Electronic equipment shell and manufacturing method thereof

Abstract

The invention discloses an electronic equipment shell and a manufacturing method thereof. The manufacturing method comprises the following steps: manufacturing a magnesium alloy frame; manufacturing an aluminum alloy middle plate; the magnesium alloy frame and the aluminum alloy middle plate are fixedly connected through brazing in a vacuum environment to form a magnesium / aluminum complex; a plastic structure is formed on the magnesium / aluminum composite through injection molding; and the electronic equipment shell is formed through CNC machining. According to the invention, the magnesium alloy frame and the aluminum alloy middle plate are fixed through brazing, so that the bonding strength of the magnesium alloy frame and the aluminum alloy middle plate is increased, and the problem of connection of magnesium-aluminum dissimilar metals is solved.

Description

Technical Field

[0001] The present invention belongs to the field of electronic devices, and particularly relates to an electronic device housing and a manufacturing method thereof. Background Art

[0002] The housing of electronic devices such as mobile phones generally includes a frame, a middle plate, and a plastic structure. Among them, both the frame and the middle plate are made of metal materials. Generally, the same metal material (such as aluminum alloy, titanium alloy, etc.) is used for the frame and the middle plate. This choice is beneficial for achieving stable connection through welding technology and can form a complete electromagnetic shielding system. However, this same material structure will enhance the conduction of electromagnetic waves within the metal frame, resulting in a significant electromagnetic interference shielding effect. Currently, there are also cases where different metal materials are used for the frame and the middle plate. For example, a magnesium alloy frame and an aluminum alloy middle plate are used. At this time, due to the physical property differences between magnesium and aluminum, it is difficult to achieve reliable connection by traditional welding technology. To solve this problem, generally, a method of forming a plastic structure by injection molding is used to connect the magnesium alloy frame and the aluminum alloy middle plate into one body through the plastic structure. However, the intervention of this plastic medium, although it can achieve the physical connection of dissimilar metals, inevitably leads to a decrease in the overall structural strength of the housing, forming a new technical contradiction. Summary of the Invention

[0003] Aiming at the deficiencies of the above-mentioned prior art, the technical problem to be solved by the present invention is: to provide an electronic device housing and a manufacturing method thereof.

[0004] To solve the above technical problem, the present invention provides the following technical solutions:

[0005] A manufacturing method of an electronic device housing includes the following steps:

[0006] S100. Manufacture a magnesium alloy frame;

[0007] S200. Manufacture an aluminum alloy middle plate;

[0008] S300. Fix and connect the magnesium alloy frame and the aluminum alloy middle plate by brazing in a vacuum environment to form a magnesium / aluminum composite;

[0009] S400. Form a plastic structure on the magnesium / aluminum composite by injection molding;

[0010] S500. Form an electronic device housing by CNC machining.

[0011] Further, manufacturing the magnesium alloy frame includes the following sub-steps:

[0012] S110. Form a rough frame blank by die-casting the magnesium alloy material;

[0013] S120. Perform CNC rough machining on the rough frame blank to obtain a frame blank;

[0014] S130. Grind the upper and lower surfaces of the frame blank.

[0015] S140. Finish the CNC machining of the frame blank to obtain a magnesium alloy frame.

[0016] Furthermore, the magnesium alloy frame and the aluminum alloy middle plate are brazed using an active filler metal.

[0017] Furthermore, the composition of the active filler metal is Zn - 15% Al.

[0018] Furthermore, when the magnesium alloy frame and the aluminum alloy middle plate are fixedly connected by brazing, the brazing seam width ≤ 0.3 mm, the brazing temperature is 380°C - 420°C, and the holding time ≥ 8 min.

[0019] Furthermore, before the magnesium alloy frame and the aluminum alloy middle plate are fixedly connected by brazing, first perform micro - arc oxidation pretreatment on the welding surface of the magnesium alloy frame to form a micro - arc oxidation film, and the film thickness of the micro - arc oxidation film is 10 μm - 20 μm; and perform laser treatment on the welding surface of the aluminum alloy middle plate to make the surface roughness Ra of the welding surface 3 μm - 5 μm.

[0020] Furthermore, before injection molding, first form a staggered grid - shaped micro - groove in the injection area of the magnesium / aluminum composite, and the groove width of the micro - groove is 0.1 mm - 0.3 mm, and the groove depth is 0.07 mm - 0.1 mm.

[0021] Furthermore, when forming a plastic structure by injection molding, the injection mold uses a segmented temperature control system; among them, the mold temperature of the metal area is 110°C - 130°C, and the mold temperature of the plastic area is 70°C - 90°C.

[0022] Furthermore, when forming an electronic device housing by CNC machining, when the machining area is a plastic structure, the CNC device uses a first spindle speed; when the machining area is a magnesium alloy frame, the CNC device uses a second spindle speed; when the machining area is an aluminum alloy middle plate, the CNC device uses a third spindle speed; the first spindle speed is less than the second spindle speed, and the second spindle speed is less than the third spindle speed.

[0023] An electronic device housing is made by using the manufacturing method of the electronic device housing described in any one of the above.

[0024] In the present invention, the magnesium alloy frame and the aluminum alloy middle plate are fixed by brazing, which increases the bonding strength between the magnesium alloy frame and the aluminum alloy middle plate. Through the improvement of the brazing process, low-temperature brazing is achieved, and the bonding strength between the magnesium alloy frame and the aluminum alloy middle plate is increased, solving the connection problem of dissimilar magnesium and aluminum metals. By processing micro-grooves before injection molding and adopting a segmented temperature control method during injection molding, the peel strength of the plastic structure is greatly improved. By using different CNC spindle speeds according to the material hardness, the life of the CNC tool can be extended, costs can be saved, and the CNC processing time can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0026] Figure 1 It is a flowchart of an embodiment of the method for manufacturing the housing of the electronic device of the present invention.

[0027] Figure 2 It is a schematic structural diagram of the rough blank of the frame.

[0028] Figure 3 It is a schematic structural diagram of the frame blank.

[0029] Figure 4 It is a schematic structural diagram of the magnesium alloy frame.

[0030] Figure 5 It is Figure 4 The enlarged view of part A in

[0031] Figure 6 It is a schematic structural diagram of the aluminum alloy middle plate.

[0032] Figure 7 It is a schematic structural diagram of the magnesium / aluminum composite.

[0033] Figure 8 It is Figure 7 The enlarged view of part B in

[0034] Figure 9 It is a schematic structural diagram after injection molding to form the plastic structure.

[0035] Figure 10 It is a schematic diagram of forming the micro-grooves.

[0036] Figure 11 It is a schematic structural diagram of the housing of the electronic device.

[0037] The reference numerals in the specification drawings are as follows:

[0038] Magnesium alloy frame - 100; upper surface - 101; lower surface - 102; positioning hole - 103; brazing groove - 104; rough frame blank - 110; frame blank - 120; aluminum alloy middle plate - 150; positioning post - 151; brazing head - 152; magnesium / aluminum composite - 200; microgroove - 201; plastic structure - 300. Detailed implementation mode

[0039] The following uses specific specific examples to illustrate the implementation modes of the present invention. The diagrams provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0040] Please refer to Figure 1 , Figure 1 which is a flowchart of an embodiment of the manufacturing method of the electronic device housing of the present invention. The manufacturing method of the electronic device housing in this embodiment includes the following steps:

[0041] S100. Manufacture the magnesium alloy frame 100. This step may include the following sub - steps:

[0042] S110. Please refer to Figure 2 , and form the rough frame blank 110 by die - casting the magnesium alloy material. The magnesium alloy material can be AZ91 D, and AZ91 D belongs to the category of casting magnesium alloys, which is mainly processed by die - casting with a pressure die followed by post - processing.

[0043] S120. Please refer to Figure 3 , and perform CNC rough machining on the rough frame blank 110 to form the prototype of each feature structure on the frame, and obtain the frame blank 120.

[0044] S130. Grind the upper surface 101 and the lower surface 102 of the frame blank 120 so that the upper surface 101 and the lower surface 102 of the frame blank 120 form a smooth surface.

[0045] S140. Please refer to Figure 4 , and perform CNC finish machining on the frame blank 120 to obtain the relevant feature structures for the connection and positioning of the frame and the middle plate and other partial feature structures of the frame, and obtain the magnesium alloy frame 100.

[0046] Please refer to Figure 5 , the relevant feature structures for the connection and positioning of the frame and the middle plate include positioning holes 103, brazing grooves 104, etc. Of course, Figure 5 is only the structure of a partial area of the magnesium alloy frame 100, and positioning holes 103 and brazing grooves 104 are also provided in other areas of the magnesium alloy frame 100.

[0047] S200. Please refer to Figure 6, an aluminum alloy middle plate 150 is made of aluminum alloy material, and the process of making the aluminum alloy middle plate 150 is a conventional process, which will not be elaborated here. The aluminum alloy middle plate 150 is provided with positioning posts 151 at the positions of the positioning holes 103, and brazing heads 152 are provided at the positions corresponding to the brazing grooves 104.

[0048] S300. Please refer to Figure 7 and Figure 8 , place the aluminum alloy middle plate 150 inside the magnesium alloy frame 100, insert the positioning posts 151 into the positioning holes 103 for positioning, and at the same time insert the brazing heads 152 into the brazing grooves 104 to facilitate brazing fixation. Then, in a vacuum environment, the magnesium alloy frame 100 and the aluminum alloy middle plate 150 are fixedly connected by brazing to form a magnesium / aluminum composite body 200, and the magnesium / aluminum composite body 200 is the middle frame. The environmental vacuum degree during brazing is generally less than or equal to 5×10 -3 Pa; the brazing seam width (i.e., the gap width between the brazing head 152 and the groove wall of the brazing groove 104) ≤ 0.3 mm, preferably 0.05 mm - 0.3 mm.

[0049] In order to firmly connect the magnesium alloy frame 100 and the aluminum alloy middle plate 150, an active filler metal added with active elements can be used during brazing. The active elements form chemical bonds with the surface of the ceramic material to improve the bonding strength of the brazing connection interface. The composition of the active filler metal is preferably Zn-15%Al. In this embodiment, the magnesium alloy material is AZ91D, the aluminum alloy material is 6061 aluminum alloy, and the filler metal composition is Zn-15%Al-0.5%Si, and its melting point ≤ 380°C. Before fixedly connecting the magnesium alloy frame 100 and the aluminum alloy middle plate 150 by brazing, first perform micro-arc oxidation pretreatment on the welding surface of the magnesium alloy frame 100 to form a micro-arc oxidation film, and the film thickness of the micro-arc oxidation film is preferably 10 μm - 20 μm. And perform laser treatment on the welding surface of the aluminum alloy middle plate 150 to form a rough surface, and its surface roughness Ra is preferably 3 μm - 5 μm. Thereby, the wettability and bonding strength of the filler metal can be improved (shearing strength ≥ 80 MPa, 60% higher than the traditional one). Therefore, in this embodiment, by adopting the method of active filler metal + surface micro-nano structure (micro-arc oxidation film), the connection problem of magnesium-aluminum dissimilar metals is solved.

[0050] The traditional brazing temperature generally needs to be greater than or equal to 450°C. Since the middle aluminum alloy plate 150 will undergo obvious deformation at a high temperature of greater than or equal to 450°C, and the magnesium alloy material is also prone to combustion at high temperatures, resulting in high-temperature oxidation or interface aging problems of the magnesium alloy frame 100. Therefore, in order to ensure product quality, it is necessary to reduce the brazing temperature. In this embodiment, by using Zn-15%Al filler metal and combining the micro-arc oxidation film formed on the magnesium alloy frame 100 and the laser treatment of the middle aluminum alloy plate 150, when the magnesium alloy frame 100 and the middle aluminum alloy plate 150 are fixedly connected by brazing, the brazing temperature can be reduced to 380°C - 420°C. For example, the brazing temperature can be 380°C, 390°C, 400°C, 410°C, 420°C; the holding time ≥ 8 min, preferably 8 min - 12 min, so that the deformation amount of the welding < 0.05 mm / m.

[0051] Compare the microstructures (SEM images) of the 450°C brazing of the traditional solution and the 400°C low-temperature brazing of this embodiment: There are a large number of Mg 17 Al 12 brittle phases at the interface of the traditional solution, while the interface of this embodiment is a uniform Zn-Al solid solution. Perform a salt spray test on the magnesium / aluminum brazed joint. Cracks appear in the traditional solution after 200 h, while the solution of this embodiment has no corrosion cracking after 500 h.

[0052] S400. Please refer to Figure 9 , and a plastic structure 300 is formed by injection molding on the magnesium / aluminum composite 200. Conventional metal insert injection molding directly uses a smooth surface and relies on adhesives for bonding, which is prone to delamination during long-term use. In this embodiment, before injection molding, an interlaced grid-like micro-groove 201 is formed by CNC machining in the injection molding area of the magnesium / aluminum composite 200. The matching relationship between the structural parameters of the micro-groove 201 and the injection molding material is:

[0053] The groove width / depth ratio is 1:0.7 - 1:0.33, and the LCP melt viscosity ≤ 200 Pa·s.

[0054] Injection molding material characteristics: Melt flow index (MFI) 20 g / 10 min - 30 g / 10 min (220°C / 5 kg), carbon fiber length 200 μm - 300 μm.

[0055] Please refer to Figure 10, the groove width of the micro-grooves 201 can be 0.1 mm to 0.3 mm, and the groove depth can be 0.07 mm to 0.1 mm. When machining the micro-grooves 201, the tool is machined in the arrow direction, and the rotational speed and feed are adjusted to control the pitch of the cross-grid micro-grooves 201. Additionally, when forming the plastic structure 300 by injection molding, the injection mold of this embodiment adopts a segmented temperature control system. Among them, the mold temperature of the metal area is 110°C to 130°C, preferably 120°C, to reduce thermal stress; the mold temperature of the plastic area is 70°C to 90°C, preferably 80°C, to ensure fluidity and avoid cracking caused by temperature difference.

[0056] In this embodiment, the micro-grooves 201 and segmented temperature control are used to achieve a glue-free and high-strength combination of the plastic structure 300. During injection molding, the molten plastic (such as 30% glass fiber-reinforced LCP) penetrates to form a mechanical interlock, and the peel strength ≥ 15 N / mm (3 times higher than flat injection molding). Through the aging experiment of injection molding reliability: In this embodiment, the scheme with micro-grooves 201 has a peel strength retention rate ≥ 90% after aging at 85°C for 1000 h, while the traditional scheme without micro-grooves 201 ≤ 60%.

[0057] S500, please refer to Figure 11 , and an electronic device housing is formed by CNC machining. For example, machining feature structures such as microphone holes, SIM card tray holes, power buttons, volume buttons, copper foil positions, rivet holes, welding positions, rivet positions, and thread positions, thereby obtaining the final electronic device housing.

[0058] Conventional CNC machining uses unified parameters for multi-material composites, which may cause plastic melting or metal burrs. In this embodiment, the response time of hardness mapping cutting ≤ 0.1 s, and there is an inverse relationship between the feed rate and the hardness value of the material in the machining area (i.e., F = K / H, where F represents the feed rate, K is a constant, K = 1200 - 1500, and H represents the hardness value of the material).

[0059] In this embodiment, when forming an electronic device housing by CNC machining, when the machining area is the plastic structure 300, the CNC device adopts the first spindle speed; when the machining area is the magnesium alloy frame 100, the CNC device adopts the second spindle speed; when the machining area is the aluminum alloy middle plate 150, the CNC device adopts the third spindle speed; the first spindle speed is less than the second spindle speed, and the second spindle speed is less than the third spindle speed. The first spindle speed is 6000 rpm, the second spindle speed is 8000 rpm, and the third spindle speed is 11000 rpm. Sequential machining can also be adopted, giving priority to machining the plastic area, then the aluminum alloy area, and finally the magnesium alloy, which can avoid chip scratches on the plastic surface and make the single-piece machining time ≤ 65 min.

[0060] In this embodiment, a CNC device with a hardness detection function is adopted. When the CNC device detects that the hardness of the material in the machining area matches the hardness of the plastic structure 300 (i.e., HV20 - 30), the first spindle speed, which is 6000 rpm, is adopted. When the CNC device detects that the hardness of the material in the machining area matches the hardness of the magnesium alloy material (i.e., HV80 - 100), the second spindle speed, which is 8000 rpm, is adopted. When the CNC device detects that the hardness of the material in the machining area matches the hardness of the aluminum alloy material (i.e., HV120 - 150), the third spindle speed, which is 11000 rpm, is adopted. Of course, for mass-produced products, since the areas where various materials are located are fixed, the spindle speeds of each area can also be preset through programming to achieve the same effect. By dynamically adjusting the spindle speed in this embodiment, the tool life can be extended, the CNC machining time can be reduced by about 35%, and the tool cost can be saved by 40%.

[0061] In this embodiment, through the improvement of the brazing process, low-temperature brazing is achieved, and the bonding strength between the magnesium alloy frame 100 and the aluminum alloy middle plate 150 is increased, solving the connection problem of dissimilar magnesium-aluminum metals. By machining the micro-grooves 201 before injection molding and adopting a segmented temperature control method during injection molding, the peeling strength of the plastic structure 300 is greatly improved. By adopting different CNC spindle speeds according to the material hardness, the life of the CNC tool can be extended, the cost can be saved, and the CNC machining time can be reduced.

[0062] The present invention also discloses an electronic device housing. The electronic device housing can be made by using the manufacturing method of the electronic device housing in any of the above embodiments. The electronic device housing can be a mobile phone housing or a housing of other electronic devices such as a tablet. For the electronic device housing manufactured by the above method, the bonding strength between the magnesium alloy frame 100 and the aluminum alloy middle plate 150 is high, and the peeling strength of the plastic structure 300 is large, effectively improving the structural performance of the electronic device housing.

[0063] The above embodiments only represent the preferred embodiments of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A manufacturing method of an electronic device housing, characterized in that, It includes the following steps: S100. Fabricate a magnesium alloy frame; S200. Fabricate an aluminum alloy middle plate; S300. Under a vacuum environment, fixedly connect the magnesium alloy frame and the aluminum alloy middle plate by brazing to form a magnesium / aluminum composite; S400. Form a plastic structure on the magnesium / aluminum composite by injection molding; S500. Form an electronic device housing by CNC machining.

2. The manufacturing method of the electronic device housing according to claim 1, wherein, Fabricating the magnesium alloy frame includes the following sub-steps: S110. Form a rough frame blank by die-casting the magnesium alloy material; S120. Conduct rough CNC machining on the rough frame blank to obtain a frame blank body; S130. Grind the upper surface and the lower surface of the frame blank body; S140. Conduct fine CNC machining on the frame blank body to obtain the magnesium alloy frame.

3. The manufacturing method of the electronic device housing according to claim 1, characterized in that: The magnesium alloy frame and the aluminum alloy middle plate are brazed using an active filler metal.

4. The manufacturing method of the electronic device housing according to claim 3, wherein: The composition of the active filler metal is Zn-15% Al.

5. The manufacturing method of the electronic device housing according to claim 4, characterized in that: When the magnesium alloy frame and the aluminum alloy middle plate are fixedly connected by brazing, the brazing seam width ≤ 0.3 mm, the brazing temperature is 380°C to 420°C, and the holding time ≥ 8 min.

6. The manufacturing method of the electronic device housing according to claim 5, characterized in that: Before the magnesium alloy frame and the aluminum alloy middle plate are fixedly connected by brazing, first conduct micro-arc oxidation pretreatment on the welding surface of the magnesium alloy frame to form a micro-arc oxidation film, and the film thickness of the micro-arc oxidation film is 10 μm to 20 μm; and conduct laser treatment on the welding surface of the aluminum alloy middle plate to make the surface roughness Ra of the welding surface 3 μm to 5 μm.

7. The manufacturing method of the electronic device housing according to any one of claims 1 to 6, characterized in that: Before injection molding, first form staggered grid-shaped micro-grooves in the injection molding area of the magnesium / aluminum composite, and the groove width of the micro-grooves is 0.1 mm to 0.3 mm, and the groove depth is 0.07 mm to 0.1 mm.

8. The manufacturing method of the electronic device housing according to any one of claims 1 to 6, characterized in that: When forming the plastic structure by injection molding, the injection mold uses a segmented temperature control system; among them, the mold temperature in the metal area is 110°C to 130°C, and the mold temperature in the plastic area is 70°C to 90°C.

9. The manufacturing method of the electronic device housing according to any one of claims 1 to 6, characterized in that: When forming the electronic device housing by CNC machining, when the machining area is the plastic structure, the CNC device uses a first spindle speed; when the machining area is the magnesium alloy frame, the CNC device uses a second spindle speed; when the machining area is the aluminum alloy middle plate, the CNC device uses a third spindle speed; the first spindle speed is less than the second spindle speed, and the second spindle speed is less than the third spindle speed.

10. An electronic device housing, characterized in that: It is made by using the manufacturing method of the electronic device housing described in any one of 1 to 9.

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