Smart card gradient dielectric packaging structure

Abstract

This utility model discloses a gradient dielectric packaging structure for smart cards, including an antenna and a circuit layer with the chip exposed upwards. A first protective layer and a second protective layer are respectively disposed on the upper and lower surfaces of the circuit layer. The first protective layer consists of a high-dielectric protective layer and a low-dielectric packaging layer from bottom to top, with a dielectric gradient transition layer filling the space between the high-dielectric protective layer and the low-dielectric packaging layer. The second protective layer also consists of a high-dielectric protective layer and a low-dielectric packaging layer from bottom to top. The high-dielectric protective layer only covers the surface of the chip and antenna, with other areas hollowed out and filled with conductive foam. The low-dielectric packaging layer is attached to the outer surface of the high-dielectric protective layer and the conductive foam. This gradient dielectric packaging structure for smart cards optimizes electromagnetic compatibility and signal integrity by using a directional high-dielectric layer to locally shield sensitive areas and conductive foam to absorb interference, combined with a dielectric gradient transition layer to reduce signal reflection and a low-dielectric packaging layer to reduce high-frequency loss.

Description

Technical Field

[0001] This utility model relates to the field of smart card technology, specifically to a gradient dielectric packaging structure for smart cards. Background Technology

[0002] With the widespread application of smart card technology, smart cards have penetrated various fields such as social security, healthcare, and public transportation, bringing great convenience to people's lives. However, smart cards also face many challenges during use, among which electromagnetic interference is particularly prominent.

[0003] Smart cards integrate microchips that are highly sensitive to electromagnetic environments. In daily life and work, smart cards are frequently near various sources of electromagnetic radiation, such as mobile phones, computers, and wireless devices. These devices generate electromagnetic waves during operation, which can interfere with the chips inside the smart card. Electromagnetic interference can not only cause smart card reading failures, affecting normal use, but can also damage the chip and shorten the smart card's lifespan.

[0004] Traditional smart card designs have shortcomings in protecting against electromagnetic interference. On one hand, the materials and structure of smart cards often fail to effectively shield against external electromagnetic interference. For example, many common smart cards are made of polyvinyl chloride (PVC), a material with poor electromagnetic shielding properties, which cannot effectively prevent the intrusion of external electromagnetic waves. On the other hand, the internal chip layout and circuit design of smart cards also lack protective measures against electromagnetic interference. In complex electromagnetic environments, chips are easily interfered with, leading to data transmission errors or functional failures. Summary of the Invention

[0005] To overcome the shortcomings of existing technical solutions, this utility model provides a gradient dielectric packaging structure for smart cards, which can effectively solve the problems of electromagnetic interference and signal attenuation in traditional smart cards mentioned in the background art.

[0006] The technical solution adopted by this utility model to solve its technical problem is: a smart card gradient dielectric packaging structure, including an antenna and a circuit layer with the chip exposed upwards, wherein a first protective layer and a second protective layer are respectively provided on the upper and lower surfaces of the circuit layer; The first protective layer consists of a high-dielectric protective layer and a low-dielectric encapsulation layer from bottom to top. A dielectric gradient transition layer is filled between the high-dielectric protective layer and the low-dielectric encapsulation layer, and the dielectric gradient transition layer is wrapped around the outside of the high-dielectric protective layer. The second protective layer consists of a high-dielectric protective layer and a low-dielectric encapsulation layer from bottom to top. The high-dielectric protective layer covers only the surface of the chip and antenna, while other areas are hollowed out and filled with conductive foam. The low-dielectric encapsulation layer is attached to the outer surface of the high-dielectric protective layer and the conductive foam.

[0007] Furthermore, the high dielectric protective layer is a polyvinylidene fluoride composite layer with a dielectric constant ε_r of 6 to 8.

[0008] Furthermore, the polyvinylidene fluoride composite layer is made by mixing polyvinylidene fluoride and nano-alumina in a mass ratio of 8:2.

[0009] Furthermore, the dielectric gradient transition layer is a composite layer of nano-silica and polyimide with a dielectric constant that decreases from ε_r=6 to ε_r=4.

[0010] Furthermore, the low-dielectric encapsulation layer is a porous fluorinated polyimide layer with a dielectric constant ε_r ≤ 3.5.

[0011] Furthermore, the conductive foam is filled in the hollow area of ​​the high dielectric protective layer in a tight filling manner, and the outer surface of the conductive foam is flush with the outer surface of the high dielectric protective layer.

[0012] Furthermore, the first protective layer and the second protective layer are respectively fixedly connected to the upper and lower surfaces of the circuit layer through an adhesive layer, wherein the adhesive layer is an epoxy resin adhesive layer.

[0013] Compared with the prior art, the beneficial effects of this utility model are: Optimized electromagnetic compatibility: A directional high-dielectric layer shields sensitive areas, and conductive foam is grounded to absorb local electromagnetic interference. The overall structure balances signal transmission and anti-interference capabilities.

[0014] Improved signal integrity: The dielectric gradient transition layer reduces signal reflection caused by abrupt changes in dielectric constant, and the low-dielectric encapsulation layer reduces high-frequency loss, making it suitable for high-frequency applications such as RFID.

[0015] Enhanced structural reliability: The layered protection design provides multiple mechanical protections to prevent chip failure due to bending, impact, or moisture.

[0016] Lightweight and miniaturized: The hollowed-out area is filled with conductive foam to replace the traditional full-encapsulation material, reducing weight and encapsulation thickness, which is suitable for the needs of ultra-thin smart cards. Attached Figure Description

[0017] Figure 1 This is an exploded view of the structure of this utility model. Figure 1 ; Figure 2 This is an exploded view of the structure of this utility model. Figure 2 .

[0018] Numbering on the map: 1-Circuit layer, 2-High dielectric protective layer, 3-Dielectric gradient transition layer, 4-Low dielectric encapsulation layer, 5-Conductive foam, 11-Antenna, 12-Chip. Detailed Implementation

[0019] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0020] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure. Example

[0021] like Figure 1-2 As shown, this utility model provides a smart card gradient dielectric packaging structure, including an antenna 11 and a circuit layer 1 with the chip 12 exposed upwards. The upper and lower surfaces of the circuit layer 1 are respectively provided with a first protective layer and a second protective layer. The first protective layer consists of a high-dielectric protective layer 2 and a low-dielectric encapsulation layer 4 from bottom to top. A dielectric constant transition layer 3 is filled between the high-dielectric protective layer 2 and the low-dielectric encapsulation layer 4. The dielectric constant transition layer 3 is wrapped around the outside of the high-dielectric protective layer 2. The dielectric constant transition layer 3 is filled between the high-dielectric protective layer 2 and the low-dielectric encapsulation layer 4 and uses a material with a gradually changing dielectric constant to achieve a smooth transition of dielectric properties. The second protective layer consists of a high-dielectric protective layer 2 and a low-dielectric encapsulation layer 4 from bottom to top. The high-dielectric protective layer 2 covers only the surface of the chip 12 and the antenna 11, while other areas are hollowed out to isolate the high-voltage electric field and suppress charge leakage. The hollowed-out areas are filled with conductive foam 5. The low-dielectric encapsulation layer 4 is attached to the outer surface of the high-dielectric protective layer 2 and the conductive foam 5 for electromagnetic compatibility and heat dissipation optimization.

[0022] Antenna 11 and chip 12 exposed: Circuit layer 1 needs to expose the upward portion of antenna 11 and chip 12 to ensure signal transmission and functional implementation.

[0023] The conductive foam 5 filler provides electromagnetic shielding in the hollowed-out area, absorbing and dispersing external electromagnetic interference and protecting the internal circuitry.

[0024] Conductive foam 5 works in synergy with the low dielectric layer: Conductive foam 5 not only provides electromagnetic shielding, but also conducts the heat of chip 12 to the encapsulation layer through its high thermal conductivity. Combined with the heat dissipation design of the low dielectric encapsulation layer 4, it achieves efficient thermal management.

[0025] The high dielectric protective layer 2 is a polyvinylidene fluoride composite layer with a dielectric constant ε_r of 6-8 and a thickness of 50-80 μm.

[0026] The high-dielectric protective layer 2 is based on PVDF resin. By doping with low-dielectric-constant materials (such as fluorinated ethylene propylene copolymer FEP, whose ε_r≈2.1) or inorganic dielectric fillers (such as barium strontium titanate nanoparticles), the overall dielectric constant is adjusted to the range of 6-8, so as to achieve uniform electric field distribution and charge leakage suppression. Specifically, the high-dielectric-constant filler (such as barium titanate, ε_r≈2000) is uniformly dispersed in the PVDF matrix at a volume fraction of 5-10% through melt blending or solution casting processes.

[0027] The polyvinylidene fluoride composite layer is made by mixing polyvinylidene fluoride and nano-alumina in a mass ratio of 8:2.

[0028] The high dielectric constant of nano-alumina synergistically enhances the overall dielectric properties of the composite material through interfacial polarization, stabilizing the dielectric constant within the 6-8 range. The uniform dispersion of nano-alumina reduces defects and voids in the composite material, lowering dielectric loss and improving energy storage efficiency. Furthermore, the relatively small amount of nano-alumina required, coupled with its lower cost compared to high-end inorganic fillers such as barium strontium titanate, reduces the overall production cost of the composite material.

[0029] The dielectric gradient transition layer 3 is a composite layer of nano-silica and polyimide with a dielectric constant decreasing from ε_r=6 to ε_r=4, the nanofiller orientation degree is >85%, and the tensile strength is ≥320MPa.

[0030] The dielectric gradient transition layer 3 achieves a smooth change in dielectric constant from high to low through the composite design of nano-silica and polyimide, avoiding electromagnetic wave reflection and signal loss caused by abrupt changes in dielectric constant between traditional materials, and improving the transmission efficiency of electromagnetic waves in the packaging structure.

[0031] Nano-silica, as an inorganic filler, significantly improves the mechanical strength and modulus of the polyimide matrix, making the transition layer less prone to cracking or deformation under mechanical stress, thus ensuring the long-term reliability of the encapsulation structure.

[0032] The low-dielectric encapsulation layer 4 is a porous fluorinated polyimide layer with a dielectric constant ε_r ≤ 3.5. Its porosity is 20%-60% and its pore size is 5-50nm. The porous structure reduces the effective dielectric constant of the material through air pores, reduces the reflection and scattering of electromagnetic waves inside the material, thereby suppressing electromagnetic interference. In addition, the porous structure gives the material excellent flexibility, making it less prone to cracking or breaking when repeatedly bent or deformed.

[0033] See Figure 1 The conductive foam 5 is filled in the hollow area of ​​the high dielectric protective layer 2 in a tight filling manner, and the outer surface of the conductive foam 5 is flush with the outer surface of the high dielectric protective layer 2.

[0034] The three-dimensional mesh conductive structure of the foam provides a low-impedance path, guiding electromagnetic wave energy into heat energy. The flush design eliminates gaps, preventing electromagnetic waves from leaking through. The shielding effectiveness drops sharply when the gap width exceeds 1 / 10 of the wavelength.

[0035] The first protective layer and the second protective layer are fixedly connected to the upper and lower surfaces of the circuit layer 1 by an adhesive layer. The adhesive layer is an epoxy resin adhesive layer, which provides high-strength adhesion to firmly bond the protective layer to the circuit layer 1 and form an integrated structure.

[0036] In the description of this utility model, it should be understood that the terms "middle", "length", "upper", "lower", "front", "rear", "vertical", "horizontal", "inner", "outer", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0037] In this invention, unless otherwise expressly specified and limited, the first feature "on" the second feature may be in direct contact with the first feature, or indirect contact with the first feature through an intermediate medium. "A plurality of" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0038] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0039] The above description is merely illustrative of the embodiments of this utility model and is not intended to limit the scope of this utility model. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model without creative labor should be included within the protection scope of this utility model.

Claims

1. A smart card gradient dielectric packaging structure, including an antenna and a circuit layer with the chip exposed upwards, characterized in that, The upper and lower surfaces of the circuit layer are respectively provided with a first protective layer and a second protective layer; The first protective layer consists of a high-dielectric protective layer and a low-dielectric encapsulation layer from bottom to top. A dielectric gradient transition layer is filled between the high-dielectric protective layer and the low-dielectric encapsulation layer, and the dielectric gradient transition layer is wrapped around the outside of the high-dielectric protective layer. The second protective layer consists of a high-dielectric protective layer and a low-dielectric encapsulation layer from bottom to top. The high-dielectric protective layer covers only the surface of the chip and antenna, while other areas are hollowed out and filled with conductive foam. The low-dielectric encapsulation layer is attached to the outer surface of the high-dielectric protective layer and the conductive foam.

2. The smart card gradient dielectric packaging structure according to claim 1, characterized in that: The high dielectric protective layer is a polyvinylidene fluoride composite layer with a dielectric constant ε_r of 6 to 8.

3. The smart card gradient dielectric packaging structure according to claim 2, characterized in that: The polyvinylidene fluoride composite layer is made by mixing polyvinylidene fluoride and nano-alumina in a mass ratio of 8:

2.

4. The smart card gradient dielectric packaging structure according to claim 1, characterized in that: The dielectric gradient transition layer is a composite layer of nano-silica and polyimide with a dielectric constant that decreases from ε_r=6 to ε_r=4.

5. The smart card gradient dielectric packaging structure according to claim 1, characterized in that: The low-dielectric encapsulation layer is a porous fluorinated polyimide layer with a dielectric constant ε_r ≤ 3.

5.

6. The smart card gradient dielectric packaging structure according to claim 1, characterized in that: The conductive foam is tightly filled into the hollow area of ​​the high dielectric protective layer, and the outer surface of the conductive foam is flush with the outer surface of the high dielectric protective layer.

7. The smart card gradient dielectric packaging structure according to claim 1, characterized in that: The first protective layer and the second protective layer are respectively fixedly connected to the upper and lower surfaces of the circuit layer through an adhesive layer, which is an epoxy resin adhesive layer.

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