WO1998059319A1

WO1998059319A1 - Electronic micromodule, in particular for smart card

Info

Publication number: WO1998059319A1
Application number: PCT/FR1998/001198
Authority: WO
Inventors: Jacek Kowalski; Didier Serra
Original assignee: Inside Technologies
Priority date: 1997-06-20
Filing date: 1998-06-11
Publication date: 1998-12-30
Also published as: FR2765010B1; FR2765010A1

Abstract

The invention concerns an electronic micromodule (1), in particular for hybrid smart card, comprising a support wafer (2), including on its front face (2-2) electric contact ranges (C1-C8) and on its rear face (2-1) an integrated circuit (3) and a coil (5).

Description

ELECTRONIC MICROMODULE, ESPECIALLY FOR CHIP CARDS

The present invention relates to smart cards operating without contact as well as smart cards with two operating modes, with or without contact.

The smart card market currently comprises two fields: that of so-called "contact" cards, equipped with electrical contact pads, and that of so-called "contactless" cards, equipped with an antenna coil for receiving by electromagnetic induction. data, clock signal, supply voltage ...

In the near future, it is expected that contactless smart cards will grow strongly while many contact cards will still be used. Also, in order to rationalize the smart card market, integrated circuits with two operating modes, with or without contact, can be provided which can communicate with any type of smart card reader. By way of example, such an integrated circuit with two operating modes is described in patent application FR .96 10032 in the name of the applicant.

The present invention relates more particularly to the manufacture of a smart card with two operating modes, or hybrid card, essentially comprising an antenna coil and an electronic micromodule. Conventionally, the micromodule comprises a support plate comprising on its front face contact pads and on its rear face an integrated circuit with two operating modes of the type mentioned above. The antenna coil is generally an electric wire embedded in the body of the card, forming one or more turns and connected to the pads of the integrated circuit.

This prior art hybrid smart card has the disadvantage of being expensive to manufacture in because of the difficulty in connecting the antenna coil to the integrated circuit. Indeed, the integrated circuit is first fixed on the micromodule and connected to the contact pads, and its connection with the antenna coil only occurs when the micromodule is mounted on the card.

Also known, from document JP 07 239922, is a micromodule comprising a coil engraved on the front face of the support plate, near the contact pads. Such a micromodule is likely to suffer, in practice, from a significant problem of wear of the coil, the conductive track forming the coil being of small width and extremely fragile. Localized deposition of a protective material is possible, without covering the contact pads, but represents a handicap with regard to manufacturing costs.

An objective of the present invention is to provide an electronic micromodule which overcomes the drawbacks mentioned above while being simple to manufacture and low cost.

To achieve this objective, the present invention provides an electronic micromodule comprising a coil and a support plate comprising on its front face electrical contact pads and on its rear face an integrated circuit, in which the coil is arranged on the rear face of the support plate.

According to an advantageous embodiment, the integrated circuit overlaps the coil. This arrangement facilitates and makes more reliable the connection of the coil to the integrated circuit, whether the connection is made by wires or by soldering.

More generally, the integrated circuit is preferably arranged substantially in the center of the coil, with or without overlapping. According to one embodiment, the coil is a conductive strip in the form of a spiral.

According to one embodiment, the coil is arranged in a magnetically permeable zone located on the periphery of the location occupied on the front face by the contact pads.

According to one embodiment, the micromodule comprises a central conductive pad forming an extension of one of the contact pads, the integrated circuit being fixed to the central pad via an opening made in the. support plate.

According to one embodiment, the coil is integrated in a microchip and the integrated circuit is fixed on the rear face of the support plate by means of the microchip.

Advantageously, the contact pads are formed by a stamped or engraved metallic pattern attached to the support plate. According to one embodiment, the contact pads present in arms extending to the edges of the support plate.

Advantageously, the contact pads each occupy a reduced surface of the order of five to ten square millimeters.

The present invention also relates to an electronic portable object comprising a micromodule according to the invention.

These objectives, characteristics and advantages, as well as others of the present invention, will be explained in more detail in the following description of various exemplary embodiments of micromodules according to the invention, given without limitation in relation to the attached figures, among which: - Figures 1, 2 and 3 show respectively in a sectional view, a top view and a bottom view of a first embodiment of a micromodule according to the invention, - Figures 4 and 5 show in a view of above and a sectional view of a second embodiment of a micromodule according to the invention,

- Figure 6 is a top view of an alternative embodiment of the micromodule of Figure 1, and - Figures 7, 8 and 9 show respectively a top view, a bottom view and a sectional view a third embodiment of a micromodule according to the invention.

Figures 1, 2 and 3 show an electronic micromodule 1 according to the invention which can be mounted on a plastic card or any other portable object.

The support plate 2 of the micromodule 1, made of an electrically insulating material, conventionally comprises on its rear face 2-1 an integrated circuit 3 taking the form of a silicon microchip

(FIG. 1 and 3), and on its front face 2-2 (FIG. 2) of? -3 metallic contact pads C1 to C8 corresponding by their shape and arrangement to ISO 7816 standard. According to the invention, the face rear 2-1 of the support plate also comprises a coil 5, formed here by a conductive strip 4 arranged in a spiral around the integrated circuit 3 (FIG. 3}.

The advantage of the micromodule according to the invention is that it is compact and autonomous, ready to be mounted on a plastic card without the need to connect it to a coil embedded in the card.

In addition, the coil 5 is not subject to wear when contact pads rub on the front face 2-2 of the micromodule. The present invention is also based on the observation that, with regard to the minimum dimensions of the contact pads regulated by the ISO 7816 standard, it is possible to provide contact pads of a dimension substantially smaller than that generally used in the prior art, not covering the entire surface of the micromodule, so as to allow the integration of the coil without prohibitively increasing the dimensions of the micromodule, while obtaining good magnetic permeability of the micromodule, or "magnetic behavior" , necessary for the optimal functioning of the coil, despite the fact that contact pads form screens opposing the circulation of a magnetic field. Indeed, if we refer to the above-mentioned ISO standard, we see that the minimum authorized dimension of the contact pads is of the order of 1.7 x 2 mm, ie a dimension much smaller than that generally used in the prior art. Thus, in FIGS. 2 and 3, substantially on a scale of 10, it can be seen that the dimensions of the micromodule are of the order of 14 x 15 mm, ie an area of 2.1 cm ² satisfactory in terms of space. The dimensions of the ranges C1 to C8 are approximately 2 x 3 mm,

2 ^• _. „About 6 mm. The integrated circuit has a conventional dimension of 2.54 x 4.24 mm. The coil 5 is here square in shape and has thirteen turns centered on the integrated circuit. The innermost turn is approximately 10 x 10 mm and the outermost turn is approximately 13 X 13 mm. The conductive strip 4 forming the coil 5 is not shown to scale for the sake of readability of the figure. The conductive strip 4 is for example of a width of 60 micrometers and has a space between turns of about 40 micrometers. The total length of the conductive strip 4 is of the order of 60 cm and its inductance of the order of 3.6 microhenry, a usual value for operation of the integrated circuit 3 at the standard frequency of 13.56 MHz in contactless mode. Despite the presence of the metal contact pads C1 to C5, the magnetic permeability of the micromodule is sufficient for an induced voltage to appear at the terminals of the coil 5 when the latter is immersed in an alternating magnetic field. In fact, the surface occupied by the contact pads C1 to C5 is substantially less than the total surface of the support plate 2, so that there remain magnetically permeable zones on the surface thereof.

More particularly, in the micromodule shown in FIGS. 1 to 3, these magnetically permeable zones comprise a first central rectangular area of approximately 3 × 10 mm, lying in the middle of the ranges C1 to C8 in the axis of the coil 5, and a second peripheral area in the form of a frame, with a width of approximately 2 mm, corresponding substantially to the location of the coil 5. Of course, the integrated circuit 3 of silicon has good magnetic permeability, the silicon having on this point the properties of glass. It can be noted that, if the contact pads covered the entire surface of the support plate, the maximum operating distance of the coil relative to the source of a magnetic field would be very small, of the order of a few millimeters. However, the present invention does not exclude such an embodiment which could be suitable for certain applications. For example, smart card readers of the insertion or slot type can make it possible to hold the coil 5 very close to the source of the magnetic field. Problems related to permeability magnetic of the micromodule are then of less importance.

In practice, the support plate 2 can be produced from a printed circuit board, for example made of epoxy or a flexible material such as polyester, with a thickness of the order of a hundred micrometers. This printed circuit board is initially covered with a conductive material with a thickness of the order of a few tens of micrometers, for example copper, which is then etched so as to reveal the coil 5.

Advantageously, the contact pads C1 to C8 can be produced from a precut metal pattern, or "lead frame", assembled on the front face 2-2 of the support plate 2, for example by gluing. In FIG. 2, it can thus be seen that the contact pads C1 to C8 have thinned parts, or arms 6, which extend to the edges of the support plate. These arms 6 result from the aforementioned manufacturing process and allow, after stamping or etching of a band of golden metal, to maintain between them the patterns produced collectively, before their mounting on support plates.

Thus, yet another advantage of the micromodule according to the invention is that it lends itself well to mass production at low cost thanks to the possibility of collectively producing the contact pads as has just been described.

Likewise, the support plates and their coils can be produced collectively on a mother plate and the assembly of the precut patterns (contact pads) with the support plates can be carried out on the mother plate before cutting.

Furthermore, the integrated circuit 3 can be connected to the ranges C1 to C8 and to the coil 5 by wiring. ultrasonic wedge bonding. In FIG. 3, it can thus be seen that the integrated circuit has various input / output pads 7 connected by means of metallic wires 8, for example aluminum wires, to the contact pads C1 to C8, as well as to connection pads 9, 10 provided at the two ends of the conductive strip 4. The wires 8 are welded to the backs of pads C1 to C8 by means of openings 11 made in the support plate 2. Once the wiring operation has been carried out, the integrated circuit 3, the connection wires 8 and the coil 5 are embedded in a protective resin 12, for example an epoxy resin (FIG. 1).

FIGS. 4 and 5 represent, by a top view and a sectional view, a micromodule 20 further comprising a central conductive pad 21 forming an extension of the pad C5 (ie the ground pad GND according to ISO standard 7816). This embodiment allows the mounting of an integrated circuit 3 with a conductive bottom, for example an NMOS integrated circuit. The support plate 2 includes a rectangular opening 22 for fixing the integrated circuit 3 on the rear face of the track 21, by bonding or soldering. In FIG. 4, it can be seen that the track 21 does not occupy the cost of the space available between the tracks C1 to C8, so that the center of the support plate 2 has magnetically permeable areas.

6 shows a top view of a micromodule 30 which differs from that of Figure 3 by the fact that the integrated circuit 3, fixed on the support plate 2 by means of an electrically insulating adhesive, overlaps the coil 5 while remaining substantially arranged towards the center thereof. This advantageous arrangement of the integrated circuit 3 makes it possible to reduce the lengths of the wiring wires 8, in particular the wires leading to the areas 9, 10 for connecting the coil. Thus, the integrated circuit 3 comprises a pad 7-1 arranged facing the pad 9, and a pad 7-2 arranged opposite the pad 10. The wire connections are short, reliable, and the number of manufacturing defects is statistically decreased.

Of course, the micromodule according to the invention is susceptible of numerous other variants and embodiments. Although it has been described in the foregoing a connection of the integrated circuit by means of metal wires, it is obvious that other conventional methods may be used. In particular, a method which can be implemented, known under the designation of "flip chip", consists in mounting the integrated circuit upside down and directly soldering the pads 7 on metallized pads.

The embodiment of Figure 6 lends itself well to such a "flip chip" assembly with a low manufacturing cost, because it is possible to bring the pads 9, 10 below the integrated circuit 3 without it being necessary to bring the external range 10 inside the coil 5 (which would be inevitable if the integrated circuit did not overlap the coil).

On the other hand, the location, size and shape of the coil 5 are subject to modification and further study, the embodiments previously described being given only by way of example.

Furthermore, a variant of the present invention consists in using a coil integrated in a microchip and in mounting this microchip on the support plate of the micromodule. Various conventional technologies make it possible to produce such an integrated coil. For example, the polysilicon / copper technology used for the manufacture of magnetic read heads makes it possible to integrate on a silicon substrate a copper strip having a large number of turns separated by layers of polysilicon. Also, the thin film technology (deposition of a conductive material by vacuum evaporation) makes it possible to produce a spiral strip on the surface of a silicon or ceramic chip. Depending on the technology chosen, the coil can be integrated into the surface of the chip or in its thickness.

To fix the ideas, FIGS. 7, 8 and 9 respectively represent, from above, from below and in section, an example of an embodiment of an electronic micromodule 50 comprising a coil integrated in a microchip 51. As indicated above, the chip 51 can be made of silicon, ceramic, or any other material allowing a coil to be integrated. Pads 52, 53 for connecting the coil are provided on the surface of the chip 51. The chip 51 is fixed to the rear face 2-1 of the support plate 2 and the integrated circuit 3 is mounted on the chip 51, l 'together forming a stack. In FIG. 9, it can be seen that the connection of the pads 7 of the integrated circuit to the contact pads C1 to C8 as well as to the pads 52, 53 for connection of the coil is made by means of the metal wires 8 already described. On the front face 2-2 (FIG. 8, 10), the contact pads C1 to C8 extend to the edges of the plate 2 but do not cover the central part of the plate 2 corresponding to the location, on the rear face 2-1, of the chip 51 and of the integrated circuit 3 (shown in dotted lines in FIG. 8). In addition to the various possible embodiments, it will be clear to those skilled in the art that the present invention can be advantageously applied to the production of smart cards operating exclusively without contact. If we refer to the figures previously described, we can see that each of the variants 1, 20, 30, 50 of the micromodule of the invention can be produced without predicting the contact areas C1 to C8. The proposed shapes and arrangement of the coil 5 can be kept. The surface available on the support plate 2 however being greater due to the absence of the contact pads, there is greater freedom of design and the coil 5 can take a wide variety of shapes.

In this exclusively contactless application, the present invention offers, as before, a compact and autonomous electronic micromodule which can be mounted directly in a plastic card without the need to connect it to a coil. In addition, the micromodule can be completely embedded in the body of a plastic card. For example, conventional manufacturing methods by overmolding or by assembling plastic sheets lend themselves well to insertion of a micromodule according to the invention in the body of a plastic card. In this case, an alternative embodiment of the micromodule shown in FIGS. 7, 8, 9 consists in eliminating the support plate 2. The coil being in the form of a micro-plate 51 on which the integrated circuit 3 is fixed, the assembly microchip 51 and integrated circuit 3 form a functional whole which can be directly embedded in a plastic card.

Finally, as already indicated, the present invention is not reserved for the production of plastic cards but generally relates to portable objects comprising an electronic chip, for example electronic labels, electronic tokens, electronic keys ...

Claims

1. Electronic micromodule (1, 20, 30, 50} comprising a coil (5, 51) and a support plate (2) comprising on its front face (2-2) electrical contact pads (C1-C8) and on its rear face (2-1) an integrated circuit (3), characterized in that the coil (5, 51) is arranged on the rear face (2-1) of the support plate (2).

2. Micromodule (30) according to claim 1, characterized in that the integrated circuit (3) overlaps the coil (5).

3. Micromodule (1, 20) according to one of claims 1 and 2, wherein the integrated circuit (3) is arranged substantially in the center of the coil (5), with or without overlapping.

4. Micromodule according to one of claims 1 to 3, wherein the coil (5) is a conductive strip (4) in the form of a spiral.

5. Micromodule according to one of the preceding claims, in which the coil (5) is arranged (2) in a magnetically permeable zone located at the periphery of the location occupied on the front face (2-2) by the pads contact (C1-C8).

6. Micromodule (20) according to one of the preceding claims, comprising a central conductive pad (21) forming an extension of one (C5) of the contact pads, the integrated circuit (3) being fixed to the central pad (21 ) via an opening (22) in the support plate (2).

7. Micromodule (50) according to one of claims 1 and 2, in which the coil is integrated in a microchip (51) and the integrated circuit (3) is fixed. on the rear face (2-1) of the support plate (2) by means of said microchip (51).

8. Micromodule according to one of the preceding claims, in which the contact pads (C1-C8) are formed by a stamped or engraved metallic pattern attached to the support plate (2).

9. Micromodule according to claim 8, in which the contact pads have arms (6) extending to the edges of the support plate (2).

10. Micromodule according to one of the preceding claims, in which the contact pads (C1-C8) each occupy a reduced area of the order of five to ten square millimeters.

11. Electronic portable object, comprising an electronic micromodule according to one of the preceding claims.