Tin-zinc alloy, electric connecting piece, preparation method of electric connecting piece and electric equipment

Abstract

The embodiment of the invention provides a tin-zinc alloy, an electric connecting piece, a preparation method of the electric connecting piece and electric equipment, the tin-zinc alloy comprises, by mass, 3%-5% of zinc element and 95%-97% of tin element, and the tin-zinc alloy can effectively slow down the growth defect of tin whiskers.

Description

Technical Field

[0001] The present application relates to the field of alloys, and in particular to a tin-zinc alloy, an electrical connector, a preparation method thereof, and electrical equipment. Background Art

[0002] Copper substrates are widely used in electrical connection components such as copper cables, copper busbars, and copper terminals in new energy vehicles and consumer electronics. However, copper is highly susceptible to oxidation, forming cuprous oxide at room temperature, significantly increasing contact resistance and severely impairing electrical connection performance.

[0003] Adding a matte tin coating on the surface of a copper substrate can reduce oxidation of the copper substrate, thereby improving the electrical connection performance of the copper substrate. However, growth defects such as tin whiskers are prone to occur on the surface of the matte tin coating. Summary of the Invention

[0004] The embodiments of the present application provide a tin-zinc alloy, an electrical connector, a preparation method thereof, and electrical equipment, which can effectively mitigate growth defects such as tin whiskers.

[0005] To achieve the above objectives, in a first aspect, embodiments of the present application provide a tin-zinc alloy. Based on the total mass of the tin-zinc alloy, the tin-zinc alloy comprises, in terms of mass percentage, the following:

[0006] 3% to 5% elemental zinc; and

[0007] 95% to 97% elemental tin.

[0008] Optionally, in some embodiments of the present application, in the tin-zinc alloy, the mass percentage of zinc element is 3% to 4%, and the mass percentage of tin is 96% to 97%; or

[0009] The mass percentage of zinc element is 4% to 5%, and the mass percentage of tin is 95% to 96%.

[0010] Optionally, in some embodiments of the present application, the crystal structure of the tin-zinc alloy includes equiaxed crystals.

[0011] In a second aspect, an embodiment of the present application provides a method for preparing a tin-zinc alloy, which is used to prepare the aforementioned tin-zinc alloy, and the preparation method comprises the following steps:

[0012] Provide tin and zinc sources;

[0013] The tin-zinc alloy is prepared.

[0014] Optionally, in some embodiments of the present application, providing a zinc source and a tin source includes providing a surface treatment medium containing a tin salt and a zinc salt.

[0015] Optionally, in some embodiments of the present application, the surface treatment medium includes an electroplating solution.

[0016] Optionally, in some embodiments of the present application, the tin salt includes a divalent tin ion salt and / or a tetravalent tin ion salt.

[0017] Optionally, in some embodiments of the present application, the zinc salt includes one or more of zinc sulfate, zinc sulfonate, zinc chloride, zinc bromide, zinc nitrate, zinc fluoride, zinc citrate, zinc tartrate, zinc malonate, zinc amino acid, zinc hydroxide, and zinc oxide.

[0018] In a third aspect, an embodiment of the present application provides an electrical connector, comprising a copper substrate and a tin-zinc alloy layer disposed on the copper substrate, wherein the tin-zinc alloy layer comprises the aforementioned tin-zinc alloy or a tin-zinc alloy prepared by the aforementioned method for preparing the tin-zinc alloy.

[0019] Optionally, in some embodiments of the present application, the thickness of the tin-zinc alloy layer ranges from 0.5 μm to 50 μm.

[0020] Optionally, in some embodiments of the present application, the thickness of the tin-zinc alloy layer ranges from 3 μm to 10 μm.

[0021] Optionally, in some embodiments of the present application, the tin-zinc alloy layer directly covers the surface of the copper substrate.

[0022] In a fourth aspect, an embodiment of the present application provides a method for preparing an electrical connector, comprising the following steps:

[0023] Provide copper substrate;

[0024] providing a surface treatment medium containing a zinc source and a tin source;

[0025] The copper substrate is surface treated with a surface treatment medium to prepare the tin-zinc alloy layer, thereby obtaining an electrical connector.

[0026] Optionally, in some embodiments of the present application, the surface treatment includes any one of electroplating, chemical vapor deposition, spraying, and dipping.

[0027] In a fifth aspect, an embodiment of the present application provides an electrical device, comprising the electrical connector as described above or an electrical connector made by the method for making the electrical connector as described above.

[0028] Optionally, in some embodiments of the present application, the electrical equipment includes a vehicle or a consumer electronic product.

[0029] The embodiments of the present application provide a tin-zinc alloy that can effectively mitigate defects such as tin whisker growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0031] Figure 1 This is a surface micromorphology image of the matte tin coating of Comparative Example 1 of the present application after the room temperature storage whisker test;

[0032] Figure 2 This is a surface micromorphology image of the tin-zinc alloy of Example 1 of the present application after the room temperature storage whisker test;

[0033] Figure 3 This is a metallographic microscope image of the interface of the matte tin coating of Comparative Example 1 of the present application after the room temperature storage whisker test;

[0034] Figure 4 This is a 3D metallographic microscope image of the interface of the tin-zinc alloy of Comparative Example 2 of the present application after the room temperature storage whisker test;

[0035] Figure 5 This is a metallographic microscope image of the interface of the tin-zinc alloy of Example 1 of the present application after the room temperature storage whisker test;

[0036] Figure 6 This is a 3D metallographic microscope image of the interface of the tin-zinc alloy of Example 2 of the present application after the room temperature storage whisker test;

[0037] Figure 7 This is a microscopic morphology of the matte tin coating of Comparative Example 1 of the present application after the temperature cycle whisker test;

[0038] Figure 8 This is a microscopic morphology of the tin-zinc alloy of Example 1 of the present application after the temperature cycling whisker test;

[0039] Figure 9 This is a microscopic morphology of the matte tin coating of Comparative Example 1 of the present application after microindentation test;

[0040] Figure 10 This is a microscopic morphology of the double-layer coating of Comparative Example 2 of the present application after microindentation test;

[0041] Figure 11 This is a microscopic morphology of the tin-zinc alloy of Example 1 of the present application after microindentation testing;

[0042] Figure 12 This is a microscopic morphology of the tin-zinc alloy of Example 2 of the present application after microindentation testing;

[0043] Figure 13 This is a microscopic morphology of the tin-zinc alloy of Example 3 of the present application after microindentation testing;

[0044] Figure 14 This is a microscopic morphology of the tin-zinc alloy of Example 4 of the present application after microindentation testing;

[0045] Figure 15 This is a microscopic morphology of the tin-zinc alloy of Example 5 of the present application after microindentation testing;

[0046] Figure 16 This is a microscopic morphology of the tin-zinc alloy of Example 6 of the present application after microindentation testing;

[0047] Figure 17 This is a microscopic morphology of the tin-zinc alloy of Comparative Example 4 of the present application after microindentation test;

[0048] Figure 18 This is a photograph of the appearance of the tin-zinc alloy of Example 1 of the present application after being subjected to a 96-hour neutral salt spray test;

[0049] Figure 19 This is a photograph of the appearance of the tin-zinc alloy of Example 2 of the present application after being subjected to a 96-hour neutral salt spray test;

[0050] Figure 20 This is a photograph of the appearance of the tin-zinc alloy of Example 3 of the present application after being subjected to a 96-hour neutral salt spray test;

[0051] Figure 21 This is a photograph of the appearance of the matte tin coating of Comparative Example 1 of the present application after being subjected to a 96-hour neutral salt spray test;

[0052] Figure 22 This is a photograph of the appearance of the double-layer coating of Comparative Example 2 of the present application after being subjected to a 96-hour neutral salt spray test;

[0053] Figure 23 1 is a comparison chart of electrochemical impedance spectroscopy data of Example 1 and Comparative Example 1 of the present application;

[0054] Figure 24 1 is a comparison diagram of the electrochemical polarization curves of Example 1 and Comparative Example 1 of the present application;

[0055] Figure 25 This is a schematic diagram of copper busbar overlap when measuring contact resistance;

[0056] Figure 26 This is a graph showing the results of a hundred-grid test of the tin-zinc alloy of Example 1 of the present application;

[0057] Figure 27 This is a graph showing the results of a hundred-grid test of the tin-zinc alloy of Example 2 of the present application;

[0058] Figure 28This is a graph showing the results of a hundred-grid test of the tin-zinc alloy of Example 3 of the present application;

[0059] Figure 29 This is a graph showing the hundred-grid test results of the matte tin coating of Comparative Example 1 of the present application;

[0060] Figure 30 This is a graph showing the hundred-grid test results of the double-layer coating of Comparative Example 2 of the present application;

[0061] Figure 31 This is a graph showing the results of a hundred-grid test of the bright nickel plating of Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0063] Copper substrates are materials containing copper or copper alloys, offering excellent electrical and thermal conductivity, good mechanical properties, corrosion resistance, and high ductility. Currently, copper substrates are widely used in electrical connection components in new energy vehicles and consumer electronics. However, copper substrates are highly susceptible to oxidation, resulting in poor electrical conductivity, increased contact resistance, and compromised electrical connection performance.

[0064] Related technologies use a matte tin coating on the surface of a copper substrate to help slow oxidation, reduce contact resistance, and improve electrical connection performance. However, the matte tin coating is prone to the growth of defects such as tin whiskers and tin pests. For example, they can nucleate and grow even at room temperature. Tin whiskers have microscopic appearances such as hillocks, nodules, and needles. Whiskers generally range in length from 10μm to 100μm. In exceptional cases, long needle-like whiskers can reach several millimeters, which can easily lead to short-circuit failures in products and, in severe cases, thermal runaway fires. Therefore, there is an urgent need to address the problem of tin whisker growth defects.

[0065] In view of this, the present application proposes a tin-zinc alloy, an electrical connector, a preparation method thereof, and an electrical device.

[0066] According to a first aspect of the present application, a tin-zinc alloy is provided. Based on the total mass of the tin-zinc alloy, the tin-zinc alloy may include, in terms of mass percentage, the following:

[0067] 3% to 5% elemental zinc; and

[0068] 95% to 97% elemental tin.

[0069] An embodiment of the present application provides a tin-zinc alloy including 3% to 5% by mass of zinc, which helps to inhibit the growth of tin whiskers on the surface of the tin-zinc alloy.

[0070] It's understandable that zinc readily forms zinc oxide, which competes with tin oxide, promoting the flow of surface vacancies to form a small amount of oxygen vacancies, which facilitates stress release and slows tin whisker growth. Furthermore, adding an appropriate amount of zinc to the tin-zinc alloy can help compensate for the inherent corrosion resistance of tin oxide.

[0071] It should be noted that the tin-zinc alloy of the embodiment of the present application also has excellent corrosion resistance and electrical connection performance. This is because the atomic radius of zinc and tin is similar, with a difference of only 3pm, which can reduce the large lattice distortion caused by the introduction of zinc, thereby ensuring the density of the tin-zinc alloy, helping to improve the corrosion resistance of the tin-zinc alloy, and greatly reducing the application thickness of the tin-zinc alloy. Moreover, the zinc element can also play a purifying role, helping to reduce the defect content on the surface of the tin-zinc alloy, reducing electron scattering, thereby improving the corrosion resistance and electrical connection performance of the coating. In addition, the electrical conductivity of the zinc element is better than that of the tin element, which helps to improve the electrical conductivity of the tin-zinc alloy itself. It should also be noted that since the copper busbar overlap method is adopted when measuring the contact resistance, the overlap surface contact resistance is low, which reduces the electron transmission loss and helps to further improve the electrical connection performance of the tin-zinc alloy.

[0072] In some embodiments of the present application, in the tin-zinc alloy, the mass percentage of zinc element is 3% to 4%, and the mass percentage of tin is 96% to 97%.

[0073] In some embodiments of the present application, in the tin-zinc alloy, the mass percentage of zinc element is 4% to 5%, and the mass percentage of tin is 95% to 96%.

[0074] It should be noted that, the surface of the tin-zinc alloy with a zinc content of 3% to 4% or 4% to 5% has no tin whisker growth and has fine, uniform and dense grains.

[0075] In some embodiments of the present application, the crystal structure of the tin-zinc alloy includes equiaxed crystals.

[0076] It should be noted that the crystal structure of the tin-zinc alloy in the embodiment of the present application is transformed from columnar crystals to equiaxed crystals, which increases the proportion of transverse grain boundaries, so that the compressive stress can be released at the transverse grain boundaries without being transmitted longitudinally to the surface of the substrate, which fundamentally reduces the driving force for tin whisker growth.

[0077] According to a second aspect of the present application, a method for preparing a tin-zinc alloy is provided, comprising the following steps:

[0078] S100, providing a tin source and a zinc source;

[0079] S200, preparing a tin-zinc alloy.

[0080] The present application provides a method for preparing a tin-zinc alloy. The tin-zinc alloy prepared by this method helps to inhibit the growth of tin whiskers and ensures that the grains on the surface of the tin-zinc alloy are fine. In step S100, "providing a tin source and a zinc source" refers to providing the raw materials of tin and zinc in the tin-zinc alloy. The tin source and the zinc source can be different substances, for example, the tin source includes a compound containing the element tin, and the zinc source includes a compound containing the element zinc; alternatively, the tin source and the zinc source can be the same substance, for example, using a compound containing both the elements tin and zinc as the tin source and the zinc source.

[0081] In some embodiments of the present application, in step S100 , providing a tin source and a zinc source includes providing a surface treatment medium containing a tin salt and a zinc salt.

[0082] It should be noted that the surface treatment medium refers to the material used for surface treatment, where the material can be liquid or solid. For example, a liquid material can be deposited on the surface of a substrate under appropriate temperature, pressure, or other process parameters to prepare a tin-zinc alloy; for example, a solid material can be converted to a gaseous state through sublimation or direct heating to participate in a chemical reaction to prepare a tin-zinc alloy. In the embodiments of the present application, the surface treatment medium can be used to provide the two metal elements required to prepare the tin-zinc alloy.

[0083] In some embodiments of the present application, the surface treatment medium includes but is not limited to an electroplating solution.

[0084] It is understandable that when the surface treatment medium adopts an electroplating solution, it indicates that the tin-zinc alloy can be prepared by electroplating, which helps to improve the corrosion resistance and conductivity of the tin-zinc alloy.

[0085] In some embodiments of the present application, the electroplating solution includes a tin salt, a zinc salt, a free acid or base, and an additive.

[0086] In some embodiments of the present application, the tin salt may include a divalent tin ion salt and / or a tetravalent tin ion salt.

[0087] Specifically, the tin salt may include, but is not limited to, acidic tin salts such as stannous sulfate, stannous methanesulfonate, stannous fluoroborate, stannous pyrophosphate, and stannous halides, and basic tin salts such as sodium stannate and potassium stannate.

[0088] In some embodiments of the present application, the zinc salt may include one or more of zinc sulfate, zinc sulfonate, zinc chloride, zinc bromide, zinc nitrate, zinc fluoride borate, zinc citrate, zinc tartrate, zinc malonate, zinc amino acid, zinc hydroxide, and zinc oxide.

[0089] In some embodiments of the present application, the free acid or base can be selected from sulfuric acid, benzenesulfonic acid, benzenefluoric acid, halogen acid, sodium hydroxide, potassium hydroxide, etc. as the conductive salt and buffer.

[0090] In some embodiments of the present application, the additives may include, but are not limited to, brighteners, bath stabilizers, bath dispersants, pH adjusters, hydrogen evolution inhibitors, and chelating agents.

[0091] In some embodiments of the present application, the brightener may include but is not limited to vinyl benzophenone brightener, acrolein brightener or methacrolein brightener, and the brightener is mainly used to improve the glossiness of the tin-zinc alloy.

[0092] In some embodiments of the present application, the plating solution stabilizer can be selected from two or more compounds including but not limited to chelating agents, reducing agents, antioxidants and potential regulators. The plating solution stabilizer is mainly used to improve the stability of the plating solution and prevent the plating solution from becoming turbid.

[0093] In some embodiments of the present application, the complexing agent may use citric acid as the main complexing agent.

[0094] In some embodiments of the present application, the complexing agent may also use an auxiliary complexing agent, including but not limited to tartaric acid, malic acid, phenol, resorcinol, toluenesulfonic acid, glycolic acid, lactic acid or ascorbic acid, to improve the stability of the plating solution and prevent the plating solution from becoming turbid.

[0095] In some embodiments of the present application, the plating solution dispersant may include but is not limited to anionic surfactants such as OP emulsifier and polyethylene glycol.

[0096] In some embodiments of the present application, hydrogen evolution inhibitors and chelating agents can reduce cathode hydrogen evolution and zinc ion disproportionation reactions during the electroplating process, thereby improving the quality of the tin-zinc alloy and the stability of the electroplating solution.

[0097] In some embodiments of the present application, the hydrogen evolution inhibitor may be epichlorohydrin.

[0098] In some embodiments of the present application, the chelating agent may be phosphates, aminocarboxylic acids, hydroxycarboxylic acids, and the like.

[0099] In some embodiments of the present application, the additives may also be β-naphthol and gelatin, which help to promote the degree of cathode polarization, increase the crystal density of the tin-zinc alloy, and also make the grains finer.

[0100] According to a third aspect of the present application, an electrical connector is provided, comprising a copper substrate and a tin-zinc alloy layer disposed on the copper substrate, wherein the tin-zinc alloy layer comprises the tin-zinc alloy described in the first aspect or the tin-zinc alloy prepared by the preparation method of the tin-zinc alloy described in the second aspect.

[0101] It is understandable that adding a tin-zinc alloy layer to an electrical connector helps improve its electrical connection performance and corrosion resistance. However, related art uses a matte tin coating on the surface of a copper substrate. The oxide film on the matte tin coating is generally thin, approximately 3nm, and has limited corrosion resistance. This often requires increasing the coating thickness to improve corrosion resistance, resulting in increased material and process costs.

[0102] In some embodiments of the present application, the thickness of the tin-zinc alloy layer may range from 0.5 μm to 50 μm.

[0103] It should be noted that the growth of tin whiskers is also related to the thickness of the tin-zinc alloy layer. The thicker the tin-zinc alloy layer, the more conducive it is to suppressing tin whisker growth. However, the thickness of the tin-zinc alloy layer should not be too large, as excessive thickness is not conducive to the thinning application of the tin-zinc alloy layer. For example, the thickness of the tin-zinc alloy layer can range from 0.5μm to 10μm, 10μm to 20μm, 20μm to 30μm, 30μm to 40μm, or 40μm to 50μm.

[0104] In some embodiments of the present application, the thickness of the tin-zinc alloy layer may range from 3 μm to 10 μm. When the thickness of the tin-zinc alloy layer in the embodiment of the present application is 3 μm to 10 μm, it can effectively inhibit the growth of tin whiskers.

[0105] It should be noted that the thickness of the tin-zinc alloy layer is also related to the corrosion resistance of the tin-zinc alloy. For example, the greater the thickness, the better the corrosion resistance of the tin-zinc alloy layer. The tin-zinc alloy layer of the embodiment of the present application has excellent corrosion resistance when the thickness is 3μm to 10μm, which is conducive to the application of thinner tin-zinc alloy.

[0106] In some embodiments of the present application, the tin-zinc alloy layer directly covers the surface of the copper substrate.

[0107] It should be noted that the tin-zinc alloy layer is directly covered on the surface of the copper substrate, and no intermediate layer is required between the tin-zinc alloy layer and the surface of the copper substrate. This is because zinc helps to pin the crystal lattice, effectively avoiding the mutual diffusion between tin and the substrate to form hard and brittle intermetallic compounds, avoiding the generation of internal compressive stress, and thus inhibiting the growth of tin whiskers. Related technologies also have an additional nickel intermediate layer between the copper substrate and the tin-zinc alloy layer, but this will reduce production efficiency and increase additional economic costs, and fundamentally the microscopic grains of the alloy are still columnar crystals, which fails to effectively reduce the driving force for tin whisker growth. In addition, the nickel intermediate layer will gradually be consumed during long-term service to generate ternary intermetallic compounds, and the risk of tin whisker growth will be greatly increased after long-term service.

[0108] According to a fourth aspect of the present application, a method for preparing an electrical connector is provided, comprising the following steps:

[0109] S100, providing a copper substrate;

[0110] S200, providing a surface treatment medium containing a zinc source and a tin source;

[0111] S300 , performing surface treatment on the copper substrate using a surface treatment medium to prepare a tin-zinc alloy layer, thereby obtaining an electrical connector.

[0112] For an understanding of the surface treatment medium, please refer to the description of the surface treatment medium in the second aspect of the present application. In some embodiments of the present application, in step S200, the surface treatment medium may include but is not limited to an electroplating solution.

[0113] In some embodiments of the present application, in step S300, the surface treatment includes, but is not limited to, electroplating, chemical vapor deposition, spraying, or dipping. Electroplating, chemical vapor deposition, spraying, or dipping can all be used to prepare the tin-zinc alloy layer and help ensure that the tin-zinc alloy layer has excellent deposition quality.

[0114] It should be noted that electroplating requires the selection of a suitable electroplating solution, a suitable temperature, a suitable current density and a pH value for co-deposition to prepare a tin-zinc alloy.

[0115] Illustratively, a suitable temperature may be 15-40°C.

[0116] For example, a suitable current density may be 0.5-3 A / dm 2 , 1-2A / dm 2 .

[0117] In some embodiments of the present application, the current density can also be selected as a graded setting scheme. For example, 0.5A / dm 2 The current density was then increased to 1 A / dm 2 Up to 2A / dm 2 .

[0118] For example, the pH value may be 4.5-7. A pH in this range helps to reduce cathode hydrogen evolution and disproportionation reactions.

[0119] In some embodiments of the present application, the co-deposition time is related to the thickness of the tin-zinc alloy layer. The longer the co-deposition time is, the thicker the tin-zinc alloy layer is, and the shorter the co-deposition time is, the thinner the tin-zinc alloy layer is.

[0120] In some embodiments of the present application, co-deposition can adopt mechanical and ultrasonic assisted stirring processes to promote the efficiency of alloy electrodeposition, while ensuring the timely diffusion of anions and cations in the electroplating solution, thereby improving the density of the tin-zinc alloy.

[0121] In some embodiments of the present application, the surface of the copper substrate may be pretreated before electroplating.

[0122] In some embodiments of the present application, the pretreatment may be electroplating or mechanical treatment. For example, polishing processes such as mechanical polishing, chemical polishing, and electrolytic polishing, or other mechanical treatment processes such as grinding and tumbling, or processes such as sandblasting and shot blasting, can help improve the flatness of the copper substrate surface.

[0123] In some embodiments of the present application, the pretreatment may also include a degreasing process, for example, chemical degreasing, electrolytic degreasing, etc.

[0124] In some embodiments of the present application, the pretreatment may also include an etching process. For example, the etching process may include etching to remove oxides. For example, the etching may include weak etching, strong etching, etc.

[0125] In some embodiments of the present application, a pre-plating process may be added before electroplating to help improve the adhesion and bonding strength of the tin-zinc alloy.

[0126] According to a fifth aspect of the present application, an electrical device is provided, comprising the aforementioned electrical connector or an electrical connector produced by the aforementioned method for producing the electrical connector. Because the electrical connector of the present application has excellent electrical connection performance and corrosion resistance, it helps improve the electrical connection performance and corrosion resistance of the electrical device, thereby increasing the applicability of the electrical device to a wide range of applications.

[0127] In some embodiments of the present application, electrical devices may include vehicles or consumer electronics. The electrical connector of the present application may be used in vehicles to prevent failure of the electrical connector due to chloride ions contacting the electrical connector when the vehicle is traveling in coastal areas or on roads with snow-melting agents, thereby helping to expand the application range of the vehicle.

[0128] The present invention is described in detail below by means of specific examples, which are only some examples of the present invention and are not intended to limit the present invention. The raw materials used in the following examples, unless otherwise specified, are all commercially available products.

[0129] Example 1

[0130] An electrical connector is prepared by the following method:

[0131] S100, preparing electroplating solution:

[0132] The electroplating solution includes the following components in parts by weight: 22 parts of stannous sulfate, 3 parts of zinc sulfate, 75 parts of citric acid, 20 parts of tartaric acid, 5 parts of epichlorohydrin and 4 parts of chelating agent EDTA;

[0133] The components of the above electroplating solution are mixed and stirred to prepare an electroplating solution.

[0134] S201. Pretreatment of copper substrate:

[0135] The copper substrate is subjected to mechanical polishing and degreasing pretreatment, followed by electrolytic degreasing;

[0136] Use sulfonic acid to etch, then rinse with water and set aside;

[0137] Among them, the copper substrate adopts T2 copper substrate;

[0138] S202, electroplating:

[0139] Immerse the pretreated copper substrate in the electroplating solution with a temperature of 30°C, a pH of 5-7, and a current density of 1A / dm 2 The deposition was performed for 30 minutes, and an ultrasonic stirring process was used for co-deposition for 40 minutes to prepare a tin-zinc alloy layer to obtain an electrical connector.

[0140] Example 2

[0141] An electrical connector differs from Example 1 in S100 and S202. The composition of the electroplating solution in S100 is different; the electroplating solution in this example comprises 22 parts stannous sulfate, 7 parts zinc sulfate, 72 parts citric acid, 22 parts tartaric acid, 5 parts epichlorohydrin, and 4 parts chelating agent EDTA.

[0142] The electroplating conditions in S202 are: the temperature of the electroplating solution is 30°C, the pH is 5-7, and the current density is selected as 1A / dm 2 The deposition was performed for 30 minutes, and an ultrasonic stirring process was used for co-deposition for 40 minutes to prepare a tin-zinc alloy layer to obtain an electrical connector.

[0143] Example 3:

[0144] An electrical connector differs from Example 2 in that the composition of the electroplating solution in S100 is different. The electroplating solution in this example comprises 23 parts stannous sulfate, 5 parts zinc sulfate, 75 parts citric acid, 21 parts tartaric acid, 5 parts epichlorohydrin, and 4 parts chelating agent EDTA.

[0145] Example 4:

[0146] An electrical connector, which differs from Example 1 in that the deposition time during the electroplating process in step S202 is different. This embodiment uses a current density of 1A / dm 2 The deposition was carried out for 10 min, and the ultrasonic stirring process was used for co-deposition for 12 min to prepare a tin-zinc alloy with a thickness of 3 μm.

[0147] Example 5:

[0148] An electrical connector, which differs from Example 1 in that the deposition time during the electroplating process in step S202 is different. This embodiment uses a current density of 1A / dm 2 The deposition was carried out for 15 min, and the ultrasonic stirring process was used for co-deposition for 20 min to prepare a tin-zinc alloy with a thickness of 5 μm.

[0149] Example 6:

[0150] An electrical connector, which differs from Example 1 in that the deposition time during the electroplating process in step S202 is different. This embodiment uses a current density of 1A / dm 2 The deposition was carried out for 24 min, and the ultrasonic stirring process was used for co-deposition for 32 min to prepare a tin-zinc alloy layer with a thickness of 8 μm.

[0151] Comparative Example 1

[0152] A matte tin coating is prepared by the following method:

[0153] S201. Pretreatment of copper substrate:

[0154] The copper substrate is subjected to mechanical polishing and degreasing pretreatment, followed by electrolytic degreasing;

[0155] Use sulfonic acid to etch, then rinse with water and set aside;

[0156] S202, electroplating matte tin layer:

[0157] The electroplating solution is stannous sulfate. The pretreated copper substrate is immersed in the electroplating solution. The temperature of the electroplating solution is set to 25°C, the pH is 2-3, and the current density is 1A / dm 2 Deposition was performed for 20 minutes to prepare a matte tin coating.

[0158] Comparative Example 2

[0159] A double-layer coating is prepared by the following method:

[0160] S201. Pretreatment of copper substrate:

[0161] The copper substrate is subjected to mechanical polishing and degreasing pretreatment, followed by electrolytic degreasing;

[0162] Use sulfonic acid to etch, then rinse with water and set aside;

[0163] S202, nickel plating intermediate layer

[0164] Nickel sulfate was used as the electroplating solution. The pretreated substrate was immersed in the electroplating solution. The temperature of the electroplating solution was set to 30°C, the pH was 2-3, and the current density was selected to be 1A / dm 2 Deposition for 20 min to prepare a nickel intermediate layer;

[0165] S203, electroplating matte tin coating:

[0166] The electroplating solution is stannous sulfate. The copper substrate with the nickel intermediate layer is immersed in the electroplating solution. The temperature of the electroplating solution is 25℃, the pH is 2-3, and the current density is 1A / dm 2 The deposition was carried out for 20 minutes to prepare a matte tin coating.

[0167] Comparative Example 3:

[0168] A bright nickel plating layer is prepared by the following method:

[0169] S201, pretreatment of substrate:

[0170] The substrate is mechanically polished and degreased before being electrolytically degreased;

[0171] Use sulfonic acid to etch, then rinse with water and set aside;

[0172] S202, electroplating bright nickel layer:

[0173] Nickel sulfate was used as the electroplating solution. The pretreated copper substrate was immersed in the electroplating solution. 10 wt% sodium dodecyl sulfate was added. The temperature of the electroplating solution was 35 ° C, the pH was 3.6-5.8, and the current density was 1 A / dm 2 Deposition was performed for 20 min to prepare a bright nickel layer.

[0174] Comparative Example 4:

[0175] An electrical connector differs from Example 3 in that the composition of the electroplating solution in S100 is different. The electroplating solution in this example comprises 23 parts stannous sulfate, 1.5 parts zinc sulfate, 75 parts citric acid, 21 parts tartaric acid, 5 parts epichlorohydrin, and 4 parts chelating agent EDTA.

[0176] Detection methods:

[0177] 1. Coating thickness and composition test: Use X-ray film thickness meter to test the thickness and composition of the tin-zinc alloy layer.

[0178] 2. Whisker growth test:

[0179] (1) Whisker growth test at room temperature - micromorphology of coating surface:

[0180] According to the Japanese JEITA standard, Example 1 and Comparative Example 1 were subjected to a whisker environmental test. The whisker growth conditions for room temperature storage were an ambient temperature of 30±2°C, a humidity of 60±3%, an observation period of 1000h (42d), and a minimum test time of 3000h (125d).

[0181] (2) Room temperature storage whisker growth test - interface intermetallic compound detection:

[0182] The interfaces of the samples of Examples 1-2 and Comparative Examples 1-2 were polished, and the metallographic structures of the interfaces were observed using a metallographic microscope. The whisker growth conditions for room temperature storage were an ambient temperature of 30±2° C., a humidity of 60±3%, an observation period of 1000 h (42 d), and a minimum test time of 3000 h (125 d).

[0183] (3) Temperature cycle whisker growth test:

[0184] Example 1 and Comparative Example 1 were subjected to a temperature cycling whisker test according to Japanese JEITA standards. The samples were placed in a thermal shock chamber and subjected to a 20-minute cycle from -55°C to 85°C. Three cycles were performed in one hour, for a total test duration of 500 hours. After drying, the samples were observed using a scanning electron microscope (SEM) to detect the presence of whiskers.

[0185] (4) Micro-indentation tin whisker growth test:

[0186] Whisker growth testing through microindentation testing can effectively verify the sensitivity of coating samples to whisker growth and significantly reduce testing time and costs. The specific test steps include:

[0187] ① Place the quartz glass tube with a base on a horizontal table, place the sample to be tested at the bottom of the glass tube, and ensure that the ambient temperature and humidity are constant;

[0188] ②Press a 1mm diameter zirconia ball onto a 1mm thick glass slide. Gently place the zirconia ball on the sample surface with the glass slide facing up, ensuring that the ball is in contact with the sample.

[0189] ③ Place a 200g weight into the quartz glass tube and gently press the ball to ensure that the weight does not tilt and the ball is in constant contact with the sample.

[0190] ④ Keep the experimental device still and let it stand for 72 hours, then gently remove the weights and pressure ball and save the sample;

[0191] ⑤ Use SEM scanning electron microscope to observe the whisker growth around the indentation.

[0192] 3. Salt spray test

[0193] The samples of Examples 1-3 and Comparative Examples 1-2 were placed in a salt spray chamber that complies with the GB / T 10587-2006-1 standard, tested for 336 hours according to the GB / T 10125-2021 test standard, and the results were judged according to relevant standards such as GB / T 6461-2002.

[0194] This test was conducted in a standard salt spray chamber. Every 24 hours, the surface was observed for signs of corrosion. The surface was cleaned with a 5% nitric acid solution, dried, and then weighed. The weight loss data for the relevant specimens was recorded and calculated. The total test time was 336 hours. Weight loss = (initial mass - mass after cleaning and drying) / initial mass * 1000‰.

[0195] 4. Electrochemical corrosion test:

[0196] Using a CHI-660 electrochemical workstation, sample 1 and control sample 1 were prepared according to the test sample dimensions and polished. For the electrochemical corrosion test, the sample served as the working electrode. The reference, auxiliary, and working electrodes were placed in a 3.5 wt.% NaCl solution. The test apparatus was held at open circuit potential for 30 minutes. The test began after the system stabilized.

[0197] 5. Contact resistance test:

[0198] Contact resistance testing was performed on the samples of Examples 1-3 and Comparative Examples 1-3, and the testing steps were as follows:

[0199] ① Two straight copper bars of the same size and with the same plating, with the plating surfaces in contact with each other;

[0200] ②Install the corresponding bolts and nuts in the reserved installation holes;

[0201] ③ Apply 15N·m torque using a standard torque wrench, with a torque tolerance within ±10%;

[0202] ④ Measure the contact resistance between the bolted copper bars multiple times using an internal resistance meter and take the average value.

[0203] 6. Adhesion test:

[0204] The adhesion of the samples of Examples 1-3 and Comparative Examples 1-3 was measured using a cross-hatch method, and the test standard complied with the requirements of GB / T9286-1998.

[0205] Test results:

[0206] 1. The thickness and zinc content of the tin-zinc alloy layer of Examples 1-6 and Comparative Examples 1-4 are shown in Table 1.

[0207] Table 1

[0208]

[0209] 2. Test results of whisker growth:

[0210] (1) After storage at room temperature for 60 days, the microscopic morphology of the surfaces of the samples of Example 1 and Comparative Example 1 was observed. Figure 1The microscopic morphology of the sample surface of Comparative Example 1 is shown in FIG. Figure 2 The microscopic morphology of the sample surface in Example 1. Figure 1 It can be seen that the matte tin coating of Comparative Example 1 has nodular whiskers growing therein, and the nodules are the growth points of subsequent needle-shaped whiskers. Figure 2 It can be seen that the surface of the tin-zinc alloy of Example 1 is smooth and flat, without any whisker formation, and the density of the tin-zinc alloy is relatively high.

[0211] (2) Figure 3 and Figure 4 The interface metallographic structures of the samples of Comparative Example 1 and Comparative Example 2 are shown in FIG. Figure 5 and Figure 6 The interface metallographic structure of the samples of Example 1 and Example 2 is shown in FIG. Figure 3 and Figure 4 It can be seen that there are intermetallic compounds between the matte tin coating and the copper substrate. The presence of intermetallic compounds will produce compressive stress and promote the growth of whiskers. Figure 5 and Figure 6 It can be seen that no intermetallic compound is formed between the tin-zinc alloy and the copper substrate in Examples 1 and 2, which reduces the driving force for tin whisker growth. This is because the zinc element effectively stabilizes the diffusion of tin atoms, fundamentally reducing the driving force for tin whisker growth.

[0212] (3) Figure 7 This is the surface micromorphology of the matte tin coating of comparative example 1 after temperature cycling test. Figure 8 This is the surface micromorphology of the tin-zinc alloy of Example 1 after temperature cycling test. Figure 7 It can be seen that whiskers appear on the nodular protrusions on the matte tin coating surface of Comparative Example 1. Under the thermal shock, the stress generated by the intermetallic compound promotes the growth of whiskers. Figure 8 It can be seen that after the temperature cycle test, there is no obvious difference in the surface of the sample of Example 1, and no whiskers appear.

[0213] (4) Figure 9 This is the surface micromorphology of the matte tin coating sample of comparative example 1 after micro-indentation test. Figure 10 This is the surface micromorphology of the coating sample of Comparative Example 2 after microindentation test. Figure 11-13 These are the surface micromorphologies of the tin-zinc alloy samples of Examples 1-3 after microindentation testing.

[0214] When external pressure is applied through microindentation test, the external pressure forms an environment that promotes the accelerated growth of whiskers. Figure 9 It can be seen that a large number of needle-shaped whiskers appear in the area around the indentation of the matte tin coating, indicating that after applying pressure to the surface of the matte tin coating, the tin grains are subjected to stress, which accelerates the growth of whiskers. Figure 10It can be seen that a large number of needle-shaped whiskers were also found around the indentation of the coating in Comparative Example 2, proving that the nickel intermediate layer cannot effectively inhibit whisker formation. Figure 11-13 It can be seen that for the samples of Examples 1-3, the difference lies in the different doping ranges of zinc content. After microindentation testing, when external pressure is applied, the stress is transmitted to both sides through the grains, and the driving force for tin whisker growth is reduced, so no tin whiskers grow on the surface of the tin-zinc alloy. Figure 17 It can be seen that for the sample of Comparative Example 4, the zinc content is 1.5%, and there are obvious whiskers in the area around the indentation, indicating that when the zinc content in the sample is 1.5%, the whisker growth cannot be effectively suppressed.

[0215] In addition, if Figure 11 、 14 -16 It can be seen that after the micro-indentation test on the tin-zinc alloy surfaces of Example 1 and Examples 4-6, there is no obvious whisker formation in the area around the micro-indentation, that is, the tin-zinc alloy layers of different thicknesses are helpful in inhibiting the growth of tin whiskers, and the thickness of the tin-zinc alloy layer is preferably 3μm to 10μm.

[0216] 3. Salt spray test results:

[0217] Figure 18-20 The following are photos of the surface conditions of the samples of Examples 1-3 after being corroded by neutral salt spray. Figure 21-22 The following is a photo of the surface condition of the sample of comparative example 1-2 after being corroded by neutral salt spray. Figure 18-22 It can be seen that no matter whether it is tin-zinc alloy or the sample containing matte tin coating, there is no pitting pit on the surface, and the corrosion resistance is excellent, which meets the salt spray requirements of most electrical connection coating applications.

[0218] 4. Electrochemical corrosion test results:

[0219] Figure 23 and Figure 24 The output impedance curves and electrochemical polarization curves of Example 1 and Comparative Example 1 are respectively shown. The tin-zinc alloy of Example 1 has a larger impedance radius, a more positive polarization potential, and a smaller corrosion current; while the matte tin coating of Comparative Example 1 has a smaller impedance radius, a negative polarization potential, and a higher corrosion current. In summary, the corrosion resistance of Example 1 is significantly better than that of Comparative Example 1, and can meet application requirements under harsh conditions.

[0220] 5. Contact resistance test results:

[0221] The contact resistances of the tin-zinc alloys of Examples 1-3 and Comparative Examples 1-3 are shown in Table 3.

[0222] Table 3

[0223]

[0224] Combining the test results of Examples 1-3, Comparative Examples 1-3, and Table 3, we can see that the contact resistance of the tin-zinc alloys of Examples 1-3 ranges from 0.0022 mΩ to 0.0028 mΩ, while the contact resistance of the coating of Comparative Examples 1-2 is greater than 0.003 mΩ. This indicates that the contact resistance of the coatings of Examples 1-3 is lower than that of the coating of Comparative Examples 1-2, indicating good point contact performance. The contact resistance of the coating of Comparative Example 3 is close to 0.008 mΩ, indicating that the contact position is primarily point contact, the contact area is smaller, and the contact resistance is higher. Figure 25 Schematic diagram of copper busbar overlap when measuring contact resistance.

[0225] 6. Adhesion test results:

[0226] Figures 26-28 The results of the hundred-grid test of the tin-zinc alloy of Examples 1-3 are shown in FIG. Figures 29-31 The figure is a hundred-grid test result diagram of the coating of comparative examples 1-3. Figures 26-28 It can be seen that the 100-grid test of the tin-zinc alloy of Examples 1-3 is level 0, the cutting edge is completely smooth, and no grid falls off, indicating that the tin-zinc alloy of Examples 1-3 has excellent adhesion. Figures 29-30 It can be seen that the coating of Comparative Example 1-2 is grade 0 in the 100-grid test, and the cutting edge is completely smooth without any grid falling off, indicating that the coating of Comparative Example 1-2 has excellent adhesion. Figure 31 It can be seen that the coating of Comparative Example 3 scored level 0 in the 100-grid test, but there was obvious cross-cutting at the intersection of the grids, the edges were peeling, and the adhesion was lower than that of the coatings of Comparative Examples 1-2. In summary, the tin-zinc alloys of Examples 1-3 maintained the flexibility and high adhesion characteristics of the matte tin coatings of Comparative Examples 1-2, while the adhesion of Comparative Example 3 was inferior to that of the matte tin coating.

[0227] The above is a detailed introduction to a tin-zinc alloy, an electrical connector, a preparation method thereof, and an electrical equipment provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, based on the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A tin-zinc alloy, characterized in that: Based on the total mass of the tin-zinc alloy, the tin-zinc alloy comprises, in terms of mass percentage: 3% to 5% elemental zinc; and 95% to 97% elemental tin.

2. The tin-zinc alloy according to claim 1, characterized in that In the tin-zinc alloy, the mass percentage of zinc element is 3% to 4%, and the mass percentage of tin is 96% to 97%; or The mass percentage of zinc element is 4% to 5%, and the mass percentage of tin is 95% to 96%.

3. The tin-zinc alloy according to claim 1, characterized in that The crystal structure of the tin-zinc alloy includes equiaxed crystals.

4. A method for preparing a tin-zinc alloy, characterized in that: For preparing the tin-zinc alloy according to any one of claims 1 to 3, the preparation method comprises the following steps: Provide tin and zinc sources; The tin-zinc alloy is prepared.

5. The method for preparing the tin-zinc alloy according to claim 4, wherein: Providing a tin source and a zinc source includes providing a surface treatment medium containing a tin salt and a zinc salt.

6. The method for preparing the tin-zinc alloy according to claim 5, characterized in that: The surface treatment medium includes an electroplating solution.

7. The method for preparing a tin-zinc alloy according to claim 5, wherein: The tin salt includes a divalent tin ion salt and / or a tetravalent tin ion salt.

8. The method for preparing a tin-zinc alloy according to claim 5, wherein: The zinc salt includes one or more of zinc sulfate, zinc sulfonate, zinc chloride, zinc bromide, zinc nitrate, zinc fluoride, zinc citrate, zinc tartrate, zinc malonate, zinc amino acid, zinc hydroxide, and zinc oxide.

9. An electrical connector, characterized in that: The invention comprises a copper substrate and a tin-zinc alloy layer provided on the copper substrate, wherein the tin-zinc alloy layer comprises the tin-zinc alloy according to any one of claims 1 to 3 or the tin-zinc alloy prepared by the preparation method of the tin-zinc alloy according to any one of claims 4 to 8.

10. The electrical connector according to claim 9, characterized in that: The thickness of the tin-zinc alloy layer ranges from 0.5 μm to 50 μm.

11. The electrical connector according to claim 9, characterized in that The thickness of the tin-zinc alloy layer ranges from 3 μm to 10 μm.

12. The electrical connector according to claim 9, characterized in that The tin-zinc alloy layer directly covers the surface of the copper substrate.

13. A method for preparing an electrical connector, characterized in that: For preparing the electrical connector according to any one of claims 9 to 12, the preparation method comprises the following steps: Provide copper substrate; providing a surface treatment medium containing a zinc source and a tin source; The copper substrate is surface treated with a surface treatment medium to prepare the tin-zinc alloy layer, thereby obtaining an electrical connector.

14. The method for preparing an electrical connector according to claim 13, wherein: The surface treatment includes any one of electroplating, chemical vapor deposition, spraying, and dipping.

15. An electrical device, characterized in that: An electrical connector comprising the electrical connector according to any one of claims 9 to 12 or an electrical connector made by the method for making the electrical connector according to claim 13 or 14.

16. The electrical equipment according to claim 15, characterized in that: The electrical equipment includes vehicles or consumer electronic products.

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