Fine metal wire

Abstract

This invention provides a fine metal wire with a lower sintering temperature than previously possible. The fine metal wire has a length of 0.5 μm or more and 200 μm or less, and a thickness of 30 nm or more and 10 μm or less. When the length of the metal crystal constituting the fine metal wire 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 three boundary regions where the length of the fine metal wire is divided into four equal parts along its extension direction, the ratio of X to Y, i.e., X / Y, is 4 or less.

Description

Technical Field

[0001] This invention relates to fine metal wires. Background 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) not found in previous materials. Prior art concerning the manufacture of such nanowires includes techniques described in Patent Document 1 and Non-Patent Document 1.

[0003] Patent Document 1 describes a method for chemically manufacturing copper nanowires by adding hydrazine as a reducing agent to an aqueous solution containing ethylenediamine, o-phenylenediamine, and copper nitrate. This method utilizes the fact that ethylenediamine and o-phenylenediamine readily adsorb onto the (001) and (111) planes of copper but are difficult to adsorb onto the (110) plane, allowing copper to selectively precipitate on the (110) plane, thereby forming a wire-like shape. Non-Patent Document 1 also describes a method for chemically manufacturing copper nanowires.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2015 / 097808

[0007] Non-patent literature

[0008] Non-patent literature 1: MJ Kim, et al., Journal of the American Chemical Society, 2017, vol. 139, pp. 277-284 Summary of the Invention

[0009] In the copper nanowires manufactured using the method described in Patent Document 1, due to their formation mechanism, the copper crystals become elongated and large single crystals with their

[110] orientation preferentially oriented in the length direction of the wire. It is known that the smaller the size of the crystal, the lower the sintering temperature of the metal powder will be. However, for copper nanowires manufactured using the method described in Patent Document 1, where the size of the crystal will inevitably increase, it is not easy to lower the sintering temperature.

[0010] Therefore, the objective of this invention is to provide a fine metal wire that has a lower sintering temperature than before, or a sintered portion with reduced resistance after heat treatment at the same heating temperature.

[0011] This invention provides a fine metal wire with a length of 0.5 μm or more and 200 μm or less, and a thickness of 30 nm or more and 10 μm or less.

[0012] When the length of the crystal of the metal constituting the aforementioned fine metal wire along the extension direction of the fine metal wire is defined as X, and the length along the direction orthogonal to the aforementioned 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 its extension direction, 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.

[0013] This invention provides a fine metal wire with a length of 0.5 μm or more and 200 μm or less, and a thickness of 30 nm or more and 10 μm or less.

[0014] When the length of the crystal of the metal constituting the aforementioned fine metal wire is defined as Y along a direction orthogonal to the extension direction of the fine metal wire, the arithmetic mean of Y of the aforementioned crystal is less than 10 nm at three boundary regions where the length of the fine metal wire is divided into four equal parts along its extension direction.

[0015] In addition, the present invention provides a fine metal wire with a length of 0.5 μm or more and 200 μm or less, and a thickness of 30 nm or more and 10 μm or less.

[0016] At the three boundary regions where the aforementioned fine metal wire is divided into four equal parts along its extension direction, the proportion of the metal crystals constituting the fine metal wire, as evaluated by electron diffraction or electron backscatter diffraction of a transmission electron microscope within ±30° of the extension direction of the fine metal wire, is less than 50% and oriented in the

[110] direction.

[0017] 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, comprising a step of using an electrolyte containing a metal element source to electrolytically reduce and deposit the metal at the cathode.

[0018] Electrolytic reduction is performed while an oily substance is present on the surface of the aforementioned cathode. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the fine metal wire obtained in Example 1.

[0020] Figure 2 Scanning electron microscope images of the fine metal wires obtained in Comparative Example 1.

[0021] Figure 3 This is the grain map of electron backscatter diffraction (EBSD) of the fine metal wire obtained in Example 1.

[0022] Figure 4For comparison, the grain map of electron backscatter diffraction of the fine metal wire obtained in Example 1 (EBSD Grain Map). Detailed Implementation

[0023] The present invention will now be described based on preferred embodiments. The present invention relates to fine metal wires. When referring to "fine metal wires" in the following description, depending on the context, it sometimes refers to individual wires, and sometimes to an aggregate of multiple wires. The fine metal wires of the present invention use metal as the constituent material. The fine metal wires typically extend in one direction. The state in which the wire extends in one direction varies depending on how the wire is observed. For example, the wire extends in a straight line, or extends in one direction while meandering in a curve. The characteristic of this wire is that, although very thin, it is long.

[0024] The micro-metal wires are very fine, preferably with a thickness of 30 nm or more and 10 μm or less, more preferably 30 nm or more and 1000 nm or less, even more preferably 40 nm or more and 500 nm or less, and even more preferably 45 nm or more and 300 nm or less. Despite being very fine as described above, the micro-metal wires are also relatively long, preferably with a length of 0.5 μm or more and 200 μm or less, more preferably 1 μm or more and 100 μm or less, and even more preferably 2 μm or more and 70 μm or less. By combining such thickness and length, the micro-metal wires exhibit excellent processability, for example, excellent filling properties when used as bonding materials.

[0025] Furthermore, the aspect ratio (length [m] of the fine metal wire / thickness [m] of the fine metal wire) is preferably 5 or more and 5000 or less, more preferably 10 or more and 5000 or less, even more preferably 20 or more and 5000 or less, even more preferably 20 or more and 3000 or less, and even more preferably 20 or more and 1500 or less.

[0026] The thickness of the fine metal wires was obtained by reading more than 10 images using an electron microscope and averaging them. The length was obtained by reading more than 20 images using an electron microscope and averaging them.

[0027] The fine metal wires can be of approximately the same thickness along their entire length, or they can be in the form of beads of varying thicknesses. Preferably, at least one end of the fine metal wire is tapered. "Tapered" means that when observing the end region of the fine metal wire, the thickness gradually decreases as one moves toward the tip.

[0028] By making at least one end of the micro-metal wire into a tapered shape, when using the micro-metal wire as a raw material for, for example, wiring materials, the connection in the extension direction (hereinafter also referred to as the "length direction") of the micro-metal wire can be made on the side of its tapered portion, not in the cross-section of the micro-metal wire. That is, the area of ​​its side surface is larger than that of the cross-section of the wire, thus having the advantage of increasing the contact area of ​​the micro-metal wire and reducing the resistance at the interface. In addition, from the viewpoint that the gap between the micro-metal wires can be reduced, it is also convenient to reduce the resistance.

[0029] From the viewpoint of making this advantage more significant, the angle of the pointed front end is preferably 60 degrees or less, more preferably 50 degrees or less, and even more preferably 45 degrees or less.

[0030] It should be noted that "the extension direction of the fine metal wire" refers to the length direction of the fine metal wire as described above, and in the case of a bend, it refers to its tangential direction.

[0031] The angle of the pointed tip is determined according to the following steps. First, as described above, the thickness of the fine metal wire is pre-determined based on an electron microscope image. Then, 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, resulting in two points of contact between the arc and the fine metal wire. The angle between these two points and the tip of the fine metal wire is then measured. It should be noted that when the cross-section of the tip of the fine metal wire is straight or nearly straight, its center is considered the tip. Furthermore, when the cross-section of the tip of the fine metal wire is straight or nearly straight, if its cross-sectional length is greater than half the thickness of the fine metal wire, that fine metal wire is excluded from the measurement. This measurement is performed on 10 or more fine metal wires, and the arithmetic mean is taken as the angle of the pointed tip.

[0032] The shape of a fine metal wire is typically a wire extending in one direction. This fine metal wire may have a main chain extending in one direction and branch structures branching from the middle of the main chain, or it may not have these. From the viewpoint of imparting sufficient conductivity to an object with a small amount, and from the viewpoint that the conductivity of the object is not easily reduced when it is stretched or bent, the fine metal wire preferably has only a non-branched structure in the main chain. On the other hand, from the viewpoint that the aggregate of fine metal wires has a large volume structure, the fine metal wire preferably has one or two or more branch sections.

[0033] There are no particular restrictions on the type of metal constituting the fine metallic wire; various metals can be used. Considering the balance between electrical conductivity and ease of industrial application, at least one metal or alloy containing the group consisting of copper, silver, gold, nickel, lead, palladium, platinum, cobalt, tin, iron, bismuth, and zinc is preferred. Alternatively, the wire may be formed in a mixture of crystals of various metals or alloys. Among these, wires with copper or copper alloys or zinc or zinc alloys as the base material are particularly preferred, and wires with copper or copper alloys as the base material are especially preferred. It should be noted that "with copper or zinc as the base material" means that copper or zinc accounts for 80% or more by mass in the fine metallic wire. It should be noted that the state of the mixture of crystals of various metals or alloys can include, for example, a state in which different types of metal crystals are linked together, such as Cu crystal-Zn crystal-Cu crystal-Zn crystal.

[0034] The fine metal wire may have a structure comprising a main body and a coating layer, wherein the main body is formed of a first metal element or an alloy containing the first metal element, and the coating layer is a coating layer of a second metal element other than the first metal element disposed on the surface of the main body.

[0035] Examples of the first metallic element include, for example, copper, silver, gold, nickel, lead, palladium, platinum, cobalt, tin, iron, bismuth, and zinc, as described above. Examples of the second metallic element, differing from the first metallic element, include, for example, 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.). In particular, from the viewpoint of further improving the conductivity of the object, the second metallic element preferably has higher conductivity than the first metallic element constituting the main body or an alloy of that metallic element. From this viewpoint, when the first metallic element is, for example, copper or zinc, silver is preferably the second metallic element.

[0036] To form a coating on the surface of the main body, examples include: electroplating in an electrolyte containing a metal element after forming the main body using the method described later; coating a target metal by applying a catalyst capable of displacement plating or chemical plating onto a fine metal wire; or formation based on a dry method. Alternatively, the surface of the wire can be treated with an organic reagent.

[0037] The crystal structure of the fine metal wire of the present invention differs from that of fine metal wires known to date. Specifically, the fine metal wire of the present invention exhibits a polycrystalline structure formed by multiple crystals connected along the extension direction of the wire. In contrast, fine metal wires known to date, such as those manufactured by the chemical method described in Patent Document 1, exhibit a single-crystal structure with long and large crystals along the extension direction of the wire. Furthermore, due to its characteristic crystal structure, the fine metal wire of the present invention allows for a lower sintering temperature than previously possible. Alternatively, when heat-treated at the same heating temperature as conventional fine metal wires, the resistance of the sintered portion after heat treatment can be lower than previously possible.

[0038] The crystal structure of the fine metal wire of the present invention will be described in detail. For the crystal 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 value of the ratio of X to Y, i.e., X / Y, is preferably 4 or less.

[0039] Thus, the length of the metal crystals constituting the micro-metal wire of the present invention has little difference from the length in the longitudinal direction to the length in the width direction, exhibiting a shape with approximately isotropic properties. As mentioned above, the thickness of the micro-metal wire of the present invention is 30 nm or more and 10 μm or less; therefore, it can be understood that the metal crystals constituting this micro-metal wire are fine. Because the metal crystals constituting the micro-metal wire of the present invention have such a structure, as described above, the sintering temperature of the micro-metal wire of the present invention can be lowered than before. Alternatively, when heat treatment is performed at the same heating temperature as conventional micro-metal wires, the resistance of the sintered portion after heat treatment can be lower than before.

[0040] From the viewpoint of making this advantage more significant, the value of X / Y is further preferably 3 or less.

[0041] The X / Y ratio mentioned above is calculated by taking the arithmetic mean of the X / Y values ​​of the crystals present at the three boundary regions when the length of the fine metal wire is divided into four equal parts along its length. The first decimal place of the arithmetic mean is rounded off.

[0042] In this specification, "crystal" refers to a grain, the size of which can be obtained by using a grain pattern obtained through electron backscatter diffraction (EBSD). It is important to note that a grain size is different from the crystallite size determined from an XRD pattern. When the crystal in this specification is a twin, each crystal constituting the twin is defined as a distinct crystal, and the X / Y value is calculated for each crystal.

[0043] When the value of X / Y is 4 or less, there is no restriction on the values ​​of X and Y. However, from the viewpoint that the sintering temperature can be lowered further than before, 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. From the same viewpoint, 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.

[0044] The fine metal wires of the present invention can be characterized solely by the value of Y described above. That is, the value of Y is preferably 10 nm or less.

[0045] If expressed in terms of the number of metal atoms, Y of 10 nm or less refers to a fine state with a width of only 100 or fewer atoms. This is the same design concept as setting the X / Y value to 4 or less, both indicating fine crystals. For this reason, the fine metal wires according to the present invention can achieve a lower sintering temperature than before. Alternatively, when heat-treated at the same heating temperature as conventional fine metal wires, the resistance of the sintered portion after heat treatment can be lower than before. It should be noted that if Y is 10 nm or less, the value of X / Y is not limited.

[0046] The Y value mentioned above is obtained by calculating the Y values ​​of the crystals present at the three boundary regions when the length of the fine metal wire is divided into four equal parts along its length, and then taking the arithmetic mean of these values. The first decimal place of the arithmetic mean is rounded off.

[0047] The fine metal wires of the present invention can also be characterized by the orientation of the crystals of the metals constituting them.

[0048] Specifically, when considering crystals present at three boundary regions where the length of the fine metal wire of the present invention is divided into four equal parts along its extension direction, the proportion of

[110] oriented crystals within ±30° of the extension direction of the fine metal wire, as evaluated by electron diffraction of transmission electron microscopy (hereinafter also referred to as "TEM") or EBSD, is preferably 50% or less, more preferably 45% or less, and even more preferably 40% or less. This relationship means that the

[110] orientation of the crystals is not preferentially oriented along the length direction of the fine metal wire.

[0049] The proportion of grains in the

[110] orientation is calculated as follows: Two or more fine metal wires are randomly extracted, and the boundary lines that divide the length of the fine metal wires into four equal parts along their respective length directions are drawn. The three boundary regions of the boundary are measured and calculated.

[0050] When evaluated using electron diffraction of TEM, the percentage of grains in the

[110] orientation is determined at a total of 6 or more locations at the midpoint of the boundary line in each boundary region (e.g., 6 locations when extracting 2 fine metal wires, and 15 locations when extracting 5 fine metal wires).

[0051] When evaluating with EBSD, measurements are taken at a total of 18 or more points (e.g., 18 points when extracting 2 fine metal filaments, and 45 points when extracting 5 fine metal filaments) where the boundary line of each boundary region is divided into four equal parts.

[0052] The first decimal place of a percentage is rounded up or down.

[0053] When observing grains oriented

[110] using TEM, electrons are passed through a fine metal wire. However, when the thickness of this fine metal wire is 200 nm or more, electrons cannot pass through it, and an electron diffraction pattern cannot be obtained. Therefore, when the thickness of this fine metal wire is 200 nm or more, the proportion of grains oriented

[110] is evaluated using EBSD.

[0054] In contrast, known fine metal wires, such as those manufactured by the chemical method described in Patent Document 1, have a manufacturing method that results in the orientation of

[110] being preferentially oriented along the length of the wire.

[0055] Furthermore, Non-Patent Document 1 also reports the synthesis of micro-metallic wires based on a chemical method. As described in the comparative examples below, the inventors' experiments have shown that the micro-metallic wires synthesized by the chemical method of Non-Patent Document 1 also have a

[110] orientation preferentially oriented in the length direction. This document describes the side surface of the micro-metallic wire as a (100) plane. This document also describes that the (100) plane is more easily oxidized than other planes, thereby forming an oxide film on the surface. That is, the side surface of the micro-metallic wire with the

[110] orientation preferentially oriented in the length direction is easily oxidized, which is one of the reasons for the increase in resistance in the width direction of the micro-metallic wire. Therefore, the micro-metallic wire of the present invention, which is a micro-metallic wire that does not grow in the

[110] orientation in the length direction, has the advantage of being difficult to oxidize.

[0056] Because of the characteristic crystal structure of the micro-metal wire of the present invention, in which the

[110] orientation of the crystal is not preferentially oriented in the length direction, the sintering temperature can be lowered than before. Alternatively, when heat treatment is performed at the same heating temperature as conventional micro-metal wires, the resistance of the sintered portion after heat treatment can be lower than before.

[0057] From the viewpoint of lowering the sintering temperature further than before, for the three crystals present in the boundary region when the length of the fine metal wire is divided into four equal parts along its extension direction, the proportion of grains in the

[111] orientation as evaluated by TEM electron diffraction or EBSD within ±30° of the extension direction of the fine metal wire is preferably 50% or more, more preferably 52% or more, even more preferably 60% or more, and even more preferably 70% or more.

[0058] The proportion of grains in the

[111] orientation is calculated as follows: arbitrarily extract two or more fine metal wires, draw the boundary lines that divide the length of the fine metal wires into four equal parts along the length direction, and measure and calculate the three boundary regions of the boundary.

[0059] When evaluated using electron diffraction of TEM, the percentage of grains in the

[111] orientation is determined at a total of 6 or more locations at the midpoint of the boundary line in each boundary region (e.g., 6 locations when extracting 2 fine metal wires, and 15 locations when extracting 5 fine metal wires).

[0060] When evaluating with EBSD, measurements are taken at a total of 18 or more points (e.g., 18 points when extracting 2 fine metal filaments, and 45 points when extracting 5 fine metal filaments) where the boundary line of each boundary region is divided into four equal parts.

[0061] The first decimal place of a percentage is rounded up or down.

[0062] The following relationship indicates that the

[111] orientation is preferentially oriented along the length of the fine metal wire. From a crystallographic perspective, the preferential orientation of the

[111] orientation along the length of the crystal indicates that its side (100) face is not exposed, which is therefore preferred.

[0063] Furthermore, for the three crystals present at the boundary region when the length of the fine metal wire is divided into four equal parts along its extension direction, the proportion of crystals with

[100] orientation,

[110] orientation and

[111] orientation as evaluated by TEM electron diffraction or EBSD within ±30° of the extension direction of the fine metal wire is preferably 50% or less, and more preferably 40% or less.

[0064] The proportion of grains in the

[110] ,

[111] , and

[100] orientations is calculated as follows: Two or more fine metal wires are randomly extracted, and boundary lines are drawn to divide the length of the fine metal wires into four equal parts along the length direction. The three boundary regions of the boundary are measured and calculated.

[0065] When evaluating using electron diffraction with TEM, the percentage of grains with orientations of

[110] ,

[111] , and

[100] is determined at a total of 6 or more locations at the midpoint of the boundary line in each boundary region (e.g., 6 locations when extracting 2 fine metal wires, and 15 locations when extracting 5 fine metal wires).

[0066] When evaluating with EBSD, measurements are taken at a total of 18 or more points (e.g., 18 points when extracting 2 fine metal filaments, and 45 points when extracting 5 fine metal filaments) where the boundary line of each boundary region is divided into four equal parts.

[0067] The first decimal place of a percentage is rounded up or down.

[0068] The following relationship indicates that the crystals of the metal constituting the fine metal wire are randomly oriented. The random orientation of the crystals of the metal constituting the fine metal wire indicates that the crystals of the metal constituting the fine metal wire are polycrystalline and small. As mentioned above, small crystals lead to lower sintering temperatures. Furthermore, "random orientation of crystals" indicates that the (100) plane is not preferentially exposed on the side of the wire, and oxidation of the side of the fine metal wire is not promoted.

[0069] When the micro-metal wire of the present invention is an assembly comprising multiple micro-metal wires, the number of micro-metal wires having a curved portion with a radius of curvature of 5 times or less than the length of the micro-metal wire is preferably 5% or more of the total number of micro-metal wires in the assembly, more preferably 20% or more, even more preferably 40% or more, and even more preferably 60% or more. This is preferable from the perspective of facilitating contact across multiple micro-metal wires in the transverse (width) direction and achieving low resistance in the assembly of micro-metal wires.

[0070] The radius of curvature is calculated as follows. The 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 perpendicular to the straight line is drawn from its midpoint towards the side of the fine metal wire, and the distance (sagitta) 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.

[0071] r=(C×C) / (8×h)+h / 2

[0072] (In the formula, r represents the radius of curvature, C represents the chord length, and h represents the sag.)

[0073] The radius of curvature mentioned above is preferably 0.5 μm or more and 1000 μm or less.

[0074] It should be noted that when the micro-metal wire is bent, the micro-metal wire is made to approximate the shape of having a bent portion, and the radius of curvature is calculated according to the aforementioned formula. Furthermore, when the two ends of the micro-metal wire are connected by a straight line, and the line crosses the micro-metal wire, the radius of curvature is measured for different micro-metal wires, with the crossing point as the boundary.

[0075] When the fine metal wire of the present invention is an assembly comprising multiple fine metal wires, the assembly may also contain particles having shapes other than wires. Of course, from the viewpoint that conductivity is not easily reduced even when subjected to deformation such as bending or stretching, it is preferable that the aforementioned assembly contains as few particles as possible that have shapes other than wires.

[0076] When the proportion of particles with shapes other than filaments in the aforementioned aggregate is defined as the "irregularity rate," this irregularity rate is preferably 50% or less, more preferably 40% or less, even more preferably 30% or less, even more preferably 10% or less, and even more preferably 2% or less. If fine metal filaments are manufactured by the manufacturing method described later, the irregularity rate can easily be made to be 50% or less.

[0077] The irregularity rate is calculated as follows: In a field of view 5 to 30 times the average length of the fine metal wire, the longitudinal and transverse dimensions of the sample are observed simultaneously using SEM, and the percentage of [area of ​​irregularly shaped material / area of ​​the wire] is calculated. "Irregular shape" refers to shapes other than wire (e.g., spherical, blocky, fern-like, etc.).

[0078] Next, a suitable manufacturing method for the fine metal wires of the present invention will be described. Electrolysis is suitable for manufacturing the fine metal wires. The reason is that electrolysis not only makes it easy to control the desired shape, but also allows for the reuse of the electrolyte. Only a small amount of liquid is needed to manufacture the fine metal wires, thus reducing the amount of waste liquid that needs to be treated. Another method for manufacturing metal powder is atomization, but it cannot produce substances with anisotropic shapes like fine metal wires. Another method is wet reduction (electrolysis-free reduction), but this method cannot reuse the solution, and it cannot increase the concentration of the target metal element to a certain level, thus failing to produce fine metal wires with good productivity.

[0079] When manufacturing fine metal wires by electrolysis, the following steps can be exemplified, for example: immersing the anode and cathode in an acidic electrolyte containing a metal element source of sulfuric acid, electrolytically reducing them by passing a direct current through them, causing fine metal wires to be deposited on the surface of the cathode, recovering the deposited fine metal wires as scrape-off material by mechanical or electrical methods, cleaning and drying the recovered fine metal wires with water or organic solvent, and sieving them as needed.

[0080] The type of metallic element used in this manufacturing method is not particularly limited as long as it can produce fine metallic wires. Considering the balance between electrical conductivity and ease of industrial application, copper, silver, gold, nickel, lead, palladium, platinum, cobalt, tin, iron, bismuth, and zinc are examples. These metallic elements share the characteristic that they can be electrolyzed 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.

[0081] The fine metal wire obtained by this manufacturing method may, for example, consist solely of the target metal element except for unavoidable impurities, or may consist of an alloy of the target metal element except for unavoidable impurities. Furthermore, it may also consist of a combination of two or more of the aforementioned metal elements except for unavoidable impurities.

[0082] The inventors' research results indicate that when manufacturing fine metal wires using the above steps, it is advantageous to perform electrolytic reduction while the cathode surface is coated with an oily substance. By reducing metal ions in this state, the reduction reaction can be controlled. Details are as follows.

[0083] When the amount of oily substance adhering to the cathode surface is expressed as thickness, it is on average several hundred nm or more, preferably several μm to several hundred μm. The thickness can vary locally due to electrolyte fluctuations. Metal ions are rarely found in the oily substance. Within the oily substance, a very small amount of electrolyte containing metal ions is intermittently adsorbed near the negative electrode by the electric field force generated by the applied electricity, or by being suspended in droplets within the oily substance. In this case, a metal reduction reaction occurs on the cathode surface, generating locally deposited metal protrusions. Compared to other areas, the thickness of the oily substance directly above these protrusions is thin, thus reducing the resistance in this area, concentrating the current there, and causing the protrusion to grow into a linear structure. In this way, fine metallic linear structures are formed through electrolysis.

[0084] As the growth of fine metal wires proceeds, the wires droop due to their own weight, making them prone to bending. Alternatively, the resistance introduced by the oily substance may hinder linear growth, causing the fine metal wires to easily become bent. Essentially, fine metal wires are formed through electrolysis using the mechanisms described above, but the shape and structure of the finer parts can vary further depending on the type of oily substance used. Similar to the electrolytic extraction of ordinary metals, the composition of the electrolyte and additives also affect the process.

[0085] As a method for attaching an oily substance to the surface of the cathode, examples include: directly coating the surface of the cathode with the oily substance; immersing the cathode in a container containing the oily substance to allow it to adhere; suspending the oily substance in an electrolyte and immersing the cathode from above, thereby allowing the oily substance to adhere to the cathode surface; and so on. Furthermore, examples include: suspending the oily substance in an electrolyte and stirring the suspended electrolyte, thereby causing the suspended oily substance to impact the cathode surface and directly adhere to it. Additionally, if the oily substance has the property of dissolving in small amounts in the electrolyte, even if the suspended oily substance does not directly contact the electrode, the oily substance temporarily dissolved in the electrolyte will continuously adsorb onto the electrode surface, resulting in the same effect as adhering to the surface.

[0086] By fabricating a fine metal wire using the above method, the fine metal wire becomes a polycrystalline structure formed by multiple crystals connected along its length. Furthermore, the

[110] orientation of the crystals becomes less likely to be preferentially oriented along the length direction. Moreover, in the fine metal wire, the

[111] orientation of the crystals becomes more likely to be preferentially oriented along the length direction, or the orientation direction of the crystals becomes more random.

[0087] Furthermore, by using the above method to manufacture fine metal wires, the generation of irregularly shaped particles with shapes other than wires can be suppressed as much as possible.

[0088] Oily substances that adhere to the surface of the cathode can be categorized as various organic compounds that, after adhering to the cathode surface, possess a viscosity that allows them to remain at the surface level, in addition to being sparingly soluble to insoluble relative to water. It should be noted that "sparingly soluble to insoluble relative to water" refers to a solubility of less than 100g relative to 1L of water at the temperature used in manufacturing the fine metal wire.

[0089] Oily substances can be categorized into liquid and solid forms. Oily substances can also be used if they dissolve in a liquid solvent at room temperature (20–30°C).

[0090] It should be noted that, for the purpose of easily controlling the physical properties of the precipitated fine metal wires, additives such as benzoic acid, fumaric acid, citric acid, and benzotriazoles can also be used in the aforementioned oily substances.

[0091] As for the aforementioned organic compounds, those that are sparingly soluble to insoluble relative to 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, organosilicones (e.g., dimethylsiloxane), aliphatic amines, aromatic amines, nitrogen-containing heterocyclic compounds, tributyl phosphate, thiols, fluorinated solvents, ionic liquids, etc. It should be noted that "aliphatic alcohols" in this specification refer to alcohols with 5 or more carbon atoms.

[0092] The inventors' research has found that fine metal wires can be successfully manufactured as oily substances, particularly when fatty acids or their salts, esters or their amides, aromatic carboxylic acids, aliphatic hydrocarbons, aliphatic alcohols, aliphatic amines, organosilicon (e.g., dimethylsiloxane), or mixtures thereof.

[0093] As for the aforementioned fatty acids, lower fatty acids and higher fatty acids can be listed. As lower fatty acids, saturated or unsaturated aliphatic carboxylic acids with a carbon number of 9 or less can be listed. As higher fatty acids, saturated or unsaturated aliphatic carboxylic acids with a carbon number of 10 or more and 25 or less, more preferably 10 or more and 22 or less, and even more preferably 11 or more and 20 or less can be listed.

[0094] Examples of saturated aliphatic carboxylic acids include hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, eicosanoic acid, dodecanoic acid, tridecanoic acid, and tetradecanoic acid.

[0095] As unsaturated aliphatic carboxylic acids, carboxylic acids with one or more unsaturated carbon bonds in their molecules can be listed.

[0096] Examples of unsaturated aliphatic carboxylic acids with one unsaturated carbon bond in their molecules include crotonic acid, myristic acid, palmitoleic acid, hexadecenoic acid, oleic acid, transoleic acid, isoleic acid, codoleic acid, arachidic acid, erucic acid, and nervonic acid.

[0097] Examples of unsaturated aliphatic carboxylic acids with two or more unsaturated carbon bonds in their molecules include linoleic acid, eicosadienoic acid, and linolenic acid.

[0098] Examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, triphenylcarboxylic acid, trimellitic acid, pyromellitic acid, benzotetrate, 1,2,3,4-phenyltetracarboxylic acid, pyromellitic acid, hexabenzoic acid, biphenylcarboxylic acid, o-methylbenzoic acid, 2,4-dimethylbenzoic acid, 2,3-dimethylbenzoic acid, mesitylenic acid, 2,3,4-trimethylbenzoic acid, γ-isobenzoic acid, amino acid, β-isobenzoic acid, 5-methylphthalic acid, α-isobenzoic acid, cumic acid, and urvedic acid. Acids, α-toluic acid, hydrogenated atrobic acid, atrobic acid, hydrogenated cinnamic acid, cinnamic acid, salicylic acid, anisic acid, cresolic acid, o-homosalic acid, o-cresolic acid, m-homosalic acid, m-cresolic acid, p-homosalic acid, p-cresolic acid, o-pyrocatechinic acid, β-rezoic acid, gentic acid, γ-rezoic acid, protocatechinic acid, α-rezoic acid, vanillic acid, isovanillic acid, veratric acid, o-veratric acid, sphygmonic acid, m-peninic acid, gallic acid, syringic acid, asaric acid, mandelic acid, vanillylmandelic acid, homoanitrile acid, homogentic acid, high-alcoholic catechinic acid, homovanillic acid High isovanthan acid, high resveratrol acid, o-high resveratrol acid, high phthalic acid, high isophthalic acid, high terephthalic acid, 2-(carboxycarbonyl)benzoic acid, m-(carboxycarbonyl)benzoic acid, 4-(carboxycarbonyl)benzoic acid, diphenylethanolic acid, alpha-lactate, tropine, succinic acid, stigmacanetic acid, hydrogenated caffeic acid, hydrogenated ferulic acid, hydrogenated isoflavone acid, p-coumaric acid, umbelliferic acid, caffeic acid, ferulic acid, isoflavone acid, sinapic acid, benzoyl, phthaloyl, isophthaloyl, terephthaloyl, toluyl, xylene, cumyl, α- Toluyl, hydrogenated atoryl, atoryl, hydrogenated cinnamicyl, cinnamicyl, salicyl, anisyl, cresolyl, o-pyrocatechol, β-resorcyloyl, gentioyl, γ-resorcyloyl, protocatechuicol, α-resorcyloyl, vanillyl, isovanillyl, o-veratrol, veratrolyl, gallyl, syringoyl, mandelicyl, vanillyl mandelicyl, high gentioyl, high vanillyl, high veratrolyl, diphenylhydroxyacetyl, tropinyl, caffeoyl, ferulic acid, perbenzoic acid, ibuprofen, ketoprofen, biphenylacetic acid.

[0099] Among the aforementioned fatty acids, saturated aliphatic carboxylic acids and unsaturated aliphatic carboxylic acids are preferred because they can more easily produce fine metal wires.

[0100] The aforementioned fatty acid ester is preferably an ester of a saturated aliphatic alcohol or an unsaturated aliphatic alcohol. The alcohol preferably has 1 or more carbon atoms and 18 or fewer. More preferably, the aforementioned fatty acid ester is an ester of a saturated aliphatic alcohol with 1 or more carbon atoms and 18 or fewer. Ethyl acetate is an example of such a substance.

[0101] The amount of oily substance adhering to the cathode surface is preferably set at 0.1 g / m² per unit surface area of ​​the cathode. 2 Above and 500g / m2 Hereinafter, it is more preferable to set it to 1g / m 2 Above and 500g / m 2 The following is a further preferred setting: 3g / m 2 Above and 200g / m 2 The following is a further preferred setting: 5g / m 2 Above and 100g / m 2 the following.

[0102] Materials used for the anode and cathode can be any materials known to date without particular restriction. For example, anodes and cathodes made of titanium or copper can be used. Regarding the anode, a dissolved metal electrode (DSE) can also be used.

[0103] Relatedly, the current density during reduction is preferably set to 5 A / m. 2 Above and 3000A / m 2 Hereinafter, a further preferred value is set to 10A / m. 2 Above and 1000A / m 2 Hereinafter, a further preferred setting is 50A / m 2 Above and 500A / m 2 the following.

[0104] Typically, in the electrolytic deposition of metals, a good surface shape (e.g., a metallic luster on the surface, if plating) can be obtained by applying an amount of electricity equivalent to the reduction rate, which is slower than the supply rate of metal ions from the electrolyte. Similarly, in the electrolysis of this invention, the concentration of metal ions in the electrolyte is preferably such that the reaction rate of metal ion reduction is adequately supplied with a metal ion concentration. From this viewpoint, the metal ion concentration 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.

[0105] From the same perspective, during electrolysis, it is preferable to stir or circulate the electrolyte within the electrolytic cell.

[0106] The electrolyte can be used in a non-heated state, such as at room temperature (25°C), or it can be used in a heated state.

[0107] Furthermore, from the same viewpoint, it is preferable to adjust the size of the electrolytic cell, the number of electrodes, the shape of the electrodes (plate-shaped, drum-shaped), the distance between the electrodes, the swaying of the electrodes, and the circulation rate of the electrolyte, so as to adjust the electrolyte so that the concentration of metal ions in the electrolyte near the electrodes is always kept high in advance.

[0108] The fine metal wires of the present invention obtained by the above methods can be composited 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 bonding materials. 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 sintered bodies. These bonding materials and sintered bodies can be used, for example, as materials for bonding semiconductor devices to substrates.

[0109] Specifically, in a joining structure comprising a first component, a second component, and a joining portion connecting the first component and the second component, the joining portion may be constituted 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 comprising a first component, a second component, and a joining portion connecting the first component and the second component, a semiconductor element may be used as at least one of the first component and the second component, and the joining portion may be constituted by a sintered body comprising a composition of the fine metal wires and a dispersion medium of the present invention.

[0110] The fine metal wires of the present invention can also be used to manufacture electronic circuit components. For example, in an electronic circuit component having a substrate and a conductive pattern formed on the substrate, the aforementioned 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.

[0111] Various organic solvents can be used as the dispersion medium in the aforementioned composition. Examples of such organic solvents include monohydric alcohols, polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, esters, ketones, nitrogen-containing heterocyclic compounds, amides, amines, and saturated hydrocarbons. These organic solvents can be used alone or in combination of two or more.

[0112] The fine metal wires of the present invention can also be contained in resin to obtain a resin composition comprising the fine metal wires and the resin. This resin composition exhibits conductivity by containing the fine metal wires.

[0113] To impart conductivity to the resin, fine metal wires can be dispersed in the resin, for example. Alternatively, a layer containing fine metal wires can be formed on the surface of a resin-containing substrate. In any of these methods, 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 exhibits sufficient conductivity with a relatively small amount of fine metal wires added. Regarding the resin composition, from the viewpoint that its conductivity decreases little before and after stretching or bending, it differs from conventional conductive resin compositions using copper powder as filler. From this viewpoint, when the resin composition is made stretchable or bendable, the characteristics of the fine metal wires of the present invention can be effectively utilized. With conventional conductive resin compositions, conductivity tends to decrease when stretched or bent.

[0114] As described above, the micro-metallic wires of the present invention can be used in various ways. 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 used in the form of attachment 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-filling materials for printed circuit board holes, sensors, switches, adsorption separation devices, electrode catalysts for various electrochemical reactions, and current collectors for power generation elements.

[0115] Example

[0116] The present invention will now be described in further detail through examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" means "mass %".

[0117] [Example 1]

[0118] In this embodiment, a wire-like body made of copper is manufactured.

[0119] An electrolyte was prepared by mixing copper sulfate and sulfuric acid at a concentration of 4 g / L for copper ions and 5 g / L for free sulfuric acid. 800 mL of the electrolyte was added to 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.

[0120] An 8cm x 8cm copper plate was used as the cathode. Oleic acid was evenly coated onto the surface of the cathode. The coating amount was set to 7g / m². 2 An 8cm x 8cm copper plate is used as the anode. The two electrodes are suspended in the electrolytic cell with an 8cm gap between the cathode and anode.

[0121] Adjust the current density to 160 A / m 2 Electrolysis is performed for 30 minutes. This allows copper to be electrodeposited on the surface of the cathode.

[0122] Copper electrodeposited on the cathode surface was recovered and washed with ethanol. The electrodeposited material was observed using SEM, confirming it as a filamentous structure. Each end of the filamentous structure was tapered.

[0123] Figure 1 The SEM image of the linear body obtained in this embodiment is shown. In this figure, the 30,000x SEM image is displayed to observe the shape of the leading edge of the linear body.

[0124] [Example 2]

[0125] The concentration of copper ions was changed to 1 g / L to prepare the electrolyte, and the current density was changed to 63 A / m. 2 Electrolysis was then performed. Otherwise, the procedure was the same as in Example 1 to obtain the electrodeposited material.

[0126] The electrodeposited material was observed using SEM, and the results confirmed it to be a filamentous structure. Each end of the filamentous structure was tapered.

[0127] [Example 3]

[0128] The concentration of copper ions was changed to 7 g / L to prepare the electrolyte, and the current density was changed to 63 A / m. 2 Electrolysis was then performed. Otherwise, the procedure was the same as in Example 1 to obtain the electrodeposited material.

[0129] The electrodeposited material was observed using SEM, and the results confirmed it to be a filamentous structure. Each end of the filamentous structure was tapered.

[0130] [Example 4]

[0131] The concentration of copper ions was changed to 10 g / L to prepare the electrolyte. Otherwise, the procedure was the same as in Example 1 to obtain the electrodeposited material.

[0132] The electrodeposited material was observed using SEM, and the results confirmed it to be a filamentous structure. Each end of the filamentous structure was tapered.

[0133] [Example 5]

[0134] The concentration of copper ions was changed to 40 g / L to prepare the electrolyte, and the current density was changed to 310 A / m. 2 Electrolysis was then performed. Otherwise, the procedure was the same as in Example 1 to obtain the electrodeposited material.

[0135] The electrodeposited material was observed using SEM, and the results confirmed it to be a filamentous structure. Each end of the filamentous structure was tapered.

[0136] [Comparative Example 1]

[0137] This comparative example corresponds to Non-Patent Literature 1.

[0138] In a 100 mL four-necked flask, 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, 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 aforementioned flask using a syringe. Stir with a stirrer for 60 minutes, then turn off the heater. Afterward, cool in a water bath to below 30 °C to obtain a filamentous substance. Filter to disperse it in ethanol, perform ultrasonic dispersion, let stand for 10 minutes, and separate the supernatant (suspended matter) and precipitate.

[0139] Figure 2 The SEM image of the filament obtained in this comparative example is shown. In this figure, the 30,000x SEM image is displayed to observe the shape of the leading edge of the filament.

[0140] [Evaluation 1]

[0141] For the linear bodies obtained in Examples 1-5 and Comparative Example 1, the length, thickness, and radius of curvature were measured using the methods described above. In particular, for the thickness of the linear bodies, a sufficient magnification of thickness was measured. Specifically, in Example 1, a 20,000x SEM image was used; in Example 2, an 80,000x SEM image was used; in Example 3, a 10,000x SEM image was used; in Example 4, a 100x SEM image was used; in Example 5, a 100x SEM image was used; and in Comparative Example 1, a 20,000x SEM image was used. Ten or more thicknesses were read and their arithmetic averages were taken to obtain the thickness. Similarly, for length, the length can be measured at a sufficient multiple. Specifically, in Example 1, a 10,000x SEM image was used; in Example 2, a 20,000x SEM image was used; in Example 3, a 5,000x SEM image was used; in Example 4, SEM images of 1,000x, 2,000x, and 5,000x were used; in Example 5, SEM images of 100x, 200x, and 500x were used; and in Comparative Example 1, a 5,000x SEM image was used. The lengths of more than 20 lengths were read and the arithmetic average was calculated to obtain the result.

[0142] In addition, the irregularity rate of the assemblages of linear bodies obtained in Examples 1-5 and Comparative Example 1 was measured using the methods described above.

[0143] Furthermore, the X, Y, and X / Y values ​​of the crystal, as well as its orientation, were determined using the following methods. These results are shown in Table 1 below.

[0144] [The values ​​of X, Y, and X / Y of the crystal, as well as the orientation of the crystal]

[0145] The X, Y, and X / Y values ​​of the crystal were determined using the following method. Fine metallic wires were coated onto a copper plate using carbon paste. The coating was then cross-sectionalized using an argon ion beam cross-sectioning device (JEOL Ltd. Cross Section Polisher (CP)) to create and observe the EBSD grain pattern of the cross-section. The carbon paste used was Colloidal Graphite (Isopropanol Base) from Electron Microscopy Sciences. EBSD was performed using a Carl Zeiss SEMCrossbeam 540 and an Oxford Symmetry EBSD detector mounted on it. In the resulting grain pattern, the X and Y values ​​of the crystal at three boundary regions where the fine metallic wires were divided into four equal parts along their length were measured with reference to the scale in the diagram, and the X / Y value was calculated. The arithmetic mean was then calculated and rounded to the nearest decimal place.

[0146] The grain diagrams of EBSD obtained by measuring the linear structures of Example 1 and Comparative Example 1 are shown below. Figure 3 and Figure 4 .

[0147] The orientation of the crystal was determined using the following method. For the fine metal wires of Examples 1-4 and Comparative Example 1, the fine metal wires were sprinkled onto a copper grid to load them. Observation was performed using a JEOL Ltd. JEM-ARM200F. Boundary lines dividing the length of the fine metal wires into four equal parts along their extension direction were drawn. Shape observation based on TEM was performed at the midpoints of the boundary lines at three boundary regions, and electron diffraction patterns were obtained. Orientation analysis based on electron diffraction was performed using a GATAN digital micrograph.

[0148] Additionally, for the fine metallic wires of Example 5, after mixing in carbon paste, they were coated onto a copper plate, and the coating was cross-sectionally processed using an argon ion beam cross-sectioning apparatus (JEOL Ltd. Cross Section Polisher (CP)). Observation was performed using a SEM Crossbeam 540 and an EBSD detector (Symmetry) mounted on it. Boundary lines dividing the length of the fine metallic wires into four equal parts along their extension direction were drawn. At three points along the four-part boundary lines in the three boundary regions, the crystal orientation based on EBSD was determined. The crystal orientation based on EBSD was determined using an Oxford AZtec Crystal 2.0.

[0149] The orientations (

[100] ,

[110] , and

[111] ) evaluated by TEM electron diffraction or EBSD were determined to be within ±30° of the extension direction of the fine metal wire or its tangential direction (each orientation was determined by the normal to the range of ±30° from the length direction. If two or more orientations were within ±30°, the orientation closer to 0° was taken. If three orientations were not within ±30°, no preferred orientation was considered).

[0150] Regarding Examples 1-4 and Comparative Example 1, five randomly extracted fine metal wires were evaluated, and the percentage of grains with preferred orientations in each orientation (

[100] orientation,

[110] orientation, and

[111] orientation) was calculated based on a total of 15 evaluation results. Regarding Example 5, five randomly extracted fine metal wires were evaluated, and the percentage of grains with preferred orientations in each orientation (

[100] orientation,

[110] orientation, and

[111] orientation) was calculated based on a total of 45 evaluation results.

[0151] The percentage of grains with preferred orientations (

[110] orientation and

[111] orientation).

[0152] [Evaluation 2]

[0153] The resistivity of the filaments and particles obtained in Examples 1-5 and Comparative Example 1 was measured in the sintered bodies subsequently manufactured according to the following method. The results are shown in Table 1.

[0154] [Measurement of resistivity]

[0155] The filaments and particles obtained in Examples 1-5 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 proportion of solid components 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.

[0156] 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 (Mitsubishi Chemical Corporation MCP-T600) via the four-probe method.

[0157] It should be noted that, for the sintered bodies fired at 220°C and 240°C in Comparative Example 1, since the resistance value is greater than the upper limit of 10 for measurement, 6 The value was Ω·cm, therefore it could not be determined. It is recorded as ">10" in Table 1. 6 ".

[0158] [Table 1]

[0159]

[0160] Based on the results shown in Table 1, it is clear that the sintered body formed from the linear body obtained in the examples exhibits good low-temperature sintering properties. Furthermore, it is determined that, compared to the linear body obtained in the comparative examples, the sintered portion of the linear body obtained in the examples has lower resistance after heat treatment at the same heating temperature.

[0161] Industrial availability

[0162] The present invention provides a fine metal wire with a lower sintering temperature than before, or with reduced resistance of the sintered portion after heat treatment at the same heating temperature.

Claims

1. A fine metal linear body having a length of 0.5 μm or more and 200 μm or less and a thickness of 30 nm or more and 10 μm or less, 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, the fine metal linear body has a polycrystal structure in which a plurality of crystals are connected along the extension direction of the linear body, when the fine metal linear body is divided into four equal lengths along the extension direction thereof, the arithmetic mean of the ratio of the length of the crystal of the metal constituting the fine metal linear body in the extension direction of the fine metal linear body to the length in a direction orthogonal to the extension direction, i.e., the value of X / Y, is 4 or less at the three boundary regions.

2. A fine metal linear body having a length of 0.5 μm or more and 200 μm or less and a thickness of 30 nm or more and 10 μm or less, 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, the fine metal linear body has a polycrystal structure in which a plurality of crystals are connected along the extension direction of the linear body, at the three boundary regions when the fine metal linear body is divided into four equal lengths along the extension direction thereof, the proportion of grains in the [110] orientation evaluated by electron diffraction or electron backscattering diffraction of a transmission electron microscope of the crystal of the metal constituting the fine metal linear body in the range of ±30° from the extension direction of the fine metal linear body is 50% or less.

3. The fine metal linear body according to claim 1 or 2, when the length of the crystal of the metal constituting the fine metal linear body in a direction orthogonal to the extension direction of the fine metal linear body is Y, at the three boundary regions when the fine metal linear body is divided into four equal lengths along the extension direction thereof, the arithmetic mean of Y is 10 nm or less.

4. The microfine wire-shaped body according to claim 1 or 2, wherein at the three boundary regions when the fine metal linear body is divided into four equal lengths along the extension direction thereof, the proportion of grains in the [111] orientation evaluated by electron diffraction or electron backscattering diffraction of a transmission electron microscope of the crystal of the metal constituting the fine metal linear body in the range of ±30° from the extension direction of the fine metal linear body is 50% or more, or the proportion of grains in the [100] orientation, the [110] orientation, and the [111] orientation evaluated by electron diffraction or electron backscattering diffraction of a transmission electron microscope of the crystal of the metal constituting the fine metal linear body in the range of ±30° from the extension direction of the fine metal linear body is 50% or less.

5. The fine metal linear body according to claim 1 or 2, at least one end portion of which has a front end tapered shape, the angle of the front end at the front end tapered shape being 60 degrees or less.

6. The microfine wire-shaped body according to claim 1 or 2, wherein the metal constituting the fine metal linear body is copper or a copper alloy.

7. A method for producing the fine metal linear body according to claim 1 or 2, which is a method for producing a fine metal linear body using a metal as a base material, comprising a step of causing the metal to be deposited on a cathode by electrolytic reduction using an electrolyte solution containing a source of a metal element, 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 is an alloy containing the metal, the electrolytic reduction is performed in a state in which an oily substance is attached to a surface of the cathode, the oily substance is a saturated aliphatic carboxylic acid or an unsaturated aliphatic carboxylic acid, attaching 5 g / m 2 above and 100 g / m 2 the oily substance below.

8. A collection of fine metal linear bodies, which is a collection of fine metal linear bodies according to claim 1 or 2, the number of fine metal linear bodies having a curved portion with a radius of curvature of 5 times or less the length of the fine metal linear body accounts for 5% or more of the total number of fine metal linear bodies.

9. A collection of fine metal linear bodies, which is a collection of fine metal linear bodies according to claim 1 or 2, the proportion of particles having a shape other than a linear shape in the collection is 50% or less.

10. A composition comprising the fine metal linear body according to claim 1 or 2 and a dispersion medium.

11. A joined structure comprising a first member, a second member, and a joining portion joining the first member and the second member, the joining portion is formed of a sintered body of the composition according to claim 10.

12. A semiconductor device comprising a first member, a second member, and a joining portion joining the first member and the second member, the joining portion is formed of a sintered body of the composition according to claim 10, at least one of the first member and the second member is a semiconductor element.

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

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