Method for making contactless cards

IS 2 189 461 T3

DESCRIPTION

Contactless card manufacturing procedure.

The present invention concerns the manufacture of smart cards, and in particular cards capable of contactless operation with an antenna integrated in the card.

Said cards are intended to carry out various operations, such as banking operations, telephone communications, identification operations, debit operations or unit of account recharge operations, and all kinds of operations that can be carried out remotely, by means of high-frequency electromagnetic coupling. , between an emission-reception terminal and a card placed in the action area of ​​that terminal.

One of the main problems that remains to be solved in the manufacture of said cards is the connection of the antenna to the integrated circuit chip that takes care of the electronic operation of the card. Another problem that remains to be solved is the reduction, to the maximum, of the thickness of the card. Obviously, the classic obligations of mechanical strength, reliability and cost of manufacture must be taken into account in this manufacture.

A known solution from the prior art, described in PCT document WO 96/07985, to make the connection between the antenna and the integrated circuit chip, consists of forming metallic pads on two contact pads of the chip, and then connecting those pads on the ends of an antenna wire. In that case, the antenna wire is a copper wire formed on a substrate and the pads are applied to that antenna wire by hot compression.

However, the interconnection block thus obtained presents problems of mechanical resistance and brittleness in tension of the connection. Indeed, when the chip is subjected to mechanical stresses, the pads suffer deteriorations that affect the quality of the electrical connection. Mechanical stresses can even go as far as causing the pads to break, and consequently, the chip to be pulled out. The contactless chip cards made following this previous procedure therefore have a relatively short useful life.

In another known solution from the previous article, the connection between the antenna and the chip is made by means of conductive glue applied between the antenna and the metallic pads formed in two contact ridges of the chip. However, in this case, a significant excess thickness appears due to the presence of the glue and the padding. Furthermore, the manufacture of the card requires an additional stage of distribution of glue points.

The pads, and where appropriate, the conductive glue points, have a non-negligible thickness that is added to that of the antenna and that of the chip, which increases the overall dimensions of the interconnection block obtained. Now, an attempt is made to obtain an interconnection block of minimal overall dimensions, in order to make an ultra-flat contactless chip card, that is, with a thickness less than the standardized thickness.

ISO.

The present invention makes it possible to solve the problems found in art. above, since it proposes to manufacture a contactless chip card, in which the chip is directly connected to the antenna by means of metallic pads that are embedded in the thickness of the antenna, at the time of transfer of the chip on the antenna.

The object of the invention is mainly a method for manufacturing a contactless smart card, comprising an integrated circuit chip and an antenna, in which metallized pads are made on two contact protrusions of the chip, characterized in that the connection of the chip to the antenna is carried out by embedding the metallized pads in the thickness of the antenna, at the time of transfer of the chip in said antenna.

Thanks to the procedure according to the invention, the connection obtained between the antenna and the chip is of excellent quality. Indeed, since the metallized pads are embedded in the antenna, they do not run the risk of deteriorating, let alone breaking, when the chip card is subjected to mechanical stress. The mechanical resistance of the connection is improved, the contactless chip cards manufactured according to this procedure therefore have an increased useful life.

Furthermore, in view of the fact that the pads are embedded in the thickness of the antenna, the interconnection assembly formed by the chip and the antenna has reduced overall dimensions, which is very advantageous for making an ultra-flat card, with a thickness less than 760 μm.

Furthermore, according to another characteristic of the invention, the antenna has been made of a material capable of presenting a viscous state at the time of transfer of the chip, in order to allow the embedding of the metallic pads.

In this way, the antenna can be made of a thermoplastic material loaded with metallic particles and the chip is transferred on the antenna by thermocompression. In this case, the heat makes it possible to soften the antenna material and the compression facilitates the penetration of the pads into the thickness of the softened material.

Following another embodiment, the antenna can be made of a non-polymerized conductive material, and then the chip is moved over the antenna by compression, and a contribution of heat allows the antenna material to be polymerized. In this case, before the chip is transferred, since the antenna is made of a non-polymerized material, it has a soft appearance. The compression stage then makes it possible to facilitate the penetration of the pads into the antenna material and the heating allows, as regards it, to polymerize the antenna material in order to harden it.

Follow another way of realization, the antenna is made with a thermoplastic material loaded with metallic particles, the chip is previously glued on an insulating sheet to the format of the chip card to be made, then it is done

ES 2 189 461 T3 the connection of the chip to the antenna by means of hot lamination. Also in this case, the heat allows to soften the antenna material, while the lamination allows to facilitate the penetration of the pads in the softened material.

Other particularities and advantages of the invention will appear when the description given by way of an illustrative and non-limiting example is read, and which is made with reference to the attached figures, which represent:

- Figures 1a and 1b diagrams in section of the assembly of a chip during its connection to an antenna,

Figures 2a and 2b, cross-sectional diagrams of the assembly of a chip during its connection to an antenna, according to another embodiment.

In Figures 1a and 1b we have represented a chip 3 during its assembly in an antenna 2. The interconnection set formed by chip 3 and antenna 2 is intended to be inserted into a contactless chip card, with an ultra-thin thickness and less than the thickness ISO standardized.

A preliminary stage of the manufacturing process according to the invention consists in forming metallized pads 5 on one of the contact shoulders 4 of chip 3. The pads 5 are intended to ensure the electrical connection between chip 3 and antenna 2. Consequently, they are necessarily made of a conductive material. They can, for example, be made of gold, or of a polymeric material charged with metallic particles.

Preferably the pads 5 are made on two contact projections 4 of the chip in order to be able to make a connection in conductive fields of the antenna 2 located at its ends.

In view of the fact that the pads 5 are intended to be embedded in the thickness of the antenna 2, they preferably have a thickness more or less equal to or slightly less than that of the antenna.

Furthermore, to allow a good penetration of the pads 5 into the thickness of the antenna 2, it is preferred that they be practically conical in shape.

As for the antenna 2, it is made of an insulating substrate 1. Made of a conductive material able to soften at the time of transfer of the chip 3, to allow a better penetration of the pads 5. Its shape is of little importance, for example, it can represent a spiral or any other reason.

The insulating substrate 1 is, for example, a plastic sheet in the format of the chip card to be produced. It can also be made of polyvinyl chloride (PVC) or polyethylene (PE).

A first embodiment consists in making the antenna 2 in a thermoplastic material loaded with metal particles. This material is supplied, for example, by the AIT company under the reference LZTP 8550-FT. In that case, the antenna was formed by screen printing of conductive ink based on thermoplasty. The metallic particles are constituted, for example, of small silver balls. In this case, the subsequent stage, which consists of transferring the chip 3 onto the antenna 2, is carried out by hot compression 6. The fact of heating allows, in effect, to soften the thermoplastic material that constitutes the antenna 2, and the simultaneous compression allows to facilitate the penetration of the pads 5 in the thickness of the antenna with a view to making the connection of the chip 3 in the antenna. two. When the thermocompression operation has been completed, the interconnection assembly obtained is allowed to cool to ambient air. Cooling allows the antenna material to regain its solid state and initial shape. The thermoplastic antenna generally exhibits adhesive properties during softening that allow the chip to be fixed.

Another sheet of plaestics to the format of the chip card to be made, not represented in figures 1a and 1b, can then be applied above the interconnection set obtained and fixed by gluing, to enclose the chip and the antenna, and thus form a contactless card.

Thanks to this manufacturing procedure, the connection of the chip 3 in the antenna 2 is made, by means of the embedding of the pads 5 in the antenna 2, and the fixation of the chip 3 on the antenna 2 in a single and same stage.

In a variant embodiment, the antenna 2 is made of a conductive thermosetting polymer material, that is to say loaded with metallic particles. In this case, an attempt is made not to polymerize the antenna material before the stage of transferring the chip onto the antenna, so that this material is present in a viscous state, for example, between 8000 CPS and 6000 CPS. The chip 3 is then translated by compression 6, in order to facilitate the penetration of the pads 5 into the thickness of the antenna material. A supply of heat also makes it possible to polymerize the antenna material 2 so that it hardens. This heating operation can be carried out indifferently after or simultaneously with the compression operation. Also in this case, the electrical connection is made between the chip and the antenna, and the fixation of the chip on the antenna in a single stage.

In another variant of embodiment, the antenna 2 is made of a non-dried conductive polymer material. In this case, the fact that the polymer is huomer is sufficient for it to retain a soft appearance. The chip 3 can then be translated on the antenna 2 by compression 6, in order to facilitate the penetration of the metallized pads 5 into the thickness of the antenna material. Subsequently, it is enough to allow the interconnection block obtained to dry in ambient air, in order for the antenna material to harden. In this case, a heat input is no longer necessary.

Figures 2 a and 2b represent another embodiment of an assembly of a chip 3 connected to an antenna 2. In these figures the same references have been taken as in Figures 1a and 1b to designate the same elements. In this embodiment, the antenna 2 is also made on an insulating substrate 1, such as a plastic sheet for example, in the format of the chip card to be produced. Antenna 2 is made in

ES 2 189 461 T3 a thermoplastic material loaded with metallic particles. Metallized pads 5 are also formed on the contact projections 4 of the chip 3.

However, this mode of implementation differs from the previous ones, because the stage of transferring the chip 3 onto the antenna 2 is not carried out in the same way.

Indeed, in the example of Figures 2a and 2b, an additional preliminary step consists of gluing the chip 3 on an insulating substrate 7. This substrate 7 is, for example, a plastic sheet made of polyvinyl chloride (PVC) or polyethylene (PET) to the format of the card you want to make. In this case, therefore, the non-active rear face of the chip 3 is glued onto the substrate 7, that is to say on the opposite face to the one bearing the contact projections 4 and the metallized pads 5.

In this way, the chip 3 and the antenna 2 are placed between two plastic sheets 1 and 7, preferably made to the format of the card to be manufactured.

The transfer of the chip 3 on the antenna 2 and the electrical interconnection are then carried out during a hot lamination operation 8 of the two plastic sheets 1 and 7. The heat effectively softens the thermoplastic material that makes up the antenna, while lamination, which consists in pressing the two plastic sheets 1 and 7 against each other, makes it possible to facilitate the penetration of the pads 5 into the softened antenna material.

When the hot rolling operation has been completed, the interconnection assembly obtained is cooled, so that the antenna material 2 recovers its initial solid state. The chip 3 and the antenna 2 are interconnected and then enclosed between two plastic sheets 1 and 7, thus forming a contactless chip card.

Thanks to the manufacturing process according to the invention, it is possible to manufacture contactless chip cards, with an ultra-thin thickness and less than 760 µm. Indeed, the thickness of the card obtained is equal to the sum of the thicknesses of the two plastic sheets 1 and 7, of chip 3 and of the antenna

two. We provide below orders of amplitude of these thicknesses simply for illustrative purposes. The antenna 2 can be made on a thickness between 20 and 30 μm, the integrated circuit chip 3 can be made on a thickness of less than 300 μm, and the plastic sheets 1 and 7 can be made on a thickness between 40 and 100 μm .

Furthermore, since the pads are completely embedded in the thickness of the antenna 2, they do not run the risk of being damaged by mechanical stresses. The interconnection assembly obtained then exhibits excellent mechanical resistance and increased useful life.