Method for manufacturing an electrical circuit board, electrical circuit board obtained by this method and smart card comprising such an electrical circuit board

Abstract

The invention relates to a method for manufacturing an electrical circuit board. It includes the provision of a sheet of electrically conductive material and a layer of adhesive material. In order to have a color appear in spaces cut or etched into the sheet of electrically conductive material, the adhesive material includes a coloring agent. The invention also relates to an electrical circuit board for a smart card, which circuit board is manufactured using this method, and a smart card including such an electrical circuit board.

Claims

1. Method for manufacturing an electrical circuit board designed to connect a chip to a conductive layer, the method comprising: the provision of a layer of dielectric material having two main sides for forming a substrate; the provision of a sheet of electrically conductive material, with two main sides; the production of an electrical circuit pattern in the sheet of electrically conductive material; the provision of a layer of adhesive material; the placing in contact of one of the main sides of the layer of electrically conductive material with the layer of adhesive material; and the lamination of the layer of dielectric material, the sheet of electrically conductive material and the layer of adhesive material, wherein a colouring agent is added to the adhesive material forming the layer of adhesive material, in order to form a layer of tinted adhesive material; wherein areas are cut or etched into the sheet of electrically conductive material between which the tinted adhesive is visible.

2. Method according to claim 1, comprising a step of coating one of the main sides of the layer of dielectric material with the tinted adhesive material before placing one of the main sides of the electrically conductive material in contact with the layer of tinted adhesive material that is positioned on the layer of dielectric material, and laminating the sheet of electrically conductive material with the layer of dielectric material.

3. Method according to claim 1, in which the colouring agent is a dye, a powdered pigment or a pre-dispersed pigment.

4. Method according to claim 1, in which the colouring agent represents between 0.5 and 50 phr of the adhesive material.

5. Method according to claim 1, in which the colouring agent belongs to at least one of the families of chemical compounds from the list composed of metal complexes, diazos, azos, anthraquinones, diketopyrrolopyrroles, phthalocyanines, perylenes, quinacridone, and quinolines.

6. Method according to claim 1, comprising a step of producing contacts in the sheet of electrically conductive material.

7. Method according to claim 6, in which the contacts are etched into the sheet of electrically conductive material by electrochemical etching.

8. Electrical circuit board comprising a sheet of electrically conductive material, with two main sides, an electrical circuit pattern in the sheet of electrically conductive material, and a layer of adhesive material in contact with one of the main sides of the sheet of electrically conductive material, wherein a colouring agent is added to the adhesive material forming the layer of adhesive material, in order to form a layer of tinted adhesive material; further comprising areas cut or etched into the sheet of electrically conductive material between which the tinted adhesive is visible.

9. Electrical circuit board according to claim 8, additionally comprising a layer of dielectric material, the layer of tinted adhesive material being placed between the layer of dielectric material and the sheet of electrically conductive material and maintaining adhesion between the layer of dielectric material and the sheet of electrically conductive material.

10. Electrical circuit board according to claim 8, in which the colouring agent represents between 0.5 and 50 phr of the adhesive material.

11. Electrical circuit board according to claim 8, in which the colouring agent belongs to at least one of the families of chemical compounds from the list composed of metal complexes, diazos, azos, anthraquinones, diketopyrrolopyrroles, phthalocyanines, perylenes, quinacridones, and quinolines.

12. Smart card comprising a card body and a cavity made in the card body and in which an electronic module, comprising an electrical circuit board according to claim 8, is placed, the electronic module comprising contacts flush with the surface of the card body and a colour that is visible on at least a portion of the surface of the module not occupied by the contacts, this colour being produced by a colouring agent present in a layer of adhesive subjacent to the contacts and added to an adhesive material in order to form the layer of tinted adhesive material.

Description

(1) Other features and advantages of the invention will become apparent upon reading the detailed description and the appended drawings in which:

(2) FIG. 1 is a schematic representation in perspective of a smart card intended to receive a module comprising an electrical circuit board;

(3) FIGS. 2a to 2l schematically represent in succession the various steps of an exemplary method for manufacturing an electrical circuit board; and

(4) FIG. 3 is a schematic representation of an exemplary card with a module obtained via the method illustrated by FIGS. 2a to 2l.

(5) An exemplary method for manufacturing an electrical circuit board according to the invention is described below. It belongs to the field of smart cards but, as already mentioned, what is described here may be easily transferred to applications in other fields (RFID antennas, LEDs, etc.).

(6) As shown in FIG. 1, a smart card 1 comprises a module 2. The module 2 comprises a flexible electrical circuit board 3, equipped with a connector 5, and a chip 100. The module 2 is generally produced in the form of a separate element which is inserted into a cavity 4 made in the card 1.

(7) The flexible electrical circuit board 3 therefore comprises a connector 5 with multiple contact lands 15 to which the chip 100 is connected. The flexible circuit board 3 is shown (above) from its front side 6 (contact side). It is also shown (below) from its back side 7, or bonding side. The flexible electrical circuit board 3 thus shown corresponds to a single-sided flexible electrical circuit board for a contact card. However, it could equally be a double-sided flexible electrical circuit board, for a dual card for example.

(8) FIGS. 2a to 2l schematically illustrate various steps of an exemplary method according to the invention for manufacturing the flexible electrical circuit board 3.

(9) This method comprises the provision (FIG. 2a) of an adhesive material or glue 20, in liquid form. The adhesive material 20 is, for example, composed of (potentially modified) epoxy. At this stage, the adhesive material 20 is naturally light yellow in colour and transparent.

(10) In the following step (FIG. 2b), the pre-formulated adhesive material 20 is coloured by the addition of a colouring agent, an actual dye or a pigment. This colouring agent may dye the adhesive material 20 e.g. red, magenta, blue, green, orange, grey, black, etc. A dyed adhesive material 30 is obtained.

(11) Examples of dyes are given in the table below:

(12) TABLE-US-00001 Colouring agent Chemical family Supplier Orasol Red 365 Metal complex BASF Pylam Solvent Red 24 Conc Diazo Pylam Pylam Magenta LX-7042 Anthraquinone Pylam Pylam Blue LX-9699 Phthalocyanine; Pylam anthraquinone Pylakrome Bright Green LX-10687 Anthraquinone; Pylam quinoline Pylakrome Orange LX-10113 Azo Pylam

(13) The concentrations used for the dyes vary between 0.5 and 5 phr (parts per hundred resin), i.e. between 0.5 and 5 percent by weight of colouring agent with respect to the solid resin(s) (hence without the solvents) that are present in the adhesive material 20.

(14) The colouring agent may also be a pigment. It may then be a powdered pigment (or a mixture of multiple pigments) or a pre-dispersed pigment (again with one or more pigments).

(15) Powdered pigments are to be dispersed in a medium. Their concentration in the medium is, for example, between 0.5 and 5 phr.

(16) Pre-dispersed pigments take the form of products containing resins and/or solvents, one or more pigments, and potential dispersing agents, additives, etc. The composition of these pre-dispersed pigments varies depending on the product itself and/or its manufacturer. Pre-dispersed pigments are easy to use as they have only to be mixed into the adhesive material. The concentration of the pigments in pre-dispersed pigments may vary widely: e.g. 10% to 70% by weight of pigment in the pre-dispersed pigment.

(17) Chromaflo is, for example, a supplier of pre-dispersed pigments. The reference Temacolor EP RM15 by Chromaflo is a red pre-dispersed pigment. Used at a concentration of 20 phr, it gives good results, without negatively affecting the properties of the adhesive material. More generally, the concentration of pre-dispersed pigment in the adhesive material may be made to vary from 1 to 50 phr (or even more).

(18) Other examples of pigments and pre-dispersed pigments are given in the table below:

(19) TABLE-US-00002 Colour Physical index Supplier Product name state (C.I.) Chemistry BASF Orasol Microlith Powdered Red 254 Diketopyrrolopyrrole 3630K pigment pre-dispersed in a vinyl copolymer resin Chromaflo Temacolor EP Pre-dispersed Red 254 Diketopyrrolopyrrole RM15 pigment pre-dispersed in a liquid epoxy resin Temacolor EP Blue 15:3 Copper phthalocyanine BM15 pre-dispersed in a liquid epoxy resin Protec DecoTint Premium Pre-dispersed Red 254 Diketopyrrolopyrrole I Red 644 RB pigment pre-dispersed in a solvent- based PGMA resin DecoTint Premium Blue 15:4 Copper phthalocyanine I Blue 675 BR pre-dispersed in a solvent- based PGMA resin Clariant(via Hostatint Red A-P2Y Pre-dispersed Red 179 Perylene pre-dispersed in a Univar) 100-ST pigment dibasic ester solvent Hostatint Blue A-BTR Blue 15:1 Copper phthalocyanine 100-ST pre-dispersed in a dibasic ester solvent Trustchem Pigment Red 254 Powdered Red 254 Diketopyrrolopyrrole Pigment Red 122 pigment Red 122 Quinacridone Pigment Blue 60 Blue 60 Anthraquinone

(20) A layer of dielectric material 40, for forming a substrate 50, is provided (FIG. 2c). This dielectric material 40 is, for example, epoxy-glass. This dielectric material 40 may be grey, yellow or white in colour, for example. Its thickness is, for example, in the vicinity of 100 m.

(21) The layer of dielectric material 40 is next coated (FIG. 2d) with a tinted adhesive material 30 obtained in the step corresponding to FIG. 2b. The thickness of the layer of adhesive material 40 is, for example, between 10 and 70 m after drying, and more preferably between 10 and 50 m after drying, its thickness being, for example, 18 m, plus or minus 3 m.

(22) After drying, the assembly composed of the layer of dielectric material 40 and the tinted adhesive material 30 is perforated all the way through (FIG. 2e), for example mechanically by punching, in order to form holes 42 corresponding to connection wells and, potentially, openings for receiving one or more electronic components.

(23) A sheet of electrically conductive material 60 is placed in contact with the layer of adhesive material 30 (FIG. 2f). The sheet of electrically conductive material 60 covers the holes 42. The assembly composed of the sheet of electrically conductive material 60, of the layer of tinted adhesive material 30 and of the layer of dielectric material 40 is laminated. The layer of tinted adhesive material 30 is cured in an oven (FIG. 2g).

(24) Resist patterns 72 are formed on the sheet of electrically conductive material 60 via photolithography, by depositing, exposing (FIG. 2h) and developing a light-sensitive resist 70 (FIG. 2i).

(25) A step of etching patterns electrochemically allows patterns 62 to be formed in the sheet of electrically conductive material 60 (FIG. 2j). Spaces 64 between the various elements of the patterns 62 (contacts, logos) are etched into the sheet of electrically conductive material 60 and the layer of tinted adhesive material 30 is visible between these spaces 64.

(26) The resist protecting the patterns 62 during etching is removed (FIG. 2k) and finishing layers 80 (nickel and gold for example) are potentially deposited onto the front side 6 via electrodeposition on at least a portion of the patterns 62 (FIG. 2l).

(27) In steps that are not illustrated, a chip is fixed to the back of each module. Each chip is connected, for example via conductive wires, from the bottom of and through connection wells (like the holes 42), to contacts 15. The chip and the conductive wires are encapsulated and the modules are singulated and each one is individually transferred to a card cavity. The result is shown in FIG. 3. The colour of the tinted adhesive material 30 is visible between the contacts 15.

(28) Numerous variants of the method described above may be envisaged. For example: the method is implemented on a double-sided circuit board, instead of the single-sided circuit board of FIG. 2l; the circuit board then comprises a sheet of conductive material on each of the two opposite sides of the layer of dielectric material; in this case, the sheet of conductive material on one of the sides may correspond to that of a copper-clad laminate with a epoxy-glass dielectric substrate, for example; and/or instead of etching the sheet of conductive material 60 after having laminated it onto the layer of dielectric material 40, the patterns 62 are cut into a sheet of conductive material 60, before being transferred to the layer of dielectric material 40 (lead frame technology).