JP2017071822A - Sn-COATED COPPER POWDER AND CONDUCTIVE PASTE USING THE SAME, AND PRODUCTION PROCESS FOR Sn-COATED COPPER POWDER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dendritic-shaped Sn-coated copper powder that can be suitably used in an application as a conductive paste by increasing the number of contact points during the time when Sn-coated dendritic copper powders contact each other to ensure excellent conductivity as well as by preventing aggregation.SOLUTION: An Sn-coated copper powder 1 according to the present invention has a dendritic shape having a main trunk 2 grown linearly and a plurality of branches 3 branched from the main trunk 2, and in which the main trunk 2 and the branch 3 are a flat plate shape having an average cross-sectional thickness of 0.2 μm to 5.0 μm and are constituted by copper particles having Sn or Sn alloy coated on the surface thereof, and have an average particle diameter (D50) as measured by a laser diffraction scattering type particle size distribution measurement method of 1.0 μm to 100 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a copper powder (tin-coated copper powder) coated with tin (Sn) or an Sn alloy on the surface, and more specifically, the conductivity can be improved by using it as a material such as a conductive paste. The present invention relates to a new dendritic Sn-coated copper powder.

  For the formation of wiring layers and electrodes in electronic devices, pastes and paints using metal fillers such as copper powder and silver powder, such as resin pastes, fired pastes, and electromagnetic wave shielding paints, are often used. Metal filler pastes such as copper powder and silver powder are applied or printed on various base materials, and are subjected to heat curing or heat baking treatment to form a conductive film to be a wiring layer or an electrode.

  In addition, as integration and density increase in the electronic material field, as a multilayering method, a through hole (through hole) is provided in the wall surface portion to obtain conduction between the front surface and the back surface of the printed wiring board. There is a method of performing through-hole plating and further filling the through-hole with a conductive paste.

  For example, a resin-type conductive paste is made of a metal filler, a resin, a curing agent, a solvent, etc., printed on a conductor circuit pattern or terminal, and cured by heating at 100 ° C. to 200 ° C. An electrode is formed. In the resin-type conductive paste, since the thermosetting resin is cured and contracted by heat, when the metal filler is pressed and brought into contact, the metal filler overlaps and an electrically connected current path is formed. Since the resin-type conductive paste is processed at a curing temperature of 200 ° C. or less, it is used for a substrate using a heat-sensitive material such as a printed wiring board. As the metal filler used in this resin-type conductive paste, silver powder, copper powder, silver-coated copper powder, or the like is used.

  Firing-type conductive paste is made of a metal filler, glass, solvent, etc., printed on a conductor circuit pattern or terminal, and heated and fired at 600 ° C. to 800 ° C. to form wiring and electrodes as a conductive film. To do. The fired conductive paste is processed at a high temperature to sinter the metal filler and ensure conductivity. Since the fired conductive paste is treated at such a high firing temperature, the metal particles are diffused and alloyed to conduct, and high connection reliability can be expected. Examples of the metal filler used in the fired conductive paste include eutectic solder (Sn—Pb alloy), Pb-free solder powder (eg, Sn—Ag—Cu alloy), copper powder with tin (Sn) plating, and silver powder. And those plated with Sn.

  However, in the case of lead-containing solder, when a wiring board or the like using it is discarded, lead is eluted and there is a risk of environmental pollution. .

  As a Pb-free solder powder that is an alternative to the Sn—Pb alloy, a binary or multi-element Sn alloy containing silver, bismuth, copper, indium, antimony, zinc or the like can be cited as a candidate. With this Pb-free solder powder, from the viewpoint of producing a higher-performance wiring board, it is required that the conductive paste composition in the via is highly metal-diffused to reduce the resistance value of the via. However, the Sn alloy having a melting point lower than the stacking temperature is melted by the temperature at the time of stacking, and there is a problem that the connection reliability in the via hole is lowered due to deformation and shrinkage behavior of the filled shape.

  In order to solve these problems, it is necessary to minimize shape deformation due to melting, and it is necessary to reduce as much as possible the region of the Sn alloy that is melted by the lamination temperature. For that purpose, the metal filler particles used are not Pb-free solder powder, but are made of metal filler particles coated with an Sn alloy with copper or silver as the core, so that the Sn alloy region melts and shrinks. Can be minimized, and the connection reliability in the via hole can be ensured.

  On the other hand, in the field where high conductivity or high thermal conductivity is required as the baked conductive paste, it is necessary to increase the blending amount of the conductive powder in order to increase the conductivity and thermal conductivity. As a method for producing the highly filled conductive powder, there is a method in which large and small spherical particles are combined and mixed. In this way, the filling rate can be increased by combining large and small particles. In addition, it is reported that a packing density of 80% or more is theoretically obtained by arranging spherical particles regularly and filling small spherical particles between large spherical particles (Non-patent Document 1). . However, actual spherical particles do not exist as completely independent particles, and the particles are partially agglomerated, resulting in a packing rate lower than the theoretical packing density.

  In general, when filling a through hole with a conductive paste filled in a hole and performing interlayer connection of multilayer wiring boards, in order to increase the conductivity, fill as much of the conductive paste as possible in the through hole to eliminate gaps. It is necessary to embed a metal filler. Therefore, conventionally, in the conductive paste for filling holes used for this purpose, it is desired to increase the blending amount of the metal filler. However, when the compounding amount of the metal filler is increased, the viscosity of the conductive paste is increased and the filling property to the through hole is deteriorated. On the other hand, when the ratio of the binder in the conductive paste is increased, the viscosity is decreased and the filling property to the through hole is improved, but there is a disadvantage that the conductivity is deteriorated.

  Here, when a spherical metal filler is used, contact between particles or a particle plane becomes point contact, and the contact efficiency deteriorates. Therefore, in order to improve this, it is necessary to bring the particles into contact with each other by making the metal filler into a flake shape.

  As a method for producing a flaky metal filler, for example, Patent Document 1 discloses a method of obtaining a flaky copper powder by mechanically processing a spherical copper powder into a flat shape. Specifically, a spherical copper powder with an average particle size of 0.5 μm to 10 μm is used as a raw material, and a ball mill or a vibration mill is used to mechanically process into a flat plate shape by the mechanical energy of the media loaded in the mill. is there.

  Further, for example, Patent Document 2 discloses a technique relating to a copper powder for conductive paste, more specifically, a disk-shaped copper powder that provides high performance as a copper paste for through holes and external electrodes, and a manufacturing method thereof. Specifically, the granular atomized copper powder is put into a medium stirring mill, a steel ball having a diameter of 1/8 inch to 1/4 inch is used as a grinding medium, and the fatty acid is added to the copper powder by 0.5 by weight. % To 1%, and processed into a flat plate shape by pulverization in air or in an inert atmosphere.

  In general, in order to produce metal filler particles coated with Sn alloy with flaky copper powder as a core, mechanically plastically deforming copper powder into flakes as described above, It can be produced by coating Sn on the surface of the copper particles.

  As a method for coating the surface of the copper powder with Sn, for example, an electroless Sn plating method can be used. Electroless Sn plating is a substitutional Sn plating in which Sn ions in the plating solution are reduced and precipitated with elution of the underlying copper powder, and a reduction in which Sn ions in the plating solution are reduced with a reducing agent to perform Sn coating. Type Sn plating and disproportionation reaction type Sn plating in which Sn coating is performed by utilizing the fact that Sn is disproportionated to form metal Sn.

  Further, when the Sn alloy is coated by Sn alloy plating, silver, bismuth, zinc, or the like constituting the alloy is included in the substitutional Sn plating solution, the reduction Sn plating solution, or the disproportionation reaction type Sn plating solution. By adding a soluble salt and precipitating these metals simultaneously with Sn, a film of Sn alloy can be produced.

  As the copper powder, electrolytic copper powder deposited in a dendritic shape called a dendritic shape is known. Since the shape is a dendritic shape, it is characterized by a large surface area. Due to the dendritic shape as described above, when this is used for a conductive film or the like, the dendritic branches are overlapped with each other, conduction is easy, and the number of contact points between particles is larger than that of spherical particles. Therefore, there is an advantage that the amount of conductive filler such as conductive paste can be reduced. For example, Patent Document 3 discloses a technique for ensuring oxidation resistance by forming an Ni alloy layer on a copper surface and performing Ag coating thereon, and the copper powder used here is a dendritic electrolytic copper powder. Is preferable from the viewpoint of entanglement between particles.

  On the other hand, when developing a branch of electrolytic copper powder, when used in conductive paste, etc., the electrolytic copper powder is entangled more than necessary and agglomeration occurs, so that it does not disperse uniformly in the resin, and the fluidity is It is pointed out in Patent Document 4 that it decreases and becomes very difficult to handle, causing problems in wiring formation by printing or the like and reducing productivity. In addition, in this patent document 4, in order to raise the intensity | strength of electrolytic copper powder itself, the strength of electrolytic copper powder itself is improved by adding tungstate in the copper sulfate aqueous solution of the electrolytic solution for depositing electrolytic copper powder. It is said that the tree branches can be made difficult to break and can be molded with high strength.

  As described above, it is not easy to use dendritic copper powder as a metal filler such as a conductive paste, and it has been a cause of difficulty in improving the conductivity of the paste.

  In order to ensure conductivity, a dendritic shape having a three-dimensional shape is easier to secure a contact than a granular one, and it can be expected to ensure high conductivity as a conductive paste. However, conventional flakes are obtained by mechanically flattening spherical powder, which has a simple structure from the viewpoint of securing the contact, and has a shape that effectively secures the contact using less Sn-coated copper powder. Is not an ideal shape.

Japanese Patent Laid-Open No. 2005-200734 JP 2002-15622 A JP 2002-075057 A JP 2011-58027 A

Edited by Powder Engineering Society, Handbook of Powder Engineering, First Edition p. 101-p. 107 (Nikkan Kogyo Shimbun)

  The present invention has been proposed in view of such circumstances, and agglomerates while ensuring excellent conductivity by increasing the number of contacts when dendritic copper powders coated with tin (Sn) are in contact with each other. An object of the present invention is to provide a dendritic Sn-coated copper powder that can be suitably used as a conductive paste.

  This inventor repeated earnest examination for solving the subject mentioned above. As a result, it exhibits a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk, and the main trunk and the branch are flat and have a predetermined cross-sectional thickness and Sn or Sn alloy on the surface. Is a dendritic Sn-coated copper powder composed of copper particles coated with copper, and the average particle diameter is in a specific range, thereby increasing the number of contacts between the copper powders and showing excellent conductivity, The present invention was completed by finding that it can be uniformly mixed with a resin or the like. That is, the present invention provides the following.

  (1) A first invention according to the present invention has a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk, and the main trunk and the branch have a cross-sectional average thickness. The average particle diameter (D50) measured by the laser diffraction scattering particle size distribution measurement method, which is composed of copper particles having a surface of 0.2 μm to 5.0 μm and coated with tin (Sn) or Sn alloy on the surface. Is a dendritic Sn-coated copper powder characterized by being 1.0 μm to 100 μm.

  (2) In the second invention according to the present invention, in the first invention, the content of Sn coated as Sn or an Sn alloy is 1 with respect to 100% by mass of the entire dendritic Sn-coated copper powder. It is dendritic Sn coat | cover copper powder which is the mass%-50 mass%.

  (3) According to a third aspect of the present invention, in the first or second aspect, the surface of the copper particles is coated with an Sn alloy, and at least one selected from silver, bismuth, and zinc is used. The dendritic Sn-coated copper powder is coated with a Sn alloy containing 0.1 to 50% by mass with respect to 100% by mass of the Sn alloy.

(4) Fourth aspect of the present invention, in any one of the first to third invention, the bulk density is in the range of ^{0.5g / cm 3 ~5.0g / cm 3} , the dendritic Sn coating Copper powder.

(5) A fifth invention is according to the present invention, in the first to fourth invention of any one of, BET specific surface area is 0.2m ² /g~5.0m ² / g, dendritic Sn coating Copper powder.

  (6) A sixth invention according to the present invention is a metal filler containing the dendritic Sn-coated copper powder according to any one of the first to fifth inventions in a proportion of 20% by mass or more of the whole.

  (7) A seventh invention according to the present invention is a conductive paste obtained by mixing the metal filler according to the sixth invention with a resin.

(8) An eighth invention according to the present invention is a method for producing a dendritic Sn-coated copper powder according to any one of the first to fifth inventions, wherein the copper powder is deposited on the cathode from the electrolytic solution by an electrolytic method. And a step of coating the copper powder with tin (Sn) or an Sn alloy, and the electrolytic solution has copper ions and a compound having a phenazine structure represented by the following formula (1) It is a manufacturing method of dendritic Sn coat | covered copper powder characterized by performing electrolysis by containing 1 type, or 2 or more types selected from these.
[In Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, CN, SCN. , SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl, R ₅ is hydrogen, halogen were selected amino, OH, -O, CN, SCN , SH, COOH, COO salt, COO _ester, SO 3 H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, from the group consisting of lower alkyl, and aryl And A ⁻ is a halide anion. ]

  According to the dendritic Sn-coated copper powder according to the present invention, it is possible to sufficiently secure a contact point when Sn-coated copper powders are in contact with each other while ensuring excellent conductivity, and to prevent aggregation and resin. Etc., and can be suitably used for the use of conductive paste.

It is the figure which showed typically the specific shape of dendritic tin coat copper powder. It is a photograph figure which shows an example of an observation image when the dendritic copper powder before tin coating | cover is observed with a scanning electron microscope at a magnification of 5,000 times. It is a photograph figure which shows an example of an observation image when dendritic tin coat copper powder is observed with a scanning electron microscope at a magnification of 5,000 times. It is a photograph figure which shows an example of an observation image when dendritic tin coat copper powder is observed by 1000-times multiplication factor with a scanning electron microscope. It is a photograph figure which shows an observation image when the tin coat copper powder obtained in the comparative example 1 is observed with a scanning electron microscope at a magnification of 5,000 times.

  Hereinafter, specific embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and Various modifications can be made without departing from the scope of the invention. In this specification, “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

<< 1. Dendritic Sn-coated copper powder >>
The tin-coated copper powder according to the present embodiment is a copper powder whose surface is coated with tin. In the present specification, tin-coated copper powder is referred to as “Sn-coated copper powder”. Further, tin or tin alloy to be coated is expressed as “Sn” and “Sn alloy”, respectively, and the case where Sn is coated on the copper powder surface or the case where Sn alloy is coated on the copper powder surface is generally “Sn coat”. ".

  FIG. 1 is a schematic diagram showing a specific shape of the Sn-coated copper powder according to the present embodiment. As shown in the schematic diagram of FIG. 1, the Sn-coated copper powder 1 is a two-dimensional or three-dimensional tree branch having a main trunk 2 that grows linearly and a plurality of branches 3 separated from the main trunk 2. (Hereinafter, the Sn-coated copper powder according to the present embodiment is also referred to as “dendritic Sn-coated copper powder”). The dendritic Sn-coated copper powder 1 is a flat plate having a predetermined average cross-sectional thickness, and is composed of copper particles whose surface is coated with Sn or an Sn alloy.

  As will be described later, the Sn coating amount of the dendritic Sn-coated copper powder 1 is 1% by mass to 50% by mass with respect to 100% by mass of the entire dendritic Sn-coated copper powder, but the thickness of the Sn (Coating thickness) is an extremely thin coating of 0.1 μm or less. Therefore, the dendritic Sn-coated copper powder 1 has a shape that retains the shape of the dendritic copper powder before Sn coating. Therefore, both the shape of the dendritic copper powder before coating Sn and the shape of the Sn-coated copper powder after coating Sn with the copper powder are two-dimensional or three-dimensional as shown in the schematic diagram of FIG. It is a dendritic shape that is a dimensional form.

  More specifically, the dendritic Sn-coated copper powder 1 according to the present embodiment has a dendritic Sn coat having a main trunk 2 that grows linearly and a plurality of branches 3 that are linearly separated from the main trunk 2. The copper particles which are copper powder and constitute the main trunk 2 and the branch 3 branched from the main trunk 2 have a flat plate shape with a cross-sectional average thickness of 0.2 μm to 5.0 μm. Moreover, the average particle diameter (D50) of the dendritic Sn coat | covered copper powder 1 comprised from such a flat copper particle is 1.0 micrometer-100 micrometers. The branch 3 in the dendritic Sn-coated copper powder 1 means both a branch 3a branched from the main trunk 2 and a branch 3b further branched from the branch 3a.

  The dendritic Sn-coated copper powder 1 will be described in detail later. For example, the dendritic copper is deposited on the cathode by immersing the anode and the cathode in a sulfuric acid electrolytic solution containing copper ions and conducting a direct current to perform electrolysis. It can be produced by depositing powder and coating the surface of the obtained dendritic copper powder with Sn or an Sn alloy by an electroless plating method or the like.

  FIG. 2 is a photographic diagram showing an example of an observation image when the dendritic copper powder before coating Sn constituting the dendritic Sn-coated copper powder 1 is observed with a scanning electron microscope (SEM). In addition, FIG. 2 observes dendritic copper powder at a magnification of 5,000 times. Moreover, FIG. 3 is a photograph figure which shows an example of the observation image when it observes with SEM about the dendritic Sn coat | covered copper powder which coat | covered Sn on the dendritic copper powder of FIG. In addition, FIG. 3 observes the dendritic Sn coat copper powder 1 at a magnification of 5,000 times. Moreover, FIG. 4 is a photograph figure which shows an example of an observation image when it observes by SEM about dendritic Sn coat | covered copper powder which coat | covered Sn on dendritic copper powder similarly. FIG. 4 shows the dendritic Sn-coated copper powder 1 observed at a magnification of 1,000 times.

  The dendritic Sn-coated copper powder 1 is a two-dimensional or three-dimensional tree branch having a main trunk 2 and branches 3 (3a, 3b) branched from the main trunk 2 as shown in the observation images of FIGS. The shape is formed.

  Here, as described above, the flat copper particles constituting the main trunk 2 and the branch 3 have an average cross-sectional thickness of 0.2 μm to 5.0 μm. The thinner the cross-sectional average thickness of the flat copper particles, the more the flat plate effect is exhibited. That is, the main trunk 2 and the branch 3 are composed of flat copper particles having a cross-sectional average thickness of 5.0 μm or less, thereby increasing the area where the Sn-coated dendritic Sn-coated copper powders 1 are in contact with each other. Since the contact area can be ensured and the contact area becomes large, low resistance, that is, high conductivity can be realized. By this, it is more excellent in electroconductivity, can maintain the electroconductivity favorably, and can use it suitably for the use of an electroconductive coating material or an electroconductive paste. In addition, the dendritic Sn-coated copper powder 1 is composed of fine Sn particles coated with a flat Sn plate, which can contribute to thinning of the wiring material and the like.

  In addition, even if the cross-sectional average thickness of the copper particles coated with Sn or Si alloy is as thin as 5.0 μm or less, if the size of the flat copper particles is too small, the dendritic Sn-coated copper powder 1 When they come into contact with each other, the number of contacts is reduced. Therefore, as described above, the lower limit value of the average cross-sectional thickness of the copper particles is preferably 0.2 μm or more, which can increase the number of contacts.

  Moreover, in the dendritic Sn coat | cover copper powder 1, the average particle diameter (D50) is 1.0 micrometer-100 micrometers. In addition, an average particle diameter (D50) can be measured by the laser diffraction scattering type particle size distribution measuring method, for example.

  Here, as pointed out in Patent Document 4, for example, as a problem of dendritic copper powder, when used as a metal filler for conductive paste, the shape of the metal filler in the resin developed into a dendritic shape In this case, the dendritic copper powders are entangled with each other and agglomeration occurs, which may not be uniformly dispersed in the resin. In addition, the agglomeration increases the viscosity of the paste and causes problems in wiring formation by printing. This occurs because the shape of the dendritic copper powder is large, and in order to solve this problem while effectively utilizing the dendritic shape, it is necessary to reduce the shape of the dendritic copper powder. It becomes. However, if it is too small, a dendritic shape cannot be secured. Therefore, the effect of being in a dendritic shape, that is, a three-dimensional shape, has a large surface area and excellent moldability and sinterability, and can be molded with high strength by being firmly connected via a branch-like portion. In order to secure the effect, it is necessary that the dendritic copper powder is larger than a predetermined size.

  In this respect, in the dendritic Sn-coated copper powder 1 according to the present embodiment, the average particle diameter is 1.0 μm to 100 μm, so that the surface area is increased and good moldability and sinterability are ensured. be able to. The dendritic Sn-coated copper powder 1 has a dendritic shape, and the main trunk 2 and the branch 3 are composed of flat copper particles. And the contact point of dendritic Sn coat | court copper powder 1 can be ensured more by the effect that the copper particle which comprises the dendritic shape is flat form.

≪2. Sn coverage >>
As described above, the dendritic Sn-coated copper powder 1 according to the present embodiment is a flat plate having a cross-sectional average thickness of 0.2 μm to 5.0 μm, and the surface thereof is coated with Sn or Sn alloy. It is composed of dendritic particles. Below, Sn coating | cover with respect to the surface of dendritic Sn coat | cover copper powder 1 is demonstrated.

  The dendritic Sn-coated copper powder 1 according to the present embodiment is preferably used as Sn content with respect to 100% of the total mass of the dendritic Sn-coated copper powder coated with Sn on the dendritic copper powder before Sn coating. The Sn or Sn alloy is coated at a ratio of 1% by mass to 50% by mass, and the thickness (coating thickness) of the Sn or Sn alloy is an extremely thin film of 0.1 μm or less. From this, the dendritic Sn-coated copper powder 1 has a shape that maintains the shape of the dendritic copper powder before Sn coating. Therefore, the shape of the copper powder before coating Sn or Sn alloy and the shape of the Sn-coated copper powder after coating Sn or Sn alloy on the copper powder are both dendritic shapes.

  As described above, the content of Sn coated as Sn or Sn alloy in the dendritic Sn-coated copper powder 1 is 1% by mass to 50% with respect to 100% by mass of the entire dendritic Sn-coated copper powder coated with Sn. It is preferably in the range of mass%. The content of Sn coated as Sn or Sn alloy is preferably as small as possible from the viewpoint of cost, but if it is too small, a uniform Sn or Sn alloy film cannot be secured on the copper surface, resulting in a decrease in conductivity. Cause. Therefore, as content of Sn coat | covered as Sn or Sn alloy, it is preferable that it is 1 mass% or more with respect to 100 mass of the whole dendritic Sn coat | covered copper powder coated with Sn, and is 2 mass% or more. More preferably, it is more preferably 5% by mass or more.

  On the other hand, if the content of Sn coated as Sn or Sn alloy increases, it is not preferable from the viewpoint of cost. From this, as content of Sn coat | covered as Sn or Sn alloy, it is preferable that it is 50 mass% or less with respect to 100 mass of the whole dendritic Sn coat | covered copper powder coated with Sn, and is 15 mass%. More preferably, it is more preferably 10% by mass or less.

  Further, in the dendritic Sn-coated copper powder 1 according to the present embodiment, the average thickness of Sn or Sn alloy coated on the surface of the dendritic copper powder is about 0.001 μm to 0.1 μm, and 0.005 μm to It is preferably 0.02 μm. If the Sn or Sn alloy coating thickness is less than 0.001 μm on average, a uniform Sn or Sn alloy coating cannot be secured on the surface of the copper powder, and this causes a decrease in conductivity. On the other hand, when the coating thickness of Sn or Sn alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of cost.

  Thus, the average thickness of Sn or Sn alloy coated on the surface of the dendritic copper powder is about 0.001 μm to 0.1 μm, and the cross-sectional average thickness of the flat copper particles constituting the dendritic copper powder is Very small compared. Therefore, before and after coating the surface of the dendritic copper powder with Sn or an Sn alloy, the cross-sectional average thickness of the tabular copper particles does not substantially change.

  Further, as will be described later, in the dendritic Sn-coated copper powder, Sn covered with the dendritic copper powder may be a Sn alloy. The element added as the Sn alloy is preferably at least one selected from silver, bismuth, and zinc.

Further, the dendritic Sn coating copper powder 1 according to the present embodiment is not particularly limited, it is preferable the value of the BET specific surface area of 0.2m ² /g~5.0m ² / g. When the BET specific surface area value is less than 0.2 m ² / g, the copper particles coated with Sn or the Sn alloy may not have the desired shape as described above, and high conductivity cannot be obtained. There is. On the other hand, when the BET specific surface area value exceeds 5.0 m ² / g, the Sn or Sn alloy coating on the surface of the dendritic Sn-coated copper powder 1 is not uniform, and high conductivity may not be obtained. Moreover, the copper particle which comprises Sn coat | court copper powder 1 will become fine too much, and dendritic Sn coat | court copper powder 1 will be in a fine beard-like state, and electroconductivity may fall. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

As the bulk density of the dendritic Sn coating copper powder 1 it is not particularly ^limited, is preferably in the range of ^{0.5g / cm 3 ~5.0g / cm 3} . If the bulk density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the dendritic Sn-coated copper powders 1 cannot be secured. On the other hand, if the bulk density exceeds 5.0 g / cm ³ , the average particle diameter of the dendritic Sn-coated copper powder 1 also increases, the surface area decreases, and the moldability and sinterability may deteriorate.

  In addition, when the dendritic Sn-coated copper powder having the shape as described above is occupied at a predetermined ratio in the obtained copper powder when observed with an electron microscope, Sn-coated copper of other shapes is used. Even if the powder is mixed, the same effect as the copper powder consisting only of the dendritic Sn-coated copper powder can be obtained. Specifically, when observed with an electron microscope (for example, 500 to 20,000 times), the dendritic Sn-coated copper powder having the shape described above is 65% by number or more, preferably 80% by number of the total copper powder. As described above, Sn-coated copper powder having other shapes may be included as long as it occupies a ratio of 90% by number or more.

≪3. Method for producing dendritic Sn-coated copper powder >>
Next, the manufacturing method of the dendritic Sn coat | cover copper powder 1 which has the above characteristics is demonstrated. Below, the manufacturing method of the dendritic copper powder which comprises the dendritic Sn coat copper powder 1 is demonstrated first, Then, Sn or Sn alloy is coat | covered with respect to the dendritic copper powder, and dendritic Sn coat copper A method for obtaining powder will be described.

<3-1. Method for producing dendritic copper powder>
The dendritic copper powder before coating with Sn or Sn alloy can be produced, for example, by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

  In electrolysis, for example, the above-described sulfuric acid-containing electrolytic solution containing copper ions is accommodated in an electrolytic cell in which metallic copper is used as an anode (anode) and a stainless steel plate or a titanium plate is used as a cathode (cathode). The electrolytic solution is subjected to electrolytic treatment by applying a direct current at a predetermined current density. Thereby, a dendritic copper powder can be deposited (electrodeposition) on a cathode with electricity supply. In particular, in this embodiment, the fine copper particles in the form of a plate are gathered only by the electrolysis without mechanically deforming the granular copper powder obtained by electrolysis using a medium such as a ball. Thus, the dendritic copper powder having a dendritic shape can be deposited on the cathode surface.

  More specifically, as the electrolytic solution, for example, a solution containing a water-soluble copper salt, sulfuric acid, an additive such as an amine compound, and chloride ions can be used.

  The water-soluble copper salt is a copper ion source that supplies copper ions, and examples thereof include copper sulfate such as copper sulfate pentahydrate, copper chloride, and copper nitrate, but are not particularly limited. The copper ion concentration in the electrolytic solution can be about 1 g / L to 20 g / L, preferably about 5 g / L to 10 g / L.

  Sulfuric acid is for making a sulfuric acid electrolyte. The sulfuric acid concentration in the electrolytic solution can be about 20 g / L to 300 g / L, preferably about 50 g / L to 150 g / L, as the free sulfuric acid concentration. Since the sulfuric acid concentration affects the conductivity of the electrolyte, it affects the uniformity of the copper powder obtained on the cathode.

  As the additive, for example, an amine compound can be used. The amine compound contributes to shape control of the copper powder to be deposited together with chloride ions to be described later, and the copper powder to be deposited on the cathode surface is composed of flat copper particles having a predetermined cross-sectional thickness; A dendritic copper powder having branches branched from the main trunk can be obtained.

  As an amine compound, you may add individually by 1 type and may add it in combination of 2 or more types. Further, the amount of amine compounds added is preferably such that the concentration in the electrolytic solution is in the range of 0.1 mg / L to 500 mg / L, and the amount in the range of 1 mg / L to 400 mg / L. More preferably.

Specifically, the amine compound is not particularly limited, but a compound having a phenazine structure that can be represented by the following formula (1) can be used. More preferably, for example, safranine (3,7-diamino-2,8-dimethyl-5-phenyl-5-phenazinium chloride, C ₂₀ H ₁₉ N ₄ Cl, CAS number: 477-73-64) is used. Can do.

Here, in Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, CN, SCN, a group SH, COOH, COO salt, COO _ester, SO 3 H, SO ₃ salt, is selected SO ₃ ester, benzenesulfonic acid, and from the group consisting of C1~C8 alkyl. R ₅ is hydrogen, halogen, amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion.

  As a chloride ion, it can be made to contain by adding the compound (chloride ion source) which supplies chloride ions, such as hydrochloric acid and sodium chloride, in electrolyte solution. By containing chloride ions in the electrolytic solution, the shape of the deposited copper powder can be controlled more effectively. The chloride ion concentration in the electrolytic solution can be about 1 mg / L to 1000 mg / L, preferably about 5 mg / L to 800 mg / L, more preferably about 10 mg / L to 500 mg / L.

In the method for producing the dendritic copper powder according to the present embodiment, for example, the dendritic copper powder is produced by depositing on the cathode by electrolysis using the electrolytic solution having the composition described above. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ^{2 to} 30 A / dm ² when electrolyzing using a sulfuric acid electrolytic solution, and the electrolyte is energized while stirring. Moreover, as a liquid temperature (bath temperature) of electrolyte solution, it can be set as about 20 to 60 degreeC, for example.

<3-2. Method of coating Sn or Sn alloy (production of Sn-coated copper powder)>
The dendritic Sn-coated copper powder 1 according to the present embodiment is manufactured by coating the surface of the dendritic copper powder produced by the above-described electrolytic method with, for example, Sn or an Sn alloy using an electroless plating method. be able to.

  In order to coat Sn or Sn alloy with a uniform thickness on the surface of the dendritic copper powder, it is preferable to wash before Sn plating, and the dendritic copper powder is dispersed in the cleaning solution and washed with stirring. It can be carried out. This washing treatment is preferably carried out in an acidic solution, and after washing, filtration, separation and washing of the dendritic copper powder are repeated as appropriate to obtain a water slurry in which the dendritic copper powder is dispersed in water. In addition, what is necessary is just to use a well-known method about filtration, isolation | separation, and water washing.

  Specifically, when Sn coating is performed by the electroless Sn plating method, the electroless Sn plating solution is added to the copper slurry obtained after washing the dendritic copper powder, or the copper slurry is added to the electroless plating solution. By uniformly stirring, the surface of the dendritic copper powder can be coated more uniformly with Sn or Sn alloy.

  The method for coating Sn or the Sn alloy by the electroless plating method is not particularly limited. As electroless Sn plating, substitution type Sn plating in which Sn ions in the plating solution are reduced and precipitated with elution of the copper powder as a base, and Sn ions in the plating solution are reduced with a reducing agent to perform Sn coating. Examples include reduction-type Sn plating and disproportionation-type Sn plating in which Sn coating is performed using the fact that Sn ions are disproportionated to form metal Sn, and any method may be used.

  Specifically, as the substitutional Sn plating solution, a tin compound and a complexing agent for keeping the tin compound stable in an aqueous solution are essential components, and a surfactant, a pH adjuster, etc. are added as necessary. Can be used. Further, as the reduced Sn plating solution, a composition obtained by adding a reducing agent to the above-described substitutional Sn plating solution can be used.

In the disproportionation reaction type Sn plating, Sn ions are present as HSnO ₂ ⁻ ions in an alkaline aqueous solution, and the HSnO ₂ ⁻ ions become metal Sn by a disproportionation reaction represented by the following formula. In the disproportionation reaction type Sn plating, Sn plating is performed with metal Sn generated by the reaction, and a plating solution having the same composition as the substitutional Sn plating solution in the strong alkali bath can be used.
2HSnO ² + + 2H ₂ O ⇔ Sn (OH) ₆ ² + + Sn

  As the tin compound, there are a divalent tin compound and a tetravalent tin compound, and the divalent tin compound and the tetravalent tin compound may be used alone or in combination, respectively.

  Specifically, as the tin compound, for example, stannous borofluoride, stannous sulfosuccinate, stannous chloride, stannic chloride, stannous sulfate, stannic sulfate, stannous oxide, stannous oxide Distinous, stannous methanesulfonate, stannous ethanesulfonate, stannous 2-hydroxypropane-1-sulfonate, stannous p-phenolsulfonate, tin borofluoride, tin silicofluoride, tin sulfamate , Tin oxalate, tin tartrate, tin gluconate, tin sulfosuccinate, tin pyrophosphate, tin 1-hydroxyethane-1,1-bisphosphonate, tin tripolyphosphate and the like.

  As the complexing agent, a thiourea derivative, a carboxylic acid or an amine compound, titanium chloride, or the like can be used.

  Specifically, thiourea derivatives include thiourea, 1,3-dimethylthiourea, trimethylthiourea, diethylthiourea (eg, 1,3-diethyl-2-thiourea), N, N′-diisopropylthiourea, Examples include allyl thiourea, acetyl thiourea, ethylene thiourea, 1,3-diphenyl thiourea, thiourea dioxide, and thiosemicarbazide. In addition, as carboxylic acid or amine compound, citric acid, tartaric acid, malic acid, gluconic acid, golcoheptonic acid, glycolic acid, lactic acid, trioxybutyric acid, ascorbic acid, isocitric acid, tartronic acid, glyceric acid, hydroxybutyric acid, leucine acid , Citramalic acid, succinic acid, mercaptosuccinic acid, sulfosuccinic acid, glutaric acid, malonic acid, adipic acid, oxalic acid, maleic acid, citraconic acid, itaconic acid, mesaconic acid, glycolic acid, sodium citrate, glycine, hydroxyethylethylenediamine Triacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid disodium salt, ethylenediaminetetrapropionic acid, nitrilotriacetic acid, iminodiacetic acid, hydroxyethylimino Acetic acid, iminodipropionic acid, aminotrimethylene phosphate, aminotrimethylene phosphate pentasodium salt, benzylamine, 2-naphthylamine, isobutylamine, isoamylamine, 1,3-propanediaminetetraacetic acid, 1,3-diamino- 2-hydroxypropanetetraacetic acid, glycol etherdiaminetetraacetic acid, metaphenylenediaminetetraacetic acid, 1,2-diaminocyclohexane-N, N, N ′, N′-tetraacetic acid, diaminopropionic acid, ethylenediaminetetramethylene phosphate, diethylenetriamine Pentamethylene phosphoric acid, glutamic acid, dicarboxymethyl glutamic acid, ornithine, cysteine, N, N-bis (2-hydroxyethyl) glycine, (S, S) -ethylenediamine succinic acid, methylenediamine, ethylenediamine, Ethylenediamine tetraacetic acid, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, diethylenetriamine, tetraethylene pentamine, pentaethylene hexamine, hexaethyleneheptamine, cinnamylamine, p- methoxy cinnamyl amine.

  Examples of the reducing agent include phosphoric acid compounds, borohydride compounds, hydrazine derivatives, and the like, and these can be used alone or in combination of two or more.

  Specifically, examples of the phosphoric acid compound include hypophosphorous acid, phosphorous acid, pyrophosphoric acid, polyphosphoric acid, and the like. Examples of the borohydride compound include methylhexaborane, dimethylamineborane, diethylamineborane, morpholineborane, pyridineamineborane, piperidineborane, ethylenediamineborane, ethylenediaminebisborane, t-butylamineborane, imidazoleborane, methoxyethylamineborane, hydrogen Examples thereof include sodium borohydride. As the hydrazine derivative, hydrazine salts such as hydrazine sulfate and hydrazine hydrochloride, hydrazine derivatives such as pyrazoles, triazoles and hydrazides, and the like can be used. Among these, as pyrazoles, pyrazole derivatives such as 3,5-dimethylpyrazole and 3-methyl-5-pyrazolone can be used in addition to pyrazole. As triazoles, 4-amino-1,2,4-triazole, 1,2,3-triazole, and the like can be used. As hydrazides, adipic hydrazide, maleic hydrazide, carbohydrazide, and the like can be used.

  In addition, additives such as a pH buffer, a pH adjuster, and a surfactant can be contained as necessary. Furthermore, you may use an antifoamer and a dispersing agent as needed.

  A known complexing agent can be used as the pH buffering agent. For example, ammonium chloride, ammonium sulfate, boric acid, sodium acetate and the like can be mentioned.

  A known complexing agent can be used as the pH adjuster. For example, an acid or alkali compound can be used, and examples thereof include alkali metal hydroxides such as ammonia and sodium hydroxide, nickel carbonate, sulfuric acid, and hydrochloric acid. In addition, when using ammonia, it can supply as ammonia water.

  Surfactants can be used to improve the permeability of the plating solution. Specifically, any of nonionic, cationic, anionic, amphoteric, etc. surfactants should be used as the surfactant. It can be used alone or in combination of two or more.

  Furthermore, by making Sn other than Sn contain in the Sn film to be formed, that is, by forming a film of Sn alloy on the surface of the copper powder, the properties such as melting point and wettability are changed. be able to. For example, as a specification of Pb-free solder, use temperature, wettability, and mechanical strength become problems depending on the use and material to be used. In this respect, by forming a film of Sn alloy, it is possible to change to a property suitable for the intended use and material.

  Specifically, as an element to be contained in the Sn film, that is, as an element other than Sn constituting the Sn alloy, silver, bismuth, copper, indium, antimony, zinc and the like can be cited. The Sn alloy can be a binary or multi-component alloy containing these elements. Among them, elements that can be alloyed when Sn coating is performed by electroless plating include silver, bismuth, and zinc. By adding one or more compounds containing these elements to the electroless Sn plating solution described above. The Sn alloy film can be easily coated.

  Specifically, when a silver-containing Sn alloy is used, examples of the silver compound added to the electroless Sn plating solution include silver oxide, silver nitrate, silver sulfate, silver chloride, silver bromide, silver iodide, and benzoic acid. Silver, silver sulfamate, silver citrate, silver lactate, silver mercaptosuccinate, silver phosphate, silver trifluoroacetate, silver pyrophosphate, silver 1-hydroxyethane-1,1-bisphosphonate, silver borofluoride, silver tartrate Silver gluconate, silver oxalate, silver methanesulfonate, silver p-phenolsulfonate, silver benzoate and the like.

  In addition, when a Sn alloy containing bismuth is used, examples of the bismuth compound added to the electroless Sn plating solution include bismuth nitrate, bismuth chloride, bismuth methanesulfonate, bismuth ethanesulfonate, bismuth p-phenolsulfonate Is mentioned.

  Moreover, when setting it as Sn alloy containing zinc, as a zinc compound added in electroless Sn plating liquid, zinc oxide, zinc chloride, zinc sulfate etc. are mentioned, for example.

  The content ratio of metal elements other than Sn constituting these Sn alloys is 0 with respect to 100% by mass of the entire Sn alloy coating film coated with the dendritic Sn-coated copper powder from the viewpoint of melting point and wettability. It is preferable that it is content of 1 mass%-50 mass%. If the content is too large, it causes an increase in melting point and a decrease in mechanical strength, and therefore it is preferably 50% by mass or less. On the other hand, if the content is less than 0.1% by mass, the effect of lowering the melting point or improving the wettability may not be sufficiently obtained even if the metal element that becomes the Sn alloy is contained. . From this, it is preferable that it is content of 0.1 mass%-50 mass% with respect to 100 mass of the whole Sn alloy film, It is more preferable that it is content of 1 mass%-20 mass%, More preferably, the content is 2% by mass to 10% by mass.

  In addition, content of the metal which comprises Sn alloy can be measured by converting content of each element which comprises Sn coat | court copper powder, for example with a high frequency inductively coupled plasma (ICP) emission spectroscopy analysis method. In addition, each element in the Sn alloy coating can be quantitatively analyzed from the cross section of the Sn-coated copper powder or the like by energy dispersive X-ray spectroscopy (EDX) method or Auger electron spectroscopy (AES) method.

  Furthermore, the method for forming the Sn alloy film is not limited to the above-described electroless plating method. For example, an element other than Sn constituting the Sn alloy is included in the dendritic copper powder before coating Sn, and after forming a film composed only of Sn (Sn film), it is included in the copper powder in advance. A Sn alloy film can also be formed by diffusing the elements that have been deposited in the Sn film.

<< 4. Use of conductive paste >>
As described above, the dendritic Sn-coated copper powder 1 according to the present embodiment has a dendritic shape having a main trunk that grows linearly and a plurality of branches 3 branched from the main trunk 2, and has an average cross-sectional thickness. The plate-shaped copper particles covered with Sn having a thickness of 0.2 μm to 5.0 μm are aggregated, and the average particle diameter (D50) is 1.0 μm to 100 μm.

  In such a dendritic Sn-coated copper powder 1, the dendritic shape increases the surface area, and the moldability and sinterability are excellent, and the main trunk 2 and the branch 3 have a predetermined flat plate shape. By being composed of copper particles, a large number of contacts can be secured, and excellent conductivity is exhibited.

  Further, according to the dendritic Sn-coated copper powder 1 having such a predetermined structure, even when it is a copper paste or the like, aggregation can be suppressed and it can be uniformly dispersed in the resin. In addition, it is possible to suppress the occurrence of poor printability due to an increase in the viscosity of the paste. Therefore, the dendritic Sn-coated copper powder 1 can be suitably used for applications such as conductive paste and conductive paint.

  For example, as a conductive paste (copper paste), the dendritic Sn-coated copper powder 1 according to the present embodiment is included as a metal filler, a binder resin, a solvent, and further, a curing agent, an antioxidant, and a coupling agent as necessary. It can be prepared by kneading with additives such as corrosion inhibitors.

  Specifically, the binder resin is not particularly limited, and an epoxy resin, a phenol resin, an unsaturated polyester resin, or the like can be used. As the solvent, organic solvents such as ethylene glycol, diethylene glycol, triethylene glycol, glycerin, terpineol, ethyl carbitol, carbitol acetate, and butyl cellosolve can be used. The amount of the organic solvent added is not particularly limited, and should be adjusted in consideration of the particle size of the dendritic Sn-coated copper powder so as to have a viscosity suitable for a conductive film forming method such as screen printing or dispenser. Can do.

  Furthermore, other resin components can be added for viscosity adjustment. For example, a cellulose-based resin typified by ethyl cellulose can be used, and it can be added as an organic vehicle dissolved in an organic solvent such as terpineol. In addition, it is necessary to suppress the addition amount of the resin component to an extent that does not impair the sinterability, and is preferably 5% by weight or less.

  Moreover, as an additive, in order to improve the electroconductivity after baking, antioxidant etc. can be added. Although it does not specifically limit as antioxidant, For example, a hydroxycarboxylic acid etc. can be mentioned. More specifically, hydroxycarboxylic acids such as citric acid, malic acid, tartaric acid, and lactic acid are preferable, and citric acid or malic acid that has high adsorptive power to copper coated with Sn or Sn alloy is particularly preferable. The addition amount of the antioxidant can be, for example, about 1% by weight to 15% by weight in consideration of the antioxidant effect, the viscosity of the paste, and the like.

  Moreover, conventionally used 2-ethyl 4-methylimidazole etc. can be used also about a hardening | curing agent. Furthermore, conventionally used benzothiazole, benzimidazole, and the like can also be used for the corrosion inhibitor.

  Further, when the dendritic Sn-coated copper powder 1 according to the present embodiment is used as a metal filler for a conductive paste, other shapes of copper powder, Sn-coated copper powder, and conductive materials such as nickel, silver, and tin It can be used by being mixed with a metal filler having the following. At this time, the proportion of the dendritic Sn-coated copper powder 1 in the total amount of the metal filler used as the conductive paste is preferably 20% by mass or more, more preferably 30% by mass or more, and 40% by mass. More preferably, it is the above. Thus, when using as a metal filler, by mixing metal fillers, such as copper powder of another shape, with the dendritic Sn coat copper powder 1 which concerns on this Embodiment, the dendritic Sn coat copper powder 1 is mixed. The gap is filled with copper powder of another shape, and this makes it possible to secure more contacts for ensuring conductivity. As a result, it is also possible to reduce the total amount of dendritic Sn-coated copper powder 1 and other shapes of copper powder.

  When the dendritic Sn-coated copper powder 1 is less than 20% by mass of the total amount of copper powder used as the metal filler, the contacts between the dendritic Sn-coated copper powders 1 are reduced and mixed with copper powder of other shapes. Even if the increase of the contact by carrying out is taken into consideration, as a metal filler, electroconductivity will fall.

  Furthermore, it does not specifically limit about the shape of the metal powder which comprises another metal filler, The metal powder of shapes, such as dendritic shape, granular form, and flake shape, can be used. In order to ensure conductivity, it is necessary to secure a contact between metal fillers. For example, in the case of a flake-shaped metal filler, the contact can be secured with the flake shape with the dendritic Sn-coated copper powder 1. In the case of a granular metal filler, the contact can be secured by filling the gap between the dendritic Sn-coated copper powder 1 with the granular metal filler. The shape to be used can be selected depending on the type and viscosity of the resin used in the conductive paste or the like.

  Various electric circuits can be formed using the conductive paste prepared using the metal filler described above. Even in this case, the circuit pattern forming method or the like conventionally used can be used without being limited to use under particularly limited conditions. For example, a conductive paste produced using the metal filler is applied or printed on a fired substrate or an unfired substrate, heated, and then pressed and cured as needed to cure and print. An electric circuit of an electronic component, an external electrode, or the like can be formed.

  Examples of the present invention will be described below in more detail with reference to comparative examples, but the present invention is not limited to the following examples.

≪Evaluation method≫
For the Sn-coated copper powder obtained in the following Examples and Comparative Examples, the following methods were used to observe the shape, measure the average particle diameter, and measure the specific resistance of the conductive paste.

(Observation of shape)
With a scanning electron microscope (manufactured by JEOL Ltd., JSM-7100F type), 20 visual fields were arbitrarily observed with a predetermined magnification, and the appearance of the copper powder contained in the visual field was observed.

(Measurement of average particle size)
The average particle size (D50) of the obtained Sn-coated copper powder was measured using a laser diffraction / scattering particle size distribution measuring instrument (manufactured by Nikkiso Co., Ltd., HRA9320 X-100).

(Specific resistance measurement)
About the specific resistance value of a film, a sheet resistance value is measured by a four-terminal method using a low resistivity meter (manufactured by Mitsubishi Chemical Corporation, Loresta-GP MCP-T600). The film thickness of the coating film was measured by SURFCOM130A, manufactured by Tokyo Seimitsu Co., Ltd., and the sheet resistance value was determined by dividing the film thickness by the film thickness.

≪Example, comparative example≫
[Example 1]
<Preparation of electrolytic copper powder>
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode, and an electrolytic solution is charged into the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

  At this time, an electrolytic solution having a composition with a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L was used. In addition, safranin (manufactured by Kanto Chemical Co., Inc.) as an additive is added to the electrolytic solution so that the concentration in the electrolytic solution is 85 mg / L, and a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is further added to the electrolytic solution. It added so that it might become 55 mg / L as a chloride ion (chlorine ion) density | concentration in it.

Then, the current density of the cathode is 18 A / dm ² under the condition that the temperature is maintained at 25 ° C. while circulating the electrolytic solution whose concentration is adjusted as described above at a flow rate of 15 L / min using a metering pump. Was energized to deposit copper powder on the cathode plate.

  The electrolytic copper powder deposited on the cathode plate was recovered by mechanically scraping it off the bottom of the electrolytic cell using a scraper, and the recovered copper powder was washed with pure water and then put in a vacuum dryer and dried. .

  As a result of observing the shape of the copper powder thus obtained in the field of view with a magnification of 1,000 times by the method using the scanning electron microscope (SEM) described above, the deposited copper powder was a main chain that grew linearly and the main trunk. It was a dendritic copper powder having a two-dimensional or three-dimensional dendritic shape having a plurality of branches branched linearly from and branches further branched from the branches.

<Preparation of dendritic Sn-coated copper powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the dendritic copper powder prepared by the above-described method to prepare Sn-coated copper powder.

  Specifically, as the electroless Sn plating solution, stannous borofluoride 20 g / L, borofluoric acid 200 g / L, thiourea 50 g / L, sodium borohydride 40 g / L, sodium borate 10 g / L at each concentration. The plating solution added in was prepared. In this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 60 ° C. and stirred for 60 minutes.

  After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Sn-coated copper powder in which Sn was coated on the surface of the dendritic copper powder was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 10.2% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

  In addition, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Sn-coated copper powder is uniformly on the surface of the dendritic copper powder before Sn coating A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with Sn, the main trunk growing linearly, and a plurality of branches linearly branched from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

  Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.40 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 27.9 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.61 g / cm ³ . Moreover, the BET specific surface area was 0.92 m < ² > / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

  That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder, and the small size Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.2 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 2]
<Preparation of electrolytic copper powder>
As the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L is used, and safranin is added to the electrolytic solution so that the concentration in the electrolytic solution is 200 mg / L. Further, copper powder was deposited on the cathode plate under the same conditions as in Example 1 except that a hydrochloric acid solution was added so that the chlorine ion concentration in the electrolytic solution was 100 mg / L.

<Preparation of dendritic Sn-coated copper powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the dendritic copper powder prepared by the above-described method to prepare Sn-coated copper powder.

  Specifically, as an electroless Sn plating solution, a plating solution prepared by adding stannous chloride 10 g / L, sodium citrate 40 g / L, ethylenediaminetetraacetic acid 20 g / L, and titanium chloride 50 g / L at each concentration was prepared. . In this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 65 ° C. and stirred for 60 minutes.

  After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Sn-coated copper powder in which Sn was coated on the surface of the dendritic copper powder was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 17.4% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

  In addition, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Sn-coated copper powder is uniformly on the surface of the dendritic copper powder before Sn coating A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with Sn, the main trunk growing linearly, and a plurality of branches linearly branched from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

  Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.19 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 9.8 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.63 g / cm ³ . Further, the BET specific surface area was 2.01 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

  That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder, and the small size Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.9 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 3]
<Preparation of dendritic Sn-coated copper powder>
Using 100 g of the dendritic copper powder obtained in Example 2, Sn coating was performed on the surface of the copper powder by electroless Sn plating to produce Sn-coated copper powder.

  Specifically, as an electroless Sn plating solution, a plating solution in which stannous chloride 10 g / L, sodium hydroxide 100 g / L, and sodium citrate 40 g / L were added at respective concentrations was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 80 ° C. and stirred for 60 minutes.

  After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Sn-coated copper powder in which Sn was coated on the surface of the dendritic copper powder was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 8.1% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

  In addition, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Sn-coated copper powder is uniformly on the surface of the dendritic copper powder before Sn coating A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with Sn, the main trunk growing linearly, and a plurality of branches linearly branched from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

  Also, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat cross-sectional shape with an average cross-sectional thickness of 0.18 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 9.7 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.71 g / cm ³ . The BET specific surface area was 2.10 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

  That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder, and the small size Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.8 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 4]
<Preparation of Dendritic Sn Coated Copper Powder (Coating with Sn-Ag Alloy)>
Using 100 g of the dendritic copper powder obtained in Example 2, the surface of the copper powder was coated with Sn alloy (Sn—Ag alloy) by electroless Sn plating to produce Sn-coated copper powder.

  Specifically, 50 g / L of stannous methanesulfonate, 20 g / L of silver citrate, 100 g / L of thiourea, and 30 g / L of sodium hypophosphite were added at various concentrations as the electroless Sn plating solution for alloys. A plating solution was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

  After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder in which the surface of the dendritic copper powder was coated with Sn-Ag alloy was obtained. As a result of recovering the Sn-coated copper powder and measuring the coating amount of the Sn-Ag alloy, it was 18.4% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Moreover, content of Ag contained in Sn alloy was 24.8 mass% with respect to 100 mass of Sn alloy.

  Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before being coated with the Sn alloy. A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with a Sn-Ag alloy, and a main trunk that grows linearly and a plurality of branches that branch linearly from the main trunk And a dendritic Sn-coated copper powder having a dendritic shape having branches further branched from the branches.

  Also, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat cross-sectional shape with an average cross-sectional thickness of 0.18 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 10.2 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.60 g / cm ³ . Moreover, the BET specific surface area was 2.08 m < ² > / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

  That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder, and the small size Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.2 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 5]
<Preparation of Dendritic Sn Coated Copper Powder (Coating with Sn-Bi Alloy)>
Using 100 g of the dendritic copper powder obtained in Example 2, the surface of the copper powder was coated with Sn alloy (Sn—Bi alloy) by electroless Sn plating to produce Sn-coated copper powder.

  Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 40 g / L, bismuth methanesulfonate 40 g / L, thiourea 100 g / L, ethylenediaminetetraacetic acid 20 g / L, sodium hypophosphite 80 g A plating solution to which / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

  After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Sn-coated copper powder in which the surface of the dendritic copper powder was coated with an Sn—Bi alloy was obtained. As a result of recovering the Sn-coated copper powder and measuring the coating amount of the Sn-Bi alloy, it was 42.3 mass% with respect to 100 mass of the entire Sn-coated copper powder. Further, the content of Bi contained in the Sn alloy was 41.9% by mass with respect to 100% by mass of the Sn alloy.

  Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before being coated with the Sn alloy. A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with a Sn-Bi alloy, and a main trunk that grows linearly and a plurality of branches that branch linearly from the main trunk And a dendritic Sn-coated copper powder having a dendritic shape having branches further branched from the branches.

  Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat shape with a cross-sectional thickness of 0.16 μm on average, and the copper particles were constituted into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 10.4 μm.

Moreover, the bulk density of the obtained dendritic Sn-coated copper powder was 0.65 g / cm ³ . The BET specific surface area was 2.12 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

  That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder, and the small size Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 7.9 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 6]
<Preparation of Dendritic Sn Coated Copper Powder (Coating with Sn-Zn Alloy)>
Using 100 g of the dendritic copper powder obtained in Example 2, the surface of the copper powder was coated with Sn alloy (Sn—Zn alloy) by electroless Sn plating to prepare Sn-coated copper powder.

  Specifically, as the electroless Sn plating solution for alloys, stannous chloride 10 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, and sodium hypophosphite 70 g / L. A plating solution added at a concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

  After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Sn-coated copper powder in which the surface of the dendritic copper powder was coated with Sn—Zn alloy was obtained. As a result of collecting the Sn-coated copper powder and measuring the coating amount of the Sn—Zn alloy, it was 11.4% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy was 2.1% by mass with respect to 100% by mass of the Sn alloy.

  Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before being coated with the Sn alloy. A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with a Sn—Zn alloy, and a main trunk that grows linearly and a plurality of branches that branch linearly from the main trunk And a dendritic Sn-coated copper powder having a dendritic shape having branches further branched from the branches.

  Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.19 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 10.4 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.66 g / cm ³ . Further, the BET specific surface area was 2.03 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

  That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder, and the small size Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.6 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 7]
<Preparation of Dendritic Sn Coated Copper Powder (Coating with Sn-Ag-Bi Alloy)>
Using 100 g of the dendritic copper powder obtained in Example 2, the surface of the copper powder was coated with Sn alloy (Sn—Ag—Bi alloy) by electroless Sn plating to prepare Sn-coated copper powder.

  Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 50 g / L, bismuth methanesulfonate 5 g / L, silver citrate 20 g / L, thiourea 100 g / L, sodium hypophosphite 30 g A plating solution to which / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

  After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Sn-coated copper powder in which the surface of the dendritic copper powder was coated with the Sn—Ag—Bi alloy was obtained. As a result of recovering the Sn-coated copper powder and measuring the coating amount of the Sn-Ag-Bi alloy, it was 18.9 mass% with respect to 100 mass of the entire Sn-coated copper powder. In addition, the content of Ag contained in the Sn alloy is 14.8% by mass with respect to the mass of Sn alloy of 100%, and the content of Bi contained in the Sn alloy is based on 100% of the mass of Sn alloy. 3.1% by mass.

  Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before being coated with the Sn alloy. A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with a Sn-Ag-Bi alloy, and a plurality of linearly branched main trunks and a plurality of linear branches from the main trunks And a dendritic Sn-coated copper powder having a dendritic shape having a branch further branched from the branch.

  Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder have a flat shape with a cross-sectional thickness of 0.22 μm on average, and the copper particles were constituted into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 10.8 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.67 g / cm ³ . The BET specific surface area was 2.11 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

  That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder, and the small size Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.7 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 8]
<Preparation of dendritic Sn-coated copper powder (Sn—Zn—Bi alloy)>
Using 100 g of the dendritic copper powder obtained in Example 2, the surface of the copper powder was coated with Sn alloy (Sn—Zn—Bi alloy) by electroless Sn plating to prepare Sn-coated copper powder.

  Specifically, as an electroless Sn plating solution for alloys, stannous chloride 10 g / L, bismuth chloride 5 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, hypophosphorous acid A plating solution to which 70 g / L of sodium was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

  After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Sn-coated copper powder in which the surface of the dendritic copper powder was coated with the Sn—Zn—Bi alloy was obtained. As a result of recovering the Sn-coated copper powder and measuring the coating amount of the Sn—Zn—Bi alloy, it was 11.1% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy is 2.0% by mass with respect to 100% by mass of the Sn alloy, and the content of Bi contained in the Sn alloy is based on 100% by mass of the Sn alloy. It was 1.4% by mass.

  Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before being coated with the Sn alloy. A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with a Sn—Zn—Bi alloy, and a main trunk that grows linearly and a plurality of linear branches branched from the main trunk And a dendritic Sn-coated copper powder having a dendritic shape having a branch further branched from the branch.

  Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.19 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 10.4 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.66 g / cm ³ . Further, the BET specific surface area was 2.03 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

  That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder, and the small size Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.9 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 9]
<Preparation of electrolytic copper powder>
As the electrolytic solution, a composition having a copper ion concentration of 5 g / L and a sulfuric acid concentration of 150 g / L was used, and safranin was added to the electrolytic solution so that the concentration in the electrolytic solution was 100 mg / L. Further, copper powder was deposited on the cathode plate under the same conditions as in Example 1 except that a hydrochloric acid solution was added so that the chlorine ion concentration in the electrolytic solution was 10 mg / L.

  As a result of observing the shape of the copper powder thus obtained in the field of view with a magnification of 1,000 times by the SEM method described above, the deposited copper powder was linearly grown and branched linearly from the main trunk. The copper powder had a two-dimensional or three-dimensional dendritic shape having a plurality of branches and branches further branched from the branches.

<Preparation of dendritic Sn-coated copper powder>
Next, using the dendritic copper powder produced by the method described above, Sn coating was performed on the surface of the copper powder by electroless Sn plating under the same conditions as in Example 1 to produce Sn-coated copper powder.

  After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Sn-coated copper powder in which Sn was coated on the surface of the dendritic copper powder was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 10.7% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

  In addition, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Sn-coated copper powder is uniformly on the surface of the dendritic copper powder before Sn coating A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with Sn, the main trunk growing linearly, and a plurality of branches linearly branched from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

  The copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat cross-sectional shape with an average cross-sectional thickness of 3.9 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 62.0 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 3.10 g / cm ³ . The BET specific surface area was 0.99 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

  That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder, and the small size Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.4 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Comparative Example 1]
<Preparation of electrolytic copper powder>
Copper powder was deposited on the cathode plate in the same manner as in Example 1 except that the conditions were such that safranin as an additive and chlorine ions were not added to the electrolytic solution.

<Preparation of Sn-coated copper powder>
The obtained copper powder was coated with Sn on the copper surface in the same manner as in Example 1 to obtain Sn-coated copper powder. When the Sn coating amount of the Sn-coated copper powder was measured, it was 12.2% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

  FIG. 5 shows the result of observing the shape of the obtained Sn-coated copper powder with a SEM field of view at a magnification of 1,000 times. As shown in the photograph of FIG. 5, the shape of the obtained Sn-coated copper powder is a dendritic shape in which granular copper particles are aggregated, and the surface of the copper powder is in a state where Sn is coated. The average particle diameter (D50) of the Sn-coated copper powder was 25.2 μm.

<Conductive paste>
Next, 20 g of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of Sn-coated copper powder produced by the above-described method. Then, using a small kneader (Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 82.0 × 10 ⁻⁵ Ω · cm, and the specific resistance value is extremely high and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 2]
The characteristic of the conductive paste by Sn coat copper powder which coat | covered Sn on the conventional flat copper powder was evaluated, and it compared with the characteristic of the conductive paste produced using the dendritic Sn coat copper powder in an Example.

  The flat copper powder was prepared by mechanically flattening granular electrolytic copper powder. Specifically, 5 g of stearic acid was added to 500 g of granular atomized copper powder (manufactured by Mekin Metal Powders Co., Ltd.) having an average particle diameter of 7.9 μm, and flattened with a ball mill. The ball mill was charged with 5 kg of 3 mm zirconia beads, and flattened by rotating for 90 minutes at a rotation speed of 500 rpm.

  Sn was coated by the same method as Example 1 with respect to the obtained flat copper powder. The coating amount of Sn of the produced flat Sn-coated copper powder was 12.8% by mass with respect to 100% by mass of the flat Sn-coated copper powder.

  Moreover, as a result of measuring with a laser diffraction / scattering method particle size distribution measuring instrument, the average particle diameter (D50) was 22.7 μm for the flat Sn-coated copper powder produced in this way, and as a result of observation by SEM, The cross-sectional average thickness was 0.4 μm.

  Next, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the obtained flat Sn-coated copper powder. Then, using a small kneader (Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 35.4 × 10 ⁻⁵ Ω · cm, which is higher in specific resistance value and inferior in conductivity than the copper paste obtained in Example 1. there were.

1 Sn-coated copper powder (dendritic Sn-coated copper powder)
2 trunk 3, 3a, 3b branch

Claims (8)

A dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk,
The main trunk and the branch are made of copper particles having a cross-sectional average thickness of 0.2 μm to 5.0 μm and having a surface coated with tin (Sn) or Sn alloy,
An average particle diameter (D50) measured by a laser diffraction / scattering particle size distribution measurement method is 1.0 μm to 100 μm. The dendritic Sn-coated copper according to claim 1, wherein the content of Sn coated as Sn or Sn alloy is 1% by mass to 50% by mass with respect to 100% by mass of the entire dendritic Sn-coated copper powder. powder. Sn alloy is coated on the surface of the copper particles,
The Sn alloy containing at least one selected from silver, bismuth, and zinc at a content of 0.1% by mass to 50% by mass with respect to 100% by mass of the Sn alloy is coated. 2. Sn coated copper powder according to 2. Dendritic Sn coating copper powder according to any one of claims 1 to 3 bulk density is in the range of ^{0.5g / cm 3 ~5.0g / cm 3} . Dendritic Sn coating copper powder according to any one of claims 1 to 4 BET specific surface area is 0.2m ² /g~5.0m ² / g.   A metal filler comprising the dendritic Sn-coated copper powder according to any one of claims 1 to 5 in a proportion of 20% by mass or more of the whole.   A conductive paste comprising the metal filler according to claim 6 mixed with a resin. A method for producing the dendritic Sn-coated copper powder according to any one of claims 1 to 5,
A step of depositing copper powder on the cathode from the electrolyte by an electrolytic method;
Coating the copper powder with tin (Sn) or Sn alloy,
In the electrolyte,
Copper ions,
One or more selected from compounds having a phenazine structure represented by the following formula (1);
A method for producing a dendritic Sn-coated copper powder, characterized by comprising electrolysis.
[In Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, CN, SCN. , SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl, R ₅ is hydrogen, halogen , selected amino, OH, -O, CN, SCN , SH, COOH, COO salt, COO _ester, SO 3 H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, from the group consisting of lower alkyl, and aryl And A ⁻ is a halide anion. ]