JP2005209739A - Production process of resistor paste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure the lifetime of resistor paste and to ensure both temperature characteristics (TCR) and withstand voltage characteristics (STOL) when a thick film resistor having a resistance not lower than 10 kΩ/square is formed. <P>SOLUTION: In the production process of resistor paste where a glass composition, a conductive material and an additive are dispersed into an organic vehicle, the conductive material and the additive are premixed and a mixture thus produced is mixed and kneaded with the glass composition and the organic vehicle. Premixing is performed using a ball mill. Mixing and kneading of the mixture with the glass composition and the organic vehicle is performed using three ball mill. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a resistor paste used for forming a thick film resistor.

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 that the resistor paste contains, for example, CaTiO ₃ more than 0 vol%, 13 vol% or less, or NiO more than 0 vol%, 12 vol% or less, and further additives 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, as in the invention described in Patent Document 1, in a resistor formed using a resistor paste whose TCR characteristics are adjusted by adding a large amount of additives, a resistor paste having a conventional lead-based composition is used. The STOL characteristic tends to be lower than that in the case of the above. Therefore, for example, it is desired to further improve STOL characteristics in a state where an additive is not added in a large amount.

  Moreover, when mass production of a thick film resistor is considered, it is preferable that the paste life of the resistor paste is as long as possible. If the paste life of the resistor paste is short, the process management becomes complicated, which is disadvantageous in terms of workability and yield. From this point of view, the conventional resistor paste is not always satisfactory.

  Therefore, the present invention has been proposed in view of such a conventional situation. For example, when used for forming a thick film resistor having a high resistance value of 10 kΩ / □ or more, a temperature characteristic (TCR) and It aims at providing the manufacturing method of the resistor paste which can make a withstand voltage characteristic (STOL) compatible. Furthermore, an object of the present invention is to provide a method of manufacturing a resistor paste that can greatly improve the paste life of the resistor paste.

  The present inventors have made various studies over a long period of time for the purpose of achieving both temperature characteristics (TCR) and withstand voltage characteristics (STOL) in thick film resistors. As a result, the method of manufacturing the resistor paste used to form the thick film resistor has a great influence on the characteristics of the thick film resistor formed using the resistor paste, and the characteristics can be improved by optimizing this. I came to the conclusion that it was feasible.

  The present invention has been completed based on such findings. That is, the method of manufacturing a resistor paste according to the present invention is a method of manufacturing a resistor paste in which a glass composition, a conductive material, and an additive are dispersed in an organic vehicle. Premixing is performed, and the resulting mixture is mixed and kneaded with a glass composition and an organic vehicle.

  In preparing the resistor paste, by premixing the conductive material and the additive, the dispersion state in these resistor pastes is optimized, and as a result, the thick film resistor formed using the resistor paste Thus, both TCR and STOL can be realized. At the same time, the paste life of the resistor paste is also improved, and the increase in viscosity is suppressed over a long period of time.

  By using the resistor paste manufactured by the manufacturing method of the present invention, it is possible to achieve both TCR characteristics and STOL characteristics particularly in a thick film resistor having a high resistance value. In addition, the resistor paste manufactured by the manufacturing method of the present invention has a long paste life and suppresses the increase in viscosity over a long period of time, so that the process management is simple and advantageous in terms of workability and yield. .

  Hereinafter, the manufacturing method of the resistor paste which concerns on this invention is demonstrated.

  The resistor paste to be manufactured in the present invention is used for forming a thick film resistor, and is usually composed of a glass composition, a conductive material, an additive, and an organic vehicle.

Here, the conductive material has a role of imparting conductivity to the thick film resistor as the structure by being dispersed in the glass as the insulator. As the conductive material, a conductive material containing Ru is used. For example, RuO ₂ or Ru composite oxide is used. As the Ru composite oxide, at least one selected from CaRuO ₃ , SrRuO ₃ , BaRuO ₃ , and Bi ₂ Ru ₂ O ₇ is preferable.

  The content of the conductive material in the resistor paste is 9.4 wt% to 53.3 wt% when the total weight of the glass composition, the conductive material, and the additive is 100 wt%. 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 composition of the glass composition is not particularly limited as long as it is produced by the above-described method. However, in the present invention, it is preferable to use a lead-free glass composition that does not substantially 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 weight 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, etc., among which at least one selected from ZrO ₂ , Al ₂ O ₃ , and MnO is preferable.

  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 wt% to 90.6 wt% when the total weight of the conductive material, the glass composition, and the additive is 100 wt%. 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 weight of the glass composition, the conductive material, and the additive is 100% by weight. It is more preferable to set it as weight%-27.2 weight%. 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, like _{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 and the like It is done. Among these, CuO, NiO, and MgO, 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 weight (W1) of the glass composition, the conductive material, and the additive to the weight (W2) of the organic vehicle (0.25). -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.

  The resistor paste is prepared by mixing the above-described components, that is, the glass composition, the conductive material, and the additive with the organic vehicle. At this time, in the present invention, the process of mixing the components is improved. .

  That is, in the past, each component (glass composition, conductive material, additive) was put into an organic vehicle and mixed together, but here, the conductive material and additive were premixed in advance. The mixture is mixed and kneaded with the glass composition and the organic vehicle.

Here, the pretreatment is preferably performed by, for example, a ball mill. The mixing by the ball mill is pulverized and mixed, which is suitable for controlling the dispersion state of the conductive material and the additive. In the premixing by this ball mill, it is preferable to use a ceramic pot or a ZrO ₂ ball. The premixing time by the ball mill is preferably 4 hours or more. If the premixing time is less than 4 hours, the dispersion state of the conductive material and the additive is not sufficiently uniform, and the predetermined effect may not be obtained.

  On the other hand, the mixing and kneading with the organic vehicle is preferably performed by a three-roll mill. The three-roll mill is excellent in mass productivity and can be easily mixed and kneaded.

In order to form a thick film resistor, a resistor paste containing the above-mentioned components may be printed (applied) on a substrate by a method such as screen printing and fired at a temperature of 800 ° C. to 900 ° C., for example, 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.

  When forming a thick film resistor, a conductive pattern to be an electrode is usually formed on a substrate, and this conductive pattern is printed with a conductive paste containing an Ag-based highly conductive material including Ag, Pt, Pd, etc., 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 thick film resistor of the present invention can be applied to various electronic components. The applicable electronic component is not particularly limited. For example, a single-layer or multilayer circuit board, a resistor such as a chip resistor, an isolator element, a CR composite element, a module element, a capacitor such as a multilayer chip capacitor, Examples include inductors, and the present invention can also be applied to electrode parts such as capacitors and inductors.

  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>
CaCO ₃ powder and RuO ₂ powder were weighed to become CaRuO ₃ , mixed in a ball mill and dried. The obtained powder was heated to 1200 ° C. at a rate of 5 ° C./min, held at that temperature for 5 hours, and then cooled to room temperature at a rate of 5 ° C./min to obtain a CaRuO ₃ powder. The obtained conductive material was pulverized by a ball mill.

<Preparation of glass composition>
B ₂ O ₃ , SiO ₂ , CaCO ₃ and ZrO ₂ were weighed in predetermined amounts, mixed in a ball mill, and then dried. The obtained powder was heated to 1300 ° C. at a rate of 5 ° C./min, held at that temperature for 1 hour, then rapidly cooled and vitrified. The obtained vitrified product was pulverized with a ball mill to obtain a glass composition powder.

<Additives>
CuO, NiO, and MgO were used as additives.

<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, mixed and kneaded to obtain a resistor paste. The composition of the resistor paste, the conductive material (CaRuO ₃₎ 19.8 wt%, the glass composition _{(B 2 O 3 -SiO 2 -CaCO} 3 -ZrO 2) 55.0 % by weight and additives NiO16. 7 wt%, MgO 5.0 wt%, and CuO 3.5 wt%. In addition, a composition is a weight ratio of each component when the total weight of an electroconductive material, a glass composition, and an additive is 100.

In the production of this resistor paste, in the comparative paste, the resistor paste is prepared by the usual method, that is, by weighing and mixing each powder in an organic vehicle and kneading in a three-roll mill. did. In the example paste, among the weighed powders, only the conductive material and the additive are premixed in a ball mill, and the obtained mixture is put into an organic vehicle together with the glass composition and kneaded in a three-roll mill. Thus, a resistor paste was prepared. As premixing conditions, the pot material was an Al ₂ O ₃ pot and the ball was a ZrO ₂ ball, and pulverized and mixed for 4 hours.

  In any case, the ratio of the total weight of the conductive material powder, the glass composition powder and the additive powder to the weight of the organic vehicle is such that the obtained resistor paste has a viscosity suitable for screen printing. The resistor paste was prepared in a weight ratio of 1: 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 weight, and the Pt ratio was 5% by weight. 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 is formed in this way, the resistor paste (the comparative example paste and the example paste) prepared previously is patterned in a predetermined shape (1 mm × 1 mm square shape) by screen printing. Applied and dried. Thereafter, the resistor paste was baked under the same conditions as the conductor baking to obtain a thick film resistor. A thick film resistor manufactured using the comparative paste is a comparative resistor, and a thick film resistor manufactured using the example paste is an example resistor.

<Evaluation of resistor paste>
(1) Paste life The time until the viscosity of the resistor paste changed by ± 50% or more and became unsuitable for screen printing was measured. This time is preferably about one month, ie 1000 hours or more.

<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. TCR (ppm / ° C) = [(R-55-R25) / R25 / 80] x resistance values of -55 ° C, 25 ° C, 125 ° C are R-55, R25, R125 (Ω / □) 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.

<Evaluation results>
First, the paste life of the comparative example paste was within 500 hours. Therefore, the paste life is shorter than required. Moreover, the resistance value of the comparative example resistor was 1.726 MΩ, the TCR was −95 ppm / ° C., and the STOL was −15.1%.

  Similarly, when the paste life of the example paste was examined, a sufficient paste life of 2000 hours or more was secured. Moreover, the resistance value of the example resistor was 1.807 MΩ, the TCR was −64 ppm / ° C., and the STOL was −4.9%.

  As is clear when comparing the characteristics of the resistor pastes of these comparative examples and examples, and thick film resistors, by optimizing the resistor paste manufacturing method, the paste life can be sufficiently secured, It can also be seen that both the TCR characteristic and the STOL characteristic can be achieved in the formation of the thick film resistor having a high resistance value.

Claims (11)

A method of manufacturing a resistor paste in which a glass composition, a conductive material, and an additive are dispersed in an organic vehicle,
A method for producing a resistor paste, wherein a conductive material and an additive are premixed in advance, and the resulting mixture is mixed and kneaded with a glass composition and an organic vehicle.   2. The method of manufacturing a resistor paste according to claim 1, wherein the premixing is performed by a ball mill.   3. The method of manufacturing a resistor paste according to claim 2, wherein pre-mixing by the ball mill is performed using a ceramic pot. The method for producing a resistor paste according to claim 2, wherein premixing is performed by the ball mill using ZrO ₂ balls.   The method of manufacturing a resistor paste according to claim 1, wherein the premixing time is 4 hours or more.   The method for producing a resistor paste according to any one of claims 1 to 5, wherein the kneading is performed by a three-roll mill. The method for producing a resistor paste according to claim 1, wherein the conductive material is at least one of RuO ₂ and Ru composite oxide. The conductive _{material, RuO 2, CaRuO 3, SrRuO} 3, BaRuO 3, Bi 2 process according to claim 7, wherein the resistive paste, characterized in that at least one selected from Ru ₂ O _7. 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 method for producing a resistor paste according to claim 1, wherein the resistor paste is produced. The method for producing a resistor paste according to claim 9, wherein the glass composition contains ZrO ₂ as another modified oxide component.   The method of manufacturing a resistor paste according to any one of claims 1 to 10, wherein the additive is at least one selected from NiO, CuO, and MgO.