METHOD AND MEASURING DEVICE FOR MATERIAL TESTING OF A CARD-SHAPED DATA CARRIER

Description

[0001] The invention relates to a method for material testing of a card-shaped data carrier.

[0002] Card-shaped data storage devices, especially chip cards, are used in many areas, for example, for cashless payment transactions, as identification documents, or for verifying access authorizations. A chip card comprises a card body and an integrated circuit embedded in the card body, for example, in the form of a chip module with a chip. The chip module is inserted into a cavity or module opening in the card body.

[0003] The following section examines chip cards with an integrated coil that enables contactless or contactless communication. For example, chip card controllers with RFID functionality can be used. The coil, along with an additional capacitor, forms an oscillating circuit on the chip module.

[0004] There are also chip cards with dual interface (DI) functionality, in which the card body is made partially or entirely of metal. Such a card works by using a chip module that contains a coil (coil-on module). This coil couples to the metallic card body.

[0005] Certain material structures cannot be examined or determined non-destructively. While an ID card may appear visually correct, determining the material or composition is impossible without mechanically or chemically destroying the structure.

[0006] EP 2765432 A2 describes a method for testing a circuit with an inductively coupling antenna for a terminal device, comprising the following steps: The circuit is excited to oscillate using an energy pulse. In a further step, the oscillation of the circuit is detected in response to the excitation of the circuit by the energy pulse. The detected oscillation of the circuit is finally evaluated, in particular with regard to a natural resonant frequency of the circuit. Preferably, the step of evaluating the detected oscillation can be carried out as a function of a field strength (H) in which the circuit is located. For this purpose, the steps of generating an alternating magnetic field of predetermined field strength (H) and arranging the circuit in the alternating field can precede the step of exciting the circuit. The detection of the oscillation of the circuit can be carried out using a broadband measuring antenna.

[0007] EP 2779031 A2 describes a method for measuring a property of a resonant circuit intended for contactless data communication and a corresponding measuring device. The measuring device is guided to the resonant circuit. The resonant circuit is excited by the measuring device using an energy pulse, and a decaying oscillation of the resonant circuit in response to the excitation by the energy pulse is detected by the measuring device. For this purpose, the measuring device comprises a handle for guiding the measuring device, an excitation antenna for the exciting energy pulse, and a measuring antenna for detecting the decaying oscillation.

[0008] The object of the present invention is therefore to improve the control of a card-shaped data carrier.

[0009] This object is achieved by a method for material testing of a card-shaped data carrier according to the independent patent claim. Embodiments and developments of the invention are specified in the dependent claims.

[0010] A method according to the invention for material testing of a card-shaped data carrier, comprising the steps: Arranging a reference oscillating circuit comprising a coil on a measuring head of a pulse measuring device that is configured to emit a pulse of an electromagnetic oscillation and to detect an oscillation response of the coil in response to the pulse; moving the reference oscillating circuit relative to the data carrier; emitting a pulse, detecting an oscillation response of the coil in response to the pulse, and determining at least one parameter from the oscillation response; and determining the material and / or composition of the data carrier based on the at least one determined parameter. A basic idea of ​​the present invention is to determine the structure and / or material of a card-shaped data carrier such as a chip card, ID card, passport, film coating, etc. with the aid of the relative permittivity ε r. In this way, a data carrier can be non-destructively tested for authenticity or integrity.

[0011] When such a material, which has a relative permittivity ε r , is placed in front of the reference resonant circuit, its vibration response to the pulse of a pulse measuring device changes. Using at least one of the parameters, such as resonance frequency, quality factor, and amplitude, from the vibration response, a material or structure can be characterized and tested non-destructively. The parameter can be a physical parameter, such as voltage or time, or a mathematical parameter, such as an average value or an integral.

[0012] A resonant circuit is also understood here to be an open resonant circuit with only one coil and the parasitic capacitance (C p ) that forms around the resonant circuit. The resonant circuit is influenced by the parasitic capacitance (C DuT ) of the material or structure under test. The total capacitance of the resonant circuit is calculated as follows: C total = C p + C DuT . This can increase the sensitivity or measurement resolution to values ​​down to below 1 pF (C DuT ), since C p itself is less than 5 pF, preferably less than 2 pF.

[0013] In principle, a test procedure can include exciting the coil to be tested to oscillate, recording the free, damped oscillation of the coil in response to the excitation, and evaluating the recorded oscillation.

[0014] This takes advantage of the fact that the presence of a material in the reference resonant circuit changes the resonance frequency, the quality factor and also the amplitude of the coil or the resonant circuit.

[0015] A Dirac measurement system (DiraTest ®< measurement system), for example, can be used as a measuring device. The measuring head is modified so that, for example, a card with RFID properties can be permanently attached underneath the measuring head. This enables a measurement using a simple reference card.

[0016] The method proposed here has the advantage that card-shaped data carriers can be examined or tested easily and quickly and, above all, non-destructively.

[0017] It can be provided that the reference resonant circuit is calibrated by emitting a pulse, detecting the coil's oscillation response in response to the pulse, and determining at least one calibration parameter from the oscillation response. The material and / or composition of the data carrier is determined based on the at least one specific parameter relative to at least one calibration parameter. This allows a comparison of individual measurement points with each other. This allows a relative deviation between individual measurement points to be determined, and conclusions can be drawn from this regarding the material and / or structure of a tested data carrier.

[0018] It can further be provided that the material and / or composition of the data carrier is determined absolutely based on the at least one specific parameter and a specified material and / or composition of the data carrier. In this way, absolute values ​​can be determined. Information about the material and / or structure of a data carrier can be provided at one or more reference points. Calibration then takes place at this or these reference points. By converting the deviation of the measured values ​​at the measuring points, the material and / or structure of a data carrier can then be determined at all measuring points.

[0019] It can also be provided that the transmission and detection take place contactlessly. Since electromagnetic pulses are used, the data carrier can be measured from a defined distance, making measurements comparable. The data carrier thus remains contactless, preventing any damage to the data carrier.

[0020] It can also be provided that the coil is part of an RFID transponder. Due to its widespread use, suitable measuring systems are available, and accurate and comparable measurement results can be achieved.

[0021] The reference resonant circuit can be configured to include a coil, a capacitor, and a resistor. This creates a defined resonant circuit, which can simplify the comparability of measurements.

[0022] It can further be provided that the reference resonant circuit comprises a coil and a capacitor of an integrated circuit of the data carrier. Thus, the reference resonant circuit can be designed as a reference data carrier. This allows identical electromagnetic properties to those on a card-shaped data carrier during measurement, material testing, or quality control.

[0023] It can be provided that at least one parameter is selected from the group of resonance frequency, quality factor, amplitude, and mean error. Experiments have shown that these parameters, individually and in combination, are well suited for characterizing the material or the card-shaped data carrier. Using the parameter(s), a signature of the material or the card-shaped data carrier can be generated, enabling recognition and comparison.

[0024] It can be provided that the quality factor of the coil is determined from a decay coefficient of the oscillation response. The quality factor of the coil or antenna coil can be determined from the decay coefficient δ. The longer the decay process, the higher the quality factor of the corresponding resonant circuit. Thus, an evaluation of the free damped oscillation of the coil, i.e., its decay immediately after excitation, allows the quality factor and the natural resonant frequency of the coil to be determined.

[0025] A measuring device for material testing of a card-shaped data carrier, configured to emit a pulse of an electromagnetic oscillation and to detect an oscillation response of the coil in response to the pulse, comprises a measuring head and a reference oscillating circuit with a coil, which is arranged on the measuring head, wherein the reference oscillating circuit is trimmable by means of at least one capacitor.

[0026] Using the trimmable reference resonant circuit, different frequency bands can be scanned during a single measurement. This allows frequency-dependent characteristics of the materials being tested to be taken into account. This can increase the accuracy and significance of the measurement.

[0027] Otherwise, the same advantages and modifications apply as previously described. The present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1: a top view of a chip card; Fig. 2: an equivalent circuit diagram of a chip module of the chip card with an oscillating circuit with an internal capacitance of a chip; Fig. 3: an equivalent circuit diagram of a chip module of the chip card with an open oscillating circuit; Fig. 4: an equivalent circuit diagram of a chip module of the chip card with an oscillating circuit with a capacitor, coil, and resistor; Fig. 5: a schematic diagram of a measuring device for material testing of a card-shaped data carrier such as a chip card; and Fig. 6: a flowchart of a method for material testing of a card-shaped data carrier such as a chip card.

[0028] Fig. 1 As an example of a card-shaped data carrier, FIG. 1 shows a chip card 10 with a card body 11. The card body 11 can be made of a plastic such as PVC, polycarbonate, or the like. The thickness of the card body 11 can be, for example, between 50 µm and 920 µm.

[0029] The chip card 10 further comprises a chip module 12, which is inserted into a main surface 13 of the card body 11 or the chip card 10. The chip module 12 can be inserted into a module opening or cavity. The cavity can comprise a central blind hole and a peripheral edge area. Here, the cavity is concealed by the inserted chip module 12. The chip module 12 can be glued into the cavity.

[0030] The chip module 12 comprises a coil that can be arranged on a module tape (not shown here). The coil can have approximately 12 to 16 turns, which here run concentrically around a chip or an electronic circuit of the chip module 12. The width of a turn can be 50 µm to 70 µm, and the spacing between two turns can be 100 µm. The turns can have copper thicknesses of up to approximately 30 µm. A maximum of 2.5 µH can be achieved with such a coil.

[0031] The chip can be implemented, for example, in the form of an integrated circuit and is secured, for example, in a potting compound on the underside of the chip module 12. The chip is supplied with energy and / or signals via the coil. This allows an electromagnetic field to be coupled into the coil. For example, the chip can be or contain a chip card controller with RFID functionality.

[0032] Fig. 2 shows an equivalent circuit diagram of the chip module 12 of the chip card 10. The chip module 12 comprises the chip 14, for example in the form of an integrated circuit. The chip 14 can, for example, be soldered onto the chip module 12 or applied to the chip module 12 using flip-chip assembly. The chip 14 contains a card controller for the chip card 10. The chip 14 typically contains a processor for executing control functions for the chip card 10 and for communication, and for executing computing operations, for example, for security functions. Furthermore, the chip 14 contains a memory area for storing and / or making data available.

[0033] Chip 14 also contains a capacitor 15 with a capacitance of, for example, 78 pF. Coil 16 is connected in parallel to chip 14 and has a maximum inductance of 2.5 µH.

[0034] Coil 16 and capacitor 15 of chip 14 form an oscillating circuit 17. This oscillating circuit 17 allows chip module 12 to communicate with a reader or measuring device external to chip card 10. The reader applies energy to coil 16 via an electromagnetic field, activating chip 14.

[0035] The chip card 10 can be used as a measuring device with a reference oscillating circuit 17. This chip card 10 can then be used to measure other chip cards or similar devices.

[0036] Fig. 3 shows an equivalent circuit diagram of a chip module 12 of the chip card with a reference resonant circuit in the form of an open resonant circuit 17.

[0037] The open resonant circuit 17 is represented by the two contact points 18. The capacitor 15 shown here corresponds to the capacitance of a card-shaped data carrier to be tested when it is attached to the chip module 12 or the measuring device. During measurement, material testing, or quality control, the data carrier can be placed directly against the two contact points 18 or be positioned at a short distance from them. The short distance ranges from millimeters to a few centimeters.

[0038] A parasitic capacitance 15a is present in parallel with the capacitor 15. This parasitic capacitance 15a is formed by the coil 16 and the material in which the coil 16 is located. In the Figuren 2 and 4 In the structures shown, the parasitic capacitance is also present, but is negligible in the closed resonant circuits there.

[0039] This configuration has a resonant frequency between 45 MHz and 75 MHz, depending on the coil design. The frequency is determined exclusively by the inductance L of coil 16 and the parasitic capacitance 15a of coil 16 and the material supporting coil 16. Depending on the size of coil 16 and the number of turns, almost any frequency can be achieved. Changing the capacitor 15 causes a significant change in the resonant circuit 17. With such a configuration, the capacitance is, for example, between 1 pF and 3 pF.

[0040] Instead of a chip module 12, a circuit board or similar carrier can also be used for the oscillating circuit 17. Then, the form factor of the measuring head can be smaller.

[0041] Fig. 4 shows an equivalent circuit diagram of a chip module 12 of the chip card with an oscillating circuit 17 comprising capacitor 15, coil 16, and resistor 19. In this example, the oscillating circuit 17 is formed without the object to be tested. However, the object to be tested changes the oscillating circuit through its presence, as previously described.

[0042] Instead of a chip module 12, a circuit board or similar carrier can also be used for the oscillating circuit 17. This allows for a smaller form factor of the measuring head. The capacitance of the capacitor 15 can be in a range from 1 pF to approximately 100 pF. The value of the resistor 19 can be in a range from approximately 0 ohms to 5 kOhms. The oscillating circuit 17 can therefore also be constructed without a resistor.

[0043] Fig. 5 shows a schematic diagram of a measuring device 20 for material testing of a card-shaped data carrier, here in the form of a chip card 10. The chip card 10 is shown enlarged. While only reference is made to the chip card 10 below for reasons of clarity, all card-shaped data carriers are included.

[0044] The measuring device 20 may be a pulse measuring device with a measuring head 21 arranged to emit a pulse of an electromagnetic oscillation and to detect an oscillation response of the oscillating circuit 17 in response to the pulse.

[0045] The measuring head 21 or the measuring device 20 is configured to excite the reference resonant circuit 17 to oscillate. An evaluation device 22 of the measuring device 20 is configured to evaluate an oscillation of the reference resonant circuit 17 detected in response to the excitation by the measuring head 21 or the measuring device 20. The oscillation behavior of the reference resonant circuit 17 changes depending on the material and / or structure, such as a layer sequence, of the chip card 10.

[0046] Using such an evaluation device 22, the resonant frequency, quality factor, and amplitude of the oscillation response or the antenna coil can be determined simply and reliably. An evaluation of these parameters then allows conclusions to be drawn about the material and / or composition of the chip card 10.

[0047] At least one of the parameters resonance frequency, quality factor, and amplitude from the vibration response is used to characterize the chip card 10. The more parameters used, the more accurately the measurement or test can be performed.

[0048] For example, a feature matrix can be set up in which the three parameters resonance frequency, quality and amplitude are plotted against different materials or layer sequences of a chip card 10.

[0049] The measuring device 20 can, for example, be a test device for testing the functionality of the coil 16 for a contactless chip card 10 or comprise such a test device. For this purpose, the measuring device 20 comprises a pulse generator 23. This is configured to contactlessly excite the reference resonant circuit 17 via an excitation coil 24 connected to the pulse generator 23. Furthermore, the measuring device 20 comprises a measuring antenna 25, which, like the excitation coil 24, can be arranged in the measuring head 21.

[0050] Thus, a test device can be used to test the functionality of coil 16 for material testing of chip card 10. For this purpose, the measuring head 21 is expanded with the reference oscillating circuit 17. The chip card 10 to be measured then changes the oscillating circuit 17, which is then measured. The measuring head 21 and the reference oscillating circuit 17 essentially form a measuring unit for the chip card 10. In other words, the reference oscillating circuit 17 is used as a sensor for the chip card 10. The reference oscillating circuit 17 can be part of another chip card (not shown here). In this case, this other chip card (not shown here) is used as a sensor for the chip card 10.

[0051] The measuring antenna 25 is configured to contactlessly detect a free, damped oscillation of the reference resonant circuit 17. The evaluation device 22 is connected to the measuring antenna 25 and configured to evaluate the free, damped oscillation detected by the measuring antenna 25.

[0052] For measurement, the chip card 10 can be placed on a base with a low dielectric constant of less than 10, preferably less than 5. For example, a POM plate can be used as a base. This material has a very low dielectric constant of approximately 4, which is also constant across the entire plate surface. This creates a defined environment that increases test quality and makes different test runs more comparable. Likewise, the chip card 10 can be stored in air, or as close to air as possible, for example, using thin strips such as fishing line. This allows the dielectric constant behind the chip card 10 to be further reduced.

[0053] The measurement or material testing may include moving the chip card 10 and / or the measuring head 21 to a single measuring point or moving or traveling along a movement route.

[0054] Instead of a continuous movement route, individual measuring points can also be approached, or the chip card 10 can be moved past one or more stationary measuring heads, for example, during production. In the case of measurements at continuous time intervals, individual measuring points are defined by the time interval, which can then be located on a movement route.

[0055] The reference resonant circuit 17 can, for example, be trimmable using at least one capacitor. This allows different frequency bands to be scanned during a single measurement. This allows frequency-dependent characteristics of the materials under test to be taken into account.

[0056] Fig. 6shows a flow chart of a method for material testing of a card-shaped data carrier, for example in the form of a chip card 10.

[0057] In a first step 100, the reference resonant circuit 17 is arranged on a measuring head 21 of the pulse measuring device 20. The reference resonant circuit 17 is attached to the measuring head 21, for example as a component of a reference chip card, so that a clear position relative to the measuring head 21 is achieved.

[0058] The coil 16 of the reference resonant circuit 17 and the excitation coil 24 of the measuring head 21 are arranged parallel and overlapping, preferably one above the other, i.e., completely overlapping. The reference resonant circuit 17 and the measuring head 21 are arranged relative to one another in such a way that a pulse of an electromagnetic oscillation can be transmitted from the excitation coil 24 to the coil 16 and that a vibration response of the coil 16 in response to the pulse can be detected.

[0059] In an optional step, calibration can be performed by emitting a pulse, detecting the oscillation response of coil 16 or the reference resonant circuit 17 in response to the pulse, and determining at least one calibration parameter: resonance frequency, quality factor, and amplitude from the oscillation response. The quality factor of coil 16 can be determined, for example, from a decay coefficient δ of the oscillation response. The longer the decay process, the higher the quality factor of the corresponding resonant circuit. Thus, an evaluation of the free damped oscillation of coil 16, i.e., its decay immediately after excitation, allows the quality factor and the natural resonant frequency of coil 16 to be determined. The amplitude can, for example, be simply determined as the maximum amplitude.

[0060] Calibration of the reference resonant circuit 17 can be performed in the open air, i.e., without the presence of any material in the vicinity of the measuring head 21. Known materials, data carriers, or layer sequences of materials can also be calibrated. These materials, etc., are then arranged on the measuring head 21 for a measurement.

[0061] In a second step 110, the reference resonant circuit 17 is moved relative to at least one measuring point on the chip card 10. The reference resonant circuit 17 is moved together with the measuring head 21. The measurement or material testing can be performed in a movement path across the surface of the chip card 10 or purely at specific points.

[0062] In a third step 120, a pulse is transmitted, the oscillation response of coil 16 in response to the pulse is recorded, and one of the parameters resonant frequency, quality factor, and amplitude is determined from the oscillation response. This step is analogous to the optional calibration step, with the chip card 10 located in the area of ​​the reference oscillating circuit 17 now changing the oscillation response of coil 16.

[0063] For example, the reference resonant circuit 17 changes when subjected to a capacitive influence by material in the area of ​​the measuring head 21. If, for example, an additional capacitance is introduced into the resonant circuit 17, the frequency drops significantly and the Q factor decreases slightly.

[0064] For each material, form of data carrier, intermediate product of data carrier, or material, an identification can be created based on at least one of the parameters resonance frequency, quality factor, and amplitude. This assignment of parameter values ​​to materials or compositions can be stored in a list or matrix.

[0065] In a fourth step 130, the material and / or composition of the data carrier, here the chip card 10, is determined based on at least one of the determined parameters. For this purpose, for example, current values ​​of the determined parameter(s) can be compared with a list or matrix in which an assignment of parameter values ​​to materials or compositions is stored.

[0066] It is also possible to compare multiple measurement results from multiple measurement points, allowing for a relative conclusion. The measurement points can come from one or more measurement objects.

[0067] In addition, further variables or subparameters can be determined from the individual parameters, such as maximum values, minimum values, and average values, or spatial distributions of the parameters. These variables can then be used, for example, to identify materials or compositions.

Claims

1. Method for material testing of a card-shaped data carrier (10), comprising the steps of: - arranging (100) a reference resonant circuit (17) having a coil (16) on a measuring head (21) of a pulse measuring device (20) that is configured for emitting a pulse of an electromagnetic oscillation and for detecting an oscillation response of the coil (16) in response to the pulse; - moving (120) the reference resonant circuit (17) relative to the data carrier (10); - emitting (130) a pulse, detecting an oscillation response of the coil (16) in response to the pulse, and determining at least one parameter from the oscillation response; and - ascertaining (140) material and / or a composition of the data carrier (10) based on the at least one determined parameter.

2. Method according to Claim 1, characterized in that the reference resonant circuit (17) is calibrated by emitting a pulse, an oscillation response of the coil (16) in response to the pulse is detected, and at least one calibration parameter is determined from the oscillation response, and in that the material and / or the composition of the data carrier (10) is ascertained based on the at least one determined parameter relative to at least one calibration parameter.

3. Method according to either of Claims 1 and 2, characterized in that the quality of the coil (16) is ascertained from a decay coefficient (δ) of the oscillation response.

4. Method according to one of Claims 1 to 3, characterized in that the emitting and the detecting are effected contactlessly.

5. Method according to one of Claims 1 to 4, characterized in that the coil (16) is part of an RFID transponder.

6. Method according to one of Claims 1 to 5, characterized in that the reference resonant circuit (17) includes the coil (16), a capacitor (15) and a resistor (19) .

7. Method according to one of Claims 1 to 6, characterized in that the reference resonant circuit (17) includes the coil (16) and a capacitor (15) of an integrated circuit of the data carrier (10).

8. Method according to one of Claims 1 to 7, characterized in that the at least one parameter is selected from the group consisting of resonant frequency, quality, amplitude and average error.