Patent Description:
This application relates to the field of electronic device technologies, and in particular, to a middle frame assembly and an electronic device.

For a common user, a weight of a mobile phone is approximately in a range of <NUM> to <NUM>, and a thickness is less than <NUM>, which has a more comfortable hand feeling. Excessive weight leads to an uncomfortable hand feeling, especially with an increase of use time, the discomfort increases. The main factors affecting the weight of the mobile phone include a mobile phone size, a body material, a battery capacity, and a functional module. With an increase in the mobile phone size, the battery capacity, and the functional module, the weight of the mobile phone gradually increases. Therefore, currently, a selection of a material of a mobile phone housing is one of the research directions of a mobile phone lightweight.

Metal alloys such as magnesium alloy, stainless steel, aluminum alloy, and zinc alloy are commonly used in a middle frame of the mobile phone. Using plastics with high strength and high toughness, such as glass fiber reinforced polyurethane (PC+GF), instead of the metal alloys can reduce the weight of the mobile phone, but the plastics cause a dielectric constant and loss tangent of the middle frame to become larger, which has an impact on a function of antennas.

<CIT> describess a composite substrate, electronic equipment and a manufacturing method of the composite substrate, the composite substrate is formed by arranging a transition layer between a substrate layer and a conducting layer, the transition layer is made of a first adhesive material, and the first adhesive material is used for being tightly combined with a carbon fiber composite material of the substrate layer and a metal material of the conducting layer respectively, so that the adhesive force between a metal layer and the substrate layer is enhanced, and the phenomenon that the metal layer falls off is avoided.

<CIT> discloses an electronic product frame structure made of a carbon fiber ceramic composite material. The structure comprises a ceramic frame and a carbon fiber middle frame plate which is located at the inner side of the ceramic frame and is integrally composited with the ceramic frame. The carbon fiber middle frame plate is integrally moulded with the ceramic frame by hot-press solidification. The invention also discloses a manufacturing method of the electronic product frame structure made of the carbon fiber ceramic composite material. The method comprises following steps of S1, preparing the ceramic frame; S2, placing carbon fiber cloth at the inner side of the ceramic frame; carrying out 3D moulding and hot-press solidification to the carbon fiber cloth; and forming the carbon fiber middle frame plate integrally combined with the ceramic frame after processing. The electronic product frame structure is liable to carry out postprocessing, satisfies the assembly demand of a ceramic element and a structure element, is beneficial for realizing precise assembly and is light in weight.

<CIT> describes a middle frame, a manufacturing method of the middle frame and electronic equipment, wherein the middle frame comprises a first frame and a second frame, the second frame is arranged on the periphery of the first frame in an enclosing mode, one side, deviating from the first frame, of the second frame is an anodic oxidation surface, one side, deviating from the first frame, of the second frame is an appearance surface of the middle frame, and therefore the appearance surface of the middle frame has an anodic oxidation effect.

<CIT> discloses a frame body assembly and electronic equipment, and belongs to the technical field of communication equipment. The frame body assembly includes: the metal frame is positioned on the outer side of the frame body assembly, and an accommodating space is defined by the metal frame and is suitable for accommodating components of the electronic equipment; the metal middle plate is arranged on the inner side of the frame body assembly and is positioned in the accommodating space; the metal middle plate is used for mounting and supporting components; the injection molding piece is arranged between the metal frame and the metal middle plate; and the connecting piece is connected with and conducted with the metal frame and the metal middle plate.

This application provides a middle frame assembly and an electronic device, which resolves a problem that reducing a weight of the electronic device and maintaining a function of the antenna cannot be simultaneously implemented. The dependent claims define further aspects and features of the invention.

To achieve the foregoing objective, this application provides the following technical solutions:
a middle frame assembly, including a middle plate and a frame disposed around an outer edge of the middle plate, where the middle plate comprises a first carbon fiber reinforced resin composite material base body and a first metal plating layer compounded on a surface of the base body.

The embodiments of this application use a carbon fiber reinforced resin composite material, for example, a carbon fiber reinforced epoxy resin composite material, a carbon fiber reinforced phenolic resin composite material, or a carbon fiber reinforced polytetrafluoroethylene resin composite material, as a middle plate base body of the middle frame assembly, which significantly reduces a weight of the middle frame assembly and has advantages of good rigidity and high strength. In addition, the metal plating layer compounded on the surface of the carbon fiber reinforced resin composite material base body resolves problems of a wave absorption effect and a PIM of the carbon fiber reinforced resin composite material, so that an antenna function of the electronic device is not affected.

According to the claimed invention, a thickness of the first metal plating layer is greater than or equal to a skin depth of the first metal plating layer. Further, when a resistivity of the first metal plating layer is <NUM> × <NUM>-<NUM> ohm·cm or below, or even in a range of <NUM>×<NUM>-<NUM> ohm·cm to <NUM>×<NUM>-<NUM> ohm·cm, and is close to a resistivity of a metal middle plate, for example, an aluminum alloy middle plate, an antenna performance is not lost. In some embodiments, to prevent the first metal plating layer on the middle plate from falling off, the middle plate further includes a protective layer compounded on a surface of the first metal plating layer. The protective layer may be formed on the surface of the first metal plating layer through surface coating treatment, passivation liquid treatment, spraying, anodic oxidation, micro-arc oxidation, or electrophoresis, to prevent the first metal plating layer from falling off under a larger pressure.

In some embodiments, to prevent the first metal plating layer from falling off, the first metal plating layer may be partially compounded on the carbon fiber reinforced resin composite material base body on the middle plate, for example, the first metal plating layer is compounded on a part of the carbon fiber reinforced resin composite material base body that is not connected to the frame. In addition, a through hole is provided on the carbon fiber reinforced resin composite material base body, and a second metal plating layer is compounded on a surface of the through hole to implement electricity continuity of an upper surface and a lower surface of the carbon fiber reinforced resin composite material base body. Alternatively, the first metal plating layer is compounded on a part of the carbon fiber reinforced resin composite material base body that is not connected to the frame, after the frame is connected to the middle plate, a second metal plating layer is compounded on a part of the carbon fiber reinforced resin composite material base body that is connected to the frame, to implement electricity continuity and prevent the first metal plating layer from falling off.

In some possible implementations, the middle frame assembly further includes an antenna radiator, and the antenna radiator may be formed from at least a portion of a frame body of a metallized frame (that is, the antenna radiator is disposed on an outer surface of the frame), or may be disposed on a side of the frame facing a middle plate (that is, the antenna radiator is disposed on an inner surface of the frame). The antenna radiator may be electrically connected to the first metal plating layer on the middle plate through a conductive layer or a conductive auxiliary material, for example, a metal elastic piece, a metal gasket, a conductive fabric, a conductive adhesive, or a conductive foam, to implement grounding of the antenna radiator.

In other possible implementations, the antenna radiator may not be electrically connected to the middle plate, but when used in an electronic device, the antenna radiator may be electrically connected to a screen component or a printed circuit board of the electronic device to implement grounding of the antenna radiator. When the antenna radiator is electrically connected to the printed circuit board, a wire may be arranged on the printed circuit board to implement the grounding of the antenna radiator, which saves costs of a structure.

In some possible implementations, both a middle plate and a frame are formed of a carbon fiber reinforced resin composite material compounded with a metal plating layer, which can further reduce weights of a middle frame assembly and an electronic device.

According to an example outside the scope of the invention as claimed, but useful for understanding the invention, there is provided a preparation method for a middle frame assembly, including the following steps:.

In some possible implementations, a middle frame assembly may be formed by performing metallized surface treatment on a carbon fiber reinforced resin composite material base body. The metallized surface treatment includes, but is not limited to, spraying, metal spray pattern (Metal Spray Pattern, MSP), printing direct constructing (which is also referred to pad printing, printing direct constructing, PDS), laser direct constructing (Laser Direct Constructing, LDS), laser-activating-plating (Laser-Activating-Plating, LAP), or chemical plating.

In some possible implementations, a frame of a middle plate may be connected in a mechanical manner such as welding, or clamping, to form a middle frame assembly. In some possible implementations, to simplify a process and improve performance, a middle plate and a frame material may further be connected through integral injection molding, for example, a nano molding technology (Nano Molding Technology, NMT) or a metal device antenna (Metal Device Antenna, MDA), to form a middle frame assembly.

The embodiments of this application further provide an electronic device, including the middle frame assembly in the technical solutions. The electronic device not only has a light weight, but also has no impact on the antenna performance.

In some possible embodiments, in an electronic device, an antenna radiator is electrically connected to a middle plate. In some other possible embodiments, an antenna radiator may be electrically connected to a screen component or a printed circuit board, which saves costs of a structure.

In the embodiments of this application, a carbon fiber reinforced resin composite material with a metal plating layer compounded on a surface is used as a main material of a middle frame assembly, which not only implements a lightweight of an electronic device, but also has no impact on an antenna function of the electronic device.

The following clearly and completely describes technical solutions in embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Terms used in the following embodiments are merely intended for describing specific embodiments, but are not intended to limit this application. As used in the specification of this application and the appended claims, singular expressions "one", "a/an", "the", "the foregoing", and "this" are intended to also intended to include, for example, an expression "one or more" unless expressly indicated to the contrary in the context. It should be further understood that in the embodiments of this application, "one or more" refers to one, two, or more than two.

Reference to "an embodiment" or "some embodiments", or the like described in the specification of this application means that particular features, structures, or characteristics described with reference to the embodiment are included in one or more embodiments of this application. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in still some other embodiments" appearing at different positions in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise particularly emphasized in other ways. The terms "comprise", "include", "have", and variations thereof all mean "include but is not limited to", unless otherwise specially emphasized.

In the embodiments of this application, words such as "exemplary" or "for example" is used to represent giving an example, an illustration, or a description. Any embodiment or design scheme described as an "exemplary" or "for example" in the embodiments of this application should not be explained as being more preferred or having more advantages than another embodiment or design scheme. To be precise, the use of the words such as "exemplary" or "for example" is intended to present a related concept in a specific manner.

In the embodiments of this application, an example in which a mobile phone <NUM> is the electronic device is used for description. As shown in <FIG> is a three-dimensional schematic structural diagram of the mobile phone, and <FIG> is a schematic structural exploded view of the mobile phone. The mobile phone <NUM> mainly includes a display module <NUM>, a middle frame assembly <NUM>, and a rear housing <NUM>, and the middle frame assembly <NUM> is located between the display module <NUM> and the rear housing <NUM>. The display module <NUM> is configured to display an image, and the rear housing <NUM> is connected to the middle frame assembly <NUM> to form an accommodation cavity for accommodating an electronic device, for example, a printed circuit board, a camera, or a battery. The printed circuit board <NUM> and the battery <NUM> may further be arranged on the middle frame assembly <NUM>. For example, the printed circuit board <NUM> and the battery <NUM> are arranged on a surface of the middle frame <NUM> facing the rear housing <NUM>, or arranged on a surface of the middle frame <NUM> facing the display module <NUM>. When the printed circuit board <NUM> is arranged on the middle frame <NUM>, an opening may be formed on the middle frame <NUM> for placing an element on the printed circuit board <NUM> at the opening of the middle frame <NUM>.

It may be understood that, a structure illustrated in the embodiments of this application does not constitute a specific limitation on the mobile phone <NUM>. In some other embodiments of this application, the mobile phone <NUM> may include more or fewer components than those shown in the figure, or combine some components, or split some components, or have a different component arrangement. For example, the mobile phone <NUM> may further include components such as a camera, including a front-facing camera and a rear-facing camera, and a flash.

In a first embodiment of this application, a middle frame assembly <NUM> includes a middle plate <NUM> and a frame <NUM> disposed around an outer edge of the middle plate. As shown in <FIG> is a three-dimensional schematic structural diagram of a middle frame assembly according to an embodiment of this application, and <FIG> is a schematic structural exploded view of a middle frame assembly according to an embodiment of this application. To reduce a weight of the mobile phone, the middle plate <NUM> may be made of a plastic with high strength and high toughness such as a carbon fiber reinforced resin composite material instead of a metal such as an aluminum alloy.

The carbon fiber reinforced resin composite material has advantages of high strength, high toughness, and low specific gravity, where a carbon fiber is a special fiber composed of carbon, and carbon content of the carbon fiber varies with different types, and is generally <NUM>% or more. The carbon fiber has characteristics of a common carbon material, for example, high temperature resistance, friction resistance, electrical conduction, heat conduction, and corrosion resistance, but a difference from the common carbon material is that the appearance of the carbon fiber is obviously anisotropic and soft, and the carbon fiber may be processed into various fabrics. The carbon fiber may be processed into fabrics, felt, mats, tapes, paper and other materials, which are generally added into resin, metal, ceramics, concrete, and other materials as reinforcing materials to form composite structural materials. The carbon fiber reinforced resin composite material has comprehensive indexes such as a high specific strength and a specific modulus, and becomes a commonly used material in aerospace field because of advantages of small specific gravity, good rigidity, and high strength. Table <NUM> is a performance comparison between a carbon fiber reinforced resin composite material and other materials.

A magnesium alloy also has low density, and can implement a lightweight of an electronic device. However, the magnesium alloy is unstable, and electrochemical corrosion occurs at normal temperature, resulting in function failure and non-wear resistance. As shown in <FIG> and <FIG>, <FIG> is a waveform diagram of an attenuation life curve of a fretting wear resistance test of a magnesium alloy (there are <NUM> tests), and <FIG> is a waveform diagram of an attenuation life curve of a fretting wear resistance test of an aluminium magnesium alloy (there are <NUM> tests). When fretting is performed on the magnesium alloy for about <NUM> times, an impedance starts to rise from <NUM> ohm to about <NUM> ohm. With the surface wear of laser engraving, powder continues to accumulate. When the fretting is performed on the magnesium alloy for about <NUM> times, the impedance rises to about <NUM> ohm, and when the fretting is performed on the magnesium alloy for about <NUM> times to <NUM> times, with the powder being cut by a ball head, the impedance gradually decreases. As the friction continues, new powder is formed, and after <NUM> times, the impedance returns to <NUM> ohm+. Compared with a conventional aluminum alloy, rise time of the impedance is short, and an absolute value of the impedance is doubled.

The density of the carbon fiber reinforced resin composite material is only <NUM>% of the stainless steel and <NUM>% of the aluminum alloy, the strength of the carbon fiber reinforced resin composite material is close to <NUM> times of the stainless steel and <NUM> times of the aluminum alloy, and the carbon fiber reinforced resin composite material has a low linear expansion coefficient and high size accuracy; The carbon fiber reinforced resin composite material has good corrosion resistance. The carbon fiber reinforced resin composite material is inert in an alkaline environment and has good corrosion resistance to organic solvents, acids, alkalis, and the like, which is suitable for replacing metal materials to implement the lightweight of the electronic device. However, the carbon fiber reinforced resin composite material has a characteristic of hysteresis and a serious passive intermodulation (PIM) problem is caused when the carbon fiber reinforced resin composite material is directly used as the middle frame material. Table <NUM> is an equivalent dielectric constant and a magnetic permeability of a carbon fiber reinforced resin composite material (Carbon Fiber Reinforced Polymer/Plastic, CFRP).

In this application, a carbon fiber reinforced resin composite material is used as a main material of a middle frame, and at the same time, a surface of the carbon fiber reinforced resin composite material is performed metallization to form a metal plating layer, so as to resolve problems of a wave absorption effect and a PIM of the carbon fiber reinforced resin composite material. Table <NUM> is power values of second harmonic and third harmonic of a carbon fiber reinforced resin composite material and a carbon fiber reinforced resin composite material with a nickel plated surface under a same scenario.

In Table <NUM>, non-nickel-plated sample <NUM> is a continuous carbon fiber phenolic resin composite material, and non-nickel-plated sample <NUM> is the same as sample <NUM>. Nickel-plated sample <NUM> is the non-nickel-plated sample <NUM> compounded with a nickel layer with a thickness of <NUM>, and nickel-plated sample <NUM> is the non-nickel-plated sample <NUM> compounded with a nickel layer with a thickness of <NUM>.

Based on this, the middle plate <NUM> provided in the embodiments of this application includes a carbon fiber reinforced resin composite material base body <NUM> and a metal plating layer <NUM> compounded on a surface of the base body. As shown in <FIG> is a schematic diagram of a laminated structure of a middle plate according to an embodiment of this application. The carbon fiber reinforced resin composite material base body <NUM> has characteristics of high strength, high toughness, and low specific gravity, which can significantly reduce the weight of the electronic device. The metal plating layer <NUM> can resolve problems of a wave absorption effect and a PIM of the base body <NUM>, so that an antenna function of the electronic device is not affected. The middle plate <NUM> may be provided with an opening for placing an element on the circuit board at the opening of the middle plate <NUM>.

The carbon fiber reinforced resin composite material base body <NUM> is formed by a carbon fiber reinforced resin composite material, and the carbon fiber reinforced resin composite material includes, but is not limited to, a carbon fiber reinforced epoxy resin composite material, a carbon fiber reinforced phenolic resin composite material, or a carbon fiber reinforced polytetrafluoroethylene resin composite material, where the carbon fiber reinforced epoxy resin composite material has higher comprehensive performance indexes such as a specific strength and a specific modulus, so that the middle frame assembly have lighter weight and better strength as the base body.

In the carbon fiber reinforced resin composite material, a carbon fiber includes, but is not limited to, a continuous fiber or a short fiber, where the short fiber reinforced resin composite material is also referred to as a forged carbon fiber reinforced resin composite material, which has the advantages of high strength, short production cycle, being used on Grade A surfaces, and diversified surface treatment processes. In the short fiber reinforced resin composite material, an addition amount of the short fiber is not more than <NUM>%, generally in a range of 10wt% to 30wt%. The continuous fiber is also referred to as a long fiber, and the continuous fiber reinforced resin composite material is generally prepared by soaking resin with dry fiber cloth and then hot pressing. A diameter of the continuous fiber is generally in a range of <NUM> to <NUM>, and each bundle of fibers is <NUM>,<NUM> to <NUM>,<NUM>.

In a possible implementation, the carbon fiber reinforced resin composite material base body <NUM> may be provided with an opening for placing an element and a battery on the circuit board.

In a possible implementation, to increase a bonding force between the frame <NUM> and the middle plate <NUM>, a notched structure or a meshing structure may be arranged on an outer periphery of the carbon fiber reinforced resin composite material base body <NUM>. Alternatively, in other possible implementations, a carbon fiber reinforced resin composite material sidewall is formed on a portion of an outer periphery of the carbon fiber reinforced resin composite material base body <NUM>, for example, an outer periphery of the middle plate <NUM> close to the battery, to increase a bonding force between the frame <NUM> and the middle plate <NUM>.

The carbon fiber reinforced resin composite material serves as the base body of the middle plate <NUM>, and a metal plating layer <NUM> is compounded on the surface of the carbon fiber reinforced resin composite material. After the metal plating layer <NUM> is compounded, the middle plate <NUM> is equivalent to the metal middle plate. When a current flows through the reference ground of the middle frame assembly, the current distribution inside the conductor is uneven based on a skin effect of electromagnetic waves, and the current concentrates on a thin layer (that is, a "skin" part) outside the conductor. The closer the conductor surface is, the higher the current density is, and an actual current inside the conductor is smaller. That is, when a thickness of the metal plating layer <NUM> is larger than a skin depth corresponding to the frequency, and a resistivity is similar to that of the metal, an effect of the metal plating layer <NUM> is similar to that of an ordinary metal middle frame, and there is no loss of antenna performance.

For example, when phosphorus copper is used as the metal plating layer <NUM>, after a thickness of the phosphorus copper reaches the skin depth, performance deterioration < <NUM> dB, which has little impact on antenna performance. Referring to <FIG> and <FIG>, <FIG> is a system radiation efficiency curve of a metal plating layer and a metal material in a range of <NUM> to <NUM>, and <FIG> is a system radiation efficiency curve of a metal plating layer and a metal material in a range of <NUM> to <NUM>, where curve <NUM> is a system radiation efficiency in dB [Magnitude] of aluminum alloy (Al content is over <NUM>% and a resistivity is about <NUM>×<NUM>-<NUM> ohm·cm), and curve <NUM> is a system radiation efficiency curve of a phosphorus copper plating layer (a resistivity is about <NUM>×<NUM>-<NUM> ohm·cm). As can be seen from <FIG> and <FIG>, when the thickness of the metal plating layer meets the skin depth, and the resistivity is equivalent to that of the metal material, the performance hardly deteriorates.

In another example, when a silver plating layer is formed with silver paste as the metal plating layer <NUM>, after a thickness of the silver plating layer reaches a skin depth, because the resistivity of silver paste is higher than that of the metal material, the performance of the silver plating layer deteriorates, but the degree of deterioration is low, approximately in a range of <NUM> dB to <NUM> dB. Referring to <FIG> and <FIG>, <FIG> is a S-parameters (S-parameters [Magnitude in dB]) curve of a silver plating layer and a metal material in a range of <NUM> to <NUM>, and <FIG> is a system radiation efficiency curve of a silver plating layer and a metal material in a range of <NUM> to <NUM>, where curve <NUM> is a correlation curve of aluminum alloy (Al content is over <NUM>%, and the resistivity is about <NUM>×<NUM>-<NUM> ohm·cm), and curve <NUM> is a correlation curve of a silver plating layer (formed by silver paste, and the silver paste includes silver and silicone resin, and the resistivity is about <NUM>-<NUM> ohm·cm to <NUM>-<NUM> ohm·cm). As can be seen from <FIG> and <FIG>, when the thickness of the metal plating layer meets the skin depth, and the resistivity is higher than that of the metal material, the performance deteriorates, but the degree of deterioration is low and within an acceptable range.

When the thickness of the metal plating layer <NUM> reaches the skin depth and the resistivity is less than <NUM>-<NUM> ohm·cm, there is little or no impact on the antenna performance. Specifically, the metal plating layer <NUM> may be an alloy of one or more of metals such as zinc, copper, nickel, gold, silver, tin, or aluminum, which is not specially limited in the embodiments of this application. The metal plating layer <NUM> may be a single plating layer, and the single plating layer may be a single metal layer or may be a metal alloy layer; and The metal plating layer <NUM> may further be a multi-layer metal plating layer, each layer of the multi-layer metal plating layer may be the same or different, and each layer of the multi-layer metal plating layer may be a single metal layer or a metal alloy layer. In a possible embodiment, the metal plating layer <NUM> is a single plating layer, for example, a zinc-copper plating layer or a copper plating layer, and a thickness of the metal plating layer is in a range of <NUM> to <NUM>; for example, a thickness of the copper plating layer is in a range of <NUM> to <NUM>; and for example, a thickness of the nickel plating layer is in a range of <NUM> to <NUM>. In a possible embodiment, the metal plating layer <NUM> is a multi-layer metal plating layer. For example, including sequentially compounded copper plating layer and nickel plating layer, or sequentially compounded copper plating layer, nickel plating layer, and gold plating layer, where a thickness of the copper plating layer may be in a range of <NUM> to <NUM>, a thickness of the nickel plating layer may be in a range of <NUM> to <NUM>, and a thickness of the gold plating layer may be in a range of <NUM> to <NUM>. In a possible embodiment, a thickness of the metal plating layer may be in a range of <NUM> to <NUM>.

An objective of the metal plating layer <NUM> is to make the carbon fiber reinforced resin composite material base body <NUM> equivalent to a metal. Therefore, the metal plating layer <NUM> may be formed on an entire surface of the carbon fiber reinforced resin composite material base body <NUM>, or may be formed on a partial surface of the carbon fiber reinforced resin composite material base body <NUM>, for example, the metal plating layer <NUM> is formed on a partial surface that is not connected to the frame <NUM>. However, it should be noted that, when the metal plating layer <NUM> is formed on the partial surface of the carbon fiber reinforced resin composite material base body <NUM>, the metal plating layers on an upper surface and a lower surface of the carbon fiber reinforced resin composite material base body <NUM> are required to be connected in a manner such as drilling or grooving at an edge of a portion connected to the frame <NUM>, to ensure that the continuity of an electrical connection of the metal plating layer <NUM>.

The frame <NUM> is disposed around an outer edge of the middle plate <NUM>. In a possible implementation, the frame <NUM> includes a plastic frame <NUM> and a metallized frame <NUM> connected to the middle plate <NUM> through the plastic frame <NUM>. <FIG> is a schematic structural diagram of a frame according to an embodiment of this application. The plastic frame <NUM> can reduce a weight of the electronic device on the one hand, and facilitate a connection between the metallized frame <NUM> and the middle plate <NUM> on the other hand. The connection between the frame <NUM> and the middle plate <NUM> includes, but is not limited to, welding, clamping, locking, and integral injection molding. A person skilled in the art may understand that, when a manner of connecting the frame <NUM> and the middle plate <NUM> is welding, clamping, or locking, a region or a slot is arranged on the middle plate <NUM> and the frame <NUM> for implementing the welding, clamping, or locking.

The plastic frame <NUM> is made of a plastic material, for example, polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), glass fiber reinforced polycarbonate (PC+GF), ABS reinforced polycarbonate (ABS+PC), or carbon fiber reinforced resin composite material. When the plastic frame <NUM> is made of the carbon fiber reinforced resin composite material, a body of the plastic frame <NUM> may be the same as or different from that of the carbon fiber reinforced resin composite material of the middle plate <NUM>. The plastic frame <NUM> may be a closed annular structure or a semi-closed annular structure, or the plastic frame <NUM> may be a semi-frame structure. In this embodiment, the plastic frame <NUM> is a closed annular structure. In a possible embodiment, the plastic frame <NUM> is a semi-frame structure, and is located in a clearance area of the antenna radiator.

The metallized frame <NUM> is disposed around an outer edge of the plastic frame <NUM>, and may be formed by a section of a frame body connected end to end, that is, the metallized frame is an integral frame, and may be formed by a plurality of sections of the frame body connected end to end in turn, or may be formed by a plurality of discontinuous sections of the frame body. In a possible embodiment, the metallized frame <NUM> may be a metal frame, including, but is not limited to, aluminum, aluminum-magnesium alloy, or the like. In other possible embodiments, the metallized frame <NUM> may be a plastic frame with a metal plating layer compounded on a surface. For example, glass fiber reinforced polycarbonate compounded with the metal plating layer on the surface, carbon fiber reinforced resin composite material compounded with the metal plating layer on the surface, or the like.

In other possible implementations, a frame <NUM> is a plastic frame; or the frame includes a plastic frame and a ceramic frame or a glass frame, and the ceramic frame or the glass frame is connected to the middle plate <NUM> through the plastic frame. A person skilled in the art may understand that, a manner of connecting and disposing the ceramic frame and the glass frame are similar to a manner of connecting and disposing the metallized frame <NUM> and the plastic frame described above, and details are not described again in this application.

In a possible implementation, in an electronic device, a side of the frame <NUM> facing away from the middle plate <NUM> may be a vertical panel. For example, a side of the metallized frame <NUM> facing outward may be perpendicular to a display screen. Alternatively, in an electronic device, a side of the metallized frame <NUM> facing outward is an outwardly arcuate surface, which is convenient for hand-holding the electronic device on the one hand, and makes an outer frame of the metallized frame <NUM> more beautiful on the other hand.

<FIG> is a flowchart of a preparation process of a middle frame assembly according to an embodiment of this application, and the middle frame assembly in the embodiments of this application is prepared according to the following steps:
Step <NUM>): Process carbon fiber reinforced resin composite material to obtain a base body <NUM> of a middle plate <NUM> which can be used as a middle frame.

The carbon fiber reinforced resin composite material is the same as that described above, and details are not described again in this application. The carbon fiber reinforced resin composite material is processed through stamping or computer number control (Computer number control, CNC) to form the base body <NUM>, and an opening for placing an element on a circuit board and a battery compartment for a battery may be formed on the base body. In a possible implementation, a notched structure or a meshing structure is arranged on an edge of the base body <NUM>. Alternatively, in other possible implementations, a carbon fiber reinforced resin composite material sidewall is formed on a portion of an outer periphery of the carbon fiber reinforced resin composite material base body <NUM>, to increase a bonding force between the frame <NUM> and the middle plate <NUM>.

Step <NUM>): Form a metal plating layer <NUM> on a surface of the carbon fiber reinforced resin composite material base body to obtain a middle plate; and.

the metal plating layer <NUM> may be formed by performing metallized surface treatment on a carbon fiber reinforced resin composite material base body <NUM>. The metallized surface treatment includes, but is not limited to, spraying, metal spray pattern (Metal Spray Pattern, MSP), printing direct structuring (which is also referred to pad printing, printing direct structuring, PDS), laser direct structuring (Laser Direct Structuring, LDS), laser-activating-plating (Laser-Activating-Plating, LAP), or chemical plating. The metallized surface treatment methods are different, and adopted metals and formed metal plating layers are also different.

For example, a cold spraying uses compressed air to accelerate metal particles to a critical speed, and sprays the metal particles through a nozzle. After hitting the surface of the base body, the metal particles perform physical deformation, and after impact, the metal particles deform and firmly adhere to the surface of the base body. The whole process features a high speed and a low temperature, which have little thermal impact on the base body, and a dense plating. In a possible embodiment, a metal plating layer <NUM> is formed on the base body <NUM> through a cold spraying method, and the metal plating layer <NUM> may be a single metal plating layer of zinc, copper, nickel, gold, silver, tin, or an alloy plating layer formed by a plurality of metals. In a possible embodiment, the metal plating layer <NUM> is a single plating layer, for example, a zinc-copper plating layer or a copper plating layer, and a thickness of the metal plating layer is in a range of <NUM> to <NUM>; for example, a thickness of the copper plating layer is in a range of <NUM> to <NUM>; and for example, a thickness of the nickel plating layer is in a range of <NUM> to <NUM>. In a possible embodiment, the metal plating layer <NUM> is a multi-layer metal plating layer. For example, including sequentially compounded copper plating layer and nickel plating layer, or sequentially compounded copper plating layer, nickel plating layer, and gold plating layer, where a thickness of the copper plating layer may be in a range of <NUM> to <NUM>, a thickness of the nickel plating layer may be in a range of <NUM> to <NUM>, and a thickness of the gold plating layer may be in a range of <NUM> to <NUM>.

For example, PDS refers to an application of a principle of gravure printing, conductive ink including metal powder such as silver powder, copper powder, aluminum powder, and nickel powder is directly transferred to the base body through pad, and the metal plating layer is formed after thermal curing. The conductive ink includes not only the metal powder, but also silicone resin, epoxy resin, and the like. In a possible embodiment, a resistivity of the conductive ink is in a range of <NUM>-<NUM> ohm·cm to <NUM>-<NUM> ohm·cm. In a possible embodiment, a thickness of the metal plating layer may be in a range of <NUM> to <NUM>. In a possible embodiment, a thickness of the metal plating layer may be in a range of <NUM> to <NUM>.

For example, chemical plating is a process in which a metal is deposited to form a metal plating layer through redox reaction under catalysis of the metal. In a possible embodiment, a metal plating layer <NUM> is formed on the base body <NUM> through a chemical plating method, and the metal plating layer <NUM> may be a single metal plating layer of zinc, copper, nickel, gold, or an alloy plating layer formed by a plurality of metals. In a possible embodiment, the metal plating layer <NUM> is a single plating layer, for example, a zinc-copper plating layer or a copper plating layer, and a thickness of the metal plating layer is in a range of <NUM> to <NUM>; for example, a thickness of the copper plating layer is in a range of <NUM> to <NUM>; and for example, a thickness of the nickel plating layer is in a range of <NUM> to <NUM>. In a possible embodiment, the metal plating layer <NUM> is a multi-layer metal plating layer. For example, including sequentially compounded copper plating layer and nickel plating layer, or sequentially compounded copper plating layer, nickel plating layer, and gold plating layer, where a thickness of the copper plating layer may be in a range of <NUM> to <NUM>, a thickness of the nickel plating layer may be in a range of <NUM> to <NUM>, and a thickness of the gold plating layer may be in a range of <NUM> to <NUM>.

Step <NUM>): Connect the middle plate <NUM> to the frame <NUM>.

Specifically, the middle plate <NUM> and the frame <NUM> may be connected in a mechanical manner such as welding, clamping, or the like, or may be connected through an integral injection molding.

In a possible implementation, the middle plate <NUM> is connected to the frame <NUM> through screw fastening. As shown in <FIG> is a schematic structural diagram of a connection of a middle frame assembly according to an embodiment of this application. Corresponding screw holes are respectively arranged on the middle plate <NUM> and the frame <NUM>, and a fastening connection between the middle plate <NUM> and the frame <NUM> is implemented through a nut <NUM>. In this case, the frame <NUM> may be a preformed metal frame. In a possible embodiment, the nut <NUM> is a hot-melt nut and is bonded with the carbon fiber reinforced resin composite material base body <NUM> through a hot-melt adhesive <NUM>, thereby implementing a higher locking strength between the middle plate <NUM> and the frame <NUM>. In other possible embodiments, tapping may be directly performed on the carbon fiber reinforced resin composite material base body <NUM>, or may be performed metallization after tapping on the carbon fiber reinforced resin composite material base body <NUM>.

When the middle plate <NUM> is connected to the frame <NUM> through integral injection molding, the frame <NUM> may be a plastic frame or a composite frame including a plastic frame and a metallized frame or a glass frame or a ceramic frame. The integral injection molding may include nano molding technology (Nano Molding Technology, NMT) or metal device antenna (Metal Device Antenna, MDA).

A typical NMT process is:
The middle plate <NUM> including a metal plating layer and a carbon fiber reinforced resin composite material base body is processed to etch a honeycomb-shaped nano-pore with a smaller size on the surface of the metal plating layer, and then perform injection molding with plastic particles and a metal frame, a glass frame or a ceramic frame to obtain the middle frame assembly.

Compared with an NMT treatment with a metal middle plate directly, the NMT treatment with the middle plate includes a metal plating layer and a carbon fiber reinforced resin composite material base body that are not required for stamping treatment (that is, a molding treatment), and injection molding is performed by etching honeycomb nano-holes with a smaller size on the surface of the metal plating layer directly through T treatment and E treatment. When the frame is a plastic frame, the middle plate may be directly injected with plastic particles; when the frame is a composite frame including a plastic frame and a metallized frame or a glass frame or a ceramic frame, and during injection molding, the plastic particles are used to inject the metallized frame, the glass frame, or the ceramic frame into an integrated structure.

A typical MDA process is:
The middle plate <NUM> including a metal plating layer and a carbon fiber reinforced resin composite material base body is processed to etch a honeycomb-shaped nano-pore with a smaller size on the surface of the metal plating layer, and then perform injection molding with plastic particles and a metal frame, a glass frame or a ceramic frame to obtain the middle frame assembly.

Compared with an MDA treatment with a metal middle plate, the MDA treatment with the middle plate including metal plating layer and the carbon fiber reinforced resin composite material base body that are not required for die casting and punching treatment, and injection molding is performed directly. When the frame is a plastic frame, the middle plate may be directly injected with plastic particles; when the frame is a composite frame including a plastic frame and a metallized frame or a glass frame or a ceramic frame, and during injection molding, the plastic particles are used to inject the metallized frame, the glass frame, or the ceramic frame into an integrated structure.

In a possible implementation, a plastic particle used for injection molding includes, but is not limited to, polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), glass fiber reinforced polycarbonate (PC+GF), ABS reinforced polycarbonate (ABS+PC), or carbon fiber reinforced resin composite material.

To implement signal transmission and reception, at least one antenna assembly is arranged in an electronic device, where the antenna assembly includes an antenna radiator and a feed point and a ground point electrically connected to the antenna radiator. In the embodiments of this application, the antenna radiator is arranged on the middle frame assembly. As shown in <FIG> is a schematic structural exploded view of the middle frame assembly according to a second embodiment of this application. The middle plate <NUM> is connected to the metallized frame <NUM> through the plastic frame <NUM>, and at least a portion of a frame body of the metallized frame <NUM> is used as the antenna radiator <NUM>. The metallized frame <NUM> has a plurality of slots <NUM> that are used as antenna slots for spacing apart two adjacent antenna radiators.

The feed point (not shown in the figure) of the antenna assembly may be located on a circuit board (not shown in the figure), and electrically connected to a radio frequency chip or a main chip (not shown in the figure) on the circuit board through a feed. The feed feeds a high frequency current to each antenna radiator <NUM> through the feed point, and the high frequency current is emitted outward in a form of an electromagnetic wave on the antenna radiator. Because a ground point of the circuit board is electrically connected to the middle plate <NUM>, one end of the ground point of the antenna assembly is electrically connected to the antenna radiator, and the other end of the ground point of the antenna assembly is electrically connected to the middle plate <NUM> to implement grounding.

In a possible implementation, the antenna radiator <NUM> is electrically connected to the metal plating layer of the middle plate <NUM> through a conductive layer <NUM>, and the conductive layer <NUM> electrically connects the antenna radiator <NUM> to the metal plating layer of the middle plate <NUM>, to implement grounding of the antenna radiator <NUM>. The conductive layer <NUM> may be formed in a manner such as ultrasonic welding, silver paste printing, or spraying, and the manner is not specially limited in the embodiments of this application. In a possible implementation, the metal frame <NUM> and the plastic frame <NUM> are connected to the middle plate <NUM> through injection molding. The metal frame <NUM> is processed to form the antenna slot <NUM> and the antenna radiator <NUM>, and then the conductive layer <NUM> is formed on the metal plating layer of the middle plate <NUM> and the antenna radiator <NUM> through silver paste printing, thereby implementing the grounding of the antenna radiator <NUM>.

In other possible implementations, the antenna radiator <NUM> is electrically connected to the metal plating layer <NUM> of the middle plate <NUM> through a conductive auxiliary material, such as a metal elastic piece, to implement the grounding of the antenna radiator <NUM>. As shown in <FIG> is a schematic structural exploded view of a middle frame assembly according to a third embodiment of this application. Corresponding screw holes are respectively arranged on the middle plate <NUM> and the frame <NUM>, and a fastening connection between the middle plate <NUM> and the frame <NUM> is implemented through a nut <NUM>. The metal elastic piece <NUM> is arranged between the antenna radiator <NUM> and the metal plating layer of the middle plate <NUM>, to implement an electrical connection between the antenna radiator and the middle plate <NUM>. The metal elastic piece <NUM> may be one, or may be two or more. When there are a plurality of metal elastic pieces, the plurality of metal elastic pieces are electrically connected.

In some possible implementations, the metal elastic piece <NUM> may be electrically connected in a spot welded manner, and a welding region is arranged on the antenna radiator <NUM>. In some possible implementations, the metal elastic piece <NUM> may be in a form of a double-sided convex hull gasket, for example, a group of four convex hulls. Two convex hulls facing the antenna radiator <NUM> are in contact with the antenna radiator <NUM>, and the other two convex hulls facing the metal plating layer <NUM> are connected to the metal plating layer <NUM>, to implement an electrical connection between the antenna radiator <NUM> and the middle plate <NUM>.

When the metal elastic piece <NUM> is used for the electrical connection, to reduce a contraction resistance of the metal elastic piece <NUM>, a clamping force between the middle plate <NUM> and the frame <NUM> needs to be more than 100N. When a contact pressure increases, two contact surfaces move closer to each other, and a quantity of contact spots increases accordingly, so that a real contact area increases and the contraction resistance decreases. In addition, deformation of some contact spots changes from elastic deformation to plastic deformation, which makes the contact surface permanently flattened, and can also reduce the contraction resistance of the metal elastic piece. Table <NUM> is changes of a contraction resistance caused by a contact form of a metal elastic piece.

In other possible implementations, an antenna radiator <NUM> may further be electrically connected to a metal plating layer of a middle plate <NUM> through a convex hull, a conductive fabric, a conductive adhesive, or a conductive foam.

In other possible implementations, <FIG> is a schematic diagram of a connection between an antenna radiator and a PCB according to an embodiment of this application; and the antenna radiator <NUM> may be electrically connected to the PCB <NUM> through an elastic piece <NUM>. The elastic piece <NUM> may be one, two, or more, and an electrical connection is implemented through the PCB, which saves costs of a structure. Alternatively, <FIG> is a schematic diagram of a connection between an antenna radiator and a screen component according to an embodiment of this application; and the antenna radiator <NUM> may be electrically connected to a metal frame or copper foil of a screen <NUM> through a foam <NUM>.

In the embodiments of this application, there is a plurality of antenna assemblies, including a main antenna and a parasitic antenna; or including a low frequency antenna (<NUM> to <NUM>), an intermediate frequency antenna (<NUM> to <NUM>), a medium and high frequency antenna (<NUM> to <NUM>), and a high frequency antenna (<NUM> to <NUM>), and may further include an antenna in frequency bands of <NUM> to <NUM> and <NUM> to <NUM>. The antenna assembly may further include a WIFI antenna, a global positioning system (Global Positioning System, GPS) antenna, or a Bluetooth antenna.

When at least a portion of a frame body of the metallized frame is used as the antenna radiator, the antenna radiator may be formed by processing after the frame including the metal frame and the plastic frame and the middle plate are molded, or may be formed by electroplating, laser engraving, or printing after the plastic frame and the middle plate are firstly connected. In the embodiments of this application, a material of the antenna radiator includes, but is not limited to, silver, gold, nickel, stainless steel, and the like.

In other possible implementations, an antenna radiator in an antenna assembly is arranged on a side of a plastic frame facing a middle plate, that is, the antenna radiator is arranged inside of the plastic frame. In this case, the antenna radiator may be formed by integral injection molding with the plastic frame and the middle plate.

When the frame is connected to the middle plate including the metal plating layer and the carbon fiber reinforced resin composite material base body in a manner of integrally injection molding, an injection pressure is approximately in a range of 50MPa to 100MPa, and a joint surface of the metal plating layer and a plastic particle on the middle plate is subjected to great pressure during the injection molding, which leads to peeling of the metal plating layer on the middle plate and has an impact on antenna performance or conductivity performance of the electronic device.

To prevent the metal plating layer on the middle plate from falling off, the middle frame assembly provided in the embodiments of this application may be added with a protective layer. <FIG> is a schematic structural exploded view of a middle frame assembly according to a fourth embodiment of this application. The carbon fiber reinforced resin composite material base body <NUM>, the metal plating layer <NUM> compounded on a surface thereof, and the protective layer <NUM> compounded on the surface of the metal plating layer constitute the middle plate <NUM>, and the frame <NUM> is connected to the middle plate <NUM>. When the middle plate <NUM> is connected to the frame <NUM>, the protective layer <NUM> is arranged on the surface of the metal plating layer <NUM>, which can prevent the metal plating layer <NUM> from falling off.

In this embodiment, the carbon fiber reinforced resin composite material base body <NUM>, the metal plating layer <NUM> compounded on the surface thereof, and the frame <NUM> are described above, and details are not described again in this application. The protective layer <NUM> may be a metal oxide protective layer, a paint protective layer, or a paint protective layer, and is used to passivate the metal plating layer <NUM> and prevent the metal plating layer <NUM> from falling off.

The protective layer <NUM> may be arranged on an entire surface of the metal plating layer <NUM>, or may be arranged on a portion of the surface, for example, the protective layer <NUM> may be arranged on a portion connected to the frame <NUM>. The protective layer <NUM> arranged on a portion of the surface does not require a thickness of the metal plating layer without the protective layer, which is beneficial to reduce a weight of the electronic device.

Generally, the protective layer <NUM> may be formed by using surface coating treatment, passivation liquid treatment, spraying, anodic oxidation, micro-arc oxidation, or electrophoresis. Specifically, the surface coating treatment refers that the middle plate <NUM> including the metal plating layer <NUM> and the carbon fiber reinforced resin composite material base body <NUM> is performed chemical dipping treatment to form an antioxidative protective layer on the surface of the metal plating layer <NUM>, where the chemical dipping treatment may be phosphoric acid treatment, manganate treatment, or vanadate treatment, which is not specifically limited in this application.

The passivation liquid treatment is similar to the surface coating treatment, and the difference lies in that the middle plate <NUM> including the metal plating layer <NUM> and the carbon fiber reinforced resin composite material base body <NUM> is performed passivation in passivation solution, and a thin protective film is formed on the surface of the metal plating layer <NUM> to isolate the metal plating layer from an external medium, so that the metal plating layer is prevented from falling off and being corroded at the same time.

The spraying treatment is to disperse paint or other covering into uniform and fine droplets with the help of pressure or centrifugal force through a spray gun or dish vaporizer, and apply the paint or other covering to the surface of metal plating layer <NUM> to form a protective layer.

The anodic oxidation refers that the middle plate <NUM> including the metal plating layer <NUM> and the carbon fiber reinforced resin composite material base body <NUM> is used as an anode to perform electrolysis in the electrolyte, so that an oxide film is formed on the surface of the metal plating layer <NUM>, to protect the metal plating layer <NUM>.

The micro-arc oxidation, which is also referred to plasma electrolytic oxidation (PEO). In the electrolyte, under an instantaneous high temperature and high pressure generated by arc discharge, a modified ceramic plating layer mainly composed of metal oxide and supplemented by electrolyte components is grown on the surface of metal plating layer <NUM> as a protective layer, to protect the metal plating layer <NUM>.

In the electrophoresis, the middle plate <NUM> including the metal plating layer <NUM> and the carbon fiber reinforced resin composite material base body <NUM> is used as a cathode. Under an action of a voltage, the electrophoresis coating reacts with the surface of the metal plating layer <NUM> to form an insoluble substance, which is deposited on the surface of the metal plating layer <NUM>, to protect the metal plating layer <NUM>.

In a possible implementation, in this application, the metal plating layer is not compounded on a portion where the middle plate and the frame are combined, to prevent the metal plating layer from falling off and have an impact on the performance of the middle frame. As shown in <FIG> is a schematic structural exploded view of a middle frame assembly according to a fifth embodiment of this application. The middle plate <NUM> includes a carbon fiber reinforced resin composite material base body <NUM> and a metal plating layer <NUM>, the metal plating layer <NUM> is compounded on a surface of the carbon fiber reinforced resin composite material base body <NUM> which is not in contact with a frame <NUM>, and the frame <NUM> is directly connected to the carbon fiber reinforced resin composite material base body <NUM>. That is, the metal plating layer <NUM> is not compounded on the surface of the carbon fiber reinforced resin composite material base body <NUM> at a portion where the middle plate <NUM> is in contact with the frame <NUM>, and the metal plating layer <NUM> is compounded only on the portion where the middle plate <NUM> is not in contact with the frame <NUM>. To implement continuity of an electrical connection of the metal plating layer on the upper and lower surfaces of the carbon fiber reinforced resin composite material base body <NUM>, at an edge of the metal plating layer <NUM>, that is, an edge of a portion where the frame <NUM> is directly connected to the carbon fiber reinforced resin composite material base body <NUM>, a through hole <NUM> is formed in the carbon fiber reinforced resin composite material base body <NUM>, so that a metal plating layer on the upper surface and a metal plating layer on the lower surface of the carbon fiber reinforced resin composite material base body <NUM> are implemented the continuity of the electrical connection in a manner of compounding the metal plating layer and connecting the metal plating layer to the metal plating layer <NUM>. There may be a plurality of through holes <NUM>, as shown in <FIG>, and there may be one, as shown in <FIG>. In other possible implementations, continuity of an electrical connection may further be implemented in a manner of connecting a conductive material to the metal plating layer <NUM>, for example, a metal sheet or a conductive ink, on the through hole <NUM>.

In another possible implementation, the metal plating layer <NUM> may further be directly compounded at an edge of a portion where the frame <NUM> is directly connected to the carbon fiber reinforced resin composite material base body <NUM>, so that a metal plating layer on the upper surface and a metal plating layer on the lower surface of the carbon fiber reinforced resin composite material base body <NUM> are implemented the continuity of the electrical connection, as shown in <FIG>. The middle plate <NUM> includes a carbon fiber reinforced resin composite material base body <NUM> and a metal plating layer <NUM>, the metal plating layer <NUM> is compounded on a surface of the carbon fiber reinforced resin composite material base body <NUM> which is not in contact with a frame <NUM>, and the frame <NUM> is directly connected to the carbon fiber reinforced resin composite material base body <NUM>. That is, the metal plating layer <NUM> is not compounded on the surface of the carbon fiber reinforced resin composite material base body <NUM> at a portion where the middle plate <NUM> is in contact with the frame <NUM>, and the metal plating layer <NUM> is compounded only on the portion where the middle plate <NUM> is not in contact with the frame <NUM>. To implement continuity of an electrical connection of the metal plating layer <NUM> on the upper and lower surfaces of the carbon fiber reinforced resin composite material base body <NUM>, the metal plating layer <NUM> is directly compounded on a portion where the frame <NUM> is connected to the carbon fiber reinforced resin composite material base body <NUM>, so that a metal plating layer on the upper surface and a metal plating layer on the lower surface of the carbon fiber reinforced resin composite material base body <NUM> are implemented the continuity of the electrical connection. In other possible implementations, a conductive sheet may further be directly connected, so that a metal plating layer on the upper surface and a metal plating layer on the lower surface of the carbon fiber reinforced resin composite material base body <NUM> are implemented the continuity of the electrical connection.

In a possible implementation, when an antenna assembly is required to be coupled with a metal reference ground, in this application, a second metal plating layer may be further compounded on a portion where a middle plate and a frame are combined, as shown in <FIG>. The middle plate <NUM> includes a carbon fiber reinforced resin composite material base body <NUM> and a metal plating layer <NUM>, the metal plating layer <NUM> is compounded on a surface of the carbon fiber reinforced resin composite material base body <NUM> which is not in contact with a frame <NUM>, and the frame <NUM> is directly connected to the carbon fiber reinforced resin composite material base body <NUM>. That is, the metal plating layer <NUM> is not compounded on the surface of the carbon fiber reinforced resin composite material base body <NUM> at a portion where the middle plate <NUM> is in contact with the frame <NUM>, and the metal plating layer <NUM> is compounded only on a portion where the metal plating layer <NUM> is not in contact with the frame <NUM>, to prevent the metal plating layer <NUM> from falling off at a contact portion during subsequent injection molding. At an edge of the metal plating layer <NUM>, that is, an edge of a portion where the frame <NUM> is directly connected to the carbon fiber reinforced resin composite material base body <NUM>, a through hole <NUM> is formed in the carbon fiber reinforced resin composite material base body <NUM>, so that a metal plating layer on the upper surface and a metal plating layer on the lower surface of the carbon fiber reinforced resin composite material base body <NUM> are implemented the continuity of the electrical connection in a manner of compounding the metal plating layer. There may be a plurality of through holes <NUM>, or there may be one. A second metal plating layer <NUM> is compounded at an edge of a portion where the frame <NUM> is connected to the middle plate <NUM>, to facilitate a metal reference ground coupling of an antenna assembly.

To further reduce the weight of the electronic device, in a fifth embodiment of this application, <FIG> is a schematic structural diagram of a middle frame assembly according to a sixth embodiment of this application. The middle frame assembly includes a middle plate <NUM> and a frame <NUM>, and the middle plate <NUM> includes a first carbon fiber reinforced resin composite material base body and a first metal plating layer compounded on the first carbon fiber reinforced resin composite material base body; and the frame <NUM> includes a plastic frame <NUM> and a metallized frame <NUM> connected to the middle plate <NUM> through the plastic frame <NUM>. The metallized frame includes a second carbon fiber reinforced resin composite material base body and a second metal plating layer compounded on the second carbon fiber reinforced resin composite material base body, that is, the middle plate <NUM> and the frame <NUM> are both formed by the carbon fiber reinforced resin composite material compounded with the metal plating layer, which has high strength and low weight at the same time. At least a portion of the frame body of the metallized frame <NUM> forms an antenna radiator, and the antenna radiator is connected to the middle plate <NUM> through the conductive layer. The arrangement of the antenna radiator and the conductive layer may be referred to the description above, and details are not described again in the present invention.

It should be understood that, the electronic device mentioned in this application may be any device with communication and storage functions. For example, a smart phone, a cellular phone, a cordless phone, a session initiation protocol (Session Initiation Protocol, SIP) phone, a tablet computer, a personal digital assistant (Personal Digital Assistant, PAD), a notebook computer, a digital camera, an electronic book reader, a portable multimedia player, a handheld device with a wireless communication function, a computing device or another processing device connected to a wireless modem, an in-vehicle device, a wearable device, a <NUM> terminal device, or the like, which is not limited in this application.

Claim 1:
A middle frame assembly, comprising a middle plate (<NUM>, <NUM>, <NUM>, <NUM>) and a frame (<NUM>, <NUM>, <NUM>, <NUM>) disposed around an outer edge of the middle plate (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>), wherein the middle plate (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprises a first carbon fiber reinforced resin composite material base body and a first metal plating layer compounded on a surface of the base body (<NUM>, <NUM>, <NUM>), wherein a thickness of the first metal plating layer (<NUM>, <NUM>, <NUM>) is greater than or equal to a skin depth of the first metal plating layer (<NUM>, <NUM>, <NUM>) corresponding to a given frequency.