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

Abstract

The embodiment of the invention provides a tin-cerium alloy, an electric connecting piece, a preparation method of the electric connecting piece and electric equipment, and the tin-cerium alloy comprises the following components in parts by mass: 0.5-55 parts of cerium element and 45-99.5 parts of tin element; the tin-cerium alloy can effectively slow down growth defects such as tin whiskers.

Description

Technical Field

[0001] The present application relates to the field of alloys, and in particular to a tin-cerium 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-cerium alloy, a preparation method thereof, and electrical equipment, which can effectively solve defects such as tin whisker growth in the tin-cerium alloy.

[0005] To achieve the above objectives, in a first aspect, embodiments of the present application provide a tin-cerium alloy, which comprises, in parts by mass:

[0006] 0.5 to 55 parts of cerium,

[0007] 45 to 99.5 parts of elemental tin.

[0008] Optionally, in some embodiments of the present application, in the tin-cerium alloy, the mass percentage of cerium element is 0.5% to 5%, and the mass percentage of tin element is 95% to 99.5%.

[0009] Optionally, in some embodiments of the present application, in the tin-cerium alloy, the mass percentage of cerium element is 1% to 5%, and the mass percentage of tin element is 95% to 99%.

[0010] Optionally, in the tin-cerium alloy, the mass percentage of cerium element is 0.5% to 1%, and the mass percentage of tin element is 99% to 99.5%; or the mass percentage of cerium element is 1% to 2%, and the mass percentage of tin element is 98% to 99%; or the mass percentage of cerium element is 2% to 5%, and the mass percentage of tin element is 95% to 98%.

[0011] Optionally, in some embodiments of the present application, the crystal structure of the tin-cerium alloy includes equiaxed crystals.

[0012] According to a second aspect of the present application, a method for preparing a tin-cerium alloy is provided, for preparing the aforementioned tin-cerium alloy, the preparation method comprising the following steps:

[0013] Provide tin source and cerium source;

[0014] The tin-cerium alloy is prepared.

[0015] Optionally, in some embodiments of the present application, providing a tin source and a cerium source includes providing a surface treatment medium containing a tin salt and a cerium salt.

[0016] Optionally, in some embodiments of the present application, the surface treatment medium includes an electroplating solution.

[0017] Optionally, in some embodiments of the present application, the tin salt includes a divalent tin ion salt.

[0018] Optionally, in some embodiments of the present application, the cerium salt includes a tetravalent cerium ion salt.

[0019] According to a third aspect of the present application, an electrical connector is provided, comprising a copper substrate and a tin-cerium alloy layer disposed on the copper substrate, wherein the tin-cerium alloy layer comprises a tin-cerium alloy.

[0020] Optionally, in some embodiments of the present application, the tin-cerium alloy includes 0.5 to 55 parts of cerium and 45 to 99.5 parts of tin.

[0021] Optionally, in some embodiments of the present application, in the tin-cerium alloy, the mass percentage of cerium element is 0.5% to 5%, and the mass percentage of tin element is 95% to 99.5%.

[0022] Optionally, in some embodiments of the present application, in the tin-cerium alloy, the mass percentage of cerium element is 1% to 5%, and the mass percentage of tin element is 95% to 99%.

[0023] Optionally, in some embodiments of the present application, in the tin-cerium alloy, the mass percentage of cerium element is 0.5% to 1%, and the mass percentage of tin element is 99% to 99.5%; or the mass percentage of cerium element is 1% to 2%, and the mass percentage of tin element is 98% to 99%; or the mass percentage of cerium element is 2% to 5%, and the mass percentage of tin element is 95% to 98%.

[0024] Optionally, in some embodiments of the present application, the crystal structure of the tin-cerium alloy includes equiaxed crystals.

[0025] Optionally, in some embodiments of the present application, the thickness of the tin-cerium alloy layer ranges from 0.5 μm to 50 μm.

[0026] Optionally, in some embodiments of the present application, the thickness of the tin-cerium alloy layer ranges from 3 μm to 10 μm.

[0027] Optionally, in some embodiments of the present application, the tin-cerium alloy layer directly covers the surface of the copper substrate.

[0028] According to a fourth aspect of the present application, a method for preparing an electrical connector is provided, for preparing the aforementioned electrical connector, the method comprising the following steps:

[0029] Provide copper substrate;

[0030] providing a surface treatment medium containing a tin source and a cerium source;

[0031] The copper substrate is surface treated with a surface treatment medium to obtain the tin-cerium alloy layer, thereby obtaining the electrical connector.

[0032] Optionally, in some embodiments of the present application, the surface treatment includes any one of electroplating, chemical vapor deposition, spraying, and dipping.

[0033] According to a fifth aspect of the present application, an electrical device is provided, comprising the aforementioned electrical connector or an electrical connector manufactured by the aforementioned method for manufacturing the electrical connector.

[0034] In some embodiments of the present application, the electrical equipment includes a vehicle or a consumer electronic product.

[0035] The embodiments of the present application provide a tin-cerium alloy that can effectively mitigate the growth of defects such as tin whiskers. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 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.

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

[0038] Figure 2 This is a surface microscopic morphology image of Example 1 of the present application after the room temperature storage tin whisker test;

[0039] 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 undergoing a tin whisker test at room temperature;

[0040] Figure 4 This is a 3D metallographic microscope image of the interface of Comparative Example 2 of the present application after the room temperature storage tin whisker test;

[0041] Figure 5This is a metallographic microscope image of the interface of Example 1 of the present application after the room temperature storage tin whisker test;

[0042] Figure 6 This is a 3D metallographic microscope image of the interface of Example 2 of the present application after the room temperature storage tin whisker test;

[0043] 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;

[0044] Figure 8 This is a microscopic morphology image of Example 1 of the present application after the temperature cycle tin whisker test;

[0045] Figure 9 This is a microscopic morphology of the matte tin coating of Comparative Example 1 of the present application after microindentation test;

[0046] Figure 10 This is a microscopic morphology of the double-layer coating of Comparative Example 2 of the present application after microindentation test;

[0047] Figure 11 This is a microscopic morphology diagram of Example 1 of the present application after microindentation test;

[0048] Figure 12 This is a microscopic morphology diagram of Example 2 of the present application after microindentation test;

[0049] Figure 13 This is a microscopic morphology diagram of Example 3 of the present application after microindentation test;

[0050] Figure 14 This is a microscopic morphology diagram of Example 4 of the present application after microindentation test;

[0051] Figure 15 This is a microscopic morphology diagram of Example 5 of the present application after microindentation test;

[0052] Figure 16 This is a microscopic morphology diagram of Example 6 of the present application after microindentation test;

[0053] Figure 17 This is a microscopic morphology diagram of Example 7 of the present application after microindentation test;

[0054] Figure 18 This is a photograph of the appearance of Example 1 of the present application after a 96-hour neutral salt spray test;

[0055] Figure 19 This is a photograph of the appearance of Example 2 of the present application after a 96-hour neutral salt spray test;

[0056] Figure 20 This is a photograph of the appearance of Example 3 of the present application after a 96-hour neutral salt spray test;

[0057] Figure 21 This is a photograph of the appearance of Example 4 of the present application after a 96-hour neutral salt spray test;

[0058] Figure 22 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;

[0059] Figure 23 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;

[0060] Figure 24 1 is a comparison chart of electrochemical impedance spectroscopy data of Example 1 and Comparative Example 1 of the present application;

[0061] Figure 25 1 is a comparison diagram of the electrochemical polarization curves of Example 1 and Comparative Example 1 of the present application;

[0062] Figure 26 This is a schematic diagram of copper busbar overlap when measuring contact resistance;

[0063] Figure 27 This is a graph showing the results of a hundred-grid test in Example 1 of the present application;

[0064] Figure 28 This is a graph showing the results of a hundred-grid test in Example 2 of the present application;

[0065] Figure 29 This is a graph showing the results of a hundred-grid test in Example 3 of the present application;

[0066] Figure 30 This is a graph showing the results of a hundred-grid test in Example 4 of the present application;

[0067] Figure 31 This is a graph showing the hundred-grid test results of the matte tin coating of Comparative Example 1 of the present application;

[0068] Figure 32 This is a graph showing the hundred-grid test results of the double-layer coating of Comparative Example 2 of the present application;

[0069] Figure 33 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

[0070] 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.

[0071] Copper substrates refer to materials containing copper or copper alloys, offering excellent electrical and thermal conductivity, good mechanical properties, corrosion resistance, and high ductility. Currently, new energy vehicles utilize a large number of electrical connector components, such as cables, conductive connectors, and terminals. However, the copper substrate surface of conductive connectors is highly susceptible to oxidation, increasing contact resistance and reducing service life.

[0072] Related technologies can add a matte tin coating to the surface of copper substrates, which helps slow oxidation of the copper substrate, 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. The length of tin whiskers is generally 10μm to 100μm. In special cases, long needle-like whiskers can reach several millimeters, which can easily cause short circuit failures in products and, in severe cases, cause thermal runaway fires. Therefore, there is an urgent need to improve the problem of tin whisker growth.

[0073] In view of this, the present application proposes a tin-cerium alloy, an electrical connector, a preparation method thereof, and an electrical device.

[0074] According to a first aspect of the present application, there is provided a tin-cerium alloy comprising, in parts by mass:

[0075] 0.5 to 55 parts of cerium, and

[0076] 45 to 99.5 parts of elemental tin.

[0077] An embodiment of the present application provides a tin-cerium alloy, to which 0.5 to 55 parts of cerium are added. The atomic radius of cerium is relatively large, which can cause lattice distortion on the alloy surface, increase the concentration of surface oxygen vacancies, help promote stress release, and slow down tin whisker growth.

[0078] In some embodiments of the present application, in the tin-cerium alloy, the mass percentage of the cerium element is 0.5% to 5%, and the mass percentage of the tin element is 95% to 99.5%.

[0079] In some embodiments of the present application, in the tin-cerium alloy, the mass percentage of cerium element is 1% to 5%, and the mass percentage of tin element is 95% to 99%.

[0080] It can be understood that when the mass percentage of cerium is 0.5% to 5%, or the mass percentage of cerium is 1% to 5%, the ability to inhibit tin whisker growth can be further improved.

[0081] In some embodiments of the present application, in the tin-cerium alloy, the mass percentage of the cerium element is 0.5% to 1%, and the mass percentage of the tin element is 99% to 99.5%.

[0082] In some embodiments of the present application, in the tin-cerium alloy, the mass percentage of cerium element is 1% to 2%, and the mass percentage of tin element is 98% to 99%.

[0083] In some embodiments of the present application, in the tin-cerium alloy, the mass percentage of the cerium element is 2% to 5%, and the mass percentage of the tin element is 95% to 98%.

[0084] It should be noted that the mass percentage of cerium element is 0.5% to 1%, 1% to 2% or 2% to 5%. No tin whiskers grow on the surface of the tin-cerium alloy containing cerium content within the above range, and the grains of the tin-cerium alloy are fine and the density is high. Therefore, the mass percentage of cerium element is in the range of 0.5% to 1%, 1% to 2% or 2% to 5%, which can significantly inhibit the growth of tin whiskers.

[0085] In some embodiments of the present application, the crystal structure of the tin-cerium alloy includes equiaxed crystals.

[0086] It can be understood that the micromorphology of the tin-cerium alloy 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, fundamentally reducing the driving force for tin whisker growth, thereby slowing down defects such as tin whisker growth.

[0087] According to a second aspect of the present application, a method for preparing a tin-cerium alloy is provided, which is used to prepare the aforementioned tin-cerium alloy. The preparation method may include the following steps:

[0088] Provide tin source and cerium source;

[0089] Preparation of tin-cerium alloy.

[0090] It is understood that the tin-cerium alloy prepared by the preparation method of the tin-cerium alloy provided in the second aspect of the present application can inhibit the growth of tin whiskers and ensure that the grains on the surface of the tin-cerium alloy are fine. In step S100, "providing a tin source and a cerium source" refers to providing a raw material for tin and a raw material for cerium in the tin-cerium alloy. The tin source and the cerium source can be different substances, for example, the tin source includes a compound containing the element tin, and the cerium source includes a compound containing the element cerium; alternatively, the tin source and the cerium source can be the same substance, for example, using a compound containing both the element tin and the element cerium as the tin source and the cerium source.

[0091] In some embodiments of the present application, providing a tin source and a cerium source may include providing a surface treatment medium containing a tin salt and a cerium salt.

[0092] It should be noted that the surface treatment medium refers to the material used for surface treatment, which can be either 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 produce a tin-cerium 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 produce a tin-cerium 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-cerium alloy.

[0093] In some embodiments of the present application, the surface treatment medium includes but is not limited to an electroplating solution. When the surface treatment medium is an electroplating solution, it indicates that the tin-cerium alloy can be prepared by electroplating, which helps to improve the corrosion resistance and conductivity of the tin-cerium alloy.

[0094] In some embodiments of the present application, the electroplating solution may include tin salt, cerium salt, free acid or base, and additives.

[0095] In some embodiments of the present application, the tin salt may include a divalent tin ion salt.

[0096] Specifically, divalent tin ion salts are those containing Sn 2+ The divalent tin ion salt includes, but is not limited to, acidic tin salts such as stannous sulfate, stannous methanesulfonate, stannous borofluoride, and stannous halides, and basic tin salts such as sodium stannate and potassium stannate.

[0097] In some embodiments of the present application, the cerium salt may include a tetravalent cerium ion salt.

[0098] Specifically, the tetravalent cerium ion salt includes but is not limited to cerium nitrate Ce(NO3)4, cerium sulfate Ce(SO4)2·4H2O, cerium chloride CeCl4, cerium oxide CeO2 and the like.

[0099] 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.

[0100] In some embodiments of the present application, the additives include but are not limited to brighteners, bath stabilizers, bath dispersants, pH adjusters, hydrogen evolution inhibitors, and chelating agents.

[0101] 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-cerium alloy.

[0102] In some embodiments of the present application, the plating solution stabilizer may be a compound of two or more agents including but not limited to a chelating agent, a reducing agent, an antioxidant, and a potential regulator. The plating solution stabilizer is mainly used to improve the stability of the plating solution, prevent the plating solution from becoming turbid, and reduce the redox reaction between the divalent tin ion salt and the tetravalent cerium ion salt.

[0103] In some embodiments of the present application, the complexing agent may be cerium tartrate or the like.

[0104] 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.

[0105] In some embodiments of the present application, hydrogen evolution inhibitors and chelating agents prevent cathode hydrogen evolution and cerium ion disproportionation reaction during the electroplating process, thereby improving the quality of the tin-cerium alloy and the stability of the electroplating solution.

[0106] In some embodiments of the present application, the hydrogen evolution inhibitor may be epichlorohydrin.

[0107] In some embodiments of the present application, the chelating agent may be phosphates, aminocarboxylic acids, hydroxycarboxylic acids, and the like.

[0108] 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, thereby increasing the crystal density of the tin-cerium alloy and making the grains finer.

[0109] In a third aspect, an embodiment of the present application provides an electrical connector, comprising a copper substrate and a tin-cerium alloy layer disposed on the copper substrate, wherein the tin-cerium alloy layer comprises a tin-cerium alloy.

[0110] It is understandable that since the tin-cerium alloy layer has excellent electrical connection performance and corrosion resistance, adding a tin-cerium alloy layer to the electrical connector helps to make the electrical connector have excellent electrical connection and corrosion resistance. This is because the cerium element can stabilize the crystal lattice, avoid the formation of too many hard and brittle intermetallic compounds between the copper substrate and the tin-cerium alloy layer, and the compressive stress is relatively small; moreover, the cerium element has a purifying effect on the tin-cerium alloy, and can effectively adsorb impurities such as carbon / nitrogen / oxygen contained in the alloy structure, reducing the defect content on the surface of the tin-cerium alloy, thereby improving the corrosion resistance and electrical connection performance of the electrical connector. In addition, the atomic radius of the cerium element is relatively large, and it can act as a second phase particle to hinder the excessive growth of tin grains, increase the density of the tin-cerium alloy, and enhance the corrosion resistance of the tin-cerium alloy layer. In the related art, a matte tin coating is added to the surface of the copper substrate. The oxide film on the surface of the matte tin coating is generally thin, about 3nm, and has limited corrosion resistance. It is often necessary to increase the coating thickness to improve corrosion resistance, resulting in increased material and process costs.

[0111] In some embodiments of the present application, the tin-cerium alloy may include 0.5 to 55 parts of cerium and 45 to 99.5 parts of tin, in parts by mass. Using a tin-cerium alloy containing cerium and tin within the above ranges of parts by mass helps inhibit tin whisker growth.

[0112] In some embodiments of the present application, the tin-cerium alloy has a cerium content of 0.5% to 5% by weight, and a tin content of 95% to 99.5% by weight. Adding these cerium content to the tin-cerium alloy has a certain inhibitory effect on the growth of tin whiskers on the surface of the tin-cerium alloy.

[0113] In some embodiments of the present application, the tin-cerium alloy comprises 1% to 5% by weight of cerium and 95% to 99% by weight of tin. Adding these cerium weight percentages to the tin-cerium alloy further enhances the ability to inhibit tin whisker growth on the surface of the tin-cerium alloy.

[0114] In some embodiments of the present application, in the tin-cerium alloy, the mass percentage of the cerium element is 0.5% to 1%, and the mass percentage of the tin element is 99% to 99.5%.

[0115] In some embodiments of the present application, in the tin-cerium alloy, the mass percentage of cerium element is 1% to 2%, and the mass percentage of tin element is 98% to 99%.

[0116] In some embodiments of the present application, in the tin-cerium alloy, the mass percentage of the cerium element is 2% to 5%, and the mass percentage of the tin element is 95% to 98%.

[0117] It should be noted that, in the tin-cerium alloy, when the mass percentage of cerium element is 0.5% to 1%, 1% to 2%, or 2% to 5%, it is beneficial to significantly inhibit the growth of tin whiskers in the tin-cerium alloy.

[0118] In some embodiments of the present application, the crystal structure of the tin-cerium alloy may include equiaxed crystals.

[0119] It can be understood that the microstructure of the tin-cerium alloy of the present application is transformed from columnar crystals to equiaxed crystals, which increases the proportion of lateral grain boundaries and releases compressive stress at the lateral grain boundaries, which essentially reduces the driving force for tin whisker growth.

[0120] In some embodiments of the present application, the thickness of the tin-cerium alloy layer may be 0.5 μm to 50 μm.

[0121] It should be noted that the growth of tin whiskers is also related to the thickness of the tin-cerium alloy layer. The thicker the tin-cerium alloy layer, the better the effect of suppressing tin whisker growth. Therefore, the thickness of the tin-cerium alloy layer can be any value between 0.5μm and 50μm. Its thickness can be as thin as 0.5μm or as thick as 50μm. Both thin and thick tin-cerium alloy layers can suppress tin whisker growth.

[0122] In some embodiments of the present application, the thickness of the tin-cerium alloy layer may range from 0.5 μm to 10 μm, 10 μm to 20 μm, 20 μm to 30 μm, 30 μm to 40 μm or 40 μm to 50 μm.

[0123] In some embodiments of the present application, the thickness of the tin-cerium alloy layer may be 3 μm to 10 μm.

[0124] The thickness of the tin-cerium alloy layer is also related to its corrosion resistance. The thicker the tin-cerium alloy layer, the better its corrosion resistance. However, excessive thickness can hinder its application. The tin-cerium alloy layer of the embodiment of the present application exhibits excellent corrosion resistance with a thickness of less than 10 μm, helping to expand the application range of electrical connectors.

[0125] In some embodiments of the present application, the tin-cerium alloy layer directly covers the surface of the copper substrate.

[0126] It should be noted that the cerium element can stabilize the crystal lattice, which helps to avoid the formation of brittle and hard intermetallic compounds between the copper substrate and the tin element. The compressive stress is small, which can suppress tin whiskers. At the same time, there is no intermediate layer between the tin-cerium alloy layer and the surface of the copper substrate, which can save costs and improve production efficiency. The related art uses an additional nickel intermediate layer between the copper substrate and the matte tin plating layer, which will reduce production efficiency and increase additional economic costs. 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 form ternary intermetallic compounds, which greatly increases the risk of tin whisker growth after long-term service.

[0127] In a fourth aspect, a method for preparing an electrical connector is provided, comprising the following steps:

[0128] Provide copper substrate;

[0129] providing a surface treatment medium containing a tin source and a cerium source;

[0130] The copper substrate is surface treated with a surface treatment medium to prepare a tin-cerium alloy layer, thereby obtaining an electrical connector.

[0131] For an understanding of the surface treatment medium, please refer to the description of the surface treatment medium in the second aspect of this application. In some embodiments of this application, the surface treatment includes, but is not limited to, electroplating, chemical vapor deposition, spraying, and dipping. Electroplating, chemical vapor deposition, spraying, and dipping can all be used to prepare the tin-cerium alloy and help ensure that the tin-cerium alloy has excellent deposition quality.

[0132] In some embodiments of the present application, electroplating requires selecting a suitable temperature, a suitable current density, and a suitable pH value for co-deposition to produce a tin-cerium alloy layer.

[0133] Illustratively, a suitable temperature may be 20-50°C.

[0134] For example, a suitable current density may be 0.5-4 A / dm 2 For example, the current density can be 0.5A / dm 2 , 0.55A / dm 2 , 0.6A / dm 2 , 0.65A / dm 2 , 0.70A / dm 2 or 0.75A / dm 2 .

[0135] For example, suitable pH values may be 1-3, 2-3, 1-2, etc., which help to avoid cathode hydrogen evolution and disproportionation reactions.

[0136] In some embodiments of the present application, co-deposition can use 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-cerium alloy.

[0137] In some embodiments of the present application, the surface of the copper substrate may be pretreated before electroplating.

[0138] 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 lapping and tumbling, or pretreatment processes such as sandblasting and shot blasting, can help improve the flatness of the substrate surface.

[0139] In some embodiments of the present application, the pretreatment may be performed by a degreasing process, for example, chemical degreasing, electrolytic degreasing, etc.

[0140] 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.

[0141] 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-cerium alloy layer.

[0142] 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.

[0143] In some embodiments of the present application, electrical devices may include vehicles or consumer electronics. When the electrical connector of the present application is applied to a vehicle, it can prevent the electrical connector from failing due to chloride ions contacting the vehicle 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.

[0144] 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.

[0145] Example 1

[0146] An electrical connector is prepared using the following process:

[0147] S100, Pretreatment of copper substrate:

[0148] S101, mechanically polishing and degreasing the copper substrate, and then performing electrolytic degreasing;

[0149] S102, using sulfonic acid etching;

[0150] S103, rinse with water after etching and set aside;

[0151] Among them, the copper substrate adopts T2 copper substrate;

[0152] S200, preparing electroplating solution:

[0153] The electroplating solution includes the following components in parts by weight: 27 parts of stannous sulfate, 2 parts of ceric sulfate, 59 parts of sulfuric acid, 3 parts of cerium tartrate, 5 parts of epichlorohydrin and 4 parts of chelating agent EDTA.

[0154] The components of the above electroplating solution are mixed and stirred to prepare an electroplating solution.

[0155] S300, electroplating:

[0156] Immerse the pretreated copper substrate in the electroplating solution with a temperature of 40°C and a pH of 2-3. First, select a current density of 0.5A / dm 2Deposition for 15 minutes, increase the current density to 1A / dm 2 The deposition was continued for 25 minutes, and an ultrasonic stirring process was used for co-deposition to prepare a tin-cerium alloy layer to obtain an electrical connector.

[0157] Example 2

[0158] An electrical connector, which differs from Example 1 in that the composition of the electroplating solution in S200 is different; the composition of the electroplating solution in this embodiment is 32 parts of stannous sulfate, 2 parts of ceric sulfate, 55 parts of sulfuric acid, 3 parts of cerium tartrate, 4 parts of epichlorohydrin, and 4 parts of chelating agent EDTA.

[0159] Example 3

[0160] An electrical connector differs from Example 1 in that S200 and S300 differ. The composition of the electroplating solution in S200 is different; the electroplating solution in this example comprises 25 parts stannous sulfate, 10 parts ceric sulfate, 55 parts sulfuric acid, 3 parts cerium tartrate, 4 parts epichlorohydrin, and 3 parts EDTA, a chelating agent.

[0161] The electroplating conditions in S300 are: the temperature of the electroplating solution is 40°C, the pH is 2-3, and the current density is 0.5A / dm 2 Deposition for 15 minutes, increase the current density to 1A / dm 2 The deposition was continued for 25 minutes, and an ultrasonic stirring process was used for co-deposition to prepare a tin-cerium alloy layer to obtain an electrical connector.

[0162] Example 4:

[0163] An electrical connector differs from Example 1 in that S200 and S300 differ. The composition of the electroplating solution in S200 is different; the electroplating solution in this example comprises 25 parts stannous sulfate, 5 parts ceric sulfate, 59 parts sulfuric acid, 3 parts cerium tartrate, 4 parts epichlorohydrin, and 4 parts chelating agent EDTA.

[0164] The electroplating conditions in S300 are: the temperature of the electroplating solution is 30°C, the pH is 2-3, and the current density is 0.5A / dm 2 Deposition for 15 minutes, increase the current density to 1A / dm 2 The deposition was continued for 25 minutes, and an ultrasonic stirring process was used for co-deposition to prepare a tin-cerium alloy layer to obtain an electrical connector.

[0165] Example 5:

[0166] An electrical connector, which differs from Example 1 in that the current density and the deposition time at different current densities during the electroplating process in step S300 are different, and the current density is selected to be 0.5A / dm 2The deposition time was 12 minutes; in this embodiment, the thickness of the tin-cerium alloy layer was 3 microns.

[0167] Example 6:

[0168] An electrical connector, which differs from Example 1 in that the current density and the deposition time at different current densities during the electroplating process in step S300 are different. First, the current density is selected to be 0.5A / dm 2 Deposition for 8 minutes, increase the current density to 1A / dm 2 The deposition was continued for 12 minutes; the thickness of the tin-cerium alloy layer in this embodiment was 5 microns.

[0169] Example 7:

[0170] An electrical connector, which differs from Example 1 in that the current density and the deposition time at different current densities during the electroplating process in step S300 are different. First, the current density is selected to be 0.5A / dm 2 Deposition for 12 minutes, increase the current density to 1A / dm 2 The deposition was continued for 20 minutes; the thickness of the tin-cerium alloy layer in this embodiment was 8 microns.

[0171] Comparative Example 1

[0172] An electrical connector is prepared by the following method:

[0173] S100, Pretreatment of copper substrate:

[0174] S101, mechanically polishing and degreasing the copper substrate, and then performing electrolytic degreasing;

[0175] S102, using sulfonic acid etching;

[0176] S103, rinse with water after etching and set aside;

[0177] S200, electroplating matte tin layer:

[0178] The electroplating solution is stannous sulfate. The pretreated copper substrate is immersed in the electroplating solution. The temperature of the electroplating solution is 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 plating layer to obtain an electrical connector.

[0179] Comparative Example 2

[0180] An electrical connector is prepared by the following method:

[0181] S100, Pretreatment of copper substrate:

[0182] S101, mechanically polishing and degreasing the copper substrate, and then performing electrolytic degreasing;

[0183] S102, using sulfonic acid etching;

[0184] S103, rinse with water after etching and set aside;

[0185] S200, electroplated nickel intermediate layer

[0186] Nickel sulfate is used as the electroplating solution. The pretreated copper substrate is immersed in the electroplating solution. The temperature of the electroplating solution is 30°C, the pH is 2-3, and the current density is 1A / dm 2 Deposition for 20 min to prepare a nickel intermediate layer;

[0187] S300, electroplated matte tin coating:

[0188] 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 Deposition was performed for 20 minutes to prepare a matte tin plating layer to obtain an electrical connector.

[0189] Comparative Example 3:

[0190] A bright nickel plating layer is prepared by the following method:

[0191] S100, Pretreatment of copper substrate:

[0192] S101, mechanically polishing and degreasing the copper substrate, and then performing electrolytic degreasing;

[0193] S102, using sulfonic acid etching;

[0194] S103, rinse with water after etching and set aside;

[0195] S200, electroplating bright nickel layer:

[0196] 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 and obtain an electrical connector.

[0197] Detection methods:

[0198] 1. Thickness and composition test of tin-cerium alloy layer: Use X-ray film thickness meter to test the thickness and composition of tin-cerium alloy layer.

[0199] 2. Whisker growth test:

[0200] (1) Room temperature storage whisker growth test - surface micromorphology of tin-cerium alloy:

[0201] 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).

[0202] (2) Room temperature storage whisker growth test - interface intermetallic compound detection:

[0203] 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).

[0204] (3) Temperature cycle whisker growth test:

[0205] 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.

[0206] (4) Micro-indentation tin whisker growth test:

[0207] Whisker growth testing through microindentation testing can effectively verify the sensitivity of each sample to tin whisker growth and significantly reduce testing time and cost. The specific test steps include:

[0208] 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;

[0209] 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.

[0210] 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.

[0211] 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;

[0212] ⑤ Use SEM scanning electron microscope to observe the whisker growth around the indentation.

[0213] 3. Salt spray test

[0214] The samples of Examples 1-4 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.

[0215] 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‰.

[0216] 4. Electrochemical corrosion test:

[0217] 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.

[0218] 5. Contact resistance test:

[0219] Contact resistance testing was performed on the samples of Examples 1-4 and Comparative Examples 1-3, and the testing steps were as follows:

[0220] ① Two straight copper bars of the same size and with the same plating, with the plating surfaces in contact with each other;

[0221] ②Install the corresponding bolts and nuts in the reserved installation holes;

[0222] ③ Apply 15N·m torque using a standard torque wrench, with a torque tolerance within ±10%;

[0223] ④ Measure the contact resistance between the bolted copper bars multiple times using an internal resistance meter and take the average value.

[0224] 6. Adhesion test:

[0225] The adhesion of the samples of Examples 1-4 and Comparative Examples 1-3 was measured using a cross-hatch method, and the test standard complied with the requirements of GB / T9286-1998.

[0226] Test results:

[0227] 1. The thickness and cerium content of Examples 1-7 and Comparative Examples 1-3 are shown in Table 1.

[0228] Table 1

[0229]

[0230]

[0231] 2. Test results of whisker growth:

[0232] (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 1 The 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, large surface grains, and poor coating density. Figure 2 It can be seen that the surface micromorphology of the sample of Example 1 has no whisker growth, the grains are fine, and the density of the tin-cerium alloy is relatively high.

[0233] (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 compounds were formed between Examples 1 and 2 and the copper substrate, reducing the driving force for tin whisker growth. This is because the grain morphology of the tin-cerium alloy changes from columnar to equiaxed, changing the direction of force, and the cerium element effectively slows lattice interdiffusion, preventing the formation of intermetallic compounds and reducing the driving force for tin whisker growth.

[0234] (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 sample of Example 1 after temperature cycle test. Figure 7 It can be seen that tin whiskers appear on the nodular protrusions on the matte tin coating surface of Comparative Example 1, while 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 tin whiskers appear.

[0235] (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 11-17 The surface micromorphology of the samples of Examples 1-7 after micro-indentation test are shown respectively. Figure 9It 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 10 It can be seen that a large number of needle-shaped whiskers were also found around the indentation of Comparative Example 2, proving that the nickel intermediate layer cannot effectively inhibit the whisker formation. Figure 11-14 It can be seen that there is no obvious tin whisker growth around the surfaces of Examples 1-4 after micro-indentation, indicating that the cerium in the tin-cerium alloy can stabilize the lattice and essentially reduce the driving force for tin whisker growth. The mass percentage of cerium in the tin-cerium alloy can be 0.5% to 5%.

[0236] In summary, the whisker growth test results show that the surface micromorphology of the sample of the embodiment shows no tin whisker growth, the grains are small, and the density of the tin-cerium alloy is high; and there is no intermetallic compound between the tin-cerium alloy and the copper substrate, which reduces the driving force for tin whisker growth, indicating that no tin whisker growth occurs on the surface of the tin-cerium alloy.

[0237] In addition, if Figure 15-17 It can be seen that no obvious whiskers are generated around the tin-cerium alloy surfaces of Examples 5-7 after micro-indentation, that is, tin-cerium alloys of different thicknesses can effectively inhibit the growth of tin whiskers, and the thickness of the tin-cerium alloy layer is preferably 3 μm to 10 μm.

[0238] 3. Salt spray test results:

[0239] Figure 18-21 The following are photos of the surface conditions of the samples of Examples 1-4 after being corroded by neutral salt spray. Figure 22-23 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 18-23 It can be seen that both the tin-cerium alloy and the sample with matte tin coating have no pitting pits on the surface, and have excellent corrosion resistance, meeting the salt spray requirements of most electrical connection coating applications.

[0240] 4. Electrochemical corrosion test results:

[0241] Figure 24 and Figure 25 The output impedance curve and electrochemical polarization curve of Example 1 and Comparative Example 1 are shown in FIG. Figures 24-25 It can be seen that the tin-cerium 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 the tin-cerium alloy of Example 1 is significantly better than that of the matte tin coating of Comparative Example 1, and can meet application requirements under harsh conditions.

[0242] 5. Contact resistance test results:

[0243] The contact resistance of the coatings of Examples 1-4 and Comparative Examples 1-3 is shown in Table 2.

[0244] Table 2

[0245]

[0246] Combining the test results of Examples 1-4, Comparative Examples 1-3 and Table 2, it can be seen that the contact resistance of the alloy coatings of Examples 1-4 is less than 0.0021 mΩ, the contact resistance of the coatings of Comparative Examples 1-2 is about 0.003 mΩ, and the contact resistance of the coatings of Comparative Example 3 is close to 0.008 mΩ. It can be seen that the contact resistance of the coatings of Examples 1-4 is less than the contact resistance of the coatings of Comparative Examples 1-3, indicating that the electrical connectors of the embodiments of the present application have better electrical connection performance. Figure 26 Schematic diagram of copper busbar overlap when measuring contact resistance.

[0247] 6. Adhesion test results:

[0248] Figures 27-30 This is a graph showing the test results of the hundred grids of Examples 1-4. Figures 31-33 The figure is a hundred-grid test result diagram of the coating of comparative examples 1-3. Figures 27-30 It can be seen that the 100-grid test of Examples 1-4 is level 0, the cutting edge is completely smooth, and no grid falls off, indicating that the adhesion of Examples 1-4 is excellent. Figures 31-32 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 33 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 peeled, and the adhesion was lower than that of the coatings of Comparative Examples 1-2. In summary, the alloy coatings of Examples 1-4 maintain the flexibility and excellent adhesion characteristics of the matte tin coatings of Comparative Examples 1-2, while the adhesion of the coating of Comparative Example 3 is inferior to that of the matte tin coating.

[0249] The above is a detailed introduction to a tin-cerium alloy, its preparation method and electrical equipment provided in the embodiments of the present application. Specific examples are used in this article 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 technical personnel in this field, 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-cerium alloy, characterized in that: In parts by mass, the tin-cerium alloy comprises: 0.5 to 55 parts of cerium, and 45 to 99.5 parts of elemental tin.

2. The tin-cerium alloy according to claim 1, characterized in that In the tin-cerium alloy, the mass percentage of cerium element is 0.5% to 5%, and the mass percentage of tin element is 95% to 99.5%.

3. The tin-cerium alloy according to claim 2, characterized in that In the tin-cerium alloy, the mass percentage of cerium element is 1% to 5%, and the mass percentage of tin element is 95% to 99%.

4. The tin-cerium alloy according to claim 2, characterized in that In the tin-cerium alloy, the mass percentage of cerium element is 0.5% to 1%, and the mass percentage of tin element is 99% to 99.5%; or the mass percentage of cerium element is 1% to 2%, and the mass percentage of tin element is 98% to 99%; or the mass percentage of cerium element is 2% to 5%, and the mass percentage of tin element is 95% to 98%.

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

6. A method for preparing a tin-cerium alloy, characterized in that: For preparing the tin-cerium alloy according to any one of claims 1 to 5, the preparation method comprises the following steps: Provide tin source and cerium source; The tin-cerium alloy is prepared.

7. The method for preparing a tin-cerium alloy according to claim 6, wherein: Providing the tin source and the cerium source includes providing a surface treatment medium containing a tin salt and a cerium salt.

8. The method for preparing a tin-cerium alloy according to claim 7, wherein: The surface treatment medium includes an electroplating solution.

9. The method for preparing a tin-cerium alloy according to claim 7, wherein: The tin salt includes a divalent tin ion salt.

10. The method for preparing a tin-cerium alloy according to claim 7, wherein: The cerium salt includes a tetravalent cerium ion salt.

11. An electrical connector, characterized in that: The invention comprises a copper substrate and a tin-cerium alloy layer arranged on the copper substrate, wherein the tin-cerium alloy layer comprises a tin-cerium alloy.

12. The electrical connector according to claim 11, characterized in that The tin-cerium alloy includes 0.5 to 55 parts of cerium and 45 to 99.5 parts of tin, based on parts by mass.

13. The electrical connector according to claim 11, characterized in that In the tin-cerium alloy, the mass percentage of cerium element is 0.5% to 5%, and the mass percentage of tin element is 95% to 99.5%.

14. The electrical connector according to claim 11, characterized in that In the tin-cerium alloy, the mass percentage of cerium element is 1% to 5%, and the mass percentage of tin element is 95% to 99%.

15. The electrical connector according to claim 11, wherein: In the tin-cerium alloy, the mass percentage of cerium element is 0.5% to 1%, and the mass percentage of tin element is 99% to 99.5%; or the mass percentage of cerium element is 1% to 2%, and the mass percentage of tin element is 98% to 99%; or the mass percentage of cerium element is 2% to 5%, and the mass percentage of tin element is 95% to 98%.

16. The electrical connector according to claim 11, characterized in that The crystal structure of the tin-cerium alloy includes equiaxed crystals.

17. The electrical connector according to claim 11, wherein: The thickness of the tin-cerium alloy layer ranges from 0.5 μm to 50 μm.

18. The electrical connector according to claim 17, wherein: The thickness of the tin-cerium alloy layer ranges from 3 μm to 10 μm.

19. The electrical connector according to claim 11, wherein: The tin-cerium alloy layer directly covers the surface of the copper substrate.

20. A method for preparing an electrical connector, characterized in that: For preparing the electrical connector according to any one of claims 11 to 19, the preparation method comprises the following steps: Provide copper substrate; providing a surface treatment medium containing a tin source and a cerium source; The copper substrate is surface treated with a surface treatment medium to obtain the tin-cerium alloy layer, thereby obtaining the electrical connector.

21. The method for preparing an electrical connector according to claim 20, wherein: The surface treatment includes any one of electroplating, chemical vapor deposition, spraying, and dipping.

22. An electrical device, characterized in that: An electrical connector comprising the electrical connector according to any one of claims 11 to 19 or an electrical connector made by the method for making the electrical connector according to claim 20 or 21.

23. The electrical equipment according to claim 22, characterized in that: The electrical equipment includes vehicles or consumer electronic products.

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