Capacitive Pressure Sensor with Reference Chamber

• US 20070234814A1
• Filed: 06/17/2007
• Published: 10/11/2007
• Est. Priority Date: 10/18/2004
• Status: Active Grant

• Current Assignee: Precision Mechatronics Pty Ltd
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia, Mallinson, Samuel
• Granted Patent: US 7,430,919 B2
• Time in Patent Office: Days
• US Class Current: 73/724
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver

Abstract

A capacitive pressure sensor includes a substrate assembly having a conductive layer. A conductive membrane is mounted to the substrate assembly so that a sealed reference chamber is defined by the conductive membrane and the substrate assembly. A cap is arranged on the substrate assembly and defines one or more apertures so that an antechamber is defined between the cap and the conductive membrane. Differential pressure between the reference chamber and antechamber can cause deflection of the conductive membrane which, in turn, varies the capacitance between the conductive membrane and the conductive layer.

Claims

1. A capacitive pressure sensor comprising:

a substrate assembly having a conductive layer;

a conductive membrane mounted to the substrate assembly so that a sealed reference chamber is defined by the conductive membrane and the substrate assembly; and

a cap arranged on the substrate assembly and defining one or more apertures so that an antechamber is defined between the cap and the conductive membrane, such that differential pressure between the reference chamber and antechamber can cause deflection of the conductive membrane which, in turn, varies the capacitance between the conductive membrane and the conductive layer.

2. A pressure sensor as claimed in claim 1, wherein the substrate assembly includes a silicon substrate, a CMOS layer deposited on the substrate, the conductive layer deposited on the CMOS layer and a passivation layer deposited on the conductive layer.

3. A pressure sensor as claimed in claim 1, wherein the conductive membrane defines a foot which is located between the substrate assembly and cap and a leg which extends away from the substrate assembly and terminates in a substantially planar deflectable portion.

4. A pressure sensor as claimed in claim 1, wherein the substrate assembly defines a plurality of channels terminating in closed ends and forming part of the sealed reference chamber.

5. A pressure sensor as claimed in claim 4, wherein the substrate assembly comprises a silicon substrate defining through-channels and a termination layer mounted to the silicon substrate to terminate the channels in closed ends.

6. A capacitive pressure sensor comprising:

a substrate assembly having a conductive layer;

a conductive membrane mounted to the substrate assembly so that a sealed reference chamber is defined by the conductive membrane and the substrate assembly;

a cap arranged on the substrate assembly and defining one or more apertures so that an antechamber is defined between the cap and the conductive membrane, such that differential pressure between the reference chamber and antechamber can cause deflection of the conductive membrane which, in turn, varies the capacitance between the conductive membrane and the conductive layer; and

a cover configured to be engaged with the cap to define a main chamber in fluid communication with the antechamber.

7. A pressure sensor as claimed in claim 6, wherein the cover defines a vent so that the main chamber is unsealed.

8. A pressure sensor as claimed in claim 7, wherein the cap defines a circular wall to which a circular internal wall of the cover can be snugly fitted.