CAPACITIVE DOME SWITCH

• US 20110241442A1
• Filed: 09/29/2010
• Published: 10/06/2011
• Est. Priority Date: 04/01/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Merz, Nicholas, Mittleman, Adam
• Granted Patent: US 8,450,627 B2
• Time in Patent Office: Days
• US Class Current: 307/112
• CPC Class Codes: H01H 2215/006 Only mechanical function
• CPC Class Codes: H01H 2239/006 Containing a capacitive switch or usable as such
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 17/975 using a capacitive movable element
• CPC Class Codes: H03K 2217/96062 with tactile or haptic feedback
• CPC Class Codes: H03K 2217/960755 Constructional details of capacitive touch and proximity switches
• CPC Class Codes: Y10T 29/49105 Switch making

Abstract

This is directed to a dome switch that includes a capacitive sensor. A dome switch can include a dome operative to deform to provide tactile feedback to a user. To provide an electrical instruction to the device, the region underneath the dome can define a free space separating conductive regions forming a capacitor. For example, a tip of the dome, a button placed between the dome and a circuit board, or a user'"'"'s finger can form a first conductor of a capacitor, and a support structure for the dome can include a terminal forming a second conductor completing the capacitor. When the dome deflects, the distance between the conductors can change and provide a measurable capacitance variation, which the device can detect. To protect the dome switch from damage due to contaminants, the terminal can be integrated within a volume of the circuit board such that it is not exposed to the environment of the dome switch. In one implementation, the terminal may not be exposed to air.

Claims

1. A dome switch comprising:

a circuit comprising a terminal, wherein the terminal is electrically conductive, and wherein no external surface of the terminal is exposed;

a dome positioned adjacent to the circuit, wherein a portion of the dome is operative to deflect to decrease a distance between the portion of the dome and the terminal; and

a controller electrically connected to the terminal, wherein the controller is operative to measure a change in capacitance of a capacitor for which the terminal serves as a conductor when the portion of the dome deflects.

2. The dome switch of claim 1, further comprising:

a housing placed over the dome, wherein the portion of the dome deflects in response to a force applied to the housing.

3. The dome switch of claim 2, wherein:

the housing comprises a conductive component, wherein the conductive component of the housing forms another conductor of the capacitor.

4. The dome switch of claim 2, further comprising:

a button integrated in the housing, wherein the button is operative to move relative to a portion of the housing to cause the dome to deflect.

5. The dome switch of claim 4, wherein:

the button comprises a conductive portion, wherein the conductive portion of the button forms another conductor of the capacitor.

6. The dome switch of claim 1, wherein:

the circuit comprises another terminal, wherein the other terminal is conductive, and wherein the other terminal is electrically isolated from the terminal; and

the controller is electrically connected to the terminal and to the other terminal, wherein the controller is operative to measure a change in capacitance of a capacitor for which the terminal and the other terminal serve as conductors.

7. The dome switch of claim 1, wherein:

the terminal is integrated within an internal volume of the circuit board.

8. The dome switch of claim 1, wherein:

the terminal extends from an external surface of the circuit; and

the dome switch further comprises a protective layer applied over the terminal such that no surface of the terminal is exposed.

9. A method for constructing a capacitive dome switch, comprising:

defining a terminal that is not exposed to an environment of the dome switch;

placing a dome over the terminal, wherein the dome can deflect to change a distance between a tip of the dome and the terminal; and

connecting a controller to the terminal, wherein the controller is operative to detect a change in capacitance corresponding to the terminal when the dome deflects.

10. The method of claim 9, further comprising:

providing a circuit board; and

defining an internal region of the circuit board in which the terminal is located.

11. The method of claim 10, further comprising:

coring an internal volume in the circuit board;

inserting a conductive material in the internal volume to form the terminal; and

closing an opening to the internal volume with a non-conductive material.

12. The method of claim 10, further comprising:

overlaying a plurality of layers to form a circuit board, wherein at least one of the layers includes an opening;

placing a conductive material in the opening to form the terminal; and

overlaying at least one layer over the conductive material, wherein the plurality of layers surround all external surfaces of the conductive material.

13. The method of claim 9, further comprising:

providing a flex circuit;

depositing the terminal on an external surface of the flex circuit; and

covering the terminal with a protective layer.

14. The method of claim 13, further comprising:

connecting the protective layer to the terminal and to the external surface of the flex circuit using an adhesive.

15. An electronic device, comprising:

a support structure;

a conductive terminal, wherein the conductive terminal is coupled to the support structure such that no air external to the support structure comes into contact with the conductive terminal;

a controller electrically coupled to the conductive terminal, wherein the controller is operative to detect a capacitance value corresponding to the conductive terminal;

a dome placed adjacent to the support structure, wherein the dome can be at least partially inverted; and

a housing enclosing the support structure, the conductive terminal, the controller, and the dome, wherein a tip of the dome is in contact with the housing such that a force applied to the housing can cause the dome to be at least partially inverted.

16. The electronic device of claim 15, further comprising:

a second conductive terminal, wherein the second conductive terminal is coupled to a portion of the housing.

17. The electronic device of claim 16, wherein:

a distance between the conductive terminal and the second conductive terminal changes when the force is applied to the housing to cause the dome to be at least partially inverted.

18. The electronic device of claim 17, wherein:

the controller is operative to detect a change in capacitance value corresponding to the conductive terminal when the distance between the conductive terminal and the second conductive terminal changes.

19. The electronic device of claim 17, wherein:

the distance between the conductive terminal and the second conductive terminal decreases when the force is applied.

20. The electronic device of claim 15, further comprising:

control circuitry, wherein the control circuitry is operative to perform an electronic device operation in response to receiving an indication from the controller that the capacitance value corresponding to the conductive terminal has changed.