Manufacturing method for an integrated circuit card

The electronic card comprises an electrically insulating card support provided with a cavity for accommodating an integrated circuit and, on one surface, with metal contact pads which are electrically connected to contacts of the integrated circuit. The invention comprises the steps of: (i) the application by an MID technique (Moulded Interconnection Devices) of electrical conductor tracks, all arranged on the bottom and the lateral walls of the cavity, and each connected to one of the metal contact pads arranged on the surface of the support which comprises the cavity, (ii) the realization of electrical connections connecting the contacts of the integrated circuit arranged in the cavity to the conductor tracks on the bottom of the cavity, and (iii) filling up of the cavity with a protective resin which is subsequently polymerized.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a manufacturing and assembling method for an 
electronic card comprising an electrically insulating card support 
provided with a cavity for accommodating an integrated circuit and, on one 
surface, metal contact pads electrically connected to contacts of said 
integrated circuit. 
The invention also relates to the electronic card obtained by this method. 
The integrated circuit (or chip) inserted in the cavity of the support may 
be an electronic memory or a microprocessor of greater surface area than 
the simple memory. 
2. Discussion of the Related Art 
The methods used at present for realising electronic chip cards use a 
printed circuit which is deposited on a support foil, generally made of 
epoxy glass, polyimide, or polyester, as described, for example, in 
European Patent EP 0 201 952 B1 in the name of the present Applicant (PHF 
85.533). The use of a moulded grid is also known. The support foil or grid 
carries the external metal contact pads of the card on one of its 
surfaces, the other surface serves as a support for the electronic chip 
which is electrically connected to the external contacts through the foil 
or grid. The material of the support foil and the material used for 
moulding the grids are insulating materials so as to insulate the external 
contacts and the internal connections of the electronic chip from one 
another electrically. 
The assembly of the chip card accordingly comprises the following steps: 
gluing of the integrated circuit (the chip) on the internal surface of the 
foil or` grid, 
realisation of electrical connections connecting the chip contacts to 
external metal contact pads (by means of conductive wires), 
protecting the chip and the connections by means of a protective resin. 
cutting off the electronic module thus formed so as to detach it from the 
support foil or grid, 
insertion and gluing of the module in a card support of synthetic resin 
material (usually PVC, ABS, or polycarbonate) in which an accommodation 
space (cavity) has previously been realised for accommodating said module 
with its side which supports the integrated circuit (the chip). This 
cavity may be realised by moulding, injection-moulding, or by spot-facing. 
With these methods, the operation of protecting the electronic chip and the 
connections is often a delicate one because the thickness of this 
protection must be perfectly controlled for rendering possible the 
insertion into the cavity of the card support which has a depth of no more 
than 650 .mu.m. 
The insertion of the electronic module into the card is also delicate and 
demands very narrow tolerances as to the planeness and lateral position so 
as to avoid practical problems with the use of card readers, or with the 
accommodation in the cavity. 
On the other hand, the gluing of the electronic module must be very 
effective so as to comply with torsion and bending test requirements. 
Finally, these methods necessitate the use of a foil or grid which 
contribute considerably to the final cost of the product. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to reduce the number of process 
steps in the manufacture and assembly of an integrated circuit card. 
It is another object to dispense with the manufacture of an intermediate 
module formed by a foil or grid supporting the external metal contact pads 
of the card on one surface and the integrated circuit on the other 
surface. 
Yet another object is to do away with the mechanical positioning 
constraints for the external metal contact pads on the card. 
These objects are achieved and the disadvantages mentioned above of the 
prior art are attenuated or suppressed thanks to the fact that the method 
described in the opening paragraph is characterized in that it comprises 
the following steps: 
the application of electrical conductor tracks by an MID (Moulded 
Interconnection Devices) technique, all provided against the bottom and 
the lateral walls of said cavity and each connected to one of said metal 
contact pads arranged on the surface of the support which comprises said 
cavity, 
the realisation of electrical connections interconnecting the contacts of 
the integrated circuit positioned in the cavity and said conductor tracks 
at the bottom of the cavity, 
filling up of said cavity with a protective resin which is subsequently 
polymerized. 
The encapsulation of the integrated circuit in a flexible card, which is 
standardized as to its size and the position of its metal contact pads, is 
thus obtained by a sequence of a reduced number of comparatively simple 
operations. 
In a preferred embodiment of the method, the step of applying the 
electrical conductor tracks consists in the application of a catalyst by 
pad printing in accordance with the configuration desired for the tracks, 
followed by a metallization through autocatalysis. Preferably, the card 
support is realised with its cavity by an injection-moulding technique, 
and it may comprise elevations at the bottom of the cavity in locations 
designed for the ends of the conductor tracks. 
For placing the integrated circuit in the cavity, it is possible to glue 
said circuit with its base against the bottom of the cavity, after which a 
conductor wire is soldered between each contact of the integrated circuit 
and an end of a conductor track so as to realise the electrical 
connections. 
Preferred methods for realising this, however, utilize the flip-chip 
mounting technique: in a first modification, which is known per se, the 
connections are realised with solder or with conductive glue in given 
locations, at the areas of the contacts, and for this purpose the contacts 
of the integrated circuit are provided with conductive elevations, as are 
usually the ends of the opposing conductor tracks. 
A preferred embodiment uses a flip-chip mounting technique for establishing 
the electrical connections of the integrated circuit, which connections 
are realised by gluing in combination with pressure by means of an 
anisotropically electrically conductive glue in the form of a pre-shaped 
foil or a paste, in which case the contacts of the integrated circuit are 
without elevations. 
In this modification, it is advantageous for the anisotropic glue to be 
prepolymerized before the step in which the electrical connections are 
made, and for its final polymerization to be effected simultaneously with 
that of said protective resin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 show the active portions of an integrated circuit card where 
the metal contact pads designed to cooperate with the probes of a card 
reader are present. The card support 1 comprises these pads 2, which have 
standardized dimensions and positions, on an upper surface 3 of the card. 
The metal pads, at least some of them, are electrically connected to 
contacts of an integrated circuit (or chip) 4 which is present within the 
thickness of the body or card support 1. 
To carry out the method according to the invention, the support I comprises 
a cavity 5, which has lateral walls which are, for example, oblique as 
shown with 6, and whose bottom 7 is designed to accommodate the integrated 
circuit chip 4, and conductor tracks 8 (also called metallization lines) 
which form an electrical continuity with the pads 2 and extend from the 
surface 3 of the card body to the bottom 7 of the cavity where their 
respective free ends 9 are arranged, passing over the lateral walls of the 
cavity 5, which they traverse. The cavity 5 must have a depth smaller than 
650 .mu.m in order to leave a sufficient synthetic resin thickness at the 
bottom of the card for avoiding a fracture of said bottom of the card and 
for protecting the electronic chip. Various processes may be used for 
fixing the tracks 8, substantially made of copper, on the support 1 which 
is preferably realised with its cavity 5 by injection-moulding from a 
thermoplastic material such as ABS or polycarbonate. Some of these 
preferred processes will be described further below. It is also possible 
to choose from several processes for realising the electrical connections 
between the contacts of the integrated circuit arranged in the cavity and 
said conductor tracks at the bottom of the cavity. A conventional method, 
shown in FIG. 1, consists in mounting of the integrated circuit 4 to the 
bottom of the cavity 5 by means of a layer of polymerizable glue 11 at its 
base, usually an epoxy glue, and subsequently soldering conductor wires 
12, for example made of gold or aluminium, between the contacts of the 
integrated circuit 4 and the ends 9 of the conductor tracks. Various 
mounting and wire bonding processes for the integrated circuit are known 
to those skilled in the art and are described in numerous publications, 
among which may be cited the Patents FR 2 439 438, FR 2 548 857, EP 0 116 
148, FR 2 520 541. In such a mounting method, when the nickelled base of 
the integrated circuit forms the ground (earth) terminal, it is so 
arranged that an end of a track occupies the central portion of the bottom 
of the cavity (not shown in FIG. 1) and that this metallized base is glued 
thereon by means of a conductive glue, for example a glue filled with 
silver to 70% of its volume. The gluing operation may be carried out with 
standard glues and equipment used in the semiconductor industry (types KS, 
ESSEC, or other). The mounting method shown in FIG. 1 is that in which the 
integrated circuit has all its contacts, including the ground contact, on 
one and the same surface (the upper surface in FIG. 1). 
Gold or aluminium wires may be used for the interconnection by soldering of 
conductor wires, although the gold wire may be preferred for reasons of 
speed (the thermosonic process used for soldering gold wires is 3 to 4 
times quicker than the soldering of aluminium wires). This operation is 
the most delicate of the assembling method because it renders necessary a 
pre-heating of the synthetic resin support. Since it is undesirable that 
this preheating should exceed the glass transition temperature Tg of the 
synthetic resin support (deformation risk), it is preferable to use cards 
made of materials having a high Tg value (polycarbonate, ABS, ABS-PVC 
compounds or ABS-polycarbonate compounds). 
After mounting and gluing of the chip, the operation of filling the cavity 
5 may be carded out by a simple potting process which consists in the 
deposition of a drop of resin 13 in the cavity 5. To obtain a plane 
external surface, resins of very low viscosity are preferably used, such 
as, for example, the resin with reference number 931-1 from the American 
ABLESTICK Company. This resin must have a high ion purity and have a good 
resistance to water absorption in order to protect the electronic chip 
effectively during climatic tests. After its application in the cavity the 
resin is polymerized, which forms the final step in the manufacturing and 
assembling method according to the invention. 
Preferred methods of applying conductor tracks 8 on the support 1 on a 
non-planar 3-dimensional surface are: 
hot foil embossing of a configuration of gluable tracks, 
pad printing followed by metallization through autocatalysis, 
lithography based on laser holograms. 
Of these three methods, the first two are comparatively well known and 
proven, comparatively economical, but they do not render possible a high 
resolution in the realisation of the tracks. Where a high resolution is 
required, the third method may be used as it is more accurate. 
The pad printing and lithographic techniques are compatible with the 
creation of elevations on the ends 9 of the conductor tracks provided on 
the bottom of the cavity during injection-moulding of the support 1. 
The contents of Patent EP 0 063 347 may be cited by way of example of the 
hot foil embossing (or stamping) method. A metal track configuration of 12 
to 70 .mu.m thickness may be provided against the card support with a 
thermal cycle of a duration of the order of 2 s at the area of the cavity 
5 of which the shape is designed for this purpose, i.e. preferably with 
inclined walls, the application pressure being of the order of 80 
N/mm.sup.2 and the temperature of the order of 200.degree. C. For this 
purpose, the foils for hot embossing which comprise the track 
configurations have the structure shown in FIG. 3: one or several layers 
of glue which can be reactivated by heat 31 (usually a phenol-based glue), 
having a thickness of 1 to 4 .mu.m, a layer of copper 32, comparatively 
ductile, with a thickness lying between 12 and 35 .mu.m, and possibly a 
tin or nickel layer 33 of a few .mu.m thickness. The portion of the foil 
which is not embossed may subsequently be removed by means of a roller 
station with an adhesive tape. 
In the pad printing process, with a cycle duration of 2 s, a lacquer 
containing palladium may be imprinted on the card support 1, against the 
walls and the bottom of the cavity 5, and around the latter on the surface 
3 in accordance with the pattern required for the metal track 
configuration to be created in that location. The printing quality is good 
because it is possible here to obtain an accuracy of the order of 50 .mu.m 
for the conductor track width and for the interspacings between tracks. 
The lacquer containing Pd, which forms a catalyst and which is deposited on 
the support 1 in suitable locations, is subsequently heated to 100.degree. 
C. Then a metallization (copper or nickel) is achieved by autocatalysis, 
the latter operation having been known and tested for a long time: the 
copper (nickel) is deposited on the support 1 exclusively in locations 
where the catalyst is present. The copper thickness deposited lies between 
1 and 10 .mu.m. The main advantage of this electrochemical metallization 
process is that several thousands to several tens of thousands of cards 
may be treated simultaneously, immersed together in the same bath, in the 
space of a few hours. 
If a higher accuracy is necessary for the pattern of conductor tracks in 
the cavity 5, it is possible to use a photolithographical process, which 
is more expensive than the preceding ones. This technique involves the 
transposition of the conventional photolithographical technique for 
metallizing plane surfaces to the metallization of skew surfaces, in this 
case the walls and the bottom of the cavity 5 and its immediate 
surroundings on the surface 3 of the support. For this purpose, a focusing 
technique through 3D masks or a laser hologram has been developed, which 
involves the realisation of the image of tracks in three dimensions on a 
surface which coincides with that of the cavity, which renders it possible 
to obtain the polymerization of a varnish exclusively in regions on the 
surface of the cavity where this is wanted. 
For example, a semi-additive process may be used for realising the tracks. 
This process, which is at present used in the main developed countries, 
comprises a treatment of the synthetic resin support for improving the 
adhesion of a deposited metal, preferably copper, on which subsequently 
electrical contact layers are made to grow with the use of a photoresist 
mask. After exposure, the mask and the layers around the contacts are 
eliminated. This process thus renders possible metallizations on 
non-planar supports through the use of 3D masks or laser techniques 
(generation of holograms), and provides a resolution of the order of 50 
.mu.m. With the various metallization processes mentioned above, the 
electrical contacts are no longer supported by a foil or grid, as in the 
prior art, but by the card support itself. In addition, the operations for 
providing through-holes through an insulating material for establishing 
the contacts are no longer necessary. 
Besides the conventional mounting technique shown in FIG. 1, where the 
ground contact is arranged on the same surface of the integrated circuit 
as the other contacts, which is increasingly the case, a preferred 
technique as described below is that of flip-chip mounting. For this 
purpose, the ends 9 of the conductor tracks 8 may comprise elevations 
whose configuration is symmetrical (relative to a plane) with that of the 
chip contacts with which they are to cooperate. Such elevations, 
diagrammatically indicated in FIGS. 4A and 4B, are preferably realised 
during moulding of the card support 1: their shape may be cylindrical as 
at 41, FIG. 4A, or have the shape of a spherical bulge 42, FIG. 4B, while 
the height is a few tens of .mu.m. The metallization of the elevations 41 
or 42 may be effected simultaneously with that of the tracks 8 by the pad 
printing or lithographical processes described above. 
According to known, conventional flip-chip mounting processes, the contacts 
of the integrated circuit, made of aluminium, must be provided with 
elevations before mounting, which elevations are made of gold or copper 
through electroplating (which implies a delicate positioning operation of 
the integrated circuit after its manufacture) or by soldering of gold 
bumps by means of a conventional thermosonic gold soldering unit. Several 
processes are available for mounting, which involves the fixed 
interconnection two-by-two of the elevations of the chip and those of the 
conductor tracks so that a good electrical contact is established: quick 
heating of the chip in combination with pressure, which results in each 
pair of elevations being brazed together; or alternatively the application 
of a pressure in combination with ultrasonic vibration at 60 kHz induced 
by the press which supports the chip (known since a long time for 
soldering conductor wires). A third connection process uses a conductive 
glue, for example an epoxy glue charged with 70% silver, previously 
deposited in the form of calibrated droplets exactly on the elevations at 
the ends of the conductor tracks, or on the elevations of the component 
through immersion of said elevations in a glue reservoir. These 
conventional techniques have not been depicted or described so as to keep 
the description brief. They are described, in particular, in the Patent 
Applications WO 92/13319 and WO 92/13320. An insulating glue may also be 
used, which means that the deposition need not be carried out exactly on 
the metal elevations provided on the metallization pads of the component. 
In that case, a drop of insulating glue is deposited on the bottom of the 
cavity before the component is provided. During the prepolymerization of 
the glue it is necessary to apply a pressure on the component for 
obtaining a good ohmic contact. 
A preferred flip-chip mounting technique is shown in FIG. 5, though this is 
more critical than those indicated in the previous paragraph. Here the 
operation of providing elevations on the contacts of the chip may be 
dispensed with. The ends of the conductor tracks 9 on the bottom 7 of the 
cavity 5 may preferably still comprise elevations, which are preferably of 
cylindrical shape (41, FIG. 4A). 
The glue used is a special anisotropically electrically conductive glue 
which is already used for surface mounting of passive components in 
particular. This type of glue contains conductive particles in a low 
concentration. These particles, which are elastically deformable and have 
a diameter of the order of 10 to 20 .mu.m, provide electrical conduction 
when they are compressed between two contacts, whereas the glue remains 
insulating in locations where there are no contacts. Square metallizations 
with sides of 100 .mu.m, interspaced by 100 .mu.m, are compatible with the 
use of these glues as far as the conduction aspect is concerned (particle 
density present over the metallization at the moment of gluing--there must 
in fact be several particles present rather than a single one, which would 
theoretically be sufficient, for achieving a good contact--), while the 
risk of short-circuits between conductor tracks is excluded. These glues 
are at present available in the form of a foil (manufactured by the 
American 3M Company or the Japanese HITACHI Company) or in the form of a 
paste (manufactured by the American AIT and ZYMET Companies or the German 
LCD Mikroelektronic Company). UV-curing versions are also available. To 
implement the invention, the anisotropic glue in paste form is preferred 
to that in foil form. It will be noted that a compromise is to be found 
between the establishment of a good electrical conduction at the level of 
each contact of the chip and the absence of short-circuits caused by 
agglomerations of particles between tracks when this contacting technique 
is used. With the dimensioning of the contacts as an equal constraint, 
this compromise is easier to achieve in proportion as it is possible to 
increase the concentration of particles while decreasing their size. It is 
necessary, however, for rendering possible this smaller size, to achieve a 
good planeness of the set of track ends on the bottom 7 of the cavity 
(while that of the contacts of the integrated circuit is achieved 
otherwise). Another element which favours the absence of short-circuits 
between tracks is the accuracy which can be obtained in the configuration 
of the track ends and in the correct positioning of the integrated circuit 
during gluing: a good accuracy in these two respects renders it possible 
to make the ends of the tracks narrower and thus to increase the 
interspacings between tracks, which reduces the probability of 
short-circuits. 
FIG. 5 shows in detail the connections made with anisotropic glue. The 
integrated circuit 4 is shown with its contacts 51 and a surface 
passivating layer 52 between contacts; the bottom 7 of the cavity in the 
card support 1 is provided with track ends 9 which in this case do not 
comprise elevations. In the gluing process combined with a certain 
pressure, conductive particles such as 55 have become trapped in the glue 
56 and subsequently compressed between pairs of contacts 9 and 51. Other 
particles, such as 57, are situated outside the contacts and do not take 
part in any electrical conduction. During the gluing operation, the 
integrated circuit has been prepositioned so as to have its metallization 
pads (contacts) substantially aligned with the track ends (with or without 
elevations). A drop of anisotropic glue was deposited on the bottom of the 
cavity, and subsequently the integrated circuit was laid down and pressed 
onto the glue. The polymerization of the glue was subsequently effected, 
either by means of an oven or by means of a UV system (in the case of 
UV-curing resins). 
As described above with reference to FIG. 1, the cavity 5 is subsequently 
filled up (not shown) in a simple potting operation. The simplicity of 
this operation renders possible the use of a system which fills several 
cavities at a time, thus leading to high manufacturing capacities per 
equipment unit. The resin used is preferably a resin of high ion purity 
which offers a good resistance to the absorption of humidity and 
effectively protects the integrated circuit chip during bending and 
torsion of the card. 
It is to be noted that the use of a glue for gluing the chip and of a 
protective resin which are mutually compatible and have the same 
polymerization modes (thermal or UV) renders it possible to carry out the 
gluing operation for the chip and the filling operation for the cavity 
with the same equipment. The sequence of operations then is the following: 
gluing of the chip, 
filling of the cavity by means of a resin dispenser mounted on the gluing 
equipment loader, 
simultaneous polymerization of the glue of the integrated circuit and of 
the enveloping resin. In this case, it is indeed recommended to 
prepolymerize the anisotropic glue before its application on the bottom of 
the cavity. In this case, a single piece of equipment is capable of 
realising the entire assembling operation.