Capacitive type humidity sensor

• US 20050188764A1
• Filed: 02/22/2005
• Published: 09/01/2005
• Est. Priority Date: 02/27/2004
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Itakura, Toshikazu, Yokura, Hisanori
• Granted Patent: US 7,387,024 B2
• Time in Patent Office: Days
• US Class Current: 73/335.40
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825

Abstract

A capacitive type humidity sensor includes: a semiconductor substrate; a plurality of humidity devices having a capacitance variable in accordance with a humidity; a standard capacitance device having a standard capacitance, a capacitance change of which in accordance with the humidity is smaller than that of the capacitance of each humidity device; and a CV converter circuit for converting a capacitance difference between the capacitance of each humidity device and the standard capacitance of the standard capacitance device to a signal voltage. The humidity devices, the standard capacitance device and the CV converter circuit are disposed on one side of the substrate.

Claims

1. A capacitive type humidity sensor comprising:

a semiconductor substrate;

a plurality of humidity devices having a capacitance variable in accordance with a humidity;

a standard capacitance device having a standard capacitance, a capacitance change of which in accordance with the humidity is smaller than that of the capacitance of each humidity device; and

a CV converter circuit for converting a capacitance difference between the capacitance of each humidity device and the standard capacitance of the standard capacitance device to a signal voltage, wherein

the humidity devices, the standard capacitance device and the CV converter circuit are disposed on one side of the substrate.

2. The sensor according to claim 1, wherein

the standard capacitance of the standard capacitance device is constant without depending on the humidity.

3. The sensor according to claim 1, further comprising:

a plurality of standard capacitance devices, each of which corresponds to the humidity device.

4. The sensor according to claim 1, wherein

the humidity devices share the standard capacitance device commonly.

5. The sensor according to claim 1, wherein

the humidity devices are disposed on the standard capacitance device through an insulation layer.

6. The sensor according to claim 1, wherein

at least one of the humidity devices and the standard capacitance device is disposed on the CV converter circuit through an insulation layer.

7. The sensor according to claim 1, further comprising:

a plurality of CV converter circuits, each of which corresponds to the humidity device.

8. The sensor according to claim 1, wherein

the humidity devices share the CV converter circuit commonly.

9. The sensor according to claim 1, wherein

the substrate includes a separation region for separating the humidity devices, and

the separation region of the substrate has no electric part except for a wiring thereon.

10. The sensor according to claim 1, wherein

the humidity devices are disposed on the substrate to sandwich the CV converter circuit.

11. The sensor according to claim 1, wherein

the CV converter circuit is disposed on a center of the substrate, and

the humidity devices are disposed on the substrate symmetrically with respect to a center of the substrate.

12. The sensor according to claim 1, wherein

the humidity devices are two humidity devices,

the substrate has a rectangular shape,

two humidity devices are disposed on both sides of the substrate.

13. The sensor according to claim 1, further comprising:

a plurality of temperature sensor devices, each of which corresponds to the humidity device, and

the temperature sensor devices are disposed on the substrate symmetrically with respect to a center of the substrate.

14. The sensor according to claim 1, wherein

the humidity device is a comb-teeth electrode capacitance device having a pair of comb-teeth electrodes,

the comb-teeth electrodes are disposed on the substrate to face and to engage each other,

the humidity device includes a moisture sensitive film disposed on the substrate to cover the comb-teeth electrodes, and

the moisture sensitive film has a dielectric constant variable in accordance with the humidity.

15. The sensor according to claim 14, wherein

the standard capacitance device is a comb-teeth electrode capacitance device having a pair of comb-teeth electrodes, and

the comb-teeth electrodes are disposed on the substrate to face and to engage each other.

16. The sensor according to claim 15, wherein

the standard capacitance device has a distance between the comb-teeth electrodes,

the humidity device has a distance between the comb-teeth electrodes, and

the distance of the standard capacitance device is narrower than that of the humidity device.

17. The sensor according to claim 15, wherein

the comb-teeth electrode of the standard capacitance device has a height in a vertical direction perpendicular to the substrate,

the comb-teeth electrode of the humidity device has a height in the vertical direction perpendicular to the substrate, and

the height of the comb-teeth electrode of the standard capacitance device is higher than that of the humidity device.

18. The sensor according to claim 1, wherein

the substrate is mounted on a circuit board in such a manner that the humidity devices, the standard capacitance device and the CV converter circuit of the substrate face the circuit board to provide a flip chip.

19. The sensor according to claim 18, wherein

the circuit board includes a heater, which faces the humidity device.