WO2025083441A1

WO2025083441A1 - Sensor module

Info

Publication number: WO2025083441A1
Application number: PCT/IB2023/000629
Authority: WO
Inventors: Daniel Riegler; Carsten Nieland
Original assignee: Linxens Holding SAS
Current assignee: Linxens Holding SAS
Priority date: 2023-10-17
Filing date: 2023-10-17
Publication date: 2025-04-24
Anticipated expiration: 2026-04-17

Abstract

The present invention refers to a sensor module for a contactless smart card with biometric functionality. The sensor module comprises a biometric sensor, for instance a fingerprint sensor; a micro-controller configured to process signals detected by the biometric sensor; a secure chip configured to store data processed by the micro-controller; a multi-layered PCB substrate having a PCB area; wherein the micro-controller and the secure chip are mounted directly on the biometric sensor, and the biometric sensor is mounted on the multi-layered PCB substrate, so as to form a stacked structure having a maximum area corresponding to the PCB area. The present invention also refers to a biometric contactless smart card comprising said sensor module, and to the methods for forming the sensor module and the smart card.

Description

SENSOR MODULE

Field of the Invention

The present invention relates to a sensor module, a method of forming a sensor module, a smart card comprising a sensor module and a method of forming a smart card.

State of the art

Smart cards provided with biometric sensors, such as fingerprint sensors, are commonly employed in the field. The biometric sensor represents an additional security feature for the smart card.

In view of the large use of smart cards with biometric sensors for banking applications or access permissions, there is a constant need of optimization, for instance of reducing production and manufacturing costs and of improving reliability and security features.

Document US 2021/0117743 A1 discloses for example a sensor device and a corresponding dual-interface smart card. The sensor device comprises a fingerprint sensor and an antenna coupled to the fingerprint sensor for inductive coupling of the fingerprint sensor with a booster antenna of the smart card.

However, the sensor device of US 2021/0117743 A1 has a complex and large structure, which requires specific tools for implanting into the final card body, hence the manufacturing process and the resulting sensor device and smart card are expensive.

It is therefore an object of the present invention to provide a sensor module and a corresponding smart card that overcome one or more of these disadvantages.

Summary

The present invention refers to an all-in-one sensor module having a reduced and compact size, for instance a size of an ISO 8 PIN as defined in ISO 7816.

According to a first aspect of the present invention, a sensor module for a contactless smart card with biometric functionality is provided. The sensor module comprises:

A biometric sensor, for instance a fingerprint sensor;

A micro-controller configured to process signals detected by the biometric sensor;

A secure chip configured to store data processed by the micro-controller; A multi-layered printed circuit board (PCB) substrate having a PCB area;

Wherein the micro-controller and the secure chip are mounted directly on the biometric sensor and the biometric sensor is mounted on the multi-layered PCB substrate, so as to form a stacked structure, having a maximum area corresponding to the PCB area.

The advantage of this configuration is that the sensor module comprises, in a single unit, all the electronic components and biometric features necessary for carrying out contactless payments or transactions, or access operations. In this way, during manufacturing of the final biometric, contactless smart card, there is only a need to insert the sensor module in the card body, without having to add other electronic components.

According to the present invention, the multi-layered PCB substrate is used as a basis for the entire sensor module. The biometric sensor is directly formed on the multi-layered PCB substrate by means of surface mounting technology. The micro-controller and the secure chip are formed on the biometric sensor by means of surface mounting technology. In this way, a stacked structure with a compact and reduced size is produced.

In the present disclosure, it is to be understood that the expression “multi-layered PCB substrate” is used to indicate a PCB substrate comprising two or more distinct PCBs.

It should be appreciated that the sensor module having a stacked structure comprises several components, each having an area (defined by a width and a length) and a thickness. The area of the biometric sensor is preferably smaller than the area of the PCB substrate. The area of each of the micro-controller or the secure chip is preferably smaller than the area of the biometric sensor. Therefore, the maximum area of the sensor module corresponds to the area of the multilayered PCB substrate. In this way, by forming a multi-layered PCB substrate having a reduced size, it is possible to form a compact sensor module also having a reduced size.

Preferably, the biometric sensor has the shape of a square or a rectangle. Preferably, the biometric sensor has a width equal to or larger than 5 mm, and/or a length equal to or larger than 5 mm.

Preferably, the sensor module is inserted into a smart card with biometric functionality operating in a contactless mode. Therefore, there is no need to insert ISO contacts in the sensor module nor in the final smart card with biometric functionality and the dimensions of the sensor module can be reduced even further. Preferably, the secure chip is configured to store the fingerprint data and to process the secure payment transaction and the fingerprint verification by comparing the fingerprint template with the actual fingerprint presented to the fingerprint sensor.

According to a preferred embodiment of the present invention, a sensor module is provided, wherein the PCB area of the sensor module, corresponding to the maximum area of the stacked structure, has a width comprised in the range from 6 mm to 13.1 mm, preferably equal to 12.6 mm, and a length comprised in the range from 6 mm to 11 .9 mm, preferably equal to 11 .4 mm. Preferably, the multi-layered PCB substrate and the corresponding sensor module have dimensions compliant with ISO 8 PIN standards, as defined in ISO 7816.

The advantage of this configuration is that it is possible to produce a sensor module having standard dimensions. Therefore, when implanting the sensor module into the final biometric, contactless smart card, there is no need to build new equipment for manufacturing the smart card, nor to adapt the pre-existing equipment to new standards, but it is possible to simply use preexisting tools for producing ISO 8 PIN modules, as defined in ISO 7816. In this way, production and manufacturing costs are reduced.

According to an embodiment of the present invention, a sensor module is provided wherein the multi-layered PCB substrate comprises a first PCB and a second PCB.

According to an illustrative embodiment, the first PCB and the second PCB may be made of two different base materials to better adapt each PCB to its predefined function. For example, the first PCB may be made of black PET and the second PCB may be made of epoxy glass.

According to another embodiment of the present invention, a sensor module is provided, wherein the second PCB comprises a cutout portion for accommodating the biometric sensor mounted on the first PCB.

The advantage of this configuration is that the first PCB is used as a common substrate for the electronic components and the biometric sensor and the second PCB acts as a frame for accommodating the biometric sensor.

According to another embodiment of the present invention, a sensor module is provided, wherein the first PCB comprises a first metal layer and the second PCB comprises a second metal layer and a third metal layer formed on opposite sides of a central layer, and the first metal layer of the first PCB is mechanically and/or electrically connected to the second metal layer of the second PCB. This solution enables forming the mechanical and electrical connection between the two PCBs in a simple and efficient way.

According to another embodiment of the present invention, a sensor module is provided wherein the first metal layer is mechanically and/or electrically connected to the second metal layer by means of an adhesive layer, an Anisotropic Conductive Film (ACF), a stud bump connections, and/or a solder bump connection.

These solutions enable forming stable and efficient mechanical and/or electrical connections between the two PCBs, in particular between the first metal layer of the first PCB and the second metal layer of the second PCB facing the corresponding metal layer of the first PCB.

According to another embodiment of the present invention, a sensor module is provided, further comprising two antenna pads for enabling a galvanic connection with a card antenna of the smart card.

The advantage of this configuration is that it enables forming a stable, galvanic connection between the sensor module and the card antenna of the biometric, contactless smart card.

According to another embodiment of the present invention, a sensor module is provided, further comprising a coupling antenna formed on the multi-layered PCB and configured to be inductively coupled to a card antenna of the smart card.

The advantage of this configuration is that the connection between the sensor module and the card antenna of the contactless smart card is performed by means of inductive coupling, without the need to add any electrical connection nor any electrical wiring.

According to another embodiment of the present invention, a sensor module is provided, wherein the first PCB is made of black PET.

Preferably, at least a portion of the first PCB may be visible through the card body of the contactless smart card. Preferably, the smart card may be of a black color and the first PCB may be made of black PET for aesthetic reasons, so that the sensor module is not visible in the card body.

According to another embodiment of the present invention, a sensor module is provided, further comprising a passive component for antenna matching, for instance, a capacitor, mounted on the biometric sensor. The advantage of this configuration is that any additional passive component for antenna matching, for instance, an additional capacitor, may be formed on the biometric sensor by means of surface mounting technology, so as to form a stacked structure having reduced dimensions.

According to another embodiment of the present invention, a sensor module is provided, wherein the micro-controller and the secure chip are integrated into a single chip.

This configuration is advantageous because the number of components is reduced.

According to a second aspect of the present invention, a contactless smart card with biometric functionality is provided, the smart card comprising a sensor module as the ones described above, and a card antenna configured to be inductively coupled or electrically connected to the sensor module.

The advantage of this configuration is that manufacturing of the contactless smart card with biometric functionality is simplified and improved. In fact, the sensor module comprises, in a single unit, all the electronic and biometric components for performing transactions or access operations. The sensor module according to the invention is compact and small, hence it can be easily implanted into the card body of the biometric contactless smart card and can be easily and efficiently connected to the card antenna of the contactless smart card for enabling communication with an external reader. The sensor module may be inductively coupled to the card antenna or, alternatively, it may be electrically connected to the sensor module.

Preferably, the card antenna is suitable for enabling contactless communication in the High- Frequency field, for example in the frequency band of 13,56 MHz.

According to a third aspect of the present invention, a method for forming a sensor module is provided, the method comprising the following steps: a) Providing a multi-layered PCB substrate; b) Mounting a biometric sensor, for instance a fingerprint sensor, on a side of the multilayered PCB substrate; c) Mounting a micro-controller configured to process signals detected by the biometric sensor on a side of the biometric sensor opposite to the multi-layered PCB substrate; d) Mounting a secure chip configured to store data processed by the micro-controller on a side of the biometric sensor opposite to the multi-layered PCB substrate, thereby forming a stacked structure having a maximum area corresponding to an area of the multi-layered PCB substrate.

The method of the present invention is advantageous because it enables forming a sensor module including all the electronic and biometric components for a biometric contactless smartcard, wherein the sensor module has reduced size and dimensions. Preferably the sensor module may have a maximum area compliant with ISO 8 PIN standards, as defined in ISO 7816. In this way, there is no need to create new tools or to adapt pre-existing tools for punching and implanting the sensor module, but the sensor module may be easily and efficiently produced by using standard tools compliant with ISO 8 PIN standard, as defined in ISO 7816. Therefore, manufacturing costs are reduced.

Preferably, the method of the present invention may be used to produce a sensor module of the present invention, as the ones described above.

According to an embodiment of the present invention, a method is provided, wherein the multilayered PCB substrate comprises a first PCB and a second PCB and the step b) of the previous method comprising the following sub steps: b1 ) Mounting the biometric sensor on the first PCB; b2) Forming a cutout portion within the second PCB; b3) Attaching the second PCB to the first PCB, for instance by means of an adhesive layer, an ACF, a stub bump connection, and/or a solder bump connection so that the biometric sensor is placed in the cutout portion.

The advantage of this method is that it enables mechanically and/or electrically connecting the biometric sensor to the first PCB, which acts as a common basis for the other electronic and biometric components. On the other hand, the second PCB comprising a cutout portion acts as a frame for the biometric sensor for making the entire structure more stable and robust.

Preferably the biometric sensor is mounted on the first PCB by means of surface mounting technology.

Preferably, the adhesive layer is laminated to the second PCB, when the second PCB already comprises the cutout portion. Afterwards, the second PCB comprising the cutout portion and the adhesive material is mounted to the first PCB by means of hot tools. According to another embodiment of the present invention, a method is provided, further comprising the following step: e) Filling the cutout portion of the second PCB with an underfill material or using transfer molding, to cover the micro-controller and the secure chip.

The advantage of this configuration is that the electronic components such as the micro-controller and the secure chip are protected by the underfill material. Preferably, the electrical wiring connecting the electronic components, such as the micro-controller and the secure chip, to the biometric sensor are also covered with a protective material. Preferably, the wire bond connections to electrically connect the electronic components to each other or to the metal layers of one of the PCBs are also covered with a protective material.

For instance, the cutout portion of the second PCB may be filled by using side-gate transfer molding, or top-gate transfer molding.

According to a third aspect of the present invention, a method for forming a contactless smart card with biometric functionality is provided, the method comprising the following steps: f) Providing a card body for a smart card, said card body comprising a card antenna for contactless communication; g) Forming a cavity in the card body; h) Forming a sensor module according to one of the methods described above; i) Inserting the sensor module in the cavity; j) Connecting the card antenna to the sensor module by means of inductive coupling or galvanic connection.

The method for producing a contactless smart card with biometric functionality according to the present invention is extremely efficient and simple and production costs are reduced.

The card body for a smart card may be formed by means of any known technology. Preferably, a cavity is milled in the card body and the sensor module according to the present invention is implanted in the cavity by means of ACF technology, edge link technology, TE connect technology, or similar ways for attaching the module in the card cavity.

Brief Description of the Drawings The present invention will be explained in greater detail with regard to the accompanying drawings in which:

Fig. 1 A schematically represents a top view of a front side of a sensor module according to an embodiment of the present invention.

Fig. 1 B schematically represents a top view of a back side of a sensor module according to an embodiment of the present invention.

Fig. 2 schematically represents a cross-section view of a sensor module according to an embodiment of the present invention.

Fig. 3 schematically represents a detail of a base layer of a sensor module according to an embodiment of the present invention.

Fig. 4 schematically represents a top view of a smart card comprising a sensor module according to an embodiment of the present invention.

Detailed Description

In the following, the present invention is described with reference to particular embodiments, as is illustrated in the enclosed figures. However, the present invention is not limited to the particular embodiments described in the following detailed description and shown in figures. Instead, the described embodiments simply exemplify the different features of the present invention, the scope of which is defined in the claims. Further modifications and variations of the present invention will be clear to the skilled person.

The sensor module 100, according to the present invention, is an all-in-one sensor module for a contactless smart card having biometric functionality.

Fig. 1A schematically represents a top view of a front side of a sensor module 100 according to an embodiment of the present invention.

Fig. 1 B schematically represents a top view of a back side of the sensor module 100 according to an embodiment of the present invention.

The sensor module 100 comprises a biometric sensor 110, such as a fingerprint sensor, a microcontroller 120 configured to process signals detected by the biometric sensor 110, and a secure chip 130 configured to store data processed by the micro-controller 120. As shown in Fig. 1 B, the biometric sensor 110, the micro-controller 120, and the secure chip 130 are directly or indirectly formed on a multi-layered PCB substrate 150. In particular, the biometric sensor 110 is formed on the multi-layered PCB substrate 150, and the chips 120 and 130 are formed on the biometric sensor 110. Preferably, the biometric sensor 110 is mounted on the multilayered PCB substrate 150 by means of surface mounting technology. Preferably, the microcontroller 120 and the secure chip 130 are formed on the biometric sensor 110 by means of surface mounting technology. In this way, the multi-layered PCB 150, the biometric sensor 110, the micro-controller 120 and the secure chip 130 form a stacked structure.

As it can be seen in Fig. 1 B, each component of the sensor module 100 has a predefined area. The multi-layered PCB substrate 150 has a PCB area having a width W and a length L, as shown in Fig. 1A. As visible from the figures, the maximum area of the stacked structure of the sensor module 100 corresponds to the PCB area.

Thanks to the fact that the biometric and electronic components are stacked on the multi-layered PCB substrate 150, and that the PCB area has a small area, the entire sensor module 100 may have a compact and small size.

The PCB area is preferably designed so as to be compliant with ISO 8 PIN standards, as defined in ISO 7816. In this way, the entire sensor module 100 has an area compliant with ISO 8 PIN standards, as defined in ISO 7816. For instance, as schematically shown in Figure 1A and Figure 4, the width of the multi-layered PCB substrate 150 may be comprised in the range from 6 mm to 13.1 mm, preferably equal to 12.6 mm, and the length of the multi-layered PCB substrate 150 may be comprised in the range from 6 mm to 11 .9 mm, preferably equal to 11 .4 mm. Accordingly, the width of the sensor module 100 may be comprised in the range from 6 mm to 13.1 mm, preferably equal to 12.6 mm, and the length of the sensor module 100 may be comprised in the range from 6 mm to 11 .9 mm, preferably equal to 11 .4 mm.

According to the illustrative configuration of Fig. 1A, the sensor module 100 may have a substantially rectangular shape, wherein the corners of the rectangle are designed to be slightly rounded. Preferably, the radius of each corner may be comprised in the range from 1 .7 mm to 2.3 mm, preferably equal to 2 mm.

With respect to the reference system of Fig. 1 A, the width is defined as the dimension along the X-axis and the length is defined as the dimension along the Y-axis. However, it is to be understood that the preferred orientation of the sensor module 100 in Fig. 1A should not be limiting for the scope of protection of the present invention. The fact that the sensor module 100 is compliant with ISO 8 PIN standards, as defined in ISO 7816, enables using pre-existing standard tools for manufacturing the sensor module 100. On the contrary, if the sensor module 100 had larger or not-standardized dimensions, there would be a need to build specific tools for manufacturing the sensor module 100.

In the schematically representation of Fig. 1 B, an additional capacitor 160 for matching the antenna frequency of the card antenna of the smartcard is also mounted on the biometric sensor 110.

It is to be understood that the additional capacitor 160 is an optional electronic component of the sensor module 100. Alternatively or in addition to the capacitor 160, other electronic components, for instance passive components for antenna matching, may be formed on the sensor module 100.

Moreover, in the configuration of the sensor module 100 of Figure 1 B, two antenna pads 140A and 1406 are represented. The two antenna pads 140A and 1406 may be advantageously used to connect the sensor module 100 to the card antenna of the biometric contactless smartcard.

According to an alternative configuration (not shown), the antenna pads 140A and 1406 may not be formed on the multi-layered PCB substrate 150 and the connection between the sensor module 100 and the card antenna of the biometric contactless smart card may be realized by means of inductive coupling. According to this configuration, an inductive coupling antenna (not shown) may be formed around the biometric sensor 110, on the top surface of the multi-layered PCB substrate 150. Preferably, the inductive coupling antenna may be formed on the second PCB 154, which is described below with reference to Fig. 2.

The biometric sensor 110 may be a fingerprint sensor. The biometric sensor 110 may include an array of touch-sensitive sensor pads that are exposed or at least partially covered with, for instance, a thin protective layer without affecting their measurement sensitivity for fingerprints. The signals detected by the touch-sensitive sensor pads of the biometric sensor 110 may be processed by the micro-controller 120, which may be a microprocessor for converting the signals detected by the biometric sensor 110, for instance, capacitive sensors, into electronic signals. The electronic signals of the micro-controller 120 may then be further processed and stored in the secure chip 130, which acts as the memory for the sensor module 100. In this way, during transactions or access operations, the user does not need to provide any PIN or security code for enabling the transactions or the access operations, because these procedures may be confirmed by simply pressing the user’s finger on the sensor module 100. In this way, the capacitive sensor of the biometric sensor 110 may generate an image by measuring the changes in capacitance between the ridges and valleys that make up the fingerprint. The data measured by the biometric sensor 110 and processed by the micro-controller 120 may finally be compared with the memory data of the secure chip 130.

Fig. 2 schematically represents a cross-section of the sensor module 100 along the axis ll-ll shown in Fig. 1 B, according to an embodiment of the present invention.

In Fig. 2, the stacked structure of the all-in-one sensor module 100 is clearly visible. With reference to the orientation of Fig. 2, it is possible to see, from bottom to top, the multi-layered PCB substrate 150, the biometric sensor 110 and the micro-controller 120 (the secure chip 130 is not visible in the cross-section). The electronic and biometric components are formed on top of each other so as to form a stacked structure with a compact and small size, wherein the maximum area of the sensor module 100 corresponds to the area of the multi-layered PCB substrate 150.

As shown in Fig. 2, the multi-layered PCB substrate 150 comprises two PCBs, a first PCB 152 and a second PCB 154. The first PCB 152 forms a common substrate for all the electronic and biometric components. The biometric sensor 110 is directly mounted on the first PCB 152. The second PCB 154 forms a frame around the biometric sensor 110 and the chips 120 and 130. In this way, the sensor module 100 is more stable and robust.

The antenna pads 140A and 140B are formed on top of the second PCB 154, on opposite sides of the biometric sensor 110. The antenna pads 140A and 1406 are metal pads for enabling a galvanic connection with the card antenna of the contactless smartcard. The antenna pads 140A and 1406 are preferably formed on the second PCB 154, so as to have a height suitable for enabling a connection with the card antenna of the smartcard once the sensor module 100 is implanted into a corresponding cavity of the smartcard (as shown in Fig. 4 below).

Fig. 3 schematically shows a detail of the PCB substrate 150 according to the present invention. As described with reference to Fig. 2, the multi-layered PCB substrate 150 preferably comprises a first PCB 152 and a second PCB 154. The first PCB 152 comprises a base layer 151 and a metal layer 152A. The second PCB 154 comprises a central layer 155 and two metal layers 154A and 154B attached on opposite sides of the central layer 155. The first metal layer 152A is preferably attached to the second metal layer 154A by means of an adhesive layer 158. The adhesive layer 158 may be made of any adhesive material suitable for making an electronic or mechanical connection between the two metal layers, for instance, it may be an Anisotropic Conductive Film (ACF), a plurality of stub bumps, and/or a plurality of solder bumps. In this way, the electronic and mechanical connection between the two PCBs of the multi-layered PCB substrate 150 is stable and reliable. In the configuration shown in Fig. 2, wherein two antenna pads 140A and 1406 are formed on the second PCB 154, they are obtained directly from the metal layer 154B of the second PCB 154.

According to an alternative configuration, wherein an inductive antenna is formed on the second PCB 154, the inductive coupling antenna may be formed directly from the metal layer 154B.

Fig. 4 schematically illustrates a top view of a contactless smartcard comprising a sensor module according to an embodiment of the present invention.

Even if in the smart card 1000 of Fig. 4 the sensor module 100 is shown to be positioned at the corner at the right bottom of the card, it is to be understood that this configuration is not limiting for the present invention. In fact, the sensor module 100 may be positioned at any corner of the smart card 100, for instance even in a position not defined in ISO 7816.

In Fig. 4, the sensor module 100 is positioned at a distance y from the horizontal line delimiting the smart card 1000 and at a distance x from the vertical line delimiting the smart card 1000.

The smartcard 1000 is a contactless smartcard having biometric functionality. Preferably, the smartcard 1000 does not comprise any contact pads for operating the card in contact mode. In this way, the number of electronic components included in the smartcard is reduced.

Preferably, the smartcard 1000 has a width y* and a length x* and the comers are rounded with a radius of curvature z.

The card body 500 of the smartcard 1000 may be formed according to any known technique. A cavity 510 is then milled in the card body 500. The sensor module 100 is post-implanted in the cavity 510 milled in the card body 500. Since the sensor module 100 has a reduced size and is compact and easy to handle, it can be efficiently implanted into the cavity 510 of the card body 500 of the smartcard 1000.

Since the size of the sensor module 100 is determined by the size of the PCB substrate 150, and the size of the PCB substrate 150 is preferably compatible with the ISO 8 PIN standards, as defined in ISO 7816, the manufacturing tools that are commonly employed in the field of smartcards compliant with ISO 8 PIN standards, as defined in ISO 7816, may be re-used for implanting the all-in-one sensor module 100 in the card body 500. Accordingly, there is no need to modify nor adapt the existing manufacturing tools for producing or implanting the sensor module 100. Therefore, the process for manufacturing the smartcard 1000 can be cost-effective and efficient. Preferably, the card body 500 of the smartcard 1000 is made of a black color. Preferably, the side of the multi-layered PCB substrate 150 forming the front side of the sensor module 100, which is visible through the card body 500, is also made of a black color. In this way, the color of the visible side of the sensor module 100 is not in contrast with the color of the card body 500 and the sensor module 100 is not immediately visible from the outside of the smartcard. Preferably, the first PCB of the multi-layered PCB substrate 150 is visible through the card body 500 and it is accordingly made of black PET material.

According to alternative configurations, the side of the multi-layered PCB substrate 150 forming the front side of the sensor module 100, which is visible through the card body 500, may be made of any other color, such as red, gold, or the like, and may be clearly visible through the card body 500.

Even if the present invention has been described with reference to the embodiments described above, it is clear to the skilled person that it is possible to apply different modifications, variations and improvements of the present invention in light of the teachings described above and the field, and within the scope of the enclosed claims, without departing from the scope and purpose of the present invention.

Finally, those fields considered known to the skilled person have not been described to avoid covering in a useless way the described invention.

Reference numbers

100: sensor module

110: biometric sensor

120: micro-controller

130: secure chip

140A, 1406: antenna pads

142: coupling antenna

150: PCB substrate

152: first PCB

152A: first metal layer of first PCB 154: second PCB

154A, 154B: second and third metal layers of second PCB

155: central layer of second PCB

156: cutout portion

158: adhesive layer

160: passive component for antenna matching 00: card antenna

500: card body

510: cavity

1000: smart card

Claims

1 . A sensor module (100) for a contactless smart card with biometric functionality, said sensor module (100) comprising:

A biometric sensor (110), for instance a fingerprint sensor;

A micro-controller (120) configured to process signals detected by said biometric sensor (110);

- A secure chip (130) configured to store data processed by said micro-controller (120);

A multi-layered Printed Circuit Board “PCB” substrate (150) having a PCB area;

Wherein said micro-controller (120) and said secure chip (130) are mounted directly on said biometric sensor (110), and said biometric sensor (110) is mounted on said multi-layered PCB substrate (150), so as to form a stacked structure having a maximum area corresponding to said PCB area.

2. The sensor module (100) of claim 1 , wherein said multi-layered PCB substrate (150) comprises a first PCB (152) and a second PCB (154).

3. The sensor module of claim 2, wherein said second PCB (154) comprises a cutout portion (156) for accommodating said biometric sensor (110) mounted on said first PCB (152).

4. The sensor module (100) of claim 2 or 3, wherein said first PCB (152) comprises a first metal layer (152A) and said second PCB (154) comprises a second metal layer (154A) and a third metal layer (154B) formed on opposite sides of a central layer (155), and said first metal layer (152A) is mechanically and/or electrically connected to said second metal layer (154A) of said second PCB (154).

5. The sensor module (100) of claim 4, wherein said first metal layer (152A) is mechanically and/or electrically connected to said second metal layer (154A) by means of an adhesive layer (158), an Anisotropic Conductive Film “ACF”, a stub bump connection, and/or a solder bump connection.

6. The sensor module (100) of any of previous claims, further comprising two antenna pads (140A, 1406) for enabling a galvanic connection with a card antenna of said contactless smart card.

7. The sensor module (100) of any of claims 1 to 5, further comprising a coupling antenna (142) formed on said multi-layered PCB (150) and configured to induce an inductive coupling of said biometric sensor (110) with a card antenna of said contactless smart card.

8. The sensor module (100) of any of claims 2 to 7, wherein said first PCB (152) is made of colored PET, for example PET made of any color, such as black, red, or gold.

9. The sensor module (100) of any of previous claims, further comprising a passive component (160) for antenna matching, for instance a capacitor, mounted on said biometric sensor (110).

10. The sensor module (100) of any of previous claims, wherein said multi-layered PCB substrate (150) has a width (W) comprised in the range from 6 mm to 13.1 mm, preferably equal to 12.6 mm, and/or a length (L) comprised in the range from 6 mm to 11 .9 mm, preferably equal to 11 .4 mm, for instance has a width (W) and a length (L) compliant with ISO 8 PIN standards, as defined in ISO 7816.

11 . The sensor module (100) of any of previous claims, wherein said micro-controller (120) and said secure chip (130) are integrated into a single chip.

12. A contactless smart card (1000) with biometric functionality comprising:

A sensor module (100) of any of claims 1 to 11 ;

A card antenna (200) configured to be inductively coupled or electrically connected to said sensor module (100).

13. A method forforming a sensor module (100) for a contactless smart card (1000) with biometric functionality comprising the following steps: a) Providing a multi-layered Printed Circuit Board “PCB” substrate (150) having a PCB area; b) Mounting a biometric sensor (110), for instance a fingerprint sensor, on a side of said multi-layered PCB substrate (150); c) Mounting a micro-controller (120) configured to process signals detected by said biometric sensor (110) on a side of said biometric sensor (100) opposite to said multi-layered PCB substrate (150); d) Mounting a secure chip (130) configured to store data processed by said micro-controller (120) on a side of said biometric sensor (100) opposite to said multi-layered PCB substrate (150), thereby forming a stacked structure having a maximum area corresponding to said PCB area.

14. The method of claim 13, wherein said multi-layered PCB substrate (150) comprises a first PCB (152) and a second PCB (154) and said step b) comprises the following sub-steps: b1 ) Mounting said biometric sensor (110) on said first PCB (152); b2) Forming a cutout portion (156) within said second PCB (154); b3) Attaching said second PCB (154) to said first PCB (152) for instance by means of an adhesive layer (158), an Anisotropic Conductive Film “ACF”, a stub bump connection, and/or a solder bump connection, so that said biometric sensor (110) is placed in said cut-out portion (156).

15. The method of claim 13 or 14, further comprising the following step: e) Filling said cut-out portion (156) of said second PCB (154) with an underfill material or using gate transfer molding, to cover said micro-controller (120) and said secure chip (130).

16. A method for forming a contactless smart card (1000) with biometric functionality comprising the following steps: f) Providing a card body (500) for a smart card (1000), said card body (500) comprising a card antenna for contactless communication; g) Forming a cavity (510) in said card body (500); h) Forming a sensor module (100) according to a method of any of claims 13 to 15; i) Inserting said sensor module (100) in said cavity (510); j) Connecting said card antenna to said sensor module (100) by means of inductive coupling or galvanic connection.