Device for shielding a transponder, method for producing a corresponding shielding and transponder provided with said shielding

• US 7,053,854 B2
• Filed: 10/07/2002
• Issued: 05/30/2006
• Est. Priority Date: 10/05/2001
• Status: Expired due to Fees

• Current Assignee: Flexchip AG
• Original Assignee: Flexchip AG
• Inventors: Plettner, Andreas, Stein, Arno
• Primary Examiner(s): PHAN, THO GIA
• Application Number:
  US10/491,744
• Publication Number:
  US 20050104796A1
• Time in Patent Office: 1,331 Days
• Field of Search: 343/787, 343/788, 343/841
• US Class Current: 343/841
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07771 the record carrier comprising means for minimising adverse effects on the data communication capability of the record carrier, e.g. minimising Eddy currents induced in a proximate metal or otherwise electromagnetically interfering object

Abstract

A unit for shielding a transponder includes at least a chip and an antenna structure with application-specific spatial dimensions and which is secured to an electrically conductive surface. The unit includes a film having formed thereon or therein a highly permeable material at least in an area having the spatial dimensions of the antenna structure of the transponder. The highly permeable material is subdivided into elongate shielding elements and free spaces arranged between the respective shielding elements such that when the substrate has been attached to the transponder, the shielding elements will be oriented parallel to a magnetic field induced in the antenna structure of the transponder, so as to suppress eddy currents which are generated by the electrically conductive surface in the antenna structure, when the transponder is being introduced in a magnetic field of a respective reading device.

Claims

1. A method of producing a shielding for a transponder, which comprises at least a chip and an antenna structure with application-specific spatial dimensions, the shielding being formed on a substrate, said method comprising:

applying ferromagnetic particles to an area of the substrate having at least the spatial dimensions of the antenna structure of the transponder;

orienting the ferromagnetic particles by a constant magnetic field in such a way that, when the substrate has been attached to the transponder, the particles will be oriented parallel to a magnetic field induced in the antenna structure of the transponder; and

fixing the oriented particles.

2. The method according to claim 1, wherein the ferromagnetic particles are oriented by one or a plurality of permanent magnets.

3. The method according to claim 1, wherein the ferromagnetic particles are oriented by one or a plurality of electrically excited magnets with a constant magnetic field.

4. The method according to claim 1, wherein the oriented particles are fixed by an adhesive.

5. The method according to claim 4, wherein the ferromagnetic particles are applied together with the adhesive and the fixing takes place during or immediately after the orienting of the ferromagnetic particles.

6. The method according to claim 1, wherein the ferromagnetic particles are contained in a lacquer which is applied to the substrate.

7. The method according to claim 6, wherein the oriented particles are fixed by thermal drying and hardening of the lacquer.

8. The method according to claim 1, wherein the ferromagnetic particles are highly permeable and elongate in shape.

9. The method according to claim 8, wherein the ferromagnetic particles each have a length of about 300μ

m, a width of about 50μ

m, and a thickness of about 10μ

m.

10. The method according to claim 1, wherein the ferromagnetic particles are made of soft-magnetic iron or of a ferroelectric material producing a similar effect or of an alloy or mixture producing an effect of the type in question.

11. The method according to claim 1, wherein the respective ferromagnetic particles have a longitudinal dimension which is comparable with the width of the induced magnetic field.

12. The method according to claim 11, wherein the said longitudinal dimension of the ferromagnetic particles amounts to 1/20 to ⅕

of the width of the induced magnetic field.

13. The method according to claim 1, wherein the substrate is applied to the transponder after the fixing of the ferromagnetic particles.

14. The method according to claim 1, wherein the transponder is formed prior to producing the shielding on the substrate.

15. The method according to claim 1, wherein the ferromagnetic particles are applied by a printing technique.

16. The method according to claim 1, wherein the shielding layer and the antenna are combined by folding or laminating.

17. A unit for shielding a transponder, which comprises at least a chip and an antenna structure with application-specific spatial dimensions and which is attached to an electrically conductive surface, said unit comprising:

a substrate having formed thereon a plurality of fixed ferromagnetic particles in an area having at least the spatial dimensions of the antenna structure of the transponder;

wherein

the respective ferromagnetic particles are oriented such that when the substrate has been attached to the transponder, the ferromagnetic particles will be oriented parallel to a magnetic field induced in the antenna structure of the transponder so as to suppress eddy currents which are generated by the electrically conductive surface in the antenna structure when the transponder is being introduced in a magnetic field of a respective reading device.

18. The unit according to claim 17, wherein the substrate is provided with ferromagnetic particles on the front and on the back.

19. The unit according to claim 17, wherein a plurality of ferromagnetic layers are provided one on top of the other, said layers being, however, separated by insulators.

20. The unit according to claim 17, wherein the substrate is made of an electrically non-conductive material.

21. The unit according to claim 20, wherein the substrate is made of an organic polymer.

22. The unit according to claim 21, wherein the substrate represents a transponder or an inlay for a transponder.

23. The unit according to claim 17, wherein the substrate is made of paper.

24. The unit according to claim 17, wherein the antenna structure represents an antenna coil.

25. The unit according to claim 17, wherein the antenna structure represents a closed or an open dipole.

26. The unit according to claim 25, wherein the antenna structure represents a slot antenna.

27. The unit according to claim 17, wherein the ferromagnetic particles are made of iron.

28. The unit according to claim 17, wherein the ferromagnetic particles belong to the garnet group of substances (yttrium-aluminium compounds).

29. A transponder which comprises at least a chip and an antenna structure and which is attached to an electrically conductive surface, wherein at least one unit according to claim 17 is provided between the transponder and the electrically conductive surface.

30. A unit for shielding a transponder, which comprises at least a chip and an antenna structure with application-specific spatial dimensions and which is attached to an electrically conductive surface, said unit comprising:

a film having formed thereon or therein a highly permeable material at least in an area having the spatial dimensions of the antenna structure of the transponder;

wherein

the highly permeable material is subdivided into elongate shielding elements and free spaces arranged between the respective shielding elements such that when the substrate has been attached to the transponder, the shielding elements will be oriented parallel to a magnetic field induced in the antenna structure of the transponder so as to suppress eddy currents which are generated by the electrically conductive surface in the antenna structure when the transponder is being introduced in a magnetic field of a respective reading device.