Improved chip card with a flip-chip module
A flexible material interposed between the flip-chip and card body cavity in smart cards addresses the issue of mechanical stress, enhancing module reliability by acting as a shock absorber during tests.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SMART PACKAGING SOLUTIONS SPS
- Filing Date
- 2025-11-28
- Publication Date
- 2026-07-02
AI Technical Summary
Flip-chip modules in smart cards are prone to damage during mechanical stress, such as the three-roller test, due to the brittle nature of thin chips and rigid card bodies, leading to potential breakage or detachment of electrical connections.
Interpose a flexible material, such as a heat-activated adhesive or specific resin, between the flip-chip and the card body cavity to act as a mechanical damper, protecting the chip during use and tests without altering conventional manufacturing processes.
The flexible material effectively cushions mechanical stress, ensuring the reliability of flip-chip modules by preventing damage during tests like the three-roller test, with minimal additional investment required.
Smart Images
Figure EP2025084798_02072026_PF_FP_ABST
Abstract
Description
[0001] Improved flip-chip module smart card
[0002] The present invention relates to a smart card provided with an electronic module comprising a microelectronic chip mounted on the module in a so-called "flip-chip" position.
[0003] STATE OF THE ART
[0004] A method for manufacturing a smart card consisting of a card body and an electronic module housed in a cavity within the card body is known from document EP 2 811 427 A1 (Gemalto). The electronic module comprises a microelectronic chip mounted on a dielectric substrate in a conventional, non-flip-chip configuration, and the electrical contacts of the chip are connected, in a well-known manner, to electrical contacts of the module by metallic wires. Furthermore, the electrical contacts of the module are connected to contact areas of an antenna on the card body by means of an anisotropic conductive adhesive. This adhesive can also extend to the gap between the cavity in the card body and the top of the module, thereby partially reducing the mechanical stresses within the smart card.
[0005] The flip-chip configuration, also known as "inverted chip," refers to a method of assembling electronic chips onto a substrate. The microelectronic chip has connection pads made of solder balls (called "bumps") and is mounted on the substrate side of the module opposite the side with the module's exposed metal contacts. Assembling the chip using the flip-chip method requires specialized equipment to precisely position the chip on the substrate. Once the chip is correctly positioned, its solder balls are heated to form a strong metallic bond between the chip and the substrate. This technology enables significant miniaturization of electronic modules for smart cards. The direct connections between the chip and the substrate make the modules less sensitive to mechanical shocks and thermal variations.
[0006] A method for mounting a microelectronic chip in a flip-chip configuration onto a smart card module is known from document EP 1 050 845 B1 (Oberthur Technologies). According to this method, a liquid encapsulating resin is dispensed into the bottom of a cavity in the card body, and the electronic module is then fixed in the cavity by causing the liquid resin to spread, filling part of the cavity and completely encapsulating the microelectronic chip, forming an air ring that acts as protection against mechanical stress.
[0007] However, despite the flip-chip design, difficulties arose in ensuring the module's reliability once assembled within the smart card. Smart card modules have indeed struggled to withstand certain reliability tests, such as the three-wheel test, which is mandatory for smart cards intended for certain card issuers, like Mastercard, Visa, etc.
[0008] The problem stems from the play between the potentially brittle chip and the fairly rigid card body. It has been observed that the chip is more brittle the thinner it is, particularly when it is less than 75 µm thick, and / or when it is larger than 3-4 mm. 2When the chip comes into contact with the bottom of the cavity during a three-roller test, or during significant board flexing that can occur during board use, damage can occur. This destructive contact can easily happen with a flip-chip mounted, unlike non-flip-chip mounted chips, which are protected by a drop of encapsulating resin. Furthermore, the electrical connection between the chip's contact pads (the "bumps") and the substrate contact area, located at the chip-substrate interface and achieved, for example, by gluing, can also be stressed and destroyed directly by mechanical forces or induced deformation. Moreover, a laminated board body is more rigid and will transmit even more stress to the chip, potentially damaging it.
[0009] If the space between the chip and the bottom of the card body cavity is insufficient, the chip will directly contact the bottom of the cavity during insertion or testing, and the chip may break. However, simply providing space between the chip surface and the bottom of the card body cavity is not necessarily enough to solve the problem. Indeed, it has been observed that if the space between the chip and the cavity bottom is large, the chip surface is exposed, and the chip can still detach due to the cleavage of the adhesive that attaches it to the module during mechanical testing. Alternatively, the fabric lining the bottom of the card body cavity may be too thin and could be dented by the roller, which could impact and break the chip or disconnect it from the module during the three-roller test.
[0010] The technical problem posed is therefore to protect the flip-chip of the electronic module during the use of the smart card or during a resistance test such as the 3-roller test, and to make the whole thing reliable once the module is fixed in the cavity of the card body.
[0011] PURPOSE OF THE INVENTION
[0012] The invention therefore aims to propose a new electronic module and smart card structure capable of addressing the above problem, and ensuring the reliability of flip-chip modules in the field, without significantly altering the usual, particularly efficient smart card manufacturing processes.
[0013] SUBJECT OF THE INVENTION
[0014] In principle, the invention involves interposing a flexible material between the surface of the flip-chip and the bottom of the card body cavity. This flexible material serves to hold the module without impacting the chip. It fills the space between the chip and the cavity bottom and acts as a protective cushion or shock absorber, cushioning any impacts between the chip and the cavity. In a particularly effective embodiment, this flexible material can be made of a heat-activated adhesive, also known as a "hot melt" adhesive, which is used for the insertion process of securing the electronic module in the card body cavity.In this case, this insert adhesive will have a dual function, namely to fix the periphery of the electronic module to the bottom of the PI depth cavity area, and to form a non-adhesive mechanical damper between the chip and the bottom of the P2 depth cavity area.
[0015] In another embodiment, the flexible material can consist of a specific resin, different from the encapsulation adhesive, and be added to the bottom of the cavity at level P2 or to the external surface of the chip. However, this scenario will require an additional step to dispense this specific resin, in addition to applying the encapsulation adhesive.
[0016] According to another aspect of the invention, it is planned to machine level P2 of the card body cavity, namely the deepest level of the cavity, to a depth that allows the chip, equipped with the flexible material, to simply make contact with the material of the bottom P2 of the cavity, typically made of PVC, PC, or PET. The aim is not to glue the chip to the bottom of the cavity but only to make it contact with the flexible material forming the damper, thus leaving no gap, or perhaps a minimal gap on the order of 10 micrometers, during stress between the chip and the material of the bottom of the card body cavity.
[0017] The invention therefore relates to a smart card comprising a card body and an electronic module comprising a dielectric substrate the upper face of which is provided with metallic contacts and the lower face of which has a microelectronic chip mounted as a flip-chip, said electronic module being intended to be placed in a cavity of the smart card body having a first zone of depth PI receiving said substrate and a second zone of depth P2 greater than PI receiving the microelectronic chip, characterized in that a flexible non-adhesive material capable of forming a mechanical damper is simply interposed, without gluing, between the surface of the microelectronic chip and the bottom of said second zone of the cavity, said flexible material being chosen to be capable of protecting the microelectronic chip during the use of the smart card or during mechanical resistance tests.
[0018] According to one embodiment, the flexible material located above the microelectronic chip and forming a mechanical damper has a thickness of 50 micrometers + / - 20 micrometers. According to another embodiment, the flexible material forming a mechanical damper is dimensioned to be substantially flush with the surface of the microelectronic chip on one side, and with the bottom of the second zone of the cavity of depth P2 on the other, with a tolerance of the order of 10 micrometers.
[0019] According to one embodiment, the flexible material forming the mechanical damper is extended by a part which extends over the periphery of the lower surface of the electronic module and which serves as an adhesive for fixing the electronic module to the bottom of the first area of the cavity, and a part (not glued) which extends over the microelectronic chip and which serves as a mechanical damper.
[0020] According to one embodiment, the flexible material is cut at the level of the microelectronic chip so as not to cover it, and the mechanical damper is formed by a specific flexible resin, different from the adhesive used to fix the module in the cavity.
[0021] According to one embodiment, said flexible material is a thermo-activatable adhesive, which is activated in its part located at the periphery of the electronic module and not activated in its part covering the microelectronic chip, so as to remain flexible over said microelectronic chip and not stuck to it.
[0022] According to one embodiment, said specific flexible resin includes a copolyamide, a polyurethane, or a phenolic resin.
[0023] According to one embodiment, said specific flexible resin is dispensed at the bottom of the cavity area of depth P2.
[0024] According to one embodiment, said specific flexible resin is dispensed over the microelectronic chip.
[0025] DETAILED DESCRIPTION
[0026] The invention will be described in more detail with the aid of the drawings, in which:
[0027] - Figure 1 represents an exploded perspective view of the structure of a smart card module with a chip mounted in a flip chip configuration.
[0028] - Figure 2 shows the module of Figure 1, in cross-section; - Figure 3 shows a cross-sectional view of a smart card comprising an electronic module conforming to the prior art, provided with a chip mounted in flip-chip and a hotmelt film cut at the level of the chip so as not to cover the chip;
[0029] - Figure 4 shows a cross-sectional view of a smart card similar to that in Figure 3, but with a shallower cavity;
[0030] - Figure 5 represents a first embodiment of an improved smart card according to the invention but not optimal;
[0031] - Figure 6 represents a cross-sectional view of an optimal embodiment of the invention;
[0032] - Figure 7 represents a cross-sectional diagram corresponding to a manufacturing step of a module equipped with a flip-chip chip;
[0033] - Figure 8 represents a cross-sectional view of a module and a smart card body according to the invention, before the module is inserted.
[0034] We refer to Figure 1. The components of a module 1 for a smart card conforming to the prior art are shown in exploded perspective, comprising a dielectric substrate 2 above which is positioned a metal foil for making the contacts 3 conforming to ISO 7816, and below which are positioned conductive tracks 4, and a microelectronic chip 5 whose connection pads 6 (or "bumps") are intended to be connected to the conductive tracks 4. The conductive tracks 4 are connected to the contacts 3 of the upper metal foil by metal vias (not shown) passing through the substrate 2.
[0035] Figure 2 shows a cross-sectional view of the assembled module 1 of Figure 1. Some vias 7 connecting the traces 4 to the contacts 3 on the top face of the module are shown, as are the solder pads or "bumps" 6 that electrically connect the flip-chip 5 to the metal contacts 3 on the top face of the module. The flip-chip 5 is also mechanically held in place by a bead of adhesive 8 surrounding its entire periphery.
[0036] Figure 3 shows a partial cross-sectional view of a smart card 10 according to the prior art, comprising a card body 11 with a cavity 12, in which an electronic module 1 is mounted, like that of Figure 2. The thickness of the smart card 10 is shown greatly enlarged for clarity. The cavity 12 conventionally has two zones: a first zone 13 of depth PI, against the bottom of which the periphery of the module 1 rests, and a second zone 14 of greater depth P2 than PI, into which the flip-chip 5 is inserted. Furthermore, the periphery of the module 1 is fixed to the bottom of zone 13 of the cavity 12 of depth PI by means of a heat-activated adhesive 15, also known as "hotmelt." During the assembly of the smart card 10, the components are heated by a thermode and pressed together in a known manner.In the configuration shown, the portion of the card body 11 located beneath the cavity 12, also referred to as the card body web 16, is relatively thin, on the order of 200 microns, given that the smart card 10 has an overall thickness of approximately 800 microns. It is also observed that the area 14 of the cavity 12 located beneath the chip 5 is relatively large, and that the free surface of the chip 5 is far from the bottom of area 14 of the cavity 12. This arrangement has detrimental consequences for the three-roller test. Indeed, it was observed that during the test, the roller which passes under the web 16 of the card body 11 deforms it to the point that the bottom 17 of the cavity 12 can come to hit the chip 5 and damage it or detach it from the substrate 2, the electrical connections being then broken, and the smart card 10 being then out of use.
[0037] In the embodiment of Figure 4, also known, the web 16 at the bottom 17 of the cavity in the card body 11 is much thicker, on the order of 400 to 420 micrometers, so that the free surface of the chip 5 is very close to, or even touches, the bottom 17 of the area 14 of the cavity 12. The hotmelt adhesive 15 for fixing the module is cut so as not to cover the microelectronic chip 5. In this case, flexing of the smart card, or the 3-roller test, causes stresses to be transmitted through the bottom 17 of the cavity to the chip 5, and these stresses eventually damage the chip 5 or its connections.
[0038] The configuration in Figure 5 partially resolves the problems posed by the configurations in Figures 3 and 4. In this embodiment, rather than cutting the heat-activated adhesive 15 above the chip 5, this adhesive is applied to the entire lower surface of the module 1, including over the flip-chip 5. In this configuration, the adhesive film 15 then comprises two parts: a peripheral part 15a which serves to adhere the periphery of the electronic module 1 to the bottom of the area 13 of the cavity at depth PI, and a central part 15b which surmounts the chip 5 and is therefore located in the area 14 at depth P2 of the cavity 12. However, in this configuration, the board body fabric 16 delimiting the bottom of the area 14 of the cavity 12 is thin, with a small thickness denoted e. It deforms significantly under the impact of the test roller, in the direction of chip 5.Above chip 5, the adhesive 15b is not pressed during smart card assembly and retains relative flexibility compared to the pressed adhesive 15a interposed between area 13 of the PI depth cavity and the periphery of module 1. This configuration allows the adhesive portion 15b to act as a mechanical damper in case of contact with the bottom 17 of the cavity. It therefore offers some improvement over the configurations shown in Figures 3 and 4.
[0039] The configuration in Figure 6 corresponds to the preferred embodiment of the invention. This configuration combines a card body 11 provided with a fabric 16 of greater thickness E than in Figure 5, on the order of 400-420 micrometers, and a chip 5 covered with the hotmelt adhesive 15b as in Figure 5. Furthermore, the dimensions are calculated such that when the module 1 is assembled in the cavity of the smart card, the gap (not shown) between the surface of the chip and the bottom 17 of the depth P2 zone 14 of the cavity corresponds substantially, to within + / -10 microns, to the thickness of the unactivated portion 15b of the hotmelt adhesive. In other words, the chip 5 covered with the hotmelt adhesive 15b is simply brought into contact, but not glued, with the bottom 17 of the zone 14 of the cavity, and is flush with it.It has been observed that in this embodiment, the mechanical stresses resulting from the bending of the smart card or from a 3-roller test dissipate at the interface between the chip 5 and the bottom 17 of the cavity, because the hotmelt adhesive 15b, preferably unactivated and therefore non-sticky, simply acts as a mechanical shock absorber for the stresses.The same result can be obtained when the hotmelt adhesive 15b is replaced in the area of the chip 5 by another specific flexible material (not shown) dispensed above the chip 5 or in the bottom of the area 14 of the cavity 12, but this embodiment requires an additional dispensing step, whereas the use of the hotmelt adhesive 15 in two contiguous parts 15a, 15b, namely an activated part 15a and an unactivated part 15b which are used respectively for the two functions of fixing the module 1 in the cavity and shock absorber makes it possible to achieve all the desired functions in a simpler and more efficient way.
[0040] Figure 7 shows a manufacturing step of module 1. The chip 5 is electrically connected to the substrate 2 by the bumps 6, and mechanically fixed to the substrate 2 by a bead of glue 8. During dispensing, this tends to slightly exceed the height of the chip, as shown in 18. To flatten module 1, an absorbent interposition sheet 19 is applied over the chip 5 and the glue bead 8, then a thermode-type tool 20 is applied which heats and presses the absorbent sheet 19 against module 1. The glue area 18 is flattened at the level of the chip 5, and polymerized by heat, then the interposition sheet 19 is removed.
[0041] As shown in Figure 8, the module 1 produced as illustrated in Figure 7 is then transferred to the opposite side of the cavity 12 of a card body 11, with an interposed hotmelt adhesive film 15. As shown, the hotmelt adhesive film 15 is hot-laminated over the module 1, including the area of the chip 5, which is thus protected by the hotmelt adhesive 15. Then, the module 1, now with its adhesive layer 15, is simply transferred into the cavity 12 of the card body 11, applying the appropriate temperatures and pressures, resulting in the formation of the smart card 10 according to the invention, as shown in Figure 6.
[0042] ADVANTAGES OF THE INVENTION
[0043] The invention achieves its stated objectives. Tests have shown that the proposed solution ensures the reliability of the flip-chip module once inserted. The modifications to the electronic module compared to known conventional modules are simple for the customer to implement, requiring no additional investment from either the module supplier or the customer assembling the smart card.
[0044] Thanks to this invention, the chip will be protected when the roller passes over it during the three-roller test, making the module much more reliable. Indeed, a card body made of rigid material, but locally compensated by a flexible material (such as the mounting adhesive or a specific flexible material), will provide optimal durability. Tests have shown that this method allows the smart card to withstand a pressure force of more than 12 Newtons, or even 15 Newtons, during the three-roller test.
Claims
DEMANDS 1. Smart card (10) comprising a card body (11) and an electronic module (1) comprising a dielectric substrate (2) the upper face of which is provided with metallic contacts (3) and the lower face of which has a microelectronic chip (5) mounted as a flip-chip, said electronic module (1) being intended to be placed in a cavity (12) of the smart card body having a first zone (13) of depth PI receiving said substrate (2) and a second zone (14) of depth P2 greater than PI receiving the microelectronic chip (5), characterized in that a flexible material (15b) non-adhesive and capable of forming a mechanical damper is simply interposed, without gluing, between the surface of the microelectronic chip (5) and the bottom (17) of said second zone (14) of the cavity (12), said flexible material (15b) being chosen to be capable of protecting the microelectronic chip (5) during the use of the smart card (10) or during mechanical resistance tests.
2. Smart card (10) according to claim 1, characterized in that said flexible material (15b) located above the microelectronic chip (5) and forming a mechanical damper has a thickness of 50 micrometers + / - 20 micrometers.
3. Smart card (10) according to claim 1 or claim 2, characterized in that the flexible material (15b) forming a mechanical damper is dimensioned to come substantially flush on one side with the surface of the microelectronic chip (5), and on the other side with the bottom (17) of the second zone (14) of the cavity of depth P2, with a tolerance of the order of 10 micrometers.
4. Smart card (10) according to claim 1, characterized in that the flexible material (15b) forming the mechanical damper is extended by a part (15a) which extends over the periphery of the lower surface of the electronic module (1) and which serves as an adhesive for fixing the electronic module (1) to the bottom of the first zone (13) of the cavity (12).
5. Smart card (10) according to claim 1, characterized in that the flexible adhesive material (15a) is cut at the level of the chip (5) so as not to cover it, and in that the mechanical damper (15b) is formed by a specific flexible resin, different from the fixing adhesive (15a).
6. Smart card (10) according to claim 4, characterized in that said flexible material (15) is a thermo-activatable adhesive, which is activated in its part (15a) located at the periphery of the electronic module (1) and not activated in its part (15b) covering the microelectronic chip (5), so as to remain flexible and not stuck on top of said chip (5).
7. Smart card (10) according to claim 5, characterized in that said specific flexible resin includes a co-polyamide, a polyurethane, or a phenolic resin.
8. Smart card (10) according to claim 5, characterized in that said specific flexible resin is dispensed at the bottom of the area (14) of the cavity (12) of depth P2.
9. Smart card (10) according to claim 5, characterized in that said specific flexible resin is dispensed over the microelectronic chip (5).