JP2015074806A - AgCu-BASED CONDUCTIVE FILLER POWDER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AgCu-based conductive filler powder having electric conductivity comparable to pure Ag and being an alloy powder as atomization without needs for Ag coating by controlling a component enhancing effects which an AgCu phase that there are many ultrafine eutectic structures and Ag and less Cu occupies a powder surface layer.SOLUTION: There is provided an AgCu-based conductive filler powder haing an AgCu phase 3 which is atomization alloy powder containing Cu-Ag alloy having the Ag percentage content of 1 to 30 mass% and the atomization alloy powder is as atomization and the Ag mass ratio to Cu, X=(M/M), is 1.2 or more on an atomization powder outermost surface 2 shown schematically in a figure 2.

Description

  The present invention relates to an Ag conductive filler powder that is excellent in electrical conductivity and heat dissipation, has a low manufacturing cost, and is used for medical sensors, electronic devices and the like.

  Conventionally, in an Ag conductive filler powder used as a conductive adhesive, silver particles are widely used as a conductive filler to be blended. Silver itself is a metal excellent in thermal conductivity and electrical conductivity, and has an advantage that the extension of the oxide film layer formed on the surface of silver particles is difficult to proceed. In addition, it is excellent in ductility and malleability, and after agglomeration due to contact between silver particles, the contact area between the silver particles easily expands, so that a conductive adhesive layer showing good conductivity is formed. The

  Such Ag conductive filler powder can be obtained by using pure Ag or by coating Ag on Cu as a base material. However, pure Ag is costly, and Ag coating is costly in terms of process. There is no detailed examination example of a conductive filler powder in which Ag is concentrated on the powder surface by rapid cooling, which simultaneously solves this problem.

  Currently, it is known that the Ag conductive filler powder is characterized in that the weight ratio of copper is 50 or less when the total weight of copper and silver is 100 (see, for example, Patent Document 1). .

  In addition, Ag conductive filler powder having a core-shell structure in which silver particles are arranged on the surface of a copper-based metal as a core material is known to have an Ag coating layer between the metal as the core material and the Ag particles. (For example, refer to Patent Document 2).

  On the other hand, an alloy powder in which Ag is concentrated in the powder outermost layer is described (for example, see Patent Document 3). However, the ratio of Ag and Cu in the powder surface layer and the abundance ratio of the AgCu phase are not clarified.

JP 2007-99851 A JP 2011-249257 A Japanese Patent Laid-Open No. 10-21742

  By the way, in the conductive filler formed by coating the surface of the core material made of a conventional copper-based metal with silver particles, by using the copper-based metal as the core material, the Sn (tin) electrode used for the electrode of the electronic component The potential difference with the filler is reduced to prevent galvanic corrosion.

  However, since this is one in which silver particles are arranged on the surface of the core material, there is a production method in which the obtained copper-based powder is coated with silver after the copper-based powder is produced.

  The manufacturing method for coating silver on a copper-based powder as described above produces an atomized powder, and after collection, it is processed by an apparatus for applying the coating. Moreover, in order to avoid the coating process, the use of silver powder instead of copper-based powder causes a further problem of cost.

  In order to solve the above-described problems, the present invention aims to exhibit a conductivity equivalent to that of pure Ag only by an atomizing method without performing a coating treatment.

In order to solve the problems as described above, the inventors have made extensive developments. As a result, the outermost layer of an atomized alloy powder made of a Cu-Ag alloy having an Ag content of 1 to 30% by mass contains Ag with respect to Cu. It was possible to produce an AgCu-based conductive filler powder having excellent conductivity in which 10% or more of an AgCu phase having a mass ratio X = (M _Ag / M _Cu ) of 1.2 or more was present.

Therefore, as means for solving the problems of the present invention, in the means of claim 1, an atomized alloy powder made of a Cu-Ag alloy having an Ag content of 1 to 30% by mass, the atomized alloy powder being It is an AgCu-based conductive filler powder characterized by having an AgCu phase in an atomized powder outermost layer with an Ag mass ratio X = (M _Ag / M _Cu ) of 1.2 or more as atomized. The powder outermost layer refers to a layer of 20 nm from the outermost surface of the powder to the inside.

  The AgCu-based conductive filler powder according to claim 1, wherein the atomized alloy powder has an AgCu phase having a ratio X of 1.2 or more in 10% or more of the powder outermost layer. It is.

  The atomized alloy powder includes gas atomized alloy powder, disk atomized alloy powder, and the like, but is not limited thereto.

  Ag and Cu are effective in forming a fine eutectic structure, and the AgCu phase with a large amount of Ag and a small amount of Cu occupies the powder surface layer, thereby reducing the contact resistance and increasing the electrical conductivity compared to pure Cu. In particular, when the mass ratio X of Ag to Cu in the outermost AgCu phase is 1.2 or more, it is possible to obtain excellent electrical conductivity substantially inferior to pure Ag. This is because when the ratio X is 1.2 or more, it becomes difficult to form an oxide, and even when an oxide is formed, the formation of Cu-based oxides with high specific resistance is suppressed, and Ag-based with low specific resistance This is because the oxide is formed.

  In addition, the AgCu phase having a mass ratio X of Ag with respect to Cu of 1.2 or more occupies 10% or more of the area ratio of the powder surface layer, so that Cu present in the powder inner layer which is a CuAg phase with a small amount of Ag and a large amount of Cu. Can be prevented from being exposed to the atmosphere as much as possible. As a result, the metal bonding between Ag is performed well, and the bonding reliability can be ensured.

  As described above, the present invention has an extremely excellent effect of providing an AgCu-based conductive filler powder that has an electrical conductivity comparable to pure Ag and is an atomized alloy powder that does not require Ag coating. .

It is a figure which shows the schematic diagram of the cross section of the atomized alloy powder of the eutectic alloy of Ag and Cu which concerns on this invention. The enlarged view of the powder outermost layer part enclosed with the circle | round | yen of the sectional drawing of the atomized alloy powder of FIG. 1 is shown.

The present invention is described in detail below.
The electric conductivity of the conductive filler powder is determined by the amount of electron movement. There is a demand for a state in which a large amount of electrons are moved and there is no such thing that inhibits the movement. Therefore, pure Au, pure Ag, and pure Cu may be used as the conductive filler material. However, pure Au and pure Ag have a problem in terms of cost, and pure Cu is easily oxidized. Then, the research of the alloy which can move more electrons was advanced, and it turned out that the alloy which made Ag exist on the Cu type alloy surface among these alloys is promising. Therefore, Ag is adopted.

  The feature of the present invention is that an AgCu phase in which the mass ratio of Ag to Cu is controlled to 1.2 or more is present in the outermost layer of the powder.

  In addition, when the molten metal is cooled, CuAg with a large amount of Cu and a low amount of Ag has a high melting point, so that it first solidifies first, and around the solidified CuAg is covered with AgCu with a low melting point and a large amount of Cu. To solidify.

  In addition to the above eutectic structure of Ag and Cu, further improvement of the AgCu-based conductive filler powder is expected by controlling the Ag ratio. When there is too little Ag content rate, it will become difficult to show an AgCu phase with much Ag and few Cu in a powder surface layer. Moreover, when there is too much Ag content rate, the AgCu phase in which much Ag is contained in the powder surface layer is likely to appear, but there is a problem in terms of cost. From this, Ag content rate of the whole powder shall be 1-30 mass%.

  The eutectic structure of Ag and Cu can be controlled by controlling the cooling rate at the time of solidification after dissolving the raw metal in addition to the control of the components defined above. Examples of the production method include a gas atomization method, a disk atomization method, and a water atomization method, but are not limited thereto.

  The gas atomization method can change the solidification rate of the molten metal by adjusting the pressure of the spray gas when the molten metal is discharged. For example, by lowering the pressure of the spray gas and optimizing other manufacturing conditions, the cooling rate at which the molten metal solidifies becomes slow, and the AgCu phase with a high amount of Ag and a low amount of Cu tends to segregate on the surface layer of the AgCu powder. .

  The disc atomizing method does not use a spray gas when discharging molten metal, so that the cooling rate can be controlled slower than the gas atomizing method. From this, together with optimization of other production conditions, the AgCu phase with a large amount of Ag in the surface layer of the AgCu powder is likely to segregate.

  By using an AgCu-based conductive filler powder produced by controlling the Ag ratio, an atomized alloy powder that does not require Ag coating and exhibits excellent electrical conductivity comparable to pure Ag can be obtained. .

  In addition to Cu and Ag, a metal having a low melting point, Cu, Ag, Zn, In, Ga, Sn, Bi, Pb, or the like that undergoes liquid phase separation may be added.

Hereinafter, the present invention will be specifically described with reference to examples.
AgCu-based conductive filler powder having the composition shown in Table 1 was produced by a gas atomizing method and a disk atomizing method.

  As for the gas atomization method, a raw material having a predetermined composition is placed in a quartz crucible having pores at the bottom, heated and melted in a high-frequency induction melting furnace in an Ar gas atmosphere, and then heated in an Ar gas atmosphere by gas injection. Then, gas atomized fine powder was obtained by rapid solidification.

  The rate of rapid solidification can be changed by adjusting the gas injection pressure. When the gas injection pressure is lowered, the cooling of the molten metal by the gas is reduced, so that the rapid solidification rate is reduced. On the other hand, when the gas injection pressure is increased, the cooling of the molten metal by the gas increases, so that the rapid solidification speed increases.

  In the disk atomization method, a raw material having a predetermined composition is placed in a quartz crucible having pores at the bottom, heated and melted in a high-frequency induction melting furnace in an Ar gas atmosphere, and then in an Ar gas atmosphere, 40000 to 60000 r. p. m. The hot water was discharged onto a rotating disk of No. 1 and rapidly solidified to obtain a disk atomized fine powder.

  In order to evaluate the atomized alloy powder produced by the gas atomizing method, the disk atomizing method, etc., the electric conductivity of the atomized alloy powder was measured using a 4-terminal sample holder for powder impedance measurement manufactured by Toyo Technica.

  The atomized alloy powder used for electrical conductivity measurement is aligned to a particle size of 45 μm or less using a sieve, then filled into a cylindrical sample holder having a diameter of 25 mm and a height of 10 mm, and then 4 Newton meters from the top and bottom in the height direction. The load of was applied.

  For electrical conductivity measurement, a positive terminal of current I and a positive terminal of voltage V are attached in the load direction, a negative terminal of current I and a negative terminal of voltage V are attached in the lower direction of load, and the voltage is measured by flowing current. A four probe method was used.

Table 1 represents Examples 1 to 12 in the present invention, and Table 2 represents Comparative Examples 1 to 24. As these characteristics, Ag with respect to the filler material is 1% by mass or more and 30% by mass or less, the ratio X is 1.2 or more, the abundance ratio Y of the AgCu phase as the filler material is 10% or more, and about the same as Ag. A material having an electrical conductivity of 4000 AV ⁻¹ m ⁻¹ is evaluated as A. Evaluation B has an electric conductivity of 3500AV ⁻¹ m ⁻¹ or more, Evaluation C has an electric conductivity of 3500AV ⁻¹ m ⁻¹ or less, and Evaluation D has an Ag of less than 1 mass% or more than 30 mass% with respect to the filler material. The ratio X is less than 1.2 and the abundance Y of the AgCu phase as the filler material corresponds to any of less than 10%. In Tables 1 and 2, electric conductivity is simply described as conductivity. In Table 2, the underline in the ratio X indicates that the value of the ratio X is less than 1.2. The underline of the Ag value in the structure of the filler material indicates less than 1% by mass or more than 30% by mass.

  That is, the best example is evaluation A, the second best example is evaluation B, the third best example is evaluation C, and the fourth best example is evaluation D.

  For example, in Example 12, Ag with respect to the filler material is 30% by mass, the ratio X is 1.2 or more, and the abundance Y is 10% or more. The present invention satisfying such conditions of the present invention and having an electric conductivity of 4140 S / m exhibited the best characteristics.

  Comparative Examples 1 to 24 do not satisfy this condition because the Ag content is less than 1% by mass or greater than 30% by mass, and the ratio X is less than 1.2.

For example, in Comparative Example 4, the Ag content is 20% and the abundance Y is 14%, but the ratio X is not 1.2 or more, and the electrical conductivity is 2210AV ⁻¹ m ⁻¹ . It does not show good characteristics.

In Comparative Example 20, the ratio X is 2.2%, the abundance Y is 22%, and the electrical conductivity is 4070AV ⁻¹ m ⁻¹ , but the Ag relative to the filler material is 90% by mass. The Ag content ratio of 1 to 30% by mass is not satisfied.

  The abundance Y is a TEM in which an AgCu phase having a mass ratio X of Ag with respect to Cu of 1.2 or more is present in the outermost layer (20 nm from the surface to the inside) of one particle, and 20 points are measured at arbitrary points. It is obtained from the image analysis results.

  As described above, in the present invention, as shown in FIG. 2, the AgCu phase 3 having a mass ratio X of Ag with respect to Cu of 1.2 or more is present in the powder outermost layer 2 of the atomized alloy powder 1 shown in FIG. By controlling in this way, it is possible to provide an AgCu-based conductive filler powder that has an electrical conductivity comparable to pure Ag and is an atomized alloy powder that does not require Ag coating.

1 Atomized alloy powder 2 Powder outermost layer (20 nm)
3 AgCu phase with Ag mass ratio X to Cu of 1.2 or more A A Enlarged portion

Claims (2)

It is an atomized alloy powder made of a Cu-Ag alloy with an Ag content of 1 to 30% by mass, for the conductive filler used in the conductive adhesive, and the atomized alloy powder remains atomized, and the mass ratio of Ag to Cu An AgCu-based conductive filler powder characterized by having an AgCu phase with X = (M _Ag / M _Cu ) of 1.2 or more in the outermost layer of the atomized powder.
However, the powder outermost layer refers to a layer of 20 nm from the outermost surface of the powder to the inside.   2. The AgCu-based conductive filler powder according to claim 1, wherein the atomized alloy powder has an AgCu phase having a ratio X of 1.2 or more in 10% or more of a powder outermost layer.

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