DE202021004169U1 - Bronze layer as a substitute for precious metals in smart cards - Google Patents

Abstract

Smart card foil, in which the electronically conductive contact surfaces are connected by a sequence of layers on the foil to connect a chip to a read/write device consisting of:1. Laminated copper base layer;2. Bronze layer as the top metal layer with a composition of 70% by weight - 90% by weight Cu, 1% by weight - 10% by weight Sn and 5% by weight - 30% by weight Zn (based on the bronze layer) is formed.

Description

The present invention is directed to a stack of layers. This has bronze deposits as a substitute for galvanic precious metal deposits in external contact surfaces of smart cards.

The electrolytic deposition of brass (Cu-Zn alloy) and bronze (Cu-Sn alloy) on consumer or decorative goods is well known (Praktische Galvanotechnik, Eugen G. Leuze Verlag KG, 7th edition 2013, p. 261 ff. ). Among other things, they serve as a replacement for nickel-containing finishing layers and are applied inexpensively to corresponding substrates, for example in galvanic drum or rack coating processes.

When depositing brass and bronze layers, the solderability and, if necessary, their mechanical adhesive strength are decisive properties that these layers that produce have to reproduce. In electronic applications, the appearance of the layers is generally less important than their functionality. On the other hand, for the production of bronze or brass layers on consumer goods, e.g. electronic payment cards, the decorative effect is an important target parameter in addition to the surface robustness and long durability of the layer with an appearance that is as unchanged as possible.

The deposition of a ternary alloy consisting of copper, tin and zinc is well known to those skilled in the art. A deposition from a cyanide-free electrolyte is, for example, in EP2116634 explained. There, in addition to a high concentration of pyrophosphate anions in the electrolyte, a special reaction product of hexamethylenetetramine and epichlorohydrin is used at an almost neutral pH of the electrolyte. the US20010014407 mentions in passing the deposition of a ternary alloy of Cu/Sn/Zn on copper surfaces as a protection against corrosion.

From the US20100147696 is known to deposit Cu-Zn-Sn alloy from phosphonic acid-containing electrolytes. The deposits described here result in white coatings which, however, are relatively poor in zinc.

A cyanide-free, pyrophosphate-containing electrolyte for depositing ternary copper-zinc-tin alloys is described in Thin Solid Films, 517 (2009) 2511-2514. Here, an unspecified layer is deposited from an alkaline electrolyte with the metals copper in the +2 oxidation state, zinc in the +2 oxidation state and tin in the +4 oxidation state.

In the EP2037006 describes the electrolytic deposition of copper-tin-zinc alloys in a very specific atomic ratio to each other. The deposited layers have a composition which is said to be close to the formula Cu2ZnSn. The layers obtained in this way can serve as a basis for the production of kesterite (CZTS or Cu2ZnSn(S,Se)4), which is a promising material for the production of photovoltaically active modules (Solar Energy Materials & Solar Cells 2011, 95, 2136-2140; Chemical Physics Letters 2011, 501, 619-622).

Leadframe - in German carrier strips, is a carrier for semiconductors in the form of a stamped band. It is a solderable, metallic lead carrier in the form of a frame or comb for machining semiconductor chips or other electronic components. In addition to the chip carrier, the leads of the later component are also realized on the leadframe. Chips are attached to the leadframe by die bonding. The contact surfaces of the chips are connected to the leads with wire bonds. After bonding, the leadframe is overmoulded with a duroplastic material. The connecting pins protrude from the plastic housing and are then shaped (https://www.kurtzersa.de/electronics-production-equipment/loetlexikon/term/leadframe.html). Leadframes are therefore the metal structures within a chip housing that transmit signals from the chip to the outside (https://de.vvikipedla.com/wiki/Lead_frame). In addition, leadframe also refers to the shape of the microchips produced with leadframes, i.e. the shapes with (protruding) connections. Leadframes are mounted on an insulating carrier or in a housing. If the contacts are mechanically fixed, they can be separated from each other. Leadframes are stamped, but can also be laser cut for smaller quantities. They are used, for example, in smart cards or chip cards.

Smart cards, chip cards or integrated circuit cards are typically plastic cards that have a chip on their surface. You know these smart cards from ID cards, credit cards or the like. The integrated chip is controlled via various metal surfaces, which make contact an external read/write device. An introduction can be found here: https://en.wikipedia.org/w/index.php?title=Smart_card&oldid=1009449492.

The contacts or metal surfaces mentioned above must be able to establish contact with the read/write device under very different environmental conditions. For example, corrosive liquids must not affect the conductivity of the metal surfaces. Optimally, their external appearance is not negatively influenced. For these reasons, very noble metals, such as gold, have been used in the metal surfaces to date. In these applications, the noble metal layers are usually deposited on other metal surfaces, in particular copper and nickel.

The use of expensive precious metals makes the leadframes or smart cards themselves expensive. It would therefore be an important and innovative advance if the precious metal-containing layers in the metal surfaces on these products could be replaced with less expensive but equally resistant, visually appealing metal surfaces.

These and other problems resulting from the state of the art for the person skilled in the art are solved by the use according to present claims 1 to 3.

1. 1. Auflaminierte Kupferbasisschicht;
2. 2. Bronzeschicht als oberste Metallschicht mit einer Zusammensetzung von 70 Gew.-% - 90 Gew.-% Cu, 1 Gew.-% - 10 Gew.-% Sn und 5 Gew.-% - 30 Gew.-% Zn (bezogen auf die Bronzeschicht) gebildet wird.

The invention relates to a smart card film in which the electronically conductive contact surfaces are connected by a layer sequence on the film for connecting a chip to a read/write device consisting of:

1. 1. Laminated copper base layer;
2. 2. Bronze layer as the top metal layer with a composition of 70% by weight - 90% by weight Cu, 1% by weight - 10% by weight Sn and 5% by weight - 30% by weight Zn (based on on the bronze layer) is formed.

The bronze layer preferably has a thickness of 0.3 µm - 0.7 µm (by weight of the bronze layer). Surprisingly, the bronze layers are very similar in color to the gold layers to be replaced. In terms of processability and durability, they are in no way inferior to precious metal layers. These are used in chip cards and replace existing precious metal layers, which makes the corresponding products cheaper.

The present invention can be found in smart cards. Here they are used - as explained above - in order to be able to connect a chip to a read/write device via a metal surface attached to the smart card. In 2 a corresponding smart card with a gold surface containing precious metals is shown as the contact surface.

According to the present invention, the bronze layer is applied to conductive substrates. The latter are immersed in a bronze electrolyte as a cathode and a current flow is established between the cathode and anode via an anode that is also in contact with the electrolyte. The expert knows how to proceed here. According to the invention, the layer sequence consists of a copper sub-layer, optionally followed by a nickel layer and the bronze layer. In 1 a very particularly preferred schedule for the application of the bronze layer is mentioned.

In a first step, the underlayer can be cleaned and etched. The person skilled in the art knows how to proceed here (Praktische Galvanotechnik, Eugen G. Leuze Verlag KG, 7th edition of 2013, page 167 ff.). A nickel layer can then optionally be applied to the underlayer. This ensures that the corrosion resistance of the entire system is improved. Here, too, the person skilled in the art is guided by well-known procedures (https://de.wikipedia.org/w/index.php?title=Galvanisch_Nickel&oldid=206755991). The bronze layer is applied to the possibly existing nickel layer after an optional renewed cleaning step. The yellow top layer looks very similar to a layer of gold. An electrolyte that can preferably be used for these purposes can be found in the following published patent applications ( EP1961840A1 , EP2116634A1 , EP2310558A1 , EP2606164A1 , DE102011121799A1 , DE102011121798A1 ). Corresponding electrolytes are also commercially available, for example from Umicore Galvanotechnik GmbH under the name Miralloy® 2847 1N HS.

For a bronze electrolyte that results in a golden-yellow deposit, a copper-rich bronze electrolyte such as Miralloy® 2847 1N HS is preferred. A high temperature at the Deposition, too high a tin content or too high a cyanide content in the electrolyte leads to a rather whitish, grayish deposition. High current densities or copper contents in the electrolyte as well as too high a pH result in reddish deposits. Here, it is up to the person skilled in the art to choose the appropriate parameters in such a way that a separation that is acceptable to him or her is produced.

With regard to the color of the bronze layer replacing the golden layer, it should be noted that these can be characterized as follows in the CieLab system. The deposited yellow (copper rich) bronze layer advantageously has an L* value of over +97. The a* value is preferably -0.2 to 0.2 and the b* value is between +2 and +4 according to the Cielab color system (EN ISO 11664-4 - latest version on the filing date). The values were determined with a Konica-Minolta CM-700d.

The nickel sub-layer mentioned above can be produced by a person skilled in the art (e.g DE102018133244A1 and literature cited there). Such a nickel layer preferably originates from a nickel sulfamate electrolyte. A bath for nickel deposition that has been known for a long time and is still used today in a variety of modified forms is the nickel sulfamate bath with its basic components of 300-450 g/l nickel sulfamate, 0-30 g/l nickel chloride and 30-45 g/l Boric acid (Practical Electroplating, Eugen G. Leuze Verlag KG, 7th edition 2013, p. 272 ff.). Others are commercially available, for example from Umicore Galvanotechnik GmbH under the name NIPHOSO 964 or NIPHOSO 964 HS, and for example here (https://www.microchemicals.com/de/produkte/galvanik/nickel_elektrolyt_nb_semiplate_ni_100.html). The thickness of the nickel layer is between 2.75 - 3.25 µm.

The thickness of the bronze layers is preferably 0.3 - 0.7 µm. The bronze layer commonly forms the top layer of the contact surfaces. Finally, they are advantageously only provided with a transparent organic protective film, known to those skilled in the art as tarnish protection, a top coat and/or a passivation. The person skilled in the art knows how to carry out these work steps (Praktische Galvanotechnik, Leuze Verlag, 7th edition of 2013, page 167 ff.). The attachment of a tarnish protection is a protective procedure for e.g. decorative precious metals. This absolutely transparent layer in the nanometer range protects the base material from oxidation, discoloration and mechanical stress. The color and gloss are not affected by this. The coating is chemically resistant, dirt and water-repellent and has a long service life.

In tests, the present invention has proven to be surprisingly advantageous. Corresponding tests and the results of a layer sequence according to the invention as just mentioned are listed in Table 1 below in comparison to standard gold surfaces. In comparison to gold, the bronze deposit impresses with its lower scratch resistance, comparable resistance in the required corrosion test and an almost identical appearance. Table 1: Comparison of interfaces for SmartCard applications Testing specification testing details bronze Ouch salt water test ISO 10373-1 24 hours (.+++.) (.++.) solderability IPC J-STD-003B >96% surface wetting OK OK scratch test ISO 7816-1 and simple pen cap test metal pin/pen cap (.+++.) (.+.) Resistance ISO 7816-1 <0.5ohm beforejafter OK OK 4K noxious gas test EN60068-2-60 96h (.++.) (.+++.) Pressure cooker storage test IPC-TM-650 Method 3.4.8.3 OK OK SO2 wet test ISO 6988 24 hours OK OK Chemical resistance : ISO 10373-1 OK OK NaCl 5% short term 1 min OK OK AcOH 5% short term 1 min OK OK Na2CO3 5% short term 1 min OK OK EtOH 60% short term 1 min OK OK sugar 10% short term 1 min OK OK Fuel B short term 1 min OK OK glycol 50% short term 1 min OK OK sweat (basic) long term 24 hours OK OK sweat (sour) long term 24 hours OK OK

In order to uncover the corrosion susceptibility of the entire layer structure, the 4-component harmful gas test was used for testing.

The 4-component noxious gas test (EN 60068-2-60) consisting of SO2, NO2, CI2, H2S, which is also carried out in a special noxious gas air conditioning system.

The Pressure Cooker Storage Test (https://storage.googleapis.com/verasol-assets/Global-LEAP-EPC-Test-Method_v1.pdf) is a delamination test typically performed on printed circuit board products under high pressure and temperature. This test also reveals outgassing from the deposited layers, which can lead to delamination of the deposited layers. The list in Table 1 shows that the more cost-effective bronze layer can definitely replace the precious metal layer without impairing use in the area of application considered here. This was by no means to be expected on the priority date.

• 1a) Basismaterial (z.B. eine kupferkaschierte L/F Smart Card Folie) + Kupferaktivierung + 1-2µm Nickel + 0.2µm - 1µm Gelbbronze + Anlaufschutz / Topcoat / Passivierung.
• 1b) Basismaterial (z.B. eine kupferkaschierte L/F Smart Card Folie) + Kupferaktivierung + 1-2µm Nickel + 0.2µm - 1µm Gelbbronze.
• 1c) Basismaterial (z.B. eine kupferkaschierte L/F Smart Card Folie) + Kupferaktivierung + 0.2µm - 1µm Gelbbronze + Anlaufschutz / Topcoat / Passivierung.
• 1d) Basismaterial (z.B. eine kupferkaschierte L/F Smart Card Folie) + Kupferaktivierung + 0.2µm - 1µm Gelbbronze.

The following procedures have proven to be particularly successful in connection with the present invention:

• 1a) Base material (e.g. a copper-clad L/F smart card foil) + copper activation + 1-2µm nickel + 0.2µm - 1µm yellow bronze + tarnish protection / top coat / passivation.
• 1b) Base material (eg a copper-clad L/F smart card foil) + copper activation + 1-2µm nickel + 0.2µm - 1µm yellow bronze.
• 1c) Base material (e.g. a copper-clad L/F smart card foil) + copper activation + 0.2µm - 1µm yellow bronze + tarnish protection / top coat / passivation.
• 1d) Base material (eg a copper-clad L/F smart card foil) + copper activation + 0.2µm - 1µm yellow bronze.

Examples:

1. 1. Vorbereiten, Reinigen und Aktivieren des Substrates
2. 2. Ggf. Abscheiden einer haftvermittelnden Schicht aus Nickel
3. 3. Ggf. Vorbereiten für den nächsten Schritt
4. 4. Elektrolytisches Abscheiden einer Gelb-Bronze-Legierungsschicht
5. 5. Optional Vorbereiten für den nächsten Schritt
6. 6. Abscheiden einer Passivierung/Anlaufschutz/TopCoats
7. 7. Nachbereiten, Trocknen.

The person skilled in the art proceeds with the above embodiment as in 1 shown, but prefers as follows:

1. 1. Prepare, clean and activate the substrate
2. 2. If necessary, deposition of an adhesion-promoting layer of nickel
3. 3. If necessary, prepare for the next step
4. 4. Electrolytic deposition of a yellow-bronze alloy layer
5. 5. Optionally prepare for the next step
6. 6. Deposition of a passivation/tarnish protection/top coats
7. 7. Post-processing, drying.

• • Spülen in einer Sparspüle
• • mehrmaliges Spülen in Wasser bevorzugt in Kaskadenspültechnik
• • Abschließend erfolgt ein Trocknen der erhaltenen mit Bronzelegierung beschichteten Artikel.

It is advantageous that when the layer sequence according to the invention is deposited, steps for electrolytic cleaning, degreasing, rinsing and activating the respective basis for the deposition are incorporated. The preparatory steps in the procedure just mentioned can include these activities. The preferred procedure for preparing for the next electrolytic step is as follows:

• • Flushing in a economy sink
• • Repeated rinsing in water, preferably in cascade rinsing technology
• Finally, the bronze alloy coated articles obtained are dried.

According to the invention, the term electrolytic means that external power sources (e.g. electrolytic) are used.

More execution information:

Step 1:

For pre-cleaning; Acid cleaner, e.g. Umicore Cleaner 865, Umicore Galvanotechnik (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

• Umicore Reiniger 865 Konzentrat: 30 ml/l g/l (20 - 40 ml/l)

Components:

• Umicore cleaner 865 concentrate: 30 ml/lg/l (20 - 40 ml/l)

• pH-Wert 1-2;
• Temperatur 35 °C (25 - 40 °C)
• Zur Kupferaktivierung: Kupfer Microätze;
• z.B. Umicore Micro-Etch 910, Fa. Umicore Galvanotechnik (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

Working conditions:

• pH 1-2;
• Temperature 35 °C (25 - 40 °C)
• For copper activation: copper micro etching;
• e.g. Umicore Micro-Etch 910, Umicore Galvanotechnik (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

• Umicore Micro-Etch 910 Salzgemisch 50 g/l (40 - 60 g/l).
• Weitere Komponenten nach Herstellerangabe laut Arbeitsanleitung.

Components:

• Umicore Micro-Etch 910 salt mixture 50 g/l (40 - 60 g/l).
• Further components according to the manufacturer's information according to the work instructions.

• pH ca. 1-2;
• Temperatur 25 °C (25 -35°C)

Working conditions:

• pH about 1-2;
• Temperature 25 °C (25 -35 °C)

2nd step (optional)

• z.B. Umicore NIRUNA 808 (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

To create the adhesion-promoting nickel layer:

• e.g. Umicore NIRUNA 808 (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

• NIRUNA 808 Ansatzkonzentrat: Nickel 80 g/l (75 - 85 g/l)
• Nickelchlorid 8 g/l (6 - 10 g/l)
• Borsäure 45 g/l (42 - 48 g/l). Weitere Komponenten nach Herstellerangabe laut Arbeitsanleitung.

Components:

• NIRUNA 808 batch concentrate: nickel 80 g/l (75 - 85 g/l)
• Nickel chloride 8 g/l (6 - 10 g/l)
• Boric acid 45 g/l (42 - 48 g/l). Further components according to the manufacturer's information according to the work instructions.

• pH-Wert 3,8 (3,5 - 4,1)
• Temperatur 57 °C (55 - 59 °C)
• Stromdichte 5 A/dm² (2 - 8 A/dm²)

Working conditions:

• pH 3.8 (3.5 - 4.1)
• Temperature 57 °C (55 - 59 °C)
• Current density 5 A/dm ² (2 - 8 A/dm ² )

3rd step (optional):

For alkaline cleaning, e.g. Umicore degreasing 6032, Umicore Galvanotechnik (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

• Ansatzsalz 60 g/l (50 - 100 g/l)
• Weitere Komponenten nach Herstellerangabe laut Arbeitsanleitung.

Components:

• Preparation salt 60 g/l (50 - 100 g/l)
• Further components according to the manufacturer's information according to the work instructions.

• pH-Wert 11,5 (10 - 13)
• Temperatur 55 °C (40 - 60 °C)
• Stromdichte 12 A/dm² (5 - 15 A/dm²)

Working conditions:

• pH 11.5 (10 - 13)
• Temperature 55 °C (40 - 60 °C)
• Current density 12 A/dm ² (5 - 15 A/dm ² )

4th step:

Process for applying a layer of bronze as a substitute for gold

• Zur Erzeugung einer goldgelb ähnlichen Bronzeschicht, z.B. MIRALLOY® 2847 1N HS, Fa. Umicore Galvanotechnik (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

The following procedures:

• To produce a bronze layer similar to golden yellow, e.g. MIRALLOY® 2847 1N HS, Umicore Galvanotechnik (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

• MIRALLOY Zinksalz 1 6,25 g/l
• MIRALLOY Kupfersalz 1 25,4 g/l
• MIRALLOY Zinnsalz 2 67 g/l
• Weitere Komponenten nach Herstellerangabe laut Arbeitsanleitung.

Components:

• MIRALLOY zinc salt 1 6.25 g/l
• MIRALLOY copper salt 1 25.4 g/l
• MIRALLOY tin salt 2 67 g/l
• Further components according to the manufacturer's information according to the work instructions.

• pH-Wert alkalisch
• Temperatur 60 °C (58 - 62 °C)
• Stromdichte 9 A/dm² (7 - 10 A/dm²)

Working conditions:

• pH alkaline
• Temperature 60 °C (58 - 62 °C)
• Current density 9 A/dm ² (7 - 10 A/dm ² )

5th step (optional):

For alkaline cleaning, e.g. Umicore degreasing 6032, Umicore Galvanotechnik (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

• Ansatzsalz 60 g/l (50 - 100 g/l)
• Weitere Komponenten nach Herstellerangabe laut Arbeitsanleitung.

Components:

• Preparation salt 60 g/l (50 - 100 g/l)
• Further components according to the manufacturer's information according to the work instructions.

• pH-Wert 11,5 (10 - 13)
• Temperatur 55 °C (40 - 60 °C)
• Stromdichte 12 A/dm² (5 - 15 A/dm²)

Working conditions:

• pH 11.5 (10 - 13)
• Temperature 55 °C (40 - 60 °C)
• Current density 12 A/dm ² (5 - 15 A/dm ² )

6th step (optional):

Process for applying a passivation, tarnish protection or top coat, e.g. Umicore Sealing 692 EL (https://ep.umicore.com/storaqe/ep/umicoreqt-list-of products-april-2021.pdf)

• Umicore Sealing 692 Konzentrat 10 ml/l (2 -50 ml/l)
• Weitere Komponenten nach Herstellerangabe laut Arbeitsanleitung.

Components:

• Umicore Sealing 692 concentrate 10 ml/l (2 -50 ml/l)
• Further components according to the manufacturer's information according to the work instructions.

• pH-Wert 9,5 (9 -10)
• Temperatur 55 °C (53 - 57 °C)
• Spannung 3V (2,0 - 4,0 V)

Working conditions:

• pH 9.5 (9 -10)
• Temperature 55 °C (53 - 57 °C)
• Voltage 3V (2.0 - 4.0V)

The process steps between the individual process steps are usually rinsing processes with water of the appropriate quality.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 2116634 [0004]
• US20010014407 [0004]
• US20100147696 [0005]
• EP 2037006 [0007]
• EP 1961840 A1 [0017]
• EP 2116634 A1 [0017]
• EP 2310558 A1 [0017]
• EP 2606164 A1 [0017]
• DE 102011121799 A1 [0017]
• DE 102011121798 A1 [0017]
• DE 102018133244 A1 [0020]

Claims (3)

Smart card foil in which the electronically conductive contact surfaces are connected by a sequence of layers on the foil to connect a chip to a read/write device consisting of: 1. Laminated copper base layer; 2. Bronze layer as the top metal layer with a composition of 70% by weight - 90% by weight Cu, 1% by weight - 10% by weight Sn and 5% by weight - 30% by weight Zn (based on on the bronze layer) is formed. Smart card foil after claim 1 , characterized in that the bronze layer has a thickness of 0.3 µm - 0.7 µm. Smart card foil after claim 1 , characterized in that the bronze layer has an L* value of more than +97, an a* value of -0.2 to 0.2 and a b* value of between +2 and +4 according to the Cielab color system.

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