Middle frame, preparation method thereof and electronic device

Abstract

The application provides a middle frame, a preparation method thereof and an electronic device. The special corrosion prevention and surface decoration design of the middle frame can achieve corrosion prevention of a complex structure, and can give the middle frame a high-quality appearance decoration effect. Application of the middle frame in an electronic device such as a mobile phone can effectively improve the market competitiveness of the electronic device.

Description

Technical Field

[0001] This application relates to the field of electronic product technology, specifically to the mid-frame and its manufacturing method, and electronic devices. Background Technology

[0002] Currently, with the continuous development of terminal devices such as mobile phones and tablets, the industry has increasingly higher requirements for the strength of structural components in these devices in order to reduce material usage and thus improve the lightweight nature of the devices. Taking aluminum alloy, a commonly used structural material, as an example, in order to improve the strength of aluminum alloys, the doping amount of other metals is increasing. This has led to a decline in the treatment effect of traditional aluminum alloy anodizing processes on these types of aluminum alloys, failing to meet the market's demand for high-brightness and high-quality appearance decoration of aluminum alloy structural components. To solve the above technical problems, some manufacturers use physical vapor deposition (PVD) coating technology to decorate aluminum alloy structural components; however, for complex structural components, the PVD coating material cannot fully adhere or has weak adhesion in some small structures, causing the aluminum alloy in these areas to be easily exposed to air, forming galvanic cell reaction channels and accelerating the corrosion failure of the structural components. Summary of the Invention

[0003] Therefore, embodiments of this application provide a mid-frame, a method for its fabrication, and an electronic device. The special anti-corrosion and surface decoration design of this mid-frame can achieve corrosion protection for complex structural components and give the mid-frame a high-quality aesthetic appearance. Applying this mid-frame to mobile phones and other electronic devices can effectively enhance the market competitiveness of these devices.

[0004] A first aspect of this application provides a mid-frame applied to an electronic device; the mid-frame includes a mid-plate and a frame, the frame being fixedly connected to the periphery of the mid-plate and forming a receiving space; the frame includes a first alloy substrate;

[0005] The first alloy substrate includes an adjacent inner side and an outer side, the inner side being disposed facing the receiving space and the outer side being disposed away from the receiving space;

[0006] A passivation layer is stacked on the inner side surface;

[0007] A PVD layer is provided on the outer surface.

[0008] The mid-frame provided in this embodiment has a PVD layer on its outer surface, which effectively isolates moisture and corrosive substances from penetrating the first alloy substrate beneath the PVD layer and imparts a superior aesthetic texture to the outer surface, such as a high-gloss finish and multi-colored effects. The passivation layer adheres well to the inner surface, preventing moisture and corrosive substances from penetrating the first alloy substrate through the inner surface, thereby effectively preventing galvanic reactions and enhancing the corrosion resistance of the first alloy substrate. Through the synergistic effect of the PVD layer and the passivation layer, superior corrosion resistance and aesthetic appearance of the mid-frame can be achieved simultaneously.

[0009] In some embodiments of this application, the frame has a perforated structure, and the inner wall of the perforated structure is covered with the passivation layer. When the frame also has a perforated structure, the use of the passivation layer to achieve corrosion protection inside the perforated structure can effectively inhibit the penetration of substances such as moisture from the perforated structure into contact with the first alloy substrate, thereby improving the corrosion resistance of the middle frame.

[0010] In some embodiments of this application, the frame is provided with an antenna slot, and the antenna slot is filled with plastic; a passivation layer is provided between the plastic and the first alloy substrate. When the frame is also provided with an antenna slot, the use of a passivation layer to protect the first alloy substrate at the antenna slot from corrosion can improve the corrosion resistance of the middle frame.

[0011] In some embodiments of this application, the outer surface is a curved surface;

[0012] Alternatively, the outer surface includes a first surface, a second surface, and a third surface; the third surface connects the first surface and the second surface, and the first surface and the second surface are respectively adjacent to the inner surface. The first surface, the second surface, and the third surface are independently flat or curved surfaces. In this way, the outer surfaces of the middle frame have a better aesthetic effect and are more conducive to improving the corrosion resistance of the middle frame.

[0013] In some embodiments of this application, the PVD layer is formed on the region where the inner side and the outer side are adjacent.

[0014] In some embodiments of this application, the surfaces of the first alloy substrate not covered by the PVD layer are all covered with the passivation layer. This effectively prevents the formation of galvanic cells in the frame, ensuring high corrosion resistance of the mid-frame.

[0015] In some embodiments of this application, the thickness of the passivation layer is 10nm-1000nm; the material of the passivation layer includes metal salts, or includes metal salts and organic matter. This ensures good corrosion resistance of the passivation layer, facilitates the assembly of the mid-frame with other electronic device components, and is easy to manufacture.

[0016] In some embodiments of this application, the material of the PVD layer includes one or more of elemental metals, oxides, nitrides, oxynitrides, carbides, and oxycarbides.

[0017] In some embodiments of this application, the PVD layer includes multiple sub-layers; the multiple sub-layers include a first sub-layer, a second sub-layer, and a third sub-layer stacked sequentially.

[0018] The first sublayer is disposed close to the first alloy substrate, and the material of the first sublayer includes one or more of Cr, Al, Ti, Si, Zr, and Ni; the thickness of the first sublayer is 0.1 μm-2 μm; and / or,

[0019] The material of the second sublayer includes one or more of the following: a first metal nitride, a first metal oxide, a first metal carbide, elemental Si, silicon oxide, silicon carbide, silicon nitride, and elemental carbon; the metal in the first metal nitride, the metal in the first metal oxide, and the metal in the first metal carbide independently includes one or more of Cr, Al, Ti, Zr, and Ni; the thickness of the second sublayer is 0.1 μm-6 μm; and / or,

[0020] The material of the third sub-layer includes one or more of the following: a second metal nitride, a second metal oxide, a second metal carbide, elemental Si, silicon oxide, silicon carbide, silicon nitride, and elemental carbon; the metal in the second metal nitride, the metal in the second metal oxide, and the metal in the second metal carbide independently include one or more of Cr, Al, Ti, Zr, and Ni; the thickness of the third sub-layer is 0.1μm-3μm. This design improves both the corrosion resistance and aesthetics of the frame.

[0021] In some embodiments of this application, the thickness of the PVD layer is 2μm-10μm. This helps to ensure that the PVD layer has both superior corrosion resistance and wear resistance, as well as high hardness, thereby improving the service life of the middle frame.

[0022] In some embodiments of this application, a diamond-like carbon film is disposed on the surface of the PVD layer facing away from the first alloy substrate; the thickness of the diamond-like carbon film is 10nm-1000nm. This avoids damaging the appearance of the original sharp structure of the frame while achieving a superior lubrication effect.

[0023] In some embodiments of this application, an anti-fingerprint layer is further provided on the surface of the diamond-like film facing away from the first alloy substrate; the thickness of the anti-fingerprint layer is 10nm-50nm.

[0024] In some embodiments of this application, a transition layer is further provided between the anti-fingerprint layer and the diamond-like carbon film. In some embodiments of this application, the thickness of the transition layer is 5nm-1000nm. This is beneficial for improving the adhesion between the diamond-like carbon film and the anti-fingerprint layer.

[0025] In some embodiments of this application, the material of the transition layer includes a third metal nitride, a third metal oxide, a third metal carbide, an oxide of silicon, a nitride of silicon, and an oxide nitride of silicon; the metals in the third metal nitride, the third metal oxide, and the third metal carbide independently include Al and / or Cr.

[0026] In some embodiments of this application, the material of the first alloy substrate includes aluminum alloy and / or magnesium alloy.

[0027] In some embodiments of this application, the middle frame has a neutral salt spray corrosion resistance time of ≥96h; and / or, the adhesion of the film layer on the surface of the first alloy substrate is ≥40N.

[0028] In some embodiments of this application, the surface Vickers hardness of the outer side of the frame is ≥1100HV; and / or, the linear wear resistance of the outer side of the frame is ≥1000 cycles; and / or, the surface roughness Ra of the outer side of the frame is <0.08μm; and / or, the gloss of the outer side of the frame is ≥700GU.

[0029] The second aspect of this application provides a method for preparing a middle frame, comprising:

[0030] A middle frame blank is provided, the middle frame blank including a middle plate portion and a frame portion formed by a first alloy substrate, the frame portion being fixedly connected to the middle plate portion and forming a receiving space;

[0031] The first alloy substrate includes an adjacent inner side and an outer side; the inner side is disposed facing the receiving space, and the outer side is disposed away from the receiving space;

[0032] A passivation layer is formed on the inner surface, and a PVD layer is formed on the outer surface.

[0033] The above preparation method is suitable for large-scale industrial production, and has high process reliability and low production cost.

[0034] In some embodiments of this application, forming a passivation layer on the inner surface and forming a PVD layer on the outer surface includes:

[0035] (1) The first alloy substrate is pretreated, and then the PVD layer is physically deposited on the outer surface in a vacuum environment to obtain the first preform;

[0036] The first preform is immersed in the passivation solution of the first alloy substrate for passivation treatment, and then a diamond-like carbon film is deposited on the surface of the PVD layer.

[0037] or,

[0038] (2) The first alloy substrate is pretreated, and then the middle frame blank is immersed in the passivation liquid of the first alloy substrate for passivation treatment to form a passivation layer on the surface of the first alloy substrate to obtain the second preform.

[0039] The second preform is placed in a vacuum environment, and the PVD layer is physically deposited on the outer surface.

[0040] A diamond-like carbon film is deposited on the surface of the PVD layer.

[0041] In some embodiments of this application, the physical deposition uses a high-power pulsed power supply; or, the power supply is a radio frequency power supply and / or a medium-frequency magnetron sputtering power supply, as well as a high-power pulsed power supply; the discharge voltage of the high-power pulsed power supply is 500V-1000V, the pulse width is 10-500μs, and the pulse frequency is 40Hz-400Hz; the power of the medium-frequency magnetron sputtering power supply is 1kW-20kW; and the power of the radio frequency power supply is 1kW-20kW. This facilitates the preparation of a uniform and dense PVD layer and improves the adhesion between the PVD layer and the first alloy substrate.

[0042] A third aspect of this application provides an electronic device, including a display module and a mid-frame fixedly connected to the display module; the mid-frame is the mid-frame provided in the first aspect of this application, or the mid-frame is prepared by the method of the mid-frame provided in the first aspect of this application.

[0043] The electronic device provided in this application has superior corrosion resistance, strong wear resistance of its appearance parts, and can have a colorful appearance with a high gloss texture, thus possessing high market competitiveness.

[0044] In some embodiments of this application, the electronic device includes, but is not limited to, consumer electronic products such as mobile phones, tablets, and watches. Attached Figure Description

[0045] Figure 1 A schematic diagram of the overall structure of an electronic device according to one embodiment;

[0046] Figure 2 for Figure 1 A simplified schematic diagram of the overall structure of the middle frame;

[0047] Figure 3A for Figure 2A cross-sectional schematic diagram of the middle frame at point AA in one embodiment;

[0048] Figure 3B for Figure 2 Another embodiment provides a cross-sectional schematic diagram of the middle frame at AA;

[0049] Figure 4A A partial cross-sectional schematic diagram of the middle frame provided in an embodiment of this application;

[0050] Figure 4B A partial cross-sectional schematic diagram of the middle frame provided in another embodiment of this application;

[0051] Figure 5A A partial cross-sectional schematic diagram of the middle frame provided in yet another embodiment of this application;

[0052] Figure 5B A partial cross-sectional schematic diagram of the middle frame provided in yet another embodiment of this application;

[0053] Figure 6A A partial cross-sectional schematic diagram of the middle frame provided in yet another embodiment of this application;

[0054] Figure 6B A partial cross-sectional schematic diagram of the middle frame provided in yet another embodiment of this application;

[0055] Figure 7 A partial cross-sectional schematic diagram of the middle frame provided in yet another embodiment of this application;

[0056] Figure 8 for Figure 2 A simplified schematic diagram of the overall structure of the middle frame;

[0057] Figure 9 A partial cross-sectional schematic diagram of the middle frame provided in yet another embodiment of this application;

[0058] Figure 10 A partial cross-sectional schematic diagram of the middle frame provided in yet another embodiment of this application;

[0059] Figure 11A A partial cross-sectional schematic diagram of the middle frame provided in yet another embodiment of this application;

[0060] Figure 11B A partial cross-sectional schematic diagram of the middle frame provided in yet another embodiment of this application;

[0061] Figure 12 A partial cross-sectional schematic diagram of the middle frame provided in yet another embodiment of this application;

[0062] Figure 13A A process flow diagram of process flow A provided in an embodiment of this application;

[0063] Figure 13B A process flow diagram of process flow B provided in an embodiment of this application.

[0064] Explanation of icon numbers:

[0065] 100 - Electronic devices;

[0066] 1-Middle frame;

[0067] 10-Frame; 11-First alloy substrate; 111-Inner side; 112-Outer side; 1121-First surface; 1122-Second surface; 1123-Third surface; 13-Passivation layer; 14-PVD layer; 141-First sub-layer; 142-Second sub-layer; 143-Third sub-layer; 15-Diamond-like carbon film; 16-Anti-fingerprint layer; 17-Transition layer;

[0068] 20-middle plate; 21-second alloy base material;

[0069] 2-Display module. Detailed Implementation

[0070] With the development of technology, market competition for electronic devices such as mobile phones, tablets, and smartwatches is becoming increasingly fierce. Consumers not only have higher and higher requirements for the performance of electronic devices, but also for other aspects such as appearance and feel. For example, consumers are pursuing lighter weight and better drop resistance. To meet these demands simultaneously, the industry is trying to use higher-strength alloy materials to manufacture structural components of electronic devices, such as higher-strength aluminum alloys and magnesium alloys. These metal materials are prone to corrosion in this usage scenario and generally require anti-corrosion treatment. However, for some structural components, they also contribute to the appearance of electronic devices; the mid-frame is a typical example. Therefore, manufacturers also have high requirements for the appearance of these structural components. Aluminum alloy is one of the common mid-frame materials. To meet the above demands simultaneously, in the 3C electronics field, most manufacturers use anodizing processes to treat aluminum alloy mid-frames, achieving both corrosion resistance and aesthetic decoration. However, in the existing technology, in order to improve the strength of aluminum alloys, the industry has been continuously increasing the doping amount of other metals. This has led to a decrease in the treatment effect of traditional anodizing processes on such aluminum alloys, which cannot meet the market's demand for high-brightness and high-quality appearance decoration of aluminum alloy structural parts; and the surface flatness of the anodized film is low and porous.

[0071] In response, the industry has adopted PVD coating technology to treat the mid-frame. Based on the characteristics of PVD coating, the coating particles are directly deposited onto the alloy substrate under the influence of an electromagnetic field. However, some complex structures exist on surfaces parallel to the incident direction of the coating particles, such as the inner side of the mid-frame frame, some end faces, and small structures like holes on the frame. This results in low density of the PVD film formed in these areas, weak adhesion to the alloy substrate, or even incomplete adhesion, leading to accelerated galvanic corrosion of the structural components. Furthermore, considering communication requirements, in some applications, plastic strips are needed on the mid-frame frame. This typically requires breaking the mid-frame frame and filling the break with plastic. To improve the bonding strength between the plastic and the frame alloy substrate, the aluminum alloy surface in this area needs to be etched to create micron-sized voids at the aluminum alloy cross-section. However, the plastic cannot completely fill these micron-sized voids, and neither can the PVD coating. These voids are thus retained in the electronic device, forming galvanic reaction channels, accelerating the galvanic reaction, and causing corrosion failure of the mid-frame.

[0072] Please see Figure 1 , Figure 1 An example of a middle frame 1 is provided, which is applied to an electronic device 100; see [link to documentation]. Figure 2 The middle frame 1 includes a side frame 10 and a middle plate 20. The side frame 10 is fixedly connected to the periphery of the middle plate 20, and the side frame 10 and the middle plate 20 form a receiving space. Figure 3A The middle frame 1 of one embodiment is along Figure 2 A cross-sectional view at point AA shows that frame 10 includes a first alloy substrate 11; the first alloy substrate 11 includes an adjacent inner side surface 111 and an outer side surface 112, the inner side surface 111 facing the aforementioned receiving space, and the outer side surface 112 facing away from the aforementioned receiving space; in some embodiments, please refer to Figure 3A The outer surface 112 is curved. Figure 3B It is the middle frame edge of another embodiment. Figure 2 The cross-sectional view at point AA shows that the outer surface 112 includes a first surface 1121, a second surface 1122, and a third surface 1123. The third surface 1123 connects the first surface 1121 and the second surface 1122. The first surface 1121 connects to the inner surface 111, and the second surface 1122 connects to the inner surface 111. The first surface 1121, the second surface 1122, and the third surface 1123 are independently flat or curved surfaces. For some embodiments, please refer to... Figure 3B The first surface 1121, the second surface 1122 and the third surface 1123 are all flat surfaces; in other embodiments, the first surface 1121 and the second surface 1122 are flat surfaces and the third surface 1123 is a curved surface.

[0073] It should be noted that, Figure 1 This is just an example drawing method. Figure 1 The type, appearance, and size of the electronic device shown do not constitute a limitation on this application. This application does not limit the shape of the border 10 and the middle plate 20 of the middle frame 1; the middle frame 1 can be any middle frame suitable for the electronic device 100. Figures 1 to 3B The figures are for illustrative purposes only and do not constitute a limitation on this application. When the mid-frame 1 provided in the embodiments of this application is applied to terminal electronic devices such as mobile phones, the mobile phone can be a candybar phone or a foldable phone, etc. Those skilled in the art can design the specific structure of the mid-frame 1 according to the actual application needs.

[0074] The following is based on Figure 3B Taking the middle frame 1 shown as an example, the technical solution of this application will be described in detail. Please refer to... Figure 4A , Figure 4A A cross-sectional view of a partial area of ​​the middle frame 1 provided in an embodiment of this application, specifically... Figure 3B Enlarged view of the area corresponding to circle III; a passivation layer 13 is stacked on the inner side 111, and a PVD layer 14 is disposed on the outer side 112. It should be noted that the passivation layer 13 stacked on the inner side 111 means that the inner side 111 is covered with a passivation layer 13 to effectively reduce the risk of water vapor and salt spray, and other corrosive substances, penetrating through the inner side 111 of the first alloy substrate 11, thus preventing galvanic corrosion of the first alloy substrate 111. Simultaneously, to achieve beneficial anti-corrosion and aesthetic design effects, a PVD layer 14 is disposed on the outer side 112; specifically, the outer side 112 is covered with a PVD layer 14.

[0075] In this application, when the outer surface 112 of the frame 10 is curved, please refer to... Figure 4B , Figure 4B This is a partial cross-sectional view of the middle frame 1 provided in an embodiment of this application. The outer side 112 of the first alloy substrate 11 is an arc surface, the PVD layer 14 covers the outer side 112, and the passivation layer 13 covers the inner side 111.

[0076] In this field, the PVD layer 14 refers to a uniform and dense film layer formed by physical deposition, and its appearance color can be controlled by adjusting the material of the PVD layer 14. The passivation layer 13 is a uniform and dense film layer formed on the surface of a metal material through passivation treatment. The middle frame 1 provided in this application embodiment has the PVD layer 14 disposed on the outer side 112, which can effectively isolate moisture and corrosive substances from intruding into the first alloy substrate 11 below the PVD layer 14, and can give the outer side 112 a better appearance texture, such as a high-gloss texture and a multi-colored effect. At the same time, the passivation layer 13 can be well attached to the inner side 111, which can isolate moisture and corrosive substances from intruding into the first alloy substrate 11 through the inner side 111, thereby effectively preventing galvanic cell reactions and improving the corrosion resistance of the first alloy substrate 11. Under the synergistic effect of the PVD layer 14 and the passivation layer 13, a better anti-corrosion and decorative effect of the middle frame can be achieved simultaneously.

[0077] In this embodiment, the frame 10 and the middle plate 20 can be integrally formed. For some embodiments, please refer to... Figure 5A The middle plate includes a second alloy substrate 21, and the first alloy substrate 11 and the second alloy substrate 21 can be integrally formed.

[0078] In this application, the first alloy substrate 11 is selected from aluminum alloys and magnesium alloys. In some embodiments, the first alloy substrate 11 is an aluminum alloy. In other embodiments, the first alloy substrate 11 is a magnesium alloy. In some embodiments of this application, the frame 10 includes the first alloy substrate 11, and the middle plate 20 includes the second alloy substrate 21, wherein the first alloy substrate 11 and the second alloy substrate 21 are independently selected from magnesium alloys and / or aluminum alloys. In some embodiments, both the first alloy substrate 11 and the second alloy substrate 21 are aluminum alloys. In other embodiments, both the first alloy substrate 11 and the second alloy substrate 21 are magnesium alloys. In this application, the aluminum alloy may include 2-series aluminum alloys, 6-series aluminum alloys, 7-series aluminum alloys, etc.

[0079] For some embodiments of this application, please refer to [link / reference]. Figure 5A The middle plate 20 includes a second alloy substrate 21, and a passivation layer 13 is provided on the surface of the second alloy substrate 21 adjacent to the inner side surface 111 of the first alloy substrate 11. In some specific embodiments, the portion of the surface of the second alloy substrate 21 adjacent to the inner side surface 111 of the first alloy substrate 11 is covered with the passivation layer 13. This effectively reduces the risk of water vapor, salt spray, and other corrosive substances penetrating into the second alloy substrate 21 and causing corrosion. In other words, the area along the outer contour of the second metal substrate that covers a first width away from the frame 10 and towards the center of the middle plate 20 is designated as the X region (…). Figure 5A The X region (marked by a black dashed line) has a passivation layer 13 covering its surface. This application does not limit the specific dimensions of the first width. For some specific embodiments, please refer to... Figure 5B The surface of the second alloy substrate 21 is fully covered by a passivation layer 13.

[0080] In some embodiments of this application, the surfaces of the first alloy substrate 11 not covered by the PVD layer 14 are all covered with a passivation layer 13. This effectively prevents the formation of galvanic cells in the frame 10, ensuring high corrosion resistance of the middle frame 1. This includes, but is not limited to, the following situations: (1) Please refer to... Figures 4A to 5B The inner side 111 is covered with a passivation layer 13, and the outer side 112 is covered with a PVD layer. The passivation layer 13 is stacked in contact with the first alloy substrate 11, and the PVD layer 14 is stacked in contact with the first alloy substrate 11. The passivation layer 13 and the PVD layer 14 are adjacent to each other; (2) Please refer to Figure 6A The inner surface is covered with a passivation layer 13, and the outer surface is covered with a PVD layer 14, with the passivation layer 13 extending to region Y. Figure 6A (The area marked by the black dashed line in the middle) Area Y includes the part of the outer side 112 and the inner side 111 that are adjacent to each other; (3) Please refer to Figure 6B The inner surface is covered with a passivation layer 13, and the outer surface is covered with a PVD layer 14. A passivation layer 13 is also provided between the PVD layer 14 and the first alloy substrate 11. The orthogonal projection of the PVD layer 14 on the first alloy substrate 11 falls within the boundary of the orthogonal projection of the passivation layer 13 on the first alloy substrate 11.

[0081] In this embodiment, the passivation layer 13 is obtained by passivating an alloy substrate (e.g., a first alloy substrate 11 or a second alloy substrate 21) in a passivation solution. The passivation layer 13 is formed by the reaction of the alloy substrate material with the passivation solution. A passivation solution known in the art for aluminum or magnesium alloys can be used to passivate the first alloy substrate 11. In some specific embodiments, when the middle plate 20 includes a second alloy substrate 21, a passivation solution known in the art for both the first and second alloy substrates 11 can be used for passivation. In some embodiments of this application, the material of the passivation layer 13 includes a metal salt, or includes a metal salt and an organic compound. Specifically, in some embodiments, the material of the passivation layer 13 includes a metal salt. In other embodiments, the material of the passivation layer 13 includes a metal salt and also includes an organic compound. In some specific embodiments, the first alloy substrate 11 is an aluminum alloy, and the material of the passivation layer 13 on the surface of the first alloy substrate 11 includes zirconium oxide, aluminum phosphate, sodium fluoroaluminate, and zirconium hydrogen phosphate. Thus, the passivation layer 13 is denser, which is more conducive to improving the corrosion resistance of the middle frame 1. In some specific embodiments, the material of the passivation layer 13 also includes organic matter. Similarly, when the middle plate 20 includes a second alloy substrate 21, and the surface of the second alloy substrate 21 has a passivation layer 13, the material of the passivation layer 13 on the surface of the second alloy substrate 21 includes a salt of the metal in the second alloy substrate 21; further, it also includes organic matter. This will not be elaborated further here. In other embodiments, the first alloy substrate 11 is a magnesium alloy, and the material of the passivation layer 13 on the surface of the first alloy includes magnesium phosphate; further, it also includes organic matter, and / or one or more of tungstate, chromate, molybdate, silicate, and titanium salt; the aforementioned organic matter includes silane. Thus, the passivation layer 13 is denser, which is more conducive to improving the corrosion resistance of the middle frame 1.

[0082] In some embodiments of this application, the thickness of the passivation layer 13 is 10nm-1000nm. This ensures good corrosion resistance of the passivation layer 13, facilitates the assembly of the middle frame 1 with other electronic device components, and is easy to manufacture. Specifically, the thickness of the passivation layer 13 can be, for example, 10nm, 20nm, 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, etc. In some specific embodiments, the thickness of the passivation layer 13 is 10nm-150nm. Controlling the thickness of the passivation layer 13 within the range of 10nm-150nm is more conducive to improving the interfacial adhesion between the passivation layer and the PVD layer 14, effectively reducing the poor adhesion at the interface between the passivation layer 13 and the PVD layer 14, which could become a weakness in corrosion resistance (e.g., Figures 4A to 5B The risk of corrosion in the area marked by the dashed circle (a) can be mitigated, thereby further enhancing the corrosion resistance of the middle frame 1 and extending its service life. Furthermore, controlling the thickness of the passivation layer 13 within the aforementioned range can avoid the risk of fogging on the surface of the middle frame 1, and will not damage the original sharp structure of the frame 10. This allows for further optimization of the appearance and decorative effect of the middle frame 1 while ensuring its corrosion resistance.

[0083] In this application, the material of the PVD layer 14 can be any material suitable for deposition on the surface of the corresponding alloy, serving the purpose of corrosion protection and imparting a certain aesthetic texture. For example, in some embodiments of this application, the material of the PVD layer 14 includes one or more of the following: elemental metals, oxides, nitrides, oxynitrides, carbides, and oxycarbides. Specifically, it can be, for example, metal oxides, metal nitrides, metal carbides, and metal oxycarbides. Of course, it can also include non-metallic oxides, non-metallic carbides, etc., and may also include elemental Si, elemental C, etc. The aforementioned metals include, but are not limited to, one or more of Cr, Ti, Zr, Al, and Ti.

[0084] Understandably, during the deposition of the PVD layer 14, although the incident direction of the deposited particles is parallel to the inner surface 111, some deposited particles may still be deposited in the area adjacent to the inner surface 111 and the outer surface 112. Since the passivation layer 13 is present under the inner surface 111 of the frame 10, it not only does not reduce the corrosion resistance and appearance of the middle frame 1, but also helps reduce the risk of the passivation layer 13 being exposed on the surface of the electronic device after the middle frame 1 is assembled, thus improving the corrosion resistance of the middle frame 1. Please refer to... Figure 7In some embodiments of this application, a PVD layer 14 is formed in a portion of the area where the inner side 111 and the outer side 112 are adjacent.

[0085] Please see Figure 8 In some embodiments, to achieve functions such as charging and volume adjustment, the frame 10 also has a perforated structure (e.g., headphone jack, charging port, speaker hole, noise reduction port, etc.). In some embodiments of this application, the frame 10 has a perforated structure, and the inner wall of the perforated structure is covered with a passivation layer 13 to achieve corrosion protection for the small and complex structures such as the perforated structure. It should be noted that the inner wall of the perforated structure is covered with a passivation layer 13, specifically meaning that the surface of the first alloy substrate 11 of the inner wall of the perforated structure is covered with a passivation layer 13, and the passivation layer 13 does not fill the perforated structure. In the embodiments of this application, the perforated structure can be a through hole or a non-through hole. In some embodiments of this application, when the electronic device 100 also needs to achieve communication functions, the frame 10 has an antenna slot, and the antenna slot is filled with plastic; a passivation layer 13 is provided between the plastic and the first alloy substrate 11. Understandably, the essence of an antenna slot is to create an antenna slot on the first alloy substrate 11 to provide a clearance area for the metal antenna. The first alloy substrate 11 has a cross-section at the antenna slot, and a passivation layer 13 is covered on the cross-section. The clearance area for the metal antenna is filled with plastic. Similarly, when a hole structure or an antenna slot is formed on the frame 10, the inner wall of the hole structure may also contain material of the PVD layer 14, and the material of the PVD layer 14 is attached to the surface of the passivation layer 13. When an antenna slot is formed on the frame 10, the first alloy substrate 11 may also contain material of the PVD layer 14 at the cross-section of the antenna slot, and the material of the PVD layer 14 is attached to the surface of the passivation layer 13.

[0086] To further enhance the corrosion resistance, wear resistance, and hardness of the PVD layer 14, and to further optimize the high-gloss texture of the PVD layer 14, please refer to some embodiments of this application. Figure 9The PVD layer 14 includes multiple sublayers; these sublayers include a first sublayer 141, a second sublayer 142, and a third sublayer 143 stacked sequentially, with the first sublayer 141 disposed close to the first alloy substrate 11. In some embodiments, all sublayers possess a certain degree of corrosion resistance, but their focuses differ. For example, the first sublayer 141 focuses on achieving a base coat effect, meaning it has high adhesion to the first alloy substrate 11, thereby improving the adhesion of the film layer on the first alloy substrate 11 and thus facilitating corrosion resistance. In some embodiments of this application, the material of the first sublayer 141 includes one or more of Cr, Ti, Zr, Al, and Si. Specifically, the material of the first sublayer 141 can be elemental Cr, elemental Ti, elemental Zr, elemental Al, elemental Si, or an alloy formed from one or more of the above metals and semi-metals. PVD films formed from the above materials exhibit good adhesion to aluminum alloys and magnesium alloys. In some embodiments, the thickness of the first sublayer 141 is 0.1μm-2μm. This ensures a better priming effect of the first sublayer 141. Specifically, the thickness of the first sublayer 141 can be, for example, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, etc.

[0087] In some embodiments of this application, the second sublayer 142 focuses on corrosion resistance; in this case, the second sublayer 142 can also be referred to as an anti-corrosion layer. In some specific embodiments, the material of the second sublayer 142 includes one or more of the following: a first metal nitride, a first metal oxide, a first metal carbide, elemental Si, silicon oxide, silicon carbide, silicon nitride, and elemental carbon; the metal in the first metal nitride, the metal in the first metal oxide, and the metal in the first metal carbide independently include one or more of Cr, Al, Ti, Zr, and Ni. The above materials have superior corrosion resistance and can form a uniform, dense film. In some specific embodiments, the second sublayer 142 is a dense composite film, that is, its material includes a combination of multiple of the above materials; thus, the corrosion resistance is even better. It should be noted that when the second sublayer 142 simultaneously includes multiple of the first metal nitride, the first metal oxide, and the first metal carbide, the first metal can be the same or different; for example, the metals in the first metal nitride and the first metal oxide can be the same or different. In some embodiments, the thickness of the second sublayer 142 is 0.1 μm-6 μm. This improves the corrosion resistance of the second sublayer 142, and the second sublayer 142 also possesses certain hardness and wear resistance, which helps to improve the overall performance of the PVD layer 14. Specifically, the thickness of the second sublayer 142 can be, for example, 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5 μm, 5.2 μm, 5.5 μm, 5.8 μm, 6 μm, etc.

[0088] In some embodiments of this application, the third sublayer 143 combines corrosion resistance with a focus on providing a high-gloss finish; the third sublayer 143 may also be referred to as a high-gloss layer. In some embodiments, the high-gloss layer serves as the outer layer of the PVD layer 14. In some embodiments, one or more of the following are used: a second metal nitride, a second metal oxide, a second metal carbide, elemental Si, an oxide of silicon, a carbide of silicon, a nitride of silicon, and elemental carbon; the metal in the second metal nitride, the metal in the second metal oxide, and the metal in the second metal carbide independently include one or more of Cr, Al, Ti, Zr, and Ni. The above materials have superior corrosion resistance and can provide a superior high-gloss appearance. It should be noted that the color of the third sublayer 143 can be adjusted by adjusting the material of the third sublayer 143 or by adjusting the relative content of different materials, that is, by adjusting the Lab value of the third sublayer 143; for example, the presence of Cr is beneficial for giving the third sublayer a silver color. In some specific embodiments, the third sublayer 143 is a composite film layer of multiple materials. It should be noted that when the third sublayer 143 simultaneously includes multiple types of second metal nitride, second metal oxide, and second metal carbide, the second metal can be the same or different; for example, the metals in the second metal nitride and the second metal oxide can be the same or different. In some embodiments, the thickness of the third sublayer 143 is 0.1μm-3μm. Thus, the third sublayer 143 can achieve a superior high-gloss texture, improving the appearance of the PVD layer 14, and can also possess certain corrosion resistance and wear resistance. Specifically, the thickness of the third sublayer 143 can be, for example, 0.1μm, 0.2μm, 0.5μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.8μm, 2μm, 2.2μm, 2.5μm, 2.8μm, 3μm, etc.

[0089] In some embodiments of this application, the thickness of the PVD layer 14 is 0.5 μm-20 μm. In some embodiments, the thickness of the PVD layer 14 is 2 μm-10 μm. Specifically, the thickness of the PVD layer 14 can be, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc. Controlling the thickness of the PVD layer 14 within the aforementioned range helps ensure that the PVD layer 14 has both superior anti-corrosion and wear-resistant properties, as well as high hardness, thereby improving the service life of the middle frame 1. In addition, controlling the thickness within the aforementioned range results in better cooperation with the passivation layer and also improves the appearance of the middle frame 1.

[0090] For some embodiments of this application, please refer to Figure 10 A diamond-like carbon (DLC) film 15 is disposed on the surface of the PVD layer 14 facing away from the first alloy substrate 11. The DLC film 15 on the surface of the PVD layer 14 effectively protects the PVD layer 14, provides lubrication, reduces the surface friction coefficient, and lowers the risk of wear or even damage to the PVD layer 14 during abrasive or subsequent use; furthermore, the DLC film 15 has a good surface finish. In some specific embodiments, the diamond-like carbon film 15 is a hydrogen-free diamond-like carbon (TaC) film. In this embodiment, the orthographic projection of the PVD layer 14 onto the first alloy substrate 11 falls within the orthographic projection of the DLC film 15 onto the first alloy substrate 11. Specifically, the PVD layer 14 is covered on the outer surface 112 of the first alloy substrate 11, and the surface of the PVD layer 14 facing away from the first alloy substrate 11 is covered with the DLC film 15.

[0091] In some embodiments of this application, the thickness of the DLC film 15 is 10nm-1000nm. Controlling the thickness of the DLC film 15 within this range does not impair the appearance of the sharp structure of the frame 10, while simultaneously achieving a superior lubrication effect and improving the wear resistance of the frame 10. Specifically, the thickness of the DLC film 15 can be, for example, 10nm, 20nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, etc. In some cases, when it is necessary to retain the color of the PVD layer 14 as the appearance color of the border 10, the thickness of the DLC film 15 can be controlled to be 10nm-50nm; in other cases, for example, when the color of the PVD layer 14 is dark such as black, the thickness of the DLC film 15 can also be controlled to be >50nm. In this case, the DLC film 15 mainly contributes to the appearance color of the border 10, but can still retain the high gloss texture of the PVD layer 14.

[0092] To improve the feel of the electronic device, an anti-fingerprint (AF) layer is also provided on the surface of the bezel 10 that forms the outer surface of the electronic device. In some embodiments, an anti-fingerprint layer is also provided on the surface of the PVD layer 14 facing away from the first alloy substrate 11. For further understanding, please refer to [link to relevant documentation]. Figure 11A On the outer surface 112 of the first alloy substrate 11, an anti-fingerprint layer 16 covers the PVD layer 14, facing away from the surface of the first alloy substrate 11. When the surface of the PVD layer 14 is also provided with a DLC film 15, please refer to [link to relevant documentation]. Figure 11BAn anti-fingerprint layer 16 is disposed on the surface of the diamond-like carbon film 15 facing away from the PVD layer 14. At this time, the anti-fingerprint layer 16 covers the surface of the DLC film 15 facing away from the PVD layer 14 on the outer side 112 of the first alloy substrate 11. In some embodiments of this application, the thickness of the anti-fingerprint layer 16 is 10nm-50nm. This results in good anti-fingerprint performance and a good tactile feel. In this application, the AF layer 16 can be any AF layer known in the art, and the material of the AF layer is not limited.

[0093] To improve the adhesion between the DLC film 15 and the AF layer 16, further optimize the adhesion of the film layer on the first alloy substrate 11, and enhance its wear resistance, please refer to [link to relevant documentation]. Figure 12 In some embodiments of this application, a transition layer 17 is further provided between the DLC film 15 and the AF layer 16. The material of the transition layer 17 includes oxides. In some embodiments, the material of the transition layer 17 includes, but is not limited to, a third metal nitride, a third metal oxide, a third metal carbide, an oxide of silicon, a nitride of silicon, and an oxide oxynitride of silicon; the metal in the third metal nitride, the third metal oxide, and the third metal carbide independently includes Al and / or Cr. The transition layer 17 of the above materials has high adhesion to both the DLC film 15 and the AF layer 16, and is corrosion resistant. In some specific embodiments, the material of the transition layer 17 includes one or more of the oxides of Al, the oxides of Si, and the oxides of Cr. This is more conducive to improving the bonding force between the transition layer and the AF layer 16, thereby improving the adhesion of the film layer on the first alloy substrate 11, and further improving the corrosion resistance and wear resistance of the frame 10. In some embodiments, the transition layer 17 is also doped with carbon. In this embodiment, the orthographic projection of the transition layer 17 on the PVD layer 14 falls within the orthographic projection of the DLC film 15 on the AF layer 16; furthermore, the orthographic projections of the transition layer 17, the AF layer 16, and the DLC film 15 on the PVD layer 14 coincide.

[0094] In some embodiments of this application, the thickness of the transition layer 17 is 5nm-1000nm. Maintaining the thickness of the transition layer 17 within this range facilitates the bridging between the DLC film 15 and the AF layer 16, improving adhesion, without affecting the appearance and feel of the frame 10. Specifically, the thickness of the transition layer 17 can be, for example, 5nm, 10nm, 20nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, etc. In some embodiments, the thickness of the transition layer 17 is 5nm-500nm. By further controlling the thickness of the transition layer 17 within the aforementioned range, the flatness of the PVD layer 14 can be further improved, ensuring a higher adhesion between the transition layer 17 and the AF layer 16. This is more conducive to improving the bonding force between the transition layer and the DLC film 15 and the AF layer 16, as well as the appearance effect, without reducing the improvement of the wear resistance performance of the DLC film 15.

[0095] Based on the anti-corrosion design of the frame 1 in this application, the frame 1 provided in this embodiment has a neutral salt spray corrosion resistance time of ≥96 hours. For example, the frame 1 provided in this embodiment shows no corrosion spots after 96 hours of neutral salt spray testing. It meets the anti-corrosion requirements of 3C products and has a good appearance. It should be noted that the plate 20 of the frame 1 undergoing the neutral salt spray resistance test has also been treated with anti-corrosion measures; for example, the surface of the second alloy substrate 21 is also covered with a passivation layer 13. The second alloy substrate 21 can be the same as or different from the first alloy substrate 11. In some embodiments, the second alloy substrate 21 is an aluminum alloy and / or a magnesium alloy. The second alloy substrate 21 can be treated with anti-corrosion measures as needed. For example, the surface of the second alloy substrate 21 is covered with a passivation layer 13.

[0096] In this embodiment, a scanning electron microscope (SEM) can be used to observe the cross-sectional sample of the frame to test the thickness of each layer. Specifically, during SEM testing, the magnification can be controlled to be ≥10000x.

[0097] In this embodiment of the application, energy dispersive spectroscopy (EDS) can be used to measure the material composition of each layer.

[0098] It should be noted that all the illustrations in this application are exemplary drawings used to assist in the explanation, and the parameters such as the thickness and shape of each film layer do not constitute a limitation on this application.

[0099] In some embodiments of this application, the adhesion of the film layer on the surface of the first alloy substrate 11 is ≥40N. Specifically, it can be 40N, 41N, 42N, 43N, 44N, or 45N. In this application, an automatic coating adhesion scratch tester is used to test the adhesion of the film layer on the surface of the first alloy substrate 11. Specifically, the experimental load is 10N, the scratching speed is 5mm / min, the loading rate is 10N / min, the scratch length is 5mm, and a standard diamond indenter (set angle 120°, tip curvature radius 0.2mm) is used for the test. The film layer on the surface of the first alloy substrate 11 includes all film layers on the surface of the first alloy substrate 11 of the frame 10 to be tested.

[0100] In some embodiments of this application, the surface Vickers hardness of the outer side of the frame 10 is ≥1100HV. For example, 1100HV, 1120HV, 1150HV, 1180HV, 1200HV. In this application, a Vickers hardness tester is used to test the above-mentioned surface Vickers hardness. Specifically, the tester uses a pyramidal diamond indenter with a 136° apex angle, a 1kg load, and a holding time of 10s. The surface Vickers hardness is measured after unloading the indenter. It should be noted that the outer side of the frame 10 corresponds to the outer side 112 of the first alloy substrate 11, and the outer side of the frame 10 constitutes the appearance surface of the frame 10.

[0101] In some embodiments of this application, the linear wear resistance of the outer surface of the frame 10 is ≥1000 cycles. For example, after 1000 cycles of linear wear, the film layer on the outer surface of the frame 10 is not worn through or peeled off. In this application, the outer surface of the frame 10 meets the standard after 1000 cycles of linear wear. The judgment criteria include: linear wear with obvious discoloration less than 0.3 mm in width is allowed to be continuous for no more than 25 mm; linear wear with a width of 0.3-1.0 mm is allowed to be continuous for no more than 15 mm; the total length of continuous linear wear does not exceed 40 mm (width 0.3 mm, length less than 2 mm is not counted); point wear does not exceed 1*1 mm; and the width of linear wear does not exceed 1.0 mm.

[0102] In some embodiments of this application, the surface roughness Ra of the outer side of the frame 10 is <0.08 μm. In this application, a laser interferometer is used to test the surface roughness of the frame 10. Specifically, the Ra of the outer side of the frame 10 can be, for example, 0.004 μm, 0.005 μm, 0.006 μm, 0.007 μm, 0.0075 μm, etc.

[0103] In some embodiments of this application, the gloss level of the outer surface of the frame 10 is ≥700 GU; GU stands for Gloss Units. This application uses a gloss meter to measure the gloss level of the frame 10. The middle frame 1 provided in the embodiments of this application has a glossy and refined appearance on the surface of its frame 10, which meets the application requirements of 3C products.

[0104] This application also provides a method for preparing a middle frame, including:

[0105] A middle frame blank is provided, the middle frame blank including a middle plate portion and a frame portion formed by a first alloy substrate, the frame portion being fixedly connected to the middle plate portion and forming a receiving space;

[0106] The first alloy substrate includes an inner side and an outer side disposed opposite to each other, wherein the inner side faces the receiving space and the outer side faces away from the receiving space.

[0107] A passivation layer is formed on the inner surface, and a PVD layer is formed on the outer surface. It should be noted that the preparation method provided in this application does not limit the order in which the passivation layer and the PVD layer are prepared; the middle frame can be prepared according to either process flow A or process flow B.

[0108] The above preparation method can be used to prepare the aforementioned middle frame 1, and is suitable for large-scale industrial production.

[0109] In this application, the middle frame blank can be integrally formed or not integrally formed. In some embodiments, the middle plate includes a second alloy substrate. In this application, the first alloy substrate and the second alloy substrate can be the same or different; the material selection of the first alloy substrate and the second alloy substrate can be referred to the description of the frame section above, and will not be repeated here.

[0110] Process Flow A

[0111] Please see Figure 13A In some embodiments of this application, forming a passivation layer on the inner surface of the first alloy substrate and forming a PVD layer on the outer surface includes:

[0112] S11. The first alloy substrate is pretreated, and then a PVD layer is physically deposited on the outer surface of the first alloy substrate in a vacuum environment to obtain the first preform.

[0113] S12. The first preform is immersed in a passivation solution of the first alloy substrate for passivation treatment. Immersing the first preform in the passivation solution can at least coat the surface of the first alloy substrate not covered by the PVD layer with a uniform, dense, and highly smooth passivation layer; the above method can achieve surface corrosion protection for complex or delicate structures, including the inner surface of the first alloy substrate. When the frame portion has a hole structure or antenna slot, the inner wall of the hole structure and the surface of the antenna slot will also be covered with a uniform and dense passivation layer.

[0114] S13. Deposit a DLC film on the surface of the PVD layer of the first preform after passivation treatment.

[0115] Step S11

[0116] Specifically, in step S11, the pretreatment of the first alloy substrate before physical deposition includes polishing, which for ease of description is referred to as "substrate polishing". Substrate polishing includes:

[0117] 1) Based on the dimensions and specifications of the middle frame blank, write a suitable polishing program, especially for polishing the CNC machine tool marks and the outer surface of the first alloy substrate;

[0118] 2) Fix the middle frame blank on the polishing equipment and select a suitable diamond polishing paste;

[0119] 3) Fix the middle frame blank on the polishing equipment and polish it with polishing cloth wheel mixed with diamond polishing paste according to the pre-written program. For example, the polishing sequence can be to use sandpaper with a roughness of 6μm (3000 mesh) and sandpaper with a roughness of 3μm (8000 mesh) in sequence. Of course, the second substrate can be polished at the same time.

[0120] 4) After polishing, inspect the polished mid-frame blank, including checking for scratches, orange peel, pitting, or unevenness.

[0121] In step S11, the pretreated frame blank is placed in the coating chamber of the PVD coating equipment. During the deposition of the PVD layer, the base vacuum of the coating chamber is controlled to be 3 × 10⁻⁶. -3 Pa.

[0122] For step S11, in some embodiments of this application, the physical deposition uses a high-power pulsed power supply. High-power pulsed (HiPIMS) power supplies can increase the sputtering energy of the deposited particles. In other embodiments of this application, the physical deposition uses a radio frequency (RF) power supply and / or a mid-frequency magnetron sputtering power supply, as well as a high-power pulsed power supply. In some specific embodiments, the physical deposition uses a combination of RF power supply, high-power pulsed power supply, and mid-frequency power supply. This facilitates high-energy sputtering of deposited ions, effectively improving the density, corrosion resistance, and adhesion of the PVD layer. For example, the adhesion of the film layer on the first alloy substrate can be increased to 40N or higher.

[0123] In some embodiments of this application, during the physical deposition of the PVD layer, the discharge voltage of the high-power pulse power supply is controlled to be 500V-1000V, the pulse width to be 10μs-500μs, and the pulse frequency to be 40Hz-400Hz. In some embodiments of this application, the power of the intermediate frequency magnetron sputtering power supply is controlled to be 1kW-20kW. In some embodiments of this application, the power of the radio frequency power supply is controlled to be 1kW-20kW.

[0124] In some embodiments of this application, step S11, which involves physically depositing a PVD layer on the outer surface of the first alloy substrate under vacuum conditions, includes:

[0125] 1) Place the pre-treated frame blank into the coating chamber of the PVD coating equipment and evacuate to a pressure of 5×10⁻⁶. -3 The pressure is increased by 10 Pa to remove impurities and gases from the coating chamber; then argon gas is introduced into the coating chamber until the pressure inside the vacuum chamber is 2 × 10⁻⁶. -2 Pa, and turn on the ion source of the equipment for argon ion cleaning;

[0126] 2) Deposition of the first sublayer:

[0127] The background vacuum level is controlled at 3×10 -3 Pa, control the sample bias voltage to -40V to 250V, introduce argon and acetylene (argon to acetylene gas flow ratio of 7:3, unit is SCCM), the gas pressure is 2Pa-6Pa, and the sample temperature is controlled to be 50℃-150℃; then turn on the HiPIMS power supply, control its discharge voltage to be 500V-1000V, pulse width to be 10μs-500μs, pulse frequency to be 40Hz-400Hz, and the target material is one or more of Cr, Ti and Zr; in some specific embodiments, the intermediate frequency power supply is also turned on and controlled to be 70A-110A, and the target material is one or more of Cr, Al, Ti, Si, Zr and Ni; the thickness of the first sublayer is 0.1μm-2μm.

[0128] Deposition of the second sublayer:

[0129] The background vacuum level is controlled at 3×10 -3 Pa, control the sample bias voltage to -40V to 250V, introduce argon and acetylene (argon and acetylene gas flow ratio is 7:3, unit is SCCM), gas pressure is 2Pa-6Pa, control the sample temperature to 50℃-150℃.

[0130] Turn on the intermediate frequency power supply, controlling the current to 70A-100A, with the target material being one or more of Cr, C, Si, and Zr; simultaneously turn on the HiPIMS power supply, controlling its discharge voltage to 500V-1000V, pulse width to 10μs-500μs, pulse frequency to 40Hz-400Hz, and duty cycle to 1%-50%, with the corresponding target material being one or more of Cr, Al, Ti, Si, Zr, and Ni; turn on the radio frequency power supply, controlling the power to 2kW-5kW, with the corresponding target material being, for example, Al2O3 ceramic target and SiO2 quartz target; the thickness of the second sublayer is 0.1μm-6μm.

[0131] Deposition of the third sublayer:

[0132] The background vacuum level is controlled at 3×10 -1 Pa, control the sample bias voltage to -40V to 250V, introduce argon and acetylene (argon and acetylene gas flow ratio is 9:1, unit is SCCM), gas pressure is 2Pa-6Pa, control the sample temperature to 50℃-150℃.

[0133] When the second sublayer focuses on corrosion protection and the third sublayer focuses on high brightness and multi-color effects, the production conditions of the third sublayer can be appropriately relaxed to reduce the preparation cost. For example, in some embodiments, a medium-frequency power supply can be used alone when depositing the third sublayer, and the power of the medium-frequency power supply can be controlled to be 1kW-20kW. The target material can be selected according to the required appearance color to deposit and form the third sublayer. Specifically, the material of the third sublayer includes one or more of the following: second metal nitride, second metal oxide, second metal carbide, elemental Si, silicon oxide, silicon carbide, silicon nitride, and elemental carbon. The metal in the second metal nitride, the metal in the second metal oxide, and the metal in the second metal carbide independently include one or more of Cr, Al, Ti, Zr, and Ni. The thickness of the third sublayer is 0.1μm-3μm.

[0134] 3) Break the vacuum, remove the middle frame blank with the deposited PVD layer, and inspect it.

[0135] In some embodiments of this application, polishing is also performed on the PVD layer obtained by physical deposition; specifically, the thickness of the PVD layer is generally not intentionally reduced, which can also be called polishing.

[0136] Step S12

[0137] In some embodiments of this application, before immersing the first preform in the passivation solution, the first preform is further subjected to pretreatment; the pretreatment includes: ultrasonically rinsing the first preform with deionized water, then placing it in an aqueous solution of degreasing cleaning agent for a certain period of time, such as 5 minutes; after cleaning, it is repeatedly rinsed with deionized water and then dried.

[0138] For example, when the middle frame blank is an aluminum alloy middle frame blank, the aqueous solution of the degreasing cleaning agent may include the following components: 15 g / L sodium pyrophosphate (Na4P2O7), 8 g / L sodium carbonate (Na2CO3), 3 g / L sodium silicate (Na2O·nSiO2), 0.3 g / L disodium ethylenediaminetetraacetate, 3 g / L triethanolamine, and the balance being water.

[0139] In some embodiments of this application, the first preform is immersed in a passivation solution for passivation treatment, including:

[0140] The passivation solution is controlled at a pH of 2.8-3.8 and a temperature of 25℃-60℃, maintained for 10-30 minutes. The first preform is then immersed in the passivation solution and allowed to stand for 30-200 seconds. After standing, it is removed and suspended in air for 5-15 seconds, then placed in an oven (e.g., an electric forced-air drying oven) and dried at 60℃-80℃ for 20-40 minutes to form a passivation layer. This process facilitates the preparation of a uniform, dense, and appropriately thick passivation layer, which can stably adhere to the inner surface of the first alloy substrate. Furthermore, when the middle plate includes a second alloy substrate, and the material of the second alloy substrate is the same as or similar to that of the first alloy substrate, a passivation layer can also be formed on the surface of the second alloy substrate, achieving corrosion protection for the second alloy substrate. This improves the corrosion resistance of the middle frame. Specifically, the pH value of the passivation solution can be, for example, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, etc.; the temperature of the passivation solution can be, for example, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, etc.; and the standing time of the first preform in the passivation solution can be, for example, 30s, 40s, 50s, 80s, 100s, 120s, 150s, 180s, 200s, etc.

[0141] In some embodiments of this application, the passivation solution includes fluorozirconate, fluorozirconic acid, sodium fluoride, phosphoric acid, hydrochloric acid, and water. In some embodiments, the passivation solution also includes calcium nitrate. In some specific embodiments, the passivation solution includes the following components in the following amounts: 80 g / L-95 g / L Na₂ZrF₆, 11 g / L-25 g / L H₂ZrF₆, 20 g / L-32 g / L NaF, 110 g / L-130 g / L H₃PO₄, 40 g / L-55 g / L HCl, 35 g / L-55 g / L Ca(NO₃)₂, and water. The above passivation solution is beneficial for forming a uniform and dense passivation layer on the surface of aluminum alloys, and has a better anti-corrosion effect. Specifically, the passivation solution can be prepared by dissolving the passivation components in water, and the above process can be carried out in a passivation tank suitable for passivation treatment.

[0142] The following is a simple, exemplary explanation of the passivation mechanism of aluminum alloys:

[0143] 1) Activation process. The surface of aluminum alloys is generally covered with a natural oxide film. Under the action of an acidic passivation solution, this oxide film is dissolved, and simultaneously, the reduction by hydrogen or oxygen causes the aluminum alloy substrate to undergo activation and dissolution. The chemical reactions may include, for example:

[0144] Al-3e - →Al 3+ ;

[0145] O 2 +4H + +4e - →2H₂O, 2H + +2e - →H2.

[0146] 2) Passivation process. As the above reaction proceeds, the pH value at the aluminum alloy / passivation solution interface increases, and the components in the passivation solution react with the aluminum alloy to form a passivation layer; for example, the chemical reaction may include:

[0147] ZrF6 2- +4OH - →ZrO2·2H2O+6F - ;

[0148] Al 3+ +PO4 3- →AlPO4;

[0149] Al 3+ +3Na + +6F - →Na3AlF6;

[0150] Zr 4+ +2HPO42- →Zr(HPO4)2.

[0151] The following is a simplified explanation of the passivation mechanism of magnesium alloys in phosphoric acid-based passivation solutions:

[0152] 1) Activation process. Similarly, the surface of magnesium alloys is generally covered with a natural oxide film. Under the action of acidic passivation solution, the surface oxide film is dissolved, and the reduction by hydrogen or oxygen causes the magnesium alloy to undergo activation dissolution; the chemical reaction may include, for example:

[0153] Mg→Mg 2+ +2e - ;

[0154] O 2 +4e - +2H₂O→4OH⁻ - ,2H + +2e - →H2.

[0155] 2) Passivation process. As the above reaction proceeds, the pH value at the magnesium alloy / passivation solution interface increases, and the components in the passivation solution react with the magnesium alloy to form a passivation layer; for example, the chemical reaction may include:

[0156] Mg + H3PO4 → Mg3(PO4)2 + H2.

[0157] In some embodiments of this application, step S12 further includes polishing the passivated workpiece after passivation treatment; for ease of description, this is referred to as passivation polishing. Specifically, passivation polishing includes the following steps:

[0158] Based on the dimensions and specifications of the workpiece, write a suitable polishing program for the outer surface of the middle frame (including the outer side of the frame);

[0159] Fix the workpiece on the polishing equipment and select the appropriate diamond polishing paste;

[0160] The polishing equipment is used to polish the outer surface according to the program written above, with a polishing time of 15 seconds.

[0161] After polishing, the workpiece is visually inspected, including checking for scratches, orange peel texture, pitting, or unevenness.

[0162] It should be noted that the above-mentioned passivation polishing generally does not intentionally thin the passivation layer, and can also be called "polishing treatment". Understandably, since the material of the PVD layer is generally different from that of the first alloy substrate, the surface of the PVD layer generally does not form a passivation layer, but impurities may adhere to it. Therefore, it also includes performing the above-mentioned polishing treatment on the surface covered with the PVD layer; specifically, polishing treatment is performed on the PVD layer on the outer side of the first alloy substrate.

[0163] Step S13

[0164] In some embodiments of this application, after the passivation treatment described above is completed, a DLC film is deposited on the surface of the PVD layer.

[0165] Deposited DLC films include:

[0166] 1) Place the workpiece obtained in step S12 into the coating chamber of the coating equipment, and evacuate to a pressure of 5×10⁻⁶. -3 The pressure is increased by 10 Pa to remove impurities and gases from the coating chamber; then argon gas is introduced into the coating chamber until the pressure inside the vacuum chamber is 2 × 10⁻⁶. - 2 Pa, and turn on the ion source of the equipment for argon ion cleaning;

[0167] 2) Control the background vacuum level to 3×10 -1 Pa, control the sample bias voltage to -40V to 250V, introduce argon and acetylene (argon to acetylene gas flow ratio of 5:5, unit is SCCM), the gas pressure is 2Pa-6Pa, control the sample temperature to 50℃-150℃; turn on the intermediate frequency power supply, control the power to 1kW-5kW, the corresponding target material is carbon target; the film thickness of DLC film is 10nm-1000nm, to obtain the first preform;

[0168] 3) Break the vacuum, remove the first preform, and inspect it.

[0169] In some embodiments of this application, step S14 is included after step S13: forming an AF layer on the surface of the DLC film. The preparation of the AF layer includes:

[0170] 1) Place the workpiece obtained in step S13 into the coating chamber of the coating equipment, load it with AF pellets, and evacuate to a pressure of 5×10⁻⁶. -3 The pressure is increased to 2 × 10 Pa to remove impurities and gases from the coating chamber; then argon gas is introduced into the coating chamber until the pressure inside the chamber reaches 2 × 10 Pa. -2 Pa, and turn on the ion source of the equipment for argon ion cleaning;

[0171] 2) Open the evaporation barrier and begin AF deposition. The process parameters are: base vacuum degree of 5×10⁻⁶. -3Pa, the evaporation current is 150A-210A, the coating chamber temperature is 50℃; the thickness of the AF layer is 10nm-50nm.

[0172] 3) Break the vacuum, remove the middle frame, and inspect it.

[0173] In some specific embodiments of this application, before evaporating the AF, a transition layer is further prepared on the surface of the DLC film; specifically, step S14 includes:

[0174] 1) Place the workpiece obtained in step S13 into the coating chamber of the coating equipment, load it with AF pellets, and evacuate to a pressure of 5×10⁻⁶. -3 The pressure is increased to 2 × 10 Pa to remove impurities and gases from the coating chamber; then argon gas is introduced into the coating chamber until the pressure inside the chamber reaches 2 × 10 Pa. -2 Pa, and turn on the ion source of the equipment for argon ion cleaning;

[0175] 2) Preparation of the transition layer: The background vacuum in the coating cavity is controlled to be 3×10⁻⁶. -1 Pa, control the sample bias voltage to -40V to 250V, introduce argon and acetylene at a pressure of 2Pa to 6Pa, control the sample temperature to 50℃ to 150℃; turn on the RF power supply and control the power to 2kW to 5kW, and the corresponding target material can be, for example, Al2O3 and SiO2 target materials.

[0176] 3) Open the evaporation barrier and begin AF deposition. The process parameters are: base vacuum degree of 5×10⁻⁶. -3 Pa, the evaporation current is 150A-210A, the coating chamber temperature is 50℃; the thickness of the AF layer is 10nm-50nm.

[0177] 4) Break the vacuum, remove the middle frame, and inspect it. The middle frame surface is smooth, the Vickers hardness of the outer side of the frame is ≥1100HV, the adhesion between the film and the first alloy substrate is ≥40N, and after 1000 cycles of linear abrasion, the film is not worn through or peeled off. After 96 hours of neutral salt spray corrosion, the middle frame surface shows no pitting corrosion marks.

[0178] In some embodiments of this application, after step S12, an AF layer can be directly formed on the surface of the PVD layer. The fabrication process of the AF layer can be referred to the above description, and will not be repeated here.

[0179] Process Flow B

[0180] Please see Figure 13B In other embodiments of this application, forming a passivation layer on the inner surface of the first alloy substrate and forming a PVD layer on the outer surface includes:

[0181] S21. The first alloy substrate is pretreated, and then the middle frame blank is immersed in the passivation solution of the first alloy substrate for passivation treatment, forming a passivation layer on the surface of the first alloy substrate to obtain the second preform; it is understood that the entire surface of the first alloy substrate is covered with a passivation layer; similarly, when the middle plate includes the second alloy substrate, and the material of the second alloy substrate has the same or similar reactivity with the passivation solution as the first alloy substrate, the passivation treatment can also form a passivation layer on the surface of the second alloy substrate to achieve corrosion protection of the second alloy substrate;

[0182] The pretreatment in step S21 includes sequential substrate polishing and degreasing cleaning. For substrate polishing, please refer to the relevant description in step S11 above. The degreasing cleaning includes: ultrasonically rinsing the middle frame blank with deionized water, then immersing it in a degreasing cleaning agent solution for a certain duration, such as 5 minutes; after cleaning, repeatedly rinsing with deionized water and then drying. For the relevant process parameters and passivation solution in step S21, please refer to the description in step S13 above, and will not be repeated here.

[0183] In some embodiments of this application, after passivation treatment, the passivation layer of the second preform is further subjected to passivation polishing treatment. The specific polishing process can be found in the previous description of passivation polishing, and will not be repeated here. At this time, the thickness of the passivation layer on the inner side of the frame is not intentionally reduced. In some cases, the passivation layer on the outer side of the frame can be removed, in which case the subsequently physically deposited PVD layer is stacked on the first alloy substrate. In other cases, only the passivation layer on the outer side of the frame can be polished. This application does not impose any particular limitation on this.

[0184] S22. Place the second preform in a vacuum environment and physically deposit a PVD layer on its outer surface; for the specific process of physically depositing the PVD layer, please refer to the relevant description in step S11 above, which will not be repeated here.

[0185] S23. Deposit a diamond-like carbon (DLC) film on the surface of the PVD layer. The preparation of the diamond-like carbon film can be found in the relevant description in step S13 above, and will not be repeated here.

[0186] In some embodiments, an AF layer is formed on the surface of the diamond-like carbon (DLC) film. Alternatively, a transition layer and an AF layer are sequentially formed on the surface of the DLC film. For details, please refer to the preceding descriptions regarding the preparation of the DLC film and the AF layer.

[0187] Please continue reading Figure 1This application also provides an electronic device 100, including a display module 2 and a middle frame 1 fixedly connected to the display module 2; wherein, the middle frame 1 is the aforementioned middle frame 1 provided in this application embodiment, or, the middle frame 1 is prepared by the aforementioned middle frame preparation method provided in this application embodiment.

[0188] The electronic device 100 provided in this application embodiment has superior corrosion resistance, strong wear resistance of its appearance parts, and can have a colorful appearance with high gloss, thus possessing high market competitiveness.

[0189] In some embodiments of this application, the electronic device 100 includes, but is not limited to, consumer electronic products such as mobile phones, tablets, and watches. Figure 1 This is just an example drawing method. Figure 1 The type, appearance, and size of the electronic devices shown do not constitute a limitation on this application.

[0190] It should be understood that the use of the terms "first," "second," and various numerical designations in this document is merely for descriptive convenience and is not intended to limit the scope of this application.

[0191] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after it are in an "or" relationship.

[0192] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0193] In this application, "-" indicates a range value, including the endpoint values ​​at both ends. For example, the value of a can be 0.5-15, meaning that the value of a can be between 0.5 and 15, and includes the endpoint values ​​of 0.5 and 15.

[0194] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

Claims

1. A middle frame, characterized in that, The mid-frame is used in electronic devices; the mid-frame includes a frame and a mid-plate, the frame is fixedly connected to the periphery of the mid-plate and forms a receiving space; the frame includes a first alloy substrate; The first alloy substrate includes an adjacent inner side and an outer side, the inner side being disposed facing the receiving space and the outer side being disposed away from the receiving space; A passivation layer is stacked on the inner side surface; A PVD layer is provided on the outer surface.

2. The middle frame according to claim 1, characterized in that, The frame has a hole structure, and the inner wall of the hole structure is covered with the passivation layer.

3. The middle frame according to claim 1 or 2, characterized in that, The frame is provided with an antenna slot, which is filled with plastic; the passivation layer is provided between the plastic and the first alloy substrate.

4. The middle frame according to any one of claims 1-3, characterized in that, The outer surface is curved. Alternatively, the outer surface includes a first surface, a second surface, and a third surface; the third surface connects the first surface and the second surface, and the first surface and the second surface are respectively adjacent to the inner surface; the first surface, the second surface, and the third surface are independently flat surfaces or curved surfaces.

5. The middle frame according to claim 4, characterized in that, The PVD layer is formed on the area where the inner side and the outer side are adjacent.

6. The middle frame according to any one of claims 1-5, characterized in that, The passivation layer covers all surfaces of the first alloy substrate that are not covered by the PVD layer.

7. The structural component according to any one of claims 1-6, characterized in that, The passivation layer has a thickness of 10nm-1000nm; the material of the passivation layer includes metal salts, or includes metal salts and organic matter.

8. The middle frame according to any one of claims 1-7, characterized in that, The material of the PVD layer includes one or more of the following: elemental metals, oxides, nitrides, nitrogen oxides, carbides, and nitrogen carbides.

9. The structural component according to any one of claims 1-8, characterized in that, The PVD layer includes multiple sub-layers; the multiple sub-layers include a first sub-layer, a second sub-layer, and a third sub-layer stacked sequentially. The first sublayer is disposed close to the first alloy substrate, and the material of the first sublayer includes one or more of Cr, Al, Ti, Si, Zr, and Ni; the thickness of the first sublayer is 0.1 μm-2 μm; and / or, The material of the second sublayer includes one or more of the following: a first metal nitride, a first metal oxide, a first metal carbide, elemental Si, silicon oxide, silicon carbide, silicon nitride, and elemental carbon; the metal in the first metal nitride, the metal in the first metal oxide, and the metal in the first metal carbide independently includes one or more of Cr, Al, Ti, Zr, and Ni; the thickness of the second sublayer is 0.1 μm-6 μm; and / or, The material of the third sublayer includes one or more of the following: a second metal nitride, a second metal oxide, a second metal carbide, elemental Si, silicon oxide, silicon carbide, silicon nitride, and elemental carbon; the metal in the second metal nitride, the metal in the second metal oxide, and the metal in the second metal carbide independently include one or more of Cr, Al, Ti, Zr, and Ni; the thickness of the third sublayer is 0.1 μm-3 μm.

10. The structural member according to any one of claims 1-9, characterized in that, The thickness of the PVD layer is 2μm-10μm.

11. The middle frame according to any one of claims 1-10, characterized in that, A diamond-like carbon film is disposed on the surface of the PVD layer away from the first alloy substrate; the thickness of the diamond-like carbon film is 10nm-1000nm.

12. The middle frame according to claim 11, characterized in that, The diamond-like carbon film has an anti-fingerprint layer on the side facing away from the first alloy substrate; the thickness of the anti-fingerprint layer is 10nm-50nm.

13. The structural component according to claim 12, characterized in that, A transition layer is also provided between the anti-fingerprint layer and the diamond-like carbon film; The transition layer is made of a third metal nitride, a third metal oxide, a third metal carbide, an oxide of silicon, a nitride of silicon, or an oxide nitride of silicon; the metals in the third metal nitride, the third metal oxide, and the third metal carbide independently include Al and / or Cr; The thickness of the transition layer is 5nm-1000nm.

14. The middle frame according to any one of claims 1-13, characterized in that, The first alloy substrate is made of aluminum alloy and / or magnesium alloy.

15. The middle frame according to any one of claims 1-14, characterized in that, The middle frame has a neutral salt spray corrosion resistance time of ≥96h; and / or, the adhesion of the film layer on the surface of the first alloy substrate is ≥40N.

16. The middle frame according to any one of claims 1-15, characterized in that, The outer surface of the frame has a Vickers hardness ≥1100HV; And / or, the linear wear resistance of the outer surface of the frame is ≥1000 cycles; And / or, the surface roughness Ra of the outer side of the frame is <0.08 μm; And / or, the gloss level of the outer surface of the frame is ≥700 GU.

17. A method for preparing a middle frame, characterized in that, include: A middle frame blank is provided, the middle frame blank including a middle plate portion and a frame portion formed by a first alloy substrate, the frame portion being fixedly connected to the middle plate portion and forming a receiving space; The first alloy substrate includes an adjacent inner side and an outer side; the inner side is disposed facing the receiving space, and the outer side is disposed away from the receiving space; A passivation layer is formed on the inner surface, and a PVD layer is formed on the outer surface.

18. The preparation method according to claim 17, characterized in that, The step of forming a passivation layer on the inner surface and forming a PVD layer on the outer surface includes: (1) The first alloy substrate is pretreated, and then the PVD layer is physically deposited on the outer surface in a vacuum environment to obtain the first preform; The first preform is immersed in the passivation solution of the first alloy substrate for passivation treatment, and then a diamond-like carbon film is deposited on the surface of the PVD layer. or, (2) The first alloy substrate is pretreated, and then the middle frame blank is immersed in the passivation liquid of the first alloy substrate for passivation treatment to form a passivation layer on the surface of the first alloy substrate to obtain the second preform. The second preform is placed in a vacuum environment, and the PVD layer is physically deposited on the outer surface. A diamond-like carbon film is deposited on the surface of the PVD layer.

19. The preparation method according to claim 17 or 18, characterized in that, The physical deposition is performed using a high-power pulsed power supply; or, the power supply is an RF power supply and / or a mid-frequency magnetron sputtering power supply, as well as a high-power pulsed power supply. The high-power pulse power supply has a discharge voltage of 500V-1000V, a pulse width of 10-500μs, and a pulse frequency of 40Hz-400Hz; the medium-frequency magnetron sputtering power supply has a power of 1kW-20kW; and the radio frequency power supply has a power of 1kW-20kW.

20. An electronic device, characterized in that, It includes a display module and a mid-frame fixedly connected to the display module; the mid-frame is as described in any one of claims 1-16, or the mid-frame is prepared by the method described in any one of claims 17-19.

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