U.S. patent application number 11/882871 was filed with the patent office on 2010-01-14 for method for making smart cards capable of operating with and without contact.
This patent application is currently assigned to GEMPLUS. Invention is credited to Stephane Ayala, Christine Beausoleil, Gerard Bourneix, David Martin, Laurent Oddou, Philippe Patrice, Michael Zafrany.
Application Number | 20100011223 11/882871 |
Document ID | / |
Family ID | 9511956 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100011223 |
Kind Code |
A9 |
Ayala; Stephane ; et
al. |
January 14, 2010 |
METHOD FOR MAKING SMART CARDS CAPABLE OF OPERATING WITH AND WITHOUT
CONTACT
Abstract
The invention concerns a method for making smart cards capable
of operating with or without contact called mixed cards and
contactless smart cards. In order to avoid the risk of
deteriorating the antenna the method consists in producing an
antenna comprising at least two turns, on a support sheet, said
antenna having its turns located outside the connecting pads, and
in providing an insulating bridge so as to connect each of the
antenna ends to a connection pad respectively.
Inventors: |
Ayala; Stephane; (Marseille,
FR) ; Bourneix; Gerard; (Greasque, FR) ;
Beausoleil; Christine; (Marseille, FR) ; Martin;
David; (La Ciotat, FR) ; Oddou; Laurent; (La
Ciotat, FR) ; Patrice; Philippe; (Allauch, FR)
; Zafrany; Michael; (Marseille, FR) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
GEMPLUS
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20070271467 A1 |
November 22, 2007 |
|
|
Family ID: |
9511956 |
Appl. No.: |
11/882871 |
Filed: |
August 6, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09545288 |
Apr 7, 2000 |
|
|
|
11882871 |
Aug 6, 2007 |
|
|
|
PCT/FR98/02147 |
Oct 8, 1998 |
|
|
|
09545288 |
Apr 7, 2000 |
|
|
|
Current U.S.
Class: |
713/185 ;
29/600 |
Current CPC
Class: |
G06K 19/07769 20130101;
G06K 19/07783 20130101; G06K 19/07749 20130101; Y10T 29/49002
20150115; G06K 19/07779 20130101; Y10T 29/49016 20150115; G06K
19/0775 20130101 |
Class at
Publication: |
713/185 ;
029/600 |
International
Class: |
H04L 9/00 20060101
H04L009/00; H01P 11/00 20060101 H01P011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 8, 1997 |
FR |
97/12530 |
Claims
1. A support sheet, comprising: an antenna winding with at least
two turns, a pair of connection pads both disposed on a common side
of said antenna winding, an insulating material covering a zone
across said antenna winding, and a conductive element on said
insulating material that connects an end of said winding on a side
opposite said common side to one of said connection pads.
2. A smart card including the support sheet of claim 1.
3. A smart card including the support sheet of claim 1 and an
integrated circuit chip connected to said connection pads.
4. A support sheet, comprising: an antenna winding with at least
two turns and a pair of ends that are respectively associated with
two connection points located on a common side of said turns, said
antenna being incrusted on said sheet and including a link that
crosses said turns to connect a terminating one of said turns to
one of said connection points, with said link being insulated from
said turns to avoid a short circuit.
5. The support sheet of claim 4 wherein said antenna is incrusted
on said support sheet by means of an ultrasound technique.
6. The support sheet of claim 4 wherein said connection points are
located at the interior of said turns, and said link connects the
outside turn to one of said connection points.
7. A smart card including the support sheet of claim 4.
8. A smart card including the support sheet of claim 4 and an
integrated circuit chip connected to said connection pads.
9. A method for manufacturing smart cards, comprising the following
steps: providing a support sheet having an antenna with a plurality
of turns, a pair of connection pads disposed on a common side of
said turns, and a link crossing said turns that connects the
opposite side of said turns to one of said connection pads;
laminating said support sheet between a pair of plastic sheets;
machining a cavity in one of said plastic sheets subsequent to said
laminating step to expose said connection pads; and placing an
integrated circuit chip within said cavity so as to be in
electrical contact with said connection pads.
10. The method of claim 9 wherein said integrated circuit chip is
disposed within a module having conductors on one side for
connecting said chip to said connection pads, and conductors on the
opposite side that provide access to the smart card.
Description
[0001] This application is a divisional of application Ser. No.
09/545,288 filed Apr. 7, 2000, which is based on French Patent
Application No. 97/12530, filed Oct. 8, 1997.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The invention concerns the manufacture of smart cards
capable of operating with or without contact. These cards are
provided with an antenna integrated in the card and a micromodule
connected to the antenna. Information is exchanged with the
exterior either by the antenna (therefore without contact) or by
contacts flush with the surface of the card.
[0004] Throughout the rest of the description this type of card
will be called a mixed card or mixed smart card.
[0005] The manufacturing method also concerns contactless smart
cards, that is smart cards capable of operating without contact,
information being exchanged with the exterior only through the
antenna.
[0006] However, to simplify the following explanation only mixed
cards will be referred to in what follows, although the method also
extends to contactless smart cards, as has just been stated.
[0007] 2. Related Background
[0008] Mixed smart cards are intended to facilitate various
operations, such as banking operations, telephonic communications,
identification operations, operations for discharging or recharging
units for account, and all kinds of operations which can be carried
out either by inserting the card in a reader or remotely by
electromagnetic coupling (in principle of the inductive type)
between an emitter-receiver terminal and a card placed within the
field of action of this terminal.
[0009] Mixed cards must have standardised dimensions identical to
those of conventional smart cards fitted with contacts. This is
also desirable for cards operating only without contact.
[0010] It will be recalled that cards with contact are defined by
the usual standard ISO 7810, this definition being: a card which is
85 mm long, 54 mm wide and 0.76 mm thick. The flush contacts are at
clearly defined positions on the surface of the card.
[0011] These standards impose severe constraints on manufacture. In
particular, the very low thickness of the card (800 .mu.m) is a
major constraint, still more severe for mixed cards than for cards
simply fitted with contacts, as incorporation of an antenna in the
card must be provided for.
[0012] The technical problems which are posed are problems of
positioning the antenna in relation to the card, as the antenna
occupies almost the whole surface of the card, problems of
positioning the integrated circuit module (comprising the microchip
and its contacts) which makes possible the electronic operation of
the card, and problems of the precision and reliability of the
connection between the module and the antenna; finally, constraints
of mechanical strength, reliability and manufacturing cost have to
be taken into account.
[0013] The antenna is generally formed by a conductive element
deposited as a thin layer on a plastic support sheet. At the ends
of the antenna connecting pads are provided; these must be exposed
in order to be able to connect with the contacts of the electronic
module.
[0014] In the following description the conductive element forming
the antenna will be called the antenna filament, given that,
depending on the technology used, it may comprise a filament inlaid
in the support sheet or printed tracks.
[0015] One approved solution for manufacturing mixed smart cards
consists in using plastic foils pre-perforated in the area of the
connecting pads of the antenna formed by the two ends of the
antenna filament, in superimposing them on the sheet supporting the
antenna and in assembling them by hot or cold lamination. The
position of the connection pads of the antenna is limited by the
position of the electronic module which is itself defined by the
ISO standards.
[0016] A cavity to accommodate the electronic module must then be
machined in the body of the card, between the connection pads of
the antenna and above the perforations formed in the plastic foils
covering the antenna; then the contacts of the electronic module
must be connected to the connection pads of the antenna by
depositing a conductive adhesive in the perforations. The antenna
filament generally comprises several turns. These turns pass
between the connection pads in such a way that they can be
connected to these pads, which are located near the
micromodule.
[0017] A first problem then arises from the nature of this
structure. The turns may be damaged when the cavity is machined.
Indeed, the turns can even be destroyed during this stage if the
antenna is not positioned very precisely in relation to the
position of the cavity.
SUMMARY
[0018] The invention provides a solution for this first problem of
the risk of damaging or even destroying the antenna. To this end
the invention proposes a manufacturing method for smart cards, the
said smart card comprising an antenna at the ends of which pads are
provided for connection to an electronic module, characterised in
that the method includes at least one stage consisting in producing
the antenna comprising at least two turns, on a support sheet, the
said antenna having its turns located outside the connecting pads,
and in providing an insulating bridge so as to connect each of the
antenna ends to a connection pad respectively.
[0019] This stage of the manufacturing method enables a free space
to be provided between the connection pads of the antenna, in which
space it is possible to form a cavity for the module without risk
of damaging the turns of the antenna.
[0020] The insulating bridge is produced by covering the turns of
the antenna with an insulating layer in one zone, then by
depositing a conductive element on this insulating layer so as to
connect one outside end of the antenna to one connection pad.
[0021] Another method of producing the insulating bridge consists
in forming the antenna on each side of the support sheet, the
connection pads being produced on the same side of the support
sheet.
[0022] In addition, in the solution approved by the prior art,
since the body of the card consists of a stack of several foils,
the perforations formed in each foil must be superimposed. However,
during the laminating stage the geometry of the perforations is not
controlled and can fluctuate. Moreover, during this laminating
stage the pressure becomes zero perpendicularly to the perforations
whereas it is high over the body of the card. This difference in
pressure causes the creation of a fault in the surface of the
cards.
[0023] To avoid this problem of the deformation of the card, the
invention proposes, in addition, to assemble together all the
plastic foils which form the body of the card and then to machine
the body of the card to form the cavity for the electronic module
and the connection recesses provided to expose the connection pads
of the antenna.
[0024] This machining is preferably done in a single stage, this
being made possible thanks to the precise control of the position
of the antenna in relation to the position of the cavity.
[0025] The fact that the cavity and the connecting recesses are
machined simultaneously greatly simplifies and accelerates the
manufacturing method.
[0026] In addition, the invention proposes a second solution to the
problem of the risk of damaging or even destroying the antenna. It
proposes, indeed, a method for manufacturing a smart card, said
smart card comprising an antenna at the ends of which are provided
pads connecting it to the electronic module, characterised in that
the method comprises at least one stage consisting in machining a
cavity and connecting recesses in an upper face of the body of the
card, in such a way that the machining plane of the bottom of the
cavity is situated above the plane of the antenna and the
connection recesses are situated above the connection pads of the
antenna and allow them to be exposed.
[0027] In addition, the connecting elements between the module and
the antenna, which will be called the interconnection in what
follows, can be damaged during testing of the cards by bending and
twisting. To minimise the stresses on the interconnection during
these tests the invention proposes that the antenna be located in
an area of the card where the stresses are lowest. Thus, the foil
supporting the antenna is located on or near the elastic neutral
axis of the card. The neutral axis of a card is defined as being
the layer situated at the centre of the thickness of the card.
[0028] In addition, after the machining of the cavity the antenna
is generally connected to the electronic module by filling the
connecting recesses with a conductive adhesive. When the module is
installed in the card the heating time is too short to ensure
correct polymerisation of the adhesive. In these conditions cards
must spend a long period in an oven. In addition, given that the
maximum temperature which the body of the card can withstand is
generally below 100.degree. C., it is difficult to ensure a good
interconnection without deforming the body of the card. As a
result, the manufacture of the card in these conditions is long and
difficult, and cannot be adapted to mass-production.
[0029] The invention provides different solutions to this problem
of interconnection. In particular, it proposes the use of a solder
with low melting point, that is, a melting point well below
180.degree. C., to produce the connection between the connection
pads of the antenna and the electronic module. To this end, the
solder comprises an alloy with a basis of indium and tin, or with a
basis of bismuth, tin and lead, or with a basis of bismuth, indium
and tin.
[0030] According to other characteristics, the connection between
the connection pads of the antenna and the electronic module is
formed by means of a conductive grease, or by means of a silicon
gasket charged with metallic particles.
BRIEF DESCRIPTION OF THE FIGURES
[0031] Other features and advantages of the invention will emerge
from a reading of the description given by way of a non-limiting
example, with reference to the attached drawings, in which
[0032] FIG. 1 shows a schematic perspective view of an antenna of a
smart card formed on a support sheet,
[0033] FIG. 2 shows a schematic sectional view of an insulating
bridge of the antenna of FIG. 1,
[0034] FIG. 3 shows a schematic perspective view of another method
of producing an antenna of a smart card,
[0035] FIG. 4 shows a schematic perspective view of another method
of producing an antenna of a smart card,
[0036] FIGS. 5A to 5C show sectional views of a card during
different stages of a manufacturing process according to the
invention,
[0037] FIG. 6 shows a schematic sectional view of a card produced
according to another manufacturing method according to the
invention
[0038] FIG. 7A shows a top view of the flush contacts of a
single-sided module,
[0039] FIG. 7B shows a perspective view illustrating the position
of the connection recesses in relation to a cavity formed in the
body of a card,
[0040] FIGS. 7C and 7D show two views of contacts on the interior
face of double-sided modules,
[0041] FIG. 7E shows a perspective view illustrating the position
of the connection recesses in the cavity.
DETAILED DESCRIPTION
[0042] In general, mixed smart cards will be produced by the
bonding (hot or cold lamination) of foils of plastic material in
which the antenna conductor has been inserted or interposed; then
by forming a cavity in the assembled foils, between the connection
pads provided at the ends of the antenna conductor, in order to
create a space intended to accommodate the electronic module with
integrated circuit; and by installing this module so that two
conductive pads of the module come into electrical contact with the
connection pads of the antenna conductor, either directly or, more
frequently, through the intermediary of a conductive linking
element.
[0043] FIG. 1 shows a first method of producing an antenna 11
comprising at least two turns and intended to be enclosed in the
body of a contactless smart card. Two connection pads 12 are
provided at the ends of the antenna filament 11. An important stage
in a manufacturing method of such a contactless smart card consists
in producing the antenna 11, on a support sheet 10, in such a way
as to define precisely its position in the body of the card in
relation to the position of a cavity to be machined and intended to
accommodate the electronic module.
[0044] According to a first manner of production, the turns of this
antenna 11 are located outside the connection pads 12, and an
insulating bridge 13 is formed so as to connect each end of the
antenna to a connection pad 12 respectively, without creating a
short-circuit. This manner of production allows a free space to be
located between the connection pads 12 of the antenna 11, since no
turn passes through it. The free space having been formed, the
tracks of the antenna do not risk being damaged during a later
stage when the cavity for the micromodule is machined, and the
positioning tolerances are greatly increased.
[0045] FIG. 2 shows a sectional view along A-A of FIG. 1 and shows
the insulating bridge 13 of the antenna 11. This insulating bridge
13 is produced by covering the turns of antenna 11 with an
insulating layer 14 in a zone Z, then by depositing a conductive
element 15 on this insulating layer 14, the conductive element 15
allowing the end of one turn, and in particular the end of the last
turn situated the furthest towards the outside of the support sheet
10, to be connected to one of the connection pads 12 of the
antenna.
[0046] According to another method of production, illustrated in
FIGS. 3 and 4, the antenna 11 is formed on each side of the support
sheet 10. In this case, connecting paths (metallic holes) 16, 17
are formed in the support sheet. The connection pads 12 of the
antenna are formed on one face. The insulating bridge 13 is
therefore produced by means of metallic holes to provide the
connection between the antenna filaments located on each side of
the support sheet 12 [sic], as shown schematically by broken lines
in FIGS. 3 and 4.
[0047] The insulating bridge 13 thus allows the turns of the
antenna to cross without directly overlapping and therefore without
causing short-circuits.
[0048] After having produced this antenna on the support sheet 10,
of plastic material, this support sheet 10 is assembled with other
plastic sheets or foils 20, 30, 40, 50 and the sheets are bonded
together by hot or cold lamination. This assembly stage is
illustrated in FIG. 5A.
[0049] Foils 20 and 40 represent the upper and lower foils, which
may be printed, of the body of the card. Foils 30 and 50 are upper
and lower protective foils respectively, and are intended to
protect the printed foils 20 and 40.
[0050] In one variant of the realisation, it is possible to add a
sixth plastic foil and to position it just above the support sheet
10 in order to enclose antenna 11.
[0051] A later stage, illustrated in FIG. 5B, consists in machining
a cavity 61 and connection recesses 62 in an upper face of the body
of the card formed by the assembly of foils 10, 20, 30, 40 and 50.
This machining may be done, for example, in a single stage.
[0052] The machining plane of cavity 61 is situated lower than the
connection pads 12 of antenna 11. The connection recesses 62 are
situated above the connection pads 12 of the antenna and enable
these pads to be exposed.
[0053] The cavity and the connection recesses are machined by means
of a milling cutter the feed depth of which is controlled.
[0054] The last stage of the procedure, shown in FIG. 5C, then
consists in fixing an electronic module M in the cavity 61. The
module M comprises on its lower side, facing towards the inside of
the cavity, conductive pads 72 in electrical contact with
connection pads 12 of the antenna by means of a conductive linking
element 66 located in the connection recesses 62. The way in which
the connection between the module and the antenna is established is
explained in more detail in what follows.
[0055] A procedure for manufacturing a mixed smart card according
to a different method of production and illustrated in FIG. 6 can
be additionally envisaged to position the antenna precisely in
relation to the cavity of the module.
[0056] According to this other method of realisation, antenna 11 is
produced in the conventional way on a support sheet; that is, the
turns of the antenna pass between the connection pads 12. The sheet
supporting the antenna is then assembled with the other plastic
foils; then the cavity 61 and the connection recesses 62 are
machined in the upper surface of the body of the card formed by the
assembly of foils. This stage is carried out in such a way that the
machining plane of the bottom of the cavity 61 is situated above
the plane of the tracks of the antenna 11 and that the connection
recesses 62 are situated above the connection pads 12 of the
antenna, enabling them to be exposed. The electronic module M is
then fixed in the cavity and its conductive pads 72 are
electrically connected to the connection pads 12 of the antenna
through the connection recesses 62.
[0057] In all cases, the antenna 11 can be produced by incrustation
on a plastic support sheet. The incrustation is carried out in a
known manner by an ultrasound process.
[0058] Moreover, to minimise the stresses on the interconnection,
especially during testing of the cards by bending or twisting, the
invention proposes that the antenna be located on the elastic
neutral axis of the card. Thus, it is envisaged that the sheet 10
supporting the antenna be located so as to form the neutral axis of
the card. The neutral axis of a card is defined as being located at
the centre of the thickness of the card.
[0059] In addition, in one variant of the procedure according to
the invention it is possible to carry out the machining in such a
way that the connection recesses pass through the connection pads
12 of the antenna. In this case, the electronic module is connected
laterally, that is, through the cut edges of the connection pads,
by applying a conductive connecting element to the connection
recesses and to the lateral edges of the connection pads.
[0060] In general, the contact surface of the connection pads of
the antenna is small, since it is of the same order of magnitude as
the width of the conductive filament used to form the antenna (that
is, some ten[s of] .mu.m). As a result, the interconnection with
the electronic module is difficult to carry out since it requires a
high degree of precision. It is therefore preferable to produce the
connection pads 12 such that they present a zigzag pattern in order
to increase their contact surface. This zigzag pattern is produced
by twists in the antenna filament (see FIGS. 1, 3, 4).
[0061] The module M can be a single-sided printed circuit module or
a double-sided printed circuit module, and in the latter case it
can have two possible configurations, to which this description
will return later.
[0062] A module M is shown in FIGS. 5 and 6 above the cavity 61. In
these examples it is a double-sided printed circuit module
comprising upper conductors 70 on the side which will face towards
the outside of the cavity and lower conductors 72 on the side which
will face towards the inside of the cavity. The conductors are
formed on an insulating foil 80 and conductive paths which can link
the upper conductors 70 and the lower conductors 72 [are provided].
A microchip embedded in a protective resin 74 is mounted on the
lower face and connected to conductors 72 (and through them to
conductors 70).
[0063] The module fits into the cavity 61 which has been machined
to its dimensions. Two conductive pads of the lower face of the
module, located just above the connection pads 12 of the antenna,
are connected electrically to these two connection pads by a
conductive linking element 66.
[0064] In one particularly interesting variant of the realisation,
the module consists of a double-sided printed circuit carrying the
integrated-circuit microchip, but this double-sided circuit is
formed without a conductive path between the conductors on the two
faces, making it less costly. In this case, the double-sided
circuit comprises an insulating foil 80 carrying on one face a
first set of conductive pads 70 intended to serve as access
contacts to the smart card and on the other face a second set of
conductive pads 72 intended to be connected to the antenna.
Connecting filaments are soldered between the microchip and the
first conductive pads through open zones of the insulating foil and
other linking filaments are soldered between the microchip and the
second set of conductive pads without passing through the
insulating foil.
[0065] The definition of a single-sided module for a mixed card
consists in finding the position of the contacts for the antenna,
which presents the following difficulties: [0066] the contact zones
defined by ISO and AFNOR standards cannot receive the contacts of
the antenna since this can cause short-circuiting of the reader,
[0067] on the assembly side, the resin protecting the microchip and
the bonding resin eliminates the central zone of the module, [0068]
the performance of the card with regard to resistance to bending
necessitates the presence of a preferential deformation line
without producing zones of embrittlement of the metal on the
contact side.
[0069] FIG. 7A shows schematically a top view of the flush contacts
of a smart card with a single-sided module which responds to these
problems. The module comprises contact pads 1, 2, 3, 4, 5 and 1',
2', 3' 4' and 5', the positions of which are standardised by ISO
and AFNOR standards. These contact pads are connected to the
microchip to enable the module to operate. The position of the
contact zones to be used to connect the module to the antenna can
only be situated in the upper zones 6 and 7 and the lower zones 8
and 9 on either side of an axis 65 of the module, that is, outside
the contact zones defined by the ISO standard.
[0070] In these conditions, therefore, the positions of the
connection pads of the antenna and of the connection recesses in
the body of the card are limited by the standardised position of
the contact zones of the electronic module and by the position of
this module in the body of the card, which is itself defined by the
ISO standards.
[0071] FIG. 7B illustrates the case in which the connection
recesses 62, and therefore the corresponding connection pads, are
situated side-by-side and on each side of the mid-perpendicular 65
of the cavity 61. This case corresponds to the case in which the
contact zones 6 and 7 of the module in FIG. 7A are electrically
connected to the connection pads of the antenna.
[0072] Furthermore, the use of a double-sided module must also be
able to overcome the disadvantages mentioned with regard to the
single-sided module.
[0073] The contacts illustrated in FIGS. 7C and 7D provide a
solution to these problems. In particular, the presence of two
tracks 100, 101 on either side of the circuit allows different
configurations of microchips to be connected to the same
module.
[0074] These two methods of producing the contacts for the
double-sided module comprise at least one track with its edge
parallel to the microchip, connected to contact zones 110 and 120.
These zones 110 and 120 represent the possible contact zones with
the antenna.
[0075] FIG. 7E illustrates the case in which the connection
recesses 62, and therefore the connection pads of the antenna, are
diametrically opposite each other and situated on a
mid-perpendicular 65 of the cavity. This case corresponds to that
in which the contact zones 110 and 120 of the module in FIG. 7C are
electrically connected to the connection pads of the antenna.
[0076] FIGS. 7B and 7E illustrate connection recesses formed
continuously with the cavity, giving them the special shape shown
in the diagrams. Of course, these recesses could be formed
non-continuously with the cavity and appear as holes of any shape
provided that their positioning is as defined previously.
[0077] The interconnection between the electronic module and the
antenna may be made with the aid of a conductive linking element of
the type of solder. However, in general the remelt temperature of
these products is very high, in the region of 180.degree. C. These
temperatures are incompatible with the plastic materials used to
form the body of the card, which cannot withstand temperatures much
above 100.degree. C.
[0078] The invention proposes that a solder with low melting point
be used to ensure good compatibility with the card body. For this,
it is preferable to use a solder comprising an alloy with a basis
of indium and tin, or with a basis of bismuth, tin and lead, or a
basis of bismuth, tin and indium.
[0079] In the case of an alloy of indium and tin, the solder
comprises not more than 52% by weight of indium and 48% by weight
of tin. With this composition the melting point of the solder is
118.degree. C.
[0080] In the case of an alloy of bismuth, tin and lead, the solder
comprises not more than 46% by weight of bismuth and 34% by weight
of tin and 20% by weight of lead. With this composition the melting
point of the solder is 100.degree. C.
[0081] In the case of an alloy of bismuth, indium and tin, the
solder comprises not more than 57% by weight of bismuth, 26% by
weight of indium and 17% by weight of tin. With this composition
the melting point of the solder is 79.degree. C.
[0082] Another method of producing the interconnection consists in
depositing conductive grease charged with metallic particles in the
connection recesses. Contact is then made by friction and ensures
electrical conduction between the antenna and the module, and does
so regardless of the mechanical stresses applied to the card.
[0083] A third method of producing the interconnection consists in
using a silicon gasket charged with metallic particles. This
solution has the advantage of providing a very supple connecting
joint. In this case, the dimensions of the silicone gasket are
greater than the depth of the connection recesses so that the
silicon is compressed and the metallic particles are brought into
contact.
[0084] Regardless of which solution is adopted, the reliability of
the interconnection between the antenna and the module can be
increased by using balls of gold deposited on the conductive pads
72 of the module. These balls of gold do not provide the connection
but increase the bonding surface and modify the distribution of
stresses in the conductive joint when the card is subjected to
mechanical loads. These balls are deposited by thermo-compression.
Moreover, they can be stacked in order to increase the height of
the contact surface.
* * * * *