JP2010055850A - Conductive powder and method of producing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive powder with excellent dispersibility in paste, from which superior electrical characteristics can be obtained when a resistor is made of the paste, and which is industrially easily usable even from a point of view of cost and supply and is free from lead for a thick film resistor, and to provide a method of producing the conductive powder. <P>SOLUTION: The conductive powder is made of a ruthenium oxide power covered with iridium oxide, the average particle diameter is 20-80 nm, the thickness of an iridium oxide coating film is 0.5-2 nm, and it contains 9-30 mass% of iridium oxide and 0.1-6 mass% of copper for the sum of ruthenium oxide and iridium oxide. This conductive powder is produced by weighing and mixing the ruthenium oxide powder, chloroiridate salt, and copper chloride or copper oxide, or the ruthenium oxide powder containing copper and chloroiridate salt, and then roasting the obtained mixture at 560-640°C in an oxidizing atmosphere. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  When the present invention is a paste for forming a thick film resistor, the dispersibility in the paste is good, and a resistor having excellent electrical characteristics can be formed. The present invention relates to a conductive powder that is easy to use and does not contain lead, and a manufacturing method thereof.

  Thick film resistors are widely used in chip resistors, thick film hybrid ICs, resistor networks, and the like. As a method for manufacturing a thick film resistor, there is usually a process in which a paste in which conductive powder is uniformly dispersed is printed on a conductor circuit pattern or an electrode formed on the surface of an insulating substrate, and this is fired. Used.

The thick film resistor forming paste is manufactured by uniformly dispersing conductive powder and a glass binder in an organic medium called a vehicle. The conductive powder plays the most important role in determining the electrical characteristics of the thick film resistor, and fine powders of ruthenium oxide (RuO ₂ ) and lead ruthenate (Pb ₂ Ru ₂ O ₇ ) are widely used. In addition, ruthenium oxide is used as a wide range of conductive substances in a medium resistance value range from a low resistance range to 1 kΩ, and lead ruthenate is often used in a high resistance range of 10 kΩ or more.

In recent years, it has been required to eliminate the use of toxic lead from electronic equipment, and as a conductive powder for thick film resistors in the high resistance region, conductive powder containing no lead instead of lead ruthenate powder is desired. It is rare. Accordingly, various ruthenium-based oxide powders represented by chemical formulas such as Bi ₂ Ru ₂ O ₇ , CaRuO ₃ , SrRuO ₃ , BaRuO ₃ , LaRuO _{3 and the} like (see, for example, Patent Document 1) as conductive powder not containing lead. Alternatively, iridium oxide (IrO ₂ ) powder (see, for example, Patent Document 2) has been proposed.

  However, no ruthenium-based oxide powder has been put to practical use because the electrical properties of the resistor obtained by printing and baking the paste in a film form are poor. On the other hand, iridium oxide powder has characteristics useful as a conductive powder containing no lead in place of lead ruthenate powder. However, iridium is less produced than ruthenium and its price is unstable, so the price of paste and thick film resistors is likely to fluctuate and the supply is also unstable. There is a problem in industrial use as an alternative material for lead acid powder.

  By the way, about the medium resistance side (10 to 100 kΩ) in the high resistance region in which the lead ruthenate powder is used, the use region of the ruthenium oxide powder conventionally used in the low and middle resistance region is extended to the high resistance side. This is also one of the solutions, and therefore it has been studied to use ruthenium oxide powder in the middle resistance region. However, when ruthenium oxide powder is used in the resistance range of 10 to 100 kΩ, the absolute value of the resistance temperature coefficient (hereinafter referred to as TCR), which is one of the electrical characteristics of the thick film resistor, is greater than 100 ppm / ° C. Could not solve the problem of becoming.

  There is also a method in which ruthenium oxide powder and iridium oxide powder are mixed and used in a resistance range of 10 to 100 kΩ. However, in order to obtain sufficient electrical characteristics, it becomes necessary to contain iridium oxide powder in excess of 50% by mass with respect to the total amount of the mixture, resulting in price fluctuations of the paste and the thick film resistor. The problem could not be satisfied.

JP 2006-069836 A JP 2006-273636 A

  The present invention is suitable as a conductive powder for thick film resistors in view of the above-described problems of the prior art, has good dispersibility in the paste, and is excellent when the paste is baked into a resistor. It is an object to provide a conductive powder that does not contain lead, and a method for manufacturing the same, and can be used industrially in terms of price and supply. .

  In order to achieve the above object, the present inventors have conducted extensive research on the conductive powder of the thick film resistor forming paste and the manufacturing method thereof, and as a result, the ruthenium oxide powder containing copper and coated with iridium oxide. It has been found that a conductive powder consisting of

  In particular, by adjusting the average particle size of the conductive powder, the thickness of the iridium oxide coating film, the iridium oxide content, and the copper content, the dispersibility in the paste is good, and further good electrical properties The present invention has been completed by finding that a resistor having a characteristic can be formed and being industrially easy to use, and repeatedly studying a preferable method for producing the conductive powder.

  That is, the conductive powder provided by the present invention is a conductive powder used in the thick film resistor forming paste, and is composed of ruthenium oxide powder coated with iridium oxide, and has an average particle size of 20 to 80 nm, The thickness of the iridium oxide coating film is 0.5 to 2 nm, and 9 to 30% by mass of iridium oxide and 0.1 to 6% by mass of copper with respect to the total of ruthenium oxide and iridium oxide. Features.

  The present invention also provides a method for producing a conductive powder comprising a ruthenium oxide powder used in a thick film resistor forming paste and coated with iridium oxide. First, in the first production method, ruthenium oxide powder, chloroiridate, and copper chloride or copper oxide are mixed in a proportion of iridium oxide / (ruthenium oxide + iridium oxide) as a percentage of 9 to 30 mass. %, And the mixture ratio of copper is 0.1 to 6% by mass as a percentage of copper / (ruthenium oxide + iridium oxide), and after mixing these, the resulting mixture is oxidative atmosphere It is characterized by roasting at 560 to 640 ° C. and washing the obtained roasted product with water.

  In the first method for producing a conductive powder according to the present invention, the ruthenium oxide powder, chloroiridate and copper chloride or copper oxide are mixed by dissolving chloroiridate in water and oxidizing the resulting aqueous solution. Ruthenium powder and copper chloride or copper oxide can be added and stirred, and the resulting slurry can be dried.

  Moreover, the 2nd manufacturing method of the electroconductive powder in this invention is 9- in the ratio of the iridium compounding ratio of iridium oxide / (ruthenium oxide + iridium oxide), and ruthenium oxide powder containing copper, and iridium chloride. Weigh so that the amount of copper is 30% by mass and the blending ratio of copper is 0.1 to 6% by mass as a percentage of copper / (ruthenium oxide + iridium oxide), and after mixing these, the resulting mixture is oxidized It is characterized by roasting at 560-640 ° C. in a neutral atmosphere and washing the obtained roasted product with water.

  In the second method for producing a conductive powder according to the present invention, the mixing of the ruthenium oxide powder containing copper and chloroiridate is performed by dissolving chloroiridate in water and oxidizing the resulting aqueous solution with copper. The ruthenium powder can be added and stirred, and the resulting slurry can be dried.

  In the second method for producing a conductive powder in the present invention, the ruthenium oxide powder containing copper is obtained by mixing copper oxide or copper chloride with ruthenium hydroxide powder or ruthenium chloride salt, and 500 to 800 in an oxidizing atmosphere. A method of baking at 500 ° C. or 800 ° C. in an oxidizing atmosphere after adding a water-soluble copper compound to a ruthenium chloride aqueous solution and then reducing the resulting ruthenium hydroxide starch Or by mixing either ruthenium hydroxide starch obtained by reducing an aqueous solution of ruthenium chloride with copper oxide or copper chloride and baking at 500 to 800 ° C. in an oxidizing atmosphere. Can be manufactured.

  In the first and second methods for producing conductive powder according to the present invention, the chloroiridate is preferably ammonium hexachloroiridium (IV) and / or potassium hexachloroiridium (IV).

  According to the present invention, it is possible to provide a conductive powder suitable for paste used for the formation of a thick film resistor, particularly a conductive powder not containing lead in a high resistance region in place of lead ruthenate powder, and a method for producing the same. it can. In addition, the conductive powder of the present invention has good dispersibility in the paste, and when the paste is baked to form a resistor, it has excellent electrical characteristics such as an absolute value of TCR of 100 ppm / ° C. or less. Resistors can be formed and are industrially easy to use in terms of price and supply.

  Accordingly, the thick film resistor forming paste using the conductive powder of the present invention is a thick film resistor in a resistance region of 10 to 100 kΩ that does not contain lead, such as a chip resistor, a thick film hybrid IC, and a resistor network. Can be widely used for forming.

  The conductive powder of the present invention is a conductive powder made of ruthenium oxide powder coated with iridium oxide used in a thick film resistor forming paste having excellent electrical characteristics, and has an average particle size of 20 to 80 nm, and The thickness of the iridium oxide coating film is 0.5 to 2 nm. The conductive powder made of ruthenium oxide powder coated with iridium oxide contains 9 to 30% by mass of iridium oxide and 0.1 to 6% by mass of copper with respect to the total of ruthenium oxide and iridium oxide. is doing.

  In the conductive powder of the present invention, it is important that the ruthenium oxide powder has a specific average particle diameter and is coated with iridium oxide having a specific thickness. Thereby, since the ratio of iridium oxide with respect to the sum total of ruthenium oxide and iridium oxide in the conductive powder can be set to 9 to 30% by mass and the amount of iridium used can be suppressed, it becomes industrially easy to use. That is, it is possible to obtain a conductive powder having a large effect of improving electrical characteristics, despite a small iridium content, as compared with a conventional mixed powder of ruthenium oxide powder and iridium oxide powder, or a composite powder having uniform both.

  Specifically, the average particle size of the conductive powder of the present invention is in the range of 20 to 80 nm. Thereby, the dispersibility of the conductive powder in the paste is improved, and a resistor having good electrical characteristics can be formed. When the average particle diameter exceeds 80 nm, when the paste is produced using the conductive powder, the dispersibility in the paste is deteriorated and the electrical characteristics are deteriorated. On the other hand, when the average particle size is less than 20 nm, the conductive powder is strongly aggregated, and on the contrary, the dispersibility in the paste is deteriorated. Here, the average particle diameter of the conductive powder means the average particle diameter calculated from the specific surface area obtained by the BET method.

  The thickness of the iridium oxide coating film of the conductive powder is in the range of 0.5 to 2 nm, and the iridium oxide content is in the range of 9 to 30% by mass with respect to the total of ruthenium oxide and iridium oxide. That is, if the coating film thickness is less than 0.5 nm or the iridium oxide content is less than 9% by mass, the entire surface of the ruthenium oxide powder cannot be completely covered with iridium oxide, and the effect of improving electrical characteristics, particularly TCR, is sufficient. Is not. On the other hand, when the thickness of the coating film exceeds 2 nm or the content of iridium oxide exceeds 30% by mass, not only the improvement in electrical characteristics is no longer greatly increased, but also the amount of iridium used is increased. Therefore, it is not preferable.

  Furthermore, in the conductive powder of the present invention, it is necessary to contain 0.1 to 6% by mass of copper with respect to the total of ruthenium oxide and iridium oxide. In the conductive powder in which the ruthenium oxide powder is simply coated with iridium oxide, the TCR becomes smaller than −100 ppm / ° C., but the TCR can be increased (from negative to positive) by further adding copper. When the copper content is less than 0.1% by mass, the improvement effect of changing the TCR to the plus side is not sufficient. Moreover, when content of copper exceeds 6 mass%, aggregation will become strong at the time of baking of an electroconductive powder manufacturing process, and a desired particle size will no longer be obtained.

  The shape of the particles constituting the conductive powder is not particularly limited. However, in the preparation of the paste, a substantially spherical shape that can be uniformly dispersed in the organic vehicle is preferable. FIG. 1 shows an SEM (scanning electron microscope) photograph of the conductive powder of the present invention. From FIG. 1, it can be seen that the particle shape of the conductive powder is substantially spherical. The control of the particle shape of the conductive powder depends on the particle shape of the ruthenium oxide powder used in the production method. That is, it is preferable to use a spherical ruthenium oxide powder as a raw material as much as possible.

  Next, the manufacturing method of the electrically conductive powder of this invention is demonstrated. First, in the first production method, ruthenium oxide powder, chloroiridate, and copper chloride or copper oxide are weighed and mixed, and the resulting mixture is 560 to 640 ° C. in an oxidizing atmosphere. Roasting and washing the resulting roasted product with water. When the raw materials are weighed, the proportion of iridium is 9 to 30% by mass as a percentage of iridium oxide / (ruthenium oxide + iridium oxide), and the proportion of copper is copper / (ruthenium oxide + iridium oxide). Is weighed so as to be 0.1 to 6% by mass.

  In the second production method, ruthenium oxide powder containing copper and iridium chloride are weighed and mixed, and the resulting mixture is roasted at 560 to 640 ° C. in an oxidizing atmosphere. Then, the obtained roasted product is washed with water. In the above weighing, the iridium compounding ratio is 9 to 30% by mass as a percentage of iridium oxide / (ruthenium oxide + iridium oxide), and the copper compounding ratio is copper / (ruthenium oxide + iridium oxide) percentage. To be 0.1 to 6% by mass.

  According to the first or second manufacturing method, the conductive powder is made of ruthenium oxide powder coated with iridium oxide, the average particle diameter is 20 to 80 nm, and the thickness of the iridium oxide coating film is 0.5. In addition to ˜2 nm, conductive powder containing 9 to 30% by mass of iridium oxide and 0.1 to 6% by mass of copper with respect to the total of ruthenium oxide and iridium oxide is obtained. That is, when the mixing ratio of ruthenium and iridium and the conditions for roasting are out of the specific range described above, the conductive powder having the above-described characteristics cannot be obtained.

  As the ruthenium oxide powder and the ruthenium oxide powder containing copper used in the production method, those which are not strongly aggregated are desirable. That is, when the agglomeration of these ruthenium oxide powders is strong, it is difficult to disperse at the time of mixing, and the particle surface cannot be uniformly coated with iridium oxide. Further, the particle shape of these ruthenium oxide powders is not particularly limited, but is preferably substantially spherical in order to obtain conductive powder that can be easily dispersed uniformly in the organic vehicle in the preparation of the paste.

  As a method for producing the ruthenium oxide powder (not including copper), for example, a commercially available ruthenium hydroxide powder or ruthenium chloride salt is subjected to roasting at a temperature of 500 to 800 ° C. in an oxidizing atmosphere (Method A). ) As another method, an aqueous solution such as ruthenium chloride is reduced with caustic soda to obtain a ruthenium hydroxide starch, and then the ruthenium hydroxide starch is roasted in an oxidizing atmosphere (Method B). ) Can also be used.

  In addition, in the case of the above-mentioned method A, the production of ruthenium oxide powder containing copper is performed by mixing copper oxide or copper chloride with ruthenium hydroxide powder or ruthenium chloride salt and baking at 500 to 800 ° C. in an oxidizing atmosphere. . In the case of the above-mentioned method B, after adding a water-soluble copper compound to an aqueous solution of ruthenium chloride, the ruthenium hydroxide starch obtained by reduction is roasted at 500 to 800 ° C. in an oxidizing atmosphere. Alternatively, copper oxide or copper chloride may be mixed with ruthenium hydroxide starch obtained by reducing an aqueous solution of ruthenium chloride and roasted at 500 to 800 ° C. in an oxidizing atmosphere.

  As the particle size of the ruthenium oxide powder or the ruthenium oxide powder containing copper, the thickness of the coating film is taken into consideration so that the average particle size of the conductive powder obtained by coating with iridium oxide is 20 to 80 nm. select. For example, when the content ratio of iridium oxide is the lower limit of 4% by mass, the coating film is extremely thin, and the average particle size of the conductive powder before and after coating does not substantially change, so the average particle size is about 20 ˜80 nm ruthenium oxide powder may be used. However, when the content ratio of iridium oxide is the upper limit of 0% by mass, the average particle size of the conductive powder after coating increases, so that the increase and the desired average particle size after coating are taken into account. The particle size of the ruthenium oxide powder is selected. In addition, the particle diameter of ruthenium oxide powder used what was measured by SEM observation. This is because the average particle size obtained by the BET method is larger than the actual particle size when the particles are aggregated.

The iridium chloride salt used in the above production method, is not particularly limited, hexachloroiridate (IV) ammonium _{((NH 4) 2 IrCl 6} ) or potassium hexachloroiridate (IV) _(K 2 IrCl ₆ ), Or a mixture thereof. These chloroiridates are preferably powders in a dry state, but may contain water.

  In the first production method, ruthenium oxide powder, iridium chloride and copper chloride or copper oxide are mixed by dissolving iridium chloride in water, and ruthenium oxide powder and copper chloride or oxidation in the resulting aqueous solution. A method in which copper is added and stirred, and the resulting slurry is dried is preferred. In the second production method, when ruthenium oxide powder containing copper and iridium chloride are mixed, ruthenium oxide containing copper produced by the above-described method in an aqueous solution in which chloroiridate is dissolved. The powder may be added and stirred, and the resulting slurry may be dried.

  In the mixture obtained by these methods, iridium chloride and copper chloride or copper oxide are uniformly dispersed on the surface of ruthenium oxide powder or ruthenium oxide powder containing copper. Therefore, through the subsequent roasting step, it is possible to obtain ruthenium oxide powder containing copper and uniformly coated on the entire surface with a homogeneous iridium oxide coating film.

  The concentration of the aqueous solution of chloroiridate is not particularly limited, and a slurry containing iridium in a desired ratio with respect to ruthenium oxide powder or ruthenium oxide powder containing copper is used. Since it is dried later, it is preferable to have a concentration as high as possible. Further, the concentration of the slurry is not particularly limited, but since this slurry is dried later, a slurry having a concentration as high as possible is preferable.

  The method used for the mixing is not particularly limited, and any method that does not change the average particle diameter of the ruthenium oxide powder, that is, a powder that does not have a large pulverizing ability to pulverize the powder particles, such as a mortar, a shaker, etc. The following general mixing apparatus can be used. However, when the iridium chloride particle size is large, it is preferable to crush with a mortar, ball mill or the like before mixing with the ruthenium oxide powder. This improves the uniformity of the coating on the ruthenium oxide powder. Further, although iridium chloride can be pulverized, it can be mixed with ruthenium oxide powder while pulverizing iridium acid salt by using a pulverizing apparatus having a pulverizing ability within a range that does not pulverize ruthenium oxide particles.

  The roasting method used in the above production method is not particularly limited, and it may be roasted using a container having no reactivity with raw materials such as iridium chloride and ruthenium oxide and having heat resistance. . For example, a mixture made of the above raw materials is put in an alumina container, and the container is placed in a general baking apparatus such as a tubular furnace or a muffle furnace, and then roasted by heating at a predetermined temperature. Can do. The roasting atmosphere is not particularly limited as long as it is an oxidizing atmosphere. For example, an atmosphere such as oxygen gas can be used, but an air atmosphere is economical and preferably in an air stream. .

  The roasting temperature in the said manufacturing method shall be the range of 500-800 degreeC. When the roasting temperature is less than 500 ° C., the decomposition and oxidation of the chloroiridate are insufficient. On the other hand, when the roasting temperature exceeds 800 ° C., agglomeration becomes strong and conductive powder with good dispersibility cannot be obtained, and iridium in the iridium oxide coating film and ruthenium in the ruthenium oxide powder diffuse to each other. This is not preferable because a composite oxide powder in which iridium oxide and ruthenium oxide are dissolved is formed.

  The roasting time is appropriately selected according to the thickness of the iridium oxide coating film, the roasting temperature, etc., but sufficient time for the iridium chloride to decompose and produce iridium oxide. It is sufficient if it is 0.5 to 5 minutes. When the iridium oxide coating film is thin or when the baking temperature is high, agglomeration is likely to proceed, and because of the diffusion phenomenon, the form of the powder coated with iridium oxide is not easily obtained, and it becomes easy to obtain a uniform oxide powder. It is necessary to set the roasting time as short as possible. Further, even when the iridium oxide coating film is thick, if it is baked at a high temperature for a long time, aggregation proceeds, which is not preferable.

  As described above, a relatively low temperature and a short time are selected as the roasting conditions, so that the decomposition product of chloroiridate is likely to remain in the roasted product only by roasting. Examples of the decomposition products include potassium chloride, ammonium chloride, chlorine, potassium, and the like, but these decomposition products can be removed by washing with water in a subsequent step.

  Although it does not specifically limit as a water washing | cleaning method used for the said manufacturing method, For example, a roasted material is thrown into water and it stirs using a stirrer or an ultrasonic cleaner. The roasted product after stirring and washing is recovered as conductive powder by filtration. In this water washing step, it is preferable to repeat the operations consisting of charging into water, stirring washing and filtration several times. As water used for washing, water which does not contain an impurity element harmful to conductive powder is preferable, and pure water is particularly preferable. The concentration of the water slurry of the roasted product is not particularly limited and may be selected so that the decomposed product is sufficiently removed.

  The conductive powder collected after the water washing is dried by evaporating moisture. The drying method is not particularly limited. For example, the conductive powder after washing with water is placed on a stainless steel pad, and a commercially available drying apparatus such as an atmospheric oven or a dryer is used. There is a method of heating at a temperature of several hours.

  The conductive powder of the present invention thus obtained can be prepared as a paste for forming a thick film resistor by uniformly dispersing it in an organic vehicle together with a glass binder. A thick film resistor having excellent electrical characteristics can be formed by applying and baking the obtained paste according to a normal method.

As a method for preparing the paste, for example, a method in which conductive powder, a glass binder, and an organic vehicle are mixed and then kneaded and dispersed by a three roll mill or the like is used. Here, the glass binder is selected according to the target part using the paste, the use conditions, etc., and preferably glass frit containing no lead, such as SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , CaO, etc. Including glass frit is used. Further, the organic vehicle can be selected according to the target part using the paste, the use conditions, and the like. For example, an organic vehicle in which an organic binder such as a cellulose resin is dissolved in a solvent such as terpineol is used.

  EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following examples and comparative examples, the evaluation method of the average particle diameter of the ruthenium oxide powder and the average particle diameter of the conductive powder and the evaluation method of the electrical characteristics of the resistor are as follows.

(1) Average particle diameter of ruthenium oxide powder: About the SEM image image | photographed by 100,000 times, the diameter of 200-300 particle | grains was measured and the average was calculated | required.
(2) Average particle size of conductive powder: The specific surface area was determined by a BET 1-point method using a specific surface area measuring device (manufactured by Yuasa Ionics Co., Ltd., Multisorb-16).
(3) Thickness of the coating film of the conductive powder: The iridium oxide weight generated from the iridium weight of the chloroiridate used was calculated and divided by the density to calculate the volume of iridium oxide. Assuming that the coating film was formed on the ruthenium oxide powder, the thickness of the coating film was calculated.
(4) Electrical characteristics of resistor: Area resistance value and noise were measured. The resistance value was measured by a 4-terminal method using a digital multimeter (manufactured by KEITHLEY, Model 2001 Multimeter). The TCR was measured with respect to a temperature change at 125 ° C. and −55 ° C. with a reference temperature of 25 ° C.

[Example 1]
As raw materials, 2.00 g of ruthenium oxide powder having an average particle size of about 50 nm, 0.40 g of ammonium hexachloroiridium (IV) (Sumitomo Metal Mining Co., Ltd., grade: 99.9%), and copper oxide powder ( 0.15 g of Takanan Inorganic Co., Ltd. was weighed. The weight of ammonium hexachloroiridium (IV) is 0.20 g of iridium oxide produced by roasting, and the thickness of the iridium oxide coating film formed on the surface of ruthenium oxide powder is 0.20 g. The weight obtained by calculation so as to be 5 nm.

The content ratio of iridium oxide in the obtained conductive powder is 9% by mass as a percentage of iridium oxide (IrO ₂ ) / (ruthenium oxide (RuO ₂ ) + iridium oxide (IrO ₂ )). Further, the content ratio of copper in the conductive powder is 5.6% by mass as a percentage of copper (Cu) / (ruthenium oxide (RuO ₂ ) + iridium oxide (IrO ₂ )).

  First, ammonium hexachloroiridium (IV) was dissolved in 50 ml of pure water, and ruthenium oxide powder and copper oxide powder were put into it and stirred to form a slurry. This slurry is transferred to an evaporating dish and dried for about 2 hours in a drier set at 120 ° C., and then the resulting dried product is crushed in a mortar to obtain a mixture of ruthenium oxide powder, iridium chloride chloride and copper oxide powder. Obtained.

  This mixture was placed on an alumina dish and baked using a tubular furnace. At the time of this roasting, the atmosphere was made to flow at 3 liters per minute from the start of the temperature rise, and when the temperature on the alumina pan reached 560 ° C., it was held for 3 minutes, then the heating of the furnace was stopped, and the inside of the furnace was left as it was It was cooled with.

  Subsequently, the obtained roasted product was put into 200 ml of pure water, stirred for 10 minutes using an ultrasonic cleaner, and then filtered through a filter paper to collect a powder. After repeating the above operations consisting of charging into pure water, stirring and filtration two more times, the powder was transferred to a stainless steel pad and dried at 90 ° C. for 8 hours in an air dryer to obtain a conductive powder of Sample 1. .

About the obtained electrically conductive powder of the sample 1, the average particle diameter was measured by the above-mentioned method. Also, 1-2 g of the conductive powder of Sample 1 was added to a glass binder (main component: 10 wt% SrO-43 wt% SiO ₂ -16 wt% B ₂ O ₃ -4 wt% Al ₂ O ₃ -20 wt% ZnO. -7 wt% _Na 2 O) and vehicle (main component: by mixing the total 4~6g of the main component) ethylcellulose and terpineol, make a paste. This paste was printed in the form of a film having a size of 1 mm × 1 mm (film thickness: 7 to 9 μm) and baked at 850 ° C. for 30 minutes in an air atmosphere to form a resistor. At this time, the dispersibility in the paste was good. The electrical characteristics (resistance value and TCR) of the resistor (1 mm × 1 mm) of the obtained sample 1 were measured by the above method.

Table 1 below shows the conductive powder design of Sample 1 (the average particle diameter of the RuO ₂ raw material powder and the film thickness of the IrO ₂ coating film), and the composition ratio of IrO ₂ and Cu (both RuO ₂ as the production conditions of the conductive powder) _The ratio to the total of ₂ and IrO ₂ ), and the temperature and time during roasting are shown. In addition, Table 2 below shows the design of the conductive powder in Table 1 above for reference, the average particle diameter of the obtained conductive powder (calculated from the specific surface area), and the resistance formed by the conductive powder. Electrical characteristics (resistance value and TCR) are shown.

[Example 2]
Although it implemented similarly to the said Example 1, as shown in the samples 2-9 of the following Table 1, changing the measured value (mixing ratio) of ammonium hexachloro iridium (IV) and copper oxide, the surface of ruthenium oxide powder The conductive powders of Samples 2 to 9 were produced by changing the thickness of the iridium oxide coating film formed on and the content ratio of iridium oxide and copper in the conductive powder and changing the baking temperature and baking time. .

  About the obtained electrically conductive powder of samples 2-9, while measuring an average particle diameter, the resistor was formed using the paste adjusted similarly to the said Example 1, and the electrical property was evaluated. At this time, the dispersibility in the paste was good. Samples 2 to 9 in Table 2 below show the evaluation results of the electrical characteristics of the obtained resistors.

[Example 3]
Ammonium hexachlororuthenium (IV) (Sumitomo Metal Mining Co., Ltd., grade: 99.9%) 8.05 g, copper chloride hydrate (Wako Pure Chemical Industries, Ltd., reagent) 0.041 g, and 0.2 g of potassium chloride (made by Wako Pure Chemical Industries, Ltd., reagent) is put into 140 ml of pure water, mixed for 10 minutes using an ultrasonic cleaner, and then about 2 hours in a dryer set at 120 ° C. Dried.

  The obtained dried product was crushed with a mortar, placed on an alumina dish, and baked using a tubular furnace. At the time of this roasting, the air was flowed at 3 liters per minute from the start of the temperature elevation, and was kept for 1 hour when the temperature on the alumina dish reached 7000 ° C., and then cooled in the furnace as it was. Next, the obtained roasted product was put into 200 ml of pure water, stirred for 10 minutes using an ultrasonic cleaner, and then filtered to collect powder.

  This operation consisting of addition to pure water, stirring and filtration was repeated twice more, then transferred to a stainless steel pad and dried in an air dryer at 90 ° C. for 8 hours to obtain ruthenium oxide powder containing copper. The average particle size of the ruthenium oxide powder containing copper was about 50 nm as a result of evaluating the particle size by SEM.

  2.00 g of the obtained ruthenium oxide powder containing copper and 1.70 g of ammonium hexachloroiridium (IV) (manufactured by Sumitomo Metal Mining Co., Ltd., grade: 99.9%) were weighed. In addition, the weight value of ammonium hexachloroiridium (IV) is the thickness of the iridium oxide coating film formed on the surface of the ruthenium oxide powder containing copper, and the weight of iridium oxide produced by roasting is 0.8 g. Is a weight obtained by calculation so that the value becomes 2 nm.

The content ratio of iridium oxide in the obtained conductive powder is 30% by mass as a percentage of iridium oxide (IrO ₂ ) / (ruthenium oxide (RuO ₂ ) + iridium oxide (IrO ₂ )). Further, the content ratio of copper in the conductive powder is 0.5% by mass as a percentage of copper (Cu) / (ruthenium oxide (RuO ₂ ) + iridium oxide (IrO ₂ )).

  First, ammonium hexachloroiridium (IV) was dissolved in 120 ml of pure water, into which the ruthenium oxide powder containing copper was added, and stirred to obtain a slurry. This slurry was transferred to an evaporating dish, dried for about 5 hours with a dryer set at 120 ° C., and then crushed with a mortar. This mixture was placed on an alumina dish and baked using a tubular furnace. In this roasting, air was passed at a rate of 3 liters per minute from the start of the temperature rise, and when the temperature on the alumina dish reached 640 ° C., it was held for 1 minute, and then cooled in the furnace as it was.

  Next, the obtained roasted product was put into 200 ml of pure water, stirred for 10 minutes using an ultrasonic cleaner, and then filtered to collect powder. Here, after repeating the operations of adding pure water, stirring, and filtration two more times, it was transferred to a stainless steel pad and dried in an air dryer at 90 ° C. for 8 hours to obtain a conductive powder of Sample 10. It was. Table 1 below shows the design, blending ratio, and roasting conditions of the conductive powder of Sample 10.

  Moreover, while measuring an average particle diameter by the said evaluation method about the electrically conductive powder of the obtained sample 10, the paste was adjusted like the said Example 1, and the electrical characteristic of the resistor formed using the paste Was evaluated. At this time, the dispersibility in the paste was good. The obtained results are also shown in Table 2 below.

[Example 4]
A ruthenium oxide powder containing copper was prepared in the same manner as in Example 3 except that the amount of copper chloride hydrate used was 0.016 g and the copper concentration was lowered. Manufactured. Table 1 below shows the design, blending ratio, and roasting conditions of the conductive powder of Sample 11.

  About the obtained conductive powder of sample 11, while measuring an average particle diameter by the said evaluation method, the paste was adjusted like the said Example 1, and evaluation of the electrical property of the resistor formed using the paste Went. At this time, the dispersibility in the paste was good. The obtained results are also shown in Table 2 below.

[Comparative Example 1]
Except not adding copper oxide powder, it carried out similarly to the said Example 1, and manufactured the electrically conductive powder which does not contain copper. However, in this case, the weighed value of ammonium hexachloroiridium (IV) is 0.80 g, the thickness of the iridium oxide coating film formed on the surface of the ruthenium oxide powder is 1 nm, and the content ratio of iridium oxide in the conductive powder is It was set to 17% by mass. Table 1 below shows the design, blending ratio, and roasting conditions of the conductive powder of Sample 12.

  For the conductive powder of Sample 12 of Comparative Example 1, the average particle diameter was measured by the above evaluation method, and the paste was prepared in the same manner as in Example 1 above, and the electrical characteristics of the resistor formed using the paste Was evaluated. At this time, the dispersibility in the paste was good. The obtained results are also shown in Table 2 below.

[Comparative Example 2]
The weight of ammonium hexachloroiridium (IV) is 1.7 g, the thickness of the iridium oxide coating film formed on the surface of the ruthenium oxide powder is 2 nm, and the content of iridium oxide in the conductive powder is 30% by mass. A conductive powder not containing copper was produced in the same manner as in Comparative Example 1 except that the above was performed and the roasting conditions were 560 ° C. for 4 minutes. Table 1 below shows the design, blending ratio, and roasting conditions of the conductive powder of Sample 13.

  For the conductive powder of Sample 13 of Comparative Example 2, the average particle diameter was measured by the above evaluation method, and the paste was prepared in the same manner as in Example 1 above, and the electrical characteristics of the resistor formed using the paste Was evaluated. At this time, the dispersibility in the paste was good. The obtained results are also shown in Table 2 below.

  From the above results, even in samples 1 to 9 according to the first production method of the present invention using ruthenium oxide powder, iridium chloride, copper chloride or copper oxide as raw materials, ruthenium oxide powder and iridium chloride added with copper as raw materials Even in the samples 10 to 11 according to the second production method of the present invention using an acid salt, a conductive powder is obtained that has excellent electrical characteristics when a thick film resistor is formed as a paste, despite a small iridium content. You can see that

  On the other hand, in Comparative Examples 1 and 2, even though the conductive powder was the surface of the ruthenium oxide powder coated with iridium oxide, since it does not contain copper, the resistance formed using this conductive powder It can be seen that the body has a TCR of less than −100 ppm / ° C. and does not provide satisfactory results in electrical properties.

It is a SEM (scanning electron microscope) photograph showing an example of the conductive powder of the present invention.

Claims (7)

  Conductive powder used for thick film resistor forming paste, which is made of ruthenium oxide powder coated with iridium oxide, has an average particle diameter of 20 to 80 nm, and the thickness of the iridium oxide coated film is 0. A conductive powder comprising 5 to 2 nm and containing 9 to 30% by mass of iridium oxide and 0.1 to 6% by mass of copper with respect to the total of ruthenium oxide and iridium oxide.   A method for producing a conductive powder comprising a ruthenium oxide powder coated with iridium oxide, used in a thick film resistor forming paste, comprising ruthenium oxide powder, iridium chloride, and copper chloride or copper oxide. The blending ratio of iridium is 9 to 30% by mass as a percentage of iridium oxide / (ruthenium oxide + iridium oxide), and the blending ratio of copper is 0.1 to 6 mass as a percentage of copper / (ruthenium oxide + iridium oxide). %, And after mixing these, the obtained mixture is roasted at 560 to 640 ° C. in an oxidizing atmosphere, and the obtained roasted product is washed with water. Manufacturing method.   The ruthenium oxide powder, iridium chloride and copper chloride or copper oxide are mixed by dissolving the iridium chloride in water, adding the ruthenium oxide powder and copper chloride or copper oxide to the resulting aqueous solution, and stirring. The method for producing a conductive powder according to claim 2, wherein the obtained slurry is dried.   A method for producing a conductive powder comprising a ruthenium oxide powder coated with iridium oxide, which is used in a thick film resistor forming paste, wherein the ruthenium oxide powder containing copper and the iridium chloride salt are mixed in a proportion of iridium. So that the percentage of iridium oxide / (ruthenium oxide + iridium oxide) is 9-30% by mass, and the blending ratio of copper is 0.1-6% by mass of copper / (ruthenium oxide + iridium oxide). A method for producing a conductive powder, characterized in that after weighing and mixing these, the resultant mixture is roasted at 560 to 640 ° C. in an oxidizing atmosphere, and the obtained roasted product is washed with water.   The ruthenium oxide powder containing copper and iridium chloride are mixed by dissolving the iridium chloride in water, adding the ruthenium oxide powder containing copper to the resulting aqueous solution, stirring, and stirring the resulting slurry. It dries, The manufacturing method of the electrically-conductive powder of Claim 4 characterized by the above-mentioned.   The ruthenium oxide powder containing copper is a method of mixing ruthenium hydroxide powder or ruthenium chloride with copper oxide or copper chloride and baking at 500 to 800 ° C. in an oxidizing atmosphere, or an aqueous solution of ruthenium chloride. A method of roasting ruthenium hydroxide starch obtained by adding a water-soluble copper compound to the mixture at 500 to 800 ° C. in an oxidizing atmosphere, or reducing an aqueous solution of ruthenium chloride. 6. The method according to claim 4, wherein the obtained ruthenium hydroxide starch is mixed with copper oxide or copper chloride, and is manufactured by any one of methods of baking at 500 to 800 ° C. in an oxidizing atmosphere. The manufacturing method of the electroconductive powder of description.   The method for producing a conductive powder according to claim 2, wherein the chloroiridate is ammonium hexachloroiridium (IV) and / or potassium hexachloroiridium (IV).

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