Titanium-aluminum composite electronic equipment shell and manufacturing method thereof

Abstract

The invention discloses a titanium-aluminum composite electronic equipment shell and a manufacturing method thereof. The manufacturing method comprises the following steps: manufacturing a titanium alloy frame; manufacturing an aluminum alloy middle plate; the titanium alloy frame and the aluminum alloy middle plate are welded and fixed by adopting a pulse laser welding process to form a titanium / aluminum complex; an in-mold injection molding layer is formed on the titanium / aluminum composite through injection molding; and the electronic equipment shell is formed through CNC machining. According to the electronic equipment shell, functional partition of the inner cavity aluminum alloy and the outer titanium alloy is adopted, compared with a full titanium alloy scheme, the weight and cost of the electronic equipment shell can be reduced, and attenuation of 5G signals can be reduced; the titanium alloy frame and the aluminum alloy middle plate are welded and fixed through the pulse laser welding technology, the connection strength can be improved, and the problem that welding connection of dissimilar metal made of titanium / aluminum materials is not firm is solved. By adopting the mode of injection molding first and then CNC machining on the whole, it can be ensured that all functional characteristics are accurately machined and formed while the in-mold injection molding layer and the metal base body are tightly combined, and mass production is facilitated.

Description

Technical Field

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

[0002] The frames of current high-end mobile phones and other electronic device housings are mostly made of a single material of all-titanium alloy or all-aluminum alloy. Among them, the all-titanium alloy solution has high strength (tensile strength ≥ 800 MPa) and corrosion resistance, but has high costs (the processing cost of titanium alloy is about 5-10 times that of aluminum alloy), low CNC processing efficiency (the material removal rate of titanium alloy is less than 1 / 3 of that of aluminum alloy), and significant electromagnetic shielding effect (conductivity 1.8×10 6 S / m, which is likely to interfere with 5G millimeter wave signals). Although the all-aluminum alloy solution has controllable costs (6063 aluminum alloy is about 3 $ / kg, while TC4 titanium alloy is about 30 $ / kg), its yield strength is only 215 MPa, which cannot meet extreme drop tests (such as dropping from 1.5 m on marble); and the hardness of the anodic oxidation layer (HV400-600) is significantly lower than that of titanium alloy (HV800+), and it is easy to produce appearance scratches. 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 a lightweight, low-cost, and high-performance titanium-aluminum composite electronic device housing and a manufacturing method thereof.

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

[0005] A manufacturing method of a titanium-aluminum composite electronic device housing includes the following steps:

[0006] S100. Manufacture a titanium alloy frame;

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

[0008] S300. Weld and fix the titanium alloy frame and the aluminum alloy middle plate by adopting a pulsed laser welding process to form a titanium / aluminum composite body;

[0009] S400. Form an in-mold injection layer on the titanium / aluminum composite body by injection molding;

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

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

[0012] S110. Take a strip of titanium alloy material, bend the first end of the strip of titanium alloy material to form a first bent portion, and bend the second end of the strip of titanium alloy material to form a second bent portion to obtain a left frame;

[0013] S120. Take a plate-shaped titanium alloy material, form a first positioning notch at the position corresponding to the first bending part on the plate-shaped titanium alloy material, and form a second positioning notch at the position corresponding to the second bending part to obtain a right frame.

[0014] S130. Insert the end of the first bending part of the left frame into the first positioning notch of the right frame, and insert the end of the second bending part of the left frame into the second positioning notch of the right frame.

[0015] S140. Weld and fix the end of the first bending part in the first positioning notch and the end of the second bending part in the second positioning notch by vacuum diffusion welding to obtain a frame blank.

[0016] S150. Perform CNC finishing on the frame blank to obtain a titanium alloy frame.

[0017] Further, in the step S140, the temperature of the vacuum diffusion welding is 450°C to 550°C, the pressure is 12 MPa to 18 MPa, and the holding time is 25 min to 35 min.

[0018] Further, a plurality of long strip-shaped trapezoidal transition grooves are provided at the injection molding interface between the titanium alloy frame and the aluminum alloy middle plate. The width of the trapezoidal transition groove is 0.2 mm to 1.0 mm, the depth is 0.5 mm to 1.0 mm. Both ends of the trapezoidal transition groove are provided with arc chamfering structures, and the radius of the arc chamfering structure is greater than or equal to 1.05 mm. The remaining thickness of the titanium alloy frame at the trapezoidal transition groove is greater than or equal to 0.5 mm.

[0019] Further, before welding the titanium alloy frame and the aluminum alloy middle plate, first screw-fix the titanium alloy frame and the aluminum alloy middle plate through bolts.

[0020] Further, after the CNC machining is completed, the following steps are also performed:

[0021] S600. Form a titanium alloy coating layer on the surface of the electronic device housing, and generate a ceramic film layer on the surface of the titanium alloy coating layer; the thickness of the titanium alloy coating layer is 1.5 mm to 2.5 mm; the thickness of the ceramic film layer is 5 μm to 10 μm.

[0022] Further, the following steps are also included:

[0023] S700. Form a nano-scale bump array on the inner cavity surface of the electronic device housing.

[0024] Further, the following steps are also included:

[0025] S800. Bond a carbon fiber composite material plate to the weak area of the aluminum alloy middle plate on the housing of the electronic device with an adhesive.

[0026] Furthermore, the carbon fiber composite material plate is formed by bonding and fixing 2 to 5 layers of carbon fiber composite material layers in an orthogonal laminated laying method with a modified acrylate structural adhesive.

[0027] Furthermore, the single-layer thickness of the carbon fiber composite material layer is 0.06 mm to 0.08 mm, and the thickness of the carbon fiber composite material plate is 0.12 mm to 0.3 mm.

[0028] Furthermore, the carbon fiber composite material layer is formed by hot pressing and curing a carbon fiber prepreg. Among them, the carbon fiber is a T700 grade high-strength carbon fiber, and the matrix material is a bisphenol A type epoxy resin.

[0029] A titanium-aluminum composite electronic device housing includes a titanium alloy frame, an aluminum alloy middle plate, and an in-mold injection layer. The titanium alloy frame and the aluminum alloy middle plate are welded and fixed by a pulsed laser welding process; at the interface where the titanium alloy frame and the aluminum alloy middle plate contact the in-mold injection layer, there are a plurality of long strip-shaped trapezoidal transition grooves, and the in-mold injection layer is formed with protruding strips extending into the trapezoidal transition grooves, so as to form a mechanical interlock with the titanium alloy frame and the aluminum alloy middle plate; a titanium alloy coating layer is formed on the surface of the electronic device housing, and a ceramicized film layer is generated on the surface of the titanium alloy coating layer by micro-arc oxidation; a carbon fiber composite material plate is bonded and fixed to the weak area of the aluminum alloy middle plate.

[0030] In the present invention, a functional partition of the inner cavity aluminum alloy and the external titanium alloy, as well as a composite structure of the functional partition of the inner cavity aluminum alloy plate and the outer layer titanium alloy coating, reduces the overall weight of the electronic device housing relative to the all-titanium alloy solution and improves the strength relative to the all-aluminum alloy solution. The left frame and the right frame are connected by vacuum diffusion welding, which improves the interface strength of the welding. The titanium alloy frame and the aluminum alloy middle plate are welded and fixed by a pulsed laser welding process, which can improve the connection strength and avoid the brittle phase problem of direct welding of titanium / aluminum materials. Trapezoidal transition grooves are respectively machined at the injection interface of the titanium alloy frame and the aluminum alloy middle plate, which can disperse stress and improve the connection strength of the in-mold injection layer. By adopting the method of injection first and then overall CNC machining, while ensuring the tight combination of the in-mold injection layer and the metal matrix, the formation of each functional feature can be precisely processed, which can improve the yield and facilitate mass production. The present invention breaks through the technical bottlenecks of the existing process in the interface bonding strength, signal compatibility, and mass production cost of the electronic device housing and has a wide application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0032] Figure 1 It is a flowchart of an embodiment of the manufacturing method of the titanium-aluminum composite electronic device housing of the present invention.

[0033] Figure 2 It is a schematic structural diagram of the left frame.

[0034] Figure 3 It is a schematic structural diagram of the right frame.

[0035] Figure 4 It is a schematic structural diagram after the combination of the left frame and the right frame.

[0036] Figure 5 It is a schematic structural diagram of the titanium alloy frame.

[0037] Figure 6 It is a schematic structural diagram of forming a crack through hole and a trapezoidal transition groove on the titanium alloy frame.

[0038] Figure 7 It is Figure 6 The enlarged view of part A in

[0039] Figure 8 It is a schematic structural diagram of the aluminum alloy middle plate.

[0040] Figure 9 It is a schematic structural diagram of the titanium / aluminum composite.

[0041] Figure 10 It is a schematic structural diagram after forming an in-mold injection layer by injection molding.

[0042] Figure 11 It is a schematic structural diagram of the rib formed on the in-mold injection layer.

[0043] Figure 12 It is a schematic structural diagram after CNC machining.

[0044] Figure 13 It is a schematic structural diagram after bonding the carbon fiber composite board.

[0045] The reference numerals in the specification drawings are as follows:

[0046] Titanium alloy frame - 100; fracture through hole - 101; threaded hole - 102; left frame - 110; first bending part - 111; second bending part - 112; connecting part - 113; right frame - 120; first positioning notch - 121; second positioning notch - 122; aluminum alloy middle plate - 200; inner cavity - 201; screw connection through hole - 202; titanium / aluminum composite - 300; trapezoidal transition groove - 301; arc chamfer structure - 302; in - mold injection layer - 400; rib - 401; carbon fiber composite material plate - 500. Detailed implementation manners

[0047] The following specific examples are used to illustrate the implementation manners of the present invention. The diagrams provided in the following examples only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following examples and the features in the examples can be combined with each other.

[0048] Please refer to Figure 1 , Figure 1 which is a flowchart of an embodiment of the manufacturing method of the titanium - aluminum composite electronic device housing of the present invention. The manufacturing method of the titanium - aluminum composite electronic device housing in this embodiment includes the following steps:

[0049] S100. Manufacture the titanium alloy frame 100. The manufacture of the titanium alloy frame 100 includes the following sub - steps:

[0050] S110. Please refer to Figure 2 , take a strip - shaped titanium alloy material. In this embodiment, the strip - shaped titanium alloy material is made of titanium alloy Ti - 6Al - 4V, and its yield strength ≥ 800 MPa. Of course, the strip - shaped titanium alloy material can also be made of other titanium alloy materials such as Ti - 4 series. Bend the first end of the strip - shaped titanium alloy material by 90° to form the first bending part 111, and bend the second end of the strip - shaped titanium alloy material by 90° to form the second bending part 112, obtaining a "U" - shaped left frame 110. Among them, the un - bent part between the first bending part 111 and the second bending part 112 is the connecting part 113.

[0051] S120. Please refer to Figure 3 , take a plate - shaped titanium alloy material. Generally, the material selection of the plate - shaped titanium alloy material is the same as that of the strip - shaped titanium alloy material. Form a first positioning notch 121 at the position corresponding to the first bending part 111 on the plate - shaped titanium alloy material, and form a second positioning notch 122 at the position corresponding to the second bending part 112 on the plate - shaped titanium alloy material, thereby obtaining the right frame 120.

[0052] S130. Please refer to Figure 4, Combine the left frame 110 and the right frame 120, so that the end of the first bent portion 111 of the left frame 110 extends into the first positioning notch 121 of the right frame 120, and the end of the second bent portion 112 of the left frame 110 extends into the second positioning notch 122 of the right frame 120.

[0053] S140. Weld and fix the end of the first bent portion 111 in the first positioning notch 121, and weld and fix the end of the second bent portion 112 in the second positioning notch 122 by vacuum diffusion welding, so as to weld the left frame 110 and the right frame 120 into a whole to obtain the frame blank 130. In this step, the temperature of vacuum diffusion welding is generally 450°C to 550°C, preferably 500°C; the pressure is 12 MPa to 18 MPa, preferably 15 MPa; the holding time is 25 min to 35 min, preferably 30 min. By adopting the above process, the interface strength of the welding can reach 90% of the base material.

[0054] Vacuum diffusion welding is to make the welding surfaces of the workpieces to be welded contact with each other under a certain temperature and pressure. Through microscopic plastic deformation or by generating a small amount of liquid phase on the welding surface to expand the physical contact of the welding surface, so that the distance reaches within 1×10 -8 cm to 5×10 -8 cm (in this way, the attraction between atoms can play a role and it is possible to form a metal bond), and then through the continuous diffusion and mutual penetration of atoms for a long time to achieve a welding method of metallurgical bonding. Since welding is generally completed in a high-temperature environment, in order to avoid oxidation of the welded parts at high temperature, vacuum protection is generally adopted.

[0055] In the range of vacuum diffusion welding, the higher the welding temperature, the faster the atomic diffusion. The welding temperature is generally 0.5 times to 0.8 times the melting point of the material, and generally the effect is the best when it is 0.7 times. In a vacuum state, the gas at the welding interface during the welding process will be sucked into the vacuum, so that the quality of the joint can be improved. The diffusion welding pressure is small, and the workpieces will not produce macroscopic plastic deformation.

[0056] S150. Please refer to Figure 5 , perform CNC finish machining on the frame blank 130 to obtain the titanium alloy frame 100. Please refer to Figure 6 and Figure 7 , in this step, a strip-shaped slit through hole 101 can be first machined at the position on the left frame 110 where the antenna slit needs to be formed, so that the left frame 110 is only connected through the relatively narrow areas at both ends of the long axis of the slit through hole 101, so as to facilitate subsequent truncation of the relatively narrow connection areas at both ends along the long axis of the slit through hole 101 to form an antenna slit. In this embodiment, two slit through holes 101 are formed in each of the first bent portion 111, the second bent portion 112 and the connecting portion 113.

[0057] S200. Refer to Figure 8 to fabricate the aluminum alloy middle plate 200. The aluminum alloy middle plate 200 is generally formed by stamping an aluminum alloy sheet and then machining it by CNC. In this embodiment, the aluminum alloy sheet is 7075-T6 with a yield strength of ≥500 MPa. Of course, the aluminum alloy sheet can also be other aluminum alloy materials such as 6-series aluminum alloys (e.g., 6061 / 6063). In this embodiment, the inner cavity 201 of the aluminum alloy middle plate 200 is made of a topologically optimized thin-walled multi-cavity aluminum alloy with a wall thickness of 0.6 mm to 1.2 mm. By using the above method, the cost is reduced by 60% compared with the method of machining the middle plate with titanium alloy by CNC.

[0058] S300. Refer to Figure 9 to weld and fix the titanium alloy frame 100 and the aluminum alloy middle plate 200 by using the pulsed laser welding process to form a titanium / aluminum composite body 300, that is, a metal middle frame. Pulsed laser welding is mainly used for the welding of single-point fixed continuous and thin materials, and the beam pulse width can be adjusted. Each laser pulse forms a solder joint on the welded part, mainly used for the welding of micro-precision components and microelectronic components. The pulsed laser of the pulsed laser welding machine is mainly used for spot welding and seam welding of thin-walled metal materials within 1 mm in thickness. Its welding process belongs to the heat conduction type, that is, the laser radiation heats the surface of the workpiece, and then diffuses into the material interior through heat conduction. By controlling parameters such as the waveform, width, peak power, and repetition frequency of the laser pulse, a good connection is formed between the workpieces.

[0059] In this embodiment, since the inner cavity 201 of the aluminum alloy middle plate 200 can be directly in contact with the VC heat sink plate, the heat dissipation efficiency can be increased by about 30% by using its high thermal conductivity (160 W / m˙K), solving the defect of insufficient thermal conductivity of the titanium alloy middle plate in the prior art.

[0060] Since the titanium alloy frame 100 and the aluminum alloy middle plate 200 are welded with dissimilar metals, in order to ensure firm welding, pulsed laser welding is adopted in this embodiment, avoiding the brittle phase problem of direct welding of titanium / aluminum materials.

[0061] In addition, before welding the titanium alloy frame 100 and the aluminum alloy middle plate 200, the titanium alloy frame 100 and the aluminum alloy middle plate 200 can be first bolted and fixed. At this time, when performing CNC machining on the frame blank 130, threaded holes 102 can be machined on the titanium alloy frame 100, and screw-through holes 202 corresponding to the threaded holes 102 are provided at the positions of the aluminum alloy middle plate 200 corresponding to the threaded holes 102; when performing CNC machining on the aluminum alloy middle plate 200, screw-through holes 202 can be machined at the positions of the aluminum alloy middle plate 200 corresponding to the threaded holes 102, and bolts (not shown in the figure) are used to pass through the screw-through holes 202 and be screwed with the threaded holes 102 to achieve the bolted and fixed connection between the titanium alloy frame 100 and the aluminum alloy middle plate 200.

[0062] S400. Please refer to Figure 10 , an in-mold injection layer 400 is formed by injection molding on the titanium / aluminum composite body 300, and the in-mold injection layer 400 covers the joint of the titanium alloy frame 100 and the aluminum alloy middle plate 200, so as to form an integrated support structure through the injection molding process.

[0063] Please continue to refer to Figure 6 and Figure 7 , in the step S300, trapezoidal transition grooves 301 can also be machined at the injection molding interfaces of the titanium alloy frame 100 and the aluminum alloy middle plate 200 during CNC machining, which are used to disperse stress and improve the connection strength during injection molding. The width of the trapezoidal transition groove 301 is 0.2 mm to 1.0 mm, preferably 0.5 mm; the depth of the trapezoidal transition groove 301 is 0.5 mm to 1.0 mm, preferably 0.4 mm; the lengths of the respective trapezoidal transition grooves 301 can be set according to the actual situation. The remaining thickness of the titanium alloy frame 100 at the trapezoidal transition groove 301 is generally greater than or equal to 0.5 mm to ensure the structural strength of the titanium alloy frame 100.

[0064] Please refer to Figure 11 , by providing the trapezoidal transition grooves 301, ridges 401 extending into the trapezoidal transition grooves can be formed on the in-mold injection layer 400 during injection molding, so as to expand the contact area of the in-mold injection layer 400, and enable the titanium alloy frame 100 and the aluminum alloy middle plate 200 to form a mechanical interlock with the in-mold injection layer 400, enhancing the anchoring and anti-peeling ability. According to the actual situation, multiple rows of trapezoidal transition grooves 301 can also be provided along the height direction of the titanium / aluminum composite body 300 to further increase the anchoring depth of the in-mold injection layer 400, and the distance between adjacent two rows of trapezoidal transition grooves 301 is generally not less than 0.5 mm.

[0065] Both ends of the trapezoidal transition groove 301 may also be provided with an arc chamfer structure 302, which can further disperse stress and reduce the stress concentration coefficient. The radius of the arc chamfer structure 302 is greater than or equal to 1.05 mm, preferably 2 mm. In this embodiment, by providing the trapezoidal transition groove 301, the contact area of the in-mold injection layer 400 can be enlarged, and the external impact load received by the electronic device housing can be dispersed to the adjacent area of the impact point. Through finite element analysis, it is shown that the peak stress at the impact point can be reduced by 35%.

[0066] In this step, the in-mold injection layer 400 is made of polyamide (PA) or polyetheretherketone (PEEK) material, and the injection temperature is 280°C to 320°C, and the pressure is 80 MPa to 120 MPa. The selection of polyamide (PA) or polyetheretherketone (PEEK) material for the in-mold injection layer 400 is mainly considered from aspects such as the coefficient of thermal expansion, thermal conductivity, dielectric constant, and heat resistance.

[0067] Coefficient of thermal expansion: PA is 50 - 80×10 -6 / °C, PEEK is 40 - 60×10 -6 / °C, and the difference rate from titanium alloy (8.6×10 -6 / °C) and aluminum alloy (23×10 -6 / °C) is ≤150%. By using the above materials, the coefficient of thermal expansion of the in-mold injection layer 400 can be matched with that of the titanium alloy frame 100 and the aluminum alloy middle plate 200, so that the interfacial stress (ΔL = α·ΔT·L) caused by the temperature difference between titanium / aluminum dissimilar metals can be absorbed through the thermoplastic deformation ability of the in-mold injection layer 400, avoiding cracking; thus, the dimensional deviation caused by thermal expansion can be corrected by CNC machining after injection molding.

[0068] Thermal conductivity: PA ≤ 0.3 W / (m·K), PEEK ≤ 0.25 W / (m·K), which can achieve thermal isolation between the metal middle frame (i.e., the titanium / aluminum composite body 300) and the internal components.

[0069] Dielectric constant: PA ≤ 3.5 (1 GHz), PEEK ≤ 3.2 (1 GHz), which can ensure that the antenna signal transmission rate ≥ 85%.

[0070] In this embodiment, the injection material is selected as PA / PEEK instead of the conventional PC / ABS, and its high heat resistance (PA melting point 220°C) can also be utilized to adapt to subsequent CNC machining.

[0071] S500. Please refer to Figure 12, an electronic device housing is formed by CNC machining. The CNC machining process includes machining the titanium alloy frame 100, the aluminum alloy middle plate 200, and the in-mold injection layer 400. For example: precision milling the inner cavity 201 structure, finishing the outer shape and upper and lower chamfers of the titanium alloy frame 100, and machining various functional features on the titanium alloy frame 100 and the aluminum alloy middle plate 200. Machining functional features includes: machining microphone holes, card slot holes, speaker holes, power keys, volume keys, thread positions (i.e., internal threads of threaded holes), and other characteristic structures. At this time, the connection areas on both sides of each slit through-hole 101 are also cut off, thereby truncating the left frame 110 to form an antenna slit, and dividing the left frame 110 into multiple segmented structures to solve the signal shielding problem of the metal middle frame.

[0072] In the prior art, direct molding after injection molding is mostly used, which cannot meet the high-precision assembly requirements, and the yield of the hot isostatic pressing process is ≤75%, making mass production difficult. In this embodiment, the method of first injection molding and then overall CNC machining is adopted, which can ensure the tight combination of the in-mold injection layer 400 and the metal matrix (i.e., the titanium / aluminum composite 300) while precisely machining and forming various functional features, and the yield is increased to 88%, facilitating mass production.

[0073] In this embodiment, in order to suppress the drop deformation of the electronic device housing, the following steps can also be performed after the CNC machining in step S500:

[0074] S600, form a titanium alloy coating layer (not shown in the figure) on the surface of the electronic device housing, the thickness of the titanium alloy coating layer is 1.5 mm to 2.5 mm, preferably 2 mm. Then, a ceramic film layer (not shown in the figure) is generated on the surface of the titanium alloy coating layer by micro-arc oxidation, and the thickness of the ceramic film layer is 5 μm to 10 μm. By adding the titanium alloy coating layer and the ceramic film layer, the hardness of the electronic device housing can reach HV1500, the wear resistance exceeds that of sapphire glass, and the elastic modulus reaches 110 GPa, which can effectively suppress the drop deformation, and the finite element simulation shows that the 1.8 m drop stress dispersion rate is increased by 40%.

[0075] The functions of the titanium alloy coating layer are as follows:

[0076] (1) Improve corrosion resistance: Titanium alloy has excellent corrosion resistance, with extremely few dissolved ions in environments such as seawater, and is non-toxic. Coating other materials with it can improve the corrosion resistance of the coated materials.

[0077] (2) Enhance wear resistance: Titanium alloy has a relatively high hardness, and the formed coating layer can improve the surface hardness and wear resistance of the base material, reduce material loss caused by friction and wear, and extend the service life.

[0078] (3) Enhancement of aesthetics: The titanium alloy coating layer can obtain different surface colors and textures through special processing techniques, enhancing the aesthetics and added value of the product.

[0079] In addition, due to the low dielectric property (ε≈1.05) of the outer layer of titanium alloy, combined with the optimized layout of electromagnetic shielding in the aluminum alloy inner cavity 201, the attenuation of 5G signals can be reduced. The measured 5G signal loss is only -0.7 dB, which is a 61% improvement compared to the all-aluminum alloy solution (-1.8 dB).

[0080] The all-titanium alloy solution (i.e., the frame and the middle plate are both made of titanium alloy materials formed by CNC machining) has a high cost (the titanium processing cost is 5 to 10 times that of aluminum); the 3D printing titanium alloy solution (i.e., the frame and the middle plate are both made of titanium alloy materials formed by 3D printing) reduces material waste, but the equipment investment cost increases by more than 40%. In the present invention, by using aluminum alloy materials to replace the titanium alloy materials in the middle plate in a partitioned manner, the titanium alloy usage is reduced to only a 2-mm-thick titanium alloy coating layer on the outside, and the comprehensive cost is 45% of the all-titanium solution, while the specific strength is close to that of the all-titanium alloy solution.

[0081] S700. Form a nanoscale bump array (not shown in the figure) on the surface of the inner cavity 201 of the electronic device housing to achieve the synergistic enhancement of mechanical bite and metallurgical bonding. The diameter of the bumps in the nanoscale bump array can be 50 μm, and the spacing between adjacent bumps can be 200 μm. The nanoscale bump array can be used as an electrical interconnection structure between the chip and the substrate to achieve signal transmission. And the nanoscale bump array can also provide high-density interconnection, shorten the signal transmission distance, reduce signal delay, improve the performance and operating frequency of the chip, and increase the mechanical stability of the packaging structure.

[0082] Generally, the nanoscale bump array is formed after the titanium alloy coating layer is formed. The reasons are as follows:

[0083] (1) Process feasibility: First forming the titanium alloy coating layer can provide a stable, flat and substrate with specific properties for the preparation of the nanoscale bump array. If the nanoscale bump array is prepared first, the structure of the nanoscale bump array may be damaged or deformed during the subsequent process of forming the titanium alloy coating layer. For example, during the processes of titanium alloy coating, deposition, etc., conditions such as high temperature and high pressure may change the shape and size of the bumps in the nanoscale bump array, or even cause the bumps to disappear.

[0084] (2) Functional implementation: The titanium alloy coating layer can protect the underlying material and endow the material with properties such as corrosion resistance. On this basis, a nanoscale bump array is formed, which can further improve the surface performance of the material; in the semiconductor field, it can be used as an electrical interconnection structure between the chip and the substrate. If the nanoscale bump array is prepared first and then coated with titanium alloy, it may affect the function of the nanoscale bump array. For example, the titanium alloy coating layer may cover the nanoscale bump array, resulting in its inability to effectively contact the outside world, and thus unable to achieve functions such as the expected electrical interconnection function.

[0085] S800. Please refer to Figure 13 , a carbon fiber composite board 500 is adhesively bonded to the weak area corresponding to the aluminum alloy middle plate 200 on the electronic device housing through an adhesive to form a carbon fiber reinforcement area, and the carbon fiber composite board 500 can be adhesively bonded to the stress concentration area of the aluminum alloy middle plate 200 through an acrylate structural adhesive.

[0086] The carbon fiber composite board 500 can be formed by laying 2 to 5 layers of carbon fiber composite layers in a [0° / 90°] orthogonal stacking method and adhesively fixing them through a modified acrylate structural adhesive. The single-layer thickness of the carbon fiber composite layer can be 0.06 mm to 0.08 mm, preferably 0.07 mm. The thickness of the carbon fiber composite board 400 can be 0.12 mm to 0.3 mm.

[0087] The carbon fiber composite layer is formed by hot pressing and curing a carbon fiber prepreg. Among them, the carbon fiber uses T700 grade high-strength carbon filaments, the single-filament tensile strength ≥ 4.9 GPa, and the fiber volume content is 55%-65%; the matrix material uses bisphenol A epoxy resin, and the glass transition temperature after curing ≥ 120 °C; the modified acrylate structural adhesive is used for bonding between the carbon fiber composite layers, and the shear strength after curing ≥ 20 MPa.

[0088] In this embodiment, according to the stress distribution simulation results of the aluminum alloy middle plate 200, carbon fibers are adhesively bonded only in the weak areas (such as the periphery of the camera opening, etc.), and the balance between light weight and strength can be achieved; the anti-bending performance of the carbon fiber reinforcement area is improved by 60%, meeting the IP68 protection requirements, while the weight only increases by 3%. In this embodiment, the local reinforcement and symmetric layup design of the carbon fiber composite board 500 can retain the metallic texture appearance and reduce costs compared with the full-wrap design of the carbon fiber composite board 500.

[0089] In this embodiment, a functional partition of inner cavity 201 aluminum alloy and external titanium alloy is adopted (i.e., the frame is made of titanium alloy material and the middle plate is made of aluminum alloy material), as well as a functional partition composite structure with aluminum alloy plate in inner cavity 201 and outer titanium alloy coating (i.e., a 2-mm titanium alloy coating layer is added outside the aluminum alloy middle plate 200), so that the overall weight of the electronic device housing is reduced by 25% compared with the all-titanium alloy solution, and the strength is increased by 40% compared with the all-aluminum alloy solution (i.e., both the frame and the middle plate are made of aluminum alloy material). The left frame 110 and the right frame 120 are connected by vacuum diffusion welding, and the interfacial strength of the welding can reach 90% of the base material. The titanium alloy frame 100 and the aluminum alloy middle plate 200 are welded and fixed by a pulsed laser welding process, which can improve the connection strength and avoid the brittle phase problem of direct welding of titanium / aluminum materials. Trapezoidal transition grooves 301 are respectively machined at the injection molding interfaces of the titanium alloy frame 100 and the aluminum alloy middle plate 200, which can disperse stress and improve the connection strength of the in-mold injection layer 400. By adopting the method of first injection molding and then overall CNC machining, while ensuring the close combination of the in-mold injection layer 400 and the metal matrix, each functional feature can be accurately machined and formed, which can improve the yield rate and facilitate mass production. By adopting the electromagnetic shielding optimization layout of the titanium alloy coating layer combined with the aluminum alloy inner cavity 201, the attenuation of 5G signals can also be reduced, and the specific strength is close to the all-titanium alloy solution. A nanoscale bump array is formed on the surface of the inner cavity 201, which can provide high-density interconnection, shorten the signal transmission distance, reduce signal delay, improve the performance and working frequency of the chip, and increase the mechanical stability of the packaging structure. By adopting the above method, this embodiment breaks through the technical bottlenecks of the existing process in terms of the interfacial bonding strength, signal compatibility and mass production cost of the electronic device housing.

[0090] The present invention also discloses a titanium-aluminum composite electronic device housing. An embodiment of the titanium-aluminum composite electronic device housing of the present invention may include a titanium alloy frame 100, an aluminum alloy middle plate 200, and an in-mold injection layer 300. The titanium alloy frame 100 and the aluminum alloy middle plate 200 are welded and fixed by a pulsed laser welding process.

[0091] A plurality of elongated trapezoidal transition grooves 301 are provided at the interfaces where the titanium alloy frame 100 and the aluminum alloy middle plate 200 are in contact with the in-mold injection layer 400. The in-mold injection layer 400 is formed with protruding strips 401 extending into the trapezoidal transition grooves 301, so as to form a mechanical interlock with the titanium alloy frame 100 and the aluminum alloy middle plate 200. Arc chamfer structures 302 are provided at both ends of the trapezoidal transition grooves 301, so as to disperse stress and reduce the stress concentration coefficient.

[0092] A titanium alloy coating layer is formed on the surface of the electronic device housing, and a ceramic film layer is formed on the surface of the titanium alloy coating layer by micro-arc oxidation. Using aluminum alloy material to replace the titanium alloy material of the middle plate in zones, reducing the titanium alloy usage to only a 2-mm-thick titanium alloy coating layer on the exterior can greatly reduce the overall cost, optimize the electromagnetic shielding layout, and reduce the attenuation of 5G signals.

[0093] On the surface of the inner cavity 201 of the electronic device housing, a nanoscale bump array can also be formed. The diameter of the bumps in the nanoscale bump array can be 50 μm, and the pitch between adjacent bumps can be 200 μm. The nanoscale bump array can serve as an electrical interconnection structure between the chip and the substrate, realizing signal transmission, providing high-density interconnection, shortening the signal transmission distance, reducing signal delay, improving the performance and operating frequency of the chip, and increasing the mechanical stability of the packaging structure.

[0094] A carbon fiber composite material plate 500 is adhesively fixed in the weak area of the aluminum alloy middle plate 200, which can improve the anti-bending performance of the carbon fiber reinforcement area, with a lower cost than the carbon fiber full-wrap solution and capable of being compatible with a metallic texture appearance.

[0095] The titanium-aluminum composite electronic device housing of this embodiment can achieve a relatively high structural strength while reducing the weight and cost of the electronic device housing, reduce the attenuation of 5G signals, and has wide application value.

[0096] The above embodiments only represent the preferred implementation modes of the present invention. 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 modifications 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 shall be subject to the appended claims.

Claims

1. A manufacturing method of a titanium-aluminum composite electronic device housing, characterized in that, It includes the following steps: S100. Fabricate a titanium alloy frame; S200. Fabricate an aluminum alloy middle plate; S300. Adopt a pulsed laser welding process to weld and fix the titanium alloy frame and the aluminum alloy middle plate to form a titanium / aluminum composite body; S400. Form an in-mold injection layer on the titanium / aluminum composite body by injection molding; S500. Form an electronic device housing by CNC machining; 2. The manufacturing method of the titanium-aluminum composite electronic device housing according to claim 1, characterized in that Fabricating the titanium alloy frame includes the following sub-steps: S110. Take a strip-shaped titanium alloy material, bend the first end of the strip-shaped titanium alloy material to form a first bent portion, and bend the second end of the strip-shaped titanium alloy material to form a second bent portion to obtain a left frame; S120. Take a plate-shaped titanium alloy material, form a first positioning notch at a position corresponding to the first bent portion on the plate-shaped titanium alloy material, and form a second positioning notch at a position corresponding to the second bent portion to obtain a right frame; S130. Insert the end of the first bent portion of the left frame into the first positioning notch of the right frame, and insert the end of the second bent portion of the left frame into the second positioning notch of the right frame; S140. Weld and fix the end of the first bent portion in the first positioning notch and the end of the second bent portion in the second positioning notch by vacuum diffusion welding to obtain a frame blank; S150. Conduct CNC finishing on the frame blank to obtain a titanium alloy frame.

3. The manufacturing method of the titanium-aluminum composite electronic device housing according to claim 2, characterized in that: In the step S140, the temperature of the vacuum diffusion welding is 450°C to 550°C, the pressure is 12 MPa to 18 MPa, and the holding time is 25 min to 35 min.

4. The manufacturing method of the titanium-aluminum composite electronic device housing according to claim 1, characterized in that: At the injection interface between the titanium alloy frame and the aluminum alloy middle plate, there are a plurality of long strip-shaped trapezoidal transition grooves. The width of the trapezoidal transition grooves is 0.2 mm to 1.0 mm, the depth is 0.5 mm to 1.0 mm, which form a mechanical interlock with the in-mold injection layer. Both ends of the trapezoidal transition grooves are provided with arc chamfer structures. The radius of the arc chamfer structures is greater than or equal to 1.05 mm, and the remaining thickness of the titanium alloy frame at the trapezoidal transition grooves is greater than or equal to 0.5 mm.

5. The manufacturing method of the titanium-aluminum composite electronic device housing according to claim 1, characterized in that: Before welding the titanium alloy frame and the aluminum alloy middle plate, first screw-fix the titanium alloy frame and the aluminum alloy middle plate with bolts.

6. The manufacturing method of the titanium-aluminum composite electronic device housing according to any one of claims 1 to 5, characterized in that After the CNC machining is completed, the following steps are also executed: S600. Form a titanium alloy coating layer on the surface of the electronic device housing, and generate a ceramicized film layer on the surface of the titanium alloy coating layer; the thickness of the titanium alloy coating layer is 1.5 mm to 2.5 mm; the thickness of the ceramicized film layer is 5 μm to 10 μm.

7. The manufacturing method of the titanium-aluminum composite electronic device housing according to any one of claims 1 to 5, characterized in that, It also includes the following steps: S700. Form a nanoscale bump array on the inner cavity surface of the electronic device housing.

8. The manufacturing method of the titanium-aluminum composite electronic device housing according to any one of claims 1 to 5, characterized in that, It also includes the following steps: S800. Bond a carbon fiber composite material plate to the weak area of the electronic device housing corresponding to the aluminum alloy middle plate with an adhesive.

9. The manufacturing method of the titanium-aluminum composite electronic device housing according to claim 8, characterized in that, The carbon fiber composite material plate is formed by orthogonally laminating 2 to 5 layers of carbon fiber composite material layers and bonding and fixing them with a modified acrylate structural adhesive.

10. The manufacturing method of the titanium-aluminum composite electronic device housing according to claim 9, characterized in that, The single-layer thickness of the carbon fiber composite material layer is 0.06 mm to 0.08 mm, and the thickness of the carbon fiber composite material plate is 0.12 mm to 0.3 mm.

11. The manufacturing method of the titanium-aluminum composite electronic device housing according to claim 9, characterized in that, The carbon fiber composite layer is formed by hot pressing and curing a carbon fiber prepreg. Among them, the carbon fiber is T700 grade high-strength carbon wire, and the matrix material is bisphenol A epoxy resin.

12. A titanium-aluminum composite electronic device housing, characterized in that: It includes a titanium alloy frame, an aluminum alloy middle plate and an in-mold injection layer. The titanium alloy frame and the aluminum alloy middle plate are welded and fixed by a pulsed laser welding process; a plurality of long strip-shaped trapezoidal transition grooves are provided at the interfaces where the titanium alloy frame and the aluminum alloy middle plate are in contact with the in-mold injection layer, and the in-mold injection layer is formed with convex strips extending into the trapezoidal transition grooves, so as to form a mechanical interlock with the titanium alloy frame and the aluminum alloy middle plate; a titanium alloy coating layer is formed on the surface of the electronic device housing, and a ceramic film layer is generated on the surface of the titanium alloy coating layer by micro-arc oxidation; a carbon fiber composite board is adhesively fixed in the weak area of the aluminum alloy middle plate.

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