RFID tag with bridge circuit assembly and methods of use

• US 6,693,541 B2
• Filed: 07/19/2001
• Issued: 02/17/2004
• Est. Priority Date: 07/19/2001
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Egbert, William C.
• Primary Examiner(s): Lee, Benjamin C.
• Application Number:
  US09/909,154
• Publication Number:
  US 20030016133A1
• Time in Patent Office: 943 Days
• Field of Search: 340/572.7, 340/572.8, 340/572.1, 340/572.5, 361/813, 361/600, 361/821, 257/288, 257/528, 257/529, 257/531, 257/532, 29/254.2, 296/01, 343/895, 343/700.R, 343/750, 235/487, 235/442, 235/449, 235/451, 235/444, 235/492, 235/493
• US Class Current: 340/572.7
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: Y10T 29/49018 with other electrical component

Abstract

Radio frequency identification tag devices with bridge circuit assemblies and methods for high-volume, low-cost production are disclosed. The bridge circuit assemblies and methods of the present invention can reduce the complexity of the RFID tag devices by providing a one-sided circuit design. The resonant frequency of the circuits formed on the devices may be tuned by severing selected connections to one or more tuning capacitor plates that form a part of the capacitor structure. Severing connections to the tuning capacitor plates changes the capacitance of the circuit that, in turn, changes the resonant frequency of the circuit. Further, the devices and methods of the present invention allow for the option of placing a die either on the antenna substrate or on the bridge circuit assembly.

Claims

1. A radio frequency identification tag device comprising:

a radio frequency identification tag base comprising;

a base substrate comprising first and second major surfaces;

an antenna pattern comprising first and second ends and a plurality of coils, wherein the first end of the antenna pattern is located within an inner space defined by the plurality of coils and the second end of the antenna pattern is located outside of the plurality of coils;

a first connection pad and a second connection pad, wherein the first connection pad is in electrical communication with the first end of the antenna pattern and the second connection pad is in electrical communication with the second end of the antenna pattern; and

a plurality of severable tuning capacitor plates, each of the tuning capacitor plates in electrical communication with the antenna pattern through a tuning capacitor plate connection;

a bridge circuit assembly comprising a conductive layer; and

a capacitor comprising the plurality of severable tuning capacitor plates and a common capacitor plate, wherein the conductive layer of the bridge circuit assembly forms the common capacitor plate, and further wherein the first connection pad is electrically connected to the second connection pad through the conductive layer of the bridge circuit assembly.

2. A device according to claim 1, further comprising adhesive located between the common capacitor plate and each of the tuning capacitor plates.

3. A device according to claim 1, wherein the capacitor further comprises a dielectric layer comprising a backing and adhesive located on each of two major surfaces of the backing.

4. A device according to claim 1, further comprising electrically conductive adhesive between the conductive layer of the bridge circuit assembly and first and second connection pads of the radio frequency identification tag base.

5. A device according to claim 1, further comprising a die connection site located on the first major surface of the base substrate, the die connection site in electrical communication with the antenna.

6. A device according to claim 5, further comprising a die attached to the die connection site.

7. A device according to claim 1, wherein the bridge circuit assembly further comprises a die connection site in electrical communication with the conductive layer of the bridge circuit assembly.

8. A device according to claim 7, further comprising a die attached to the die connection site.

9. A device according to claim 1, further comprising at least one disconnected tuning capacitor plate located opposite the common capacitor plate and separated from the common capacitor plate by a dielectric layer, wherein the disconnected tuning capacitor plate is not in electrical communication with the antenna.

10. A device according to claim 1, wherein the first connection pad and second connection pad are electrically connected to the conductive layer of the bridge circuit assembly through at least two openings in the bridge substrate.

11. A method for fabricating a radio frequency identification tag device, the method comprising:

providing a radio frequency identification tag base comprising a base substrate comprising first and second major surfaces, and a circuit pattern on the first major surface of the base substrate, the circuit pattern comprising;

an antenna pattern comprising first and second ends and a plurality of coils, wherein the first end of the antenna pattern is located within an inner space defined by the plurality of coils and the second end of the antenna pattern is located outside of the plurality of coils;

a first connection pad and a second connection pad, wherein the first connection pad is in electrical communication with the first end of the antenna pattern and the second connection pad is in electrical communication with the second end of the antenna pattern; and

a plurality of tuning capacitor plates, each of the tuning capacitor plates in electrical communication with the antenna pattern through a tuning capacitor plate connection;

providing a bridge circuit assembly, the bridge circuit assembly comprising;

a bridge substrate comprising first and second major surfaces; and

a conductive layer on the first major surface of the bridge substrate;

providing a dielectric layer between the radio frequency identification tag base and the bridge circuit assembly, wherein the conductive layer and plurality of tuning capacitor plates are separated by the dielectric layer;

electrically connecting the first connection pad to the second connection pad through the conductive layer of the bridge circuit assembly;

forming a capacitor, the capacitor comprising the plurality of tuning capacitor plates, the dielectric layer, and a common capacitor plate, wherein the conductive layer of the bridge circuit assembly forms the common capacitor plate;

measuring a resonant frequency of the device; and

selectively severing at least one of the tuning capacitor plate connections.

12. A radio frequency identification tag device comprising:

a radio frequency identification tag base comprising;

a base substrate comprising first and second major surfaces;

an antenna pattern comprising first and second ends and a plurality of coils, wherein the first end of the antenna pattern is located within an inner space defined by the plurality of coils and the second end of the antenna pattern is located outside of the plurality of coils;

a first connection pad and a second connection pad, wherein the first connection pad is in electrical communication with the first end of the antenna pattern and the second connection pad is in electrical communication with the second end of the antenna pattern; and

a plurality of severable tuning capacitor plates, each of the tuning capacitor plates in electrical communication with the antenna pattern through a tuning capacitor plate connection;

a bridge circuit assembly comprising a conductive layer;

a capacitor comprising the plurality of severable tuning capacitor plates, a dielectric layer, and a common capacitor plate, wherein the conductive layer of the bridge circuit assembly forms the common capacitor plate, and further wherein the plurality of severable tuning capacitor plates and the common capacitor plate are separated by the dielectric layer; and

at least one disconnected tuning capacitor plate located opposite the common capacitor plate and separated from the common capacitor plate by the dielectric layer, wherein the disconnected tuning capacitor plate is not in electrical communication with the antenna, and further wherein the first connection pad is electrically connected to the second connection pad through the conductive layer of the bridge circuit assembly.

13. A method for fabricating a radio frequency identification tag device, the method comprising:

providing a base substrate comprising first and second major surfaces;

providing a circuit pattern on the first major surface of the base substrate, the circuit pattern comprising;

an antenna pattern comprising first and second ends and a plurality of coils, wherein the first end of the antenna pattern is located within an inner space defined by the plurality of coils and the second end of the antenna pattern is located outside of the plurality of coils;

a first connection pad and a second connection pad, wherein the first connection pad is in electrical communication with the first end of the antenna pattern and the second connection pad is in electrical communication with the second end of the antenna pattern; and

a plurality of severable tuning capacitor plates, each of the tuning capacitor plates in electrical communication with the antenna pattern through a tuning capacitor plate connection;

providing a bridge circuit assembly comprising a conductive layer;

electrically connecting the first connection pad to the second connection pad through the conductive layer of the bridge circuit assembly; and

forming a capacitor, the capacitor comprising the plurality of severable tuning capacitor plates and a common capacitor plate, wherein the conductive layer of the bridge circuit assembly forms the common capacitor plate.

14. A method according to claim 13, wherein the bridge circuit assembly traverses the plurality of coils between the first end and the second end of the antenna pattern above the first major surface of the base substrate.

15. A method according to claim 13, wherein the bridge circuit assembly further comprises a bridge substrate having a first major surface and a second major surface, wherein the conductive layer is located on the first major surface of the bridge substrate.

16. A method according to claim 15, further comprising:

locating the bridge circuit assembly such that the second major surface of the bridge substrate faces the first major surface of the base substrate; and

providing a first and second via connection through the bridge substrate, wherein the first and second via connection electrically connect the first connection pad and the second connection pad to the conductive layer of the bridge circuit assembly.

17. A method according to claim 15, wherein the bridge circuit assembly further comprises an edge zone on the first major surface of the bridge substrate, wherein the edge zone comprises an area around a periphery of the first major surface of the substrate, and further wherein the edge zone is substantially free of the conductive layer.

18. A method according to claim 15, wherein the bridge circuit assembly further comprises a die connection site on the first major surface of the bridge substrate, the die connection site in electrical communication with the conductive layer of the bridge circuit assembly.

19. A method according to claim 18, further comprising attaching a die to the die connection site.

20. A method according to claim 18, wherein the die connection site comprises an integrated die connection pad, and wherein the method further comprises separating the die connection site into a plurality of die connection terminals.

21. A method according to claim 13, further comprising:

measuring a resonant frequency of the device; and

selectively severing at least one of the tuning capacitor plate connections.

22. A method according to claim 13, wherein the circuit pattern further comprises a die connection site on the first major surface of the base substrate, the die connection site in electrical communication with the antenna pattern.

23. A method according to claim 22, further comprising attaching a die to the die connection site.

24. A method according to claim 22, wherein the die connection site comprises an integrated die connection pad, and wherein the method further comprises separating the die connection site into a plurality of die connection terminals.

25. A method according to claim 13, further comprising providing a dielectric layer between the common capacitor plate and each of the tuning capacitor plates.

26. A method according to claim 25, wherein the dielectric layer comprises an adhesive.

27. A method according to claim 25, wherein the dielectric layer comprises a backing and adhesive located on each of two major surfaces of the backing.

28. A method according to claim 13, further comprising providing an electrically conductive material between the first and second connection pads and the bridge circuit assembly.

29. A method according to claim 28, wherein the electrically conductive material comprises electrically conductive adhesive.

30. A method according to claim 13, wherein providing a base substrate further comprises providing a substrate web comprising a plurality of circuit patterns.

31. A method according to claim 30, further comprising separating the substrate web between adjacent circuit patterns.

32. A method for fabricating a radio frequency identification tag device, the method comprising:

providing a radio frequency identification tag base comprising a base substrate comprising first and second major surfaces, and a circuit pattern on the first major surface of the base substrate, the circuit pattern comprising;

an antenna pattern comprising first and second ends and a plurality of coils, wherein the first end of the antenna pattern is located within an inner space defined by the plurality of coils and the second end of the antenna pattern is located outside of the plurality of coils;

a first connection pad and a second connection pad, wherein the first connection pad is in electrical communication with the first end of the antenna pattern and the second connection pad is in electrical communication with the second end of the antenna pattern, and further wherein the first connection pad and the second connection pad define a first axis that intersects both the first and second connection pads; and

a plurality of severable tuning capacitor plates, each of the tuning capacitor plates in electrical communication with the antenna pattern through a tuning capacitor plate connection;

providing a bridge circuit assembly having a longitudinal axis, the bridge circuit assembly comprising;

a bridge substrate comprising first and second major surfaces; and

a conductive layer on the first major surface of the bridge substrate;

providing a dielectric layer between the radio frequency identification tag base and the bridge circuit assembly, wherein the conductive layer and plurality of tuning capacitor plates are separated by the dielectric layer;

electrically connecting the first connection pad to the second connection pad through the conductive layer of the bridge circuit assembly;

forming a capacitor, the capacitor comprising the plurality of severable tuning capacitor plates, the dielectric layer, and a common capacitor plate, wherein the conductive layer of the bridge circuit assembly forms the common capacitor plate, and further wherein each tuning capacitor plate of the plurality of tuning capacitor plates comprises an opposed portion that is directly opposed by the common capacitor; and

defining a capacitance for the capacitor by locating the bridge circuit assembly to selectively define the area of the opposed portions of each of the tuning capacitor plates.

33. A method according to claim 32, wherein the bridge circuit assembly comprises a width transverse to the longitudinal axis, and further wherein defining a capacitance for the capacitor comprises selecting the width of the bridge circuit assembly.

34. A method according to claim 32, wherein the bridge circuit assembly traverses the plurality of coils between the first end and the second end of the antenna pattern above the first major surface of the base substrate.

35. A method according to claim 32, wherein the bridge circuit assembly further comprises a bridge substrate having a first major surface and a second major surface, wherein the conductive layer is located on the first major surface of the bridge substrate.

36. A method according to claim 35, further comprising:

locating the bridge circuit assembly such that the second major surface of the bridge substrate faces the first major surface of the base substrate; and

providing a first and second via connection through the bridge substrate, wherein the first and second via connection electrically connect the first connection pad and the second connection pad to the conductive layer of the bridge circuit assembly.

37. A method according to claim 35, wherein the bridge circuit assembly further comprises an edge zone on the first major surface of the bridge substrate, wherein the edge zone comprises an area around a periphery of the first major surface of the substrate, and further wherein the edge zone is substantially free of the conductive layer.

38. A method according to claim 35, wherein the bridge circuit assembly further comprises a die connection site on the first major surface of the bridge substrate, the die connection site in electrical communication with the conductive layer of the bridge circuit assembly.

39. A method according to claim 38, further comprising attaching a die to the die connection site.

40. A method according to claim 38, wherein the die connection site comprises an integrated die connection pad, and wherein the method further comprises separating the die connection site into a plurality of die connection terminals.

41. A method according to claim 32, further comprising:

measuring a resonant frequency of the device; and

selectively severing at least one of the tuning capacitor plate connections.

42. A method according to claim 32, wherein the circuit pattern further comprises a die connection site on the first major surface of the base substrate, the die connection site in electrical communication with the antenna pattern.

43. A method according to claim 42, further comprising attaching a die to the die connection site.

44. A method according to claim 42, wherein the die connection site comprises an integrated die connection pad, and wherein the method further comprises separating the die connection site into a plurality of die connection terminals.

45. A method according to claim 32, further comprising providing a dielectric layer between the common capacitor plate and each of the tuning capacitor plates.

46. A method according to claim 45, wherein the dielectric layer comprises an adhesive.

47. A method according to claim 45, wherein the dielectric layer comprises a backing and adhesive located on each of two major surfaces of the backing.

48. A method according to claim 32, further comprising providing an electrically conductive material between the first and second connection pads and the bridge circuit assembly.

49. A method according to claim 48, wherein the electrically conductive material comprises electrically conductive adhesive.

50. A method according to claim 32, wherein providing a base substrate further comprises providing a substrate web comprising a plurality of circuit patterns.

51. A method according to claim 50, further comprising separating the substrate web between adjacent circuit patterns.

52. A radio frequency identification tag device comprising:

a radio frequency identification tag base comprising;

a base substrate comprising first and second major surfaces;

an antenna pattern comprising first and second ends and a plurality of coils, wherein the first end of the antenna pattern is located within an inner space defined by the plurality of coils and the second end of the antenna pattern is located outside of the plurality of coils;

a first connection pad and a second connection pad, wherein the first connection pad is in electrical communication with the first end of the antenna pattern and the second connection pad is in electrical communication with the second end of the antenna pattern; and

a plurality of severable tuning capacitor plates, each of the tuning capacitor plates in electrical communication with the antenna pattern through a tuning capacitor plate connection;

a bridge circuit assembly comprising a conductive layer; and

a capacitor having a capacitance, the capacitor comprising the plurality of severable tuning capacitor plates and a common capacitor plate, wherein the conductive layer of the bridge circuit assembly forms the common capacitor plate, wherein the first connection pad is electrically connected to the second connection pad through the conductive layer of the bridge circuit assembly, and further wherein at least one tuning capacitor plate of the plurality of tuning capacitor plates comprises an opposed portion that is directly opposed by the common capacitor and an unopposed portion that is not directly opposed by the common capacitor.

53. A device according to claim 52, further comprising adhesive located between the common capacitor plate and each of the tuning capacitor plates.

54. A device according to claim 52, wherein the capacitor further comprises a dielectric layer comprising a backing and adhesive located on each of two major surfaces of the backing.

55. A device according to claim 52, further comprising electrically conductive adhesive between the conductive layer of the bridge circuit assembly and first and second connection pads of the radio frequency identification tag base.

56. A device according to claim 52, further comprising a die connection site located on the first major surface of the base substrate, the die connection site in electrical communication with the antenna.

57. A device according to claim 56, further comprising a die attached to the die connection site.

58. A device according to claim 52, wherein the bridge circuit assembly further comprises a die connection site in electrical communication with the conductive layer of the bridge circuit assembly.

59. A device according to claim 58, further comprising a die attached to the die connection site.

60. A device according to claim 52, further comprising at least one disconnected tuning capacitor plate located opposite the common capacitor plate and separated from the common capacitor plate by a dielectric layer, wherein the disconnected tuning capacitor plate is not in electrical communication with the antenna.

61. A device according to claim 52, wherein the first connection pad and second connection pad are electrically connected to the conductive layer of the bridge circuit assembly through at least two openings in the bridge substrate.