KR20140107160A - Anisotropic conductive film used for connecting wiring and manufacturing method for the same - Google Patents

Abstract

The invention provides a spherical nickel-phosphorous (NiP) particle having excellent self-particle monodispersity and a preparing method thereof. The reduction-precipitation spherical NiP particle includes nickel (Ni) as a main body, and phosphorous (P) (preferably 1 to 15 wt%) and copper (Cu) (preferably 0.01-18 wt%), or further includes Sn (preferably 0.05-10 wt%). The preparing method of the reduction-precipitation spherical NiP particle prepares the reduction-precipitation spherical NiP particle including Ni as the main body and P, by mixing a mixed water solution composed of a water solution of nickel salt, a pH regulator, and a pH buffer with a phosphorous water solution of a reductant, and by reducing and precipitating the mixture, wherein the water solution of the nickel salt includes the Cu (preferable mol ratio of Ni/Cu= 4.0-10000), or further includes the Sn (preferable mol ratio of Ni/Sn=2.0-2000), and mixes the materials to make the pH value exceed 7 when the reduction-precipitation begins.

Description

TECHNICAL FIELD [0001] The present invention relates to an anisotropic conductive film used for wiring connection, and an anisotropic conductive film used for wiring connection.

The present invention relates to, for example, metal microparticles which are not only fine metal particles used as conductive particles for anisotropic conductive films but also used as a material for wiring formation of substrates and the like, and a method for producing the same.

2. Description of the Related Art With the spread of terrestrial digital broadcasting, FPD (Flat Panel Display) such as LCD (Liquid Crystal Display) or PDP (Plasma Display Panel) is rapidly expanding. Anisotropic conductive films are widely used for electrically connecting driver ICs and fine wiring circuits.

The anisotropic conductive film is an adhesive in which conductive particles are dispersed in a thermosetting or thermoplastic insulating resin film. The anisotropic conductive film is placed between wires facing each other, and then thermocompression-bonded to conduct the wires through the conductive particles. It is a connecting material that maintains electrical insulation between adjacent wirings. The conductive particles include a conductive resin ball which is made by plating a metal material such as Ni or Au on the surface of a resin ball such as polystyrene or acrylic to make it conductive, a metal powder such as Ni, Cu, Al, Au, Ag, Or powders obtained by plating a metal on the surface thereof are widely used.

The conductive resin balls generally used as the conductive particles of the anisotropic conductive film are advantageous in that the resin balls are elastically deformed by the pressure and the temperature at the time of thermocompression bonding so that the contact area with the wiring can be increased. However, since the resin ball is an insulator, it is difficult to obtain good conduction, and a metal must be plated on the surface by a special treatment, which is a drawback that the cost is extremely high.

On the other hand, metal powder such as Ni powder is used for anisotropic conductive films such as TCP (Tape Carrier Package), FPC (Flexible Printed Circuit) connection, TCP and PWB (Printed Wiring Board) connection. Circuit boards such as TCP, FPC, and PWB are formed with a fine wiring circuit by Cu or a material on which Sn plating is performed, and which is relatively soft and easy to form an oxide film. The anisotropic conductive film using the metal powder has characteristics such as breaking the oxide film on the wiring circuit and securing conductivity. However, when the metal powder obtained by the gas atomization method is used as the conductive particles for the anisotropic conductive film, it is very difficult to obtain particles with sharp particle size distribution. There is a problem in that it is costly to make particles of unequal size from a particle size capable of satisfying the specification of an anisotropic conductive film by classifying treatment.

In view of the above problems, the present inventors have proposed a conductive particle dispersed in an anisotropic conductive film used for fine wiring of a circuit board (Patent Document 1). These conductive particles have excellent conductive properties and have a uniform shape and particle size distribution while having high hardness, and thus are suitable for anisotropic conductive films.

For formation of fine circuit wiring on an FPC or a glass substrate, a screen printing method using an Ag paste or the like is employed. In this method, after a wiring is printed with a high-conductivity Ag paste on a substrate, a carbon paste is laminated and printed by a method of coating an Ag wiring so as to prevent electromigration of Ag, . According to this method, a substrate or the like can be manufactured inexpensively in a large amount.

Japanese Patent Application Laid-Open No. 2006-131978

In the above background art, for example, when observing conductive particles for an anisotropic conductive film, the method of Patent Document 1 is an effective method showing some effect to the above problem. In this kind of NiP microparticles, , There was a room for improvement because the particle size was uneven.

When a finer wiring with a wiring interval of 0.2 mm or less is formed, the accuracy of screen printing, that is, the Ag wiring and the carbon paste for preventing electron migration laminated thereon are printed There is a problem that it is difficult to form a wiring circuit with high precision because the position is shifted. Therefore, in the wiring forming material, conductive particles replacing the Ag paste are required in order to solve the deterioration in the accuracy of the circuit wiring resulting from the electron transfer problem.

An object of the present invention is to provide spherical NiP microparticles, which are most suitable for use in conductive particles of an anisotropic conductive film, and which are excellent in single dispersibility and conductivity, and a method for producing the same. In addition, the present invention provides spherical NiP microparticles, which are optimum for forming circuit wiring such as FPC or glass substrate, excellent in electron migration resistance, conductivity, and low temperature sintering property, and a method for producing the same.

The present inventors have studied in detail the conductive particles for an anisotropic conductive film which can be applied to a fine circuit of high precision. Also, as a material capable of forming a circuit wiring for a substrate or the like with a high degree of precision, a conductive particle suitable for the circuit wiring has been studied. As a result, it is possible to suppress the non-uniformity of the particle size by providing a composition containing Cu to the conductive particles for an anisotropic conductive film of the above-mentioned Patent Document 1 and further providing a composition containing Sn therein, And the conductive property of the conductive layer is improved.

That is, the present invention is a spherical NiP microparticle mainly composed of Ni and composed of a component composition including P, for example, a component composition containing P in an amount of 1 to 15 mass% It is a spherical NiP microparticle of reduced precipitation type. Further, it is a reduced precipitation-type spherical NiP microparticle characterized by containing 0.01 to 18 mass% of Cu in the above composition.

Further, the present invention is a spheroidal NiP microparticle of reduced precipitation type characterized by containing Sn in addition to the above-mentioned composition including Cu, and it is characterized by containing, for example, 0.05 to 10 mass% of Sn In the form of spherical NiP microparticles.

The spherical NiP microparticles of reduced precipitation type of the present invention preferably have an average particle diameter d ₅₀ of 0.1 to 70 탆 and a particle size distribution of [(d ₉₀ -d ₁₀ ) / d ₅₀ ] ≤0.8 (d ₉₀ , d ₁₀ , d ₅₀ : particle diameter representing 90% by volume, 10% by volume, and 50% by volume in the cumulative distribution curve). In this case, by including Cu, it is advantageous to adjust the particle size distribution particularly on the large-diameter side having an average particle diameter d _{50 of 1} to 70 μm. Further, by further containing Sn, it is advantageous for adjusting the particle size distribution on the small-diameter side having an average particle diameter d ₅₀ of 0.1 to 10 μm.

The present invention relates to a method for producing spherical NiP microparticles containing P by reducing and precipitating an aqueous solution of a nickel salt, a mixed aqueous solution of a pH adjusting agent and a pH buffer, and a reducing agent aqueous solution containing phosphorus, Wherein the aqueous solution of the nickel salt contains Cu and is mixed and adjusted so that the pH at the time of initiating the reduction precipitation becomes higher than 7 in alkalinity. The aqueous solution of the nickel salt preferably contains Cu so that Ni / Cu = 4.0 to 10,000 at a molar ratio.

Further, the aqueous solution of the nickel salt at the time of the reduction precipitation is prepared in such a manner that the aqueous solution contains Sn in addition to the above-mentioned Cu and has an alkaline pH higher than 7 at the time of starting reduction precipitation. NiP. ≪ / RTI > The aqueous solution of the nickel salt at this time preferably contains Sn at a molar ratio of Ni / Sn = 2.0 to 2,000.

The spherical NiP microparticles of reduced precipitation type containing Cu or Sn of the present invention have a spherical shape, so that when they are incorporated into a thermosetting or thermoplastic insulating resin film, the aggregation of the particles is small and the dispersibility is good Therefore, short-circuiting between the electrodes is suppressed when the conductive particles of the anisotropic conductive film are used. In addition, it is also possible to obtain a low connection resistance and a high connection reliability even in connection between metal electrodes which are easy to form an oxide film such as an Al or Cr electrode, which is a material which is difficult to obtain good connection reliability in the past.

The spherical NiP microparticles of the present invention are not only excellent in electron migration resistance and conductivity, but also have a fine and uniform particle size because their component compositions are Ni-based metal particles. Therefore, the FPC or glass substrate , It is possible to reduce the damage to the substrate because the sintering property at low temperature is good.

1 is an electron micrograph showing an example of spherical NiP microparticles of the present invention.
2 is an electron micrograph showing an example of spherical NiP microparticles of the present invention.
3 is an electron micrograph showing an example of the cross-sectional structure of spherical NiP microparticles of the present invention.
4 is a mapping photograph of the Ni concentration distribution observed in the cross section of Fig.
Fig. 5 is a mapping photograph of the Cu concentration distribution observed in the cross section of Fig. 3; Fig.
FIG. 6 is a mapping picture of the P concentration distribution observed in the cross section of FIG. 3; FIG.
7 is an electron micrograph showing an example of spherical NiP microparticles of the present invention.
8 is an electron micrograph showing an example of spherical NiP microparticles of the present invention.
9 is an electron micrograph showing an example of the cross-sectional structure of spherical NiP microparticles of the present invention.
10 is a mapping photograph of the Ni concentration distribution observed in the cross section of Fig.
11 is a mapping photograph of the Cu concentration distribution observed in the cross section of Fig.
12 is a mapping picture of the Sn concentration distribution observed in the section of FIG.
13 is a mapping picture of the P concentration distribution observed in the cross section of Fig.

It is a feature of the present invention that, among reduced-precipitation-type spherical NiP microparticles constituted mainly of Ni and containing at least a semi-metal P as essential elements, for example, as disclosed in Patent Document 1, It is clear that it is effective in suppressing non-uniformity of size. Concretely, the Cu content is 0.01 to 18% by mass.

It is a feature of the present invention that it is clear that even when Sn is contained in spherical NiP microparticles containing Cu, the same nonuniformity suppressing effect can be exerted.

The spherical NiP microparticles containing such Cu or two elements of Cu and Sn have an average particle diameter d ₅₀ of 0.1 to 70 μm and a particle size distribution of [(d ₉₀ -d ₁₀ ) / d ₅₀ ] ≦ 0. 8, spherical NiP microparticles having a uniform particle size. At this time, the spherical NiP microparticles having Cu selected in the two elements are excellent in the effect of suppressing the unevenness on the large diameter side having an average particle diameter of 1 to 70 mu m. The spherical NiP fine particles containing Cu and Sn at the same time are particularly excellent in the effect of suppressing the unevenness on the small-diameter side having an average particle diameter of 0.1 to 10 占 퐉.

In the production of the spherical NiP microparticles of the present invention, for example, an aqueous solution of a nickel salt containing Cu or Cu and Sn, a mixed aqueous solution of a pH adjusting agent and a pH buffer, and a reducing agent aqueous solution containing phosphorus are mixed and reduced Wherein the pH of the mixed aqueous solution for initiating the reduction precipitation is adjusted to be alkaline with a pH of higher than 7. It is preferable that the amount of Cu is controlled such that the aqueous solution of the nickel salt containing Cu is in a molar ratio of Ni / Cu = 4.0 to 10,000. If Sn is added to the aqueous solution of the nickel salt containing Cu, it is preferable that the amount of Sn is controlled so that Ni / Sn = 2.0 to 2,000 at a molar ratio.

First, the spherical NiP microparticle of the present invention is based on a composition including P, for example, 1 to 15 mass% of P, which essentially contains Ni as a main component. As an effective method for imparting necessary hardness and conductivity when used as conductive particles for anisotropic conductive films, the present inventors have found that the particles have a crystal structure in the central portion and an intermetallic compound in amorphous form in the surface layer portion A spherical NiP microparticle having a dispersed structure is proposed in Patent Document 1.

According to the method of Patent Document 1, this is an effective method showing some effect in securing the uniformity of the particle size distribution. However, as a result of repeated research, the present inventors have found that among the spherical NiP microparticles of Patent Document 1, Proving that the nonuniformity of the particles is further suppressed, and the conductivity can also be improved.

The Cu content of the reduced precipitation type spherical NiP fine particles of the present invention is preferably 0.01 to 18 mass%. When the content of Cu is less than 0.01% by mass, it is difficult to obtain an effect of suppressing the unevenness of the particles. When the Cu content exceeds 18 mass%, the particles tend to agglomerate easily and the single dispersibility tends to deteriorate. In addition, when the Cu content is applied to, for example, an anisotropic conductive film, It is difficult to obtain particles having a size of 20 탆 or less, for example. In addition, it is preferable that the component composition containing 0.40 to 17 mass% of Cu makes it easy to obtain metal fine particles having less uniformity in particle size and excellent conductivity.

Further, in addition to the above-mentioned Cu-containing precipitated NiP microparticles, addition of Sn also has the effect of suppressing unevenness of the particle size. In this case, the Sn content of the spherical NiP fine particles of the present invention is preferably 0.05 to 10% by mass. When the content of Sn is less than 0.05 mass%, it is difficult to obtain the effect of suppressing the unevenness of the particles, and in particular, it is difficult to obtain the advantage of the above-described effect on the small-diameter side described later. When the Sn content exceeds 10% by mass, the particles are not only amorphous but also monodisperse particles are difficult to obtain. In addition, it is preferable that the component composition containing Sn in an amount of 0.25 to 5% by mass makes it easy to obtain metal fine particles having small particle size unevenness and excellent conductivity.

Cu, or the average particle size of the reduced precipitated NiP-type spherical fine particles containing Cu and Sn two elements of the present invention, it is preferable that a value of d ₅₀ to O.1~7O㎛ but (d _50: in the accumulated distribution curve , And 50% by volume), and the particle diameter needs to be selected according to the application. However, when the particle diameter is less than 0.1 mu m, the particles tend to aggregate, which makes handling very difficult. On the other hand, when the average particle diameter d ₅₀ exceeds 70 탆, it takes a long time to grow the particles, and it becomes difficult to obtain uniform particles efficiently. Preferably 50 mu m or less, more preferably 30 mu m or less. On the other hand, if it exceeds 20 탆, it becomes difficult to use functional materials as conductive particles for anisotropic conductive films, and materials used for wiring such as FPC and substrate.

Here, when the spherical NiP microparticles of the present invention are used, for example, as conductive particles for anisotropic conductive films, it is preferable to set the value of d ₅₀ to 1 to 20 탆. If the particle diameter is less than 1 占 퐉, the height unevenness of the fine wiring formed on the circuit board such as TCP, FPC, PWB or the like can not be buffered when anisotropically conductive connection is made, so that the contact becomes unstable and the connection reliability is lowered. On the other hand, when d ₅₀ is more than 20 m, there is a possibility that the insulating property deteriorates and the stable connection reliability can not be ensured in the connection of fine wirings having a narrow pitch with a wiring interval of several tens of micrometers. Therefore, in order to make the spherical NiP microparticles of the present invention particularly optimum as the conductive particles for the anisotropic conductive film, the value of d ₅₀ is preferably 1 to 20 탆, more preferably 1 to 10 탆, It is preferable to arbitrarily select it according to the wiring interval and the shape of the electrode connected by the anisotropic conductive film.

In the reduced-precipitation spherical NiP microparticle of the present invention wherein the d ₅₀ is in the range of 0.1 to 70 탆, d ₅₀ is adjusted to the diameter of 1 탆 or more, further 5 탆 or more, and the particle size The effect of suppressing the unevenness is excellent when Cu in the element containing both of Cu and Sn is contained alone.

Next, even when the spherical NiP microparticle of the present invention is used as a material for forming a circuit wiring such as an FPC or a glass substrate, the average particle diameter d _{50 thereof} is arbitrarily selected in accordance with the application, but is preferably 0.1 to 10 μm . If d ₅₀ exceeds 10 μm, it may not be possible to apply to minute wiring intervals, and the sintering temperature at the time of forming the circuit wiring may increase, and the substrate may be damaged. On the other hand, if d ₅₀ is less than 0.1 탆, handling of the particles becomes very difficult, and since the particles themselves are expensive, it is difficult to cope with mass production.

In the spheroidal NiP microparticles of reduced precipitation type of the present invention, in which the d ₅₀ is in the range of 0.1 to 70 탆, d ₅₀ is adjusted to the small-diameter side of 10 탆 or less, further, less than 5 탆, Is superior when the two elements Cu and Sn are contained.

Next, the spherical NiP microparticles of reduced precipitation type of the present invention are also characterized in that they exhibit a uniform particle size distribution. In the case where the particle size distribution is [(d ₉₀ -d ₁₀ ) / d ₅₀ ]> 0.8 (d ₉₀ , d ₁₀ : particle size indicating 90 volume% and 10 volume% in the cumulative distribution curve) When anisotropic conductive connection is made, the number of particles involved in conduction is reduced, which may lower the connection reliability. Therefore, it is preferable that the particle size distribution given by the above formula is as small as possible. However, since the classification process for reducing this value is expensive, [(d ₉₀ -d ₁₀ ) / d ₅₀ ] Is preferably 0.8 or less. More preferably, it is 0.7 or less.

A preferred method for producing spherical NiP microparticles of the present invention will be described. First, the inventors of the present invention propose a method for producing spherical NiP microparticles containing P mainly composed of Ni by mixing a nickel salt aqueous solution and a reducing agent aqueous solution containing P in a reducing atmosphere, and proposing an electroless reduction method did. The basic principle of this reduction precipitation can be used in the production of spherical NiP microparticles of the present invention. In this case, however, it is important in the present invention that Cu ions are added to the nickel salt aqueous solution. That is, free electrons released by the oxidation reaction of the reducing agent can reduce Ni ions and reduce and precipitate Cu, and NiP microparticles containing Cu with small particle size irregularity can be obtained.

In addition, an important feature of the present invention is that Sn ions are added to an aqueous nickel salt solution to which the Cu ions are added as needed. Accordingly, at the time of the reduction precipitation reaction, Sn also precipitates together, and NiP microparticles containing Sn with small particle size irregularity can be obtained.

The reaction mechanism will be described in detail. In the electroless reduction method adopted in the present invention, an oxidation reaction of a reducing agent, that is, phosphinic acid including phosphorous, occurs in the initial stage of the reaction immediately after the aqueous solution of the nickel salt and the reducing agent aqueous solution containing phosphorus are mixed. As the oxidation reaction progresses, phosphonic acid ions generated in the solution are accumulated. When the concentration reaches the limit, phosphonic acid ions and free Ni ions are combined to form nickel phosphonate . On the surface of the nucleus, that is, the surface of Ni, the phosphinic acid ion exhibits catalytic activity and causes an oxidation reaction through elimination reaction of hydrogen, which is the fundamental process of the reaction. The metal ions of Ni, Cu, and / or Sn are continuously reduced and precipitated by the free electrons released during the oxidation reaction to form target spherical NiP microparticles.

However, in general electroless Ni-P plating, in order to prevent the plating film from being deposited or spontaneously decomposed in addition to the object to be plated, sulfur compounds such as thiourea or heavy metal ions such as Pb, Bi, Tl and Sb And is used as a stabilizer. The stabilizer is preferentially adsorbed on the precipitate causing the spontaneous decomposition of the plating solution and acts as a catalyst poison. Sn and Cu are known as the elements that lower the catalytic activity, following the heavy metal. In the production of the spherical NiP microparticles of the present invention, by adding Cu or Sn to an aqueous solution of a nickel salt, it is possible to reduce the amount of nickel phosphonate produced later by the action of the catalyst poison during the reaction of the electroless reduction method Generation can be suppressed. As a result, the distribution of the component in the cross section of the spherical NiP fine particles obtained by the production method of the present invention was analyzed. It was confirmed that Cu or Cu and Sn ions were densely distributed in the center portion (Same as the FE-SEM (field emission scanning electron microscope) image of Figs. 3 to 6 and 9 to 13 described later).

In the above-mentioned operation, particularly suitable conditions for suppressing the unevenness of the particle size are set when the Cu is prepared and added so as to have a molar ratio of Ni / Cu = 4.0 to 10,000 in the aqueous solution of the nickel salt. When the Ni / Cu ratio is low, it is confirmed that each particle size itself can be largely prepared, while the unevenness as the particle size distribution tends to be small. It is also confirmed that, when the above ratio is increased, the respective particle sizes themselves can be made small, while the unevenness as the particle size distribution tends to be reduced. In the molar ratio, when the reduction precipitation reaction is 100% completed when an aqueous solution of a nickel salt prepared with Ni / Cu = about 4.56 is used, the theoretical amount of Cu contained in the obtained spherical NiP microparticles is about 7 mass% And is 18% by mass. When the reduction precipitation reaction is 100% completed when an aqueous solution of a nickel salt prepared with Ni / Cu = about 9,999 is used, the theoretical amount of Cu contained in the spherical NiP microparticles obtained is about 7 mass% 0.01% by mass.

Further, when Sn is additionally added to an aqueous solution of a nickel salt containing Cu, the effect of suppressing the unevenness of the particle size on the small diameter side is superior to the case where only Cu is added. 2,000 of Sn was added. When the Ni / Sn ratio is low, it is confirmed that each particle size itself can be prepared small, while the unevenness as the particle size distribution tends to be small. It is also confirmed that when the above-mentioned ratio is increased, each particle size itself can be largely prepared, while the unevenness as the particle size distribution tends to be reduced.

In this method, another important point is the preparation of pH at the time of starting reduction precipitation. By preparing this so as to be alkaline more than 7, the precipitation reaction can be rapidly promoted and NiP microparticles containing Cu or Sn and Sn can be obtained with good efficiency. In addition to this action effect, it is also possible to lower the concentration of P in the center portion of the microparticles in the initial stage of the reaction (same as in Figs. 3 to 6 and 9 to 13). This is also described in Patent Document 1 as an advantageous method for improving the conductivity and hardness of the fine particles.

On the other hand, even in the case of the Cu of the present invention or the reduced-precipitation-type NiP microparticles containing Cu and Sn provided by the above method, as in Patent Document 1, it is preferable that the heat treatment for hardening and / A surface coating treatment such as Au may be performed.

[Example]

(Example 1)

The nickel sulfate hexahydrate and the copper sulfate pentahydrate were prepared so that the molar ratio of Ni and Cu was Ni / Cu = 239 and dissolved in pure water to prepare a metal salt aqueous solution 15 (dm ³ ). Subsequently, sodium acetate was dissolved in purified water to a concentration of 1.0 (kmol / m ³ ), and further sodium hydroxide was added to prepare a pH-adjusting aqueous solution of 15 (dm ³ ). The metal salt aqueous solution and the pH adjusting aqueous solution were mixed with stirring to prepare a mixed aqueous solution of 30 (dm ³ ). The pH value was 8.1, as a result. The mixed aqueous solution was heated and maintained at 343 (K) by an external heater while bubbling with N ₂ gas, and stirring was continued.

Next, a reducing agent aqueous solution 15 (dm ³ ) in which sodium phosphinate was dissolved in purified water at a concentration of 1.8 (kmol / m ³ ) was prepared and heated to 343 (K) by an external heater. The mixed aqueous solution of 30 (dm ³ ) and 15 (dm ³ ) of the reducing agent was prepared so as to have a temperature of 343 ± 1 (K) and then mixed to obtain fine particles by electroless reduction.

After the microparticles thus obtained were dried, the particle size was measured by a particle size distribution meter by laser diffraction scattering method. The value of the average particle diameter d ₅₀ was 3.7 탆, d ₉₀ and d ₁₀ were 5.3 탆 and 2.8 탆, respectively, and the particle size distribution given by the formula [(d ₉₀ -d ₁₀ ) / d ₅₀ ] was 0.68. The shape of the particle was observed by SEM (scanning electron microscope), and it was confirmed that it was a monodisperse spherical shape as shown in Fig. As a result of analyzing the composition of the fine particles, the composition was NiP microparticles containing 0.40 mass% of Cu as shown in Table 1 below.

(Example 2)

The ratio of the nickel sulfate hexahydrate and the copper sulfate pentahydrate was adjusted so that the molar ratio of Ni to Cu was 5, and the liquid amount of the metal salt aqueous solution, the pH adjusting aqueous solution and the reducing agent aqueous solution was 0.25 (dm ³ ), respectively In the same manner as in Example 1 except for the above, microparticles were produced by the electroless reduction method. On the other hand, the pH of the mixed aqueous solution was 9.0.

When the distribution of particle diameters was confirmed by the laser diffraction scattering method, the value of the average particle diameter d ₅₀ was 8.9 μm, the value of [(d ₉₀ -d ₁₀ ) / d ₅₀ ] was 0.58, and the spherical NiP smile Particles were obtained. The distribution of each element was observed by FE-SEM (Field Emission Scanning Electron Microscope), and as a result, it was found that the average particle size was about 2/3 It was confirmed that Cu was densely distributed on the inner side. On the other hand, as a result of analysis of the composition of the components, as shown in Table 1, it was confirmed that Cu was 14.36% by mass.

(Example 3)

The concentrations of nickel sulfate hexahydrate and copper sulfate pentahydrate were adjusted to be Ni / Cu = 39 at a molar ratio of 0.65 (kmol / m ³ ) and 0.175 (kmo1 / m < ³ >) to prepare a pH-adjusting aqueous solution, fine particles were prepared by the electroless reduction method in the same manner as in Example 1. On the other hand, the pH of the mixed aqueous solution was 8.2.

The particle diameter of the obtained fine particles was measured by a particle size distribution meter of the laser diffraction scattering method. As a result, the average particle size d ₅₀ value was 67.1 μm and the value of [(d ₉₀ -d ₁₀ ) / d ₅₀ ] was 0.5 l. The result of observation of the fine particles by SEM was confirmed to be a monodisperse spherical shape as shown in Fig. On the other hand, as a result of the analysis of the composition of the components, it was confirmed that Cu was 2.750 mass% as shown in Table 1.

(Example 4)

According to Patent Document 1, 0.25 (dm ³ ) of a nickel salt aqueous solution not containing Cu and a mixed aqueous solution of sodium hydroxide 0.9 (kmol / m ³ ) and 1.00 (kmol / m ³ ) The mixture was stirred while heating from the outside, and two solutions were mixed to prepare a mixed aqueous solution. N ₂ gas was flowed to generate bubbles, and the mixed aqueous solution was adjusted to have a temperature of 343 ± 1 (K).

On the other hand, 0.25 (dm ³ ) of a reducing agent aqueous solution in which sodium phosphinate was dissolved in pure water at a concentration of 1.8 (kmol / m ³ ) was also heated by an external heater at 343 (K) Thereby obtaining spherical NiP microparticles. When the particle size distribution was confirmed by the laser diffraction scattering method, the value of the average particle diameter d ₅₀ was 2.9 μm and the value of [(d ₉₀ -d ₁₀ ) / d ₅₀ ] was 0.76. From the analysis results of the composition of Table 1, Cu was found only at an impurity level (less than 0.001 mass%).

(Example 5)

Nickel sulfate hexahydrate, sodium sulfate tetrahydrate and sodium tartrate trihydrate were used so that the molar ratio of Ni / Cu was 24 and the molar ratio of Ni / Sn was 4.8. Particles were prepared. On the other hand, the pH of the mixed aqueous solution was 9.6.

When the distribution of particle diameters was confirmed by the laser diffraction scattering method, the value of the average particle diameter d ₅₀ was 1.2 탆, the value of [(d ₉₀ -d ₁₀ ) / d ₅₀ ] was 0.67, NiP microparticles were obtained. Samples of cross-section observation of the particles were prepared and the distribution of each element was observed by FE-SEM. As shown in Figs. 9 to 13, it was confirmed that Cu and Sn were distributed. On the other hand, as shown in Table 1, the analysis results of the composition of the components were 3.96% by mass of Cu and 0.67% by mass of Sn.

Component composition (mass%) of fine particles Remarks Cu Sn P Ni * Example 1 0.402 <0.01 7.0 residual
The present invention
Example 2 14.363 <0.01 6.7 residual Example 3 2.750 <0.01 6.0 residual Example 4 <0.001 <0.01 7.5 residual Reference Example (Patent Document 1) Example 5 3.960 0.67 10.3 residual The present invention

* Contains impurities

[Industrial applicability]

The spherical NiP microparticles of the present invention having a uniform particle size can be used as conductive particles such as anisotropic conductive paste or heat seal connector requiring the same characteristics as the conductive particles for the anisotropic conductive film.

Claims (6)

As an anisotropic conductive film in which conductive particles are dispersed in an insulating resin film,
Wherein the conductive particles are spherical NiP microparticles composed of Ni as a main component and having a composition of P, and the composition contains 0.01 to 18 mass% of Cu,
Wherein the conductive particles have an average particle diameter d _{50 of 1} to 20 μm and a particle size distribution of [(d ₉₀ -d ₁₀ ) / d ₅₀ ] ≦ 0.8 (d ₉₀ , d ₁₀ , d ₅₀ : , 90% by volume, 10% by volume, and 50% by volume) of spherical NiP microparticles,
Anisotropic conductive film used for wiring connection. The method according to claim 1,
Wherein said spherical NiP microparticles are used for wire connection mainly composed of Ni with a composition of component containing P of 1 to 15 mass%. A method for producing an anisotropic conductive film in which conductive particles are dispersed in an insulating resin film,
Mixing an aqueous solution of a nickel salt, a mixed aqueous solution of a pH adjusting agent and a pH buffer and a reducing agent aqueous solution containing phosphorus to perform reduction-precipitation reaction to prepare spherical NiP microparticles containing P mainly composed of Ni,
The aqueous solution of the nickel salt contains Cu and is mixed and prepared so that the pH at the time of initiating the reduction precipitation reaction becomes alkaline higher than 7,
Wherein the spherical NiP microparticles are dispersed in an insulating resin film as conductive particles,
A method for producing an anisotropic conductive film used for wiring connection. The method of claim 3,
Wherein the spherical NiP microparticles consist of a composition of P containing 1 to 15 mass% of P, mainly Ni. The method of claim 3,
Wherein the aqueous solution of the nickel salt includes Cu having a molar ratio of Ni / Cu = 4.0 to 10,000. 5. The method of claim 4,
Wherein the aqueous solution of the nickel salt includes Cu having a molar ratio of Ni / Cu = 4.0 to 10,000.

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