CN1212733A - Data carrier for storing binary data and method for producing the same - Google Patents

Abstract

A data carrier for storing binary data, for example a telephone card, and a process for producing said data carrier. Known storage media with an irreversible storage mechanism contain superficially applied patterns which consist of metal layers. The first layer adjacent to the substrate material is made of a nickel/phosphorus alloy and the second is made of a tin/lead alloy. The disclosed data carriers, however, contain as second metallic layer a tin/zinc alloy which is less toxic than the known tin/lead alloys and are remarkably suitable for the given purpose on storage media.

Description

Data carrier for storing binary data and method for producing the same

The invention relates to a data carrier for storing binary data by irreversibly altering the structure of a metal layer applied to a planar, non-conductive carrier plane and to a method for producing the data carrier.

Credit cards are increasingly being used for cashless payments at vending machines. Such cards can be used, for example, to make calls in public telephone booths. Likewise, the card can be used for cashless payments in any buying or selling transaction. The card can also be used for digital data collection during doctor's visits.

Usually, the data on the data carrier, such as payment by cash deposit stored on an account, is recorded by means of a magnetic card or, when expensive card systems are likewise used, on a semiconductor memory integrated into the card.

However, this system has various drawbacks. Especially in the case where the stored money is recorded once by paying a certain cash deposit, and each time only the certain sum is subtracted from the stored deposit and a new sum is stored, the above-mentioned storage medium is not suitable. Economical and error-prone system. In particular, cards equipped with magnetic stripes cannot be adequately protected against misuse, since changing the stored funds is relatively simple.

Therefore, a new storage method needs to be sought. Disclosed in BR-A-910 55 85 is a method for producing counting cards used in public telephones, wherein a first conductive layer is applied over the entire plane of an impermeable, non-porous substrate, which is chemically method and have higher resistance, preferably a nickel coating with a maximum thickness of 0.3 microns, and then coat a metal or alloy layer of 2 to 15 microns, preferably 2 to 8 microns, electrolytically deposited on the entire plane, This deposited layer has a significantly lower electrical resistance and melting point than the first coating, which is preferably a tin/lead coating. When conducting electrolytic deposition, a current density of 0.5-2A/dm ² should be used.

The storage of cash deposits is carried out by means of a memory card produced according to the method in that a matrix of storage areas is produced in the card during the production process, which consists of a small number of electrically conductive storage areas bonded to each other electrically , here, the storage area always consists of an angular or round structure in which there is a metal-free zone, which induces a circulation around the storage area. In order to withdraw stored cash deposits by means of a reading device, no coils are placed above the individual storage areas, and it is measured by current induction in the ring structure how many such rings are closed. In each position, the metallic ring structure is closed by elongated tabs. When the cash deposit changes, for example when the cash deposit decreases, the slits of the storage area are gradually destroyed by the induction of the current (in this case the current is turned up), so that when it is subsequently read, it can be determined how much is still present Unbroken closed loop.

Media for irreversible information storage are substantially less prone to failure and counterfeiting than conventional memory cards.

A method of making such a telephone card is disclosed in the above-mentioned Brazilian patent application. Accordingly, the metal layer described is first produced over the entire area and the individual storage areas are formed by means of a textured etching mask by suitable etching methods.

However, this method is expensive and therefore uneconomical. In particular, elongated webs (for example only 100 μm wide) in the ring can only be produced in a very complex manner using the erosion method. Because such telephone cards should be produced in large numbers and should be produced cheaply, it is preferred to produce such cards on large plastic substrates in the production process, so that due to the unavoidable use of filling materials when processing the metal layers by means of suitable masks, As a result, the elongated tab is installed in an inappropriate position. This often leads to the problem of always reproducibly adjusting the width of the web. Therefore, it often happens that when the stored information is read out, such a web is already destroyed if the width of the web does not exceed a certain limit and therefore the resistance of the web does not exceed a lower limit value.

Therefore, DE 44 38 799 A1 proposes an improved method for producing such storage media. In this method, a catalyst suitable for the electroless deposition of metals is first coated on an electrically non-conductive card carrier. Subsequently, the interconnected structures are formed on the surface of the carrier by means of masking techniques. Then, first a thin first metal layer is deposited electrolessly and then a thick second metal layer is deposited electrolytically. Again it is suggested to use a nickel plating as the first metal layer and a tin/lead alloy plating as the second metal layer. The method can also be carried out without an erosion step.

The disadvantage of this method is that the second metal layer contains the toxic metal lead, and therefore on the one hand presents problems with the purification of the waste water produced in the electroplating process and with the storage of waste materials from the process. On the other hand, the cards themselves also pose a serious waste problem, since telephone cards are often discarded inadvertently together with general waste and cause an increased environmental load due to the lead component.

It is therefore the object of the present invention to provide a data carrier and a method for its production which produce a significantly lower environmental load when cleaning waste water and storing waste.

The object of the invention is achieved by a data carrier for storing binary data according to claim 1 and by a method for producing a data carrier according to claim 5 . An advantageous use of the data carrier is given in claim 14 .

The data carrier according to the invention is characterized in that it comprises a planar, non-conductive carrier with a surface coating structure consisting of a metal coating, where the metal coating has a structural form corresponding to the data, and the first metal coating consists essentially of nickel, Cobalt or an alloy based on nickel, cobalt or an alloy of nickel and cobalt, and the second metal plating layer consists of a tin/zinc alloy.

The working principle of this data card is the same as that described in BR-A-910 55 85 and DE 44 38 799 A1. For this card, the surface-coated metal structure consists of interbonded storage areas, wherein these storage areas mainly consist of a metal area surrounding the free area, in which an electric current can be induced, and wherein the metal area is passed through the elongated tab Closed in at least one position, this produces sufficient induced current to melt the tin/zinc plating deposited on the tab and interrupt the tab. These structures can consist, for example, of angular or rounded rings with elongated webs, or also of planar areas in which there is always a free area and a gradual change in position. Thin, become long and narrow tab (referring to embodiment 1 and accompanying drawing 1).

Individual binary data can be stored and read independently of each other. During production, only metal structures with the same binary number, ie "0" or "1", can be formed on the carrier, or metal structures with different binary numbers can be formed, for example in order to generate a certain combination of binary numbers.

In contrast to conventional memory cards, the metal coating applied to the data carrier according to the invention has a significantly lower toxicity. This data carrier does not contain toxic lead. The tin/zinc alloy coating deposited instead of the tin/lead alloy has proven to be very less toxic than known alloy coatings on cards. Likewise, only non-toxic substances are treated during wastewater purification and the storage of the resulting electroplating sludge.

Furthermore, the tin/zinc alloy coatings in the data carriers according to the invention are very suitable as functional coatings. Due to its relatively low melting point, this alloy coating can be melted by a low induced current, so that stored cash deposits can be written off without problems, which can easily destroy the ring structure made of this alloy coating on the carrier (their Play the role of inductance) long and narrow tabs. Due to its low melting point, very little energy is consumed when canceling the deposit unit, and the card is subjected to only negligible thermal loads, so that the decorative protective varnish applied to the card's casing is not damaged.

In addition, the raw materials for the preparation of this alloy coating are very suitable. It also has the advantage that it is possible to use a soluble anode where the two alloying elements coexist or use an insoluble anode. Finally, alloy coatings can also be deposited from acid baths.

It is also advantageous that the production process of the data carrier can be carried out without an etching process.

For this purpose, the following electrodepositable alloy systems have proven unsuitable: tin/antimony, tin/bismuth, tin/indium, tin/silver, tin/antimony/silver and tin/copper/silver. Although these alloys are known as brazeable alloys. However, they are unsuitable for the above-mentioned purposes of use.

Depending on its composition, the alloy of the present invention has a melting point ranging from 196°C (eutectic alloy) to about 230°C. Suitable alloy systems according to the invention therefore have a zinc content of 0.5 to a maximum of 20% by weight and a tin content of 80 to 95.5% by weight. In principle, other metals can be contained in the alloy besides tin and zinc, as long as the alloy has a melting point in the above-mentioned temperature range.

Deposition of tin/zinc alloy coatings from aqueous electrolytic metallization baths comprising sources of tin and zinc ions in addition to at least one complexing agent and agents for pH adjustment and other components such as grain refiners agents, antioxidants, brighteners (Glanzbildner), stabilizers, wetting agents and other substances.

The pH of the alloy plating bath is preferably adjusted below 7, so that the resist applied to the carrier material during the electrowinning process is not destroyed, if necessary. Depending on the composition of the alloy plating bath, acid or base is used to adjust the pH. Useful as complexing agents are, for example, salts or esters of gluconic acid or salts of phosphonic acid. As salts of phosphonic acids, preference is given to using salts of 2-phosphono-1,2,4-butanetricarboxylic acid, for example alkali metal salts. Tables 1 and 2 list the composition of the alloy plating baths with a pH below 7. The most favorable values are given in parentheses. Such an electroplating bath is disclosed, for example, by J.W. Price, Tin and Tin-Alloy Plating, Electrochemical Publications Limited, UK, 1983.

In principle, it is of course possible to use alloy plating baths with a pH higher than 7, if alkali-resistant resists are used or if another embodiment is chosen, ie the resist is removed from the support surface before the deposition of the metal coating. Such plating cells are described in Tables 3-6.

A plating bath that can be operated at normal temperature is preferred because it does not damage the matrix material.

Table 1: Gluconate Plating Baths Tin(II) sulfate, calculated as Sn ²⁺ 10 to 30g/l (15g/l) Zinc sulfate as Zn ²⁺ 0.5 to 20g/l (8g/l) sodium gluconate 50 to 200g/l (110g/l) Triethanolamine 15 to 50ml/l (33ml/l) Polyethylene glycol as a grain refiner 0.1 to 20g/l (1.0g/l) Pyrocatechol as Antioxidant 0.1 to 10g/l (1.0g/l) pH-value 4 to 5 operating temperature 20°C Table 2: Phosphonate Plating Baths Tin(II) sulfate, calculated as Sn ²⁺ 10 to 30g/l (20g/l) Zinc sulfate as Zn ²⁺ 0.5 to 20g/l (10g/l) Potassium salt of 2-phosphono-1,2,4-butanetricarboxylic acid 50 to 300ml/l (150ml/l) Polyethylene glycol as a grain refiner 0.1 to 20g/l (1.0g/l) Pyrocatechol as Antioxidant 0.1 to 10g/l (1.0g/l) pH-value, adjusted with _NH3 3 to 4 operating temperature 20°C The alloy is deposited at a current density of 20 A/dm ² , preferably 1 to 4 A/dm ² .

Table 3: Potassium Stannate/Cyanide Plating Baths Potassium stannate as Sn ²⁺ 20 to 50g/l (38g/l) Zinc cyanide as Zn ²⁺ 8 to 20g/l (14g/l) Total cyanide content, calculated as NaCN 25 to 48g/l (34g/l) Potassium hydroxide 4 to 30g/l (10g/l) pH-value 12.5 to 13 operating temperature 50 to 75°C (65°C) Table 4: Pyrophosphate Plating Baths Tin(II) chloride, calculated as Sn ²⁺ 2 to 4g/l (3g/l) Zinc oxide 2.5 to 6g/l (4g/l) potassium pyrophosphate 55 to 110g/l (80g/l) Hydrazine sulfate 2.5 to 5.8g/l (4g/l) Sodium chloride 40 to 250g/l (96g/l) Gelatin (as a grain refiner) 0.03 to 1.0g/l (0.15g/l) Ethylenediamine 0.9 to 4.5g/l (2g/l) operating temperature 20°C Table 5: Stannate/complex electroplating bath Ⅰ Sodium stannate (calculated as Sn ²⁺ ) 18 to 50g/l (30g/l) Zinc sulfate (calculated as Zn ²⁺ ) 0.5 to 2g/l (1g/l) N-Hydroxyethyl-ethylenediamine-triacetic acid-trisodium salt 23 to 39g/l (30g/l) Free sodium hydroxide content 2 to 12g/l (5g/l) operating temperature 65 to 77°C (70°C) Table 6: Stannate/Complex - Plating Bath II Potassium stannate (calculated as Sn ²⁺ ) 53 to 68g/l (60g/l) Zinc sulfate (calculated as Zn ²⁺ ) 0.8 to 2.5g/l (1.2g/l) 1-Hydroxyethylene-(1,1-diphosphonic acid) 220 to 350ml/l (300ml/l) Free Potassium Hydroxide Content 15 to 60g/l (35g/l) operating temperature 50 to 70°C (57°C)

As anodes used are soluble anodes made of tin/zinc alloys with the same composition that can be deposited, or insoluble anodes, for example consisting of special steel, platinized titanium-extruded metal electrodes or mixed oxide electrodes anodes, they are all coated with _IrO2 . In principle, both soluble and insoluble anodes could be used, for example so that the ratio of the current flows through the two anodes adjusts the ratio of tin and zinc ions in the deposition bath. If necessary, the tin and zinc ions must be replenished by the corresponding salts.

Plants for alloy deposition are usually additionally equipped with various auxiliary equipment. Such equipment includes, for example, means for the circulation of the bath liquid and means for the filtration of the treatment liquid.

The preparation of the storage medium is described below:

The conventional acrylonitrile-butadiene-styrene copolymer (ABS) is used as carrier material. In order to produce as many data carriers according to the invention as possible during the production process, two substrates in the form of foils are always bonded back-to-back each time by fusing their edges to one another. Thus, on the one hand, the substrate is sufficiently stabilized in the electroplating bath, and on the other hand, the carrier material is prevented from being coated on both sides, since the sides of the carrier are supposed to carry the circuit pattern.

For the electroplating treatment, the soldered carrier material is fixed on a suitable holder and dipped vertically one after the other into the different treatment electroplating baths.

The ABS surface is roughened by means of the chromium/sulfuric acid method in order to provide sufficient adhesive strength for the metal coating on the non-conductive substrate. To this end, the substrate is first brought into contact with a wetting agent or a solution comprising an organic swelling agent. After the rinsing process, the surface is roughened in a conventional chromium/sulfuric acid solution. For this, for example a solution comprising 360 g/l of chromium trioxide and 360 g/l of concentrated sulfuric acid is used. However, chromium/sulfuric acid solutions having other concentrations can likewise be used.

Subsequently, the ABS-sandwich structure is rinsed again and then treated with a solution such as sodium bisulfite to remove chromium(VI) ions.

After further rinsing with water, the surface is activated. For this purpose, a suitable catalyst must be applied in order to activate the surface for electroless metallization. Conventional catalysts are used, for example palladium colloids stabilized with tin(II) salts or polymers such as polyvinyl alcohol or polyvinylpyrrolidone. The palladium clusters adsorbed on the substrate mixed with the protective colloid are removed (accelerated) from the latter in a second process step.

Furthermore, so-called ion-generating palladium activators can likewise be used in catalysis, in which palladium complexes with organic complex ligands such as 2-aminopyridine are used as catalyst precursors. The complexes adsorbed on the support material are reduced to metallic palladium in a second process step by means of strong reducing agents such as dimethylamineborane or sodium borohydride.

After further rinsing with water, a resist layer with one channel is applied to the carrier to produce the metal structure according to the invention, the surface regions of the carrier on which the metal structure will later be formed being left uncovered.

Not only photoresist but also non-photosensitive resist can be used as the resist. If a photoresist is used, the photoresist is exposed to light and subsequently developed after the entire surface or part of the surface of the carrier carrying the circuit pattern of the metal structure has been coated. Thus, channels are formed in the resist coating. If a non-photoresist is used, the circuit pattern is already formed when the resist is printed—typically by screen printing—on the surface of the carrier.

Particularly suitable are positively operating resists (positiv arbeitende Resist), in which the exposed areas are soluble so that they can be removed in a subsequent development step. Thereby forming a channel here. However, negatively operating resists can also be used.

In principle, photoresist foils can be used. However, in view of cost, it is preferable to coat a liquid resist on the carrier. In the latter case, the resist is applied over the entire surface using a curtain coating casting process, a roll coating process or, in the absence of a substrate, by spin coating or by means of screen printing techniques.

In the latter case, for example in the case of multiple uses, the liquid photoresist is first printed only on the surface corresponding to the circuit pattern, without processing the individual structural elements. In the second process, circuit structures are formed in an exposure/development step. Thus, fine structural elements can be formed, while unused surfaces between individual circuits are freed by screen printing over multiple uses.

Another embodiment is that the photoresist is printed on the surface of the carrier in a screen printing process, so that the circuit mask is already produced during printing and the elongated tabs are formed by a subsequent exposure/development step.

Next, a metal coating consisting of nickel, cobalt or an alloy based on nickel, cobalt or nickel and cobalt is deposited in the channels without current, preferably at a pH below 7.

For these metallic coatings, nickel/phosphorous alloys are preferably used. A particularly suitable plating bath uses a nickel electrolyte containing hypophosphite as a reducing agent for nickel ions. For this purpose, commercially available plating baths can be used.

In addition, nickel or nickel/boron coatings can likewise be deposited. In the latter case, for example dimethylamine borane is used as reducing agent.

To produce the data carrier according to the invention, a nickel, nickel/boron or nickel/phosphorous coating or a corresponding cobalt-containing coating is deposited to a thickness of preferably 0.3 μm.

Thereafter, the surface was rinsed with water again, and then the above-mentioned tin/zinc alloy plating layer was electrolytically deposited on the nickel plating layer to a thickness of about 8 micrometers.

After the preparation of the metal structure from the galvanically deposited metal and tin/zinc alloy coating, the resist is removed (stripping process). Afterwards, the carrier is covered with a decorative lacquer coating.

In another preferred embodiment, the catalyst required for the electroless metallization is applied after the formation of the circuit mask by the resist coating. In this case, the exposed surfaces of the support and of the resist coating are activated after formation of the resist coating with channels and prior to electroless metallization. In this embodiment, the resist is removed from the support prior to galvanic metallization.

The advantage of this method is that the production process does not have to be interrupted several times, since the process steps for activating the surface with the catalyst and for forming the metal coating are usually carried out in the electroplating plant, preferably without interruption, and at the same time in another plant In , the mask is produced, for example by means of screen printing or using a photoresist.

In the above-described embodiment, the production process is interrupted twice, that is, once after activation, in which the carrier material has to be fed into another device for further processing to prepare the mask, and once after the mask preparation , in order to get the metal coating in the electroplating device. Such a procedure is uneconomical because, logically, it generally prolongs the preparation process and produces defects due to interruptions, such as the formation of an oxide layer or other detrimental layer on the catalyst layer, which reduces or cancels the catalyst layer. active.

Therefore, the second method is the preferred embodiment. In this case, the carrier material is first processed in the device for producing the mask. The carrier material is then fed into the electroplating unit. This ensures that the machining process is performed more quickly and the chance of defects is reduced.

If the procedure described above is used, it is particularly advantageous to remove the resist mask from the carrier material again before the metallization is formed. Various processes are known for this, since the preferred resist materials are generally chemically unstable compared to metallization baths. Depending on the chosen process, the choice of resist material can be made independent of the metallization bath, so that no stringent requirements are imposed on the chemical resistance of the resist material for the metallization bath. In this case, therefore, the above-mentioned alkaline deposition tanks for tin/zinc alloys can also be used.

The treatment of the substrates takes place in conventional immersion plants, in which the substrates are dipped one behind the other into containers containing the corresponding treatment liquids. Another preferred process is to move the horizontally or vertically arranged substrates in the horizontal direction by suitable equipment for this purpose, and by means of suitable means for bringing the treatment liquid into contact in the equipment, for example by means of pressure regulation Nozzle, in which the substrate is treated.

The present invention will be described in further detail below with the aid of examples.

According to the example, a circuit diagram identical to the schematic diagram of FIG. 1 is prepared on a carrier material. In this figure, the darker areas represent the metal coating, and the lighter areas represent the surface of the support that was not coated with metal. Reference numeral 1 designates an annular storage area, in which a circulating current is induced by means of coils arranged above the storage area. Reference numeral 2 designates a web which can be fused by a strong induced current so that the ring is interrupted. By means of such an interruption, an irreversible data unit is stored in the circuit: when read again by means of a coil arranged above the storage area, the interrupted loop no longer induces a current in it.

All disclosed features and combinations of these disclosed features are the subject matter of the invention, insofar as these features are not explicitly stated as prior art.

Example 1:

Two 40 cm x 60 cm ABS foils were welded back to back in such a way that only their edges were fused to each other. The photosensitive screen-printing paint Imagecure ^@ (AQ Firma ASI, Phoenix, USA) was then printed on the resulting sandwich structure by covering a large side-by-side storage area of 50 mm x 80 mm with the paint. The size is the same as the size of the circuit diagram to be prepared.

Next, the circuit pattern is exposed through a mask with leads on the storage area of the individual card, followed by development in a suitable developer, such as dilute sodium carbonate solution.

Afterwards, the ABS sandwich structure is immersed in an aqueous wash solution containing a wetting agent. After rinsing with water, the ABS surface not covered with resist was treated by means of a chromium/sulfuric acid solution containing 360 g/l chromium trioxide and 360 g/l concentrated sulfuric acid at 60°C for a treatment time of 5 minutes. Roughening, while slightly roughening the resist surface.

After rinsing the substrate, it was immersed in an aqueous solution containing 10 g/l of sodium bisulfite in order to remove the attached residual chromium ions (VI).

After rinsing again, the sandwich was treated for 3.5 minutes in a pre-dip solution comprising 10 ml/l of concentrated sulfuric acid. Immediately thereafter, the sandwich structure is immersed in the catalyst solution without an additional rinsing step. This gives a complex of palladium sulfate and 2-aminopyridine at a concentration of 200 mg/l as Pd ²⁺ .

After activation, the sandwich was rinsed again and treated for 3.5 minutes in a reducing solution containing 1 g/L sodium borohydride. Here, metallic, catalytically active palladium clusters are formed on the ABS surface.

Next, the resist is completely removed in an aqueous solution of concentrated sodium hydroxide or potassium hydroxide. For this, the matrix is introduced and allowed to contact the solution for about 2 minutes.

Metallization was then formed by coating the rinsed ABS sandwich in an electroless nickel plating bath with sodium hypophosphite as reducing agent. A nickel electroplating bath (Noviganth Ni AK ^@ , Firma Atotech Deutschland GmbH, Berlin, DE) with pH adjusted to 6.5-6.9 was used here. The nickel/phosphorous coating was deposited at an operating temperature of 45°C. In order to be able to deposit a coating approximately 0.3 microns thick, the substrate was allowed to dwell in the electroplating bath for 7 minutes.

After rinsing the panels again, they were immersed in a tin/zinc electroplating bath, the composition of which is shown in Table 1 (values in brackets). The electroplating cell was operated at a cathodic current density of 2 A/dm ² . The soluble anode is a tin/zinc plate with a composition of about 67% by weight tin and 37% by weight zinc. The electroplating bath was operated at normal temperature. Deposition was continued until a coating about 8 microns thick was deposited.

An alloy coating having a composition of 67% by weight tin and 37% by weight zinc was obtained.

After metal deposition, the panels are rinsed, dried, and then wrapped with a decorative protective paint. The individual cards are then separated by cutting for multiple use.

Example 2

Basically repeat the process of embodiment 1.

However, in contrast to the procedure of Example 1, the resist coating is applied only after the activation step and including subsequent reduction, and the structure is produced by exposure and development. Also, the resist on the substrate remains after the deposition of the tin/zinc alloy plating. Additionally, the tin/zinc alloys were deposited using the electroplating baths given in Table 2 (concentration values in parentheses) instead of the gluconate baths given in Table 1.

The cathode current density was 2A/dm ² . The anode was a soluble tin/zinc anode (pellet) in a titanium basket with a composition of 84% by weight tin and 16% by weight zinc. Process at room temperature.

The composition of the 8 micron thick tin/zinc coating was determined after its deposition. The tin and zinc content of the resulting alloy was the same as that of the anode used.

Example 3:

Example 1 was repeated. However, the stannate/complex bath II given in Table 6 (concentration values in brackets) was used instead of the gluconate bath.

The operating temperature of the electroplating bath was 65°C and the cathodic current density was 2A/dm ² . An insoluble anode in the form of platinized titanium-rolled metal is employed. Therefore, the depleted bath components must be replenished by adding salt.

After depositing an alloy coating about 8 microns thick, its composition was determined. The alloy contains about 80% by weight tin and about 20% by weight zinc.

Example 4:

Example 3 was repeated. However, ABS-sandwich structures are processed in horizontal equipment, where the ABS sheets are continuously moved in horizontal position and direction, and thus only come into contact with individual processing liquids.

In this equipment, on the one hand, it is equipped with hydraulic pressure rollers and pressure regulating nozzles. Spaces above the plates are set between the hydraulic pressure rollers. In these spaces, the treatment liquid can be accumulated into a liquid electroplating tank. The pressure regulating nozzles are installed Below the conveying plane and responsible for the introduction of the liquid so that the plate can move through the treatment plating tank, on the other hand nozzles are installed above and below the moving plane.

Claims (14)

1. A data carrier for storing binary data by irreversibly changing a structure consisting of a metal layer coated on a planar non-conductive carrier, wherein the form of the structure corresponds to the data and is next to the first part of the carrier. The metallic coating consists of nickel, cobalt or an alloy based on nickel, cobalt or nickel and cobalt, which is characterized in that the second coating on the first coating consists of a tin/zinc alloy. 2. Data carrier according to claim 1, characterized in that 0.5 to 20% by weight of zinc is contained in the alloy. 3. The data carrier as claimed in claim 1, characterized in that the first metal coating consists of a nickel/phosphorous or nickel/boron coating. 4. The data carrier as claimed in claim 1, characterized in that the surface-coated metal structure consists of mutually bonded storage areas, wherein the storage areas essentially comprise a metal area surrounding a free area, in which the metal A current can be induced in the area, and wherein the metal area is closed at at least one point by an elongated web such that the induced current is sufficient to melt the tin/zinc coating deposited on the web and interrupt the web. 5. A method for preparing a data carrier according to any one of the preceding claims, comprising the following main steps; a) forming a channeled resist coating on the carrier, wherein the surface area of the carrier corresponding to the metal structure to be formed later is uncovered; b) electroless deposition of a coating consisting of nickel, cobalt or an alloy based on nickel, cobalt or nickel and cobalt in the channels; c) electrolytically depositing a tin/zinc alloy coating in the first coating, In this case, before step a) or between step a) and step b), the uncovered free surface of the support is activated by means of a suitable catalyst for the subsequent electroless metal deposition. 6. The method as claimed in claim 5, characterized in that between steps a) and b), the free surface of the carrier is activated and the resist is removed from the carrier before carrying out step b). 7. The method according to one of claims 5 and 6, characterized in that the tin/zinc alloy coating is deposited in an aqueous electrolytic metallization bath comprising at least one tin- and a zinc ion source, At least one complexing agent and an agent for adjusting the pH. 8. A method according to claim 7, characterized in that the pH of the tank is adjusted below 7. 9. Process according to one of claims 7 and 8, characterized in that the complexing agent is a salt or ester of gluconic acid. 10. Process according to one of claims 7 and 8, characterized in that the complexing agent is a salt of phosphonic acid. 11. Process according to claim 10, characterized in that the salt of phosphonic acid is the salt of 2-phosphoryl-1,2,4-butanetricarboxylic acid. 12. The method as claimed in one of the preceding claims, characterized in that a nickel/phosphorus coating is deposited as the first metal coating. 13. The method as claimed in one of claims 5 to 12, characterized in that the resist is applied only to those surface regions of the carrier which are not subsequently covered by the metal structure. 14. Use of a data carrier according to claims 1 to 4 as an electronic counting card or as a telephone card.

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