Bronze layers as noble metal substitutes

Abstract

The invention is directed to the use of electrolytic bronze deposits as substitutes for the noble metal electroplating of electronic circuits, e.g. for use in electronic payment cards and identity cards. The invention also relates to a novel layer sequence of bronze layers.

Claims

1. A layer sequence comprising two successive, electrolytically deposited bronze layers, and at least one metallic underlayer, wherein one of the electrolytically deposited bronze layers has the following composition: Cu 45-60 wt %, Sn 30-50 wt %, and Zn 5-15 wt % of the given layer; and the other of these two layers has the following composition: Cu 70-90 wt %, Sn 1-10 wt %, and Zn 5-30 wt % of the given layer, wherein the at least one metallic underlayer, upon which one of the electrolytically deposited bronze layers is deposited, is a nickel layer.

2. The layer sequence according to claim 1, wherein one or both of the electrolytically deposited bronze layers each have a thickness of 0.1-2 m.

3. The layer sequence according to claim 1, wherein the at least one metallic underlayer comprises a nickel layer deposited on a copper layer.

4. A smart card comprising a leadframe having an outer contact surface; and electrolytically deposited bronze layers deposited on the outer contact surface, wherein the electrolytically deposited bronze layers comprise two successive, electrolytically deposited bronze layers, wherein one of the electrolytically deposited bronze layers has the following composition: Cu 45-60 wt %, Sn 30-50 wt %, and Zn 5-15 wt % of the given layer; and the other of these two layers has the following composition: Cu 70-90 wt %, Sn 1-10 wt %, and Zn 5-30 wt % of the given layer.

5. The smart card according to claim 4, wherein one or both of the electrolytically deposited bronze layers each have a thickness of 0.1-2 m.

6. The smart card according to claim 4, and further comprising at least one metallic underlayer upon which the electrolytically deposited bronze layers are deposited.

7. The smart card according to claim 6, wherein the at least one metallic underlayer is selected from the group consisting of Cu, Ni, nickel-phosphorus, Pd, PdNi, Au, and platinum.

8. The smart card according to claim 6, wherein the at least one metallic underlayer, upon which one of the electrolytically deposited bronze layers is deposited, is a nickel layer.

9. The smart card according to claim 6, wherein the at least one metallic underlayer comprises a copper layer.

10. The smart card according to claim 6, wherein the at least one metallic underlayer comprises a nickel layer deposited on a copper layer.

11. The smart card according to claim 4, wherein the smart card lacks galvanically deposited noble metal layers on the outer contact surface of the leadframe.

12. The smart card according to claim 4, wherein the smart card further comprises a microchip to which the leadframe and the electrolytically deposited bronze layers form an electrically conductive pathway thereto whereby the microchip is capable of being connected to a read/write device.

13. A method of providing an electrically conductive pathway between a microchip in a smart card and a read/write device, said smart card comprises a leadframe having an outer contact surface, which comprises electrolytically depositing two successive bronze layers as the uppermost layers on the outer contact surface, wherein one of the electrolytically deposited bronze layers has the following composition: Cu 45-60 wt %, Sn 30-50 wt %, and Zn 5-15 wt % of the given layer; and the other of these two layers has the following composition: Cu 70-90 wt %, Sn 1-10 wt %, and Zn 5-30 wt % of the given layer.

14. The method according to claim 13, wherein one or both of the electrolytically deposited bronze layers each have a thickness of 0.1-2 m.

15. The method according to claim 13, which further comprises providing on the outer contact surface at least one metallic underlayer upon which the electrolytically deposited bronze layers are deposited.

16. The smart card according to claim 15, wherein the at least one metallic underlayer is selected from the group consisting of Cu, Ni, nickel-phosphorus, Pd, PdNi, Au, and platinum.

Description

EXAMPLES

(1) The following layers were electrolytically applied to a polyimide foil laminated pre-structured copper foil: a layer of nickel with a thickness between 1-2 m; a layer of white bronze e.g. Umicore Miralloy 2841 HS with a thickness between 0.1-2 m; or a layer of yellow bronze e.g. Umicore Miralloy 2847 1N HS with a thickness between 0.1-2 m; or a combination of both these white and yellow bronze processes with a thickness between 0.1-2 m in each case.

(2) The person skilled in the art will proceed with the above embodiment as shown in FIG. 1, but preferably as follows: 1. Preparing, cleaning and activating the substrate 2. Deposition of an adhesion-promoting layer of nickel 3. Preparing for the next step 4. Electrolytic deposition of a white bronze alloy layer 5. or electrolytic deposition of a yellow bronze alloy layer 6. or electrolytic deposition of a white+yellow bronze alloy layer 7. Preparing for the next step 8. Deposition of a passivation/anti-tarnish protection/topcoat 9. Post-processing, drying.

(3) It is advantageous that steps for electrolytic cleaning, degreasing, rinsing and activation of the respective base for deposition are included in the deposition of the layer sequence according to the invention. Thus, the preparation steps in the method step just mentioned can comprise these activities. Preferably, the preparation for the next electrolytic step is as follows: rinsing in an economizing rinse repeated rinsing in water, preferably in a cascade rinsing technique finally, drying of the obtained articles coated with bronze alloy is carried out.

(4) According to the invention, the term electrolytic means that the process is carried out using external power sources (e.g. electrolytically).

(5) Further information on execution:

(6) 1st Step:

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

(8) Components:

(9) Umicore Cleaner 865 concentrate: 30 ml/l g/l (20-40 ml/l)
Working Conditions: pH 1-2; Temperature 35 C. (25-40 C.)

(10) For copper activation: copper micro etchants; e.g. Umicore Micro-Etch 910, from Umicore Galvanotechnik (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)
Components: Umicore Micro-Etch 910 salt mixture 50 g/l (40-60 g/l).

(11) Further components according to manufacturer's instructions as per instruction sheet.

(12) Working Conditions:

(13) pH approx. 1-2; Temperature 25 C. (25-35 C.)
2nd Step:

(14) To produce the adhesion-promoting nickel layer: E.g. Umicore NIRUNA 808 (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)
Components: NIRUNA 808 Make-up 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 manufacturer's instructions as per instruction sheet.
Working Conditions: pH 3.8 (3.5-4.1) Temperature 57 C. (55-59 C.) Current density 5 A/dm.sup.2 (2-8 A/dm.sup.2)
3rd Step:

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

(16) Components:

(17) Make-up salt 60 g/l (50-100 g/l)

(18) Further components according to manufacturer's instructions as per instruction sheet.

(19) Working Conditions:

(20) pH 11.5 (10-13) Temperature 55 C. (40-60 C.) Current density 12 A/dm.sup.2 (5-15 A/dm.sup.2)
4th-6th Steps:

(21) Method for applying a bronze layer as a gold or palladium substitute

(22) The following methods:

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

(24) Components:

(25) MIRALLOY zinc salt 1 6.25 g/l MIRALLOY copper salt 1 25.4 g/l MIRALLOY tin salt 2 67 g/l

(26) Further components according to manufacturer's instructions as per instruction sheet.

(27) Working Conditions:

(28) pH value: alkaline Temperature 60 C. (58-62 C.) Current density 9 A/dm.sup.2 (7-10 A/dm.sup.2)

(29) To produce a bronze layer similar to palladium, e.g. MIRALLOY 2841 HS, from Umicore Galvanotechnik (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

(30) Components:

(31) MIRALLOY tin salt 2 69 g/l MIRALLOY zinc salt 1 3.375 g/l MIRALLOY copper salt 1 14.8 g/l

(32) Further components according to manufacturer's instructions as per instruction sheet.

(33) Working Conditions:

(34) pH value: alkaline Temperature 60 C. (58-62 C.) Current density 4 A/dm.sup.2 (3-4 A/dm.sup.2)
7th Step:

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

(36) Components:

(37) Make-up salt 60 g/l (50-100 g/l)

(38) Further components according to manufacturer's instructions as per instruction sheet.

(39) Working Conditions:

(40) pH 11.5 (10-13) Temperature 55 C. (40-60 C.) Current density 12 A/dm.sup.2 (5-15 A/dm.sup.2)
8th Step:

(41) Method for applying passivation, anti-tarnish protection or topcoat, e.g. Umicore Sealing 692 EL (https://ep.umicore.com/storage/ep/umicoregt-list-of-products-april-2021.pdf)

(42) Components:

(43) Umicore Sealing 692 concentrate 10 ml/l (2-50 ml/l)

(44) Further components according to manufacturer's instructions as per instruction sheet.

(45) Working Conditions:

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

(47) The method steps between the individual process steps are generally rinsing processes with water of appropriate quality.