Low EMI capacitive trackpad

• US 20060066581A1
• Filed: 09/24/2004
• Published: 03/30/2006
• Est. Priority Date: 09/24/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Hotelling, Steven P., Lyon, Benjamin
• Granted Patent: US 7,394,458 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 2203/04111 Cross over in capacitive digitiser, i.e. details of structures for connecting electrodes of the sensing pattern where the connections cross each other, e.g. bridge structures comprising an insulating layer, or vias through substrate
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: H05K 1/0219 Printed shielding conductors for shielding around or between signal conductors, e.g. coplanar or coaxial printed shielding conductors
• CPC Class Codes: H05K 1/11 Printed elements for providing electric connections to or between printed circuits

Abstract

A printed circuit board (PCB) assembly provides a two layer capacitive trackpad sensor in which an EMI ground grid is interposed among the sensor'"'"'s capacitive elements on each of its layers. The EMI grid on each of the two layers is electrically coupled via, typically, vias. The described arrangement of sensor elements (capacitor plates) and EMI ground grid traces may be incorporated into a PCB having additional layers (e.g., a four, six or eight layer PCB). If used in this manner, additional vias are provided on the PCB which permit electrical coupling between these “additional layers” and which are electrically isolated from, and shielded by, the EMI ground grid.

Claims

1. A trackpad printed circuit board, comprising:

a first layer having a first plurality of metal surfaces forming columns of capacitor plates and a second plurality of metal surfaces electrically isolated from, and interposed between, each pair of the first plurality of metal surfaces;

a second layer having a third plurality of metal surfaces forming rows of capacitor plates that are aligned substantially orthogonal to the first plurality of metal surfaces, a fourth plurality of metal surfaces electrically isolated from, and interposed between, each pair of the third plurality of metal surfaces and a fifth plurality of metal surfaces forming capacitor plate regions that are electrically isolated from the third and fourth plurality of metal surfaces and, further, substantially aligned over the first plurality of metal surfaces on the first layer; and

vias for electrically coupling the second plurality of metal surfaces on the first layer to the fourth plurality of metal surfaces on the second layer.

2. The trackpad printed circuit board of claim 1, wherein the vias comprise thru-hole vias.

3. The trackpad printed circuit board of claim 1, further comprising two or more additional layers.

4. The trackpad printed circuit board of claim 3, further comprising second vias for electrically coupling between the two or more additional layers, wherein the second vias are electrically isolated from the first, second, third, fourth and fifth plurality of metal surfaces and extend through the second plurality of metal surfaces in the first layer, through the fourth plurality of metal surfaces in the second layer and the two or more additional layers.

5. The trackpad printed circuit board of claim 4, wherein the second vias comprise thru-hole vias.

6. The trackpad printed circuit board of claim 1 wherein one or more of the metal surfaces comprise copper metal surfaces.

7. The trackpad circuit board of claim 1 wherein the first and second layers comprise two sides of a common woven epoxy glass material substrate.

8. A trackpad printed circuit board, comprising:

a first layer having a first plurality of metal surfaces and a second plurality of metal surfaces electrically isolated from, and interposed between, each pair of the first plurality of metal surfaces;

a second layer having a third plurality of metal surfaces aligned substantially orthogonal to the first plurality of metal surfaces, a fourth plurality of metal surfaces electrically isolated from, and interposed between, each pair of the third plurality of metal surfaces and a fifth plurality of metal surfaces electrically isolated from the third and fourth plurality of metal surfaces and, further, substantially aligned over the first plurality of metal surfaces on the first layer; and

means for electrically coupling the second plurality of metal surfaces on the first layer to the fourth plurality of metal surfaces on the second layer.

9. The trackpad printed circuit board of claim 8, wherein the means for electrically coupling comprises:

a plurality of vias in the first layer located in the second plurality of metal surfaces; and

a plurality of vias in the second layer located in the fourth plurality of metal surfaces.

10. The trackpad printed circuit board of claim 9, wherein the vias comprise thru-hole vias.

11. The trackpad printed circuit board of claim 8, further comprising two or more additional layers adapted to receive components.

12. The trackpad printed circuit board of claim 11, wherein each pair of adjacent layers are separated by a preimpregnated bonding layer material.

13. The trackpad printed circuit board of claim 11, further comprising means for electrically coupling between the two or more additional layers, wherein the second means is electrically isolated from the first, second, third, fourth and fifth plurality of metal surfaces.

14. The trackpad printed circuit board of claim 13, wherein the means for electrically coupling between the two or more additional layers comprises a plurality of vias extending through the second plurality of metal surfaces in the first layer, through the fourth plurality of metal surfaces in the second layer and the two or more additional layers.

15. The trackpad printed circuit board of claim 14, wherein the means for electrically coupling between the two or more additional layers comprising a plurality of vias comprises thru-hole vias.

16. The trackpad printed circuit board of claim 8, wherein:

each of the first plurality of metal surfaces is adapted to electrically couple to a first electrical circuit; and

each of the third plurality of metal surfaces is adapted to electrically couple to a second electrical circuit.

17. The trackpad printed circuit board of claim 16, wherein the first circuit and second circuit are adapted to process trackpad sensor output signals.

18. The trackpad printed circuit board of claim 8 wherein one or more of the metal surfaces comprise copper metal surfaces.

19. The trackpad circuit board of claim 8 wherein the first and second layers comprise two sides of a common glass substrate.

31. The computer system of claim 8, wherein:

each of the first plurality of metal surfaces is adapted to electrically couple to a first electrical circuit;

each of the third plurality of metal surfaces is adapted to electrically couple to a second electrical circuit; and

32. The computer system of claim 31, wherein the first circuit and second circuit are adapted to process trackpad sensor output signals.

20. A method to fabricate a trackpad printed circuit board, comprising:

forming, on a first surface of the printed circuit board, a first plurality of metal surfaces and a second plurality of metal surfaces electrically isolated from, and interposed between, each pair of the first plurality of metal surfaces;

forming, on a second surface of the printed circuit board, a third plurality of metal surfaces aligned substantially orthogonal to the first plurality of metal surfaces on the first surface, a fourth plurality of metal surfaces electrically isolated from, and interposed between, each pair of the third plurality of metal surfaces and a fifth plurality of metal surfaces electrically isolated from the third and fourth plurality of metal surfaces and, further, substantially aligned over the first plurality of metal surfaces on the first surface; and

forming an electrically conductive path between the second plurality of metal surfaces on the first surface and the fourth plurality of metal surfaces on the second surface.

21. The method of claim 20, wherein the act of forming the first, second, third, fourth and fifth metal surfaces comprises using copper metal.

22. The method of claim 20, wherein the act of forming an electrically conductive path comprises creating a plurality of vias that extend between the second plurality of metal surfaces on the first and the fourth plurality of metal surfaces on the second surface.

23. The method of claim 22, wherein the act of creating a plurality of vias comprise creating a plurality of thru-hole vias.

24. The method of claim 20, further comprising the act of mechanically coupling two or more additional layers beneath the first surface.

25. The method of claim 24, wherein the act of mechanically coupling comprises separating the first surface from a first layer of the two or more additional layers with a preimpregnated bonding layer material.

26. The method of claim 24, further comprising the act of forming electrically conductive paths between each of the two or more additional layers that are electrically isolated from the first, second, third, fourth and fifth plurality of metal surfaces.

27. The method of claim 26, wherein the act of forming electrically conductive paths comprise forming thru-hole vias in the trackpad printed circuit board that pass through the second and fourth plurality of metal surfaces.

28. A computer system comprising:

a display unit adapted to display a cursor;

a central processor operatively coupled to the display unit; and

a trackpad operatively coupled to the display unit for controlling the cursor'"'"'s location, the trackpad comprising—

a first layer having a first plurality of metal surfaces and a second plurality of metal surfaces electrically isolated from, and interposed between, each pair of the first plurality of metal surfaces,

a second layer having a third plurality of metal surfaces aligned substantially orthogonal to the first plurality of metal surfaces, a fourth plurality of metal surfaces electrically isolated from, and interposed between, each pair of the third plurality of metal surfaces and a fifth plurality of metal surfaces electrically isolated from the third and fourth plurality of metal surfaces and, further, substantially aligned over the first plurality of metal surfaces on the first layer, and

means for electrically coupling the second plurality of metal surfaces on the first layer to the fourth plurality of metal surfaces on the second layer.

29. The computer system of claim 28, wherein the means for electrically coupling comprises:

a plurality of vias in the first layer located in the second plurality of metal surfaces; and

a plurality of vias in the second layer located in the fourth plurality of metal surfaces.

30. The computer system of claim 29, wherein the vias comprise thru-hole vias.