Soldering aid formula for lead coating of copper terminal of lead-acid storage battery and preparation method of soldering aid formula

Abstract

The invention provides a soldering-aid formula for coating lead on a copper terminal of a lead-acid storage battery, which is characterized by comprising the following components in parts by mass: 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 ethylenediamine tetraacetic acid and 15-20 parts of glycerol, and the mass fraction of sodium stannate in a soldering-aid tinning aqueous solution prepared by the formula is 6-12%. According to the invention, the surface tension of lead liquid can be effectively destroyed, the surface activity of a copper piece is improved, and meanwhile, the formula has a tin plating function, so that a tin-containing compound is formed on the surface of the copper piece at high temperature, and the strength between a copper terminal and lead is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of circuit welding, in particular to a flux formula for lead-coated copper terminals of a lead-acid battery and a preparation method thereof. Background Art

[0002] Lead-acid batteries are still widely used in transportation, communications, and energy. Battery terminals, as crucial current-carrying components, have diverse structural designs. For example, starting batteries utilize a lead alloy cage structure, UPS batteries utilize a copper-silver-plated sheet structure, and backup power supplies and forklift power batteries utilize copper terminals encased in lead. Copper terminals facilitate battery assembly and wiring, while also being wear- and corrosion-resistant. However, these terminals require a secure bond with the internal lead components of the battery, ensuring low resistivity and corrosion resistance. Therefore, the use of flux is necessary when using lead-encased copper terminals.

[0003] Copper terminals are typically formed by turning copper rods, then cleaned, degreased, and dried before being cast and lead-clad. The specific process is as follows: ① Apply flux to the copper terminal → ② Dry the surface → ③ Tin the copper component → ④ Remove the terminal and place it in an oven → ⑤ Place the terminal into a mold while still hot → ⑥ Pour liquid lead alloy into the mold → ⑦ Cool and demold. Flux removes metal oxides, reduces the surface tension of the liquid metal, and improves casting quality. Tin diffuses across metal surfaces, allowing dissimilar metals to fuse and bond. The polyphosphoric acid contained in this flux formula fulfills the fluxing function, while the tinning solution, at high temperatures, allows the terminal to be tinned. Summary of the Invention

[0004] The present invention provides a soldering tinning agent capable of improving the strength of lead plating and reducing the welding process. The soldering formula for lead plating of copper terminals of lead-acid batteries comprises the following components by weight: 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 tinning solution prepared using this formula contains 6% to 12% sodium stannate by mass. The addition of sodium stannate and ammonium nitrate allows tin ions to adhere to the surface of copper terminals when they are dipped, eliminating the traditional process of applying flux followed by tinning.

[0005] Preferably, the conductivity of the pure water is ≤10µs / cm, which ensures the purity of the pure water and reduces the interference of miscellaneous ions.

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

[0007] A method for preparing a flux formula for lead-coated copper terminals of a lead-acid battery comprises the following steps: Step 1: Prepare Solution A: First, take 10 parts of phosphoric acid, stir and heat, during which black smoke is generated. After the liquid color darkens, continue heating to restore transparency; then raise the temperature to 250-350°C, continue stirring for 0.5-2 hours, and then cool with stirring; finally, after cooling to room temperature, add 10 parts of pure water, stir for 0.5-1 hour, and then let it stand to obtain Solution A, which is mainly an aqueous solution of polyphosphoric acid; Step 2: Prepare solution B: Take 30 parts of pure water, gradually add 10 parts of sodium stannate, 5 parts of ammonium nitrate and 3 parts of potassium permanganate while stirring at room temperature, and 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: Prepare the soldering tinning agent: Stir Solution B at room temperature, then slowly add Solution A to Solution B to obtain Solution C. Add 5 parts ethylenediaminetetraacetic acid and 20 parts glycerol to Solution C and stir for 0.5 to 1 hour. The tin salts formed by sodium stannate, ammonium nitrate, and potassium permanganate at the high casting temperature will diffuse onto the copper surface. The resulting compound promotes fusion of the lead and copper surfaces, improving the mechanical strength of the joint.

[0008] Preferably, the mass fraction of the polyphosphoric acid used to prepare the soldering tin plating solution is 8% to 15%.

[0009] Preferably, the mass fraction of glycerol used to prepare the soldering tinning solution is 15% to 30%. Other alcohols with a carbon chain length of 3 to 6, such as isopropyl alcohol and butanol, can also be used.

[0010] The beneficial effects of the present invention are as follows: the polyphosphoric acid, ethylenediaminetetraacetic acid and glycerol contained in the present invention meet the basic soldering requirements, and also contain sodium stannate, ammonium nitrate and potassium permanganate. The tin salt formed under the high casting temperature will diffuse on the surface of the copper part, and the formed compound can promote the fusion of the lead and copper surfaces, thereby improving the mechanical strength of the connection. DETAILED DESCRIPTION

[0011] The present invention will be further explained below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Example 1

[0012] A flux formula for lead-coating copper terminals of lead-acid batteries, comprising the following by weight: 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 mass fraction of sodium stannate in the soldering tin plating solution prepared by the formula is 6% to 12%.

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

[0014] A method for preparing a flux formula for lead-coated copper terminals of a lead-acid battery comprises the following steps: Step 1: Prepare Solution A: First, take 10 parts of phosphoric acid and stir and heat it. During this period, black smoke is generated. After the liquid color darkens, continue heating and return to transparency. Then, raise the temperature to 250-350°C and continue stirring for 0.5-2 hours. Then, stir and cool it down. Finally, after cooling to room temperature, add 10 parts of pure water, stir for 0.5-1 hour, and then let it stand to obtain the solution. Step 2: Prepare solution B: Take 30 parts of pure water, gradually add 10 parts of sodium stannate, 5 parts of ammonium nitrate and 3 parts of potassium permanganate while stirring at room temperature, and stir for 0.5 to 2 hours until the mixture is uniform; 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 formed compounds can promote the fusion of the lead and copper surfaces, thereby improving the mechanical strength of the joint.

[0015] Step 3: Prepare the soldering tinning solution: Stir Solution B at room temperature. Slowly add Solution A to Solution B to obtain Solution C. Add 5 parts EDTA and 20 parts glycerol to Solution C and stir for 0.5 to 1 hour. EDTA acts as a corrosion inhibitor, preventing the solution from corroding the copper.

[0016] The mass fraction of polyphosphoric acid used in preparing soldering and tinning solutions ranges from 8% to 15%. As a soldering flux, polyphosphoric acid breaks down the surface tension of the lead solution during terminal casting, destroying the oxide layer on the copper terminal surface, promoting soldering and reducing cracking.

[0017] The mass fraction of glycerol in the preparation of soldering tinning solution is 15% to 30%. Glycerol can increase the viscosity of the solution, improve the internal concentration distribution of the solution, and make the solution effectively adhere to the surface of the copper parts. Example 3

[0018] Experimental testing was conducted using the soldering tinning agent prepared in Example 2, and a conventional soldering flux was selected for comparison. The specific process is as follows: Two groups 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 conventional soldering flux consisting of an aqueous solution of phosphoric acid and zinc chloride was used. The lead coating process is as follows: dip the brass terminal in flux → dry → tin → cool the terminal → heat before lead coating → lead coating, and then wait for testing. For B, the soldering tinning agent prepared in Example 2 was used, and the lead coating process was as follows: brass terminal dipping agent → drying → heating before lead coating → lead coating, and then waiting for testing.

[0020] The tools used in the test include bolts compatible with brass terminals, a vise, and a torque wrench. The torque wrench is from PAKE TOOL and has a range of 0 to 10 N·m.

[0021] Clamp the lead-clad portion of the lead-clad brass terminal in a vise, then fit the bolt onto the brass terminal. Use a torque wrench on the bolt to perform a rotation test. When damage occurs between the brass terminal and the lead-clad portion, read the torque. The results are as follows: Grouping 1 2 3 4 5 6 7 8 9 10 average value 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 From the above table, it can be concluded that the soldering tinning agent prepared by this scheme can effectively improve the connection strength between the lead-clad part and the brass terminal.

[0022] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above-mentioned embodiment, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A flux formula for lead-coated copper terminals of lead-acid batteries, characterized in that: The composition comprises the following components by mass: 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 mass fraction of sodium stannate in the soldering tin plating solution prepared by the formula is 6% to 12%.

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

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

4. A method for preparing a flux formula for lead-coated copper terminals of a lead-acid battery, based on the flux formula for lead-coated copper terminals of a lead-acid battery according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Prepare Solution A: First, take 10 parts of phosphoric acid and stir and heat it. During this period, black smoke is generated. After the liquid color darkens, continue heating and return to transparency. Then, raise the temperature to 250-350°C and continue stirring for 0.5-2 hours. Then, stir and cool it down. Finally, after cooling to room temperature, add 10 parts of pure water, stir for 0.5-1 hour, and then let it stand to obtain the solution. Step 2: Prepare solution B: Take 30 parts of pure water, gradually add 10 parts of sodium stannate, 5 parts of ammonium nitrate and 3 parts of potassium permanganate while stirring at room temperature, and stir for 0.5 to 2 hours until the mixture is uniform; Step 3: Prepare soldering tinning agent: Stir solution B at room temperature, slowly add solution A to solution B to obtain solution C, then add 5 parts of ethylenediaminetetraacetic acid and 20 parts of propylene glycol to solution C, and stir for 0.5 to 1 hour to obtain solution C.

5. The method for preparing a flux formula for lead-coated copper terminals of a lead-acid battery according to claim 4, characterized in that: The mass fraction of polyphosphoric acid used to prepare soldering tin plating solution is 8% to 15%.

6. The method for preparing a flux formula for lead-coated copper terminals of a lead-acid battery according to claim 4, characterized in that: The mass fraction of glycerol used to prepare soldering tin plating solution is between 15% and 30%.