Pre-packaging body for printed circuit board for smart card and forming method of pre-packaging body

Abstract

The invention relates to a prepackage for a flexible printed circuit board for a smart card. The pre-package includes a flexible printed circuit board including one or more non-planar circuit portions; a first material of a first layer at least partially covering the first side of the flexible printed circuit board to form a planar layer; a second layer of a second material covering a second side of the flexible printed circuit board; and a third layer comprising a hardened material at least partially covering the first side to form a planar layer. The third layer has a third hardness value higher than the first hardness value and / or the second hardness value of the first dielectric material and the second dielectric material, respectively. The pre-package can advantageously be inserted into a smart card having a suitable window for receiving the pre-package comprising electronic components. The invention also relates to a method for forming the pre-packaging body and the smart card comprising the pre-packaging body.

Description

Technical Field

[0001] The present invention generally relates to any type of smart card, such as a credit card, payment card, key card, electronic tag, data page of a security document, etc., in which a card-type substrate includes electronic components for providing information and / or responding to external stimuli, etc. Background Art

[0002] A smart card is a card comprising a plurality of plastic layers that are processed to form a substantially single piece of material and a plurality of electronic components contained therein. The electronic components may include one or more antennas, such as those used to give the smart card RFID (Radio Frequency Identification) capabilities, electronic modules for storing and processing information, a network of corresponding electrical connections, additional components for capacitively and / or capacitively interconnecting the internal components of the card, etc.

[0003] Due to the widespread use of smart cards in different fields and applications, such as in the financial services sector, there is a constant need to develop new technologies for connecting various plastic layers to form a substantially monolithic block of material while appropriately encapsulating the relevant functional and electronic components.

[0004] Current approaches include integrating dispersed electronic and / or optical components, power supply devices, etc. into smart cards to provide superior functionality. For example, a preform for a smart card can be provided that can be continuously combined with specific additional components to provide a customized smart card with specific functionality. Many of these additional components can have a substantially non-planar configuration, i.e., a configuration with an increased height dimension compared to the corresponding lateral dimension of any such component, thereby requiring a great deal of effort to be invested in the smart card. In addition, the additional components must be combined on the basis of efficient mass production technology while ensuring a high degree of integrity of the smart card in terms of tamper resistance and robustness, taking into account any environmental influences and mechanical stresses, to achieve the desired long service life of any such smart card.

[0005] Patent document EP2715619 relates to a security document and a method for producing the same, wherein the security document comprises a card body made of a plurality of layers and at least one display module having a non-planar configuration, the display module having a thickness greater than the thickness of a single layer of the card body. At least one compensation layer is added between the display module and a card substrate layer receiving an antenna connected to the display module to compensate for the height difference between the card body layer and the display module. According to the method, the display module and other non-planar electronic components are directly incorporated into the smart card by forming corresponding openings in the compensation layer, by inserting corresponding components and by laminating the corresponding layers together. Since the electronic components are directly incorporated into the card body, they are easily damaged during use.

[0006] Patent application WO2021 / 176247 relates to a preform for a smart card and a method for producing the same, wherein the electronic components to be incorporated into the preform are initially "packaged" and encapsulated in a plurality of plastic layers and subsequently inserted into corresponding windows of the preform. In this way, excellent robustness and production yield are achieved. However, the prepackage structure comprises a plurality of layers encapsulating the electronic components, since compensation layers are also required to compensate for the different heights of the electronic components. Accordingly, it is difficult to meet the smart card size requirements. In addition, the outer surface of the prepackage is not planar, since it tends to shrink during the lamination process, which makes the insertion process into the smart card even more complicated.

[0007] In view of the above problems, there is a need to provide a preform for a smart card and a smart card, wherein electronic components are preliminarily packaged into a simple structure before being incorporated into the smart card, thereby providing the electronic components with improved mechanical robustness while still ensuring high flexibility and meeting standard size requirements. Summary of the invention

[0008] According to a first aspect of the present invention, there is provided a prepackage for a flexible printed circuit board for a smart card, the prepackage comprising the following elements:

[0009] - a flexible printed circuit board including one or more non-planar circuit portions, the flexible printed circuit board having a first side and a second side opposite the first side;

[0010] - a first layer of a first material at least partially covering the first side of the flexible printed circuit board to form a planar layer;

[0011] - a second layer of a second material covering a second side of the flexible printed circuit board; and

[0012] - a third layer comprising a hardened material at least partially covering the first side to form a planar layer;

[0013] Wherein the first material has a first VICAT softening temperature, and the second material has a second VICAT softening temperature, and the third layer has a third VICAT softening temperature, wherein the third VICAT softening temperature is higher than the first VICAT softening temperature and / or the second VICAT softening temperature.

[0014] The advantage of this solution is that the flexible printed circuit board including the non-planar circuit part is encapsulated in the pre-package of dielectric material and protected. The pre-package has a simple structure because it includes a limited number of layers, preferably three layers. In this way, the pre-package and the smart card including the pre-package can meet the ISO7810 / 7816 card quality requirements. In addition, since the third layer includes a hardening material, the VICAT softening temperature of the hardening material is higher than the VICAT softening temperature of the material of the first layer and / or the second layer, the third layer will not shrink due to the applied temperature and pressure during the smart card lamination. In this way, the flatness of the outermost layer of the pre-package is optimized, and the surface visibility is improved.

[0015] In the present disclosure, it is understood that the flexible printed circuit board has the shape of a plate having a major top surface and a major bottom surface, which are respectively referred to as the "first side" and the "second side". However, since the flexible printed circuit board has no preferred orientation, the major top surface may also be referred to as the "second side", and the major bottom surface may also be referred to as the "first side".

[0016] Furthermore, in this disclosure, the VICAT softening temperature is defined as the temperature at which a specimen of a given material is softened by a 1 mm 2 The temperature at which a flat-ended needle of circular or square cross-section penetrates to a depth of 1 mm. For the VICAT A test, a load of 10 N is used. For the VICAT B test, the load is 50 N. Standards for determining the VICAT softening point may include, for example, ASTM D 1525 and / or ISO 306. The VICAT softening temperature can be used to compare the thermal properties of different materials: In the present disclosure, it should be understood that the same VICAT test (e.g., VICAT A test or VICAT B test) must be used to compare the first hardened material, the second hardened material, and the third hardened material.

[0017] For example, the first material may include a first dielectric material. For example, the second material may include a second dielectric material.

[0018] According to one embodiment of the invention, a prepackage is provided, wherein the hardened material has a flexural strength comprised between 40 MPa and 150 MPa, and / or a flexural modulus comprised between 0.5 GPa and 3 GPa.

[0019] An advantage of this construction is that, due to the high values ​​of flexural strength and flexural modulus, the third layer does not shrink nor deform during the lamination process and during exposure to high temperatures and pressures.

[0020] Flexural strength, also known as modulus of rupture, flexural strength or transverse rupture strength, is a material property that represents the maximum stress experienced by a material at the point of yield in a flexural test.

[0021] Flexural modulus or bending modulus is a strength property calculated as the ratio of stress to strain in bending deformation, or the tendency of a material to resist bending.

[0022] According to another embodiment of the present invention, a pre-package is provided, wherein the hardened material has a VICAT softening temperature comprised between 68°C and 150°C.

[0023] An advantage of this construction is that the hardened material neither shrinks nor deforms during the lamination process and during exposure to high temperatures and pressures.

[0024] According to another embodiment of the present invention, a pre-package is provided, wherein the hardening material comprises PET and / or PI.

[0025] The advantage of this construction is that the PET and / or PI neither deforms nor shrinks during the lamination process.

[0026] According to another embodiment of the present invention, a prepackage is provided, wherein a first layer has an opening, and a third layer is placed in the opening to complete the first planar layer.

[0027] The advantage of this construction is that the third layer covers the flexible printed circuit board and can form a continuous layer with the first layer. In addition, the third layer flattens the adhesive material used to connect the third layer to the flexible printed circuit board and prevents the adhesive material from overflowing during coating and before polymerization, for example by means of UV radiation. Preferably, the third layer is flush with the first layer to form a continuous planar layer. In this way, the flatness of the prepackage is optimized and the surface visibility is improved.

[0028] According to another embodiment of the present invention, there is provided a prepackage, wherein the third layer is attached to the first side of the flexible printed circuit board and / or the first layer via an adhesive layer.

[0029] The advantage of this configuration is that the third layer is firmly attached to the first side and / or the first layer of the flexible printed circuit board due to the adhesive material. According to a preferred configuration, the adhesive material is initially deposited on the first side of the flexible printed circuit board in a viscous configuration so that it can flow and fill the discontinuities between one or more non-planar circuit portions of the flexible printed circuit board. Then, the third layer is placed on the viscous adhesive layer. Ultimately, curing of the adhesive layer is caused. In this way, the third layer is attached to the first side of the flexible printed circuit board by the adhesive material and will not be deformed by the discontinuities of the non-planar circuit portions formed on the flexible printed circuit board.

[0030] According to a preferred configuration, the third layer is partially attached to the outer surface of the first layer of the prepackage by means of an adhesive layer.

[0031] According to another embodiment of the present invention, there is provided a pre-package, wherein the adhesive layer comprises a UV curing adhesive material.

[0032] An advantage of this configuration is that the adhesive material can initially be deposited in a viscous state on the first side of the flexible printed circuit board and it can subsequently be cured and hardened via UV radiation.

[0033] According to another embodiment of the present invention, a prepackage is provided, wherein the first layer and the second layer include PVC, PETG, PLA, PU and / or polycarbonate.

[0034] The advantage of using PVC, PETG, PLA, PU and / or polycarbonate to form the first and second layers is that these materials have high mechanical resistance and they can strengthen the prepackage and protect the IC chip.

[0035] According to another embodiment of the present invention, a prepackage is provided, wherein the first layer and / or the second layer comprises one or more windows for accommodating one or more non-planar circuit parts.

[0036] This configuration has the advantage that mechanical robustness and stability can be provided to the flexible printed circuit board while still ensuring electrical contact between the protruding non-planar circuit portion and other components of the smart card since the circuit portion is not completely covered by the first and / or second layer.

[0037] Preferably, the second layer comprises a window for accommodating a display module formed on the second side of the flexible printed circuit board. In this way, a portion of the display module can be seen through the window.

[0038] According to another embodiment of the present invention, a smart card is provided, wherein the smart card comprises a stack of card layers forming a smart card body having a window; and the pre-package as described above embedded in the window.

[0039] The advantage of this configuration is that the flexible printed circuit board including the electronic components is encapsulated and protected by the pre-package before being inserted into the window of the smart card. Accordingly, a higher mechanical resistance of the electronic components is ensured. In addition, since the pre-package has a simple structure with a reduced number of plastic layers, the smart card complies with card size requirements, such as ISO7810 / 7816 standards.

[0040] According to another aspect of the present invention, there is provided a method for forming a prepackage of a flexible printed circuit board for a smart card, the method comprising the following steps:

[0041] a) providing one or more flexible printed circuit boards, each flexible printed circuit board comprising at least one non-planar circuit portion and having a first side and a second side opposite to the first side;

[0042] b) at least partially covering said first side of each flexible printed circuit board with a first layer of dielectric material so as to form a first planar layer on the first side;

[0043] c) covering the second side of each flexible printed circuit board with a second layer of dielectric material;

[0044] d) further covering the first side with a third layer of hardening material,

[0045] The first material has a first VICAT softening temperature, the second material has a second VICAT softening temperature, and the third layer has a VICAT softening temperature higher than the first VICAT softening temperature and / or the second VICAT softening temperature.

[0046] The advantage of this method is that it provides a higher mechanical resistance for a flexible printed circuit board including non-planar electronic components, since the flexible circuit board is preliminarily encapsulated in a prepackage. In addition, according to this method, card size requirements, such as ISO7810 / 7816 requirements, are met, since the prepackage has a simple structure, including a reduced number of layers, preferably three layers. In addition, since the third layer has a VICAT softening temperature that is higher than the VICAT softening temperature of the first layer and / or the second layer, the flatness of the prepackage is optimized. In fact, during the lamination process, high temperatures and pressures are applied, and the hardened material prevents shrinkage or deformation of the third layer.

[0047] According to another embodiment of the present invention, there is provided a method for forming a prepackage, the method further comprising the following steps:

[0048] e) Attaching the third layer to the first side and / or the first layer of the flexible printed circuit board by means of a fourth layer of adhesive material, such as a UV curing adhesive material.

[0049] The advantage of this method is that, due to the adhesive layer, the third layer is firmly attached to the first side and / or the first layer of the flexible printed circuit board. The adhesive material is preferably deposited on the first side of the flexible printed circuit board in a viscous state, and it is subsequently cured after applying the third layer. In this way, the different heights of the non-planar circuit parts formed on the flexible printed circuit board are compensated by filling the adhesive material, and the third layer can be reliably attached to the flexible printed circuit board. Preferably, the curing of the adhesive material is caused by UV radiation.

[0050] According to another embodiment of the present invention, a method for forming a prepackage is provided, wherein the first layer of material has an opening, and step d) is performed by placing a third layer into the opening to complete the first planar layer.

[0051] The advantage of this construction is that the third layer covers the flexible printed circuit board and can form a continuous layer with the first layer. In addition, the third layer flattens the adhesive material used to connect the third layer to the flexible printed circuit board and prevents the adhesive material from escaping during coating and before polymerization, for example by UV radiation.

[0052] Preferably, the third layer is positioned in the opening so as to form a continuous planar layer with the first layer of dielectric material.

[0053] According to another embodiment of the present invention, a method for forming a pre-package is provided, wherein one or more flexible printed circuit boards are arranged in a first roll and they are configured to form an array, and wherein a first layer and a second layer are arranged in a second roll and a third roll, respectively, and the method is performed using a reel-to-reel process.

[0054] The method has the advantage that the process for forming the prepackage for the flexible printed circuit board is performed in a fast and efficient manner due to the roll-to-roll process. Furthermore, the number of layers applied to the flexible printed circuit board is limited, thus further simplifying the process.

[0055] According to another embodiment of the present invention, the pre-package can be formed by means of a plurality of foils having a predetermined size, for example A4 size or larger, wherein the first foil comprises a plurality of elements forming the first layer, the second foil comprises a plurality of elements forming the second layer, and the third foil comprises a plurality of flexible printed circuit boards. Preferably, in order to form the pre-package, the first foil, the second foil and the third foil are stacked so that the first element forming the first layer, the second element forming the second layer and the flexible printed circuit board are stacked and attached to each other. Preferably, the first foil, the second foil and the third foil have A4 size.

[0056] Preferably, the pre-packages can be formed by means of a roll-to-roll process with a predefined layout, for example an A4 layout or larger.

[0057] According to another embodiment of the present invention, there is provided a method for forming a pre-laminate for a smart card, the method comprising the following steps:

[0058] f) providing a stack of card layers to form a pre-laminate having a window;

[0059] g) forming a prepackage according to one of the above methods;

[0060] h) Inserting the pre-package into the window of the stack of card layers.

[0061] The advantage of this method is that the electronic components of the smart card are primarily encapsulated and protected in the prepackage structure and they are not in direct contact with other layers of the prelaminate for the smart card.

[0062] According to another embodiment of the present invention, there is provided a method for forming a smart card, the method comprising the following steps:

[0063] i) forming a pre-laminate according to the foregoing method, the pre-laminate having a first side and a second side;

[0064] j) Attaching one or more outer layers to the first side and / or the second side to cover the pre-laminate and form a smart card.

[0065] The advantage of this method is that the electronic components of the smart card are primarily encapsulated and protected in the pre-package structure, and they are not in direct contact with other layers of the smart card. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The present invention will be described with reference to the accompanying drawings, in which like reference numerals and / or designations indicate like parts of the structure and / or similar and / or corresponding parts.

[0067] Figure 1 The cross section of a pre-package for a smart card according to an embodiment of the present invention is schematically shown.

[0068] Figure 2 A cross section of a smart card comprising a pre-laminate and a pre-package according to an embodiment of the present invention is schematically shown.

[0069] Figure 3a A top view of a first side of a flexible printed circuit board according to an embodiment of the present invention is schematically shown.

[0070] Figure 3b A top view of a second side of a flexible printed circuit board according to an embodiment of the present invention is schematically shown.

[0071] Figure 4 The steps of a process for forming a pre-package for a smart card according to an embodiment of the present invention are schematically shown.

[0072] Figure 5 The steps of a process for forming a pre-package for a smart card according to an embodiment of the present invention are schematically shown.

[0073] Figure 6 The steps of a process for forming a pre-package for a smart card according to an embodiment of the present invention are schematically shown. DETAILED DESCRIPTION

[0074] Hereinafter, the present invention is described with reference to specific embodiments, as shown in the accompanying drawings. However, the present invention is not limited to the specific embodiments described in the following detailed description and shown in the accompanying drawings. On the contrary, the described embodiments are merely illustrative of 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 apparent to those skilled in the art.

[0075] Figure 1 A cross-sectional view of a pre-package 100 according to an embodiment of the present invention is schematically shown.

[0076] The prepackage 100 includes a flexible printed circuit board 110 having a first side 110a at the top and a second side 110b at the bottom. The flexible printed circuit board 110 includes one or more non-planar electronic components 111, 112, 113. It should be understood that the flexible printed circuit board 110 includes a board substrate on which one or more electronic components 111, 112, 113 are formed, such as a display module, a keyboard or a separate button, an energy storage component such as a battery, an optical component, etc. The electronic components 111, 112, 113 protrude from the board substrate of the flexible printed circuit board 110, and they have different heights relative to the substrate. Accordingly, they are called non-planar electronic components.

[0077] The first side 110a of the flexible printed circuit board 110 is covered with a first layer of material 121 and a third layer of material 123. The second side 110b of the flexible printed circuit board 110 is covered with a second layer of material 122. For example, the first layer 121 and the second layer 122 may include PVC and / or polycarbonate materials. The first layer 121 includes an opening 125 in which the material of the third layer 123 is placed. The third layer 123 is flush with the first layer 121, thereby forming a continuous layer of dielectric material. The third layer 123 is attached to the first side 110a of the flexible printed circuit board 110 by a layer of adhesive material 124. Preferably, the adhesive material 124 includes a UV adhesive material. The third layer 123 also has the function of an "anti-settling layer". In fact, the third layer 123 flattens the adhesive material 124 and prevents the adhesive material 124 from overflowing during liquid coating and before polymerization (e.g., UV polymerization).

[0078] Alternatively or additionally, the third layer 123 may be attached to a portion of the top surface of the first layer 121 by an adhesive material 124 .

[0079] The material of the third layer 123 has a VICAT softening temperature that is higher than the VICAT softening temperature of the dielectric material of the first layer 121 and / or the second layer 122. In this way, during the lamination process used to form the prepackage 100 and the smart card 500 (described below), the third layer 123 does not shrink or deform due to the application of high temperature and pressure.

[0080] After formation, the pre-package 100 can be inserted into the corresponding window 520 of the smart card 500. Figure 2 As can be seen in the cross-sectional view of Figure 2 As seen in FIG. 5 , the smart card 500 includes a pre-laminated structure 200 having a window 520 and a first and a second stack of outer layers 300 .

[0081] The pre-laminated structure 200 comprises a central plastic layer 210 of the smart card 500 and electronic components 110, 111, 112, 113 representing the core of the smart card 500. In other words, the term "pre-laminate" refers to the structure of the smart card comprising the plastic layer 210 and the electronic components 110, 111, 112, 113, which are assembled together before lamination to the outer layer 310, which are then added to the smart card 500 for aesthetic purposes and to provide additional mechanical robustness.

[0082] The pre-laminate 200 includes a window 520 , the size of which is set to match the size of the pre-package 100 .

[0083] The pre-laminate 200 further comprises a layer 211 comprising an embedded wire antenna 250 configured to be connected to an electronic component of the pre-package 100, such as a flexible printed circuit board 110 and / or circuit portions 111, 112, 113. Accordingly, the pre-package 100 comprises a layer 122 comprising contact pads 150 to be connected to the wires of the antenna 250 so as to enable communication with an external device. The layer 122 protrudes from the edge of the second side 110b of the pre-package 100.

[0084] The prepackage 100 according to the present invention can advantageously be Figure 3a , Figure 3b , Figure 4 , Figure 5 and Figure 6 The roll-to-roll process described is formed.

[0085] Figure 3a Schematically shows details of a roll 600 comprising a plurality of flexible printed circuit boards 110. In particular, Figure 3a The first side 110a of the flexible printed circuit board 110 formed on the roll 600 is schematically shown. A non-planar electronic component 111 is formed on the first side 110a.

[0086] Figure 3b Schematically shows details of a roll 600 comprising a plurality of flexible printed circuit boards 110. In particular, Figure 3bThe second side 110b of the flexible printed circuit board 110 formed on the roll 600 is schematically shown. A non-planar electronic component 112 is formed on the second side 110b. For example, the non-planar electronic component 112 may include a display module.

[0087] Figure 4 The steps of the method for forming a pre-package 100 for a smart card according to an embodiment of the present invention are schematically shown. Figure 4 In the embodiment, the second roll 620 of material is placed on the first roll 600 of the flexible printed circuit board 110, and in particular the second roll 620 is attached to the second side 110b of the roll 600. The second roll 620 includes a plurality of openings corresponding to the non-planar electronic components 112. For example, the non-planar electronic components 112 may include a display module that must be visible from the back of the pre-package 100 during use of the final smart card 500.

[0088] Figure 5 Another step of the process for forming a pre-package 100 according to an embodiment of the present invention is schematically shown. A third roll 610 of material is applied to the first roll 600 including a plurality of flexible printed circuit boards 110. In particular, the third roll 610 is placed on the first side 110a of the roll 600 of flexible circuit boards 110. The third roll 610 includes a plurality of holes 113' corresponding to the non-planar electronic components 113 of the flexible printed circuit boards 110, so that the non-planar electronic components 113 can contact other electronic components of the smart card.

[0089] The third roll 610 also includes a plurality of windows 125 that accommodate the electronic components 111 .

[0090] Figure 6 Detail of a third roll 610 of material is schematically shown. Figure 6 In the figure, the opening 113' for accommodating the electronic component 113 and the window 125 for accommodating the electronic component 111 are clearly visible. The opening 113' is not filled with any dielectric material to ensure the electrical connection between the electronic component 113 and other electronic components of the smart card 500. On the other hand, each window 125 is filled with an adhesive material, such as a UV adhesive material.

[0091] The adhesive material is preferably applied to the windows 125 in a viscous state so that it can flow in the windows 125 and fill the gaps on top of or between the non-planar electronic components 111 formed on the first side 110a. After applying the adhesive material, a hardening material, such as epoxy glass, is placed on each window 125 to further cover and protect the first side 110a of the flexible printed circuit board 110. The hardening material includes a solid layer of material that forms the third layer 123 of the prepackage 100 and is not deformed by contact with the non-planar electronic components 111 of the flexible printed circuit board 110. After attaching the hardening layer 123, the adhesive material is cured, for example via UV radiation, to provide a stable attachment between the first side 110a of the flexible printed circuit board 110 and the dielectric material of the third layer 123.

[0092] In this way, a multilayer roll is obtained comprising a plurality of prepackages 100. The multilayer roll comprises a central roll 600 of a flexible printed circuit board 600 laminated between two outer rolls 610 and 620 of dielectric material.

[0093] Even though the invention has been described with reference to the above embodiments, it is clear to those skilled in the art that different modifications, variations and improvements of the invention may be applied within the scope of the appended claims according to the above description and field without departing from the scope and purpose of the invention.

[0094] For example, it should be appreciated that any layout may be used in a roll-to-roll process.

[0095] Finally, areas that are considered to be already known by a person skilled in the art have not been described in order to avoid obscuring the described invention in an unnecessary manner.

[0096] Description of Reference Numerals

[0097] 100: Pre-packaged

[0098] 110: Flexible printed circuit board

[0099] 110a: First side of flexible printed circuit board

[0100] 110b: Second side of the flexible printed circuit board

[0101] 111, 112, 113: Non-planar circuit parts

[0102] 113': Kong

[0103] 121: The first material of the first layer

[0104] 122: The second dielectric material of the second layer

[0105] 123: The third layer of hardened material

[0106] 124: Adhesive material

[0107] 125: Opening

[0108] 130: Anti-sinking layer

[0109] 140: Additional layer of dielectric material

[0110] 150: Antenna contact part

[0111] 200: Pre-laminated

[0112] 210, 211: Layers of pre-laminate

[0113] 250: Card antenna

[0114] 300: Cover

[0115] 310: Outer layer

[0116] 500: Smart card

[0117] 520: Smart Card Window

[0118] 600, 610, 620: Volume

Claims

1. A prepackage (100) of a flexible printed circuit board (110) for a smart card (500), the prepackage comprising the following elements: - a flexible printed circuit board (110) comprising one or more non-planar circuit portions (111, 112, 113), the flexible printed circuit board (110) having a first side (110a) and a second side (110b) opposite to the first side (110a); - a first layer of a first material (121) at least partially covering the first side (110a) of the flexible printed circuit board (110) to form a planar layer; - a second layer of a second material (122) covering the second side (110b) of the flexible printed circuit board (110); and - a third layer (123) comprising a hardened material at least partially covering said first side (110a) to form a planar layer; The first material (121) has a first VICAT softening temperature, the second material (122) has a second VICAT softening temperature, and the third layer (123) has a third VICAT softening temperature, wherein the third VICAT softening temperature is higher than the first VICAT softening temperature and / or the second VICAT softening temperature.

2. Prepackage (100) according to claim 1, wherein the hardened material has a flexural strength comprised between 40 MPa and 150 MPa, and / or a flexural modulus comprised between 0.5 GPa and 3 GPa.

3. Prepackage (100) according to claim 1 or 2, wherein the hardening material has a VICAT softening temperature comprised between 68°C and 150°C.

4. The prepackage (100) according to any one of the preceding claims, wherein the stiffening material comprises PET and / or PI.

5. The prepackage (100) according to any one of the preceding claims, wherein the first layer (121) has an opening (125), and the third layer (123) is placed in the opening (125) to complete the first planar layer.

6. The prepackage (100) according to any one of the preceding claims, wherein the third layer (123) is attached to the first side (110a) of the flexible printed circuit board (110) and / or the first layer (121) by an adhesive layer (124).

7. The prepackage (100) according to claim 6, wherein the adhesive layer (124) comprises a UV curing adhesive material.

8. The prepackage (100) according to any one of the preceding claims, wherein the first layer (121) and the second layer (122) comprise PVC, PETG, PLA, PU and / or polycarbonate.

9. The prepackage (100) according to any one of the preceding claims, wherein the first layer (121) and / or the second layer (122) comprises one or more windows (113') for accommodating the one or more non-planar circuit parts (111, 112, 113).

10. A smart card (500), comprising: A stack of card layers (210, 310) forming a smart card body having a window (520); and A prepackage (100) according to any one of claims 1 to 9 embedded in the window (520).

11. A method for forming a prepackage (100) of a flexible printed circuit board (110) for a smart card (500), the method comprising the following steps: a) providing one or more flexible printed circuit boards (110), each flexible printed circuit board (110) comprising at least one non-planar circuit portion (111, 112, 113) and having a first side (110a) and a second side (110b) opposite to the first side (110a); b) at least partially covering the first side (110a) of each flexible printed circuit board (110) with a first layer of material (121) so as to form a first planar layer on the first side (110a); c) covering the second side (110b) of each flexible printed circuit board (110) with a second layer of material (122); d) further at least partially covering the first side (110a) with a third layer (123) of hardened material, The first material (121) has a first VICAT softening temperature, the second material (122) has a second VICAT softening temperature, and the third layer (123) has a third VICAT softening temperature, wherein the third VICAT softening temperature is higher than the first VICAT softening temperature and / or the second VICAT softening temperature.

12. The method for forming a prepackage (100) according to claim 11, further comprising the following steps: e) attaching the third layer (123) to the first side (110a) and / or the first layer (121) of the flexible printed circuit board (110) by means of a fourth layer (124) of adhesive material, such as a UV curing adhesive material.

13. A method for forming a prepackage (100) according to claim 11 or 12, wherein the material (121) of the first layer has an opening (125), and step d) is performed by placing the third layer (123) into the opening (125) to complete the first planar layer.

14. A method for forming a prepackage (100) according to any one of claims 11 to 13, wherein the one or more flexible printed circuit boards (110) are arranged in a first roll (600) and are configured to form an array, and wherein the first (121) layer and the second (122) layer are arranged in a second roll (610) and a third roll (620), respectively, and the method is performed using a roll-to-roll process.

15. A method for forming a pre-laminate (200) for a smart card (500), comprising the steps of: f) providing a stack of card layers (210, 310) to form a pre-laminate having a window (520); g) forming a prepackage (100) according to the method of any one of claims 11 to 14; h) inserting the pre-package (100) into the window (520) of the stack of card layers (210, 310).

16. A method for forming a smart card (500), comprising the steps of: i) forming a pre-laminate (200) according to the method of claim 15, the pre-laminate (200) having a first side and a second side; j) attaching one or more outer layers (310) to the first side and / or the second side to cover the pre-laminate and form the smart card (500).

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