Card lamination

1. A method of manufacturing an RFID structure, the method comprising:

providing an antenna substrate;

providing a first stack layer;

forming, on a first surface of the antenna substrate, an antenna assembly including an antenna track, and at least two contact pads;

coupling an integrated circuit unit to the at least two contact pads;

coating a first surface of the first stack layer, the first surface of the antenna substrate, or both with a unidirectional thermally expansive coating material;

positioning the first surface of the antenna substrate to be adjacent to the first surface of the first stack layer; and

heating the coating material, wherein gaps formed by the antenna track or integrated circuit unit between the antenna substrate and the first stack layer before heating the coating material are at least 25% filled by thermal expansion of the coating material and the first stack layer exhibits a uniformly flat outer surface after heating.

2. The method of claim 1 , further comprising:

providing a second stack layer;

coating a first surface of the second stack layer or a second surface of the antenna substrate opposite the first surface of the antenna substrate with the thermally expansive coating material;

positioning the first surface of the second stack layer to be adjacent to the second surface of the antenna substrate; and

wherein the second stack layer exhibits a uniformly flat outer surface after heating.

3. The method of claim 1 , further comprising forming, on the second surface of the antenna substrate, a second antenna assembly including a second antenna track.

4. The method of claim 1 , further comprising:

forming, on the first surface of the antenna substrate, a plurality of other antenna assemblies each including an antenna track, and at least two contact pads; and

coupling integrated circuit units to the at least two contact pads on each of the plurality of other antenna assemblies.

5. The method of claim 1 , wherein the antenna assembly comprises etched copper, deposited copper, etched aluminum, deposited aluminum, etched gold, deposited gold, conductive pastes, conductive ink, conductive polymers, molybdenum, embedded copper, or any combination thereof.

6. The method of claim 1 , wherein the antenna substrate comprises one or more non-conductive carrier materials including PET (polyester), FR-4 (or any other printed circuit board (PCB) material), PI (polyimide), BT (bismaleimide-triazine), PE (polyethylene), PVC (polyvinylchloride), PC (polycarbonate), PEN (polyethylene naphthalate), Teslin (silica-filled polyethylene), paper, or any combination thereof.

7. The method of claim 1 , wherein the first stack layer comprises PET (polyester), PI (polyimide), BT (bismaleimide-triazine), PE (polyethylene), PVC (polyvinylchloride), PC (polycarbonate), PEN (polyethylene naphthalate), Teslin (silica-filled polyethylene), paper, or any combination thereof.

8. The method of claim 1 , further comprising:

laminating the first stack layer and the antenna substrate between first and second laminate layers; and

providing first and second overlay layers to the first and second laminate layers.

9. The method of claim 1 , wherein the first and second laminate layers comprise PET (polyester), PI (polyimide), BT (bismaleimide-triazine), PE (polyethylene), PVC (polyvinylchloride), PC (polycarbonate), PEN (polyethylene naphthalate), Teslin (silica-filled polyethylene), paper, or any combination thereof.

10. The method of claim 1 , further comprising printing visual display information on the first overlay layer, the second overlay layer, or both the first and second overlay layers.

11. The method of claim 1 , wherein the integrated circuit unit is positioned in a recess in the antenna substrate, in a recess in the first or second stack layer, or recesses in both the antenna substrate, the first stack layer, and/or the second stack layer.

12. The method of claim 1 , wherein the RFID structure comprises a RFID card component, a smartcard component, a ticket component, a passport component, a RFID label, a RFID sticker, a RFID poster, or any combination thereof.

13. The method of claim 1 , wherein the unidirectional thermally expansive coating material includes at least 60% of polyurethane polymers, at least 0.1% of acrylic copolymers, and at least 0.1% of hydrocarbons.

14. The method of claim 13 , wherein the unidirectional thermally expansive coating material includes 80-98% of polyurethane polymers and 20-2% of acrylic copolymers and hydrocarbons.

15. The method of claim 13 , wherein the acrylic copolymers and hydrocarbons include thermoexpandable microcapsules that encapsulate volatile hydrocarbons with acrylic copolymers.

16. The method of claim 15 , wherein the average particle size of the microcapsules is between 6 and 12 μm.

17. The method of claim 15 , wherein expansion of the microcapsules begins at between 80° and 90° Celsius.

18. The method of claim 15 , wherein expansion of the microcapsules ends at between 110° and 120° Celsius.

19. An RFID structure comprising:

an antenna substrate including, on a first surface, an antenna assembly having an antenna track and at least two contact pads;

an integrated circuit unit coupled to the at least two contact pads;

a first stack layer positioned adjacent to the first surface of the antenna substrate; and

an unheated unidirectional thermally expansive material separating the antenna substrate and the first stack layer, wherein gaps are defined between one or more portions of the antenna assembly and the thermally expansive material; and

wherein upon heating the material, the gaps are at least partially filled by thermal expansion of the material and the first stack layer exhibits a uniformly flat outer surface after heating.

20. An RFID structure comprising:

an antenna substrate including, on a first surface, an antenna assembly having an antenna track and at least two contact pads;

an integrated circuit unit coupled to the at least two contact pads;

a first stack layer positioned adjacent to the first surface of the antenna substrate; and

a previously heated unidirectional thermally expansive material separating the antenna substrate and the first stack layer, wherein gaps formed between the antenna substrate and the first stack layer are at least partially filled by the thermally expansive material and the first stack layer exhibits a uniformly flat outer surface.