Method and apparatus for detecting defective traces in a mutual capacitance touch sensing device

• US 8,279,197 B2
• Filed: 08/25/2009
• Issued: 10/02/2012
• Est. Priority Date: 08/25/2009
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Murphy, Thomas, Leong, Keen Hun, Rathburn, Kevin, Narasimhan, Sarangan
• Primary Examiner(s): Chow, Van
• Application Number:
  US12/547,354
• Publication Number:
  US 20110050617A1
• Time in Patent Office: 1,134 Days
• Field of Search: 345173-178
• US Class Current: 345/174
• CPC Class Codes: G06F 11/2221 to test input/output devices or peripheral units
• CPC Class Codes: G06F 3/04164 Connections between sensors and controllers, e.g. routing lines between electrodes and connection pads
• 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

Abstract

Several different methods of testing the integrity and proper operation of the drive and sense electrodes in a mutual capacitance sensing device such as a touchscreen or touchpad are disclosed herein. According to one embodiment, measured values of mutual capacitance corresponding to individual cells in a mutual capacitance sensing device are compared to one another and to predetermined thresholds. The results of the comparison are employed to determine whether any of the traces forming the electrodes in the device are defective. By way of example, traces can be defective if they are broken, too thin, too thick, or shorted together. The various embodiments of the methods disclosed herein may be used for touchscreen or touchpad quality control in a manufacturing setting, or may be used to test touchscreens or touchpads that have already been incorporated into electronic devices. The various methods disclosed herein lower manufacturing costs, increase product quality and yield, and may be carried out quickly.

Claims

1. A method of testing a mutual capacitance sensing device, comprising:

applying a drive signal to a first row or column of drive electrodes from among a plurality of drive electrodes arranged substantially parallel to one another;

measuring respective relative mutual capacitances generated by the drive signal using a plurality of columns or rows of sense electrodes which intersect the rows or columns of drive electrodes at an angle, the columns or rows of sense electrodes being arranged substantially parallel to one another;

associating the measured respective relative mutual capacitances with cells corresponding to intersecting drive and sense electrode locations;

determining differences between the measured relative capacitances of adjoining cells;

determining whether any of the differences exceed or fall below predetermined thresholds corresponding thereto, and

identifying one or more defective traces on the basis of the differences exceeding or falling below the predetermined thresholds.

2. The method of claim 1, further comprising sequentially measuring the respective relative mutual capacitances in the plurality of columns or rows of sense electrodes.

3. The method of claim 1, further comprising further identifying locations of one or more defective traces corresponding to one or more of the cells in the capacitive sensing device.

4. The method of claim 1, further comprising comparing measured capacitances of pairs of neighboring cells to one another and determining the respective differences therebetween.

5. The method of claim 1, further comprising determining whether any differences in measured capacitance fall below predetermined thresholds corresponding thereto, thereby indicating shorted traces.

6. The method of claim 1, further comprising determining whether any differences in measured capacitance fall above predetermined thresholds corresponding thereto, thereby indicating broken traces.

7. The method of claim 1, wherein the angle between the rows and columns of drive electrodes and the columns or rows of sense electrodes is about 90 degrees.

8. The method of claim 1, wherein the mutual capacitance sensing device is a touchscreen.

9. The method of claim 1, wherein the mutual capacitance sensing device is a touchpad.

10. The method of claim 1, wherein the sense electrodes are interleaved.

11. The method of claim 1, wherein the sense electrodes are non-interleaved.

12. The method of claim 1, wherein the method is carried out during a process of manufacturing the device.

13. The method of claim 1, wherein the method is carried out after the device has been incorporated into an electronic device.

14. The method of claim 1, wherein the method is carried out in the field.

15. The method of claim 1, wherein the sense and drive electrodes are disposed in substantially parallel but vertically-offset first and second planes, respectively.

16. The method of claim 1, wherein the sense and drive electrodes comprise indium tin oxide (“

ITO”

).

17. The method of claim 1, wherein the drive and sense electrodes form a 9×

16 sensor array or an 8×

12 sensor array.

18. The method of claim 1, further comprising disposing a liquid crystal display beneath the sensing device.

19. The method of claim 1, wherein the drive and sense electrodes are disposed on a substrate comprising an electrically insulative material.

20. The method of claim 19, wherein the substrate is substantially optically transparent.

21. The method of claim 1, wherein the method is carried out using an integrated circuit having steps corresponding thereto stored in a machine readable medium thereof.

22. The method of claim 1, further comprising incorporating the sensing device into an LCD, a computer display, a laptop computer, a personal data assistant (PDA), a mobile telephone, a radio, an MP3 player, a portable music player, a stationary device, a television, a stereo, an exercise machine, an industrial control, a control panel, an outdoor control device and a household appliance.

23. A method of testing a mutual capacitance sensing device for defective traces, comprising:

applying a drive signal to a first row or column of drive electrodes;

measuring, in at least first and second columns or rows of sense electrodes arranged at an angle with respect to the first row or column, first and second capacitances resulting from the drive signal being applied to the first row or column, the first and second columns and rows being arranged substantially parallel to one another;

applying the drive signal to a second row or column of drive electrodes arranged substantially parallel to the first row or column;

measuring, in the first and second columns or rows of sense electrodes, third and fourth capacitances resulting from the drive signal being applied to the second row or column, the first, second, third and fourth measured capacitances corresponding to respective first, second, third and fourth cells in the sensing device;

determining, for adjoining cells, differences between measured capacitances, and

determining whether any of the differences exceed or fall below predetermined thresholds corresponding to the first, second, third or fourth cells, thereby indicating the presence of one or more defective traces in or near such cells.

24. The method of claim 23, further comprising sequentially measuring the respective relative mutual capacitances in the plurality of columns or rows of sense electrodes.

25. The method of claim 23, further comprising further identifying locations of one or more defective traces corresponding to one or more of the cells in the capacitive sensing device.

26. The method of claim 23, further comprising determining whether any differences in measured capacitance fall below predetermined thresholds corresponding thereto, thereby indicating shorted traces.

27. The method of claim 23, further comprising determining whether any differences in measured capacitance fall above predetermined thresholds corresponding thereto, thereby indicating broken traces.

28. The method of claim 23, wherein the mutual capacitance sensing device is a touchscreen.

29. The method of claim 23, wherein the mutual capacitance sensing device is a touchpad.

30. The method of claim 23, wherein the sense electrodes are interleaved.

31. The method of claim 23, wherein the sense electrodes are non-interleaved.

32. The method of claim 23, wherein the method is carried out during a process of manufacturing the device.

33. The method of claim 23, wherein the method is carried out after the device has been incorporated into an electronic device.

34. The method of claim 23, wherein the method is carried in the field.

35. The method of claim 23, wherein the sense and drive electrodes comprise indium tin oxide (“

ITO”

).

36. The method of claim 23, wherein the method is carried out using an integrated circuit having steps corresponding thereto stored in a machine readable medium thereof.

37. The method of claim 23, further comprising incorporating the sensing device into an LCD, a computer display, a laptop computer, a personal data assistant (PDA), a mobile telephone, a radio, an MP3 player, a portable music player, a stationary device, a television, a stereo, an exercise machine, an industrial control, a control panel, an outdoor control device and a household appliance.

38. A method of testing a mutual capacitance sensing device for defective traces, comprising:

applying a drive signal to a first row or column of drive electrodes;

measuring a first capacitance resulting from the drive signal being applied to the first row or column of drive electrodes in a first column or row of sense electrodes forming an angle with respect to the first row or column;

measuring a second capacitance resulting from the drive signal being applied to the first row or column of drive electrodes in a second column or row of sense electrodes arranged substantially parallel to the first column or row of sense electrodes;

applying the drive signal to a second row or column of drive electrodes arranged substantially parallel to the first row or column of drive electrodes;

measuring a third capacitance resulting from the drive signal being applied to the second row or column of drive electrodes in the first column or row of sense electrodes;

measuring a fourth capacitance resulting from the drive signal being applied to the second row or column of drive electrodes in the second column or row of sense electrodes, the first, second, third and fourth measured capacitances corresponding to respective first, second, third and fourth cells in the sensing device, and

comparing the first, second, third and fourth measured capacitances to predetermined thresholds corresponding thereto.

39. The method of claim 38, further comprising determining differences between any pair of the first, second, third and fourth measured capacitances.

40. The method of claim 39, further comprising identifying one or more defective traces on the basis of the differences exceeding or falling below the predetermined thresholds.

41. A method of testing a mutual capacitance touch sensing device, comprising:

applying a drive signal to a first row or column of drive electrodes arranged substantially parallel to one another;

sequentially measuring respective relative mutual capacitances generated by and corresponding to the drive signal using a plurality of columns or rows of sense electrodes which intersect the rows or columns of drive electrodes at an angle, the columns or rows of sense electrodes being arranged substantially parallel to one another;

storing, in a computer readable medium, and associating with a processor, measured respective relative mutual capacitances with specific areas of the device;

determining with the processor whether any of the determined relative capacitances associated with different portions of the device exceed or fall below a predetermined threshold;

identifying one or more defective traces corresponding to one or more portions of the device associated with determined relative capacitances exceeding or falling below the threshold.