JP2005235754A - Conductive material, its manufacturing method, resistor paste, resistor and electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To balance a temperature characteristic (TCR) with a withstand voltage characteristic (STOL), in a resistor having a high resistance value, for instance, above 10 kΩ/square. <P>SOLUTION: This conductive material mainly contains RuO<SB>2</SB>particles. The crystallite size and the average particle diameter of each RuO<SB>2</SB>particle satisfies a relationship of 0.14<crystallite size<average particle diameter. The conductive material is used for resistor paste containing a glass composition and the conductive material and prepared by mixing them with an organic vehicle. The resistor formed by using the resistor paste has a high resistance value above 10 kΩ/square, and capable of balancing a TCR characteristic with an STOL characteristic. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a conductive material mainly composed of RuO ₂ and a manufacturing method thereof, and further relates to a resistor paste, a resistor, and an electronic component using the same.

For example, a resistor paste is generally composed of a glass composition for adjusting a resistance value and imparting bonding properties, a conductive material, and an organic vehicle as main components, and after printing this on a substrate, By baking, a thick film resistor having a thickness of about 5 to 20 μm is formed. In this type of resistor paste (thick film resistor), usually, ruthenium oxide (RuO ₂ ), lead ruthenium oxide or the like is used as the conductive material, and lead oxide (PbO) glass or the like is used as the glass. It is used.

  In recent years, environmental issues have been actively discussed, and elimination of harmful substances such as lead from electronic components is being promoted. The resistor paste and the thick film resistor are no exception, and research is being conducted to make them lead-free.

  As one of the problems in making the resistor paste lead-free, there is a compatibility between temperature characteristics (TCR) and withstand voltage characteristics (STOL) particularly in a resistor paste having a high resistance (10 kΩ / □ or more). For example, when adjusting the TCR by adding a metal oxide, which has been used in conventional lead-based resistor pastes, to a lead-free composition as it is, changes in resistance due to voltage application are compared with the lead-based composition. As a result, it is difficult to achieve both TCR and STOL.

Under such circumstances, in a resistor paste mainly composed of a lead-free glass composition, a lead-free conductive material, and an organic vehicle, CaTiO ₃ or NiO is added as an additive, and temperature characteristics (TCR ) And withstand voltage characteristics (STOL) have been attempted (see, for example, Patent Document 1).

In Patent Document 1, it is preferable to contain, for example, CaTiO ₃ in an amount of more than 0 vol%, 13 vol% or less, or NiO in an amount of more than 0 vol% and 12 vol%, and further, an additive such as CuO, ZnO, MgO, etc. There is a description that it is preferable to add them at the same time, and as a result, lead suitable for obtaining a resistor having a low temperature characteristic (TCR) and a low withstand voltage characteristic (STOL) while having a high resistance value. It is said that it is possible to provide a free resistor paste.
JP 2003-197405 A

  However, especially in the high resistance region of 1 MΩ level, the STOL characteristic of the lead-free resistor paste does not reach the same level as that of the Pb resistor paste as compared with the conventional Pb resistor paste. At present, it is necessary to improve the characteristics. For example, in a resistor formed using a resistor paste whose TCR characteristics are adjusted by adding a large amount of additives as in the invention described in Patent Document 1, a resistor paste having a conventional lead-based composition is used. The STOL characteristics tend to be lower than in the case of the above. Therefore, it is necessary to further improve STOL characteristics in a state where no additive is added, that is, in the stage of a resistor formed using a resistor paste having a composition composed of a glass composition and a conductive material.

  Therefore, the present invention has been proposed in view of such a conventional situation, for example, a resistance having a high resistance value of 10 kΩ / □ or more and capable of achieving both temperature characteristics (TCR) and withstand voltage characteristics (STOL). It is an object of the present invention to provide a conductive material capable of realizing a body and a manufacturing method thereof. The present invention also provides a resistor paste having high resistance, excellent temperature characteristics (TCR) and withstand voltage characteristics (STOL), and excellent thermal stability by using the conductive material, and the resistor. It is an object of the present invention to provide a resistor manufactured using a paste, and an electronic component having the resistor.

The inventors of the present invention have conducted long-term research on a conductive material capable of achieving both temperature characteristics (TCR) and withstand voltage characteristics (STOL). As a result, in a conductive material mainly composed of RuO ₂ , And the ratio of crystallite size was made appropriate, the conclusion was reached that this was feasible.

The present invention has been completed based on such findings. That is, the conductive material according to the present invention, characterized in that the RuO ₂ particles as a main component, the mean particle size and crystallite size of the RuO ₂ particles satisfies 0.14 <crystallite size / average particle size the relationship And Similarly, the resistor paste of the present invention is a resistor paste containing a glass composition and a conductive material, which are mixed with an organic vehicle, and the conductive material is mainly composed of RuO ₂ particles. The crystallite size and the average particle size of the RuO ₂ particles satisfy the relationship of 0.14 <crystallite size / average particle size. Furthermore, the resistor according to the present invention is formed using the resistor paste, and the electronic component according to the present invention includes the resistor.

By using RuO ₂ particles with a specific ratio of average particle size and crystallite size as resistor paste and conductive material for resistors, TCR characteristics and STOL characteristics are compatible in a high resistance region of 10 kΩ / □ or more. The

The crystallite size of the RuO ₂ particles can be controlled by heat treatment, and this is defined by the method for producing a conductive material of the present invention. That is, in the method for producing a conductive material of the present invention, RuO ₂ particles are heat-treated at a temperature of 1000 ° C. or more and less than 1400 ° C., and the RuO ₂ particles have a crystallite size and an average particle size of 0.14 <crystallite size / It is characterized by controlling the average particle size.

  According to the present invention, it is possible to provide a conductive material capable of satisfying both TCR characteristics and STOL characteristics. By using the conductive material, a high resistance value can be provided, and temperature characteristics (TCR) and withstand voltage characteristics (STOL) can be provided. It is possible to provide a resistor paste, a resistor, and an electronic component that are superior to the above.

  Hereinafter, a conductive material according to the present invention, a manufacturing method thereof, a resistor paste containing the conductive material, a resistor formed using the resistor paste, and an electronic component having the resistor will be described.

Conductive material of the present invention are those composed mainly of RuO ₂ particles, that the average particle size and crystallite size of the RuO ₂ particles satisfies 0.14 <crystallite size / average particle size the relationship It is an important element. This means that it is advantageous that the crystallite size is as large as possible with respect to the average grain size. Here, only the lower limit of the crystallite size / average particle size is tested in the above rule, but when the crystallite size = average particle size (crystallite size / average particle size = 1) is the upper limit. Is self-evident, and this is the ideal state.

The average particle size and crystallite size of the RuO ₂ particles, wherein at relationship is arbitrary as long as it satisfies the, in the present invention, are intended for crushing particles as RuO ₂ particles, therefore, the average particle size It is preferable that the thickness is 1.0 μm or less and the crystallite size is 0.014 μm or more. The crystallite size of RuO ₂ particles can be determined by X-ray diffraction, and the average particle size can be measured by observation with a scanning electron microscope.

The crystallite size of RuO ₂ particles can be controlled by heat treatment. Therefore, in the production of the conductive material of the present invention, RuO ₂ particles are heat-treated at a temperature of 1000 ° C. or more and less than 1400 ° C., and the RuO ₂ particles have a crystallite size and an average particle size of 0.14 <crystallite size / The average particle size is controlled. Here, in order to make the crystallite size / average particle size the above relationship, it is preferable to pulverize the RuO ₂ particles after heat treatment to adjust the average particle size. By controlling the crystallite size by the heat treatment and adjusting the average particle size by pulverization, it is possible to easily satisfy 0.14 <crystallite size / average particle size.

The resistor paste of the present invention contains a glass composition, a conductive material, and, if necessary, an additive, and these are mixed with an organic vehicle. Then, as the conductive material, use of RuO ₂ particles having an average particle size of the above, the crystallite size. The content of the conductive material in the resistor paste is 9.4 mass% to 53.3 mass% when the total mass of the glass composition, the conductive material, and the additive is 100 mass%. Is preferred. When the content of the conductive material is less than the above range, the resistance value becomes too high, which may make it unsuitable for use as a resistor paste. On the contrary, if the content of the conductive material exceeds the above range, the binding of the conductive material by the glass composition becomes insufficient, and the reliability may be lowered.

  The glass composition is not particularly limited, but in the present invention, it is preferable to use a lead-free glass composition that substantially does not contain lead for environmental protection. In the present invention, “substantially free of lead” means not containing lead exceeding the amount that cannot be said to be an impurity level, and the amount of impurity level (for example, the content in the glass composition). Is about 0.05% by mass or less). Lead may be contained in a trace amount as an inevitable impurity.

When the glass composition is a resistor, it has a role of binding the conductive material and the additive to the substrate in the resistor. The glass composition can be used by mixing a modified oxide component, a network-forming oxide component, or the like as a raw material. Examples of the main modifying oxide component include alkaline earth oxides, specifically, at least one selected from CaO, SrO, and BaO. Examples of the network forming oxide component include B ₂ O ₃ and SiO ₂ . In addition to the main modified oxide component, any other metal oxide can be used as another modified oxide component. Specific metal oxides, for example _{ZrO 2, Al 2 O 3,} ZnO, CuO, NiO, CoO, MnO, Cr 2 O 3, V 2 O 5, MgO, Li 2 O, Na 2 O, K 2 O , TiO ₂ , SnO ₂ , Y ₂ O ₃ , Fe ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O _5, etc., among which ZrO ₂ , Al ₂ O ₃ , MnO, and ZnO are selected. It is preferable that it is at least one kind.

  There is an optimum range for the content of each component in the glass composition. For example, if the content of the main modifying oxide component is too small, the reactivity with the conductive material is lowered and the TCR and STOL characteristics are deteriorated. There is a fear. On the other hand, when the content of the main modifying oxide component is too large, when a resistor is formed, excessive metal oxide may be deposited, which may deteriorate the characteristics and reliability. When the content of the network-forming oxide component is small, the softening point of the glass composition becomes high. Therefore, when a resistor is formed at a predetermined firing temperature, the resistor is not sufficiently sintered and the reliability is remarkably improved. May decrease. On the other hand, when the content of the network-forming oxide component is too large, the water resistance of the glass composition is lowered, and thus there is a possibility that the reliability when a resistor is used is significantly lowered. Moreover, when there is too little content of another modification oxide component, since the water resistance of a glass composition falls, there exists a possibility that the reliability when it may be set as a resistor may fall remarkably. On the other hand, when the content of other modified oxide components is too large, when a resistor is formed, excessive metal oxide may be deposited, which may deteriorate the characteristics and reliability.

  The content of the glass composition in the resistor paste is 47.7 mass% to 90.6 mass% when the total mass of the conductive material, the glass composition, and the additive is 100 mass%. preferable. When the content is small, the binding of the conductive material and the additive becomes insufficient, and the reliability may be significantly lowered. On the other hand, if the content of the glass composition exceeds the above range, the resistance value becomes too high, which may make it unsuitable for use as a resistor paste.

  In addition to the glass composition and the conductive material described above, the resistor paste may contain an additive for the purpose of adjusting characteristics. The content of the additive in the resistor paste is preferably 0 to 27.2% by weight when the total mass of the glass composition, the conductive material, and the additive is 100% by weight. It is more preferable to set it as the mass%-27.2 mass%. When the content of the additive is small, it is difficult to sufficiently adjust the characteristics. On the other hand, when the content of the additive is too large, the binding of the conductive material and the additive becomes insufficient, and the reliability may be significantly reduced.

Any metal oxide can be used as the additive. _{Specifically, MgO, TiO 2, SnO 2} , ZnO, CoO, CuO, NiO, MnO, Mn 3 O 4, Fe 2 O 3, Cr 2 O 3, Y 2 O 3, V 2 O 5, MgTiO 3 , SrTiO ₃ , BaTiO ₃ , CaTiO _{3 and the} like. Among them, CuO, NiO, MgO, SrTiO ₃ , BaTiO ₃ , CaTiO ₃ , MgTiO ₃ , Mn ₃ O ₄ , ZnO and the like, which are highly effective oxides as a TCR adjuster, are preferable. When there is too much content of each additive, there exists a possibility that a STOL characteristic may deteriorate.

  The organic vehicle has a role of kneading the glass composition, the conductive material, and the additive into a paste, and any of those used for this type of resistor paste can be used. An organic vehicle is prepared by dissolving a binder in an organic solvent. It does not specifically limit as a binder, For example, what is necessary is just to select suitably from various binders, such as an ethyl cellulose and polyvinyl butyral. The organic solvent is not limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene. Furthermore, in order to adjust the physical properties of the resistor paste, various additives such as a dispersant may be added.

  The organic vehicle compounding ratio is a ratio (W2 / W1) of the total mass (W1) of the glass composition, the conductive material, and the additive to the mass of the organic vehicle (W2) (W2 / W1). -4 (W2: W1 = 1: 0.25 to 1: 4) is preferable. More preferably, the ratio (W2 / W1) is 0.5-2. If the ratio is outside the above range, a resistor paste having a viscosity suitable for forming a resistor on, for example, a substrate may not be obtained.

In order to form the resistor, the resistor paste containing the above-described components may be printed (applied) on the substrate by a method such as screen printing and fired at a temperature of about 850 ° C. As the substrate, a dielectric substrate such as an Al ₂ O ₃ substrate or a BaTiO ₃ substrate, a low-temperature fired ceramic substrate, an AlN substrate, or the like can be used. The substrate form may be any of a single layer substrate, a composite substrate, and a multilayer substrate. In the case of a multilayer substrate, the resistor may be formed on the surface or inside.

  In forming the resistor, a conductive pattern to be an electrode is usually formed on the substrate, and this conductive pattern is printed with a conductive paste containing an Ag-based highly conductive material containing Ag, Pt, Pd, or the like, for example. Can be formed. Further, a protective film such as a glass film may be formed on the surface of the formed resistor.

  The electronic component to which the resistor of the present invention can be applied is not particularly limited. For example, a single-layer or multi-layer circuit board, a resistor such as a chip resistor, an isolator element, a CR composite element, a module element, and a laminated layer Capacitors such as chip capacitors, inductors and the like can be mentioned, and the present invention can also be applied to electrode portions such as capacitors and inductors.

  Further, the conductive material of the present invention is not limited to the resistor paste or the conductive material of the resistor, but can be used as a conductive material for any application. For example, the conductive material of the present invention is directly included on a substrate. It is also possible to form a pattern and use it as an electrode or wiring.

  Hereinafter, specific examples to which the present invention is applied will be described based on experimental results. Needless to say, the present invention is not limited to the following examples.

<Production of conductive material>
And the non-heat treated RuO ₂ particles, 500 ° C. in air, 1000 ℃, 1350 ℃, were prepared RuO ₂ particles was carried out for 5 hours heat treatment respectively at 1400 ° C.. The heat-treated sample was pulverized by a ball mill so that the average particle diameter was 1 μm or less. In the sample heat-treated at 1400 ° C., some RuO ₂ particles were decomposed during the heat treatment, and the yield was extremely poor.

For each RuO ₂ particles obtained as described above (conductive material), the X-ray diffraction to determine the crystallite size from the half-width of the diffraction line. Moreover, the obtained particle | grains were observed with the scanning electron microscope (SEM), and the average particle diameter was computed. Furthermore, the value of crystallite size / average particle diameter was calculated from these values. Table 1 shows the measured values of the obtained samples.

<Preparation of glass composition>
A predetermined amount of B ₂ O ₃ , SiO ₂ , CaCO ₃ , SrCO ₃ , BaCO ₃ , ZrO ₂ , MnO, ZnO, Al ₂ O _{3 and the} like were weighed, mixed in a ball mill, and then dried. The obtained powder was heated to 1300 ° C. at a rate of 5 ° C./minute, held at that temperature for 1 hour, and then rapidly cooled by being poured into water to be vitrified. The obtained vitrified product was pulverized with a ball mill to obtain a glass composition powder. The obtained glass composition is shown in Table 2.

<Additives>
As additives, CuO, NiO, MgO, MgTiO ₃ , CaTiO ₃ , SrTiO ₃ , BaTiO ₃ , Mn ₃ O ₄ , ZnO and the like were used.

<Preparation of organic vehicle>
Using ethyl cellulose as the binder and terpineol as the organic solvent, the binder was dissolved while heating and stirring the organic solvent to prepare an organic vehicle.

<Preparation of resistor paste>
The above-mentioned conductive material powder, glass composition powder, additive, and organic vehicle were weighed so as to have each composition, and kneaded with a three-roll mill to obtain a resistor paste. The ratio of the total mass of the conductive material powder, the glass composition powder, and the additive powder to the mass of the organic vehicle is 1: 1 by mass so that the obtained resistor paste has a viscosity suitable for screen printing. A resistor paste was prepared by blending in the range of 0.25 to 1: 4.

<Fabrication of resistor>
On a 96% alumina substrate, the Ag—Pt conductor paste was screen printed in a predetermined shape and dried. The Ag ratio in the Ag-Pt conductor paste was 95% by mass, and the Pt ratio was 5% by mass. This alumina substrate was placed in a belt furnace and baked in a pattern of 1 hour from charging to discharging. The baking temperature at this time was 850 ° C., and the holding time at that temperature was 10 minutes.

  On the alumina substrate on which the conductor was formed in this manner, the resistor paste prepared previously was applied in a pattern of a predetermined shape (1 mm × 1 mm square shape) by screen printing and dried. Thereafter, the resistor paste was baked under the same conditions as the conductor baking to obtain a thick film resistor.

<Evaluation of resistor characteristics>
(1) Resistance value
Measured with Agilent Technologies product number 34401A. The average value of 24 samples was determined.

(2) TCR
The resistance value change rate when the temperature was changed to −55 ° C. and 125 ° C. was obtained based on the room temperature of 25 ° C. The average value of 10 samples. When the resistance values at −55 ° C., 25 ° C., and 125 ° C. are R-55, R25, and R125 (Ω / □), TCR (ppm / ° C.) = [(R-55-R25) / R25 / 80] × 1000000, or TCR (ppm / ° C.) = [(R125−R25) / R25 / 100] × 1000000. The larger value was taken as the TCR value.

(3) STOL (withstand voltage characteristics)
A test voltage was applied to the thick film resistor for 5 seconds, and the change rate of the resistance value before and after that was determined. The average value of 10 samples. Test voltage = 2.5 × rated voltage, rated voltage = √ (R / 8), and R is a resistance value (Ω / □). For resistors having a resistance value with the calculated test voltage exceeding 200V, the test voltage was 200V.

(4) Constant temperature and humidity load test This is one of the reliability tests of resistors. While applying a voltage of 15 V to the resistor, it was left in an atmosphere having a temperature of 85 ° C. and a relative humidity of 85%, and the resistance value fluctuation after 1000 hours was evaluated. When the resistance value fluctuation before and after the test is ΔR (%), it is preferably ± 1.0% or less.

<Examination on crystallite size and average particle size of conductive material>
While using glass 1 as a glass composition, samples 1 to 5 were prepared using samples A to E as conductive materials, and the characteristics of the resistor (resistance value, TCR, STOL, constant temperature and humidity load test) were evaluated. . Samples 6 and 7 were similarly prepared by adding appropriate amounts of NiO, CuO, and MgO. Sample 6 is the same as Sample 1 except that the additive is added, and Sample 7 is the same as Sample 4 except that the additive is added. For comparison, Sample 8 was prepared using CaRuO ₃ as a conductive material. The results are shown in Table 3.

As is apparent from Table 3, in samples 3 to 5 in which the crystallite size / average particle size of RuO ₂ particles, which are conductive materials, exceeds 0.14, the STOL value is extremely small. . In addition, the TCR is a large value in the samples 3 to 5, but the TCR is improved without increasing the STOL value in the sample 7 to which the additive is added. On the other hand, Samples 1 and 2 in which the crystallite size / average particle diameter of RuO ₂ particles is 0.14 or less have a large STOL value. However, although the improvement effect of TCR is seen, STOL is a large value on the contrary. Further, in the sample 8 using CaRuO ₃ as the conductive material, although improvement is seen in terms of TCR and STOL, resistance value fluctuation is seen before and after the test in the constant temperature and humidity load test.

<Examination on additives>
Next, Sample 9 to Sample 16 in which the additive was changed were prepared, and the characteristics of the resistor were evaluated. Samples 9 to 16 are samples obtained by changing the additives (NiO and MgO) to MgTiO ₃ , CaTiO ₃ , SrTiO ₃ , BaTiO _{3, and the} like. The results are shown in Table 4.

As is apparent from Table 4, when MgTiO ₃ , CaTiO ₃ , SrTiO ₃ , and BaTiO ₃ are added as additives, the crystallite size / average particle diameter of RuO ₂ particles that are conductive materials exceeds 0.14. In the samples 10, 12, 14, and 16, the STOL value was remarkably small, and the thermal stability was also improved. In Samples 10, 12, 14, and 16, the STOL value is remarkably small, and a good TCR value is also obtained.

<Examination on glass composition>
Next, while using glass 2 to glass 6 shown in Table 1 as the glass composition, various additives were added to prepare samples 17 to 26, and the characteristics of the resistors were evaluated. Samples 17 to 26 are samples obtained by changing the glass composition and / or additive. The results are shown in Table 5.

As is apparent from Table 5, even when any of CaO, SrO or BaO is used as the modified oxide component in the glass composition, or when other components in the glass composition are changed, In samples 18, 20, 22, 24, and 26 in which the crystallite size / average particle diameter of RuO ₂ particles, which is a conductive material, exceeds 0.14, the STOL value is remarkably small, and ΔR (%) Is kept within ± 1.0%. In Samples 18, 20, 22, 24, and 26, good results were also obtained for the TCR characteristics. Furthermore, in the samples 20, 22, and 24 using CuO, NiO, MgO or the like as an additive, a high resistance value of 10 kΩ or more is realized.

Claims (18)

A conductive material comprising RuO ₂ particles as a main component and satisfying the relationship of crystallite size and average particle size of the RuO ₂ particles of 0.14 <crystallite size / average particle size. The conductive material according to claim 1, wherein an average particle diameter of the RuO ₂ particles is 1.0 μm or less. The conductive material according to claim 1, wherein a crystallite size of the RuO ₂ particles is 0.014 μm or more. The conductive material according to claim 1, wherein the RuO ₂ particles are pulverized particles. The conductive material according to any one of claims 1 to 4, wherein the average particle diameter of the RuO ₂ particles is a value measured by observation with a scanning electron microscope. The RuO ₂ particles are heat-treated at a temperature of 1000 ° C. or more and less than 1400 ° C., and the crystallite size and average particle size of the RuO ₂ particles are controlled to be 0.14 <crystallite size / average particle size. A method for producing a conductive material. 7. The heat-treated RuO ₂ particles are pulverized and controlled so that the crystallite size and average particle size of the RuO ₂ particles are 0.14 <crystallite size / average particle size. A method for producing a conductive material. A resistor paste containing a glass composition and a conductive material, which is mixed with an organic vehicle,
The conductive material, the RuO ₂ particles mainly, resistor paste having an average particle size of the crystallite size of the RuO ₂ particles and satisfies 0.14 <crystallite size / average particle size the relationship . The resistor paste according to claim 8, wherein the RuO ₂ particles have an average particle size of 1.0 μm or less. The resistor paste according to claim 8, wherein a crystallite size of the RuO ₂ particles is 0.014 µm or more. The resistor paste according to claim 8, wherein the RuO ₂ particles are pulverized particles. The resistor paste according to any one of claims 8 to 11, wherein the average particle diameter of the RuO ₂ particles is a value measured by observation with a scanning electron microscope. The glass composition contains at least one selected from CaO, SrO, and BaO as a main modifying oxide component, and at least one selected from B ₂ O ₃ and SiO ₂ as a network-forming oxide component. The resistor paste according to claim 8, wherein the resistor paste is a paste. The resistor paste according to claim 13, wherein the glass composition contains at least one selected from MnO, ZrO ₂ , Al ₂ O ₃ , and ZnO as another modified oxide component. 15. At least one selected from NiO, CuO, MgO, SrTiO ₃ , BaTiO ₃ , CaTiO ₃ , MgTiO ₃ , Mn ₃ O ₄ , ZnO is contained as an additive. The resistor paste according to item.   The ratio of the total mass of the glass composition, the conductive material, and the additive to the mass of the organic vehicle is 1: 0.25 to 1: 4. The resistor paste according to any one of the above.   A resistor formed using the resistor paste according to any one of claims 8 to 16.   An electronic component comprising the resistor according to claim 17.