Micro-metal wires and their manufacturing methods, as well as assemblies, compositions, bonding structures, semiconductor devices, and electronic circuit components of micro-metal wires.

Abstract

This invention provides a fine metal wire with a sintering temperature lower than previously known. The length of the fine metal wire is 0.5 μm to 200 μm and the thickness is 30 nm to 10 μm. Regarding the crystallization of the metal constituting the fine metal wire, when the length along the extension direction of the fine metal wire is defined as X and the length along a direction orthogonal to the extension direction is defined as Y, at the three boundary regions where the length of the fine metal wire is divided into four equal parts along the extension direction, the ratio of X to Y, i.e., X / Y, is 4 or less.

Description

Technical Field

[0001] This invention relates to a fine metal wire. Prior Technology

[0002] Nanowires, due to their tiny size and high aspect ratio, are expected to exhibit physical and chemical properties (such as electrical conductivity, thermal conductivity, luminescence properties, and catalytic activity) that are not present in previous materials. Prior art related to the manufacture of such nanowires is known as described in Patent Document 1 or Non-Patent Document 1.

[0003] Patent Document 1 describes a method for manufacturing copper nanowires by adding hydrazine as a reducing agent to an aqueous solution containing ethylenediamine, o-phenylenediamine, and copper nitrate, thereby utilizing an electroless method. This method utilizes the fact that ethylenediamine and o-phenylenediamine readily adsorb onto the (001) and (111) surfaces of copper, but are difficult to adsorb onto the (110) surface, thus selectively precipitating copper onto the (110) surface to form a linear shape. Non-Patent Document 1 also describes a method for manufacturing copper nanowires using an electroless method. Previous technical documents Patent documents

[0004] Patent Document 1: International Publication No. 2015 / 097808 Non-patent literature

[0005] Non-patent literature 1: MJ Kim, et al., Journal of the American Chemical Society, 2017, vol. 139, pp. 277-284 Summary of the Invention

[0006] Regarding the copper nanowires manufactured by the method described in Patent Document 1, the formation mechanism results in copper crystals becoming elongated and larger single crystals preferentially aligned along the length direction of the

[0110] orientation of the nanowires. It is known that the sintering temperature of metal powder decreases as the crystal size decreases. Therefore, it is not easy to lower the sintering temperature of copper nanowires manufactured by the method described in Patent Document 1, where the crystal size will inevitably increase.

[0007] Therefore, the objective of this invention is to provide a fine metal wire whose sintering temperature is lower than before, or whose resistance decreases after heat treatment when the heating temperature is the same as before.

[0008] This invention provides a fine metal wire with a length of 0.5 μm to 200 μm and a thickness of 30 nm to 10 μm. Regarding the crystallization of the metal constituting the aforementioned fine metal wire, when the length along the extension direction of the fine metal wire is defined as X, and the length along the direction orthogonal to the extension direction is defined as Y, the arithmetic mean of the ratio of X to Y of the aforementioned crystal, i.e., the value of X / Y, is 4 or less at the three junction regions where the length of the fine metal wire is divided into four equal parts along the extension direction of the fine metal wire.

[0009] This invention provides a fine metal wire with a length of 0.5 μm to 200 μm and a thickness of 30 nm to 10 μm. Regarding the crystallization of the metal constituting the aforementioned fine metal wire, when the length along a direction orthogonal to the extension direction of the fine metal wire is defined as Y, the arithmetic mean of Y of the crystallization at the three junction regions where the length of the fine metal wire is divided into four equal parts along the extension direction of the fine metal wire is less than 10 nm.

[0010] Furthermore, the present invention provides a fine metal wire with a length of 0.5 μm to 200 μm and a thickness of 30 nm to 10 μm. At the three junctions where the length of the aforementioned fine metal wire is divided into four equal parts along the extension direction of the aforementioned fine metal wire, the proportion of crystals constituting the metal wire within ±30° of the extension direction of the fine metal wire, as evaluated by electron diffraction or electron beam backscattering diffraction using a transmission electron microscope, is less than 50% in the orientation of

[0110] .

[0011] Furthermore, the present invention provides a method for manufacturing fine metal wires, which is a method for manufacturing fine metal wires using metal as the base material. This method includes the step of using an electrolyte containing a metal element source to electrolytically reduce and deposit the metal onto the cathode. Electrolytic reduction is performed while the surface of the cathode is covered with an oily substance. Simple Explanation of the Diagram

[0012] Figure 1 is a scanning electron microscope image of the fine metal wire obtained in Example 1. Figure 2 is a scanning electron microscope image of the fine metal wire obtained in Comparative Example 1. Figure 3 is a grain map of the backscattered electron beam diffraction of the fine metal wire obtained in Example 1 (EBSD). Figure 4 is a grain map of the fine metal wire obtained in Comparative Example 1, obtained by backscattering of an electron beam (EBSD). Implementation

[0013] The present invention will now be described based on preferred embodiments. The present invention relates to a fine metal wire. In the following description, when referring to a "fine metal wire," the term may refer to a single wire or an assembly of multiple wires, depending on the context. The fine metal wire of the present invention uses metal as its constituent material. Typically, the fine metal wire extends in one direction. The state in which the wire extends in one direction varies depending on how it is observed. For example, the wire may extend in a straight line, or it may be curved while extending in one direction. The wire is characterized by being very thin, yet relatively long.

[0014] The micro-metallic wires are very fine, preferably with a thickness of 30 nm to 10 μm, more preferably 30 nm to 1000 nm, further preferably 40 nm to 500 nm, and even more preferably 45 nm to 300 nm. Despite their fineness, the micro-metallic wires are also long, preferably 0.5 μm to 200 μm, further preferably 1 μm to 100 μm, and even more preferably 2 μm to 70 μm. By combining this thickness and length, the micro-metallic wires exhibit excellent properties, such as superior filling performance when used as bonding materials. Furthermore, the aspect ratio (length of the fine metal wire [m] / thickness of the fine metal wire [m]) is preferably 5 to 5000, more preferably 10 to 5000, further preferably 20 to 5000, further preferably 20 to 3000, and even more preferably 20 to 1500. The thickness of the fine metallic wires is the arithmetic mean obtained from reading the thickness of more than 10 wires in the electron microscope image. The length is the arithmetic mean obtained from reading the length of more than 20 wires in the electron microscope image.

[0015] The fine metal wires can take the form of having a substantially uniform thickness along their entire length, or a bead-like form with varying thicknesses. Preferably, the fine metal wires have at least one pointed end. The term "pointed end" refers to the shape that tapers towards the tip when the end region of the fine metal wire is observed. By making at least one end of a fine metal wire into a pointed shape, when the fine metal wire is used, for example, as a raw material for wiring materials, the connection in the extension direction (hereinafter also referred to as the "length direction") of the fine metal wire can be made on the side of the tapered portion, rather than on the cross-section of the fine metal wire. That is, it has the following advantages: the side surface area of ​​the wire is larger than the cross-sectional area of ​​the wire, thus increasing the contact area of ​​the fine metal wire and reducing the resistance at the interface. Furthermore, from the viewpoint of reducing the gap between the fine metal wires, it is also easier to reduce resistance. From the perspective of making this advantage more obvious, the angle of the front end of the pointed shape is preferably less than 60 degrees, more preferably less than 50 degrees, and even more preferably less than 45 degrees. Furthermore, the so-called "extension direction of the fine metal wire" refers to the length direction of the fine metal wire as described above, and when it has a curved part, it refers to its tangential direction.

[0016] The angle of the pointed tip is determined in the following order: First, the thickness of the fine metal wire is determined based on an electron microscope image, as described above. Next, an arc with a diameter equal to the thickness of the fine metal wire is drawn, centered on the tip of the fine metal wire, obtaining two points where the arc meets the fine metal wire. These two points are then connected to the tip of the fine metal wire with a straight line, and the angle between them is measured as the angle of the tip. Furthermore, when the cross-section of the tip of the fine metal wire is straight or nearly straight, its center is taken as the tip. Also, when the cross-section of the tip of the fine metal wire is straight or nearly straight, if its cross-sectional length exceeds half the thickness of the fine metal wire, the fine metal wire is excluded from the measurement. This measurement was performed on 10 or more fine metal wires, and the arithmetic mean of their values ​​was used as the angle of the tip of the pointed shape.

[0017] The shape of a fine metal wire is typically a wire extending in one direction, but it may have a main chain extending in one direction and branching structures branching off from the main chain, or it may not have such branching structures. To impart sufficient conductivity to an object with a small amount, and to ensure that the conductivity of the object does not easily decrease when it is stretched or bent, the fine metal wire is preferably a non-branched structure with only a main chain. On the other hand, to give the aggregate of fine metal wires a loose structure, the fine metal wires preferably have one or more branching sections.

[0018] There are no particular restrictions on the types of metals constituting the fine metallic wires; various metals can be used. However, considering the balance between high conductivity and ease of industrial application, it is preferable to select at least one metal from the group consisting of copper, silver, gold, nickel, lead, palladium, platinum, cobalt, tin, iron, bismuth, and zinc, or an alloy containing that metal. Alternatively, the wires can be formed by mixing the crystals or alloys of these multiple metals. Among these, wires using copper or copper alloys, or zinc or zinc alloys as the base material are particularly preferred, and those using copper or copper alloys as the base material are especially desirable. Furthermore, "using copper or zinc as the base material" means that the proportion of copper or zinc in the fine metallic wires is 80% by mass or more. Moreover, a state of mixing the crystals or alloys of multiple metals can include, for example, a state where different types of metal crystals are linked together, such as Cu crystal-Zn crystal-Cu crystal-Zn crystal.

[0019] The fine metal wire may also have the following structure: a body portion containing a first metal element or an alloy containing the first metal element; and a coating layer of a second metal element other than the first metal element disposed on the surface of the body portion. As described above, examples of the first metallic element include copper, silver, gold, nickel, lead, palladium, platinum, cobalt, tin, iron, bismuth, and zinc. Examples of the second metallic element, which differs from the first metallic element, include silver, cobalt, iron, nickel, zinc, lead, tin, platinum, gold, palladium, copper, bismuth, and alloys containing one or more of these metals (e.g., nickel alloys, iron alloys, etc.). It is preferable that the conductivity of the second metallic element is higher than that of the first metallic element constituting the body or the alloy of that metallic element, thereby further improving the conductivity imparted to the object. From this perspective, it is preferable that when the first metallic element is, for example, copper or zinc, the second metallic element is silver.

[0020] To form a coating on the surface of the body, methods such as the following can be used: forming the body using the following methods and then electroplating it in an electrolyte containing a metal element for coating; coating the target metal onto a fine metal wire using a displacement plating or electroless plating method; or a dry method. Alternatively, the surface of the wire can be treated with an organic agent.

[0021] The crystalline structure of the fine metal wire of the present invention differs from that of currently known fine metal wires. Specifically, the fine metal wire of the present invention is a polycrystalline structure formed by multiple crystals connected along the extension direction of the wire. In contrast, currently known fine metal wires, such as the fine metal wire manufactured by an electroless method as described in Patent Document 1, have a single-crystal structure with longer and larger crystals along the extension direction of the wire. Furthermore, due to its characteristic crystalline structure, the fine metal wire of the present invention allows for a lower sintering temperature than previously known. Alternatively, when heat treatment is performed at the same heating temperature as previously known fine metal wires, the resistance of the sintered portion after heat treatment can be lower than previously known.

[0022] The crystal structure of the fine metal wire of the present invention will be described in detail below. Regarding the crystal structure of the metal constituting the fine metal wire, when the length along the length direction of the fine metal wire is defined as X, and the length along the direction orthogonal to the length direction (hereinafter also referred to as the "width direction") is defined as Y, the ratio of X to Y, i.e., the value of X / Y, is preferably 4 or less. Thus, the metal crystals constituting the fine metal wires of the present invention exhibit a generally isotropic shape, with little difference between the length in the length direction and the length in the width direction. Since the thickness of the fine metal wires of the present invention is, as described above, 30 nm to 10 μm, it can be understood that the metal crystals constituting these fine metal wires are relatively fine. Because the metal crystals constituting the fine metal wires of the present invention have this structure, as described above, the fine metal wires of the present invention can achieve a lower sintering temperature than before. Alternatively, when heat treatment is performed at the same heating temperature as for previous fine metal wires, the resistance of the sintered portion after heat treatment can be lower than before. From the perspective of making this advantage more obvious, the value of X / Y is even better to be 3 or less. The X / Y values ​​mentioned above are calculated as follows: by dividing the length of the fine metal wire into four equal parts along its length, the X / Y values ​​of the crystals located at the three junction regions are calculated, and their arithmetic mean is obtained. The first decimal place of the arithmetic mean is rounded to the nearest whole number.

[0023] The term "crystal" as used in this specification refers to a grain, the size of which can be obtained from a grain pattern obtained by electron beam backscattering diffraction (hereinafter also referred to as "EBSD"). It should be noted that the concept of a grain differs from the crystallite size determined from an XRD (X-ray diffraction) pattern. When the crystal described in this specification is a twin crystal, each crystal constituting the twin is defined as a different crystal, and the X / Y values ​​are determined for each crystal.

[0024] When the X / Y value is 4 or less, there is no restriction on the values ​​of X and Y. From the perspective of achieving a sintering temperature lower than previously considered, the value of X is preferably 10 μm or less, more preferably 5 nm or more and 2 μm or less, and even more preferably 10 nm or more and 500 nm or less. Similarly, from the same perspective, the value of Y is preferably 3 μm or less, more preferably 5 nm or more and 1 μm or less, even more preferably 10 nm or more and 400 nm or less, and even more preferably 10 nm or more and 200 nm or less.

[0025] The characteristic of the fine metal wires of the present invention is also reflected only in the value of Y mentioned above. That is, the value of Y is preferably below 10 nm. The term "Y = 10 nm or less" refers to a finer state, expressed in terms of the number of metal atoms, resulting in a width of only 100 or fewer atoms. This is the same design concept as setting the X / Y value to 4 or less, and has the same meaning as finer crystals. Therefore, with the fine metal wire of the present invention, the sintering temperature can be lower than before. Alternatively, when heat treatment is performed at the same heating temperature as with the previous fine metal wire, the resistance of the sintered portion after heat treatment can be lower than before. Furthermore, if Y = 10 nm or less, the value of X / Y can be any value. The value of Y mentioned above is obtained as follows: by dividing the length of the fine metal wire into four equal parts along its length, the Y values ​​of the crystals located in the three junction regions are calculated, and their arithmetic mean is obtained. The first decimal place of the arithmetic mean is rounded to the nearest whole number.

[0026] The characteristics of the fine metal wires of this invention are also reflected in the orientation of the crystals of the metals that constitute them. In detail, when the length of the micro-metal wire of the present invention is divided into four equal parts along the extension direction of the micro-metal wire, and considering the crystals located in the three junction regions, the proportion of grains with the

[0110] orientation obtained by electron diffraction of transmission electron microscopy (hereinafter also referred to as "TEM") or EBSD within ±30° of the extension direction of the micro-metal wire is preferably 50% or less, more preferably 45% or less, and more preferably 40% or less. Satisfying this relationship means that the

[0110] orientation of the crystals is not preferentially aligned in the length direction of the micro-metal wire. The proportion of grains constituting the

[0110] orientation is calculated by randomly selecting two or more fine metal wires, drawing boundary lines that divide the length of each fine metal wire into four equal parts along its length direction, and measuring the three boundary regions of the boundary to calculate the proportion. When the evaluation is performed by electron diffraction of TEM, the percentage of the presence of the grains constituting the

[0110] orientation is the percentage of the grains constituting the

[0110] orientation obtained by measuring a total of 6 or more midpoints of the boundary lines of each boundary region (for example, 6 when 2 fine metal wires are selected, and 15 when 5 fine metal wires are selected). When using EBSD for evaluation, measurements are taken at 18 or more points in total, where the boundary line is divided into four equal parts in each boundary region (for example, 18 points when 2 fine metal wires are selected, and 45 points when 5 fine metal wires are selected). Round the first decimal place of the percentage. When observing the grains constituting the

[0110] orientation using TEM, electrons are allowed to penetrate a fine metal wire for observation. However, if the thickness of the fine metal wire is 200 nm or more, electrons will not penetrate the fine metal wire, and the target electron diffraction pattern cannot be obtained. Therefore, when the thickness of the fine metal wire is 200 nm or more, the presence ratio of the grains constituting the

[0110] orientation is evaluated using EBSD.

[0027] In contrast, currently known fine metal wires, such as the fine metal wires manufactured by an electroless method as described in Patent Document 1, have a manufacturing method that preferentially aligns the

[0110] orientation along the length direction of the wire. Furthermore, Non-Patent Document 1 also reports the synthesis of fine metal wires by an electroless method. As described in the comparative examples below, experiments conducted by the inventors show that the fine metal wires synthesized by the electroless method in Non-Patent Document 1 also exhibit a

[0110] orientation preferentially aligned along the length direction. Non-Patent Document 1 states that the side surface of this fine metal wire is a (100) surface. Non-Patent Document 1 also states that the (100) surface is more easily oxidized than other surfaces, resulting in the formation of an oxide film on the surface. That is, the side surface of the fine metal wire with the

[0110] orientation preferentially aligned along the length direction is easily oxidized, which is one of the reasons for the increased resistance in the width direction of the fine metal wire. Therefore, the fine metal wire of the present invention, which is not grown in the

[0110] orientation along the length direction, has the advantage of being less prone to oxidation. According to the present invention, the fine metal wire whose crystal orientation

[0110] is not preferentially aligned in the length direction, the sintering temperature can be lower than before due to its characteristic crystal structure. Alternatively, when heat treatment is performed at the same heating temperature as the previous fine metal wire, the resistance of the sintered part after heat treatment can be lower than before.

[0028] Regarding the view that the sintering temperature is lower than previously, when the length of the fine metal wire is divided into four equal parts along the extension direction of the fine metal wire, the crystallization in the three junction regions is preferably within ±30° of the extension direction of the fine metal wire, and the presence ratio of the grains in the

[0111] orientation obtained by evaluation by TEM electron diffraction or EBSD is 50% or more, more preferably 52% or more, more preferably 60% or more, and even more preferably 70% or more. The proportion of grains constituting the

[0111] orientation is calculated by randomly selecting two or more fine metal wires, drawing boundary lines that divide the length of each fine metal wire into four equal parts along its length direction, and measuring the three boundary regions of the boundary to calculate the proportion. When the evaluation is performed by electron diffraction of TEM, the percentage of the presence of the grains constituting the

[0111] orientation is the percentage of the grains constituting the

[0111] orientation obtained by measuring a total of 6 or more midpoints of the boundary lines of each boundary region (for example, 6 when 2 fine metal wires are selected, and 15 when 5 fine metal wires are selected). When evaluating using EBSD, measurements are taken at least 18 points in total, where the boundary is divided into four equal parts by a line in each boundary region (for example, 18 points when selecting 2 fine metal wires, and 45 points when selecting 5 fine metal wires). Round the first decimal place of the percentage. This relationship means that the

[0111] orientation is preferentially aligned along the length of the fine metal wire. The preferential alignment of the

[0111] orientation of the crystal along the length means that, in terms of crystallography, its side faces are not exposed (100) planes, which is preferred.

[0029] Furthermore, when the length of the fine metal wire is divided into four equal parts along the extension direction of the fine metal wire, the crystals located in the three junction regions are preferably within ±30° of the extension direction of the fine metal wire, and the proportion of grains in the

[0100] ,

[0110] and

[0111] orientations obtained by evaluation by electron diffraction of TEM or EBSD is 50% or less, and more preferably 40% or less. The ratio of the number of grains in the

[0110] ,

[0111] , and

[0100] orientations is calculated by randomly selecting two or more fine metal wires, drawing boundary lines that divide the length of each fine metal wire into four equal parts along its length, and measuring the three boundary regions of the boundary to calculate the ratio. When the evaluation is performed by electron diffraction of TEM, the percentage of the presence of grains in the

[0110] ,

[0111] , and

[0100] orientations is the percentage of grains in the

[0110] ,

[0111] , and

[0100] orientations obtained by measuring at a total of 6 or more midpoints of the boundary lines of each boundary region (for example, 6 when 2 fine metal wires are selected, and 15 when 5 fine metal wires are selected). When using EBSD for evaluation, measurements are taken at least 18 points in total, where the boundary line is divided into four equal parts in each boundary region (for example, 18 points when selecting 2 fine metal wires, and 45 points when selecting 5 fine metal wires). Round the first decimal place of the percentage.

[0030] This relationship implies that the crystals of the metal constituting the fine metal wires are randomly oriented. The random orientation of the crystals in the fine metal wires means that the crystals are polycrystalline, implying smaller crystal size. As mentioned above, smaller crystal size leads to lower sintering temperatures. Furthermore, the "random orientation of the crystals" means that the side surface (100) of the wires is not preferentially exposed, meaning that oxidation of the side surface of the fine metal wires will not be promoted.

[0031] When the micro-metal wire of the present invention is an assembly comprising a plurality of micro-metal wires, the assembly preferably has micro-metal wires having a curved portion with a radius of curvature of less than 5 times the length of the micro-metal wires accounting for 5% or more of the total number of micro-metal wires in the assembly, more preferably 20% or more, more preferably 40% or more, and even more preferably 60% or more. This facilitates contact across the plurality of micro-metal wires in the transverse (width) direction, resulting in a low-resistance assembly of micro-metal wires, which is preferable in this respect. The radius of curvature is calculated as follows: A fine metal wire is observed using a scanning electron microscope (SEM). The two ends of the fine metal wire are connected by a straight line, and its length (chord length) is measured. Then, an auxiliary line orthogonal to the straight line is drawn from the midpoint of the line toward the side of the fine metal wire, and the distance (curvature) between the midpoint and the point where the line intersects the fine metal wire is measured. The radius of curvature is then calculated using the following formula. r=(C×C) / (8×h)+h / 2 (In the formula, r represents the radius of curvature, C represents the chord length, and h represents the curvature) The aforementioned radius of curvature is preferably between 0.5 μm and 1000 μm. Furthermore, when the micro-metal wire is bent, the micro-metal wire is brought close to the shape of the bent portion, and the radius of curvature is calculated according to the above formula. Also, when the two ends of the micro-metal wire are connected by a straight line, and the straight line cuts across the micro-metal wire, the radius of curvature is measured for different micro-metal wires, with the cut portion as the boundary.

[0032] When the fine metal wire of the present invention is an assembly comprising a plurality of fine metal wires, the assembly may contain particles having shapes other than wires. However, from the viewpoint that conductivity is not easily reduced even when deformations such as bending or stretching occur, it is preferable that particles having shapes other than wires are as non-wire-like as possible are absent from the aforementioned assembly. When the ratio of particles with shapes other than linear bodies in the above-mentioned aggregate is defined as the "irregularity rate", the irregularity rate is preferably 50% or less, more preferably 40% or less, further preferably 30% or less, further preferably 10% or less, and even more preferably 2% or less. If the fine metal linear bodies are manufactured by the following manufacturing method, the irregularity rate can be easily made to be 50% or less. The irregularity rate can be determined by observing the test specimen in both the longitudinal and transverse directions using SEM within a field of view 5 to 30 times the average length of the fine metal filaments, and calculating the percentage of [area of ​​irregularities / area of ​​the filaments]. "Irregularity" refers to shapes other than filaments (e.g., spherical, blocky, fern-like, etc.).

[0033] Next, a preferred method for manufacturing the fine metal wires of the present invention will be described. Electrolysis is preferred for manufacturing the fine metal wires. This is because electrolysis not only makes it easy to control the desired shape, but also allows for repeated use of the electrolyte. Only a small amount of liquid is needed when manufacturing the fine metal wires, reducing the amount of waste liquid that needs to be treated simultaneously. Other methods for manufacturing metal powder include atomization, but these cannot produce anisotropic shapes like fine metal wires. Furthermore, wet reduction (non-electrolytic reduction) is another method, but this method cannot repeatedly use the solution and cannot increase the concentration of the target metal element above a certain fixed value, thus hindering the productive production of fine metal wires.

[0034] When manufacturing fine metal wires by electrolysis, the following steps can be illustrated: immersing the anode and cathode in an acidic sulfuric acid electrolyte containing a metal element source, introducing a direct current to perform electrolytic reduction to deposit the fine metal wires onto the cathode surface, scraping off and recovering the deposited fine metal wires by mechanical or electrical methods, washing the recovered fine metal wires with water or an organic solvent, drying them, and screening them as needed.

[0035] The types of metallic elements used in this manufacturing method are not particularly limited as long as they can be used to manufacture fine metallic wires. Considering the balance between high conductivity and ease of industrial application, the following can be listed: copper, silver, gold, nickel, lead, palladium, platinum, cobalt, tin, iron, bismuth, and zinc. These metallic elements share the characteristic that they can be electrolytically extracted from aqueous solutions; therefore, regardless of the metallic element used, the manufacturing process can be carried out in the same manner according to this method. Copper or copper alloys, or zinc or zinc alloys, are particularly preferred as the base material. The fine metal wire obtained by this manufacturing method may, for example, contain only the target metal element except for unavoidable impurities, or may be an alloy containing the target metal element except for unavoidable impurities. Furthermore, it may be configured as a combination of two or more of the aforementioned metal elements except for unavoidable impurities.

[0036] The inventors' research indicates that, when manufacturing fine metal wires in the above-described order, it is advantageous to perform electrolytic reduction while an oily substance is adhered to the cathode surface. By reducing metal ions under these conditions, the reduction reaction can be controlled. Details are as follows. Regarding the oily substance adhering to the cathode surface, if expressed in terms of thickness, its average thickness is several hundred nm or more, preferably several μm to several hundred μm. However, its thickness can vary locally due to factors such as electrolyte movement. Although metal ions hardly coexist in the oily substance, electrolyte containing metal ions may be suspended in the oily substance as droplets, or a very small amount of electrolyte may be intermittently attracted to the vicinity of the electrode by the force of the electric field generated by the applied electricity. Under these conditions, a metal reduction reaction occurs on the cathode surface, producing locally deposited metal protrusions. The thickness of the oily substance directly above these protrusions is thinner than in other areas, thus the resistance in that area decreases, the current concentrates there, and the protrusion becomes a filament and grows. In this way, fine metal filaments are formed through electrolysis. As the fine metal wires continue to grow, they droop due to their own weight, making them prone to bending. Alternatively, the resistance of the oily substance may hinder the straight growth of the fine metal wires, making them prone to bending. Essentially, fine metal wires are formed through electrolysis based on the above mechanisms; the detailed shape or structure will vary depending on the type of oily substance used. Similar to the electrolytic deposition of ordinary metals, the shape will also vary depending on the composition of the electrolyte or additives.

[0037] Methods for attaching oily substances to the surface of the cathode include: directly coating the cathode surface with the oily substance; immersing the cathode in a container containing the oily substance and attaching it; floating the oily substance on the electrolyte and immersing the cathode from above to attach the oily substance to the cathode surface; etc. Furthermore, methods such as suspending the oily substance in the electrolyte and stirring the suspended electrolyte to cause the suspended oily substance to collide with the cathode surface and directly attach to it are also possible. Additionally, if the oily substance has the property of dissolving in a small amount in the electrolyte, even if the suspended oily substance does not directly contact the electrode, the temporarily dissolved oily substance will continuously adsorb onto the electrode surface, ultimately exhibiting the same effect as surface attachment.

[0038] By using the above method to manufacture fine metal wires, the fine metal wires become a polycrystalline structure formed by multiple crystals connected along the length direction. Furthermore, the

[0110] orientation of the crystals becomes less likely to preferentially align along the length direction. Consequently, in the fine metal wires, the

[0111] orientation of the crystals becomes more likely to preferentially align along the length direction, or the orientation direction of the crystals becomes more likely to become random. Furthermore, by using the above methods to manufacture fine metal wires, the generation of irregular particles with shapes other than wires can be suppressed to the greatest extent.

[0039] As an oily substance to be attached to the surface of the cathode, various organic compounds can be listed below. These organic compounds are sparingly soluble or insoluble in water and have a viscosity sufficient to remain on the cathode surface after attachment. Furthermore, "sparingly soluble or insoluble in water" means that at the temperature at which the fine metal wires are manufactured, they exhibit a solubility of less than 100 g relative to 1 L of water. As an oily substance, it can be listed in liquid or solid form. Oily substances can also be used if dissolved in a liquid solvent at room temperature (20~30℃). Furthermore, in order to easily control the physical properties of the precipitated fine metal wires, additives such as benzoic acid, fumaric acid, citric acid, and benzotriazoles can be used in the above-mentioned oily substances.

[0040] Examples of the aforementioned organic compounds that exhibit poor or insoluble solubility in water include: aliphatic hydrocarbons, aromatic hydrocarbons, aliphatic alcohols, aromatic alcohols, aliphatic aldehydes, aromatic aldehydes, aliphatic ethers, aromatic ethers, aliphatic ketones, aromatic ketones, aliphatic carboxylic acids and their salts, aromatic carboxylic acids and their salts, amides of aliphatic carboxylic acids, amides of aromatic carboxylic acids, esters of aliphatic carboxylic acids, esters of aromatic carboxylic acids, silicones (e.g., dimethyl silicone), aliphatic amines, aromatic amines, nitrogen-containing heterocyclic compounds, tributyl phosphate, thiols, fluorinated solvents, ionic liquids, etc. Furthermore, the term "aliphatic alcohol" as used in this specification refers to alcohols with 5 or more carbon atoms. The inventors' research results indicate that fine metal wires can be manufactured more smoothly if fatty acids or their salts, esters or their amides, aromatic carboxylic acids, aliphatic hydrocarbons, aliphatic alcohols, aliphatic amines, silicones (e.g., dimethyl silicone), or mixtures thereof are used as oily substances.

[0041] As examples of the aforementioned fatty acids, lower fatty acids and higher fatty acids can be listed. Lower fatty acids can be saturated or unsaturated aliphatic carboxylic acids, preferably with 9 or fewer carbon atoms. Higher fatty acids can be saturated or unsaturated aliphatic carboxylic acids, preferably with 10 to 25 carbon atoms, more preferably with 10 to 22 carbon atoms, and even more preferably with 11 to 20 carbon atoms. Examples of saturated aliphatic carboxylic acids include: hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptanoic acid, octadecanoic acid, nonadecanoic acid, icosanoic acid, icosanoic acid, didecanoic acid, tridecanoic acid, and tetradecanoic acid.

[0042] As unsaturated aliphatic carboxylic acids, those with one or more unsaturated carbon bonds in their molecules can be listed. Examples of unsaturated aliphatic carboxylic acids with one unsaturated carbon bond in their molecules include: butenoic acid, myristoleic acid, palmitoleic acid, hexadecenoic acid, oleic acid, transoleic acid, isoleic acid, codoleic acid, eicosenoic acid, erucic acid, and icosenoic acid. Examples of unsaturated aliphatic carboxylic acids with two or more unsaturated carbon bonds include linoleic acid, eicosadienoic acid, and linolenic acid.

[0043] Examples of aromatic carboxylic acids include: benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,2,3-triphenylcarboxylic acid, trimellitic acid, 1,3,5-triphenylcarboxylic acid, 1,2,3,5-benzenetetracarboxylic acid, 1,2,3,4-benzenetetracarboxylic acid, pyromellitic acid, hexabenzoic acid, biphenylcarboxylic acid, toluene, succinic acid, 2,3-dimethylbenzoic acid, 3,5-dimethylbenzoic acid, 2,3,4-trimethylbenzenenic acid, γ-isobenzoic acid, isobenzoic acid, β-isobenzoic acid, 2,4,6-trimethylbenzoic acid, α-isobenzoic acid, anisolic acid, and 5-methylisophthalic acid. α-Toluic acid, hydroatroic acid, atroic acid, hydrocinnamic acid, cinnamic acid, salicylic acid, anisic acid, cresol carboxylic acid, o-salicylic acid, o-cresol carboxylic acid, m-salicylic acid, m-cresol carboxylic acid, p-salicylic acid, p-cresol carboxylic acid, o-pyrocatechinic acid, β-resorcinic acid, 2,5-dihydroxybenzoic acid, γ-resorcinic acid, protocatechinic acid, α-resorcinic acid, vanillic acid, isovanillic acid, veratric acid, o-veratric acid, sphygmonic acid, m-semipigmentic acid, gallic acid, syringic acid, asaric acid, mandelic acid, vanillylmandelic acid, p-methoxyphenylacetic acid, 2,5-dihydroxyphenylacetic acid, high-altitude catechinic acid, homovanillic acid, isohomovanillic acid High-purine acid, o-high-purine acid, high-phthalic acid, high-isophthalic acid, p-phthalic acid, phthaloyl ketone acid, isophthaloyl ketone acid, p-phthaloyl ketone acid, diphenylethanolic acid, 2-phenyllactic acid, belladonnaic acid, o-hydroxydihydrocinnamic acid, phloroglucinic acid, hydrogenated caffeic acid, hydrogenated ferulic acid, hydrogenated isoflavone acid, p-coumaric acid, umbelliferic acid, caffeic acid, ferulic acid, isoflavone acid, sinapic acid, benzoic acid, phthalic acid, isophthalic acid, p-phthalic acid, toluene, xylene, cumyl, α-toluene, hydrogenated atropine, 2-phenylpropenyl ketone, benzoyl propionate, cinnamic acid, o-hydroxybenzoic acid, anisole, creosote (C resotoyl), pyrocatechoyl, β-resorcyloyl, gentisoyl, γ-meta-dihydroxyyl, protocatechoyl, α-meta-dihydroxyyl, vanilla, isovanilla, veratrum, gallic acid, syringin, amygdalin, vanilla amygdalin, high gentian, high vanilla, high veratrum, diphenylethanol, tropine, caffeine, asafoetida, peroxybenzoic acid, ibuprofen, ketoprofen, biphenylacetic acid.

[0044] Of the fatty acids mentioned above, saturated or unsaturated aliphatic carboxylic acids are preferred as they can more easily produce fine metallic filaments.

[0045] The esters of the aforementioned fatty acids are preferably esters with saturated or unsaturated aliphatic alcohols. The alcohol preferably has 1 to 18 carbon atoms. More preferably, the esters of the aforementioned fatty acids are esters with saturated aliphatic alcohols having 1 to 18 carbon atoms. Ethyl acetate is an example of such an ester with a saturated aliphatic alcohol having 1 to 18 carbon atoms.

[0046] Regarding the amount of oily substance adhering to the surface of the cathode, it is preferably set to 0.1 g / m2 or more and 500 g / m2 or less per unit surface area of ​​the cathode, more preferably 1 g / m2 or more and 500 g / m2 or less, further preferably 3 g / m2 or more and 200 g / m2 or less, and even more preferably 5 g / m2 or more and 100 g / m2 or less.

[0047] As for the materials of the anode and cathode, there are no particular restrictions on the use of currently known materials. For example, anodes and cathodes containing titanium or copper can be used. Insoluble metal electrodes (DSEs) can also be used as the anode. Relatedly, the current density during reduction is preferably set to 5 A / m² to 3000 A / m², more preferably 10 A / m² to 1000 A / m², and even more preferably 50 A / m² to 500 A / m².

[0048] Typically, when metal is deposited by electrolysis, an electric current is applied at a rate that is slower than the rate at which metal ions are supplied from the electrolyte, thereby obtaining a good surface shape (e.g., a metallic luster on the surface in the case of plating). Similarly, in the electrolysis of the present invention, the concentration of metal ions in the electrolyte is preferably such that the concentration of metal ions supplied is precisely at the rate of metal ion reduction reaction. From this point of view, the concentration of metal ions is preferably 1 g / L or more and 80 g / L or less, and more preferably 1 g / L or more and 60 g / L or less. From the same point of view, it is preferable to stir the electrolyte or circulate it in the electrolytic cell during electrolysis. The electrolyte can be used at room temperature (25°C) or under heating conditions. Furthermore, from the same perspective, it is preferable to make the following adjustments: adjusting the size of the electrolytic cell, the number of electrodes, the shape of the electrodes (plate-shaped, roller-shaped), the distance between the electrodes, the oscillation of the electrodes, and the circulation volume of the electrolyte, so as to maintain the concentration of metal ions in the electrolyte near the electrodes at a high level in advance.

[0049] The fine metal wires of the present invention obtained by the above methods can be combined with other substances to impart conductivity to those substances. For example, the fine metal wires of the present invention can be combined with granular materials of the same or different metal elements to form a bonding material. Alternatively, a composition comprising the fine metal wires of the present invention and a dispersion medium can be used as a bonding material. These bonding materials can also be sintered to form a sintered body. These bonding materials and sintered bodies can, for example, be used as materials for bonding semiconductor devices to substrates.

[0050] Specifically, in a joining structure having a first component, a second component, and a joining portion for joining the first component and the second component, the joining portion can be formed by a sintered body comprising a composition of the fine metal wires and a dispersion medium of the present invention. Alternatively, in a semiconductor device having a first component, a second component, and a joining portion for joining the first component and the second component, a semiconductor element can be used as at least one of the first component and the second component, and the joining portion can be formed by a sintered body comprising a composition of the fine metal wires and a dispersion medium of the present invention.

[0051] The fine metal wires of the present invention can also be used to manufacture electronic circuit components. For example, in electronic circuit components having a substrate and a conductive pattern formed on the substrate, the conductive pattern can be formed from a sintered body comprising a composition of the fine metal wires of the present invention and a dispersion medium.

[0052] Various organic solvents can be used as the dispersion medium in the above composition. Examples of such organic solvents include: monools, polyols, polyol alkyl ethers, polyol aryl ethers, esters, ketones, nitrogen-containing heterocyclic compounds, amides, amines, saturated hydrocarbons, etc. These organic solvents can be used alone or in combination of two or more.

[0053] Alternatively, the fine metal wires of the present invention can be contained in the resin to obtain a resin composition comprising the fine metal wires and the resin. The resin composition exhibits conductivity by containing the fine metal wires. To impart conductivity to a resin, one can simply disperse fine metal wires within it. Alternatively, a layer containing fine metal wires can be formed on the surface of a resin-containing substrate. Regardless of the form, the resin composition can be molded into various shapes. For example, it can be molded into one-dimensional shapes such as fibers; two-dimensional shapes such as films, plates, and strips; and various three-dimensional shapes. Regardless of the shape, the resin composition can exhibit sufficient conductivity by adding a relatively small amount of fine metal wires. The resin composition differs from previous conductive resin compositions using copper powder as a filler in that its conductivity decreases less before and after stretching or bending. From this perspective, the characteristics of the fine metal wires of this invention can be effectively utilized when the resin composition is stretchable or bendable. The conductivity of previous conductive resin compositions tends to decrease when stretched or bent.

[0054] As described above, the micro-metallic wires of the present invention can be used in various forms. Specific applications of the micro-metallic wires of the present invention include those requiring conductivity and deformability under external force, such as wearable devices and flexible displays that are attached to living organisms. Furthermore, the micro-metallic wires of the present invention can be used in low linear expansion wiring materials, anisotropic conductive films, anisotropic thermal conductive films, anode current collectors for lithium batteries, via plugging materials for through holes in printed circuit boards, sensors, switches, adsorption separation devices, electrode catalysts for various electrochemical reactions, and current collectors for power generation elements. [Example]

[0055] The present invention will be further described in detail below by way of embodiments. However, the scope of the present invention is not limited to these embodiments. Unless otherwise specified, "%" means "mass %".

[0056] [Example 1] In this embodiment, a wire containing copper is manufactured. An electrolyte was prepared using copper sulfate and sulfuric acid, with a copper ion concentration of 4 g / L and a free sulfuric acid concentration of 5 g / L. 800 mL of this electrolyte was placed into an electrolytic cell measuring 10 cm × 8 cm × 12 cm (approximately 1000 mL in capacity) and stirred. The electrolyte temperature was set to 40°C. An 8 cm × 8 cm copper plate was used as the cathode. Oleic acid was uniformly coated onto the surface of the cathode at a coating amount of 7 g / m². An 8 cm × 8 cm copper plate was used as the anode. The two electrodes were suspended in the electrolytic cell with an 8 cm gap between them. The current density was adjusted to 160 A / m² and electrolysis was performed for 30 minutes. This allowed copper to be electrodeposited onto the surface of the cathode. Copper electrodeposited on the cathode surface was recovered and washed with ethanol. SEM observation of the electrodeposited material confirmed the presence of filamentous structures. The ends of these filaments were tapered. The SEM image of the linear body obtained in this embodiment is shown in Figure 1. In this figure, a 30,000x SEM image is shown to observe the shape of the front end of the linear body.

[0057] [Example 2] The electrolyte was prepared by changing the concentration of copper ions to 1 g / L, and electrolysis was performed by changing the current density to 63 A / m². Except as described above, the electrodeposited material was obtained in the same manner as in Example 1. SEM observation of the electrodeposited material confirmed the presence of filamentous structures. The ends of these filamentous structures were tapered.

[0058] [Example 3] The electrolyte was prepared by changing the concentration of copper ions to 7 g / L, and electrolysis was performed by changing the current density to 63 A / m². Except as described above, the electrodeposited material was obtained in the same manner as in Example 1. SEM observation of the electrodeposited material confirmed the presence of filamentous structures. The ends of these filamentous structures were tapered.

[0059] [Example 4] The electrolyte was prepared by changing the concentration of copper ions to 10 g / L. Except as described above, the electrodeposited material was obtained in the same manner as in Example 1. SEM observation of the electrodeposited material confirmed the presence of filamentous structures. The ends of these filamentous structures were tapered.

[0060] [Example 5] An electrolyte was prepared by changing the concentration of copper ions to 40 g / L, and electrolysis was performed by changing the current density to 310 A / m². Except as described above, electrodeposit was obtained in the same manner as in Example 1. SEM observation of the electrodeposited material confirmed the presence of filamentous structures. The ends of these filamentous structures were tapered.

[0061] [Comparative Example 1] This comparative example corresponds to Non-Patent Literature 1. Add 40 mL of 15 mol / L sodium hydroxide aqueous solution, 0.30 mL of ethylenediamine, and 2.0 mL of 0.1 mol / L copper nitrate aqueous solution to a 100 mL four-necked flask, and stir with a stirrer. The concentration of ethylenediamine in the copper salt aqueous solution is 137 mmol / L. Set the heater to 40 °C and heat. Inject 50 μL of 35% hydrazine aqueous solution into the flask using a syringe. Stir with a stirrer for 60 minutes, then disconnect the heater. Then, cool in a water bath to below 30 °C to obtain filamentous solids. Filter to disperse in ethanol, perform ultrasonic dispersion, and let stand for 10 minutes. Separate the supernatant (suspended solids) from the precipitate. The SEM image of the linear body obtained in this comparative example is shown in Figure 2. In this figure, a 30,000x SEM image is shown to observe the shape of the anterior end of the linear body.

[0062] [Assessment 1] The length, thickness, and radius of curvature of the linear bodies obtained in Examples 1-5 and Comparative Example 1 were determined using the method described above. In particular, the thickness of the linear bodies was determined by taking the arithmetic mean of the thickness from at least 10 lines from the following SEM images at a magnification sufficient to measure the thickness: specifically, a 20,000x SEM image in Example 1, an 80,000x SEM image in Example 2, a 10,000x SEM image in Example 3, a 10,000x SEM image in Example 4, a 100x SEM image in Example 5, and a 20,000x SEM image in Comparative Example 1. Furthermore, the length should be obtained by taking the arithmetic mean of the lengths of at least 20 SEM images from the following SEM images, which are capable of fully measuring the magnification of the length. Specifically, the lengths are: 10,000 times in Example 1, 20,000 times in Example 2, 5,000 times in Example 3, 1,000, 2,000, and 5,000 times in Example 4, 100, 200, and 500 times in Example 5, and 5,000 times in Comparative Example 1. Furthermore, the irregularity rate of the linear aggregates obtained in Examples 1-5 and Comparative Example 1 was determined by the above method. Furthermore, the values ​​of X, Y, and X / Y, as well as the orientation of the crystallization, were determined using the following methods. These results are shown in Table 1 below.

[0063] [Regarding the values ​​of X, Y, and X / Y in crystallization, as well as the orientation of crystallization] The X, Y, and X / Y values ​​of the crystallization were determined using the following method. Fine metal wires were coated onto a copper plate using carbon paste. The coating was then cross-sectionally processed using an argon ion beam cross-section processing device (a cross-section polisher (CP) manufactured by NEC Corporation) to generate an EBSD grain map for observation of the cross-section. The carbon paste used was Colloidal Graphite (Isopropanol Base) from Electron Microscopy Sciences. EBSD was performed using a Carl Zeiss SEM Crossbeam 540 and an Oxford Symmetry EBSD detector mounted on the SEM Crossbeam 540. In the obtained grain map, the X and Y values ​​of the crystallization at three junctions where the length of the fine metal wires was divided into four equal parts along its length were measured with reference to a scale, and the X / Y value was calculated. This value was expressed as the arithmetic mean. Round the first decimal place of the arithmetic mean. The grain patterns of EBSD measured for the linear bodies of Example 1 and Comparative Example 1 are shown in Figures 3 and 4, respectively.

[0064] The orientation of the crystals was determined using the following method. For the fine metal wires of Examples 1 to 4 and Comparative Example 1, the fine metal wires were sprinkled onto a copper mesh and supported. Observation was performed using a JEM-ARM200F manufactured by Nippon Electronics Corporation. Boundary lines dividing the length of the fine metal wires into four equal parts along their extension direction were drawn. The shape was observed using a TEM at the midpoint of the boundary lines in the three boundary regions, simultaneously obtaining electron diffraction patterns. The orientation was determined using a digital micrograph manufactured by GATAN Corporation. Furthermore, for the fine metal wires of Example 5, after being mixed into carbon slurry, they were coated onto a copper plate, and the coating was cross-sectionally processed using an argon ion beam cross-section processing device (a cross-section polisher (CP) manufactured by Nippon Electron Ltd.). Observation was performed using a SEM Crossbeam 540 and an EBSD detector: Symmetry mounted on the SEM Crossbeam 540. A boundary line was drawn along the extension direction of the fine metal wires, dividing its length into four equal parts. At the three points in the three boundary regions that divide the boundary line into four equal parts, the orientation of the crystals was determined by EBSD. An AZtec Crystal 2.0 manufactured by Oxford Ltd. was used to determine the orientation of the crystals by EBSD. Determine whether each orientation (

[0100] orientation,

[0110] orientation, and

[0111] orientation) obtained by evaluation through electron diffraction of TEM or EBSD falls within ±30° of the extension direction or tangential direction of the fine metal wire (using the normal that is close to the ±30° range of each orientation and length direction for judgment; when two or more orientations fall within the ±30° range, the orientation closer to 0° is taken; and when none of the three orientations fall within the ±30° range, it is determined that there is no preferred alignment). Regarding Examples 1 to 4 and Comparative Example 1, five randomly selected micro-metallic wires were evaluated, and the percentage of grains preferentially aligned in each orientation (

[0100] orientation,

[0110] orientation, and

[0111] orientation) was calculated from a total of 15 evaluation results. Regarding Example 5, five randomly selected micro-metallic wires were evaluated, and the percentage of grains preferentially aligned in each orientation (

[0100] orientation,

[0110] orientation, and

[0111] orientation) was calculated from a total of 45 evaluation results.

[0065] [Evaluation 2] The resistivity of sintered bodies made from the linear bodies and particles obtained in Examples 1 to 5 and Comparative Example 1 was determined by the following method. The results are shown in Table 1.

[0066] [Measurement of resistivity] The filaments and particles obtained in Examples 1 to 5 and Comparative Example 1 were mixed with varnish (terpineol and ethyl cellulose), degassed, and dispersed using a three-roll mill to obtain a composition. The percentage of solids in the composition was set to 60% in Example 1, 55% in Example 2, 51% in Example 3, 57% in Example 4, 39% in Example 5, and 62% in Comparative Example 1. The composition was coated onto an alumina substrate and heated to 220°C, 240°C, 260°C, and 300°C respectively at a heating rate of 10°C / min in a nitrogen atmosphere. After reaching the target temperature, the substrate was allowed to cool naturally to obtain a sintered body. The resistivity of the sintered body was measured using a resistivity meter (MCP-T600 manufactured by Mitsubishi Chemical Co., Ltd.) via a four-probe method. Furthermore, regarding the sintered bodies obtained by calcination at 220°C and 240°C in Comparative Example 1, the resistivity could not be measured because it exceeded the upper limit for measuring the resistivity, which is 10⁶ Ω·cm. This is marked as ">10⁶" in Table 1.

[0067] [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Physical properties of fine metallic wires and their aggregates Length (μm) 2.7 1.0 3.8 11 97 3.5 Coarseness (nm) 78 30 110 170 1260 94 Aspect ratio (length / thickness) 35 33 35 65 77 37 Radius of curvature (µm) 2.4 2.4 12.8 26.2 346 31.3 radius of curvature / length 0.89 2.4 3.4 2.4 3.6 8.9 A ratio of (radius of curvature / length) of 5 or less 90% 92% 70% 80% 70% 32% The angle (°) at the front end of the pointed shape. 33 46 41 34 32 Non-slender Irregularity rate (%) 1.0 9.6 1.0 3.0 2.4 20 Properties of crystals X(nm) 114 95 94 268 203 990 Y(nm) 97 62 63 139 220 90 X / Y 1.18 1.53 1.49 1.93 0.92 11 The ratio of the number of grains constituting the

[0100] orientation 40% 27% 33% 40% 42% 0% The ratio of the number of grains constituting the

[0110] orientation 20% 13% 27% 33% twenty two% 93% The ratio of the number of grains in the

[0111] orientation 33% 53% 40% 27% 36% 0% Evaluate Specific resistance (Ω·cm) 220℃ 8.12×10³ Undetermined Undetermined Undetermined Undetermined >106 240℃ 1.54×10⁵ 2.74×10³ 3.63×10⁴ 6.75×10⁻³ 3.85×10⁻¹ >106 260℃ 6.46×10⁻⁴ 4.63×10⁻⁵ 2.07×10⁻⁴ 6.74×10⁻⁵ Undetermined 1.79×10⁻³ 300℃ 1.20×10⁻⁵ 3.27×10⁻⁵ 3.65×10⁻⁵ 2.93×10⁻⁵ 3.45×10⁻⁴ 6.26×10⁻⁴

[0068] As clearly shown in Table 1, the sintered body formed from the linear body obtained in the examples exhibits good low-temperature sintering properties. Furthermore, it is evident that the sintered portion of the linear body obtained in the examples, compared to the linear body obtained in the comparative examples, has a lower resistance after heat treatment at the same heating temperature. [Potential for industrial application]

[0069] According to the present invention, a fine metal wire body can be provided, which has a lower sintering temperature than before, or, under the same heating temperature, has a lower resistance in the sintered portion after heat treatment.

Claims

1. A fine metallic wire having a length of 0.5 μm to 200 μm and a thickness of 30 nm to 10 μm, wherein the fine metallic wire is a polycrystalline structure formed by multiple crystals connected along the extension direction of the wire, and wherein, regarding the crystal of the metal constituting the fine metallic wire, when the length along the extension direction of the fine metallic wire is defined as X and the length along a direction orthogonal to the extension direction is defined as Y, the arithmetic mean of the ratio of X to Y of the crystals, i.e., the value of X / Y, at the three junction regions where the length of the fine metallic wire is divided into four equal parts along the extension direction of the fine metallic wire is 4 or less, wherein the metal is at least one metal selected from the group consisting of copper, gold, nickel, lead, palladium, platinum, cobalt, tin, iron, bismuth and zinc, or an alloy containing the metal.

2. A fine metal wire having a length of 0.5 μm to 200 μm and a thickness of 30 nm to 10 μm, wherein the fine metal wire is a polycrystalline structure formed by connecting a plurality of crystals along the extension direction of the wire, wherein at the three junctions where the length of the fine metal wire is divided into four equal parts along the extension direction of the fine metal wire, the proportion of crystals constituting the metal in the orientation of the fine metal wire, as evaluated by electron diffraction or electron beam backscattering diffraction by a transmission electron microscope, is 50% or less within ±30° of the extension direction of the fine metal wire, wherein the metal is at least one metal selected from the group consisting of copper, gold, nickel, lead, palladium, platinum, cobalt, tin, iron, bismuth and zinc, or an alloy containing the metal.

3. As in claim 1 or 2, regarding the crystallization of the metal constituting the fine metal wire, when the length along a direction orthogonal to the extension direction of the fine metal wire is defined as Y, the arithmetic mean of Y of the crystallization at the three junctions where the length of the fine metal wire is divided into four equal parts along the extension direction of the fine metal wire is 10 nm or less.

4. For the fine metal wire as claimed in claim 1 or 2, wherein at the three junctions where the length of the fine metal wire is divided into four equal parts along the extension direction of the fine metal wire, the presence rate of grains in the [111] orientation, as evaluated by electron diffraction or electron beam backscattering diffraction using a transmission electron microscope, is 50% or more within ±30° of the extension direction of the fine metal wire; or the presence rate of grains in the [100], [110], and [111] orientations, as evaluated by electron diffraction or electron beam backscattering diffraction using a transmission electron microscope, is 50% or less within ±30° of the extension direction of the fine metal wire.

5. The fine metal wire as claimed in claim 1 or 2, at least one end of which is tapered, and the angle of the front end of the tapered shape is less than 60 degrees.

6. The fine metal wire as claimed in claim 1 or 2, wherein the metal constituting the fine metal wire is copper or a copper alloy.

7. A method for manufacturing a fine metal wire, which is the method for manufacturing a fine metal wire as claimed in any one of claims 1 to 3, comprising the steps of using an electrolyte containing a metal element source to electrolytically reduce and deposit metal onto a cathode, and attaching an oily substance of 5 g / m² to 100 g / m² onto the surface of the cathode, and performing electrolytic reduction while the oily substance is attached to the surface of the cathode, wherein the fine metal wire uses a metal as a base material, the metal being at least one metal selected from the group consisting of copper, gold, nickel, lead, palladium, platinum, cobalt, tin, iron, bismuth and zinc, or an alloy containing such metal, and the oily substance being a saturated aliphatic carboxylic acid or an unsaturated aliphatic carboxylic acid.

8. An assembly of fine metal wires, which is an assembly of fine metal wires as claimed in claim 1 or 2, wherein the number of fine metal wires having a curved portion accounts for more than 5% of the total number of fine metal wires, and the curved portion has a radius of curvature of less than 5 times the length of the fine metal wire.

9. An aggregate of fine metal wires, which is an aggregate of fine metal wires as claimed in claim 1 or 2, wherein particles having shapes other than wires account for 50% or less of the aggregate.

10. A composition comprising fine metal wires as claimed in claim 1 or 2 and a dispersion medium.

11. A joining structure having a first member, a second member, and a joining portion for joining the first member and the second member, wherein the joining portion comprises a sintered body of the composition of claim 10.

12. A semiconductor device comprising a first component, a second component, and a junction for joining the first component and the second component, wherein the junction comprises a sintered body of the composition of claim 10, and at least one of the first component and the second component is a semiconductor element.

13. An electronic circuit component comprising a substrate and a conductive pattern formed on the substrate, wherein the conductive pattern comprises a sintered body of the composition of claim 10.

Images