JP2005190907A - Surface treatment metal powder, conductive paste using same, and printed wiring board and chip components obtained by using conductive paste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide metal powder with which conductive paste doing without a viscosity adjustment as far as possible can be obtained and the conductive paste. <P>SOLUTION: A surface treatment layer that surface treatment metal powder is equipped with on the powder surface is formed of an organic compound having both an acid radical and a base. The organic compound having the both acid radical and base has an acid number within the range of 10(KOHmg/g) to 110(KOHmg/g), and an amine value within the range of 15(KOHmg/g) to 150(KOHmg/g). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface-treated metal powder, a method for producing the surface-treated metal powder, a conductive paste using the metal powder, and a printed wiring board obtained using the conductive paste. Among them, the conductive paste can obtain long-term storage that is not found in conventional conductive pastes, and can effectively suppress a change with time from its initial viscosity.

  Metal powder has long been used as a conductive paste material. Conductive pastes have been used in a wide range of areas, from experimental use to electronics industry applications, due to their ease of handling. In the electronics industry, it has been applied to the formation of printed wiring board circuits using screen printing and the formation of electrical contact portions of various chip components such as multilayer ceramic capacitors, and has been used as a means for ensuring electrical continuity.

  The metal powder has been subjected to a surface treatment for achieving various purposes, and many types have been supplied to the market. For example, Patent Document 1 discloses a surface-treated copper powder surface-treated with oleic acid. In Patent Document 2 and Patent Document 3, an organic layer using a fluorine-based surface treatment agent such as saturated fatty acid such as stearic acid, perfluoroalkyl phosphate ester, perfluoroalkyltrimethylammonium salt is provided on the surface of copper powder. It is a thing. These surface-treated copper powders improve the oxidation resistance performance of the copper powder. If the oxidation resistance is inferior, the conductive paste is thickened in relation to the organic vehicle, which is a binder resin when the conductive paste is manufactured, and circuit formation becomes difficult.

  Further, as disclosed in Patent Document 4, the conductive paste may be used for forming a conductor for ensuring interlayer conduction such as a via hole of a printed wiring board. For today's printed wiring board industry, Japan's electrical industry is exposed to severe international price competition, and cost reduction requirements are becoming more severe. In response to such market trends, in recent years, conductive paste has been used instead of through-hole plating and via-hole forming methods as a means to ensure interlayer conductivity in multilayer printed wiring boards with four or more layers. Thus, a method for ensuring interlayer conduction of multilayer printed wiring boards has been performed.

  For such applications, it has been desired to maintain the paste viscosity in a proper range as much as possible when used as a conductive paste, and to maintain the fillability of via holes in a printed wiring board at a certain level. In order to meet these market requirements, various solution means such as particle size, which is a physical property of the metal powder of the conductive paste, reduction of the specific surface area of the powder, surface treatment with an organic agent on the surface of the powder are adopted, It has been attempted to reduce the viscosity of the conductive paste and ensure long-term quality stability.

Japanese Patent Laid-Open No. 10-330801 JP 2002-332502 A US Pat. No. 5,126,915 JP-A-3-137174

  However, the viscosity control of the conductive paste can be achieved simply by managing the physical properties of the metal powder for conductive paste, such as the reduction of the specific surface area of the powder, the surface treatment with the organic agent on the surface of the powder. However, there was a tendency that the variation from lot to lot was large. Moreover, there has been no product with a small change in paste viscosity over a long period of time.

  In addition, it is natural that the metal powder for conductive paste is required to have a low conductor resistance after the conductor is formed, and the conductor film density is good, and a low-resistance conductor can be formed. There is a need to have both of these properties.

  Furthermore, if a conductive paste is used to form a conductor for ensuring interlayer conduction of a printed wiring board, stricter paste viscosity management is required. The means for ensuring the interlayer conduction of the printed wiring board is as follows: “A hole in which an interlayer conduction portion is formed in a base material in advance, a conductive paste is filled in this hole and cured, and a copper foil is attached to the surface layer. A method of manufacturing a printed wiring board using a stretched laminated board "or" a protrusion formed by curing a conductive paste that constitutes an interlayer conductor is formed on an adhesive surface with a copper foil base material in advance. Various methods have been adopted, such as “interlayer conduction is ensured during the production of a copper-clad laminate by the method of laminating and pasting”. For these technologies, conductive paste is used, and screen printing technology is diverted. Therefore, supply of metal powder that can ensure complete viscosity control and excellent filling property of the conductive paste has been demanded in the market.

  In addition, when forming a conductor of a printed wiring board by processing into a conductive paste, it has also been required to reduce the conductor resistance. A printed wiring board with two or more layers that incorporates interlayer conductors is used in so-called high-end home appliances such as notebook computers, mobile phones, and AV devices. Become. If the resistance of the interlayer conductor increases, the signal transmission speed between the circuits between the layers may be delayed, which may cause a malfunction of a computer device or the like, and may generate extra heat. Therefore, it is required to use metal powder that has not undergone oxidation as much as possible.

  Moreover, in the case of a conductive paste, the viscosity of the conductive paste is characterized by changes over time due to polymerization or decomposition of the paste components, and in this respect, it is said to be a material that is difficult to use. I came. When the viscosity of the conductive paste changes, the viscosity must be adjusted by adding an organic solvent afterwards according to the degree of change. Therefore, when a conductor is formed using a metal powder and a conductive paste that can realize a conductive paste that does not require viscosity adjustment as much as possible, a good film density can be obtained. Metal powders that can be obtained have been desired.

  Thus, as a result of earnest research, the inventors have arrived at the invention described below. The present invention relates to a surface-treated metal powder capable of minimizing changes in paste viscosity with time, particularly when processed into a conductive paste.

<Surface-treated metal powder>
The surface-treated metal powder according to the present invention is most conceptually described as "a metal powder having a surface-treated layer on the particle surface, and the surface-treated layer is an organic having both an acid group and a base. A surface-treated metal powder characterized by being formed using a compound. " That is, the surface treatment layer was formed by putting the metal powder into a solvent containing an organic compound having both an acid group and a base, adsorbing it on the surface of the metal powder particles by stirring for a predetermined time, and drying. Is.

  First, metal powder used as a core material will be described. Copper powder, silver powder, nickel powder, etc. can be used for the metal powder as the core material. This is because it is easy to form a surface treatment layer with an organic compound having both an acid group and a base according to the present invention. In particular, the ability to form a surface treatment film on copper powder and silver powder tends to increase.

  The acid group and base mentioned here will be described. In general, an acid group is used as a term indicating a remaining portion obtained by removing one or more hydrogen atoms capable of replacing a metal from an acid molecule. On the other hand, a base is said to refer to a substance that generates a hydroxide ion by dissociating in an aqueous solution, and neutralizes the acid to generate a salt. However, the concept of the acid group and base in the present invention is not limited to the concept in a narrow sense. As defined by Lewis, the acid group can be an electron acceptor group (Lewis acid group), and the base can be an electron donor. It can be recognized as a group (Lewis base). According to the proton theory, an acid is regarded as a proton donor that tends to release protons to a base, and a base is regarded as a proton acceptor that tends to accept protons from an acid.

Therefore, the acid group and the base in the present invention may be those that meet the above definition, but it is preferable to use an organic compound having at least a group of —COOH, —NH _X , and —CONH. . The metal powder surface-treated with an organic compound having these groups exhibits good oxidation resistance in a wide range of environments. In the conductive paste obtained by mixing the surface-treated metal powder and an organic agent. Also, the effect of preventing deterioration due to oxidation or the like of the surface of the surface-treated metal powder by the organic agent is enhanced. As a result, by using the surface-treated metal powder according to the present invention, it is possible to suppress a change in viscosity over time of the conductive paste.

Here, it will be clarified how much acid groups and bases should be used together. However, the group included in the structural formula when the organic compound is formed may include groups other than the above-described —COOH, —NH _X , and —CONH groups. Therefore, it was decided to specify the acid value and amine value of an organic compound having both an acid group and a base. As a result, an organic compound having both an acid group and a base has an acid value of 10 (KOHmg / g) to 110 (KOHmg / g) and an amine value of 15 (KOHmg / g) to 150 (KOHmg / g). It is preferable to use it. In the range of acid value and amine value listed here, the metal powder particle surface can be uniformly coated best and good oxidation resistance performance can be obtained. This makes it possible to minimize changes with time.

Further, organic compounds having groups of —COOH, —NH _X , and —CONH can be specifically described as: long-chain polyaminoamide salt of polyester acid, amide / amine salt of polyester acid, amine salt of polyester acid, polyether phosphorus Long chain polyaminoamide salt of acid, Amide amine salt of polyether phosphate, Amine salt of polyether phosphate, Long chain polyaminoamide salt of polyether ester acid, Amide amine salt of polyether ester acid, Polyether ester Any one or two or more of acid amine salts are mixed. And it is preferable to use a molecular weight of 30000 or less. More preferably, those having a molecular weight in the range of 500 to 3000 are used.

  As an effect that seems to be caused by the difference in molecular weight of the organic compound, when the molecular weight is in the range of 500 to 3000, the best effect of suppressing the change in paste viscosity with time is obtained. It is thought that if the molecular weight is too large, the surface of the metal powder particles tends not to be uniformly coated. On the other hand, if the molecular weight is too small, it is necessary to increase the treatment amount, and the stability of the paste is impaired. Accordingly, the organic compound has a molecular weight within a certain range depending on the type of the organic compound, but as long as the inventors confirm, it is appropriate to selectively adopt the molecular weight within the range of 30000 or less. It can be judged.

<Method for producing surface-treated metal powder>
In producing the surface-treated metal powder described above, it is not necessary to employ a special production method as the surface treatment method. Rather, it should be noted that a highly dispersible metal powder is obtained during the production of the metal powder as the core material. However, with respect to the method for producing this highly dispersible metal powder, it is possible to apply a conventional production method and have powder characteristics according to the required quality. Therefore, some surface treatment methods will be exemplified and briefly described.

(Surface treatment method 1) Simply speaking, this surface treatment method is a method in which a metal powder and a solvent containing an organic compound having both a predetermined concentration of acid groups and bases are brought into contact with each other for a certain period of time and dried. You get metal powder. At this time, before the metal powder is brought into contact with a solvent containing an organic compound having both an acid group and a base, the surface of the powder is preferably washed with an organic solvent such as alcohol. This is because by performing the cleaning treatment with the organic solvent, it is possible to remove the contamination by the fat and oil components and the like on the surface of the granule and form a uniform surface treatment layer.

  And the organic substance density | concentration of the solvent containing the organic compound which has both an acid group and a base should just employ | adopt the density | concentration range of about 1 g / l-50 g / l. Considering all types of organic compounds used in the present invention, when the concentration of the organic compound is less than 1 g / l, the uniform coverage of the metal powder particle surface is impaired, and the paste after processing into a conductive paste It is difficult to obtain the effect of preventing the increase in viscosity. On the other hand, even if the organic compound concentration exceeds 50 g / l, the effect of preventing the viscosity increase of the paste after being processed into a conductive paste is not improved.

  In addition, it is preferable to use a single solvent such as an alcohol which is an organic solvent, a mixed solvent of alcohols and xylene, or the like as a dispersion solvent of a solvent containing an organic compound having both an acid group and a base. An organic compound having both an acid group and a base is difficult to disperse in water, and uniform coverage on the surface of metal powder particles cannot be ensured unless an organic solvent is used. Accordingly, the solution temperature of the solvent containing an organic compound having both an acid group and a base is preferably in the range of room temperature to about 40 ° C. in consideration of the properties of the dispersion solvent.

  Further, the contact time between the “metal powder” and the “solvent containing an organic compound having both an acid group and a base at a predetermined concentration” is the organic substance concentration of the solvent containing the organic compound having both an acid group and a base, and the solution temperature. However, the contact time of 20 to 40 minutes may be employed while stirring the solution. When the contact time is less than 20 minutes, uniform surface treatment of the metal powder particles becomes impossible under the above conditions. On the other hand, even if the contact time exceeds 40 minutes, surface treatment that is more uniform than that cannot be performed, which results in only inhibiting productivity.

  Then, drying prevents unnecessary oxidation of the surface-treated metal powder, and does not promote thickening when processed into a paste. Etc. are preferably employed.

(Surface treatment method 2) Briefly speaking, a predetermined amount of metal powder is put in a solvent containing an organic compound having both a predetermined concentration of acid groups and bases, and the solvent is heated in that state. By volatilizing and drying, a concentrated state of the organic compound is created to obtain a surface-treated metal powder. Regarding the solution concentration and the like at this time, the above-described concept may be used, and thus a duplicate description is omitted here. However, in this method, since the utilization efficiency of the organic compound having both an acid group and a base in the solvent is increased, it is possible to form a surface treatment layer at a lower concentration than the surface treatment method 1 at the same level.

(Surface Treatment Method 3) This surface treatment method is applicable particularly to coarse particles having an average primary particle size of metal powder particles of 10 μm or more. That is, an organic compound having both an acid group and a base is directly sprayed or dropped onto a metal powder without diluting with a solvent. Although such a method is the simplest method, it tends to be impossible to form a uniform surface treatment layer as the particle becomes finer.

<Conductive paste> The conductive paste manufactured using the surface-treated metal powder according to the present invention described above has a small variation in paste viscosity even when stored for a long period of time, and viscosity management becomes easy. If the surface-treated metal powder according to the present invention is used, the rate of change is within 50% when the paste viscosity after one week is viewed on the basis of the viscosity immediately after processing into a paste. The rate of change referred to here is a value calculated by ([paste viscosity after one week] − [viscosity immediately after processing]) / [viscosity immediately after processing] × 100 (%).

  The conductive paste according to the present invention covers all materials such as terpineol-based conductive paste and epoxy-based conductive paste. The characteristics of the viscosity of the terpineol conductive paste are as follows. When metal powder that has not been subjected to any surface treatment is used, the viscosity immediately after being processed into a conductive paste is the highest, and the viscosity tends to decrease with time. In this way, it is almost impossible to return the viscosity, which decreases with time, to the initial viscosity, as a post hoc adjustment. On the other hand, when the surface-treated metal powder according to the present invention is used, the viscosity immediately after being processed into a conductive paste is the lowest, and the viscosity tends to increase with the passage of time. If a solvent is added, the viscosity is adjusted. Can be easily achieved. Moreover, this level of thickening is very small. Moreover, the characteristic in the viscosity of an epoxy-type conductive paste has the tendency for a viscosity to rise with progress of time even if any metal powder is used, the viscosity immediately after processing into a conductive paste is the lowest. However, the time-dependent change of the conductive paste obtained by mixing the surface-treated metal powder according to the present invention with an epoxy resin is also small. In addition, it is possible to use butyl carbitol acetate, butyl carbitol, ethyl cellulose, acrylic resin, etc. as a viscosity modifier.

<Application range of conductive paste containing surface-treated metal powder according to the present invention>
As described above, the fact that the change with time of the viscosity of the conductive paste is small means that the viscosity of the conductive paste can be easily managed and the quality fluctuation of the conductive paste is small. Among the fields where conductive paste is used, chip components such as printed wiring boards and multilayer ceramic capacitors that require high precision in the thickness, width, circuit edge linearity, etc. of circuits manufactured using conductive paste Is useful.

  By using the surface-treated metal powder according to the present invention, changes with time of the conductive paste can be minimized. Accordingly, the conductive paste can be stored for a long time, and the viscosity of the paste can be easily managed. In addition, since the change in the viscosity of the conductive paste is small, the film density of a circuit or the like manufactured using the conductive paste after a certain time has elapsed after the manufacturing of the conductive paste is also very stable. Hereinafter, in the embodiment, these effects will be shown.

  Hereinafter, the effects of the present invention will be described in detail through comparison with comparative examples through examples. First, the production of copper powder and silver powder used in common in the following examples and comparative examples will be described.

(Manufacture of copper powder used as core material)
Here, copper powder was manufactured by the wet method described below. First, 100 kg of copper sulfate (pentahydrate) was dissolved in warm water to obtain 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.

  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.

  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 having a concentration of 20% by mass was added at a constant rate over 60 minutes, and cuprous oxide was reduced to form a copper powder slurry as copper powder.

Subsequently, the copper powder slurry was filtered, sufficiently washed with pure water, further washed with methanol, and the copper powder was separated by filtration. The average particle diameter _{D 50} of the laser diffraction scattering particle size distribution measurement method of a copper powder 4.6 _{.mu.m, D 90} is 9.0 .mu.m, the tap bulk density (TD) is 4.4 g / cm ^3, specific surface area (SSA ) Was 0.32 m ² / g.

(Method for producing silver powder used as a core material)
First, a silver chelate complex slurry was prepared. Here, 175 g of silver nitrate solution was dissolved in 1750 ml of pure water. On the other hand, 392 g of ethylenediaminetetraacetate was dissolved in 5250 ml of pure water. The silver nitrate solution and the ethylenediaminetetraacetate solution were mixed and stirred to obtain a silver chelate complex slurry. The liquid temperature at this time is room temperature.

  The silver chelate complex slurry was filtered, and the silver chelate complex was once collected by filtration and washed with 350 ml of pure water. This is because the solution at the time of producing the silver chelate complex slurry is not used in the following reduction step. When the pure water washing was completed, 7000 ml of pure water was added to the silver chelate complex to form a reslurry.

  Next, a solution in which 200 g of potassium sulfite was dissolved in 1750 ml of pure water was added to the reslurry, and the solution temperature was maintained at 50 ° C., followed by reduction for 30 minutes to obtain fine silver powder. Thereafter, the produced fine silver powder was collected by filtration, washed with 350 ml of pure water and 175 ml of methanol, and dried to obtain a fine silver powder.

Here silver powder average particle diameter _{D 50} of the laser diffraction scattering particle size distribution measurement method obtained is _{2.78μm, D 90} is 10.3, tap packing density (TD) is 4.2 g / cm ^3, the ratio The surface area (SSA) was 0.35 m ² / g. The average particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method in the present specification, mixed with 0.1% aqueous solution of SN Dispersant 5468 silver powder 0.1 g (manufactured by San Nopco Limited), ultrasonic homogenizer ( After dispersion for 5 minutes using US Seiki Seisakusho (US-300T), a Micro Trac HRA 9320-X100 type (Leeds + Northrup) manufactured as a laser diffraction / scattering particle size distribution measuring apparatus was used.

  In this example, the copper powder is used as a core material, and a surface-treated copper powder is produced using a solvent containing an organic compound having both an acid group and a base. A terpineol-based material is produced using the surface-treated copper powder. Conductive pastes were manufactured, and the rate of change in paste viscosity and film density were compared with conventional products.

  First, the surface treatment process of copper powder will be described. 1 kg of the above-mentioned copper powder is immersed in a solution of 1 g of a high molecular weight polyester acid amine salt (acid value 70 / amine value 140) having a molecular weight of 1000 to 2000 dissolved in 500 ml of methanol for 30 minutes with stirring. The body was separated by filtration and dried in an air atmosphere at 70 ° C. for 5 hours to obtain surface-treated copper powder.

  Subsequently, a terpineol-based conductive paste was produced using this surface-treated copper powder. The terpineol-based conductive paste produced here had a composition of 80 parts by weight of the surface-treated copper powder and 20 parts by weight of the binder, and these were mixed and kneaded for 3 hours to obtain a terpineol-based conductive paste. It is. As the binder at this time, a binder having a composition of 93 parts by mass of terpineol and 7 parts by mass of ethyl cellulose was used.

  Table 1 shows other examples of the viscosity of the terpineol-based conductive paste obtained as described above immediately after production, the viscosity after one week, the rate of change in viscosity based on the viscosity immediately after production, and other film densities. It is described at the same time as the comparative example. 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. The film density is expressed as a film density when a circuit shape is formed on an alumina substrate by a printing method using the conductive paste after a predetermined time has elapsed from manufacture and dried at 80 ° C.

  In this example, the copper powder is used as a core material, and a surface-treated copper powder is produced using a solvent containing an organic compound having both an acid group and a base. A terpineol-based material is produced using the surface-treated copper powder. Conductive pastes were manufactured, and the rate of change in paste viscosity and film density were compared with conventional products. Basically, it is the same as in Example 1, but the type of organic compound having both an acid group and a base is different.

  Therefore, the surface treatment process of the copper powder was carried out in a solution obtained by dissolving 1 g of the above-mentioned copper powder in 1 ml of a high molecular weight polyester acid amide salt (acid value 80 / amine value 20) having a molecular weight of 10,000 to 20,000 in 500 ml of methanol. It was immersed for 30 minutes with stirring, and the powder was filtered off and dried in an air atmosphere at 70 ° C. for 5 hours to obtain a surface-treated copper powder.

  Subsequently, a terpineol-based conductive paste was produced using this surface-treated copper powder. Since the terpineol-based conductive paste produced here is the same as in Example 1, detailed description thereof is omitted. As in Example 1, the viscosity immediately after the production of the terpineol-based conductive paste, the viscosity after one week, the rate of change in viscosity based on the viscosity immediately after the production, and other film densities are shown in Table 1. It is described at the same time as the comparative example.

  In this example, 3 kg of the copper powder used in Example 1 and 1 g of a high molecular weight polyester acid amine salt (acid value 70 / amine value 140) having a molecular weight of 1000 to 2000 were dissolved in 500 ml of methanol using a Henschel mixer. The polymer polyester acid amine salt was concentrated by heating with stirring to perform surface treatment. Then, the powder was separated by filtration and dried in an air atmosphere at 80 ° C. for 3 hours to obtain a surface-treated copper powder.

  Subsequently, a terpineol-based conductive paste was produced using this surface-treated copper powder. Since the terpineol-based conductive paste produced here is the same as in Example 1, detailed description thereof is omitted. As in Example 1, the viscosity immediately after the production of the terpineol-based conductive paste, the viscosity after one week, the rate of change in viscosity based on the viscosity immediately after the production, and other film densities are shown in Table 1. It is described at the same time as the comparative example.

  In this example, instead of the copper powder used in Example 1, 3 kg of the above silver powder and 1 g of a high molecular polyester acid amine salt (acid value 70 / amine value 140) having a molecular weight of 1000 to 2000 were dissolved in 500 ml of methanol. The solution was heated with stirring with a Henschel mixer to concentrate the high-molecular polyester acid amine salt for surface treatment. Then, the powder was separated by filtration and dried in an air atmosphere at 80 ° C. for 3 hours to obtain surface-treated silver powder.

  Subsequently, a terpineol-based conductive paste was produced using this surface-treated silver powder. Since the terpineol-based conductive paste produced here is the same as in Example 1, detailed description thereof is omitted. As in Example 1, the viscosity immediately after the production of the terpineol-based conductive paste, the viscosity after one week, the rate of change in viscosity based on the viscosity immediately after the production, and other film densities are shown in Table 1. It is described at the same time as the comparative example.

Comparative Example 1

  In this comparative example, the copper powder was used without surface treatment to produce a terpineol-based conductive paste, and the rate of change in paste viscosity and film density were compared with those of the examples. Basically, it is the same as in the case of Example 1, and the surface treatment process is omitted.

  As in Example 1, the viscosity immediately after the production of the terpineol-based conductive paste, the viscosity after one week, the rate of change in viscosity based on the viscosity immediately after the production, and other film densities are shown in Table 1. It is described at the same time as the comparative example.

Comparative Example 2

  In this comparative example, the copper powder which processed the oleic acid which is the conventional surface treatment copper powder was manufactured. And it processed into the same terpineol type electrically conductive paste using this copper powder.

  The oleic acid treatment process of the copper powder at this time will be described. 1 kg of the copper powder was put into a 500 ml methanol solution in which 1 g of oleic acid was dissolved, and stirred for 30 minutes. Then, the copper powder and the methanol solution are separated by suction filtration, the separated copper powder is dried at a temperature of 70 ° C. for 5 hours, and a surface treatment layer is formed on the particle surface by oleic acid. Treated copper powder was produced.

  Using this surface-treated copper powder, a terpineol-based conductive paste was produced. Since these manufacturing methods are exactly the same as those described in the first embodiment, a description thereof is omitted here. As in Example 1, the viscosity immediately after the production of the terpineol-based conductive paste, the viscosity after one week, the rate of change in viscosity based on the viscosity immediately after the production, and other film densities are shown in Table 1. It is described at the same time as the comparative example.

Comparative Example 3

  In this comparative example, a terpineol-based conductive paste was produced using the above silver powder without any surface treatment, and the rate of change in paste viscosity and film density were compared with those of the examples. Basically, it is the same as the case where the copper powder of Example 1 is changed to silver powder, and the surface treatment process is omitted.

  As in Example 1, the viscosity immediately after the production of the terpineol-based conductive paste, the viscosity after one week, the rate of change in viscosity based on the viscosity immediately after the production, and other film densities are shown in Table 1. It is described at the same time as the comparative example.

<Contrast with Examples and Comparative Examples> As can be seen from Table 1, the rate of change in paste viscosity (described as “viscosity change rate” in Table 1) in all of Examples 1 to 4 and the above It can be seen that the measured film density is very stable and low. On the other hand, in the case of Comparative Example 1 and Comparative Example 3 where no surface treatment was performed, it can be seen that the film density is small, the viscosity change rate is large, and the viscosity is difficult to adjust. is there. Moreover, in the case of the copper powder processed with the fatty acid of Comparative Example 2, there is no particular problem in the film density, but it can be understood that the paste viscosity is gradually increased and the viscosity adjustment is required.

  By using the surface-treated metal powder according to the present invention, it is possible to minimize changes with time in paste viscosity after processing into a conductive paste. In addition, there is no significant difference in film density between the conductive paste immediately after manufacturing and the circuit formed using the conductive paste after about one week has passed since manufacturing. It becomes. Therefore, it is almost unnecessary to adjust the viscosity of the conductive paste, and the management cost of the paste can be reduced.

  In addition, the fact that the viscosity change is small suggests that there is little change in film density over time, and electric circuits such as circuits obtained using the conductive paste using the surface-treated metal powder according to the present invention are used. It is conceivable that the static resistance value is stabilized, and it becomes possible to provide high quality printed wiring boards and chip parts to the market.

Claims (6)

Metal powder with a surface treatment layer on the surface of the powder,
The surface-treated metal powder, wherein the surface-treated layer is formed using an organic compound having both an acid group and a base. An organic compound having both an acid group and a base is included in an acid value of 10 (KOH mg / g) to 110 (KOH mg / g) and an amine value of 15 (KOH mg / g) to 150 (KOH mg / g). The surface-treated metal powder according to claim 1, which is an organic compound. Organic compounds having both acid groups and bases include polyester acid long chain polyaminoamide salts, polyester acid amide / amine salts, polyester acid amine salts, polyether phosphoric acid long chain polyaminoamide salts, polyether phosphoric acid Any one or two of: amine amide salt, polyether phosphate amine salt, polyether ester acid long chain polyamino amide salt, polyether ester acid amide amine salt, polyether ester acid amine salt The surface-treated metal powder according to claim 1 or 2, which is a mixture of the above. The electroconductive paste manufactured using the surface-treated metal powder in any one of Claims 1-3. A printed wiring board, wherein a conductive circuit is formed using the conductive paste according to claim 3. A chip part, wherein a conductor is formed using the conductive paste according to claim 3.