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WO1997011332A1 - Device and process for determining film thickness and pattern register in cells plated on inductive debit cards - Google Patents

Device and process for determining film thickness and pattern register in cells plated on inductive debit cards

Info

Publication number
WO1997011332A1
WO1997011332A1 PCT/BR1996/000041 BR9600041W WO1997011332A1 WO 1997011332 A1 WO1997011332 A1 WO 1997011332A1 BR 9600041 W BR9600041 W BR 9600041W WO 1997011332 A1 WO1997011332 A1 WO 1997011332A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
thickness
sensing
cards
cells
film
Prior art date
Application number
PCT/BR1996/000041
Other languages
French (fr)
Inventor
Oliveira Lopes Paulo Henrique De
Original Assignee
TELECOMUNICAÇõES BRASILEIRAS S/A - TELEBRÁS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

Links

Classifications

    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06KRECOGNITION OF DATA; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/08Methods or arrangements for sensing record carriers, e.g. for reading patterns by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes
    • G06K7/082Methods or arrangements for sensing record carriers, e.g. for reading patterns by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes using inductive or magnetic sensors
    • G06K7/083Methods or arrangements for sensing record carriers, e.g. for reading patterns by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes using inductive or magnetic sensors inductive
    • G06K7/086Methods or arrangements for sensing record carriers, e.g. for reading patterns by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes using inductive or magnetic sensors inductive sensing passive circuit, e.g. resonant circuit transponders
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00Measuring arrangements characterised by the use of electric or magnetic means
    • G01B7/02Measuring arrangements characterised by the use of electric or magnetic means for measuring length, width or thickness
    • G01B7/06Measuring arrangements characterised by the use of electric or magnetic means for measuring length, width or thickness for measuring thickness
    • G01B7/10Measuring arrangements characterised by the use of electric or magnetic means for measuring length, width or thickness for measuring thickness using magnetic means, e.g. by measuring change of reluctance

Abstract

A device for determining the thickness of conductive metal patterns plated on insulating surfaces, such as credit cells in prepaid telephone debit cards, comprising a plurality of sensing modules equal in number to the credit cells in said cards, each module consisting of an oscillator (30) wherein the inductance is provided by a pair of collinear sensing coils (24a, 24b), aligned with the true position of its relative credit cell (25), the output (26) of said sensing assembly being connected to the input of an A/D converter (40) whose output is connected to computing means (11, 21) provided with memory means. Said oscillators are enabled by turns, the output voltage being converted to a numeric value. The converter parameters are adjusted for each sensing module according to coefficients stored in said memory, to compensate for component variations, sensing coil position and so on. The resultant numeric value is processed by the computing means according to a transfer curve (53) which is specific for each sensing module, so as to furnish the film thickness. Said coefficients and transfer curves are previously determined for each one of the positions in the cell array by means of individual calibration, using standard cards of known metal film thickness.

Description

Specification DEVICE AND PROCESS FOR DETERMINING FILM THICKNESS AND PATTERN REGISTER IN CELLS PLATED ON INDUCTIVE DEBIT CARDS The present invention refers to the determination of thickness of conductive metal layers deposited over insulating surfaces, and more specifically to the thickness measurement of the metal film employed in the production of credit cells on inductive debit cards such as those described in the patent documents PI(BR) 7804885, PI(BR) 9201380-5 and PI(BR) 9304503-4, here incorporated by reference.

Methods for measuring the thickness of metal layers based on X-ray diffraction are already well known, however their cost, as well as the time required by them restrict their use to high precision measurements in laboratories. Moreover, the currently known methods do not detect adequately the register errors that crop up in the card's manufacture, i.e., the position mismatch of the metallic cell pattern plated over the card with relation to its edges.

In view of the above, the present invention has as its major aim the provision of a device capable of measuring expeditiously the thickness of said metallic films, with minimal error margin and at low cost.

An additional objective is the detection of faulty register during the plating of cells, i.e., the mismatch between the real position of those cells and the ideal one in relation to the card edges, said mismatch rendering the card useless.

The above aims are accomplished by the invention by means of a device comprising a sensing assembly consisting of a plurality of sensing modules, each module consisting of an oscillator wherein the inductance is provided by a sensing coil coincidentally placed at true position of its relative credit cell, each sensor being, one at a time, individually enabled by a pulse originated by computing means which control the process, the oscillator output voltage being coupled to means for converting it into a numerical value, to be processed by said computing means according to coefficients stored in memory means so as to inform the thickness of the metal layer. According to another feature of the invention, said coefficients are previously determined for each one of the positions in the cell array by means of individual callibration, using standard cards of known metal film thickness.

According to a further feature of the invention, sensors placed outside the cell matrix are provided, to enable the measurement of register errors in the plated cell pattern. According to yet another feature of the invention, the device allows the integrity check of all cells in the card, thus permitting the rejection of those cards in which one or more cells are open due to manufacturing defects.

The previous characteristics, as well as other aspects and advantages of the present invention, will become more evidente from the description of a specific embodiment, taken as an example and not in a limiting sense, as shown by the attached drawings in which:

Figure 1 shows the block diagram of the test device built according to the principles of the invention, as well as its connections to external control equipment, such as a PC-compatible micro-computer.

Figure 2 shows a more detailed view of the proposed device, according to the invention.

Figure 3 illustrates a calibration curve for one sensing module, showing the elements which allow conversion of the measured voltage values into metal layer thicknesses, according to the invention.

Figure 4 shows the principle of register misalignment detection, according to the invention.

Referring now, more specifically, to the block diagram in figure 1, the proposed device 20 comprises the following blocks: • Control board 21 - CPU-A/D — consisting of micro-controller, analog to digital converter (A/D), memories and accessories; • Decoding card CEO 22, consisting of the address decoders, which controls the operation of each oscillator in the sensor matrix by means of individual lines 23; • Sensing assembly 27, consisting of as many sensing modules as the number of cells in the card, each of these modules containing, in addition to the oscillator, a pair of colinear sensing coils 24a - 24b, the internal ends of their cores forming a gap into which lies a credit cell 25, the width of said gap being slightly greater than the card thickness, to allow for accidental irregularities.

Still according to figure 1, device 20 is connected to a PC microcomputer 11, which controls the measuring process through a serial communication line 46 making use of a standardized protocol such as, for instance, the RS 232.

Referring now to figure 2, it can be seen that the sensing assembly 27 comprises a plurality of test modules 30, each one consisting of a Colpitts oscillator in which the coils that make up the tank are the inductive sensors 24a and 24b. Such oscillators have the property of producing an alternating signal whose amplitude is proportional to the inductive coil loading. Considering that said loading depends on the characteristics (thickness, conductivity) of the metal layer, as well as on the cell condition (open or shorted), it follows that for a known alloy, the signal amplitude between the leads of the sensing coil will be inversely proportional to the thickness of the metal film.

Transistor 31 in all oscillators is normally cut-off, the oscillation being enabled individually by block CEO 22 through a positive voltage pulse 32 applied to the transistor's base through one of the lines of group 23. Duration 33 of this pulse is substantially greater than the time needed by the oscillator to reach steady-state operation, thus eliminating the effects of any possible transients. Part of the oscillation voltage present in transistor's 31 collector is rectified by diode 34 and filtered by capacitor 35, resulting in a fairly rectangular pulse 36 with a duration equal to the above mentioned command pulse 32.

Magnitude of pulse 36 is much greater than the maximum voltage that can be applied to A/D converter 40. For that reason, a Zener diode 37 is connected in series with the converter input, in order to subtract a constant voltage from said pulse 36, resulting in a lower amplitude pulse 38, which is forwarded to the input of said converter 40 for translation into a numerical value.

Said transmission is done trough a digitally controlled potentiometer 39, whose value is adjusted by CPU 21 by means of a signal applied to control terminal 39'. This adjustment is individual for each one of the test modules 30, since there are differences between the components of each oscillator; moreover, the oscillation voltage is influenced by the position of the sensing coils within the array (more or less distant from the edges, etc.). Data for adjustment of this potentiometer are determined during the previous calibration of the device, using standard cards of known thickness, and stored in the CPU's memory (not shown).

The controlled potentiometers 41 and 42 are trimmed in the same way by control signals from the CPU, their adjustment being specific for each one of the 104 sensing modules; the first one adjusts the A D converter span and the second one establishes the lowest voltage signal (V null) for said converter (corresponding to the thickest metal film). As said before, the controlled potentiometer 39 limits the maximum value of voltage applied to the input of the converter.

After those potentiometers have been correctly adjusted, the output of the converter will be zero for the thickest foreseen metal layer, and 255 for the thinnest film that is to be expected during manufacture of the debit cards. In order to provide a direct relation between the numeric value and the metal thickness (E), the output of converter 40 is processed by CPU 21 to generate its 255's complement.

After this step, said CPU sends to CEO 23 the address of the next position to be tested, in case of several positions having been programmed for testing. Through serial interface 45 and line 46, said numeric value is transmitted to micro-computer 11 (shown in figure 1), which will process this result in order to inform the actual thickness of the metal layer.

Calculation of this thickness is done with the aid of the transfer curve of each test module, which depends, as already said, on the characteristics of the components and on the position of the sensor within the matrix. Thus, each one of the 104 modules (in the present example) has a transfer curve which can be approximated by one or more straight line segments. Figure 3 exemplifies the approximation of this curve with a single segment 53 which is defined by two coefficients: linear coefficient b and angular coefficient m. Therefore, for each position within the matrix the thickness shall be calculated by expression E = (VN x m) + b, where VN is the numerical value transmitted to the CPU.

As previously mentioned, the characteristic curve of each test module can be more exactly approximated through 2, 3 or more straight line segments, each segment being defined by a specific angular coefficient (ml, m2, etc.) as well as by a specific linear coefficient (bl, b2, etc.). Evidently, in those cases, the formula for calculating the film thickness will be considerably more complex than the one utilized for approximation through one single segment. Once the values of thickness in one or more cells in the card have been calculated, they can be stored, printed, transmitted to other units, etc.. or even be used to trigger alarms (for thickness values beyond tolerance limits) for card rejection, and so on. In case the cell is broken due to manufacturing defect, such a fact will be interpreted by the device as "insufficient thickness", leading to card rejection.

In addition to thickness determination, the proposed device allows the determination of occasional register errors. To this end, non- metallized windows are provided in the card, said windows - rectangular or square in sahpe ~ being located in plated areas outside the credit cell array. The inductive sensor set shall, in a similar way, be provided with additional test modules, with coils placed coincidentally with said windows. Figure 4 shows the principle of the register error determination.

Considering one of the edges 61 of window 60, it can be seen that roughly 3 positions are possible with regard to the inductive sensor core. In figure 4-a, core 62 lies entirely over a non-plated portion, so the current induced in the metal layer is lowest; therefore the voltage at the oscillator terminals will be the greatest. Figure 4-b shows a position where core 63 lies partially over a plated region and partially over a window; in this case some loading occurs and, therefore, the oscillation amplitude is smaller than before. Finally, in figure 4-c, core 64 lies entirely over a metal-plated region. Oscillator coil loading is the highest; hence, the voltage of the oscillations is the smallest. Through proper choice of window sizes and positions, as well as positions of the corresponding inductive sensors it becomes possible to detect deviations of the metal pattern plated on the card, either on the longitudinal or in the transversal directions, as well as pattern rotation relative to the axes of the card. Obviously, the voltage values detected by the sensors will vary according with the thickness of the metal layer on the card, thus requiring an adequate software for interpretation of the values furnished by said register sensors.

As before, maximum and minimum acceptable measured levels must be previously determined through standard cards with known register mismatches. Those values will be stored in the computer's memory, to enable rejection of cards in which said register errors exceed allowable deviation from true position.

Although the invention has been described with base in a specific embodiment, it becomes clear that variations and modifications may be introducad without overstepping the scope of the inventive concept. Thus, for example, all data processing can be made by the device's CPU 21, provided that enough memory is available and all necessary software is loaded, eliminating, therefore, the need for the use of micro-computer 11.

Moreover, although the description shows a device designed to test cards with 104 cells (100 credit cells and 4 for positioning/validity), it shall be understood that the principle of the invention is equally applicable to cards with any amount of cells and even for measurement of thickness of continuos metal layers applied over an insulating material.

Claims

Claims
1. DEVICE FOR DETERMINING FILM THICKNESS AND PATTERN REGISTER IN CELLS PLATED ON INDUCTIVE DEBIT CARDS characterised by comprising a sensing assembly (27) consisting of a plurality of sensing modules equal in number to the credit cells in said cards, each module consisting of an oscillator (30) wherein the inductance is provided by a pair of collinear sensing coils (24a, 24b), having their longitudinal axis aligned with the true position of its relative credit cell (25), the output (26) of said sensing assembly being connected to the input of an A/D converter (40) whose output is connected to computing means (11, 21) provided with memory means loaded with specific software for thickness calculation as well as data related to each individual sensing module.
2. DEVICE FOR DETERMINING FILM THICKNESS AND PATTERN REGISTER IN CELLS PLATED ON INDUCTIVE DEBIT CARDS as claimed in Claim 1, characterized in that the pattern register is checked by additional sensing modules wherein the sensing coils ( 62, 63, 64) are placed outside the region of the array of credit cells.
3. DEVICE FOR DETERMINING FILM THICKNESS AND PATTERN REGISTER IN CELLS PLATED ON INDUCTIVE DEBIT CARDS as claimed in Claim 1 , characterised in that each one of said sensing modules comprises a Colpitts oscillator.
4. DEVICE FOR DETERMINING FILM THICKNESS AND PATTERN REGISTER IN CELLS PLATED ON INDUCTIVE DEBIT CARDS as claimed in Claim 1, characterised by the insertion of a Zener diode (37) between the sensing assembly (27) output and the A/D converter (40) input.
5. DEVICE FOR DETERMINING FILM THICKNESS AND PATTERN REGISTER IN CELLS PLATED ON INDUCTIVE DEBIT CARDS as claimed in Claim 1, characterized by the connection of a digitally controlled potentiometer (39) to the input path of said A/D converter (40), wherein said potentiometer's control terminal (39') is connected to said computing means (21).
6. DEVICE FOR DETERMINING FILM THICKNESS AND PATTERN REGISTER IN CELLS PLATED ON INDUCTIVE DEBIT CARDS as claimed in Claim 1 , characterized by the fact that digitally controlled potentiometers (41, 42) are connected to the span and V-null terminals of the A/D converter, wherein said potentiometers' control terminals (41', 42') are connected to said computing means (21).
7. PROCESS FOR DETERMINING FILM THICKNESS AND PATTERN REGISTER IN CELLS PLATED ON INDUCTIVE DEBIT CARDS characterized by: • selecting at least one position to be tested within the credit cell array;
• reading-off from the computing means' ( 11, 21) memory the coefficients associated with the test module related to said selected position;
• presetting the A/D converter (40) by means of control signals generated by the CPU (21) fed into the control terminals (39', 41', 42') of the digitally controlled potentiometers (39, 41, 42), respectively connected to the signal input, span and V-null terminals of said converter, said control signals being derived from said coefficients;
• calculating the film thickness by processing the numerical value forwarded from said A/D converter to the computing means (21, 11) according to a transfer curve associated with said position within the array as well as with the metallic alloy which makes up said film.
8. PROCESS FOR DETERMINING FILM THICKNESS AND PATTERN REGISTER IN CELLS PLATED ON INDUCTIVE DEBIT CARDS as claimed in Claim 7, characterized in that the values of said coefficients and of said transfer curves stored in the computing means' (11, 21) memory are previously determined by measurements performed on standard cards of known metallic film thicknesses.
PCT/BR1996/000041 1995-09-18 1996-09-17 Device and process for determining film thickness and pattern register in cells plated on inductive debit cards WO1997011332A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
BR9504681-0 1995-09-18
BR9504681 1995-09-18

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP51225397A JPH11512526A (en) 1995-09-18 1996-09-17 Apparatus and method for measuring the film thickness and the pattern register in plated on the induction debit cells

Publications (1)

Publication Number Publication Date
WO1997011332A1 true true WO1997011332A1 (en) 1997-03-27

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PCT/BR1996/000041 WO1997011332A1 (en) 1995-09-18 1996-09-17 Device and process for determining film thickness and pattern register in cells plated on inductive debit cards

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JP (1) JPH11512526A (en)
CN (1) CN1121604C (en)
CA (1) CA2232162A1 (en)
WO (1) WO1997011332A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2361999B (en) * 2000-03-24 2005-02-23 Helmut Fischer Gmbh & Co Method and apparatus for the nondestructive measurement of the thickness of thin layers

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3473111A (en) * 1965-04-29 1969-10-14 Nederlanden Staat Thin metal marking and method for detecting the same
US4029945A (en) * 1975-08-27 1977-06-14 Stanley Electric Co., Ltd. Card and card reader apparatus therefor
DE2621989A1 (en) * 1976-04-28 1977-11-03 Sodeco Compteurs De Geneve Identification system with card reading device - uses identification cards with layer containing ferromagnetic code marks, sandwiched between two steel sheets
US4181958A (en) * 1978-04-21 1980-01-01 The Valeron Corporation Multiple probe gage system
US4678994A (en) * 1984-06-27 1987-07-07 Digital Products Corporation Methods and apparatus employing apparent resonant properties of thin conducting materials
WO1988002519A1 (en) * 1986-10-01 1988-04-07 Dalson Artacho Writing and reading data system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3473111A (en) * 1965-04-29 1969-10-14 Nederlanden Staat Thin metal marking and method for detecting the same
US4029945A (en) * 1975-08-27 1977-06-14 Stanley Electric Co., Ltd. Card and card reader apparatus therefor
DE2621989A1 (en) * 1976-04-28 1977-11-03 Sodeco Compteurs De Geneve Identification system with card reading device - uses identification cards with layer containing ferromagnetic code marks, sandwiched between two steel sheets
US4181958A (en) * 1978-04-21 1980-01-01 The Valeron Corporation Multiple probe gage system
US4678994A (en) * 1984-06-27 1987-07-07 Digital Products Corporation Methods and apparatus employing apparent resonant properties of thin conducting materials
WO1988002519A1 (en) * 1986-10-01 1988-04-07 Dalson Artacho Writing and reading data system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2361999B (en) * 2000-03-24 2005-02-23 Helmut Fischer Gmbh & Co Method and apparatus for the nondestructive measurement of the thickness of thin layers
DE10014348B4 (en) * 2000-03-24 2009-03-12 Immobiliengesellschaft Helmut Fischer Gmbh & Co. Kg Apparatus for non-destructive measurement of the thickness of thin layers

Also Published As

Publication number Publication date Type
CN1200171A (en) 1998-11-25 application
CN1121604C (en) 2003-09-17 grant
JPH11512526A (en) 1999-10-26 application
CA2232162A1 (en) 1997-03-27 application

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