WO2023169429A1 - 一种结构件及其制备方法和电子设备 - Google Patents

一种结构件及其制备方法和电子设备 Download PDF

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Publication number
WO2023169429A1
WO2023169429A1 PCT/CN2023/080126 CN2023080126W WO2023169429A1 WO 2023169429 A1 WO2023169429 A1 WO 2023169429A1 CN 2023080126 W CN2023080126 W CN 2023080126W WO 2023169429 A1 WO2023169429 A1 WO 2023169429A1
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Prior art keywords
film
thinning
chemical conversion
structural member
structural
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PCT/CN2023/080126
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English (en)
French (fr)
Inventor
熊真敏
李恒
耿永红
杨雄
袁德增
肖望
章心怡
张世君
唐巍
Original Assignee
华为技术有限公司
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Priority claimed from CN202210599198.4A external-priority patent/CN116779216A/zh
Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Publication of WO2023169429A1 publication Critical patent/WO2023169429A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form

Definitions

  • the embodiments of the present application relate to the field of electrical connection technology, and specifically relate to a structural component, a preparation method thereof, and electronic equipment.
  • electronic equipment In order to improve the working performance of electronic equipment, reduce radio frequency interference between devices, increase the isolation between devices, and reduce the risk of electronic static electricity, electronic equipment usually needs to be electrically connected to ground, and each device in the electronic equipment also needs to be electrically connected to ground.
  • the camera module needs to be electrically connected to the ground to avoid interference from radio frequency signals from the antenna; the display module also needs to be electrically connected to the ground to avoid electromagnetic noise from affecting the normal operation of the display module.
  • Magnesium alloy has the advantages of low density and high strength and can be used as structural parts of electronic equipment. Building a conductive anti-corrosion layer on its surface can improve its corrosion resistance and ensure good conductivity on the surface to achieve electrical connection with conductive parts in electronic equipment. connection to achieve grounding.
  • the chemical conversion film formed through chemical conversion treatment (which can be referred to as "chemical conversion treatment") is a low-cost conductive anti-corrosion layer.
  • the film-forming solution currently used in actual production has poor film-forming quality, many film-forming defects, and poor density, resulting in a film with excessive film resistance and unable to be directly used for electrical connection and grounding.
  • embodiments of the present application provide a structural component, a preparation method thereof, and electronic equipment to solve the problems of poor film formation quality and excessive resistance of the chemical conversion film on the surface of the structural component.
  • the first aspect of the embodiments of the present application provides a method for manufacturing a structural member.
  • the preparation method includes the following steps:
  • the structural member substrate is subjected to n chemical conversion treatments, n ⁇ 2, and after the i-th chemical conversion treatment and before the i+1th chemical conversion treatment, the film formed by the i-th chemical conversion treatment is thinned; where, i is Any integer between 1 and n-1; the thinning treatment method includes chemical thinning or physical thinning.
  • the structural component substrate is subjected to n (n ⁇ 2) formation treatments, and the previously formed film is thinned between any two adjacent formation treatments, so that the defective film can be made thin with the help of chemical thinning. Fall off and retain a good-quality film as the film-forming nucleus for the next formation process, or use physical thinning to increase the density of metal atom arrangement on the surface of the structural component base and the accompanying formation of a dense oxide film to reduce the next formation process.
  • the hydrogen evolution reaction in the film can achieve the preparation of a good film with high density and low defects, ensuring the stable and low resistance of the obtained film, so as to facilitate the electrical connection and grounding of structural parts.
  • the thinning process includes overall thinning of the film formed by the i-th chemical conversion process, or partial thinning to remove the film in a predetermined area.
  • the overall thinning method includes chemical thinning
  • the local thinning method includes physical thinning
  • the chemical thinning is alkali washing thinning
  • the alkaline thinning agent used is a strong alkali aqueous solution with pH ⁇ 12
  • the alkaline thinning time is more than 60s
  • the temperature is 50-50 within the range of 90°C.
  • the physical thinning method includes laser engraving or ion beam thinning.
  • the local thinning is performed by the laser engraving.
  • the preparation method further includes: forming an alloy layer on the structural component substrate that has been subjected to n-th chemical conversion treatment to cover the film formed by the n-th chemical conversion treatment.
  • the contact between the alloy layer and the film is good, the contact resistance is small, and it can improve the wear resistance and strength of the overall film layer.
  • the second aspect of the embodiments of the present application provides a structural component, which is produced by the preparation method provided by the first aspect of the embodiments of the present application.
  • the third aspect of the embodiment of the present application provides a structural member.
  • the structural member includes a structural member base, and a first film structure disposed on the surface of the structural member base, wherein the first film structure is located on the structure.
  • the preset area of the component base has a plurality of pits, and the first film structure is arranged on the surface of the pits.
  • the structural component base further includes a non-preset area, and a second film structure is provided on the non-preset area, and the thickness of the second film structure is greater than that of the first film structure.
  • an alloy layer is further provided on the first film structure.
  • the fourth aspect of the embodiment of the present application provides a structural component, which includes a structural component base, and a first film structure and an alloy layer sequentially laminated on the surface of the structural component base.
  • the first film structure completely covers one side surface of the structural member base.
  • the first film structure partially covers one side surface of the structural member base, and the first film structure is located in a preset area of the structural member base, and the preset area includes a plurality of a pit, and the first film structure is arranged on the surface of the pit.
  • the fifth aspect of the embodiments of the present application provides an electronic device, which includes the structural member described in the second, third or fourth aspect of the embodiments of the present application.
  • FIG. 1 is a schematic structural diagram of an electronic device provided by an embodiment of the present application.
  • Figure 2 is a complete process flow diagram of a primary chemical conversion treatment on a structural component substrate provided by some embodiments of the present application.
  • Figure 3 is a complete process flow diagram of a primary chemical conversion treatment on a structural component substrate provided by other embodiments of the present application.
  • Figure 4 is a complete process flow chart for forming a film structure on a structural component substrate according to an embodiment of the present application.
  • Figure 5 is a schematic diagram of the manufacturing process of a structural component provided by an embodiment of the present application.
  • Figure 6 is a schematic diagram of the manufacturing process of a structural component provided by another embodiment of the present application.
  • Figure 7 is a schematic diagram of the manufacturing process of a structural component provided by yet another embodiment of the present application.
  • FIGS 8a, 8b, 8c, and 8d are schematic structural diagrams of several structural components provided by embodiments of the present application.
  • Figure 9 is a comparative diagram of the surface micromorphology and energy spectrum analysis results of the primary film formed by primary chemical formation in Example 1 of the present application and the secondary film formed by secondary chemical formation after thinning.
  • Figure 10 provides a surface microtopography diagram of the preset area of the substrate after laser engraving in Example 2.
  • Figure 11 provides a surface micromorphology diagram of the secondary film formed based on Figure 10.
  • the embodiments of the present application provide structural parts with chemical conversion coatings and preparation methods thereof, as well as electrical devices that can use the structural parts. sub-device.
  • the technical solution provided by this application is suitable for electronic devices using one or more of the following communication technologies: Bluetooth (blue-tooth, BT) communication technology, global positioning system (GPS) communication technology, wireless fidelity (wireless) Fidelity (WiFi) communication technology, global system for mobile communications (GSM) communication technology, wideband code division multiple access (WCDMA) communication technology, long term evolution (LTE) communication technology, 5G communication technology and other future communication technologies, etc.
  • Bluetooth blue-tooth, BT
  • GPS global positioning system
  • WiFi wireless fidelity
  • GSM global system for mobile communications
  • WCDMA wideband code division multiple access
  • LTE long term evolution
  • the electronic device in the embodiment of the present application may be a mobile phone, a tablet computer, a laptop computer, a smart bracelet, a smart watch, a smart helmet, smart glasses, etc.
  • the electronic device may also be a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a device with wireless communications Functional handheld devices, computing devices or other processing devices connected to wireless modems, vehicle-mounted devices, electronic devices in 5G networks or electronic devices in future evolved public land mobile communications networks (public land mobile network, PLMN), etc., this
  • SIP session initiation protocol
  • WLL wireless local loop
  • PDA personal digital assistant
  • PLMN public land mobile network
  • FIG 1 exemplarily shows a schematic structural diagram of an electronic device provided by this application.
  • the electronic device is a mobile phone for description.
  • the electronic device 10 may include: a cover glass (cover glass) 13, a display module (display) 15, a printed circuit board (PCB) 17, a middle frame (housing) 19 and a back cover. (rear cover)21.
  • the cover glass (CG) 13 can be placed close to the display module 15 and is mainly used to protect the display module 15 from dust. It should be understood that in some embodiments, the glass cover 13 can also be replaced with a cover made of other materials, such as an ultra-thin glass cover, a PET (Polyethylene terephthalate, polyethylene terephthalate) cover, etc. .
  • the display module 15 may include a liquid crystal display panel (LCD), a light emitting diode (LED) display panel or an organic light-emitting semiconductor (organic light-emitting diode, OLED) display panel, etc. , this application does not limit this.
  • LCD liquid crystal display panel
  • LED light emitting diode
  • OLED organic light-emitting semiconductor
  • the printed circuit board PCB17 can use a flame-resistant material (FR-4) dielectric board, a Rogers dielectric board, or a mixed dielectric board of Rogers and FR-4, etc.
  • FR-4 is the code for a flame-resistant material grade
  • Rogers dielectric board is a high-frequency board.
  • a metal layer may be provided on the side of the printed circuit board PCB 17 close to the middle frame 19 , and the metal layer may be formed by etching metal on the surface of the PCB 17 . This metal layer can be used to ground the electronic components carried on the printed circuit board PCB17 to prevent users from electric shock or equipment damage. This metal layer can be called the PCB floor.
  • the electronic device 10 may also have other floors used for grounding, such as a metal middle frame.
  • the electronic device 10 may also include a battery (not shown in the figure).
  • the battery can be arranged in the middle frame 19.
  • the battery can divide the PCB 17 into a main board and a sub-board.
  • the main board can be arranged between the middle frame 19 and the upper edge of the battery, and the sub-board can be arranged between the middle frame 19 and the lower edge of the battery.
  • the middle frame 19 mainly plays a supporting role of the whole machine.
  • the middle frame 19 may include a frame 11 , which may extend around the periphery of the electronic device 10 and the display module 15 .
  • the frame 11 may specifically surround four sides of the display module 15 to help fix the display module 15 .
  • the frame 11 may be formed of conductive materials such as metal.
  • the frame 11 made of metal material can be directly used as the metal frame of the electronic device 10 to form the appearance of a metal frame, which is suitable for metal industrial design (ID).
  • the outer surface of the frame 11 can also be made of non-metal material, such as a plastic frame, forming the appearance of a non-metal frame, which is suitable for non-metal IDs.
  • the back cover 21 may be made of metal material, or may be made of non-conductive material, such as glass back cover, plastic back cover and other non-metal back covers.
  • the back cover 21 is mainly used to seal the battery, circuit board and other components in the inner cavity of the housing, and to protect various components of the electronic device.
  • FIG. 1 only schematically shows some components included in the electronic device 10, and the actual shapes, actual sizes and actual structures of these components may not be limited by FIG. 1 .
  • the above-mentioned middle frame 19 can be made of the structural member with a chemical conversion film according to the embodiment of the present application.
  • the structural component includes a structural component base and a chemical conversion film disposed on the structural component base.
  • the material of the structural component base may be magnesium or magnesium alloy.
  • magnesium or magnesium alloys are less dense, they can help reduce the weight of electronic devices when used in them. However, due to the high activity of magnesium or magnesium alloys, they are easily oxidized and corroded during use. Therefore, surface treatment is required to improve their corrosion resistance without sacrificing their surface conductive properties. Compared with other surface protection technologies, chemical conversion treatment has the advantages of low cost and simple operation.
  • the chemical conversion film formed on the structural component substrate through chemical conversion treatment is a good conductive anti-corrosion layer, which can have good corrosion resistance and High conductivity.
  • the chemical conversion film on the surface can not only play an anti-corrosion protection role, but can also be used for electrical connection with the conductive components in the electronic device 10 to achieve grounding, thereby reducing the risk of Electronic static electricity risks, reducing radio frequency interference between devices, etc., improve the working performance of the electronic device 10 .
  • the grounding of the middle frame 19 can guide the static electricity that enters the gap between the display module and the middle frame of the electronic device to the ground in a timely manner, thereby preventing accumulation of static electricity from damaging the display module and preventing electromagnetic interference. Therefore, the structural parts provided by this application have good anti-corrosion properties and can achieve highly reliable electrical connections at preset positions.
  • the above-mentioned structural member can be prepared by the following preparation method, which specifically includes:
  • the structural member substrate is subjected to n chemical conversion treatments, n ⁇ 2, and after the i-th chemical conversion treatment and before the i+1th chemical conversion treatment, the film formed by the i-th chemical conversion treatment is thinned; where, i is Any integer between 1 and n-1; the thinning treatment method includes chemical thinning or physical thinning.
  • Figure 4 shows a complete process flow chart for forming a film structure on a structural component substrate.
  • the process flow shown in Figure 4 includes the following steps: (1) First perform a primary chemical conversion treatment on the structural component base to form a primary film on its surface; (2) Then perform a thinning process on the primary film; (3) Tape the The base body of the structural member with the thinned primary film is subjected to another chemical conversion treatment (that is, a second chemical conversion treatment is performed). After that, the secondary-formed structural component matrix is washed and dried in order for later use. Among them, drying can be carried out at a temperature of about 80°C.
  • the material of the structural component substrate may include but is not limited to magnesium or magnesium alloy, aluminum or aluminum alloy, zinc or zinc alloy, titanium or titanium alloy, etc.
  • magnesium or magnesium alloys with high chemical activity are particularly necessary to be treated by the above method provided in this application.
  • the magnesium alloy grades may be AZ91D, AZ31B, etc.
  • the structural member base before the structural member base is subjected to the first chemical conversion treatment, the structural member base is also pre-treated (as shown in Figure 4).
  • This application does not limit the method of pretreatment, which may include a combination of acid washing and alkali washing, or a combination with other treatment methods.
  • the pretreatment includes: pre-degreasing/degreasing, pickling, and alkali etching. Understandably, each step of pre-treatment should also be washed with water separately to prevent residual reagents from the previous step from interfering with the next step. Each step of water washing can be carried out at room temperature for 1-2 minutes.
  • the pre-degreasing/degreasing treatment can be carried out with an alkaline degreasing agent at a temperature of 55-65°C for 5-10 minutes.
  • This step can also be called “alkali washing”; the pickling can be done with an organic acid pickling solution. Conduct it at a temperature of 45-55°C for 0.5-2 minutes; alkali etching can be carried out using a strong alkaline solution at a temperature of 80-90°C for 3-10 minutes.
  • the dirt on the surface of the structural part substrate especially magnesium alloy die-casting parts
  • an active clean surface can be obtained, which provides a good prerequisite for subsequent chemical formation treatment.
  • the pretreatment includes: alkali washing, pickling, and surface conditioning in sequence.
  • alkali cleaning is to remove surface oil stains
  • pickling can be performed in citric acid, acetic acid or tartaric acid solution at 20-30°C.
  • Pickling can remove oxides, metal impurities, etc. on the surface of the structural component base.
  • the surface conditioning solution used for surface conditioning i.e., surface conditioning
  • the acid-washed structural component substrate can be placed into the surface conditioning solution to achieve surface conditioning. surface adjustment.
  • the pretreatment before the first formation can be In turn, it includes cold pickling, neutralization, hot pickling and neutralization.
  • cold pickling can be carried out with fluorine-containing inorganic acid
  • hot pickling can be carried out with organic weak acids (such as citric acid, acetic acid or tartaric acid, etc.), and the temperature of hot pickling is higher than that of cold pickling; two steps Neutralization can be carried out independently using strong alkaline solutions.
  • Chemical conversion treatment is to form a surface film (i.e., film) on the surface of a substrate through chemical or electrochemical means.
  • the type of film formed through chemical conversion treatment can be determined according to the chemical conversion liquid used.
  • Common coatings include but are not limited to phosphide conversion coating, chromate conversion coating, stannate conversion coating, zirconate conversion coating, molybdate conversion coating, vanadate conversion coating, titanate conversion coating, high manganese conversion coating Acid conversion coating, etc.
  • the chemical conversion solution (can also be called a "coating agent") used in the chemical conversion treatment can include but is not limited to phosphate system, chromate system, stannate system, zirconate system, molybdate system, and vanadate system , titanate system, permanganate system, hydrotalcite system, rare earth salt system, plant acid system and fluoride, etc., or any combination of the aforementioned systems.
  • the common film on the surface is usually a phosphate conversion coating.
  • the chemical conversion liquid used for the first conversion treatment of the structural component substrate may be a P-Ca-V composite phosphating liquid with a pH of 2.2-3.2, and its composition may be: 85% phosphoric acid 4 ⁇ 20ml/L, sodium dihydrogen phosphate 5 ⁇ 30g/L, calcium nitrate 10 ⁇ 40g/L, sodium benzenesulfonate 0.5 ⁇ 10g/L, ammonium metavanadate 0.5 ⁇ 5g/L, the balance is water.
  • this chemical conversion solution at a temperature of 18-60°C.
  • the composition of the chemical conversion liquid may include sodium dihydrogen phosphate, phosphoric acid, calcium salts, water and rare earth metals; the pH of the chemical conversion liquid is 1.8-2.2, and the structural parts can be treated at 12-15°C.
  • the substrate is processed.
  • the chemical conversion liquid used in the chemical conversion treatment includes phosphates, transition metal salts, and the like.
  • the chemical conversion liquid used in each chemical conversion treatment may be the same or different.
  • the execution time of each formation treatment may be the same or different.
  • the first chemical conversion treatment takes longer than other chemical conversion treatments.
  • the above-mentioned thinning process may include: overall thinning of the film formed by the i-th chemical conversion process, or partial thinning to remove the film in a predetermined area.
  • "overall thinning" can make the film formed by the i-th chemical conversion process thin along its thickness direction, and each area of the film away from the surface of the structural member base can be thinned toward the direction of the structural member base, and each area Areas can be thinned to the same or different thicknesses.
  • the overall thinning or partial thinning includes chemical thinning or physical thinning.
  • the chemical thinning is more suitable for overall thinning, and the physical thinning is more suitable for local thinning.
  • the thinning method for the film formed by any i-th chemical conversion treatment between the 1st time and the n-1th time may be the same or different.
  • the structural component substrate when performing chemical thinning, can be soaked in a chemical thinning agent, or the chemical thinning agent can be sprayed or coated on the film formed by the i-th chemical conversion treatment.
  • specific implementation methods of chemical thinning include but are not limited to immersion, spraying or coating.
  • the chemical thinning may specifically include, but is not limited to, alkali washing thinning, pickling thinning, etc.
  • the chemical thinning agent includes an alkaline thinning agent or an acidic thinning agent.
  • the chemical thinning is alkali washing thinning
  • the alkaline thinning agent used may be a strong alkali aqueous solution with pH ⁇ 12.
  • the solute-strong base in the strong alkali aqueous solution may be NaOH, KOH or a combination thereof.
  • the time for alkaline thinning can be more than 60s, such as 60s, 80s, 90s, 120s, etc.; the temperature can be in the range of 50-90°C, for example, the temperature is 55, 60, 75, 80 or 85°C.
  • ultrasonic waves may also be applied during the alkali washing and thinning process. That is, the alkali washing thinning is performed in the presence of ultrasonic waves.
  • 1 perform pre-treatment on the structural member base and then perform primary chemical conversion treatment so that the surface of the structural member base is covered with a primary film; 2 then use chemical thinning to thin the primary film as a whole, 3 then apply Structural parts of the primary film after thinning
  • the base body is subjected to secondary formation treatment to form a secondary film on the basis of the thinned primary film, thereby obtaining a structural member with a film structure.
  • chemical thinning of the primary film can promote the thinning/shedding of the film in the film-forming defective area of the primary film (such as the surface film with low density and large pores), so that the better quality of the primary film can be retained (e.g., high-density bottom film) and act as crystal nuclei.
  • the requirement for supersaturation of the formation solution during secondary formation can be greatly reduced and play a role It can guide the growth of the secondary film, thereby improving the film quality of the secondary film (such as increasing film density and reducing film defects), and obtaining a high-density, low-defect film with low film resistance.
  • the retained crystal nuclei can reduce the supersaturation degree of the chemical solution used for secondary chemical transformation, the duration of the secondary chemical transformation can be shortened and a low-thickness film can be obtained.
  • n ⁇ 3 the structural component base with the thinned primary film is subjected to n-1 chemical conversion treatments, and the previously formed film is thinned between two adjacent chemical conversion treatments.
  • the total number of chemical conversion treatments can be determined according to corrosion resistance and resistance requirements.
  • appearance parts with adjustable film color can also be produced to adapt to more application scenarios.
  • the film structure formed on the surface of the structural component base is the superposition of the film after the 1st to n-1th thinning and the nth formed film (as shown in Figure 5). Since the film is a highly dense film layer that remains after each thinning, and the last formed film is seeded on the basis of the n-1th film, therefore, the density of the overall film structure along its thickness direction Basically the same, they are all high-density film layers, unlike the existing primary film whose density gradually decreases along its thickness direction away from the structural component base (in other words, the bottom-up direction).
  • the film formed by the i-th (i is any integer between 1 and n-1) chemical conversion treatment is chemically thinned
  • it in some embodiments of the present application, in the n times of chemical conversion treatment performed on the structural component substrate , it can also be controlled to meet at least one of the following conditions to achieve the preparation of a film structure with low film thickness and few film formation defects: a) The i-th (i ⁇ 2) chemical conversion treatment takes less time than the first chemical conversion treatment. ; b) The chemical conversion liquid used for n times of chemical conversion treatment forms a concentration gradient.
  • the concentrations of the chemical conversion liquid for the first chemical conversion, the chemical conversion liquid for the second chemical conversion, the chemical conversion liquid for the third chemical conversion, and the chemical conversion liquid for the fourth chemical conversion can be Gradient increase or gradient decrease, for example, a gradually decreasing trend.
  • the execution time of the i+1th transformation process is less than the i-th transformation process. In this way, multiple formation processes with gradually reduced formation times can be used to further reduce the time to obtain the overall film structure, reduce the film thickness, and ensure the film quality.
  • the time of the first chemical conversion treatment can be 20-40s
  • the time of the second chemical conversion treatment can be 1-10s.
  • the method of physically thinning the film formed by the i-th chemical conversion treatment may include but is not limited to laser engraving or ion beam thinning. These physical thinning methods can generate enough heat to remelt the surface material of the structural component substrate, while their narrow processing depth will not excessively damage the substrate.
  • physical thinning is used to perform the above-mentioned local thinning to thin the film in a predetermined area.
  • the preset area is usually a partial area of one side surface of the structural component base.
  • laser engraving is used to perform the local thinning.
  • the laser power during laser engraving can be controlled at 25-30W (the rated power of the laser engraving machine can be greater than or equal to 35W); the laser engraving speed is less than or equal to 3000mm/s. This will help ensure that the primary film in the preset area is completely carved through.
  • the laser engraving includes linear laser engraving, the line spacing of the laser engraving is less than or equal to 0.05 mm, and the laser engraving lines need to cross once each. In the laser engraving circuit cross processing, the metal elements on the surface of the structural part base can be melted more smoothly.
  • picture In 6, 1 perform pre-treatment on the structural part base and then perform primary chemical conversion treatment to form a primary film on the surface of the structural part base; 2 then partially thin the primary film through physical thinning such as laser engraving, so as to Remove the film in the preset area; 3 Then perform a secondary formation process on the structural component base with the thinned primary film to form a secondary film in the preset area that is thinner than the film thickness in the non-preset area to obtain the structural member .
  • step 2 there is no primary film in the area that has been physically thinned by laser engraving or other processing (i.e., the preset area), while other areas that have not been physically thinned (i.e., the non-preset area) still have The primary film is retained, and the retained primary film has a protective effect.
  • the subsequent chemical conversion process it can ensure that the chemical conversion liquid will basically not corrode the film in the area that has not been physically thinned, thereby ensuring The film thickness in the non-preset area is thicker and has better corrosion resistance.
  • the film thickness in the preset area is thin and the resistance is low, which facilitates the structural parts to achieve high-reliability electrical connections in this area.
  • the penetration depth of release agents accounts for an increasing proportion (for example, the penetration depth exceeds 10 ⁇ m) , the existing technology cannot effectively remove the release agent with stable chemical properties, resulting in a sharp deterioration in the resistance of the area where the release agent remains on the base of the structural part (for example, the resistance value exceeds 20 ⁇ ), and cannot meet the grounding requirements of 3C electronic equipment; if Extending the pickling time will increase the amount of corrosion on the base of the structural parts and reduce their yield.
  • the oxide film contains magnesium oxide, which can provide Mg 2+ for chemical formation.
  • the base of the structural part is a magnesium alloy, during physical thinning processes such as laser engraving, the Mg in the alloy is easier to melt out than the Al element, and it is easier to form a high-density aluminum segregation ⁇ phase (i.e., Mg 17 Al 12 ), its existence is more conducive to improving the density of the secondary film.
  • the material on the surface of the structural part base can be melted to a certain extent, and during the process of cooling to become a solid, defects on the surface of the structural part base can be reduced.
  • the arrangement of metal atoms is made more dense. In the salt spray test, the electrolyte solution is less likely to penetrate into the matrix of the structural component and cause corrosion, which is beneficial to improving its corrosion resistance/weather resistance.
  • the film formed by the i-th chemical conversion treatment is physically thinned, in the n-time chemical conversion treatment performed on the structural component substrate, at least one of the following conditions can also be controlled to achieve low film thickness and few film formation defects.
  • Preparation of film structure a) The i-th (i ⁇ 2) chemical conversion treatment takes less time than the first chemical conversion treatment; b) The chemical conversion solution used in the n-th chemical conversion treatment forms a concentration gradient, such as a gradient increase Or the gradient decreases.
  • the execution time of the i+1th transformation process is less than the i-th transformation process. In this way, multiple formation processes with gradually reduced formation times can be used to further reduce the time to obtain the overall film structure, reduce the film thickness, and ensure the film quality.
  • the total number n of chemical conversion treatments performed on the structural component substrate may be equal to 2. At this time, the manufacturing of such structural parts
  • the preparation method can better take into account the shorter process time and lower film resistance.
  • the preparation method when physical thinning is used to perform the local thinning, the preparation method further includes: forming an alloy layer on the structural component substrate that has been subjected to n times of chemical conversion treatment to cover the nth A film formed by secondary chemical conversion treatment.
  • the alloy layer is formed on the surface of the film in the preset area (specifically, the surface of the film formed in the preset area by the n-th chemical conversion treatment); there may be no alloy layer on the film in non-preset areas.
  • This alloy layer can serve as a protective layer. It can be formed by spot-coating liquid low-melting-point alloy material. It has good wettability in the liquid state and can have profiling contact with the uneven surface of the film formed after physical thinning. Compared with directly bonding or welding metal sheets to the film, this profiling contact can effectively increase the contact area with the film, reduce contact resistance, and improve bonding stability. It can also make the surface of the film with an alloy layer smooth and more Conducive to subsequent stable electrical connection with conductive components of electronic equipment. In addition, after the alloy layer is attached to the film in the preset area, the adhesion strength of the film to the substrate is guaranteed, and the wear resistance and strength of the overall film layer are significantly improved, so that the film can have both high wear resistance and stability. The low resistance effect can adapt to more application scenarios.
  • the melting point of the alloy layer is lower than that of the structural component matrix, and preferably its melting point is significantly lower than the soldering temperature of the solder, for example, its melting point is below 200°C.
  • the alloy layer has higher wear resistance than the structural component matrix.
  • the material of the alloy layer may include but is not limited to an alloy of indium, tin, and bismuth, or an alloy of indium, tin, and gallium.
  • the preparation method may also include: forming an alloy on the structural component substrate that has been subjected to the n-th chemical conversion treatment. layer to cover the film formed by the nth chemical conversion treatment. At this time, the alloy layer can cover all surfaces of the epithelial film structure of the structural component base. The contact between the alloy layer and the film structure is good and the contact resistance is small. It can also improve the wear resistance and strength of the film structure.
  • the thinning methods for the film formed by the i-th (i is any integer between 1 and n-1) conversion treatment can be the same or different.
  • the film formed by the first chemical conversion treatment can be partially physically thinned, and then the structural member base is subjected to n-1 chemical conversion treatments, and after the i-th chemical conversion treatment and the i-th chemical conversion treatment, Before the +1th chemical conversion treatment, the film formed by the i-th chemical conversion treatment is chemically thinned, where i is any integer between 2 and n-1.
  • the concentration of the chemical conversion liquid used in the n-th chemical conversion treatment can also be gradient controlled, and the execution time of the second and subsequent chemical conversion treatments can be controlled to be shorter than the first chemical conversion treatment.
  • an alloy layer can also be formed on the structural component substrate that has been subjected to n-th chemical conversion treatment to cover the film formed by the n-th chemical conversion treatment.
  • the surface of the structural component produced by the above-mentioned preparation method in the embodiment of the present application has a highly dense film structure with few defects and low resistance.
  • the existence of the film can avoid the problem of deterioration of overlap resistance.
  • the film structure further has an alloy layer, the wear resistance and contact strength of the entire film layer can be improved without affecting the reliability of the electrical connection between the structural component and the conductive device.
  • Embodiments of the present application also provide a structural member, the surface of the base of the structural member has a film structure.
  • the structural member can be manufactured using the preparation method described above in this application example.
  • the structural member 100 includes a structural member base 101, and a first film structure 201 is provided on one side surface of the structural member base 101.
  • the surface of the structural member base 101 may be completely covered by the first film structure 201 or may be partially covered.
  • the density of the first film structure 201 is substantially unchanged.
  • the first film structure 201 is basically highly dense along its thickness direction, has few surface defects, and can effectively form the problem of film surface overlap resistance deterioration caused by film defects.
  • the film structure on the surface of the structural member base is dense along the direction shown by the arrow in Figure 8a (that is, along the direction of the film from the structural member base 101, that is, the bottom-up direction). The degree is gradually reduced.
  • the above “density is basically unchanged” can be understood as: the porosity of the first film structure 201 along its thickness direction is also basically unchanged.
  • the porosity a of the side of the first film structure 201 away from the structural member base 101 is different from the porosity a of the side of the first film structure 201 that is close to the structure.
  • an alloy layer 30 is also provided on the first film structure 201 , and the first film structure 201 and the alloy layer 30 are sequentially stacked on the structural member base 101 .
  • the existence of the alloy layer 30 can ensure high wear resistance and good weather resistance of the entire film layer on the structural component base 101, as well as good contact strength and low contact resistance between the structural component 100 and the conductive components electrically connected thereto.
  • the structural member 100 provided includes a structural member base 101 and a first film structure 201' located on one side surface thereof.
  • the first film structure 201' is located on the structure.
  • the preset area of the structural member base 101 may be the entire surface area of one side of the structural member base 101, or may be a partial area as shown in Figure 8c.
  • the preset area has a plurality of pits, and the first film structure 201' is disposed on the surface of the pits.
  • the morphology of the first film structure 201' is different from the existing chemical conversion film, and its film layer quality is better, such as high density, few defects, and almost no chemical stability in this preset area.
  • the release agent can solve the problem in the existing film technology that the release agent cannot be cleaned, resulting in the deterioration of the overlap resistance of the film surface.
  • the depth of the pits may be 2-6 ⁇ m, such as 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, etc.; the diameter of the pits may be 30-60 ⁇ m, such as 35 ⁇ m, 40 ⁇ m, 50 ⁇ m, etc.
  • the first film structure 201' is located on the inner wall of each pit.
  • the first membrane structure 201' may partially cover the inner wall of the pit.
  • the first film structure 201' may be a continuous film structure, which may completely cover the inner wall of the pit, but partially fill the pit, that is, the pit is not covered by the first film.
  • the surface of the first film structure 201' away from the structural component base 101 may be non-planar.
  • the first film structure 201' may be in the shape of a continuous valley, with its concave direction facing the structural member base 101.
  • the structural component base 101 also includes a non-preset area with a second film structure 202 on the non-preset area, and the thickness of the second film structure 202 may be greater than the first film structure 201'.
  • the thickness of the film on the non-preset area of the structural component base 101 is thicker and has better corrosion resistance.
  • the thickness of the film on the preset area is thinner and the resistance is low, which facilitates the structural component to achieve high reliability electrical connection in this area. . Therefore, the structural component 100 can have stronger market competitiveness.
  • an alloy layer 30 is also provided on the first film structure 201'.
  • the alloy layer 30 can fill the depressions of the continuous valley-shaped first film structure 201'.
  • the alloy layer 30 can completely fill the depressions of the continuous valley-shaped first film structure 201' and cover the structural member base in the predetermined area.
  • the surface of the alloy layer 30 facing away from the first film structure 201' is a plane, which is beneficial to increasing the contact force and contact area between the structural component 100 and other conductive components and achieving stable electrical connection.
  • the presence of the alloy layer 30 can ensure high wear resistance and high weather resistance of the entire film layer on the structural component base 101, as well as good contact strength and low contact resistance between the structural component 100 and the conductive components electrically connected to it. wait.
  • the structural component 100 in the embodiment of the present application needs to be electrically connected to ground, the structural component 100 can be directly electrically connected to the electronic device that needs to be grounded, or the structural component 100 can be electrically connected to the electronic device that needs to be grounded.
  • An elastic conductive medium for example, conductive foam
  • An elastic conductive medium that can absorb structural tolerances is filled between electronic devices to ensure the reliability of electrical connections.
  • electrical connection in this application should be understood in a broad sense.
  • electrical connection can be understood as the physical contact and electrical conduction of components; It is understood as the form of connection between different components in the circuit structure through physical lines that can transmit electrical signals, such as printed circuit board (PCB) copper foil or wires. It can also be understood as coupling connection.
  • Communication connection may refer to the transmission of electrical signals, including wireless communication connections and wired communication connections. Wireless communication connections do not require physical media and are not connection relationships that limit product construction.
  • Connect and “connected” can both refer to a mechanical connection relationship or a physical connection relationship.
  • connection between A and B or the connection between A and B can refer to the existence of fastening components (such as screws, bolts, rivets) between A and B. etc.), or A and B are in contact with each other and A and B are difficult to separate.
  • fastening components such as screws, bolts, rivets
  • Embodiments of the present application provide an electronic device, which may include any of the structural components described in the above embodiments.
  • the electronic equipment uses the structural parts with good conductivity and excellent anti-corrosion properties described in the above embodiments of the present application, the electronic equipment has high quality and reliability, and the use experience and market competitiveness of the electronic equipment can be improved.
  • the disclosed systems, devices and methods can be implemented in other ways.
  • the device embodiments described above are only illustrative.
  • the division of the units is only a logical function division. In actual implementation, there may be other division methods.
  • multiple units or components may be combined or can be integrated into another system, or some features can be ignored, or not implemented.
  • the coupling or direct coupling or communication connection between each other shown or discussed may be through some interfaces, and the indirect coupling or communication connection of the devices or units may be in electrical or other forms.
  • the preparation method includes the following steps:
  • a chemical conversion solution such as a phosphate system is used to perform a conversion treatment on the structural component substrate.
  • the conversion time can be 20s-40s, and the surface of the magnesium alloy substrate is covered with a phosphate film of a certain thickness.
  • Thinning of primary film Soak the magnesium alloy structural component matrix obtained in step (1) in a NaOH aqueous solution with pH>12 for overall thinning for at least 50 seconds. Ultrasound is applied during the thinning process, and the temperature is controlled at 10-90°C. , wash with water after the thinning is completed.
  • the magnesium alloy structural component substrate with the thinned primary film is subjected to a secondary formation treatment to form a secondary film, wherein the concentration of the formation solution used for the secondary formation can form a gradient with the concentration of the formation solution used for the primary formation,
  • the time of secondary film formation can be controlled between 1s and 10s.
  • the secondary-formed structural component substrate is washed and dried in sequence (the temperature can be 80°C).
  • a high-density and low-thickness film can be generated on the magnesium alloy structural parts, achieving stable low resistance of the film in the preset area and low corrosion of the structural parts.
  • the resistance value of the epithelial film on the structural part was measured to be about 0.2 ⁇ .
  • the corrosion amount is about 5 ⁇ m (the corrosion amount is compared with the structural component substrate before primary chemical formation).
  • Example 1 of the present application achieves the effect of lower epithelial film resistance of magnesium alloy structural parts and low corrosion amount of structural parts.
  • Figure 9 summarizes the Scanning Electron Microscope (SEM) images and Energy Dispersive X-Ray Spectroscopy (Energy Dispersive X-Ray Spectroscopy) of the film on the magnesium alloy structural component substrate after primary formation in Example 1 EDX) image, as well as the SEM image and EDX image of the secondary film formed after thinning.
  • SEM Scanning Electron Microscope
  • EDX Energy Dispersive X-Ray Spectroscopy
  • the formation of the above film characteristics is mainly due to the alkali washing and thinning after primary formation, which can promote the hydrolysis of monohydrogen phosphate, dihydrogen phosphate or phosphate in the primary film, and can also promote the shedding of hydrogen phosphate in some film formation defect areas. , the thinning of the film is achieved, and some crystal nuclei with good film quality can be retained at one time.
  • the secondary formation time can be shortened and the film quality can be improved.
  • the secondary formation time is shortened, a magnesium alloy film with high density and low thickness can be obtained, thereby achieving stable low resistance of the magnesium alloy film and low corrosion of structural parts.
  • the preparation method includes the following steps:
  • Thinning of the primary film Carry out local high-power laser engraving on the preset area of the magnesium alloy structural component substrate after step (1) to thin the primary film in the preset area, leaving the non-radium engraved area
  • the film is made once; among them, laser engraving is specifically linear laser engraving.
  • the line spacing of laser engraving is less than or equal to 0.05mm.
  • the laser engraving lines need to cross once.
  • the laser engraving speed is less than or equal to 3000mm/s.
  • the laser power during laser engraving is 25-30W. After the laser engraving is completed, clean the surface of the structural component base.
  • the concentration of the formation solution used for the secondary formation can be the same as that of the formation solution used for the primary formation, and the secondary formation time is 5-8 seconds; during the secondary formation, the primary film in the non-laser engraved area has basically no change.
  • the cross-processing process of laser engraving lines can melt the alloy on the surface of the base of the magnesium alloy structural part.
  • the metal defects on the surface of the magnesium alloy can be reduced and the metal arrangement can be made denser, improving its durability. Salt spray properties.
  • the release agent and primary film on the surface of the magnesium alloy structural part corresponding to the laser engraving area are removed, forming a dense oxide film. This oxide film can slow down the magnesium alloy during the secondary formation process.
  • the hydrogen evolution reaction on the alloy surface also provides magnesium ions for film formation, which is conducive to the formation of a dense secondary film.
  • Figure 10 provides a surface microtopography diagram of the preset area of the substrate after laser engraving in Example 2.
  • Figure 11 provides a surface micromorphology diagram of the secondary film formed after laser engraving and chemical formation. The right picture is an enlarged view of part of the left picture. It can be seen from these figures that after the laser engraving process, multiple continuously distributed pits are produced in the preset area of the structural component base. When the structural component base is subjected to secondary formation after laser engraving, a secondary film will be formed on the inner wall of the pit.
  • a high-density and low-thickness film can be generated in the preset area of the magnesium alloy structural component, achieving stable low resistance of the film in the preset area and low corrosion of the structural component.
  • a gold-plated ball-head probe with a diameter of 1.4mm (the elastic force of the probe probe is about 0.7N) was used to conduct a resistance test on the structural part produced in Example 2, and the film resistance value of the preset area of the structural part was measured to be 0.2 ⁇ , and the corrosion amount is about 3 ⁇ m.
  • the resistance value of all areas of the film measured by the above test method is greater than 5 ⁇ , and the corrosion amount is about 10 ⁇ m.
  • step (3) it also includes the following step (4): secondary laser engraving in the corresponding local laser engraving area.
  • the film is coated with a layer of liquid low-melting-point alloy (melting point below 200°C) by dispensing.
  • the low-melting-point alloy will adhere to the secondary film after cooling.
  • a high-density and low-thickness film can also be generated in the preset area of the magnesium alloy structural part, achieving stable low resistance of the film in the preset area and low corrosion of the structural part. Specific effects See the description in the Example 2 section.
  • an alloy layer is formed on the surface of the secondary film by dot-pointing a low-melting-point alloy.
  • the alloy layer When the alloy layer is in a liquid state, it can have profiling contact with the uneven surface after laser engraving. The profiling contact can increase the resistance between the two. contact area and reduce contact resistance.
  • the wear resistance and strength of the film can be significantly improved.

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Abstract

本申请提供了一种结构件及其制备方法和电子设备。该结构件的制备方法包括：对结构件基体进行n次化成处理，n≥2，其中，在第i次化成处理之后和第i+1次化成处理之前，对第i次化成处理形成的皮膜进行减薄处理，其中，i是1至n-1之间的任意整数；所述减薄处理的方式包括化学减薄或物理减薄。通过上述制备方法，可使结构件上形成致密度高、缺陷少的皮膜结构，且具有稳定的低电阻。

Description

一种结构件及其制备方法和电子设备
本申请要求于2022年3月11日提交至中国专利局、申请号为202210237506.9、申请名称为“一种方法及电子设备”的中国专利申请的优先权，以及于2022年5月30日提交至中国专利局、申请号为202210599198.4、申请名称为“一种结构件及其制备方法和电子设备”的中国专利申请的优先权，这些在先申请的全部内容通过引用结合在本申请中。
技术领域
本申请实施例涉及电连接技术领域，具体涉及一种结构件及其制备方法和电子设备。
背景技术
为了提升电子设备的工作性能、降低器件之间的射频干扰、增加器件之间的隔离度，降低电子静电风险等，电子设备通常需要电连接接地，电子设备中的各器件也需要电连接接地。例如，摄像头模组需要电连接接地，避免来自天线的射频信号的干扰；显示模组也需要电连接接地，避免电磁噪声对显示模组的正常工作造成影响。
镁合金具有因密度低、强度高等优点可用作电子设备的结构件，在其表面构建导电防腐层可提升其耐蚀性及保证表面的良好导电性，以实现与电子设备中导电部件的电连接，进而实现接地。其中，通过化学转化处理(可简称为“化成处理”)形成的化学转化皮膜是一种成本较低的导电防腐层。而当前在实际生产中采用的皮膜方案的成膜质量较差，成膜缺陷较多、致密性差，导致皮膜的膜电阻过大，无法直接应用于电连接接地。
发明内容
鉴于此，本申请实施例提供了一种结构件及其制备方法和电子设备，以解决结构件表层的化学转化皮膜存在的成膜质量差、电阻过大的问题。
具体地，本申请实施例第一方面提供了一种结构件的制备方法，所述制备方法包括以下步骤：
对结构件基体进行n次化成处理，n≥2，并在第i次化成处理之后和第i+1次化成处理之前，对第i次化成处理形成的皮膜进行减薄处理；其中，i是1至n-1之间的任意整数；所述减薄处理的方式包括化学减薄或物理减薄。
本申请对结构件基体进行了n次(n≥2)化成处理，并在任意相邻两次化成处理之间都对前一次形成的皮膜进行减薄处理，这样可以借助化学减薄使缺陷皮膜脱落、保留质量良好的皮膜作为下一次化成处理的成膜晶核，或者借助物理减薄来增大结构件基体表面的金属原子排列致密度及伴随形成的致密氧化物薄膜来减少下次化成过程中的析氢反应，进而实现高致密度、低缺陷的良好皮膜制备，保证所得皮膜的稳定低电阻，以便于结构件的电连接接地。
本申请实施方式中，所述减薄处理包括对第i次化成处理形成的皮膜进行整体减薄，或者进行局部减薄以去除预设区域的皮膜。
本申请一些实施方式中，所述整体减薄的方式包括化学减薄，所述局部减薄的方式包括物理减薄。
本申请一些实施方式中，所述化学减薄为碱洗减薄，所用碱性减薄剂是pH≥12的强碱水溶液，进行所述碱性减薄的时间在60s以上，温度在50-90℃的范围内。
本申请实施方式中，所述物理减薄的方式包括镭雕或离子束减薄。
本申请一些实施方式中，通过所述镭雕进行所述局部减薄。
本申请一些实施方式中，所述制备方法还包括：在进行了n次化成处理后的所述结构件基体上形成合金层，以覆盖第n次化成处理形成的皮膜。合金层与皮膜之间的接触情况良好、接触电阻较小，且其可以提升整体膜层的耐磨性和强度。
本申请实施例第二方面提供了一种结构件，其采用本申请实施例第一方面提供的制备方法制得。
本申请实施例第三方面提供了一种结构件，所述结构件包括结构件基体，以及设置在所述结构件基体表面的第一皮膜结构，其中，所述第一皮膜结构位于所述结构件基体的预设区域，所述预设区域具有多个凹坑，所述第一皮膜结构设置在所述凹坑的表面。
本申请一些实施方式中，所述结构件基体还包括非预设区域，所述非预设区域上具有第二皮膜结构，所述第二皮膜结构的厚度大于所述第一皮膜结构。
本申请一些实施方式中，所述第一皮膜结构上还设置有合金层。
本申请实施例第四方面提供了一种结构件，其包括结构件基体，以及依次层叠设置在所述结构件基体表面的第一皮膜结构和合金层。
本申请一些实施方式中，所述第一皮膜结构完全覆盖所述结构件基体的一侧表面。
本申请另一些实施方式中，所述第一皮膜结构部分覆盖所述结构件基体的一侧表面，所述第一皮膜结构位于所述结构件基体的预设区域，所述预设区域包括多个凹坑，所述第一皮膜结构设置在所述凹坑的表面。
本申请实施例第五方面提供了一种电子设备，其包括如本申请实施例第二方面或第三方面或第四方面所述的结构件。
附图说明
图1是本申请实施例提供的一种电子设备的结构示意图。
图2是本申请一些实施方式提供的对结构件基体进行一次化成处理的完整工艺流程图。
图3是本申请另一些实施方式提供的对结构件基体进行一次化成处理的完整工艺流程图。
图4是本申请实施例提供的在结构件基体上形成皮膜结构的一种完整工艺流程图。
图5是本申请一实施例提供的结构件的制备流程示意图。
图6是本申请另一实施例提供的结构件的制备流程示意图。
图7是本申请又一实施例提供的结构件的制备流程示意图。
图8a、图8b、图8c、图8d为本申请实施例提供的结构件的几种结构示意图。
图9是本申请实施例1中一次化成形成的一次皮膜、减薄后二次化成形成的二次皮膜的表面微观形貌及能谱分析结果的对比图。
图10提供了实施例2中经镭雕处理后的基体预设区域的表面微观形貌图。
图11提供了在图10的基础上再化成形成的二次皮膜的表面微观形貌图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请技术方案进行说明。
本申请实施例提供了带化学转化皮膜的结构件及其制备方法，以及可使用该结构件的电 子设备。本申请提供的技术方案适用于采用以下一种或多种通信技术的电子设备：蓝牙(blue-tooth，BT)通信技术、全球定位系统(global positioning system，GPS)通信技术、无线保真(wireless fidelity，WiFi)通信技术、全球移动通讯系统(global system for mobile communications，GSM)通信技术、宽频码分多址(wideband code division multiple access，WCDMA)通信技术、长期演进(long term evolution，LTE)通信技术、5G通信技术以及未来其他通信技术等。其中，本申请实施例中的电子设备可以是手机、平板电脑、笔记本电脑、智能手环、智能手表、智能头盔、智能眼镜等。电子设备还可以是蜂窝电话、无绳电话、会话启动协议(session initiation protocol，SIP)电话、无线本地环路(wireless local loop，WLL)站、个人数字助手(personal digital assistant，PDA)、具有无线通信功能的手持设备、计算设备或连接到无线调制解调器的其它处理设备、车载设备，5G网络中的电子设备或者未来演进的公用陆地移动通信网络(public land mobile network，PLMN)中的电子设备等，本申请实施例对此并不限定。
图1示例性示出了本申请提供的一种电子设备的结构示意图。在本申请实施例中，以电子设备为手机进行说明。如图1所示，电子设备10可以包括：玻璃盖板(cover glass)13、显示模组(display)15、印刷电路板(printed circuit board，PCB)17、中框(housing)19和后盖(rear cover)21。
其中，玻璃盖板(cover glass，CG)13可以紧贴显示模组15设置，主要用于对显示模组15起到保护防尘作用。应理解，在一些实施例中，玻璃盖板13也可以被替换为其他材料的盖板，例如超薄玻璃材料盖板，PET(Polyethylene terephthalate，聚对苯二甲酸乙二酯)材料盖板等。
在一个实施例中，显示模组15可以包括液晶显示面板(liquid crystal display，LCD)，发光二极管(light emitting diode，LED)显示面板或者有机发光半导体(organic light-emitting diode，OLED)显示面板等，本申请对此并不做限制。
其中，印刷电路板PCB17可以采用耐燃材料(FR-4)介质板，也可以采用罗杰斯(Rogers)介质板，也可以采用Rogers和FR-4的混合介质板，等等。这里，FR-4是一种耐燃材料等级的代号，Rogers介质板是一种高频板。印刷电路板PCB17靠近中框19的一侧可以设置一金属层，该金属层可以通过在PCB17的表面蚀刻金属形成。该金属层可用于印刷电路板PCB17上承载的电子元件接地，以防止用户触电或设备损坏。该金属层可以称为PCB地板。不限于PCB地板外，电子设备10还可以具有其他用来接地的地板，可例如金属中框。
其中，电子设备10还可以包括电池(图中未示出)。电池可以设置于中框19内，电池可以将PCB17分为主板和子板，主板可以设置于中框19和电池的上边沿之间，子板可以设置于中框19和电池的下边沿之间。
其中，中框19主要起整机的支撑作用。中框19可以包括边框11，边框11可以绕电子设备10和显示模组15的外围延伸，边框11具体可以包围显示模组15的四个侧边，以帮助固定显示模组15。边框11可以由金属等传导性材料形成。在一种实现方式中，金属材料制成的边框11可以直接用作电子设备10的金属边框，形成金属边框的外观，适用于金属工业设计(industrial design，ID)。在另一种实施方式中，边框11的外表面还可以为非金属材料，例如塑料边框，形成非金属边框的外观，适用于非金属ID。
其中，后盖21可以是金属材料制成的后盖，也可以是非导电材料制成的后盖，如玻璃后盖、塑料后盖等非金属后盖。后盖21主要用于将电池、电路板等部件封堵于壳体的内腔，并对电子设备的各部件起到保护作用。
需要说明的是，图1仅示意性地示出了电子设备10所包括的一些部件，这些部件的实际形状、实际大小和实际构造可不受图1的限定。
本申请实施方式中，上述中框19可以采用本申请实施例的带化学转化皮膜的结构件制成。该结构件包括结构件基体和设置在该结构件基体上的化学转化皮膜。其中，结构件基体的材料可以是镁或镁合金。
由于镁或镁合金的密度较小，当其用于电子设备时能有助于减轻电子设备的重量。但由于镁或镁合金的活性较高，在使用过程中容易被氧化和腐蚀，因此需要通过表面处理来提高其耐蚀性，同时不能牺牲其表面导电性能。相比于其他表面防护技术，化学转化处理具有成本低、操作简单等优点，通过化学转化处理在结构件基体上形成的化学转化皮膜是一种良好的导电防腐层，可具有良好耐蚀性及高电导率。这样，当该结构件用于电子设备的中框19时，表面的化学转化皮膜不仅能够起到防腐保护作用，还能用于与电子设备10中导电部件的电连接，以实现接地，进而降低电子静电风险、降低器件之间的射频干扰等，提升电子设备10的工作性能。具体地，中框19的接地，可将进入电子设备的显示模组与中框间隙的静电及时导向大地，避免静电积累损伤显示模组以及防电磁干扰等。因此，本申请提供的结构件具有良好的防腐性能，并能在预设位置实现可靠性较高的电连接。
本申请实施例中，上述结构件可以通过下述制备方法制备，该制备方法具体包括：
对结构件基体进行n次化成处理，n≥2，并在第i次化成处理之后和第i+1次化成处理之前，对第i次化成处理形成的皮膜进行减薄处理；其中，i是1至n-1之间的任意整数；所述减薄处理的方式包括化学减薄或物理减薄。
图4中以n＝2为例，示出了在结构件基体上形成皮膜结构的一种完整工艺流程图。图4示出的工艺流程包括以下步骤：(1)先对结构件基体进行一次化成处理，以在其表面形成一次皮膜；(2)接着对该一次皮膜进行减薄处理；(3)对带有减薄后一次皮膜的结构件基体再进行一次化成处理(即，进行第2次化成处理)。此后，对二次化成后的结构件基体依次进行水洗、烘干，以备后用。其中，烘干可在80℃左右的温度下进行。
本申请实施方式中，所述结构件基体的材质可以包括但不限于是镁或镁合金、铝或铝合金、锌或锌合金、钛或钛合金等。其中，对化学活性性高的镁或镁合金特别有必要采用本申请提供的上述方法进行处理。示例性地，镁合金的牌号可以是AZ91D、AZ31B等。
本申请实施方式中，在对结构件基体进行第1次化成处理之前，还对该结构件基体进行前处理(如图4中所示)。本申请对前处理的方式不作限制，可以包括酸洗和碱洗的组合，还可以包括与其他处理方式的组合等。在一些实施方式中，如图2所示，所述前处理包括：预脱脂/脱脂、酸洗、碱蚀。可以理解地，在各步前处理之后还应分别进行水洗，以免上步处理残留的试剂干扰下一步处理。各步水洗可在室温下进行1-2分钟。其中，预脱脂/脱脂处理可以采用碱性脱脂剂于55-65℃的温度下进行5-10分钟，也可以将该步处理称之为“碱洗”；酸洗可以采用有机酸酸洗液于45-55℃的温度下进行0.5-2分钟；碱蚀可以采用强碱性溶液于80-90℃的温度下进行3-10分钟。经过三步式前处理后，可有效去除结构件基体(特别是镁合金压铸件)表面的脏污，得到具有活性的洁净表面，为后续的化成处理提供良好的前提。在另一些实施方式中，如图3所示，所述前处理依次包括：碱洗、酸洗、表调。其中，碱洗是为了去除表面油污；酸洗可以在柠檬酸、乙酸或酒石酸溶液中于20-30℃下进行，酸洗可去除结构件基体表面的氧化物、金属杂质等。表调(即，表面调整)所采用的表调剂溶液可以是含氢氧化钠、碳酸钠、磷酸钠和水的混合溶液，将酸洗后的结构件基体放入表调剂溶液中可实现对其的表面调整。在又一些实施方式中，如图4所示，第1次化成之前的前处理可以 依次包括冷式酸洗、中和、热式酸洗及中和。虽然图4中未示出，但可以理解地，在各步前处理之后还应分别进行水洗，以免残留的上步处理试剂干扰下一步处理。其中，冷式酸洗可以采用含氟无机酸进行，热式酸洗可以采用有机弱酸(如柠檬酸、乙酸或酒石酸等)进行，且热式酸洗的进行温度大于冷式酸洗；两步中和可独立地采用强碱溶液进行。
化成处理是通过化学或电化学的方式在基体表面形成一种表面膜(即，皮膜)，通过化成处理形成的皮膜类型可根据所采用化学转化液决定。常见的皮膜包括但不限于磷化物转化膜、铬酸盐转化膜、锡酸盐转化膜、锆酸盐转化膜、钼酸盐转化膜、钒酸盐转化膜、钛酸盐转化膜、高锰酸盐转化膜等。化成处理所采用的化学转化液(也可成为“皮膜剂”)可以包括但不限于磷酸盐体系、铬酸盐体系、锡酸盐体系、锆酸盐体系、钼酸盐体系、钒酸盐体系、钛酸盐体系、高锰酸盐体系、水滑石体系、稀土盐体系和植物酸体系以及氟化物等，或前述体系的任意组合等。
对于镁或镁合金来说，其表面常见的皮膜通常是磷酸盐转化膜。在一些实施方式中，对结构件基体进行第1次化成处理所采用的化学转化液可以是pH为2.2-3.2的P-Ca-V复合磷化液，其组成可以是：85％的磷酸4～20ml/L，磷酸二氢钠5～30g/L，硝酸钙10～40g/L，苯磺酸钠0.5～10g/L，偏钒酸铵0.5～5g/L，余量为水。在18-60℃的温度下使用该化学转化液进行处理。在另一些实施方式中，化学转化液的组成可以包括磷酸二氢钠、磷酸、钙盐、水及稀土金属；该化学转化液的pH为1.8-2.2，可在12-15℃下对结构件基体进行处理。在又一些实施方式中，化成处理所用化学转化液包括磷酸盐和过渡金属盐等。
本申请中，对结构件基体所进行的n次化成处理中，各次化成处理所采用的化学转化液可以相同，或者不同。各次化成处理的进行时间可以相同或者不同。一般地，第1次化成处理的进行时间较其他次的化成处理长。
本申请实施方式中，上述减薄处理可以包括：对第i次化成处理形成的皮膜进行整体减薄，或者进行局部减薄以去除预设区域的皮膜。其中，“整体减薄”可使第i次化成处理形成的皮膜沿其厚度方向均变薄，且该皮膜背离结构件基体表面的各区域均可朝结构件基体的方向被减薄，且各区域被减薄的厚度可以相同或者不同。其中，所述整体减薄或局部减薄的方式包括化学减薄或物理减薄。一般地，所述化学减薄更适用于整体减薄，所述物理减薄更适合于局部减薄。其中，对第1次至第n-1次之间的任意第i次化成处理形成的皮膜所进行的减薄方式可以相同，或者不同。
本申请实施方式中，在进行化学减薄时，可将结构件基体浸泡在化学减薄剂中，或将化学减薄剂喷淋或涂覆在第i次化成处理形成的皮膜上。即，化学减薄的具体实现方式包括但不限于是浸泡、喷淋或涂覆。其中，所述化学减薄可以具体包括但不限于是碱洗减薄、或酸洗减薄等。换言之，所述化学减薄剂包括碱性减薄剂或酸性减薄剂。本申请一些实施方式中，所述化学减薄为碱洗减薄，所采用的碱性减薄剂可以是pH≥12的强碱水溶液。该强碱水溶液中的溶质-强碱可以是NaOH、KOH或其组合等。进行碱性减薄的时间可以在60s以上，例如60s、80s、90s、120s等；温度可以在50-90℃的范围内，例如温度是55、60、75、80或85℃等。在一些具体实施例中，当将结构件基体浸泡在碱性减薄剂中进行碱洗减薄时，为保证良好的减薄效果，还可以在该碱洗减薄过程中还可以施加超声波。即，在超声波存在下进行所述碱洗减薄。
图5中以化成处理进行的总次数n＝2为例，示出了结构件的一种制备流程示意图。图5中，①对结构件基体进行前处理后进行一次化成处理，以使结构件基体的表面覆盖一次皮膜；②接着通过化学减薄的方式将该一次皮膜整体减薄，③随后对带有减薄后一次皮膜的结构件 基体进行二次化成处理，以在减薄后的一次皮膜基础上形成二次皮膜，得到带皮膜结构的结构件。
其中，对一次皮膜进行化学减薄处理，可以促进一次皮膜中成膜缺陷区域的皮膜(如，致密度低、孔隙大的表层皮膜)的减薄/脱落，这样可以保留一次皮膜中质量较好的部分(如，致密度高的底层皮膜)并充当晶核，借助减薄后留下来的质量良好的晶核，能大幅降低二次化成时对化成溶液的过饱和度的要求，并起到引导二次皮膜生长的作用，进而可以提高二次化成的成膜质量(如提高成膜致密度、降低成膜缺陷)，获得高致密度、低缺陷的皮膜，其膜层电阻较低。进一步地，由于保留的晶核能降低二次化成用化成溶液的过饱和度，因此可缩短二次化成处理的进行时间，获得低厚度的皮膜。
类似地，当n≥3时，对带有减薄后的一次皮膜的结构件基体进行n-1次化成处理、并在相邻两次化成处理之间都对前一次形成的皮膜进行减薄处理，也能取得与n＝2时类似的技术效果，均可以实现保留前一次化成处理形成的质量良好晶核，起到引导下一次化成处理时皮膜快速、致密的沉积生长。其中，化成处理的进行总次数可根据耐腐蚀性和电阻要求来决定。此外，当n≥3时，通过调控各次化成处理用化学转化液的配方，还可以制得皮膜颜色可调的外观件，以适配更多的应用场景。
通过上述技术方案，形成在结构件基体表面的皮膜结构是第1次至第n-1次减薄后皮膜，与第n次化成皮膜的叠加(如图5所示)。由于各次减薄后皮膜都是保留下来的高致密性膜层、最后一次化成皮膜是在第n-1次皮膜的基础上引晶形成，因此，整体的皮膜结构沿其厚度方向的致密度基本不变，都是高致密膜层，而非像现有的一次皮膜沿其背离结构件基体的厚度方向(换言之，自下而上的方向)是致密度逐渐降低的。
当对第i次(i为1至n-1之间的任意整数)化成处理形成的皮膜均进行化学减薄处理，本申请一些实施方式中，在对结构件基体进行的n次化成处理中，还可以控制满足以下至少一个条件，以实现膜厚低、成膜缺陷少的皮膜结构制备：a)第i次(i≥2)化成处理的进行时间少于第1次化成处理的进行时间；b)n次化成处理所用的化学转化液形成浓度梯度。
对于条件b)，以n＝4为例，第1次化成用化学转化液、第2次化成用化学转化液、第3次化成用化学转化液、第4次化成用化学转化液的浓度可以呈梯度增加、或梯度降低，例如呈逐渐降低的趋势。此外，对于各次化成处理的时间，还可以进一步满足：第i+1次化成处理的进行时间少于第i次化成处理。这样可借助化成时间逐渐降低的多次化成处理，进一步降低整体皮膜结构的获得时间、降低膜厚，并保障成膜质量。以两次化成处理进行示例，第1次化成处理的时间可以为20-40s，第2次化成处理的时间可以为1-10s。
本申请实施方式中，对第i次化成处理形成的皮膜所进行的物理减薄的方式可以包括但不限于镭雕或离子束减薄。这些物理减薄方式可以产生足以使结构件基体表面材料重熔的热量，同时其较窄的加工工艺深度又不会过度破坏基体。在一些实施方式中，采用物理减薄的方式进行上述局部减薄，以减薄掉预设区域的皮膜。其中，预设区域通常是结构件基体的一侧表面的部分区域。
本申请一些实施方式中，采用镭雕的方式进行所述局部减薄。其中，镭雕时的激光功率可以控制在25-30W(镭雕机的额定功率可大于或等于35W)；镭雕速度小于或等于3000mm/s。这样有利于保证预设区域的一次皮膜被完全雕穿。在一些实施方式中，镭雕包括线状镭雕，镭雕的线间距小于等于0.05mm，镭雕线路需要各交叉一次。镭雕线路交叉处理中，能够更顺利地使结构件基体表面的金属元素熔化。
图6中以化成处理进行的总次数n＝2为例，示出了结构件的另一种制备流程示意图。图 6中，①对结构件基体进行前处理后进行一次化成处理，以使结构件基体的表面形成一次皮膜；②接着通过诸如镭雕的物理减薄的方式对该一次皮膜进行局部减薄，以去除预设区域的皮膜；③随后对带有减薄后一次皮膜的结构件基体进行二次化成处理，在预设区域形成厚度比非预设区域的皮膜厚度薄的二次皮膜，得到结构件。
其中，经步骤②的处理后，经镭雕等物理减薄处理的区域(即，预设区域)不存在一次皮膜，而未经物理减薄处理的其他区域(即，非预设区域)还保留有一次皮膜，保留下来的一次皮膜具有保护作用，在后续再进行的化成处理过程中，其可保证化学转化液基本不会对该未经物理减薄的区域的皮膜产生腐蚀量，从而保证非预设区域的皮膜厚度较厚，耐腐蚀性更好，同时预设区域处的皮膜厚度薄、电阻低，便于结构件在此区域实现可靠性高的电连接。
一般在结构件基体的成型过程中(例如压铸成型过程中)，通常需要引入脱模剂来帮助成型件脱模。随着电子设备的结构件的厚度日益变薄的趋势(例如镁合金结构件的最薄处可达到0.38mm)，脱模剂的侵入深度占比越来越大，(例如侵入深度超过10μm)，现有技术并未能有效祛除化学性质稳定的脱模剂，导致结构件基体残留有脱模剂区域的电阻急剧恶化(如电阻值超过20Ω)，不能满足3C类电子设备的接地要求；若采用延长酸洗时间的处理则会加大结构件基体的腐蚀量、降低其良率。而本申请对带一次皮膜的结构件基体进行局部镭雕等物理减薄处理，该处理过程中产生的热量可使结构件基体预设区域表面存在的一次皮膜和脱模剂被清除干净，同时结构件基体的金属元素(如Mg、Al等)的重熔可在此区域形成一层致密的氧化物薄膜，该氧化物薄膜在二次化成处理的成膜过程中能够减缓结构件基体表面的析氢反应，且其与化学转化液之间反应不会产生氢气，同时提供成膜用的金属离子，从而保证在预设区域形成致密度高、缺陷少、电阻低的二次皮膜。其中，当结构件基体为镁或镁合金时，该氧化物薄膜包含氧化镁，其可提供化成用Mg2+。再者，当结构件基体为镁合金时，在镭雕等物理减薄处理时，合金中的Mg较Al元素更易熔出，较易形成致密度高的铝偏析β相(即，Mg17Al12)，其存在更利于提升二次皮膜的致密度。
此外，对带一次皮膜的结构件基体进行局部镭雕等物理减薄处理时，能够使结构件基体表面的材质发生一定熔化，在冷却成为固体的过程中可使结构件基体表面的缺陷减少、使金属原子的排列情况更加致密，在盐雾试验中电解质溶液不易渗入结构件基体而引起其腐蚀，利于提升其耐蚀性/耐候性。
需要说明的是，当采用镭雕或离子束减薄进行所述物理减薄时，会在结构件基体的预设区域产生多个凹坑，且多个凹坑通常是连续分布，相邻凹坑之间是邻接的。当在物理减薄后再进行二次化成处理时，在各凹坑的表面会形成二次皮膜。
类似地，当对结构件基体共进行n次(n≥3)化成处理并对第i次化成处理形成的皮膜进行物理减薄处理时，也能取得与n＝2时类似的技术效果。
类似地，当对第i次化成处理形成的皮膜进行物理减薄，在对结构件基体进行的n次化成处理中，也还可以控制满足以下至少一个条件，实现膜厚低、成膜缺陷少的皮膜结构制备：a)第i次(i≥2)化成处理的进行时间少于第1次化成处理的进行时间；b)n次化成处理所用的化学转化液形成浓度梯度，例如呈梯度增加或梯度降低的趋势。此外，对于各次化成处理的时间，还可以进一步满足：第i+1次化成处理的进行时间少于第i次化成处理。这样可借助化成时间逐渐降低的多次化成处理，进一步降低整体皮膜结构的获得时间、降低膜厚，并保障成膜质量。
本申请一些实施方式中，当对第i次化成处理形成的皮膜均采用物理减薄的方式进行局部减薄时，对该结构件基体进行的化成处理的总次数n可以等于2。此时，这样结构件的制 备方法能较好地兼顾较短工艺时长、较低的皮膜电阻。
本申请一些实施方式中，在采用物理减薄的方式进行所述局部减薄时，所述制备方法还包括：在进行了n次化成处理后的结构件基体上形成合金层，以覆盖第n次化成处理形成的皮膜。此时，预设区域的皮膜表面(具体是第n次化成处理在该预设区域形成的皮膜表面)就形成了合金层；非预设区域的皮膜上可以没有合金层。例如，当n＝2时，如图7所示，位于预设区域的二次皮膜上形成了合金层。
该合金层可以充当保护层，其可以通过点涂液态低熔点合金料的方式形成，其在液态时的浸润性好，能与物理减薄后再形成的皮膜的凹凸不平表面有仿形接触，相较于直接在皮膜贴合或焊接金属片，该仿形接触能有效增大与皮膜的接触面积、减少接触电阻，并提高结合稳定性，还可使表面带合金层的皮膜表面平整，更利于后续与电子设备的导电部件之间的稳定电连接。此外，预设区域的皮膜上有了该合金层附着后，皮膜在基体上的附着强度得到保证，同时整体膜层的耐磨性和强度得到显著提高，从而使皮膜可以兼顾高耐磨、稳定低电阻的效果，能适配更多的应用场景。
本申请实施方式中，合金层的熔点比结构件基体低，其熔点最好明显低于焊锡的焊接温度，例如其熔点在200℃以下。此外，该合金层的耐磨性比结构件基体高。本申请一些实施方式中，该合金层的材质可以包括但不限于是铟、锡、铋的合金，或者铟、锡、镓的合金等。
类似地，当采用前述化学减薄的方式对第i次化成处理形成的皮膜进行整体减薄时，所述制备方法也还可以包括：在进行了n次化成处理后的结构件基体上形成合金层，以覆盖第n次化成处理形成的皮膜。此时，合金层可以覆盖结构件基体上皮膜结构的所有表面。合金层与皮膜结构之间的接触情况良好、接触电阻较小，还可以提升皮膜结构的耐磨性和强度。
需要说明的是，本申请中，当对第i次(i为1至n-1之间的任意整数)化成处理形成的皮膜进行的减薄方式可以相同或者不同。例如，本申请其他实施方式中，可以对第1次化成处理形成的皮膜进行局部物理减薄，之后对结构件基体再进行n-1次化成处理，并在第i次化成处理之后和第i+1次化成处理之前，对第i次化成处理形成的皮膜进行化学减薄，i为2至n-1之间的任意整数。同样地，如本申请前文所述，也可以对n次化成处理所用化学转化液的浓度进行梯度控制、控制第2次及以后次的各化成处理的进行时间少于第1次化成处理等。当然，也可以在进行了n次化成处理后的结构件基体上形成合金层，以覆盖第n次化成处理形成的皮膜。
采用本申请实施例上述制备方法制得的结构件，表面具有致密高、缺陷少、电阻低的皮膜结构，当该结构件需要电连接接地时，该皮膜的存在可以避免搭接电阻恶化的问题。此外，当该皮膜结构上进一步具有合金层时，能提升整体膜层的耐磨性和接触强度，且不影响结构件与导电器件之间电连接的可靠性。
本申请实施例还提供了一种结构件，该结构件基体的表面具有皮膜结构。该结构件可以采用本申请例上述制备方法制得。
如图8a所示，本申请一些实施方式中，结构件100包括结构件基体101，结构件基体101的一侧表面上设置第一皮膜结构201。其中，结构件基体101的该表面可以被第一皮膜结构201完全覆盖，也可以部分覆盖。
在一些实施方式中，沿第一皮膜结构201的厚度方向，第一皮膜结构201的致密度基本不变。这样第一皮膜结构201沿其厚度方向基本都是高致密性的，表面缺陷少，能有效成膜缺陷导致皮膜表面搭接电阻恶化的问题。而其他现有技术中，结构件基体表面的皮膜结构沿图8a中箭头示出的方向(即，沿结构件基体101向皮膜的方向，也即自下而上的方向)致密 度是逐渐降低的。上述“致密度基本不变”可理解为：第一皮膜结构201沿其厚度方向的孔隙率也基本不变，其中，第一皮膜结构201远离结构件基体101一侧的孔隙率a与其靠近结构件基体101一侧的孔隙率b之间的相对偏离程度k不超过30％，即，k＝|a-b|/b，k≤30％。进一步地，k≤20％，或者k≤10％，或者k≤5％，甚至k≤2％等。
进一步地，如图8b所示，在一些实施方式中，第一皮膜结构201上还设置有合金层30，第一皮膜结构201、合金层30依次层叠设置在结构件基体101上。合金层30的存在能保证结构件基体101上整体膜层的高耐磨性、良好耐候性，以及结构件100和与其电连接的导电部件之间的良好接触强度、低接触电阻等。
如图8c所示，本申请另外一些实施方式中，所提供的结构件100包括结构件基体101，及位于其一侧表面上的第一皮膜结构201’，该第一皮膜结构201’位于结构件基体101的预设区域，其中，该预设区域可以是结构件基体101一侧表面的全部表面区域，也可以是如图8c示出的部分区域。其中，该预设区域具有多个凹坑，第一皮膜结构201’设置在该凹坑的表面。
此种情况下，第一皮膜结构201’的形貌与现有化学转化皮膜不同，且其膜层质量较好，如致密度高、缺陷少，且在此预设区域几乎不存在化学性质稳定的脱模剂，能解决现有皮膜技术中脱模剂无法清洗干净导致皮膜表面搭接电阻恶化的问题。其中，凹坑的深度可以是2-6μm，例如3μm、4μm、5μm等；凹坑的直径可以是30-60μm，例如35μm、40μm、50μm等。
一般地，预设区域的多个凹坑通常是连续分布的，相邻凹坑之间是邻接的、没有间隙。第一皮膜结构201’位于各凹坑的内壁上。在一些实施例中，第一皮膜结构201’可以部分覆盖所述凹坑的内壁。在另一些实施例中，第一皮膜结构201’可以是一连续膜层结构，其可以完全覆盖所述凹坑的内壁，但其部分填充所述凹坑，即，凹坑不被第一皮膜结构201’填平。其中，第一皮膜结构201’远离结构件基体101的表面可以为非平面。第一皮膜结构201’可以呈连续山谷状，其凹陷方向朝着结构件基体101。
请继续参见图8c，结构件基体101还包括非预设区域，该非预设区域上具有第二皮膜结构202，且第二皮膜结构202的厚度可以大于第一皮膜结构201’。这样，结构件基体101的非预设区域上的皮膜厚度较厚，耐腐蚀性更好，预设区域处的皮膜厚度较薄、电阻低，便于结构件在此区域实现可靠性高的电连接。从而，结构件100能具有更强的市场竞争力。
进一步地，如图8d所示，本申请另一些实施方式中，第一皮膜结构201’上还设置有合金层30。其中，合金层30可以填充连续山谷状的第一皮膜结构201’的凹陷处。在某些情况下，合金层30可以将连续山谷状的第一皮膜结构201’的凹陷处完全填平，并覆盖预设区域的结构件基体。此时，合金层30背离第一皮膜结构201’的表面为一平面，这利于增大结构件100后续与其他导电部件之间的接触力、接触面积，实现稳定的电连接。与上述类似，合金层30的存在能保证结构件基体101上整体膜层的高耐磨性、高耐候性，以及结构件100和与其电连接的导电部件之间的良好接触强度、低接触电阻等。
其中，需要说明的是，当本申请实施例的结构件100需要电连接接地时，可以将该结构件100与需要接地的电子器件直接进行电连接，也可以在该结构件100与需要接地的电子器件之间填充可吸收结构公差的弹性导电介质(例如，导电泡棉)，以保证电连接的可靠性。
需要说明的是，除非另有明确的规定和限定，本申请术语“电连接”应作广义理解，例如，在本申请中“电连接”可理解为元器件的物理接触并电导通；也可理解为线路构造中不同元器件之间通过印制电路板(printed circuit board，PCB)铜箔或导线等可传输电信号的实体线路进行连接的形式，也可以理解为耦合连接。“通信连接”可以指电信号传输，包括无线通信连 接和有线通信连接。无线通信连接不需要实体媒介，且不属于对产品构造进行限定的连接关系。“连接”、“相连”均可以指一种机械连接关系或物理连接关系，例如A与B连接或A与B相连可以指，A与B之间存在紧固的构件(如螺钉、螺栓、铆钉等)，或者A与B相互接触且A与B难以被分离。
本申请实施例提供一种电子设备，可以包括上述实施例中所述的任一种结构件。
需要说明的是，本申请上述实施例虽然以结构件用作手机这一电子设备的中框为例进行了应用说明，但可以理解的是，本申请实施例提供的结构件还可以用于其他电子设备的壳体。其他可行的电子设备可如本申请前文的举例，但本申请电子设备的范围并不限于前文的举例。
由于电子设备采用了本申请上述实施例所述的导电性好、防腐性能优良的结构件，该电子设备的质量可靠性高，该电子设备的使用体验和市场竞争力可以得到提升。
在本申请所提供的实施例中，应该理解到，所揭露的系统、装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施例仅仅是示意性的，例如，所述单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，装置或单元的间接耦合或通信连接，可以是电性或其它的形式。
下面分多个具体实施例对本申请实施例进行进一步的说明。其中，本申请实施例不限定于以下的具体实施例。
实施例1
一种结构件的制备方法，请一并参阅图4和图5，该制备方法包括以下步骤：
(1)先对材质为镁合金AZ91D、厚度≥0.2mm的结构件基体进行如下前处理：采用含氟无机酸对结构件基体进行冷式酸洗，温度可以是0-10℃；之后采用诸如NaOH的水溶液进行中和处理；接着采用诸如柠檬酸等有机弱酸进行热式酸洗，且温度比冷式酸洗高，例如50-90℃；
然后采用诸如磷酸盐体系的化学转化溶液对结构件基体进行一次化成处理，化成时间可以是20s-40s，在镁合金基体表面覆盖一定厚度的磷酸盐皮膜。
(2)一次皮膜的减薄：将步骤(1)得到的镁合金结构件基体浸泡在pH＞12的NaOH水溶液进行整体减薄至少50s，减薄过程中施加超声，温度控制在10-90℃，减薄完成后进行水洗。
(3)对带有减薄后一次皮膜的镁合金结构件基体进行二次化成处理以形成二次皮膜，其中，二次化成用的化成溶液浓度可与一次化成用的化成溶液浓度形成梯度，二次成膜的时间可控制在1s～10s。之后，将二次化成后的结构件基体依次进行水洗、烘干(温度可为80℃)。
通过实施实施例1的方案，可以在镁合金结构件上生成高致密度和低厚度的皮膜，实现了预设区域皮膜的稳定低电阻及对结构件的低腐蚀量。其中，对实施例1制得的结构件采用直径为1.4mm的镀金球头探针(探针探头弹力0.7N左右)进行电阻测试时，测得该结构件上皮膜的电阻值在0.2Ω左右，腐蚀量在5μm左右(该腐蚀量是与一次化成之前的结构件基体比)。而参照现有技术做出来的皮膜(即，在结构件基体上进行一次化成形成的皮膜)，用上述测试方法测得的皮膜电阻值大于5Ω，腐蚀量在10μm左右。这表明，本申请实施例1的方案达到了镁合金结构件上皮膜电阻较低，且对结构件的腐蚀量低的效果。
图9汇总了实施例1中镁合金结构件基体上一次化成后皮膜的扫描电子显微镜(Scanning Electron Microscope，SEM)图和能量色散X射线光谱仪(Energy Dispersive X-Ray Spectroscopy， EDX)图，以及减薄后二次化成形成的二次皮膜的SEM图和EDX图。经过对比分析发现，一次皮膜样品呈无规律碎块状分布，存在明显的沟壑状裂纹，裂纹平均宽度≥1μm；减薄后形成的二次皮膜表面呈现连续网状分布，晶界铝偏析β相(Mg17Al12)凸起，仅在晶内存在微小裂纹，平均宽度≤0.5μm；说明减薄后形成的二次皮膜的致密度大幅提升。同时，减薄后形成的二次皮膜中磷含量大幅降低，间接说明化学转化反应的产物减少，即膜层变薄。因此，初始的一次皮膜经减薄后，表面非致密部分被去除，所得二次皮膜的致密度高，且膜层较薄，这既有利于提升皮膜的耐盐雾性，同时其较薄的厚度还能满足低电阻值的要求。
以上皮膜特征的形成，主要是由于一次化成后的碱洗减薄可以促进一次皮膜中磷酸一氢盐、磷酸二氢盐或者磷酸盐的水解，也可以促进部分成膜缺陷区磷酸氢盐的脱落，实现了皮膜的减薄，并且可以保留部分一次化成成膜质量良好的晶核。借助保留下来的质量良好的一次皮膜作晶核，能够缩短二次化成的进行时间、提高成膜质量。当二次化成的进行时间缩短时，可利于得到高致密度和低厚度的镁合金皮膜，从而实现镁合金皮膜稳定低电阻和对结构件的低腐蚀量。
实施例2
一种结构件的制备方法，请参阅图6的流程，该制备方法包括以下步骤：
(1)先对材质为镁合金的结构件基体进行前处理及一次化成处理，形成一定厚度的一次皮膜，具体操作步骤可参见上述实施例1；
(2)一次皮膜的减薄：对步骤(1)处理后的镁合金结构件基体的预设区域进行局部高功率的镭雕，以减薄掉预设区域的一次皮膜，未镭雕区域保留了一次皮膜；其中，镭雕具体是线状镭雕，镭雕的线间距小于等于0.05mm，镭雕线路需要交叉各一次，镭雕速度小于或等于3000mm/s，镭雕时的激光功率为25-30W。镭雕完成后，将结构件基体表面清理干净。
(3)对镭雕后的镁合金结构件基体进行二次化成处理以在镭雕区域形成二次皮膜，之后将二次化成后的结构件基体进行水洗、烘干。其中，二次化成用的化成溶液可与一次化成用的化成溶液的浓度一样，二次化成时间为5-8s；在二次化成时，未镭雕区域的一次皮膜基本无变化。
其中，镭雕线路的交叉处理过程能够使镁合金结构件基体表面的合金熔化，在熔化并冷却为固体状态过程中，可以使镁合金表面的金属缺陷减少及使金属排列更加致密，提升其耐盐雾性。通过镭雕处理后，对应镭雕区域的镁合金结构件基体表面的脱模剂和一次皮膜被清除干净，形成一层致密的氧化物薄膜，该氧化物薄膜在二次化成过程中能够减缓镁合金表面的析氢反应，同时提供成膜用的镁离子，有利于形成致密的二次皮膜。
图10提供了实施例2中经镭雕处理后的基体预设区域的表面微观形貌图。图11提供了镭雕后再化成形成的二次皮膜的表面微观形貌图，其中右图是左图部分区域的放大图。从这些图可以获知，经镭雕处理后，在结构件基体的预设区域产生了多个连续分布的凹坑。当在镭雕后再对结构件基体进行二次化成时，在该凹坑的内壁上会形成二次皮膜。
通过实施实施例2的方案，可以在镁合金结构件的预设区域生成高致密度和低厚度的皮膜，实现了预设区域皮膜的稳定低电阻及对结构件的低腐蚀量。其中，对实施例2制得的结构件采用直径为1.4mm的镀金球头探针(探针探头弹力0.7N左右)进行电阻测试，测得该结构件的预设区域的皮膜电阻值在0.2Ω左右，腐蚀量在3μm左右。而参照现有技术做出来的皮膜(即，在结构件基体上进行一次化成形成的皮膜)，用上述测试方法测得的皮膜的全部区域的电阻值均大于5Ω，腐蚀量在10μm左右。
实施例3
一种结构件的制备方法，请参阅图7的流程，该制备方法与实施例2的区别在于，在步骤(3)之后，还包括以下步骤(4)：在对应局部镭雕区域的二次皮膜上，以点胶的方式镀上一层液态低熔点合金(熔点在200℃以下)，低熔点合金在冷却后会附着在二次皮膜上。
通过实施实施例3的方案，也可以在镁合金结构件的预设区域生成高致密度和低厚度的皮膜，实现了预设区域皮膜的稳定低电阻及对结构件的低腐蚀量，具体效果可参见实施例2部分的描述。
此外，采用通过点低熔点合金的方式在二次皮膜表面形成合金层，该合金层在液态时能够与镭雕后凹凸不平的表面有仿形的接触，仿形的接触能够增大二者的接触面积、减小接触电阻。此外，二次皮膜上附着该合金层后，还能显著提高膜层的耐磨性和强度。
以上所述仅表达了本申请的示例性实施方式，其描述较为具体和详细，但并不能因此而理解为对本申请专利范围的限制。应当指出的是，对任何熟悉本技术领域的技术人员来说，在本申请揭露的技术范围内，可轻易想到若干变化或替换，这些都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以所述权利要求的保护范围为准。

Claims (21)

  1. 一种结构件的制备方法，其特征在于，所述制备方法包括以下步骤：
    对结构件基体进行n次化成处理，n≥2，并在第i次化成处理之后和第i+1次化成处理之前，对第i次化成处理形成的皮膜进行减薄处理；其中，i是1至n-1之间的任意整数；所述减薄处理的方式包括化学减薄或物理减薄。
  2. 如权利要求1所述的制备方法，其特征在于，所述减薄处理包括对第i次化成处理形成的皮膜进行整体减薄，或者进行局部减薄以去除预设区域的皮膜。
  3. 如权利要求2所述的制备方法，其特征在于，所述整体减薄的方式包括所述化学减薄，所述局部减薄的方式包括所述物理减薄。
  4. 如权利要求1-3任一项所述的制备方法，其特征在于，采用所述化学减薄时，将所述结构件基体浸泡在化学减薄剂中，或将化学减薄剂喷淋或涂覆在所述第i次化成处理形成的皮膜上。
  5. 如权利要求4所述的制备方法，其特征在于，所述化学减薄为碱洗减薄，所用碱性减薄剂是pH≥12的强碱水溶液，进行所述碱性减薄的时间在60s以上，温度在50-90℃的范围内。
  6. 如权利要求1-3任一项所述的制备方法，其特征在于，所述物理减薄的方式包括镭雕或离子束减薄。
  7. 如权利要求6所述的制备方法，其特征在于，所述镭雕时的激光功率为25-30W，镭雕速度小于或等于3000mm/s。
  8. 如权利要求7所述的制备方法，其特征在于，所述镭雕包括线状镭雕，镭雕的线间距小于等于0.05mm。
  9. 如权利要求1-8任一项所述的制备方法，其特征在于，对所述结构件基体进行的n次化成处理中，满足以下至少一个条件：
    a)当i≥2时，第i次化成处理的进行时间少于所述第1次化成处理的进行时间；
    b)n次化成处理所用的化学转化液形成浓度梯度。
  10. 如权利要求1-9任一项所述的制备方法，其特征在于，所述制备方法还包括：在进行了n次化成处理后的所述结构件基体上形成合金层，以覆盖第n次化成处理形成的皮膜。
  11. 如权利要求1-10任一项所述的制备方法，其特征在于，在对所述结构件基体进行第1次化成处理之前，所述制备方法还包括：对所述结构件基体进行前处理。
  12. 一种结构件，其采用如权利要求1-11任一项所述的制备方法制得。
  13. 一种结构件，其特征在于，包括结构件基体，以及设置在所述结构件基体表面的第一皮膜结构，其中，所述第一皮膜结构位于所述结构件基体的预设区域，所述预设区域具有多个凹坑，所述第一皮膜结构设置在所述凹坑的表面。
  14. 如权利要求13所述的结构件，其特征在于，所述第一皮膜结构完全覆盖所述凹坑的内壁。
  15. 如权利要求13或14所述的结构件，其特征在于，所述结构件基体还包括非预设区域，所述非预设区域上具有第二皮膜结构，所述第二皮膜结构的厚度大于所述第一皮膜结构。
  16. 如权利要求13-15任一项所述的结构件，其特征在于，所述第一皮膜结构上还设置有合金层。
  17. 一种结构件，其特征在于，包括结构件基体，以及依次层叠设置在所述结构件基体表面的第一皮膜结构和合金层。
  18. 如权利要求17所述的结构件，其特征在于，所述第一皮膜结构完全覆盖所述结构件基体的一侧表面。
  19. 如权利要求17所述的结构件，其特征在于，所述第一皮膜结构部分覆盖所述结构件基体的一侧表面，所述第一皮膜结构位于所述结构件基体的预设区域，所述预设区域包括多个凹坑，所述第一皮膜结构设置在所述凹坑的表面。
  20. 如权利要求18或19所述的结构件，其特征在于，沿所述第一皮膜结构的厚度方向，所述第一皮膜结构的致密度基本不变。
  21. 一种电子设备，其特征在于，包括如权利要求12所述的结构件或如权利要求13-16任一项所述的结构件或如权利要求17-20任一项所述的结构件。
PCT/CN2023/080126 2022-03-11 2023-03-07 一种结构件及其制备方法和电子设备 WO2023169429A1 (zh)

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