Radio frequency identification transponder apparatus and method

• US 5,574,470 A
• Filed: 10/11/1995
• Issued: 11/12/1996
• Est. Priority Date: 09/30/1994
• Status: Expired due to Fees

• Current Assignee: Assa Abloy AB
• Original Assignee: Palomar Technologies Incorporated
• Inventors: de Vall, Franklin B.
• Primary Examiner(s): Le, Hoanganh
• Application Number:
  US08/540,785
• Time in Patent Office: 398 Days
• Field of Search: 343/895, 343/872, 343/873, 343/742, 343/867, 340/572, 340/505, 29/848, 29/600
• US Class Current: 343/895
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• 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 19/07779 the inductive antenna being a coil
• CPC Class Codes: G06K 19/07783 the coil being planar
• CPC Class Codes: G06K 19/07784 the inductive antenna consisting of a plurality of coils stacked on top of one another
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: H01L 2224/05554 being square
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/30107 Inductance
• CPC Class Codes: H01Q 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop

Abstract

A transponder is formed of a very thin flexible substrate (10) on opposite sides of which are formed first (26) and second (31) series connected halves of a single antenna coil having ends connected to an integrated circuit die (50) mounted to a corner of the substrate. A plurality of bond pads (12a-12e) and programming pads (14a-14e) are also formed on the substrate and operatively connected to couple the antenna coils and the programming pads through the bond pads to the integrated circuit die. Unique configurations and arrangements of a die mounting site (46), bond pads (12a-12e), program pads (14a-14e), and vias (22,24) through the substrate enable an inexpensive simple construction. Protective laminates (58,60) on either side of the substrate are bonded to one another around the edges that circumscribe the substrate and also are bonded to one another at interior portions through a slot (20) formed in the substrate. In one embodiment narrow closely spaced coil turns are grouped in a perimetrical area of the substrate, leaving a large area in the center of the substrate free of antenna coil turns. The thin flexible substrate is stiffened in the area of the die and bond site by thin copper stiffener sheets (46,202,234) that are laid down as part of the antenna coil forming process.

Claims

1. A method for making a radio frequency identification transponder comprising the steps of:

forming a thin dielectric substrate having first and second sides;

forming a die bond site on said first side;

forming a plurality of bond pads on said first side adjacent said die bond site;

forming a first multi-turn flat antenna coil on said first side having a first end at an interior portion of said substrate, and having a second end at one of said bond pads;

forming a first via extending through said substrate and connected to said first end on said first side of said substrate;

forming a second via through said substrate adjacent one of said bond pads;

forming a second multi-turn antenna coil on said second side of said substrate having a first end at an interior portion of said substrate connected to said first via and having a second end connected to said second via on said second side of said substrate;

connecting said second via on said first side of the substrate to one of said bond pads;

mounting a die to said substrate at said die bond site;

electrically connecting said die to said bond pads;

forming a dielectric protective coating over both said first and second sides of said substrate and over said antenna coils;

securing a first protective cover to said second side of said substrate over said second antenna coil;

applying a nonconductive encapsulation over said die and said bond pads; and

applying a second protective dielectric cover to said first side of said substrate covering and protecting said first antenna coil, said die, and said bond pads.

2. The method of claim 1 including the steps of forming a plurality of programming pads on said first side, and forming a plurality of programming leads on said first side interconnecting said programming pads with said bond pads.

3. The method of claim 2 wherein said step of forming said second via includes forming said second via at a position on said substrate that connects to one of the connecting leads between said bond pads and said die pads.

4. The method of claim 1 including the step of forming a slot in an interior portion of said substrate, and wherein said step of securing a first protective cover and applying a second protective cover comprise bonding said first and second laminates to each other around the periphery of said substrate and through said slot.

5. The method of claim 1 wherein said step of forming a die bond site comprises forming said die bond site as a metallic sheet having a recess, said step of forming a plurality of bond pads comprising forming said bond pads in a pattern within said metallic sheet recess, said step of mounting a die comprising the-steps of providing a die having die contact pads adjacent one corner thereof arranged in a pattern that matches the pattern of said bond pads, and positioning said die on said die bond site with said die contact pads in electrical contact with said bond pads.

6. The method of claim 5 including the step of forming a die support pad on said die bond site for supporting, leveling and stabilizing said die.

7. The method of claim 1 wherein said step of forming a die bond site comprises positioning said die bond site at a first corner of said dielectric substrate, said step of forming first and second protective covers including the step of forming first and second fastener apertures at corresponding end portions of said covers and securing said covers with said fastener apertures in mutual alignment with each other.

8. The method of claim 1 wherein said steps of forming first and second antenna coils include forming turns of said coils winding in like directions as viewed from one side of said substrate and forming said coils with turns of said first coil in direct alignment and registration with turns of said second coil.

9. The method of claim 1 wherein said step of forming said first and second coils includes the step of forming coil turns of said first and second coils in a relatively narrow perimetrical area circumscribing interior portions of said thin substrate, whereby a major portion of said substrate on both said first and second sides is free of said antenna coils to provide a large central coil turn free area.

10. The method of making a transponder set forth in claim 1 wherein said step of forming a thin dielectric substrate comprises forming said substrate as a body of generally rectangular configuration, having a pair of opposite short edges and a pair of opposite longer edges, and including the step of forming said die bond site and said bond pads at one corner of said substrate adjacent a first one of said short edges, forming programming pads on said first side at an opposite corner of said first short edge, and positioning said die bond site and said bond pads adjacent one of said long edges and spaced inwardly from said first short edge, said step of forming programming pads including the step of positioning said programming pads closer to said first short edge than said die bond site and said bond pads, employing said program pads to program said die, and further including the step of removing an end portion of said substrate extending along said first mentioned short edge, said step of removing an end portion of said substrate including the step of removing at least outermost portions of said programming pads.

11. The method of making a transponder set forth in claim 10 wherein said step of applying a dielectric protective coating includes applying said protective coating to cover only innermost portions of said programming pads to said bond pads, said step of electrically connecting said programming pads to said bond pads comprising connecting inner sides of said programming pads, said step of removing an outermost portion of said substrate comprising the step of removing outermost portions of said programming pads that are not covered by said protective layer, whereby all remaining portions of said programming pads are covered by said protective layer.

12. The method for making a radio frequency identification transponder as set forth in claim 1 wherein said bond site comprises a metallized stiffening sheet, and including the step of forming a second metallized stiffening sheet on the second side of said substrate in alignment with said first mentioned die bond site.

13. The method for making a radio frequency identification transponder as set forth in claim 1 wherein said die bond site has a recess, and wherein said bond pads are positioned within said bond site recess, and including the step of mounting said die by connecting die pads of the die directly to said bond pads, said bond pads being arranged in a configuration that mates with the configuration of a set of connecting pads on said die.

14. A radio frequency identification transponder comprising:

a thin dielectric substrate having first and second sides, said first side having a die bond site and a plurality of bond pads formed thereon adjacent said die bond site;

a first multi-turn flat antenna coil on said first side having a first end at an interior portion of said substrate, and having a second end connected to one of said bond pads;

a first via extending through said substrate and connected to said first end on said first side of said substrate;

a second via extending through said substrate adjacent one of said bond pads;

a second multi-turn flat antenna coil on said second side of said substrate having a first end at an interior portion of said substrate connected to said first via, and having a second end connected to said second via on said second side of said substrate;

a dielectric protective coating over both said first and second sides of said substrate and over said first and second antenna coils, said protective coating being open at said die bond site and at said bond pads, whereby said die bond site and said bond pads are not covered by said protective coating;

an electrical lead connecting said second via on said first side of the substrate to one of said bond pads;

a die mounted to said substrate at said die bond site and electrically connected to said bond pads;

a first protective cover secured to said second side of said substrate over said second antenna coil;

a non-conductive encapsulation secured to said first side of said substrate, over said die and over said bond pads; and

a second protective dielectric cover secured to said first side of said substrate covering and protecting said first antenna coil and said die and bond pads.

15. The transponder of claim 14 wherein said substrate is a flexible material having a thickness of not more than about twenty-five microns, and wherein said die bond site comprises a stiffening sheet of metallization on at least one side.

16. The radio frequency identification transponder of claim 14 wherein said substrate has an opening at an interior portion thereof, said first and second antenna coils being clear of said opening, said first and second protective covers being bonded to each other at peripheral edges thereof, and through said opening.

17. The radio frequency identification transponder of claim 14 including a plurality of programming pads formed on said first side of said substrate, a plurality of programming leads on said first side interconnecting said programming pads with said bond pads, said second protective dielectric cover covering and protecting said programming pads.

18. The radio frequency identification transponder of claim 17 wherein said die bond site is positioned at a first corner of said dielectric substrate, and said programming pads are positioned at a second corner of said substrate, said substrate having a portion thereof between said die bond site and said programming pads rebated, said first and second protective covers including mutually aligned fastener apertures aligned with each other and with said rebated portion of said substrate.

19. The radio frequency identification transponder of claim 18 wherein said die bond site comprises a layer of relatively stiff material on said first side.

20. The radio frequency identification transponder of claim 18 including means for stiffening said thin substrate in the region of said die bond site and said bond pads.

21. The radio frequency identification transponder of claim 20 wherein said means for stiffening comprises a first thin sheet of metal bonded to said first side at a region of said first side that covers said die bond site, and a second thin sheet of metal bonded to and covering a portion of said second site that extends along said second side in the region of said die bond site and said bond pads of said first side.

22. The radio frequency identification transponder of claim 14 wherein said antenna coils on said first and second sides of said substrate are wound in like directions, as viewed from one side of said substrate, and include at least a major portion of the turns of said first coil in direct alignment and registration with the turns of said second coil.

23. The radio frequency identification transponder of claim 14 wherein coil turns of said first and second coils are positioned in a relatively narrow perimetrical area circumscribing inner portions of said thin substrate, whereby a major portion of said substrate on both said first and second sides is free of said antenna coils to provide a large central area free of coil turns.

24. The radio frequency identification transponder of claim 14 including a layer of heat bondable adhesive secured to said dielectric protective coating on said second side, and configured and arranged to bond said transponder to a garment, and a strip of cloth covering said substrate and dielectric protective coating on said first side and configured and arranged to further secure said transponder to said garment.

25. A radio frequency identification transponder comprising:

a thin dielectric substrate having first and second sides, said substrate having a perimetrical edge and an opening formed in an interior portion thereof;

first and second antenna coils on said first and second sides respectively;

a die mounted on said substrate and connected to both said antenna coils; and

first and second protective covers enclosing said substrate, coils and die, said covers each being continuous and having mutually aligned perimetrical edges extending beyond the perimetrical edge of said substrate, said protective covers being bonded to one another at portions of their perimetrical edges, said protective covers including interior portions thereof extending through said opening in said substrate interior portion and being bonded to one another through said opening, said protective covers having substantially smooth continuous planar exterior surfaces that extend beyond said opening and said interior portion.

26. The radio frequency identification transponder of claim 25 including a dielectric protective coating covering substantially all of the surface of one side of said substrate and substantially all of the surface of the opposite side of said substrate, the area of said substrate at and around said substrate opening being free of said dielectric coating, said first and second protective covers being bonded to one another only at said interior portion of the substrate through said substrate opening and at perimetrical portions of said protective covers that extend beyond the perimetrical edge of said substrate.

27. The radio frequency identification transponder of claim 26 wherein said die is mounted on a die bond site of said substrate, and including a stiffening sheet extending over said die bond site and a small distance beyond said die bond site on said first side of said substrate.