Electronic document such as a chip card with reduced metallization
View Patent ↗The fabrication of an electronic document includes the following steps: —obtaining of a flat body in which is made a cavity of globally rectangular shape including a deep portion surrounded by a countersink and which contains an electronic component having connection terminals situated on this countersink while having the shape of meanders 5 A, 5 B, —obtaining of a module including a support furnished on a so-called external face with a plurality of external contact zones and on a so-called internal face with a printed circuit including connection pads 4 A, 4 B of hefty form while being connected to certain at least of the external contact zones, the support being furthermore furnished, on this internal face, with a microcircuit connected to this printed circuit, this module being encased in the cavity by an anisotropic conducting adhesive whose overlap coefficient lies between 5 and 8%.
1. A method for manufacturing an electronic document, having the following steps:
obtaining a flat body with a constant thickness, at least 5 times smaller than its length and than its width, in which body is formed a cavity ( 2 ) of rectangular overall shape having a deep portion ( 2 A) surrounded by a counterbore ( 2 B) and that contains an electronic component having connection terminals that are situated on this counterbore,
obtaining a module having a flat carrier with a thickness at most equal to the depth of the counterbore and equipped, on a face termed external face, with a plurality of external contact zones and, on a face termed internal face, with a printed circuit forming connection tracks and having connection pads ( 4 A, 4 B), in solid form, at two peripheral locations of the carrier, this printed circuit being connected to at least some of the external contact zones, the carrier furthermore being equipped, on this internal face, with a microcircuit connected to this printed circuit,
inlaying the module into the cavity, such that the connection pads ( 4 A, 4 B) of the module face the connection terminals ( 5 A, 5 B) of the component and together define an area of coverage/overlap, with interposition, between the module and the counterbore of the cavity, of an electrically conductive anisotropic adhesive formed of a plurality of conductive particles in an adhesive matrix and providing both a mechanical link between the module and the body and an electrical connection between the connection terminals of the component and the connection pads of the module,
wherein the connection terminals of the component are formed by meanders ( 5 A, 5 B, 20 ) extending parallel to the edges of the counterbore at a distance from the corners of this counterbore, and the anisotropically electrically conductive adhesive is chosen so as to have a coefficient of overlap, by the particles, of the area of overlap, of between 5 and 8%.
2. The method as claimed in claim 1 , wherein the cavity is obtained by machining after the body containing the component has been formed, this machining exposing the meanders at the surface of the counterbore.
3. The method as claimed in claim 1 , wherein the meanders are formed by a wire with a diameter of between 120 and 160 microns.
4. The method as claimed in claim 1 , wherein the meanders are formed by a wire with a circular cross section that is embedded in the body, the cavity being formed by machining this body, a checking step being provided to measure the area of this wire exposed by the machining, the inlaying step taking place only under the proviso that this area represents at least ⅔ of the maximum area that is able to be exposed by this machining.
5. The method as claimed in claim 1 , wherein the anisotropic conductive adhesive is formed of an electrically insulating matrix containing particles with a diameter of between 20 and 60 microns, this adhesive being applied with an initial thickness of between 35 and 100 microns.
6. An electronic document having
a flat body with a constant thickness, at least 5 times smaller than its length and than its width, in which body is formed a cavity ( 2 ) of rectangular overall shape having a deep portion ( 2 A) surrounded by a counterbore ( 2 B) and that contains an electronic component having connection terminals ( 5 A, 5 B) that are situated on this counterbore,
a module having a flat carrier with a thickness at most equal to the depth of the counterbore and equipped, on a face termed external face, with a plurality of external contact zones and, on a face termed internal face, with a printed circuit forming connection tracks and having connection pads ( 4 A, 4 B), in solid form, at two peripheral locations of the carrier, this printed circuit being connected to at least some of the external contact zones, the carrier furthermore being equipped, on this internal face, with a microcircuit connected to this printed circuit, this module being inlaid into the cavity, such that the connection pads ( 4 A, 4 B) of the module face the connection terminals ( 5 A, 5 B) of the component and together define an area of coverage/overlap, with interposition, between the module and the counterbore of the cavity, of an anisotropically electrically conductive adhesive formed of a plurality of conductive particles in an adhesive matrix and providing both a mechanical link between the module and the body and an electrical connection between the connection terminals of the component and the connection pads of the module,
wherein the connection terminals ( 5 A, 5 B) of the component are formed by meanders extending parallel to the edges of the counterbore at a distance from the corners of this counterbore, and the anisotropically electrically conductive adhesive has a coefficient of overlap, by the particles, of the area of overlap, of between 5 and 8%.
7. The document as claimed in claim 6 , wherein the anisotropic conductive adhesive is formed of an electrically insulating matrix containing particles with a diameter of between 20 and 60 microns, this adhesive being applied with an initial thickness of between 35 and 100 microns.
8. The document as claimed in claim 6 , wherein the meanders extend over a distance at least approximately equal to the dimension of the deep central portion of the cavity that is parallel to these meanders.
9. The document as claimed in claim 6 , wherein the meanders extend over a distance of at most 1.60 mm in a direction perpendicular to these meanders, and have a spacing of between two and three times the width of these meanders.
10. The document as claimed in claim 6 , wherein the area of overlap represents 20 to 30% of the area of a connection pad that faces the counterbore of the cavity.
11. The document as claimed in claim 6 , forming a card of rectangular shape.
12. The document as claimed in claim 6 , the component of which is an antenna.
13. The electronic document as claimed in claim 6 , wherein the module has dimensions of: 8.5 mm*11 mm.
14. The method as claimed in claim 2 , wherein the meanders are formed by a wire with a diameter of between 120 and 160 microns.
15. The method as claimed in claim 2 , wherein the meanders are formed by a wire with a circular cross section that is embedded in the body, the cavity being formed by machining this body, a checking step being provided to measure the area of this wire exposed by the machining, the inlaying step taking place only under the proviso that this area represents at least ⅔ of the maximum area that is able to be exposed by this machining.
16. The method as claimed in claim 3 , wherein the meanders are formed by a wire with a circular cross section that is embedded in the body, the cavity being formed by machining this body, a checking step being provided to measure the area of this wire exposed by the machining, the inlaying step taking place only under the proviso that this area represents at least ⅔ of the maximum area that is able to be exposed by this machining.
17. The method as claimed in claim 2 , wherein the anisotropic conductive adhesive is formed of an electrically insulating matrix containing particles with a diameter of between 20 and 60 microns, this adhesive being applied with an initial thickness of between 35 and 100 microns.
18. The method as claimed in claim 3 , wherein the anisotropic conductive adhesive is formed of an electrically insulating matrix containing particles with a diameter of between 20 and 60 microns, this adhesive being applied with an initial thickness of between 35 and 100 microns.
19. The method as claimed in claim 4 , wherein the anisotropic conductive adhesive is formed of an electrically insulating matrix containing particles with a diameter of between 20 and 60 microns, this adhesive being applied with an initial thickness of between 35 and 100 microns.
20. The document as claimed in claim 7 , wherein the meanders extend over a distance at least approximately equal to the dimension of the deep central portion of the cavity that is parallel to these meanders.