JP2013196936A - Conductive paste, conductor, base material with conductive film, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste capable of forming a conductor which has excellent conductivity and its durability, and also has excellent heat resistance; the conductor; a base material with a conductive film which uses the conductor and has excellent conductivity, its durability and heat resistance; and a manufacturing method therefor.SOLUTION: The conductive paste includes: particles (A) having an average particle size of 1-20 μm selected from a single particle made from a metal having a melting point of 300°C or higher, a single particle made from a metal compound which has a melting point of 300°C or higher and becomes a metal by being heated at the melting point or lower, and an aggregate of fine particles of metal compounds having an average primary particle size of 1 nm-1 μm; low melting point metal particles (B) having a melting point of 200°C or lower; inorganic fine particles (C) which have an average particle size smaller than that of the particle (A), may produce an alloy with a low melting point metal, and have a melting point of 300°C or higher; and an organic compound (D) having two or more OH groups; and substantially does not contain a resin. A conductor is formed of conductive fine particles dispersed in a binder component which mainly has the alloy containing the low melting point metal having a melting point of 200°C or lower.

Description

  The present invention relates to a conductive paste, a conductor, a substrate with a conductive film using the conductor, and a method for manufacturing the same.

  Conventionally, a method using a conductive paste is known for forming wiring conductors such as electronic components and printed wiring boards. Among these, a printed wiring board is manufactured by applying a conductive paste in a desired pattern shape on an insulating base material and curing it to form a wiring pattern (see, for example, Patent Document 1).

  As the conductive paste, a conductive paste in which silver or copper metal particles are dispersed in a vehicle in which a curable resin is dissolved in an organic solvent is generally used. A conductor obtained by curing such a conductive paste has a structure that maintains the shape of the conductor by filling a gap between conductive metal particles with a resin as a binder component. When the conductor is made of metal particles and a resin as a binder component in this way, the resin deteriorates when exposed to strong UV irradiation even under direct sunlight for a long period of time or for a short period of time, thereby packing the conductor. There was a problem that the structure was weakened and the conductivity was lowered. In order to solve the problems caused by resin deterioration, it is effective to change the binder component from an organic material such as a resin to an inorganic material, and to form a structure in a low-temperature process, a low melting point metal is used as the inorganic material. Is considered effective.

  In order to obtain a conductor in which the binder component is composed of a low melting point metal, for example, Patent Document 2 discloses a composition containing a resin and conductive particles, and the conductive particles include not only a high melting point metal but also a low melting point. A technique is described that uses a conductive composition for a conductor pattern that contains a metal and the low melting point metal has a composite structure. According to Patent Document 2, a conductive pattern obtained on a substrate using this conductive composition has a conductive layer made of high melting point metal particles and a low melting point metal as a binder component on the substrate side, The structure has an insulating layer made of resin on the surface.

  Since the conductor pattern according to Patent Document 2 has the above structure, there is little problem of conductivity deterioration due to deterioration of the resin, and the conductive layer is also excellent in conductivity. However, since the surface of the conductive layer is covered with an insulating layer, the conductive pattern has a problem that it is difficult to form an electrical connection when bonding to another device. Furthermore, for example, when trying to join other devices using solder or the like, if the temperature is raised above the melting point of the low melting point metal, the low melting point metal that maintains the shape of the conductor pattern melts, and the conductor There was a problem that the pattern was broken.

JP 2007-227156 A JP 2011-142093 A

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a conductive paste capable of forming a conductor having excellent conductivity and durability and excellent heat resistance.
In addition, the present invention provides a conductor excellent in conductivity and durability, and further excellent in heat resistance, a conductivity using the conductor, and a substrate with a conductive film excellent in durability and heat resistance, and It aims at providing the manufacturing method.

The present invention provides a conductive paste, a conductor, a substrate with a conductive film, and a method for producing the same, having the following configuration.
[1] Single particles made of a metal having a melting point of 300 ° C. or higher, single particles made of a metal compound that becomes a metal by heating at a melting point of 300 ° C. or higher, and an average primary particle size of 1 nm to 1 μm One or more particles (A) selected from aggregates of fine particles of the metal compound and having an average particle size of 1 to 20 μm, low melting point metal particles (B) having a melting point of 200 ° C. or less, and the particles (A ) Inorganic fine particles (C) having a smaller average particle diameter and capable of forming an alloy with the low melting point metal at a temperature equal to or higher than the melting point of the low melting point metal, and at least two OHs in one molecule A conductive paste containing an organic compound (D) having a group and substantially not containing a resin.

[2] The conductive paste according to [1], wherein the particles (A) are at least one selected from the group consisting of gold, silver, copper, nickel, aluminum, silver oxide, and copper hydride.
[3] The conductive paste according to [1] or [2], wherein the low-melting-point metal particles (B) are made of an alloy containing at least one selected from the group consisting of tin, indium, and bismuth.
[4] The inorganic fine particles (C) are one or more selected from the group consisting of gold, silver, copper, nickel, aluminum, silver oxide, and copper hydride, according to any one of [1] to [3]. Conductive paste.
[5] The conductive paste according to any one of [1] to [4], wherein the boiling point of the organic compound (D) is 150 to 300 ° C.

[6] A conductor in which conductive particles (X) are dispersed in a binder component, wherein the binder component is mainly composed of a low melting point metal having a melting point of 200 ° C. or lower and a metal having a melting point of 300 ° C. or higher. A conductor composed of (Y).
[7] By heating the conductive paste according to any one of claims 1 to 5 at a temperature equal to or higher than the melting point of the low melting point metal, the particles (A) are made conductive particles (X), and the inorganic paste The conductor according to claim 6, which is obtained by forming an alloy (Y) from the fine particles (C) and the low melting point metal particles (B).
[8] A base material with a conductive film comprising a conductive film made of the conductor according to [6] or [7] on a base material.
[9] After applying the conductive paste according to any one of [1] to [5] on a substrate, the conductive paste is heated at a temperature equal to or higher than the melting point of the low-melting-point metal, and the inorganic fine particles ( A conductive film-coated base, wherein a conductive film obtained by dispersing conductive particles obtained from the particles (A) is formed in a binder component mainly composed of an alloy obtained from C) and low-melting-point metal particles (B). A method of manufacturing the material.

  According to the present invention, it is possible to provide a conductive paste capable of forming a conductor having excellent conductivity and durability and excellent heat resistance. Also provided are a conductor excellent in conductivity and its durability and also in heat resistance, a conductive material using the conductor, a substrate with a conductive film excellent in durability and heat resistance, and a method for producing the same it can.

It is a figure which shows typically an example of the electrically conductive paste of embodiment of this invention, and an example of the conductor obtained using it. It is a cross-sectional schematic diagram which shows an example of the base material with an electrically conductive film of embodiment of this invention.

Hereinafter, embodiments will be described in detail.
[Conductive paste]
The conductive paste of the embodiment of the present invention includes single particles made of a metal having a melting point of 300 ° C. or higher, single particles made of a metal compound that becomes a metal by heating at a melting point of 300 ° C. or higher and lower than the melting point, and average primary particles One or more particles (A) having an average particle size of 1 to 20 μm selected from aggregates of fine particles of the metal compound having a diameter of 1 nm to 1 μm, and low melting point metal particles (B ), An inorganic fine particle (C) having an average particle size smaller than that of the particles (A) and capable of forming an alloy with the low melting point metal at a temperature equal to or higher than the melting point of the low melting point metal, and one molecule And an organic compound (D) having at least two OH groups therein, and a paste-like composition containing substantially no resin.

  According to the conductive paste of the embodiment of the present invention, by heating, specifically, by heating at a temperature higher than the melting point of the low melting point metal particles (B), the particles (A) contained in the conductive paste become conductive. Thus, the low melting point metal particles (B) and the inorganic fine particles (C) are alloyed to form a binder component, and a conductor having a structure filling the space between the conductive particles can be formed. In addition, since the conductive paste does not substantially contain a resin, the binder component of the obtained conductor is composed of an inorganic substance mainly composed of the alloy.

The conductor having the above-described configuration obtained by the conductive paste according to the embodiment of the present invention has excellent conductivity and particularly excellent durability because the conductive particles and the binder component are substantially composed of only a metal material. Furthermore, since the alloy that is the main component of the binder component is an alloy having a melting point higher than that of the low-melting-point metal particles (B) of the raw material, a conductor obtained by the conductive paste and a member having the same can be processed by, for example, soldering Even when exposed to a relatively high temperature treatment such as, or when subjected to high temperature use, the conductor is excellent in heat resistance, such as being able to maintain its shape sufficiently.
Hereinafter, each component which the electrically conductive paste of embodiment of this invention contains is demonstrated.

<Particle (A)>
The particles (A) are a single particle made of a metal having a melting point of 300 ° C. or higher, a single particle made of a metal compound that becomes a metal by heating at a melting point of 300 ° C. or higher, and an average primary particle diameter of 1 nm to It is comprised by 1 or more types chosen from the aggregate of the fine particle of the said metal compound which is 1 micrometer, The average particle diameter is 1-20 micrometers. When the conductive paste of the present invention is used as a conductor, the particles (A) have a function of ensuring good conductivity in the conductor by forming conductive chains and forming a chain structure.

  As will be described later, the conductive paste of the present invention becomes a conductor by being heated at a predetermined temperature equal to or higher than the melting point of the low melting point metal particles (B) having a melting point of 200 ° C. or lower. When the particle (A) is a single particle, the material constituting the particle (A) is a conductive metal material having a melting point of 300 ° C. or higher, or heating having a melting point of 300 ° C. or higher and lower than the melting point. If it is a metal compound used as a metal material which has electroconductivity by this, it will not restrict | limit in particular. Further, when the particle (A) is an aggregate of fine particles, there is no particular limitation as long as it is a metal compound that becomes a conductive metal material by heating at a melting point of 300 ° C. or higher and lower than the melting point. Since the constituent material of the particles (A) has a melting point higher than the above-mentioned predetermined temperature, it does not melt at the heating temperature and becomes a conductive particle while maintaining its shape, thereby forming a chain structure. In addition, particle | grains (A) may be comprised by 1 type chosen from the said single particle | grain and the aggregate of fine particles, and may be comprised by 2 or more types. Moreover, in this specification, a single particle means the form in which a primary particle exists independently, without forming an aggregate.

  Specifically, as the material constituting the particles (A), for a conductive metal material having a melting point of 300 ° C. or higher, a known metal having a melting point of 300 ° C. or higher can be mentioned. From the viewpoint of conductivity, gold, Silver, copper, nickel, aluminum and the like are preferable. Examples of the metal compound that becomes a conductive metal material by heating at a melting point of 300 ° C. or higher and lower than the melting point include silver oxide and copper hydride.

When the particle (A) is a conductor, it becomes a conductive particle and forms a chain structure, so that the form is a single particle or an aggregate of fine particles having an average primary particle diameter of 1 nm to 1 μm, and an average particle diameter Is 1 to 20 μm. The average particle diameter is preferably 2 to 10 μm, more preferably 3 to 7 μm. In order to ensure the fluidity of the conductive paste, the average particle diameter of the particles (A) is 1 μm or more, and in order to produce a fine wiring, the average particle diameter of the particles (A) is 20 μm or less.
In addition, 1-20 micrometers which is the range of the said average particle diameter, when particle | grains (A) are comprised with a single particle, since this particle | grain is a form in which a primary particle exists independently, an average primary particle diameter In the case of being composed of aggregates of fine particles, the range of average aggregated particle diameter is indicated. Hereinafter, the particles (A) composed of single particles are referred to as particles (A1) and the particles (A) composed of aggregates of fine particles are referred to as particles (A2) as necessary.

When the particle (A1) is composed of a metal having a melting point of 300 ° C. or higher, the particle (A1) may be composed of a single material, for example, two types such as silver whose core part is copper and whose surface is hardly oxidized. These materials may be used, and further materials may be used as necessary. The case where the particles (A1) are composed of a metal compound that becomes a metal by heating at a melting point of 300 ° C. or higher and lower than the melting point may be composed of a single material or two or more materials. You may be comprised from the material.
Moreover, about the constituent material of particle | grains (A2), if it is the said metal compound, it may be single or may be 2 or more types. Examples of the shape of the particles (A) include a spherical shape, a plate shape, and a dendrite. In the present invention, the particle (A1) is preferably a plate-like particle (A), and the particle (A2) is preferably a spherical particle (A).

  When the particle (A) is a particle (A2) composed of an aggregate of fine particles, the average primary particle diameter of the fine particles constituting the particle (A2) is 1 nm to 1 μm, preferably 10 to 100 nm. The average primary particle diameter of the fine particles constituting the particles (A2) is 1 nm or more for ensuring the fluidity of the conductive paste, and 1 μm or less is essential for ensuring good conductivity at a temperature of 150 to 200 ° C. It is. The particles (A2) may be aggregates of inorganic fine particles (C) described later as long as the above conditions as the particles (A) are satisfied, and the average primary particle size of the fine particles in this case is inorganic. This is the same as the average primary particle diameter of the fine particles (C).

  Here, in this specification, an average particle diameter is calculated | required as follows. Depending on the size of the particle size, specifically, the average particle size of particles having a particle size of about 0.5 to 20 μm is randomly selected from a scanning electron microscope (hereinafter referred to as “SEM”) image. The Feret diameter of 100 particles is measured, and the average of these particle diameters is calculated. The average particle size of particles having a particle size of about 1 to 500 nm is measured by measuring the Feret size of 100 particles randomly selected from a transmission electron microscope (hereinafter referred to as “TEM”) image. These particle sizes are calculated by averaging.

  Moreover, about the particle | grains (A) which an electrically conductive paste contains, 1 type may be used independently and 2 or more types may be used together. Single composition particles (A) are preferred. Furthermore, the particles (A) may be used in combination with inorganic particles (C) described later.

<Low melting point metal particles (B)>
The low-melting-point metal particles (B) are metal particles having a melting point of 200 ° C. or less. When the conductive paste of the present invention is used as a conductor, the low-melting-point metal particles (B) are alloyed with inorganic fine particles (C) to be described later. ) Function as a binder component that fills the gaps that are conductive particles and form a chain structure.

  The material constituting the low melting point metal particles (B) is not particularly limited as long as it is a metal material having a melting point of 200 ° C. or lower. Such a metal material may be a single metal or an alloy composed of a plurality of metals. Specifically, an alloy having a melting point of 200 ° C. or lower including tin (Sn), indium (In), bismuth (Bi), and the like can be given. As such an alloy having a melting point of 200 ° C. or lower, a solder having a melting point of 200 ° C. or lower can be appropriately selected from various alloys known as solder. In addition, in order to improve adhesion to a substrate, particularly a glass substrate, a small amount of a metal such as zinc (Zn), antimony (Sb), titanium (Ti), or silicon (Si) can be added to the alloy. .

  The low melting point metal particles (B) are heated and melted when obtaining a conductor from the conductive paste of the present invention containing the low melting point metal particles (B). From the viewpoint of thermal efficiency at this time, the melting point of the low melting point metal particles (B) is more preferably 180 ° C. or less. The low melting point metal particles (B) are alloyed with inorganic fine particles (C) described later in the conductive paste during heating and melting. The alloy thus obtained becomes an alloy having a melting point higher than that of the low melting point metal particles (B). Therefore, the obtained conductor becomes a conductor that can withstand a temperature equal to or higher than the melting point of the low melting point metal particles (B). For example, when a member having this conductor is further subjected to soldering or the like, or a member that becomes high in use Can also be widely applied.

  Regarding the melting point of the alloy obtained by alloying the low melting point metal particles (B) and the inorganic fine particles (C), the types and blends of the materials constituting the low melting point metal particles (B) and the inorganic fine particles (C) to be used, respectively. By percentage. These are appropriately selected and adjusted in consideration of required heat resistance characteristics depending on the use of the conductor. From the viewpoint of heat resistance of the obtained conductor, the melting point of the low melting point metal particles (B) is preferably 130 ° C. or higher.

  The low melting point metal particles (B) may be single particles or aggregates in which fine particles are aggregated. The average particle diameter of the low melting point metal particles (B) is preferably 1 to 50 μm. As in the case of the particles (A), the range of the average particle diameter indicates the range of the average primary particle diameter when the low melting point metal particles (B) are composed of single particles, and is an aggregate of fine particles. When constituted, the range of the average aggregate particle diameter is shown.

  If the average particle diameter of the low melting point metal particles (B) is 1 μm or more, the flow characteristics of the conductive paste containing them will be good, and voids will not easily be formed. Moreover, if the average particle diameter of the low-melting-point metal particles (B) is 50 μm or less, it becomes easy to produce fine wiring with a conductive paste containing the same. The average primary particle size of the fine particles when the low melting point metal particles (B) are composed of fine particle aggregates is not particularly limited.

  Examples of the shape of the low melting point metal particles (B) include a spherical shape, a plate shape, and a dendritic shape, and a spherical shape is preferable from the viewpoint of paste fluidity. The content of the low melting point metal particles (B) in the conductor paste of the present invention is appropriately selected from the relationship between the content of the particles (A) and the content of the following inorganic fine particles (C). The specific relationship of the content of each component will be described in the inorganic fine particles (C).

<Inorganic fine particles (C)>
The inorganic fine particles (C) are inorganic fine particles having an average particle size smaller than that of the particles (A) and a melting point capable of forming an alloy with the low melting point metal at a temperature equal to or higher than the melting point of the low melting point metal. When the inorganic fine particles (C) are made into the conductor of the conductive paste of the present invention, the inorganic fine particles (C) are alloyed with the low melting point metal particles (B), and the particles (A) become conductive particles and form a chain structure. Functions as a binder component.

  As a material constituting the inorganic fine particles (C), a melting point of 300 ° C. or higher capable of forming an alloy with the low melting point metal particles (B) constituting the low melting point metal particles (B) at a temperature equal to or higher than the melting point of the low melting point metal particles (B). There is no particular limitation as long as it is an inorganic material, specifically a metal or a metal compound. Preferably, it is a metal or a metal compound that makes the melting point of the obtained alloy higher, although it depends on the metal composition of the finally obtained alloy.

Specific examples of such a metal or metal compound include gold, silver, copper, nickel, aluminum, silver oxide, and copper hydride. When the inorganic fine particles (C) are silver oxide, copper hydride or the like, these usually change to silver, copper or the like, respectively, at the time of heating when producing a conductor from the conductive paste.
The inorganic fine particles (C) may be single particles or an aggregate in which the fine particles are aggregated in a range where the average particle size is smaller than the average particle size of the particles (A). The average particle diameter of the inorganic fine particles (C) is preferably 1 to 500 nm, and more preferably 10 to 100 nm.
If the average particle diameter of the inorganic fine particles (C) is 500 nm or less, a fine wiring can be easily produced with a conductive paste containing the inorganic fine particles (C), and alloying with the low melting point metal particles (B) can be easily performed. If the average particle diameter of the inorganic fine particles (C) is 1 nm or more, the flow characteristics of the conductive paste containing the inorganic fine particles (C) will be good. Examples of the shape of the inorganic fine particles (C) include a spherical shape, a plate shape, and a fibrous shape, and a spherical shape is preferable because the surface area is maximized and alloying proceeds smoothly.

  In the conductive paste of the present invention, the inorganic fine particles (C) may be used in combination with the particles (A). Specific examples of the composite form include a form in which the inorganic fine particles (C) are attached or bonded to the surface of the particles (A), particularly the particles (A1) composed of single particles. When particles (A) having inorganic fine particles (C) on such a surface, particularly particles (A1), are used, when the conductive paste is heated, specifically, a predetermined temperature equal to or higher than the melting point of the low melting point metal particles (B). When the inorganic fine particles (C) existing on the surface of the particles (A) are heated at the temperature of 1, the fusion of the inorganic fine particles (C) sandwiched between and in contact with the particles (A) proceeds, and the particles (A) The conductive path can be satisfactorily formed. Therefore, it is preferable to use the inorganic fine particles (C) and particles (A) combined in this way. In this case, the inorganic fine particles (C) present on the surface of the particles (A) are incorporated into the low melting point metal in which the low melting point metal particles (B) are melted and alloyed at other portions.

  Here, even when the particles (A) and the inorganic fine particles (C) are combined and used as described above, the inorganic fine particles (C) that are not attached to and bonded to the particles (A) are treated with the particles (A ) And composite inorganic fine particles (C), which is preferable from the viewpoint of securing the content of the inorganic fine particles (C) in the conductive paste.

  FIG. 1 is a diagram schematically showing a structural change when a conductor is obtained from the conductive paste. That is, in FIG. 1, as an example of the conductive paste of the embodiment of the present invention, the conductive paste containing particles (A1) having inorganic fine particles (C) on the surface is obtained using the conductive paste in the lower stage. An example of the conductor to be used is schematically shown. The conductive paste shown in FIG. 1 includes particles (A1) having inorganic fine particles (C) on the surface, low melting point metal particles (B), and inorganic fine particles (C) that do not adhere to or bind to the particles (A1). In a form dispersed in the organic compound (D).

  In such a conductive paste, the organic compound (D) is removed by heating at a predetermined temperature equal to or higher than the melting point of the low melting point metal particles (B). Further, when the particles (A1) are metal, the conductive particles 3 are formed as they are, and when the particles (A1) are metal compounds, the conductive particles 3 are formed by heating to form a metal. Further, the inorganic fine particles (C) that are sandwiched between and in contact with the particles (A1) are fused together to form a connecting portion indicated by P between the conductive particles 3 in the conductor of FIG. Forming a conductive material. On the other hand, the low melting point metal particles (B) become the binder component 4 which is alloyed with the inorganic fine particles (C) which have not been melted and used for the connection and fills the gaps between the particles (A1).

  Here, in FIG. 1, the portion indicated by P and the portion indicated by the binder component 4 are not actually clearly distinguished, both of which are inorganic fine particles (C) and low melting point metal particles, particularly at the boundary. It is considered that the alloy composition with (B) gradually changes. That is, the central portion of the region indicated by P is substantially made of a metal material obtained by heating the inorganic fine particles (C), and most of the binder component 4 excluding the vicinity of the boundary with the region indicated by P is inorganic. It is assumed that the fine particles (C) and the low melting point metal particles (B) are made of an alloy that is uniformly alloyed at a constant ratio. In the boundary region between the two, it is assumed that the concentration of the metal material derived from the inorganic fine particles (C) gradually decreases from the region indicated by P toward the binder component region.

  As the content ratio of the particles (A), the low melting point metal particles (B), and the inorganic fine particles (C) in the conductive paste of the present invention, the low melting point metal particles (B) and the inorganic fine particles with respect to 100 parts by mass of the particles (A). The total mass of (C) is preferably 5 to 80 parts by mass, and more preferably 40 to 70 parts by mass. The total mass of the low melting point metal particles (B) and the inorganic fine particles (C) is an amount corresponding to a binder component including, for example, the connecting portion P between the conductive particles 3 shown in FIG. When the conductor is formed using this, it becomes possible to achieve good conductivity and shape retention as a conductor at the same time.

  The content ratio of the low melting point metal particles (B) and the inorganic fine particles (C) in the conductive paste of the present invention depends on the kind of materials constituting them, but the inorganic fine particles (C) with respect to 100 parts by mass of the low melting point metal particles (B). ) Is preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass. By incorporating low-melting-point metal particles (B) and inorganic fine particles (C) in the above proportion in the conductive paste, a high melting point and uniform alloy can be formed as a binder component when a conductor is formed using this. Thus, a conductor excellent in durability and heat resistance can be obtained.

<Organic compound (D)>
The organic compound (D) is an organic compound having at least two OH groups in one molecule, and the particles (A), the low melting point metal particles (B), and the inorganic fine particles (C) are dispersed therein. It has the function of forming a paste. Further, when the conductive paste is heated, specifically, when heated at a predetermined temperature equal to or higher than the melting point of the low melting point metal particles (B), it acts as a flux component, and the particles (A), low melting point metal particles (B), By removing the oxide film on the surface of the inorganic fine particles (C), the conductive connection between the particles (A), preferably the conductive connection by fusing the inorganic fine particles (C) between the particles (A) is assisted. To do. Furthermore, it has a function of improving the wettability of the low melting point metal in which the low melting point metal particles (B) are melted on the surfaces of the particles (A) and the inorganic fine particles (C).

  Since the organic compound (D) has at least two OH groups in one molecule, the low melting point metal particles (B) melted on the surfaces of the particles (A) and the inorganic fine particles (C). Improve wettability. In order to improve wettability, the number of OH groups that the organic compound (D) has in one molecule is preferably 3 or more, and the organic compound (D) melts at the heating temperature and gradually volatilizes during the heating. From the viewpoint of having an appropriate vapor pressure that disappears from the conductor, three or four are preferable.

  In addition, when the conductive paste is heated to form a conductor, if the organic compound (D) or a heat-modified product thereof remains as a residue, it must be washed. The organic compound (D) is preferably a non-residue flux that does not require this in order to prevent an increase in the number of steps due to washing and an influence on the conductor. The organic compound (D) for functioning as a residue-free flux functions as a flux at the beginning of heating of the conductive paste, but is required to have a property of volatilizing and disappearing upon further heating. Therefore, 150-300 degreeC is preferable and, as for the boiling point of an organic compound (D), 180-250 degreeC is more preferable.

  Specific examples of the organic compound (D) include 1,3 dioxane-5,5-dimethanol, 1,4-dioxane-2,3-diol, 1,5-pentanediol, and 3-methyl-1,5. -Pentanediol, 2,5-furandiethanol, n-butanediethanolamine, diethanolamine, tetraethylene glycol, triethylene glycol, hexaethylene glycol, pentaethylene glycol, 1,2,3-hexanetriol, 1,2,6-hexane Triol, 1,2,4-butanetriol, 2,3,4-trihydroxybenzophenone, 3-methylpentane-1,3,5-triol, glycerin, triethanolamine, trimethylolpropane, trimethylolethane, pyrogallol, Erythritol, N-N-bis (2- Dorokishiechiru) isopropanolamine, pentaerythritol, ribitol, and bis (2-hydroxymethyl) iminotris (hydroxymethyl) methane, and the like. Among these, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2,3-hexanetriol, 1,2,6-hexanetriol, 1,2,4-butanetriol , Trimethylolethane, pyrogallol, erythritol and the like are preferable. In this invention, these 1 type may be used independently and 2 or more types may be used together.

  The content of the organic compound (D) in the conductive paste of the present invention is 3 to 50 with respect to 100 parts by mass of the total mass of the particles (A), the low melting point metal particles (B), and the inorganic fine particles (C). A mass part is preferable and 5-40 mass parts is more preferable. By making the content of the organic compound (D) in the above range, the moldability of the conductor paste is good, and it functions sufficiently as the above-mentioned flux when heated to make a conductor, preferably as a residue-free flux Is possible.

<Other ingredients>
The electrically conductive paste of this invention can contain arbitrary components other than the said particle | grain (A), a low melting-point metal particle (B), an inorganic fine particle (C), and an organic compound (D) in the range which does not impair the effect of this invention. Examples of such optional components include an antioxidant, a dispersant, a thixotropic agent, and a substrate adhesion-imparting agent.

[conductor]
The conductor of the embodiment of the present invention can be formed using the above-described conductive paste of the present invention. That is, by heating the conductive paste of the present invention at a predetermined temperature equal to or higher than the melting point of the low melting point metal, the particles (A) become conductive particles (X), and the inorganic fine particles (C) and the low melting point are heated. By forming the alloy (Y) from the metal particles (B), the conductor according to the embodiment of the present invention is obtained.
The conductor of the embodiment of the present invention is a conductor in which conductive particles (X) are dispersed in a binder component, and the binder component mainly includes a low melting point metal having a melting point of 200 ° C. or less, and a melting point of 300. It is comprised with the alloy (Y) which consists of a metal more than ° C. The conductor having such a configuration has excellent conductivity and durability.

  As electroconductive particle (X), a constituent material is at least 1 sort (s) chosen from gold | metal | money, silver, copper, nickel, and aluminum, the average particle diameter is 1-20 micrometers, or an average primary particle diameter is 1 nm- Conductive particles composed of aggregates of fine particles of 1 μm are preferable. As the alloy (Y), a low melting point metal having a melting point of 200 ° C. or less, particularly an alloy containing at least one selected from tin, indium and bismuth, specifically, a known solder material having a melting point of 200 ° C. or less An alloy with at least one metal selected from gold, silver, copper, nickel and aluminum is preferred.

  In addition, although a binder component is mainly comprised with an alloy (Y), you may contain antioxidant etc. arbitrarily in the range which does not impair the effect of this invention. In the conductor of the present invention, preferably, the binder component is made of an alloy (Y) only. If the content rate of electroconductive particle (X) and the alloy (Y) in the conductor of this invention is a ratio which can ensure favorable electroconductivity because conductor particle (X) forms a chain structure in a conductor. More specifically, the alloy (Y) is preferably 5 to 80 parts by mass and more preferably 40 to 70 parts by mass with respect to 100 parts by mass of the conductor particles (X).

[Substrate with conductive film and method for producing the same]
This invention provides the base material with a electrically conductive film which has further the electrically conductive film which consists of a conductor of the said invention on the base material. Hereinafter, the conductor of the present invention will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view illustrating an example of a base material with a conductive film according to an embodiment of the present invention.
The base material 10 with a conductive film has the conductive film 2 made of the conductor of the present invention on the base material 1. As the base material 1, an inorganic substrate (for example, a glass substrate, a silicon substrate, a metal substrate, etc.), a plastic substrate (for example, a polyimide substrate, a polyester substrate, etc.), a substrate made of a fiber reinforced composite material (for example, a glass fiber reinforced resin substrate) Etc.). In order to improve the wettability and adhesion between the substrate 1 and the conductive paste, the substrate 1 may be subjected to a surface treatment.

The conductive film 2 is composed of a conductor in which conductive particles 3 are dispersed in a binder component 4. The configurations of the conductive particles 3 and the binder component 4 are as described above in the conductor of the present invention.
Such a base material 10 with a conductive film is obtained by, for example, applying the conductive paste of the present invention on the base material 1 and then heating the conductive paste at a temperature equal to or higher than the melting point of the low melting point metal to thereby form the inorganic fine particles. It can be produced by forming a conductive film 2 in which conductive particles 3 obtained from the particles (A) are dispersed in a binder component 4 mainly composed of an alloy obtained from (C) and the low melting point metal particles (B).

Examples of the method for applying the conductive paste include known methods such as screen printing, roll coating, air knife coating, blade coating, bar coating, gravure coating, die coating, and slide coating.
Among these, since a smooth wiring shape in which the occurrence of irregularities on the surface and side surfaces is suppressed can be efficiently formed on the substrate 1, the screen printing method is preferably used.

  Next, the conductive paste applied on the substrate is heated at a predetermined temperature equal to or higher than the melting point of the low melting point metal particles (B). At the time of heating, the low melting point metal particles (B) in the conductive paste are melted and alloyed with the inorganic fine particles (C). At that time, the organic compound (D) preferably functions as a flux and then volatilizes and is removed. Thus, the electrically conductive paste apply | coated on the base material hardens | cures by heating and cooling, and turns into an electrically conductive film. In addition, when the particles (A) contain a metal compound such as copper hydride or silver oxide as a constituent material, they become a metal conductive material such as copper or silver by the heating. Furthermore, when the inorganic fine particles (C) are attached and bonded to the surfaces of the particles (A), particularly the particles (A1), the inorganic fine particles (C) sandwiched between the particles (A) by the heating described above. ) Are fused together to form a chain structure of conductive particles in the resulting conductive film.

  Here, the alloy obtained by alloying the low melting point metal particles (B) and the inorganic fine particles (C) becomes the binder component 4 of the conductive film, and the melting point of the alloy is compared with the melting point of the low melting point metal particles (B). To rise. Due to this phenomenon, once the conductive paste is melted and cured to form a conductive film, the binder portion 4 does not melt even if the conductive film is raised again to the temperature used for melting.

  The heating temperature and the heating time are changed by the heating in consideration of the thermal characteristics of the particles (A), the low melting point metal particles (B), the inorganic fine particles (C), and the organic compound (D) constituting the conductive paste. What is necessary is just to determine suitably according to the characteristic calculated | required by the electrically conductive film so that each may be performed. The heating temperature is equal to or higher than the melting point of the low melting point metal particles (B) and is preferably in the range of 150 to 200 ° C.

If the heating temperature is 150 ° C. or higher, however, if the melting point of the low melting point metal particles (B) exceeds 150 ° C., if the melting point of the low melting point metal particles (B) is higher than the melting point of the inorganic fine particles (C) Fusion, melting of low melting point metal particles (B), and alloying of low melting point metal particles (B) and inorganic fine particles (C) proceed smoothly, improving the connection between conductive particles and improving conductivity. At the same time, the bond with the conductive particles is improved and the structure of the conductor is strengthened. The organic compound (D) can exhibit a flux function at the beginning of heating. Further, when the organic compound (D) is a residue-free flux, it can be volatilized and removed thereafter.
If heating temperature is 200 degrees C or less, since a plastic substrate can be used as a base-material main body, the freedom degree of base-material selection increases. In addition, the influence on other mounted elements can be reduced.
Examples of the heating method include warm air heating, thermal radiation, and IR heating. Note that the conductive film may be formed in the air or in a nitrogen atmosphere with a small amount of oxygen.

The thickness of the conductive film 2 on the substrate 1 is preferably 1 to 200 μm and more preferably 5 to 100 μm from the viewpoint of ensuring stable conductivity and facilitating the maintenance of the wiring shape. . The volume resistivity of the conductive film 2 is preferably 1.0 × 10 ⁻⁴ Ωcm or less. When the volume resistivity of the conductive film 2 exceeds 1.0 × 10 ⁻⁴ Ωcm, there is a possibility that sufficient conductivity cannot be obtained as a conductor for electronic equipment.

  In the base material 10 with a conductive film according to the present invention, since the conductive film 2 is formed using the conductive paste of the present invention described above, the conductive film 2 does not substantially contain a resin component and is mainly composed of metal. It is formed. Therefore, the conductive film of the base material with a conductive film 10 is excellent in conductivity and excellent in durability. Furthermore, for example, when exposed to a relatively high temperature (about 200 to 300 ° C.) treatment such as soldering, or when subjected to high temperature use, the conductive film can sufficiently maintain its shape and has excellent heat resistance. .

  As mentioned above, although an example was given and demonstrated about the base material with an electrically conductive film of this invention, in the limit which is not contrary to the meaning of this invention, a structure can be changed suitably as needed. Moreover, in the manufacturing method of the base material with a conductive film of this invention, it can change suitably in the limit in which manufacture of a base material with a conductive film is possible also about the formation order of each part.

  The conductive paste of the present invention can be used for various applications, for example, for the formation and repair of wiring patterns on printed wiring boards, interlayer wiring in semiconductor packages, and bonding between printed wiring boards and electronic components.

DESCRIPTION OF SYMBOLS 10 ... Base material with a conductive film, 1 ... Base material, 2 ... Conductive film, 3 ... Conductive particle, 4 ... Binder component.

Claims (9)

Single particles made of a metal having a melting point of 300 ° C. or higher, single particles made of a metal compound that becomes a metal by heating at a melting point of 300 ° C. or higher, and the average primary particle diameter is 1 nm to 1 μm Particles (A) having an average particle diameter of 1 to 20 μm selected from one or more aggregates of fine particles;
Low melting point metal particles (B) having a melting point of 200 ° C. or less;
Inorganic fine particles (C) having an average particle size smaller than that of the particles (A) and having a melting point of 300 ° C. or higher capable of forming an alloy with the low melting point metal at a temperature equal to or higher than the melting point of the low melting point metal;
An organic compound (D) having at least two OH groups in one molecule,
A conductive paste substantially free of resin.   The conductive paste according to claim 1, wherein the particles (A) are at least one selected from the group consisting of gold, silver, copper, nickel, aluminum, silver oxide, and copper hydride.   The conductive paste according to claim 1 or 2, wherein the low-melting-point metal particles (B) are made of an alloy containing at least one selected from the group consisting of tin, indium, and bismuth.   The conductive paste according to any one of claims 1 to 3, wherein the inorganic fine particles (C) are at least one selected from the group consisting of gold, silver, copper, nickel, aluminum, silver oxide, and copper hydride. .   The conductive paste according to any one of claims 1 to 4, wherein a boiling point of the organic compound (D) is 150 to 300 ° C.   An electrical conductor in which conductive particles (X) are dispersed in a binder component, wherein the binder component is mainly composed of a low melting point metal having a melting point of 200 ° C. or lower and a metal having a melting point of 300 ° C. or higher. Conductor composed of   By heating the conductive paste according to any one of claims 1 to 5 at a temperature equal to or higher than the melting point of the low melting point metal, the particles (A) are made conductive particles (X), and the inorganic fine particles (C ) And the low-melting-point metal particles (B) to form the alloy (Y).   The base material with a electrically conductive film which has the electrically conductive film which consists of a conductor of Claim 6 or 7 on a base material.   After apply | coating the electrically conductive paste of any one of Claims 1-5 on a base material, this electrically conductive paste is heated at the temperature more than melting | fusing point of the said low melting metal, and the said inorganic fine particle (C) and low A method for producing a substrate with a conductive film, comprising forming a conductive film in which conductive particles obtained from the particles (A) are dispersed in a binder component mainly composed of an alloy obtained from the melting point metal particles (B). .

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