Middle frame and preparation method therefor, and electronic device

Abstract

Embodiments of the present application relate to the field of electronic devices, and provide a middle frame and a preparation method therefor, and an electronic device, for use in realizing a reliable connection between a middle plate and an outer frame, thereby improving the impact resistance of the middle frame, and ensuring the consistency of the radio frequency performance of bezel antennas in the electronic device. The middle frame comprises a middle plate, an outer frame and a connecting member. The middle plate comprises a mounting hole. The outer frame is located on the outer side of the middle plate. The outer frame comprises a main body part and an extension part connected to each other, and the extension part and the middle plate are stacked. The connecting member is located in the mounting hole and is connected to the middle plate. The connecting member is welded to the extension part. The material of the middle plate comprises one of a magnesium alloy, a magnesium-based composite material, and an aluminum alloy. The material of the outer frame comprises one of an aluminum alloy, a titanium-based material, an iron-based material, a titanium-aluminum composite material, and a steel-aluminum composite material. The microhardness of the connecting member is greater than that of the middle plate. The middle frame is applied to an electronic device to improve the performance of the electronic device.

Description

Middle frame and preparation method thereof, and electronic device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on August 15, 2023, with application number 202311030853.5 and application name “Middle frame and its preparation method, electronic device”, all contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of electronic devices, and in particular to a middle frame and a preparation method thereof, and electronic devices. Background Art

[0003] The midframe is a crucial piece of hardware in electronic devices, supporting important components like the motherboard and battery. The display and back cover of the electronic device also need to be secured to the midframe. The structure of the midframe significantly impacts the production cost and weight of the electronic device.

[0004] At present, the middle frame generally includes a middle plate and an outer frame. The material of the middle plate includes magnesium alloy, magnesium-based composite material or aluminum alloy, and the material of the outer frame includes aluminum, titanium, steel, etc. The middle plate and the outer frame are connected by welding. However, when the material of the middle plate includes magnesium alloy or magnesium-based composite material, due to the disadvantages of magnesium alloy or magnesium-based composite material such as low melting point and easy evaporation, high activity and easy oxidation, when the middle plate and the outer frame are directly welded, welding defects are likely to occur at the weld between the middle plate and the outer frame. When the material of the middle plate includes aluminum alloy, the middle plate is usually prepared by a die-casting process. However, a large number of pores are likely to appear inside the middle plate prepared by the die-casting process. Therefore, when the middle plate and the outer frame are directly welded, welding defects are also likely to occur at the weld between the middle plate and the outer frame. The presence of welding defects will make the stability of the solder joints poor, resulting in a reduction in the impact resistance of the middle frame.

[0005] At the same time, with the rapid development of communication technology, electronic devices are generally equipped with antennas for communication, enabling functions such as making calls and surfing the Internet. The midframe, as a good radiator, can be used as an antenna, effectively reducing the space occupied by the built-in antenna in electronic devices. Welding defects between the midframe and the outer frame can also lead to poor impedance consistency of the solder joints, affecting the consistency of the RF performance of the electronic device's frame antenna.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a middle frame and a preparation method thereof, and an electronic device, which are used to achieve a reliable connection between a middle plate and an outer frame, improve the impact resistance of the middle frame, and ensure the consistency of the radio frequency performance of the border antenna of the electronic device.

[0008] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0009] In a first aspect, a middle frame is provided, which includes a middle plate, an outer frame and a connecting piece. The middle plate includes a mounting hole. The outer frame is located on the outside of the middle plate. The outer frame includes a main body and an extension portion that are connected, the extension portion is located on the side of the main body facing the middle plate, and the thickness of the extension portion is less than the thickness of the main body portion. The extension portion is stacked with the middle plate. The connecting piece is located in the mounting hole and is connected to the middle plate. The connecting piece is welded to the extension portion. The material of the middle plate includes one of a magnesium alloy, a magnesium-based composite material and an aluminum alloy; the material of the outer frame includes one of an aluminum alloy, a titanium-based material, an iron-based material, a titanium-aluminum composite material and a steel-aluminum composite material; the microhardness of the connecting piece is greater than the microhardness of the middle plate.

[0010] In the embodiment of the present application, the connector is placed in the mounting hole of the middle plate, so that the connector is connected to the middle plate, and the connector is welded to the outer frame, so that the middle plate and the outer frame are fixed to form a middle frame. Among them, when the material of the middle plate includes magnesium alloy and / or magnesium-based composite material, since the density of magnesium alloy and magnesium-based composite material is relatively small, the weight of the middle plate can be made smaller, and the weight of the middle frame can be made smaller, which is beneficial to reduce the weight of the electronic equipment using the middle frame. In the case where the material of the middle plate includes aluminum alloy, the middle plate can be prepared by a die-casting process. In this way, compared with the method of preparing the middle plate by CNC machine tool processing, the preparation cost of the middle plate can be lower, and the production efficiency of the middle plate can be higher, which is beneficial to realize mechanical automation production.

[0011] In an embodiment of the present application, the material of the outer frame includes one of aluminum alloy, titanium-based material, iron-based material, titanium-aluminum composite material and steel-aluminum composite material, so that the appearance area of ​​the middle frame can have a metallic texture, which is beneficial to improving the competitiveness of electronic equipment using the middle frame.

[0012] In the embodiment of the present application, a connecting piece is used to connect the middle plate and the outer frame. The microhardness of the connecting piece is greater than the microhardness of the middle plate, which effectively improves the problem of welding defects at the welding position between the middle plate and the outer frame when the middle plate and the outer frame are directly welded together due to the low melting point and easy evaporation of magnesium alloy or magnesium-based composite materials, high activity and easy oxidation, or the presence of a large number of pores in the die-cast aluminum material. This makes the connection reliability between the middle plate and the outer frame higher, which is beneficial to improving the stability of the middle frame and improving the impact resistance of the middle frame.

[0013] The middle frame is a good radiator and can therefore be used as an antenna. In the middle frame provided in the embodiment of the present application, the middle plate is connected to the connector, and the outer frame is also welded to the connector. This makes it less likely for welding defects to occur at the connection between the middle plate and the outer frame, thereby ensuring the consistency of the impedance value at the connection between the middle plate and the outer frame, and thus ensuring the consistency of the RF performance of the frame antenna in the electronic device.

[0014] Furthermore, in the middle frame provided in the embodiment of the present application, the outer frame and the connector are connected by welding. Compared to directly connecting the middle plate and outer frame with rivets, the stress at the connection between the connector and the outer frame can be reduced, and the stress at the connection between the middle plate and the outer frame can be reduced, thereby making the middle frame less susceptible to distortion and effectively improving the flatness of the middle frame. Compared to connecting the middle plate and the outer frame using rivetless riveting, the thickness of the connection between the middle plate and the outer frame provided in the embodiment of the present application can be reduced, thereby reducing the thickness of the middle frame and the thickness of the electronic device using the middle frame, thereby realizing ultra-thin electronic devices.

[0015] In some embodiments, the connecting member includes a first connecting portion and a second connecting portion perpendicular to each other, the first connecting portion is located in the mounting hole and welded to the extension portion, and a portion of the mid-plate is located between the second connecting portion and the extension portion.

[0016] In this way, on the one hand, the middle plate is confined between the second connecting portion of the connector and the extension of the outer frame. Relative displacement between the middle plate and the connector is unlikely to occur in the thickness direction of the middle plate, as well as in directions parallel to the middle plate, making separation difficult. On the other hand, both the first and second connecting portions of the connector are in contact with the middle plate, increasing the contact area between the middle plate and the connector. This improves the connection stability between the middle plate, outer frame, and connector, thereby further improving the yield rate and operational stability of the middle frame.

[0017] In some embodiments, the mounting hole is a stepped hole, and the first connecting portion and the second connecting portion are both located in the stepped hole; the end surface of the second connecting portion away from the first connecting portion is flush with the surface of the middle plate away from the extension portion.

[0018] At this point, the end surface of the second connecting portion away from the first connecting portion is flush with the surface of the middle plate away from the extension portion. This can improve the flatness of the middle frame, allowing the middle frame to better support electronic components or displays, and improve the yield of electronic devices using the middle frame.

[0019] In some embodiments, the connecting member is a column, and the connecting member is interference-fitted with the mounting hole. In this way, the connecting member has a simple structure and is easy to obtain, which is conducive to simplifying the structure of the middle frame.

[0020] In some embodiments, the material of the connector is the same as that of the outer frame. Thus, the melting points of the connector and the outer frame can be the same. This reduces the yield rate of the weld between the connector and the outer frame due to a significant difference in their melting points, thereby further improving the strength and stability of the connection between the connector and the outer frame.

[0021] In some embodiments, the mounting holes include through holes or blind holes.

[0022] In some embodiments, the extension portion includes a first part and a second part, the second part is arranged around the first part, and the first part and the connecting member have a molten pool, and the molten pool extends from the surface of the first part away from the midplate to the connecting member; or, the molten pool extends from the surface of the connecting member away from the extension portion to the inside of the first part.

[0023] In some embodiments, the main body includes a first surface and a second surface relative to each other, and a first side surface and a second side surface connecting the first surface and the second surface, the first surface is farther away from the extension portion than the second surface, and the second surface is connected to the extension portion; the middle frame also includes a decorative layer, and the decorative layer covers at least the first surface.

[0024] The embodiment of the present application provides a decorative layer, which can, on the one hand, color the surface of the outer frame, improve the appearance of the outer frame, and increase users' liking for the electronic device; on the other hand, the decorative layer can also be used to protect the outer frame to prevent the outer frame from being corroded by water vapor and oxygen in the environment.

[0025] In some embodiments, the molten pool extends from the surface of the first portion distal from the midplate toward the connector, and the decorative layer also covers the surface of the second portion distal from the midplate, the first side surface, the second side surface, and the portion of the second surface not in contact with the extended portion. As the molten pool extends from the surface of the first portion distal from the midplate toward the connector, the decorative layer exposes both the surface of the first portion distal from the connector and the surface of the first portion proximal to the connector, thereby preventing the decorative layer's higher melting point from affecting welding yield.

[0026] In some embodiments, the molten pool extends from the surface of the connector away from the extension portion into the first portion; the decorative layer also covers the surface of the first portion away from the middle plate, the surface of the second portion away from the middle plate, the first side surface, the second side surface, and the portion of the second surface that is not in contact with the extension portion.

[0027] When the molten pool extends from the surface of the connector away from the extension portion into the first portion, the decorative layer exposes the surface of the first portion close to the connector, which helps to avoid affecting the welding yield due to the high melting point of the decorative layer.

[0028] In some embodiments, the shear strength of the weld between the extension and the connector is greater than or equal to 100 N, and the pull-out strength of the weld between the extension and the connector is greater than or equal to 90 N. This improves the stability of the connection between the extension and the connector, as well as the stability of the connection between the outer frame, the middle plate, and the connector. This increases the stability of the middle frame and improves its impact resistance, thereby improving the service life of the electronic device.

[0029] In some embodiments, the material of the outer frame includes a titanium-aluminum composite material, the main body includes a first sublayer and a second sublayer, the first sublayer is farther away from the extension part than the second sublayer, the second sublayer is connected to the extension part, the material of the first sublayer includes titanium, and the material of the second sublayer and the material of the extension part both include aluminum alloy.

[0030] In the outer frame provided in the embodiment of the present application, the material of the first sublayer of the main body is set to titanium metal, the material of the second sublayer is set to aluminum alloy, and the material of the extension is set to aluminum alloy. The density of aluminum alloy is lower than that of titanium metal. As a result, the middle frame can have a metallic texture and appearance while having a smaller weight, which is beneficial to reducing the production cost of the middle frame.

[0031] Alternatively, the material of the outer frame includes a steel-aluminum composite material, the main body includes a third sublayer and a fourth sublayer, the third sublayer is farther away from the extension part than the fourth sublayer, the fourth sublayer is connected to the extension part, the material of the third sublayer includes stainless steel, and the material of the fourth sublayer and the material of the extension part both include aluminum alloy.

[0032] In the outer frame provided in the embodiment of the present application, the material of the first sublayer of the main body is set to stainless steel, the material of the second sublayer is set to aluminum alloy, and the material of the extension is set to aluminum alloy. The density of aluminum alloy is lower than that of stainless steel. As a result, the middle frame can have a metallic texture and appearance while having a smaller weight, which helps to reduce the production cost of the middle frame.

[0033] In a second aspect, a method for preparing a middle frame is provided. The preparation method includes: providing a middle plate, an outer frame and a connector. The outer frame includes a main body and an extension portion that are connected to each other, and the thickness of the extension portion is less than the thickness of the main body portion. The connector is installed on the middle plate; the connector is located in the mounting hole of the middle plate. The middle plate and the outer frame are fixed; the outer frame is located on the outside of the middle plate, the extension portion is located on the side of the main body facing the middle plate, and the extension portion is stacked with the middle plate. The extension portion is welded to the connector. The material of the middle plate includes one of magnesium alloy, magnesium-based composite material and aluminum alloy, and the material of the outer frame includes one of aluminum alloy, titanium-based material, iron-based material, titanium-aluminum composite material and steel-aluminum composite material; the microhardness of the connector is greater than the microhardness of the middle plate.

[0034] In some embodiments, welding the extension portion to the connection piece includes: welding the extension portion to the connection piece using a laser welding process.

[0035] In the embodiments of this application, laser welding is used to weld the extension to the connector. This results in high welding precision, minimal deformation of the extension and connector, and low stress between the extension and connector. This reduces deformation of the middle frame after welding, improving the flatness of the middle frame. Laser welding also offers high welding speeds, and utilizing this process to weld the extension and connector increases the speed and efficiency of middle frame production.

[0036] In some embodiments, the material of the outer frame includes aluminum alloy, and the preparation method further includes: forming a decorative layer using an anodizing process; or, the material of the outer frame includes one of a titanium-based material, an iron-based material, a titanium-aluminum composite material, and a steel-aluminum composite material, and the preparation method further includes: forming a decorative layer using a physical vapor deposition process.

[0037] The main body includes a first surface and a second surface relative to each other, and a first side surface and a second side surface connecting the first surface and the second surface. The first surface is farther away from the middle plate than the second surface, and the second surface is connected to the extension portion. The decorative layer covers at least the first surface.

[0038] In a third aspect, an electronic device is provided, comprising a display screen, a rear housing, and a middle frame as described in any of the above embodiments, wherein the middle frame is located between the display screen and the rear housing, and an outer frame of the middle frame serves as a side of the electronic device.

[0039] Among them, the technical effects brought about by any design method in the second to third aspects can refer to the technical effects brought about by different design methods in the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] To more clearly illustrate the technical solutions of this application, the following briefly introduces the drawings required for use in some embodiments of this application. Obviously, the drawings described below are only drawings of some embodiments of this application, and those skilled in the art can also derive other drawings based on these drawings. Furthermore, the drawings described below are schematic diagrams and are not intended to limit the actual dimensions of the products, actual processes of the methods, actual timing of signals, and the like involved in the embodiments of this application.

[0041] FIG1 is a schematic structural diagram of an electronic device provided in an embodiment of the present application;

[0042] FIG2 is a schematic structural diagram of a middle frame provided in an embodiment of the present application;

[0043] FIG3 is a schematic top view of a middle frame provided in an embodiment of the present application;

[0044] FIG4 is an enlarged schematic diagram of the middle frame shown in FIG3 at position AA;

[0045] FIG5 is a schematic cross-sectional view of the middle frame shown in FIG3 at BB';

[0046] FIG6A is another cross-sectional schematic diagram of the middle frame shown in FIG3 at BB′;

[0047] FIG6B is another cross-sectional schematic diagram of the middle frame shown in FIG3 at BB′;

[0048] FIG6C is another cross-sectional schematic diagram of the middle frame shown in FIG3 at BB′;

[0049] FIG7A is another cross-sectional schematic diagram of the middle frame shown in FIG3 at BB′;

[0050] FIG7B is another cross-sectional schematic diagram of the middle frame shown in FIG3 at BB′;

[0051] FIG8 is another cross-sectional schematic diagram of the middle frame shown in FIG3 at BB';

[0052] FIG9A is another cross-sectional schematic diagram of the middle frame shown in FIG3 at BB′;

[0053] FIG9B is another cross-sectional schematic diagram of the middle frame shown in FIG3 at BB′;

[0054] FIG10 is a physical diagram of the connection between a connector and an extension portion provided in an embodiment of the present application;

[0055] FIG11 is an element detection diagram of the connection between the connector and the extension portion provided in an embodiment of the present application;

[0056] FIG12 is a physical diagram of the connection between another connecting member and the extension portion provided in an embodiment of the present application;

[0057] FIG13 is another cross-sectional schematic diagram of the middle frame shown in FIG3 at BB';

[0058] FIG14 is another cross-sectional schematic diagram of the middle frame shown in FIG3 at BB';

[0059] FIG15 is a flow chart of a method for preparing a middle frame provided in an embodiment of the present application;

[0060] FIG16 is a flow chart of another method for preparing a middle frame provided in an embodiment of the present application;

[0061] FIG17 is a state diagram corresponding to step S410 in the flowchart shown in FIG16 ;

[0062] FIG18 is another state diagram corresponding to step S410 in the flowchart shown in FIG16 ;

[0063] FIG19 is a flow chart of another method for preparing a middle frame provided in an embodiment of the present application;

[0064] FIG20 is a flow chart of another method for preparing a middle frame provided in an embodiment of the present application. DETAILED DESCRIPTION

[0065] The following describes the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings. In the description of the present application, unless otherwise specified, " / " indicates that the objects associated with each other are in an "or" relationship. For example, A / B can represent A or B.

[0066] The "and / or" in this application is only a way to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0067] In the description of this application, unless otherwise specified, "plurality" means two or more than two. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: a, b, c, a and b, a and c, b and c, or a, b, and c, where a, b, and c can be single or plural.

[0068] To facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first" and "second" are used to distinguish between identical or similar items with substantially the same functions and effects. Those skilled in the art will understand that the words "first" and "second" do not limit the quantity or execution order, and the words "first" and "second" do not necessarily mean different.

[0069] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner to facilitate understanding.

[0070] The embodiment of the present application provides an electronic device, which is, for example, a consumer electronic product, a home electronic product, a vehicle-mounted electronic product, a financial terminal product, and a communication electronic product. Among them, consumer electronic products include mobile phones, tablet computers, laptop computers, e-readers, personal computers (PCs), personal digital assistants (PDAs), desktop displays, smart wearable products (for example, smart watches, smart bracelets), virtual reality (VR) electronic devices, augmented reality (AR) electronic devices, drones, etc. Home electronic products include smart door locks, televisions, remote controls, refrigerators, rechargeable small household appliances (for example, soybean milk machines, sweeping robots), etc. Vehicle-mounted electronic products include car navigation systems, car high-density digital video discs (DVDs), etc. Financial terminal products include automated teller machines (ATMs), self-service terminals, etc. The embodiment of the present application does not impose any special restrictions on the specific form of the electronic device.

[0071] For ease of explanation, the following description uses a tablet computer as an example. As shown in FIG1 , the electronic device 100 primarily includes a display screen 10, a middle frame 20, and a rear housing 30. The middle frame 20 is positioned between the display screen 10 and the rear housing 30. The display surface of the display screen 10 faces away from the middle frame 20.

[0072] Exemplarily, the display screen 10 may be a liquid crystal display (LCD). In this case, the LCD screen includes a liquid crystal display panel and a backlight module. The liquid crystal display panel is arranged on a side of the backlight module away from the middle frame. The backlight module is used to provide a light source for the liquid crystal display panel.

[0073] Alternatively, the display screen 10 may be an organic light emitting diode (OLED) display screen. Since OLED displays are self-luminous, a backlight module is not required. In this case, the display screen 10 may also be a flexible screen with bendability, i.e., a foldable screen, or a rigid display screen.

[0074] The electronic device 100 may further include electronic components such as printed circuit boards (PCBs), a battery, and a camera. These components may be disposed on the middle frame 20. For example, the printed circuit board (mainboard), battery, and camera may be located on a side of the middle frame 20 facing away from the display screen 10.

[0075] As a key component of electronic device 100, the printed circuit board (PCB) can be mounted with various components that make up the electronic device's circuit system, such as circuits, processors, chips, capacitors, resistors, inductors, as well as structures and plug-ins. Optionally, the PCB can be equipped with an integrated circuit chip, a power management unit chip, or a radio frequency chip. Furthermore, the PCB is typically equipped with various processors, including, but not limited to, a central processing unit (CPU), various application processors, a graphics processor, or an image signal processor.

[0076] The battery serves as an energy storage tool for the electronic device 100 and may be a lithium battery, a nickel-metal hydride battery, or a sodium-ion battery.

[0077] The camera may include components such as a front camera, a rear camera, and a flash.

[0078] The back cover 30 can protect the electronic components in the electronic device 100 and prevent moisture and / or dust from affecting the normal operation of the electronic components. At the same time, the back cover 30 can also ensure the neat appearance of the electronic device. In the embodiment of the present application, there is no limitation on the material of the back cover 30. For example, the material of the back cover 30 can be a conductive material such as metal. For another example, the material of the back cover 30 can be a non-conductive material such as glass or plastic. When the material of the back cover 30 is a conductive material, the back cover 30 can serve as a reference ground for the electronic components or radio frequency devices in the electronic device 300.

[0079] In some examples, the electronic device 100 may further include a cover plate, which is disposed on a side of the display screen 10 away from the middle frame 20 to protect the display screen 10 .

[0080] When the electronic device 100 is a mobile phone, the electronic device 100 may be a foldable mobile phone or a straight-screen mobile phone, which is not limited in this application.

[0081] 2 to 14 , the middle frame 20 provided in the embodiment of the present application will be described in detail.

[0082] Figure 2 is an exploded view of the middle frame 20 provided in an embodiment of the present application. Figure 3 is a top schematic diagram of the middle frame 20 provided in an embodiment of the present application. Figure 4 is an enlarged structural diagram of the middle frame 20 at AA shown in Figure 3. Figure 5 is a cross-sectional schematic diagram of the middle frame 20 at BB' shown in Figure 3. Figure 6A is another cross-sectional schematic diagram of the middle frame 20 at BB' shown in Figure 3. Referring to Figures 2 to 6A, an embodiment of the present application provides a middle frame 20. As shown in Figure 2, the middle frame 20 includes a middle plate 1, an outer frame 2 and a connector 3.

[0083] The middle plate 1 includes a mounting hole 11 . Exemplarily, the middle plate 1 may include a plurality of mounting holes 11 , and the plurality of mounting holes 11 are distributed on the edge of the middle plate 1 .

[0084] When the middle plate 1 includes multiple mounting holes 11, the sizes of the multiple mounting holes 11 can be the same or different. The phrase "different sizes of the multiple mounting holes 11" here means that at least one mounting hole 11 among the multiple mounting holes 11 has different sizes from the remaining mounting holes 11. In the embodiments of the present application, the specific number and size of the mounting holes 11 in the middle plate 1 are not limited and can be designed based on actual needs.

[0085] The distribution of mounting holes 11 in the embodiments of the present application is also not limited. The specific distribution of mounting holes 11 can be designed based on the structure of the middle plate 1 and the structure of the outer frame 2 to ensure a stable connection between the middle plate 1 and the outer frame 2. For example, as shown in FIG4 , the distribution density of mounting holes 11 can be greater at the corners of the middle plate 1, and the distribution density of mounting holes 11 can be less on the sides of the middle plate 1.

[0086] The material of the middle plate 1 may include one of magnesium alloy, magnesium-based composite material and aluminum alloy. For example, the magnesium alloy may be AZ91D, AM60, AZ31, AZ80, AZ91D or ZK61.

[0087] As shown in FIG3 , the outer frame 2 is located outside the middle plate 1. Referring to FIG2 and FIG3 , the outer frame 2 can serve as a side of the electronic device 100.

[0088] Referring to Figure 5 , the outer frame 2 includes a main portion 21 and an extension portion 22, which are connected. The extension portion 22 is located on the side of the main portion 21 facing the middle plate 1, and the thickness d1 of the extension portion 22 is less than the thickness d2 of the main portion 21. The extension portion 22 is stacked with the middle plate 1. In this embodiment of the present application, the specific values ​​of the thickness d1 of the extension portion 22 and the thickness d2 of the main portion 21 are not limited and can be designed according to actual needs.

[0089] In some examples, as shown in Figure 5 , the sum of the thickness d3 of the portion of the middle plate 1 in contact with the extension 22 and the thickness d1 of the extension is less than the thickness d2 of the main body 21 of the outer frame 2. This allows the sum of the thickness d3 of the portion of the middle plate 1 in contact with the extension 22 and the thickness d1 of the extension to be smaller, thereby facilitating a reduction in the thickness of the middle frame 20. Furthermore, the sum of the thickness d3 of the portion of the middle plate 1 in contact with the extension 22 and the thickness d1 of the extension can be smaller, allowing for the placement of electronic components where the middle plate 1 and the extension 22 overlap, thereby improving space utilization at the location where the middle plate 1 and the extension 22 overlap.

[0090] In some examples, as shown in FIG5 , the main body 21 and the extension 22 may be integrally formed. In this case, the main body 21 and the extension 22 are not easily separated, and the connection between the main body 21 and the extension 22 is more stable, thereby improving the structural stability of the outer frame 2 and, in turn, the structural stability of the middle frame 20.

[0091] In other examples, as shown in FIG6A , the main body 21 and the extension 22 can be connected by welding. In this way, the main body 21 and the extension 22 provided in the embodiment of the present application can be manufactured separately, and the raw materials used in the manufacturing process of the main body 21 and the extension 22 can be smaller in size, thereby reducing the manufacturing cost of the outer frame 2 and, in turn, the manufacturing cost of the middle frame 20.

[0092] At this time, as shown in FIG. 6A , a molten pool U may be present in a portion of the main body portion 21 that contacts the extension portion 22 , and in a portion of the extension portion 22 that contacts the main body portion 21 .

[0093] For example, the main body 21 and the extension portion 22 may be welded by spot welding or seam welding.

[0094] In some examples, as shown in FIG2 , the outer frame 2 may include multiple frame bars 201 . For example, the outer frame 2 may include two frame bars 201 , and the two frame bars 201 may be located on opposite sides of the middle plate 1 . Alternatively, the outer frame 2 may include three frame bars, which are connected end to end to form a roughly U-shaped structure. In this case, the middle frame 20 can be used in a foldable electronic device. Alternatively, the outer frame 2 may include four frame bars 201 , which are connected end to end in sequence to form a closed structure. In this case, the outer frame 2 can be arranged around the middle plate 1 . Each frame bar 201 may include the above-mentioned main body 21 and extension 22 .

[0095] The material of the outer frame 2 may include one of an aluminum alloy, a titanium-based material, an iron-based material, a titanium-aluminum composite material, and a steel-aluminum composite material. For example, the aluminum alloy may include a fifth-series aluminum alloy, a sixth-series aluminum alloy, or a seventh-series aluminum alloy. The titanium-based material may include, for example, titanium and a titanium alloy. The iron-based material may include, for example, stainless steel.

[0096] In some examples, the stainless steel is defined in GB / T20878-2007, having a chromium content of at least 10.5% and a carbon content of no more than 1.2%. In embodiments where the outer frame 2 is made of stainless steel, the type of stainless steel is not limited, and the type of stainless steel may be, for example, SUS316L. Stainless steel has the advantages of a high elastic modulus and high strength. The outer frame 2 made of stainless steel can provide excellent support for the structure of the electronic device 100 (e.g., a display screen, a cover plate), thereby providing a foundation for a thin and strong outer frame 2.

[0097] In the embodiment where the outer frame 2 is made of titanium alloy, there is no limitation on the type of titanium alloy, for example, the type of titanium alloy may be TC4. Similarly, titanium alloy also has the advantages of high elastic modulus and high strength, and the outer frame 2 made of titanium alloy can be both light and strong.

[0098] Connector 3 is positioned within mounting hole 11 and connected to midplate 1. Connector 3 is welded to extension 22. The microhardness of connector 3 is greater than that of midplate 1. Exemplarily, connector 3 can be made of one of aluminum-based, titanium-based, iron-based, copper-based, nickel-based, and zirconium-based materials. It should be understood that connectors 3 positioned within mounting holes 11 should be present in the same number as mounting holes 11.

[0099] In the embodiment of the present application, the connector 3 is placed in the mounting hole 11 of the middle plate 1, so that the connector 3 is connected to the middle plate 1, and the connector 3 is welded to the outer frame 2, so that the middle plate 1 and the outer frame 2 are fixed to each other to form the middle frame 20. When the material of the middle plate 1 includes magnesium alloy and / or magnesium-based composite material, since the density of magnesium alloy and magnesium-based composite material is relatively low, the weight of the middle plate 1 can be reduced, and the weight of the middle frame 20 can be reduced, which is conducive to reducing the weight of the electronic device 100 using the middle frame 20. When the material of the middle plate 1 includes aluminum alloy, the middle plate 1 can be prepared by a die-casting process. In this way, compared with the method of preparing the middle plate by using computer numerical control machine tools (CNC), the preparation cost of the middle plate 1 can be lower, and the production efficiency of the middle plate 1 can be higher, which is conducive to realizing mechanical automation production.

[0100] In the embodiment of the present application, the material of the outer frame 2 includes one of aluminum alloy, titanium-based material, iron-based material, titanium-aluminum composite material and steel-aluminum composite material, so that the appearance area of ​​the middle frame 20 can have a metallic texture, which is beneficial to improving the competitiveness of the electronic device 100 using the middle frame 20.

[0101] In the embodiment of the present application, a connector 3 is used to connect the middle plate 1 and the outer frame 2. The microhardness of the connector 3 is greater than that of the middle plate 1, which effectively improves the problem of welding defects at the welding position between the middle plate and the outer frame when the middle plate and the outer frame are directly welded together due to the low melting point and easy evaporation of magnesium alloy or magnesium-based composite materials, high activity and easy oxidation, or the presence of a large number of pores in the die-cast aluminum material. This ensures that the connection reliability between the middle plate 1 and the outer frame 2 can be higher, which is beneficial to improving the stability of the middle frame 20 and improving the impact resistance of the middle frame 20.

[0102] The middle frame 20 is a good radiator and can therefore be used as an antenna. In the middle frame 20 provided in the embodiment of the present application, the middle plate 1 is connected to the connector 3, and the outer frame 2 is welded to the connector 3. This makes it less likely for welding defects to occur at the connection between the middle plate 1 and the outer frame 2, thereby ensuring the consistency of the impedance value at the connection between the middle plate 1 and the outer frame 2, and thus ensuring the consistency of the RF performance of the frame antenna in the electronic device 100.

[0103] The embodiment of the present application tests the impedance value at the position where the connector 3 is located in the middle frame 20. The test equipment is a resistance tester, and the test results are shown in Table 1. It can be seen from Table 1 that at the position where the connector 3 is located, the impedance measured at each test point is small, and the difference between the impedances measured at different test points is also small. Good metal conduction can be achieved between the middle plate 1 and the outer frame 2 of the middle frame 20. In this way, when the middle frame 20 is used as an antenna, it can not only work in low frequency bands such as 2.4GHz, but also in high frequency bands such as 5GHz. In particular, when the middle frame 20 is used as an antenna such as a 4GHz band antenna, a 5GHz band antenna, a WIFI antenna, etc. with a frequency greater than 2GHz, the resistance at the position where the connector 3 is located in the embodiment of the present application is small, and the loss of the RF operation is also low. The impedance fluctuation range at the position where the connector 3 is located is small (that is, the impedance difference at different points is small), and the frequency deviation of the RF operation can also be reduced.

[0104] Table 1

[0105] At the same time, in the middle frame 20 provided in the embodiment of the present application, the outer frame 2 and the connector 3 are connected by welding. Compared with the case where the middle plate and outer frame are directly connected with rivets, the stress at the connection between the connector 3 and the outer frame 2 can be reduced, and the stress at the connection between the middle plate 1 and the outer frame 2 can be reduced, thereby making the middle frame 20 less susceptible to distortion and effectively improving the flatness of the middle frame 20. Compared with the case where the middle plate and outer frame are connected using a rivetless riveting method, the thickness of the connection between the middle plate 1 and the outer frame 2 provided in the embodiment of the present application can be reduced, thereby facilitating a reduction in the thickness of the middle frame 20, and thus reducing the thickness of the electronic device 100 using the middle frame 20, thereby achieving an ultra-thin electronic device 100.

[0106] In some embodiments, referring to Figures 2 to 4 , the outer frame 2 may further include an antenna slot 23, and the middle frame 20 may further include a filling portion 4 located within the antenna slot 23. The filling portion 4 is made of an insulating material. The antenna slot 23 divides the outer frame 2 into multiple sections, and the filling portion 4 located within the antenna slot 23 insulates adjacent sections from each other. These multiple sections can each function as a separate antenna.

[0107] The "different antennas" mentioned here may be, for example, a main antenna, a WIFI antenna, a Bluetooth antenna, etc. The embodiment of the present application does not impose any specific restrictions on the types of antennas.

[0108] For example, the filling portion 4 may be made of a thermosetting or thermoplastic material, such as plastic, resin, and the like.

[0109] When multiple parts of the outer frame 2 are used as antennas, the outer frame 2 includes multiple feed points, which are electrically connected to the middle plate 1 at the feed points. The outer frame 2 is insulated from the middle plate 1 at all other locations except the feed points. In the present embodiment, there is no restriction on the number or location of the feed points in the outer frame 2, as long as the antenna can be electrically connected to the middle plate 1.

[0110] Figures 5, 6A, and 6B illustrate three possible cross-sectional views of the connection between the feed point and the midplane 1 in the outer frame 2. As shown in Figure 5, the filler portion 4 may not extend between the feed point and the midplane 1. Alternatively, as shown in Figures 6A and 6B, the filler portion 4 may extend between the extension portion 22 and the midplane 1 in a direction X parallel to the midplane 1. However, the filler portion 4 does not affect signal transmission between the feed point and the midplane 1.

[0111] At locations other than the feed point on the outer frame 2, as shown in Figure 6C , the filler portion 4 can extend into the extension portion 22 of the outer frame 2. The sum of the thickness d3 of the portion of the midplane 1 in contact with the extension portion 22 and the thickness d1 of the extension portion 22 is less than or equal to the thickness d4 of the filler portion 4. The filler portion 4 serves to separate the portion of the extension portion 22 connected to the main body 21 from the portion of the extension portion 22 connected to the midplane 1, thereby insulating the outer frame 2 from the midplane 1.

[0112] In some embodiments, as shown in Figure 6C , the mounting hole 11 may be a through hole. In other embodiments, as shown in Figures 7A and 7B , the mounting hole 11 may be a blind hole.

[0113] When the middle plate 1 includes multiple mounting holes 11, the multiple mounting holes 11 may all be through holes, or the multiple mounting holes 11 may all be blind holes, or some of the multiple mounting holes 11 may be through holes and others may be blind holes.

[0114] When the mounting hole 11 is a blind hole, as shown in FIG7A , the mounting hole 11 can be located on the side of the middle plate 1 away from the extension 22 . Alternatively, as shown in FIG7B , the mounting hole 11 can also be located on the side of the middle plate 1 close to the extension 22 .

[0115] In some embodiments, the material of the connector 3 can be the same as that of the outer frame 2. In this way, the melting point of the connector 3 and the outer frame 2 can be the same. When welding the connector 3 and the outer frame 2, the yield of the welding point between the connector and the outer frame 2 is not easily affected due to the large difference in the melting point of the connector 3 and the outer frame 2. This is conducive to further improving the connection strength and stability of the connector 3 and the outer frame 2.

[0116] In some examples, the shear strength of the weld between the extension 22 and the connector 3 is greater than or equal to 100 N, and the pull-out strength of the weld between the extension 22 and the connector 3 is greater than or equal to 90 N. This improves the connection stability between the extension 22 and the connector 3, and the connection stability between the outer frame 2, the middle plate 1, and the connector 3. The stability of the middle frame 20 can be higher, and the impact resistance of the middle frame 20 can also be better, thereby facilitating the improvement of the service life of the electronic device 100.

[0117] Referring to Figures 2, 5 and 7A, in some embodiments, the connecting member 3 may include a first connecting portion 31 and a second connecting portion 32 that are perpendicular to each other, the first connecting portion 31 is located in the mounting hole 11 and is welded to the extension portion 22, and part of the middle plate 1 is located between the second connecting portion 32 and the extension portion 22.

[0118] In this way, on the one hand, the middle plate 1 is confined between the second connection portion 32 of the connector 3 and the extension portion 22 of the outer frame 2. Relative displacement between the middle plate 1 and the connector 3 is unlikely in the thickness direction Z of the middle plate 1, as well as in the direction X parallel to the middle plate 1, making separation difficult. On the other hand, both the first connection portion 31 and the second connection portion 32 of the connector 3 are in contact with the middle plate 1, thereby increasing the contact area between the middle plate 1 and the connector 3. This improves the connection stability between the middle plate 1, the outer frame 2, and the connector 3, thereby further improving the yield of the middle frame 20 and enhancing the operational stability of the middle frame 20.

[0119] It is understood that, as shown in FIG7A , when mounting hole 11 is a blind hole and is located on the side of middle plate 1 away from extension portion 22, connector 3 is welded not only to outer frame 2 but also to middle plate 1. However, compared to a solution in which middle plate 1 and outer frame 2 are directly welded, the thickness of middle plate 1 between first connection portion 31 and outer frame 2 is smaller, and less material is contained in middle plate 1 at the weld between first connection portion 31 and outer frame 2. Consequently, the material of middle plate 1 has less impact on the performance of the weld formed between first connection portion 31 and extension portion 22. This can also alleviate the problem of welding defects at the weld between middle plate and outer frame caused by direct welding of the middle plate and outer frame, which can occur due to the low melting point and evaporation of magnesium alloy or magnesium-based composite materials, their high reactivity and oxidation, or due to the large number of pores in die-cast aluminum materials. This improves the connection reliability between middle plate 1 and outer frame 2, thereby improving the stability and impact resistance of middle frame 20 and ensuring the consistency of RF performance of the frame antenna in electronic device 100.

[0120] In some examples, as shown in Figure 5, the first connecting portion 31 is located inside the mounting hole 11, and the second connecting portion 32 can be located outside the mounting hole 11. At this time, the end surface 321 of the second connecting portion 32 connected to the first connecting portion 31 can contact the surface S1 of the middle plate 1 away from the extension portion 22.

[0121] Figure 8 is another schematic cross-sectional view of the middle frame 20 shown in Figure 3 at the BB' line. Referring to Figure 8 , in other examples, the mounting hole 11 is a stepped hole, with both the first connecting portion 31 and the second connecting portion 32 located within the stepped hole. In this case, the end surface 322 of the second connecting portion 32, distal from the first connecting portion 31, is flush with the surface S1 of the middle plate 1, distal from the extension portion 22. This improves the flatness of the middle frame 20, allowing it to better support electronic components or displays, thereby improving the yield of the electronic device 100 employing the middle frame 20.

[0122] In some examples, the connector 3 may be a flat-head rivet. The rivet head of the flat-head rivet corresponds to the second connecting portion 32, and the rivet shank of the flat-head rivet corresponds to the first connecting portion 31. When the connector 3 is a flat-head rivet, the end surface of the second connecting portion 32 facing away from the first connecting portion 31 is flat, which helps improve the surface flatness of the middle plate 1 to which the connector 3 is mounted.

[0123] 7B , in other embodiments, the connector 3 is a column, and the connector 3 is interference-fitted with the mounting hole 11 . Thus, the connector 3 has a simple structure and is easily available, which helps simplify the structure of the middle frame 20 .

[0124] It is understandable that in order to improve the flatness of the middle frame 20 , when the connecting member 3 is a column, the surface of the connecting member 3 can be flush with the surface of the middle plate 1 close to the extension portion 22 or the surface of the middle plate 1 away from the extension portion 22 .

[0125] In some embodiments, as shown in Figures 9A and 9B, the extension portion 22 includes a first portion 221 and a second portion 222. The second portion 222 is disposed around the first portion 221. A molten pool R is formed between the first portion 221 and the connector 3. In the embodiments of the present application, the depth and width of the molten pool R are not limited and can be designed according to actual needs.

[0126] Figure 10 is a physical image of the middle frame 20 provided in an embodiment of the present application at the weld between the extension portion 22 and the connector 3. The extension portion 22 is made of aluminum alloy, and the connector 3 is made of titanium. As shown in Figure 10 , because the diffusion capacity of the connector 3 material (titanium) is greater than that of the extension portion 22 material (aluminum alloy), the material of the connector 3 extends from the interface where the connector 3 and the extension portion 22 contact each other into the extension portion 22.

[0127] Figure 11 shows the elemental analysis results of the weld between the extension portion 22 and the connector 3 of the middle frame 20 provided in an embodiment of the present application. As shown in Figure 11, within the molten pool R, the element (Al) of the outer frame 2 can pass through the interface between the extension portion 22 and the connector 3 and diffuse into the connector 3. The element (Ti) of the connector 3 can pass through the interface between the extension portion 22 and the connector 3 and diffuse into the extension portion 22.

[0128] Figure 12 shows another physical representation of the extension portion 22 welded to the outer frame 2 and the connector 3, according to an embodiment of the present application. The material of the extension portion 22 and the connector 3 are identical: titanium. As shown in Figure 12 , the materials of the extension portion 22 and the connector 3 remelt within the molten pool R after welding, forming distinct crystalline bonds between the atoms.

[0129] In some examples, as shown in FIG. 9A , the molten pool R may extend from the first portion 221 away from the surface S2 of the midplate 1 toward the connector 3 .

[0130] In other examples, as shown in FIG. 9B , the molten pool R may extend from a surface S3 of the connector 3 away from the extension portion 22 into the first portion 221 .

[0131] In some embodiments, referring to Figures 9A, 9B and 13, the main body 21 includes a first surface 211 and a second surface 212 relative to each other, and a first side surface 213 and a second side surface 214 connecting the first surface 211 and the second surface 212. The first surface 211 is farther away from the extension portion 22 than the second surface 212, and the second surface 212 is connected to the extension portion 22.

[0132] For example, as shown in Figures 9A, 9B, and 13, the first surface 211 can be a curved surface. In this way, different positions of the first surface 211 can have the same mechanical strength. Compared with the solution where the first surface 211 is flat, the first surface 211 being a curved surface can also reduce the material used in the outer frame 2, thereby helping to reduce the weight of the outer frame 2. At the same time, the first surface 211 being a curved surface can also make the surface of the outer frame 2 smooth, thereby preventing the outer frame from scratching other structures of the electronic device or the user, which is conducive to improving the user experience of the electronic device 100 using the middle frame 20.

[0133] In some embodiments, as shown in FIG. 9A , FIG. 9B and FIG. 13 , the middle frame 20 further includes a decoration layer 5 , and the decoration layer 5 at least covers the first surface 211 .

[0134] When the outer frame 2 is made of aluminum alloy, the decorative layer 5 can be formed by an anodizing process, in which case the material of the decorative layer 5 may include aluminum oxide. When the outer frame 2 is made of one of a titanium-based material, an iron-based material, a titanium-aluminum composite material, and a steel-aluminum composite material, the decorative layer 5 can be formed by a physical vapor deposition process, in which case the material of the decorative layer 5 may include, for example, titanium nitride or other nitrogen- or carbon-containing film layers. In the embodiments of the present application, the thickness of the decorative layer 5 is not limited, as long as it can protect the outer frame 2.

[0135] The embodiment of the present application provides a decorative layer 5, which can, on the one hand, color the surface of the outer frame 2, improve the appearance of the outer frame 2, and increase users' preference for the electronic device 100; on the other hand, the decorative layer 5 can also be used to protect the outer frame 2 to prevent the outer frame 2 from being corroded by water vapor and oxygen in the environment.

[0136] In some examples, as shown in FIG9A , the molten pool R extends from the surface S2 of the first portion 221 away from the mid-plate 1 toward the connector 3. In this case, in addition to the first surface 211, the decorative layer 5 may also cover the surface of the second portion 222 away from the mid-plate 1, the first side surface 213, the second side surface 214, and the portion of the second surface 212 not in contact with the extension 22. In other words, the decorative layer 5 covers the surface of the main body 21 and the surface of the second portion 222 of the extension 22 away from the mid-plate 1.

[0137] In the middle frame 20 provided in the embodiment of the present application, in addition to the first surface 211, the decorative layer 5 also covers the surface of the second portion 222 away from the middle plate 1, the first side surface 213, the second side surface 214, and the portion of the second surface 212 not in contact with the extension 22. On the one hand, the decorative layer 5 can protect the second portion 222 of the extension 22 and the main body 21, making them less susceptible to corrosion from moisture and oxygen in the external environment. On the other hand, the decorative layer 5 can enhance the appearance of the second portion 222 and the main body 21, allowing them to have rich colors. This improves the appearance of the middle frame 20 provided in the embodiment of the present application and enhances the appearance of the electronic device 100 using the middle frame 20.

[0138] When the molten pool R extends from the surface S2 of the first portion 221 away from the middle plate 1 to the connector 3, the decorative layer 5 exposes the surface of the first portion 221 away from the connector 3 and the surface of the first portion 221 close to the connector 3, which helps to avoid affecting the welding yield due to the high melting point of the decorative layer 5.

[0139] In other examples, as shown in FIG9B , the molten pool R extends from the surface of the connector 3 away from the extension 22 into the first portion 221. In this case, in addition to the first surface 211, the decorative layer 5 also covers the surface of the first portion 221 away from the middle plate 1, the surface of the second portion 222 away from the middle plate 1, the first side surface 213, the second side surface 214, and the portion of the second surface 212 not in contact with the extension 22. In other words, the decorative layer 5 covers the remaining surfaces of the outer frame 2 except the surface of the first portion 221 close to the connector 3 and the surface of the second portion 222 close to the middle plate 1.

[0140] In the embodiment of the present application, in addition to the first surface 211, the decorative layer 5 also covers the surface of the first portion 221 away from the middle plate 1, the surface of the second portion 222 away from the middle plate 1, the first side surface 213, the second side surface 214, and the portion of the second surface 212 not in contact with the extension 22. On the one hand, the decorative layer 5 can protect the extension 22 and the main body 21, making them less susceptible to corrosion by moisture and oxygen in the external environment. On the other hand, the decorative layer 5 can enhance the appearance of the main body 21 and the extension 22, allowing the main body 21 and the extension 22 to have rich colors. This improves the appearance of the middle frame 20 provided by the embodiment of the present application and enhances the appearance of the electronic device 100 using the middle frame 20.

[0141] When the molten pool R extends from the surface of the connector 3 away from the extension portion 22 to the first portion 221 , the decorative layer 5 exposes the surface of the first portion 221 close to the connector 3 , which helps to avoid affecting the welding yield due to the high melting point of the decorative layer 5 .

[0142] In yet other examples, as shown in Figures 13 and 14 , the decorative layer 5 may cover only the first surface 211. This reduces the chances of the decorative layer 5 adversely affecting the weld between the connector 3 and the extension 22 during welding. Furthermore, this arrangement reduces the coverage area of ​​the decorative layer 5, thereby improving the appearance of the main body 21 and the midframe 20 while reducing the manufacturing cost of the midframe 20.

[0143] In some examples, as shown in Figure 14, the material of the outer frame 2 includes a titanium-aluminum composite material, the main body 21 includes a first sublayer 21a and a second sublayer 21b, the first sublayer 21a is farther away from the extension portion 22 than the second sublayer 21b, the second sublayer 21b is connected to the extension portion 21, the material of the first sublayer 21a includes titanium, and the material of the second sublayer 21b and the material of the extension portion 22 both include aluminum alloy.

[0144] In the outer frame 2 provided in the embodiment of the present application, the material of the first sublayer 21a of the main body 21 is set to titanium metal, the material of the second sublayer 21b is set to aluminum alloy, and the material of the extension portion 22 is set to aluminum alloy. The density of aluminum alloy is lower than that of titanium metal, so that the middle frame 20 can have a metallic texture and appearance while having a smaller weight, which is beneficial to reducing the preparation cost of the middle frame 20.

[0145] In other examples, referring to FIG14 , the material of the outer frame 2 includes a steel-aluminum composite material, the main body 21 includes a third sublayer 21c and a fourth sublayer 21d, the third sublayer 21c is farther away from the extension portion 22 than the fourth sublayer 21d, the fourth sublayer 21d is connected to the extension portion 22, the material of the third sublayer 21c includes stainless steel, and the material of the fourth sublayer 21d and the material of the extension portion 22 both include aluminum alloy.

[0146] In the outer frame 2 provided in the embodiment of the present application, the material of the first sublayer 21a of the main body 21 is set to stainless steel, the material of the second sublayer 21b is set to aluminum alloy, and the material of the extension 22 is set to aluminum alloy. The density of aluminum alloy is lower than that of stainless steel. As a result, the middle frame 20 can have a metallic texture and appearance while having a smaller weight, which helps to reduce the production cost of the middle frame 20.

[0147] As shown in FIG15 , an embodiment of the present application provides a method for preparing a middle frame, which includes steps S100 to S400 .

[0148] S100 , referring to FIG2 and FIG5 , provide a middle plate 1 , an outer frame 2 and a connector 3 . The outer frame 2 includes a main body 21 and an extension 22 connected to each other. The thickness of the extension 22 is smaller than that of the main body 21 .

[0149] For example, the middle plate 1 can be produced by die-casting or semi-solid die-casting, and the material of the middle plate can include, but is not limited to, die-cast magnesium alloys such as AZ91D and AM6. Alternatively, the middle plate 1 can be produced by stamping or cutting, and the material of the middle plate 1 can include, but is not limited to, AZ31, AZ80, AZ91D, ZK61, or magnesium-based composite materials.

[0150] In some examples, the material of the outer frame 2 includes aluminum alloy. In this case, the outer frame 2 can be obtained by a stamping process or CNC processing.

[0151] In other examples, the material of the outer frame 2 includes titanium-based materials, iron-based materials, titanium-aluminum composite materials, and steel-aluminum composite materials. In this case, if the raw material of the outer frame is in the form of a strip, the raw material can be bent and forged to obtain the outer frame 2. If the raw material of the outer frame is in the form of a plate, the outer frame 2 can be obtained by stamping and cutting.

[0152] S200 , installing the connecting member 3 on the middle plate 1 . The connecting member 3 is located in the mounting hole 11 of the middle plate 1 .

[0153] In some examples, the mounting holes 11 may be formed during the preparation of the mid-plate 1. In other examples, the mounting holes 11 may be formed during the installation of the connector 3 on the mid-plate 1. This application does not impose any limitation on this.

[0154] In some examples, after the connector 3 is mounted on the midplane 1 , the midplane 1 and the connector 3 may be subjected to a film passivation treatment, thereby forming an oxide layer on the midplane 1 and the connector 3 to protect the midplane 1 and the connector 3 .

[0155] S300: Secure the middle plate 1 and outer frame 2. The outer frame 2 is located outside the middle plate 1, and the extension 22 is located on the side of the main body 21 facing the middle plate 1. The extension 22 is stacked with the middle plate 1. For example, a clamp can be used to secure the middle plate 1 and outer frame 2.

[0156] S400 , welding the extension portion 22 to the connecting member 3 .

[0157] The material of the middle plate 1 includes one of a magnesium alloy, a magnesium-based composite material, and an aluminum alloy, and the material of the outer frame 2 includes one of an aluminum alloy, a titanium-based material, an iron-based material, a titanium-aluminum composite material, and a steel-aluminum composite material. The microhardness of the connector 3 is greater than that of the middle plate 1.

[0158] The beneficial effects that can be achieved by the preparation method provided in the embodiment of the present application are the same as the technical effects that can be achieved by the middle frame 20 provided in the above embodiment of the present application, and will not be repeated herein.

[0159] In some embodiments, as shown in FIG. 16 , step S400 may include step S410 .

[0160] S410 , as shown in FIG. 17 and FIG. 18 , the extension portion 22 and the connector 3 are welded using a laser welding process.

[0161] At this time, in some examples, as shown in Figure 17, the laser can be irradiated toward the connector 3 from the side of the extension 22 away from the connector 3. In other examples, as shown in Figure 18, the laser can be irradiated toward the extension 22 from the side of the connector 3 away from the extension 22.

[0162] In the embodiments of the present application, there is no restriction on parameters such as laser welding time and laser intensity, and they can be designed according to actual needs.

[0163] In the embodiment of the present application, a laser welding process is used to weld the extension portion 22 to the connector 3. This achieves high welding precision, minimizes deformation of the extension portion 22 and the connector 3, and reduces stress between the extension portion 22 and the connector 3. After welding the extension portion 22 and the connector 3, the middle frame 20 is less likely to deform, which helps improve the flatness of the middle frame 20. Furthermore, laser welding has a high welding speed. Using this laser welding process to weld the extension portion 22 and the connector 3 also helps increase the speed and efficiency of manufacturing the middle frame 20.

[0164] In some embodiments, the material of the outer frame 2 includes aluminum alloy. In this case, as shown in FIG. 19 , the preparation method further includes step S500 .

[0165] S500 , forming a decorative layer 5 by adopting an anodic oxidation process.

[0166] In other embodiments, the material of the outer frame 2 includes one of a titanium-based material, an iron-based material, a titanium-aluminum composite material, and a steel-aluminum composite material. In this case, as shown in FIG. 20 , the preparation method further includes step S600.

[0167] S600 , forming a decoration layer 5 by adopting a physical vapor deposition process.

[0168] Referring to Figure 13 , the main body 21 includes a first surface 211 and a second surface 212 that oppose each other, as well as a first side surface 213 and a second side surface 214 connecting the first and second surfaces 211 and 212. The first surface 211 is further away from the middle plate 1 than the second surface 212, and the second surface 212 is connected to the extension 22. The decorative layer 5 covers at least the first surface 211. As shown in Figures 19 and 20 , the decorative layer 5 can be formed before step S400.

[0169] In some examples, the outer frame 2 may be ground and polished before forming the decorative layer 5. The grinding and polishing processes can reduce the surface roughness of the outer frame 2, preventing the outer frame 2 from being too rough and affecting other structures of the electronic device.

[0170] The embodiment of the present application can color the surface of the outer frame 2 by providing a decorative layer 5, thereby improving the appearance of the outer frame 2 and increasing users' preference for the electronic device 100. On the other hand, the decorative layer 5 can also be used to protect the outer frame 2 and prevent the outer frame 2 from being corroded by water vapor and oxygen in the environment.

[0171] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0172] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A middle frame, characterized in that: include: A middle plate (1) comprising a mounting hole (11); an outer frame (2) located on the outer side of the middle plate (1); the outer frame (2) comprises a main body (21) and an extension (22) connected to each other, the extension (22) being located on a side of the main body (21) facing the middle plate (1), and the thickness of the extension (22) being smaller than the thickness of the main body (21); the extension (22) and the middle plate (1) being stacked; A connecting piece (3) is located in the mounting hole (11) and is connected to the middle plate (1); the connecting piece (3) is welded to the extension portion (22); The material of the middle plate (1) includes one of a magnesium alloy, a magnesium-based composite material and an aluminum alloy; the material of the outer frame (2) includes one of an aluminum alloy, a titanium-based material, an iron-based material, a titanium-aluminum composite material and a steel-aluminum composite material; and the microhardness of the connecting piece (3) is greater than the microhardness of the middle plate (1).

2. The middle frame according to claim 1, characterized in that: The connecting member (3) comprises a first connecting portion (31) and a second connecting portion (32) which are perpendicular to each other, the first connecting portion (31) being located in the mounting hole (11) and welded to the extending portion (22), and a portion of the middle plate (1) being located between the second connecting portion (32) and the extending portion (22).

3. The middle frame according to claim 2, characterized in that: The mounting hole (11) is a stepped hole, and the first connecting portion (31) and the second connecting portion (32) are both located in the stepped hole; the end surface of the second connecting portion (32) away from the first connecting portion (31) is flush with the surface of the middle plate (1) away from the extension portion (22).

4. The middle frame according to claim 1, characterized in that: The connecting piece (3) is a column, and the connecting piece (3) and the mounting hole (11) are interference fit.

5. The middle frame according to any one of claims 1 to 4, characterized in that: The material of the connecting piece (3) is the same as that of the outer frame (2).

6. The middle frame according to any one of claims 1 to 5, characterized in that: The mounting hole (11) comprises a through hole or a blind hole.

7. The middle frame according to any one of claims 1 to 6, characterized in that: The extension portion (22) comprises a first portion (221) and a second portion (222), wherein the second portion (222) is arranged around the first portion (221), and the first portion (221) and the connecting member (3) have a molten pool (R), and the molten pool (R) extends from the surface of the first portion (221) away from the middle plate (1) to the connecting member (3); or, the molten pool (R) extends from the surface of the connecting member (3) away from the extension portion (22) to the first portion (221).

8. The middle frame according to any one of claims 1 to 7, characterized in that: The main body (21) comprises a first surface (211) and a second surface (212) which are opposite to each other, and a first side surface (213) and a second side surface (214) which connect the first surface (211) and the second surface (212), wherein the first surface (211) is farther away from the extension portion (22) than the second surface (212), and the second surface (212) is connected to the extension portion (22); The middle frame (20) further comprises a decorative layer (5), wherein the decorative layer (5) at least covers the first surface (211).

9. The middle frame according to claim 8, characterized in that: The molten pool (R) extends from the surface of the first part (221) away from the middle plate (1) toward the connecting piece (3), and the decorative layer (5) also covers the surface of the second part (222) away from the middle plate (1), the first side surface (213), the second side surface (214), and a portion of the second surface (212) that is not in contact with the extension portion (22).

10. The middle frame according to claim 8, characterized in that: The molten pool (R) extends from the surface of the connecting member (3) away from the extension portion (22) into the first portion (221); the decorative layer (5) also covers the surface of the first portion (221) away from the middle plate (1), the surface of the second portion (222) away from the middle plate (1), the first side surface, the second side surface, and a portion of the second surface (212) that is not in contact with the extension portion (22).

11. The middle frame according to any one of claims 1 to 10, characterized in that: The shear strength of the weld between the extension part (22) and the connection piece (3) is greater than or equal to 100N, and the pull-out strength of the weld between the extension part (22) and the connection piece (3) is greater than or equal to 90N.

12. The middle frame according to any one of claims 1 to 11, characterized in that: The material of the outer frame (2) comprises a titanium-aluminum composite material, the main body (21) comprises a first sublayer (21a) and a second sublayer (21b), the first sublayer (21a) is farther away from the extension part (22) than the second sublayer (21b), the second sublayer (21b) is connected to the extension part (22), the material of the first sublayer (21a) comprises titanium, and the material of the second sublayer (21b) and the material of the extension part (22) both comprise an aluminum alloy; or, The material of the outer frame (2) comprises a steel-aluminum composite material, the main body (21) comprises a third sublayer (21c) and a fourth sublayer (21d), the third sublayer (21c) is farther away from the extension part (22) than the fourth sublayer (21d), the fourth sublayer (21d) is connected to the extension part (22), the material of the third sublayer (21c) comprises stainless steel, and the material of the fourth sublayer (21d) and the material of the extension part (22) both comprise aluminum alloy.

13. A method for preparing a middle frame, characterized in that: include: A middle plate (1), an outer frame (2) and a connecting piece (3) are provided; the outer frame (2) comprises a main body (21) and an extension (22) which are connected to each other, and the thickness of the extension (22) is smaller than the thickness of the main body (21); The connecting piece (3) is mounted on the middle plate (1); the connecting piece (3) is located in the mounting hole (11) of the middle plate (1); The middle plate (1) and the outer frame (2) are fixed; the outer frame (2) is located on the outer side of the middle plate (1), the extension portion (22) is located on the side of the main body (21) facing the middle plate (1), and the extension portion (22) and the middle plate (1) are stacked; Welding the extension portion (22) to the connecting member (3); The material of the middle plate (1) includes one of a magnesium alloy, a magnesium-based composite material and an aluminum alloy, and the material of the outer frame (2) includes one of an aluminum alloy, a titanium-based material, an iron-based material, a titanium-aluminum composite material and a steel-aluminum composite material; the microhardness of the connecting piece (3) is greater than the microhardness of the middle plate (1).

14. The preparation method according to claim 13, characterized in that: The welding of the extension portion (22) and the connection piece (3) comprises: welding the extension portion (22) and the connection piece (3) using a laser welding process.

15. The preparation method according to claim 13 or 14, characterized in that: The material of the outer frame (2) includes aluminum alloy, and the preparation method further includes: forming the decorative layer (5) by anodizing; or, The material of the outer frame (2) comprises one of a titanium-based material, an iron-based material, a titanium-aluminum composite material and a steel-aluminum composite material, and the preparation method further comprises: forming a decorative layer (5) by a physical vapor deposition process; The main body (21) comprises a first surface (211) and a second surface (212) that are opposite to each other, and a first side surface and a second side surface connecting the first surface and the second surface, the first surface (211) being farther away from the middle plate (1) than the second surface (212), and the second surface (212) being connected to the extension portion (22); and the decorative layer (5) at least covers the first surface (211).

16. An electronic device, characterized in that: include: display screen (10) and rear housing (30), The middle frame (20) according to any one of claims 1 to 12, wherein the middle frame (20) is located between the display screen (10) and the rear housing (30); and the outer frame (2) of the middle frame (20) serves as a side of the electronic device (100).

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