JP2016110738A - Powder for conductive filler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide powder for a conductive filler excellent in conductivity, obtainable at a low cost, and also lightweight.SOLUTION: The material of the particle 1 of powder for a conductive filler being an alloy containing, by mass, 0.1 to 30% of Al, Si and conductive elements X1 with inevitable impurities. This alloy includes: a plurality of Al phases 2; a plurality of silicide phases 3, and an Si phase 4. The ratio (P1/P2) between the integrated intensity P1 of the peak of the Al(111) whose 2θ measured by XRD lies in the vicinity of 38.6°±0.3° and the integrated intensity P2 of the peak of the Si(111) whose 2θ lies in the vicinity of 28.3°±0.3° being 0.01 to 0.30. The density of this powder being 2.0 to 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.

JP 2004-47404 A JP 2004-232699 A JP 2008-136475 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 0.1% by mass or more and 30% by mass or less of Al, Si, the conductive element X1, and inevitable impurities. This alloy has a plurality of Al phases, a plurality of silicide phases containing Si and the element X1, and a Si phase. The integrated intensity P1 of the peak of the Al (111) surface, measured by XRD, whose 2θ is near 38.6 ° ± 0.3 °, and its 2θ is 28.3 ° ± 0.3 °. The ratio (P1 / P2) with the integrated intensity P2 of the peak of the Si (111) plane in the vicinity is 0.01 or more and 0.30 or less. The density of this powder is 2.0 Mg / m ³ or more and 6.0 Mg / m ³ or less.

  Preferably, the Al phase is dispersed in the Si phase. Preferably, one Al phase links a silicide phase and another silicide phase.

  Preferably, the element X1 is one or two selected from the group consisting of B, C, Na, Mg, P, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Au. That's it.

  Preferably, the alloy further includes element X2. The element X2 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 and the silicide phase contribute to conductivity.

FIG. 1 is a cross-sectional view illustrating 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 an aggregate of a large number of particles. FIG. 1 shows an enlarged cross section of the particle 1. The material of the particles 1 is an alloy. This alloy contains Al, Si, and element X1. The element X1 is conductive. The electric conductivity of the element X1 is 100 AV ⁻¹ m ⁻¹ or more.

Preferably, the alloy is
(1) Al
(2) Si
(3) Element X1
And (4) Contains only inevitable impurities.

  As shown in FIG. 1, this alloy has a plurality of Al phases 2, a plurality of silicide phases 3 and a Si phase 4. These Al phases 2 are dispersed and precipitated in the Si phase 4. Silicide phase 3 is also dispersed and precipitated in Si phase 4.

  The main component of each Al phase 2 is Al. The Al phase 2 may contain only Al. The Al phase 2 may contain a small amount of other elements together with Al. The ratio of Al in the Al phase 2 is 90% by mass or more. Al is conductive.

  Each silicide phase 3 contains Al, Si, and element X1. The silicide phase 3 can contain a compound of Al and Si. The silicide phase 3 can include a compound of Si and the element X1. The silicide phase 3 can include a compound of Al, Si, and the element X1. In the silicide phase 3, Al and the element X1 can be dissolved in Si. This silicide phase 3 is conductive because it contains Al and the element X1.

  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 2 and the silicide phase 3 suppress the electrical resistance of the particles 1. The conductive filler powder containing the Al phase 2 and the silicide phase 3 is excellent in conductivity. In particular, the powder having the Al phase 2 is excellent in conductivity. An object (for example, an electronic device) containing this powder is excellent in conductivity.

  As shown in FIG. 1, the Al phase 2 links the silicide phase 3 and another silicide phase 3. In this alloy, electricity flows through the Al phase 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 Al is 2.698 Mg / m ³ and the density of Si is 2.329 Mg / m ³ . The density of Al and Si is small among metals. The conductive filler powder containing Al and Si is lightweight. The object containing this powder is lightweight.

  Al and Si are less expensive than noble metals. The conductive filler powder containing Al and 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 Al ratio 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 the particles 1 is inferior in conductivity. From the viewpoint that generation of alumina is suppressed and from the viewpoint of low cost, the Al ratio in the alloy is preferably 30% by mass or less, and particularly preferably 10% by mass or less.

  From the viewpoint of conductivity, the ratio of the element X1 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 X1 is preferably 50% by mass or less.

  From the viewpoint of light weight and low cost, the Si ratio in the alloy is preferably 45% by mass or more, more preferably 65% by mass or more, and particularly preferably 75% by mass or more. From the viewpoint that the alloy can contain sufficient Al and the element X1, the Si ratio 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.

  Specific examples of the element X1 include B, C, Na, Mg, P, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Au. The powder may contain two or more elements X1. These elements X1 can also contribute to the thermal conductivity of the powder.

  In the present invention, the integrated intensities P1 and P2 of the powder are measured by XRD (X-ray diffraction). P1 is the integrated intensity of the peak of the Al (111) plane. The peak 2θ of the Al (111) plane is around 38.6 ° ± 0.3 °. P2 is the integrated intensity of the peak of the Si (111) plane. The peak 2θ of the Si (111) plane is in the vicinity of 28.3 ° ± 0.3 °. The ratio (P1 / P2) is preferably 0.01 or more and 0.30 or less. In a powder having a ratio (P1 / P2) of 0.01 or more, sufficient Al phase 2 is precipitated. In this respect, the ratio (P1 / P2) is more preferably equal to or greater than 0.05, and particularly preferably equal to or greater than 0.10. In a powder having a ratio (P1 / P2) of 0.30 or less, it is difficult to form an Al oxide film. In this respect, the ratio (P1 / P2) is particularly preferably equal to or less than 0.20.

The alloy may include the element X2. In this case, preferably the alloy is
(1) Al
(2) Si
(3) Element X1
(4) Element X2
And (5) Contains only inevitable impurities.

  Examples of the element X2 include Sn, In, Zn, Bi, Ga, and Pb. The alloy may include two or more elements X2.

  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 X2 improves the adhesion between the particles 1. This element X2 reduces the contact resistance.

  The content of the element X2 in the alloy is preferably 1% by mass or more and 5% by mass or less.

  The element X2 has a large melting point difference from Si, and the elements X2 and Si hardly dissolve each other. Therefore, when the Si—X2 alloy is atomized, a silicide phase containing Si and the element X2 appears. By this atomization, there is a tendency that Si simple substance and element X2 simple substance are precipitated. Since the electrical conductivity of Si alone is very small, and the proportion of Si alone in the Si—X2 alloy is large, the Si—X2 alloy is not suitable as a conductive filler powder. In the powder alloy according to the present invention, the element X2 is added along with Al and the element X1. 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 1-20 and Comparative Example 1-20 having the compositions shown in Tables 1 and 2 were obtained. Each powder contains unavoidable impurities not listed 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 into a cylindrical sample holder (four-terminal sample holder for powder impedance measurement 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 applying a current 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, the alloy of the powder of each example contains 0.1 mass% or more and 30 mass% or less of Al. This alloy is
(1) Al phase,
(2) a silicide phase containing Al, Si and element X, and (3) a Si phase. The ratio (P1 / P2) of this powder is 0.01 or more and 0.30 or less. 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
Integral intensity ratio: 0.01 or more and 0.30 or less Density: 2.0 Mg / m ³ or more and 6 Mg / m ³ or less Electrical conductivity: less than 1000 AV ⁻¹ m ⁻¹ Rating B
The integrated intensity ratio 0.01 0.30 Density: 2.0 Mg / ^{m 3} or more 6 mg / ^{m 3} or less electrical conductivity: ^500AV -1 ^{m -1} or more ^1000AV -1 ^m less than ^-1 rating C
The integrated intensity ratio 0.01 0.30 Density: 2.0 Mg / ^{m 3} or more 6 mg / ^{m 3} or less electrical conductivity: ^100AV -1 ^{m -1} or more ^500AV -1 ^m less than ^-1 rating D
Integral intensity ratio: 0.01 or more and 0.30 or less Density: 2.0 Mg / m ³ or more and 6 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 one of the Al content, the integrated intensity ratio, and the density does not satisfy the requirements of the present invention.

For example, the powder according to Example 14 has a composition of 10Al-60Si-15Cr-15Ti and an integrated intensity ratio of 0.20. Further, the density is 3.41 Mg / m ³ and the electric conductivity is 1250AV ⁻¹ m ⁻¹ . This powder exhibits the most favorable properties in this example.

For example, the electrical conductivity of the powder according to Comparative Example 12 is 840AV ⁻¹ m ⁻¹ . This powder exhibits excellent conductivity, has an Al amount of 30% by mass, and a density of 3.47 / m ³ , but does not satisfy the requirements of the present invention because the integrated intensity ratio is 0.008.

  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

Claims (5)

The material is an alloy containing 0.1% by mass or more and 30% by mass or less of Al, Si, conductive element X1, and inevitable impurities,
The alloy has a plurality of Al phases, a plurality of silicide phases containing the Si and the element X1, and a Si phase;
Measured by XRD, the integrated intensity P1 of the peak of the Al (111) surface whose 2θ is around 38.6 ° ± 0.3 ° and Si whose 2θ is around 28.3 ° ± 0.3 ° The ratio (P1 / P2) with the integrated intensity P2 of the peak of the (111) plane is 0.01 or more and 0.30 or less,
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 Al phase is dispersed in the Si phase.   The powder according to claim 2, wherein one Al phase links a silicide phase and another silicide phase.   The element X1 is one or more selected from the group consisting of B, C, Na, Mg, P, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Au. The powder according to any one of claims 1 to 3. The alloy further comprises element X2,
The powder according to any one of claims 1 to 4, wherein the element X2 is one or more selected from the group consisting of Sn, In, Zn, Bi, Ga, and Pb.

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