A surface treatment method for improving the weldability of an aluminum alloy

Abstract

The application discloses a surface treatment method for improving the weldability of aluminum alloy, which comprises the following steps: (1) alkaline degreasing: placing the aluminum alloy shell into an alkaline degreaser for cleaning; (2) etching: placing the aluminum alloy shell into an etching solution; (3) water washing: cleaning the aluminum alloy shell after etching with deionized water; (4) zinc immersion: placing the aluminum alloy shell into an alkaline zincate zinc immersion solution for immersion; (5) nickel plating: placing the aluminum alloy shell after zinc immersion into a chemical nickel tank for nickel plating; (6) after the nickel plating is completed, taking out the shell, repeating the process step (3) water washing, and then carrying out drying. Advantages: 1) the reliability of the plating layer after the aluminum alloy surface is plated is improved; 2) the cost is low, and the method is simple and easy to implement; 3) the weldability of the aluminum alloy surface is improved, the problem that the aluminum alloy and other metals are difficult to realize welding is solved, and the effect is remarkable.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and more specifically to a surface treatment method for improving the weldability of aluminum alloys. Background Technology

[0002] With the rapid development of modern electronic information technology, electronic information systems and equipment are evolving towards large-scale integration, miniaturization, lightweighting, and high reliability, placing increasingly stringent demands on the basic materials used for packaging. Aluminum alloys, with their advantages of low density, high strength, and corrosion resistance, are widely used in the automotive, aerospace, and military industries. Brazing, as an important method for joining aluminum alloys, offers advantages such as minimal dimensional deformation and high dimensional accuracy after welding, and has been widely applied in the microelectronics packaging industry in recent years. However, due to their unique physical and chemical properties, a series of difficulties arise during the welding process, such as oxidation, hot cracking, and porosity, making it difficult to join with other metals.

[0003] Therefore, there is an urgent need to develop a surface treatment method that can effectively improve the weldability of aluminum alloys, enabling them to achieve tight bonding with other metals. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a surface treatment method to improve the weldability of aluminum alloys. This method can effectively improve the weldability of aluminum alloy surfaces and realize the connection between aluminum alloys and various dissimilar metals.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a surface treatment method for improving the weldability of aluminum alloys, the treatment method comprising the following steps:

[0006] Step 1) Alkaline degreasing: Immerse the aluminum alloy casing in an alkaline degreasing agent at 50-70℃ and ultrasonically clean for 10-15 minutes;

[0007] Step 2) Etching: Place the degreased and cleaned aluminum alloy shell into etching solution A heated in a water bath for etching; then rinse with clean water and immediately place it into etching solution B to continue etching;

[0008] Step 3) Water washing: Rinse the etched aluminum alloy casing with deionized water for 10-15 seconds;

[0009] Step 4) Zinc immersion: Immerse the aluminum alloy shell in alkaline zincate immersion solution for the first zinc immersion; after rinsing with water, immerse it in etching solution B for etching again to fully activate the surface of the aluminum alloy shell, thereby improving the adhesion to the nickel layer in the subsequent nickel plating process, making the nickel layer denser, and thus improving its solderability; after rinsing with water, perform a second zinc immersion.

[0010] Step 5) Nickel plating: Immerse the aluminum alloy casing, which has undergone a second zinc immersion, in a chemical nickel plating solution for chemical nickel plating;

[0011] Step 6) After nickel plating is completed, remove the aluminum alloy shell and repeat process step 3) washing with water, and then dry it.

[0012] Furthermore, in step 1), the aluminum alloy shell is a flat plate with dimensions of 50mm×50mm×3mm; the degreasing solution used is a chemical degreasing powder with a concentration of 80-100g / L.

[0013] Further, in step 2), the etching solution A is a 40-50 g / L NaOH aqueous solution, which is stirred to dissolve completely before use; the etching solution B is an aqueous solution composed of 10-20 ml / L OP emulsifier and 100-200 ml / L 45-55 wt% nitric acid, which is stirred to dissolve completely before use.

[0014] Furthermore, in step 2), the etching temperature in etching solution A is 50-70°C and the etching time is 20-30s; the etching temperature in etching solution B is room temperature and the etching time is 60-80s.

[0015] Further, in step 4), the zinc immersion solution is an aqueous solution composed of 4-5.5 g / L zinc oxide, 90-110 g / L sodium hydroxide, 20-25 g / L potassium sodium tartrate, and 2-3 g / L copper sulfate.

[0016] Furthermore, in step 4), during the second zinc immersion, a certain amount of deionized water is added to the zinc immersion solution to dilute the first zinc immersion solution.

[0017] Furthermore, in step 4), the temperature of the first zinc immersion is 20-30°C and the immersion time is 30-60 seconds; the etching time in the etching solution B is 20-30 seconds; and the temperature of the second zinc immersion is 20-30°C and the immersion time is 15-20 seconds.

[0018] Furthermore, in step 5), the temperature of the electroless nickel solution is 60–80°C, and the plating time is 50–65 min.

[0019] Furthermore, in step 5), the phosphorus content in the electroless nickel solution is 1 wt% to 4 wt%.

[0020] The beneficial effects of this invention are as follows: Compared with the prior art, the surface treatment method for improving the weldability of aluminum alloys provided by this invention has the following advantages:

[0021] 1) This invention uses a combination of acidic and alkaline corrosion inhibitors, finding the optimal ratio for etching aluminum alloy surfaces. The method is simple and does not corrode the substrate, making it particularly useful for removing the dense alumina film from aluminum alloy surfaces. After treatment with an alkaline corrosion inhibitor, the dense oxide film on the aluminum alloy surface is removed, exposing the substrate. However, due to the poor water washability of alkali, the surface remains alkaline after rinsing with water, and the aluminum alloy will quickly oxidize and discolor under alkaline conditions. Therefore, an acidic corrosion inhibitor is needed to neutralize the alkaline substances on the surface of the workpiece, inhibiting the rate of oxide film re-formation, and removing loose, ash-like substances and relatively firm oxide films that do not participate in the alkaline reaction but are still adsorbed on the surface of the workpiece during alkaline etching.

[0022] 2) A surface treatment process of electroless nickel plating was used to improve the weldability of aluminum alloy while reducing the magnetic properties of the plating surface, thus avoiding electromagnetic interference during subsequent use.

[0023] 3) The entire surface treatment process produces minimal toxic and harmful gases, thus reducing environmental pollution.

[0024] 4) Low cost, simple and easy to implement, suitable for large-scale operations.

[0025] 5) It has a significant effect on improving the weldability of aluminum alloy surfaces. Detailed Implementation

[0026] The present invention will be further illustrated below with specific embodiments. However, these examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0027] Example 1

[0028] A method for improving the weldability of aluminum alloy surfaces includes the following steps:

[0029] ① Alkaline degreasing

[0030] The alkaline degreasing solution is an aqueous solution containing 80 g / L of chemical degreasing powder. The aluminum alloy shell is placed in the alkaline degreasing agent at 50°C and ultrasonically cleaned for 10 minutes.

[0031] ②Etching

[0032] The etching solutions include: etching solution A, which consists of NaOH and water with a volume ratio of 40 g / L; and etching solution B, which consists of OP emulsifier with a volume ratio of 10 ml / L and nitric acid and water with a volume ratio of 100 ml / L. The aluminum alloy shell after degreasing and cleaning is placed in etching solution A heated in a water bath at a temperature of 50°C for 20 seconds. It is then rinsed with clean water and immediately placed in etching solution B at room temperature for 60 seconds.

[0033] ③ Wash with water

[0034] First, rinse the etched shell with tap water for 2 minutes, then ultrasonically clean it with deionized water for 1 minute.

[0035] ④ Zinc immersion

[0036] The zinc immersion solution consisted of 4 g / L zinc oxide, 90 g / L sodium hydroxide, 20 g / L potassium sodium tartrate, 2 g / L copper sulfate, and water, with a total solution volume of 800 mL. The washed outer casing was immersed in the zinc immersion solution for the first immersion at 20°C for 30 seconds. After rinsing with clean water, it was placed in etching solution B for a second etching for 20 seconds. Then, 400 mL of water was added to the first immersion solution for dilution, followed by a second immersion at 20°C for 15 seconds.

[0037] ⑤ Nickel plating

[0038] The nickel plating system uses a chemical nickel solution with a phosphorus content of 1% and a bath temperature of 60℃. The zinc-immersed shell is then placed in the chemical nickel solution for plating for 50 minutes.

[0039] ⑥ Wash with water

[0040] The coated outer shell is cleaned in a three-stage water washing tank, with each stage lasting 30 seconds.

[0041] ⑦ Drying

[0042] The washed outer shell is dried at high temperature using a 100℃ high-temperature forced-air drying oven.

[0043] Example 2

[0044] A method for improving the weldability of aluminum alloy surfaces includes the following steps:

[0045] ① Alkaline degreasing

[0046] The alkaline degreasing solution is an aqueous solution containing 90 g / L of chemical degreasing powder. The aluminum alloy shell is placed in the alkaline degreasing agent at 60°C and ultrasonically cleaned for 13 minutes.

[0047] ②Etching

[0048] The etching solutions include: etching solution A, which consists of NaOH and water with a volume ratio of 45 g / L; and etching solution B, which consists of OP emulsifier with a volume ratio of 15 ml / L and nitric acid and water with a volume ratio of 150 ml / L. The aluminum alloy shell after degreasing and cleaning is placed in etching solution A heated in a water bath at a temperature of 60°C for 25 seconds. It is then rinsed with clean water and immediately placed in etching solution B at room temperature for 70 seconds.

[0049] ③ Wash with water

[0050] First, rinse the etched shell with tap water for 3 minutes, then ultrasonically clean it with deionized water for 2 minutes.

[0051] ④ Zinc immersion

[0052] The zinc immersion solution consisted of 5 g / L zinc oxide, 100 g / L sodium hydroxide, 23 g / L potassium sodium tartrate, 2.5 g / L copper sulfate, and water, with a total solution volume of 900 mL. The washed outer casing was immersed in the zinc immersion solution for the first immersion at 25°C for 50 seconds. After rinsing with clean water, it was placed in etching solution B for a second etching for 25 seconds. Then, 500 mL of water was added to the first immersion solution for dilution, followed by a second immersion at 25°C for 20 seconds.

[0053] ⑤ Nickel plating

[0054] The nickel plating system uses a chemical nickel solution with a phosphorus content of 2.5% and a bath temperature of 70°C. The zinc-immersed shell is then placed in the chemical nickel solution for plating for 58 minutes.

[0055] ⑥ Wash with water

[0056] The coated outer shell is cleaned in a three-stage water washing tank, with each stage lasting 40 seconds.

[0057] ⑦ Drying

[0058] The washed outer shell is dried at a high temperature using a 120℃ high-temperature forced-air drying oven.

[0059] Example 3

[0060] A method for improving the weldability of aluminum alloy surfaces includes the following steps:

[0061] ① Alkaline degreasing

[0062] The alkaline degreasing solution is an aqueous solution containing 100g / L of chemical degreasing powder. The aluminum alloy shell is placed in the alkaline degreasing agent at 70℃ and ultrasonically cleaned for 15 minutes.

[0063] ②Etching

[0064] The etching solutions include: etching solution A, which consists of NaOH and water with a volume ratio of 50 g / L; and etching solution B, which consists of OP emulsifier with a volume ratio of 20 ml / L and nitric acid and water with a volume ratio of 200 ml / L. The aluminum alloy shell after degreasing and cleaning is placed in etching solution A heated in a water bath at a temperature of 70°C for 30 seconds. It is then rinsed with clean water and immediately placed in etching solution B at room temperature for 80 seconds.

[0065] ③ Wash with water

[0066] First, rinse the etched shell with tap water for 4 minutes, then ultrasonically clean it with deionized water for 3 minutes.

[0067] ④ Zinc immersion

[0068] The zinc immersion solution consisted of 5.5 g / L zinc oxide, 110 g / L sodium hydroxide, 25 g / L sodium potassium tartrate, 3 g / L copper sulfate, and water, with a total solution volume of 800 mL. The washed outer casing was immersed in the zinc immersion solution for the first immersion at 30°C for 60 seconds. After rinsing with clean water, it was placed in etching solution B for a second etching for 30 seconds. Then, 400 mL of water was added to the first immersion solution for dilution, followed by a second immersion at 30°C for 25 seconds.

[0069] ⑤ Nickel plating

[0070] The nickel plating system uses a chemical nickel solution with a phosphorus content of 4% and a bath temperature of 80℃. The zinc-immersed shell is then placed in the chemical nickel solution for plating for 65 minutes.

[0071] ⑥ Wash with water

[0072] The coated outer shell is cleaned in a three-stage water washing tank, with each stage lasting 50 seconds.

[0073] ⑦ Drying

[0074] The washed outer shell is dried at high temperature using a 150℃ high-temperature forced-air drying oven.

[0075] Comparative Example

[0076] A method for improving the weldability of aluminum alloy surfaces includes the following steps:

[0077] ① Alkaline degreasing

[0078] The alkaline degreasing solution is an aqueous solution containing 100g / L of chemical degreasing powder. The aluminum alloy shell is placed in the alkaline degreasing agent at 70℃ and ultrasonically cleaned for 15 minutes.

[0079] ② Wash with water

[0080] First, rinse the etched shell with tap water for 4 minutes, then ultrasonically clean it with deionized water for 3 minutes.

[0081] ③ Zinc immersion

[0082] The zinc immersion solution consisted of 5.5 g / L zinc oxide, 110 g / L sodium hydroxide, 25 g / L sodium potassium tartrate, 3 g / L copper sulfate, and water, with a total solution volume of 800 mL. The washed outer casing was immersed in the zinc immersion solution for the first immersion at 30°C for 30 seconds. After rinsing with clean water, it was placed in etching solution B for a second etching for 30 seconds. Then, 400 mL of water was added to the first immersion solution for dilution, followed by a second immersion at 30°C for 25 seconds.

[0083] ④ Nickel plating

[0084] The nickel plating system uses a chemical nickel solution with a phosphorus content of 4% and a bath temperature of 80℃. The zinc-immersed shell is then placed in the chemical nickel solution for plating for 65 minutes.

[0085] ⑤ Wash with water

[0086] The coated outer shell is cleaned in a three-stage water washing tank, with each stage lasting 50 seconds.

[0087] ⑥ Drying

[0088] The washed outer shell is dried at high temperature using a 150℃ high-temperature forced-air drying oven.

[0089] Performance tests of Examples 1-3 and comparative examples

[0090] According to the requirements for coating quality in GJB2440A-2006, condition B was used: nitrogen gas was introduced into the heater, and the temperature was raised to 450℃±10℃, then baked for 15 minutes. The coating surface was checked for discoloration, bubbles, and peeling. In Examples 1-3, the nickel layer surface showed no such phenomena. The comparative example surface did not discolor, but peeling was observed, which was due to poor coating adhesion.

[0091] The surface wettability of a commonly used silver-copper alloy solder in the electronic packaging industry was tested. The wettability was determined by measuring the wetting angle of the contact surface with that of Examples 1-3 and the comparative examples. The experimental data are shown in the table below:

[0092] name Wetting angle (°) Example 1 25 Example 2 22 Example 3 20 Comparative Example 45

[0093] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention, and the patent protection scope of the present invention should be defined by the claims.

Claims

1. A surface treatment method for improving the weldability of aluminum alloys, characterized in that, The processing method includes the following steps: Step 1) Alkaline degreasing: Immerse the aluminum alloy casing in an alkaline degreasing agent at 50-70℃ and ultrasonically clean for 10-15 minutes; Step 2), Etching: The degreased and cleaned aluminum alloy casing is placed in etching solution A heated in a water bath for etching; immediately rinsed with clean water, it is then placed in etching solution B for further etching; etching solution A is a 40-50 g / L NaOH aqueous solution, stirred until completely dissolved before use; etching solution B is an aqueous solution composed of 10-20 ml / L OP emulsifier and 100-200 ml / L nitric acid, the concentration of which is 45-55 wt%; stirred until completely dissolved before use. Step 3) Water washing: Rinse the etched aluminum alloy casing with deionized water for 10-15 seconds; Step 4) Zinc Immersion: Immerse the aluminum alloy casing in an alkaline zincate immersion solution for the first zinc immersion; rinse with clean water and then etch again in etching solution B; rinse with clean water and then perform a second zinc immersion; the zinc immersion solution is an aqueous solution composed of 4-5.5 g / L zinc oxide, 90-110 g / L sodium hydroxide, 20-25 g / L potassium sodium tartrate, and 2-3 g / L copper sulfate; during the second zinc immersion, dilute the first zinc immersion solution with 400 mL or 500 mL of deionized water; the temperature of the first zinc immersion is 20-30℃, and the immersion time is 30-60 s; the etching time in etching solution B is 20-30 s; the temperature of the second zinc immersion is 20-30℃, and the immersion time is 15-20 s; Step 5) Nickel plating: Immerse the aluminum alloy casing, which has undergone a second zinc immersion, in a chemical nickel plating solution for chemical nickel plating; Step 6) After nickel plating is completed, remove the aluminum alloy shell and repeat process step 3) washing with water, and then dry it.

2. The surface treatment method for improving the weldability of aluminum alloys as described in claim 1, characterized in that: In step 1), the aluminum alloy shell is a flat plate with dimensions of 50mm×50mm×3mm; the degreasing solution used is a chemical degreasing powder with a concentration of 80-100g / L.

3. The surface treatment method for improving the weldability of aluminum alloys as described in claim 1, characterized in that: In step 2), the etching temperature in etching solution A is 50-70°C and the etching time is 20-30s; the etching temperature in etching solution B is room temperature and the etching time is 60-80s.

4. The surface treatment method for improving the weldability of aluminum alloys as described in claim 1, characterized in that: In step 5), the temperature of the electroless nickel solution is 60–80°C, and the plating time is 50–65 min.

5. The surface treatment method for improving the weldability of aluminum alloys as described in claim 1, characterized in that: In step 5), the phosphorus content in the chemical nickel solution is 1wt% to 4wt%.