Lead acid battery copper terminal lead plating soldering formula and its preparation method

Abstract

The application provides a lead-acid battery copper terminal lead plating soldering formula, which is characterized by comprising the following components in mass fraction: pure water 40-50 parts, phosphoric acid 10-15 parts, sodium stannate 9-11 parts, ammonium nitrate 4-6 parts, potassium permanganate 1-3 parts, ethylenediaminetetraacetic acid 4-6 parts, and glycerol 15-20 parts; the mass fraction of sodium stannate in the soldering tin plating water agent prepared from the formula is 6-12%. The application can effectively destroy the surface tension of lead liquid and improve the surface activity of copper parts; meanwhile, the formula contains a tin plating function, and a tin-containing compound is formed on the surface of the copper part at high temperature, thereby strengthening the strength between the copper terminal and lead.

Description

Technical Field

[0001] This invention relates to the field of circuit welding technology, and in particular to a flux formula and preparation method for lead-clad copper terminals of lead-acid batteries. Background Technology

[0002] Lead-acid batteries are still widely used in transportation, communication, and energy sectors. Battery terminals, as crucial current-conducting components, exhibit various structural designs. For example, starting batteries use a lead alloy cage structure, UPS systems use a copper-plated silver sheet structure, and backup power supplies and forklift batteries employ a copper-terminal lead-clad structure. Copper terminals facilitate battery assembly and wiring, while also being wear- and corrosion-resistant. However, a strong bond between the copper terminals and the internal lead components of the battery is essential, along with low resistivity and corrosion resistance at the connection point. Therefore, flux is required when using copper-clad lead terminals.

[0003] Copper terminals are typically machined from copper rods, then cleaned to remove oil and dried before casting for lead plating. The specific process is as follows: ① Copper terminals are coated with flux → ② Surface drying → ③ Copper parts are tinned → ④ Terminals are removed and placed in an oven → ⑤ While still hot, terminals are placed into a mold → ⑥ Liquid lead alloy is poured into the mold → ⑦ Cooling and demolding. The flux removes metal oxides, disrupts the surface tension of the molten metal, and improves the casting quality. Tin diffuses on the metal surface, allowing different metals to fuse and adhere. The polyphosphate in this flux formulation fulfills the flux function, while the prepared tinning solution tinns the terminals at high temperatures. Summary of the Invention

[0004] This invention provides a flux for tin plating that can improve the strength of lead-clad batteries and reduce the number of welding steps. A flux formula for lead-clad copper terminals of lead-acid batteries includes the following mass fractions: 40-50 parts of pure water, 10-15 parts of phosphoric acid, 9-11 parts of sodium stannate, 4-6 parts of ammonium nitrate, 1-3 parts of potassium permanganate, 4-6 parts of ethylenediaminetetraacetic acid, and 15-20 parts of glycerol. The flux for tin plating prepared by this formula contains sodium stannate at a mass fraction of 6% to 12%. The inclusion of sodium stannate, ammonium nitrate, and other components allows tin ions to adhere to the surface of copper terminals during application, reducing the need for the traditional process of applying flux followed by tin plating.

[0005] Preferably, the conductivity of the pure water is ≤10µs / cm to ensure the purity of the pure water and reduce interference from impurities.

[0006] Preferably, the formula comprises the following mass fractions: 40 parts pure water, 10 parts phosphoric acid, 10 parts sodium stannate, 5 parts ammonium nitrate, 3 parts potassium permanganate, 5 parts ethylenediaminetetraacetic acid, and 20 parts glycerol.

[0007] A method for preparing a flux formulation for lead-acid battery copper terminal lead sheathing includes the following steps: Step 1: Preparation of Solution A: First, take 10 parts of phosphoric acid and stir and heat. During this process, black smoke is produced and the liquid color darkens. Continue heating to restore transparency. Then, raise the temperature to 250-350℃ and continue stirring for 0.5-2 hours. Then, stir and cool down. Finally, after cooling to room temperature, add 10 parts of pure water, stir for 0.5-1 hour, and let stand to obtain the solution. Solution A is mainly an aqueous solution of polyphosphoric acid. Step 2: Preparation of solution B: Take 30 parts of pure water, and gradually add 10 parts of sodium stannate, 5 parts of ammonium nitrate and 3 parts of potassium permanganate while stirring at room temperature. Stir for 0.5 to 2 hours until the mixture is uniform. Potassium permanganate can be replaced with other types of permanganate salts. Step 3: Preparation of flux for tin plating: Stir solution B at room temperature, slowly add solution A to solution B to obtain solution C, and then add 5 parts ethylenediaminetetraacetic acid and 20 parts glycerol to solution C, stirring for 0.5-1 hour to obtain the final solution. The tin salts formed by sodium stannate, ammonium nitrate, and potassium permanganate at the high casting temperature will diffuse on the surface of the copper part, and the resulting compound can promote the fusion of lead and copper surfaces, improving the mechanical strength of the joint.

[0008] Preferably, the mass fraction of polyphosphate used in preparing the fluxing tin plating solution is 8% to 15%.

[0009] Preferably, the mass fraction of glycerol used in preparing the flux for tin plating is 15% to 30%. Other alcohols with a carbon chain length of 3 to 6, such as isopropanol and butanol, can also be used.

[0010] The beneficial effects of the present invention are as follows: After the polyphosphate, ethylenediaminetetraacetic acid and glycerol contained in the present invention meet the basic fluxing requirements, the present invention also contains sodium stannate, ammonium nitrate and potassium permanganate. The tin salt formed at the high temperature of casting will diffuse on the surface of the copper part, and the formed compound can promote the fusion of lead and copper surfaces and improve the mechanical strength of the joint. Detailed Implementation

[0011] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Example 1

[0012] A fluxing formula for lead-acid battery copper terminal lead sheathing includes the following mass fractions: 40-50 parts pure water, 10-15 parts phosphoric acid, 9-11 parts sodium stannate, 4-6 parts ammonium nitrate, 1-3 parts potassium permanganate, 4-6 parts ethylenediaminetetraacetic acid, and 15-20 parts glycerol. The mass fraction of sodium stannate in the flux tin plating solution prepared by this formula is 6% to 12%.

[0013] The conductivity of the pure water is ≤10µs / cm. Example 2

[0014] A method for preparing a flux formulation for lead-acid battery copper terminal lead sheathing includes the following steps: Step 1: Preparation of Solution A: First, take 10 parts of phosphoric acid, stir and heat. During this process, black smoke is produced and the liquid color darkens. Continue heating to restore transparency. Then, raise the temperature to 250-350℃ and continue stirring for 0.5-2 hours. Then, stir and cool down. Finally, after cooling to room temperature, add 10 parts of pure water, stir for 0.5-1 hour, and let stand to obtain the solution. Step 2: Preparation of Solution B: Take 30 parts of pure water and gradually add 10 parts of sodium stannate, 5 parts of ammonium nitrate and 3 parts of potassium permanganate while stirring at room temperature. Stir for 0.5 to 2 hours until the mixture is uniform. The tin salt formed by sodium stannate, ammonium nitrate and potassium permanganate at the high temperature of casting will diffuse on the surface of the copper part. The compound formed can promote the fusion of lead and copper surfaces and improve the mechanical strength of the joint.

[0015] Step 3: Preparation of flux for tin plating: Stir solution B at room temperature, slowly add solution A to solution B to obtain solution C, then add 5 parts ethylenediaminetetraacetic acid (EDTA) and 20 parts glycerol to solution C, and stir for 0.5–1 hour to obtain the final solution. EDTA acts as a corrosion inhibitor, suppressing the corrosion of copper parts by the flux.

[0016] The mass fraction of polyphosphate in the preparation of flux for tin plating is 8% to 15%. As a flux, polyphosphate can break the surface tension of the lead liquid during terminal casting, destroy the oxide layer on the surface of the copper terminal, promote the welding effect, and reduce the formation of cracks.

[0017] The glycerol content in the flux for tin plating is between 15% and 30%. Glycerol increases the viscosity of the solution, improves the concentration distribution within the flux, and allows the flux to effectively adhere to the surface of the copper workpiece. Example 3

[0018] Experimental tests were conducted using the flux-coated tin plating solution prepared in Example 2, and conventional fluxes were selected for comparison. The specific procedures are as follows: Two sets of brass terminals, A and B, are provided, and threaded holes are provided in the middle of the brass terminals.

[0019] For Group A, a standard flux is used, which consists of an aqueous solution of phosphoric acid and zinc chloride. The lead-cladding process is as follows: brass terminals are dipped in flux → dried → tinned → terminals are cooled → preheated before lead cladding → lead cladding is applied, and then testing is awaited. For B, the flux for soldering tin plating prepared in Example 2 was used. The lead plating process was as follows: brass terminals were dipped in flux → dried → preheated before lead plating → lead plating, and then the test was waited for.

[0020] The tools used for testing included: bolts compatible with the brass terminals, a bench vise, and a torque wrench. The torque wrench was from PAKE TOOL and had a range of 0–10 N·m.

[0021] Clamp and fix the lead-clad brass terminal in a vise, then bolt it onto the brass terminal. Use a torque wrench on the bolt to perform a rotation test. Take a reading when damage occurs between the brass terminal and the lead-clad part. The results are shown in the table below: A 7.3 7.8 6.7 6.6 7.1 7.8 6.2 7.2 7.4 6.9 7.10 B 7.8 7.8 8.2 8.1 7.5 8.3 8.4 7.8 8.0 8.2 8.01 The table above shows that the fluxing tin plating solution prepared in this way can effectively improve the connection strength between the lead-clad part and the brass terminal.

[0022] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A flux formula for lead-clad copper terminals in lead-acid batteries, characterized in that, The following mass fractions are included: 40-50 parts pure water, 10-15 parts phosphoric acid, 9-11 parts sodium stannate, 4-6 parts ammonium nitrate, 1-3 parts potassium permanganate, 4-6 parts ethylenediaminetetraacetic acid, and 15-20 parts glycerol. The mass fraction of sodium stannate in the flux tin plating solution prepared by this formula is 6% to 12%.

2. The flux formula for lead-clad copper terminals of a lead-acid battery according to claim 1, characterized in that: The conductivity of the pure water is ≤10µs / cm.

3. The flux formula for lead-clad copper terminals of a lead-acid battery according to claim 1, characterized in that, The formula includes the following mass fractions: 40 parts pure water, 10 parts phosphoric acid, 10 parts sodium stannate, 5 parts ammonium nitrate, 3 parts potassium permanganate, 5 parts ethylenediaminetetraacetic acid, and 20 parts glycerol.

4. A method for preparing a flux formula for lead-acid battery copper terminal lead sheathing, based on the flux formula for lead-acid battery copper terminal lead sheathing according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Preparation of Solution A: First, take 10 parts of phosphoric acid, stir and heat. During this process, black smoke is produced and the liquid color darkens. Continue heating to restore transparency. Then, raise the temperature to 250-350℃ and continue stirring for 0.5-2 hours. Then, stir and cool down. Finally, after cooling to room temperature, add 10 parts of pure water, stir for 0.5-1 hour, and let stand to obtain the solution. Step 2: Preparation of Solution B: Take 30 parts of pure water, and gradually add 10 parts of sodium stannate, 5 parts of ammonium nitrate and 3 parts of potassium permanganate while stirring at room temperature. Stir for 0.5 to 2 hours until the mixture is homogeneous. Step 3: Prepare the flux for tin plating: Stir solution B at room temperature, slowly add solution A to solution B to obtain solution C, and then add 5 parts of ethylenediaminetetraacetic acid and 20 parts of glycerol to solution C. Stir for 0.5 to 1 hour to obtain the solution.

5. The preparation method of the flux formula for lead-clad copper terminals of lead-acid batteries according to claim 4, characterized in that: The mass fraction of polyphosphate used in the preparation of fluxing tin plating solution is 8% to 15%.

6. The preparation method of the flux formula for lead-clad copper terminals of lead-acid batteries according to claim 4, characterized in that: The mass fraction of glycerol used in the preparation of flux for tin plating is 15% to 30%.