JP2007277040A - Iridium oxide powder, its manufacturing method, and paste for forming thick film resistor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an iridium oxide powder having an excellent dispersibility in a paste and being capable of forming a resistor having excellent electric characteristics when a paste is obtained by using the iridium oxide powder as a conductive powder of a thick film resistor and fired to form a resistor, a method for manufacturing it industrially at a low cost, and a paste for forming a thick film resistor using it. <P>SOLUTION: The iridium oxide powder is used as a conductive powder for a paste for a thick film resistor excellent in electric characteristics, which has an average particle diameter of 30-100 nm, a structure consisting of a single phase of iridium oxide represented by chemical formula: IrO<SB>2</SB>and having a half-value width of (110) plane of 0.20-0.40° in its X-ray diffraction, and a chlorine concentration of 0.01-0.4 wt.%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an iridium oxide powder, a method for producing the same, and a thick film resistor forming paste using the iridium oxide powder. More specifically, the paste is obtained as a conductive powder for forming a thick film resistor, and the paste is fired. When the resistor is used, the dispersibility in the paste is good, and the iridium oxide powder capable of forming a resistor having further excellent electrical characteristics, and its industrially inexpensive manufacturing method and The present invention relates to a thick film resistor forming paste using the same.

  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 paste used for manufacturing the thick film resistor is manufactured by uniformly dispersing conductive powder and a glass binder such as glass frit in an organic medium called a vehicle. Of these, conductive powder plays the most important role in determining the electrical characteristics of thick film resistors, and fine powders of ruthenium oxide (RuO ₂ ) or lead ruthenate (Pb ₂ Ru ₂ O ₇ ) are widely used. Yes. In general, ruthenium oxide is used as a conductor in a wide range from a low resistance value to a high resistance value, and in the high resistance region, lead ruthenate having a smaller variation in the resistance value with respect to the conductor concentration is often used.

However, in recent years, there has been a demand for the elimination of the use of toxic lead from electronic devices, 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. In addition, in order to completely remove lead from the thick film resistor, it is necessary to exclude lead from the glass binder used at the same time. A conductive powder that can provide the properties is required. As a solution for this, various ruthenium composite oxides for conductive powders represented by chemical formulas such as Bi ₂ Ru ₂ O ₇ , CaRuO ₃ , SrRuO ₃ , BaRuO ₃ , LaRuO ₃ have been proposed. It has not been obtained and has not been put to practical use.

By the way, in general, when iridium oxide (IrO ₂ ) is used to form a resistor with a paste using the powder, it is known that a resistor having a high resistance can be obtained as compared with the case of using ruthenium oxide powder. It is expected as a substitute for lead ruthenate powder as conductive powder for thick film resistors in the high resistance region. For example, a thick film resistor paste made of iridium oxide and fine glass frit is disclosed as an electrical resistance composition (see, for example, Patent Document 1). However, in this proposal, since glass containing lead is used as a glass binder and the characteristics as a resistor are easily improved, a glass binder containing lead is used, and lead is completely excluded. Good characteristics were not obtained. In addition, there has been no disclosure of desirable material properties when using iridium oxide powder as conductive powder for thick film resistors.

  However, as described above, the material properties of iridium oxide powder and the electrical properties of the thick film resistor obtained by using the material, for example, the resistance value and the temperature coefficient of resistance (hereinafter sometimes referred to as TCR). In addition, the thick film resistor using iridium oxide powder as a conductive powder does not exhibit excellent characteristics because it has not enough knowledge about the effect on noise and noise, and is used as a conductive powder in place of lead ruthenate powder. Was not reached.

  From the above situation, as a conductive powder that replaces the lead ruthenate powder used in the thick film resistor forming paste, the conductive powder itself does not contain lead, and it is good as a thick film resistor even when all lead is excluded from the paste There is a need for conductive powders that can provide excellent electrical characteristics.

Japanese Examined Patent Publication No. 54-1917 (Page 6)

  In view of the above-mentioned problems of the prior art, the object of the present invention is to obtain a paste as a conductive powder for a thick film resistor, and to disperse the paste in the paste when the paste is fired into a resistor. The present invention provides an iridium oxide powder capable of forming a resistor having good electrical properties and further excellent electrical characteristics, an industrially inexpensive manufacturing method thereof, and a thick film resistor forming paste using the same. There is.

In order to achieve the above object, the present inventors have conducted extensive research on iridium oxide powder used for conductive powder for thick film resistors, a method for producing the same, and paste for forming thick film resistors using the same. As a result, as the material properties of iridium oxide powder, the structure, particle size, crystallinity, and chlorine content have a great influence on the dispersibility in the paste and the electrical properties of the resistor. The structure is a single phase of iridium oxide represented by the chemical formula: IrO ₂ , and the average particle diameter, the half width of the (110) plane of the iridium oxide phase in X-ray diffraction, and the chlorine concentration are in a specific range. It has been found that a paste having good dispersibility of the iridium oxide powder and a resistor excellent in electrical characteristics such as a resistance value, a resistance temperature coefficient, and noise can be formed.
Moreover, in order to obtain iridium oxide powders in which these are controlled within a specific range, it is preferable to use specific raw materials and adjust the roasting temperature to a specific temperature when roasting in an oxidizing atmosphere. Found to be implemented. And these completed the present invention.

That is, according to the first invention of the present invention, the iridium oxide powder used as the conductive powder of the thick film resistor forming paste having excellent electrical characteristics,
The average particle size is 30 to 100 nm, the structure is a single phase of iridium oxide represented by the chemical formula: IrO ₂ by X-ray diffraction, and the half width of the (110) plane in the X-ray diffraction is 0.20. An iridium oxide powder characterized by having a chlorine concentration of 0.01 to 0.4% by weight and a chlorine concentration of ˜0.40 ° is provided.

  According to the second invention of the present invention, ammonium hexachloroiridium (IV) or a mixture of iridium hydroxide and potassium compound, ammonium hexachloroiridium (IV) containing potassium, or hexachloroiridium (IV) acid When potassium is roasted in an oxidizing atmosphere, by adjusting the roasting temperature in the range of 840 to 980 ° C., the average particle diameter, the half width of the (110) plane in X-ray diffraction, and the chlorine concentration The iridium oxide powder production method according to the first aspect of the present invention is characterized in that is controlled to a predetermined value.

  According to a third aspect of the present invention, in the second aspect, the potassium compound is at least one selected from potassium hexachloroiridium (IV), potassium chloride, potassium hydroxide or potassium carbonate. There is provided a method of producing iridium oxide powder characterized in that

  According to a fourth invention of the present invention, in the second invention, the potassium content in the mixture or ammonium hexachloroiridium (IV) containing potassium is 0.02-9 with respect to the total amount of potassium component. The manufacturing method of iridium oxide powder characterized by containing .9 weight% is provided.

  According to a fifth aspect of the present invention, in any one of the second to fourth aspects, the oxidizing atmosphere is formed by an oxygen gas stream.

  According to the sixth aspect of the present invention, there is provided a thick film resistor paste using the iridium oxide powder of the first aspect.

  Since the iridium oxide powder of the present invention has material characteristics suitable as a conductive powder for thick film resistors, the paste is obtained by kneading into an organic vehicle together with a glass binder using the conductive powder. When the resistor is baked, the dispersibility in the paste is good, and further, it is possible to form a resistor excellent in electrical characteristics such as resistance value, resistance temperature coefficient and noise, Moreover, the manufacturing method can manufacture the iridium oxide powder which controlled the substance characteristic to the predetermined value by adjusting roasting temperature industrially cheaply, and its industrial value is very large. Furthermore, as a thick film resistor paste in a high resistance region, it can be used as a substitute for lead ruthenate powder to form a thick film resistor containing no lead at all, which is more advantageous.

Hereinafter, the iridium oxide powder of the present invention, its production method, and the thick film resistor paste using the same will be described in detail.
The iridium oxide powder of the present invention is an iridium oxide powder used as a conductive powder of a thick film resistor forming paste having excellent electrical characteristics, and has an average particle size of 30 to 100 nm and a structure represented by a chemical formula by X-ray diffraction. : The iridium oxide single phase represented by IrO ₂ , the half width of the (110) plane in the X-ray diffraction is 0.20 to 0.40 °, and the chlorine concentration is 0.01 to 0 4% by weight. As a result, the material characteristics such as the desired particle size, crystallinity, and chlorine content as the conductive powder for the thick film resistor having excellent electrical characteristics such as resistance value, resistance temperature coefficient and noise are maintained.

That is, if the iridium oxide powder contains a foreign phase such as metallic iridium or potassium salt, the dispersibility in the paste becomes poor when forming the paste, and a resistor having good electrical characteristics is formed. Therefore, it is important to prevent the remaining of different phases during the production. This is done by identifying by X-ray diffraction that the tissue is a single phase of iridium oxide represented by the chemical formula: IrO ₂ .

  Further, the particle diameter of iridium oxide affects the temperature coefficient of resistance. If the average particle diameter is less than 30 nm, the TCR of the thick film resistor obtained by using this is not preferable. On the other hand, if the average particle diameter exceeds 100 nm, the noise of the thick film resistor obtained by using this becomes undesirably high.

  The crystallinity of iridium oxide affects the TCR, and the higher the crystallinity, the higher the TCR. Therefore, when the half width of the (110) plane in the X-ray diffraction of the iridium oxide phase exceeds 0.40 °, the crystallinity deteriorates, and the TCR of the thick film resistor obtained by using this is preferably low. Absent. On the other hand, the smaller the half width, the better the crystallinity, so it is more desirable, but it is sufficient if the half width is reduced to 0.20 °.

  Furthermore, the chlorine content of iridium oxide affects the TCR of iridium oxide powder, and the lower the chlorine content, the higher the TCR, which is desirable. Therefore, if the chlorine concentration exceeds 0.4% by weight, the TCR of the thick film resistor obtained by using this is undesirably low. On the other hand, since TCR tends to decrease normally due to various additives added at the time of paste adjustment, it is desirable that the TCR in the case of iridium oxide alone is appropriately high, so the chlorine concentration inevitably decreases to a low concentration. However, the TCR is not too high and there is no problem. However, it is sufficient if the chlorine concentration is reduced to at least 0.1% by weight, more preferably to 0.01% by weight.

  The method for producing iridium oxide powder of the present invention comprises ammonium hexachloroiridium (IV) or a mixture of iridium hydroxide and potassium compound, ammonium hexachloroiridium (IV) containing potassium, or potassium hexachloroiridium (IV). When roasting in an oxidizing atmosphere, by adjusting the roasting temperature within a range of 840 to 980 ° C., the average particle diameter, the half width of the (110) plane in X-ray diffraction, and the chlorine concentration are predetermined. It is characterized by being controlled to a value.

In the method of the present invention, it is important to use a specific raw material and adjust the roasting temperature to a specific temperature when roasting in an oxidizing atmosphere. That is, on the raw material side, iridium (IV) chloride salts such as potassium hexachloroiridium (IV) (K ₂ IrCl ₆ ), ammonium hexachloroiridium (IV) ((NH ₄ ) ₂ IrCl ₆ ), Alternatively, it can be obtained when iridium hydroxide (Ir (OH) ₄ ) obtained by neutralizing an aqueous solution in which these are dissolved is used, and when ammonium hexachloroiridium (IV) or iridium hydroxide is used. In order to control the particle diameter of iridium oxide, the potassium concentration contained in ammonium hexachloroiridium (IV) is adjusted, or a potassium compound is added as an additive to ammonium hexachloroiridium (IV) or iridium hydroxide. At this time, the potassium content is in a concentration range that does not affect the electrical characteristics of the thick film resistor.
Furthermore, under roasting conditions, when roasting in an oxidizing atmosphere, the average particle diameter of the iridium oxide powder, the half width of the (110) plane in X-ray diffraction, and the chlorine concentration are controlled to predetermined values. Adjust the roasting temperature. By these, iridium oxide powder suitable for thick film resistors can be produced industrially at low cost.

  On the other hand, as a conventional method for producing iridium oxide powder, a method of obtaining iridium oxide powder by heating in an oxidizing atmosphere in a tubular furnace using a metal iridium foil as a raw material (I), iridium chloride A method of roasting in an oxygen atmosphere using as a raw material (b), iridium hydroxide obtained by neutralizing the iridium chloride, iridium chloride acid, or an aqueous solution in which an iridium chloride salt is dissolved as a raw material. Although the method (c) of roasting is performed, any method has a problem as a method for producing iridium oxide powder for thick film resistors.

  That is, the method (b) has a problem that the production rate of iridium oxide is extremely slow and cannot be used industrially. In the method (b), iridium chloride as a starting material is not used. Since it is expensive, there is a problem that it is very expensive industrially, and in the method (c), if the roasting temperature is increased in order to obtain iridium oxide powder having an appropriate particle size, it is partially Coarse-grained iridium oxide powder is generated in the resistor, so that there is a problem that the electrical characteristics of the resistor formed with the paste using this powder deteriorate, and as a result, the iridium oxide powder suitable for thick film resistors is used. Could not be produced industrially at low cost.

In the method of the present invention, iridium oxide powder is produced by the following action mechanism by baking in an oxidizing atmosphere.
When a mixture of ammonium hexachloroiridium (IV) or iridium hydroxide and a potassium compound is used as a raw material, first, a metal iridium phase and an iridium oxide phase are generated by thermal decomposition of the iridium compound. The metal iridium phase is oxidized at a temperature of 600 ° C. or higher, and is produced mainly by the iridium oxide phase. Potassium chloride added as a potassium compound at a temperature of 800 ° C. or higher is melted and evaporated to finally become an iridium oxide single phase. In addition, when potassium hexachloroiridium (IV) is used, an iridium oxide phase and a potassium chloride phase are generated from around 600 ° C., and potassium chloride is melted and evaporated at a temperature of 800 ° C. or higher, and finally oxidized. It becomes an iridium single phase.
Here, when the roasting temperature rises, the grain growth of the produced iridium oxide proceeds, but the potassium chloride phase plays a role of controlling the grain growth of the iridium oxide powder. That is, potassium segregates at the grain boundary of iridium oxide, thereby suppressing the growth of iridium oxide grains.

  The potassium content in the mixture or potassium hexachloroiridium (IV) acid containing potassium used in the above method is not particularly limited, but the roasting temperature affects volatilization in order to prevent the residual of the heterogeneous phase due to the potassium compound. Is also taken into account. For example, the potassium content in the iridium raw material is preferably 0.02 to 9.9% by weight. That is, when the potassium content is less than 0.02% by weight, the effect of suppressing grain growth is weak, and iridium oxide grows rapidly. As a result, iridium oxide powder having a desired particle size cannot be obtained, so that it cannot be uniformly dispersed in the paste. The potassium content of 9.9% by weight corresponds to the potassium content in potassium hexachloroiridium (IV), and when added in excess of this, a heterogeneous phase due to the potassium salt remains.

  The potassium compound used in the above method is not particularly limited, and potassium carbonate such as potassium hexachloroiridium (IV), potassium chloride, potassium hydroxide, or potassium carbonate, potassium bicarbonate, basic potassium carbonate. It is preferable to use at least one selected from the group consisting of potassium hexachloroiridium (IV) and potassium chloride.

  Both the iridium raw material and the potassium compound used in the above method are desirably dry powder, and when it contains moisture, it is preferably used after being dried.

The roasting method used in the above method is not particularly limited, and the raw material can be put in a heat-resistant container such as alumina and can be performed using a general baking apparatus such as a tubular furnace or a muffle furnace.
The roasting atmosphere is not particularly limited as long as it is an oxidizing atmosphere, and an atmosphere containing an oxidizing gas such as oxygen is used. In particular, it is preferably performed in an oxygen gas stream. In addition, it is preferable to charge the oxidizing gas during the temperature drop after roasting.

  As the roasting temperature, the average particle diameter, the half-value width of the (110) plane in X-ray diffraction, and the chlorine concentration are controlled to predetermined values while preventing mixing of foreign phases in the obtained iridium oxide powder. Although the desired temperature which can do is selected suitably, it is preferable to adjust in the range of 840-980 degreeC. That is, the iridium oxide phase is generated at a temperature of 600 ° C. or higher, but when the roasting temperature is less than 840 ° C., the particle size of the iridium oxide powder is small, and the iridium metal phase or potassium salt phase is a different phase other than the iridium oxide phase. The iridium oxide single phase which is easy to remain and is a desirable structure cannot be obtained. On the other hand, if the roasting temperature exceeds 980 ° C., the particles of iridium oxide powder become coarse, and the dispersibility deteriorates during paste preparation.

  The roasting time is not particularly limited, and according to the roasting temperature, the average particle diameter and X-ray diffraction (110) are obtained while preventing mixing of foreign phases in the obtained iridium oxide powder. A desired time during which the half width of the surface and the chlorine concentration can be controlled to predetermined values can be selected as appropriate. That is, if the roasting time is short, a different phase other than the iridium oxide phase tends to remain, and a single phase of the iridium oxide phase which is a desirable structure cannot be obtained. Conversely, if the roasting time is long, the resulting iridium oxide powder particles become coarse, and the dispersibility deteriorates during paste preparation.

  The thick film resistor paste of the present invention uses the above-mentioned iridium oxide powder, and is a paste that is uniformly dispersed in an organic vehicle together with a glass binder not containing lead. And the paste of this invention is apply | coated in accordance with a normal method, and it bakes after that, The lead-free thick film resistor excellent in the electrical property can be obtained.

As a method for preparing the thick film resistor forming paste, a conventional method used when producing a paste using conventional lead ruthenate powder is used. For example, iridium oxide powder, a glass binder, and an organic vehicle are mixed and then kneaded with a three-roll mill or the like. Here, the glass binder is selected according to the target part using the paste, the use conditions, and the like. For example, a glass frit containing BaO, SrO, CaO, SiO ₂ , B ₂ O ₃ , Al ₂ O _{3 and the} like is used. 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.

  Here, the iridium oxide powder is obtained by the production method described above, has an average particle size of 30 to 100 nm, has a structure of iridium oxide single phase, and has a (110) plane in X-ray diffraction. The half-value width is 0.20 to 0.40 °, and the chlorine concentration is 0.01 to 0.4% by weight. Therefore, the iridium oxide powder can be uniformly dispersed in the organic vehicle together with the glass binder during paste preparation. And by applying according to a normal method using the obtained paste, and baking after that, for example, the sheet resistance value of the resistor is in the range of 10 to 1000 kΩ / □, and the sheet resistance value is 100 kΩ / □. Sometimes, it is possible to form a thick film resistor having excellent electrical characteristics with a TCR of −40 to 30 ppm / ° C. and a noise of −5 to 10 dB and not containing lead.

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, the average particle diameter of the iridium oxide powder used by the Example and the comparative example, the structure | tissue, the measuring method of crystallinity, the chlorine concentration analysis method, and the evaluation method of the electrical property of a resistor are as follows.
(1) Measurement of the average particle diameter of iridium oxide powder: The specific surface area (manufactured by Yuasa Ionics Co., Ltd., Countersorb QS-10) was determined by the BET method, and was calculated therefrom.
(2) Identification of the structure of the roasted product: It was performed using an X-ray diffractometer (manufactured by Rigaku Corporation, RINT-1400).
(3) Crystallinity of iridium oxide powder: The half-value width of the (110) plane of iridium oxide was determined using an X-ray diffractometer (manufactured by Rigaku Corporation, RINT-1400).
(4) Chlorine concentration of iridium oxide powder: Analyzed by fluorescent X-ray calibration curve method using Macix manufactured by PANalytical.
(5) Measurement of electrical characteristics of resistor: Area resistance, resistance temperature coefficient (TCR), and noise were measured as electrical characteristics. Here, the sheet resistance value was measured by a four-terminal method using a digital multimeter (Model 2001 Multimeter manufactured by KEITHLEY). The temperature coefficient of resistance was obtained by measuring resistance values at 25 ° C. and 125 ° C. Noise was determined by measuring voltage fluctuation when 1/10 W was applied using a noise meter (Model 315C, manufactured by Quan-Tech).

Example 1
(1) Preparation of iridium oxide powder 6 g of ammonium hexachloroiridium (IV) (manufactured by Furuya Metal Co., Ltd.) having a potassium concentration of less than 0.01% by weight as a starting material and potassium chloride (reagent special grade, Wako Pure Chemical) as an additive Kogyo Co., Ltd.) (0.02 g) mixed with an agate mortar is placed in an alumina container, and this is charged into a small tubular furnace in which oxygen gas is flowed at a flow rate of 3 liters / minute and roasted. did. As roasting conditions, the temperature was raised from room temperature to 883 ° C. at a rate of 10 ° C./min, and kept at this temperature for 4 hours. Next, it was cooled in a furnace to obtain a roasted product. During this period, oxygen gas was kept flowing until the furnace temperature reached 300 ° C. or lower. Then, the average particle diameter, the structure | tissue in X-ray diffraction, (110) half value width, and Cl density | concentration of the obtained roasted material were measured. The results are shown in Table 1. The structure was an iridium oxide single phase represented by the chemical formula: IrO ₂ by X-ray diffraction.

(2) Preparation of paste and resistor Next, the obtained iridium oxide powder was used as a conductive powder and kneaded with a glass binder and an organic vehicle to prepare a paste. Here, as a glass binder, lead-free having a composition of 10 wt% SrO-43 wt% SiO ₂ -16 wt% B ₂ O ₃ -4 wt% Al ₂ O ₃ -20 wt% ZnO—Na ₂ O Glass frit was used. As the organic vehicle, ethyl cellulose and terpineol were used as main components. The paste was mixed in a total of 6 g of iridium oxide powder and glass binder, and 4 g of organic vehicle. Here, the weight ratio of iridium oxide to the total of the iridium oxide powder and the glass binder was adjusted within a range of 15 to 25% so that the sheet resistance was 100 kΩ / □.
Finally, the obtained paste was applied in the form of a film on an alumina substrate using a metal squeegee and a screen, dried at 150 ° C. for 10 minutes, and then baked at 850 ° C. for 30 minutes in an air atmosphere to form a thick film resistor (1 mm × 1 mm) was formed. Thereafter, TCR and noise were measured as electrical characteristics of the obtained resistor. In addition, it was confirmed that the sheet resistance value was adjusted to be 100 kΩ / □. The results are shown in Table 1.

(Example 2)
Preparation of iridium oxide powder was performed in the same manner as in Example 1 except that the roasting temperature was 905 ° C., and then the average particle diameter of the obtained roasted product, the structure by X-ray diffraction, and (110) The half width, Cl concentration, and electrical characteristics of the obtained resistor were evaluated. The results are shown in Table 1. The structure was a single phase of iridium oxide represented by the chemical formula: IrO ₂ .

(Example 3)
Preparation of iridium oxide powder was performed in the same manner as in Example 1 except that the roasting temperature was 951 ° C., and then the average particle diameter of the obtained roasted product, the structure by X-ray diffraction, and (110) The half width, Cl concentration, and electrical characteristics of the obtained resistor were evaluated. The results are shown in Table 1. The structure was a single phase of iridium oxide represented by the chemical formula: IrO ₂ .

Example 4
6 g of ammonium hexachloroiridium (IV) (manufactured by Sumitomo Metal Mining Co., Ltd.) having a potassium concentration of 0.02% by weight as a starting material is placed in an alumina container, and oxygen gas is flowed at a flow rate of 3 liters / minute. The small tubular furnace was charged and roasted. As roasting conditions, the temperature was raised from room temperature to 841 ° C. at a rate of 10 ° C./min, and kept at this temperature for 4 hours. Next, it was cooled in a furnace to obtain a roasted product. During this period, oxygen gas was kept flowing until the furnace temperature reached 300 ° C. or lower. Then, the average particle diameter, the structure | tissue in X-ray diffraction, (110) half value width, and Cl density | concentration of the obtained roasted material were measured. The results are shown in Table 1. The structure was an iridium oxide single phase represented by the chemical formula: IrO ₂ by X-ray diffraction.

(Example 5)
As a starting material, 6 g of potassium hexachloroiridium (IV) (manufactured by Furuya Metal Co., Ltd.) is placed in an alumina container, and this is charged into a small tube furnace in which oxygen gas is flowed at a flow rate of 3 liters / minute and roasted. did. As roasting conditions, the temperature was raised from room temperature to 944 ° C. at a rate of 10 ° C./min, and kept at this temperature for 4 hours. Next, it was cooled in a furnace to obtain a roasted product. During this period, oxygen gas was kept flowing until the furnace temperature reached 300 ° C. or lower. Then, the average particle diameter of the obtained baked product, the structure and X-ray diffraction structure (110) half width, Cl concentration, and the electrical characteristics of the obtained resistor were evaluated. The results are shown in Table 1. The structure was a single phase of iridium oxide represented by the chemical formula: IrO ₂ .

(Comparative Example 1)
The preparation of iridium oxide powder was performed in the same manner as in Example 1 except that the roasting temperature was 989 ° C., and then the average particle diameter of the obtained roasted product, the structure by X-ray diffraction, and (110) The half width, Cl concentration, and electrical characteristics of the obtained resistor were evaluated. The results are shown in Table 1. The structure was a single phase of iridium oxide represented by the chemical formula: IrO ₂ .

(Comparative Example 2)
As a starting material, 6 g of ammonium hexachloroiridium (IV) having a potassium concentration of less than 0.01% by weight (manufactured by Furuya Metal Co., Ltd.) was placed in an alumina container, and oxygen gas was allowed to flow at a flow rate of 3 liters / minute. It was charged in a small tubular furnace and baked. As roasting conditions, the temperature was raised from room temperature to 681 ° C. at a rate of 10 ° C./min, and kept at this temperature for 4 hours. Next, it was cooled in a furnace to obtain a roasted product. During this period, oxygen gas was kept flowing until the furnace temperature reached 300 ° C. or lower. Then, the average particle diameter of the obtained baked product, the structure and X-ray diffraction structure (110) half width, Cl concentration, and the electrical characteristics of the obtained resistor were evaluated. The results are shown in Table 1. The structure was a single phase of iridium oxide represented by the chemical formula: IrO ₂ .

(Comparative Example 3)
Preparation of iridium oxide powder was performed in the same manner as in Example 1 except that the roasting temperature was 831 ° C., and then the average particle diameter of the obtained roasted product, the structure by X-ray diffraction, and (110) The half width, Cl concentration, and electrical characteristics of the obtained resistor were evaluated. The results are shown in Table 1. The structure was a single phase of iridium oxide represented by the chemical formula: IrO ₂ .

(Comparative Example 4)
Iridium concentration 37.3% by weight of hexachloroiridate (IV) acid hexahydrate and _{(H 2 IrCl 6 · 6H 2} O) was dissolved in pure water, and neutralized by dropwise addition of aqueous potassium hydroxide solution to the iridium solution . At this time, the pH of the aqueous solution was maintained at around 7. Thereafter, filtration was performed to collect a precipitate of iridium hydroxide (Ir (OH) ₄ ). The obtained precipitate was put into pure water and stirred, and this was repeatedly washed several times and then dried.
The obtained iridium hydroxide powder was roasted in an air atmosphere using a muffle type electric furnace. The roasting conditions were a holding temperature of 750 ° C. and a holding time of 2 hours. Thereafter, the roasted product was taken out of the furnace and rapidly cooled to obtain a roasted product. Then, the average particle diameter of the obtained baked product, the structure and X-ray diffraction structure (110) half width, Cl concentration, and the electrical characteristics of the obtained resistor were evaluated. The results are shown in Table 1. The structure was a single phase of iridium oxide represented by the chemical formula: IrO ₂ .

  From Table 1, in Examples 1-5, the average particle diameter of the obtained iridium oxide powder, the half-value width of the (110) plane, and the Cl concentration are controlled within the range defined by the iridium oxide powder of the present invention. Furthermore, the electrical characteristics of the resistors obtained by using them achieve the desired values of TCR of −40 to 30 ppm / ° C. and noise of −5 to 10 dB when the area resistance value is 100 kΩ / □. I understand that Thus, the iridium oxide powder of the present invention is suitable as a conductive powder for use in a thick film resistor forming paste, and the resulting resistor has excellent electrical characteristics as a thick film resistor in a high resistance region. It can be said. On the other hand, in Comparative Examples 1 to 4, the average particle diameter of the iridium oxide powder, the half-value width of the (110) plane, or the Cl concentration is outside the range defined by the iridium oxide powder of the present invention. It can be seen that the electrical characteristics when the area resistance value of the resistor obtained by using this is 100 kΩ / □ cannot obtain satisfactory results in either TCR or noise characteristics.

  As is clear from the above, the iridium oxide powder of the present invention, the manufacturing method thereof, and the thick film resistor paste using the same are particularly widely used for chip resistors, thick film hybrid ICs, resistor networks, and the like. It is suitable as a conductive powder for paste used in the field of film resistors and a method for producing the same, and a paste using this is particularly suitable as a paste for thick film resistors in a high resistance region that does not contain lead in place of lead ruthenate powder. Useful.

Claims (6)

An iridium oxide powder used as a conductive powder of a thick film resistor forming paste having excellent electrical characteristics,
The average particle size is 30 to 100 nm, the structure is a single phase of iridium oxide represented by the chemical formula: IrO ₂ by X-ray diffraction, and the half width of the (110) plane in the X-ray diffraction is 0.20. An iridium oxide powder characterized by being -0.40 ° and having a chlorine concentration of 0.01-0.4% by weight.   When roasting ammonium hexachloroiridium (IV) or a mixture of iridium hydroxide and potassium compound, ammonium hexachloroiridium (IV) containing potassium, or potassium hexachloroiridium (IV) in an oxidizing atmosphere, The average particle diameter, the half width of the (110) plane in X-ray diffraction, and the chlorine concentration are controlled to predetermined values by adjusting the roasting temperature within a range of 840 to 980 ° C. A method for producing the iridium oxide powder according to 1.   The method for producing iridium oxide powder according to claim 2, wherein the potassium compound is at least one selected from potassium hexachloroiridium (IV), potassium chloride, potassium hydroxide, or potassium carbonate.   3. The iridium oxide according to claim 2, wherein the potassium content in the mixture or ammonium hexachloroiridium (IV) containing potassium is 0.02 to 9.9 wt% of the potassium component with respect to the total amount. Powder manufacturing method.   The method for producing iridium oxide powder according to claim 2, wherein the oxidizing atmosphere is formed by an oxygen gas stream.   A thick film resistor-forming paste using the iridium oxide powder according to claim 1.