Metal-plastic composite shell, preparation method thereof and electronic equipment

Abstract

The invention provides a metal-plastic composite shell, a preparation method thereof and electronic equipment, and relates to the technical field of electronic product shells. The metal-plastic composite shell comprises: a metal shell layer, the inner side of which forms an accommodating space with a top opening; the soft rubber shell layer covers the first surface, deviating from the accommodating space, of the metal shell layer; and the hard rubber shell layer covers the second surface, deviating from the metal shell layer, of the soft rubber shell layer. The preparation method comprises the following steps: preparing and forming the soft rubber shell layer on the first surface of the metal shell layer through a first insert injection molding process; and preparing and forming a hard rubber shell layer on the second surface of the soft rubber shell layer through a second insert injection molding process. According to the scheme, the problem that the outer hard rubber shell layer cracks due to thermal stress during injection molding production or in the subsequent use process can be effectively solved.

Description

Technical Field

[0001] This invention relates to the field of electronic product casing technology, and in particular to a metal-plastic composite casing and its preparation method, as well as electronic devices. Background Technology

[0002] High-power electronic devices, such as high-power fast chargers, generate a large amount of unevenly distributed heat during operation from their core power components. If this heat cannot be effectively and quickly dissipated, it will not only significantly reduce the reliability and lifespan of the components but also lead to uneven internal temperature distribution, severely limiting the device's performance. To meet heat dissipation requirements, these devices are increasingly choosing to use metal casings instead of traditional plastic casings. The high thermal conductivity of metal allows it to quickly absorb heat from inside the device and evenly diffuse and conduct it across the entire casing surface, thereby dissipating it to the external environment.

[0003] However, while the exposed metal casing is highly durable, it is also easily scratched and prone to irreversible dents from impacts or drops, affecting the product's appearance and safety. Therefore, some composite casings integrating metal and plastic have emerged on the market. These are created using an insert molding process, where a rigid plastic layer is coated over the metal casing.

[0004] Direct injection molding of a rigid plastic shell onto a metal shell, especially when a large area of ​​metal is present, can lead to significant stress between the rigid plastic and metal layers due to the difference in shrinkage rates between the metal and plastic. This makes the rigid plastic layer highly susceptible to cracking, or even complete rupture, reducing product yield. Even if cracking does not occur during injection molding, the resulting composite shell is highly prone to cracking and damage during subsequent use under external forces (such as drops or impacts). Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a metal-plastic composite shell and its preparation method, as well as an electronic device, to solve the problem of how to avoid cracking of the outer hard plastic layer of the metal-plastic composite shell due to stress.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A first aspect of the present invention is to provide a metal-plastic composite housing, comprising: A metal shell, the inner side of which forms an open-top receiving space; A soft rubber shell layer, which covers the first surface of the metal shell layer that is away from the receiving space; A hard plastic shell layer, which covers the second surface of the soft plastic shell layer opposite to the metal shell layer.

[0007] In an alternative embodiment, at the location corresponding to the top opening, the rigid shell layer has a first extension bent toward the first surface, the first extension being connected to the first surface to close the soft shell layer.

[0008] In an optional embodiment, at least one through hole is provided on the bottom wall and / or the four side walls of the metal-plastic composite shell, and the through hole sequentially penetrates the hard plastic shell layer, the soft plastic shell layer and the metal shell layer and communicates with the receiving space.

[0009] In an alternative embodiment, at the location corresponding to the through hole, the rigid shell layer has a second extension bent toward the first surface, the second extension being connected to the first surface to close the soft shell layer.

[0010] In an optional embodiment, the second surface is provided with a recess, and the hard plastic shell layer has a protrusion that is embedded in the recess.

[0011] In an alternative embodiment, the recessed hole penetrates the soft rubber shell layer in a direction perpendicular to the second surface, and the end of the protrusion is connected to the first surface.

[0012] In optional embodiments, the thickness of the metal shell layer is 0.3 mm to 1.5 mm; and / or, the thickness of the soft rubber shell layer is 0.5 mm to 1.5 mm; and / or, the thickness of the hard rubber shell layer is 0.5 mm to 1.5 mm.

[0013] In optional embodiments, the metal shell layer is made of aluminum alloy, magnesium alloy, or stainless steel; and / or, the soft plastic shell layer is made of one or more of transparent silicone, TPE, and TPU; and / or, the hard plastic shell layer is made of one or more of transparent PMMA, ABS, and PC.

[0014] A second aspect of the present invention is to provide a method for preparing the metal-plastic composite shell as described above, comprising: Provide the metal shell layer; Using soft rubber material as the injection molding material and the metal shell layer as the insert, the soft rubber shell layer is prepared through a first insert injection molding process to obtain an intermediate injection molded product. Using a rigid plastic material as the injection molding material and the intermediate injection molded product as an insert, the rigid plastic shell layer is formed through a second insert injection molding process to obtain the metal-plastic composite shell.

[0015] A third aspect of the present invention is to provide an electronic device comprising, as described above, a metal-plastic composite housing, a plastic inner layer support disposed within the receiving space, and electronic components disposed on the plastic inner layer support.

[0016] The present invention provides a metal-plastic composite shell, its preparation method, and an electronic device. The metal-plastic composite shell includes a metal shell layer, a soft plastic shell layer, and a hard plastic shell layer arranged sequentially from the inside to the outside. By setting a soft plastic shell layer between the inner metal shell layer and the outer hard plastic shell layer, the stress caused by the difference in shrinkage rate between the metal shell layer and the hard plastic shell layer is absorbed based on the deformation characteristics of the soft plastic shell layer. This effectively avoids the problem of cracking of the outer hard plastic shell layer due to thermal stress during injection molding or subsequent use. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a metal-plastic composite shell according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of a metal-plastic composite shell according to an embodiment of the present invention; Figure 3 For example Figure 2 An enlarged schematic diagram of part A in the diagram; Figure 4 This is a partially enlarged view of the interface between the hard plastic shell layer and the soft plastic shell layer in one embodiment of the present invention. Figure 5 This is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention; Figure 6 This is a cross-sectional view of an electronic device according to an embodiment of the present invention.

[0018] Explanation of icon numbers: 1. Metal shell; 11. Receiving space; 12. First surface; 2. Soft plastic shell; 21. Recessed hole; 22. Second surface; 3. Hard plastic shell; 31. First extension; 32. Second extension; 33. Protrusion; 4. Through hole; 100. Metal-plastic composite shell; 200. Plastic inner support; 300. Electronic component. Detailed Implementation

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. In the following description, the expression "some embodiments" refers to a subset of all possible embodiments; however, it should be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments and can be combined with each other without conflict.

[0020] It should also be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "inner," "outer," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0021] See Figure 1 and Figure 2 An embodiment of the present invention provides a metal-plastic composite shell 100, which mainly includes a metal shell layer 1, a soft plastic shell layer 2, and a hard plastic shell layer 3. The metal shell layer 1, the soft plastic shell layer 2, and the hard plastic shell layer 3 are arranged sequentially from the inside to the outside. The inner side of the metal shell layer 1 forms a top-opening receiving space 11. The soft plastic shell layer 2 covers a first surface 12 of the metal shell layer 1 that is opposite to the receiving space 11, and the hard plastic shell layer 3 covers a second surface 22 of the soft plastic shell layer 2 that is opposite to the metal shell layer 1.

[0022] The metal-plastic composite housing 100 described in the above embodiment is mainly used as the housing of electronic devices. By setting a soft plastic housing 2 between the inner metal housing layer 1 and the outer hard plastic housing layer 3, the soft plastic housing layer 2 absorbs the stress caused by the difference in shrinkage rate between the metal housing layer 1 and the hard plastic housing layer 3 based on the deformation characteristics of the soft plastic housing layer 2. This can effectively avoid the problem of cracking of the outer hard plastic housing layer 3 due to thermal stress during injection molding or subsequent use.

[0023] As a preferred solution, such as Figure 2 As shown, at the position corresponding to the top opening, the hard plastic shell layer 3 has a first extension 31 bent toward the first surface 12 of the metal shell layer 1. The first extension 31 is connected to the first surface 12 to seal the soft plastic shell layer 2. That is, viewed from the outside of the metal-plastic composite shell 100, the soft plastic shell layer 2 is completely sealed between the metal shell layer 1 and the hard plastic shell layer 3. By forming the first extension 31 to seal the soft plastic shell layer 2, the soft material of the soft plastic shell layer 2 can be prevented from having an exposed surface on the surface of the metal-plastic composite shell 100, thereby overcoming the defects of the soft plastic shell layer 2 such as easy wear, easy aging, and poor texture.

[0024] In some alternative solutions, such as Figure 2As shown, at least one through hole 4 is provided on the bottom wall and / or the four side walls of the metal-plastic composite housing 100. The through hole 4 sequentially penetrates the hard plastic shell layer 3, the soft plastic shell layer 2, and the metal shell layer 1 and connects to the receiving space 11. By providing the through hole 4, it is convenient for the electronic device using the metal-plastic composite housing 100 to connect with other electronic devices. For example, the through hole 4 can be a charging port, through which the electronic device can be connected to an external power source via a charging cable, and charged by the external power source; or, the electronic device can be connected to other electronic devices via the through hole 4 via a charging cable, and used as a power source to charge other electronic devices.

[0025] As a preferred solution, such as Figure 2 As shown, at the position corresponding to the through hole 4, the hard plastic shell layer 3 has a second extension 32 bent toward the first surface 12 of the metal shell layer 1. The second extension 32 is connected to the first surface 12 to seal the soft plastic shell layer 2. Similar to the first extension 31, by providing the second extension 32, the soft plastic shell layer 2 is prevented from having an exposed portion at the position of the through hole 4, thereby overcoming the problems of easy wear and aging of the soft plastic shell layer 2. In particular, when the through hole 4 is used as a charging plug interface, it involves the frequent plugging and unplugging of the charging connection cable. If the soft plastic shell layer 2 has an exposed portion at the position of the through hole 4, it is very easy for the soft plastic shell layer 2 to wear and be damaged.

[0026] In some alternative solutions, the metal shell 1 can be made of aluminum alloy, magnesium alloy or stainless steel, with lighter aluminum alloy or magnesium alloy being preferred, thereby reducing the overall weight of the shell.

[0027] In some alternative solutions, both the soft plastic shell layer 2 and the hard plastic shell layer 3 are made of transparent materials, for example, materials with a light transmittance of over 90%. Thus, the metal-plastic composite shell 100 can visually represent the shape, structure, and color of the first surface 12 of the metal shell layer 1, maintaining the aesthetic appeal of the metallic surface. Furthermore, the first surface 12 of the metal shell layer 1 can be further treated with surface anodizing, spraying, electroplating, or other surface treatment processes to enhance its texture, making the metal-plastic composite shell 100 more aesthetically pleasing and improving product competitiveness.

[0028] Specifically, the material of the soft outer shell layer 2 can be selected from one or more of transparent silicone, TPE (Thermoplastic Elastomer), and TPU (Thermoplastic Polyurethane). The material of the hard outer shell layer 3 can be selected from one or more of transparent PMMA (Polymethyl Methacrylate), ABS (acrylonitrile-butadiene-styrene copolymer), and PC (Polycarbonate).

[0029] Among the alternative options, see [link / reference] Figure 2 and Figure 3 The thickness D1 of the metal shell layer 1 is preferably set to 0.3 mm to 1.5 mm. The thickness D2 of the soft rubber shell layer 2 is preferably set to 0.5 mm to 1.5 mm. The thickness D3 of the hard rubber shell layer 3 is preferably set to 0.5 mm to 1.5 mm.

[0030] As a preferred embodiment, within the thickness range described above, the thickness D3 of the hard plastic shell layer 3, the thickness D2 of the soft plastic shell layer 2, and the thickness D1 of the metal shell layer 1 are set in a ratio of 2:(0.8~1.2):(0.5~1), that is, D3:D2:D1 is 2:(0.8~1.2):(0.5~1).

[0031] In a more preferred embodiment, D3:D2:D1 is 2:1:(0.5~1), for example, 2:1:0.5, 2:1:0.8, or 2:1:1. High and low temperature thermal shock tests and drop tests show that within this thickness ratio range, the metal-plastic composite shell 100 exhibits superior crack prevention performance.

[0032] Among the alternative options, see [link / reference] Figure 4 The second surface 22 of the soft rubber shell layer 2 is provided with a recess 21, and the hard rubber shell layer 3 has a protrusion 33 that is embedded in the recess 21. By providing a structure with a concave-convex interlocking structure at the connection interface between the soft rubber shell layer 2 and the hard rubber shell layer 3, the bonding force between the soft rubber shell layer 2 and the hard rubber shell layer 3 is improved.

[0033] As a preferred solution, such as Figure 4 As shown, the concave hole 21 penetrates the soft rubber shell layer 2 in a direction perpendicular to the second surface 22, and the end of the protrusion 33 is connected to the first surface 12 of the metal shell layer 1.

[0034] The width L of the recess 21 is preferably set to 1mm to 2mm. The recess 21 can be, for example, circular or square. Specifically, the width L refers to the lateral dimension of the recess 21 on the outer surface of the soft shell layer 2. For example, when the recess 21 is circular, the width L can be understood as the diameter of the recess; when the recess 21 is square, the width L can be understood as the length and width of the recess. Within the range of the width L described above, while improving the bonding strength between the soft shell layer 2 and the hard shell layer 3, it avoids the obvious outline of the recess 21 being visible from the outside of the shell, thus preventing a reduction in the overall aesthetics of the shell.

[0035] Based on the metal-plastic composite shell 100 provided in the above embodiments, this embodiment of the invention also provides a method for preparing the metal-plastic composite shell 100. Combined with... Figures 1 to 4 As shown, the preparation method includes the following steps: Step S1: Provide the metal shell 1.

[0036] The material of the metal shell 1 can be aluminum alloy, magnesium alloy or stainless steel.

[0037] In an optional embodiment, the metal shell 1 can be prepared by forming a metal sheet of the corresponding material through a stamping process, or it can be prepared by forming a metal block of the corresponding material through machining.

[0038] Furthermore, the first surface 12 of the metal shell layer 1 can be further subjected to surface treatment processes such as surface anodizing, sandblasting, spraying, and electroplating to enhance its texture.

[0039] Step S2: Using soft rubber material as the injection molding material and the metal shell layer 1 as the insert, the soft rubber shell layer 2 is formed through the first insert injection molding process to obtain the intermediate injection molded product.

[0040] In step S2, the soft plastic shell layer 2 is obtained by injection molding the first surface 12 of the metal shell layer 1 through the first insert injection molding process. That is, the soft plastic shell layer 2 covers the first surface 12 of the metal shell layer 1 that is away from the accommodating space 11.

[0041] The soft adhesive material is preferably a transparent material, for example, a material with a light transmittance of 90% or higher. Specifically, the soft adhesive material can be selected from one or more of transparent silicone, TPE, and TPU. The hardness of the soft adhesive material is preferably 30A to 70A.

[0042] In some specific solutions, during the first insert injection molding process, after the metal shell layer 1 is placed into the corresponding mold, it is preheated before injection molding to ensure better interfacial bonding between the injection-molded soft plastic shell layer 2 and the metal shell layer 1. Specifically, when the soft plastic material is silicone, the preheating temperature of the metal shell layer 1 is 150℃~180℃, and the injection molding temperature is 160℃~200℃. When the soft plastic material is TPE or TPU, the preheating temperature of the metal shell layer 1 is 20℃~60℃, and the injection molding temperature is 160℃~220℃.

[0043] In some specific solutions, during the first insert injection molding process, the injection molding equipment requires segmented temperature control. The injection molding equipment includes a barrel and a nozzle. The barrel is typically divided into a feeding section (rear feeding zone), a compression section (middle plasticizing zone), and a metering section (rear homogenizing zone). The temperatures of each section need to work synergistically to achieve efficient plasticization. Taking TPE material as an example, the feeding section temperature is relatively low, which can be set to 120℃~140℃. Its main function is to promote smooth material transport and prevent the raw material from melting too early at the barrel inlet, resulting in poor feeding. The compression section temperature gradually increases, which can be set to 150℃~180℃. Through the shearing action of the screw, plasticization and melt mixing are enhanced. The metering section temperature remains stable, which can be set to 180℃~220℃ to ensure uniform plasticization of the melt. The nozzle temperature needs to smoothly connect with the barrel temperature, generally slightly lower than the highest barrel temperature (a difference of about 5°C~10°C), to avoid melt drooling or nozzle blockage.

[0044] Step S3: Using a hard plastic material as the injection molding material and the intermediate injection molded product as the insert, the hard plastic shell layer 3 is formed through a second insert injection molding process to obtain the metal-plastic composite shell 100.

[0045] In step S3, the hard plastic shell layer 3 is obtained by injection molding the second surface 22 of the soft plastic shell layer 2 through a second insert injection molding process. That is, the hard plastic shell layer 3 covers the second surface 22 of the soft plastic shell layer 2 that is away from the metal shell layer 1.

[0046] The rigid adhesive material is preferably a transparent material, for example, a material with a light transmittance of 90% or higher. Specifically, the rigid adhesive material can be selected from one or more of transparent PMMA, ABS, and PC.

[0047] In some specific solutions, similar to the first insert injection molding process, the second insert injection molding process requires segmented temperature control of the injection molding equipment. Taking PC material as an example, the feeding section temperature can be set to 260℃~280℃, the compression section temperature to 280℃~300℃, the metering section temperature to 290℃~300℃, and the nozzle temperature to 280℃~295℃. It is particularly important to note that the melt temperature should be ≤310℃ and the residence time ≤5min to avoid degradation and yellowing.

[0048] In the manufacturing process of the above embodiment, the soft plastic shell layer 2 is injection molded first, followed by the hard plastic shell layer 3, and the molding temperature of the hard plastic shell layer 3 is higher than that of the soft plastic shell layer 2. Therefore, in order for the soft plastic shell layer 2 to achieve a good intermediate buffering function and resist the high-temperature thermal shock during the subsequent injection molding of the hard plastic shell layer 3, the manufacturing process can be optimized in the following aspects in a preferred embodiment: I. The material of the soft rubber shell layer 2 is preferably one of the following two types of materials: 1. High-temperature vulcanizing silicone: It is vulcanized at 160℃~200℃ during the first insert injection molding, and the molecular structure changes from linear cross-linking to three-dimensional network, forming a surface inert and thermally stable elastic layer, thereby preventing yellowing due to heat during subsequent hard plastic injection molding.

[0049] 2. High-temperature resistant thermoplastic elastomers: Specialty models with short-term peak temperatures exceeding 200°C can be selected, such as DuPont Hytrel® 5556 (TPEE) or Covestro Texin® RTX 95A (polyether-based TPU). These materials maintain structural stability under the instantaneous high temperatures during subsequent injection molding of the rigid shell layer 3, avoiding discoloration or performance degradation caused by thermal degradation.

[0050] 2. After the soft rubber shell layer 2 is injection molded, its cooling time is extended to allow for full curing (e.g., the cooling time is extended from the conventional 15 seconds to 30 seconds or longer, depending on the thickness of the rubber layer and the material). After the soft rubber shell layer 2 has completely cooled and its dimensions have stabilized, the hard rubber shell layer 3 is then injection molded. This process interval ensures that the soft rubber shell layer 2 possesses sufficient structural strength and thermal stability before being subjected to the high temperatures of the second insert injection molding process.

[0051] Third, during the injection molding process of the hard plastic shell layer 3, the mold temperature is controlled within the range of 90℃~110℃. Multi-stage temperature control is employed during injection molding: the highest temperature is used only in the injection stage to ensure melt flowability, and a rapid injection method (e.g., injection time controlled within 5 seconds) is used to reduce the heat treatment time; after entering the holding pressure stage, the barrel temperature is reduced by approximately 30%, and the holding pressure time is controlled within 8~15 seconds; in the cooling stage, a lower temperature is maintained, and the holding pressure time is controlled within 25~30 seconds for sufficient cooling. Based on the above injection molding process, while ensuring the quality of the hard plastic molding, damage to the soft plastic layer due to prolonged exposure to high temperatures is effectively avoided.

[0052] Fourth, in the design of the injection mold for the hard plastic shell layer 3, the hard plastic shell layer 3 is arranged to directly contact the surface of the metal shell layer 1 at the port end to achieve a seal, for example... Figure 2 In the structure shown, the hard plastic shell layer 3 has a first extension 31 and a second extension 32 that abuts against the first surface 12 of the metal shell layer 1. This structural design allows the cavity pressure to be borne by the metal shell layer 1 and the mold during injection molding of the hard plastic shell layer 3, rather than entirely by the soft plastic shell layer 2, thereby structurally avoiding the risk that the injection pressure may cause deformation of the soft plastic shell layer 2.

[0053] Based on the metal-plastic composite housing 100 provided in the above embodiments, this invention also provides an electronic device, see below. Figure 5 and Figure 6 The electronic device mainly includes a metal-plastic composite housing 100, a plastic inner support 200, and an electronic component 300 provided in any of the foregoing embodiments of the present invention. The plastic inner support 200 is disposed within the receiving space 11 of the metal-plastic composite housing 100, and the electronic component 300 is disposed on the plastic inner support 200.

[0054] In some specific embodiments, the electronic device is, for example, a charger.

[0055] In some alternative embodiments, the plastic inner layer support 200 may be directly formed within the metal-plastic composite shell 100 by insert injection molding; or the plastic inner layer support 200 may be prepared separately first, and then assembled into the metal-plastic composite shell 100.

[0056] As described in the above embodiment, when the internal electronic component 300 generates heat, it first releases heat outward through the inner plastic support 200, and then dissipates heat to the outside through the metal-plastic composite shell 100. The metal shell layer 1 in the metal-plastic composite shell 100 has excellent thermal conductivity, allowing heat to dissipate quickly and evenly laterally, and then dissipate heat outward through the entire shell surface, resulting in a decrease in the overall product temperature and preventing localized overheating or melting. By employing the metal-plastic composite shell 100 provided in this embodiment, rapid heat dissipation is achieved while ensuring a more uniform surface temperature, thus improving the user experience.

[0057] In summary, the metal-plastic composite shell, its preparation method, and the electronic device provided by the embodiments of the present invention, by setting a soft plastic shell layer between the inner metal shell layer and the outer hard plastic shell layer, absorbs the stress caused by the difference in shrinkage rates between the metal shell layer and the hard plastic shell layer based on the deformation characteristics of the soft plastic shell layer. This effectively avoids the problem of cracking of the outer hard plastic shell layer due to thermal stress during injection molding or subsequent use. Specifically, the composite structure of metal-soft plastic-hard plastic arranged sequentially from the inside out provides excellent heat dissipation performance of the innermost metal shell layer, allows the middle soft plastic shell layer to focus on its core functions of elasticity, buffering, and stress absorption, thus protecting the interface between the metal and the hard plastic, and the outermost hard plastic shell layer, as a protective layer, provides a wear-resistant, scratch-resistant, and high-quality appearance, while ensuring the structural rigidity and dimensional accuracy of the final product.

[0058] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A metal-plastic composite shell, characterized in that, include: A metal shell, the inner side of which forms an open-top receiving space; A soft rubber shell layer, which covers the first surface of the metal shell layer that is away from the receiving space; A hard plastic shell layer, which covers the second surface of the soft plastic shell layer opposite to the metal shell layer.

2. The metal-plastic composite shell according to claim 1, characterized in that, At the location corresponding to the top opening, the hard plastic shell layer has a first extension that bends toward the first surface and is connected to the first surface to close the soft plastic shell layer.

3. The metal-plastic composite shell according to claim 1, characterized in that, At least one through hole is provided on the bottom wall and / or the four side walls of the metal-plastic composite shell. The through hole passes through the hard plastic shell layer, the soft plastic shell layer and the metal shell layer in sequence and communicates with the receiving space.

4. The metal-plastic composite shell according to claim 3, characterized in that, At the location corresponding to the through hole, the hard plastic shell layer has a second extension bent toward the first surface, the second extension being connected to the first surface to close the soft plastic shell layer.

5. The metal-plastic composite shell according to claim 1, characterized in that, The second surface is provided with a recess, and the hard plastic shell layer has a protrusion that is embedded in the recess.

6. The metal-plastic composite shell according to claim 5, characterized in that, The concave hole penetrates the soft rubber shell layer in a direction perpendicular to the second surface, and the end of the protrusion is connected to the first surface.

7. The metal-plastic composite shell according to any one of claims 1-6, characterized in that, The thickness of the metal shell layer is 0.3 mm to 1.5 mm; and / or, the thickness of the soft rubber shell layer is 0.5 mm to 1.5 mm; and / or, the thickness of the hard rubber shell layer is 0.5 mm to 1.5 mm.

8. The metal-plastic composite shell according to claim 7, characterized in that, The metal shell is made of aluminum alloy, magnesium alloy or stainless steel; and / or the soft shell is made of one or more of transparent silicone, TPE and TPU; and / or the hard shell is made of one or more of transparent PMMA, ABS and PC.

9. A method for preparing a metal-plastic composite shell as described in any one of claims 1-8, characterized in that, include: Provide the metal shell layer; Using soft rubber material as the injection molding material and the metal shell layer as the insert, the soft rubber shell layer is prepared through a first insert injection molding process to obtain an intermediate injection molded product. Using a rigid plastic material as the injection molding material and the intermediate injection molded product as an insert, the rigid plastic shell layer is formed through a second insert injection molding process to obtain the metal-plastic composite shell.

10. An electronic device, characterized in that, include: The metal-plastic composite housing as described in any one of claims 1-8; A plastic inner layer support is disposed within the accommodating space; Electronic components mounted on the inner plastic support.

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