Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
  • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
  • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
  • B22F1/054—Nanosized particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites

Definitions

• Fine silver powder and method for producing the fine silver powder are produced by Fine silver powder and method for producing the fine silver powder
• the invention according to the present application relates to a fine silver powder and a method for producing the fine silver powder.
• silver powder has been produced by a wet reduction process in which a silver ammine complex aqueous solution is produced from a silver nitrate solution and aqueous ammonia and an organic reducing agent is added thereto, as described in Patent Document 1.
• these silver powders have been mainly used for forming electrodes and circuits of chip components, plasma display panels, and the like.
• Patent Document 1 JP 2001-107101 A
• the electrodes and circuits are required to be significantly finer in the circuits and electrodes to be formed, and are required to have higher densities and higher precision as well as higher reliability. I have.
• the average particle size D of the primary particles of the silver powder obtained by the conventional production method usually exceeds 0.6 m, and the particle size is measured by a laser diffraction scattering particle size distribution method.
• the average particle size D exceeds l.O / z m, and the cohesion degree represented by D ZD exceeds 1.7.
• the fine silver powder according to the present invention will be described.
• the major feature of the fine silver powder according to the present invention is that it has the following powder characteristics a.-c.
• these powder characteristics the characteristics of the fine silver powder according to the present invention most clearly appear among the current powder measurement technologies, and the characteristics that are satisfied at the same time are listed. Hereinafter, each characteristic will be described.
• the characteristic of a Is that the average particle diameter D of the primary particles obtained by image analysis of a scanning electron microscope image is 0.6 m or less.
• image analysis of scanning electron microscope image
• the average particle diameter D of the primary particles obtained by the above is defined by using a scanning electron microscope (SEM).
• Observed images of silver powder are obtained by image analysis. Mean particle size.
• the image analysis of the fine silver powder observed using a scanning electron microscope (SEM) in the present specification was performed using an IP-1000PC manufactured by Asahi Engineering Co., Ltd.
• the circular particle analysis was performed as
• the average particle size D obtained by image processing the observation image of this fine silver powder is obtained directly from the SEM observation image.
• Fine silver powder referred to in the present invention D is almost in the range from 0.01 ⁇ m to 0.6 ⁇ m as observed by the present inventors.
• the fine silver powder according to the present invention has a higher dispersibility than the conventional silver powder, and therefore, "aggregation degree" was used as an index indicating the dispersibility.
• the agglomeration degree referred to in the present specification means the average particle diameter D of the primary particles and the laser diffraction scatter.
• D is the weight obtained using the laser diffraction scattering type particle size distribution measuring method.
• the average particle size is calculated by directly observing the two diameters and treating the aggregated particles as a single particle (agglomerated particles). That is, it is generally considered that the actual silver powder particles are in a state where a plurality of particles are aggregated, unlike the so-called monodispersed powder, in which individual particles are completely separated. As the agglomeration state of the powder particles decreases and approaches monodispersion, the average particle diameter D increases.
• the D of the fine silver powder used in the present invention is in the range of about 0.25 ⁇ ⁇ -0.80 / zm.
• the laser diffraction scattering type particle size distribution measuring method is as follows: 0.1 g of fine silver powder is mixed with ion-exchanged water and dispersed with an ultrasonic homogenizer (US-SOOT manufactured by Nippon Seiki Seisakusho) for 5 minutes. Measured using a laser diffraction scattering type particle size distribution analyzer, Micro Trac HRA 9320-X100 (Leeds + Northrup)
• the "average particle diameter D of primary particles obtained by image analysis of a scanning electron microscope image” refers to an image of a silver powder observed using a scanning electron microscope (SEM).
• the powder is a monodispersed powder having no aggregation state of the powder particles.
• the present inventors have determined the correlation between the degree of agglomeration, the viscosity of the fine silver powder paste produced using the fine silver powder of each degree of agglomeration, and the surface smoothness of a conductor obtained by sintering. I checked it. As a result, it was found that an extremely good correlation was obtained. From this fact, it can be concluded that by controlling the degree of aggregation of the fine silver powder as a component, it is possible to freely control the viscosity of the fine silver powder paste produced using the fine silver powder. Also, if the agglomeration degree is set to 1.5 or less, fluctuations in the viscosity of the fine silver powder paste, surface smoothness after sintering, etc.
• the fine silver powder according to the present invention has the powder characteristics a. To c. Described above, and when the fine silver powder according to the present invention is characterized by the characteristic power of the sintering start temperature, it can be sintered at a low temperature of 240 ° C. or less. This makes it possible to capture it as fine silver powder with binding properties. Although no lower limit is specified for the sintering start temperature, a sintering start temperature lower than 170 ° C can be obtained in consideration of the research conducted by the present inventors and general technical common sense. It is almost impossible, and it is considered to be a temperature corresponding to the lower limit.
• the tap filling density here is determined by precisely weighing 200 g of fine silver powder, placing it in a 150 cm 3 measuring cylinder, tapping repeatedly 1000 times with a stroke of 40 mm, and measuring the volume of fine silver powder! Measured by the method.
• the higher the tap filling density the higher the theoretically fine particle size and the higher the dispersibility without aggregation of the particles, the higher the value obtained.
• the tap filling density of conventional silver powder is less than 4.Og / cm 3
• the fine silver powder according to the present invention is also very fine and has excellent dispersibility. It becomes.
• the production method that is effective in the present invention is that a silver nitrate aqueous solution and ammonia water are mixed and reacted to obtain a silver ammine complex aqueous solution, and this is contacted with an organic reducing agent to reduce and precipitate silver particles.
• the method of producing silver powder by washing and drying is characterized by using an amount of a reducing agent, an amount of silver nitrate, and an amount of aqueous ammonia which become diluted after addition.
• the reducing agent solution and the silver ammine complex aqueous solution are generally mixed together in a tank, and therefore, in general, to increase the silver concentration to lOgZi or more, a large amount of silver nitrate and reducing Unless the amount of the agent and the amount of aqueous ammonia were added, it was impossible to secure the productivity for the scale of the equipment.
• the most important feature of the production method according to the present invention is that the concentration of the organic reducing agent after the contact reaction between the aqueous solution of silver ammine complex and the organic reducing agent is low, and the residual silver adsorbed on the surface of the generated silver powder particles. Or the organic reducing material taken into the inside of the powder during the growth of the powder The point is that it can be reduced. Therefore, it is most preferable to maintain the organic reducing agent concentration at lgZl-3 gZl while the silver concentration of the mixed solution is lgZl-6 gZ1.
• the silver concentration and the reducing agent amount are in a proportional relationship, and it is natural that the higher the silver concentration, the more quantitatively the silver powder can be obtained.
• the silver concentration here exceeds 6 g / l, the precipitated silver particles tend to be coarse and have a particle size that is no different from that of conventional silver powder. This makes it impossible to obtain fine silver powder with good properties.
• the silver concentration here is less than lg / 1, very fine silver powder can be obtained, but it becomes too fine and the oil absorption increases, leading to an increase in paste viscosity. It is necessary to increase the amount of the organic vehicle, which tends to lower the film density of the finally formed sintered conductor and increase the electric resistance. It is not enough to satisfy the required industrial productivity.
• the silver concentration is lgZl-6gZl
• maintaining the organic reducing agent concentration at lgZl-3gZl is the most suitable condition for obtaining the fine silver powder according to the present invention with high yield.
• the concentration of the organic reducing agent is set to lgZl to 13gZl is selected as a range most suitable for obtaining fine silver powder in relation to the silver concentration of the silver ammine complex aqueous solution.
• the concentration of the organic reducing agent exceeds 3 gZl, the amount of the reducing agent added to the aqueous solution of silver ammine complex decreases, but the aggregation of the silver powder particles that are precipitated by reduction begins to become remarkable, and the impurities contained in the powder particles become large.
• the amount (in this specification, the amount of impurities is regarded as the carbon content) begins to increase sharply.
• the organic reducing agent is regarded as the carbon content
• the "organic reducing agent” mentioned here is hydroquinone, ascorbic acid, glucose, or the like. Among them, it is desirable to selectively use hydroquinone as the organic reducing agent.
• hydroquinone has relatively high reactivity compared to other organic reducing agents, and can be said to have the most suitable reaction rate for obtaining low-crystalline silver powder having a small crystallite diameter S. It is.
• additives can be used in combination with the organic reducing agent.
• the additives referred to here are glues such as gelatin, amine-based polymer agents, celluloses, etc., which stabilize the reductive precipitation process of silver powder and simultaneously function as a certain dispersant. Is preferred, and it may be appropriately selected according to the organic reducing agent, the type of the process, and the like.
• a second flow path b that flows through a certain flow path through which S flows (hereinafter referred to as “first flow path”) and joins in the middle of the first flow path a is provided. Flow the organic reducing agent and optional additive S through the first channel a through the second channel b.
• the mixing time of the two liquids is completed in the shortest time, and the reaction proceeds in a uniform state in the system, so that powder particles having a uniform shape are formed.
• the fact that the amount of the organic reducing agent as a whole as a whole after mixing is low means that the amount of the organic reducing agent adsorbed and remaining on the surface of the fine silver powder that is reduced and precipitated is reduced.
• a silver ammine complex aqueous solution is obtained by contacting and reacting an aqueous silver nitrate solution with aqueous ammonia
• a silver nitrate concentration of 2.6 gZl to 48 gZl is used, and a silver concentration of 2 g / 1 to 12 g / It is desirable to obtain an aqueous solution of the silver ammine complex.
• defining the concentration of the silver nitrate aqueous solution is synonymous with defining the liquid volume of the silver nitrate aqueous solution.
• the silver concentration of the silver ammine complex aqueous solution is 2 gZl-12 gZl, there is The concentration and amount of the ammonia water to be added are inevitably determined.
• fine silver powder was manufactured using the above-described manufacturing method, and the powder characteristics of the fine silver powder obtained were measured. Further, a silver paste was produced using fine silver powder, a test circuit was formed, and the conductor resistance and the sintering start temperature were measured.
• this silver ammine complex aqueous solution is introduced into the first flow path a having an inner diameter of 13 mm shown in FIG. 1 at a flow rate of 1500 mlZsec, and the reducing agent is flowed through the second flow path b at a flow rate of 1500 mlZsec, and at the junction point m
• the temperature was brought to a temperature of ° C, and the fine silver powder was reduced and precipitated.
• an aqueous solution of hydroquinone in which 21 g of hydroquinone was dissolved in 10 liters of pure water was used. Therefore, the hydroquinone concentration at the end of the mixing is about 1.04 g / l, which is a very dilute concentration.
• the mixture is filtered using a nutsche, washed with 100 ml of water and 50 ml of methanol, and further dried at 70 ° C for 5 hours. Then, fine silver powder was obtained.
• Fig. 2 shows a scanning electron micrograph of the obtained fine silver powder.
• the powder characteristics of the fine silver powder obtained as described above are listed in Table 1 together with the powder characteristics of the silver powder obtained in Example 2 and Comparative Example. Therefore, here we will explain the ones whose measurement method etc. is unknown in the above explanation.
• the sintering start temperature in Table 1 was determined by precisely weighing 0.5 g of fine silver powder with a balance, pressing it at a pressure of 2 t / cm 2 for 1 minute, Using a TMA ZSS6000, a thermomechanical analyzer (TMA) manufactured by Seiko Instruments, Inc., at an air flow rate of 200 ccZ, a heating rate of 2 ° CZ, and a holding time of 0 min. It was measured in the range up to 900 ° C.
• the conductor resistances listed in Table 1 were obtained by producing silver paste using each silver powder, laying out circuits on a ceramic substrate, and sintering to the extent that resistance could be measured in a temperature range of 180-250 ° C. It was measured using the lmm width circuit provided.
• the composition of the silver paste was 85% by weight of fine silver powder, 0.75% by weight of ethyl cellulose, and 14.25% by weight of terbineol.
• FIB analysis measured the size of the precipitated crystal grains and used it to measure the crystallite diameter.
• the carbon content is used as a measure of the amount of impurities attached to the silver powder particles.
• EMIA-320V manufactured by Horiba
• 0.5 g of fine silver powder, 1.5 g of tungsten powder, and 0 g of tin powder are used. 3 g was mixed, placed in a magnetic crucible, and measured by a combustion infrared absorption method.
• fine silver powder was manufactured under manufacturing conditions different from those in Example 1, and the powder characteristics of the obtained fine silver powder were measured. Further, a silver paste was produced using the fine silver powder, a test circuit was formed, and the conductor resistance and the sintering start temperature were measured.
• this silver ammine complex solution is introduced into the first flow path a having an inner diameter of 13 mm shown in FIG. 1 at a flow rate of 1,500 mlZsec, and the reducing agent is flowed through the second flow path b at a flow rate of 1,500 mlZsec.
• the temperature was brought to a temperature of ° C, and the fine silver powder was reduced and precipitated.
• the reducing agent used at this time was a hydroquinone aqueous solution in which 21 g of hydroquinone was dissolved in 3.4 liters of pure water. Therefore, the concentration of hydroquinone at the end of mixing is about 3. OgZl, a very dilute concentration.
• the fine silver powder was produced by the following production method, and the powder characteristics of the obtained fine silver powder were measured. Further, a silver paste was produced using the fine silver powder, a test circuit was formed, and the conductor resistance and the sintering start temperature were measured.
• fine silver powder was manufactured using the manufacturing method described below, and the powder characteristics of the fine silver powder obtained were measured. Further, a silver paste was produced using the fine silver powder, a test circuit was formed, and the conductor resistance and the sintering start temperature were measured.
• the silver ammine complex solution was put into a reaction vessel, 3 g of gelatin was added to 200 ml of pure water, and hydroquinone as a reducing agent was dissolved in 700 g of pure water.
• the aqueous solution was added all at once, and the silver powder was reduced and precipitated by maintaining the liquid temperature at 20 ° C and stirring and reacting.
• the hydroquinone concentration is approximately 14.5 gZ 1, which is a high concentration.
• the fine silver powder was manufactured using the following manufacturing method, and the powder characteristics of the obtained fine silver powder were measured. Further, a silver paste was produced using the fine silver powder, a test circuit was formed, and the conductor resistance and the sintering start temperature were measured.
• the silver-containing nitric acid-based solution is put into a reaction tank, and the above-mentioned reducing solution is added thereto all at once.
• the liquid temperature is kept at 25 ° C, and the mixture is stirred and reacted, whereby silver powder is reduced and precipitated. I let it.
• the fine silver powder according to the present invention is composed of fine particles that are hardly considered in conventional silver powder, and has a lower force than conventional silver powder in which the degree of aggregation of the powder is low. Even so, it shows very good dispersibility.
• the method for producing fine silver powder according to the present invention by employing the method for producing fine silver powder according to the present invention, the amount of residual organic matter in the fine silver powder obtained is reduced, and the fine silver powder acts in combination with the high film density due to the fine silver powder. This contributes to reducing the electrical resistance of the obtained conductor.
• FIG. 1 is a diagram showing the concept of mixing an aqueous silver ammine complex solution and a reducing agent.
• FIG. 2 is a scanning electron microscope observation image of the fine silver powder according to the present invention.
• FIG. 3 is a scanning electron microscope observation image of the fine silver powder according to the present invention.
• FIG. 5 is a scanning electron microscope observation image of fine silver powder according to a conventional production method.

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• 2003
  • 2003-07-29 JP JP2003281659A patent/JP4489388B2/ja not_active Expired - Lifetime
• 2004
  • 2004-06-28 TW TW093118759A patent/TW200504166A/zh not_active IP Right Cessation
  • 2004-07-15 WO PCT/JP2004/010099 patent/WO2005009651A1/ja active Application Filing
  • 2004-07-15 CA CA002534107A patent/CA2534107A1/en not_active Abandoned
  • 2004-07-15 DE DE112004001399T patent/DE112004001399T5/de not_active Withdrawn
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  • 2004-07-15 US US10/566,365 patent/US20080138238A1/en not_active Abandoned
  • 2004-07-15 KR KR1020067001513A patent/KR101132282B1/ko not_active IP Right Cessation
• 2006
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