KR20210142175A - Silver palladium alloy powder and uses thereof - Google Patents

Abstract

ADVANTAGE OF THE INVENTION According to this invention, AgPd alloy powder excellent in heat resistance even when the Pd content rate is low is provided. In the silver palladium alloy powder mainly composed of an alloy of silver (Ag) and palladium (Pd) disclosed herein, a calcium component is contained in a calcium conversion (Ca: ppm) of 500 to 10000 ppm, Ag in the alloy powder and Pd content when the sum total of 100 mass % is 30 mass % or less.

Description

Silver palladium alloy powder and uses thereof

The present invention relates to a powder material made of an alloy of silver (Ag) and palladium (Pd) and use thereof. This application claims the priority based on Japanese Patent Application No. 2019-066904 for which it applied on March 29, 2019, The whole content of the application is taken in as a reference in this specification.

Silver palladium alloy powder (hereinafter referred to as "AgPd alloy powder") composed of silver and palladium has superior heat resistance compared to Ag powder composed of silver alone, and thus various electronic components (for example, For example, it is used for electrode formation of varistors, piezoelectric ceramics, and other multilayer ceramic capacitors). For example, the following patent document 1 describes the conventional example of AgPd alloy powder used for the internal electrode formation of this kind of electronic component.

Patent Document 1: Japanese Patent Application Laid-Open No. 8-325602 Patent Document 2: Japanese Patent Application Laid-Open No. 10-102107 Patent Document 3: Japanese Patent Application Laid-Open No. 11-80815

By the way, palladium constituting the AgPd alloy powder belongs to the platinum group and is an expensive metal among noble metals. For this reason, as one means for realizing a reduction in the cost of electronic components (varistors, etc.) in which electrodes are formed by AgPd alloy powder, it is requested to lower the Pd content in the AgPd alloy powder to lower the price of the AgPd alloy powder itself. .

However, when the Pd content in the AgPd alloy powder is reduced, for example, when the total of Ag and Pd is 100 mass %, the Pd content (the same is hereinafter) is 30 mass % or less (moreover 20 mass %). Hereinafter, in particular, when the ratio is as low as 10% by mass or less), it is difficult to maintain the heat resistance of the AgPd alloy powder at a desired level.

Here, the present invention was created so as to solve the above problems, and the object thereof is that the Pd content is 30 mass % or less (moreover 20 mass % or less, particularly 10 mass % or less) heat resistance even at a low rate such as 10 mass % or less. It is to provide this excellent AgPd alloy powder. Another object is to provide a paste-like (slurry-like) material in which such AgPd alloy powder is dispersed in a predetermined dispersion medium.

The present inventor paid attention to the calcium compound conventionally used in the process of manufacturing an alloy powder. That is, as described in Patent Documents 1 to 3, conventionally, in the case of manufacturing alloy powders of various metal compositions, calcium carbonate powder is typically added as a calcium component, Heat treatment (ie, alloying treatment) was being performed. Such calcium carbonate can suppress grain growth of the alloy during heat treatment while changing to calcium oxide during the heat treatment. For this reason, alloy powder with a comparatively small particle diameter (average particle diameter) can be obtained.

Then, as described in Patent Documents 1 to 3, after the heat treatment (alloying treatment) is completed, the obtained alloy powder is put in water, calcium oxide is converted into calcium hydroxide, and an acid such as acetic acid or nitric acid is further added to the liquid. After making the water-soluble calcium salt, the calcium component is completely separated and removed from the alloy powder.

The present inventors paid attention to such a calcium component. And, in the course of the alloy powder manufacturing process, which is conventionally used for the above purpose, the calcium component, which has been completely removed by solubilization, is left in the alloy powder at a predetermined concentration, so that the heat resistance of the alloy powder found to be able to improve, and came to complete the present invention.

As a further suitable form, the present inventors further investigated, and obtained a conventional powder material composed of Ag particles and Pd particles, that is, a mixed powder material of Ag powder and Pd powder, or a so-called coprecipitation powder material produced by a wet reduction method. Instead of using as a raw material for alloy powder production, AgPd core-shell particles in which a coating portion made of Pd is formed on the surface of a core particle made of Ag is used as a raw material for alloy powder production, so that even when the Pd content is significantly reduced, the heat resistance of the alloy powder was found to be able to improve, and it was possible to realize further improvement of the effects of the present invention.

In order to solve the above problems, the alloy powder material disclosed herein is an AgPd alloy powder mainly composed of an alloy of silver (Ag) and palladium (Pd),

The calcium component contains 500 to 10000 ppm in terms of calcium (Ca: ppm), and the Pd content when the sum of Ag and Pd in the alloy powder is 100 mass% is 30 mass% or less, characterized in that, It is a silver palladium alloy powder.

Here, "AgPd alloy powder mainly composed of an alloy of Ag and Pd" means that most of the metal particles constituting this powder are AgPd alloys, while non-alloy particles (for example, particles consisting only of Ag or Particles composed of only Pd) are allowed to coexist in a small amount. It is suitable that the particles in an amount exceeding 50 mass% of the total are AgPd alloy particles, the abundance ratio of the AgPd alloy particles is preferably 70 mass% or more, more preferably 80 mass% or more, and 90 mass% or more (e.g. For example, 95 mass % or more) is especially preferable.

As described above, the AgPd alloy powder disclosed herein is not an unavoidable contaminant, but as an intentionally contained component, calcium at a concentration of 500 to 10000 ppm (in terms of Ca) with respect to the whole (total mass) of the alloy powder. It is characterized in that it contains ingredients.

Thereby, according to the AgPd alloy powder disclosed herein, compared with the AgPd alloy powder of the conventional composition ratio, high heat resistance can be implement|achieved. For this reason, while reducing the content (use ratio) of expensive Pd, the conductor, such as an electrode of high reliability, excellent in heat resistance can be formed in various electronic components. Although 500-10000 ppm is suitable for the said calcium component in conversion of Ca, 1000 ppm or more is preferable for a more favorable improvement of heat resistance, and 8000 ppm or less is more preferable from a viewpoint of maintaining high electroconductivity.

In a preferred aspect of the AgPd alloy powder disclosed herein, it is characterized in that _{calcium palladium complex oxide (typically CaPd 3} O _{4 ) is included as the calcium component.}

By allowing such a calcium component to remain in the alloy powder (that is, AgPd alloy particles constituting the alloy powder), higher heat resistance can be realized in spite of the low Pd content.

Further, in another preferred aspect of the AgPd alloy powder disclosed herein, the Pd content when the total of Ag and Pd in the alloy powder is 100% by mass is 10% by mass or less.

By containing the calcium component in an appropriate concentration range, in the AgPd alloy powder of this embodiment, even in an alloy powder material having an extremely low Pd content such as 10 mass% or less, electrodes and other conductors exhibiting suitable heat resistance can be formed On the other hand, from the viewpoint of maintaining suitable heat resistance, the Pd content is preferably 1 mass % or more, and a ratio exceeding 1 mass %, for example, 2 mass % or more, and more preferably 3 mass % or more. If it is a content rate of this grade, cost reduction by reduction of a low-Pd content rate and maintenance of suitable heat resistance can be made compatible well.

In another preferred aspect of the AgPd alloy powder disclosed herein, the number-based average particle diameter (SEM-D ₅₀ ) based on scanning electron microscope (SEM) observation is 1 μm or less.

In the AgPd alloy powder having such a structure, grain growth at the time of manufacture is suppressed by the presence of a calcium component, and although it is an AgPd alloy powder with a comparatively small average particle diameter, high heat resistance can be exhibited by the residual calcium component.

In addition, the present invention provides a conductor paste (that is, for forming a slurry or paste-like conductor film containing any AgPd alloy powder disclosed herein as a component, and further comprising a medium for dispersing the alloy powder) composition) is provided.

According to the conductor paste having such a structure, the high heat-resistance AgPd alloy powder disclosed herein can be suitably supplied to a desired substrate (substrate), and a conductor such as a good electrode with high heat resistance can be converted into the conventional high-content AgPd alloy powder of Pd. It can be formed at a lower price than in the case of employing

FIG. 1 is a diagram showing an X-ray diffraction pattern of AgPd alloy powder according to Sample 4. FIG.
FIG. 2 is a diagram showing an X-ray diffraction pattern of AgPd alloy powder according to Sample 8. FIG.
FIG. 3 is a diagram showing an X-ray diffraction pattern of AgPd alloy powder according to Sample 9. FIG.
FIG. 4 is a diagram showing an X-ray diffraction pattern of AgPd alloy powder according to Sample 15. FIG.
FIG. 5 is a diagram showing an X-ray diffraction pattern of AgPd alloy powder according to Sample 19. FIG.
[Fig. 6] Fig. 6 is an electron microscope (SEM) photograph of the AgPd alloy powder of Sample 14. [Fig.
[Fig. 7] Fig. 7 is an electron microscope (SEM) photograph of AgPd alloy powder of Sample 11. [Fig.
FIG. 8 is an electron microscope (SEM) photograph of AgPd alloy powder of Sample 10. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is described. In addition, matters other than those specifically mentioned in this specification and necessary for carrying out the present invention can be grasped as design matters by those skilled in the art based on the prior art in this field. The present invention can be implemented based on the content disclosed in this specification and common technical knowledge in the field.

In addition, in this specification and a claim, when writing down a predetermined numerical range with A-B (A and B are arbitrary numerical values), it means A or more and B or less. Therefore, the case of exceeding A and below B is included.

The AgPd alloy powder disclosed herein is a powder material that can be characterized by including a predetermined calcium component in an appropriate content ratio (Ca conversion: ppm) in the aggregate of AgPd alloy particles constituting the main body of the powder material, AgPd alloy powder There is no particular limitation on the manufacturing method itself.

For example, AgPd alloy powder can be manufactured by heat-treating the mixed powder obtained by mechanically mixing Ag powder and Pd powder in a predetermined|prescribed mixing ratio in the temperature range which can be alloyed. Alternatively, AgPd alloy powder may be manufactured by generating mixed particles in which Ag and Pd are mixed according to the conventional co-precipitation method, and then heat treatment in an alloyable temperature range.

A particularly suitable approach in the production of AgPd alloy powder is to use AgPd core-shell particles as a raw material for producing the alloy powder. AgPd core-shell particles are particles in which a Pd shell containing Pd as a main constituent element is formed on the surface of an Ag core containing Ag as a main constituent element. In such core-shell particles, since the coated portion of Pd exists on the surface of the Ag core, even when the content of Pd is low, homogeneous alloying of Ag and Pd can be realized. Various conventionally known processes for producing core-shell particles can be employed without particular limitation.

As a method suitable for preparation of the AgPd core-shell particle used for manufacture of the AgPd alloy powder disclosed herein, the preparation method containing the following process is mentioned. in other words,

A step of preparing a first reaction solution containing a silver compound for constituting Ag core particles;

adding a first reducing agent to the first reaction solution and performing a reduction treatment to generate Ag core particles containing silver as a main constituent element in the reaction solution;

preparing a second reaction solution by adding a palladium compound for constituting a Pd shell to the generated dispersion in which the Ag core particles are dispersed; and

a step of forming a Pd shell containing palladium as a main constituent element on the surface of Ag core particles in the reaction solution by adding a second reducing agent to the second reaction solution and performing a reduction treatment;

method that includes

It is particularly suitable here to comprise at least hydroquinone as the first reducing agent. Hydroquinone and/or quinones (for example, o-benzoquinone, p-benzoquinone, naph toquinone, anthraquinone, etc.) adhere, and reduction and precipitation of Pd ions in the subsequent Pd shell formation step is selectively (preferentially) performed on the surface of the Ag core particles. For this reason, according to this preparation method, AgPd core-shell particle|grains can be prepared with a high yield even if it is a very low Pd content rate (for example, Pd content rate is 10 mass % or less). In addition, according to this preparation method, since reduction precipitation of Pd ions is selectively (preferentially) performed on the surface of Ag core particles, Pd precipitation at the contact point between Ag core particles in the Pd shell formation process is suppressed. do. For this reason, AgPd core-shell particles with a small particle diameter (for example, SEM-D ₅₀ of 1 µm or less) and a narrowly controlled particle size distribution can be manufactured by preventing aggregation and necking during Pd shell formation. Hereinafter, such a preparation method is demonstrated in more detail.

As the silver compound and palladium compound, any silver compound or palladium compound capable of forming Ag core particles and a Pd shell by performing a reduction treatment in each reaction solution, and various salts or complexes of silver and palladium can be preferably used. . As the salt, for example, a halide such as a chloride, a bromide, or an iodide, a hydroxide, a sulfide, a sulfate, or a nitrate can be used. Moreover, as a complex, an ammine complex, a cyano complex, a halogeno complex, a hydroxy complex, etc. can be used.

The first reaction solution can be prepared as a solution in which a silver compound is dissolved in an appropriate solvent or a dispersion in which a suitable dispersion medium is dispersed. Here, the solvent (including the case of a dispersion medium. The same applies hereinafter) constituting the reaction solution may be an aqueous solvent or an organic solvent. When preparing the first reaction solution with an aqueous solvent, water or a mixed solution mainly containing water (eg, a mixed solution of water and ethanol) can be used as the solvent. Moreover, when preparing the 1st reducing agent with an organic solvent, alcohols, such as methanol and ethanol, ketones, such as acetone and methyl ketone, or esters, such as ethyl acetate, etc. can be used.

Since content of the silver compound in a reaction liquid may differ according to the objective, it is not specifically limited. As an example, when the solvent is water or other aqueous solvent (eg, a mixed solvent of water and ethanol), it is preferable to prepare the reaction solution so that the molar concentration of the silver compound is about 0.1 M to 3 M. Moreover, when preparing a 1st reaction liquid, various additives can be added other than a silver compound and a solvent. As such an additive, a complexing agent is mentioned, for example. As a complexing agent, aqueous ammonia, potassium cyanide, hydrazine monohydrate, etc. can be used, for example. By adding an appropriate amount of this complexing agent, a complex having Ag as a central metal ion can be easily formed in the reaction solution. Thereby, Ag core particles can be easily deposited by the subsequent reduction treatment.

In addition, what is necessary is just to stir, maintaining temperature conditions within a certain range when preparing a 1st reaction liquid. As temperature conditions at this time, what is necessary is just about 20 degreeC - 60 degreeC (more preferably, 30 degreeC - 50 degreeC). In addition, the rotational speed of stirring should just be about 100 rpm - 1000 rpm (more preferably 300 rpm - 800 rpm, for example, 500 rpm). Ag core particles are produced by reducing the first reaction solution containing the silver compound as described above. This step can be easily carried out by adding a suitable reducing agent (first reducing agent) to the reaction solution containing the silver compound.

By using hydroquinone (C ₆ H ₆ O ₂ ) as the first reducing agent, hydroquinone and/or quinones can be present on the surface of the Ag core particles produced as described above. The first reducing agent may be prepared to contain PVP in addition to hydroquinone. By using a reducing agent including PVP in addition to hydroquinone, Ag core particles having hydroquinone and/or a complex of quinones and PVP on the surface can be efficiently produced. Incidentally, as the first reducing agent, a reducing agent other than hydroquinone and PVP may coexist. For example, you may use together hydrazine compounds, such as hydrazine carbonate, hydrazine, hydrazine monohydrate, and phenyl hydrazine.

The amount of the reducing agent to be added is not particularly limited because it is sufficient to reduce all the silver compounds contained in the first reaction liquid within a predetermined time, and may be appropriately set according to the state of the reaction system. In that case, by appropriately adjusting the concentration of the reducing agent, the particle diameter of the Ag core particles (and furthermore, the particle diameter of the AgPd core shell particles) can be controlled. In general, by increasing the concentration of the reducing agent, the particle diameter of the Ag core particles (and hence the particle diameter of the AgPd core shell particles) can be decreased. Moreover, in the case of a reduction process, it is preferable to add a pH adjuster to the 1st reaction liquid, and to adjust pH to 8 or more, for example, about 9-11. Here, as a pH adjuster, sodium hydroxide (NaOH), aqueous ammonia, and other basic substances can be used, for example.

The reduction processing time can be appropriately set. Although there is no restriction|limiting in particular, For example, 0.5 hour - about 3 hours are preferable.

The collection|recovery of Ag core particle|grains produced|generated by the said reduction process may be the same as before, and there is no restriction|limiting in particular. Preferably, the Ag core particles generated in the reaction solution are precipitated or centrifuged to remove the supernatant. Preferably, it can be recovered as a dispersion of Ag core particles by dispersing the recovered Ag core particles in a suitable dispersion medium after washing for a plurality of times.

Next, the Pd shell and the palladium compound as described above are added to the dispersion of Ag core particles to prepare a second reaction solution. Since content of the palladium compound in this 2nd reaction liquid may differ according to the objective, it is not specifically limited. As an example, the mass ratio of Ag and Pd contained in the second reaction solution: Ag/Pd is 70/30 to 99/1 (eg, Ag/Pd is 80/20 to 97/3, further Ag/Pd is When Pd is about 90/10 to 97/3), a suitable Pd shell can be formed with a high coverage while suppressing the usage-amount of expensive Pd.

In addition, since the solvent (dispersion medium) used for preparation of the 2nd reaction liquid, other additives, preparation process, etc. may be substantially the same as that of the 1st reaction liquid, the overlapping description is abbreviate|omitted. However, since the second reaction liquid can also be said to be a dispersion liquid of Ag core particles, it is preferable from the viewpoint of homogenization of the reaction liquid to perform ultrasonic treatment in addition to the stirring at the time of preparation. For example, ultrasonic homogenization may be performed at a frequency of about 15 kHz to 50 kHz and an output of about 100 W to 500 W.

As the second reducing agent for forming the Pd shell, various compounds capable of achieving a reducing action in the reaction system can be employed. For example, hydrazine compounds such as hydrazine carbonate, hydrazine, hydrazine monohydrate, and phenyl hydrazine are preferable, but are not limited thereto. For example, organic acids such as tartaric acid, citric acid and ascorbic acid and salts thereof (tartaric acid, citric acid) salt, ascorbate, etc.) or sodium borohydride.

The amount of the second reducing agent to be added is sufficient to properly form a Pd shell on the surface of the Ag core particles contained in the second reaction solution within a predetermined time, and may be appropriately set according to the state of the reaction system, There is no particular limitation. After adding the reducing agent, it is preferable to proceed with the reduction reaction while stirring the reaction solution. The reduction processing time can be appropriately set. Although there is no restriction|limiting in particular, For example, 0.25 hour - about 2 hours are preferable.

Next, the generated AgPd core-shell particles are recovered from the second reaction solution. As a method of such collection|recovery, it may be the same as that of the prior art, and there is no restriction|limiting in particular. It may be the same as the aspect which collect|recovers Ag core particle from the 1st reaction liquid mentioned above. For example, AgPd core-shell particles generated in the reaction solution are precipitated or centrifuged to remove the supernatant. Preferably, the AgPd core-shell particles having a low Pd content suitable as a raw material for producing an alloy powder can be obtained by drying and appropriately pulverizing after washing for a plurality of times.

In the AgPd alloy powder disclosed herein, the AgPd mixed powder or powder composed of core-shell particles as described above is prepared as a raw material for producing an alloy powder, and the raw material is mixed with a calcium additive such as calcium carbonate and a suitable liquid medium (typically water); Together, they are put into a suitable wet stirring and dispersing apparatus such as a planetary mill or a bead mill. Then, a suitable stirring and dispersing treatment is preferably performed using ceramic beads such as zirconia.

At this time, there is no restriction|limiting in particular as to the addition amount of calcium additives, such as calcium carbonate, It is sufficient that the amount which can suppress grain growth at the time of subsequent heat processing is ensured. For example, it is preferable to add so that the mass ratio (raw material: calcium additive) of the raw material for alloy powder manufacture and calcium additives, such as calcium carbonate, may be about 1:1-1:5. Then, it is sufficiently stirred and dispersed in the appropriate wet stirring and dispersing apparatus. The degree of stirring and dispersion is not particularly limited, and may be carried out according to the manual of the apparatus to be used.

Thereafter, the raw material (including the calcium additive) in a slurry state in which the particles are dispersed is dried in a temperature range of about 100 to 120°C. Then, the dried raw material powder is heat-treated in a predetermined temperature range to convert the metal particles constituting the raw material powder into AgPd alloy particles. At this time, conventionally, heat treatment is usually performed in a high temperature range of 1200° C. or higher, but in the technique disclosed herein, it is necessary to retain the calcium component, and therefore, it is necessary to carry out the heat treatment in a lower temperature range than in the prior art. Typically, it is 500-1000 degreeC. 600~800℃ is suitable. When the Pd content is relatively low, the heat treatment is performed in a relatively low temperature range accordingly, and when the Pd content is relatively high, the heat treatment is performed in a relatively high temperature range accordingly (see Examples to be described later). Thereby, AgPd alloy powder can be manufactured from raw material powder. In addition, formation of AgPd alloy can be confirmed by the analysis by X-ray diffraction (XRD). Moreover, the presence of a calcium component, for example, calcium palladium complex oxide (CaPd ₃ O ₄ ) can also be confirmed by analysis by X-ray diffraction (XRD).

As the heat treatment time in such a temperature range, the target alloying may be completed and may be appropriately determined according to the average particle diameter and Pd content of the raw material powder. Although it does not specifically limit, About 0.5 hour - about 2 hours is suitable, for example, around 1 hour (about +/-20 minutes) is preferable.

By performing heat treatment in such a relatively low temperature region _{, calcium palladium complex oxide (CaPd 3} O ₄ ) formed by the reaction of calcium oxide (CaO), which is a decomposition product of calcium carbonate, and calcium oxide (CaO), an undecomposed residue of _{calcium carbonate (CaCO 3 )} It is conceivable that calcium components, such as undecomposed residues and a state in which calcium derived from calcium oxide and other compounds are dissolved in an alloy phase, remain in the AgPd alloy powder. The heat resistance of the AgPd alloy powder can be improved by allowing the calcium component, which is water-insoluble in any of these forms, to remain at a predetermined concentration.

After the alloying treatment (heat treatment), the powder to be treated is put into water to convert excess calcium oxide into calcium hydroxide. Then, an acid component such as acetic acid or nitric acid is added to this system to convert calcium hydroxide into a water-soluble calcium salt (calcium acetate, calcium nitrate, etc.) Hereinafter, it is referred to as a "residual calcium component.") Excess calcium can be eluted and separated and removed from the AgPd alloy powder. In addition, the residual calcium component does not all elute by the water washing after the said acid treatment.

The AgPd alloy powder produced by the process as described above has a relatively low Pd content. For this reason, by using this AgPd alloy powder as a material which forms an electrode and other conductor films, it can contribute to the manufacturing cost reduction of the electronic component provided with the said conductor film. In addition, the AgPd alloy powder disclosed herein has excellent heat resistance due to the presence of the residual calcium component, despite the relatively low Pd content. Thereby, the improvement or maintenance of the heat resistance of the electronic component provided with the electrode formed from the AgPd alloy powder disclosed herein and other conductor film|membrane, and manufacturing cost reduction can be realized together.

The AgPd alloy powder disclosed herein may be used as a powder material as it is, but when used for applications such as forming an electrode or other conductive film on an electronic component as described above, by dispersing it in a dispersion medium such as an aqueous solvent or an organic solvent, paste It can be provided as a phase (or slurry phase) composition (conductor paste).

Incidentally, as the dispersion medium for the conductor paste, as in the prior art, any one capable of dispersing the conductive powder material satisfactorily can be used, and those conventionally used for preparing the conductor paste can be used without particular limitation. For example, in addition to water-based solvents such as water or a low-concentration alcohol aqueous solution, organic solvents include petroleum-based hydrocarbons (especially aliphatic hydrocarbons) such as mineral spirits, cellulose-based polymers such as ethyl cellulose, ethylene glycol and diethylene glycol derivatives; One type or a combination of a plurality of high boiling point organic solvents such as toluene, xylene, butyl carbitol (BC) and tapineol can be used.

In addition to the AgPd alloy powder, the conductor paste includes a dispersant, a resin material (for example, an acrylic resin, an epoxy resin, a phenol resin, an alkyd resin, a cellulosic polymer, polyvinyl alcohol, a rosin resin, etc.), a vehicle, a filler, and a glass. Additives, such as a frit, surfactant, an antifoamer, a plasticizer (For example, phthalic acid ester, such as dioctyl phthalate (DOP)), a thickener, antioxidant, a dispersing agent, and a polymerization inhibitor may be contained. About these additives, it is the same as the prior art, and since it does not characterize this invention, detailed description is abbreviate|omitted.

Hereinafter, production examples and performance of the AgPd alloy powder disclosed herein will be described by way of specific test examples, but it is not intended to limit the present invention to those described in these test examples.

<Test Example 1: Preparation of AgPd alloy powder>

(1) Procurement of raw material powder for manufacturing alloy powder:

In this test example, the following two types of raw material powders for alloy powder manufacture were prepared.

Mixed powder consisting of Ag powder and Pd powder:

Commercially available Ag powder (average particle diameter (D ₅₀ ) 1.5 μm, manufactured by Mitsui Kinzoku Kogyo Co., Ltd.) and Pd powder (average particle diameter (D ₅₀ ) 0.3 μm, manufactured by Noritake Co., Ltd.) , Ag/Pd mass ratios of 80/20 and 70/30 were prepared respectively mixed powders.

- Powder consisting of AgPd core-shell particles (hereinafter referred to as "core-shell powder"):

In this test example, AgPd core-shell powders having Ag/Pd mass ratios of 99/1, 97/3, 95/5, and 90/10 were prepared through the process described below, respectively.

15.63 g of silver nitrate (AgNO ₃ : Oura Kikinzoku Kogyo Co., Ltd. product) was dissolved in 150 mL of pure water, 13 mL of 28% aqueous ammonia (Wako Junyaku Kogyo Co., Ltd. product) was added, and stirred with a magnetic stirrer. , A first solution A containing Ag ammine complex, which is a silver compound as a raw material, was prepared.

Next, 5.07 g of hydroquinone (manufactured by Tokyo Kasei Kogyo Co., Ltd.) and 3.00 g of polyvinylpyrrolidone (PVP) K30 (manufactured by Wako Junyaku Kogyo Co., Ltd.) were mixed with alcohol (Amacas Kagaku Sangyo Co., Ltd.) The product was dissolved in 150 mL of industrial alcohol), and 0.18 mL of hydrazine monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred to prepare a first reducing agent.

Then, while stirring the first solution A with a magnetic stirrer (500 rpm), the first reducing agent was added at once, and Ag core particles were produced by the reducing action. Then, after sedimenting for about 1 hour and removing the supernatant, an additional 300 mL of the alcohol was added thereto, followed by stirring, and again for about 1 hour to settle, and the supernatant was removed.

40 mL of the alcohol was added thereto, and the slurry in which the resulting Ag core particles were dispersed was subjected to centrifugation treatment at 6000 rpm for 5 minutes with a commercially available centrifuge, and a washing process of sedimentation and removal of the supernatant was repeated twice. .

Thereafter, 40 mL of the alcohol was changed to 40 mL of a mixed solvent of alcohol:pure water = 1:1 (volume ratio), and the same process was repeated.

Then, pure water was added to the resulting Ag core particle precipitate to prepare an Ag slurry.

To 9 g of Ag slurry A (Ag core particle content: 3.00 g), 50 mL of a Pd complex solution prepared by dissolving diammine dichloropalladium (II) in 0.17% aqueous ammonia (Pd content: adjusted to 0.333 g) was added. , stirred with a magnetic stirrer, further added with 44 mL of pure water, and ultrasonic dispersion treatment for 10 minutes was performed.

Then, 0.85 mL of hydrazine carbonate (manufactured by Otsuka Chemical Co., Ltd.) as a second reducing agent was added while stirring this slurry with a magnetic stirrer, and stirring was continued for about 30 minutes. At this time, about 70 to 80 seconds after the addition of hydrazine carbonate, blackening and foaming of the slurry showing Pd precipitation by reduction of the Pd complex were observed. Then, by XRF analysis of the supernatant, it was confirmed that all of the used Pd complexes were reduced and precipitated.

The slurry in which the AgPd core-shell particles thus obtained was dispersed was allowed to settle for about 1 hour (it settled almost completely within 1 hour), and after removing the supernatant, 40 mL of a mixed solvent of the alcohol:pure water=1:1 (volume ratio) , and centrifugation was performed at 6000 rpm for 10 minutes with a commercially available centrifuge, and a washing process of removing the supernatant was performed twice. Furthermore, 40 mL of the mixed solvent of the said alcohol:pure water = 1:1 (volume ratio) was changed into 40 mL of pure water, and the same washing|cleaning process was repeated.

And, in order to replace the moisture contained in the resulting core shell powder with acetone, 40 mL of acetone was added, dispersion and centrifugation (6000 rpm, 10 minutes) were performed, and the process of removing the supernatant was performed twice. And after vacuum-drying at room temperature for about 1 hour, the core-shell powder whose Ag/Pd mass ratio is 90/10 was prepared by pulverizing with a mortar. Core-shell powders having Ag/Pd mass ratios of 99/1, 97/3 and 95/5 were also prepared by the same process by appropriately changing the amount of Ag core particles and/or the amount of Pd complex to be used.

(2) Addition of calcium carbonate and alloying treatment (heat treatment)

The alloying treatment was performed using each of the above raw material powders (mixed powder, core-shell powder) or using only the Ag powder for comparison.

Specifically, the raw material powder and its twice the amount of calcium carbonate powder are put into a stirring and dispersing device (wet bead mill) so that the mass ratio of the used raw material powder and the calcium carbonate powder is 1:2, and the diameter is further 1 to 5 An appropriate amount of mm zirconia beads and water were added, and the mixture was sufficiently mixed and dispersed.

Then, the obtained mixed slurry is placed in an electric furnace, and the temperature increase time from room temperature is set to about 60 minutes in an atmospheric atmosphere, and the predetermined temperature (heat treatment temperature) after the temperature increase is set to 400°C, 500°C, 550°C, 600°C. , 650 ℃, 700 ℃, 750 ℃, 800 ℃, set to any one of 1000 ℃ (see Table 1 to be described later), at the temperature for 30 minutes or more and within 1 hour (for example, 45 minutes), heat treatment is performed did. At this time, as the AgPd alloying proceeds, a residual calcium component may be formed as will be described later.

After completion of the predetermined heat treatment, the sample is placed in pure water to change excess calcium oxide into calcium hydroxide. Next, acetic acid in a sufficient amount (the amount at which the sample solution pH is 5 or less) is added as an acid component to convert calcium hydroxide into water-soluble calcium acetate. Thereafter, the sample was washed about three times while adding pure water appropriately to remove the water-soluble calcium salt. Then, the samples were dried to prepare metal powders according to Samples 1 to 19 shown in Table 1 below.

The metal powder manufactured in the above test example is a total of 19 types of Samples 1-19 shown in Table 1. According to Table 1, Ag/Pd mass ratio of each sample, raw material powder used, and heat treatment temperature are grasped.

<Test Example 2: Measurement of the amount of residual calcium component (Ca conversion: ppm)>

Next, the amount of the residual calcium component (Ca conversion: ppm) contained in each sample (powder sample) was measured.

Specifically, about 0.3 g of a sample was dissolved in 10 mL of an aqueous solution diluted twice with commercially available concentrated nitric acid (60 mass%), and then water was added to adjust the volume to 100 mL (sample solution: 0.3 g/ 100 mL). This solution was tested on an ICP emission spectrometer, and the calcium concentration (ppm) in the sample was measured. The results are shown in Table 2. The writing position of the amount of Ca in this table corresponds to the position of each sample in Table 1.

As is clear from the results shown in Table 2, it was confirmed that the residual calcium component could be left at a concentration of 500 ppm or more by performing the heat treatment (alloying treatment) in a relatively low temperature region as performed in the present test example. In addition, it was also confirmed that the amount of residual calcium component could be adjusted by appropriately adjusting such heat treatment temperature and treatment time. For example, as is clear from the relative comparison of the amount of Ca with respect to samples 9 to 16 (Table 1) derived from a core-shell powder having an Ag/Pd mass ratio of 90/10, in the case of such a mass ratio, about 500°C to 800°C It can be seen that the heat treatment temperature is suitable for properly generating the residual calcium component. It turns out that if it is a temperature range higher than this (for example, 1000 degreeC or more), once produced|generated calcium component (for example, CaPd ₃ O ₄ ) thermally decomposes at high temperature, and cannot remain. On the other hand, when the temperature range is less than 500°C (for example, 400°C or less), the temperature is too low, indicating that the residual calcium component is not produced.

<Test Example 3: Evaluation of heat resistance>

Next, the heat resistance of each sample (powder sample) was evaluated using a Thermomechanical Analysis (TMA). That is, a test piece press-formed into a predetermined shape suitable for the analysis apparatus is set in the test chamber of the analysis apparatus, and the analysis apparatus is tested in a temperature range from 30°C to 950°C (temperature increase rate: 10°C/min). The amount of change in the length of the test piece in the axial direction (that is, the Z-axis direction) of the inspection probe disposed in the chamber was calculated. The results are shown in Table 3. In this test example, when the length of the test piece in the Z-axis direction at 30°C is 100%, the length of the test piece in the same direction when the temperature is raised to 600°C is 90% or more as good heat resistance (circle in the table), , Conversely, the thing less than 90 % was made into heat resistance defect (Х in a table|surface).

As is clear from the results shown in Table 3, all of samples 4, 8, 10-15, and 17-19 having a residual calcium component of 500 ppm or more in terms of Ca had good heat resistance (circle). On the other hand, all of samples 1 to 3, 5 to 7, 9, and 16 in which the residual calcium component was less than 500 ppm in terms of Ca had poor heat resistance (Х).

This is because the residual calcium component is within a predetermined range (500 to 10000 rpm, more preferably from 1000 to 8000 ppm). It has shown that high heat resistance can be implement|achieved.

<Test Example 4: Confirmation of AgPd alloy and residual calcium component based on X-ray diffraction>

Next, the following five samples (see Figure 1):

・Sample 4 (Ag/Pd mass ratio: 97/3, heat treatment temperature: 550°C)

Sample 8 (Ag/Pd mass ratio: 95/5, heat treatment temperature: 650°C)

Sample 9 (Ag/Pd mass ratio: 90/10, heat treatment temperature: 1000°C)

・Sample 15 (Ag/Pd mass ratio: 90/10, heat treatment temperature: 500°C)

・Sample 19 (Ag/Pd mass ratio: 70/30, heat treatment temperature: 1000°C)

, X-ray diffraction (XRD) analysis was performed using a powder X-ray diffraction apparatus (manufactured by Rigaku Co., Ltd., RINT-TTRIII). The measurement conditions are as follows.

Excitation X-ray: CuKα ray, accelerating voltage 50 kV, current 50 mA

Measuring range: 5°≤2θ≤60°

Scan speed: 5°/min

Measurement temperature: room temperature

The results are shown in Fig. 1 (Sample 4), Fig. 2 (Sample 8), Fig. 3 (Sample 9), Fig. 4 (Sample 15), and Fig. 5 (Sample 19), respectively. (A) in each figure is an XRD pattern obtained for each sample, (B) shows the peak position of Ag, (C) shows the peak position of Pd, (D) is CaPd _{3 which is a typical example of residual calcium component} The peak position of O ₄ is shown, and (E) shows the peak position of palladium oxide (PdO).

As is clear from these figures (XRD charts), it was recognized that each sample was an AgPd alloy powder in which an AgPd alloy was produced from the shift of the Ag peak position and the disappearance of the Pd peak.

On the other hand, in the XRD patterns of FIGS. 1 (Sample 4), FIG. 2 (Sample 8), FIG. 4 (Sample 15), and FIG. 5 (Sample 19), _{the peak of CaPd 3} O ₄ is determined in FIG. 3 (Sample 9) is not judged in This shows that, among the manufactured AgPd alloy powders, _{high heat resistance when CaPd 3} O ₄ , which is a typical example of a residual calcium component, is present at the material level. In addition, although the detailed XRD pattern is not shown, it was the same result also about the other sample.

<Test Example 5: Determination of _{SEM-D 50} based on SEM observation of each sample>

Next, the following three samples (see Figure 1):

・Sample 14 (Ag/Pd mass ratio: 90/10, heat treatment temperature: 600°C)

Sample 11 (Ag/Pd mass ratio: 90/10, heat treatment temperature: 750°C)

・Sample 10 (Ag/Pd mass ratio: 90/10, heat treatment temperature: 800°C)

, observation with a scanning electron microscope (SEM) is performed, the particle size distribution (number basis) based on the circle equivalent diameter of 100 particles is obtained, and the cumulative 50% particle size is averaged. It had a particle size (SEM-D _50). 6, 7, and 8 are SEM photographs of Sample 14, Sample 11, and Sample 10, respectively. As it is clear from these figures, Sample 14, 11 and 10 of the SEM-D ₅₀ obtained in this test example is, were all less than 1μm.

In the technique disclosed herein, since the heat treatment is performed in a relatively low temperature range, it is possible to provide AgPd alloy powder having a relatively small particle diameter (particle size distribution). For this reason, it is advantageous for forming a finer electrode and other conductor film in an electronic component. Moreover, since heat resistance is also comparatively high, a high-quality conductor film can be formed in an electronic component.

As mentioned above, although the specific example of this invention was demonstrated in detail based on a test example, these are only an illustration and do not limit a claim. The description described in the claims includes various modifications and changes to the specific examples exemplified above. For example, with respect to the conditional phrase indicated by a hyphen (-) in Table 1, although it is not the above test example, it is based on the disclosure information of this specification that the same result is obtained by appropriately setting the heat treatment temperature and heat treatment time for alloying. can be easily grasped.

Claims (5)

As a silver palladium alloy powder mainly composed of an alloy of silver (Ag) and palladium (Pd),
Calcium component is included 500~10000 ppm in terms of calcium (Ca: ppm),
The silver-palladium alloy powder whose Pd content rate is 30 mass % or less when the sum total of Ag and Pd in the said alloy powder is 100 mass %. The method according to claim 1,
As the calcium component, calcium palladium complex oxide (CaPd ₃ O ₄ ) containing, silver palladium powder. The method according to claim 1 or 2,
The silver-palladium alloy powder whose Pd content rate is 10 mass % or less when the sum total of Ag and Pd in the said alloy powder is 100 mass %. 4. The method according to any one of claims 1 to 3,
A scanning electron microscope (SEM) of the mean particle diameter on a number basis, based on the observation (SEM-D ₅₀₎ less than or equal to 1μm, it is palladium alloy powder. The silver palladium alloy powder of any one of claims 1 to 4,
medium for dispersing the powder
A conductor paste comprising a.

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