at least one cavity having a circular symmetry, and said at least one cavity having a diameter of 3 mm to 10 mm;
(c) heating the glass layer to a temperature or temperature range, at which the unsupported region of the glass layer sinks; and
(d) allowing the glass layer to cool,
wherein the membrane bed obtained by said method has an aspherical surface contour, which approximates the deflection curve of a measuring membrane, supported by said membrane bed.
2. The method as claimed in claim 1 , wherein:
the glass layer, after reaching a temperature, at which the unsupported region sinks, is held for a holding time at such temperature, so that the glass layer can sink to a sufficient extent.
3. The method as claimed in claim 2 , wherein:
the holding time for a borosilicate glass is given by the relationship
t=a*d+b;
the value for a at 750 ° C. lies between 0.1 and 0.8, and the value for b lies between −60 and 20, wherein t is the time in minutes and d the thickness of the glass layer in μm.
4. The method as claimed in claim 1 , wherein:
the preparation of the membrane bed contour occurs on one undivided wafer for a plurality of membrane beds.
5. A method for manufacturing a pressure sensor, comprising:
preparing a membrane bed according to the method as claimed in claim 1 , and joining a measuring membrane with a platform, or the glass layer of the platform, which forms the membrane bed.
6. The method as claimed in claim 3 , wherein:
the value for a at 750 ° C. lies between 0.2 and 0.6.
7. The method as claimed in claim 3 , wherein:
the value for b lies between −40 and 0.