Sealed capacitive sensor

• US 20080210013A1
• Filed: 02/21/2008
• Published: 09/04/2008
• Est. Priority Date: 02/25/2005
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Kierse, Oliver, Hunt, William, O'Dowd, John, Hynes, Eamon, Meehan, Peter G.
• Granted Patent: US 7,938,014 B2
• Time in Patent Office: Days
• US Class Current: 73/780
• CPC Class Codes: G01L 1/142 using capacitors
• CPC Class Codes: G01L 1/148 using semiconductive material, e.g. silicon
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/73257 Bump and wire connectors
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

A sealed capacitive sensor includes a substrate having a diaphragm forming a first plate of a capacitor; a second fixed plate of the capacitor spaced from the diaphragm and defining a predetermined dielectric gap and a sealing medium connecting together the substrate and fixed plate in an integrated structure and hermetically sealing the gap.

Claims

1. A sealed capacitive sensor comprising:

a substrate having a diaphragm forming a first plate of a capacitor supported via supports;

a second fixed plate of the capacitor spaced from said diaphragm and defining a dielectric gap and bearing an active electronic circuit associated with the capacitive sensor; and

a frit sealing medium directly connecting together said substrate and fixed plate in an integral structure and hermetically sealing said gap.

2. The sealed capacitive sensor of claim 1 in which said substrate includes ceramic.

3. The sealed capacitive sensor of claim 1 in which said substrate includes silicon.

4. The sealed capacitive sensor of claim 1 in which said fixed plate includes silicon.

5. The sealed capacitive sensor of claim 1 in which said sealing medium includes a frit.

6. The sealed capacitive sensor of claim 5 in which said frit includes a glass frit.

7. The sealed capacitive sensor of claim 1 in which at least one of said first and fixed plates includes a metal layer.

8. The sealed capacitive sensor of claim 1 in which at least one of said first and fixed plates includes silicon.

9. The sealed capacitive sensor of claim 8 in which a said silicon plates is doped.

11. The sealed capacitive sensor of claim 1 in which said fixed plate bears on a separate chip, an active electronic circuit associated with said capacitive sensor.

12. The sealed capacitive sensor of claim 11 in which there is an insulation layer between said active electronic circuit and said fixed plate.

13. The sealed capacitive sensor of claim 1 in which said fixed plate includes a recess which defines at least a part of the gap dimension.

14. The sealed capacitive sensor of claim 1 in which the sealing medium defines at least a part of the gap dimension.

15. The sealed capacitive sensor of claim 1 in which said fixed plate is electrically accessed through a wire bonding lead.

16. The sealed capacitive sensor of claim 1 in which said first plate is electrically accessed through a conductor buried in the substrate traversing said sealing medium.

17. The sealed capacitive sensor of claim 13 in which said fixed plate includes a second recess for housing an active electric circuit associated with said capacitive sensor.

18. The sealed capacitive sensor of claim 17 further including a cover and second sealing medium for connecting said cover to said fixed plate and hermetically sealing said second recess.

19. The sealed capacitive sensor of claim 18 in which said second sealing medium includes a frit.

20. The sealed capacitive sensor of claim 18 in which said second sealing medium includes a glass frit.

21. The sealed capacitive sensor of claim 1 further including an over mold covering said fixed plate and attached to said substrate.

10. (canceled)