Conductive pastes, shielding structures and terminal devices

Abstract

The present application provides a conductive paste, which relates to the field of electrical connection technology. The conductive paste has the property of low-temperature curing. The temperature of the conductive paste is low during the curing process, which has little or no effect on related components. The conductive paste formed after the conductive paste is cured has good electrical connection performance and can achieve electrical connection between components. The conductive paste has fluidity before curing and can be used in special-shaped spaces and smaller installation spaces. The conductive paste has initial viscosity. Before curing, the conductive paste can adhere to the bonded components, reducing the welding process. The present application also provides a shielding structure and a terminal device.

Description

Technical Field

[0001] The present application relates to the field of electrical connection technology, and in particular to a conductive paste, a shielding structure and a terminal device. Background Art

[0002] As terminal devices develop towards intelligence, multi-functions and miniaturization, more and more functional devices and structural components in terminal devices usually need to be integrated in a smaller space. Multiple components may affect each other, such as electromagnetic interference, assembly impact, disassembly impact, etc. Summary of the Invention

[0003] The present application aims to provide a conductive paste with low-temperature properties, a shielding structure using the conductive paste, and a terminal device. The conductive paste can be cured under low-temperature conditions, and after curing, multiple components can be connected. The conductive paste requires a low temperature during the curing process, has little or no effect on related components, and is easy to assemble or disassemble.

[0004] In the first aspect, the present application provides a conductive paste comprising a substrate and a conductive material, wherein the conductive material is dispersed in the substrate, the conductive material comprises a first conductor and a second conductor, the size of the first conductor is less than or equal to 100 nm, and the size of the second conductor is greater than or equal to 1 μm; the structure of the first conductor includes spherical and / or needle-shaped, and the structure of the second conductor includes flake and / or spherical, and the curing temperature of the conductive paste is 25°C-100°C.

[0005] In the above design, the conductive paste has the property of low-temperature curing. The temperature of the conductive paste is low during the curing process, and the impact on related components is small or no impact; and the conductive paste formed after the conductive paste is cured has good electrical connection performance, which can achieve electrical connection between components; furthermore, the conductive paste has fluidity before curing and can be suitable for special-shaped spaces and smaller installation spaces; the conductive paste has initial viscosity, and the conductive paste can adhere to the bonded components before curing, reducing the welding process.

[0006] In some possible embodiments of the present application, the substrate includes at least one of epoxy resin, polyamide and polyacrylonitrile.

[0007] In the above design, the epoxy resin, polyamide, and polyacrylonitrile materials have high cohesive strength, which makes the conductive paste have initial viscosity.

[0008] In some possible embodiments of the present application, the viscosity of the conductive paste is 50Pa·S-100Pa·S, and the adhesion of the conductive paste is greater than or equal to 1kg / mm 2 .

[0009] In the above design, the initial viscosity and stickiness of the conductive paste are further improved. Before the curing process, the conductive paste can adhere to the bonded components without an additional activation step, reducing the welding process and the curing time, especially for welding in application scenarios with smaller welding space, which has a good improvement.

[0010] In some possible embodiments of the present application, the material of the conductive material includes at least one of silver, copper, nickel, iron, aluminum, nickel-plated carbon particles, and nickel-plated copper particles.

[0011] In the above design, the above materials are possible types of materials that can be selected for the conductive object.

[0012] In some possible embodiments of the present application, when the material of the conductive object includes silver, the mass fraction of the conductive object in the conductive paste is 43%-75%; when the material of the conductive object includes copper and / or nickel, the mass fraction of the conductive object in the conductive paste is 55%-85%; when the material of the conductive object includes aluminum, the mass fraction of the conductive object in the conductive paste is 55%-80%; when the material of the conductive object includes iron or iron and nickel, the mass fraction of the conductive object in the conductive paste is 55%-80%.

[0013] In the above design, when the material of the conductive material includes different materials, the mass fraction of the conductive material in the conductive paste is different, and the performance of the conductive paste is also different. The corresponding material can be selected according to the actual application scenario.

[0014] In some possible embodiments of the present application, the conductive paste further includes a polar monomer and / or a chain extender, the polar monomer contains amide, alcohol and / or phenol functional groups, and the chain extender includes at least one of 1,4-butanediol, 1,6-hexanediol and glycerol.

[0015] In the above design, both polar monomers and chain extenders can be used to increase the molecular weight of the substrate and increase its polarity, thereby improving the cohesive strength of the substrate, which is beneficial to further improve the initial viscosity of the conductive paste.

[0016] In some possible embodiments of the present application, the conductive paste further includes an organic elastomer, and the organic elastomer includes at least one of a carboxylated nitrile elastomer and a styrene-butadiene pyridine elastomer.

[0017] In the above design, the organic elastomer can improve the toughness and tensile strength of the conductive paste.

[0018] In some possible embodiments of the present application, the conductive paste further includes itaconic acid, and the itaconic acid is used to polymerize with the substrate.

[0019] In the above design, itaconic acid can be loaded on the surface of the conductive material and polymerize with the substrate to form chemical bonds, thereby improving the conductivity and shear strength of the conductive paste; in addition, the high content of the conductive material can hinder the deformation and movement of the substrate, thereby fixing the substrate and improving the shear strength and thermal stability.

[0020] In a second aspect, the present application provides a shielding structure comprising a circuit board, a shielding member, a conductive paste, and at least one electronic component. The shielding member is disposed on the circuit board; the conductive paste electrically connects the circuit board and the shielding member and is disposed in a ring shape. The circuit board and the shielding member enclose a chamber, wherein the conductive paste is formed by curing a conductive paste; and the at least one electronic component is located in the chamber.

[0021] In the above design, the shield is a one-piece structure, and the conductive paste is formed by curing the conductive paste. The conductive paste can be cured at a relatively low temperature; the resulting conductive paste has viscosity, allowing the shield to be welded to the circuit board. When the shield structure needs to be repaired, it can be directly disassembled and assembled at room temperature, with little or no impact on the circuit board and electronic components. When electrical connections need to be made again after disassembly, the conductive paste has a low curing temperature, with little or no impact on other components. The one-piece shield does not need to consider side overlap and overlap width issues, which can reduce the width of the overlap area in related technologies, thereby helping to reduce the space occupied by the shield.

[0022] In some possible implementations of the present application, the shielding member includes a top plate and side plates, the side plates are annularly arranged around the top plate, and the ends of the side plates facing away from the top plate are connected to the conductive paste.

[0023] The above design is a possible implementation in which the shielding element is an integrated structure.

[0024] In some possible implementations of the present application, the end of the side plate facing away from the top plate expands in an arc shape in a direction away from the electronic component, and the conductive paste connects the end of the arc-shaped side plate and the circuit board.

[0025] In the above design, when using conductive paste for connection, the effective contact area between the conductive paste and the side plate can be increased, thereby increasing the connection strength; the conductive paste has fluidity before solidifying to form a conductive paste, which can fully contact the solder feet on the circuit board, thus helping to reduce the size of the solder feet.

[0026] In some possible implementations of the present application, the side plate is connected to the circuit board, and the conductive paste is located on two opposite surfaces of the side plate and connected to the surface of the circuit board.

[0027] In the above design, the surface of the side plate is flat, and the arc-shaped structure is omitted, which can reduce the area of ​​the shielding component; at the same time, conductive paste is provided on the two opposite surfaces of the shielding component, which can improve the lateral shielding performance.

[0028] In some possible implementations of the present application, a through hole is opened on the side plate, the through hole is connected to the cavity, and the conductive paste is also located in the through hole.

[0029] In the above design, the conductive paste is located on two opposite surfaces of the side plate and in the through hole, which can further improve the connection strength of the conductive paste. In addition, the contact area between the conductive paste and the shielding component is increased, which can effectively reduce the impedance and improve the shielding performance.

[0030] In some possible embodiments of the present application, a groove is formed in the circuit board, at least a portion of the end of the side plate is located in the groove, and at least a portion of the conductive paste is located between the side plate and the circuit board and connects the side plate and the circuit board.

[0031] In the above design, compared with the side panels that expand outward in an arc shape, the side panels omit the arc structure, which can reduce the area of ​​the shielding component; in addition, the groove has a limiting function, further playing a fixing role.

[0032] In some possible implementations of the present application, the side plate and the circuit board are spaced apart, and the conductive paste is located between the side plate and the circuit board and connects the side plate and the circuit board.

[0033] In the above design, the conductive paste connects the circuit board and the side plate, and the height of the conductive paste can be increased to reduce the height of the side plate, which is equivalent to using part of the conductive paste to replace the side plate, thereby helping to reduce the overall weight of the shielding structure.

[0034] In some possible implementations of the present application, the shielding structure further includes an adhesive layer, which is located between the top plate and at least one electronic component to bond the electronic component and the shielding member.

[0035] In the above design, the height of the shielding structure can be reduced as much as possible; the electronic components are bonded with an adhesive layer, and the adhesive layer is elastic, which can not only play a buffering role, but also synchronize the movement of the electronic components and the shielding parts when the shielding structure is subjected to a large impact force (such as collision or falling), thereby reducing the effect of inertia.

[0036] In a third aspect, the present application provides a terminal device, which includes a shielding structure.

[0037] The above design is a possible application scenario of the shielding structure.

[0038] In some possible implementations of the present application, the shielding component is a middle frame of the terminal device.

[0039] The above design is a specific application scenario of the shielding structure. The middle frame is used as the shielding component, which is equivalent to the middle frame in the terminal device not only satisfying the function of the middle frame itself, but also replacing the function of the shielding component, omitting the shielding component, that is, reducing the volume occupied by the shielding component and the distance between the shielding component and the middle frame, which can reduce the overall thickness, weight and production cost of the terminal device; the thickness of some areas of the middle frame can also be increased according to the remaining space in the terminal device, thereby increasing the mechanical strength and shielding performance of the middle frame.

[0040] In some possible implementations of the present application, the terminal device further includes a heat sink, the shielding member is provided with an opening, and the heat sink seals the opening.

[0041] In the above design, the heat sink seals the opening, and the heat generated by the electronic components exposed to the opening can be quickly transferred out through the heat sink. In addition, omitting the shielding member is equivalent to shortening the heat transmission path, thereby also improving the heat dissipation rate.

[0042] In a fourth aspect, the present application provides a terminal device, which includes a conductive paste formed by curing a conductive paste.

[0043] The above design is a possible application scenario of conductive paste.

[0044] In some possible implementations of the present application, the terminal device further includes a screen and a middle frame, and the conductive paste connects the screen and the middle frame to electrically connect the screen and the middle frame.

[0045] The above design is a possible application scenario of conductive paste.

[0046] In some possible implementations of the present application, the middle frame has a curved area, and the conductive paste connects the curved area and the screen.

[0047] In the above design, the use of a conductive paste with high elasticity and high conductivity can replace the technical solution of using foam or spring clips to connect the screen and the middle frame in the related technology. During the process of curing the conductive paste to form the conductive paste, due to the fluidity of the conductive paste, it can better fill the gap between the arc area of ​​the screen and the middle frame, and can simultaneously meet the requirements of the arc top and arc bottom areas to achieve special-shaped connections; the high adhesion of the conductive paste ensures the bonding strength, and the high conductivity and low third harmonic ensure the electrical connection requirements while maintaining the stability of the RSE index; furthermore, when the conductive paste needs to be connected to the antenna fixed on the middle frame, the conductive paste formed by the aluminum-containing conductive paste is beneficial to improving the dielectric constant, and thus is beneficial to improving the antenna strength and electrical connection requirements.

[0048] In some possible implementations of the present application, the terminal device further includes a frame and a circuit board, and the conductive paste connects the frame and the circuit board.

[0049] In the above design, conductive paste connects the frame and circuit board, making it suitable for terminal devices with narrow bezels. Narrow bezels make it difficult to reserve sufficient space for electrical connections to ensure appropriate stress and impedance. Increasing the space for electrical connections could affect the positional relationships and performance of other components. Using conductive paste for connection is not limited to limited spaces or fixed shapes, making narrow bezel designs possible.

[0050] In some possible embodiments of the present application, the terminal device also includes a dial and a decorative piece, a receiving groove is provided on the dial, at least part of the decorative piece is located in the receiving groove, at least part of the conductive paste is located in the receiving groove, and is located between the decorative piece and the dial to connect the dial and the decorative piece.

[0051] In the above design, since the dial and decorative parts are relatively small, during the assembly process, the conductive paste has initial viscosity and high viscosity, so the conductive paste can initially bond the decorative parts and the dial before curing; since the conductive paste has low-temperature and fast-curing properties, the conductive paste can be quickly cured without being at a high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A cross-sectional schematic diagram of a two-piece shielding structure provided in the related art.

[0053] Figure 2 A cross-sectional schematic diagram of a two-piece shielding structure provided in another related art.

[0054] Figure 3 A cross-sectional schematic diagram of a two-piece shielding structure provided as another related art.

[0055] Figure 4 A schematic cross-sectional view of a one-piece shielding structure provided in an embodiment of the present application.

[0056] Figure 5 This is a schematic diagram of the structure of the conductive paste provided in an embodiment of the present application.

[0057] Figure 6 Schematic diagram of the structure of the conductive paste provided in an embodiment of the present application before and after curing.

[0058] Figure 7 A schematic cross-sectional view of a shielding structure provided in some embodiments of the present application.

[0059] Figure 8 A schematic cross-sectional view of a shielding structure provided in some embodiments of the present application.

[0060] Figure 9 A schematic cross-sectional view of a shielding structure provided in some embodiments of the present application.

[0061] Figure 10 A schematic cross-sectional view of a shielding structure provided in some embodiments of the present application.

[0062] Figure 11 A schematic cross-sectional view of a shielding structure provided in some embodiments of the present application.

[0063] Figure 12 A schematic cross-sectional view of a terminal device provided in some embodiments of the present application.

[0064] Figure 13 A schematic diagram of the structure of a terminal device provided by the related technology of this application.

[0065] Figure 14 A schematic diagram of the structure of a terminal device provided by the related technology of this application.

[0066] Figure 15 A schematic structural diagram of a terminal device provided in some embodiments of the present application.

[0067] Figure 16 A schematic cross-sectional view of a terminal device provided in some embodiments of the present application.

[0068] Description of main component symbols

[0069]

[0070] DETAILED DESCRIPTION

[0071] In order to more clearly understand the above-mentioned objects, features and advantages of the present application, the present application is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. In the following description, many specific details are set forth to facilitate a full understanding of the present application. The embodiments described are only a part of the embodiments of the present application, rather than all of the embodiments.

[0072] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes all and any combinations of one or more of the associated listed items.

[0073] In the various embodiments of the present application, for ease of description and not limitation, the term "connection" used in the patent specification and claims of the present application is not limited to physical or mechanical connections, whether direct or indirect. "Up," "down," "above," "below," "left," "right," etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0074] See also Figure 1 , providing a cross-sectional schematic diagram of a two-piece shielding structure 10 for related art. The shielding structure 10 includes a circuit board 11, a shielding frame 12, and a shielding cover 13. The circuit board 11 is electrically connected to at least one electronic component 14. The direction in which the electronic component 14 and the circuit board 11 are stacked is a first direction L1, and one of the directions perpendicular to the first direction L1 is a second direction L2. The shielding frame 12 includes a first side panel 124 and a first top panel 126. The first side panel 124 is annularly arranged around the electronic component 14 along the first direction L1, and an opening 127 is formed at one end of the enclosed space. One end of the first side panel 124 is connected to the circuit board 11 through a conductive paste 122 (such as solder paste). The first top panel 126 is connected to the end of the first side panel 124 away from the circuit board 11, and the first top panel 126 extends along the second direction L2 toward the enclosed space of the first side panel 124. The shielding cover 13 and the shielding frame 12 are two independent components. The shielding cover 13 includes a second side plate portion 134 and a second top plate portion 136. The second side plate portion 134 is arranged around the second top plate portion 136. The second top plate portion 136 can cover the first top plate portion 126 and seal the opening 127. Part of the second side plate portion 134 is rotatably connected to the first side plate portion 124 through the rotating member 128, and the remaining part of the second side plate portion 134 is buckled inward toward the direction of the first side plate portion 124, so that the second side plate portion 134 is buckled and abuts against the first side plate portion 124, thereby making the circuit board 11, the shielding frame 12 and the shielding cover 13 form a closed chamber 132 to shield electromagnetic waves.

[0075] The shielding cover 13 and shielding frame 12 are removable to facilitate repair of the electronic components 14 on the circuit board 11. If the shielding cover 13 and shielding frame 12 were an integral structure, the melting and welding temperatures of the conductive paste 122 would be high. Both melting the conductive paste 122 and re-welding with the conductive paste 122 could affect related components in the shielding structure 10, making it difficult to repair the electronic components 14. To achieve sufficient rigidity, the thickness of the shielding cover 13 is typically 100 μm-150 μm. Along the first direction L1, the overall thickness of the shielding structure 10 is relatively thick. Along the second direction L2, the area where the shielding frame 12 and shielding cover 13 connect is the sum of the thicknesses of the first side panel 124 and the second side panel 134. The thickness of the shielding frame 12 and shielding cover 13 is not conducive to reducing the volume of the shielding structure 10. When the shielding structure 10 has a larger cavity 132, the shielding cover 13 and the shielding frame 12 are larger in size, and alignment errors during the welding process may result in poor welding, which in turn may lead to the risk of electromagnetic leakage. If a structure with multiple small cavities 132 is used, the number and occupied area of ​​the shielding frames 12 and shielding covers 13 will increase, the overall weight and size of the shielding structure 20 will increase, and the placement of the electronic components 14 on the circuit board 11 will be restricted. For larger electronic components 14, it is usually necessary to further secure the electronic components 14 with thermosetting adhesive 15. When the electronic components 14 need to be repaired, the temperature of the molten solder paste 152 between the circuit board 11 and the electronic components 14 is relatively high (for example, the melting temperature of the solder paste is greater than 300°C), and the thermosetting adhesive 15 will overflow onto the circuit board 11 at high temperature, causing damage to the circuit board 11.

[0076] See also Figure 2 , Figure 2 A cross-sectional schematic diagram of a shielding structure 10' is provided for other related technologies, in which a thinner copper foil 16' is used instead of the thicker shielding cover 13, and the copper foil 16' is connected to the first top plate portion 126' of the shielding frame 12' through a conductive adhesive 17'. The thickness of the copper foil 16' is relatively thin. Compared with the previous related technology, the thickness of the shielding structure 10' along the first direction L1 can be reduced by 55μm-80μm. However, since the copper foil 16' is relatively thin, the area where the copper foil 16' and the shielding frame 12' are connected is located on the surface of the shielding frame 12' away from the circuit board 11', and the copper foil 16' is difficult to extend to the first side plate portion 124' of the shielding frame 12' (that is, it is not suitable for 3D morphology). Therefore, compared with the previous related technology, this related technology omits Figure 1 The second side plate portion 134 in the shield structure 10' can reduce the width of the shield structure 10' along the second direction L2, but there is a risk of electromagnetic leakage from the connection between the copper foil 16' and the shield frame 12'. In addition, since the copper foil 16' is thin, when the shield structure 10' has a large cavity 132' or when the shield structure 10' has multiple cavities 132' with a height difference H (see Figure 3), the copper foil 16' is prone to wrinkles, and the connection between the copper foil 16' and the shielding frame 12' will be tilted relative to the shielding frame 12', making it difficult for the copper foil 16' to fully fit the shielding frame 12', further posing a risk of electromagnetic leakage. The risk of electromagnetic leakage can be reduced by increasing the width of the connection between the copper foil 16' and the shielding frame 12' (greater than 0.2mm), but this will correspondingly increase the width of the shielding frame 12' along the second direction L2 (i.e., the width of the first top plate portion 126'), and the aperture of the opening 127' of the shielding frame 12' will be correspondingly reduced, affecting the inspection and maintenance of the electronic components 14' in the chamber 132'; and the width of the connection between the copper foil 16' and the shielding frame 12' is also limited by the actual application scenario of the shielding structure 10'.

[0077] See also Figure 4 , Figure 4 A cross-sectional schematic diagram of a one-piece shielding structure 10" provided in an embodiment of the present application, wherein the shielding structure 10" includes a circuit board 11" and a shielding frame 12", that is, the shielding frame 12" is an integral structure, the shielding frame 12" is covered on the circuit board 11", and the electronic component 14" is accommodated in a cavity 132' formed by the shielding frame 12" and the circuit board 11". The shielding frame 12" is electrically connected to the circuit board 11" through a conductive paste 122". With respect to Figures 1 to 3 The two-piece shielding structure 10 (or 10') and the one-piece shielding structure 10" are small in size, have a low risk of magnetic leakage, and do not have problems such as welding alignment. However, after the shielding frame 12" is welded to the circuit board 11", the inspection of the electronic component 14" is limited. If the electronic component 14" needs to be repaired, the conductive paste 122" needs to be melted to separate the shielding frame 12" and the circuit board 11". The temperature of the melted conductive paste 122" is relatively high (for example, the melting temperature of the conductive paste is greater than 300°C), which will cause damage to the circuit board 11". It also limits the automated optical inspection (AOI) of welding defects and the inspection of solder feet. If ordinary conductive silver paste is used instead of the conductive paste 122", due to the high curing temperature of ordinary conductive silver paste (for example, the curing temperature of ordinary conductive silver paste is greater than or equal to 120°C), it is difficult to meet the welding requirements in some scenarios.

[0078] See also Figure 5 , Figure 5A structural schematic diagram of a conductive paste 30 is provided for an embodiment of the present application. The conductive paste 30 has low-temperature characteristics, can usually be stored in a refrigerator, and can be cured at a relatively low temperature (25°C-100°C). The conductive paste 30 with low-temperature characteristics replaces the traditional conductive paste 122 (or 122") and can be cured at a lower temperature. In the process of curing the conductive paste 30, the impact on the components connected by the conductive paste 30 is small. When the conductive paste 30 replaces the conductive paste 122" in the one-piece shielding structure 10", the resulting shielding structure has a small volume, a small risk of magnetic leakage, and no problems such as welding alignment; and after the conductive paste 30 is cured, it can be disassembled and assembled by mechanical means, without the need for high-temperature melting for disassembly, thereby reducing or avoiding the risk of damage to related components.

[0079] The conductive paste 30 includes a base material 31 and conductive materials 33, wherein the conductive materials 33 are dispersed in the base material 31. After being cured, the conductive paste 30 can form a conductive paste having electrical conductivity.

[0080] The conductive material 33 has conductive properties. The conductive material 33 includes a first conductive body 332 and a second conductive body 334. The size (i.e., average particle size) of the first conductive body 332 is less than or equal to 100 nm, i.e., the first conductive body 332 is nanometer-sized; the size (i.e., average particle size) of the second conductive body 334 is greater than or equal to 1 μm, i.e., the second conductive body 334 is micrometer-sized. The structure of the first conductive body 332 includes spherical and / or needle-shaped structures. Figure 5 (a) and (b) in Figure 5 (a) shows that the spherical first conductor 332 and the spherical second conductor 334 are dispersed in the substrate 31. Figure 5 (b) is a spherical first conductor 332 and a sheet-like second conductor 334 dispersed in the substrate 31; the structure of the second conductor 334 includes sheet and / or spherical shapes, which can be referred to Figure 5 (a) and (b) in .

[0081] Since a regular geometric spherical shape is difficult to achieve in practice, structures that are approximately spherical can also be considered spherical. For example, particles with an aspect ratio (the ratio of the longest diameter through the particle's interior to the longest diameter perpendicular to it) in the range of 0.9-1.1 can be considered spherical. The surface of a spherical conductive object 33 is relatively smooth. A needle-shaped first conductive object 332 has a maximum dimension greater than 2.4 times the average particle size of the first conductive object 332. A sheet-shaped second conductive object 334 has a minimum dimension less than 0.4 times the average particle size of the second conductive object 334.

[0082] The micron-sized second conductors 334 are relatively large and have good conductivity. Gaps exist between the larger second conductors 334, and the smaller first conductors 332 can fill the gaps between them. Compared to the micron-sized second conductors 334, the nanometer-sized first conductors 332 have a good surface effect. The smaller the particle size of the first conductors 332, the higher the specific surface area (the ratio of the surface area to the volume of the first conductors 332), and the stronger the surface forces between the first conductors 332. During the curing process of the conductive paste 30, the first conductors 332 can preferentially aggregate with each other, welding the micron-sized second conductors 334 and filling the gaps. This allows for low-temperature and rapid curing, thereby lowering the melting point of the conductive paste 30 and shortening the curing time (e.g., less than or equal to 1 hour). Furthermore, the first conductors 332 fill the gaps between the second conductors 334, forming effective overlapping pathways and a conductive network. This improves the conductivity of the cured conductive paste 30 and reduces impedance. Furthermore, the first conductive body 332 is filled between the second conductive bodies 334 to form a conductive path, which can effectively prevent the transmission of electromagnetic waves.

[0083] After curing, ordinary conductive silver paste molecules are typically connected by van der Waals forces, resulting in weak electrical contact. This generates nonlinear products such as third harmonics (passive intermodulation, or PIM) at the contact interface, indicating non-pathway contact between the conductive particles. In the embodiment of the present application, after curing, the conductive paste 30 forms conductive pathways between the second conductors 334, and the first conductors 332 can be filled between the second conductors 334, enabling interconnection between the first and second conductors 332, 334, and forming more conductive pathways. This improves conductivity while also reducing the third harmonics of the conductive paste formed after curing.

[0084] Compared to the needle-shaped first conductors 332, the spherical first conductors 332 have a smoother surface, making them more suitable for filling between the second conductors 334. This allows for more conductive pathways to be formed between the second conductors 334, further improving conductivity and reducing third harmonics. Compared to the spherical second conductors 334, the sheet-shaped second conductors 334 have better surface flatness and conductivity, allowing for greater contact between the second conductors 334, thus forming more conductive pathways between the second conductors 334, further improving conductivity and reducing third harmonics.

[0085] The mass ratio of the first conductor 332 to the second conductor 334 can be 1:1 to 3:1. When the content of the first conductor 332 increases and the content of the second conductor 334 decreases, the conductivity of the conductive paste 30 decreases, and the nonlinear products generated at the contact surface increase. When the content of the first conductor 332 decreases and the content of the second conductor 334 increases, the smaller amount of first conductor 332 makes it difficult to fully connect with the micron-sized second conductor 334, and the resulting conductive path decreases.

[0086] The area fraction of the conductive material 33 in the conductive paste 30 is 43%-80%, so that the conductive paste 30 has a small impedance. In some embodiments, the area fraction of the conductive paste 30 is greater than or equal to 43.46%, and the conductive paste 30 maintains good impedance (the resistivity of the conductive paste formed after the conductive paste 30 is cured is less than 10 -4 Ω / m,). The area fraction is the ratio of the area occupied by the conductive material 33 in the conductive paste 30 per unit area.

[0087] The conductive material 33 may be made of, but is not limited to, single metals, metal composites, and carbon materials. Single metals include, but are not limited to, silver, copper, nickel, iron, and aluminum. Composite metals include, but are not limited to, nickel-plated carbon particles and nickel-plated copper particles. In some embodiments, the conductive material 33 may be made of silver, which has excellent conductivity. The mass fraction of the conductive material 33 in the conductive paste 30 may be 43% to 75%. In some embodiments, when the material of the conductive object 33 includes copper and / or nickel, the cost can be reduced, and the mass fraction of the conductive object 33 in the conductive paste 30 can be 55%-85%; when the material of the conductive object 33 includes nickel-plated carbon particles, nickel-plated copper particles, etc., the weight can be reduced. Compared with other metals, the strength of copper particles is lower, which is conducive to volume compression during welding; when the material of the conductive object 33 includes aluminum, the dielectric constant of aluminum is relatively high, and a high dielectric constant conductive paste 30 can be prepared. The dielectric constant of the conductive paste formed after curing can be greater than or equal to 100, and the mass fraction of the conductive object 33 in the conductive paste 30 can be 55%-80%; when the material of the conductive object 33 includes magnetic metals such as iron or iron and nickel, while having welding performance and conductive performance, the electromagnetic wave absorption performance of the conductive paste can be improved, and the mass fraction of the conductive object 33 in the conductive paste 30 can be 55%-80%.

[0088] The substrate 31 can be selected from materials with high cohesive strength (i.e., the interaction between molecules within the polymer) such as epoxy resin, polyamide, and polyacrylonitrile, so that the conductive paste 30 has initial adhesion. The viscosity of the conductive paste 30 is 50Pa·S-100Pa·S, and the adhesion of the conductive paste 30 is greater than or equal to 1kg / mm 2, in order to further improve the initial tack and viscosity of the conductive paste 30. Conventional conductive paste 30 does not have initial tack, that is, it is not viscous before curing, and is difficult to adhere to the components being bonded. Therefore, an activation step is usually required before curing, and it becomes viscous only after curing. The conductive paste 30 in this embodiment does not require an additional activation step before the curing process to adhere to the components being bonded, which reduces the welding process and curing time, especially for welding in application scenarios with small welding spaces. Please refer to Figure 6 , Figure 6 (a) is a schematic diagram of the structure of the conductive paste 30 before curing. Figure 6 (b) is a schematic diagram of the structure of the conductive paste 30 after curing. Before curing, the substrate 31 is roughly chain-shaped. After curing, the substrates 31 can be interwoven with each other.

[0089] In some embodiments, the conductive paste 30 may also include polar monomers and / or chain extenders. Polar monomers contain functional groups such as amides, alcohols, and / or phenols; chain extenders include, but are not limited to, at least one of 1,4-butanediol (BDO), 1,6-hexanediol (1,6-Hexanediol), and glycerol. Both polar monomers and chain extenders can be used to increase the molecular weight and polarity of the substrate 31, facilitate cross-linking between substrates 31, and thus enhance the cohesive strength of the substrate 31, further improving the initial adhesion of the conductive paste 30.

[0090] In some embodiments, the conductive paste 30 may further include an organic elastomer. The material of the organic elastomer includes but is not limited to carboxylated nitrile elastomer, styrene butadiene pyridine elastomer, etc. The organic elastomer can improve the toughness and tensile strength of the conductive paste.

[0091] In some embodiments, the conductive paste 30 may also include itaconic acid. Itaconic acid can be loaded onto the surface of the conductive material 33 and form a chemical bond with the substrate 31, improving the conductivity and shear strength of the conductive paste 30. Furthermore, a high content of the conductive material 33 can hinder deformation and movement of the substrate 31, securing the substrate 31 and improving shear strength and thermal stability. The mechanical strength of the conductive paste 30 can be increased by reducing the particle size of the conductive material 33 and increasing the number of nanoscale first conductors 332.

[0092] In some embodiments, the conductive paste 30 may further include an auxiliary agent, which may include at least one of a defoaming agent, a curing agent, a leveling agent, a diluent, etc. The diluent may be ethyl acetate.

[0093] In some embodiments, the method for preparing the conductive paste 30 may include the following steps:

[0094] Step S1: Mixing a diluent and a base material 31 to obtain a resin solution.

[0095] The substrate 31 may be selected from epoxy resin, polyamide, polyacrylonitrile, etc. In step S1 , a polar monomer and / or a chain extender may also be added to increase the cohesive strength of the substrate 31 .

[0096] In a specific embodiment, ethyl acetate and epoxy resin are pre-stirred in a water bath at 60° C. and stirred for 15 minutes to obtain a resin solution.

[0097] Step S2: Adding a conductive material 33 into the resin solution.

[0098] A nanometer-sized first conductor 332 and a micrometer-sized second conductor 334 are added to the resin solution and stirred. The first conductor 332 and the second conductor 334 can be added in stages. The mass ratio of the first conductor 332 to the second conductor 334 can be 1:1 to 3:1. In some specific embodiments, the mass ratio of the first conductor 332 to the second conductor 334 can be 2:1.

[0099] Step S3: After adding the conductive material 33, add the defoaming agent and the leveling agent and stir.

[0100] Step S4: After adding the defoaming agent and the leveling agent, add the curing agent and stir.

[0101] Step S5: drying the slurry formed after adding the curing agent.

[0102] In some embodiments, the slurry is placed in a drying oven and slowly heated to 60° C. for drying. The heating time is 10-15 minutes and the heat preservation time is 10 minutes to concentrate the slurry to obtain the conductive slurry 30 .

[0103] In some embodiments, the preparation method may further include step S6: subjecting the dried paste to electron beam crosslinking modification by electron beam irradiation to further enhance the cohesive strength of the conductive paste 30 and enhance the initial tack and adhesive strength of the conductive paste 30. The electron beam energy may be less than or equal to 2 MeV.

[0104] Specific examples and comparative examples are listed below to further illustrate the conductive paste 30 provided in this application.

[0105] Comparative Example 1

[0106] Provides conventional solder paste, the main component of which is tin.

[0107] Comparative Example 2

[0108] A conventional conductive silver paste is provided, wherein the conductive material is 90% silver particles, the size of the silver particles is micron-level (ie, greater than 1 μm), and the base material is epoxy resin, polyvinyl butyral ester and ethyl cellulose.

[0109] Example 1

[0110] After mixing the diluent and epoxy resin, pre-stir them in a 60°C water bath and stir for 15 minutes to obtain a resin solution. A conductive material, made of silver and composed of nano- and micron-sized silver powders, is added to the resin solution. The conductive material is prepared in a 2:1 mass ratio. A defoamer and leveling agent are then added and stirred for 20 minutes. A curing agent is then added and stirred for 15 minutes. The resulting slurry is then rolled uniformly multiple times on a three-roll mill and dried in a drying oven to obtain a conductive paste 30, wherein the conductive material accounts for 50% by mass of the conductive paste 30.

[0111] Example 2

[0112] The difference from Example 1 is that the conductive material of Example 2 is made of copper.

[0113] Example 3

[0114] The difference from Example 1 is that the conductive material of Example 3 is made of nickel.

[0115] Example 4

[0116] The difference from Example 1 is that the conductive material of Example 4 is made of iron.

[0117] The curing temperature and curing time of Comparative Examples 1-2 and Examples 1-4 were tested respectively. The main different conditions and test results of Comparative Examples 1-2 and Examples 1-4 are shown in Table 1.

[0118] Table 1

[0119] Conductive material Conductive content Curing temperature (℃) Curing time (min) Comparative Example 1 solder paste Mainly tin 300 ＜2 Comparative Example 2 silver 85％ 120 90 Example 1 silver 50％ 35 20 Example 2 copper 50％ 35 25 Example 3 nickel 50％ 35 35 Example 4 iron 50％ 35 35

[0120] The test results in Table 1 indicate that the curing temperatures and curing times of the conductive pastes 30 of Examples 1-4 are lower than those of conventional solder pastes and conventional silver pastes. Silver exhibits superior electrical and thermal conductivity compared to copper, nickel, and iron, resulting in the shortest curing temperatures and times. Nickel and iron have similar properties, resulting in similar curing temperatures and times.

[0121] Example 5

[0122] The difference from Example 1 is that the mass fraction of the conductive material in Example 5 is 35%.

[0123] Example 6

[0124] Same as Example 1.

[0125] Example 7

[0126] The difference from Example 1 is that the mass fraction of the conductive material in Example 7 is 60%.

[0127] Example 8

[0128] The difference from Example 1 is that the mass fraction of the conductive material in Example 8 is 70%.

[0129] Comparative Example 9

[0130] The difference from Example 1 is that the mass fraction of the conductive material in Example 9 is 85%.

[0131] The curing temperature and curing time of Examples 5-9 were tested respectively, and the resistivity of the conductive paste formed after curing of the conductive paste prepared in Examples 5-9 was tested. The resistivity test method is as follows: a metal mold is placed on a glass sheet (test volume: 2×4×2mm 3 ), the conductive paste was coated on a glass sheet and cured at low temperature (60°C). The resistance was tested using a two-probe method to calculate the resistivity. The main differences in conditions and test results for Examples 5-9 are shown in Table 2.

[0132] Table 2

[0133] Example Conductive material mass fraction Curing temperature (℃) Curing time (min) Resistivity (Ω / m) Example 5 35％ 50 40 <![CDATA[10 -3 ]]> Example 6 50％ 30 20 <![CDATA[10 -4 ]]> Example 7 60％ 28 20 <![CDATA[5×10 -4 ]]> Example 8 70％ 26 19 <![CDATA[5×10 -4 <!-- 11 -->]]> Example 9 85％ 19 18 <![CDATA[10 -5 ]]>

[0134] The test results of Examples 5-9 show that the curing temperature and curing time of the conductive paste 30 of Examples 5-9 are reduced to a certain extent compared with Comparative Examples 1-2. Among them, the resistivity of the conductive paste formed after curing of the conductive paste 30 of Examples 6-9 is less than or equal to 10 -4 Ω / m, which meets the electrical connection requirements; the conductive paste 30 provided in Example 9 has a short curing time and a low curing temperature, and the resistivity of the conductive paste formed after curing is small. However, due to the high mass fraction of the conductive material, the mass fraction of the substrate 31 will correspondingly decrease, and the adhesion of the conductive paste will decrease. Moreover, as the mass fraction of the conductive material increases, some conductive materials may not be connected to each other, which may increase the third harmonic of the conductive paste.

[0135] See also Figures 7 to 11, are schematic cross-sectional views of a shielding structure 20 provided in embodiments of the present application. The shielding structure 20 includes a circuit board 21, a shielding member 22, at least one electronic component 23, and a conductive paste 24. The shielding member 22 is electrically connected to the circuit board 21 via the conductive paste 24 to form a sealed, hollow chamber 225. Specifically, the conductive paste 24 is arranged in a ring shape, and the electronic component 23 is disposed on the surface of the circuit board 21 and located within the chamber 225. The shielding member 22 is a one-piece structure, and the conductive paste 24 is formed by curing the conductive paste 30. The conductive paste 30 can be cured at a relatively low temperature (room temperature to 100°C); the conductive paste 24 obtained after curing is sticky and can weld the shielding component 22 and the circuit board 21 together; when the shielding structure 20 needs to be repaired, it can be directly disassembled and assembled at room temperature, with little or no impact on the circuit board 21 and the electronic components 23. When electrical connection is required again after disassembly, the curing temperature of the conductive paste 30 is low, and the impact on other components is little or no impact; the one-piece shielding component 22 does not need to consider side overlap and overlap width issues, and can reduce the width of the overlap area in the related technology, which is beneficial to reducing the space occupied by the shielding component 22.

[0136] The electronic components 23 include but are not limited to chips, capacitors, resistors, sensors, etc., and the number of the electronic components 23 is not limited. In some embodiments, the electronic components 23 can also be electrically connected to the circuit board 21 through the conductive paste 24.

[0137] The circuit board 21 includes a circuit layer. The number of circuit layers (not shown) is not limited. The circuit layer includes solder pins, which are used to electrically connect to the conductive paste 24 .

[0138] The material of the shielding component 22 is a conductive material, including but not limited to metal, metal alloy (such as nickel silver, stainless steel, aluminum alloy, etc.), carbon-based material (including carbon-based thermal conductive material, high dielectric carbon-based material, etc.), absorbing material, etc., so as to realize the electromagnetic shielding function of the shielding component 22.

[0139] The shielding member 22 includes a top plate 221 and a side plate 223. The side plate 223 is annularly arranged around the top plate 221, with one end of the side plate 223 connected to the top plate 221 and the other end connected to the solder pin of the circuit board 21 through the conductive paste 24.

[0140] The shielding structure 20 also includes an adhesive layer 25, which is positioned between the top plate 221 and at least one electronic component 23 and is used to bond the top plate 221 and the electronic component 23. The electronic component 23 bonded by the adhesive layer 25 is taller or the tallest relative to the other electronic components 23. This allows the height of the shielding structure 20 to be minimized. Furthermore, the electronic components 23 bonded by the adhesive layer 25 are relatively large, and the adhesive layer 25 is used to secure the electronic components 23 to the shielding member 22. The adhesive layer 25 is elastic, providing a cushioning effect. Furthermore, when the shielding structure 20 is subjected to a significant impact (e.g., a collision or drop), the movement of the electronic component 23 and the shielding member 22 are synchronized, thereby reducing the effects of inertia.

[0141] See also Figure 7 In some embodiments, the ends of the side panels 223 facing away from the top panel 221 expand into an arc shape, away from the electronic components 23. This increases the effective contact area between the conductive paste 24 and the side panels 223 when connected using the conductive paste 24, thereby increasing the connection strength. Before the conductive paste 30 cures to form the conductive paste 24, it is fluid, allowing for sufficient contact with the solder fillets on the circuit board 21, thereby helping to reduce the size of the solder fillets. The conductive paste 24 is positioned between the side panels 223 and the circuit board 21, with the side panels 223 and the circuit board 21 spaced apart. Because the conductive paste 24 is also elastic, it provides a certain cushioning effect, preventing rigid contact between the side panels 223 and the circuit board 21.

[0142] In this embodiment, the shape of the integrated shielding member 22 can be adjusted accordingly according to the distribution and size of the electronic components 23 on the circuit board 21. For example, the electronic components 23 located in the middle area of ​​the cavity 225 are larger in size, while the electronic components 23 located in the edge area are smaller in size. In this way, the shielding member 22 is recessed toward the cavity 225 at the connection between the side plate 223 and the top plate 221, thereby reducing the overall volume of the shielding structure 20. Figure 1 The two-piece shielding structure 10 shown has a complex connection relationship between the shielding cover 13 and the shielding frame 12. It is also necessary to consider whether mutual interference occurs between the shielding cover 13 and the electronic component 14 when the shielding cover 13 rotates relative to the shielding frame 12 during the disassembly and assembly process, the installation position of the rotating part 128, and whether the shielding cover 13 and the shielding frame 12 are tightly fastened. As a result, many factors affect the design of the shape and size of the shielding cover 13 and the shielding frame 12. Figure 2 The two-piece shielding structure 10 ′ shown is not suitable for 3D shaping due to the thin copper foil 16 ′, which is difficult to support and cannot be recessed in the area corresponding to the smaller electronic component 23 , making it difficult to reduce the size of the shielding structure 10 ′.

[0143] See also Figure 8In some embodiments, the side plate 223 is directly connected to the circuit board 21. Specifically, the side plate 223 includes an inner surface 2234 and an outer surface 2236. The inner surface 2234 is the surface of the side plate 223 facing the cavity 225, and the outer surface 2236 is the surface of the side plate 223 facing away from the cavity 225. The conductive paste 24a is located on two opposite surfaces of the side plate 223 (i.e., the inner surface 2234 and the outer surface 2236) and is connected to the circuit board 21, i.e., part of the conductive paste 24a is located in the cavity 225, and the remaining part of the conductive paste 24a is located outside the cavity 225. The surface of the side plate 223 is flat. Compared with the previous embodiment, the arc-shaped structure is omitted, which can reduce the area of ​​the shielding member 22. At the same time, the conductive paste 24a is provided on two opposite surfaces of the shielding member 22, which can improve the lateral shielding performance.

[0144] See also Figure 9 In some embodiments, a through hole 2232 is further opened on the side plate 223 in an area close to the circuit board 21. The through hole 2232 is connected to the chamber 225. The conductive paste 24b is located on two opposite surfaces of the side plate 223 and in the through hole 2232, which can further improve the connection strength of the conductive paste 24b. In addition, the contact area between the conductive paste 24b and the shielding member 22 is increased, which can effectively reduce the impedance and improve the shielding performance.

[0145] See also Figure 10 In some embodiments, a groove 211 is defined on the surface of the circuit board 21 facing the shield 22. The solder fillet is positioned within the groove 211. At least a portion of the end of the side plate 223 facing the circuit board 21 is positioned within the groove 211. At least a portion of the conductive paste 24c is positioned within the groove 211 and connects the side plate 223 and the circuit board 21, thereby electrically connecting the shield 22 and the circuit board 21. Compared to the outwardly flared curved side plates 223, the side plates 223 of this embodiment omit the curved structure, thereby reducing the area of ​​the shield 22. Furthermore, the groove 211 serves as a limiter, further enhancing the securing effect.

[0146] See also Figure 11 In some embodiments, the side plate 223 and the circuit board 21 are spaced apart, and the conductive paste 24d is located between the side plate 223 and the circuit board 21. The conductive paste 24d connects the circuit board 21 and the side plate 223. The height of the conductive paste 24d can be increased to reduce the height of the side plate 223, which is equivalent to using part of the conductive paste 24d to replace the side plate 223, thereby helping to reduce the overall weight of the shielding structure 20; in this embodiment, a non-elastic conductive paste 24d can be used to prevent the shielding member 22 from shaking relative to the circuit board 21.

[0147] See also Figure 12The embodiment of the present application further provides a terminal device 100 , which may include but is not limited to a mobile phone, a tablet computer, a camera, a drone, a video camera, a vehicle-mounted camera, a monitor, etc. The terminal device 100 includes a shielding structure 20 .

[0148] In some embodiments, the terminal device 100 includes a structure made of a conductive material, and the structure made of the conductive material can directly serve as the shielding member 22. For example, in some specific embodiments of the present application, the terminal device 100 is a mobile phone, and the mobile phone includes a middle frame 40. The material of the middle frame 40 can be metal or metal alloy, and the middle frame 40 can serve as the shielding member 22. In the related art, due to the material limitations of the conductive paste 122 (or 122 ”), the opening of the shielding frame 12 is sealed with a copper foil 16 ′, and the middle frame 40 ′ and the shielding frame 12 are usually used as two components. The middle frame 40 ′ and the shielding frame 12 are spaced apart, and the copper foil 16 ′ and the middle frame 40 ′ are bonded by a colloid, and the overall thickness is relatively thick. In the embodiment of the present application, the middle frame 40 is used as the shielding member 22, which is equivalent to the middle frame 40 in the terminal device 100 not only fulfilling the function of the middle frame 40 itself, but also replacing the function of the shielding member 22, omitting the shielding member 22, that is, reducing the volume required for the shielding member 22 and the distance between the shielding member 22 and the middle frame 40, which can reduce the overall thickness, weight and production cost of the terminal device 100; the thickness of a part of the middle frame 40 can also be increased according to the remaining space in the terminal device 100, thereby increasing the mechanical strength and shielding performance of the middle frame 40.

[0149] In some embodiments, the terminal device 100 may further include a heat sink 50. The material of the heat sink 50 and the material of the shielding member 22 may be the same, including but not limited to metal, metal alloy, carbon-based material, wave-absorbing material, etc., all of which have the function of rapid heat conduction. The heat sink 50 may be a temperature equalizing plate and / or a heat pipe. In a specific embodiment, the heat sink 50 is a temperature equalizing plate, an opening 41 is provided on the shielding member 22, and the surface of at least one electronic component 23 is exposed to the opening 41. The heat sink 50 seals the opening 41, and the electronic component 23 exposed to the opening 41 and the heat sink 50 are bonded by the adhesive layer 25. The heat generated by the electronic component 23 can be quickly transferred out through the heat sink 50. In addition, omitting the shielding member 22 is equivalent to shortening the heat transmission path, thereby also improving the heat dissipation rate.

[0150] See also Figure 13In the related art, the terminal device 100' may also include a screen 70'. The screen 70' and the middle frame 40' have a plurality of electrical connection points. Foam 71' or springs are usually used to electrically connect the screen 70' and the middle frame 40' for grounding. However, in some application scenarios, for example, according to industrial design requirements (ID), the corner area of ​​the terminal device 100' is curved. Then, compared with the foam 71' corresponding to the flat area, the thickness of the foam 71' corresponding to the curved area assembled in the terminal device 100' is different. The thickness d2 of the foam 71' corresponding to the arc bottom 43' is less than the thickness d1 of the foam 71' corresponding to the arc top 42'. If the foam 71' corresponding to the arc bottom 43' is to be guaranteed not to be over-pressurized, the foam 71' corresponding to the arc top 42' may be insufficiently elastic, causing regulatory issues. If the elasticity of the foam 71' corresponding to the arc top 42' is to be guaranteed, the foam 71' corresponding to the arc bottom 43' may be over-pressurized, causing film marks.

[0151] In this embodiment, a conductive paste 24 with high elasticity and high conductivity is used instead of the foam 71' to connect the screen 70' and the middle frame 40'. During the process of curing the conductive paste 30 to form the conductive paste 24, due to the fluidity of the conductive paste 30, it can be well filled between the arc areas of the screen 70' and the middle frame 40', and can simultaneously meet the requirements of the arc top 42' and the arc bottom 43' areas to achieve a special-shaped connection; the high adhesion of the conductive paste 24 ensures the bonding strength, and the high conductivity and low third harmonic ensure the electrical connection requirements while maintaining the stability of the radiated spurious emission (RSE) index; furthermore, when the conductive paste 24 needs to be connected to the antenna fixed on the middle frame 40', the conductive paste 24 formed by the conductive paste 30 containing aluminum is beneficial to improving the dielectric constant, thereby improving the antenna strength and electrical connection requirements.

[0152] See also Figure 14 , the conductive paste 30 can also be applied to the terminal device 100" with a small soldering space. For example, in the related art, the terminal device 100" includes a circuit board 73", a frame 40", a middle frame and an antenna (not shown), the frame 40" is arranged around the middle frame, the antenna is fixed on the frame 40", and the circuit board 73" needs to be electrically connected to the middle frame for grounding. Due to the design of the narrow frame of the terminal device 100", the distance between the frame 40" and the circuit board 73" is small (such as Figure 14The frame 40" in the terminal device 100" moves toward the circuit board 73"), if fixed-shape components such as foam or shrapnel 75" are used for connection, it is difficult to reserve a large space in the terminal device 100" to ensure appropriate stress and impedance; if the space for electrical connection is increased, the performance of the antenna may be affected and the positional relationship of other components may need to be changed. The embodiment of the present application can use a conductive paste 24 for connection. During the process of curing the conductive paste 24 to form the conductive paste 30, since the conductive paste 30 has fluidity, the conductive paste 30 is not limited to a limited space and a fixed-shape space. Without affecting the performance of the antenna and without changing the positional relationship of other components in the terminal device 100", the electrical connection between the circuit board 73" and the frame 40" can be achieved; and the fluid conductive paste 30 can make full use of the space in the terminal device 100".

[0153] See also Figure 15 Conductive paste 30 can also be applied to terminal devices 100e with irregularly shaped welding spaces. For example, in related art, the middle frame 40e in terminal device 100e is electrically connected to the side of the screen to ensure reflow between the antenna radiator 51 and the middle frame 40e. Traditionally, ultrasonic welding and metal bonding are used for this connection. However, this connection solution has thickness limitations and cannot be applied to curved middle frames and screens. Because conductive paste 30 is fluid before curing, the present embodiment can use conductive paste 24 instead of ultrasonic welding and metal bonding.

[0154] See also Figure 16 In some embodiments, the conductive paste 30 can also be applied to terminal devices 100f that are not suitable for reflow soldering and have a small soldering space, such as watches, bracelets, and wearable products, to achieve narrow frame and small space bonding of the terminal device 100f.

[0155] In some specific embodiments, the terminal device 100f is a watch, which includes a dial 60, a decorative piece 65, and a conductive paste 24f. The dial 60 and the decorative piece 65 are bonded together by the conductive paste 24f. Specifically, the dial 60 has a receiving groove 61, and at least a portion of the decorative piece 65 is located in the receiving groove 61. At least a portion of the conductive paste 24f is located in the receiving groove 61 and between the decorative piece 65 and the dial 60.

[0156] Because the dial 60 and decorative piece 65 are relatively small, during assembly, the conductive paste 30 is dotted into the receiving groove 61, and then at least a portion of the decorative piece 65 is inserted into the receiving groove 61 of the dial 60. This squeezes the conductive paste 30 between the decorative piece 65 and the dial 60. Because the conductive paste 30 has initial tack and high viscosity, it can initially bond the decorative piece 65 to the dial 60 before curing. Furthermore, because the conductive paste 30 cures quickly at low temperatures, it can cure quickly without requiring high temperatures. The inclusion of a polar monomer or chain extender in the conductive paste 30 can further enhance its initial tack.

[0157] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present application should not depart from the spirit and scope of the technical solutions of the present application.

Claims

1. A conductive paste, characterized in that: include: a substrate comprising at least one of epoxy resin, polyamide, and polyacrylonitrile; A conductive material is dispersed in the substrate, the conductive material includes a first conductor and a second conductor, the size of the first conductor is less than or equal to 100 nm, and the size of the second conductor is greater than or equal to 1 μm; the structure of the first conductor includes a needle shape, or the structure of the first conductor includes a spherical shape and a needle shape; the structure of the second conductor includes a flake shape and / or a spherical shape; the conductive paste also includes a polar monomer and itaconic acid, the polar monomer contains amide, alcohol and / or phenol functional groups, and the itaconic acid is used to polymerize with the substrate.

2. The conductive paste according to claim 1, characterized in that The viscosity of the conductive paste is 50Pa·S-100Pa·S, and the adhesion of the conductive paste is greater than or equal to 1kg / mm 2 .

3. The conductive paste according to claim 1, characterized in that The material of the conductive material includes at least one of silver, copper, nickel, iron, aluminum, nickel-plated carbon particles and nickel-plated copper particles.

4. The conductive paste according to claim 3, characterized in that When the material of the conductive object includes silver, the mass fraction of the conductive object in the conductive paste is 43%-75%; when the material of the conductive object includes copper and / or nickel, the mass fraction of the conductive object in the conductive paste is 55%-85%; when the material of the conductive object includes aluminum, the mass fraction of the conductive object in the conductive paste is 55%-80%; when the material of the conductive object includes iron or iron and nickel, the mass fraction of the conductive object in the conductive paste is 55%-80%.

5. The conductive paste according to any one of claims 1 to 4, characterized in that: The conductive paste further includes a chain extender, which includes at least one of 1,4-butanediol, 1,6-hexanediol and glycerol.

6. The conductive paste according to any one of claims 1 to 4, characterized in that: The conductive paste further includes an organic elastomer, and the organic elastomer includes at least one of a carboxylated nitrile elastomer and a styrene-butadiene pyridine elastomer.

7. A shielding structure, characterized in that: include: circuit boards; a shielding member, disposed on the circuit board; a conductive paste electrically connecting the circuit board and the shielding member and arranged in a ring shape, wherein the circuit board and the shielding member enclose a cavity, wherein the conductive paste is formed by curing the conductive paste according to any one of claims 1 to 6; and At least one electronic component is located in the chamber.

8. The shielding structure according to claim 7, wherein: The shielding component includes a top plate and a side plate. The side plate is annularly arranged around the top plate. The end of the side plate away from the top plate is connected to the conductive paste.

9. The shielding structure according to claim 8, characterized in that: The end of the side plate away from the top plate expands in an arc shape toward a direction away from the electronic component, and the conductive paste connects the end of the side plate in an arc shape and the circuit board.

10. The shielding structure according to claim 8, characterized in that: The side plate is connected to the circuit board, and the conductive paste is located on two opposite surfaces of the side plate and connected to the surface of the circuit board.

11. The shielding structure according to claim 10, characterized in that: A through hole is formed on the side plate, the through hole is communicated with the cavity, and the conductive paste is also located in the through hole.

12. The shielding structure according to claim 8, wherein: The circuit board is provided with a groove, in which at least a portion of the end of the side plate is located, and at least a portion of the conductive paste is located in the groove and is located between and connects the side plate and the circuit board.

13. The shielding structure according to claim 8, wherein: The side plate is spaced apart from the circuit board, and the conductive paste is located between the side plate and the circuit board and connects the side plate and the circuit board.

14. The shielding structure according to any one of claims 8 to 13, characterized in that: The shielding structure further includes an adhesive layer, which is located between the top plate and at least one electronic component to bond the electronic component and the shielding member.

15. A terminal device, characterized in that: The terminal device comprises the shielding structure according to any one of claims 7 to 14.

16. The terminal device according to claim 15, characterized in that The shielding component is the middle frame of the terminal device.

17. The terminal device according to claim 16, wherein: The terminal device further includes a heat sink. An opening is formed on the shielding member, and the heat sink seals the opening.

18. A terminal device, characterized in that: The terminal device includes a conductive paste, which is formed by curing the conductive paste according to any one of claims 1 to 6.

19. The terminal device according to claim 18, characterized in that The terminal device further includes a screen and a middle frame, and the conductive paste connects the screen and the middle frame to electrically connect the screen and the middle frame.

20. The terminal device according to claim 19, wherein The middle frame has a curved area, and the conductive paste connects the curved area and the screen.

21. The terminal device according to claim 18, wherein The terminal device further includes a frame and a circuit board, and the conductive paste connects the frame and the circuit board.

22. The terminal device according to claim 18, wherein The terminal device also includes a dial and a decorative piece. The dial is provided with a receiving groove, at least part of the decorative piece is located in the receiving groove, at least part of the conductive paste is located in the receiving groove and is located between the decorative piece and the dial to connect the dial and the decorative piece.

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