JP2017007885A - Powder for conductive filler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder for conducive filler excellent in conductivity, capable of being obtained at low cost and having light weight.SOLUTION: A material of particles of a powder for conductive filler is an alloy containing Al, Ag, Si, a conductive element M1 with inevitable impurities. The total amount of Al and Ag in the alloy is 0.1 mass% to 20 mass%. The alloy has an Al phase, an Ag phase, an AlAg phase, a plurality of silicide phases containing Si and element M1 and a Si phase. The silicide phase and other silicide phase are jointed by the Al phase, the Ag phase or the AlAg phase. A ratio of mass percentage content of Ag x and mass percentage content of Al y (x/y) of 0.50 to 1.50. Density of the powder is 2.0 Mg/mto 6.0 Mg/m.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a powder suitable for a conductive filler used in a conductive resin, a conductive plastic, a conductive paste, an electronic device, an electronic component, and the like.

  As the filler contained in the conductive material, powders of noble metals such as gold, silver, platinum and copper are used. A powder in which a surface of another metal is coated with a noble metal is also used as a conductive filler. Since the electrical resistance of the noble metal is small, the filler containing the noble metal is excellent in conductivity. Since a large contact area between the particles can be obtained by aggregation of the particles containing the noble metal, the noble metal contributes to the conductivity of the filler also from this viewpoint. Precious metals are also excellent in thermal conductivity.

  Precious metals are expensive. Therefore, a conductive material containing a noble metal is expensive. Moreover, noble metals have a high specific gravity. Therefore, the conductive substance containing a noble metal is heavy. From the viewpoint of cost reduction and weight reduction, various studies have been made on alloys containing elements other than noble metals.

  Japanese Patent Application Laid-Open No. 2004-47404 discloses an alloy for conductive filler in which the surface of particles made of a silicon compound is coated with carbon. In these particles, silicon microcrystals are dispersed in the silicon compound.

  Japanese Patent Application Laid-Open No. 2004-232699 discloses an alloy for conductive filler in which the surface of particles made of Ag is coated with Si or a Si-based compound.

Japanese Patent Application Laid-Open No. 2008-136475 discloses an alloy for conductive fillers containing silver and 0.01-10% by mass of Si. In this alloy, the surface of silver particles is coated with a SiO ₂ gel.

  Japanese Patent Application Laid-Open No. 2006-302525 discloses a conductive filler alloy containing Ag and further containing Al or Si.

JP 2004-47404 A JP 2004-232699 A JP 2008-136475 A JP 2006-302525 A

  In recent years, performance enhancement and application expansion of electronic devices have progressed. There is a demand for reducing the cost and weight of the conductive material.

  An object of the present invention is to provide a conductive filler powder that is excellent in conductivity, obtained at low cost, and lightweight.

The material for the conductive filler powder according to the present invention is an alloy containing Al, Ag, Si, the conductive element M1, and inevitable impurities. The total amount of Al and Ag in this alloy is 0.1% by mass or more and 20% by mass or less. This alloy has an Al phase, an Ag phase, an AlAg phase, a plurality of silicide phases containing Si and the element M1, and an Si phase. The ratio (x / y) between the mass content x of Ag and the mass content y of Al in the AlAg phase is 0.50 or less or 1.50 or more. The density of this powder is 2.0 Mg / m ³ or more and 6.0 Mg / m ³ or less.

  Preferably, the amount of Ag in this alloy is 0.1% by mass or more and 15% by mass or less. Preferably, the ratio (x / y) is 0.30 or less or 2.00 or more.

  Preferably, the silicide phase and another silicide phase are jointed by an Al phase, an Ag phase, or an AlAg phase.

  Preferably, the element M1 is one or more selected from the group consisting of B, Na, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, and Ni.

  Preferably, the alloy further includes element M2. The element M2 is one or more selected from the group consisting of Sn, In, Zn, Bi, Ga, and Pb.

  Since the conductive filler powder according to the present invention is an alloy containing Si, it can be obtained at low cost. Compared with a powder obtained by coating a noble metal, this powder is less time-consuming to manufacture and does not cause a problem of peeling of the coating layer. This powder is also low density. In this powder, the Al phase, Ag phase, AlAg phase, and silicide phase contribute to conductivity.

FIG. 1 is a schematic cross-sectional view showing a part of particles included in a powder according to an embodiment of the present invention.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

The conductive filler powder according to the present invention is a collection of a large number of particles 1. FIG. 1 shows an enlarged cross section of the particle 1. The material of the particles 1 is an alloy. This alloy contains Al, Ag, Si, and the element M1. The element M1 is conductive. The electric conductivity of the element M1 is 100 AV ⁻¹ m ⁻¹ or more.

Preferably, the alloy is
(1) Al
(2) Ag
(3) Si
(4) Element M1
And (5) Contains only inevitable impurities. The alloy may contain other elements that are actively added. Examples of other elements include Au and Cu.

  As shown in FIG. 1, the alloy has a plurality of links 2, a plurality of silicide phases 3, and a Si phase 4. These links 2 are dispersed and precipitated in the Si phase 4. Silicide phase 3 is also dispersed and precipitated in Si phase 4. By each link 2, the silicide phase 3 and the other silicide phase 3 are jointed.

These links 2 include
(1) The structure is an Al phase (2) The structure is an Ag phase and (3) The structure is an AlAg phase.

  The main component of the Al phase is Al. The Al phase may contain only Al. The Al phase may contain a small amount of other elements along with Al. The ratio of Al in the Al phase is 90% by mass or more. Al is conductive.

  The main component of the Ag phase is Ag. The Ag phase may contain only Ag. The Ag phase may contain a small amount of other elements together with Ag. The ratio of Ag in the Ag phase is 90% by mass or more. Ag is conductive.

  The AlAg phase contains Al and Ag. The AlAg phase may contain only Al and Ag. The AlAg phase may contain a small amount of other elements along with Al and Ag. The AlAg phase is conductive.

Each silicide phase 3 contains Al, Ag, Si, and the element M1. As a compound that can be contained in the silicide phase 3,
(1) Compound of Al and Si (2) Compound of Ag and Si (3) Compound of element M1 and Si (4) Compound of Al, Ag and Si (5) Compound of Al, element M1 and Si ( 6) Compound of Ag, element M1 and Si and (7) Compound of Al, Ag, element M1 and Si. In the silicide phase 3, Al, Ag, and the element M1 can be dissolved in Si. The silicide phase 3 is conductive because it contains Al, Ag, and the element M1.

  The main component of the Si phase 4 is Si. Si phase 4 may contain only Si. The Si phase 4 may contain a small amount of other elements (such as Al) together with Si. Other elements may be doped into the Si phase 4 or may be dissolved.

  Si is a metal with low electrical conductivity. On the other hand, the Al phase, Ag phase, AlAg phase, and silicide phase 3 suppress the electrical resistance of the particles 1. The conductive filler powder containing the Al phase, Ag phase, AlAg phase, and silicide phase 3 is excellent in conductivity. In particular, a powder having an Ag phase is excellent in conductivity. An object (for example, an electronic device) containing this powder is excellent in conductivity.

  As described above, the silicide phase 3 and the other silicide phase 3 are jointed by the respective links 2. The structure of the link 2 is an Al phase, an Ag phase, or an AlAg phase. In this alloy, electricity flows through the link 2 and the silicide phase 3. This powder is extremely excellent in conductivity.

As described above, noble metals such as gold, silver, platinum and copper are used for the conventional conductive filler powder. The density of gold is 19.32 Mg / m ³ , the density of silver is 10.50 Mg / m ³ , the density of platinum is 21.45 Mg / m ³ , and the density of copper is 8.960 Mg / m ³ is there. On the other hand, the density of Si is 2.329 Mg / m ³ . The density of Si is small among metals. The conductive filler powder containing Si is lightweight. The object containing this powder is lightweight.

  Si is less expensive than noble metals. The conductive filler powder containing Si achieves the low cost of the object containing this powder. Furthermore, this powder can be produced without the hassle of coating.

  From the viewpoint of conductivity, the total amount of Al and Ag in the alloy is preferably 0.1% by mass or more, more preferably 3% by mass or more, and particularly preferably 5% by mass or more.

  From the viewpoint of conductivity, the amount of Ag in the alloy is preferably 0.1% by mass or more, more preferably 3% by mass or more, and particularly preferably 5% by mass or more.

  Al present on the surface of the particle 1 can react with oxygen in the atmosphere. This reaction produces alumina. Alumina forms an oxide film on the surface of the particles 1. Alumina is insulative. Alumina increases the contact resistance between the particles 1. The powder containing particles 1 in which alumina is excessively produced is inferior in conductivity.

  On the other hand, Ag present on the surface of the particle 1 is affected by moisture in the atmosphere. This effect causes ion migration.

  From the viewpoint of suppressing generation of alumina, the viewpoint of suppressing ion migration of Ag, and the viewpoint of low cost, the total amount of Al and Ag in the alloy is preferably 20% by mass or less, and 15% by mass or less. Is more preferable, and 10 mass% or less is especially preferable.

  From the viewpoint of suppressing ion migration of Ag and the low cost, the amount of Ag in the alloy is preferably 15% by mass or less, more preferably 12% by mass or less, and particularly preferably 10% by mass or less.

  Specific examples of the element M1 include B, Na, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, and Ni. The powder may contain two or more elements M1. These elements M1 contribute to conductivity. These elements M1 can also contribute to the thermal conductivity of the powder.

  From the viewpoint of conductivity, the ratio of the element M1 in the alloy is preferably 1% by mass or more, more preferably 3% by mass or more, and particularly preferably 5% by mass or more. From the viewpoint that the alloy can contain sufficient Si, the ratio of the element M1 is preferably 50% by mass or less.

  From the viewpoint of light weight and low cost, the Si ratio in the alloy is preferably 30% by mass or more, more preferably 40% by mass or more, and particularly preferably 45% by mass or more. From the viewpoint that the alloy can contain sufficient Al, Ag, and element M1, the ratio of Si is preferably 95% by mass or less.

From the viewpoint of weight of the object containing a conductive filler powder, the density of the powder is preferably 6.0 mg / ^{m 3} or less, more preferably 5.5 mg / ^{m 3} or less, 5.0 mg / ^{m 3} or less is particularly preferred. Density is preferably 2.0 Mg / ^{m 3} or more, more preferably 2.5 mg / ^{m 3} or more, 3.0 mg / ^{m 3} or more is particularly preferable.

  The density is measured by a dry automatic densimeter “Acupic II 340 series” manufactured by Shimadzu Corporation. The container of this apparatus is charged with powder and filled with helium gas. Based on the constant volume expansion method, the density of the powder is detected. An average value of 10 measurements is calculated.

  As described above, in this powder, the AlAg phase contributes to conductivity. When the ratio (x / y) of the mass content x of Ag and the mass content y of Al in the AlAg phase is more than 0.5 and less than 1.5, the AlAg phase is a π-phase structure or this Have a similar organization. In this case, the contribution of the AlAg phase to the conductivity is not large. From the viewpoint of conductivity, the ratio (x / y) is preferably 0.50 or less or 1.50 or more. In the particle 1 having a ratio (x / y) of 0.50 or less, an AlAg phase 4-1 having a high Al content is precipitated. This AlAg phase 4-1 is excellent in conductivity. From the viewpoint of conductivity, the ratio (x / y) is more preferably 0.45 or less, and particularly preferably 0.30 or less. In the particle 1 having a ratio (x / y) of 1.50 or more, an AlAg phase 4-2 having a high Ag content is precipitated. This AlAg phase 4-2 is excellent in conductivity. From the viewpoint of conductivity, the ratio (x / y) is more preferably 1.55 or more, and particularly preferably 2.00 or more.

The alloy may include the element M2. In this case, preferably the alloy is
(1) Al
(2) Ag
(3) Si
(4) Element M1
(5) Element M2
And (6) Contains only inevitable impurities. The alloy may contain other elements that are actively added. Examples of other elements include Au and Cu.

  Examples of the element M2 include Sn, In, Zn, Bi, Ga, and Pb. The alloy may include two or more elements M2.

  The electrical conductivity of the powder is mainly governed by the bulk resistance inside the particles 1 and the contact resistance between the particles 1. The alloy containing the soft element M2 increases the adhesion between the particles 1. This element M2 reduces the contact resistance.

  The content of the element M2 in the alloy is preferably 0.1% by mass or more and 5% by mass or less.

  Element M2 has a large melting point difference from Si. There is almost no mutual dissolution between the element M2 and Si. Therefore, if the Si-M2 alloy is subjected to atomization, the silicide phase 3 containing Si and the element M2 is unlikely to appear. Due to this atomization, the tendency for Si and element M2 to precipitate is observed. Since the electric conductivity of Si simple substance is very small and the ratio of Si simple substance in Si-M2 alloy is large, Si-M2 alloy is not suitable for conductive filler powder. In the powder alloy according to the present invention, the element M2 is added along with Al, Ag, and the element M1. This alloy is suitable for conductive filler powder.

  The conductive filler powder can be manufactured by a liquid quenching process including an atomizing process. By this process, the powder can be produced easily and inexpensively. Examples of preferable atomization include a water atomization method, a gas atomization method, a disk atomization method, and a plasma atomization method. A gas atomizing method and a disk atomizing method are particularly preferable.

  In the gas atomization method, raw materials are put into a quartz crucible having pores at the bottom. This raw material is heated and melted by a high frequency induction furnace in an argon gas atmosphere. In an argon gas atmosphere, argon gas is injected onto the raw material flowing out from the pores. The raw material is rapidly cooled and solidified to obtain a powder. The coagulation rate can be controlled by adjusting the injection pressure. The greater the injection pressure, the greater the solidification rate. By controlling the solidification rate, a powder having a desired particle size distribution can be obtained. The faster the solidification rate, the smaller the width of the particle size distribution.

  In the disk atomization method, raw materials are put into a quartz crucible having pores at the bottom. This raw material is heated and melted by a high frequency induction furnace in an argon gas atmosphere. In an argon gas atmosphere, the raw material flowing out from the pores is dropped onto a disk that rotates at high speed. The rotation speed is 40000 rpm to 60000 rpm. The raw material is rapidly cooled by the disk and solidified to obtain a powder. This powder may be milled.

  Powders may be produced by pulverizing a scale-like or thin foil-like material produced by a melt spinning method by a mechanical alloying method.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

  The powders of Example 1-17 and Comparative Example 1-17 having the compositions shown in Tables 1 and 2 were obtained. These powders contain Si and inevitable impurities in addition to the components described in Tables 1 and 2.

  The electrical conductivity of each powder was measured. First, particles having a diameter exceeding 45 μm were removed from the powder using a sieve. This powder was filled in a cylindrical sample holder (four-terminal sample holder for powder impedance measurement manufactured by Toyo Technica Co., Ltd.) having a diameter of 25 mm and a height of 10 mm. A load of 4 Nm was applied to the powder from above and below. A positive terminal for current and a positive terminal for voltage were attached to the upper side of the powder. A negative terminal for current and a negative terminal for voltage were attached to the lower side of the powder. The voltage was measured by passing a current through the powder by the so-called four-terminal method. The results are shown in Tables 1 and 2 below.

Details of the manufacturing process in Tables 1 and 2 are as follows.
G. A. : Gas atomization method A. : Disc atomization method S. : Melt spinning method

As shown in Table 1-2, in the powder alloy of each example, the total amount of Al and Ag is 0.1% by mass or more and 20% by mass or less. This alloy is
(1) Al phase,
(2) Ag phase,
(3) AlAg phase,
(4) Silicide phase containing element M1 (5) Silicide phase containing Al, Si and element M1,
(6) Silicide phase containing Ag, Si and element M1,
(7) a silicide phase containing Al, Ag, Si and the element M1,
And (8) containing a Si phase. The ratio (x / y) of this AlAg phase is 0.50 or less or 1.50 or more. The density of this powder is 2.0 Mg / m ³ or more and 6.0 Mg / m ³ or less.

In Table 1, each powder is rated with an A-D rating. The criteria for this evaluation are as follows.
Rating A
Ratio (x / y): 0.5 or less or 1.5 or more Density: 2.0 Mg / m ³ or more and 6.0 Mg / m ³ or less Electrical conductivity: 1000 AV ⁻¹ m ⁻¹ or more Rating B
The ratio (x / y): 0.5 or less or 1.5 or more density: 2.0 Mg / ^{m 3} or more 6.0 mg / ^{m 3} or less electrical conductivity: ^{500AV -1 m} -1 or more ^1000AV less than -1 ^{m -1} Rating C
The ratio (x / y): 0.5 or less or 1.5 or more density: 2.0 Mg / ^{m 3} or more 6.0 mg / ^{m 3} or less electrical conductivity: ^{100AV -1 m} -1 or more ^500AV less than -1 ^{m -1} Rating D
Ratio (x / y): 0.5 or less or 1.5 or more Density: 2.0 Mg / m ³ or more and 6.0 Mg / m ³ or less Electrical conductivity: less than 100 AV ⁻¹ m ⁻¹

  The rating of each comparative example shown in Table 2 is E. In this powder, any of the total amount, ratio (x / y) and density of Al and Ag does not satisfy the requirements of the present invention.

The composition of the powder according to Example 8 is 5Al-5Ag-20Cr-20Ti-50Si. In this powder, the ratio (x / y) is 1.53 and the density is 3.68 Mg / m ³ . The electrical conductivity of this powder is 1300AV ⁻¹ m ⁻¹ . This powder has the highest conductivity among the powders of all Examples.

In the powder according to Comparative Example 9, the electric conductivity is 1800AV ⁻¹ m ⁻¹ and the ratio (x / y) is 2.05. This powder is excellent in conductivity. However, in this powder, the total amount of Al and Ag is 80% by mass, and the density is 8.74 Mg / m ³ . This powder is not preferable from the viewpoint of low cost and light weight.

  From the above evaluation results, the superiority of the present invention is clear.

  The powder according to the present invention can be used for conductive resins, conductive plastics, conductive pastes, electronic devices, electronic components, and the like.

Japanese Patent Application Laid-Open No. 2006-54061 discloses an alloy for conductive filler in which the surface of particles made of Ag is coated with Si or a Si-based compound.

Japanese Patent Application Laid-Open No. 2008-262916 discloses a conductive filler alloy containing silver and 0.01 to 10% by mass of Si. In this alloy, the surface of silver particles is coated with a SiO ₂ gel.

JP 2004-47404 A JP 2006-54061 A JP 2008-262916 A JP 2006-302525 A

Claims (5)

The material is an alloy containing Al, Ag, Si, conductive element M1 and inevitable impurities,
The total amount of Al and Ag in the alloy is 0.1% by mass or more and 20% by mass or less,
The alloy has an Al phase, an Ag phase, an AlAg phase, a plurality of silicide phases containing the Si and the element M1, and an Si phase;
In the AlAg phase, the ratio (x / y) between the mass content x of Ag and the mass content y of Al is 0.50 or less or 1.50 or more,
A conductive filler powder having a density of 2.0 Mg / m ³ or more and 6.0 Mg / m ³ or less.   The powder according to claim 1, wherein the amount of Ag in the alloy is 0.1 mass% or more and 15 mass% or less, and the ratio (x / y) is 0.30 or less or 2.00 or more.   The powder according to claim 1 or 2, wherein a silicide phase and another silicide phase are jointed by the Al phase, the Ag phase, or the AlAg phase.   The element M1 is one or more selected from the group consisting of B, Na, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, and Ni. The described powder. The alloy further comprises an element M2,
The powder according to any one of claims 1 to 4, wherein the element M2 is one or more selected from the group consisting of Sn, In, Zn, Bi, Ga, and Pb.

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