Surface treatment method for titanium alloy vapor chamber

Abstract

The invention discloses a surface treatment method for a titanium alloy vapor chamber, and belongs to the technical field of metal surface treatment. The method comprises the steps of oil removal, titanium polishing, multiple times of cleaning and ultrasonic cleaning, two times of passivation and drying, and is characterized in that an environment-friendly weak acid polishing solution without hydrofluoric acid and nitric acid is adopted for mild polishing, and a composite passivation film is formed on the surface of the titanium alloy through the two-time passivation process that treatment is conducted through a first passivation solution and a second passivation solution in sequence. According to the structural characteristics of the vapor chamber, the temperature is controlled at 1t in the whole process; and multiple normal-temperature ultrasonic cleaning is introduced at key nodes to ensure that the cavity is clean, so that the uniform-temperature plate has lasting reliability. According to the method, environment-friendly production is achieved, an obtained passive film is uniform, compact and high in adhesive force, the gas tightness yield of the treated vapor chamber reaches 99.5%, the baking resistance exceeds 1000 hours, the titanium material perfectness rate reaches 99.80%, and the reliability and durability of a product are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and in particular to a method for surface treatment of a titanium alloy heat exchanger. Background Technology

[0002] With the rapid development of electronic devices towards high performance and high integration, their internal power density is increasing dramatically, making heat dissipation a more and more serious problem. Vapor chambers (VCs), as efficient two-dimensional phase change heat transfer elements, have become key components for solving heat dissipation problems in high-end chips and other heat sources due to their excellent heat dissipation capabilities and thermal conductivity. To meet the requirements of lightweight, miniaturized, and structurally strong equipment, titanium alloys, with their high specific strength, excellent corrosion resistance, and good biocompatibility, are gradually becoming ideal materials for manufacturing precision vapor chamber cavities (upper and lower covers). However, titanium alloys are chemically reactive, and forming a stable, dense, uniform, and well-bonded passivation film on their surface is a crucial pretreatment step to ensure the long-term reliability of the vapor chamber, prevent corrosion from the working medium, and ensure the airtightness of subsequent welding. Therefore, developing a surface treatment method that is efficient, environmentally friendly, and protects the precision structure of titanium alloy vapor chambers has significant industrial value.

[0003] Currently, there are several existing technologies involving the manufacture of heat spreaders or metal surface treatments. For example, Chinese invention patent application CN112795910A (publication date: May 14, 2021) discloses a method for manufacturing a heat spreader and the heat spreader itself. This application uses steel sheets as the cover material and treats them with a passivation solution containing transition metal compounds, phosphates, nitric acid, etc., to form a passivation film to inhibit the reaction between the steel and water. However, this technical solution is specifically designed for steel, and its pretreatment process and passivation system are based on the characteristics of steel, making it unsuitable for titanium alloys with drastically different chemical properties. Furthermore, its passivation solution still contains nitric acid, which is not environmentally friendly, and it does not consider the protection of the delicate capillary structure inside the heat spreader.

[0004] For example, Chinese invention patent application CN105297026A (publication date: February 3, 2016) discloses a chemical polishing solution for titanium alloys. This solution polishes the surface of titanium alloys by mixing various strong acids such as hydrofluoric acid, nitric acid, hydrochloric acid, and sulfuric acid, as well as hydrogen peroxide. However, this technology uses a variety of highly corrosive and hazardous chemical reagents, especially hydrofluoric acid, which places extremely high demands on operational safety, equipment corrosion prevention, and subsequent environmental protection, thus failing to meet the development trend of green manufacturing. Furthermore, this solution is only a single polishing process and does not involve passivation treatment, thus failing to provide long-term and effective corrosion protection for titanium alloys.

[0005] For example, Chinese invention patent application CN114075665A (publication date: February 22, 2022) discloses a NiSiAlY coating on a titanium alloy surface and its preparation method. This technology uses a cold spraying process to prepare a metal alloy coating on the surface of the titanium alloy to solve its high-temperature oxidation problem. However, this method is complex, costly, and requires specialized spraying and heat treatment equipment. The resulting coating is relatively thick, which may affect the overall thickness and thermal resistance of the heat spreader. Furthermore, it is not suitable for heat spreader workpieces with complex internal cavities and fine capillary structures, focusing more on high-temperature protection than improving surface activity and promoting welding.

[0006] In summary, existing technologies suffer from drawbacks such as material mismatch, poor environmental friendliness and safety, and complex processes unsuitable for precision structures. Therefore, there is an urgent need in this field for a surface treatment method that can effectively activate and passivate titanium alloy surfaces under mild conditions, fully protect the substrate and internal capillary structure during the treatment process, and ultimately achieve a uniform, dense surface with excellent corrosion resistance. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention provides a surface treatment method for a titanium alloy heat exchanger, comprising the following steps: Step S1: Degreasing. Place the upper and lower covers of the heat exchange plate in an alkaline degreasing agent for degreasing treatment. Step S2, titanium polishing: Immerse the upper and lower covers of the heat exchange plate after degreasing treatment in the prepared titanium polishing liquid for polishing to slightly etch the titanium alloy surface. Step S3: One cleaning: Use pure water at 10-30℃ and countercurrent pure water at 40-60℃ to clean the upper and lower covers of the temperature equalizer alternately, each cleaning lasts 10-20 seconds; Step S4: Ultrasonic cleaning. Place the upper and lower covers of the heat exchange plate in warm water at 10-30℃ for ultrasonic cleaning. The cleaning time is 4-6 minutes. Step S5: First passivation. The upper and lower covers of the heat exchange plate are treated with the first passivation solution to form a basic passivation film on their surface. Step S6: Secondary cleaning, using pure water at 40-60℃ for 20-40 seconds and warm water at 10-30℃ for 10-20 seconds, alternating cleaning at least twice; Step S7: Ultrasonic cleaning, ultrasonic cleaning of the upper and lower covers of the heat exchange plate; Step S8: Secondary passivation. The upper and lower covers of the heat exchange plate are immersed in the second passivation solution to form a dense passivation film on their surface. Step S9: Three cleaning cycles, using pure water at 40-60℃ and room temperature water at 10-30℃ for multi-stage countercurrent alternating cleaning, with each cleaning cycle lasting 20-40 seconds; Step S10: Ultrasonic cleaning, ultrasonic cleaning of the upper and lower covers of the heat exchanger plate; Step S11: Drying. The cleaned temperature equalization plate is dried.

[0008] Furthermore, in step S1, the alkaline degreasing agent has a pH of 9-10, and the treatment conditions are 50-60℃ for 3-5 minutes.

[0009] Furthermore, the polishing conditions in step S2 are immersion treatment at 10-30℃ for 5-10 seconds.

[0010] Furthermore, in step S2, the titanium polishing solution is prepared by mixing 15-20 parts glacial acetic acid, 15-25 parts sodium chloride, 30-40 parts sodium dihydrogen phosphate, and 20-30 parts water in the above weight ratio, and then stirring at 25-30°C for 1-2 hours.

[0011] Furthermore, in step S2, the titanium polishing slurry can be directly used to clean the product.

[0012] Steps S4, S7, and S10 involve ultrasonically cleaning the upper and lower covers of the heat exchange plate in warm water at 10-30°C for 4-6 minutes.

[0013] The first passivation solution in step S5 is prepared by dissolving 5-10 parts of potassium dihydrogen phosphate, 1-3 parts of nickel sulfate, 0.5-2 parts of ammonium bifluoride, and 0.1-1 parts of sodium dodecyl sulfate in 80-90 parts of water and stirring at 30°C for 15 minutes.

[0014] Furthermore, the first passivation solution in step S5 needs to be diluted 1.5 times before use.

[0015] Furthermore, the treatment conditions for the first passivation solution are: soaking at 50-80℃ for 10-15 minutes, followed by shaking 3-5 times after soaking.

[0016] Furthermore, in step S8, the second passivation solution treatment conditions are: immersion treatment of the upper and lower covers of the uniform temperature plate at 10-30℃ for 10-15 minutes.

[0017] The second passivation solution in step S8 is prepared by mixing 80-95 parts water and 5-20 parts inositol hexaphosphate by weight and stirring at 20-40°C for 1-2 hours.

[0018] Furthermore, the second passivation solution in step S8 needs to completely submerge the product before use, without the need for dilution.

[0019] Furthermore, step S11 involves placing the upper and lower covers of the temperature equalizer plate into an oven and drying it at 180-210℃ for 10-15 minutes.

[0020] Compared with existing technologies, the advantages and effects of this application are as follows: 1. This application optimizes the titanium polishing slurry formula, eliminating highly corrosive components such as hydrofluoric acid and nitric acid in traditional titanium polishing processes, as well as harmful hexavalent chromium in chromate passivation processes. It adopts a weakly acidic polishing slurry and an environmentally friendly passivation slurry, which significantly reduces chemical pollution and health risks, and is more in line with the requirements of green manufacturing.

[0021] 2. This application utilizes the synergistic effect of a specially formulated mild polishing liquid and a two-step passivation method to form a uniform, dense, and gradient-functional composite passivation film on the surface of titanium alloy. This film has good adhesion and high uniformity, providing a better surface condition for subsequent welding and other processes, and helping to improve the heat dissipation efficiency and long-term reliability of the product.

[0022] 3. This application optimizes the ultrasonic cleaning process and the entire low-temperature / high-temperature process (temperature always <60℃) based on the structural characteristics of the VC heat exchanger (such as precision cavity and capillary structure). This ensures that while thoroughly removing contaminants and chemical residues, it avoids thermal damage to the titanium alloy substrate and internal capillary structure that may be caused by high temperature, thereby ensuring the core performance and durability of the heat exchanger.

[0023] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings.

[0024] The above and other objects, advantages, and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments in conjunction with the accompanying drawings. This application features thorough surface pretreatment, resulting in a passivation film with good uniformity, and the reagents used are environmentally friendly. Attached Figure Description To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In all drawings, similar elements or parts are generally identified by similar reference numerals. The elements or parts in the drawings are not necessarily drawn to scale.

[0025] in: Figure 1 This is a schematic diagram of a surface treatment method for a titanium alloy heat exchanger. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. In the following description, specific details such as specific configurations and components are provided merely to help fully understand the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0027] It should be understood that the phrase "an embodiment" or "this embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "an embodiment" or "this embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0028] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0029] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it have an "or" relationship.

[0030] In this article, the term "at least one" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0031] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0032] Example 1 This embodiment describes a surface treatment method for a titanium alloy heat spreader. Please refer to the appendix. Figure 1 ; This processing method includes the following steps: Step S1: Degreasing. Place the upper and lower covers of the heat spreader in an alkaline degreasing agent for degreasing treatment. This is used to thoroughly remove oil stains and fingerprints from previous processes such as stamping, providing an absolutely clean surface for subsequent processing. Step S2, titanium polishing: Immerse the upper and lower covers of the heat spreader after degreasing in the prepared titanium polishing solution to lightly etch the surface of the titanium alloy, remove the original oxide layer and micro-unevenness, and form a fresh and activated surface. At the same time, sodium dihydrogen phosphate participates in the formation of the primary conversion layer, which serves as a firm anchor point for the subsequent passivation film. Step S3: One cleaning: Use pure water at 10-30℃ and countercurrent pure water at 40-60℃ to clean the upper and lower covers of the temperature equalizer alternately, each cleaning lasts 10-20 seconds; Step S4: Ultrasonic cleaning. Place the upper and lower covers of the heat exchange plate in warm water at 10-30℃ for ultrasonic cleaning. The cleaning time is 4-6 minutes. Step S5: First passivation. The upper and lower covers of the heat exchange plate are treated with the first passivation solution to form a basic passivation film on their surface. This film has a strong bond with the substrate and is more dense due to the catalytic effect of nickel. Step S6: Secondary cleaning, using pure water at 40-60℃ for 20-40 seconds and warm water at 10-30℃ for 10-20 seconds, alternating cleaning at least twice; Step S7: Ultrasonic cleaning, ultrasonic cleaning of the upper and lower covers of the heat exchange plate; Step S8: Secondary passivation. The upper and lower covers of the heat exchange plate are immersed in the second passivation solution to form a dense passivation film on their surface. Step S9: Three cleaning cycles, using pure water at 40-60℃ and room temperature water at 10-30℃ for multi-stage countercurrent alternating cleaning, with each cleaning cycle lasting 20-40 seconds; Step S10: Ultrasonic cleaning, ultrasonic cleaning of the upper and lower covers of the heat exchanger plate; Step S11: Drying. The cleaned temperature homogenizing plate is dried to stabilize the film structure.

[0033] Steps S3-S4 involve multi-stage countercurrent cleaning using alternating warm and ambient water, combined with ultrasonic assistance, to ensure the complete removal of any chemical residues and prevent contamination of subsequent water injection processes and working fluids.

[0034] The purpose of step S8 is to enable the multiple phosphate groups in the inositol hexaphosphate molecule to form a superstable chelate network with the base film layer and residual titanium sites, resulting in a dense top layer. This molecular structure also optimizes the surface energy of the film layer, which is beneficial for the spread of the working fluid.

[0035] The technical effect achieved in this embodiment is that by using an environmentally friendly new polishing liquid and an optimized two-step passivation process, combined with multi-stage temperature-controlled cleaning and ultrasonic treatment, a uniform, dense, and strongly bonded composite passivation film is formed on the surface of the titanium alloy.

[0036] Example 2 Based on Example 1, this example further introduces the processing conditions and reagent ratios in a surface treatment method for a titanium alloy heat exchanger.

[0037] The alkaline degreasing agent in step S1 has a pH of 9-10, and the treatment conditions are 50-60℃ for 3-5 minutes.

[0038] Furthermore, the polishing conditions in step S2 are immersion treatment at 10-30℃ for 5-10 seconds.

[0039] The titanium polishing solution in step S2 is prepared by mixing 15-20 parts glacial acetic acid, 15-25 parts sodium chloride, 30-40 parts sodium dihydrogen phosphate, and 20-30 parts water in the above weight ratio, and then stirring at 25-30℃ for 1-2 hours.

[0040] Furthermore, in step S2, the titanium polishing slurry can be directly used to clean the product.

[0041] In the titanium polishing slurry, glacial acetic acid serves as the main acidic component, providing a moderate acidification environment to avoid excessive corrosion of the titanium alloy substrate; sodium chloride enhances ionic strength, promotes uniform surface activation, and controls the reaction rate; sodium dihydrogen phosphate forms a phosphate protective layer during polishing, preventing excessive surface corrosion and providing a good substrate for subsequent passivation processes.

[0042] Furthermore, steps S4, S7, and S10 involve placing the upper and lower covers of the heat exchange plate in warm water at 10-30°C for ultrasonic cleaning, with a cleaning time of 4-6 minutes.

[0043] The first passivation solution in step S5 is prepared by dissolving 5-10 parts of potassium dihydrogen phosphate, 1-3 parts of nickel sulfate, 0.5-2 parts of ammonium bifluoride, and 0.1-1 parts of sodium dodecyl sulfate in 80-90 parts of water and stirring at 30°C for 15 minutes.

[0044] The first passivation solution treatment conditions in step S5 are: immersion treatment at 50-80℃ on the upper and lower covers of the uniform temperature plate for 10-15 minutes, followed by shaking 3-5 times after immersion.

[0045] Furthermore, the first passivation solution in step S5 needs to be diluted 1.5 times before use.

[0046] Furthermore, in step S8, the second passivation solution treatment conditions are: treating the upper and lower covers of the homogenizing plate at 10-30℃ for 10-15 minutes.

[0047] The second passivation solution in step S8 is prepared by mixing 80-95 parts of aqueous solution and 5-20 parts of inositol hexaphosphate by weight, and stirring at 20-40°C for 1-2 hours.

[0048] Furthermore, the second passivation solution in step S8 needs to completely submerge the product before use, without the need for dilution.

[0049] Furthermore, step S11 involves placing the upper and lower covers of the temperature equalizer plate into an oven and drying it at 180-210℃ for 10-15 minutes.

[0050] The technical effects achieved in this embodiment are as follows: This embodiment optimizes the formulation of titanium polishing fluid, which eliminates the strong corrosive components such as hydrofluoric acid and nitric acid in traditional titanium polishing. Through the synergistic effect of a weak acidic environment and corrosion inhibitors, mild and controllable surface polishing is achieved. A two-stage passivation process is adopted, and a composite passivation film with gradient functions is constructed through a two-step passivation method, which significantly improves the density and corrosion resistance of the passivation film.

[0051] Example 3 Based on Examples 1 and 2, this example compares the traditional heat exchanger cleaning method with the titanium alloy heat exchanger surface treatment method of this application to test the technical effect of the treatment method proposed in this application.

[0052] The results of the process comparison and analysis are shown in Table 1: Table 1 Comparison of the effects of traditional methods and the processing method of this application The technical effects achieved in this embodiment are as follows: through cross-cutting test, helium mass spectrometry leak detection, baking test and integrity test, the process of this application achieves level 0 no shedding under the same treatment conditions, and the airtightness yield reaches 99.5%, can withstand oven baking for more than 1000 hours, and the integrity rate of titanium material after treatment reaches 99.80%.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any equivalent substitutions, structural improvements, adjustments to the functional implementation methods, as well as reasonable adjustments to parameters, module integrations, or step sequences based on the concept of the present invention, made within the spirit and principles set forth in the present invention, should be included within the scope of protection of the present invention.

Claims

1. A surface treatment method for a titanium alloy heat spreader, characterized by, The method comprises the following steps: Step S1, oil removal, placing the upper and lower covers of the uniform temperature plate in an alkaline oil removal agent for oil removal treatment; Step S2, titanium polishing, placing the upper and lower covers of the uniform temperature plate after the oil removal treatment into a prepared titanium polishing solution for immersion polishing to slightly etch the surface of the titanium alloy; Step S3, first cleaning, alternately cleaning the upper and lower covers of the uniform temperature plate with pure water at 10-30 DEG C and countercurrent pure water at 40-60 DEG C, each time for 10-20 s; Step S4, ultrasonic cleaning, placing the upper and lower covers of the uniform temperature plate in warm water at 10-30 DEG C for ultrasonic cleaning, the cleaning time being 4-6 min; Step S5, first passivation, treating the upper and lower covers of the uniform temperature plate with a first passivation solution to form a basic passivation film on the surface thereof; Step S6, second cleaning, alternately cleaning at least twice with pure water at 40-60 DEG C for 20-40 s and warm water at 10-30 DEG C for 10-20 s; Step S7, ultrasonic cleaning, ultrasonic cleaning the upper and lower covers of the uniform temperature plate; Step S8, second passivation, placing the upper and lower covers of the uniform temperature plate into a second passivation solution for treatment to form a dense passivation film on the surface thereof; Step S9, third cleaning, multi-stage countercurrent alternately cleaning with pure water at 40-60 DEG C and normal temperature water at 10-30 DEG C, each time for 20-40 s; Step S10, ultrasonic cleaning, ultrasonic cleaning the upper and lower covers of the uniform temperature plate; Step S11, drying, drying the cleaned uniform temperature plate.

2. The surface treatment method of a titanium alloy heat sink plate according to claim 1, characterized by, The pH of the alkaline oil removal agent in the step S1 is 9-10, and the treatment condition is 50-60 DEG C for 3-5 min.

3. The surface treatment method of a titanium alloy heat sink plate according to claim 1, characterized in that, The polishing treatment condition in the step S2 is immersing the upper and lower covers of the uniform temperature plate into the titanium polishing solution for 5-10 s at 10-30 DEG C.

4. The surface treatment method of a titanium alloy heat sink plate according to claim 3, characterized by, The titanium polishing solution in the step S2 is prepared by mixing 15-20 parts of glacial acetic acid, 15-25 parts of sodium chloride, 30-40 parts of sodium dihydrogen phosphate and 20-30 parts of water according to the weight ratio, and then stirring at 25-30 DEG C for 1-2 h.

5. The surface treatment method of a titanium alloy heat spreader according to claim 1, characterized by, The steps S4, S7 and S10 are ultrasonic cleaning the upper and lower covers of the uniform temperature plate in warm water at 10-30 DEG C, the cleaning time being 4-6 min.

6. The surface treatment method of a titanium alloy heat spreader according to claim 1, wherein The first passivation solution in the step S5 is prepared by dissolving 5-10 parts of potassium dihydrogen phosphate, 1-3 parts of nickel sulfate, 0.5-2 parts of ammonium hydrogen fluoride and 0.1-1 part of sodium dodecyl sulfate in 80-90 parts of water according to the weight ratio, and then stirring at 30 DEG C for 15 min.

7. The surface treatment method of a titanium alloy heat spreader according to claim 6, characterized by, The treatment condition in the step S5 is immersing the upper and lower covers of the uniform temperature plate into the first passivation solution diluted by 1.5 times, and then soaking at 50-80 DEG C for 10-15 min.

8. The surface treatment method of a titanium alloy heat spreader according to claim 1, characterized by, The second passivation solution in the step S8 is prepared by dissolving 5-20 parts of inositol hexaphosphate in 80-95 parts of water according to the weight ratio, and then stirring at 20-40 DEG C for 1-2 h.

9. The surface treatment method of a titanium alloy heat spreader according to claim 8, wherein The treatment condition in the step S8 is immersing the upper and lower covers of the uniform temperature plate into the second passivation solution, and then treating at 10-30 DEG C for 10-15 min.

10. The surface treatment method of a titanium alloy heat spreader according to claim 1, characterized by, The step S11 is to put the upper and lower covers of the uniform temperature plate into an oven and dry at 180-210°C for 10-15 min.

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