Method and apparatus for testing RFID devices

• US 20060255941A1
• Filed: 05/11/2005
• Published: 11/16/2006
• Est. Priority Date: 05/11/2005
• Status: Active Grant

• Current Assignee: RUIZHANG TECHNOLOGY LIMITED COMPANY
• Original Assignee: Alien Technology Corporation
• Inventors: Hadley, Mark A., Carrender, Curtis Lee
• Granted Patent: US 7,301,458 B2
• Time in Patent Office: Days
• US Class Current: 340/572.100
• CPC Class Codes: G01R 31/2822 of microwave or radiofrequency circuits of attenuation, gain, e.g. using network analyzers G01R27/28
• CPC Class Codes: G01R 31/31905 Interface with the device under test [DUT], e.g. arrangements between the test head and the DUT, mechanical aspects, fixture
• CPC Class Codes: G01R 31/31926 Routing signals to or from the device under test [DUT], e.g. switch matrix, pin multiplexing
• CPC Class Codes: G06K 7/0095 Testing the sensing arrangement, e.g. testing if a magnetic card reader, bar code reader, RFID interrogator or smart card reader functions properly testing of electrical circuits G01R31/28
• CPC Class Codes: H01L 2924/15153 the die mounting substrate comprising a recess for hosting the device

Abstract

A method and apparatus for testing RFID straps. Arrays of RFID straps in a roll-to-roll process are coupled to an array of test elements. RF programming and interrogation signals are frequency and time multiplexed to the RFID array. Return signals are detected to determine sensitivity and programmability parameters of the RFID straps.

Claims

1. A method for testing radio frequency identification (RFID) straps, comprising:

coupling an RFID tester to an array of RFID straps;

multiplexing a plurality of test signals to test the array of RFID straps; and

detecting a plurality of return signals from the array of RFID straps.

2. The method of claim 1, wherein each RFID strap in the array of RFID straps comprises:

an RFID chip laminated in a roll material, the roll material comprising a first surface and a second surface; and

a pair of contacts on the first surface of the roll material, coupled to the RFID chip, the array of RFID straps comprising an array of paired contacts on the first surface of the roll material.

3. The method of claim 2, wherein coupling the RFID tester to the array of RFID straps comprises:

aligning the array of paired contacts with an array of paired test elements in the RFID tester; and

compressing the array of RFID straps against the array of paired test elements.

4. The method of claim 3, wherein compressing the array of RFID straps against the array of paired test elements comprises compressing the first surface of the roll material against the array of paired test elements to directly couple the array of paired contacts with the array of paired test elements.

5. The method of claim 3, wherein compressing the array of RFID straps against the array of paired test elements comprises compressing the second surface of the roll material against the array of paired test elements to capacitively couple the array of paired contacts with the array of paired test elements.

6. The method of claim 1, further comprising:

transmitting a first test signal of the plurality of test signals at a first frequency to test a first line of the array of RFID straps; and

transmitting a second test signal of the plurality of test signals at a second frequency to test a second line of the array of RFID straps.

7. The method of claim 6, wherein the first line and the second line are columns of the array of RFID straps.

8. The method of claim 7, wherein the first line and the second line are rows of the array of RFID straps.

9. The method of claim claim 1, wherein the array of RFID straps comprises a plurality of lines of RFID straps, wherein each line is coupled to one of a plurality of test signals via a switching matrix, and wherein multiplexing the plurality of test signals comprises:

frequency-division-multiplexing the plurality of test signals to the plurality of lines of RFID straps; and

time-division-multiplexing each test signal to a corresponding line of RFID straps.

10. The method of claim 9, wherein multiplexing the plurality of test signals further comprises stepping through a plurality of signal levels to test at least one of a sensitivity threshold of each RFID strap, a programmability threshold of each RFID strap, and a maximum power threshold of each RFID strap.

11. The method of claim 10, further comprising programming each RFID strap with one or more of an identification code, a lot code, a date code, a location code, or test results for the RFID strap.

12. The method of claim 10, further comprising marking RFID straps to identify RFID straps that do not meet a sensitivity specification and a programmability specification.

13. The method of claim 4, further comprising matching a source impedance of each test signal to a load impedance of a corresponding RFID strap.

14. The method of claim 3, wherein the roll material is compressed against the array of paired test elements by a pressure plate having a compressible foam layer.

15. The method of claim 3, wherein the roll material is compressed against the array of paired test elements by a pressure plate having an inflatable bladder.

16. The method of claim 3, wherein the array of paired test elements comprises a patterned layer of a printed circuit board.

17. The method of claim 16, wherein the array of paired test elements comprises a symmetrical array configured to compensate for a functional asymmetry in the RFID chip.

18. The method of claim 3, wherein the array of paired test elements comprises an array of spring-loaded test contacts.

19. The method of claim 2, wherein the array of RFID straps is one of a plurality of arrays of RFID straps on the roll material, and wherein testing the plurality of arrays is part of a roll-to-roll testing process.

20. The method of claim 1, wherein detecting the plurality of return signals from the array of RFID straps comprises at least one of:

reading a manufacturing code from each of the RFID straps;

reading a programmed test code from each of the RFID straps; and

reading an array location code from each of the RFID straps.

21. The method of claim 1, further comprising recording test results for each RFID strap in a database, the database comprising at least one of pass-fail data and performance data.

22. An apparatus for testing arrays of RFID straps, comprising:

an array of paired test elements comprising a plurality of lines of paired test elements;

a plurality of RFID readers to transmit RFID signals and to receive RFID responses;

a plurality of switching matrices, each switching matrix coupled to one of the plurality of RFID readers and to one of the plurality of lines, to switch a plurality of RFID signals to the array of paired test elements; and

a compression plate to compress an array of RFID straps against the array of paired test elements and to couple the array of RFID straps to the array of paired test elements.

23. The apparatus of claim 22, wherein each RFID strap in the array of RFID straps comprises:

an RFID chip laminated in a roll material, the roll material comprising a first surface and a second surface; and

a pair of contacts on the first surface of the roll material, coupled to the RFID chip, the array of RFID straps comprising an array of paired contacts on the first surface of the roll material.

24. The apparatus of claim 22, further comprising an imaging device to align the array of RFID straps with the array of test elements.

25. The apparatus of claim 23, wherein the first surface of the roll material is compressed against the array of paired test elements to directly couple the array of paired test elements with the array of RFID straps.

26. The apparatus of claim 25, further comprising a matching network, coupled between each pair of test elements and a corresponding switching matrix, to match a source impedance of a signal source to a load impedance of a corresponding RFID strap.

27. The apparatus of claim 22, wherein the array of paired test elements comprises a patterned layer of a printed circuit board (PCB).

28. The apparatus of claim 27, wherein the array of paired test elements comprises a symmetrical array configured to compensate for a functional asymmetry in the RFID chip.

29. The apparatus of claim 22, wherein the array of paired test elements comprises an array of spring-loaded test contacts.

30. The apparatus of claim 23, wherein the second surface of the roll material is compressed against the array of paired test elements to capacitively couple the array of paired test elements with the array of RFID straps.

31. The apparatus of claim 22, wherein each RFID reader is configured to operate at a different frequency, and wherein each RFID reader is time-division-multiplexed to a plurality of paired test elements in a corresponding line of the array of paired test elements.

32. The apparatus of claim 31, wherein each of the RFID readers is configured to step through a plurality of signal levels to test at least one of a sensitivity threshold of an RFID strap and a programmability threshold of an RFID strap.

33. The apparatus of claim 22, further comprising a marking device to mark RFID straps that do not meet one or more of a sensitivity specification and a programmability specification.

34. The apparatus of claim 22, wherein the array of RFID straps comprises one of a plurality of arrays of RFID straps on the roll material, and wherein testing the arrays of RFID straps is part of a roll-to-roll test process, further comprising:

a controller to control the alignment, coupling and testing of the arrays of RFID straps;

a processor, coupled with the controller, to process data and execute instructions;

at least one of a memory device and a mass storage device, coupled with the processor, to store data and instructions.

35. The apparatus of claim 34, wherein the processor is configured to record test data for each RFID strap in an array of RFID straps, the test data comprising at least one of a manufacturing code, an array location code, a pass-fail code and test data.

36. The apparatus of claim 22, wherein the compression plate includes one of a compressible foam layer and an inflatable bladder.

37. A machine-readable medium containing instructions which when executed on a data processing system causes the system to perform a method for testing RFID straps, the method comprising:

coupling an RFID tester to an array of RFID straps, the array of RFID straps comprising a plurality of columns of RFID straps, each column comprising a plurality of RFID straps;

multiplexing a plurality of test signals to test the array of RFID straps; and

detecting a plurality of return signals from the array of RFID straps.

38. The machine readable medium of claim 37, wherein each RFID strap in the array of RFID straps comprises:

an RFID chip laminated in a roll material, the roll material comprising a first surface and a second surface; and

a pair of electrical contacts on the first surface of the roll material, coupled to the RFID chip.

39. The machine-readable medium of claim 38, wherein coupling the RFID tester to the array of RFID straps comprises:

aligning the array of paired contacts with an array of paired test elements in the RFID tester; and

compressing the array of RFID straps against the array of paired test elements to couple the array of paired test elements with the array of paired contacts.

40. The machine-readable medium of claim 39, wherein compressing the array of RFID straps against the array of paired test elements comprises compressing the first surface of the roll material against the array of paired test elements to directly couple the array of RFID straps with the array of paired test elements.

41. The machine-readable medium of claim 39, wherein compressing the array of RFID straps against the array of paired test elements comprises compressing the second surface of the roll material against the array of paired test elements to capacitively couple the array of RFID straps with the array of paired test elements.

42. The machine-readable medium of claim 37, wherein the RFID tester comprises a plurality of lines of test elements, each line of test elements comprising a plurality of test elements, wherein each line is coupled to a test signal via a switching matrix, and wherein multiplexing the plurality of test signals comprises:

frequency-division-multiplexing the plurality of test signals to the plurality of lines of test elements; and

time-division-multiplexing each test signal to the plurality of test elements in each line.

43. The machine-readable medium of claim 42, wherein multiplexing the plurality of test signals further comprises stepping through a plurality of signal levels to test at least one of a sensitivity threshold of each RFID strap and a programmability threshold of each RFID strap.

44. The machine-readable medium of claim 43, further comprising programming each RFID strap with one or more of an identification code, a lot code, a date code, a location code, or test results for the RFID strap.

45. The machine-readable medium of claim 43, further comprising marking RFID straps to identify RFID straps that do not meet one or more of a sensitivity specification and programmability specification.

46. The machine-readable medium of claim 37, wherein the array of RFID straps is one of a plurality of arrays of RFID straps on the roll material, and wherein testing the plurality of arrays is part of a roll-to-roll testing process.

47. The machine-readable medium of claim 37, wherein detecting the plurality of return signals from the array of RFID straps comprises at least one of:

reading a manufacturing code from each of the RFID straps;

reading a programmed test code from each of the RFID straps; and

reading an array location code from each of the RFID straps.

48. The machine-readable medium of claim 37, the method further comprising recording test results for each RFID strap in a database, the database comprising at least one of pass-fail data and performance data.

49. An apparatus, comprising:

means for coupling an array of RFID straps to an RFID strap tester; and

means for reducing crosstalk between RFID straps in the array of RFID straps during an RFID strap testing procedure.

50. The apparatus of claim 49, further comprising means for impedance matching the array of RFID straps to the RFID strap tester.