System and method of testing humidity in a sealed MEMS device

• US 20060067645A1
• Filed: 07/01/2005
• Published: 03/30/2006
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Gally, Brian J., Palmateer, Lauren, Cummings, William J., Kothari, Manish
• Granted Patent: US 7,343,080 B2
• Time in Patent Office: Days
• US Class Current: 385/147
• CPC Class Codes: B81C 99/0045 End test of the packaged device
• CPC Class Codes: G01M 3/002 by using thermal means
• CPC Class Codes: G01M 3/02 by using fluid or vacuum
• CPC Class Codes: G01M 3/186 for containers, e.g. radiators
• CPC Class Codes: G01M 3/229 removably mounted in a test cell
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

One embodiment provides a method of testing humidity, comprising: determining a property of a device which encloses a plurality of interferometric modulators; and determining a relative humidity value or a degree of the relative humidity inside the device based at least in part upon the determined property. In one embodiment, the property of the device includes one of the following: i) a weight of the device, ii) a color change of a desiccant enclosed in the device, iii) a resistance inside the device, iv) whether frost formed in an inside area of the device which is contacted by a cold finger device, v) whether a desiccant enclosed in the device, when water vapor is provided into the device, is working properly, and vi) combination of at lest two of i)-v).

Claims

1. A method of testing humidity, comprising:

determining a property of a device which encloses a plurality of interferometric modulators; and

determining a relative humidity value or a degree of the relative humidity inside the device based at least in part upon the determined property.

2. The method of claim 1, wherein the property of the device includes one of the following:

i) a weight of the device, ii) color change of a desiccant enclosed in the device, iii) resistance inside the device, iv) whether frost formed in an inside area of the device which is contacted by a cold finger device set at a certain temperature, and v) whether a desiccant enclosed in the device, when water vapor is provided into the device, is working properly.

3. The method of claim 2, wherein the property of the device includes the combination of at least two of i)-iv).

4. The method of claim 1, further comprising exposing the device to a humid environment before determining the property.

5. The method of claim 4, wherein the humid environment includes a humidity chamber.

6. The method of claim 1, wherein the relative humidity value or the degree of the relative humidity inside the device is determined considering at least one of the following parameters:

i) temperature-humidity combination, ii) the thickness and width of a seal, iii) adhesive permeability, iv) a desiccant capacity, and v) a device size.

7. A system for testing humidity, comprising:

means for determining a property of a device which encloses a plurality of interferometric modulators; and

means for determining a relative humidity value or a degree of the relative humidity inside the device based at least in part upon the determined property.

8. The system of claim 7, wherein the property of the device includes one of the following:

i) a weight of the device, ii) a color change of a desiccant enclosed in the device, iii) a resistance inside the device, iv) whether frost formed in an inside area of the device which is contacted by a cold finger device set at a certain temperature, and v) whether a desiccant enclosed in the device, when water vapor is provided into the device, is working properly.

9. The system of claim 8, wherein the property of the device includes the combination of at least two of i)-iv).

10. A method of testing humidity, comprising:

measuring i) a first weight of a first device which encloses a plurality of interferometric modulators and ii) a second weight of a second device which encloses a plurality of interferometric modulators, wherein the first and second devices contain a different amount of water vapor;

comparing the weights of the first and second devices; and

determining a relative humidity value or a degree of the relative humidity inside one of the two devices based at least in part upon the weight comparison.

11. The method of claim 10, further comprising:

determining the difference between the first and second weights; and

determining that the device is defective or has a shortened lifetime if the difference is greater than a threshold value.

12. The method of claim 10, wherein the relative humidity value or the degree of the relative humidity inside the device is determined considering at least one of the following parameters:

i) temperature-humidity combination, ii) the thickness and width of a seal, iii) adhesive permeability, iv) a desiccant capacity, and v) a device size.

13. The method of claim 10, wherein the second device includes a plurality of devices each enclosing a plurality of interferometric modulators, at least one of the plurality of devices containing a different amount of water vapor from that of the first device, and wherein the second weight is an average weight of the plurality of devices.

14. The method of claim 10, wherein the second device is the same as the first device, and wherein the measuring of the second weight is performed after a predetermined period of time from the first weight measurement.

15. A system for testing humidity, comprising:

a first device enclosing a plurality of interferometric modulators;

a second device enclosing a plurality of interferometric modulators, wherein the first and second devices contain a different amount of water vapor; and

a scale configured to measure the weights of the first and second devices,

wherein a relative humidity value or a degree of the relative humidity inside one of the two devices is determined based at least in part upon the measured weights.

16. The system of claim 15, wherein the scale is accurate to about +0.1 mg.

17. The system of claim 15, wherein the scale is accurate to about ±

0.05 mg.

18. A method of testing humidity, comprising:

providing a device which encloses i) a plurality of interferometric modulators and ii) a desiccant, wherein the desiccant is configured to change its color based on an amount of water vapor absorbed therein;

determining a degree of a color change of the desiccant; and

determining a relative humidity value or a degree of the relative humidity inside the device based at least in part upon the determined degree of the color change.

19. The method of claim 18, wherein the device comprises a backplate which includes at least a transparent portion, wherein determining the degree of the color change is performed via the transparent portion of the backplate.

20. The method of claim 18, wherein the device comprises a transparent backplate, and wherein determining the degree of the color change is performed via the transparent backplate.

21. The method of claim 18, wherein determining the degree of a color change of the desiccant comprises:

exposing the device to a humid environment;

determining a first color of the desiccant before exposing the device to a humid environment;

determining a second color of the desiccant after exposing the device to the humid environment;

comparing the first and second colors; and

determining the degree of a color change of the desiccant based on the color comparison.

22. A method of manufacturing a microelectromechanical systems (MEMS) device, the method comprising:

providing a substrate;

forming a plurality of interferometric modulators on the substrate;

providing a desiccant configured to change its color based on an amount of water vapor absorbed therein;

providing a backplate; and

joining the substrate and the backplate so as to form a device which encloses the plurality of interferometric modulators and the desiccant,

wherein the backplate includes at least one transparent portion through which the color change of the desiccant can be viewed from the outside of the device.

23. The method of claim 22, wherein the relative humidity value or the degree of the relative humidity inside the device is determined considering at least one of the following parameters:

i) temperature-humidity combination, ii) the thickness and width of a seal, iii) adhesive permeability, iv) a desiccant capacity, and v) a device size.

24. A microelectromechanical systems (MEMS) device, comprising:

a substrate;

a plurality of interferometric modulators formed on the substrate;

a desiccant configured to change its color based on an amount of water vapor absorbed therein; and

a backplate;

wherein the substrate and backplate are joined to each other so as to form a device which encloses the plurality of interferometric modulators and the desiccant,

wherein the backplate includes at least one transparent portion through which the color change of the desiccant can be viewed from the outside of the device.

25. The device of claim 24, wherein the backplate is formed of a transparent material.

26. A method of testing humidity, comprising:

providing a device which encloses a plurality of interferometric modulators;

measuring a resistance of at least one interior part of the device; and

determining a relative humidity value or a degree of the relative humidity inside the device based at least in part upon the measured resistance.

27. The method of claim 26, wherein the measuring is performed with the use of a resistive sensor.

28. The method of claim 27, further comprising connecting the resistive sensor to a lead of the device, wherein the lead is connected to an interior portion of the device, and wherein the resistive sensor is configured to measure an electrical impedance or resistance around the interior portion.

29. The method of claim 27, further comprising:

patterning a lead;

connecting the resistive sensor to the patterned lead; and

removing the patterned lead after determining the relative humidity value or the degree of the relative humidity.

30. The method of claim 26, further comprising:

operably contacting an outside area of the device with a cold finger device; and

determining whether frost forms in an inside area of the interferometric modulator device corresponding to the contacted area,

wherein the relative humidity value or the degree of the relative humidity is determined based at least in part upon the combination of i) whether frost has formed in the inside area and ii) the measured resistance.

31. The method of claim 30, wherein the device comprises a backplate and a substrate, and wherein at least one of the backplate and substrate is non-transparent.

32. A system for testing humidity, comprising:

a device enclosing a plurality of interferometric modulators; and

a resistive sensor configured to measure a resistance of at least one interior part of the device,

wherein a relative humidity value or a degree of the relative humidity inside the device is determined based at least in part upon the measured resistance.

33. The system of claim 32, wherein the resistive sensor is connected to a lead of the device, wherein the lead is connected to an interior portion of the device, wherein the resistive sensor is configured to measure an electrical impedance or resistance around the interior portion.

34. The system of claim 33, wherein the lead is a patterned lead formed for the humidity testing.

35. The system of claim 34, wherein the patterned lead is configured to be removed after the humidity testing.

36. The system of claim 34, wherein the patterned lead is located in an unused portion of the device.

37. The system of claim 33, wherein the lead is connected to one of the following:

i) an electrode of at least one of the plurality of interferometric modulators, ii) a portion of the interferometric modulators, and iii) other interior portion of the device.

38. The system of claim 33, wherein the lead is connected to a portion of a backplate or a substrate of the device.

39. The system of claim 33, wherein the lead is configured to be inserted into the interior of the device via a hole that is defined for the humidity testing.

40. The system of claim 32, further comprising a cold finger device configured to make an operable contact with an outside area of the interferometric modulator device, wherein the relative humidity value or the degree of the relative humidity is determined based at least in part upon the combination of i) whether frost has formed in the inside area and ii) the measured resistance.

41. A method of testing humidity, comprising:

i) providing a device which encloses a plurality of interferometric modulators;

ii) operably contacting an outside area of the device with a cold finger device, set at a first temperature;

iii) determining whether frost forms in an inside area of the interferometric modulator device to the contacted area; and

iv) determining a relative humidity value or a degree of the relative humidity inside the interferometric modulator device based at least in part upon whether frost has formed in the inside area.

42. The method of claim 41, further comprising applying a liquid material on the contacting area of the cold finger device so as to provide better contact and thermal conductance.

43. The method of claim 41, further comprising:

v) contacting a cold finger device, set at a second temperature higher than the first temperature, on the outside area of the device if frost has formed in the inside area; and

vi) repeating iii) and iv) as needed.

44. The method of claim 43, further comprising repeating v) and vi) until no frost forms in the inside area.

45. The method of claim 41, wherein the determining iii) is performed with the use of a resistive sensor.

46. The method of claim 45, further comprising connecting the resistive sensor to a lead of the device, wherein the lead is connected to an interior portion of the device, wherein the resistive sensor is configured to measure an electrical impedance or resistance around the interior portion.

47. The method of claim 41, wherein ii) comprises contacting the cold finger device on one of the following:

a backplate, a substrate, and a border area of

     1) a seal and

     2) the substrate of the device.

48. The method of claim 47, wherein the substrate includes at least one transparent portion, and wherein the method further comprises:

contacting the cold finger device in an outside area of the backplate; and

determining whether frost forms in an inside area of the backplate, corresponding to the outside area, via the at least one transparent portion of the substrate.

49. The method of claim 47, wherein the backplate includes at least one transparent portion, and wherein the method further comprises:

contacting the cold finger device in an outside area of the substrate; and

determining whether frost forms in an inside area of the substrate, corresponding to the outside area, via the at least one transparent portion of the backplate.

50. The method of claim 41, wherein the determining (iii) is performed via at least one transparent window of a backplate, or via a portion of a transparent substrate.

51. The method of claim 41, further comprising measuring a resistance of at least one interior part of the device, wherein the relative humidity value or the degree of the relative humidity is determined based at least in part upon the combination of i) whether frost has formed in the inside area and ii) the measured resistance.

52. A system for testing humidity, comprising:

a device enclosing a plurality of interferometric modulators; and

a cold finger device configured to make an operable contact with an outside area of the device,

wherein a relative humidity value or a degree of the relative humidity inside the interferometric modulator device is determined based at least in part upon whether frost has formed in the inside area.

53. The system of claim 52, wherein the device comprises a substrate which includes at least one transparent portion, and wherein determining whether frost has formed in the inside area is performed via the at least one transparent portion of the substrate.

54. The system of claim 52, wherein the device comprises a backplate which includes at least one transparent portion, and wherein determining whether frost has formed in the inside area is performed via the at least one transparent portion of the backplate.

55. The system of claim 52, further comprising a resistive sensor configured to measure a resistance of at least one interior part of the device, wherein the relative humidity value or the degree of the relative humidity is determined based at least in part upon the combination of i) whether frost has formed in the inside area and ii) the measured resistance.

56. A method of testing humidity, comprising:

providing a device which encloses i) a plurality of interferometric modulators and ii) a desiccant;

measuring a first weight of the device;

providing water vapor into the inside of the device;

measuring a second weight of the device after the water vapor has been provided into the device;

comparing the first and second weights; and

determining a degree of the relative humidity inside the device based at least in part upon the weight comparison.

57. The method of claim 56, wherein the device includes a desiccant, and wherein the method further comprises determining that the desiccant is not working properly if the second weight is substantially the same as the first weight.

58. The method of claim 56, further comprising defining a hole at least one of the following area:

a seal, a backplate, and a substrate of the device, and wherein the water vapor is provided into the device via the hole.