KR19990045767A - Method and apparatus for pattern registration and film thickness determination in cells plated on inductive debit cards - Google Patents

Abstract

An apparatus for determining the thickness of a conductive metal pattern plated on an insulating surface, such as a credit cell of a prepaid telephone debit card, includes a plurality of recognition modules each having the same number as the credit cells of the card. The module of consists of an oscillator 30 provided by a pair of colinear recognition coils 24a, 24b whose inductance is aligned with the actual position of its relative credit cell 25, and the output of the recognition assembly ( 26 is connected to an input of the A / D converter 40 whose output is connected to arithmetic means 11, 21 where memory means are provided. The oscillators are alternately enabled to convert their output voltages to numerical values. The transducer parameters are adjusted for each recognition module according to the constants stored in the memory to compensate for component changes, recognition coil positions, and the like. The resulting numerical value is processed by the computing means according to the transfer curve 53 specified for each recognition module to provide the thickness of the film. The constant and transfer curve are predetermined for each position in the cell array by individual calibration using a standard card of known metal film thickness.

Description

Method and apparatus for determining pattern registration and film thickness in cells plated on inductive debit cards

The present invention relates to the determination of the thickness of a conductive metal layer deposited on an insulating surface, in particular the patent documents PI (BR) 7804885, PI (BR) 9201380-5 and PI (BR) 9304503-4, incorporated herein by reference. It relates to the measurement of the thickness of the metal film used for the production of credit cells on inductive debit cards as shown.

Methods of measuring metal film thickness based on X-ray diffraction are already well known, but their use is limited to measurements with high accuracy in the laboratory due to the time required and the cost thereof.

Moreover, currently known methods do not accurately detect register errors that occur suddenly during the manufacture of the card, ie position mismatches for those edges of the metal cell pattern plated on the card.

In view of the above, the present invention provides a device capable of quickly measuring the thickness of the metal film with a minimum error margin and low cost as its main purpose.

It is also a further object of the present invention to detect mismatches between the wrong registers during plating of the cell, i.e. the ideal position for the card edge which makes the card useless and the actual position of the cell.

In order to achieve the above object, the present invention provides an apparatus having a recognition assembly composed of a plurality of recognition modules, where each module is inductance by a recognition coil positioned in correspondence with the true position of its relative credit cell. And each sensor is individually enabled one at a time by pulses generated by the computing means controlling the process, and the oscillator output voltage is information about the thickness of the metal layer. Coupled to means for converting into a numerical value for processing by said computing means in accordance with a constant stored in a memory means to provide.

According to another feature of the invention, the constant is predetermined for each position in the cell array by individual calibration using a standard card with a known metal film thickness.

According to another feature of the present invention, a sensor is provided located outside the cell matrix to enable measurement of the resistor error in the plated cell pattern.

According to another feature of the present invention, a complete check of all the cells in the card is allowed such that such a card is opened where one or more cells are opened due to manufacturing defects.

The foregoing features, as well as other aspects and effects of the present invention, are more apparent from the description of the specific embodiment, which is taken as an example, and not in a limiting sense, as shown in the accompanying drawings.

1 shows a block diagram of a test apparatus made in accordance with the principles of the present invention as well as connecting to external control equipment such as a microcomputer suitable for a PC.

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

FIG. 3 shows a calibration curve for one recognition module showing components for converting measured voltage values according to the present invention into metal layer thicknesses.

4 illustrates the principle of register misalignment detection in accordance with the present invention.

Referring to the block diagram of FIG. 1 in more detail, the proposed apparatus 20 includes the following blocks. That is, a control panel 21 (CPU-A / D) composed of a microcontroller, an analog-to-digital converter (A / D), a memory, and an attachment; A decryption card (CEO) 22 consisting of an address decoder for controlling the operation of each oscillator in the sensor matrix by separate wiring 23; And recognition modules each having the same number of recognition modules as the number of cells of a card including a pair of in-line recognition coils 24a-24b in addition to the oscillator, wherein an inner end of the coil core wire is a credit cell 25 ) Has a recognition assembly which is placed and forms a gap whose width is slightly larger than the thickness of the card, which is the reason for unintended irregularities.

Still referring to FIG. 1, the device 20 is connected to a PC microcomputer 11 which controls the measurement process via a series of communication lines 46 using a standardized protocol, for example RS 232.

Referring to FIG. 2, the recognition assembly 27 has a plurality of test modules 30, each of which consists of Colpitts oscillators whose coils that make up the tank are inductive sensors 24a, 24b. Such oscillators have the property of generating an alternating signal whose amplitude is proportional to the inductive coil load. Considering the fact that the load depends not only on the cell conditions (open or short) but also on the properties (thickness and conductivity) of the metal layer, the signal amplitude between the recognition coils is inversely proportional to the thickness of the metal film for known alloys.

Transistors 31 in all oscillators are normally cut off, by the CEO 22 via a positive voltage pulse 32 applied to the base of the transistor via one of the wires 23. Oscillation is possible individually. The duration 33 of this pulse is substantially greater than the time required by the oscillator to reach steady state operation, eliminating the effect of any possible transients. A portion of the oscillation voltage present in the collector of transistor 31 is rectified by diode 34 and filtered by capacitor 35, so that the rectangular pulse 36 has the same duration as the command pulse 32 described above. Results in.

The magnitude of the pulse 36 is much greater than the maximum voltage applied to the A / D converter 40. For this reason, in order to make a lower amplitude pulse 38 transmitted to the input of the converter 40 for subtracting a constant voltage from the pulse 36 and converting it into a numerical value, a Zener diode 37 is provided. It is connected in series with the transducer input.

The transmission is made via a digitally controlled potentiometer 39 whose value is adjusted by the CPU 21 by a signal applied to the control terminal 39 '. Since there is a difference between the components of each oscillator, these adjustments are individual for each test module 30. Moreover, the oscillation voltage is affected by the position of the recognition coils in the array (somewhat farther away from the edge, etc.). This potentiometer adjustment data is determined during the entire calibration of the device using a standard card of known thickness and stored in a memory (not shown) of the CPU.

The controlled potentiometers 41 and 42 are adjusted in the same manner by control signals from the CPU, and the adjustment is specified for each of the 104 recognition modules. Here, the first adjustment is to adjust the A / D converter span and the second adjustment is to set the lowest voltage signal (V-null) (corresponding to the thickest metal film) for the converter. . As mentioned above, the controlled potentiometer 39 limits the maximum value of the voltage applied to the input of the converter.

After this potentiometer is correctly adjusted, the output of the transducer is zero for the thickest predetermined metal layer and 255 for the thinnest film that can be expected during manufacture of the debit card. In order to provide a direct relationship between the numerical value and the metal thickness E, the output of the converter 40 is processed by the CPU 21 to produce completion of 255.

After this step, if several locations have been programmed for testing, the CPU sends the address of the next location to be tested to the CEO 23. Through the serial interface 45 and the wiring 46, the numerical value is transmitted to the microcomputer 11 (shown in FIG. 1), which is adapted to convey information about the actual thickness of the metal layer. Handle these results.

The calculation of this thickness is made with the aid of a transfer curve for each test module, which depends on the properties of the component and the position of the sensor in the matrix. Thus, each of the 104 modules (in this embodiment) has a transmission curve that can be approximated by one or more straight line segments. 3 illustrates an approximation of this curve with a single line segment 53 defined by two constants, which are the linear constants (b) and angular constants (m). Therefore, for each position in the matrix, the thickness is calculated by E = (VN x m) + b, where VN is the value passed to the CPU.

As mentioned above, the characteristic curve for each test module can be approximated more accurately through two or more straight line segments, each segment being defined not only by a particular linear constant (b1, b2, etc.) but also by a particular angular constant (m1, m2, etc.). As a result, in this case, the formula for calculating the film thickness becomes considerably more complicated than the formula used to approximate through one single line segment.

Once the values of the thickness in one or more cells in the card are calculated, these values are stored, printed, transferred to another unit, and even for rejecting the card (for thickness values beyond the acceptable limits). It may be used to trigger an alert. In the event of a cell failure due to manufacturing defects, this fact is interpreted by the device as "insufficient thickness" resulting in card rejection.

In addition to the thickness determination, the proposed apparatus makes a determination for unexpected register errors. For this purpose, a non-metallic window is provided on the card, which is rectangular or square in shape and is located in the plated area outside of the credit cell array. In a similar manner, a set of inductive sensors is provided with additional test modules with coils positioned in line with the window.

4 shows the principle of resist error determination. Considering one of the edges 61 of the window 60, approximately three positions are possible with respect to the inductive sensor core. In Fig. 4A, since the core wire 62 completely lies on the unplated portion, the current induced in the metal layer is the lowest, and therefore the voltage at the oscillator terminal is the largest. 4B shows the position where the core 63 lies partially on the plated area and partly on the window, in which case a slight load occurs and the oscillation amplitude is smaller than before. Finally, in FIG. 4C, the core 64 is located on a fully metal plated region. The oscillator coil load is the highest, so the oscillation voltage is the smallest.

By appropriate selection of the size and position of the window as well as the corresponding inductive sensor position, it is possible to detect the deviation of the metal pattern plated on the card in the longitudinal or transverse direction as well as the rotation of the pattern about the axis of the card. do.

Obviously, the voltage value detected by the sensor varies with the thickness of the metal layer on the card, requiring appropriate software for analysis of the value supplied by the resistor sensor.

As mentioned above, the maximum and minimum acceptable measured levels must be predetermined through a standard card with a known register mismatch. This value is stored in computer memory to allow the rejection of the card beyond the allowable deviation of the register error from the true location.

Although the present invention has been described based on the specific embodiments, it is apparent that various changes and modifications can be made without departing from the scope of the present invention. Thus, for example, if sufficient memory is available and all the necessary software is added, all data processing is done by the CPU of the device, eliminating the need for the microcomputer 11.

Furthermore, while the foregoing describes an apparatus designed to test a card having 104 cells (100 credit cells and 4 cells for location / validity), the principles of the present invention also apply to cards with any number of cells. The same may be applied to the measurement of the thickness of the continuous metal layer deposited on the insulating material.

Claims (8)

An apparatus for determining pattern registration and film thickness in a cell plated on an inductive debit card, A recognition assembly 27 composed of a plurality of recognition modules having the same number as the credit cells of the card, Each module consists of an oscillator 30 whose inductance is provided by a pair of colinear recognition coils 24a, 24b whose longitudinal axis is aligned with the true position of the credit cells 25 relative to each other, The output 26 of the recognition assembly is an A / D converter 40 whose output is connected to arithmetic means 11, 21 which are provided with memory means appended with data relating to each individual recognition module as well as specific software for thickness calculation. Device for determining pattern registration and film thickness in a cell plated on an inductive debit card. 2. The apparatus of claim 1, wherein the pattern registration is checked by an additional recognition module in which the recognition coils (62, 63, 64) are located outside the credit cell array area. 10. The apparatus of claim 1, wherein each of the recognition modules comprises a Colpitts oscillator. 2. A device according to claim 1, wherein a zener diode is inserted between the recognition assembly (27) output and the A / D converter (40) input. A digitally controlled potentiometer (39) according to claim 1, connected to the input path of said A / D converter (40), The control terminal (39 ') of the potentiometer is connected to the calculating means (21). A digitally controlled potentiometer (41, 42) is connected to the span and the V-null terminal of the A / D converter, The control terminal (41 ', 42') of the potentiometer is connected to the calculating means (21). A method for determining pattern registration and film thickness in a cell plated on an inductive debit card, Selecting one or more locations to be tested in the credit cell array; Reading a constant associated with the test module relating to the selected position from the memory of the computing means (11, 21); A step of setting an A / D converter in advance, wherein the control terminals 39 ', 41', of the digitally controlled potentiometers 39, 41, 42 connected to the signal input, span and V-null terminals of the converter are respectively set. Presetting the A / D converter by means of a control signal fed to the controller 42 ') and derived from the constant and generated by the CPU (21); And Calculating a film thickness by processing numerical values transmitted from the A / D converter to the computing means (11, 21) according to the transfer curves associated with the positions in the array as well as the metal alloys constituting the film. A method for pattern registration and film thickness in a cell plated on an inductive debit card. 8. Method according to claim 7, characterized in that the value of said transfer curve and said constant stored in said computing means (11, 21) memory are determined by measurements performed on a standard card of known metal film thickness.