Pressure sensors with tensioned membranes
AssigneeAlfred E. Mann Foundation for Scientific Research
InventorsSiegmar Schmidt, William A. Dai, Boon Khai Ng
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Abstract
Pressure sensors having ring-tensioned membranes are disclosed. A tensioning ring is bonded to a membrane in a manner that results in the tensioning ring applying a tensile force to the membrane, flattening the membrane and reducing or eliminating defects that may have occurred during production. The membrane is bonded to the sensor housing at a point outside the tensioning ring, preventing the process of bonding the membrane to the housing from introducing defects into the tensioned portion of the membrane. A dielectric may be introduced into the gap between the membrane and the counter electrode in a capacitive pressure sensor, resulting in an improved dynamic range.
Claims11
A pressure sensor comprising:
- a housing having an opening;
- a membrane coupled to the housing at the opening, the membrane comprising a non-tensioned region bonded to the housing;
- and
- a tensioning ring coupled to the membrane to apply a tensile force to the membrane,
- wherein the non-tensioned region is an area of the membrane outside the tensioning ring;
- and
- wherein the membrane and the housing to which the membrane is coupled define a hermetically sealed cavity inside the housing.
A pressure sensor comprising:
- a housing having an opening;
- a membrane coupled to the housing at the opening, the membrane comprising a non-tensioned region bonded to the housing;
- a tensioning ring coupled to the membrane to apply a tensile force to the membrane,
- a counter electrode,
- a spacer,
- an isolator, and
- a sensor circuit in the housing to generate a pressure signal based on a deflection of the membrane;
- wherein the non-tensioned region is an area of the membrane outside the tensioning ring;
- and
- wherein:
- the membrane further comprises an electrode,
- the counter electrode is positioned parallel to the membrane,
- the spacer is positioned between the counter electrode and the membrane to provide a gap between the counter electrode and the membrane,
- the tensioning ring comprises a retaining portion to hold the counter electrode against the spacer,
- the isolator is to isolate the counter electrode from the tensioning ring, and
- the sensor circuit is to evaluate a capacitance between the electrode and the counter electrode.
A method of fabricating a pressure sensor, the method comprising:
- heating a membrane having a first coefficient of thermal expansion and a tensioning ring having a second coefficient of thermal expansion lower than the first coefficient of thermal expansion to a temperature outside an operating temperature range of the pressure sensor;
- coupling the tensioning ring to the membrane at the temperature outside the operating temperature range of the pressure sensor while the membrane experiences greater expansion than the tensioning ring so that the tensioning ring applies a tensile force to the membrane when the membrane is at about the same temperature as the tensioning ring;
- and
- coupling the membrane and the tensioning ring to an opening in a sensor housing comprising a sensor circuit while the membrane and the sensor housing are at about the same temperature,
- wherein the membrane comprises a non-tensioned region in an area of the membrane outside the tensioning ring and coupling the membrane and the tensioning ring to the opening of the sensor housing comprises bonding the non-tensioned region to the sensor housing, and
- wherein the membrane and the sensor housing to which the membrane is coupled define a hermetically sealed cavity inside the sensor housing.
Dependencies are inferred from the claim text.