JP2020193138A - Method for producing lead ruthenate powder, lead ruthenate powder, and thick film resistor paste containing lead ruthenate powder - Google Patents
Method for producing lead ruthenate powder, lead ruthenate powder, and thick film resistor paste containing lead ruthenate powder Download PDFInfo
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本発明は、ルテニウム酸鉛粉の製造方法及びルテニウム酸鉛粉、並びにルテニウム酸鉛粉を含有する厚膜抵抗ペーストに関し、更に詳しくは、ルテニウムと鉛の水和物または水酸化物の混合物を焙焼してルテニウム酸鉛粉を製造する方法及びルテニウム酸鉛粉、並びにルテニウム酸鉛粉を含有する厚膜抵抗ペーストに関する。 The present invention relates to a method for producing lead ruthenate powder, lead ruthenate powder, and a thick film resistance paste containing lead ruthenate powder, and more specifically, roasting a mixture of hydrate or hydroxide of ruthenium and lead. The present invention relates to a method for producing lead ruthenate powder by baking, lead ruthenate powder, and a thick film resistance paste containing lead ruthenate powder.
厚膜抵抗ペーストは導電粉、ガラス粉およびそれらを印刷に適したペースト状にするための有機ビヒクルから実質構成される。この厚膜抵抗ペーストを任意のパターンで印刷し、高温でガラスを焼結させることで、例えば、厚膜チップ抵抗器を構成する抵抗体として使用されている。ルテニウム酸鉛粉は、ガラス粉との混合比率を変化させることで緩やかに抵抗値を変化させることができるため、厚膜抵抗体の導電粉として広く用いられている。 The thick film resistant paste is substantially composed of conductive powder, glass powder and an organic vehicle for forming them into a paste suitable for printing. By printing this thick film resistor paste in an arbitrary pattern and sintering glass at a high temperature, for example, it is used as a resistor constituting a thick film chip resistor. Lead ruthenate powder is widely used as a conductive powder for thick film resistors because its resistance value can be changed gently by changing the mixing ratio with glass powder.
ルテニウム酸鉛粉の製造方法としては、例えば、次の特許文献１、２に、金属ルテニウムをアルカリ条件下で酸化処理し、あるいは、金属ルテニウムをアルカリ溶融して得られる固体のルテニウム酸塩を水で溶解して得たルテニウム酸塩の水溶液に鉛イオンを添加し、ｐＨを調整し、アルコール等の還元剤を用いて還元することで、ルテニウムと鉛の水和物または水酸化物の混合粉の共沈物を得、さらに、析出した混合粉を乾燥し、高温で焙焼することでルテニウム酸鉛微粉を得る等の方法が開示されている。 As a method for producing lead ruthenium powder, for example, in the following Patent Documents 1 and 2, solid ruthenium salt obtained by oxidizing metal ruthenium under alkaline conditions or melting metal ruthenium with alkali is used as water. A mixed powder of ruthenium and lead hydrate or hydroxide is added to the ruthenium acid salt aqueous solution obtained by dissolution in (1), the pH is adjusted, and the ruthenium is reduced with a reducing agent such as alcohol. Disclosed are methods such as obtaining a co-precipitate of the above, drying the precipitated mixed powder, and roasting the precipitated mixed powder at a high temperature to obtain fine powder of lead ruthenate.
近年、厚膜チップ抵抗器のような電子素子の小型化が進み、厚膜抵抗体の厚さを薄くすると同時に、電気的特性の向上が求められ、電子素子当たりの抵抗値のばらつきを小さくすることが求められている。
電子素子の小型化に対応し、かつ電気的特性の良好な厚膜抵抗体を形成するためには、導電粉として用いるルテニウム酸鉛粉等を微細化し、かつ、粗大粒子を極力少なくすることが必要である。
その理由は、粗大粒子は、導電粉とガラス粉とで構成される厚膜抵抗体内の導電部の分布構造を不均一にし、上述の抵抗値のばらつきが大きくなるなど、電気的特性に悪影響を与えることによる。
このため、導電粉として用いられるルテニウム酸鉛粉には、抵抗値、抵抗温度係数、等の電気的特性に影響を与えない大きさに、粒径が制御されていることが望まれている。
In recent years, the miniaturization of electronic devices such as thick film chip resistors has progressed, and it is required to reduce the thickness of thick film resistors and at the same time to improve the electrical characteristics, and to reduce the variation in resistance value per electronic device. Is required.
In order to correspond to the miniaturization of electronic devices and to form a thick film resistor with good electrical characteristics, it is necessary to make the lead ruthenate powder used as the conductive powder finer and to reduce the number of coarse particles as much as possible. is necessary.
The reason is that the coarse particles have a non-uniform distribution structure of the conductive portion in the thick film resistor composed of the conductive powder and the glass powder, and the above-mentioned variation in the resistance value becomes large, which adversely affects the electrical characteristics. By giving.
Therefore, it is desired that the particle size of the lead ruthenate powder used as the conductive powder is controlled to a size that does not affect the electrical characteristics such as the resistance value and the temperature coefficient of resistance.
しかしながら、特許文献１、２に開示されている従来の製造方法を用いた場合、製造条件の差異や残留した不純物量によってさまざまな粒径のルテニウム酸鉛粉が生成して、１μｍを超える粗大粒子が多く形成され、導電粉とガラス粉とで構成される厚膜抵抗体内の抵抗値のばらつきを低く抑えることができず、電気的特性を向上させることが困難となる場合がある。 However, when the conventional production methods disclosed in Patent Documents 1 and 2 are used, lead ruthenate powder having various particle sizes is produced depending on the difference in production conditions and the amount of residual impurities, and coarse particles exceeding 1 μm are produced. Is formed in large quantities, and the variation in the resistance value in the thick film resistor composed of the conductive powder and the glass powder cannot be suppressed to a low level, and it may be difficult to improve the electrical characteristics.
このような粗大粒子の形成を抑制する方法として、例えば、次の特許文献３には、鉛イオンを添加したルテニウム酸塩の水溶液に硫黄を添加し、その水溶液を還元して得られたルテニウムと鉛の水和物または水酸化物の共沈物である混合粉を焙焼する方法が開示されている。 As a method for suppressing the formation of such coarse particles, for example, in the following Patent Document 3, sulfur is added to an aqueous solution of a ruthenate salt having lead ions added, and the aqueous solution is reduced to obtain ruthenium. A method for roasting a mixed powder which is a co-deposit of lead hydrate or hydroxide is disclosed.
しかしながら、特許文献３に記載の製造方法を用いた場合、焙焼後の上記混合粉に不純物として硫黄が残留してしまう虞がある。
より小型化、微細化の進む電子部品においては、従来問題とならなかった微量の硫黄分も不具合発生の原因となり得る。そこで、不純物としての硫黄の残留を極力なくすため、洗浄工程の追加などが必要となる。このような洗浄工程の追加は、製造時間が長時間化すること等により生産性低下と製造コストの増加を招いてしまい、また、洗浄だけでは焙焼粉内部に残留する硫黄分の除去は困難であるため、好ましくない。
However, when the production method described in Patent Document 3 is used, sulfur may remain as an impurity in the mixed powder after roasting.
In electronic components that are becoming smaller and smaller, even trace amounts of sulfur, which has not been a problem in the past, can cause problems. Therefore, it is necessary to add a cleaning step in order to minimize the residual sulfur as an impurity. The addition of such a cleaning process leads to a decrease in productivity and an increase in production cost due to a long production time and the like, and it is difficult to remove sulfur remaining inside the roasted powder only by cleaning. Therefore, it is not preferable.
本発明は、上述の問題を鑑みてなされたものであり、硫黄を添加することなく、生成するルテニウム酸鉛粉の粒径を制御し、特に１μｍを超える粗大粒子の形成を抑制し、粒径の揃ったルテニウム酸鉛粉を簡便に製造することができ、全体の製造時間の長時間化を抑えることのできる、ルテニウム酸鉛粉の製造方法及びルテニウム酸鉛粉、並びにルテニウム酸鉛粉を含有する厚膜抵抗ペーストを提供することを目的とする。 The present invention has been made in view of the above-mentioned problems, and controls the particle size of the lead ruthenate powder produced without adding sulfur, particularly suppressing the formation of coarse particles exceeding 1 μm, and the particle size. Contains a method for producing lead ruthenate powder, a lead ruthenate powder, and a lead ruthenate powder, which can easily produce a complete lead ruthenate powder and can suppress an increase in the overall production time. It is an object of the present invention to provide a thick film resistance paste.
本発明者らは、生成する際のルテニウム酸鉛粉の粒径に対する各種条件の影響を鋭意調査した結果、ルテニウムと鉛の水和物または水酸化物の共沈物である混合粉の焙焼条件が、粗大粒子の形成に対して最も影響が強いことを見出した。
すなわち、通常、上記混合粉の焙焼は、所定の温度に熱せられた焙焼炉に投入して行うか、室温状態の焙焼炉に投入した後、所定の温度にまで昇温して行うが、このような従来の焙焼方法によって製造したルテニウム酸鉛粉は、粒径が十分には制御されておらず、粒度分布が広く、粒径が１μｍを超える粗大粒子が多数形成されてしまう場合がある。
本発明者らは、このような粒度分布が広く、粒径が１μｍを超える粗大粒子が多数形成される原因を鋭意調査した。その結果、その原因は焼成処理に用いる原料粉の粒径の大きさや、焙焼炉内の温度分布のばらつきなどに起因し、原料粉の粒子に過度の熱量が加わった際に短時間で急激に粒成長が起き、粗大化しやすいことを見出した。すなわち、粒径が微細な原料粉である混合粉を、粒径が所定の大きさに成長するように焼成する場合、焙焼炉の加熱温度の調整に加えて、加熱前の混合粉の粒径の大きさの制御が重要であり、粒径が微細な混合粉を用いて焼成した場合、過度の熱量が加わった粒子が必要以上に成長して粒径が粗大化してしまうことを見出した。
As a result of diligent investigation of the influence of various conditions on the particle size of lead ruthenium powder during formation, the present inventors roasted a mixed powder which is a coprecipitate of hydrate or hydroxide of ruthenium and lead. We found that the conditions had the strongest effect on the formation of coarse particles.
That is, usually, the roasting of the mixed powder is carried out by putting it in a roasting furnace heated to a predetermined temperature, or by putting it in a roasting furnace in a room temperature state and then raising the temperature to a predetermined temperature. However, in the lead ruthenate powder produced by such a conventional roasting method, the particle size is not sufficiently controlled, the particle size distribution is wide, and a large number of coarse particles having a particle size exceeding 1 μm are formed. In some cases.
The present inventors have diligently investigated the cause of the formation of a large number of coarse particles having such a wide particle size distribution and a particle size of more than 1 μm. As a result, the cause is due to the size of the particle size of the raw material powder used for the firing process and the variation in the temperature distribution in the roasting furnace, and when an excessive amount of heat is applied to the raw material powder particles, it suddenly occurs in a short time. It was found that grain growth occurs in the soil and it tends to become coarse. That is, when a mixed powder, which is a raw material powder having a fine particle size, is fired so that the particle size grows to a predetermined size, in addition to adjusting the heating temperature of the roasting furnace, the particles of the mixed powder before heating are used. It has been found that it is important to control the size of the diameter, and when firing using a mixed powder having a fine particle size, particles to which an excessive amount of heat is applied grow more than necessary and the particle size becomes coarse. ..
ルテニウム酸鉛粉の粗大粒子の形成を抑制するためには、低温で混合粉に与える供給熱量を少なくして焙焼することが効果的である。
しかしながら、低温での焙焼は、粗大粒子の形成を抑制できる一方、形成される粒子の成長が非常に遅く生産効率が悪い上、焙焼温度によっては長時間かけても十分な大きさの粒子を得ることができない場合がある。そのため、低温での焙焼では、粗大粒子は形成されないものの、近年の電子素子の小型化に対応した厚膜抵抗ペーストに要求される粒径に比べてさらに小さな、微細すぎる粒子しか得られない場合が生じ得る。
このため、低温での焙焼では、小型化した電子素子における一般的な厚膜抵抗ペースト等の製品に適用可能な粒径の酸化ルテニウム粉を生産性良く得るのは困難である。
In order to suppress the formation of coarse particles of lead ruthenate powder, it is effective to roast with a small amount of heat supplied to the mixed powder at a low temperature.
However, while roasting at a low temperature can suppress the formation of coarse particles, the growth of the formed particles is very slow and the production efficiency is poor, and depending on the roasting temperature, the particles are sufficiently large even if it takes a long time. May not be obtained. Therefore, when roasting at a low temperature does not form coarse particles, but only particles that are too fine and smaller than the particle size required for a thick film resistance paste corresponding to the recent miniaturization of electronic devices can be obtained. Can occur.
Therefore, in roasting at a low temperature, it is difficult to obtain highly productive ruthenium oxide powder having a particle size applicable to a product such as a general thick film resistance paste in a miniaturized electronic device.
また、供給熱量を少なくするためには、混合粉を高温で短時間にて焙焼する方法も考えられるが、その場合は温度の制御がより重要になる。
すなわち、ルテニウム酸鉛粉の粒径を所望の大きさに制御するためには、焙焼する混合粉全体をばらつきの小さい均一な温度で一斉に処理する必要がある。しかしながら、量産のために、焙焼炉内で一度に焙焼する混合粉の処理量が多くなると、焙焼炉内を均一な温度に制御することは困難である。
ルテニウム酸鉛粉を、粗大粒子を形成させない条件で製造するためには、炉内における、温度分布において最高温度となる箇所で、所望の粒径に形成する焙焼条件で、原料粉である水酸化ルテニウム粉を焙焼する必要がある。
しかし、この場合、炉内の最高温度となる箇所と、最高温度よりも低い温度となる箇所との間でルテニウム酸鉛粉の粒子の生成タイミングに差を生じ、最高温度よりも低い温度となる箇所で生成されるルテニウム酸鉛粉の粒子がより小さな粒径となってしまい、厚膜抵抗ペースト等の製品に要求される粒径に満たない微細すぎる粒子を含んだばらつきの大きな粒度分布となってしまう虞がある。
その結果、１μｍ以上を超える粗大粒子の形成は抑制できるものの、微細すぎる粒子を含んだ、広い粒度分布を有するルテニウム酸鉛粉となり、そのようなルテニウム酸鉛粉を用いた厚膜抵抗ペーストは、分散性等に劣り、電気特性のばらつきを生じてしまう虞があり好ましくない。
Further, in order to reduce the amount of heat supplied, a method of roasting the mixed powder at a high temperature for a short time is conceivable, but in that case, temperature control becomes more important.
That is, in order to control the particle size of the lead ruthenate powder to a desired size, it is necessary to simultaneously treat the entire roasted mixed powder at a uniform temperature with little variation. However, for mass production, if the amount of mixed powder roasted at one time in the roasting furnace is large, it is difficult to control the temperature inside the roasting furnace to a uniform temperature.
In order to produce lead ruthenate powder under conditions that do not form coarse particles, water, which is a raw material powder, is formed under roasting conditions in which a desired particle size is formed at a location in the furnace where the maximum temperature is reached in the temperature distribution. Ruthenium oxide powder needs to be roasted.
However, in this case, there is a difference in the production timing of the lead ruthenate powder particles between the place where the maximum temperature is reached in the furnace and the place where the temperature is lower than the maximum temperature, and the temperature becomes lower than the maximum temperature. The particles of lead ruthenate powder generated at the site have a smaller particle size, resulting in a highly variable particle size distribution including particles that are too fine and less than the particle size required for products such as thick film resistance paste. There is a risk that it will end up.
As a result, although the formation of coarse particles exceeding 1 μm can be suppressed, lead ruthenate powder having a wide particle size distribution containing particles that are too fine is obtained, and a thick film resistance paste using such lead ruthenate powder is produced. It is not preferable because it is inferior in dispersibility and may cause variations in electrical characteristics.
このような問題を解決するため、本発明者らは、更に鋭意検討を重ねた。その結果、ルテニウムと鉛の水和物または水酸化物の共沈物である混合粉を、低温を一定時間保持した状態で焙焼して得られるルテニウム酸鉛粉が、ばらつきが抑えられた、小さな粒径の微細粉となり得ることを見出した。
また、本発明者らは、その微細なルテニウム酸鉛粉を、さらに温度を上げて、一定時間その温度を保持した状態で焙焼すると、新たなルテニウム酸鉛粉の生成が抑制された状態で、既に生成されている微細なルテニウム酸鉛粉が成長し、焙焼温度に応じた一定の粒径のルテニウム酸鉛粉となることを見出した。
また、本発明者らは、焙焼処理時の条件を鋭意検討した結果、焙焼処理を行う対象となる粉の粒径に応じて、焙焼温度や焙焼時間を適切な条件に設定する焙焼処理を、段階的に行うことでルテニウム酸鉛粉の成長挙動を制御することが可能となり、粗大粒子の形成を抑制し、ルテニウム酸鉛粉の粒径を任意に、かつ、ばらつきを小さく制御できることを見出し、本発明を完成させるに至った。
In order to solve such a problem, the present inventors have conducted further diligent studies. As a result, the variation of the lead ruthenate powder obtained by roasting a mixed powder which is a coprecipitate of ruthenium and lead hydrate or hydroxide while keeping the low temperature for a certain period of time was suppressed. It has been found that it can be a fine powder having a small particle size.
Further, when the fine lead ruthenate powder is roasted in a state where the temperature is further raised and the temperature is maintained for a certain period of time, the present inventors suppress the production of new lead ruthenate powder. , It has been found that the fine lead ruthenate powder that has already been produced grows into lead ruthenate powder having a certain particle size according to the roasting temperature.
In addition, as a result of diligently examining the conditions during the roasting process, the present inventors set the roasting temperature and the roasting time to appropriate conditions according to the particle size of the powder to be roasted. By performing the roasting treatment step by step, it becomes possible to control the growth behavior of the lead ruthenate powder, suppress the formation of coarse particles, and make the particle size of the lead ruthenate powder arbitrary and small in variation. They have found that they can be controlled and have completed the present invention.
すなわち、本発明の第一の態様は、ルテニウムと鉛の水和物または水酸化物との混合粉を焙焼し、ルテニウム酸鉛粉を得る焙焼工程を有するルテニウム酸鉛粉の製造方法であって、前記焙焼工程は、前記混合粉を、所定の焙焼温度を一定時間保持して焙焼する第１回目の焙焼処理と、第１回目の焙焼処理温度よりも高い所定の焙焼温度を一定時間保持して焙焼する焙焼処理を１回以上繰り返して行う、複数回の焙焼工程からなり、第１回目の焙焼処理の焙焼温度が５００℃以上５７５℃以下の所定温度であり、最終の焙焼温度が６００℃以上７５０℃以下であることを特徴とするルテニウム酸鉛粉の製造方法である。 That is, the first aspect of the present invention is a method for producing lead ruthenate powder, which comprises a roasting step of roasting a mixed powder of ruthenium and lead hydrate or hydroxide to obtain lead ruthenate powder. Therefore, in the roasting step, the first roasting process in which the mixed powder is roasted while maintaining a predetermined roasting temperature for a certain period of time and a predetermined roasting process higher than the first roasting process temperature are performed. It consists of multiple roasting steps in which the roasting process of holding the roasting temperature for a certain period of time is repeated one or more times, and the roasting temperature of the first roasting process is 500 ° C. or higher and 575 ° C. or lower. This is a method for producing lead ruthenate powder, which is characterized in that the final roasting temperature is 600 ° C. or higher and 750 ° C. or lower.
また、本発明のルテニウム酸鉛粉の製造方法においては、前記焙焼工程における、第１回目の焙焼処理の次の焙焼処理が最終の焙焼処理であることが好ましい。 Further, in the method for producing lead ruthenate powder of the present invention, it is preferable that the roasting treatment following the first roasting treatment in the roasting step is the final roasting treatment.
また、本発明の第二の態様は、上記本発明のルテニウム酸鉛粉の製造方法を用いて形成されたルテニウム酸鉛粉であって、平均粒径が３５ｎｍ以上６５ｎｍ以下であることを特徴とするルテニウム酸鉛粉である。 A second aspect of the present invention is the lead ruthenate powder formed by using the method for producing lead ruthenate powder of the present invention, wherein the average particle size is 35 nm or more and 65 nm or less. It is a lead powder of ruthenate.
本発明の第三の態様は、上記本発明のルテニウム酸鉛粉を含有することを特徴とする厚膜抵抗ペーストである。 A third aspect of the present invention is a thick film resistance paste containing the lead ruthenate powder of the present invention.
本発明によれば、粗大粒子の形成を抑制するために硫黄を含んでしまうか、若しくは粒度分布が広く、微細粒子や粗大粒子を含有してしまう従来のルテニウム酸鉛粉とは異なり、硫黄の含有が無く、かつ、粒径を制御し、特に電気特性悪化の要因となる１μｍを超える粗大粒子の形成を極力低減させ、粒径の揃ったルテニウム酸鉛粉の製造方法及びルテニウム酸鉛粉、並びにルテニウム酸鉛粉を含有する厚膜抵抗ペーストが得られる。 According to the present invention, unlike the conventional lead ruthenate powder, which contains sulfur in order to suppress the formation of coarse particles, or has a wide particle size distribution and contains fine particles or coarse particles, sulfur A method for producing lead ruthenate powder having a uniform particle size and a method for producing lead ruthenate powder, which has no content and controls the particle size, and particularly reduces the formation of coarse particles exceeding 1 μm, which causes deterioration of electrical characteristics. In addition, a thick film resistance paste containing lead ruthenate powder can be obtained.
以下、本発明の実施形態について説明するが、本発明は、下記の実施形態に制限されるものではなく、本発明の範囲内で、下記実施形態に種々の変形および置換を加えることができる。 Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments, and various modifications and substitutions can be added to the following embodiments within the scope of the present invention.
（初期焙焼工程）
本発明のルテニウム酸鉛粉の製造方法では、ルテニウムと鉛の水和物または水酸化物の混合粉を用いる。混合粉の製造方法は特に限定されない。例えば、金属ルテニウムをアルカリ条件下で酸化処理して得たルテニウム酸塩の水溶液に鉛イオンを添加し、ｐＨを調整し、アルコール等の還元剤により還元することで、共沈物として混合粉を得ることができる。なお、ルテニウム酸塩の水溶液は、金属ルテニウムをアルカリ溶融して得た固体のルテニウム酸塩を水で溶解して得ることもできる。
(Initial roasting process)
In the method for producing lead ruthenium acid powder of the present invention, a mixed powder of hydrate or hydroxide of ruthenium and lead is used. The method for producing the mixed powder is not particularly limited. For example, lead ions are added to an aqueous solution of ruthenium salt obtained by oxidizing metallic ruthenium under alkaline conditions, the pH is adjusted, and the mixture is reduced with a reducing agent such as alcohol to produce a mixed powder as a co-precipitate. Obtainable. The aqueous solution of ruthenium acid can also be obtained by dissolving solid ruthenium acid salt obtained by alkali-melting metallic ruthenium with water.
得られたルテニウムと鉛を含有する混合粉を、初期焙焼することによって、近年の電子素子の小型化に伴い、厚膜抵抗ペースト等の製品に要求される粒径よりも小さく、ばらつきが抑えられた、微細な粒径のルテニウム酸鉛粉を得る。初期焙焼処理（第１回目の焙焼処理）における焙焼温度は、その後に行う焙焼回数と最終的に得る粒径に応じて、５００℃以上５７５℃以下の範囲内の所定の温度に任意に設定する。初期焙焼処理における焙焼温度が５００℃未満であると、混合粉に含まれる水酸化ルテニウムが酸化ルテニウムへと変化してしまい、酸化ルテニウムが多量に生成してしまう場合があるので好ましくない。また、初期焙焼処理における焙焼温度が５７５℃よりも高いと、生成する初期のルテニウム酸鉛粉が微細な粒径のままには留まらず、粗大粒子へと成長する場合があるので好ましくない。 By initial roasting the obtained mixed powder containing ruthenium and lead, the particle size is smaller than the particle size required for products such as thick film resistance paste due to the recent miniaturization of electronic devices, and variation is suppressed. The obtained lead ruthenate powder having a fine particle size is obtained. The roasting temperature in the initial roasting treatment (first roasting treatment) is set to a predetermined temperature within the range of 500 ° C. or higher and 575 ° C. or lower, depending on the number of subsequent roasting and the final particle size obtained. Set arbitrarily. If the roasting temperature in the initial roasting treatment is less than 500 ° C., ruthenium hydroxide contained in the mixed powder is changed to ruthenium oxide, which is not preferable because a large amount of ruthenium oxide may be produced. Further, if the roasting temperature in the initial roasting treatment is higher than 575 ° C., the initial lead ruthenate powder to be produced does not remain in the fine particle size and may grow into coarse particles, which is not preferable. ..
初期焙焼処理における焙焼時間は特に限定されないが、生成される初期のルテニウム酸鉛粉の粒径が揃うまで、初期焙焼処理における焙焼温度を一定時間保持し続けて焙焼するのが好ましい。本発明の製造方法の初期焙焼処理によって生成されるルテニウム酸鉛粉の到達粒径は、焙焼温度を十分な焙焼時間保持して焙焼処理する場合は、初期焙焼処理における焙焼温度の影響を受ける。必要以上に焙焼時間を長くしても、本発明の初期焙焼処理における焙焼温度範囲内では、殆どのルテニウム酸鉛粉がその焙焼条件（焙焼温度、焙焼時間）に応じた粒径に成長し、焙焼条件に応じた粒径を超える粒径には成長しない。そのため、生成されるルテニウム酸鉛粉の粒径のばらつきを低減させるためには、初期焙焼処理においては、上述のように５００℃以上５７５℃以下の範囲内の所定温度を粒成長が飽和するまでの十分な焙焼時間保持するのが好ましい。このように、初期焙焼処理における焙焼温度と焙焼時間を定めることによって、生成されるルテニウム酸鉛粉の初期粒径を制御することができるため、製造する最終的なルテニウム酸鉛粉の最終粒径の目標値と、その後の焙焼温度と焙焼時間、及び焙焼処理回数に応じて、それに適した初期粒径にするための初期焙焼処理における焙焼条件である焙焼温度と焙焼時間を設定する。
また、初期焙焼処理の際には、混合粉を、予め５００℃以上５７５℃以下の範囲内の所定の焙焼温度に加熱した炉内に投入し、その後その焙焼温度を所定時間保持するのが一般的であるが、室温などの５００℃未満の温度の炉内に混合粉を投入した後、所定の初期焙焼温度に昇温してもよい。その場合、初期焙焼処理における所定の焙焼温度に到達するまで所定の昇温速度で昇温した後、設定した初期焙焼処理における所定の焙焼温度を一定時間保持するのが好ましい。しかし、混合粉を３００℃以上５００℃未満の温度で昇温している時間が長いと、水酸化ルテニウム粉が鉛と反応してルテニウム酸鉛粉になる前に酸化ルテニウム粉を多く生成してしまう場合があるので、昇温速度は１０℃／分以上にするのが好ましい。また、好ましくは、生成されるルテニウム酸鉛粉の粒径のばらつきが抑え易くなるように、昇温速度は１０℃／分以上３０℃／分以下にするのがよい。
The roasting time in the initial roasting process is not particularly limited, but roasting is performed while maintaining the roasting temperature in the initial roasting process for a certain period of time until the particles of the initial lead ruthenate powder to be produced are uniform. preferable. The ultimate particle size of lead ruthenate powder produced by the initial roasting treatment of the production method of the present invention is roasting in the initial roasting treatment when the roasting treatment is performed while maintaining the roasting temperature for a sufficient roasting time. Affected by temperature. Even if the roasting time is lengthened more than necessary, most of the lead ruthenate powders correspond to the roasting conditions (roasting temperature, roasting time) within the roasting temperature range in the initial roasting process of the present invention. It grows to a particle size and does not grow to a particle size that exceeds the particle size according to the roasting conditions. Therefore, in order to reduce the variation in the particle size of the produced lead ruthenate powder, the grain growth is saturated at a predetermined temperature within the range of 500 ° C. or higher and 575 ° C. or lower as described above in the initial roasting treatment. It is preferable to maintain a sufficient roasting time up to. In this way, by determining the roasting temperature and roasting time in the initial roasting process, the initial particle size of the produced lead ruthenate powder can be controlled, so that the final lead ruthenate powder to be produced can be controlled. Depending on the target value of the final particle size, the subsequent roasting temperature and roasting time, and the number of roasting processes, the roasting temperature, which is the roasting condition in the initial roasting process to obtain the appropriate initial particle size. And set the roasting time.
Further, in the initial roasting treatment, the mixed powder is put into a furnace preheated to a predetermined roasting temperature within the range of 500 ° C. or higher and 575 ° C. or lower, and then the roasting temperature is maintained for a predetermined time. Although it is common, the temperature may be raised to a predetermined initial roasting temperature after the mixed powder is put into a furnace having a temperature of less than 500 ° C. such as room temperature. In that case, it is preferable to raise the temperature at a predetermined heating rate until the predetermined roasting temperature in the initial roasting process is reached, and then maintain the predetermined roasting temperature in the set initial roasting process for a certain period of time. However, if the temperature of the mixed powder is raised at a temperature of 300 ° C. or higher and lower than 500 ° C. for a long time, a large amount of ruthenium oxide powder is produced before the ruthenium hydroxide powder reacts with lead to become ruthenium tetrate powder. The temperature rise rate is preferably 10 ° C./min or higher because it may cause a problem. Further, preferably, the rate of temperature rise is preferably 10 ° C./min or more and 30 ° C./min or less so that the variation in the particle size of the produced lead ruthenate powder can be easily suppressed.
（最終焙焼工程）
初期焙焼工程で得られたルテニウム酸鉛粉を更に少なくとも１回、焙焼温度を上げて、その焙焼温度で一定時間焙焼する焙焼工程により、所定の粒径のルテニウム酸鉛粉を得ることができる。本発明では、この初期焙焼工程の後に、前回の焙焼工程の焙焼温度よりも高い所定の焙焼温度を一定時間保持して焙焼する焙焼工程のうち、最後の焙焼工程を最終焙焼工程、初期焙焼工程と最終焙焼工程との間の焙焼工程を中間焙焼工程と称することとする。
最終焙焼工程の焙焼温度は、形成を所望する、ルテニウム酸鉛粉の粒径に応じて任意に設定することができるが、ルテニウム酸鉛粉を用いた、小型化の進む電子素子用の厚膜抵抗ペースト用として好適に用いられる粒径（平均粒径が４５ｎｍ程度）とするために、最終焙焼工程の焙焼温度は６００℃以上７５０℃以下の範囲内の所定の温度に任意に設定する。
ルテニウム酸鉛粉の粒成長を遅くし、粒径を精密に制御するには、焙焼温度が低い方が好ましい。しかし、最終焙焼工程における焙焼温度が６００℃未満であると、ルテニウム酸鉛粉の粒成長が非常に遅く、所定の粒径に成長させるのに時間がかかりすぎるので好ましくない。ルテニウム酸鉛粉の粒成長を早くするには焙焼温度を高くするのが好ましい。しかし、最終焙焼工程における焙焼温度が７５０℃を超えると粒成長の速度が速くなり過ぎ、粒径の制御が難しくなるので好ましくない。最終焙焼工程に用いるルテニウム酸鉛粉は、初期焙焼工程あるいは更に各中間焙焼工程において、例えば一旦室温まで冷却して炉内から取り出し、その後に所定の焙焼温度に加熱した焙焼炉に投入しても良いし、初期焙焼工程あるいは更には各中間焙焼工程から一度も冷却することなく、それぞれの焙焼処理工程間の温度を所定の昇温速度で昇温することによって、段階的に焙焼温度を上げた焙焼工程を連続して行い、そのまま最終焙焼工程に移行するようにしてもよい。
なお、それぞれの焙焼工程間の昇温速度は、遅ければ遅いほど、生成されるルテニウム酸鉛粉の粒径にばらつきが生じ難くなるので好ましい。但し、昇温速度を遅くし過ぎると、ルテニウム酸鉛粉を製造する全体の処理時間が長くなり過ぎて、生産性が低下したり、低温領域では酸化ルテニウム粉が混在してしまったりする場合がある。このため、ルテニウム酸鉛粉の生産性と、生成されるルテニウム酸鉛粉の粒径のばらつき制御や酸化ルテニウム粉の混在抑制のため、昇温速度は、例えば、１０℃／分以上３０℃／分以下とするのが好ましい。
その他、本発明のルテニウム酸鉛粉の製造方法においては、生成されるルテニウム酸鉛粉の粒径のばらつき制御のため、各焙焼工程で用いる焙焼炉内の、熱処理時の炉内温度分布の指標である、炉内最高温度と炉内最低温度の差が１０℃以内であることが好ましい。
(Final roasting process)
Lead ruthenate powder with a predetermined particle size is produced by a roasting step in which the lead ruthenate powder obtained in the initial roasting step is further raised at least once and then roasted at that roasting temperature for a certain period of time. Obtainable. In the present invention, after this initial roasting step, the last roasting step of the roasting steps in which a predetermined roasting temperature higher than the roasting temperature of the previous roasting step is maintained for a certain period of time is performed. The final roasting step, the roasting step between the initial roasting step and the final roasting step is referred to as an intermediate roasting step.
The roasting temperature in the final roasting step can be arbitrarily set according to the particle size of the lead ruthenate powder desired to be formed, but for electronic devices using lead ruthenate powder, which are becoming smaller and smaller. The roasting temperature in the final roasting step is arbitrarily set to a predetermined temperature within the range of 600 ° C. or higher and 750 ° C. or lower in order to obtain a particle size (average particle size of about 45 nm) preferably used for thick film resistance paste. Set.
In order to slow down the grain growth of lead ruthenate powder and precisely control the particle size, it is preferable that the roasting temperature is low. However, if the roasting temperature in the final roasting step is less than 600 ° C., the grain growth of the lead ruthenate powder is very slow, and it takes too much time to grow to a predetermined particle size, which is not preferable. In order to accelerate the grain growth of lead ruthenate powder, it is preferable to raise the roasting temperature. However, if the roasting temperature in the final roasting step exceeds 750 ° C., the rate of grain growth becomes too high and it becomes difficult to control the particle size, which is not preferable. The lead ruthenate powder used in the final roasting step is a roasting furnace that is once cooled to room temperature, taken out of the furnace, and then heated to a predetermined roasting temperature in the initial roasting step or each intermediate roasting step. By raising the temperature between the respective roasting treatment steps at a predetermined heating rate without cooling even once from the initial roasting step or further each intermediate roasting step. The roasting process in which the roasting temperature is gradually raised may be continuously performed, and the process may be directly shifted to the final roasting process.
The slower the rate of temperature rise between the roasting steps, the less likely it is that the particle size of the lead ruthenate powder produced will vary, which is preferable. However, if the rate of temperature rise is too slow, the overall processing time for producing lead ruthenium tetrate may become too long, resulting in a decrease in productivity or a mixture of ruthenium oxide powder in the low temperature region. is there. Therefore, in order to control the productivity of the ruthenium tetrate powder, control the variation in the particle size of the produced ruthenium tetrate powder, and suppress the mixture of the ruthenium oxide powder, the temperature rise rate is, for example, 10 ° C./min or more and 30 ° C./min. It is preferably less than a minute.
In addition, in the method for producing lead ruthenate powder of the present invention, the temperature distribution in the roasting furnace used in each roasting step during heat treatment is used to control the variation in the particle size of the lead ruthenate powder produced. It is preferable that the difference between the maximum temperature in the furnace and the minimum temperature in the furnace, which is an index of the above, is within 10 ° C.
以下、本発明をさらに詳細な実施例に基づき説明するが、本発明は、これらの実施例に限定されるものではない。 Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.
（評価試験１：初期焙焼工程の焙焼温度による粗大粒子抑制効果）
１５０℃で乾燥させた、ルテニウムと鉛の水和物または水酸化物の混合粉５ｇをアルミナるつぼに入れ、最終焙焼工程の焙焼温度を７００℃、焙焼時間を１２０分とした以外は表１に示す所定の焙焼条件で三段階の焙焼処理を行い、ルテニウム酸鉛粉を得た（試料１−２〜試料１−７）。なお、各指定の焙焼温度における、炉内最高温度と炉内最低温度の差は９℃以下であった。また、各指定の焙焼温度にまで昇温する際の昇温速度は３０℃／分とした。
また、比較のために、初期焙焼処理や段階的に焙焼温度を上げる焙焼処理を行わない従来の焙焼処理方法として、７００℃の焙焼温度での焙焼処理のみを行って製造したルテニウム酸鉛粉も得た（試料１−１）。各試料の焙焼処理における焙焼条件（焙焼温度、焙焼時間）を表１に示す。
なお、本実施例（試料１−３〜試料１−６）及び比較例（試料１−１、試料１−２、試料１−７）においては、形成するルテニウム酸鉛粉の平均粒径（の目標値）が４７ｎｍ程度になる焙焼温度、焙焼時間の組合せを焙焼条件とした。
(Evaluation test 1: Effect of suppressing coarse particles due to roasting temperature in the initial roasting process)
Except that 5 g of a mixture of ruthenium and lead hydrate or hydroxide dried at 150 ° C was placed in an alumina crucible, the roasting temperature in the final roasting step was 700 ° C, and the roasting time was 120 minutes. A three-step roasting treatment was carried out under the predetermined roasting conditions shown in Table 1 to obtain lead ruthenate powder (Samples 1-2 to Samples 1-7). The difference between the maximum temperature in the furnace and the minimum temperature in the furnace at each designated roasting temperature was 9 ° C. or less. Further, the rate of temperature rise when raising the temperature to each designated roasting temperature was set to 30 ° C./min.
Further, for comparison, as a conventional roasting treatment method in which the initial roasting treatment and the roasting treatment in which the roasting temperature is gradually raised are not performed, only the roasting treatment at a roasting temperature of 700 ° C. is performed. The resulting lead ruthenate powder was also obtained (Sample 1-1). Table 1 shows the roasting conditions (roasting temperature, roasting time) in the roasting process of each sample.
In this example (Sample 1-3 to Sample 1-6) and Comparative Example (Sample 1-1, Sample 1-2, Sample 1-7), the average particle size of the lead ruthenate powder to be formed (of) The roasting condition was a combination of a roasting temperature and a roasting time at which the target value) was about 47 nm.
＜粗大粒子評価＞
夫々の焙焼条件で焙焼処理することにより製造したルテニウム酸鉛粉を０．３ｇ採取し、１００ｍＬビーカーに入れ、更に純水１００ｍＬを加えた。このビーカーに超音波を照射し、ルテニウム酸鉛粉を純水中に分散させた。その後、ビーカーを静置することでルテニウム酸鉛粉の粗大粒子をビーカー底に沈降させた。１０分間静置した後、ビーカー内の上澄みを除去することでルテニウム酸鉛粉の微細な粒子を効率的に除去し、更にフィルターでろ過することにより、ルテニウム酸鉛粉の粗大粒子を効率的に採取した。本評価においては、粒径が１μｍを超えるルテニウム酸鉛粉を粗大粒子として計測し、計測した粗大粒子数をルテニウム酸鉛粉における粒径のばらつきを示す評価値として用いた。
このような計測値をルテニウム酸鉛粉における粒径のばらつきを示す評価値として用いたのは、ルテニウム酸鉛粉中に存在する個々の粒子が非常に小さく、全ての粒子について粒径を測定して、標準偏差を算出することが非常に困難であり、当該技術分野においてルテニウム酸鉛粉の粒径のばらつきを示す基準が確立されていないことによる。
詳しくは、採取したルテニウム酸鉛粉の粒子を、走査型電子顕微鏡にて倍率２０００倍で観察し、６４μｍ×４８μｍの視野内に存在する粒径が１μｍを超える粗大粒子数を２０視野計数し、その総数を各試料のルテニウム酸鉛粉における粒径が１μｍを超える粗大粒子数（の評価値）とした。この方法により計測した、各試料のルテニウム酸鉛粉における粒径が１μｍを超える粗大粒子数（の評価値）を表１に示す。
なお、粗大粒子の採取に関しては、必要に応じて、上述の上澄みを除去する操作をした後に再び純水を追加し超音波処理を加える操作を複数回繰り返してもよい。このような操作をすることで、粒径が１μｍを超える粗大粒子数の計測の妨げとなる微細な粒子をより確実に除去することができる。
<Evaluation of coarse particles>
0.3 g of lead ruthenate powder produced by roasting under each roasting condition was collected, placed in a 100 mL beaker, and 100 mL of pure water was further added. The beaker was irradiated with ultrasonic waves to disperse lead ruthenate powder in pure water. Then, the beaker was allowed to stand so that the coarse particles of lead ruthenate powder were settled on the bottom of the beaker. After allowing to stand for 10 minutes, fine particles of lead ruthenate powder are efficiently removed by removing the supernatant in the beaker, and coarse particles of lead ruthenate powder are efficiently removed by filtering with a filter. Collected. In this evaluation, lead ruthenate powder having a particle size of more than 1 μm was measured as coarse particles, and the measured number of coarse particles was used as an evaluation value indicating variation in particle size in lead ruthenate powder.
Such a measured value was used as an evaluation value indicating the variation in particle size in the lead ruthenate powder because the individual particles present in the lead ruthenate powder were very small, and the particle size was measured for all the particles. Therefore, it is very difficult to calculate the standard deviation, and the standard indicating the variation in the particle size of the lead ruthenate powder has not been established in the technical field.
Specifically, the collected lead ruthenate powder particles were observed with a scanning electron microscope at a magnification of 2000 times, and the number of coarse particles having a particle size exceeding 1 μm existing in a field of 64 μm × 48 μm was counted in 20 fields. The total number was taken as the number of coarse particles (evaluation value) in which the particle size of the lead ruthenate powder of each sample exceeded 1 μm. Table 1 shows (evaluation values) of the number of coarse particles having a particle size of more than 1 μm in the lead ruthenate powder of each sample measured by this method.
Regarding the collection of coarse particles, if necessary, the operation of removing the supernatant and then adding pure water again and applying ultrasonic treatment may be repeated a plurality of times. By performing such an operation, it is possible to more reliably remove fine particles that hinder the measurement of the number of coarse particles having a particle size exceeding 1 μm.
＜ルテニウム酸鉛粉の平均粒径の算出＞
製造した各試料のルテニウム酸鉛粉の平均粒径を、ＢＥＴ法により測定した比表面積から算出した。算出した各試料の平均粒径を表１に示す。
The average particle size of the lead ruthenate powder of each of the produced samples was calculated from the specific surface area measured by the BET method. Table 1 shows the calculated average particle size of each sample.
表１に示すように、初期焙焼処理や段階的に焙焼温度を上げた中間焙焼処理を行わず、焙焼処理１回のみの従来の製法で製造した試料１−１は、平均粒径は４８．５ｎｍと目標値に近い平均粒径が得られてはいるものの、粒径が１μｍを超える粗大粒子数（の評価値）が９３１個と非常に多く粒径がばらつき、小型化の進む微小製品用の厚膜抵抗ペーストには適さないことが認められる結果となった。
また、本発明の範囲外である初期焙焼温度の低い試料１−２は、初期焙焼でルテニウム酸鉛粉を形成するには焙焼温度が低すぎて、酸化ルテニウム粉が優先的に形成されてしまい、中間焙焼からルテニウム酸鉛粉が形成されるものの、ルテニウム酸鉛粉の形成タイミングがずれてしまい、粒径のばらつきが大きく、粒径が１μｍを超える粗大粒子数（の評価値）が６２１個と多く、微小製品用の厚膜抵抗ペーストには適さないことが認められる結果となった。
これに対し、本発明の範囲内である試料１−３〜試料１−６は、目標値に近い平均粒径が得られ、かつ粒径が１μｍを超える粗大粒子数（の評価値）も１６１個以下と、従来品である試料１−１に比べて非常に少なくなり、粒径のばらつきが小さく抑えられているのが認められる結果となった。
初期焙焼温度を本発明の範囲よりも更に高くして、本発明の範囲外とした試料１−７は、粒径が１μｍを超える粗大粒子数（の評価値）が６２１個と非常に多く、小型化の進む微小製品用の厚膜抵抗ペーストには適さないことが認められる結果となった。これは、初期焙焼温度が高すぎるため、初期焙焼時に形成されるルテニウム酸鉛粉が粒径及びばらつきの大きな粉となってしまい、その後の中間焙焼や最終焙焼では十分にばらつきを抑えることができなかったためと考えられる。
As shown in Table 1, the sample 1-1 produced by the conventional method of only one roasting treatment without performing the initial roasting treatment or the intermediate roasting treatment in which the roasting temperature is gradually raised is the average grain size. Although the average particle size is 48.5 nm, which is close to the target value, the number of coarse particles (evaluation value) with a particle size exceeding 1 μm is as large as 931 and the particle size varies, resulting in miniaturization. The results show that it is not suitable for thick film resistance pastes for advanced micro products.
Further, in Sample 1-2 having a low initial roasting temperature, which is outside the scope of the present invention, the roasting temperature is too low to form lead ruthenium powder in the initial roasting, and ruthenium oxide powder is preferentially formed. Although lead ruthenate powder is formed from intermediate roasting, the timing of formation of lead ruthenate powder shifts, the particle size varies widely, and the number of coarse particles with a particle size exceeding 1 μm (evaluation value). ) Is as large as 621, and it is recognized that it is not suitable for thick film resistance paste for micro products.
On the other hand, Samples 1-3 to 1-6, which are within the scope of the present invention, have an average particle size close to the target value, and the number of coarse particles having a particle size exceeding 1 μm (evaluation value) is also 161. The number was less than the number, which was much smaller than that of the conventional sample 1-1, and it was confirmed that the variation in particle size was suppressed to a small extent.
Samples 1-7 in which the initial roasting temperature was further raised above the range of the present invention and were outside the range of the present invention had a very large number (evaluation value) of 621 coarse particles having a particle size exceeding 1 μm. The results show that it is not suitable for thick film resistance pastes for micro products, which are becoming smaller and smaller. This is because the initial roasting temperature is too high, so the lead ruthenate powder formed during the initial roasting becomes a powder with a large particle size and variation, and there is sufficient variation in the subsequent intermediate roasting and final roasting. It is probable that it could not be suppressed.
（評価試験２：最終焙焼工程の焙焼温度による粒子径への影響）
１５０℃で乾燥させた、ルテニウムと鉛の水和物または水酸化物の混合粉５ｇをアルミナるつぼに入れ、５２５℃で１２０分間初期焙焼し、その後所定の温度でそれぞれ１２０分間焙焼を行う三段階の焙焼処理とした以外は、評価試験１と同じ装置及び条件で行い、ルテニウム酸鉛粉を得た（試料２−１〜試料２−３）。各試料の焙焼処理における焙焼条件（焙焼温度、焙焼時間）を表２に示す。また、粗大粒子数の計測及びルテニウム酸鉛粉の平均粒径の算出を評価試験１と同様に行った。各試料のルテニウム酸鉛粉における粒径が１μｍを超える粗大粒子数（の評価値）及び平均粒径を表２に示す。
(Evaluation test 2: Effect of roasting temperature in the final roasting process on particle size)
5 g of a mixture of ruthenium and lead hydrate or hydroxide dried at 150 ° C. is placed in an alumina crucible and initially roasted at 525 ° C. for 120 minutes, and then roasted at a predetermined temperature for 120 minutes each. Except for the three-step roasting treatment, the same equipment and conditions as in Evaluation Test 1 were used to obtain lead ruthenate powder (Samples 2-1 to 2-3). Table 2 shows the roasting conditions (roasting temperature, roasting time) in the roasting process of each sample. Moreover, the measurement of the number of coarse particles and the calculation of the average particle size of the lead ruthenate powder were carried out in the same manner as in the evaluation test 1. Table 2 shows the number of coarse particles (evaluation values) and the average particle size of the lead ruthenate powder of each sample exceeding 1 μm.
表２に示すように、本評価試験における焙焼条件下では、粒径が１μｍを超える粗大粒子の形成を抑制したルテニウム酸鉛粉を得ることができることが認められる結果となった。
そして、本評価試験における条件下では、中間焙焼温度や最終焙焼温度が低いほど形成されるルテニウム酸鉛粉の平均粒径が小さく、かつ、粒径が１μｍを超える粗大粒子数（の評価値）が少なくなる傾向にあることや、中間焙焼温度や最終焙焼温度が高いほど形成されるルテニウム酸鉛粉の平均粒径が大きく、かつ、粒径が１μｍを超える粗大粒子数（の評価値）が多くなる傾向にあることが認められる結果となった。
As shown in Table 2, under the roasting conditions in this evaluation test, it was confirmed that lead ruthenate powder having suppressed formation of coarse particles having a particle size of more than 1 μm could be obtained.
Under the conditions in this evaluation test, the lower the intermediate roasting temperature and the final roasting temperature, the smaller the average particle size of the lead ruthenate powder formed, and the number of coarse particles (evaluation) in which the particle size exceeds 1 μm. The value) tends to decrease, and the higher the intermediate roasting temperature and the final roasting temperature, the larger the average particle size of the lead ruthenate powder formed, and the larger the number of coarse particles (the particle size exceeds 1 μm). The result shows that the evaluation value) tends to increase.
（評価試験３：最終焙焼工程の処理時間による粒子径への影響）
１５０℃で乾燥させた、ルテニウムと鉛の水和物または水酸化物の混合粉５ｇをアルミナるつぼに入れ、５２５℃で６０分間の初期焙焼、６００℃で６０分間の中間焙焼、７００℃で所定の時間による最終焙焼を表３に示した焙焼条件の組合せとし、それ以外は、評価試験１と同じ装置及び条件で行い、ルテニウム酸鉛粉を得た（試料３−１〜試料３−５）。
各試料の焙焼処理における焙焼条件（焙焼温度、焙焼時間）を表３に示す。また、粗大粒子数の計測及びルテニウム酸鉛粉の平均粒径の算出を評価試験１と同様に行った。各試料のルテニウム酸鉛粉における粒径が１μｍを超える粗大粒子数（の評価値）及び平均粒径を表３に示す。
(Evaluation test 3: Effect of processing time in the final roasting process on particle size)
5 g of a mixture of ruthenium and lead hydrate or hydroxide dried at 150 ° C is placed in an alumina crucible and initially roasted at 525 ° C for 60 minutes, intermediate roasted at 600 ° C for 60 minutes, 700 ° C. The final roasting for a predetermined time was performed under the same equipment and conditions as in Evaluation Test 1 except for the combination of roasting conditions shown in Table 3, to obtain lead ruthenate powder (Samples 3-1 to Sample). 3-5).
Table 3 shows the roasting conditions (roasting temperature, roasting time) in the roasting process of each sample. Moreover, the measurement of the number of coarse particles and the calculation of the average particle size of the lead ruthenate powder were carried out in the same manner as in the evaluation test 1. Table 3 shows the number of coarse particles (evaluation values) and the average particle size of the lead ruthenate powder of each sample exceeding 1 μm.
表３に示すように、中間焙焼処理を行い、最終焙焼時間が３０分と短い試料３−１は、粒径が１μｍを超える粗大粒子数（の評価値）が減少し、かつ、平均粒径が小さいことから、粒径のばらつきが小さいまま、粒成長が抑えられていることが認められる結果となった。また、中間焙焼処理を行い、最終焙焼時間が１５０分と長い試料３−２は、中間焙焼処理を行わず、最終焙焼時間が１２０分である試料３−４とほぼ変わらない粒径が１μｍを超える粗大粒子数（の評価値）と平均粒径を示しており、試料３−２の焙焼条件下での焙焼処理では、最終焙焼時間が１２０分以上で、粒成長が殆ど起きなくなることが認められる結果となった。また、試料３−１から中間焙焼を除いた二段階焙焼の試料３−３は、初期焙焼から最終焙焼までの温度差が大きく、最終焙焼の粒径のばらつきが大きくなり、試料３−１とほぼ同じ平均粒径でありながら、粒径が１μｍを超える粗大粒子数（の評価値）が多くなったことが認められる結果となった。中間焙焼を除いた二段階焙焼を行い、最終焙焼時間を１２０分とした試料３−４は、粒径のばらつきによる粒径が１μｍを超える粗大粒子数（の評価値）は試料３−３とほぼ同程度ながら、粒子の成長により、平均粒径が大きくなったことが認められる結果となった。試料３−１の初期焙焼を除いた条件に相当する試料３−５は、初期焙焼で形成されるルテニウム酸鉛粉の粒径のばらつきが大きくなり過ぎ、かつ、最終焙焼までの温度差が小さいため、平均粒径はあまり大きくならないものの、粒径が１μｍを超える粗大粒子数（の評価値）が非常に多くなることが認められる結果となった。 As shown in Table 3, in the sample 3-1 which was subjected to the intermediate roasting treatment and the final roasting time was as short as 30 minutes, the number of coarse particles (evaluation value) having a particle size exceeding 1 μm was reduced, and the average was Since the particle size was small, it was confirmed that the grain growth was suppressed while the variation in particle size was small. In addition, sample 3-2, which has undergone intermediate roasting and has a long final roasting time of 150 minutes, is almost the same as sample 3-4, which has not undergone intermediate roasting and has a final roasting time of 120 minutes. It shows the number of coarse particles (evaluation value) with a diameter of more than 1 μm and the average particle size. In the roasting treatment of sample 3-2 under roasting conditions, the final roasting time was 120 minutes or more, and grain growth occurred. The result was that it almost never occurred. Further, in the sample 3-3 of the two-stage roasting obtained by removing the intermediate roasting from the sample 3-1 the temperature difference from the initial roasting to the final roasting is large, and the particle size variation of the final roasting is large. It was confirmed that the number of coarse particles (evaluation value) having a particle size exceeding 1 μm was increased while having an average particle size almost the same as that of sample 3-1. Sample 3-4, which was subjected to two-step roasting excluding intermediate roasting and had a final roasting time of 120 minutes, had a coarse particle number (evaluation value) of more than 1 μm due to variation in particle size. Although it was almost the same as -3, it was confirmed that the average particle size increased due to the growth of the particles. In Sample 3-5, which corresponds to the conditions excluding the initial roasting of Sample 3-1 the particle size variation of the lead ruthenate powder formed in the initial roasting becomes too large, and the temperature until the final roasting is large. Since the difference is small, the average particle size is not so large, but the number of coarse particles (evaluation value) having a particle size exceeding 1 μm is found to be very large.
これらの試験結果から、５００℃以上５７５℃以下の比較的低温の焙焼温度で初期焙焼処理を行うことで、初期に形成される微細なルテニウム酸鉛粉の粒径のばらつきを抑えることができ、その後、段階的に焙焼温度を上げた焙焼処理を施し、その最終焙焼温度を６００℃以上７５０℃以下とすることで、粒径が１μｍを超える粗大粒子の形成を抑制しながら、粒径を、小型化の進む電子素子用の厚膜抵抗ペーストに適した平均粒径となるように成長させた、粒径のばらつきの小さいルテニウム酸鉛粉を容易に得ることが可能であることが分かった。 From these test results, it is possible to suppress the variation in the particle size of the fine lead ruthenate powder formed at the initial stage by performing the initial roasting treatment at a relatively low roasting temperature of 500 ° C. or higher and 575 ° C. or lower. After that, a roasting process in which the roasting temperature is gradually raised is performed, and the final roasting temperature is set to 600 ° C. or higher and 750 ° C. or lower, thereby suppressing the formation of coarse particles having a particle size exceeding 1 μm. It is possible to easily obtain lead ruthenate powder having a small particle size variation, which is grown so that the particle size becomes an average particle size suitable for a thick film resistance paste for electronic elements, which is becoming smaller and smaller. It turned out.
本発明は、小型化の進む、厚膜抵抗ペーストを用いた電子素子を製造することが求められている分野に有用である。 The present invention is useful in a field in which it is required to manufacture an electronic device using a thick film resistance paste, which is becoming smaller and smaller.
Claims (4)
前記焙焼工程は、前記混合粉を、所定の焙焼温度を一定時間保持して焙焼する第１回目の焙焼処理と、第１回目の焙焼処理温度よりも高い所定の焙焼温度を一定時間保持して焙焼する焙焼処理を１回以上繰り返して行う、複数回の焙焼工程からなり、
第１回目の焙焼処理の焙焼温度が５００℃以上５７５℃以下の所定温度であり、
最終の焙焼温度が６００℃以上７５０℃以下の所定温度であることを特徴とするルテニウム酸鉛粉の製造方法。 A method for producing lead ruthenium powder, which comprises a roasting step of roasting a mixed powder of ruthenium and lead hydrate or hydroxide to obtain lead ruthenate powder.
In the roasting step, the first roasting process in which the mixed powder is roasted while maintaining a predetermined roasting temperature for a certain period of time, and a predetermined roasting temperature higher than the first roasting treatment temperature. The roasting process consists of multiple roasting processes, in which the roasting process is repeated one or more times.
The roasting temperature of the first roasting treatment is a predetermined temperature of 500 ° C. or higher and 575 ° C. or lower.
A method for producing lead ruthenate powder, wherein the final roasting temperature is a predetermined temperature of 600 ° C. or higher and 750 ° C. or lower.
平均粒径が３５ｎｍ以上６５ｎｍ以下であることを特徴とするルテニウム酸鉛粉。 A lead ruthenate powder formed by using the method for producing lead ruthenate powder according to claim 1 or 2.
A lead ruthenate powder having an average particle size of 35 nm or more and 65 nm or less.
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| JPH01257136A (en) * | 1988-04-07 | 1989-10-13 | Sumitomo Metal Mining Co Ltd | Lead ruthenate fine powder for electrically conductive material, thick film resister paste containing same and production of lead ruthenate fine powder |
| JP2004172250A (en) * | 2002-11-19 | 2004-06-17 | Sumitomo Metal Mining Co Ltd | Thick-film resistor composition and thick-film resistor using the same, and method for manufacturing the same |
| JP2013053030A (en) * | 2011-09-02 | 2013-03-21 | Sumitomo Metal Mining Co Ltd | Plate-like ruthenium oxide powder, method for producing the same, and thick film resistor composition using the same |
| JP2018165222A (en) * | 2017-03-28 | 2018-10-25 | 住友金属鉱山株式会社 | Ruthenium acid bismuth particle containing glass, method for manufacturing the same, thick film resistor composition and thick film resistor paste |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH01257136A (en) * | 1988-04-07 | 1989-10-13 | Sumitomo Metal Mining Co Ltd | Lead ruthenate fine powder for electrically conductive material, thick film resister paste containing same and production of lead ruthenate fine powder |
| JP2004172250A (en) * | 2002-11-19 | 2004-06-17 | Sumitomo Metal Mining Co Ltd | Thick-film resistor composition and thick-film resistor using the same, and method for manufacturing the same |
| JP2013053030A (en) * | 2011-09-02 | 2013-03-21 | Sumitomo Metal Mining Co Ltd | Plate-like ruthenium oxide powder, method for producing the same, and thick film resistor composition using the same |
| JP2018165222A (en) * | 2017-03-28 | 2018-10-25 | 住友金属鉱山株式会社 | Ruthenium acid bismuth particle containing glass, method for manufacturing the same, thick film resistor composition and thick film resistor paste |
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