Aluminum alloy bus bar and method for manufacturing aluminum alloy bus bar

Abstract

An aluminum alloy bus bar (1) includes: a bus bar base material (2) made of an aluminum alloy; and a tin plating layer (3) which is formed on at least a part of the surface of the bus bar base material and is in direct contact with the surface, in which aluminum in the bus bar base material is directly bonded to tin in the tin plating layer. The method of manufacturing an aluminum alloy bus bar includes: preheating a bus bar base material by dipping the bus bar base material in a solution for a predetermined time, the solution being formed by melting a metal constituting a tin plating layer; ultrasonic waves are applied to the solution while the bus bar base material is soaked in the solution; and removing the bus bar substrate from the melt while applying ultrasonic waves to the melt.

Description

Technical Field

[0001] This invention relates to an aluminum alloy busbar and a method for manufacturing the aluminum alloy busbar. Background Technology

[0002] As the amount of electricity in automobiles increases, wiring harnesses used in electric vehicles are increasingly being replaced by busbars. Furthermore, the size of battery packs used in electric vehicles is increasing year by year to improve driving range, and the need to reduce vehicle weight is also growing from the perspective of improving fuel efficiency. Therefore, aluminum, which is lighter than traditional copper, has attracted considerable attention as a material for wiring harnesses and busbars.

[0003] Aluminum is a lightweight metal with good electrical conductivity and is relatively inexpensive, making it commonly used in wires, busbars, and electrodes. However, aluminum is highly reactive with oxygen, resulting in an oxide film approximately 10 nm thick forming on its surface. Therefore, under pressure contact conditions, the contact resistance of noble metals such as gold, silver, copper, and nickel is typically a few μΩ to tens of μΩ, while the contact resistance of aluminum is known to be above 100 μΩ, at least an order of magnitude higher. When aluminum alloys are used as conductors, plating is typically employed to reduce the impact of the surface oxide film. Furthermore, plating is necessary to reduce contact resistance and suppress heat generated at the electrical connections (terminals) between the wire harness and the busbar.

[0004] JP 2014-02977A describes a conductive component that is electrically connected to an electrical component made of aluminum or an aluminum alloy via pressurized contact. A tin plating layer reduces contact resistance by preventing the formation of a metal or alloy layer on the surface of the conductive component that contacts the electrical component. Summary of the Invention

[0005] Electroplating or electroless plating is typically used when plating aluminum surfaces. However, electroplating and electroless plating are not suitable for large-scale production because the plating process is complex and time-consuming due to the increased thickness of the deposited layer. Furthermore, when electroplating on aluminum, a pretreatment called zincate treatment is required to remove the oxide film present on the aluminum surface, and this is usually done twice using a process called double zincate treatment. Therefore, traditional methods suffer from complex plating processes and increased manufacturing costs.

[0006] This invention was made in view of these problems in the conventional art. The object of this invention is to provide an aluminum alloy busbar formed by tin plating on the surface of an aluminum alloy using a simple method, and to provide a method for manufacturing the aluminum alloy busbar.

[0007] According to a first aspect of the invention, an aluminum alloy busbar comprises: a busbar substrate made of an aluminum alloy; and a tin plating layer formed on at least a portion of the surface of the busbar substrate and in direct contact with the surface, wherein the aluminum in the busbar substrate is directly bonded to the tin in the tin plating layer.

[0008] A method for manufacturing an aluminum alloy busbar according to a second aspect of the present invention includes the following steps: preheating the busbar substrate by immersing it in a melt for a predetermined time, wherein the melt is formed by melting the metal constituting the tin plating layer; applying ultrasonic waves to the melt while the busbar substrate is immersed in the melt; and removing the busbar substrate from the melt while applying ultrasonic waves to the melt.

[0009] According to the present invention, an aluminum alloy busbar formed by tin plating on the surface of an aluminum alloy and a method for manufacturing the aluminum alloy busbar can be provided in a simple manner. Attached Figure Description

[0010] Figure 1 This is a cross-sectional view showing an example of an aluminum alloy busbar according to this embodiment.

[0011] Figure 2 This is a graph showing the softening properties of alloy A1100.

[0012] Figure 3 This is a graph showing an example of how the mechanical properties (hardness) of alloy A6101 change with temperature.

[0013] Figure 4 This is a photograph showing the appearance of the test piece of Example 1.

[0014] Figure 5 This is a photograph showing the results of scanning electron microscopy (SEM) observation of a cross-section of the test piece of Example 1.

[0015] Figure 6 This shows the Vickers hardness and tensile strength σ of the aluminum alloy substrates (base materials) of the test pieces of Examples 1-10 using A6101 after the tin plating layer was formed. uts and yield stress σ ys A diagram illustrating the relationships between them.

[0016] Figure 7A This is a photograph showing the surface condition of the test piece in Example 3.

[0017] Figure 7B This is a photograph showing the surface condition of the test piece of Comparative Example 4.

[0018] Figure 8 This is a schematic diagram showing a device for measuring contact resistance.

[0019] Figure 9 This is a diagram used to illustrate the definition of the adhesion of a coating.

[0020] Figure 10 This shows observation using a scanning electron microscope. Figure 9 The image shows a photograph of the results of scratches formed on the test piece.

[0021] Figure 11 This is a photograph showing the results of observing the interface between the tin plating layer and the aluminum alloy substrate in the test piece of Example 3 using a transmission electron microscope (TEM). Detailed Implementation

[0022] The aluminum alloy busbar and its manufacturing method according to this embodiment will be described in detail below with reference to the accompanying drawings. For ease of explanation, the dimensions in the drawings are exaggerated and may differ from the actual scale.

[0023] [Aluminum Alloy Busbar]

[0024] like Figure 1 As shown, the aluminum alloy busbar 1 according to this embodiment includes a busbar substrate 2 made of aluminum alloy and a tin-plated layer 3 formed on at least a portion of the surface of the busbar substrate and in direct contact with the surface.

[0025] Busbar substrate 2 is a conductive component primarily composed of aluminum alloy. Busbar substrate 2 can be a component made of aluminum alloy. The aluminum alloy may contain at least one element selected from the group consisting of Si, Fe, Cu, Mn, Mg, Cr, Zn, and Ti in raw aluminum, such as aluminum ingots. The aluminum alloy may contain at least one element selected from the group consisting of Si, Fe, Cu, Mn, Mg, Cr, Zn, and Ti, and the remainder may be aluminum and unavoidable impurities.

[0026] It is preferable to use pure aluminum with a purity of 99.7% by mass or higher as the aluminum ingot. Examples of aluminum ingots include Class 1 aluminum ingots with a purity of 99.7% by mass, Special Class 2 aluminum ingots with a purity of 99.85% by mass or higher, and Special Class 1 aluminum ingots with a purity of 99.90% by mass or higher, as specified in JISH 2102:2011 (Aluminum ingots for remelting). In this embodiment, not only expensive and high-purity aluminum ingots such as Special Class 1 and Special Class 2 can be used, but also relatively inexpensive Class 1 aluminum ingots can be used.

[0027] The Si content in the aluminum alloy is 0.2% by mass or more and less than 0.7% by mass, preferably 0.3% to 0.7% by mass. Preferably, the Fe content in the aluminum alloy is less than 0.5% by mass.

[0028] Preferably, the Cu content in the aluminum alloy is less than 0.1% by mass. The Mn content in the aluminum alloy can be 0.03-0.1% by mass, or less than 0.03% by mass. The Mg content in the aluminum alloy is 0.35-0.9% by mass, or preferably 0.35-0.8% by mass. The Cr content in the aluminum alloy can be 0.03-0.1% by mass, or less than 0.03% by mass. Preferably, the Zn content in the aluminum alloy is less than 0.1% by mass. The Ti content in the aluminum alloy can be 0.00-0.1% by mass, or less than 0.00% by mass. Preferably, the B content in the aluminum alloy is less than 0.06% by mass.

[0029] Aluminum may contain trace amounts of unavoidable impurities. Examples of unavoidable impurities that may be present in aluminum include nickel (Ni), rubidium (Rb), tin (Sn), vanadium (V), gallium (Ga), boron (B), sodium (Na), zirconium (Zr), etc. These impurities are unavoidably present to a degree that does not interfere with the effects of this embodiment and does not particularly affect the properties of the aluminum alloy according to this embodiment. Elements initially contained in the aluminum ingot to be used are also included in unavoidable impurities. The total content of unavoidable impurities in the aluminum alloy is preferably 0.15% by mass or less, and more preferably 0.10% by mass or less.

[0030] The shape of the busbar substrate 2 is not particularly limited, but it can be formed, for example, as a flat plate.

[0031] Examples of aluminum alloys commonly used for conductive components here can include industrial pure aluminum, such as alloys A1050, A1070, and A1100, as well as alloy A6101, as specified in JIS H4100 (Aluminum and Aluminum Alloy Extrusion Profiles). According to JIS standards (Japanese Industrial Standards), alloy A1050 guarantees 61% IACS conductivity. However, a problem with pure aluminum alloys such as A1050, A1070, and A1100 is that they soften due to a reduction in strength, such as tensile strength, caused by “annealing” which involves applying heat to the material. As a typical example, A1100 softens as… Figure 2 As shown. When the annealing temperature exceeds 200℃, mechanical properties such as tensile strength and yield stress are greatly reduced, such as... Figure 2 As shown.

[0032] When the strength of pure aluminum is insufficient, an A6101 alloy, guaranteeing 55% IACS conductivity, is typically used. The A6101 alloy undergoes a T6 treatment and has standard mechanical properties of tensile strength 220 MPa, yield stress 195 MPa, and elongation 15% (1.6 mm thick, 50 mm). This A6101 alloy exhibits fine Mg-Si precipitates in the aluminum matrix and achieves high strength through the Orowan mechanism. However, compared to industrially grade pure aluminum, the A6101-T6 alloy exhibits reduced post-processing properties in stamping, punching, and bending, which is a concern.

[0033] In automotive environments, busbars require secure fastening, vibration durability, and high-temperature durability. Furthermore, the use of industrial-grade pure aluminum is difficult due to the sufficient strength required for bolted electrical connections and vibration durability. Therefore, using A6101 alloy as the base material for busbars is ideal. However, because A6101 alloy is an age-hardening precipitation alloy and lacks heat resistance, there are concerns about changes in mechanical and other physical properties due to temperature variations. Figure 3 An example of the change in mechanical properties (hardness) of the A6101 alloy after prolonged heating is shown. For example... Figure 3 As shown, prolonged heating of the A6101 alloy reduces its Vickers hardness.

[0034] However, as described below, for the aluminum alloy busbar 1 according to this embodiment, the busbar substrate 2 is immersed in molten tin, preheated, and irradiated with ultrasound, and then removed from the molten tin to form a tin-plated layer 3. In this case, due to the short immersion and preheating time, the change in the mechanical properties of the busbar substrate 2 can be minimized.

[0035] Therefore, the aluminum alloy used as the busbar base material 2 constituting the aluminum alloy busbar 1 can appropriately be the A6101 alloy specified in JIS H4100. Table 1 shows the composition range of the A6101 alloy.

[0036] [Table 1]

[0037]

[0038] The tin plating layer 3 can be a plating layer consisting only of tin or a plating layer consisting of an alloy of tin and other metals. Other metals may include at least one selected from the group consisting of bismuth (Bi), indium (In), zinc (Zn), and lead (Pb). However, tin is preferred as the main component of the tin plating layer 3. Specifically, the tin content in the tin plating layer 3 can be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, and 90% by mass or more.

[0039] There is no particular limitation on the thickness of the tin plating layer 3, but it can be, for example, about 1 μm to 10 μm. The thickness of the tin plating layer 3 can be measured by X-ray fluorescence (XRF) according to JIS H8501 (Metallic Coating Thickness Test Method).

[0040] For the aluminum alloy busbar 1, the tin plating layer 3 can be formed on at least a portion of the surface of the busbar substrate 2, or on the entire surface of the busbar substrate 2. The tin plating layer 3 is in direct contact with the surface of the busbar substrate 2. That is, as shown... Figure 1 As shown, there is no layer formed by metals other than aluminum and tin and no oxide film between the surface (upper surface) 21 of the busbar substrate 2 and the surface (lower surface) 31 of the tin plating layer 3, and the tin plating layer 3 is in direct contact with the surface 21 of the busbar substrate 2.

[0041] As described above, aluminum, as an active metal, combines with oxygen in the atmosphere to form an aluminum oxide film on its surface. Here, for the aluminum alloy busbar 1, the busbar substrate 2 is immersed in molten tin, preheated, and irradiated with ultrasound, and then removed from the molten tin to form a tin plating layer 3. At this time, due to cavitation caused by ultrasonic irradiation, the oxide film of the busbar substrate 2 is destroyed. Therefore, the tin plating layer 3 can directly contact the aluminum of the busbar substrate 2 without an oxide film. As a result, the aluminum of the busbar substrate 2 and the tin of the tin plating layer 3 directly bond, allowing the tin plating layer 3 to adhere to the surface of the busbar substrate 2. Furthermore, the direct contact between the tin plating layer 3 and the aluminum of the busbar substrate 2 improves the conductivity between the tin plating layer 3 and the busbar substrate 2.

[0042] For the aluminum alloy busbar 1, preferably, the busbar substrate 2 on which the tin-plated layer 3 is formed has a voltage rating of 28 HV. 0.1 ~90HV 0.1 The Vickers hardness is as follows. As described below, when the Vickers hardness of the busbar substrate 2 with the tin-plated layer 3 is within this range, the yield stress of the aluminum alloy busbar 1 is 70 MPa to 220 MPa. Due to its excellent fastening reliability and vibration durability, the aluminum alloy busbar 1 with a yield stress within this range can be appropriately used as a busbar for electric vehicles. The yield stress of the aluminum alloy busbar can be measured according to JIS Z2241 (Metallic materials, tensile testing method at room temperature).

[0043] In the aluminum alloy busbar 1, the adhesion of the tin plating layer 3 to the busbar substrate 2 is preferably 4.9 N or more. In this case, the tin plating layer 3 is firmly bonded to the surface of the busbar substrate 2, thus preventing the tin plating layer 3 from peeling off even when the aluminum alloy busbar 1 is tightened with bolts and nuts. The adhesion of the tin plating layer 3 to the busbar substrate 2 can be measured by the following method.

[0044] The surface of the aluminum alloy busbar 1 preferably has a contact resistance value of 2.6 mΩ or less. The tin plating layer 3 of the aluminum alloy busbar 1 is in direct contact with the busbar substrate 2, thereby reducing the contact resistance. As a result, heat generation at the contact points where the aluminum alloy busbar 1 contacts other parts can be suppressed. The contact resistance value of the surface of the aluminum alloy busbar 1 can be measured by a method described later.

[0045] [Manufacturing method of aluminum alloy busbar]

[0046] Next, a method for manufacturing the aluminum alloy busbar 1 according to this embodiment will be described.

[0047] Typically, when electroplating or electroless plating is performed on the surface of aluminum parts, the oxide film on the surface needs to be removed. Furthermore, to improve the adhesion of the plating, methods such as nickel plating are used as a substrate when tin plating. Therefore, in traditional methods, the plating process is very complex.

[0048] However, in the manufacturing method according to this embodiment, unlike conventional electroplating and chemical plating methods, ultrasonic waves are used to form the tin plating layer 3.

[0049] Specifically, the busbar substrate 2 is first manufactured. The busbar substrate 2 is formed into any shape, and then degreased and cleaned as needed. However, it is not necessary to perform a treatment to remove the oxide film formed on the surface of the busbar substrate 2, such as zincate treatment.

[0050] Next, a melt is created by melting the metal that constitutes the tin plating layer. Specifically, after placing the metal constituting the tin plating layer into a heat-resistant container, the heat-resistant container is heated to melt the metal. That is, when the metal constituting the tin plating layer is only tin, tin is filled into the heat-resistant container and heated. When the metal constituting the tin plating layer is an alloy of tin and other metals, tin and the alloy are filled into the heat-resistant container and heated. The heating temperature is not particularly limited at this point, as long as the metal is melted, but it can be set to, for example, 260–300°C. That is, the melting point of tin is approximately 232°C, and the metal can be melted by heating it to this temperature.

[0051] Then, the busbar substrate 2 is immersed in a melt formed by melting the metal constituting the tin plating layer for a predetermined time to preheat the busbar substrate 2. Preheating the busbar substrate enhances the deposition of the tin plating layer 3 and allows the tin plating layer 3 to be formed on the surface of the busbar substrate 2 in a substantially uniform manner. Note that the immersion time of the busbar substrate 2 in the melt is preferably short, for example, within 1 minute, and more preferably within 30 seconds. The short immersion time of the busbar substrate 2 in the melt prevents deterioration of the mechanical properties of the busbar substrate 2.

[0052] After preheating the busbar substrate 2, ultrasonic waves are applied to the melt while the busbar substrate 2 is immersed in the melt. As a result, the oxide film on the surface of the busbar substrate 2 is destroyed and removed through cavitation and the vibration and mixing effect of the ultrasonic waves. There are no particular limitations on the output of the applied ultrasonic waves, as long as the output is sufficient to destroy and remove the oxide film on the surface of the busbar substrate 2. For example, the frequency of the ultrasonic waves can be set to 16–45 kHz, and the output can be set to 20 W or more.

[0053] Then, while applying ultrasonic waves to the melt, the busbar substrate 2 is removed from the melt. Specifically, while applying ultrasonic waves to the melt, the busbar substrate 2 is pulled upwards from the melt. At this time, there is no particular limitation on the pulling speed of the busbar substrate 2, but it can be set to, for example, 0.5 mm / s to 5.0 mm / s.

[0054] When the busbar substrate 2 is removed from the melt, it can be surrounded by an inert atmosphere, although it can also be surrounded by the atmosphere. When the busbar substrate 2 is surrounded by an inert atmosphere, oxidation of the busbar substrate 2 and the tin plating layer 3 can be suppressed. The inert atmosphere can be a nitrogen atmosphere or an argon atmosphere.

[0055] After removing the busbar substrate 2 from the melt, the aluminum alloy busbar 1 can be obtained by cooling it to room temperature.

[0056] Therefore, the aluminum alloy busbar 1 according to this embodiment includes a busbar substrate 2 made of aluminum alloy and a tin-plated layer 3 formed on at least a portion of the surface of the busbar substrate 2 and in direct contact with the surface. The aluminum in the busbar substrate 2 is directly bonded to the tin in the tin-plated layer.

[0057] In the aluminum alloy busbar 1, the tin plating layer 3 is in direct contact with the busbar substrate 2 without an oxide film or the like, and the aluminum in the busbar substrate 2 is directly bonded to the tin in the tin plating layer 3. Therefore, the adhesion between the busbar substrate 2 and the tin plating layer 3 is enhanced, and conductivity is further improved. As a result, the aluminum alloy busbar 1 can be appropriately used as a wiring busbar in battery packs of electric vehicles, etc.

[0058] In the aluminum alloy busbar 1, the busbar substrate 2 is preferably made of A6101 alloy as specified in JIS H4100. A6101 alloy has high electrical conductivity and excellent mechanical properties. Furthermore, during the manufacture of the aluminum alloy busbar 1, the time required to immerse the busbar substrate 2 in the melt is short, thereby minimizing changes in the mechanical properties of the busbar substrate 2. Therefore, an aluminum alloy busbar 1 with excellent electrical conductivity and mechanical properties can be obtained.

[0059] In the aluminum alloy busbar 1, the Vickers hardness of the busbar substrate 2 on which the tin plating layer 3 is formed is preferably 28 HV.0.1 ~90HV 0.1 In this case, the yield stress of the aluminum alloy busbar 1 is 70MPa to 220MPa, thus achieving good fastening reliability and vibration durability.

[0060] In the aluminum alloy busbar 1, the adhesion of the tin plating layer 3 to the busbar substrate 2 is preferably 4.9 N or more. In this case, the tin plating layer 3 is firmly bonded to the surface of the busbar substrate 2, thereby preventing the peeling of the tin plating layer 3 even when the aluminum alloy busbar 1 is fastened with fastening components.

[0061] The contact resistance of the aluminum alloy busbar surface is preferably below 1.0 mΩ. This helps to suppress heat generation at the contact points where the aluminum alloy busbar 1 contacts other parts.

[0062] The method for manufacturing an aluminum alloy busbar according to this embodiment includes: a step of preheating the busbar substrate 2 by immersing it in a melt for a predetermined time, wherein the melt is formed by melting the metal constituting the tin plating layer 3; a step of applying ultrasonic waves to the melt while the busbar substrate 2 is immersed in the melt; and a step of removing the busbar substrate 2 from the melt while applying ultrasonic waves to the melt.

[0063] In the manufacturing method according to this embodiment, during ultrasonic vibration, cavitation occurs in the molten metal within the heat-resistant container, and the oxide film on the aluminum surface (the surface of the busbar substrate 2) is physically destroyed by this phenomenon. Then, the oxide film on the aluminum surface is removed, and simultaneously, a plating layer of the molten metal is formed. Therefore, the molten metal is firmly bonded to the aluminum of the busbar substrate 2, thereby forming a tin plating layer 3 with excellent adhesion and conductivity.

[0064] Furthermore, in the manufacturing method of the aluminum alloy busbar according to this embodiment, pretreatment of the busbar substrate 2 by zincate treatment is not required. Moreover, the pretreatment step can be omitted, allowing the tin plating layer 3 to be formed in a short time. For example, the tin plating layer 3 can be formed within approximately 30 to 60 seconds. The manufacturing method according to this embodiment does not use plating solution, thus eliminating the need for a waste liquid treatment process. Furthermore, since plating solution is not used, waste liquid treatment facilities are not required, and the manufacturing location is not limited. The manufacturing facility of this embodiment is simple, saving space, and can be installed on the production line side. Furthermore, the plating process is simplified, and there is no plating solution waste liquid, thereby reducing the carbon footprint (CFP). In addition, in this manufacturing method, the tin plating layer 3 can be formed on the desired locations of the busbar substrate 2 as needed.

[0065] In the manufacturing method of aluminum alloy busbars, during the step of removing the busbar substrate 2 from the melt, it is preferable to surround the busbar substrate 1 with an inert atmosphere. This helps to suppress oxidation of the busbar substrate 2 and the tin plating layer 3.

[0066] The present embodiment will be described in more detail below with reference to the embodiments and comparative examples, but the present embodiment is not limited to these embodiments.

[0067] [Example 1]

[0068] First, an aluminum alloy substrate (base material) made of A6101-T6 alloy is fabricated. Next, the substrate is cut into plates with a length of 20mm, a width of 40mm, and a thickness of 2mm. The aluminum alloy substrate is not subjected to zincate treatment.

[0069] The crucible is then placed in an ultrasonic plating apparatus, and after being filled with tin, it is heated to 260°C. In this way, the tin melts in the crucible.

[0070] After immersing the aluminum alloy substrate in the molten tin in the crucible, the substrate is preheated for a period of time (immersion time), as shown in Table 3. After preheating, the ultrasonic oscillation switch is turned on, and the aluminum alloy substrate is pulled from the molten tin at a predetermined speed while the vibrating head vibrates in the ultrasonic plating equipment. At this time, the entire crucible is purged with N2 gas and filled with N2 gas. The ultrasonic output (vibrating head output) and the width of the vibrating head are shown in Table 2, and the pulling speed of the aluminum alloy substrate is shown in Table 3.

[0071] Subsequently, the pulled-up aluminum alloy substrate was cooled to room temperature, and a test piece of this embodiment was obtained with a tin-plated film directly formed on the surface of the aluminum alloy substrate. Table 3 shows the tin purity of the tin-plated layer formed on the surface of the aluminum alloy substrate.

[0072] [Examples 2-11]

[0073] Except for changing the material and quality of the aluminum alloy substrate, the output of the ultrasonic (vibrating head), the temperature of the molten tin, the immersion time (preheating time) of the aluminum alloy substrate in the molten tin, and the pull-up speed of the aluminum alloy substrate, the test pieces of the embodiments were obtained by the same method as in Embodiment 1, as shown in Tables 2 and 3. Table 3 also shows the tin purity of the tin plating layer formed on the surface of the aluminum alloy substrate in the test pieces of the embodiments.

[0074] [Comparative Example 1]

[0075] First, an aluminum alloy substrate made of A6101-T7 alloy is fabricated. Next, the substrate is cut into plates with a length of 20mm, a width of 40mm, and a thickness of 2mm. Then, the aluminum alloy substrate undergoes two zincate treatments.

[0076] Next, in a nickel plating solution containing 300–450 g / L nickel sulfamate and 30–40 g / L boric acid, using a zincate-treated aluminum alloy substrate as the cathode and a nickel electrode plate as the anode, an anolyte current density of 2–15 A / dm³ is applied. 2 Electroplating is performed for 80 to 120 seconds at a liquid temperature of 40–60°C, thereby forming a nickel plating layer on the aluminum alloy substrate.

[0077] Furthermore, in a typical tin plating bath composition, in a tin plating solution containing 30–50 g / L tin(II) sulfate, 40–80 g / L sulfuric acid, 30–60 g / L cresolsulfonic acid, and 0.5–1 g / L β-naphthol, with a nickel-plated aluminum alloy substrate as the cathode and a Sn electrode plate as the anode, at a liquid temperature of 15–25°C, at an efficiency of 0.5–2 A / dm³... 2 The anode current density is 0.5–4 A / dm. 2 Electroplating is performed for 450–700 seconds at a cathode current density. This forms a tin plating layer on top of the nickel plating layer on the aluminum alloy substrate.

[0078] Then, the aluminum alloy substrate with tin and nickel plating layers is cleaned and dried to obtain the test piece in this example.

[0079] [Comparative Example 2]

[0080] First, an aluminum alloy substrate made of A6101-T7 alloy is fabricated. Next, the substrate is cut into plates with a length of 20 mm, a width of 40 mm, and a thickness of 2 mm. Then, without plating, the aluminum alloy substrate is used as the test piece for this example.

[0081] [Comparative Example 3]

[0082] First, an aluminum alloy substrate made of A1050 H24 alloy is fabricated. Then, the substrate is cut into plates with a length of 20 mm, a width of 40 mm, and a thickness of 2 mm. Finally, without plating, the aluminum alloy substrate is used as the test piece for this example.

[0083] [Comparative Example 4]

[0084] Except for varying the pull-up speed of the aluminum alloy substrate as shown in Table 3, the test piece of this example was obtained using the same method as in Example 1. That is, in this example, after the aluminum alloy substrate was immersed in the molten tin in the crucible, the ultrasonic oscillation switch was immediately turned on without preheating, and the aluminum alloy substrate was pulled from the molten tin at a predetermined speed while the vibrating head was vibrating in the ultrasonic plating apparatus. Table 3 shows the tin purity of the tin plating layer formed on the surface of the aluminum alloy substrate in the test piece of this example.

[0085] [Table 2]

[0086]

[0087] [Table 3]

[0088]

[0089] [evaluate]

[0090] The cross-sectional observation, Vickers hardness of the coating and substrate (aluminum alloy substrate), appearance observation, coating thickness, contact resistance value and coating adhesion of each test piece prepared as described above were evaluated.

[0091] (Cross-section observation)

[0092] The appearance of the test piece in Example 1 was visually observed. Furthermore, the cross-section of the test piece in Example 1 was observed using a scanning electron microscope (SEM). Figure 4 The appearance of the test piece in Example 1 is shown, and Figure 5 The results of cross-sectional observation of the test piece of Example 1 using a scanning electron microscope (SEM) are shown.

[0093] like Figure 4 As shown, a tin plating layer is neatly formed on the surface of the aluminum alloy substrate, and the tin plating layer has a glossy finish. Furthermore, as... Figure 5 As shown, a tin plating layer is formed on the surface of an aluminum alloy substrate with a substantially uniform thickness, and the tin plating layer is in direct contact with the surface of the aluminum alloy substrate.

[0094] (Vickers hardness)

[0095] The Vickers hardness of the plating and substrate (aluminum alloy substrate) of the test pieces in each example was measured according to JIS Z2244 (Vickers Hardness Test - Test Method). The average of 10 measurements was taken as the Vickers hardness result. Table 4 summarizes the Vickers hardness values ​​of the plating and substrate (aluminum alloy substrate) of the test pieces in each example. The Vickers hardness of the aluminum alloy substrate before plating treatment, measured according to JIS Z2244, is also shown in Table 3.

[0096] Tables 3 and 4 show that the Vickers hardness of the substrates (aluminum alloy substrates) in Examples 1-11 did not decrease significantly before and after the plating layer was formed. In other words, when the tin plating layer was formed, the aluminum alloy substrate was immersed in molten tin, but the immersion time was short, so the mechanical properties (hardness) of the aluminum alloy substrate did not change significantly.

[0097] Here, Figure 6 Examples 1-10, which use A6101 as an aluminum alloy substrate, show the Vickers hardness of the aluminum alloy base plate and the tensile strength σ of the test piece after the formation of the tin plating layer. uts and yield stress σys The relationship between them. The tensile strength σ of the test pieces in Examples 1-10 was measured according to JIS Z 2241 (Metallic materials—Tensive testing—Test method at room temperature). uts and yield stress σ ys Then, the Vickers hardness of the aluminum alloy substrate after the tin plating layer was formed and the tensile strength σ of the test piece were measured. uts Least squares regression analysis was used to obtain an approximate straight line, and the approximate formula and coefficient of determination were calculated. Similarly, the Vickers hardness of the aluminum alloy substrate after tin plating and the yield stress σ of the test piece were used. ys The least squares method was used for regression analysis to obtain an approximate straight line, and the approximate formula and coefficient of determination were calculated.

[0098] like Figure 6 As shown, the Vickers hardness of the aluminum alloy substrate after the tin plating layer is formed is 28 HV. 0.1 ~90HV 0.1 At that time, the yield stress σ of the test piece ys The pressure is approximately 70 MPa to 220 MPa. Because the aluminum alloy substrate after the tin plating layer is formed has a yield stress within this range, it has excellent fastening reliability and vibration durability, and can be appropriately used as a busbar for electric vehicles.

[0099] (Appearance observation)

[0100] The appearance of the test pieces from Examples 1-11 and Comparative Examples 1 and 4 was visually observed to evaluate the presence of areas where no tin plating was deposited. Test pieces with fewer areas of no tin plating and a good surface condition were rated as "Good" by visual observation. Conversely, test pieces with extensive areas of no tin plating were rated as "Inferior". The evaluation results are shown in Table 4.

[0101] The “Deposition State” column in Table 4 shows that the test pieces of Examples 1 to 11 have fewer areas without deposited tin plating and have good surface conditions. Figure 7A The surface condition of the test piece in Example 3 is shown. Figure 7A The test piece in Example 3 is shown to have a uniformly formed tin plating layer with almost no areas where no tin plating layer is deposited.

[0102] In contrast, the test piece in Comparative Example 4 had many areas on which no tin plating layer was deposited and had a poorer surface condition. Figure 7B The surface condition of the test piece in Comparative Example 4 is shown. Figure 7BThe test piece in Comparative Example 4 is shown to have an unevenly formed tin plating layer, as well as many areas on which no tin plating layer has been deposited. This indicates that preheating the aluminum alloy substrate by immersing it in molten tin for a predetermined time during the immersion process improves the deposition of the tin plating layer.

[0103] (Coating thickness)

[0104] The coating thickness of the test pieces in the example was measured using X-ray fluorescence (XRF) according to JIS H8501 (Method for Testing the Thickness of Metallic Coatings). The average of three measurements of the coating thickness was taken as the measurement result. Table 4 shows the measurement results of the coating thickness in the test pieces of the sample.

[0105] Table 4 shows that the thickness of the tin plating layer in the test pieces of Examples 1-11 is not significantly different from the thickness of the plating layer formed by electroplating in Comparative Example 1. Therefore, even if the plating layer is formed by ultrasonic method, a thickness comparable to that of conventional electroplating method can be ensured.

[0106] (Contact resistance value)

[0107] use Figure 8 The apparatus shown measures the contact resistance value of the test piece in the example. Specifically, the contact member 4 is manufactured by forming a hemispherical protrusion on a metal plate with a recess. The hemispherical protrusion is formed at the lower end of the recess. The contact member 4 is made of pure copper C1020, and the radius R of the protrusion is 1 mm. In Examples 1-11 and Comparative Examples 1 and 4, which have a plating, the test pieces in the examples are arranged with the plating facing the protrusion. In Comparative Examples 2 and 3, which do not have a plating, the surface of the aluminum alloy substrate in the examples is arranged to face the protrusion.

[0108] Next, connect one terminal of the DC power supply and voltmeter to contact member 4, and connect the other terminal of the DC power supply and voltmeter to the test piece. Then, as... Figure 8 As indicated by the arrows, a load is applied to contact member 4 to bring the protrusion into contact with the surface of the test piece. When the load applied to contact member 4 reaches 10N, the contact resistance between contact member 4 and the test piece is measured. The average of the three measured values ​​of the contact resistance is taken as the measurement result. Table 4 shows the measured contact resistance values ​​of the test piece in the example.

[0109] As shown in Table 4, the contact resistance of the test pieces in Examples 1-11 is less than 1 mΩ, which is less than the contact resistance of the test piece in Comparative Example 1 formed by electroplating. The contact resistance of the test pieces in Examples 1-11 is much less than the contact resistance of the test pieces in Comparative Examples 2 and 3 without plating. Therefore, by forming a tin plating layer in the ultrasonic method, the contact resistance value is significantly reduced, and heat generation at the connection point can be suppressed.

[0110] (Coating adhesion)

[0111] The adhesion of the coatings on the test pieces in Examples 1-11 and Comparative Examples 1 and 4 was evaluated. The adhesion force (N) of the coatings was measured using Bruker's UMT TriboLab (Multifunctional Tribological Evaluator (Friction and Wear Tester)) manufactured by Bruker, as shown below.

[0112] First, a diamond indenter with R = 0.2 mm is attached to the end of the testing machine. Then, under a vertical load of 15 N, the indenter is lowered onto the coated surface of the test piece, and the indenter is moved to rub, i.e., scrape the test piece in one direction. The adhesion force (N) is then defined by the horizontal load (N) obtained from the curve. Specifically, when the indenter is lowered onto the coated surface of the test piece under a vertical load of 15 N and then moved in one direction to rub the test piece, the following curve is obtained: Figure 9 The graph shown illustrates the relationship between load and travel distance. Figure 9 The horizontal load indicated by symbol A is defined as the adhesion force of the coating. The average of the three adhesion measurements is taken as the measurement result. Table 4 shows the measurement results of the coating adhesion force on an example test piece.

[0113] Here, we will explain why the indenter is lowered onto the plated surface of the test piece when a vertical load of 15 N is applied to the diamond indenter. Figure 10 The results of observing the scratches formed on the test piece using a scanning electron microscope are shown. The observation results are also as follows... Figure 9 The graph is shown in the image. As... Figure 10 Elemental analysis of the scratches shown confirmed that the black areas represented aluminum substrate. Furthermore, the adhesion evaluation was performed by varying the vertical load applied to the diamond indenter to 5N, 10N, and 15N. The results showed that exposure of the aluminum substrate was clearly confirmed under a vertical load of 15N. Therefore, when the vertical load applied to the diamond indenter is 15N, it is considered that the tin plating layer can be intentionally peeled off at the interface between the aluminum substrate and the tin plating layer, and the horizontal load measured in this case is defined as the adhesion force (N) of the plating layer.

[0114] As shown in Table 4, the adhesion of the coatings in Examples 1-11 is not significantly different from that of the coating in Comparative Example 1 formed by electroplating. Therefore, even when the coating is formed by ultrasonic method, adhesion comparable to that of conventional electroplating method can be ensured.

[0115] [Table 4]

[0116]

[0117] Here, Figure 11The results of observation using transmission electron microscopy (TEM) of the interface between the tin plating layer and the aluminum alloy substrate in the test piece of Example 3 are shown. Figure 11 As shown, a matching interface was observed at the interface between the aluminum and the tin plating layer. Analysis of the matching interface revealed that a matching surface was formed between the Sn(220) and aluminum(200) surfaces, resulting in a strong metallic bond. Furthermore, as shown in the measurement results in Table 4, the adhesion of the tin plating film in this case was 5.04 N, which suggests that if the adhesion is approximately 5 N, a matching interface can be considered to have formed at the plating interface. Figure 11 The matching interface shown.

[0118] While specific embodiments have been described, these embodiments are disclosed by way of example only and are not intended to limit the scope of the invention. In fact, the novel embodiments described herein can be implemented in various other forms; furthermore, various omissions, substitutions, and changes in the embodiments described herein can be made without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover such forms or modifications that fall within the scope and spirit of the invention.

Claims

1. An aluminum alloy busbar, comprising: Busbar substrate, which is made of aluminum alloy; as well as A tin plating layer is formed on at least a portion of the surface of the busbar substrate and is in direct contact with the surface. In this embodiment, the aluminum in the busbar substrate is directly bonded to the tin in the tin plating layer.

2. The aluminum alloy busbar according to claim 1, wherein, The Vickers hardness of the busbar substrate on which the tin plating layer is formed is 28 HV. 0.1 ~90HV 0.1 .

3. The aluminum alloy busbar according to claim 1 or 2, wherein, The adhesion of the tin plating layer to the busbar substrate is greater than 4.9N.

4. The aluminum alloy busbar according to claim 1 or 2, wherein, The surface contact resistance of the aluminum alloy busbar is below 2.6 mΩ.

5. The aluminum alloy busbar according to claim 1 or 2, wherein, The busbar substrate is made of A6101 alloy as specified in JIS H4100.

6. A method for manufacturing an aluminum alloy busbar according to any one of claims 1 to 5, comprising: The busbar substrate is preheated by immersing it in a melt for a predetermined time, wherein the melt is formed by melting the metal constituting the tin plating layer; While the busbar substrate is impregnated in the solution, ultrasound is applied to the solution; and While applying ultrasound to the melt, the busbar substrate is removed from the melt.

7. The method for manufacturing the aluminum alloy busbar according to claim 6, wherein, During the removal of the busbar substrate from the melt, the busbar substrate is surrounded by an inert atmosphere.

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