A high shielding metal surface treatment method suitable for 5G communication modules

Abstract

The application relates to the technical field of metal surface treatment, and discloses a high-shielding metal surface treatment method suitable for a 5G communication module, which comprises the following steps: carrying out oil removal, micro-etching activation and surface adjustment on a metal base body of the 5G communication module to obtain a surface to be treated; forming a bonding transition layer on the surface to be treated; forming a high-conductivity shielding layer on the surface of the bonding transition layer; forming an anti-diffusion protective layer on the surface of the high-conductivity shielding layer; and carrying out low-contact-resistance adjustment on a shielding lap joint area, a grounding area and a screw crimping area, and carrying out corrosion-resistant sealing treatment on a non-crimped exposed area. Through cooperation of the bonding transition layer, the high-conductivity shielding layer, the anti-diffusion protective layer and the partition sealing treatment, the application improves the conductive continuity of a metal shell, a shielding cover or a heat dissipation cover plate of the 5G communication module, reduces the contact impedance of the shielding lap joint area, and improves the maintenance capability of the high-frequency electromagnetic shielding performance after salt spray and cold and hot cycle.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and more specifically, to a high-shield metal surface treatment method suitable for 5G communication modules. Background Technology

[0002] A typical 5G communication module includes a radio frequency (RF) front-end module, a power amplifier module, a filtering module, a baseband processing module, a millimeter-wave communication module, and corresponding shielding covers, metal housings, RF cavities, heat sinks, and grounding connection structures. Due to the high operating frequency and high integration of components in 5G communication modules, electromagnetic coupling interference can easily occur between RF signals, high-speed digital signals, and power signals within the module. Therefore, communication modules typically require an electromagnetic shielding structure formed by a metal shielding cover, metal housing, or conductive cover.

[0003] Existing 5G communication module metal shielding components are typically made of aluminum alloy, stainless steel, copper alloy, nickel-copper alloy, or low-carbon steel. While these metal materials possess a certain degree of conductivity, during processing, stamping, bending, welding, cleaning, and use, oxide layers, contamination layers, or localized corrosion layers easily form on their surfaces, leading to increased contact resistance in the shielding overlap area, grounding area, and screw crimping area. For high-frequency signals, the metal shielding structure not only requires the material itself to be conductive but also requires a continuous low-impedance connection between the shielding edge, grounding spring, screw fixing area, and shell overlap area. If the contact area surface is oxidized, the plating is discontinuous, or the contact resistance increases after corrosion, gaps and leakage paths can easily form, reducing the electromagnetic shielding performance of the communication module.

[0004] Existing metal surface treatment methods often employ nickel plating, tin plating, copper plating, or electroless nickel plating to improve the corrosion resistance and solderability of metal surfaces. However, for 5G communication module shielding components, simply improving the corrosion resistance of the plating layer is insufficient to guarantee high-frequency shielding stability. If the outer protective film is too thick or the surface oxide film is too dense, although the corrosion resistance is improved, the contact resistance of the shielding overlap area and the grounding area may increase. If only a highly conductive copper layer is formed, oxidation, discoloration, or corrosion expansion are likely to occur in humid, hot, salt spray, or thermal cycling environments, leading to a decrease in shielding performance.

[0005] Furthermore, 5G communication module metal components typically have complex structures such as thin walls, holes, bent edges, spring contact areas, and screw fixing areas. Conventional overall electroplating or overall sealing treatments are insufficient to simultaneously meet the requirements of high conductivity shielding, corrosion resistance protection, and low contact impedance, easily leading to problems such as insufficient corrosion resistance in non-contact exposed areas, excessively high contact resistance in contact areas, and insufficient continuity of shielding at overlapping edges.

[0006] Therefore, it is necessary to provide a high-shield metal surface treatment method suitable for 5G communication modules, so as to form a continuous high-conductivity shielding layer on the surface of the metal substrate, and improve the shielding stability of 5G communication modules in high-frequency operating environments and complex service environments by adjusting the surface in partitions to take into account the low contact resistance of the shielding overlap area and the corrosion resistance of the non-pressurized exposed area. Summary of the Invention

[0007] The purpose of this invention is to provide a high-shield metal surface treatment method suitable for 5G communication modules, so as to solve the above-mentioned technical problems.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] A method for treating highly shielded metal surfaces suitable for 5G communication modules includes the following steps:

[0010] The metal substrate of the 5G communication module is degreased, micro-etched and activated, and surface-modified to obtain the surface to be treated.

[0011] A bonding transition layer is formed on the surface to be treated;

[0012] A highly conductive shielding layer is formed on the surface of the bonding transition layer;

[0013] An anti-diffusion protective layer is formed on the surface of the highly conductive shielding layer;

[0014] The metal substrate of the 5G communication module with the anti-diffusion protective layer is subjected to partitioned surface conditioning. The partitioned surface conditioning includes adjusting the low contact resistance of the shielding overlap area, the contact area and the screw crimping area, and performing corrosion-resistant sealing treatment on the non-crimping exposed area.

[0015] The highly conductive shielding layer is a copper layer or a copper alloy layer with a thickness of 2μm-8μm; the anti-diffusion protective layer is a nickel layer, a nickel-phosphorus alloy layer, or a nickel-tin alloy layer with a thickness of 0.3μm-2.0μm; after zonal surface adjustment, the surface contact resistance of the shielding overlap area, the contact area, and the screw crimping area is ≤20mΩ.

[0016] Preferably, the metal substrate of the 5G communication module is an aluminum alloy substrate, a magnesium alloy substrate, a stainless steel substrate, a copper alloy substrate, a nickel-copper substrate, or a low-carbon steel substrate.

[0017] The metal substrate of the 5G communication module is a 5G communication module shielding cover, metal shell, heat dissipation cover, radio frequency cavity, grounding spring mounting base or module fixing bracket.

[0018] Preferably, the degreasing includes one or both of alkaline degreasing and electrolytic degreasing;

[0019] When the metal substrate of the 5G communication module is an aluminum alloy substrate or a magnesium alloy substrate, the micro-etching activation is followed by zinc replacement treatment or zinc-nickel replacement treatment.

[0020] When the metal substrate of the 5G communication module is a stainless steel substrate, the micro-etching activation is followed by cathodic activation treatment.

[0021] When the metal substrate of the 5G communication module is a copper alloy substrate or a nickel-copper substrate, the micro-etching activation adopts a persulfate-sulfuric acid system or a hydrogen peroxide-sulfuric acid system.

[0022] Preferably, the bonding transition layer is one or more of the following: chemical nickel layer, electrodeposited nickel layer, nickel-phosphorus alloy layer, and nickel-boron alloy layer;

[0023] The thickness of the bonding transition layer is 0.2 μm-1.5 μm;

[0024] After the bonding transition layer is formed, it is washed with water and then proceeds to the high conductivity shielding layer deposition step within 180 seconds.

[0025] Preferably, the highly conductive shielding layer is formed by pulsed copper electrodeposition;

[0026] The pulsed copper electrodeposition uses an acidic copper sulfate electroplating solution, which comprises 120 g / L-220 g / L copper sulfate, 40 g / L-90 g / L sulfuric acid, 30 mg / L-90 mg / L chloride ions, 0.01 g / L-0.30 g / L leveling agent, 0.01 g / L-0.20 g / L grain refiner, and water.

[0027] The average current density of the pulsed copper electrodeposition is 1A / dm²-5A / dm², the pulse frequency is 50Hz-500Hz, the duty cycle is 40%-80%, and the temperature is 20℃-35℃.

[0028] Preferably, the anti-diffusion protective layer is formed by electrodepositing nickel, electroless nickel plating, or electrodepositing a nickel-tin alloy;

[0029] When the anti-diffusion protective layer is a nickel-phosphorus alloy layer, the phosphorus content in the nickel-phosphorus alloy layer is 2wt.%-8wt.%;

[0030] When the anti-diffusion protective layer is a nickel-tin alloy layer, the tin content in the nickel-tin alloy layer is 20wt.%-45wt.%.

[0031] Preferably, the low contact resistance adjustment includes:

[0032] Selective activation is performed on the shielding overlap area, the junction area, and the screw crimping area to remove residual oxidation from the surface of the anti-diffusion protective layer;

[0033] A conductive protective film is formed in the shielding overlap area, the contact area, and the screw crimping area;

[0034] The conductive protective film has a thickness of 10nm-80nm, and includes one or more of benzotriazole protective films, mercaptotriazole protective films, and conductive organic protective films.

[0035] Preferably, the corrosion-resistant sealing treatment uses an aqueous sealing solution, which includes one or more of hydrolyzed silane, nano-silica sol, molybdate, tungstate, and phosphate.

[0036] The temperature for the corrosion-resistant sealing treatment is 35℃-70℃, and the time is 20s-180s.

[0037] After the corrosion-resistant sealing treatment, the thickness of the sealing film in the non-press-bonded exposed area is 50nm-300nm.

[0038] Preferably, after the high conductivity shielding layer and the anti-diffusion protective layer are formed, a low-temperature stress relief treatment is also performed;

[0039] The low-temperature stress relief treatment is performed at a temperature of 80℃-140℃ for a time of 30min-120min.

[0040] The low-temperature stress relief treatment is followed by zoned surface conditioning.

[0041] Preferably, the 5G communication module metal component includes a metal substrate, a bonding transition layer, a highly conductive shielding layer, an anti-diffusion protective layer, and a surface conditioning layer.

[0042] The shielding effectiveness of the metal components of the 5G communication module is ≥80dB in the 0.7GHz-6GHz frequency band;

[0043] The shielding effectiveness of the metal components of the 5G communication module is ≥60dB in the 24GHz-40GHz frequency band;

[0044] After 240 hours of neutral salt spray testing, the contact resistance growth rate of the shielding overlap area, the junction area, and the screw crimping area is ≤30%.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] First, the present invention sequentially forms a bonding transition layer, a highly conductive shielding layer, and an anti-diffusion protection layer on the surface of a metal substrate of a 5G communication module. The bonding transition layer is used to improve the bonding stability between the metal substrate and subsequent metal layers; the highly conductive shielding layer is used to provide a continuous low-impedance high-frequency current conduction path; and the anti-diffusion protection layer is used to reduce the risk of oxidation, corrosion, or diffusion failure of the highly conductive shielding layer, thereby improving the shielding stability of the metal components of the 5G communication module.

[0047] Second, the high conductivity shielding layer of the present invention uses a copper layer or copper alloy layer with a thickness of 2μm-8μm. The above thickness range can form a continuous conductive layer, which is suitable for the high frequency shielding requirements of structures such as 5G communication module shielding covers, metal shells, radio frequency cavities, and heat dissipation covers, while avoiding deformation of thin-walled structures, increased plating stress, or increased assembly dimensional deviations caused by excessively thick metal layers.

[0048] Third, this invention employs zoned surface adjustment to separately treat the shielded overlap area, grounding area, and screw crimping area from the non-crimped exposed area. The shielded overlap area, grounding area, and screw crimping area undergo low contact resistance adjustment to reduce overlap impedance and grounding impedance; the non-crimped exposed area undergoes corrosion-resistant sealing treatment to improve resistance to salt spray, damp heat, and thermal cycling. This zoned treatment avoids the increased contact resistance caused by an overall thick seal, and also avoids insufficient corrosion resistance in the non-contact exposed area due to an overall thin seal.

[0049] Fourth, this invention forms a conductive protective film with a thickness of 10nm-80nm in the shielding overlap area, the grounding area, and the screw crimping area. The conductive protective film can slow down oxidation in the contact area while maintaining a low surface contact resistance, which is beneficial for maintaining the conductive continuity between the shielding edge, the grounding spring, the screw fixing area, and the module housing.

[0050] Fifth, the present invention forms a corrosion-resistant sealing film with a thickness of 50nm-300nm in the non-pressurized exposed area, which can improve the stability of the exposed surface under salt spray, humid heat, condensate and hot and cold cycling environments, and reduce the impact of corrosion propagation on the continuity of the shielding layer.

[0051] Sixth, the present invention employs low-temperature stress relief treatment to reduce the deposition stress in the highly conductive shielding layer and the anti-diffusion protective layer, which is beneficial to reduce the cracking, peeling or contact resistance fluctuation of the coating of thin-walled metal shielding components after thermal cycling. Detailed Implementation

[0052] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0053] This invention provides a high-shield metal surface treatment method suitable for 5G communication modules, applicable to 5G communication module shielding covers, metal housings, heat sinks, radio frequency cavities, grounding spring mounting bases, or module fixing brackets. The metal substrate of the 5G communication module can be aluminum alloy, magnesium alloy, stainless steel, copper alloy, nickel-copper alloy, or low-carbon steel. This method, through pretreatment, bonding transition layer formation, high-conductivity shielding layer formation, anti-diffusion protective layer formation, zoned surface conditioning, and low-temperature stress relief treatment, enables the 5G communication module metal components to simultaneously possess high shielding effectiveness, low contact resistance, and good corrosion resistance stability.

[0054] In this invention, pretreatment is used to remove oil, oxide layers, stamping residues, and processing contaminants from the surface of the metal substrate. For aluminum alloy or magnesium alloy substrates, alkaline degreasing, micro-etching, descaling, water washing, and zinc or zinc-nickel replacement treatment can be performed sequentially to form a surface condition suitable for subsequent metal deposition. For stainless steel substrates, degreasing, pickling, cathodic activation, and water washing can be performed sequentially to remove the passivation film. For copper alloy or nickel-copper alloy substrates, micro-etching activation can be performed using a persulfate-sulfuric acid system or a hydrogen peroxide-sulfuric acid system to form a uniform micro-roughened state on the surface.

[0055] A bonding transition layer is used to improve the adhesion between the metal substrate and the highly conductive shielding layer, and to reduce the influence of different substrates on subsequent deposition layers. The bonding transition layer can be a chemically deposited nickel layer, an electrodeposited nickel layer, a nickel-phosphorus alloy layer, or a nickel-boron alloy layer, with a thickness of 0.2 μm-1.5 μm. If the bonding transition layer is too thin, differences in substrate surface activity and residual oxidation can easily affect the continuity of the highly conductive shielding layer; if the bonding transition layer is too thick, it can easily increase processing costs and plating stress. Therefore, this invention controls the thickness of the bonding transition layer within the above-mentioned range.

[0056] A highly conductive shielding layer is used to provide a continuous conductive path. The highly conductive shielding layer is preferably a copper layer or a copper alloy layer with a thickness of 2μm-8μm. The highly conductive shielding layer can be formed by pulsed copper electrodeposition. Pulsed copper electrodeposition can improve the deposition uniformity at holes, bends, overlaps, and thin-walled areas, and reduce the probability of localized scorching, pinholes, and rough deposition. The acidic copper sulfate electroplating solution may include copper sulfate, sulfuric acid, chloride ions, leveling agents, grain refiners, and water; the electrodeposition temperature is 20℃-35℃; and the average current density is 1A / dm²-5A / dm².

[0057] An anti-diffusion protective layer is used to reduce oxidation, corrosion, and surface diffusion failure of the copper layer. The anti-diffusion protective layer can be a nickel layer, a nickel-phosphorus alloy layer, or a nickel-tin alloy layer, with a thickness of 0.3 μm-2.0 μm. If the thickness of the anti-diffusion protective layer is too low, it will not adequately protect the highly conductive shielding layer; if the thickness is too high, it can easily increase the surface contact resistance or the interface impedance in high-frequency surface current paths. Therefore, this invention controls the thickness of the anti-diffusion protective layer within the above-mentioned range.

[0058] Surface conditioning in zones is used to separately meet the performance requirements of the contact conduction area and the exposed corrosion-resistant area. The shielded overlap area, the grounding area, and the screw crimping area are conductive connection areas, requiring low contact resistance; therefore, low contact resistance conditioning is performed. Low contact resistance conditioning includes selective activation and the formation of a conductive protective film. Selective activation removes residual oxidation from the surface of the anti-diffusion protective layer, while the conductive protective film slows down oxidation in the contact area and maintains stable contact conduction. The thickness of the conductive protective film is 10nm-80nm. The non-crimped exposed area is a long-term exposure area, mainly subjected to salt spray, damp heat, and thermal cycling; therefore, corrosion-resistant sealing treatment is performed. The corrosion-resistant sealing treatment forms a sealing film with a thickness of 50nm-300nm to improve corrosion resistance.

[0059] Example 1

[0060] This embodiment provides a high-shield metal surface treatment method suitable for heat dissipation covers of aluminum alloy 5G communication modules.

[0061] The 5G communication module's metal substrate is an aluminum alloy heat sink cover, which has shielding overlap edges, contact areas, screw crimping areas, and non-crimped exposed areas. First, the aluminum alloy heat sink cover undergoes alkaline degreasing at 55℃ for 5 minutes; after water washing, it undergoes micro-etching for 40 seconds; then, it is descaled and washed a second time. Finally, a zinc replacement treatment is performed for 45 seconds to obtain the surface to be treated.

[0062] A bonding transition layer is formed on the surface to be treated. The bonding transition layer is a chemical nickel layer with a thickness of 0.6 μm. After the bonding transition layer is formed, the surface is washed with water, and then proceeds to the high conductivity shielding layer deposition step within 120 s.

[0063] The highly conductive shielding layer is formed by pulsed copper electrodeposition. Based on 1L of working solution, the acidic copper sulfate electroplating solution includes 180g / L copper sulfate pentahydrate, 60g / L sulfuric acid, 60mg / L chloride ions, 0.05g / L polyethyleneimine quaternary ammonium salt, 0.03g / L Janus Green B, 0.035g / L disodium bis(3-sulfopropyl)disulfide, 0.015g / L sodium 3-mercapto-1-propanesulfonate, and water.

[0064] Polyethyleneimine quaternary ammonium salt and Janus Green B were used as leveling agents, with a total concentration of 0.08 g / L; disodium bis(3-sulfopropyl)disulfide and sodium 3-mercapto-1-propanesulfonate were used as grain refiners, with a total concentration of 0.05 g / L. The average current density of pulsed copper electrodeposition was 3 A / dm², the pulse frequency was 120 Hz, the duty cycle was 60%, and the temperature was 28 °C. A copper layer with a thickness of 5 μm was obtained after deposition.

[0065] An anti-diffusion protective layer was formed on the surface of the highly conductive shielding layer. The anti-diffusion protective layer was a nickel-phosphorus alloy layer with a thickness of 0.8 μm and a phosphorus content of 5 wt.%. Subsequently, a low-temperature stress-relieving treatment was performed at 100 °C for 60 min.

[0066] Selective activation is performed on the shielding overlap area, the junction area, and the screw crimping area to form a conductive protective film with a thickness of 35nm; corrosion-resistant sealing treatment is performed on the non-crimping exposed area at a sealing temperature of 55℃ for 80s to form a corrosion-resistant sealing film with a thickness of 150nm, resulting in a surface-treated aluminum alloy 5G communication module heat dissipation cover.

[0067] In this embodiment, the surface conditioning of the partition is as follows: First, an acid and alkali resistant silicone shielding fixture is used to shield the non-pressurized exposed areas, exposing the shielding overlap area, the junction area, and the screw pressurized area; the shielding edge extends 1.0 mm beyond the boundary of the non-pressurized exposed area. Then, a weakly acidic activation solution is used to selectively activate the shielding overlap area, the junction area, and the screw pressurized area. The weakly acidic activation solution includes 10 g / L citric acid, 3 g / L methanesulfonic acid, 5 g / L ammonium chloride, 0.10 g / L polyether nonionic wetting agent, and water, with a pH of 3.5, a treatment temperature of 25°C, and a treatment time of 25 s.

[0068] After selective activation, the material is sprayed with deionized water and bleed with an air knife, followed by treatment with a conductive protective film treatment solution for 35 seconds. The conductive protective film treatment solution comprises 1.0 g / L benzotriazole, 0.6 g / L 3-amino-1,2,4-triazole, 0.15 g / L sodium 2-mercaptobenzothiazole, 50 g / L ethanol, 0.05 g / L nonionic wetting agent, and water, with a pH of 7.0 and a treatment temperature of 30°C. After treatment, it is pre-dried at 80°C for 5 minutes to form a conductive protective film with a thickness of 35 nm in the shielding overlap area, the junction area, and the screw crimping area.

[0069] Subsequently, the shielding components for the non-pressurized exposed areas were removed, and the overlapping areas, contact areas, and screw pressurized areas were shielded with polyimide tape, with the shielding edge extending 1.0 mm beyond the contact area boundary. Then, the non-pressurized exposed areas underwent a corrosion-resistant sealing treatment. The aqueous sealing solution consisted of 2 g / L hydrolyzed silane, 4 g / L nano-silica sol, 0.8 g / L sodium molybdate, 0.5 g / L sodium tungstate, 0.5 g / L sodium dihydrogen phosphate, and water, with a pH of 6.2; the sealing temperature was 55℃, and the time was 80 s. After treatment, the shielding components were removed, and the area was dried at 100℃ for 10 min to form a corrosion-resistant sealing film with a thickness of 150 nm on the non-pressurized exposed areas.

[0070] Example 2

[0071] This embodiment provides a high-shield metal surface treatment method suitable for nickel-copper 5G communication module shielding covers.

[0072] The metal substrate of the 5G communication module is a nickel-copper shield. First, the nickel-copper shield is degreased with an alkaline solution at a temperature of 50°C for 4 minutes. After washing with water, it is activated by micro-etching with a persulfate-sulfuric acid system for 25 seconds to obtain the surface to be treated.

[0073] A bonding transition layer was formed on the surface to be treated. The bonding transition layer was an electrodeposited nickel layer with a thickness of 0.4 μm. Subsequently, pulsed copper electrodeposition was performed to obtain a copper layer with a thickness of 4 μm. The average current density of the pulsed copper electrodeposition was 2.5 A / dm², the pulse frequency was 150 Hz, the duty cycle was 55%, and the temperature was 26 °C.

[0074] An anti-diffusion protective layer was formed on the surface of the copper layer. The anti-diffusion protective layer was a nickel-tin alloy layer with a thickness of 0.6 μm and a tin content of 30 wt.%. Then, a low-temperature stress-relief treatment was performed at 90 °C for 80 min.

[0075] The contact resistance of the overlapping edge of the shield and the contact area of ​​the grounding spring is adjusted to low level to form a conductive protective film with a thickness of 25nm; the non-pressurized exposed area is subjected to corrosion-resistant sealing treatment to form a corrosion-resistant sealing film with a thickness of 120nm, thus obtaining a surface-treated nickel-copper 5G communication module shield.

[0076] Example 3

[0077] This embodiment provides a highly shielded metal surface treatment method suitable for the radio frequency cavity of a stainless steel 5G communication module.

[0078] The metal substrate of the 5G communication module is a stainless steel radio frequency cavity. First, the stainless steel radio frequency cavity is degreased with alkaline solution at a temperature of 60°C for 6 minutes. After water washing, it is then acid-washed and cathodically activated to obtain the surface to be treated.

[0079] A bonding transition layer was formed on the surface to be treated. The bonding transition layer was an electrodeposited nickel layer with a thickness of 1.0 μm. Subsequently, a copper layer with a thickness of 6 μm was formed by pulsed copper electrodeposition. The average current density of the pulsed copper electrodeposition was 3.5 A / dm², the pulse frequency was 100 Hz, the duty cycle was 65%, and the temperature was 30 °C.

[0080] An anti-diffusion protective layer was formed on the surface of the copper layer. The anti-diffusion protective layer was an electrodeposited nickel layer with a thickness of 1.0 μm. Subsequently, a low-temperature stress relief treatment was performed at 120 °C for 60 min.

[0081] Selective activation is performed on the mating area, screw crimping area, and shielding overlap area to form a conductive protective film with a thickness of 45nm; corrosion-resistant sealing treatment is performed on the non-crimping exposed area to form a corrosion-resistant sealing film with a thickness of 180nm, resulting in a surface-treated stainless steel 5G communication module RF cavity.

[0082] Comparative Example 1

[0083] It is basically the same as Example 1, except that no bonding transition layer is formed, and a highly conductive shielding layer is formed directly on the surface of the aluminum alloy heat sink cover.

[0084] Comparative Example 2

[0085] It is basically the same as Example 1, except that a highly conductive shielding layer is not formed, but only a bonding transition layer and an anti-diffusion protective layer are formed.

[0086] Comparative Example 3

[0087] It is basically the same as Example 1, except that the high conductivity shielding layer is formed by constant current copper electrodeposition instead of pulsed copper electrodeposition.

[0088] Comparative Example 4

[0089] The process is basically the same as in Example 1, except that no zoning surface adjustment is performed, and the same corrosion-resistant sealing treatment is applied to the shielding overlap area, the junction area, the screw crimping area, and the non-crimping exposed area.

[0090] Comparative Example 5 is basically the same as Example 1, except that no anti-diffusion protective layer is formed, and the surface of the highly conductive shielding layer is directly sealed.

[0091] Detection methods

[0092] The metal parts of the 5G communication modules prepared in the embodiments and comparative examples were subjected to the following tests:

[0093] I. Film Thickness Measurement. The thickness of the bonding transition layer, highly conductive shielding layer, anti-diffusion protective layer, conductive protective film, and corrosion-resistant sealing film was measured using an X-ray fluorescence thickness gauge, cross-sectional metallographic microscope, or scanning electron microscope. For each sample, at least three measurement points were selected in the shielding overlap area, junction area, screw crimping area, and non-crimped exposed area, and the average value was taken.

[0094] II. Contact Resistance Testing. A micro-ohmmeter or a four-terminal contact resistance tester is used. During testing, both the current and voltage terminals use gold-plated copper alloy probes with cylindrical, flat-ended tips, each 2.0 mm in diameter. Each testing area uses two current probes and two voltage probes to form a four-terminal test circuit, with the voltage probes positioned between the two current probes. The test current is 1A DC, and the single-pass duration is 3-5 seconds. The stabilized voltage value is read and converted to the contact resistance.

[0095] During testing, the same crimping force and contact area were applied to the shielding overlap area, the grounding area, and the screw crimping area. The crimping force was 20N, and the contact area was 4mm². For the screw crimping area, a flat-end indenter was used to simulate the screw tightening state. The indenter material was gold-plated copper alloy or stainless steel, and the indenter diameter was 2.0mm. At least 5 test points were selected for each area, and the average value was taken as the contact resistance of that area. The surface contact resistance of the same sample was the average value of the test results for the shielding overlap area, the grounding area, and the screw crimping area.

[0096] After neutral salt spray testing and thermal cycling, samples were left at room temperature for 30-60 minutes before contact resistance testing. The same probe material, probe diameter, test current, clamping force, and contact area were used during the testing. The contact resistance growth rate was calculated as (post-treatment contact resistance - initial contact resistance) / initial contact resistance × 100%.

[0097] III. Shielding Effectiveness Testing. The shielding effectiveness of the samples was tested using a shielding effectiveness testing fixture or shielding box system in the 0.7GHz-6GHz and 24GHz-40GHz frequency bands. The initial shielding effectiveness, the shielding effectiveness after the neutral salt spray test, and the shielding effectiveness after thermal cycling were recorded during the tests.

[0098] IV. Neutral Salt Spray Test. The samples were subjected to a 240-hour neutral salt spray test. After the test, the number of corrosion spots, corrosion area ratio, and changes in appearance were recorded. The corrosion area ratio was calculated as the ratio of the total projected area of ​​the corroded area to the total area of ​​the tested area multiplied by 100%.

[0099] V. Thermal Cycling Test. The thermal cycling conditions are: -40℃ for 1 hour, then heated to 85℃ and held for 1 hour, which constitutes one cycle, and a total of 20 cycles are performed. After each cycle, the blistering area ratio, crack area ratio, contact resistance growth rate, and shielding effectiveness retention rate of the coating are measured.

[0100] The test results can be recorded according to Tables 1 to 4.

[0101] Table 1. Membrane thickness test results

[0102] Table 2 Contact resistance test results

[0103] Table 3 Shielding effectiveness test results

[0104] Table 4. Results of corrosion resistance and thermal cycling stability tests

[0105] The test results of Examples 1-3 and Comparative Examples 1-5 show that the high-shield metal surface treatment method provided by the present invention exhibits good comprehensive performance in terms of shielding performance stability, interface contact reliability and environmental adaptability.

[0106] Regarding shielding effectiveness, the sample in the example exhibited high initial shielding effectiveness in the 0.7GHz to 6GHz and 24GHz to 40GHz frequency bands, and maintained relatively stable shielding performance after neutral salt spray test and thermal cycling test. This indicates that there is a synergistic effect between the combined transition layer, the highly conductive shielding layer and the anti-diffusion protective layer, which can improve the stability and resistance to environmental attenuation of the high-frequency electromagnetic shielding structure.

[0107] Regarding contact resistance, the contact resistance of the sample in the example increased to some extent after salt spray test and thermal cycling test, but the overall increase was at a low level. This indicates that the conductive protective film formed by the partitioned surface adjustment can improve the interface stability of different contact areas while maintaining conductive continuity, thereby reducing the degree of contact degradation under environmental conditions.

[0108] Comparative results show that when the bonding transition layer is missing, the interfacial bonding ability decreases, leading to a significant increase in contact resistance after salt spray and thermal cycling; when a highly conductive shielding layer is not formed, the overall shielding effectiveness decreases; when constant current electrodeposition is used instead of pulse electrodeposition, the high-frequency shielding performance and environmental stability both decrease to varying degrees; when no zonal surface conditioning is performed or an anti-diffusion protective layer is missing, contact stability decreases or long-term corrosion resistance weakens, respectively.

[0109] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A method for high-shield metal surface treatment suitable for 5G communication modules, characterized in that, Includes the following steps: The metal substrate of the 5G communication module is degreased, micro-etched and activated, and surface-modified to obtain the surface to be treated. A bonding transition layer is formed on the surface to be treated; A highly conductive shielding layer is formed on the surface of the bonding transition layer; An anti-diffusion protective layer is formed on the surface of the highly conductive shielding layer; The metal substrate of the 5G communication module with the anti-diffusion protective layer is subjected to partitioned surface conditioning. The partitioned surface conditioning includes adjusting the low contact resistance of the shielding overlap area, the contact area and the screw crimping area, and performing corrosion-resistant sealing treatment on the non-crimping exposed area. The highly conductive shielding layer is a copper layer or a copper alloy layer with a thickness of 2μm-8μm; the anti-diffusion protective layer is a nickel layer, a nickel-phosphorus alloy layer, or a nickel-tin alloy layer with a thickness of 0.3μm-2.0μm. After surface adjustment, the surface contact resistance of the shielding overlap area, the contact area, and the screw crimping area is ≤20mΩ.

2. The high-shield metal surface treatment method for 5G communication modules according to claim 1, characterized in that, The metal substrate of the 5G communication module is an aluminum alloy substrate, a magnesium alloy substrate, a stainless steel substrate, a copper alloy substrate, a nickel-copper substrate, or a low-carbon steel substrate. The metal substrate of the 5G communication module is a 5G communication module shielding cover, metal shell, heat dissipation cover, radio frequency cavity, grounding spring mounting base or module fixing bracket.

3. The high-shield metal surface treatment method for 5G communication modules according to claim 1, characterized in that, The degreasing includes one or both of alkaline degreasing and electrolytic degreasing; When the metal substrate of the 5G communication module is an aluminum alloy substrate or a magnesium alloy substrate, the micro-etching activation is followed by zinc replacement treatment or zinc-nickel replacement treatment. When the metal substrate of the 5G communication module is a stainless steel substrate, the micro-etching activation is followed by cathodic activation treatment. When the metal substrate of the 5G communication module is a copper alloy substrate or a nickel-copper substrate, the micro-etching activation adopts a persulfate-sulfuric acid system or a hydrogen peroxide-sulfuric acid system.

4. The high-shield metal surface treatment method for 5G communication modules according to claim 1, characterized in that, The bonding transition layer is one or more of the following: chemical nickel layer, electrodeposited nickel layer, nickel-phosphorus alloy layer, and nickel-boron alloy layer; The thickness of the bonding transition layer is 0.2 μm-1.5 μm; After the bonding transition layer is formed, it is washed with water and then proceeds to the high conductivity shielding layer deposition step within 180 seconds.

5. The high-shield metal surface treatment method for 5G communication modules according to claim 1, characterized in that, The highly conductive shielding layer is formed by pulsed copper electrodeposition; The pulsed copper electrodeposition uses an acidic copper sulfate electroplating solution, which comprises 120 g / L-220 g / L copper sulfate, 40 g / L-90 g / L sulfuric acid, 30 mg / L-90 mg / L chloride ions, 0.01 g / L-0.30 g / L leveling agent, 0.01 g / L-0.20 g / L grain refiner, and water. The average current density of the pulsed copper electrodeposition is 1A / dm²-5A / dm², the pulse frequency is 50Hz-500Hz, the duty cycle is 40%-80%, and the temperature is 20℃-35℃.

6. The high-shield metal surface treatment method for 5G communication modules according to claim 1, characterized in that, The anti-diffusion protective layer is formed by electrodepositing nickel, electroless nickel, or electrodepositing a nickel-tin alloy. When the anti-diffusion protective layer is a nickel-phosphorus alloy layer, the phosphorus content in the nickel-phosphorus alloy layer is 2wt.%-8wt.%; When the anti-diffusion protective layer is a nickel-tin alloy layer, the tin content in the nickel-tin alloy layer is 20wt.%-45wt.%.

7. The high-shield metal surface treatment method for 5G communication modules according to claim 1, characterized in that, The low contact resistance adjustment includes: Selective activation is performed on the shielding overlap area, the junction area, and the screw crimping area to remove residual oxidation from the surface of the anti-diffusion protective layer; A conductive protective film is formed in the shielding overlap area, the contact area, and the screw crimping area; The conductive protective film has a thickness of 10nm-80nm, and includes one or more of benzotriazole protective films, mercaptotriazole protective films, and conductive organic protective films.

8. The high-shield metal surface treatment method for 5G communication modules according to claim 1, characterized in that, The corrosion-resistant sealing treatment uses an aqueous sealing solution, which includes one or more of hydrolyzed silane, nano-silica sol, molybdate, tungstate, and phosphate. The temperature for the corrosion-resistant sealing treatment is 35℃-70℃, and the time is 20s-180s. After the corrosion-resistant sealing treatment, the thickness of the sealing film in the non-press-bonded exposed area is 50nm-300nm.

9. A method for high-shield metal surface treatment suitable for 5G communication modules according to claim 1, characterized in that, After the high conductivity shielding layer and the anti-diffusion protective layer are formed, a low-temperature stress relief treatment is also included. The low-temperature stress relief treatment is performed at a temperature of 80℃-140℃ for a time of 30min-120min. The low-temperature stress relief treatment is followed by zoned surface conditioning.

10. A method for high-shield metal surface treatment suitable for 5G communication modules according to any one of claims 1-9, characterized in that, The fabricated 5G communication module metal component includes a metal substrate, a bonding transition layer, a highly conductive shielding layer, an anti-diffusion protective layer, and a surface conditioning layer. The shielding effectiveness of the metal components of the 5G communication module is ≥80dB in the 0.7GHz-6GHz frequency band; The shielding effectiveness of the metal components of the 5G communication module is ≥60dB in the 24GHz-40GHz frequency band; After 240 hours of neutral salt spray testing, the contact resistance growth rate of the shielding overlap area, the junction area, and the screw crimping area is ≤30%.

Images