Integrated circuit micromodule obtained by the continuous assembly of patterned strips

A micromodule includes a slotted metal strip and a perforated dielectric strip having a thickness of less than 70 micrometers, preferably between 30 and 50 micrometers. The metal strip is bonded to the dielectric strip so as to overlie the slots in the metal strip. A chip is bonded to the dielectric strip and connected to the metal strip through the perforations in the dielectric strip. An insulating resin layer encapsulates the chip and is bonded to the dielectric strip. The micromodule may be used, for example, in a smart card, as a radiating antenna, or as an identification label.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an integrated circuit micromodule obtained 
by the continuous assembly of patterned strips. Such micromodules go into 
the production of the portable flat cards known as "chip cards." In these 
cards, the micromodules are formed by a set of elements comprising: a chip 
in integrated circuit form, metal contacts used for the connection of the 
micromodule with external devices, linking wires to link the chip to the 
metal contacts, and a protective coat formed by a resin covering the chip, 
the linking wires and, partially, the metal contacts. 
2. Discussion of the Related Art 
To manufacture a micromodule and then incorporate it into a card, a first 
known method consists in mounting the chip on a metal strip that has been 
pre-slotted in the form of a conductor grid, soldering the chip to a zone 
of this grid where it is connected by wires soldered to other zones of the 
grid, coating the chip and the wires with a drop of protective resin of 
the epoxy or silicone type in leaving the conductors of the grid partially 
bared, cutting up the metal strip into individual micromodules, each 
comprising a coated chip and bared external contacts, and then bonding the 
micromodule to a surface cavity of a card made of plastic material in such 
a way that grid portions not coated with resin are flush with the surface 
of the card and constitute the external connector of the card. 
According to a second method which is also known, the initial pre-cut metal 
strip is replaced with a metallized dielectric strip etched with a 
connection pattern to be determined. The dielectric strip, in this case, 
forms the main support of the chip. The connections have a very small 
thickness and are obtained by the pre-deposition of a metal layer on the 
photo-etching plastic strip of this metal layer. The chip is connected by 
soldered wires to zones of the metallized layer. 
These methods have a certain number of drawbacks. In the case of the use of 
a pre-cut metal strip, the encapsulation resin of the micromodule adheres 
poorly to the conductors of the grid, all the more so as, in practice, the 
resin is on only one side of the strip, the other side being reserved to 
leave the conductors accessible to act as connectors. The result thereof 
is a problem of reliability that is difficult to resolve, caused chiefly 
by the passage of moisture between the resin and conductors. 
In the case of the use of a metallized and photo-etched dielectric strip, 
the strip must necessarily be made of a sufficiently rigid material, and 
must stand up well to temperature so as not to warp when the temperature 
rises, which makes it necessary for the definition of the conduction 
pattern to be executed only by photo-etching on the dielectric strip and 
makes this second method far costlier than a mechanical cutting-out 
operation, for example. 
A third method is known through the European patent application published 
under No. 0 296 511 and filed under No. 88 1097420 on 18th Jun. 1988. This 
patent application relates to a method for the manufacture of a ribbon 
designed to provide modules to equip electronic cards, also called "smart 
cards." However, the approach proposed in this patent application is not 
satisfactory. 
Indeed, this method entails taking a metal strip with a thickness that is 
typically equal to 75 micrometers but may vary between 50 micrometers and 
150 micrometers. This strip is provided with (1) perforations enabling it 
to be carried along and (2) apertures obtained by stamping that demarcate 
the arrays of conductors of the circuits. A set of 125-micrometer-thick 
insulating foils having, on one face, a thermoplastic or thermosetting 
material for hot bonding, is also taken. The foils have a set of holes 
with an arrangement that corresponds to the location of the connections 
and a central hole for the location of the circuit. 
The foils are bonded to the metal strip by heating. The heating prompts a 
certain shrinkage of the insulator material which makes it difficult to 
use bigger foils, especially in the longitudinal direction. With cold 
bonding, this problem would not arise. However, the adhesion to the metal 
during cold bonding is poor. 
Furthermore, it is imperatively necessary to make a perforation in each 
insulator foil at the position reserved for the circuit in order to house 
the circuit therein and thus keep within the requisite tolerances as 
regards thickness for the manufacture of the chip cards. 
Reference could also be made, as part of the prior art, to the document GB 
2031796 A which describes a device for the assembling of an adhesive 
insulator strip to a conductive strip. In the device described, the 
adjusting of the tension is done only on the insulator strip by modifying 
the rotational speed of the wheels between which this strip passes. A 
device such as this does not enable the use of very thin (30 to 50 .mu.m) 
insulator strips as is made possible by the invention. 
OBJECTS AND SUMMARY OF THE INVENTION 
The present invention makes it possible to overcome these problems. Its 
object is to provide an integrated circuit micromodule comprising a 
pre-slotted metal grid, a perforated dielectric strip with a thickness of 
less than 70 micrometers, a chip (1) bonded either to this dielectric 
strip or to the metal strip through a perforation of the dielectric strip 
and (2) connected to the metal strip through other perforations of the 
dielectric strip. 
Another object of the present invention is to provide an integrated circuit 
module in which the dielectric strip covering the grid constitutes the 
dielectric of an electromagnetic transmission or reception antenna, the 
pre-slotted grid of which constitutes an active part. 
The dielectric strip, may, for example, constitute the dielectric of an 
electromagnetic antenna, the pre-slotted metal strip of which constitutes 
an active part. Alternatively, the dielectric strip may constitute an 
identification label.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The pre-slotted metal strip 10 which is shown in FIG. 1 is formed by a 
strip of copper or tinned copper with a thickness of about 35 to 70 
micrometers. Its width is defined to correspond to the final connection 
width to be obtained, and may be of the order of one centimeter to several 
centimeters. The strip 10 is slotted with a repetitive pattern of slots 
102 which, as the case may be, is done by stamping to define the separate 
contacts 3 used as connection pins between the interior and the exterior 
of the micromodule to be assembled on the strip. 
In the representation shown in FIG. 1, which is given by way of an example, 
the pattern of slots 102 is the one that enables the connection of a 
micromodule for flat chip cards, the contacts 3 shown being eight in 
number. The eight separate contacts 3 can be seen inside a closed line 4. 
These contacts are separated by cutting lines 5 that cut out the patterns 
2. Outside the lines 4, the contacts 3 are joined to ensure the continuity 
of the strip 10 from one micromodule to another. 
The strip 10 comprises regular perforations 6 distributed along the 
longitudinal edges of the strip on one or both of its sides. These 
perforations are used to carry the strip along by a toothed wheel system. 
The slotted metal strip 10 forms the main support of the chips constituting 
the core of the micromodules. This strip 10 is covered with a dielectric 
strip 11 of the type shown in FIG. 2, comprising pre-cut perforations 
(P.sub.1 -P.sub.8) designed to come before conductive zones 3 of the 
conductive pattern cut out of the metal strip 10. An indexing hole (I) 
serves as a reference mark and enables the precise positioning of the 
perforations (P.sub.1 -P.sub.8) facing the conductive zones 3 during the 
operation for the hot bonding of the two strips to each other. 
As indicated in FIG. 3, the indexing hole is located, when the bonding 
operation is terminated, at the intersection of the two bonding axes, 
respectively, the horizontal axis X and the vertical axis Y formed by the 
cutting lines 5. This positioning is done by the strip assembling device 
shown in FIG. 4 
This device comprises a press 7 comprising two plates or, possibly, two 
juxtaposed rollers 8 and 9, between which there move patterned strips 10 
and 11 that have to be assembled by bonding. In FIG. 4, the upper plate or 
roller 8 is heated up to a bonding temperature of about 200.degree. C. by 
an electrical resistor R supplied by an external electrical current supply 
device (not shown). The lower plate 9 is cooled by a water circulation 
circuit 12 going through a heat pump type of temperature exchanger 13 or 
any other equivalent device activated by a pump 14. The strips 10 and 11, 
once bonded, are carried along in a translation motion between the two 
plates or rollers 8 and 9 by a sprocket wheel 15, the teeth of which 
engage in the perforations 6 of the support strip or cross-motion clamp 
system. The sprocket wheel 15 is moved by a motor 16. The strips 10 and 11 
are paid out, respectively, from two loading rollers 17 and 18. Indeed, in 
order to obtain a continuous assembly of the strips 10 and 11, these 
strips are each mounted on an unwinder and moved by a motor (not shown). 
The strip 10 is mounted on the roller 17 while the strip 11 is mounted on 
the roller 18. The strip 10 is wound on itself with an interposed strip 41 
that falls away when the strip 10 unwinds. This interposed strip 41 
prevents the patterns from getting imbricated with one another. The strip 
11 is also wound on itself. An intercalary strip 51 may be planned too, to 
prevent problems during the unwinding of the strip 11. 
The traction of the supporting strip 10 is adjusted by a pressure wheel 19 
on a beam 20 of the supporting strip 10. The beam 20 then retains the 
strip 10 by friction and procures the tension of this strip. The tension 
of the strip to be bonded 11 is adjusted by two pinch rollers 21 and 22 
with calibrated friction. A controller 23 provides, firstly, for the 
rotational control of the motor 16 and the pump 14 and, secondly, for that 
of the presser wheel 19. The controller 23 receives information elements 
coming, firstly, from a camera 24 by means of an image analyzer 25 and, 
secondly, a temperature sensor 26 connected to the fluid circulation 
circuit 12, as well as a device 27 formed by a tensiometer or any other 
equivalent device to measure the tension of the supporting strip 10. Thus, 
when the two strips 10 and 11 driven by the traction of the motor 16 move 
past under the rollers or between the two plates 8 and 9, the image 
analyzer 25 can permanently provide information on the offset Delta X and 
Delta Y of the reference hole or indexation hole with respect to the 
reference axes X and Y of each pattern. The value of this arrangement is 
that, through the controller 23, it enables action jointly or separately 
on the pressure exerted on the strip 10 or the strip 11, respectively, by 
(1) the presser wheel 19 in order to adjust the tension of the strip 10 or 
the strip 11 by the pinch rollers 21 and 22 and by (2) the adjusting of 
the temperatures of the two plates or pinch rollers 8 and 9 in order to 
adjust, by extension or expansion, the position of one strip with respect 
to the other one to obtain the coinciding of the pattern pitch of the two 
strips by cancelling the offsets Delta X and Delta Y of the reference hole 
with respect to the reference axes X and Y. It must be noted, however, 
that adjustment of the pitch by the simple extension of one of the two 
strips in relation to the other is valid only for the small offsets Delta 
X and/or Delta Y of the values of the pitch, and that big offsets can be 
efficiently compensated for only by an adjustment of the relative 
temperatures of the plates or rollers 8 and 9 with respect to each other. 
In practice, when an offset Delta X exceeds a predetermined threshold, the 
compensation for this offset is achieved by the controller 23 acting on 
the cooling of the plate 9. In the case of small offsets, the compensation 
is achieved by acting on the pinch rollers 19 or 21, 22. However, for the 
system to work efficiently, it is preferable to apply the strip that has 
the highest expansion coefficient to the plate or roller 9 which is 
cooled, the other strip 11 being applied to the plate or roller 8 that is 
heated. Thus, for example, for a bonding of a copper roll which has an 
expansion coefficient of 17.times.10.sup.-6 /.degree.C. on a roll of a 
plastic material, commercially available under the registered mark 
"Kapton", which has an expansion coefficient of 20.times.10.sup.-6 
/.degree.C., the Kapton should be applied to the plate or roller 9 and the 
copper to the plate or pinch roller 8. 
During the bonding operation, it should naturally be seen to it, when the 
plates/rollers 8 and 9 come under pressure, that these elements 8 and 9 
move properly solely in the direction Z normal to the plane (X, Y) of the 
two strips. The problem can be resolved easily by using either column 
presses or presses with distribution springs. However, to avoid having the 
positions, between the axes, that evolve with the temperatures, it is 
desirable, in the case of the column presses, to use steels with a low 
expansion coefficient by using, for example, steel that is commercially 
distributed under the known registered mark "Invar" for example. 
The approach using a rod-type press, a diagram of the embodiment of which 
is shown in FIG. 5, has the advantage of being easy to make and of 
providing homogeneous pressure between the two plates. As can be seen in 
FIG. 5, where the elements homologous to those of FIG. 4 are shown with 
the same references, a press comprises a lower plate 9 formed by a steel 
board 28 mounted on an insulating board 29 and an upper plate 8 formed by 
a steel board 30 comprising a hollow insulating cap 31 enclosing the head 
32 of a rod 33. The steel board 28, on its surface facing the steel board 
30, has distribution springs 34 which enable the rod head 32, the steel 
board 30 and the spring 34 to be all in contact together before the 
pressure of the two boards 28 and 30 is exerted on the two strips 10 and 
11, thus preventing any motion in the directions X and Y during the 
clamping of the two plates. 
Once the bonding is done, it can be further homogenized, possibly by a 
second press (not shown), which then has the same temperatures on both 
plates, or by two rollers similar to those already used in the prior art. 
Naturally, the method that has just been described can equally well be 
applied with the same efficiency for the indexed assembly of any material 
with identical or multiple pitch patterns. The method can also be applied 
to the bonding of any number N of strips by the interposing of N 
pre-bonding presses before the homogenization station. The usefulness then 
is that it enables the continuous production of multilayer films. 
Thus, the method according to the invention enables the manufacture of 
integrated circuit micromodules, this manufacture comprising the formation 
of a preslotted metal strip comprising notably regular perforations 
enabling the strip to be carried along by a toothed wheel (as with the 
forward feed of a cinema film), the formation of a very thin perforated 
dielectric strip; and then bonding the two strips to each other, the 
bonding of an integrated circuit chip to the thin dielectric strip, and 
the formation of electrical connections between the chip and the metal 
strip through the slots of the dielectric strip. In principle, the 
dielectric strip will be narrower than the metal strip: it will include no 
periodic lateral slots enabling it to be carried along by a toothed wheel 
and, furthermore, it will generally be too thin to be carried along by a 
toothed wheel. During the bonding of the dielectric strip to the metal 
strip, the slots enabling the metal strip to be carried along will not be 
covered by the dielectric strip owing to the smaller width of this strip. 
The other manufacturing operations may be standard ones, for example: the 
deposition of a drop of resin to coat the chip and the connections with 
the chip, on the dielectric strip side but not on the metal strip side, 
and possibly the leveling down of the drop to a determined height; the 
separation of the micromodule from the rest of the strip. The micromodule 
is then ready to be inserted into a cavity of a plastic card. 
It is furthermore observed that, by this method, it is no longer the 
dielectric strip that is used to carry the unit along during the assembly 
line manufacture of micromodules out of a continuous strip, as might have 
been the case in the prior art technique when a dielectric strip was 
provided for. The thickness of the dielectric strip 11 is far smaller than 
in the prior art, 30 to 50 micrometers instead of 100 to 200 micrometers, 
for example. This is very important, for the total thickness of the 
micromodule is a decisive factor for the possibility of making very flat 
chip cards. 
Furthermore, in view of this very small thickness, the chip may be bonded 
to either the dielectric strip 11 or to the metal strip 10. Cases where it 
is not necessary to provide for a rear face contact are indeed frequent in 
CMOS technology. When mechanical stresses are exerted on the card, the 
thin dielectric placed beneath the card plays the role of an elastic 
buffer which, in certain cases, prevents the chip from deterioration. 
During manufacture, the small thickness of the dielectric strip 11 
facilitates a very efficient bonding of the two strips to each other, 
without any risk of their getting separated during the subsequent 
treatment. 
Finally, the bonding of the chip to the dielectric makes it possible to 
provide for only one micromodule manufacturing line, whatever the 
dimension of the chip to be encapsulated, this being achieved with a 
single model of pre-slotted metal strip, the sole condition being that 
there should be provided a modifiable or detachable punching tool for the 
formation of the slots in the electrical strip; indeed, the chip is 
insulated from the metal grid, and only the location of the perforations 
in the dielectric defines the position of the connections between the chip 
and the grid. For a larger-sized chip, the perforations will be placed at 
a greater distance from the center of the chip. For a smaller chip, the 
perforations will be brought closer to the center. It is naturally 
sufficient for the perforations to remain above the appropriate metal 
zones, but these zones may be fairly wide in the case of micromodules with 
a small number of external contacts (6 or 8 for example). 
Referring to FIGS. 6 and 7, a micromodule is illustrated which is 
constructed in accordance with a preferred embodiment of the invention and 
which may be constructed via the process described above. In FIG. 6, the 
micromodule is illustrated in an intermediate stage of manufacture in 
which it comprises a slotted metal grid or strip 10 bonded to a very thin 
perforated dielectric strip 11 (the thickness of the dielectric strip 11 
preferably being smaller than 50 micrometers, more generally between 30 
and 70 micrometers), with a chip 100 bonded either to the metal strip 10 
or to the dielectric strip 11 and connected to the metal strip 10 through 
the perforations P1, P5 of the dielectric strip 11 via conductors 103. 
The chip 100 is then coated with a protective insulator 101, preferably an 
epoxy resin or a silicone resin that can be deposited in drops above the 
chip 100 (FIG. 7). 
It will be noted that, contrary to what happens in the technique using a 
slotted metal strip without a dielectric, the resin 101 cannot flow 
between the conductors 103; i.e., in the slots 102 of the metal strip 10 
since, in principle, all of these slots 102 are covered with the 
dielectric strip 11, at least in the part that will constitute the 
micromodule after the slotting of the strip 10. 
The mechanical stresses on the chip 100 are particularly low during and 
after manufacture owing to the interposition, between the metal strip 10 
and the chip 100, of a small thickness of polyamide or another dielectric 
strip 11 which behaves like a buffer of plastic or another insulating 
material. This is important when the micromodule is incorporated into a 
flat chip card for these cards are subject to very substantial twisting 
and bending stresses. 
Given that it is possible to be satisfied with a very small thickness of 
dielectric, the height of the micromodule remains limited to an acceptable 
value despite the fact that the chip lies on the dielectric. By way of an 
indication, the chip 100 may have a thickness of about 250 micrometers and 
the strips 10 and 11 a thickness of less than 70 micrometers, typically 
about 50 micrometers each. 
The encapsulation resin 101 adheres to a dielectric surface, which is 
better than if it were to adhere to a metal surface. There is no risk of 
any penetration of moisture up to the chip which is surrounded with resin 
wherever it does not touch the dielectric strip. 
When the micromodule is finished (FIG. 7) after the leveling down of the 
resin 101 to a maximum desired height, it may, if necessary, be separated 
from the rest of the strip by being cut out mechanically along the line 4 
of FIGS. 1 and 2. If it is a micromodule for chip cards whose connector is 
constituted by the accessible face of the conductors 103, the micromodule 
is placed in a cavity of the chip card, the face that bears the chip being 
pointed towards the bottom of the cavity and the conductors remaining 
accessible at the upper part. 
In one variation of the invention (cf. FIG. 8), which is especially 
promising in the case of chip cards working in microwave applications and 
designed to receive and/or send an electromagnetic radiation, it is 
possible to provide for an arrangement where the dielectric strip 11 
constitutes the dielectric of a radiating or electromagnetic antenna, of 
which the slotted metal strip or grid 10 constitutes an active part. The 
antenna is of the microstrip type constituted, for example, by conductors 
cut out in the metal strip 10 and acting as antennas instead of as 
connectors. An electrical ground plane 25 can then be provided for on the 
other side of the dielectric. This ground plane 25 can be formed either by 
means of a second metal strip 10 mechanically cut out and bonded to the 
upper face of the dielectric strip 11 before the positioning of the chips 
100 or by means of a photo-etched metallization on the upper face of the 
dielectric strip 11. Conversely, it can be provided for the ground plane 
to be beneath (formed in the metal strip 10) and the microstrip antenna 
above (formed in the metallization of a metallized dielectric strip 11, or 
formed in a second metal strip bonded to the side of the chip). 
According to one alternative embodiment, the micromodule may constitute an 
identification label. To this end, the grid 10 forms an inductor. The chip 
100 can be placed in a metal zone and can be connected to both ends of the 
inductor 90. Advantageously, a low-cost dielectric will be used, for 
example, cardboard. A micromodule such as this is shown in FIG. 9 and 
constitutes a low-cost identification label.