JP4530617B2 - Method for producing copper powder for copper paste and copper powder for copper paste obtained by the production method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The invention according to this application isMethod for producing copper powder for copper paste and copper powder for copper paste obtained by the production methodIt is about.
[0002]
[Prior art]
Conventionally, copper powder has been widely used as a raw material for copper paste. Because of its ease of handling, copper paste has been applied to circuit formation of printed wiring boards using a screen printing method, various electrical contact portions, etc., and has been used as a means for ensuring electrical continuity.
[0003]
The copper powder used in this copper paste has been desired to reduce the paste viscosity, facilitate handling as a paste, and improve the fillability of via holes in printed wiring boards. In order to meet these market demands, various solution means such as particle size, which is the physical property of copper powder of copper paste, reduction of specific surface area of powder particles, surface treatment with organic agent on the surface of powder particles, etc. are adopted. Attempts have been made to reduce paste viscosity.
[0004]
And by controlling the physical property with which the copper powder mentioned above is provided, regarding the reduction | decrease in the viscosity of a copper paste, the outstanding effect has been mentioned.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 3-137174
[0006]
[Problems to be solved by the invention]
However, just controlling the physical properties of copper powder for copper paste, such as particle size, reduction of specific surface area of powder particles, and surface treatment with organic agent on the surface of powder particles, complete control of viscosity of copper paste. However, the target viscosity could not be cleared, and there was a tendency that the variation from lot to lot was large.
[0007]
Moreover, it is natural that the copper powder for copper paste is required to have a characteristic that the resistance of the conductor is low when it is used for conductor formation, and it is possible to form a conductor with low resistance. It is necessary to have both.
[0008]
Accordingly, the supply of copper powder that can completely control the viscosity of the copper paste and can ensure excellent filling properties has been demanded in the market. In addition, when forming a conductor by processing into a copper paste, it has also been required to reduce the conductor resistance.
[0009]
[Means for Solving the Problems]
  Therefore, the inventors of the present invention focused on the effect of the degree of aggregation of the copper powder on the viscosity at the time of making a paste, and as a result of earnest research, will be described below.Method for producing copper powder for copper paste and copper powder for copper paste obtained by the production methodI came up with an invention related to this.
[0010]
<Copper powder for copper paste> The copper powder according to the present invention was "surface-treated with a carboxylic acid-containing organic solvent.It is characterized byCopper for copper pasteIn "powder"Yes, its powder characteristics are(1)Average particle diameter D of said copper powder by laser diffraction scattering type particle size distribution measuring method₅₀Is 4.3 μm to 6.9 μm.(2)Average particle diameter D of said copper powder by laser diffraction scattering type particle size distribution measuring method₅₀And average particle diameter D obtained by image analysis_IAAnd D₅₀/ D_IAThe value of the degree of aggregation represented by is 1.2 to 1.7.(3)Specific surface area of the copper powder is 0.17m²/G-0.22m²/ G.(4)Tap filling density is 4.8 g / cm³more than. Is.
[0011]
  First, the copper powder according to the present invention isIt is obtained by a method for producing copper powder for copper paste described later,In order to eliminate the agglomeration state of powder particles found in ordinary copper powder and bring it closer to a monodispersed state, the surface treatment is performed with a carboxylic acid-containing organic solvent, and then the flocculation treatment is performed to adjust the aggregation degree appropriately. is there. The surface treatment of the copper powder with this carboxylic acid-containing organic solvent can effectively reduce the paste viscosity when a metal salt of carboxylic acid is formed on the surface of the copper powder and processed into a copper paste. It becomes. More specifically, the surface oxidation of copper powder over time is effectively achieved by the presence of a surface treatment layer in which adsorbed carboxylic acid and metal salt of carboxylic acid are mixed or a surface treatment layer of only metal salt of carboxylic acid. By preventing this, it is possible to minimize the change in electrical resistance of a conductor formed using the copper paste by processing into a copper paste.
[0012]
  Furthermore, the copper powder for copper paste according to the present invention is:(1)Average particle diameter D of said copper powder by laser diffraction scattering type particle size distribution measuring method₅₀Is 4.3 μm to 6.9 μm.(2)Average particle diameter D of said copper powder by laser diffraction scattering type particle size distribution measuring method₅₀And average particle diameter D obtained by image analysis_IAAnd D₅₀/ D_IAThe value of the degree of aggregation represented by is 1.2 to 1.7.(3)Specific surface area of the copper powder is 0.17m²/G-0.22m²/ G.(4)Tap filling density is 4.8 g / cm³more than. ofIt is desirable to have each characteristic. As will be apparent from the following description of the production method, by subjecting the agglomeration of copper powder particles having an appropriate primary particle size to a pulverization treatment,(1)~(4)Thus, a copper powder satisfying the above powder characteristics can be obtained.
[0013]
  (1)The powder characteristics of the copper powder are the average particle diameter D measured by laser diffraction scattering particle size distribution measurement of the copper powder.₅₀Is 4.3 μm to 6.9 μm. In order to express the average particle size of the copper powder particles, the average particle size obtained using a laser diffraction scattering type particle size distribution measuring method generally used by those skilled in the art is represented by D₅₀Was used. And although this inventor etc. checked the relationship between an average particle diameter and copper paste viscosity carefully, even if there existed a certain level of correlation, it could not be determined that there was a strong correlation. For example, the average particle diameter D on one axis of the XY plane₅₀Taking the viscosity of the copper paste on the other axis side, the average particle diameter D of the copper powder₅₀The correlation coefficient calculated using the least square method was 0.5 or less on average.
[0014]
However, in light of the rule of thumb, the average particle size D₅₀Is less than 4.3 μm, the viscosity increases significantly when processed into a copper paste, resulting in a copper paste that is difficult to handle. At the same time, the conductor formed using the copper paste tends to increase in electrical resistance. On the other hand, considering only from the viewpoint of paste viscosity, the average particle diameter D₅₀There is no particular upper limit to the value of the average particle diameter D, assuming that it is processed into a copper paste using copper powder and filled in the via hole of a printed wiring board having a diameter of 200 μm or less.₅₀If the thickness exceeds 6.9 μm, the filling performance of the copper paste is impaired and filling becomes difficult.
[0015]
  (2)The powder characteristics of the copper powder are the average particle diameter D measured by laser diffraction scattering particle size distribution measurement of the copper powder.₅₀And average particle diameter D obtained by image analysis_IAAnd D₅₀/ D_IAThe value of the degree of aggregation represented by is 1.2 to 1.7. This powder characteristic is considered to have the largest relationship with the viscosity.
[0016]
The inventors have determined that the average particle size D of the copper powder is₅₀Since the correlation between the viscosity of the copper paste and the copper paste was not strong, an index was found that is more correlated than the relationship between the viscosity of the copper paste and the average particle size. As a result, the average particle diameter D obtained using the laser diffraction scattering particle size distribution measurement method₅₀And the average particle diameter D obtained by image analysis of an observation image (observed at a magnification of 1000 times) of the copper powder observed using a scanning electron microscope (SEM)_IAWe focused on the ratio. In addition, as for the image analysis of the copper powder observed using the scanning electron microscope (SEM) in this specification, IPA-1000PC made by Asahi Engineering Co., Ltd. is used. Perform circular particle analysis and average particle size D_IAIs what we asked for.
[0017]
That is, the average particle diameter D obtained using the laser diffraction scattering type particle size distribution measurement method₅₀The value of is considered not to be a direct observation of the diameter of each particle. This is because the powder particles constituting most of the copper powder are not so-called monodispersed powders in which individual particles are completely separated, but a plurality of powder particles are aggregated and aggregated. In the laser diffraction / scattering particle size distribution measurement method, it can be said that the average particle size is calculated by capturing the aggregated particles as one particle (aggregated particles).
[0018]
On the other hand, the average particle diameter D obtained by image-processing the observation image of the copper powder observed using a scanning electron microscope (SEM)_IASince it is obtained directly from the SEM observation image, the primary particles are surely captured, and on the contrary, the existence of the aggregation state of the powder particles is not reflected at all.
[0019]
Therefore, the widely used average particle diameter D₅₀Value or average particle size D_IAUsing the value of, alone and contrasting with the viscosity of the copper paste does not accurately reflect the state of the copper powder used in the manufacture of the copper paste in any case Conceivable.
[0020]
As a result of the above consideration, the present inventors have determined that the average particle size D of the laser diffraction scattering type particle size distribution measurement method is as follows.₅₀And average particle diameter D obtained by image analysis_IAAnd D₅₀/ D_IAThe value calculated in (1) was taken as the degree of aggregation. That is, D in the same lot of copper powder.₅₀And D_IAAssuming that the values can be measured with the same accuracy, and considering the above-mentioned theory, the fact that there is an aggregated state is reflected in the measured values D₅₀The value of D is_IAIt is considered that the value is larger than the value of. At this time, D₅₀The value of D is endlessly enough to eliminate the agglomeration state of copper powder particles._IAD, which is the degree of cohesion₅₀/ D_IAThe value of will approach 1. It can be said that it is a monodispersed powder in which the agglomeration state of the powder is completely lost when the aggregation degree becomes 1.
[0021]
Therefore, the inventors of the present invention examined the correlation between the cohesion degree and the copper paste produced using the copper powder of each cohesion degree. As a result, a very good correlation was obtained. At this time, the correlation coefficient of the correlation line obtained by the method of least squares is 0.7 or more on average, and it can be seen that there is a strong correlation. As can be seen from this, it can be determined that if the degree of aggregation of the copper powder is controlled, the viscosity of the copper paste manufactured using the copper powder can be freely controlled. Moreover, it has been found that if the degree of aggregation is 1.7 or less, the slope of the obtained correlation line is small, and the variation in the viscosity of the copper paste can be accommodated in a very narrow region. If the cohesion value is 1.2, it can be determined that a nearly complete dispersion state is obtained.
[0022]
Further, when the degree of aggregation is actually calculated, a value less than 1 may be indicated. This is the D used to calculate the degree of aggregation_IAIs not a true sphere in theory, but in reality, it is not a true sphere, so a cohesion value of less than 1 is obtained. It is. Based on the idea described above, the value of the degree of aggregation is set to 1.2 to 1.7.
[0023]
This D₅₀/ D_IAWhen the cohesion value represented by the formula (1) is 1.7 or less, the viscosity of the copper paste can be reduced to an unprecedented level if the resin composition of the copper paste is the same. In addition, the more the agglomerated state is resolved, the more it is possible to produce a copper paste using the copper powder and improve the filling property when filling a via hole such as a printed wiring board. As a result, the electrical resistance of the conductor formed can be reduced. Note that the degree of agglomeration of the dried copper powder in the agglomerated state when the pulverization treatment is not performed is normally surely over 1.7, although there are fluctuations due to measurement errors.
[0024]
From the above, the viscosity of the copper paste is considered to change according to the change in the cohesion degree of the copper powder. In the case of the copper powder, the cohesion degree is set to 1.7 or less. It has been found that the variation of the viscosity value in the region is very small.
[0025]
That is, when the cohesion degree of copper powder becomes larger than 1.7, the viscosity of the copper paste changes greatly due to the influence of the change in the cohesion degree of copper powder. Furthermore, as a result of continuing the verification experiment, if the cohesion degree of the copper powder is maintained at 1.7 or less, the variation in the viscosity of the copper paste due to the change in the cohesion degree is reduced, and the average particle diameter of the copper powder is reduced. It has also been found that the effects of changes in the environment can be reduced.
[0026]
  (3)The powder characteristics of the copper powder are 0.17m in specific surface area.²/G-0.22m²/ G. Conventionally, it is one of the powder characteristics of copper powder that has been considered as a factor contributing to lowering the viscosity of the copper paste, and the specific surface area of the powder, if the particle diameter of the powder is similar, This means that the smaller the specific surface area, the smoother the surface of the powder, and the smaller the specific surface area, the lower the viscosity of the copper paste, and the fact is true. It can be said that. In addition, since the affinity between the surface of the copper powder and the resin constituting the copper paste differs depending on the type of the surface treatment agent for the copper powder, it also actually affects the viscosity of the copper paste. Therefore, it can be understood that when the surface of the copper powder is subjected to surface treatment, it must be selectively used in consideration of the compatibility with the resin constituting the copper paste.
[0027]
  Therefore, considering that the present inventors are copper powder used for copper paste,(1)as well as(2)Satisfying the powder characteristics of 0.17m²/G-0.22m²It was determined that controlling to the range of / g was most suitable as copper powder for copper paste. The lower limit of the specific surface area is 0.17 m of the specific surface area of the copper powder even if the above-described pulverization treatment is used.²/ G is difficult to smooth, and is determined as the limit of the manufacturing method employed in the present invention. On the other hand, the specific surface area is 0.22 m²If it exceeds / g, the tendency of thickening of the copper paste due to the increase in specific surface area becomes remarkable.
[0028]
  Furthermore,(4)As for the powder characteristics, the tap filling density is 4.8 g / cm.³That's it. The tap filling density can also be used as an index of filling property when the paste viscosity is increased and copper paste is used to fill a via hole or the like of a printed wiring board. This is because the tap filling density is determined by the relationship between the coagulation of copper powder (that is, the shape of the secondary structure) and the particle size. Therefore, if the above-mentioned powder characteristic conditions are satisfied, the tap packing density is necessarily 4.8 g / cm.³That's it. Conversely, the tap packing density is 4.8 g / cm.³If it is less than 1, the tendency to increase the viscosity when processed into a copper paste becomes remarkable.
[0029]
When a copper paste is produced using the copper powder having the above-mentioned powder characteristics, the viscosity of the copper paste is low, and within the above-mentioned powder characteristic range, a paste viscosity without significant variation can be achieved. . And the average particle diameter D by the laser diffraction scattering type particle size distribution measuring method of the copper powder used for manufacture of copper paste₅₀Is defined for a copper paste intended to fill a via hole of a printed wiring board having a diameter of 200 μm or less, and thus is very suitable for a conductor forming application of a printed wiring board. As a result, a high-quality printed wiring board can be provided by using the copper paste according to the present invention.
[0030]
<The manufacturing method of copper powder> The manufacturing method which concerns on this invention is "MosquitoA method for producing copper powder for copper paste surface-treated with a rubonic acid-containing organic solvent, wherein the copper powder in an aggregated state obtained by a wet method is contacted with a carboxylic acid-containing organic solvent, and surface-treated. Dry the copper powder with a wind circulatorThe air is blown, and the agglomerated copper powder is blown up in a circular orbit and circulated, and the centrifugal force generated at this time causes the powder particles to collide with each other in the airflow, causing the particles to agglomerate. EliminateDisaggregation treatmentI dothingAnd the manufacturing method of the copper powder for copper pastes provided with each powder characteristic of (1)-(4) shown below. (1) Average particle diameter D of said copper powder by laser diffraction scattering type particle size distribution measurement method ₅₀ Is 4.3 μm to 6.9 μm. (2) Average particle diameter D of said copper powder by laser diffraction scattering type particle size distribution measurement method ₅₀ And average particle diameter D obtained by image analysis _IA And D ₅₀ / D _IA The value of the degree of aggregation represented by is 1.2 to 1.7. (3) The specific surface area of the copper powder is 0.17 m ² /G-0.22m ² / G. (4) Tap filling density is 4.8 g / cm ³ more than.Is. Therefore, this production method is characterized in that the surface of the copper powder particles is surface-treated using a carboxylic acid-containing organic solvent, and the pulverization treatment is performed.
[0031]
First, the surface treatment will be described. The copper powder before the pulverization treatment is subjected to a surface treatment with a carboxylic acid-containing organic solvent. The “carboxylic acid-containing organic solvent” referred to here is a solution in which carboxylic acid is dissolved in an organic solvent (a mixture of one or more of ethanol, methanol, acetone, and methyl ethyl ketone). This surface treatment is carried out by bringing the carboxylic acid-containing organic solvent and the copper powder into contact with each other by a method such as mixing and stirring the copper powder in the carboxylic acid-containing organic solvent, so that the carboxylic acid component is added to the powder particle surface of the copper powder. Then, the copper powder is collected by filtration and dried. Further, in this treatment method using carboxylic acid, it is also possible to perform treatment by putting copper powder in an air stream in which carboxylic acid is vaporized. That is, the method of treating with carboxylic acid is not particularly limited as long as the surface of the copper powder can be uniformly treated.
[0032]
As the carboxylic acid referred to here, so-called saturated fatty acids and unsaturated fatty acids can be used. Specific examples of saturated fatty acids that can be used in the present invention are enanthate (C₆H₁₃COOH), caprylic acid (C₇H₁₅COOH), pelargonic acid (C₈H₁₇COOH), capric acid (C₉H₁₉COOH), undecyl acid (C₁₀H₂₁COOH), lauric acid (C₁₁H₂₃COOH), tridecylic acid (C₁₂H₂₅COOH), myristic acid (C₁₃H₂₇COOH), pentadecylic acid (C₁₄H₂₉COOH), palmitic acid (C₁₅H₃₁COOH), heptadecyl acid (C₁₆H₃₃COOH), stearic acid (C₁₇H₃₅COOH), nonadecanoic acid (C₁₈H₃₇COOH), arachidic acid (C₁₉H₃₉COOH), behenic acid (C₂₁H₄₃COOH), or a mixture of two or more.
[0033]
And when specifically listing the types of unsaturated fatty acids that can be used in the present invention, acrylic acid (CH₂= CHCOOH), crotonic acid (CH₃CH = CHCOOH), isocrotonic acid (CH₃CH = CHCOOH), undecylenic acid (CH₂= CH (CH₂)₉COOH), oleic acid (C₁₇H₃₃COOH), elaidic acid (CH₃(CH₂)₇CH = CH (CH₂)₇COOH), cetreic acid (CH₃(CH₂)₉CH = CH (CH₂)₉COOH), brassic acid (C₂₁H₄₁COOH), erucic acid (C₂₁H₄₁COOH), sorbic acid (C₅H₇COOH), linoleic acid (C₁₇H₃₁COOH), linolenic acid (C₁₇H₂₉COOH), arachidonic acid (C₁₃H₃₁COOH), or a mixture of two or more.
[0034]
When the above-described carboxylic acid is used and contacted with copper, which is a component of copper powder, and dried, a surface treatment layer in which adsorbed carboxylic acid and metal salt of carboxylic acid are mixed is formed on the surface of the copper powder particles. When processed into a copper paste, the paste viscosity can be effectively reduced. Moreover, the conductivity of the conductor formed using the copper paste is not impaired. Here, “two or more types” means that a plurality of types of saturated fatty acids and a plurality of types of unsaturated fatty acids listed above may be used in combination.
[0035]
And after performing surface treatment, it is preferable to perform the drying performed by collecting copper powder by filtration under the conditions of a drying temperature of 50 to 100 ° C. and a drying time of 2 to 8 hours. In order to prevent the surface oxidation of the copper powder, it is desirable that the drying temperature be as low as possible. This is because if the drying temperature is less than 50 ° C., the moisture adsorbed on the powder body called copper powder cannot be removed sufficiently, and the carboxylic acid cannot be firmly fixed. On the other hand, if the drying temperature exceeds 100 ° C., the surface treatment layer is likely to be damaged. In this drying temperature range, a heating time corresponding to the heating temperature should also be adopted. Even if the drying is performed at a low temperature for too long, the surface treatment layer is damaged. If the drying time is too short, the removal of the adsorbed moisture of the copper powder becomes incomplete.
[0036]
Here, “the copper powder in an agglomerated state obtained by a wet method” is targeted for the main purpose of use as a copper paste, producing fine powder when viewed as one powder. This is because a certain aggregated state is formed although it is easy to do. The agglomerated state of the copper powder particles can inevitably occur even in a wet method typified by a so-called hydrazine reduction method or a dry method typified by a high-pressure atomizing method. In particular, in the case of the wet method, there is a tendency that formation of an aggregated state of powder particles is likely to occur. That is, in general, the production of copper powder by a wet method is performed by using a copper sulfate solution as a starting material, reacting with a sodium hydroxide solution to obtain copper oxide, and performing so-called hydrazine reduction, washing, It is performed by filtering and drying. In this way, dried copper powder is obtained. And the powder of the copper powder obtained by the wet method in this way exists in a fixed aggregation state.
[0037]
In this specification, separating the agglomerated powder into a single powder is referred to as “pulverization”, and the pulverization operation is referred to as “pulverization treatment”. The pulverization treatment referred to here employs a method of bringing the copper powder in a dry agglomerated state closer to a monodispersed state by causing the powder particles of the copper powder to collide with each other using a wind circulator utilizing centrifugal force. It is preferable.
[0038]
If the purpose is simply pulverization, high energy ball mill, high-speed conductor impingement airflow pulverizer, impact pulverizer, gauge mill, medium agitation mill, high water pressure Various things such as a pulverizer can be used. However, in consideration of reducing the viscosity of the copper paste as much as possible, the specific surface area of the powder is required to be as small as possible as described above. Therefore, even if granulation is possible, it should not be a granulation technique that damages the surface of the granule during granulation and increases its specific surface area.
[0039]
Based on this recognition, the inventors of the present invention conducted extensive research, and as a result, the powder particles of the copper powder were minimized and agglomerated while coming into contact with the inner wall portion of the apparatus, the stirring blade, the grinding media, and the like. A method was adopted in which the powder particles collide with each other and the particle size was sufficiently disintegrated, and at the same time, the surface of the powder particles could be smoothed by the collision of the powder particles. A wind circulator using centrifugal force is used for the pulverization treatment. The term “wind circulator” as used herein refers to a blower of air that blows up the agglomerated copper powder in a circular orbit and circulates it. It is used to perform the pulverization work. At this time, it is also possible to use a commercially available air classifier using centrifugal force. In such a case, it is not intended only for classification, but serves as a circulator that blows up the copper powder agglomerated on the air classifier so as to draw a circular orbit.
[0040]
And the copper paste manufactured using the copper powder according to the present invention is excellent in filling properties such as via holes because the paste viscosity is low, and the paste viscosity is less likely to change over time, so the quality control of the copper paste is easy. Thus, the management cost at the manufacturing site can be reduced and the production efficiency can be expected to increase.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the present invention through an embodiment while comparing with a comparative example.
[0042]
Then, the manufacturing method of the copper powder by the wet method which becomes the content which is common in embodiment and a comparative example first is demonstrated. Here, 100 kg of copper sulfate (pentahydrate) was dissolved in warm water to form a 200 liter solution having a liquid temperature of 60 ° C. And 125 liters of 25 mass% sodium hydroxide aqueous solution was added here, stirring was performed for 1 hour, maintaining liquid temperature at 60 degreeC, and the cupric oxide was produced | generated.
[0043]
When the production of cupric oxide is completed, the liquid temperature is continuously maintained at 60 ° C., and 80 liters of an aqueous glucose solution having a concentration of 450 g / l is added thereto at a constant rate over 20 minutes. Generated. Here, the slurry was once filtered and washed, and then warm water was added to form a 320 liter reslurry.
[0044]
Next, 1.5 kg of aminoacetic acid and 0.7 kg of gum arabic were added to the reslurry and stirred to maintain the solution temperature at 50 ° C. To the reslurry in this state, 50 liters of hydrazine hydrate having a concentration of 20% by mass was added at a constant rate over 60 minutes, and cuprous oxide was reduced to produce a copper powder slurry as copper powder.
[0045]
Subsequently, the copper powder slurry was filtered, washed thoroughly with pure water, filtered to drain, and dried to obtain copper powder. This copper powder is a dried copper powder in an agglomerated state used in the first embodiment. Average particle diameter D of the laser diffraction scattering type particle size distribution measuring method of the copper powder in this aggregated state₅₀Is 5.56, and the average particle diameter D obtained by image analysis is_IAIs 3.18, so D₅₀/ D_IAThe degree of aggregation calculated in (1) was 1.75.
[0046]
Embodiment:  In the present embodiment, a low-aggregation copper powder is produced by pulverization treatment, a copper paste is produced using the copper powder, and the viscosity of the copper paste is measured.
[0047]
5 kg of “dried copper powder in a coagulated state” obtained by the above-described production method is put into Nutsche, and 5 liters of methanol solution dispersed by adding 5 g of oleic acid is added dropwise. A surface treatment layer was formed on the grain surface. Then, the copper powder and the solution were separated by suction filtration and dried at a temperature of 70 ° C. for 5 hours.
[0048]
Then, the surface-treated copper powder is circulated at a rotational speed of 6500 rpm using a commercially available air classifier, a turbo classifier manufactured by Nissin Engineering Co., and the powder particles in an agglomerated state collide with each other. A pulverization treatment was performed.
[0049]
As a result, the average particle diameter D of laser diffraction scattering type particle size distribution measurement method of the obtained copper powder₅₀Is 5.23 μm, average particle diameter D obtained by image analysis_IAIs 4.02 μm, so D₅₀/ D_IAThe agglomeration degree calculated by 1 is 1.30 and the specific surface area is 0.19 m.²/ G, tap filling density is 5.1 g / cm³Met. Average particle diameter D of laser diffraction scattering type particle size distribution measuring method in this specification₅₀Is mixed with 0.1% aqueous solution of SN Dispersant 5468 (manufactured by Sannopco) and dispersed with an ultrasonic homogenizer (US-300T, manufactured by Nippon Seiki Seisakusho) for 5 minutes, followed by laser diffraction scattering. This was carried out using a Micro Trac HRA 9320-X100 model (Leeds + Northrup), which is a particle size distribution analyzer.
[0050]
Next, an epoxy-based copper paste was manufactured using the pulverized copper powder. 85 parts by weight of the copper powder, 3 parts by weight of Epicoat 828 manufactured by Yuka Shell Co., Ltd. for the first epoxy resin, 9 parts by weight of YD-171 manufactured by Tohto Kasei Co., Ltd. for the second epoxy resin, epoxy As a resin curing agent, 3 parts by weight of Ajinomoto MY-24 manufactured by Ajinomoto Co., Inc. was mixed and kneaded for 30 minutes to obtain an epoxy copper paste.
[0051]
When the viscosity immediately after the production of the epoxy-based copper paste obtained as described above was measured, a result of 140 Pa · s was obtained. In addition, the measurement of the viscosity in this specification uses a RE-105U which is a viscometer manufactured by Toki Sangyo Co., Ltd. and measured at a rotation speed of 0.5 rpm.
[0052]
Comparative example:  A viscosity of 1013 Pa · s was obtained when the viscosity immediately after the production of the epoxy-based copper paste produced using the copper powder in an agglomerated state without performing the pulverization treatment was obtained. As is clear from the comparison of the results with the embodiment according to the present invention, the copper powder subjected to the pulverization treatment according to the present embodiment has a low degree of aggregation, and as a result, the viscosity of the copper paste is low. You can see that In addition, if the number of production lots is increased and compared, it becomes clearer. However, when the copper powder according to the present invention is used, the variation in the viscosity of the copper paste becomes very small.
[0053]
【The invention's effect】
The copper powder according to the present invention has very high dispersibility, as can be seen from its particle characteristics, and lowers the viscosity of the copper paste compared to the conventional case of using copper powder in an agglomerated state. It is possible to secure a stable paste quality. Such a low-viscosity copper paste is excellent in filling properties, and is particularly useful in the formation of a conductor such as the inside of a via hole of a printed wiring board, and facilitates the routing of a fine circuit. Therefore, the complexity of paste management at the production site of the printed wiring board is eliminated, the total production cost is reduced, and the product can be supplied with high quality connection reliability.

Claims (5)

A method of manufacturing a copper powder for copper paste surface-treated with Ca carboxylic acid-containing organic solvents,
The copper powder in an agglomerated state obtained by a wet method is contacted with a carboxylic acid-containing organic solvent, surface-treated, dried,
The copper powder is circulated by blowing air using a wind circulator and blowing the agglomerated copper powder in a circular orbit, and the centrifugal force generated at this time causes the particles to interact with each other in the airflow. The copper powder for copper paste is characterized by having the following powder characteristics (1) to (4) by performing a pulverization treatment that causes the particles to collide with each other and eliminate the aggregation state of the particles . Production method.
(1) the copper powder average particle size _{D 50} by laser diffraction scattering particle size distribution measurement method is 4.3Myuemu～6.9Myuemu.
(2) The value of the degree of aggregation represented by D ₅₀ / D _IA using the average particle diameter D ₅₀ by the laser diffraction scattering particle size distribution measurement method of the copper powder and the average particle diameter D _IA obtained by image analysis is 1.2-1.7.
(3) a specific surface area of the copper powder is 0.17m ² /g~0.22m ² / g.
(4) The tap filling density is 4.8 g / cm ³ or more. Carboxylic acid-containing organic solvents are saturated fatty acids such as enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic, arachidic, or using one or more of behenic acid, ethanol, or the organic solvent, methanol, acetone, to claim 1 is obtained by mixing any one or two or more of methyl ethyl ketone The manufacturing method of the copper powder for copper paste of description. Carboxylic acid-containing organic solvents are unsaturated fatty acids such as acrylic acid, crotonic acid, isocrotonic acid, undecylic acid, oleic acid, elaidic acid, cetreic acid, brassylic acid, erucic acid, sorbic acid, linoleic acid, linolenic acid 2. The copper paste according to claim 1, wherein one or more of arachidonic acid is used and mixed with one or more of ethanol, methanol, acetone, and methyl ethyl ketone, which are organic solvents. Copper powder manufacturing method. The method for producing a copper powder for copper paste according to any one of claims 1 to 3 , wherein the drying is performed under conditions of a drying temperature of 50C to 100C and a drying time of 2 to 8 hours. A copper powder for copper paste, which is obtained by the method for producing a copper powder for copper paste according to any one of claims 1 to 4, and which has been surface-treated with a carboxylic acid-containing organic solvent .