JP2017066443A - Ni-COATED COPPER POWDER, AND CONDUCTIVE PASTE, CONDUCTIVE PAINT AND CONDUCTIVE SHEET USING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Ni-coated copper powder capable of being suitably used for conductive pastes, electromagnetic shields or the like, while increasing the number of contact points of copper powders to ensure excellent conductivity.SOLUTION: An Ni-coated copper powder 1 according to the present invention is formed having the agglomeration by agglomerating a plurality of copper particles 2 in a piece shape, and has Ni- or Ni alloy-coated surfaces. The Ni- or Ni alloy-coated copper powder 2 is in a plate shape which has: an average major axis diameter d, measured by scanning electron microscopy (SEM), of 0.5 to 5 μm; and average cross-sectional thickness of 0.02 to 1.0 μm. The Ni-coated copper powder 1 has average particle diameter (D50), measured by laser diffraction/scattering grain size distribution measurement, of 1.0 to 30 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a copper powder (nickel-coated copper powder) whose surface is coated with nickel (Ni), and more specifically, a novel material that can improve conductivity by using as a material such as a conductive paste. The present invention relates to a nickel-coated copper powder having a shape.

  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.

  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 this 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.

  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. Although this firing-type conductive paste has a high firing temperature, it cannot be used for printed wiring boards that use resin materials, but it can realize low resistance because the metal filler is sintered by high-temperature treatment. Become. Therefore, the fired conductive paste is used for an external electrode of a multilayer ceramic capacitor.

  On the other hand, electromagnetic wave shields are used to prevent the generation of electromagnetic noise from electronic equipment. Especially in recent years, personal computers and mobile phone cases have been made of resin, so that the case is made conductive. In order to secure the properties, there are a method of forming a thin metal film by a vapor deposition method or a sputtering method, a method of applying a conductive paint, a method of attaching a conductive sheet to a necessary place and shielding an electromagnetic wave, etc. Proposed. Among them, special methods are required in the processing process for the method of applying the metal filler dispersed in the resin and the method of dispersing the metal filler in the resin and processing it into a sheet and attaching it to the housing. It has excellent flexibility and is widely used.

  However, in the case where such a metal filler is dispersed in a resin and applied or processed into a sheet shape, the dispersion state of the metal filler in the resin is not uniform. A method such as increasing the filling rate of the metal filler is required. However, in such a case, the addition of a large amount of metal filler causes problems such as an increase in sheet weight and a loss of flexibility of the resin sheet. Therefore, for example, in Patent Document 1, a method of using a flat metal filler has been proposed in order to solve these problems, and as a result, a thin sheet having excellent electromagnetic shielding effect and good flexibility. Can be formed.

Copper powder as a metal powder material used as a metal filler for such conductive paste and electromagnetic wave shielding material is covered with copper oxide when oxidized, causing adverse effects on sinterability, corrosion resistance, or conductivity Become. For this reason, in order to prevent oxidation of the copper powder, the surface of the copper particles is coated with a noble metal such as Pt, Pd, Ag, Au, etc., coated with a SiO ₂ oxide, or coated with Ni. Those with improved oxidation resistance are known. For example, Patent Document 2 discloses a nickel-coated copper powder having a copper powder surface coated with nickel (Ni).

  On the other hand, the shape of the copper powder used as the metal filler is spherical, flat, dendritic, etc., and in particular, the flat copper powder is a contact point between fillers compared to granular or dendritic copper powder. Since a large area can be secured, it is widely used as a low-resistance conductive paste. As a method for producing such a flat copper powder, Patent Document 3 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 having an average particle size of 0.5 μm to 10 μm is used as a raw material, and is processed into a flat plate shape by a mechanical energy of a medium loaded in the mill using a ball mill or a vibration mill. is there.

  Further, for example, Patent Document 4 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 method for manufacturing the same. 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.

Here, silver powder is used as the metal filler used for these conductive pastes and electromagnetic wave shields, and as described above, the surface of the copper particles is coated with a noble metal such as Pt, Pd, Ag, or Au. Thus, those having sufficient oxidation resistance are used. However, since these are expensive, the cost increases. Among them, a copper powder coated with Ag can be kept at a relatively low price, but there is a problem that migration tends to occur with Ag. Also, when the surface of the copper powder is coated with a SiO ₂ -based oxide, oxidation resistance can be secured, but there are problems such as poor sinterability.

  A method for coating copper powder with nickel is mentioned as a low cost and relatively good sinterability while ensuring oxidation resistance and the like.

  As a method for coating the surface of the copper powder with nickel, a method by electroless nickel plating may be mentioned. The coating method by electroless nickel plating is to perform nickel coating on the copper powder surface by reducing nickel ions in the plating solution with a reducing agent. The types of reducing agents are hypophosphites and borohydrides. And hydrazine compounds. Specifically, in nickel coating treatment using hypophosphite as a reducing agent, a Ni—P alloy coating is formed because phosphorus is contained in the coating during the reduction reaction. Further, in the nickel coating treatment using a borohydride compound as the reducing agent, since the boron is contained in the coating during the reduction reaction, a Ni-B alloy coating is formed. Further, in the nickel coating process using a hydrazine compound as a reducing agent, a high-purity Ni coating with few impurities is formed.

  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 5 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 6 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 patent document 6, in order to raise the intensity | strength of electrolytic copper powder itself, the intensity | strength of electrolytic copper powder itself is improved by adding tungstate in the copper sulfate aqueous solution of the electrolyte solution for depositing electrolytic copper powder. It is said that it is difficult to break the branches 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.

JP 2003-258490 A JP-A-5-342908 Japanese Patent Laid-Open No. 2005-200734 JP 2002-15622 A JP 2002-075057 A JP 2011-58027 A

  The present invention has been proposed in view of such a situation, while ensuring excellent conductivity by increasing the number of contacts when the copper powders coated with nickel are in contact with each other, preventing aggregation, It aims at providing the nickel coat copper powder which can be utilized suitably as uses, such as an electrically conductive paste and an electromagnetic wave shield.

  This inventor repeated earnest examination for solving the subject mentioned above. As a result, a plurality of pieces of copper particles in the form of aggregates have a form of aggregate, and the surface is a copper powder coated with Ni or a Ni alloy, and the pieces of copper particles are flat. It has a specific range of dimensions, and the average particle diameter of the copper powder, which is an aggregate of a plurality of tabular copper particles, is in a specific range to ensure excellent conductivity and conductivity. The present invention has been completed by finding that it can be suitably used for applications such as adhesive paste. That is, the present invention provides the following.

  (1) The first invention of the present invention is a Ni-coated copper powder in which a plurality of piece-like copper particles whose surfaces are coated with nickel (Ni) or a Ni alloy are aggregated to have an aggregate form. The copper particles coated with Ni or Ni alloy have an average major axis diameter determined by observation with a scanning electron microscope (SEM) of 0.5 μm to 5.0 μm and an average cross-sectional thickness of 0.02 μm to A Ni-coated copper powder having a flat plate shape of 1.0 μm and an average particle diameter (D50) determined by a laser diffraction / scattering particle size distribution measurement method of 1.0 μm to 30 μm.

  (2) In the second invention of the present invention, in the first invention, the content of Ni coated as Ni or Ni alloy is 1% by mass to 100% by mass of the entire Ni-coated copper powder. It is Ni coat copper powder which is 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 a Ni alloy, and cobalt, zinc, tungsten, molybdenum, palladium, platinum, tin, phosphorus And Ni-coated copper coated with a Ni alloy containing at least one selected from the group consisting of boron at a content of 0.1% by mass to 20% by mass with respect to 100% by mass of the Ni alloy It is powder.

(4) The fourth invention of the present invention, in any one of the first to third invention, the tap density is in the range of ^{0.5g / cm 3 ~5.0g / cm 3} , with Ni-coated copper powder is there.

(5) Fifth aspect of the present invention, in the first to fourth invention of any one of, BET specific surface area of 0.2m ² /g~5.0m ² / g, are Ni-coated copper powder .

  (6) A sixth aspect of the present invention is a metal filler comprising the Ni-coated copper powder according to any one of the first to fifth aspects in a proportion of 20% by mass or more of the whole. It is.

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

  (8) The eighth invention of the present invention is an electromagnetic wave shielding conductive paint characterized in that the metal filler according to the sixth invention is dispersed in a resin.

  (9) A ninth invention of the present invention is a conductive sheet for electromagnetic wave shielding, wherein the metal filler according to the sixth invention is dispersed in a resin.

  According to the Ni-coated copper powder according to the present invention, it is possible to ensure a large number of contacts and a large contact area, thereby ensuring excellent conductivity, such as a conductive paste and an electromagnetic wave shield. It can utilize suitably for a use.

It is the schematic diagram which showed an example of the specific shape of the copper powder (flat copper particle aggregation powder) by which nickel or the nickel alloy was coat | covered. It is an example of the photograph figure which shows an observation image when the flat copper particle aggregate powder coated with nickel is observed with a scanning electron microscope at a magnification of 5,000 times. It is an example of the photograph figure which shows an observation image when the flat copper particle aggregate powder coated with nickel is observed with a scanning electron microscope at a magnification of 10,000 times. It is a photograph figure which shows an observation image when the Ni coat copper powder obtained in the comparative example 1 is observed with a scanning electron microscope.

  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. Ni coated copper powder (flat Ni coated copper particle agglomerated powder) >>
The nickel-coated copper powder according to the present embodiment is a copper powder whose surface is coated with nickel. In this specification, nickel-coated copper powder is referred to as “Ni-coated copper powder”. Further, nickel or nickel alloy to be coated is expressed as “Ni” and “Ni alloy”, respectively, and when Ni is coated on the surface of copper powder or Ni alloy is coated on the surface of copper powder, “Ni coating” is generally used. ".

  FIG. 1 is a schematic diagram showing a specific shape of the Ni-coated copper powder according to the present embodiment. As shown in the schematic diagram of FIG. 1, the Ni-coated copper powder 1 according to the present embodiment is a copper powder having a form in which flattened copper particles 2 that are separated into pieces are aggregated two-dimensionally or three-dimensionally. The surface is coated with Ni or Ni alloy, and the copper particles 2 have a flat plate shape. Hereinafter, this Ni-coated copper powder is also referred to as “flat Ni-coated copper particle aggregated powder 1”.

  More specifically, the plate-like Ni-coated copper particle aggregated powder 1 includes a plurality of tabular copper particles 2 (hereinafter also referred to as “Ni-coated copper particles 2”) whose surfaces are coated with Ni or Ni alloy. The aggregated copper powder is in the form of aggregates, and the average of the major axis diameter d (average major axis diameter) of the tabular Ni-coated copper particles 2 is 0.5 μm to 5.0 μm, and the cross-sectional average thickness Is 0.02 μm to 1.0 μm. And the magnitude | size of the said tabular Ni coat copper particle aggregated powder 1 which the aggregate of the tabular Ni coat copper particle 2 aggregated and became the aggregate is 1.0 micrometer-30 micrometers in an average particle diameter (D50). .

  In addition, as described later, the Ni or Ni alloy coating amount of the tabular silver-coated copper particle aggregated powder 1 according to the present embodiment is 1 as the Ni content with respect to 100% of the mass of the entire Ni-coated copper powder. Although it is mass%-50 mass%, the thickness (coating thickness) of Ni or Ni alloy is a very thin film about 0.1 micrometer or less. Therefore, this flat Ni coated copper particle aggregated powder 1 keeps the shape of the copper powder in which the flat copper particles before coating Ni or Ni alloy are aggregated. Therefore, both the shape of the tabular copper particle aggregated powder before coating with Ni or Ni alloy and the shape of the tabular Ni-coated copper particle aggregated powder 1 after coating with Ni or Ni alloy are both two-dimensional or It is the shape which the flat plate which is a three-dimensional form aggregated.

  The flat Ni-coated copper particle agglomerated powder 1 will be described in detail below. For example, the anode and the cathode are immersed in a sulfuric acid electrolyte containing copper ions, and a direct current is applied to cause electrolysis. The agglomerated powder 1 can be deposited and the surface of the obtained agglomerated powder 1 can be formed by coating Ni or a Ni alloy by an electroless plating method or the like.

  FIG. 2 and FIG. 3 are photographic diagrams showing an example of an observation image when the flat Ni-coated copper particle aggregated powder 1 according to the present embodiment is observed with a scanning electron microscope (SEM). 2 shows the Ni-coated copper particle aggregated powder 1 observed at a magnification of 5,000 times, and FIG. 3 shows the Ni-coated copper particle aggregated copper powder 1 observed at a magnification of 10,000 times. It is.

  As shown in the observation image of FIG. 2, the tabular Ni-coated copper particle aggregated powder 1 has a form in which the tabular Ni-coated copper particles 2 are aggregated. Further, as shown in the observation image of FIG. 3, the flat Ni-coated copper particles 2 are singulated and have a flat shape having a flat surface or a curved surface.

  Here, as shown in the schematic diagram of FIG. 1, the plate-like Ni-coated copper particles 2 have a flat plate-like surface that is substantially oval, oval, or so-called cornflakes, and the like. The shape has a cross-sectional average thickness in a specific range described later. Of course, the surface having a substantially elliptic shape or the like may have protrusions and attached particles having a height of about twice or less the average cross-sectional thickness.

  As described above, the average major axis diameter d of these tabular Ni-coated copper particles 2 is 0.5 μm to 5.0 μm, more preferably 0.7 μm to 4.0 μm. Moreover, the cross-sectional average thickness of the Ni coat copper particle 2 is 0.02 micrometer-1.0 micrometer, More preferably, it is 0.05 micrometer-0.4 micrometer. Here, the average major axis diameter d of the flat copper particles 2 indicates the maximum width of a flat plate-like surface having a shape such as a substantially ellipse as shown in FIG. Moreover, the average major axis diameter d and the cross-sectional average thickness can be obtained by observation using an SEM.

  When the average major axis diameter d of the tabular Ni-coated copper particles 2 is less than 0.5 μm or the average cross-sectional thickness exceeds 1.0 μm, these aggregated powders are aggregated into aggregates It may not be possible to ensure a large area for contact with each other, and the conductivity may decrease. On the other hand, the upper limit value of the average major axis diameter d of the plate-like Ni-coated copper particles 2 is not particularly limited. However, in the method of depositing on the cathode by electrolysis described later, the upper limit is about 5.0 μm. Further, the lower limit value of the cross-sectional average thickness of the flat Ni-coated copper particles 2 is not particularly limited, but in the same method of depositing on the cathode by electrolysis, the lower limit is about 0.02 μm.

  The size of the tabular Ni-coated copper particle aggregated powder 1 obtained by aggregating the tabular Ni-coated copper particles 2 into an aggregate is 1.0 μm to 30 μm in terms of average particle diameter (D50). The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical pulverization such as a jet mill, a sample mill, a cyclone mill, and a bead mill. The average particle diameter (D50) of the tabular Ni-coated copper particle aggregated powder 1 can be measured by a laser diffraction / scattering particle size distribution measurement method.

  As described above, the flat Ni-coated copper particles 2 having an average cross-sectional thickness of 0.02 μm to 1.0 μm are aggregated to form the tabular Ni-coated copper particle aggregated powder 1. It is possible to secure a large area where the flat Ni-coated copper particle aggregated powders 1 and the Ni-coated copper particles 2 on the flat plate contact each other. And since the contact area becomes large, low resistance, that is, high conductivity can be realized. By this, it is more excellent in electroconductivity and can be used suitably for the use of a conductive paint and a conductive paste.

  Here, as pointed out in Patent Document 1, for example, when used as a metal filler such as a conductive paste or a resin for electromagnetic wave shielding, the metal filler in the resin has a dendritic shape, 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 is because the shape of the dendritic copper powder grows in a needle shape, and when trying to prevent agglomeration, the shape of the dendritic copper powder is reduced. It becomes impossible to obtain the effect of securing the contact by eliminating.

  Further, in the case where the plate is formed by the mechanical method of Patent Document 3 or Patent Document 4, it is necessary to prevent copper oxidation at the time of mechanical processing. For example, after adding a fatty acid, in the air or inactive It is crushed in an atmosphere and processed into a flat plate shape. However, oxidation cannot be completely prevented, and the fatty acid added at the time of processing needs to be removed after processing to affect dispersibility when it is made into a paste. There is a problem that the fatty acid cannot be completely removed because it may firmly adhere to the copper surface. Moreover, it becomes difficult to make the flat copper powder obtained to make a flat plate by mechanical pressure flat because it becomes flat by mechanical processing, and it becomes warped. . Since copper powder with a smooth and warped surface is difficult to secure contact points, when using it as a metal filler, not only flat copper powder but also granular copper powder can be mixed with other metal fillers. It is necessary to secure the contact points.

  On the other hand, in the flat plate Ni-coated copper particle aggregated powder 1 according to the present embodiment, since the flat plate-shaped Ni-coated copper particles 2 have an aggregated shape, the respective flat plate-shaped Ni-coated copper particles 2 are formed. Are aggregated in a three-dimensional shape, and have a structure that simultaneously satisfies a two-dimensional contact effect and a three-dimensional contact effect. Furthermore, when the tabular Ni-coated copper particle aggregated powder 1 has an average particle size (D50) of 1.0 μm to 30 μm, the surface area is increased and good moldability and sinterability are ensured. be able to.

  In addition, this demonstrates the same effect that the contact rate of metal fillers improves by using the silver powder of the shape described, for example in patent 4059486, and flat plate Ni coat copper particle aggregation Since the copper powder 1 has a three-dimensional concavo-convex structure, the contact rate between metal fillers can be improved, the filler weight contained in the paste can be reduced, and the cost can be greatly reduced.

≪2. Ni coating amount of tabular Ni-coated copper particle aggregate powder >>
As described above, the plate-like Ni-coated copper particle aggregated powder 1 according to the present embodiment has an average major axis diameter of 0.5 μm to 5.0 μm and a cross-sectional average thickness of 0.02 to 1.0 μm. A plurality of copper particles 2 whose surfaces are coated with Ni or Ni alloy are aggregated to form an aggregate. Hereinafter, the Ni or Ni alloy coating on the surface of the Ni-coated copper powder will be described.

  The tabular Ni-coated copper particle aggregated powder 1 according to the present embodiment is preferably formed on the tabular copper particle aggregated powder before being coated with Ni or Ni alloy, preferably with respect to 100% by mass of the entire Ni-coated copper powder. The Ni or Ni alloy is coated at a ratio of 1% by mass to 50% by mass as the content, and the thickness of Ni or Ni alloy (coating thickness) is 0.1 μm or less, preferably 0.02 μm or less. This is an extremely thin film. From this, flat-plate Ni coat copper particle aggregated powder 1 becomes a shape which maintained the shape of the flat-plate copper particle aggregated powder before Ni or Ni alloy coat | covers as it is.

  The content of Ni coated as Ni or Ni alloy in the flat Ni-coated copper particle aggregated powder 1 is, as described above, 1% by mass to 50% by mass with respect to 100% by mass of the entire Ni-coated copper powder. A range is preferable. The content of Ni coated as Ni or Ni alloy is preferably as low as possible because the conductivity of Ni itself is lower than that of copper, but if it is too small, a uniform Ni or Ni alloy film can be secured on the copper surface. In other words, copper is oxidized to cause a decrease in conductivity. Therefore, the content of Ni coated as Ni or Ni alloy is preferably 1% by mass or more and more preferably 5% by mass or more with respect to 100% by mass of the entire Ni-coated copper powder. More preferably, it is 10 mass% or more.

  On the other hand, when the content of Ni coated as Ni or Ni alloy increases, it is not preferable from the viewpoint of decreasing the electrical conductivity, and as the content of Ni coated as Ni or Ni alloy, the Ni coated copper powder as a whole It is preferably 50% by mass or less, more preferably 30% by mass or less, and still more preferably 20% by mass or less with respect to 100% by mass.

  Further, in the flat Ni-coated copper particle aggregated powder 1 according to the present embodiment, the average thickness of Ni or Ni alloy coated on the surface of the flat copper particles is about 0.0003 μm to 0.1 μm, It is preferable that it is 0.005 micrometer-0.02 micrometer. When the Ni or Ni alloy coating thickness is less than 0.0003 μm on average, a uniform Ni or Ni alloy coating cannot be secured on the surface of the copper powder, and copper oxidation cannot be suppressed, resulting in a decrease in conductivity. Cause. On the other hand, when the coating thickness of Ni or Ni alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of decreasing the electrical conductivity.

  Thus, the average thickness of Ni or Ni alloy coated on the surface of the plate-like Ni-coated copper particle aggregated powder 1 is about 0.0003 μm to 0.1 μm, and the plate-like copper before coating with Ni or Ni alloy. It is smaller than the cross-sectional average thickness (0.02 μm to 0.5 μm) of the flat copper particles 1 constituting the particle aggregated powder. Therefore, the form of the flat copper particles 2 does not substantially change before and after the surface of the flat copper particle aggregated powder is coated with Ni or a Ni alloy.

  Further, as will be described later, in the tabular Ni-coated copper particle aggregated powder 1, the Ni covered with the tabular copper particles 2 may be a Ni alloy. The element added as the Ni alloy is preferably an element from Group 6 to Group 14 of the periodic table, and particularly preferably at least one selected from zinc, cobalt, tungsten, molybdenum, palladium, platinum, and tin. Further, as will be described later, when electroless plating is used in the step of coating Ni on the flat copper particle agglomerated powder, and hypophosphite and a borohydride compound are used as the reducing agent, the Ni obtained The coatings are Ni-P alloy and Ni-B alloy, respectively.

Further, the tabular Ni-coated copper particles agglomerated powder 1 according to the present embodiment is not particularly limited, it is preferable that the tap density is in the range of ^{0.5g / cm 3 ~5.0g / cm 3} . If the tap density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the Ni-coated copper powders cannot be secured. On the other hand, when the tap density exceeds 5.0 g / cm ³ , the average particle diameter of the Ni-coated copper powder increases, the surface area decreases, and the moldability and sinterability may deteriorate.

As the BET specific surface area of the tabular Ni-coated copper particles agglomerated powder 1 is not particularly ^limited, it is preferably in the range of 0.2m ² /g~5.0m 2 / g. When the BET specific surface area exceeds 5.0 m ² / g, there is a possibility that sufficient contact between the Ni-coated copper powders cannot be ensured. On the other hand, when the BET specific surface area is less than 0.2 m ² / g, the average particle diameter of the Ni-coated copper powder is also increased, the surface area is decreased, and the formability and the sinterability may be deteriorated. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

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

≪3. Method for producing flat Ni-coated copper particle aggregate powder >>
Next, the manufacturing method of the flat Ni coat | court copper particle aggregate powder 1 which concerns on this Embodiment is demonstrated. Below, first, the manufacturing method of the tabular copper particle aggregated powder which comprises the tabular Ni coat copper particle aggregated powder 1 is demonstrated, Then, Ni or Ni alloy is coat | covered with respect to the tabular copper particle aggregated powder. A method for obtaining the tabular Ni-coated copper particle aggregated powder 1 will be described.

<3-1. Manufacturing Method of Flat Copper Particle Aggregated Powder>
The tabular copper particle agglomerated powder constituting the tabular Ni-coated copper particle agglomerated powder 1, that is, the tabular copper particle agglomerated powder before coating with Ni or Ni alloy is, for example, an acidic solution containing sulfuric acid containing copper ions. And can be produced by a predetermined electrolytic method.

  In electrolysis (electrolysis), for example, the above-described sulfuric acid-containing electrolytic solution containing copper ions in an electrolytic cell in which metallic copper is used as an anode (anode) and a stainless plate or titanium plate is used as a cathode (cathode) And electrolytic treatment is performed by applying a direct current to the electrolytic solution at a predetermined current density. Thereby, flat copper particle aggregation copper powder can be deposited (electrodeposition) on a cathode with electricity supply.

  In particular, in the present embodiment, for example, the granular copper powder obtained by electrolysis is not deformed mechanically using a medium such as a ball, and the like, and the flat fine copper particles are obtained only by electrolysis. Aggregated tabular copper particle aggregated powder 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 or a nonionic surfactant, and a chloride ion 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. Alternatively, copper oxide may be dissolved in a sulfuric acid solution to make a sulfuric acid acidic solution.

  The copper ion concentration in the electrolytic solution is preferably about 1 g / L to 20 g / L, more preferably about 5 g / L to 10 g / L. If the copper ion concentration is too high, it will be difficult to deposit the copper powder having the above-mentioned shape on the cathode during electrolysis, but if it is 20 g / L or less, the tabular copper particle aggregated powder can be deposited without any problem. Can do. On the other hand, the lower limit of the copper ion concentration is not particularly limited, but it is preferably 1 g / L or more in consideration of efficiently depositing copper powder on the cathode during electrolysis.

  Sulfuric acid is for making a sulfuric acid electrolyte. The concentration of sulfuric acid in the electrolytic solution is preferably about 20 g / L to 300 g / L, more preferably about 50 g / L to 150 g / L in terms of 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 or a nonionic surfactant can be used. The amine compound added as an additive contributes to the shape control of the copper powder deposited together with the chloride ion and nonionic surfactant described later, and the copper powder deposited on the cathode has a flat cross-sectional shape having a predetermined cross-sectional average thickness. It can be set as the tabular copper particle aggregation powder comprised from a copper particle.

Specifically, the amine compound is not particularly limited, for example, Janus Green _{B (C 30 H 31 N 6} Cl, CAS Number: 2869-83-2), or the like can be used.

  As an amine compound, you may add individually by 1 type and may add it in combination of 2 or more types. Moreover, it is preferable to set it as the quantity used as the addition amount of an amine compound in the range of about 0.1 mg / L-500 mg / L in the density | concentration in electrolyte solution.

  Although it does not specifically limit as a nonionic surfactant, What has an ether group is preferable. Specific examples include polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant, polyoxyethylene glycol / glyceryl ether, polyoxyethylene glycol / dialkyl ether, polyoxyethylene polyoxypropylene glycol. -Alkyl ether, aromatic alcohol alkoxylate, the compound represented by following formula (x), etc. are mentioned.

(However, in formula (x), R ₁ has a higher alcohol residue having 5 to 30 carbon atoms, an alkylphenol residue having an alkyl group having 1 to 30 carbon atoms, and an alkyl group having 1 to 30 carbon atoms. A residue of an alkyl naphthol, a residue of a fatty acid amide having 3 to 25 carbon atoms, a residue or a hydroxyl group of an alkyl amine having 2 to 5 carbon atoms, R ₂ and R ₃ represent a hydrogen atom or a methyl group, m And n represents an integer of 1 to 100.)

  The number average molecular weight of the nonionic surfactant is not particularly limited, but is preferably 100 to 200,000, more preferably 200 to 15,000, and further preferably 1,000 to 10,000. preferable. In the present embodiment, the number average molecular weight is a molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

  These nonionic surfactants may be added singly or in combination of two or more. The amount of the nonionic surfactant added is not particularly limited, but is preferably about 200 mg / L to 5000 mg / L, more preferably about 500 mg / L to 2000 mg / L in terms of concentration in the electrolytic solution. preferable.

  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. Chloride ions contribute to shape control of the deposited copper powder together with the above-described amine compound and nonionic surfactant additives. The chloride ion concentration in the electrolytic solution is not particularly limited, but is preferably about 200 mg / L to 1000 mg / L, and more preferably about 250 mg / L to 800 mg / L.

In the manufacturing method of the flat copper particle aggregation copper powder 1 which concerns on this Embodiment, it electrolyzes using the electrolyte solution of a composition as mentioned above, for example, deposits copper powder on a cathode, and manufactures it. . 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} 40 A / dm ² in electrolysis using a sulfuric acid electrolytic solution, and the electrolytic solution 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. Ni or Ni alloy coating method (production of Ni-coated copper powder)>
The plate-like Ni-coated copper particle aggregated powder 1 according to the present embodiment coats the surface of the plate-like copper particle aggregated powder prepared by the above-described electrolytic method with Ni or Ni alloy using, for example, an electroless plating method. Can be manufactured.

  In order to coat Ni or Ni alloy with a uniform thickness on the surface of the tabular copper particle aggregated powder, it is preferable to perform washing before electroless plating, and the tabular copper particle aggregated powder is dispersed in the cleaning liquid, Washing can be performed with stirring. This washing treatment is preferably performed in an acidic solution. After washing, filtration and separation of the tabular copper particle aggregated powder and washing with water are repeated as appropriate to obtain a water slurry in which the tabular copper particle aggregated 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 Ni coating is performed by the electroless plating method, the electroless plating solution is added to the copper slurry obtained after washing the tabular copper particle aggregated powder, or the copper slurry is added to the electroless plating solution. By stirring uniformly, the surface of the tabular copper particle agglomerated powder can be coated more uniformly with Ni or a Ni alloy.

  The electroless Ni plating solution is not particularly limited. The electroless Ni plating solution performs Ni coating by reducing Ni ions in the plating solution with a reducing agent. Examples of the reducing agent include hypophosphites, borohydrides, and hydrazine compounds. It is done.

  Specifically, examples of hypophosphites include hypophosphites such as potassium hypophosphite and sodium hypophosphite, and phosphites such as potassium phosphite and sodium phosphite. Can be mentioned.

  Examples of the borohydride compound include dimethylhexaborane, dimethylamineborane (DMAB), diethylamineborane, morpholineborane, pyridineamineborane, piperidineborane, ethylenediamineborane, ethylenediaminebisborane, t-butylamineborane, imidazoleborane, methoxy Examples include ethylamine borane and sodium borohydride.

  As the hydrazine compound, hydrazine and hydrates thereof, hydrazine salts such as hydrazine sulfate and hydrazine hydrochloride, hydrazine derivatives such as pyrazoles, triazoles, and hydrazides can be used. Among these hydrazine derivatives, pyrazoles such as 3,5-dimethylpyrazole and 3-methyl-5-pyrazolone can be used as pyrazoles 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. As hydrazines, hydrazine sulfate, hydrazine hydrochloride, adipic hydrazide, maleic hydrazide, carbohydrazide, and the like can be used.

  Examples of the nickel source include nickel salts such as nickel sulfate, nickel chloride, nickel acetate, and nickel sulfamate.

  Further, the plating solution can contain a complexing agent, a pH buffering agent, and a pH adjusting agent.

  Specifically, a known complexing agent can be used as the complexing agent. For example, amino acids such as glycine, citrates such as sodium citrate and ammonium citrate, lactic acid, oxalic acid, malonic acid, malic acid, tartaric acid, aspartic acid, glutamic acid, gluconic acid, sodium salts or ammonium salts, ammonia, etc. Is mentioned.

  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.

  Moreover, you may use an antifoamer and a dispersing agent as needed.

  Furthermore, in order to improve the permeability of the plating solution, a surfactant can be contained. As the surfactant, any of nonionic, cationic, anionic and amphoteric surfactants can be used, and one kind can be used alone, or two or more kinds can be used in combination.

  Here, in Ni coating by electroless plating, the Ni coating deposited differs depending on the hypophosphorous acid bath salt, the borohydride compound, and the hydrazine compound which are reducing agents in the electroless Ni plating solution. Specifically, when hypophosphorous acid bath salt is used as the reducing agent, since the phosphorus is contained in the coating during the reduction reaction, a Ni-P alloy coating is formed. Further, when a borohydride compound is used as the reducing agent, since a boron is contained in the coating during the reduction reaction, a Ni-B alloy coating is formed. Further, when a hydrazine compound is used as the reducing agent, a high-purity Ni film with few impurities is formed.

  Furthermore, by making the Ni film to be formed contain other elements, that is, by forming a Ni alloy film on the surface of the copper powder, using the Ni-coated copper powder, heat resistance and corrosion resistance In addition, an excellent conductive paste or the like can be realized.

  Specifically, as an element to be included in the Ni film, that is, as an element other than Ni constituting the Ni alloy, elements of Groups 6 to 14 of the periodic table can be mentioned, and among them, zinc, palladium, Examples include cobalt, rhodium, iron, platinum, iridium, tungsten, molybdenum, chromium, and tin. In particular, one or more elements selected from zinc, cobalt, tungsten, molybdenum, palladium, platinum, and tin are preferable, and a Ni alloy film having excellent conductivity is formed by using an Ni alloy containing these elements. be able to.

  The content of these elements constituting the Ni alloy is preferably 0.1% by mass to 20% by mass with respect to 100% by mass of the Ni alloy, from the viewpoint of conductivity and dispersibility, and preferably 1% by mass to 15%. More preferably, it is more preferably 2% by mass to 10% by mass. In addition, also about the Ni-P alloy and Ni-B alloy which are each formed with the kind of reducing agent mentioned above, the content of phosphorus or boron is 0.1 mass% with respect to 100 mass of Ni alloy film similarly. It is preferably ˜20% by mass, more preferably 1% by mass to 15% by mass, and further preferably 2% by mass to 10% by mass.

  When the Ni alloy is used, if the content of elements other than Ni is excessively increased, the conductivity is lowered, so that the content is preferably 20% by mass or less. On the other hand, if the content is less than 0.1% by mass, the effect of improving the heat resistance and corrosion resistance cannot be sufficiently obtained even if these elements are contained together with Ni to form a Ni alloy. In addition, content of the element in Ni alloy can be measured by converting content of each element which comprises Ni coat | court copper powder, for example by a high frequency inductively coupled plasma (ICP) emission spectroscopy analysis method. In addition, each element in the Ni alloy coating can be quantitatively analyzed from the cross section of the Ni-coated copper powder or the like by energy dispersive X-ray spectroscopy (EDX) method or Auger electron spectroscopy (AES) method.

  As a method for forming a Ni alloy coating, ions such as cobalt, zinc, tungsten, molybdenum, palladium, platinum, and tin are added to the above-described electroless Ni plating solution, and electroless plating using the plating solution is performed. Can be formed. The ion source such as cobalt, zinc, tungsten, molybdenum, palladium, platinum, and tin is not particularly limited as long as it is a soluble metal salt.

  Specifically, the cobalt ion source is not particularly limited as long as it is soluble in the plating solution as a cobalt compound and can obtain an aqueous solution having a predetermined concentration. Examples thereof include cobalt sulfate, cobalt chloride, and cobalt sulfamate. These cobalt compounds can be used individually by 1 type or in mixture of 2 or more types.

  The zinc ion source is not particularly limited as long as it is soluble in the plating solution as a zinc compound and can obtain an aqueous solution having a predetermined concentration. For example, zinc chloride, zinc sulfamate, zinc sulfate, zinc acetate and the like can be mentioned. These zinc compounds can be used singly or in combination of two or more.

  The tungsten ion source is not particularly limited as long as it is soluble in a plating solution as a tungsten compound and can obtain an aqueous solution having a predetermined concentration. Examples thereof include sodium tungstate, potassium tungstate, and ammonium tungstate. These tungsten compounds can be used singly or in combination of two or more.

  The molybdenum ion source is not particularly limited as long as it is soluble in a plating solution as a molybdenum compound and can obtain an aqueous solution having a predetermined concentration. Examples thereof include molybdenum trioxide, sodium molybdate, diammonium molybdate, calcium molybdate, molybdic acid, phosphomolybdic acid, and molybdate gluconic acid complex. These molybdenum compounds can be used singly or in combination of two or more.

  The palladium ion source is not particularly limited as long as it is soluble in the plating solution as a palladium compound and can obtain an aqueous solution having a predetermined concentration. For example, water-soluble palladium compounds such as palladium sulfate, palladium chloride, palladium acetate, dichlorodiethine rediamine palladium, and tetraammine palladium dichloride can be used. Further, as the palladium compound, a so-called palladium solution in which palladium is made into a solution can also be used. As the palladium solution, for example, a dichlorodiethylenediamine palladium solution or a tetraammine palladium dichloride solution can be used. These palladium compounds can be used individually by 1 type or in mixture of 2 or more types.

  The platinum ion source is not particularly limited as long as it is soluble in a plating solution as a platinum compound and can obtain an aqueous solution having a predetermined concentration. For example, platinum chloride, chloroplatinic acid, chloroplatinic acid salt, platinum hydroxide acid, platinum hydroxide salt, dinitrodiammine platinum complex salt, dinitrosulfitoplatinum complex salt, tetraammine platinum complex salt, hexaammine platinum complex salt can be mentioned. A platinum compound can be used individually by 1 type or in mixture of 2 or more types.

  The tin ion source is not particularly limited as long as it is soluble in the plating solution as a tin compound and can obtain an aqueous solution having a predetermined concentration. For example, stannous chloride, stannic chloride, stannous sulfate, stannic sulfate, stannous pyrophosphate, and other inorganic acid salts of tin, stannous citrate, stannous citrate, stannous oxalate Of tin carboxylates such as stannic oxalate, tin methanesulfonate, tin 1-ethanesulfonate, tin 2-ethanesulfonate, tin 1-propanesulfonate, tin 3-propanesulfonate Alkane sulfonate, tin methanol sulfonate, tin hydroxyethane-1-sulfonate, tin 1-hydroxypropane-1-sulfonate, tin tin hydroxyethane-2-sulfonate, tin 1-hydroxypropane-3-sulfonate, etc. Alkanol sulfonates, tin hydroxides such as stannous hydroxide and stannic hydroxide, and metastannic acid.

  The method for forming the Ni alloy film is not limited to the above-described electroless plating method. For example, the flat copper particle agglomerated powder before coating with Ni contains an element other than Ni constituting the Ni alloy, and after forming a coating made only of Ni (Ni coating), the copper powder The Ni alloy film can also be formed by diffusing the contained element into the Ni film.

<< 4. Use of conductive paste, conductive paint for electromagnetic wave shield, conductive sheet >>
As described above, the tabular Ni-coated copper particle aggregated powder 1 according to the present embodiment has the shape of an aggregated copper powder in which a plurality of tabular Ni-coated copper particles 2 are aggregated to form an aggregate. The tabular Ni-coated copper particles 2 have an average major axis diameter of 0.5 to 5 μm, an average cross-sectional thickness of 0.02 to 1.0 μm, and tabular Ni-coated copper particles 2. The size of the Ni-coated copper powder 1 formed by aggregating a plurality of particles into an aggregate is 1.0 μm to 30 μm in terms of average particle diameter (D50).

  The plate-like Ni-coated copper particle aggregated powder 1 according to the present embodiment has such a characteristic structure, so that a large number of contacts can be secured and a large contact area can be ensured. Demonstrate sex. Moreover, according to the tabular Ni-coated copper particle aggregated powder 1 having such a predetermined structure, even when a copper paste or the like is used, aggregation can be suppressed and the resin can be uniformly dispersed in the resin. In addition, it is possible to suppress the occurrence of poor printability due to an increase in paste viscosity. Therefore, the tabular Ni-coated copper particle aggregated copper powder 1 can be suitably used for applications such as conductive paste and conductive paint.

  For example, as the conductive paste (copper paste), the plate-like Ni-coated copper particle aggregated powder 1 according to the present embodiment is included as a metal filler, a binder resin, a solvent, and an antioxidant or a coupling agent as necessary. It can produce by knead | mixing with additives, such as.

  Specifically, the binder resin is not particularly limited, but an epoxy resin, a phenol resin, or the like can be used. Moreover, as a solvent, organic solvents, such as ethylene glycol, diethylene glycol, triethylene glycol, glycerol, and terpineol, can be used. Further, the amount of the organic solvent added is not particularly limited, but considering the particle size of the tabular Ni-coated copper particle aggregate powder 1 so as to have a viscosity suitable for a conductive film forming method such as screen printing or dispenser. The amount added can be adjusted.

  Furthermore, other resin components can be added for viscosity adjustment. For example, as the resin component, a cellulose resin typified by ethyl cellulose and the like can be mentioned, and the resin component 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 Ni or Ni alloy is particularly preferable. The addition amount of the antioxidant can be, for example, about 1% by mass to 15% by weight in consideration of the antioxidant effect, the viscosity of the paste, and the like.

  Here, in using the flat-plate Ni coat copper particle aggregation copper powder 1 which concerns on this Embodiment as a metal filler, the said flat-plate Ni coat copper particle aggregation copper powder 1 is 20 with respect to the whole in a metal filler. It comprises so that it may be contained in the ratio of the quantity of the mass% or more. Thus, by setting the ratio of the tabular Ni-coated copper particle aggregated powder 1 to 20% by mass or more, for example, when the metal filler is used in the copper paste, it can be uniformly dispersed in the resin. It can prevent effectively that the viscosity of a paste rises too much and printability defect arises. Moreover, as a conductive paste, the plate-like Ni-coated copper particle aggregated powder 1 composed of an aggregate of the plate-like Ni-coated copper particles 2 is contained in the metal filler in a ratio of 20% by mass or more as described above. Excellent conductivity can be exhibited.

  In addition, it is only necessary that the flat Ni-coated copper particle aggregated copper powder 1 is contained in the metal filler at a ratio of 20% by mass or more. For example, spherical copper powder or spherical Ni-coated copper powder of about 1 μm to 10 μm is included. May be mixed. Also, fillers having different compositions as well as fillers such as silver powder may be mixed.

  Further, when the flat Ni-coated copper particle agglomerated powder 1 is used as a metal filler as an electromagnetic shielding material, it is not limited to use under particularly limited conditions. Can be used by mixing with resin.

  For example, when forming the electromagnetic wave shielding layer of the conductive sheet for electromagnetic wave shielding, the resin to be used is not particularly limited, and vinyl chloride resin, vinyl acetate resin, vinylidene chloride, which are conventionally used, are not limited. Resin, acrylic resin, polyurethane resin, polyester resin, olefin resin, chlorinated olefin resin, polyvinyl alcohol resin, alkyd resin, thermoplastic resin made of various polymers and copolymers, thermosetting resin, radiation A curable resin or the like can be used as appropriate.

  As a method for producing an electromagnetic shielding material, for example, the above-described metal filler and resin are dispersed or dissolved in a solvent to form a coating material, and the coating material is applied or printed on the substrate to form the electromagnetic shielding layer. It can be manufactured by forming and drying to such an extent that the surface solidifies. Moreover, a metal filler can also be utilized for the conductive adhesive layer of a conductive sheet.

  Further, even when the metal filler according to the present embodiment is used as the material for the conductive coating material for electromagnetic wave shielding, it is not limited to use under particularly limited conditions, but a general method such as a metal filler Can be mixed with a resin and a solvent, and further mixed with an antioxidant, a thickener, an anti-settling agent, etc., if necessary, and kneaded to obtain a conductive paint.

  The binder resin and solvent used at this time are not particularly limited, and are conventionally used, such as vinyl chloride resin, vinyl acetate resin, acrylic resin, polyester resin, fluorine resin, silicon resin and phenol resin. Etc. can be used. In addition, as for the solvent, alcohols such as isopropanol, aromatic hydrocarbons such as toluene, esters such as methyl acetate, ketones such as methyl ethyl ketone, and the like that are conventionally used can be used. In addition, as an antioxidant as an additive, a fatty acid amide, a higher fatty acid amine, a phenylenediamine derivative, a titanate coupling agent, and the like, which are conventionally used, can be used.

  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≫
The Ni-coated copper powder obtained in the following Examples and Comparative Examples was subjected to shape observation, average particle diameter measurement, and the like by the following methods.

(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 copper powder contained in the visual field was observed.

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

(BET specific surface area measurement)
The BET specific surface area was measured using a specific surface area / pore distribution measuring apparatus (manufactured by Cantachrome, QUADRASORB SI).

(Tap density)
The tap density was measured using a shaking specific gravity measuring device (manufactured by Kuramochi Scientific Instruments, Tapping Machine KRS-40).

(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.

(Electromagnetic wave shielding characteristics)
The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate of the samples obtained in each example and comparative example using an electromagnetic wave having a frequency of 1 GHz. Specifically, the level in the case of Comparative Example 3 in which the surface of the flat copper powder produced by mechanically flattening is coated with Ni is “Δ”, and “x” indicates that the level is worse than this level. The better case was evaluated as “◯”, and the better case was evaluated as “◎”.

  Moreover, in order to evaluate also about the flexibility of an electromagnetic wave shield, the produced electromagnetic wave shield was bent and it was confirmed whether the electromagnetic wave shielding characteristic changed.

≪Example, comparative example≫
[Example 1]
<Preparation of flat copper particle agglomerated powder>
An electrolytic cell with a capacity of 100 L is charged with an electrolytic solution in the electrolytic cell using a titanium electrode plate with an electrode area of 200 mm × 200 mm as a cathode and a copper plate with an electrode area of 200 mm × 200 mm as an anode. Then, a direct current was passed through this 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 100 g / L was used. In addition, Janus Green B (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive was added to the electrolyte so as to have a concentration of 120 mg / L in the electrolyte, and polyethylene glycol having a molecular weight of 2,000 (Wako Pure Chemical Industries, Ltd.) was added. Yakuhin Kogyo Co., Ltd.) was added so that the concentration in the electrolyte was 850 mg / L. Furthermore, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chloride ion (chlorine ion) concentration in the electrolyte solution was 50 mg / L.

Then, while circulating the electrolyte adjusted to the concentration as described above at a flow rate of 10 L / min using a pump, the temperature is maintained at 30 ° C. and the current density of the cathode is 25 A / dm ^2. Then, copper powder was deposited 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 obtained electrolytic copper powder in a 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 has a shape in which flat copper particles are aggregated. It was the presented copper powder (flat copper particle aggregated powder).

  The flat copper particles have an average cross-sectional thickness of 0.3 μm, and an average major axis diameter (equivalent to the diameter indicated by “d” in the schematic diagram of FIG. 1) is 2.7 μm. there were. And the magnitude | size of the tabular copper particle aggregated powder which the aggregate of the tabular copper particle became the aggregate was the average particle diameter (D50) measured with the laser diffraction and the scattering method particle size distribution measuring device 7.9 micrometer. Met.

<Production of flat Ni-coated copper particle aggregated powder (reducing agent: hypophosphite)>
Next, Ni was coated on the surface of the copper powder by electroless Ni plating using the tabular copper particle aggregated powder prepared by the above-described method to prepare a Ni-coated copper powder. An electroless Ni plating solution that is a reducing agent hypophosphite was used.

  Specifically, as an electroless Ni plating solution, nickel sulfate 20 g / L, sodium hypophosphite 25 g / L, sodium acetate 10 g / L, sodium citrate 10 g / L are added at each concentration, and sodium hydroxide is further added. 500 mL of a plating solution adjusted to pH 5.0 by adding the above was prepared.

  In this electroless Ni plating solution, a slurry obtained by dispersing 100 g of tabular copper particle agglomerated powder prepared in the above-described method in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 90 ° 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, Ni-coated copper powder in which a Ni alloy containing phosphorus (P) was coated on the surface of the tabular copper particle aggregated powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 13.4% by mass with respect to 100% by mass of the entire Ni-coated copper powder. The content of P contained in the Ni alloy was 7.8% by mass with respect to 100% by mass of the Ni alloy.

  In addition, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, the Ni-coated copper powder was uniformly coated with the Ni alloy on the surface of the copper powder before being coated with the Ni alloy. A flat Ni-coated copper particle aggregated powder having a shape of agglomerated powder in which a plurality of Ni-coated copper particles having a flat plate shape are aggregated to form an aggregate.

  Moreover, since the Ni-coated copper powder obtained had a thin Ni alloy coating thickness, the shape was the same as the flat copper particle aggregated powder before the Ni alloy coating. Specifically, the plate-like Ni-coated copper particles constituting the Ni-coated copper powder have a plate-like shape with a cross-sectional thickness (cross-sectional average thickness) of 0.3 μm, and the size is the average major axis diameter (see FIG. (Diameter indicated by “d” in the schematic diagram of FIG. 1) was 2.7 μm. The size of the aggregated copper powder formed by aggregating a plurality of the flat plate-like Ni-coated copper particles into an aggregate is 7.9 μm in average particle diameter (D50). The same value as the flat copper particle aggregated powder before coating was shown.

Furthermore, the tap density of the obtained Ni-coated copper powder was 2.9 g / cm ³ . The BET specific surface area was 2.5 m ² / g.

[Example 2]
<Preparation of flat copper particle agglomerated powder>
An electrolytic solution having a copper ion concentration of 8 g / L and a sulfuric acid concentration of 110 g / L is used, and Janus Green B as an additive is added to the electrolytic solution to a concentration of 160 mg / L in the electrolytic solution. Further, polyethylene glycol having a molecular weight of 2,000 (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the concentration in the electrolytic solution was 800 mg / L. Further, a hydrochloric acid solution was added so that the chloride ion concentration in the electrolytic solution was 125 mg / L.

Then, while circulating the electrolyte adjusted to the concentration as described above at a flow rate of 20 L / min using a pump, the temperature is maintained at 35 ° C. and the current density of the cathode is 30 A / dm ^2. Except for these, copper powder was deposited on the cathode plate in the same manner as in Example 1.

  As a result of observing the shape of the obtained electrolytic copper powder by the SEM method described above, the deposited copper powder was a copper powder (plate copper particle aggregated powder) having a shape in which flat copper particles were aggregated. It was. The tabular copper particles had an average cross-sectional thickness of 0.2 μm and an average major axis diameter of 3.8 μm. The size of the agglomerated copper powder in which a plurality of tabular copper particles aggregated to form an aggregate was 12.9 μm in terms of the average particle diameter (D50) measured with a laser diffraction / scattering particle size distribution analyzer. .

<Production of flat Ni-coated copper particle agglomerated powder (reducing agent: borohydride)>
Next, using the obtained tabular copper particle aggregate powder 100g, Ni coating was performed on the surface of the copper powder by electroless Ni plating to prepare a Ni-coated copper powder. In addition, the electroless Ni plating solution whose reducing agent is a borohydride compound was used.

  Specifically, as the electroless Ni plating solution, nickel sulfate 30 g / L, sodium succinate 50 g / L, boric acid 30 g / L, ammonium chloride 30 g / L, dimethylamine borane 4 g / L are added at each concentration. Further, 500 mL of a plating solution adjusted to pH 6.0 by adding sodium hydroxide was prepared.

  Into this electroless Ni plating solution, a slurry in which 100 g of the tabular copper particle aggregate powder prepared by the above-described method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is 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, Ni-coated copper powder in which a Ni alloy was coated on the surface of the tabular copper particle aggregated powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 18.5% by mass with respect to 100% by mass of the entire Ni-coated copper powder. The content of B contained in the Ni alloy was 6.5% by mass with respect to 100% by mass of the Ni alloy.

  In addition, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, the Ni-coated copper powder was uniformly coated with the Ni alloy on the surface of the copper powder before being coated with the Ni alloy. The Ni-coated copper particles were in the form of agglomerated powder formed by aggregating a plurality of Ni-coated copper particles in which the shape of the Ni-coated copper particles was flat.

  Moreover, since the produced Ni-coated copper powder had a thin Ni alloy coating thickness, the shape was the same as the flat copper particle aggregated powder before coating the Ni alloy. Specifically, the plate-like Ni-coated copper particles had a plate shape with a cross-sectional thickness (average cross-sectional thickness) of 0.2 μm, and the size thereof had an average major axis diameter of 3.8 μm. The size of the aggregated copper powder formed by aggregating a plurality of the flat Ni-coated copper particles into an aggregate is 12.9 μm in terms of the average particle diameter (D50). The same value as the flat copper particle aggregated powder before coating was shown.

Furthermore, the tap density of the obtained Ni-coated copper powder was 3.8 g / cm ³ . The BET specific surface area was 1.8 m ² / g.

[Example 3]
<Preparation of flat copper particle agglomerated powder>
In an electrolytic cell having a capacity of 100 L, an electrode plate made of titanium having an electrode area of 200 mm × 200 mm is used as a cathode, and a copper electrode plate having an electrode area of 200 mm × 200 mm is used as an anode, and an electrolytic solution is loaded in 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, Janus Green B (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive was added to the electrolyte so as to have a concentration of 130 mg / L in the electrolyte, and polyethylene glycol having a molecular weight of 2,000 (Wako Pure Chemical Industries, Ltd.). Yakuhin Kogyo Co., Ltd.) was added as a concentration in the electrolyte solution to 900 mg / L. Furthermore, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chlorine ion concentration in the electrolytic solution was 50 mg / L.

Then, while circulating the electrolyte adjusted to the concentration as described above at a flow rate of 10 L / min using a pump, the temperature is maintained at 30 ° C. and the current density of the cathode is 25 A / dm ^2. Then, copper powder was deposited 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 obtained electrolytic copper powder in a field of view with a magnification of 5,000 times by the method using the scanning electron microscope (SEM) described above, the deposited copper powder has a shape in which flat copper particles are aggregated. It was the exhibited copper powder (plate-like copper particle aggregated powder).

  The tabular copper particles have a cross-sectional thickness (average cross-sectional thickness) of 0.1 μm and an average major axis diameter (equivalent to the diameter indicated by “d” in the schematic diagram of FIG. 1). Was 2.9 μm. The size of the agglomerated copper powder in which a plurality of the tabular copper particles were aggregated to form an aggregate was 7.1 μm as an average particle diameter (D50) measured with a laser diffraction / scattering particle size distribution analyzer. .

<Production of flat Ni-coated copper particle aggregated powder (reducing agent: hydrazine compound)>
Next, using the obtained tabular copper particle aggregate powder 100g, Ni coating was performed on the surface of the copper powder by electroless Ni plating to prepare a Ni-coated copper powder. Electroless Ni plating using a hydrazine compound as a reducing agent was performed.

  Specifically, nickel acetate was added to a slurry in which 100 g of the tabular copper particle aggregate powder obtained in Example 2 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and hydrazine monohydrate 80 mass. 6 g of a% aqueous solution was added dropwise to the bath over 60 minutes with slow stirring. At this time, the bath temperature was controlled to 60 ° C.

  After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which Ni was coated on the surface of the tabular copper particle aggregated powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 7.5% by mass with respect to 100% by mass of the entire Ni-coated copper powder.

  In addition, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, the Ni-coated copper powder was uniformly coated with the Ni alloy on the surface of the copper powder before being coated with the Ni alloy. The shape of the agglomerated powder was formed by aggregating a plurality of Ni-coated copper particles having a flat plate shape.

  Moreover, since the Ni-coated copper powder obtained had a thin Ni alloy coating thickness, the shape was the same as the flat copper particle aggregated powder before the Ni alloy coating. Specifically, the plate-like Ni-coated copper particles constituting the Ni-coated copper powder have a plate-like shape with a cross-sectional thickness (cross-sectional average thickness) of 0.1 μm, and the size is an average major axis diameter (see FIG. (Diameter indicated by “d” in the schematic diagram of FIG. 1) was 2.9 μm. The size of the aggregated copper powder formed by aggregating a plurality of the flat plate-like Ni-coated copper particles into an aggregate is 7.1 μm in terms of the average particle diameter (D50). The same value as the flat copper particle aggregated powder before coating was shown.

Furthermore, the tap density of the obtained Ni-coated copper powder was 2.8 g / cm ³ . The BET specific surface area was 2.4 m ² / g.

[Examples 4 to 10]
<Manufacture of flat Ni-coated copper particle agglomerated powder (Ni alloy)>
Using 100 g of the tabular copper particle aggregate powder obtained in Example 3, the surface of the copper powder was coated with a Ni alloy by electroless plating.

  As an electroless Ni plating solution for an alloy, nickel acetate was added to a slurry in which 100 g of the tabular copper particle aggregate powder obtained in Example 3 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and hydrazine was added. 3.2 g was added dropwise into the bath over 60 minutes with slow stirring. The bath temperature was controlled to 60 ° C.

  At this time, each metal compound was added to a bath containing copper powder slurry and nickel acetate, and hydrazine was gradually added so that each desired Ni alloy film was formed. As a metal compound, in Example 4, 1.5 g of sodium tungstate was added to form a Ni—W alloy film. In Example 5, 2 g of cobalt sulfate was added to form a Ni—Co alloy film. In Example 6, 4 g each of zinc sulfate heptahydrate and sodium citrate were added to form a Ni—Zn alloy film. In Example 7, 2 g of palladium chloride was added to form a Ni—Pd alloy film. In Example 8, 2 g of potassium tetrachloroplatinate and 1 g of glycine were added to form a Ni—Pt alloy film. In Example 9, 1 g of each of sodium molybdate and trisodium citrate was added to form a Ni-Mo alloy coating. In Example 10, 1 g of sodium stannate was added to form a Ni—Sn alloy film.

  After each reaction was completed, the powder was filtered, washed with water, and dried through ethanol to obtain Ni-coated copper powder in which Ni was coated on the surface of the flat copper particles. The Ni-coated copper powder was recovered and the Ni alloy coating amount was measured. Table 1 shows the results of measuring the content of Ni with respect to 100% by mass of the entire Ni-coated copper powder and the content of elements that become Ni alloys with respect to 100% by mass of the Ni alloy.

  In addition, as a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 times by SEM, the Ni coating in which the Ni alloy was uniformly coated on the surface of the copper powder before coating the Ni alloy. It was a copper powder and was a flat Ni-coated copper particle aggregated powder in the form of an aggregated powder in which a plurality of Ni-coated copper particles having a flat plate shape were aggregated to form an aggregate.

  Moreover, about these Ni coat copper powder, the cross-sectional average thickness of flat copper particle, the average major axis diameter (diameter shown by "d" in the schematic diagram of FIG. 1), the average of flat Ni coat copper particle aggregate powder The particle diameter (D50), tap density, and BET specific surface area were measured. Table 1 summarizes these measurement results.

[Example 11]
<Production of flat Ni-coated copper particle aggregated powder (hypophosphite + tungsten compound)>
In Example 11, Ni alloy coating was performed on the surface of the copper powder by electroless plating using 100 g of the tabular copper particle agglomerated powder prepared in Example 1.

  As the electroless Ni plating solution, a plating solution containing hypophosphite as the same reducing agent as in Example 1 was used, and a metal other than Ni was added to the plating solution to produce a Ni alloy.

  Specifically, as an electroless Ni plating solution, a plating solution in which nickel sulfate 20 g / L, sodium hypophosphite 25 g / L, sodium acetate 10 g / L, and sodium citrate 10 g / L are added at each concentration, 500 g of a plating solution prepared by adding 1.5 g of sodium tungstate and adjusting the pH to 5.0 by adding sodium hydroxide was prepared.

  In this electroless Ni plating solution, a slurry obtained by dispersing 100 g of the tabular copper particle aggregate powder prepared in Example 1 in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 90 ° 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, Ni-coated copper powder coated with a Ni-WP alloy was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 12.5% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Moreover, content of P contained in Ni alloy was 7.3 mass% with respect to 100 mass of Ni alloy. The content of W contained in the Ni alloy was 5.2% by mass with respect to 100% by mass of the Ni alloy.

  In addition, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, the Ni-coated copper powder was uniformly coated with the Ni alloy on the surface of the copper powder before being coated with the Ni alloy. A flat Ni-coated copper particle aggregated powder having a shape of agglomerated powder in which a plurality of Ni-coated copper particles having a flat plate shape are aggregated to form an aggregate.

  Moreover, since the Ni-coated copper powder obtained had a thin Ni alloy coating thickness, the shape was the same as the flat copper particle aggregated powder before the Ni alloy coating. Specifically, the plate-like Ni-coated copper particles constituting the Ni-coated copper powder have a plate-like shape with a cross-sectional thickness (cross-sectional average thickness) of 0.3 μm, and the size is the average major axis diameter (see FIG. (Diameter indicated by “d” in the schematic diagram of FIG. 1) was 2.7 μm. The size of the aggregated copper powder formed by aggregating a plurality of the flat Ni-coated copper particles into an aggregate is 7.2 μm in terms of the average particle diameter (D50). The same value as the flat copper particle aggregated powder before coating was shown.

Furthermore, the tap density of the obtained Ni-coated copper powder was 2.9 g / cm ³ . The BET specific surface area was 2.5 m ² / g.

[Example 12]
15 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 30 g of the plate-like Ni-coated copper particle aggregated powder obtained in Example 1. Using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on 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 8.3 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited. Table 2 shows these results.

[Example 13]
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 30 g of the tabular Ni-coated copper particle aggregated powder obtained in Example 2. Using a small kneader (manufactured by Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on 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. Table 1 shows these results.

[Example 14]
The tabular silver-coated copper particle aggregate powder produced in Example 1 was dispersed in a resin to obtain an electromagnetic wave shielding material.

  That is, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone are mixed with 30 g of the obtained tabular Ni-coated copper particle agglomerated powder, and kneading at 1200 rpm for 3 minutes is repeated three times using a small kneader. To make a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried using a Mayer bar on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm to form an electromagnetic wave shielding layer having a thickness of 25 μm.

  The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 1 shows these results.

[Comparative Example 1]
<Preparation of electrolytic copper powder>
Copper powder was deposited on the cathode plate under the same conditions as in Example 1 except that Janus Green B as an additive, polyethylene glycol, and chloride ions were not added to the electrolytic solution.

  As a result of observing the shape of the obtained electrolytic copper powder in the field of view of 5,000 times magnification by the method by SEM described above, the obtained copper powder is a copper powder having a dendritic shape, and in the examples It was not a shape in which flat pieces were aggregated like the obtained copper powder.

<Production of Ni-coated copper powder (reducing agent: hypophosphite)>
Next, Ni coat copper powder was produced using the obtained copper powder.

  Specifically, as an electroless Ni plating solution, nickel sulfate 20 g / L, sodium hypophosphite 25 g / L, sodium acetate 10 g / L, sodium citrate 10 g / L are added at each concentration, and sodium hydroxide is further added. 500 mL of a plating solution adjusted to pH 5.0 by adding the above was prepared.

  In this electroless Ni plating solution, a slurry in which 100 g of the copper powder prepared by the above-described method is dispersed in 100 mL of water is stirred and stirred at 25 ° C. for 10 minutes, and then the bath temperature is heated to 90 ° C. and stirred for 60 minutes. did.

  After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, a Ni-coated copper powder in which the Ni alloy containing P was coated on the surface of the copper powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 13.7% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Moreover, content of P contained in Ni alloy was 7.9 mass% with respect to 100 mass of Ni alloy.

  In FIG. 4, the result of having observed the shape of the obtained Ni coat copper powder by SEM in the visual field of magnification 5000 times is shown. As shown in the photograph of FIG. 4, the obtained Ni-coated copper powder is a copper powder having a dendritic shape, and the surface of the copper powder before being coated with the Ni alloy is uniformly coated with the Ni alloy. It is. It was not a shape in which flat pieces were aggregated like the copper powder obtained in the examples. The average particle size (D50) of this Ni-coated copper powder was 17.6 μm.

  Next, 55 parts by mass of the obtained Ni-coated copper powder was mixed with 15 parts by mass of a phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), the mixture was kneaded at 1200 rpm for 3 minutes three times to make a paste. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing is 68.2 × 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]
<Production of mechanically flattened flat copper powder>
The characteristics of the conductive paste by Ni-coated copper powder obtained by coating Ni on a conventional flat copper powder were evaluated and compared with the characteristics of the conductive paste prepared using the flat Ni-coated copper particle agglomerated powder in the examples. .

  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 size of 5.4 μm, and flattened with a ball mill. The ball mill was charged with 5 kg of 3 mm zirconia beads and rotated for 90 minutes at a rotation speed of 500 rpm.

  As a result of measuring the obtained flat copper powder with a laser diffraction / scattering particle size distribution analyzer, the average particle diameter was 21.8 μm. Moreover, the thickness (cross-sectional average thickness) of the flat copper powder measured by SEM observation was 0.4 μm.

<Production of Ni-coated copper powder (reducing agent: borohydride)>
Using 100 g of flat copper powder produced by flattening, the surface of the copper powder was coated with Ni by electroless Ni plating.

  Specifically, as an electroless Ni plating solution, nickel sulfate 30 g / L, sodium succinate 50 g / L, boric acid 30 g / L, ammonium chloride 30 g / L, dimethylamine borane 4 g / L were added at each concentration, Further, 500 mL of a plating solution adjusted to pH 6.0 by adding sodium hydroxide was prepared.

  In this electroless Ni plating solution, a slurry in which 100 g of the flat copper powder prepared by the above-described method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 60 ° C. to 60 ° C. Stir for minutes.

  After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder (flat Ni-coated copper powder) in which a Ni alloy was coated on the surface of the flat copper powder was obtained. When the Ni-coated copper powder was recovered and the Ni alloy coating amount was measured, it was 18.3% by mass relative to 100% by mass of the entire Ni-coated copper powder. Moreover, content of B contained in Ni alloy was 6.8 mass% with respect to 100 mass of Ni alloy.

  Further, the obtained flat copper powder was measured with a laser diffraction / scattering particle size distribution analyzer, and as a result, the average particle size was 21.8 μm. Moreover, the thickness (cross-sectional average thickness) of the flat copper powder measured by SEM observation was 0.40 μm.

  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 Ni-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 26.2 × 10 ⁻⁵ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 3]
The tabular Ni-coated copper powder prepared in Comparative Example 2 was dispersed in a resin to obtain an electromagnetic wave shielding material.

  Specifically, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone are mixed with 40 g of the obtained tabular Ni-coated copper powder, and kneading at 1200 rpm for 3 minutes is repeated three times using a small kneader. To make a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried using a Mayer bar on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm to form an electromagnetic wave shielding layer having a thickness of 25 μm.

  The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 1 shows these results.

1 Ni coated copper powder (flat Ni coated copper particle agglomerated powder)
2 Copper particles (flat Ni-coated copper particles)
d Major axis diameter of tabular Ni-coated copper particles

Claims (9)

A Ni-coated copper powder comprising a plurality of pieces of individual copper particles coated with nickel (Ni) or Ni alloy on the surface and having an aggregate form,
The copper particles coated with the Ni or Ni alloy have an average major axis diameter determined by observation with a scanning electron microscope (SEM) of 0.5 μm to 5.0 μm and an average cross-sectional thickness of 0.02 μm to 1.0 μm. Is a flat plate shape,
The average particle diameter (D50) calculated | required by the laser diffraction scattering type particle size distribution measuring method is 1.0 micrometer-30 micrometers. Ni coat copper powder characterized by the above-mentioned. The Ni-coated copper powder according to claim 1, wherein the content of Ni coated as Ni or Ni alloy is 1% by mass to 50% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Ni alloy is coated on the surface of the copper particles,
At least one selected from the group consisting of cobalt, zinc, tungsten, molybdenum, palladium, platinum, tin, phosphorus, and boron is 0.1% by mass to 20% by mass with respect to 100% by mass of the Ni alloy. The Ni-coated copper powder according to claim 1, wherein the Ni-coated copper powder is coated with a Ni alloy contained in a content. Ni-coated copper powder according to any one of claims 1 to 3 tap density is in the range of ^{0.5g / cm 3 ~5.0g / cm 3} . Ni-coated copper powder according to any one of claims 1 to 4 BET specific surface area of 0.2m ² /g~5.0m ² / g.   A metal filler comprising the Ni-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 conductive paint for electromagnetic wave shielding, wherein the metal filler according to claim 6 is dispersed in a resin.   An electroconductive sheet for electromagnetic wave shielding, wherein the metal filler according to claim 6 is dispersed in a resin.