This invention relates to a new method for manufacturing smart cards, in particular those designed for use in mobile telephones, as well as a smart card obtained by this process.

The smart cards concerned by the invention are particularly subscriber identification modules, known as SIM cards. SIM cards are designed to be incorporated into mobile telephones or other similar communication devices. SIM cards exist in several standardised formats defined by the form factors UICC (Universal Integrated Circuit Card) 2FF, 3FF or 4FF.

Miniaturisation and increases in the functions of mobile telephones have led to the formats of SIM cards becoming smaller and smaller. Thus, the form factor 2FF (25 x 15 mm) gave way to 3FF (15 x 12 mm) and then to 4FF, which is even smaller (12.3 x 8.80 mm), also called Nano SIM.

Typically, a SIM card comprises firstly the card body, commonly made by cutting from a sheet of ABS or PVC plastic, or by injection moulding, and secondly a chip with integrated circuit attached to this card body. The card body approximately takes the shape of a thin rectangular parallelepiped. Generally, for manufacturing and marketing 2FF, 3FF and 4FF card formats, the smaller card body is encompassed within a perimeter that corresponds to a larger format, generally the format that is immediately greater. Thus, typically, a SIM card may be manufactured and marketed in 1 FF format, corresponding to the credit card format, with a body encompassing a min-SIM card in 2FF format, which can encompass a micro-SIM card in 3FF format etc., like the card represented in figure 1 , which is then called a multi-format card. The microchip is of course fixed to the smallest card, in a slot that is hollowed out in the thickness of the card. To use the SIM card, depending on the format required by the device into which the card is to be inserted, the user detaches the card in the required format from the larger card body. In order to make the detachment process as easy as possible, the perimeter of each format is marked by a dotted line which weakens the material of the card body in order to facilitate the separation between the required card format and the larger card body, while holding the said card bodies together adequately till they are deliberately separated by the user.

A first known way of forming dotted lines is to form a groove that goes through the whole thickness of the larger card body and outlines the perimeter of the smaller card. Connecting strips are left to hold the smaller card body within the larger card body until the smaller card is separated for use.

A conventional process for making these dotted lines is the moulding process, in which the card is injection moulded and the cavity designed to house the chip and the dotted lines with connecting strips and break lines for these strips are obtained during moulding.

It is also known for dotted lines to be made by stamping. According to this last technique, tools are used containing sharp blades shaped to match the perimeter of the desired card, and these blades penetrate the material of the card, previously prepared by moulding in the form of a plastic sheet with the final thickness of the card. During stamping, however, at least certain areas of the dotted line are left with material sufficiently thick to hold the smaller card in the larger card body, but this thickness of remaining material is weak enough to allow the material in the aforesaid areas to be broken when the card is intentionally separated. This method makes it possible to obtain a dotted line and break lines that are finer than with the moulding method. Further, thanks to the fineness of the dotted lines, a SIM card can be put back into its slot after it has been detached by breaking the break lines, as the mere fitting of the card in its slot offers sufficient holding. This process is used particularly to make dotted lines of the smallest shapes in multi-format cards.

However, a problem arises for making multi-format cards including a small card thinner than larger cards. In particular, the standardised thickness (as per ETSI specifications) of a 4FF card is 650 μηι ± 50μηπ, while the thickness of larger format 3FF or 2FF cards is 680 μηι minimum to 840 μηι maximum. Multi-format cards of this type therefore cannot be made by stamping as described above, due to these nominal differences between the various formats.

One solution may be to manufacture the smaller card separately from a sheet 0.76 mm thick, for example, then to insert it into a purpose-made slot in a larger and thicker card. But this leads to a complicated manufacturing process and to the small card being poorly retained in the larger card.

The purpose of this invention is to solve the problems stated above, particularly aiming to enable manufacturing of multi-format cards incorporating one or more cards thinner than the larger card. In particular it aims to suggest a manufacturing process for such cards using known techniques such as machining and stamping. It also aims to suggest an economical manufacturing process enabling manufacturing times and costs to be reduced.

It also aims to avoid any burrs that may remain at the perimeter of a card after it is detached from a larger card body.

It also aims to limit the force required to separate a smaller card from a larger card in which it is inserted, and so reduce the risks of damaging the chip when separating the card. It also aims to enable and facilitate replacing a smaller card into the larger card, after they have separated from one another. With these objectives in mind, the subject of the invention is a manufacturing process for a multi-format smart card comprising a card body in a first format enclosing a card body in a smaller and thinner format than the first format card body.

According to the invention, the process is characterised in that, on the front face of a larger format card body, machining is used to reduce the thickness of an area corresponding to the smaller format card body, then cutting out by stamping the smaller format and hence also thinner card body, and then immediately reinserting the aforesaid cut card body into the slot made by the cutting out, far enough to make the machined surface of the smaller format card body flush with the front surface of the larger format card body.

More particularly, during a first machining step, the area corresponding to the smaller format card is machined using a machining tool to give it the reduced thickness desired, then, in a second step, a punch and counter-punch are placed on either side of the aforesaid area gripping between them the aforesaid thinner area of the card body, to cut the blank corresponding to the aforesaid area by simultaneously moving the punch and counter-punch to separate the aforesaid blank from the larger card body and form the smaller format card body and, by moving the punch and counter-punch gripping the cut blank in the opposite direction, reinserting the aforesaid blank into the slot formed in the larger format card body during cutting, far enough to make the previously machined surface of the blank flush with the front surface of the larger format card body.

The machined face is preferably the face also containing the seat for the chip, and the aforesaid seat for the chip can preferably be made by simultaneous machining at the same time as machining intended to reduce the thickness of the area corresponding to the smaller format card body. In this way a single machining step can be used to make both the seat for the chip and to reduce the thickness of the smaller format card body. In addition, the process according to the invention enables the face of the smaller format card that will later carry the electrical contact areas to be made coplanar with the front face of multi-format cards. Thus, without requiring any additional later operation, it will be ensured that the entire active surface of multi-format cards is perfectly coplanar, enabling its use as a larger format card, without the risk of problems that could result from misalignment of the surfaces of the smaller format card and the larger format card surrounding it, on the side bearing the electrical contacts. Furthermore, the process according to the invention also ensures that the rear face of the card body in the area of the smaller card is not damaged, as it could be if a machining operation was performed on this rear face to reduce its thickness, so enabling this rear face to be used for higher quality graphic personalisation.

Also, because cutting out by stamping provides complete separation of the smaller format card, the invention also avoids the risks of tearing the material or other burrs, when later separating the card for use, which can arise when a smaller format card is connected to the larger format card enclosing it by strips or break lines, as used in the prior art. In this was burrs are avoided that make it hard to insert the card afterwards in the device that should accept it. Also, due to the fact there is no need to break these areas of linking material to separate the smaller format card from the larger format card, less force is needed to separate them and so the risk of damaging the chip placed on the card is reduced. Also, as the smaller format card is reinserted after cutting into the slot formed by cutting, and as it is then held merely by the resulting tight fit, it is not only easier to separate the cards, as stated previously, but also possible to replace the smaller format card into this slot after it has been used. Also, the discontinuity of the surface of a larger card, caused by the presence of break lines for the body of a smaller format card, can create problems when inserting the larger card in a device, by snagging or jamming the contacts of this device in the surface irregularities formed by the aforesaid break lines. This process, by ensuring surface continuity between the machined face and the front face of the larger card, avoids these snagging problems. The subject of the invention is also a multi-format smart card, obtained using the previously-stated process, comprising a card body in a first format enclosing a card body in a smaller and thinner format than the first format card body. The card according to the invention is characterised in that the smaller format card body has a machine surface coplanar to the front face of the larger format card body. According to a particular manifestation, the smaller format card body contains a cavity for a chip made by machining from the same side as the machined surface.

Other characteristics and benefits will appear in the description below of a card according to the invention, and the method for manufacturing the card.

Reference will be made to the attached drawings, where:

- figure 1 is an overview of a multi-format card according to the invention,

- figures 2 and 3 are schematic illustrations of the successive stages of the method according to the invention,

- figure 4 is a partial view in cross-section of the card body obtained by the process according to the invention.

The card represented in figure 1 is a multi-format smart card comprising a first larger card body 1 in the 1 FF credit card format, demarcated by its perimeter d and incorporating a SIM card with a card body 2 in the 2FF or mini-SIM format, demarcated by a dotted line c2. This 2FF format card body in turn encloses a 3FF or micro-SIM format card body 3, demarcated by a dotted line c3, which in turn encloses a 4FF or nano-SIM format card body 4, demarcated by a dotted line c4. The smaller format card body 4 carries the electronic module 9 placed in a hollowed-out slot 41 formed in this latter card body.

In what follows, it will be considered that the explanations given relate to fabricating a 4FF format card body 4 in a 3FF larger format card body, but of course the invention can be applied to any card enclosed within a larger format card, for example a 4FF card in a 2FF car, or in a 2FF/3FF multi-format card, etc.

Figures 2 and 3 have therefore not represented the operations related to preparing a smaller format card body 4, typically 4FF format, enclosed within a larger format card body 3, being 2FF or 3FF format, from a sheet of plastic the same thickness as the aforesaid 2FF or 3FF larger format card body, typically 0.76 mm.

As illustrated in figure 2, a front face 101 of the card body 3 is machined using a mill 21 or similar tool to create a cavity 1 1 on an area 102 with dimensions and shape corresponding those of small format card body 4, demarcated by outline c4. This machining is carried out so as to leave a material thickness equal to that desired for the card body 4, typically 0.67 mm, between the machined face 103 and the rear face 104. Previously, the slot 41 for the chip is made, also by machining, on the same front face 101 as cavity 1 1 , such that the machining of cavity 1 1 can in fact be performed practically only on the edges of card body 4, around slot 41 . Alternatively, slot 41 may also be machined simultaneously or after the machining carried out to reduce the thickness of card body 4.

After having carried out the machining to reduce the thickness of card body 4, the aforesaid sheet 10 is placed between a punch 31 and a counter- punch 32 of a cutting press, the sheet 10 being supported by a matrix 33 and held against this matrix by a blank holder 34. The outline of punch 31 and counter-punch 32, as well as that of the matrix and blank holder are identical to the outline c4 of card body 4. Sheet 10 is positioned so that the previously- machined area 102 is located exactly in line with punch 31 , such that this can penetrate into cavity 1 1 , to grip the aforesaid area 102 between punch and counter-punch, as shown in figure 3. Punch 31 and counter-punch 32 are then moved simultaneously, as shown by arrow F1 , by a distance equal to the thickness of sheet 10, carrying area 102 and thus causing, through cooperation of punch 31 with the matric 33, complete cutting of this area 102, to form card body 4. The punch 31 and counter-punch 32 assembly, then gripping card body 4, is then immediately moved in the opposite direction, as shown by arrow F2, by a cylinder not shown or effected by a return spring 35, re-inserting card body 4 into card body 3 until the machined face 103 of card body 4 is exactly at the level of the front face 101 of card body 3, as represented in figure 4.

It will be noted that, by doing this, card body 4 is encased within card body 3, with enough friction at the edge of card body, over the entire perimeter c4, to hold card body 4 firmly with its machined face 103 flush with the front face 101 of card body 3 during other subsequent card manufacturing and finishing operations, and also until the 4FF format card is deliberately removed from the 3FF format card for final use.

It will also be noted that, since the machined face 103 at the end of the punching operation is brought to the level of front face 101 , the rear face 105 of card body 4 is then recessed in relation to the rear face 103 of the card 3. As this rear face 105 have not been machined, its surface state retains the same quality as surface 104 of the original plastic sheet and it therefore particularly suitable for graphic printing.

Although the previously-described example mentioned making a 4FF format card from a 3FF larger format card, what has just been described can be transposed to other formats or other combinations of card formats.