Aluminum wiring material and method for producing same

Abstract

Provided are: an aluminum wiring material which has excellent long-term reliability of bonding under a temperature cycle, excellent followability to a wedge tool, and excellent vibration resistance even when the aluminum wiring material has high purity; and a method for producing the aluminum wiring material. An aluminum wiring material having a purity of 99.9% by mass or more but less than 99.999% by mass, and a crystal orientation lt having an angular difference of 10 DEG or less in a cross section perpendicular to the longitudinal direction of the aluminum wiring material; 112gt, 112gt; the present invention relates to a sintered body which has an orientation ratio of 30% or less, an average crystal grain size of 60 [mu] m or less, a load stress ratio of 0.4-0.9, and a yield strength ratio of 1.0-2.3, and which contains at least one of element groups (a), (b), and (c), in the element group (a), the total of at least one of Ni, Zr, and Sc being 5-1000 mass ppm, in the element group (b), the total of at least one of Mg, Cr, W, Cu, and Ti being 2-100 mass ppm, and in the element group (c), the total of at least one of Fe, Si, Ga, and V being 2-100 mass ppm.

Description

Technical Field

[0001] This invention relates to an aluminum wiring material, and more particularly to a conductive aluminum wiring material with excellent bonding reliability at high temperatures, excellent weldability, and high vibration resistance, as well as a method for manufacturing the same. Background Technology

[0002] In the past, aluminum wiring materials were used as wiring materials for connecting electrodes and busbars of lithium-ion batteries, and as soldering wiring materials for power semiconductors.

[0003] Lithium-ion batteries are used as drive batteries (power sources) in hybrid electric vehicles (HV), plug-in hybrid electric vehicles (PHV, PHEV), and electric vehicles. HV and PHEV use a gasoline engine and an electric motor as driving forces. Electric vehicles use only the electric motor as driving force. Both HV and PHEVs are powered by electricity charged to lithium-ion batteries to drive the electric motor. Besides lithium-ion batteries, lead-acid batteries and nickel-metal hydride batteries are also used as drive batteries, but lithium-ion batteries are increasingly used in fuel-efficient electric vehicles due to their lightweight, small size, high output, and long lifespan.

[0004] Cylindrical batteries are commonly used as lithium-ion batteries for electric vehicles due to their small size, stable shape, and ease of replacement. A cylindrical battery has a structure in which the electrolyte and other components are sealed within a cylindrical metal casing. A battery pack using cylindrical batteries typically consists of an outer casing with connecting leads (buses), multiple cylindrical batteries housed within the casing, and wiring material connecting the electrodes of the cylindrical batteries to the leads. Aluminum wiring material, made of aluminum alloy, is widely used as the wiring material for these cylindrical batteries due to its advantages in conductivity and cost.

[0005] Power semiconductors are also known as power chips, power semiconductor devices, power components, and power semiconductor components. A power semiconductor consists of a power chip, soldering wires connecting the power chips to each other, and soldering wires connecting the power chip to external electrodes. Power semiconductors are used to drive motors, charge batteries, and supply power to microcontrollers and large-scale integrated circuits (LSI). In the automotive and other transportation sectors, the main power chips used are insulated-gate bipolar transistors (IGBTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs), which are suitable for high power applications. For the soldering wires used in power semiconductors, relatively thick aluminum wires with a diameter of 40μm or more but less than 700μm are mostly used to carry high currents. Furthermore, a structure that integrates multiple power semiconductors into a single package is called a "power module."

[0006] When bonding busbars to wiring materials or bonding power semiconductor wiring materials, the following method is generally used: a wedge tool (sometimes simply called a "tool") is used to hold the front end of the wiring material, and ultrasonic waves are applied to the wiring material while pressing the wiring material together with the wedge tool against the lead components and electrodes, squeezing and deforming them, thereby bonding the lead components, electrodes and wiring materials.

[0007] However, electric vehicles are used in a variety of external environments, including cold regions, tropical regions, high humidity, and high salinity areas. For example, when driving in cold or tropical regions, electric vehicles are exposed to low and high temperatures and temperature fluctuations for extended periods. To ensure the safety of electric vehicles, the power modules, drive batteries, and the aluminum wiring materials used in them must also be suitable for all conceivable operating environments of electric vehicles, as described above.

[0008] In addition to changes in the external environment's temperature, the power modules and drive batteries of electric vehicles are also affected by temperature variations caused by heating and cooling due to current. Electric vehicles repeatedly cycle through stopping and starting power-off. As a result, the power chip heats up and reaches high temperatures due to power-on, and then cools rapidly when power is cut off. The aluminum wiring material bonded to the power chip and drive battery is also exposed to these heating and cooling temperature cycles. When an electric vehicle operates for extended periods, it frequently undergoes repeated acceleration and braking, resulting in frequent repetition of these heating and cooling temperature cycles. During this process, for example, thermal stress is generated due to the difference in the coefficients of thermal expansion between the power chip and the aluminum wiring material. This can sometimes lead to metal fatigue at the joint between the power chip and the aluminum wiring material, as well as in the aluminum wiring material itself. Consequently, the possibility of peeling or breakage at the joint and the possibility of cracking in the aluminum wiring material increases. Therefore, there is a need for an aluminum wiring material that maintains long-term reliability of the joint even under repeated heating and cooling temperature cycles.

[0009] In addition, power transistors, a type of power semiconductor, are used in inverters. Inverters are installed in energy-saving (hereinafter referred to as "energy-saving") home appliances such as air conditioners, refrigerators, and washing machines. Power transistors control the speed of the motors driven by the inverter by switching current on and off. By using inverters, unnecessary motor operation can be reduced, energy savings can be achieved, and, for example, room temperature can be stably maintained in air conditioners. During the switching operation of the power transistors, the temperature cycle of heating and cooling of the wiring materials caused by energizing and de-energizing is repeated, similar to the above.

[0010] In the past, in order to prevent damage and failure of power modules under high temperature conditions, technologies such as avoiding chip damage, increasing the strength of bonding lines, and improving the long-term reliability of joints have been studied (for example, see Patent Documents 1-5).

[0011] Furthermore, with the miniaturization of home appliances, miniaturization, thinning, and high-density of power semiconductors have also been pursued. Consequently, the bonding space for aluminum wiring materials has decreased, resulting in greater bending of the aluminum wiring materials. Therefore, aluminum wiring materials are required to have the ability to follow this bending. When using aluminum wiring materials with poor bending followability, when laterally bent at a predetermined angle (e.g., 45°) using a wedge tool, the wiring material may not be able to follow the lateral bending motion of the wedge tool, and a portion of it may deviate from the clamp of the wedge tool. If a second bonding is performed with part of the wire deviated, the bonding position may deviate from the intended position and come into contact with other electrodes, potentially causing a short circuit. Additionally, if the wire deviates from the tool, the tip of the wedge tool may come into contact with the component, damaging the semiconductor component. In particular, conventional wiring materials aimed at long-term reliability generally tend to have high tensile strength, yield strength, and hardness (hereinafter collectively referred to as "strength"). On the other hand, the higher the strength of the wiring material, the worse the followability tends to be. Therefore, an attempt was also made to balance long-term reliability and wire followability (for example, see Patent Document 5).

[0012] The invention described in Patent Document 1 is "an aluminum alloy wire for ultrasonic welding of semiconductor devices, comprising 0.2 to 2.0% by mass of iron (Fe) and the remainder being aluminum (Al) with a purity of 99.99% by mass or higher, characterized in that 0.01 to 0.05% iron (Fe) is dissolved in the aluminum (Al) matrix of the aluminum alloy wire, and the wire drawing matrix structure in the cross section of the aluminum alloy wire is a uniform micro-recrystallized structure on the order of several μm, in which iron (Fe)-aluminum (Al) intermetallic compound particles are uniformly crystallized at the interface and inner surface of the structure." Patent document 1 describes how, by adding a solution treatment and rapid cooling process before tempering heat treatment, the amount of iron (Fe) dissolved in the aluminum (Al) matrix is ​​increased to the solution limit of 0.052% at 650°C. Through subsequent conventional cold continuous wire drawing and subsequent tempering heat treatment, the grain size of the Al-Fe alloy wire can be refined. By making Al highly pure, dynamic recrystallization will be exhibited during welding, thereby avoiding chip damage (see paragraph 0013 of the specification).

[0013] Patent Document 2 describes an invention for ultrasonic welding of aluminum alloy wire to aluminum pads of semiconductor devices composed of an alloy of iron (Fe), silicon (Si), and the remainder being high-purity aluminum (Al). The aluminum alloy wire is an alloy composed of 0.01-0.2% by mass of iron (Fe), 1-20 ppm by mass of silicon (Si), and the remainder being aluminum (Al) with a purity of 99.997% by mass or higher. It has a fine microstructure with a Fe solid solution content of 0.01-0.06%, a Fe precipitation content less than 7 times the Fe solid solution content, and an average crystal grain size of 6-12 μm. Patent Document 2 describes how the recrystallization temperature is stabilized by maintaining the ratio of Fe precipitation to Fe solid solution within a certain range, and the strength is improved by adding trace amounts of Si, resulting in stable thermal shock test results (see paragraph 0012 of this specification).

[0014] The invention described in Patent Document 3 is characterized by being "composed of Al or an Al alloy, with an average grain size of 0.01 to 50 μm in a cross-section perpendicular to the axis of the wiring material, and in the results of measuring the crystal orientation of the cross-section perpendicular to the axis of the wiring material, the crystal orientations in the length direction of the wiring material with an angle difference of 15° or less relative to the length direction of the wiring material." <111> The orientation ratio is 30-90%. Patent document 3 describes that even when the semiconductor device is used continuously for a long time in a high-temperature environment, the reliability of the junction in the semiconductor device after long-term high-temperature operation can be ensured (see paragraph 0012 of the specification).

[0015] Patent Document 4 describes an invention characterized by containing 0.02 to 1% Fe by mass, and a total of 0.05 to 0.5% of at least one of Mn and Cr, with the remainder consisting of Al and unavoidable impurities, and the total solid solution content of Fe, Mn, and Cr being 0.01 to 1%. Patent Document 4 further describes that, in addition to Fe, it contains a specified amount of one or both of Mn and Cr. During solution heat treatment and subsequent rapid cooling, the total solid solution content of Fe, Mn, and Cr is set to 0.01 to 1%. Therefore, even if the recrystallization temperature of the wire increases, recrystallization of the bonding wire can be sufficiently suppressed during prolonged use of the semiconductor device at high temperatures, preventing a decrease in wire strength (see paragraph 0014 of this specification). Furthermore, it describes that in a cross-section perpendicular to the length direction of the bonding wire (section C), the crystal... <111> The area ratio of crystals whose orientation differs from the direction of the conductor length by an angle of less than 15°. <111> The orientation area ratio is preferably 30-90%, and the recrystallization caused by the tempering heat treatment during wire drawing is carried out in a moderate manner, thereby softening the wire and preventing chip breakage during soldering and reduction of the bonding strength of the joint (see paragraph 0026 of this specification).

[0016] Patent Document 5 describes an invention entitled "An aluminum wire, composed of an aluminum alloy with an aluminum purity of 99% by mass or more, characterized in that, relative to the total amount of the aluminum alloy, it contains a total of 0.01% by mass and 1% by mass of iron and silicon, wherein the orientation index of (111) in the cross-section perpendicular to the conductor axis of the aluminum wire is 1 or more, and the orientation index of (200) is 1 or less, and the area fraction of precipitated particles is 0.02% or more and 2% or less." Patent Document 5 describes that by containing a specified amount of iron and silicon, setting the orientation index of (111) in the cross-section perpendicular to the conductor axis to 1 or more, and setting the orientation index of (200) to 1 or less, a long lifespan in power cycling tests is achieved (see paragraph 0044 of this specification). Furthermore, by making the area fraction of precipitated particles 0.02% or more and 2% or less, it is possible to prevent the conductor from deviating from the wedge tool during wire bonding for power semiconductors (see paragraph 0050 of this specification). Existing technical documents Patent documents

[0017] Patent Document 1: Japanese Patent Application Publication No. 2013-258324 Patent Document 2: Japanese Patent Application Publication No. 2014-129578 Patent Document 3: International Publication No. 2020 / 184655 Patent Document 4: Japanese Patent Application Publication No. 2020-059886 Patent Document 5: International Publication No. 2022 / 163606 Summary of the Invention The problem that the invention aims to solve

[0018] As an example of such miniaturized power semiconductors, power semiconductors with a thickness of 65 μm and IGBTs with a thickness of 50 μm have been known previously. Furthermore, efforts have been made not only to miniaturize power semiconductors but also to miniaturize and thin semiconductor packages. This is because miniaturizing and thinning semiconductor packages can, for example, lead to lighter electric vehicles, potentially improving fuel efficiency. Specifically, IGBT packages with a height (thickness) of approximately 20-40 mm became widespread in the 2000s, and IGBT packages with a height of 14 mm were used in 2014. In recent years, a next-generation general-purpose package with a height of 5 mm has also emerged. In addition, a semiconductor package includes the power semiconductor, bonding wiring materials, and resin that seals them as needed.

[0019] Furthermore, the development of high-performance and multi-functional electric vehicles and home appliances is also underway. To achieve high performance and multi-functionality, high driving force is required, thus necessitating the supply of larger currents to power semiconductors. Therefore, in power semiconductors aimed at high performance and multi-functionality, thicker aluminum wiring materials are typically used to easily carry large currents. For example, aluminum wiring materials with a wire diameter of around 300μm were previously used, while some products now use aluminum wiring materials with a wire diameter of around 500μm.

[0020] From the perspective of energy saving in electric vehicles and home appliances, reducing wiring resistance in semiconductor packaging is also important. To reduce wiring resistance—the power consumed by the resistance of the aluminum wiring material—it is effective to reduce the loop height (lower loop) and shorten the loop length (shorter loop) during bonding, thereby reducing the length of the wiring material. Furthermore, the loop height here refers to the height from the lowest point of the wiring material bonding area to the highest point of the loop, and the loop length refers to the straight-line distance between the two ends of the first and second bonding points.

[0021] However, electric vehicles are sometimes used in various environments, such as areas with poor road maintenance and uneven surfaces. For example, when an electric vehicle travels on uneven terrain, the undulations of the road surface cause not only the vehicle body but also various components and devices mounted on the vehicle to be constantly subjected to vibration. Therefore, there are concerns about the possibility of malfunctions in electric vehicles using power semiconductors made of aluminum wiring materials with insufficient vibration resistance. Furthermore, power semiconductors are also subject to temperature cycling during the operation of an electric vehicle. Therefore, to ensure safety, the aluminum wiring materials used in electric vehicles require high vibration resistance and long-term reliability of the connections.

[0022] However, compared to low-purity aluminum wiring materials, high-purity aluminum wiring materials, due to their high output and high purity, struggle to simultaneously maintain long-term reliability and vibration resistance for high-level connections, thus making it difficult to maintain good followability to wedge tools. Here, Figure 1 The image shows magnified photographs of the first and second joints of a welding example (welding example 1) where tool deviation is caused by insufficient followability of the wedge tool due to wiring material, and a welding example (welding example 2) where tool deviation is not caused. Figure 1 The top and bottom photos on the left are of the first and second joints formed by the wiring material that has deviated from the wedge tool. Figure 1 The top and bottom photos on the right show normal first and second joints formed by wiring materials where no wedge tool deviation occurred. For example, in the joint material of welding example 1, insufficient conformity resulted in a non-joint at the first joint due to tool deviation.

[0023] With the goal of applying it to higher performance and higher functionality products, the inventors conducted in-depth development of aluminum wiring materials that can achieve small size, thinness, high driving force, and energy saving. The results showed that when bonding the aluminum wiring material to a power chip with a small bonding space, the stress caused by bending at the neck of the aluminum wiring material (the upright portion of the wiring material bonded to the semiconductor) increases as the thickness of the wiring material increases.

[0024] Furthermore, it was found that in power semiconductor packages exposed to temperature cycles of heating and cooling induced by electric current, joint fractures caused by these temperature cycles occur individually, particularly cracks on the lower side of the neck (the side bonded to the chip) and cracks on the upper side caused by bending stress in the neck. Depending on the manner in which these cracks form, they may lead to breakage of the wiring material. This tendency is particularly pronounced in wiring materials made of high-purity aluminum alloys.

[0025] It was also found that in the miniaturization and thinning of semiconductor packages in recent years, the increased stress caused by bending makes it prone to cracking at the neck, especially on the upper side (the side opposite to the chip bonding), due to vibration, leading to breakage of the wiring material. Here, refer to... Figures 5-8 The cracks on the upper side of the wiring material are explained. Figure 5 This is a diagram showing the observation area R of the aluminum wiring material when observing the upper crack. Figure 5 In the process, aluminum wiring material 51 is second-joined (wedge-welded) onto aluminum pads 53 on the surface of TEG (Test Element Group) chip 52. Figure 6 The process involves soldering aluminum wiring material to a TEG chip in a low-loop wedge shape, sealing it with resin, repeating current-based heating and cooling, and applying vibration a certain number of times, and then taking a photograph of the portion corresponding to the observation area R of the necked-up portion of the aluminum wiring material using SEM-BEI (Scanning Electron Microscopy Reflection Electron Imaging). Figure 7 It is Figure 6 A portion of the enlarged photograph. From Figure 6 and Figure 7 It can be seen that small cracks exist within region P on the upper side of the wiring material in the raised neck section. In contrast, Figure 8 This is a photograph of aluminum wiring material in observation area R where no cracks were observed. In recent years, in the miniaturization and thinning of semiconductor packages, such as... Figure 6 and Figure 7 As shown, fine cracks may form on the upper side of the neck. Furthermore, cracks may also form on the lower side of the neck. If cracks develop on both the upper and lower sides of the neck, the synergistic effect of these two cracks further accelerates the development of the cracks, potentially increasing the risk of neck fracture.

[0026] This invention was made to solve the aforementioned problems, and its object is to provide an aluminum wiring material that, even when made of high-purity aluminum, exhibits excellent long-term reliability of the joint under temperature cycling, excellent wedge tool conformability, and excellent vibration resistance. Furthermore, this invention aims to provide a method for manufacturing a high-purity aluminum wiring material that exhibits excellent long-term reliability of the joint, excellent bending conformability, and excellent vibration resistance. Methods for solving problems

[0027] The aluminum wiring materials used in embodiments of the present invention are as follows. [1] An aluminum wiring material, comprising aluminum with a purity of 99.9% by mass or higher and less than 99.999% by mass, wherein, In the cross-section of the aluminum wiring material perpendicular to its length direction, Crystal orientation with an angular difference of less than 10° relative to the length direction <112> The orientation ratio is below 30%. The average crystal grain size in the cross-section is less than 60 μm. The load stress ratio defined below (1) is 0.4 or more and 0.9 or less. Load-stress ratio = fatigue limit / tensile strength (1) The yield strength ratio defined below (2) is greater than 1.0 and less than 2.3. Yield strength ratio = maximum stress / 0.2% of yield strength (2) The aluminum wiring material comprises one or more elements selected from groups (a), (b), and (c). In element group (a), the total amount of one or more elements selected from nickel (Ni), zirconium (Zr), and scandium (Sc) is 5 ppm by mass or more and 1000 ppm by mass or less. In element group (b), the total amount of one or more elements selected from magnesium (Mg), chromium (Cr), tungsten (W), copper (Cu), and titanium (Ti) is more than 2 ppm by mass and less than 100 ppm by mass. In element group (c), the total amount of one or more elements selected from iron (Fe), silicon (Si), gallium (Ga) and vanadium (V) is more than 2 ppm by mass and less than 100 ppm by mass. [2] According to the aluminum wiring material described in [1], the average crystal grain size in the cross section perpendicular to the length direction of the aluminum wiring material is less than 55 μm. [3] The aluminum wiring material according to [1] or [2], wherein the aluminum wiring material further contains less than 10 ppm by mass of one or more elements selected from zinc (Zn) and manganese (Mn). [4] The aluminum wiring material according to any one of [1] to [3], wherein the wire diameter of the aluminum wiring material is 15 μm or more and 700 μm or less. [5] The aluminum wiring material according to any one of [1] to [4], wherein the cross section of the aluminum wiring material perpendicular to the length direction is circular, oblong or elliptical.

[0028] [6] A method for manufacturing an aluminum wiring material, comprising the following steps: The preparation process involves preparing an aluminum alloy, wherein the aluminum alloy is composed of aluminum with a purity of 99.9% by mass or higher but less than 99.999% by mass. It contains one or more elements selected from groups (a), (b), and (c). In element group (a), the total amount of one or more elements selected from nickel (Ni), zirconium (Zr), and scandium (Sc) is 5 ppm by mass or more and 1000 ppm by mass or less. In element group (b), the total amount of one or more elements selected from magnesium (Mg), chromium (Cr), tungsten (W), copper (Cu), and titanium (Ti) is more than 2 ppm by mass and less than 100 ppm by mass. In element group (c), the total amount of one or more elements selected from iron (Fe), silicon (Si), gallium (Ga), and vanadium (V) is 2 ppm by mass or more and 100 ppm by mass or less; and The wire drawing process involves drawing the aluminum alloy into wires. In the cross-section of the aluminum wiring material perpendicular to its length direction, Crystal orientation with an angular difference of less than 10° relative to the length direction <112> The orientation ratio is below 30%. The average crystal grain size in the cross-section is less than 60 μm. The load stress ratio defined below (1) is 0.4 or more and 0.9 or less. Load-stress ratio = fatigue limit / tensile strength (1) The yield strength ratio defined below (2) is greater than 1.0 and less than 2.0. Yield strength ratio = maximum stress / 0.2% yield strength (2). [7] A method for manufacturing an aluminum wiring material, comprising the following steps: The preparation process involves preparing an aluminum alloy, wherein the aluminum alloy is composed of aluminum with a purity of 99.9% by mass or higher but less than 99.999% by mass. It contains one or more elements selected from groups (a), (b), and (c). In element group (a), the total amount of one or more elements selected from nickel (Ni), zirconium (Zr), and scandium (Sc) is 5 ppm by mass or more and 1000 ppm by mass or less. In element group (b), the total amount of one or more elements selected from magnesium (Mg), chromium (Cr), tungsten (W), copper (Cu), and titanium (Ti) is more than 2 ppm by mass and less than 100 ppm by mass. In element group (c), the total amount of one or more elements selected from iron (Fe), silicon (Si), gallium (Ga), and vanadium (V) is 2 ppm by mass or more and 100 ppm by mass or less; and The wire drawing process involves drawing the aluminum alloy under the condition that the section shrinkage rate (processing rate) of each die is above 3% and below 40%. In the cross-section of the aluminum wiring material perpendicular to its length direction, Crystal orientation with an angular difference of less than 10° relative to the length direction <112> The orientation ratio is below 30%. The average crystal grain size in the cross-section is less than 60 μm. The load stress ratio defined below (1) is 0.4 or more and 0.9 or less. Load-stress ratio = fatigue limit / tensile strength (1) The yield strength ratio defined below (2) is greater than 1.0 and less than 2.0. Yield strength ratio = maximum stress / 0.2% yield strength (2). In addition, the "~" symbol in this specification indicates the range of values ​​including the values ​​before and after it.

[0029] According to the present invention, a high-purity aluminum wiring material exhibiting excellent long-term reliability in bonding under temperature cycling, excellent wedge tool conformability, and excellent vibration resistance can be provided. Furthermore, according to the present invention, a method for manufacturing a high-purity aluminum wiring material exhibiting excellent long-term reliability in bonding, excellent bending conformability, and excellent vibration resistance can be provided. This facilitates the miniaturization of power semiconductors and the like using high-purity aluminum wiring materials. Attached Figure Description

[0030] Figure 1 The images show magnified photographs of the joints formed by wiring materials that have experienced wedge tool misalignment (left side) and normal joints formed by wiring materials that have not experienced wedge tool misalignment (right side). Figure 2 It is a graph of the SN curve. Figure 3 This is a schematic diagram illustrating an example of the cross-sectional shape of aluminum wiring material. Figure 4 This is a schematic diagram of an analog power semiconductor device used for evaluating power cycle life and vibration fatigue in a resin-sealed state. Figure 5 This is a diagram showing the observation area R of the aluminum wiring material when observing the upper crack. Figure 6 This is a photo of the aluminum wiring material with cracks on the upper side. Figure 7 It is Figure 6 A portion of the enlarged photograph. Figure 8 This is a photo of the aluminum wiring material on the top side, which has not developed any cracks. Detailed Implementation

[0031] The aluminum wiring material according to embodiments of the present invention will be described below. The aluminum wiring material of the embodiment is an aluminum wiring material composed of 99.9% by mass or more and less than 99.999% by mass of aluminum, and in a cross-section of the aluminum wiring material perpendicular to the length direction, the crystal orientation has an angle difference of less than 10° relative to the length direction. <112> The orientation ratio is below 30%.

[0032] The inventors fabricated multiple wiring material samples with different aluminum compositions and under various manufacturing conditions. The long-term reliability of the connections (hereinafter also referred to as "power cycle life") of each wiring material sample was evaluated as described below, and the cross-sectional microstructure perpendicular to the length direction of the wiring material samples was carefully observed. The results revealed a crystal orientation that had previously been overlooked in aluminum wiring materials. <112> The presence ratio of [certain crystal orientations] is correlated with power cycle life. Specifically, it was found that in the crystal orientations of the wiring material in a cross-section perpendicular to the length direction, crystal orientations with an angle difference of less than 10° relative to the length direction [are affected]. <112> When the presence ratio is within the specified range, the power cycle life is particularly excellent.

[0033] Crystal orientation is extensively performed in the manufacturing process of aluminum wiring materials for semiconductor packaging, including those used for conductive applications. <111> The ratio is controlled by controlling the crystal orientation. <111> This ratio has enabled the practical application of flexible and easily processable wiring materials. However, it is clear that in recent years, the development of conductive aluminum wiring materials for miniaturized, thin semiconductor packages has relied solely on controlling crystal orientation. <111> The ratio of [specific ratio] cannot solve the problems of simultaneously improving the long-term reliability of the joint under temperature cycling, improving the followability of the wedge tool, and improving vibration resistance, as mentioned above. Therefore, the inventors believe that [specific ratio] can improve the deformation resistance of the metal structure. <111> The presence of specific orientations with high orientation and the optimization of their ratio are important for solving the aforementioned problems. Furthermore, it has been found that, in particular, by... <112> By controlling the proportion of orientation within a certain range, the aforementioned problems can be solved. That is, by aligning the crystal... <112> The ratio is maintained within a certain range, and other properties of the wiring materials are adjusted in combination, so that vibration resistance and wedge tool following are maintained through their synergistic effect, and in particular, long power cycle life is achieved.

[0034] Specifically, in the aluminum wiring material of this embodiment, among the crystal orientations in a cross-section perpendicular to the length direction, the crystal orientations with an angle difference of 10° or less relative to the length direction are... <112> The presence rate is below 30%, thus achieving excellent power cycle life. From these perspectives, crystal orientation... <112> The presence ratio is preferably 5% or more and 25% or less, more preferably 10% or more and 20% or less.

[0035] (Evaluation of power cycle life) Power cycling testing refers to a test that repeats the following cycle: energizing the aluminum wiring material to raise the surface temperature of the power chip with the aluminum wiring material to 150°C, then stopping the power supply and cooling until the surface temperature reaches 25°C. In other words, it involves repeatedly performing cycles of rapid cooling and rapid heating with a temperature difference of 125°C, evaluating the number of cycles until a problem occurs with the power chip's operation. The number of cycles during which power cannot be supplied is determined as the sample life of the power cycling test (power cycle life). A longer power cycle life indicates better long-term reliability of the bonding.

[0036] Furthermore, by making the crystal grains in the crystalline structure of the aluminum wiring material of this embodiment finer, the elasticity of the crystalline structure is increased, thereby improving the following ability of the wedge tool. Specifically, in the aluminum wiring material of this embodiment, by making the average crystal grain size in the cross-section perpendicular to the length direction 60 μm or less, the long-term reliability of the joint is further improved. The average crystal grain size is preferably 55 μm or less, more preferably 45 μm or less. The average crystal grain size is typically 1 μm or more.

[0037] In the determination and analysis of the crystalline structure of the cross-section of wiring materials, the electron backscatter diffraction pattern (EBSP) method can be used. With the EBSP method, even fine wires, such as those used for semiconductor bonding, can have their cross-sectional crystalline structure determined with excellent accuracy and reproducibility.

[0038] In the EBSP method, it is often difficult to determine crystal orientation with high precision when the sample surface is uneven or has large curvature. Therefore, smoothing the surface of the cross-section is useful for observing the cross-section of wiring materials using EBSP. Methods for smoothing the cross-section surface include mechanical polishing, chemical polishing, and FIB processing. These methods can remove residual strain from the cross-section surface, resulting in a smooth surface.

[0039] If the sample is properly pretreated as described above, the crystal orientation of the wiring material cross-section can be determined and analyzed with high precision using the EBSP method. By measuring the crystal orientation at at least three locations, and if possible, at more than ten locations, average information that takes into account deviations can be obtained.

[0040] (Load stress ratio) The load stress ratio of the aluminum wiring material in this embodiment, as defined in (1) below, is 0.4 or more and 0.9 or less. Load-stress ratio = fatigue limit / tensile strength (1)

[0041] It is known that vibrations from driving a car or walking a person occur randomly in the X, Y, and Z axes, and the vibration frequency is usually below 40 Hz. For example, aluminum wiring materials used in electric vehicles are subjected to the aforementioned pressures over a long period of time, resulting in stretching, compression, and bending in the three axial directions. The inventors have studied a method for evaluating the performance under such directional vibration loads. The results showed that the vibration resistance described above is correlated with the load stress ratio shown in equation (1).

[0042] First, let's explain fatigue limit. Generally speaking, steel materials subjected to repetitive stress with a certain amplitude will fail due to fatigue after a certain number of repetitions. We'll represent this failure using a biaxial chart, with the magnitude of the repetitive stress as the Y-axis and the number of repetitions as the X-axis. Figure 2The SN curve is shown. If the repetitive stress is reduced, the SN curve will become horizontal around 10^6 to 10^7, and sometimes even an infinite number of repetitive stress loads will not lead to failure. The value of the repetitive stress at this point is called the fatigue limit. On the other hand, as... Figure 2 As shown, the SN curves of non-ferrous metals such as aluminum do not have horizontal sections, and therefore there is no fatigue limit. Therefore, the strength at a certain number of repetitions is considered the fatigue limit. For example, the repetitive stress that does not fail up to 10^7 repetitions is called the 10^7 time-limited intensity. Furthermore, by convention, the stress amplitude at approximately 10^7 to 10^8 repetitions is sometimes also referred to as the fatigue limit; in this embodiment, the 10^7 time-limited intensity is set as the fatigue limit.

[0043] Fatigue limit is usually expressed as maximum load stress (MPa). The fatigue limit of the present invention can be determined by using a tensile fatigue testing machine (ElectroPlus E3000 manufactured by Instron Corporation, hereinafter referred to as the "testing device"), in accordance with the principles of JIS Z 2273:1978, at room temperature (e.g., 25°C), as follows. The aluminum wiring material of the evaluation object is cut into lengths slightly longer than 100 mm to obtain an evaluation sample with a test length of 100 mm. In addition, in order to calculate the value of the maximum load stress described later, the value of 0.2% yield strength of the aluminum wiring material of the evaluation object is obtained in advance through tensile testing. Then, the evaluation sample is fixed in the testing device, and the loading under the maximum load stress and the unloading under the minimum load stress are repeated at a speed of 5 Hz (5 times per second) and a maximum of more than 10 to the power of 7 times (tensile fatigue test). In addition, the maximum load stress here is 90% of the 0.2% yield strength and any value less than 90%, and the minimum load stress is 10 MPa (fixed value). Using 90% of the 0.2% yield strength as the maximum value, and setting any value less than 90% in descending order, the loading and unloading were repeated at at least three different repetitive loading points. The results were plotted on a semi-logarithmic graph to create an SN curve, where the number of repetitive loadings is set as the x-axis, the maximum load stress σ is set as the y-axis, and the x-axis is the logarithm (base 10). Furthermore, in the tensile fatigue test, the test conditions were adjusted so that the intervals of the repetitive loadings plotted on the graph were greater than 1 logarithmically and greater than 10 to the power of 1 in real terms. An approximate straight line was obtained from the plotted points using the least squares method. Using this approximate straight line, the maximum load stress that did not lead to fracture after 10 to the power of 7 repetitive loadings was determined. This maximum load stress that did not lead to fracture after 10 to the power of 7 repetitive loadings is the fatigue limit (MPa). Furthermore, in cases where it is difficult to conduct assessments for 10^7 or more repeated load cycles, for example, the maximum load stress that did not lead to fracture when subjected to 10^3 to 10^6 repeated load cycles can be plotted at least three points on a semi-logarithmic graph of the SN curve. An approximate straight line can be obtained from these plotted points using the least squares method, and the fatigue limit at 10^7 repeated load cycles can be estimated using this approximate straight line. In this case, the test conditions are also adjusted so that the interval between the plotted points in the x-axis direction is at least 1 in logarithmic terms and at least 10^1 in real terms. Additionally, to conduct this tensile fatigue test more accurately, it is important to meet the following three conditions. (i) The two ends of the measured length (the stretched portion) are fixed and do not move during the test. (ii) The two ends of the measuring length are stretched perpendicularly to each other along a single axis. (iii) The fracture site caused by the tensile test is not the clamp part.

[0044] Next, tensile strength will be explained. Tensile strength (MPa) is obtained by dividing the maximum load (Kgf) at both ends of the sample under tensile testing equipment until fracture by the cross-sectional area of ​​the wiring material. This maximum load is automatically calculated in the tensile testing equipment by converting the tensile force into an electrical signal. In addition, as shown in equation (1) above, the load-stress ratio is obtained as the fatigue limit / tensile strength value, but it can also be obtained as the maximum load in the tensile fatigue test / maximum load in the tensile test value.

[0045] The load stress ratio of the aluminum wiring material in this embodiment is 0.4 or higher and 0.9 or lower, which significantly suppresses vibration-induced damage to the neck of the wiring material bonded to the semiconductor chip, thereby improving vibration resistance. The load stress ratio is preferably 0.5 or higher and 0.9 or lower, more preferably 0.6 or higher and 0.9 or lower, and even more preferably 0.7 or higher and 0.9 or lower. When the load stress ratio is within this range, the vibration resistance is significantly improved.

[0046] (Yield strength ratio) The yield strength ratio of the aluminum wiring material in this embodiment, as defined in (2) below, is greater than 1.0 and less than 2.3. Yield strength ratio = maximum stress / 0.2% of yield strength (2)

[0047] After setting the load stress ratio within the aforementioned range, by setting the yield strength ratio of the aluminum wiring material to be greater than 1.0 and less than 2.3, the toughness of the aluminum wiring material increases, and the vibration resistance can be further improved. The yield strength ratio is preferably 1.2 or more and less than 2.1, and more preferably 1.4 or more and less than 1.9.

[0048] The yield strength ratio is the value obtained by dividing the maximum stress (MPa) by 0.2% of the yield strength (stress) (MPa). First, the maximum load (kgf) and 0.2% strain load (kgf) of the wiring material are determined through the tensile test described above. The maximum stress (MPa) is obtained by dividing the maximum load by the cross-sectional area of ​​the wiring material. In addition, the 0.2% yield strength (stress) (MPa) is obtained by dividing the 0.2% strain load by the cross-sectional area of ​​the wiring material. That is, maximum stress = maximum load / cross-sectional area, 0.2% yield strength (stress) = 0.2% strain load / cross-sectional area. Applying these to the above equation (2), the yield strength ratio can be calculated. Alternatively, the yield strength ratio can also be calculated as the value of the maximum load / 0.2% strain load in the tensile test.

[0049] (Vibration resistance assessment) Using an ultrasonic welding device (REBO7 wire bonder manufactured by Ultrasonic Industry), the wiring material sample was joined to two aluminum plates with a loop height of 1 mm and a length of 7 mm, forming the first and second joints respectively, to obtain the evaluation sample. Using this evaluation sample, a vibration fatigue test was conducted using a vibration fatigue testing machine based on JIS standards (e.g., AS ONE CV-101M) to evaluate its vibration resistance. In the vibration fatigue test, each sample was vibrated at a frequency of 50 Hz, an acceleration of 1 G, and an amplitude of 0.099 mm until fracture. The higher the total number of vibrations until fracture in the vibration fatigue test, the better the vibration resistance.

[0050] As described above, electric vehicles sometimes travel in areas with poor road maintenance and uneven surfaces, requiring that the power semiconductors mounted in the electric vehicle not malfunction due to vibration. The aluminum wiring material of this embodiment, having the aforementioned structure, exhibits excellent vibration resistance, thus suppressing malfunctions under prolonged vibration. Furthermore, while the aforementioned vibrations are applied to the power semiconductors under temperature cycling caused by current, the aluminum wiring material of this embodiment, due to its structure, significantly reduces the occurrence of malfunctions such as breakage even under combined temperature cycling and vibration. Therefore, high safety can be achieved when used in electric vehicles.

[0051] Ultrasonic bonding, as a bonding method for aluminum wiring materials, involves applying ultrasonic waves while simultaneously applying a load to the aluminum wiring material, thereby breaking down the oxide film and deforming the wiring material during bonding. Therefore, the thicker the oxide film on the surface of the busbar or electrode to be bonded, the higher the load and energy required to remove this oxide film from the ultrasonic waves applied to the aluminum wiring material. However, applying ultrasonic waves at high loads and high energy can cause a decrease in the strength of the wiring material due to vibration, especially near the bonding boundary, which can easily lead to a reduction in the long-term reliability of the bond. However, in the aluminum wiring material of this embodiment, as described above, excellent vibration resistance and power cycle life can be achieved. Therefore, even aluminum wiring materials ultrasonically bonded under high loads and high energy can maintain long-term bonding reliability.

[0052] Furthermore, low-loop junctions exhibit lower vibration resistance compared to high-loop junctions. Therefore, conventionally, failures in aluminum wiring materials and their junctions are suppressed by maintaining a predetermined loop height. The aluminum wiring material according to this embodiment possesses excellent vibration resistance, allowing for further reduction in loop height during junction formation, thus contributing to the miniaturization of power semiconductors. In addition, in IGBTs, MOSFETs, etc., wiring materials and semiconductor chips are generally sealed with resin. However, the sealing resin, wiring material, and semiconductor chip are not completely sealed; sometimes a gap exists between the resin and the wiring material / semiconductor chip as a whole. Due to this gap, even in resin-sealed power semiconductors, vibration resistance is required in the same way as in unsealed power semiconductors. This is because, in wiring materials that have experienced thermal fatigue during temperature cycling, even short-amplitude vibrations generated by tiny gaps between the resin and wiring material can cause failure. However, the aluminum wiring material according to this embodiment, due to its long power cycle life and excellent vibration resistance, can suppress fractures caused by temperature cycling and vibration, even in resin-sealed power semiconductors.

[0053] The aluminum wiring material of this embodiment is composed of aluminum with a purity (amount of aluminum relative to the total amount of aluminum wiring material) of 99.9% by mass or more and less than 99.999% by mass. Because the aluminum wiring material of this embodiment contains specific elements (trace elements described later), it has sufficient conductivity and can further improve vibration resistance and long-term reliability of the connection.

[0054] The trace elements other than aluminum contained in the aluminum wiring material of this embodiment are selected from one or more of the following element groups (a), (b), and (c). Element group (a) consists of one or more elements selected from nickel (Ni), zirconium (Zr) and scandium (Sc). Element group (b) consists of one or more elements selected from magnesium (Mg), chromium (Cr), tungsten (W), copper (Cu), and titanium (Ti). Element group (c) is selected from one or more elements chosen from iron (Fe), silicon (Si), gallium (Ga), and vanadium (V). In the aluminum wiring material of this embodiment, by containing a predetermined amount of one or more elements selected from element groups (a), (b), and (c), crystal orientation is easily achieved. <112> The ratios, load stress ratios, and yield strength ratios are adjusted to the ranges described in this embodiment.

[0055] In the aluminum wiring material of this embodiment, when the elements comprising element group (a) (selected from one or more of nickel, zirconium, and scandium) are present, their total content is 5 ppm by mass or more and 1000 ppm by mass or less. By making the total content of the elements in element group (a) 5 ppm by mass or more, the crystal grains are refined, thereby effectively improving the vibration resistance and power cycle life of the wiring material while suppressing the reduction of conductivity. Therefore, the total content of these elements is preferably 8 ppm by mass or more, and more preferably 20 ppm by mass or more. In addition, by making the total content of the elements in element group (a) 1000 ppm by mass or less, high vibration resistance and power cycle life can be achieved while maintaining conductivity. From this viewpoint, the total content of the elements in element group (a) is preferably 500 ppm by mass or less, and more preferably 100 ppm by mass or less.

[0056] In the aluminum wiring material of this embodiment, when it contains elements selected from element group (b) (selected from one or more of magnesium, chromium, tungsten, copper, and titanium), the total amount of these elements is 2 ppm by mass or more and 100 ppm by mass or less. By making the total amount of elements in element group (b) 2 ppm by mass or more, the recrystallization temperature can be increased, the crystal grains can be refined, or the strength of the wiring material can be improved through their synergistic effect, effectively improving the vibration resistance and power cycle life of the wiring material while suppressing the reduction of conductivity. Therefore, the total amount of these elements is preferably 5 ppm by mass or more, and more preferably 8 ppm by mass or more. In addition, the total amount of elements in element group (b) is preferably 60 ppm by mass or less, and more preferably 40 ppm by mass or less.

[0057] In the aluminum wiring material of this embodiment, the elements in element group (c) (selected from one or more of iron, silicon, gallium, and vanadium) are not essential if the aluminum wiring material contains elements from element group (a) or (b), but if it contains elements from element group (c), their total amount is 100 ppm by mass or less. By making the total amount of elements in element group (c) 100 ppm by mass or less, the rigidity of the wiring material is moderately increased, thereby improving the vibration resistance and power cycle life of the wiring material. If elements from element groups (a) and (b) are not present, the total amount of elements in element group (c) is 2 ppm by mass or more. The total amount of elements in element group (c) is preferably 5 ppm by mass or more, more preferably 8 ppm by mass or more. Furthermore, the total amount of elements in element group (c) is preferably 60 ppm by mass or less, more preferably 50 ppm by mass or less, further preferably 40 ppm by mass or less, and most preferably 10 ppm by mass or less.

[0058] In the aluminum wiring material of this embodiment, in addition to the elements in element groups (a), (b), and (c) described above, one or more elements selected from zinc (Zn) and manganese (Mn) may be included as trace elements. In this case, the total amount of one or more elements selected from zinc (Zn) and manganese (Mn) is preferably 10 ppm by mass or less. Furthermore, the total amount of these elements is preferably 5 ppm by mass or less, and more preferably 3 ppm by mass or less.

[0059] The aluminum wiring material of this embodiment may contain only one element selected from one group of elements (a), (b), and (c) as trace elements, or it may contain any two or three groups of elements as trace elements. Preferably, the aluminum wiring material of this embodiment contains only one element selected from one group of elements (a), (b), and (c) as trace elements. In addition to the elements selected from one group of elements (a), (b), and (c), it also preferably contains one or more elements selected from zinc (Zn) and manganese (Mn). In addition, the aluminum wiring material of this embodiment may contain unavoidable impurities besides the trace elements mentioned above.

[0060] The proportion of elements contained in the aluminum wiring material of this embodiment is generally determined by chemical analysis such as inductively coupled plasma (ICP) luminescence spectrophotometry, but is not limited thereto. For example, it can also be determined by secondary ion mass spectrometry (SIMS), glow discharge mass spectrometry (GDMS), or energy-dispersive X-ray spectroscopy (EDX).

[0061] The wire diameter of the aluminum wiring material in this embodiment is typically 15 μm or more and 700 μm or less, preferably 70 μm or more and 600 μm or less, and more preferably 100 μm or more and 500 μm or less. If the cross-sectional shape is a perfect circle, the wire diameter of the aluminum wiring material is the diameter; if it is a shape other than this (such as a circular, elliptical, oblong, polygonal, or similar polygonal shape as shown below), the length of the major axis is used as the diameter. However, in the case of a polygonal or similar polygonal cross-section, its length can also be measured as the width or thickness. Figure 3 The diagram schematically illustrates an example of the cross-sectional shape of aluminum wiring material. For example... Figure 3 As shown, the cross-sectional shape of aluminum wiring materials, besides the circular shape ( Figure 3 In addition to (a), it can also be elliptical (e.g., Figure 3 (b) oblong shape (e.g., Figure 3 c) Quadrilateral shapes (e.g., Figure 3 e), triangle (e.g., Figure 3 (d) or similar polygonal shapes (e.g., Figure 3 (f, g), etc. When the cross-section of the aluminum wiring material is elliptical or oblong, the length of the major axis is preferably 0.3 mm or more and 4 mm or less, more preferably 0.5 mm or more and 3 mm or less, and the length of the minor axis is preferably 0.05 mm or more and 0.5 mm or less, more preferably 0.1 mm or more and 0.5 mm or less. When the cross-section of the aluminum wiring material is quadrilateral, the length of the long side is preferably 0.3 mm or more and 4 mm or less, more preferably 0.5 mm or more and 3 mm or less, and the length of the short side is generally preferably 0.05 mm or more and 0.5 mm or less, more preferably 0.1 mm or more and 0.5 mm or less. Furthermore, wiring materials with a polygonal, polygonal, or flat elliptical cross-section (the shape obtained by compressing an ellipse along a single axis) are called strip wires, and wiring materials with a circular, elliptical, or oblong cross-section are called conductors.

[0062] (Manufacturing method of aluminum wiring materials) Next, an example of a method for manufacturing aluminum wiring material according to the embodiment will be described. Furthermore, the method for manufacturing aluminum wiring material is not limited to the method shown below. Ideally, the conditions should be appropriately adjusted based on the weight of the aluminum wiring material to be manufactured and the processing capacity of the heat treatment furnace.

[0063] First, high-purity aluminum is prepared as raw material, and a specified amount of trace elements is added and the mixture is melted. The melted raw material is then solidified into a specified wire diameter, or shaped into a specified wire diameter after solidification. The purity of the high-purity aluminum as raw material can be 99.9% by mass or higher, 99.99% by mass or higher, or 99.99% by mass or higher. During melting, an electric arc furnace, a high-frequency furnace, a resistance furnace, or a continuous casting furnace is used. Although melting in the atmosphere is not a problem, to prevent the introduction of oxygen and hydrogen from the atmosphere, the molten aluminum in the furnace can be kept in a vacuum or an inert gas atmosphere such as argon or nitrogen during melting. Furthermore, during aluminum melting, it is preferable to perform the following inclusion removal process: after bubbling inert gases such as argon (Ar) or nitrogen in the molten aluminum, the mixture is filtered using a filter. In the inclusion removal process, inert gas bubbling condenses inclusions such as silicon dioxide (SiO2) and alumina (Al2O3) onto the surface of the molten aluminum, which are then removed from the molten aluminum through subsequent filtration. Removing inclusions makes it easier to adjust the load stress ratio to above 0.4. If argon (Ar) gas is used in the inclusion removal process, it not only increases the load stress ratio but also facilitates the removal of inclusions with higher yield strength ratios. <112> The orientation ratio is adjusted to the upper range, thereby further improving the long-term reliability and vibration resistance of the joint under temperature cycling. Furthermore, the greater the gas flow rate and the longer the bubbling time during the inclusion removal process, the higher the inclusion removal effect; therefore, it is easy to adjust the load stress ratio to 0.4 or higher. Conversely, even if the gas flow rate is too high or the bubbling time is too long, the effect will be diminished after the inclusion removal reaches its local limit, resulting in waste. Moreover, as a bubbling method, from the perspective of suppressing the dissolution of impurities into the molten aluminum, it is preferable to use a steel pipe with excellent corrosion resistance at high temperatures, through which inert gas is bubbled. As a filtration method, there is a method of circulating the molten aluminum in a filter made of ceramic foam with a porosity of approximately 0.8 to 0.9.

[0064] Table 1 shows the load stress ratio and yield strength ratio of the final wire diameter aluminum wiring material under the same manufacturing conditions, with and without an inclusion removal process (with bubbling). <112> Table 1 shows the differences in orientation ratios. In the experimental examples shown in Table 1, the effects of bubbling were compared between composition A (0.01% by mass of nickel (Ni) with the remainder being aluminum and unavoidable impurities) and composition B (0.05% by mass of scandium (Sc) and 0.03% by mass of zirconium (Zr) with the remainder being aluminum and unavoidable impurities). As shown in Table 1, when an inclusion removal process was performed in the molten aluminum, it was easier to remove the load stress ratio, yield strength ratio, and [other indices] compared to when no inclusion removal process was performed. <112> The orientation ratio is adjusted to the range of this embodiment.

[0065] [Table 1]

[0066] The molten aluminum material can be continuously cast from a heating furnace to a specified diameter, solidified to form an ingot, and then placed in an extruder for extrusion molding to produce a specified wire diameter. In the method for manufacturing aluminum wiring material according to the embodiment, a scratch-resistant treatment process is preferably performed, that is, the original wire material processed into a specified wire diameter by extrusion molding is subjected to scratch-resistant treatment. By performing the scratch-resistant treatment process, the yield strength ratio can be easily adjusted to be greater than 1.0 and less than 2.3. The scratch-resistant treatment can be performed by coating the surface of the original wire material with a treatment liquid mainly composed of surfactant. By using surfactant, compared with the use of oil-based treatment liquid, it is not only less likely to cause surface corrosion of the original wire material, but also to inhibit the sintering and high-temperature corrosion of surfactant on the surface of the aluminum wiring material in the subsequent heat treatment process, so the yield strength ratio can be easily adjusted to the above range. In addition, by performing the scratch-resistant treatment process, it is easy to adjust the yield strength ratio to the above range while also taking into account the crystal orientation. <112> The orientation ratio is adjusted to 30% or less, and the load stress ratio is adjusted to a range of 0.4 or more and 0.9 or less. Furthermore, examples of surfactants contained in the treatment solution for the anti-scratch treatment process include alcohol-based solvents such as ethanol, methanol, butanol, n-propanol, phenol, ethylene glycol, tridecanol, and glycerin. When using a surfactant as a lubricant in the subsequent wire drawing process, it is preferable to use a surfactant of the same type as that used in the wire drawing process. While the concentration of the surfactant used in the anti-scratch treatment process is not particularly limited, considering the ease of adjusting the yield strength ratio to be greater than 1.0 and less than 2.3, it is preferable to use the same concentration of surfactant as that used in the subsequent wire drawing process when using the same surfactant.

[0067] The raw wire obtained in the above process is drawn into intermediate wire with a diameter of 5.0 mm. The diameter of the intermediate wire is usually about 7 to 330 times that of the final wire. Next, the wire material (intermediate wire) after drawing is preferably subjected to homogenization treatment (homogenization process). In the homogenization process, the intermediate wire is heat-treated in an atmospheric furnace at 400°C~500°C for approximately 30 to 240 minutes, followed by rapid cooling. This homogenization process makes it easier to achieve the aforementioned specified crystal orientation. <112> The values ​​of orientation ratio and load stress ratio. Rapid cooling in the homogenization process is not particularly limited; it can be performed by immersing the heated intermediate wire in cold water stored in an immersion tank, or by using a spray to flow cold water through the heated intermediate wire. The aluminum wiring material of this embodiment has an aluminum purity of 99.9% by mass or more and less than 99.999% by mass, therefore the amount of trace elements other than aluminum in the aluminum wiring material is less than the solid solution limit of aluminum. Therefore, solid solution treatment to dissolve trace elements in the aluminum matrix may not be necessary. However, compared to solid solution treatment, by performing a low-temperature and short-time homogenization process, trace elements can be uniformly dispersed in the aluminum matrix, thus making it easier to achieve the crystal orientation specified above. <112> The values ​​of the orientation ratio and load stress ratio can improve the long-term reliability and vibration resistance of the joint, and obtain sufficient follow-through to bending. Furthermore, in the method for manufacturing aluminum wiring material according to this embodiment, in addition to the homogenization treatment described above, a solution treatment can also be performed to dissolve elements other than aluminum into the aluminum matrix. Additionally, an intermediate heat treatment can be performed on the homogenized intermediate wire before wire drawing. In the intermediate heat treatment, for example, the homogenized intermediate wire is heated at 240-300°C for approximately 30-140 minutes, and then air-cooled. The heating of the intermediate wire in the intermediate heat treatment can be either mobile heat treatment, in which the wiring material is heat-treated by passing it through a heating atmosphere heated to a specified temperature, or intermittent heat treatment, in which the wiring material is heated in a closed furnace.

[0068] Next, the homogenized intermediate wire is drawn to its final diameter. During the drawing process, the wire material is passed sequentially through multiple superhard or diamond dies, gradually reducing its diameter. To make... <112> The orientation ratio is below 30%, and the section shrinkage rate (processing rate) of each die can be above 3% and below 40%. Especially in the initial stage of wire drawing, it is ideal to set the section shrinkage rate of each die to be above 3% and below 5%. Furthermore, the wire drawing process is preferably performed while the die is being cooled. Cooling the die suppresses the temperature rise of the wiring material caused by friction between the die and the wiring material, thereby facilitating the cooling of the aluminum wiring material. <112> The orientation ratio is adjusted to below 30%, and the aluminum wiring material can achieve uniformity overall. <112> Orientation ratio. As a mold cooling method, spraying a coolant containing cold water into the mold inlet is effective. Furthermore, while cooling the mold, a lubricant, primarily composed of surfactants, can also flow into the mold, thereby easily adjusting the load-stress ratio to the aforementioned range. According to the method of cooling the mold by spraying coolant into the mold inlet, since the lubricant can be mixed into the coolant supply, the lubricant can also flow into the mold efficiently. Moreover, for mold cooling, for example, when the coolant temperature is below 20°C and the flow rate of the sprayed coolant is high, the cooling effect is high. <112> The orientation ratio is easily made uniform. Conversely, if the coolant flow rate is too high, the cooling effect will be limited, thus easily resulting in waste.

[0069] The wiring material, after being drawn to its final wire diameter, undergoes a final heat treatment. This final heat treatment primarily removes strain from the metal structure remaining within the wiring material, thereby adjusting its mechanical properties. As a final heat treatment method, there are mobile heat treatment methods, which involve heating the wiring material in a heating atmosphere to a specified temperature, and intermittent heat treatment methods, which involve heating the wiring material in a closed furnace. In this embodiment, the final heat treatment is preferably performed by intermittent heat treatment, for example, at a temperature of 150°C or higher and 400°C or lower for about 30 to 60 minutes.

[0070] Preferably, the wiring material that has undergone final heat treatment is then air-cooled. Air cooling facilitates the cooling of the aluminum wiring material. <112> The orientation ratio is uniformly adjusted to below 30%. This is because water cooling has a higher cooling effect than air cooling, but compared to water cooling, air cooling does not produce contamination or defects on the surface of aluminum wiring materials. While achieving the aforementioned yield strength ratio and load stress ratio, it is easy to uniformly and precisely control the orientation ratio to below 30%. <112> Orientation ratio. As for air cooling methods, examples include slowly cooling the final heat-treated aluminum wiring material at room temperature, and spraying cold air onto the surface of the aluminum wiring material. Among these, spraying air or cold air onto the surface of the aluminum wiring material is prone to... <112> The orientation ratio is preferably adjusted uniformly and stably to the desired range. When using air cooling by spraying air or cold air onto the surface of the aluminum wiring material, the lower the temperature of the air or cold air and the higher the spray velocity, the greater the cooling effect and the easier it is to stably obtain the aforementioned range. <112> Orientation ratio.

[0071] In the above-described method for manufacturing aluminum wiring materials, the conditions for the inclusion removal process in the molten metal, the homogenization treatment of the raw wire, the die cooling during wire drawing, the final heat treatment, and the air cooling after the final heat treatment are adjusted according to the amount and type of trace elements in the aluminum wiring material. This allows for the control of trace elements in the aluminum wiring material. <112> The orientation ratio, average crystal grain size, load stress ratio, and yield strength ratio are adjusted to the preferred range.

[0072] (Applications of aluminum wiring materials) The aluminum wiring material of this embodiment can be used in all applications where wiring materials made of ferrous, copper, and aluminum materials have been conventionally used. Specifically, it is suitable for use as conductive components such as bonding wires, bonding strips, wires, and cables for semiconductors; battery components such as screens and meshes for current collectors; and windings used in generators and motors.

[0073] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, including all the concepts of the present invention and all the ways contained in the claims, and various changes can be made within the scope of the present invention. Example

[0074] Next, embodiments will be described. The present invention is not limited to the following embodiments.

[0075] The aluminum wiring material of the embodiment was prepared as follows: A high-purity aluminum ingot with a purity of 99.9% by mass or higher was prepared. Trace elements were added to the aluminum alloy in the manner shown in Tables 2-4, and the alloy was melted under atmospheric conditions. During the melting of the aluminum alloy, argon (Ar) gas was bubbled through a steel tube into the molten aluminum alloy, and then the impurities precipitated on the surface of the molten liquid were filtered through a ceramic foam filter with a porosity of 0.85. The flow rate of argon (Ar) gas was 7 L / min, and the molten liquid flux during filtration was 22 kg / min. Then, continuous casting and extrusion molding were performed to obtain wire. The surface of the wire obtained by extrusion molding was coated with an aqueous solution of ethanol as a surfactant for scratch protection. The resulting wire was drawn to an intermediate wire diameter of 5 mm. This intermediate wire with an intermediate wire diameter of 5 mm was heated at 400°C to 500°C for approximately 30 to 240 minutes, and then rapidly cooled by passing cold water through a spray or similar means to achieve homogenization. In addition, an intermediate heat treatment is performed at 240°C to 300°C for approximately 30 to 140 minutes. After the intermediate heat treatment, the intermediate wire is cooled in the air. The intermediate wire before and after the intermediate heat treatment is then subjected to wire drawing using a cold die. During the wire drawing process, the reduction of area (reduction rate) of each diamond die is set to be 3% or more and 40% or less. Furthermore, during the wire drawing process using a die, a lubricant containing a surfactant of the same type as the aforementioned surfactant is flowed into the diamond die, making its concentration the same as the treatment liquid used in the anti-scratch treatment, thereby cooling the diamond die. In the production of the aluminum wiring material in the embodiment, the total reduction rate before processing to the final wire diameter is set to 99.36%, and the wire is drawn to the final wire diameter (400 μm). The aluminum wiring material processed to the final wire diameter is then subjected to a final heat treatment at 150°C to 400°C for 30 to 60 minutes using an intermittent furnace or salt bath. After the aluminum wiring material, which has undergone final heat treatment, is air-cooled by spraying cold air, it is rewound onto a reel in approximately 300m sections using a rewinding machine. This yields aluminum wiring material with a circular cross-section.

[0076] The comparative aluminum wiring materials were prepared as follows. Similar to the examples, aluminum ingots with a purity of 99.9% by mass or higher were prepared, and trace elements were added to make them the composition shown in Table 5. The manufacturing conditions, such as the heat treatment temperature and time at the intermediate wire diameter and the final wire diameter, the processing rate from each wire diameter to the next wire diameter, the cooling rate after intermediate heat treatment, and the section shrinkage rate of each die, were changed to be outside the range of the manufacturing conditions in the examples above, and the comparative aluminum wiring materials were prepared.

[0077] (Determination of crystal orientation and average grain size of cross-section of wiring material) The crystal orientation of the cross-section of the aluminum wiring material in the examples and comparative examples was determined as follows. Multiple evaluation samples were prepared by cutting the aluminum wiring material into lengths of several centimeters. While taking care not to elongate or loosen the evaluation samples, they were attached straight and flat to a metal (Ag-plated frame) plate. Then, the evaluation samples, along with the metal plate, were placed into a cylindrical mold, with the metal plate forming the bottom surface of the cylinder. Resin was then poured into the mold, and a curing agent was added to cure the resin. Subsequently, the cured cylindrical resin containing the evaluation samples was coarsely ground with a grinder to expose the perpendicular cross-section (hereinafter also referred to as the cross-section) along the length of the wiring material. The cut surface was then finished by final grinding, followed by ion milling to remove residual strain from the ground surface, resulting in a smooth surface. Furthermore, the ion milling apparatus was finely adjusted so that the cut surface of the wiring material was perpendicular to the length direction of the wiring material.

[0078] On the stage of a field emission scanning electron microscope (FE-SEM, JSM-7800F manufactured by NEC), the cross-section of the wiring material of the evaluation sample (i.e., the polished surface of the evaluation sample) is attached parallel to the stage. The crystal orientation and average grain size of the cross-section are determined using the FE-SEM with a magnification of 200x, an accelerating voltage of 15keV, a measurement area of ​​approximately 420×420μm, and a step size of 1.2μm. The obtained crystal orientation is then analyzed using dedicated crystal orientation analysis software (OIM analysis manufactured by TSL, hereinafter also referred to as dedicated software).

[0079] The discrimination criteria for crystal grains in the dedicated software were set to analyze the crystal orientation ratio of the measured sample, i.e., the proportion of each crystal orientation present. The discrimination criteria for crystal grains in the dedicated software can usually be set according to the purpose of the analysis, but they have almost no impact on the analysis results of the crystal orientation ratio. Therefore, in this embodiment and comparative example, it was set that when the orientation difference is less than 10° and there are more than two connected pixels, it is identified as one crystal grain, and the proportion of each crystal grain is calculated. <112> The proportion of oriented crystal grains.

[0080] Furthermore, in the analysis of EBSP measurement data, areas where crystal orientation cannot be measured may exist due to residual strain, contamination, or oxide film caused by roughness or grinding on the measurement surface. Therefore, a reliability threshold is set, and the area of ​​the measurement region where only the identifiable crystal orientation can be identified is taken as the total area. The orientation ratio is then automatically calculated using specialized software. In other words, areas where crystal orientation cannot be measured, and areas where the measurement results are unreliable even though they can be measured, are excluded to determine the orientation ratio. Sometimes, the specialized software includes parameters that can be used to set the reliability. Specifically, various parameters such as Confidential Index (CI value) and Image Quality (IQ value) can be used, and the reliability criteria are selected based on the sample condition and the purpose of the analysis. For example, the CI value can be set to 0.1 or higher, excluding areas with CI values ​​less than 0.1. Then, using the cleaning function included in the specialized software, the orientation data of pixels with low reliability is replaced with data from surrounding pixels that have undergone normal measurement, thereby supplementing the measurement results of the unreliable portions. This method is effective in removing pixel dispersion when the determination reliability is low. However, if the cleaning process is overdone, the noise in the resulting image will increase. Therefore, for example, when the orientation difference is less than 10° and more than two pixels are connected, it is identified as a single grain, and a Grain Dilation method is performed, followed by a Grain CI Standardization method.

[0081] The angle difference relative to the length direction in the cross-section of each aluminum wiring material in the embodiments and comparative examples obtained above is 10° or less. <112> Orientation ratios and average crystal grain sizes are shown in Tables 2-5 below.

[0082] (Determination of load-stress ratio) The load-stress ratio was determined using the following method. The aluminum wiring materials of the examples and comparative examples were set to a measurement length of 100 mm to obtain evaluation samples. Using these evaluation samples, tensile fatigue tests were conducted at room temperature (15–28°C) using a tensile fatigue testing machine (Instron ElectroPlus E3000) to determine the fatigue limit (MPa). The tensile evaluation samples were subjected to repeated loading at both ends under maximum load stress and unloading under minimum load stress at a speed of 5 Hz (5 times per second) for a maximum number of repetitions exceeding 10^7. The maximum load stress at three or more different repetitions was plotted on a semi-logarithmic graph of the SN curve. An approximate straight line was obtained from the plotted points using the least squares method, and the fatigue limit (MPa) at 10^7 repetitions was calculated based on this approximate straight line.

[0083] In addition, the aluminum wiring materials of the examples and comparative examples were cut into lengths slightly longer than 100 mm to obtain evaluation samples. Tensile strength, i.e., maximum load (Kgf), was determined by tensile testing at room temperature of 15–28°C. The maximum load in the tensile test can be determined using a tensile testing apparatus. The maximum load is calculated as follows: using a tensile testing apparatus (e.g., an Autograph manufactured by Shimadzu Corporation, model: AGS-5kNX), with a test length of 100 mm, the aluminum wiring material of the evaluation sample is continuously stretched at a speed of 20 mm / min and a force sensor rated at 100 N, and the maximum value until breakage is calculated. The maximum load refers to the force applied to the wiring material stretched at the above speed; typically, it is automatically calculated by converting the tensile force into an electrical signal using a force sensor. Taking into account the deviation of the measurement results, the average of three samples is calculated for the maximum load. The tensile strength (MPa) is obtained by dividing the maximum load by the cross-sectional area of ​​the wiring material.

[0084] Based on the fatigue limit and tensile strength measured above, the load stress ratio is calculated using the following formula. Load-stress ratio = fatigue limit / tensile strength The load stress ratios of each aluminum wiring material obtained through the above-described embodiments and comparative examples are shown in Tables 2-5 below.

[0085] (Determination of yield strength ratio) Regarding the yield strength ratio, the aluminum wiring materials of the examples and comparative examples were cut into lengths slightly longer than 100 mm to obtain evaluation samples for yield strength ratio determination. Under the same conditions as described above, the maximum load (Kgf) and 0.2% strain load (Kgf) of each sample were determined through tensile testing, and then divided by the cross-sectional area of ​​each sample. The yield strength ratio was calculated using the following formula. Yield strength ratio = maximum stress / 0.2% of yield strength (stress) The yield strength ratios of the aluminum wiring materials for the embodiments and comparative examples obtained above are shown in Tables 1-4 below.

[0086] (Determination of trace element concentration) The concentrations of trace elements in the aluminum wiring materials of the examples and comparative examples were determined as follows. Approximately 0.5 g of the manufactured wiring material was melted. The concentrations of each element in the solution were determined by high-frequency inductively coupled plasma optical emission spectrometry (ICPE-9000 manufactured by Shimadzu Corporation). The trace elements measured here were iron (Fe), silicon (Si), gallium (Ga), vanadium (V), magnesium (Mg), copper (Cu), nickel (Ni), zinc (Zn), chromium (Cr), manganese (Mn), titanium (Ti), zirconium (Zr), tungsten (W), and scandium (Sc), and their contents are shown in Tables 2-5 below. In the tables below, "mass" is an abbreviation for mass.

[0087] The compositions of the aluminum wiring materials obtained in the above-described embodiments and comparative examples are shown in Tables 2-9. Next, the performance of the aluminum wiring materials obtained above will be evaluated.

[0088] (Power Cycling Test) For the aluminum wiring materials used in the embodiments and comparative examples, an ultrasonic welding device (REBO7 wire bonding machine manufactured by ultrasonic industry) was used to bond the aluminum wiring materials to the aluminum alloy electrodes of the power chip. For each aluminum wiring material, the ultrasonic energy and pressure during bonding were set to ensure that the length of the wire material in the bonding part was 500 μm. After bonding the aluminum wiring materials, a power cycle test was conducted with the power chip set to a maximum temperature (Tjmax) of 150°C and a minimum temperature (Tjmin) of 25°C, i.e., a temperature difference (ΔTj) between the maximum and minimum temperatures of 125°C. The current, energizing time, and cooling time were then used. The energizing time was approximately 7 seconds, the energizing stop time was approximately 13 seconds, and each cycle was approximately 20 seconds.

[0089] The number of cycles without power supply is defined as the lifespan in the power cycling test (power cycle life). Samples with a power cycle life of 30,000 cycles or more are rated "S" (Excellent), meaning a lifespan above the target. Samples with a power cycle life of 20,000 cycles or more but less than 30,000 cycles are rated "A" (Good), meaning the target level. Samples with a power cycle life of 10,000 cycles or more but less than 20,000 cycles are rated "B" (Acceptable), meaning acceptable. Samples with a power cycle life of less than 10,000 cycles are rated "C" (Unacceptable). The evaluation of the power cycling test (thermal cycling) of the aluminum wiring materials in each embodiment and comparative example is shown in Tables 2-5.

[0090] (Vibration resistance) For the aluminum wiring materials in the examples and comparative examples, an ultrasonic bonding device (REBO7 wire bonding machine manufactured by Ultrasonic Industry) was used to bond the first and second joints on two aluminum plates respectively, with a loop height of 1 mm and a length of 7 mm, thus obtaining evaluation samples. The loop length is the straight-line distance between the two ends of the first and second joints. Using these evaluation samples, vibration fatigue tests were conducted using a vibration fatigue testing machine (CV-101M manufactured by AS ONE) based on JIS standards to evaluate vibration resistance. In the vibration fatigue test, each evaluation sample was subjected to vibration at a frequency of 50 Hz, an acceleration of 1 G, and an amplitude of 0.099 mm until fracture. In the vibration fatigue test, evaluation samples with a total number of vibrations exceeding 50,000 until fracture were classified as "S", i.e., above the target. Evaluation samples with a total number of vibrations between 10,000 and 50,000 until fracture were classified as "A", i.e., target level. Evaluation samples with a total number of vibrations between 5,000 and 10,000 until fracture were classified as "B", i.e., qualified. Samples with a total number of vibrations less than 5,000 until fracture were designated as "C", indicating they were unqualified. The evaluation of vibration fatigue tests on the aluminum wiring materials in each example and comparative example is shown in Tables 2-5.

[0091] (Tool deviation assessment) Next, using an evaluation sample of aluminum wiring material with a wire diameter of 400 μm, an ultrasonic welding device (K&S ASTERION wire bonder) was used to join the first and second joints to two aluminum plates with a distance of 5 mm between them. The second joint was performed by bending the evaluation sample horizontally at a 45° angle relative to the axis of the wiring material. The joining conditions were set to optimize the ultrasonic energy and pressure relative to the evaluation sample. Furthermore, a Kulicke & Soffa model 127591-16 welding tool was used, with a clamping jaw dimension of 0.5 mm width (inner diameter), 0.2 mm depth (height), and 1.0 mm length (penetration).

[0092] The condition of the wiring material at the second joint is observed to determine if a tool deviation fault has occurred. Using an evaluation sample, 30 soldering operations are performed (the combination of the first and second joints is considered as one operation). Unjoined and... Figure 1 The case where there are no contact marks on one side of the tool, as shown in the lower left corner, is classified as "S". The case where there is only one instance of non-joining or one contact mark is classified as "A". The case where there is only two instances of non-joining or two contact marks is classified as "B". The case where there is only three instances of non-joining or three contact marks is classified as "C". These results are shown in Tables 2-5.

[0093] Furthermore, corrosion resistance tests were conducted on the wiring materials of Example 1 and Comparative Example 26 under high humidity conditions, as described below. Using an accelerated life testing apparatus, tests were conducted at 121°C and 100% RH (saturation) for up to 1000 hours. In determining the corrosion layer thickness, the conductor cross-section was fabricated using a cross-section milling device, and the corrosion layer was observed using FE-SEM. The results showed that the corrosion layer thickness was approximately 5 μm in both cases, confirming that this level would not cause problems for the use of the wiring materials.

[0094] (Comprehensive Assessment) If only one of the three assessments is "S", the overall assessment is rated "Excellent". If only one of the three assessments is "S" or "A", the overall assessment is rated "Good". If it is a combination of assessments other than these and there is no assessment with a "C", the overall assessment is rated "Acceptable". If there is one assessment with a "C" in the sample, the overall assessment is rated "Unacceptable". Record these results in Tables 2-5.

[0095] (Thermal vibration fatigue test of the chip after resin sealing) In addition, an analog power semiconductor device was fabricated for evaluation in order to assess thermal vibration fatigue under resin-sealed conditions. Figure 4 The image schematically illustrates an analog power semiconductor device 200 for evaluation. (Example) Figure 4 As shown, two stepped aluminum terminals 202 and 203 and an IGBT chip 204 are fixed to a tungsten carbide metal plate 201, which is 45 mm long, 40 mm wide, and 2 mm thick, by die welding. Furthermore, a metal gasket is placed on the back of one aluminum terminal 203 to make it appropriately raised. Then, using the aluminum wiring material of the embodiment and comparative examples, the IGBT chip 204 is welded to the terminal 203, forming a loop with a height of 1 mm from the top of the loop to the terminal surface, a height of 10 mm from the surface of the IGBT chip 204 to the top of the loop, and a distance between the two ends of the wiring material joint, i.e., a minimum length of 7 mm and a maximum length of 20 mm. Then, a wall is formed around the IGBT 204 chip using a commercially available resin sealant, and the welded portion of the IGBT chip 204 and wiring material inside the wall is filled with an organosilicon gel-based sealing resin 205.

[0096] In the simulated power semiconductor device fabricated using the above method, a power cycling test and a vibration fatigue test are performed as part of the thermal vibration fatigue test. Specifically, to reproduce a load close to the thermal stress and vibration-induced stress in an actual device, 4,320 cycles of the aforementioned power cycling test (20 seconds × 4,320 cycles = 24 hours) and a subsequent vibration test of the semiconductor device itself (24 hours) are considered as one cycle in this test, and an energizing test is performed for each cycle. This vibration test is conducted under the conditions of the aforementioned vibration fatigue test.

[0097] The number of cycles without power supply is defined as the life in the thermal vibration fatigue test. Samples with a life of 6 cycles or more are rated "Excellent," meaning a life above the target. Samples with 4 cycles or more but less than 6 cycles are rated "Good," meaning the target level. Samples with 2 cycles or more but less than 4 cycles are rated "Acceptable," meaning qualified. Samples with less than 2 cycles are rated "Unacceptable," meaning unqualified. The evaluation of the thermal vibration fatigue test of the aluminum wiring materials in each embodiment and comparative example is shown in Tables 6-9. In addition, comparative examples 5 to 10 were not evaluated because they were deemed unqualified due to tool deviation.

[0098] (Evaluation of the rolled wiring material) Furthermore, using aluminum with the composition shown in Table 10, a sample prepared under the same processing conditions as in Example 1 was rolled into a strip with a long side length of 2 mm and a short side length of 0.2 mm. Using the obtained strip of wiring material, a loop bonding was performed between two aluminum plates, similar to Example 1. In this second bonding, the strip of wiring material was bonded with the goal of bending the wiring material 20° laterally relative to the wiring material axis. Otherwise, bonding and evaluation were performed under the same conditions as in Example 1. The results are recorded in Table 10. Additionally, aluminum wiring material with the composition shown in Table 11 was prepared in the same manner as in Example 1, and the resulting sample was rolled into a strip with a long side length of 2 mm and a short side length of 0.2 mm. Using the obtained strip of wiring material, the aforementioned "thermal vibration fatigue test of resin-sealed chip" was performed. The results are shown in Table 11.

[0099] [Table 2]

[0100] [Table 3]

[0101] [Table 4]

[0102] [Table 5]

[0103] [Table 6]

[0104] [Table 7]

[0105] [Table 8]

[0106] [Table 9]

[0107] [Table 10]

[0108] [Table 11]

[0109] As can be seen from the above, the high-purity aluminum wiring material according to the embodiments can simultaneously improve vibration resistance, heat resistance, and followability. The aluminum wiring materials for power semiconductors described in the examples can make a significant contribution to the development of the power electronics industry, the automotive industry, electric railways, and the power industry.

Claims

1. An aluminum wiring material composed of aluminum having a purity of 99.9 mass% or more and less than 99.999 mass%, wherein in a cross section perpendicular to a length direction of the aluminum wiring material, an orientation ratio of crystal orientation <112> having an angle difference of 10° or less with respect to the length direction is 30% or less, an average crystal grain diameter in the cross section is 60 μm or less, a load stress ratio defined by (1) below is 0.4 or more and 0.9 or less, Load stress ratio = fatigue limit / tensile strength (1) a yield strength ratio defined by (2) below exceeds 1.0 and is 2.3 or less, Yield strength ratio = maximum stress / 0.2% yield strength (2) the aluminum wiring material contains one or more selected from element groups (a), (b), and (c), in element group (a), a total of one or more elements selected from nickel (Ni), zirconium (Zr), and scandium (Sc) is 5 mass ppm or more and 1000 mass ppm or less, in element group (b), a total of one or more elements selected from magnesium (Mg), chromium (Cr), tungsten (W), copper (Cu), and titanium (Ti) is 2 mass ppm or more and 100 mass ppm or less, in element group (c), a total of one or more elements selected from iron (Fe), silicon (Si), gallium (Ga), and vanadium (V) is 2 mass ppm or more and 100 mass ppm or less. an average crystal grain diameter in a cross section perpendicular to a length direction of the aluminum wiring material is 55 μm or less.

2. The aluminum wiring material according to claim 1, wherein the aluminum wiring material further contains 10 mass ppm or less of one or more selected from zinc (Zn) and manganese (Mn).

3. The aluminum wiring material according to claim 1 or 2, wherein, a wire diameter of the aluminum wiring material is 15 μm or more and 700 μm or less.

4. The aluminum wiring material according to claim 1 or 2, wherein a cross section perpendicular to a length direction of the aluminum wiring material is circular, oblong, or elliptical.

5. The aluminum wiring material according to claim 1 or 2, wherein has the following steps:

6. A method for producing an aluminum wiring material, wherein a preparation step of preparing an aluminum alloy composed of aluminum having a purity of 99.9 mass% or more and less than 99.999 mass%, contains one or more selected from element groups (a), (b), and (c), in element group (a), a total of one or more elements selected from nickel (Ni), zirconium (Zr), and scandium (Sc) is 5 mass ppm or more and 1000 mass ppm or less, in element group (b), a total of one or more elements selected from magnesium (Mg), chromium (Cr), tungsten (W), copper (Cu), and titanium (Ti) is 2 mass ppm or more and 100 mass ppm or less, in element group (c), a total of one or more elements selected from iron (Fe), silicon (Si), gallium (Ga), and vanadium (V) is 2 mass ppm or more and 100 mass ppm or less; and a wire drawing step of wire drawing the aluminum alloy, in a cross section perpendicular to a length direction of the aluminum wiring material, an orientation ratio of crystal orientation <112> having an angle difference of 10° or less with respect to the length direction is 30% or less, an average crystal grain diameter in the cross section is 60 μm or less, a load stress ratio defined by (1) below is 0.4 or more and 0.9 or less, ​ Load stress ratio = fatigue limit / tensile strength (1) The yield strength ratio defined by the following (2) exceeds 1.0 and is 2.0 or less, Yield strength ratio = maximum stress / 0.2% yield strength (2).

7. A method for producing an aluminum wiring material, wherein The process has: A preparation step of preparing an aluminum alloy composed of aluminum having a purity of 99.9 mass% or more and less than 99.999 mass%, contains one or more selected from element groups (a), (b), and (c), In element group (a), the total of elements selected from one or more of nickel (Ni), zirconium (Zr), and scandium (Sc) is 5 mass ppm or more and 1000 mass ppm or less, In element group (b), the total of elements selected from one or more of magnesium (Mg), chromium (Cr), tungsten (W), copper (Cu), and titanium (Ti) is 2 mass ppm or more and 100 mass ppm or less, In element group (c), the total of elements selected from one or more of iron (Fe), silicon (Si), gallium (Ga), and vanadium (V) is 2 mass ppm or more and 100 mass ppm or less; and A wire drawing process of performing wire drawing on the aluminum alloy under conditions where the cross-sectional reduction ratio, that is, the processing rate, of each die is 3% or more and 40% or less, In a cross section of the aluminum wiring material perpendicular to the length direction, The orientation ratio of crystal orientation <112> having an angle difference of 10° or less with respect to the length direction is 30% or less, The average crystal grain diameter in the cross section is 60 μm or less, The load stress ratio defined by the following (1) is 0.4 or more and 0.9 or less, Load stress ratio = fatigue limit / tensile strength (1) The yield strength ratio defined by the following (2) exceeds 1.0 and is 2.0 or less, Yield strength ratio = maximum stress / 0.2% yield strength (2).

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