JP4687599B2 - Copper fine powder, method for producing the same, and conductive paste - Google Patents
Copper fine powder, method for producing the same, and conductive paste Download PDFInfo
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本発明は、電子材料の配線形成用として有用な銅微粉及びその製造方法、並びにその銅微粉を含有する導電性ペーストに関するものである。 The present invention relates to a copper fine powder useful for wiring formation of electronic materials, a method for producing the same, and a conductive paste containing the copper fine powder.
従来から、銅等の金属微粉は、導電性ペーストのような電子部品の配線形成材料として、プリント配線、半導体の内部配線、プリント配線板と電子部品との接続等に利用されている。特に粒径が１００ｎｍ以下の金属微粉は、通常のサブミクロン以上の粒子と異なり、極めて活性であるため融点が降下する現象が認められ、その融点降下現象を利用した低温焼成が検討されている。 Conventionally, fine metal powder such as copper has been used as a wiring forming material for electronic parts such as conductive paste for printed wiring, semiconductor internal wiring, connection between a printed wiring board and electronic parts, and the like. In particular, metal fine powder having a particle size of 100 nm or less is extremely active, unlike normal submicron or larger particles, and a phenomenon that the melting point is lowered is observed. Low-temperature firing using the melting point lowering phenomenon has been studied.
特に最近では、印刷技術の進歩により、スクリーン印刷やディスペンサーにより導電性ペーストを用いて配線パターンの印刷を行い、３００℃以下の低温焼成して配線を形成するアディティブ法が提案され、研究開発が進められている。アディティブ法は、従来の金属膜積層板へのフォトレジストによるパターニング、露光、エッチング、レジスト除去の各工程によるサブトラクティブ法と比較して、工程の大幅な簡略化と資源の節約の観点から着目されている。 In particular, due to advances in printing technology, an additive method has been proposed in which a wiring pattern is printed using conductive paste by screen printing or a dispenser, and the wiring is formed by baking at a low temperature of 300 ° C. or less, and research and development are proceeding. It has been. The additive method is attracting attention from the viewpoint of greatly simplifying the process and saving resources, compared to the conventional subtractive method of patterning, exposing, etching, and removing resist on a metal film laminate. ing.
また、電子部品の配線用材料として用いられる導電性ペーストでは、配線を形成した後の不純物の影響が問題となる。即ち、不純物元素が配線中の金属の腐食を促進し、絶縁部分にも金属元素が移動するマイグレーションが発生する結果、電界の影響もあって絶縁不良が発生する。不純物の中でも、アルカリ金属元素、アルカリ土類金属元素及びハロゲン元素が有害であることが知られている。特に３００℃以下の低温域での焼成では、高温での焼成と比較して焼成時の揮発による除去がほとんど期待できないため、金属微粉の合成段階で有害な不純物を極力低減させる必要がある。 Moreover, in the conductive paste used as a wiring material for electronic components, the influence of impurities after the wiring is formed becomes a problem. In other words, the impurity element promotes the corrosion of the metal in the wiring, and the migration of the metal element to the insulating portion occurs. As a result, the insulation failure occurs due to the influence of the electric field. Among impurities, alkali metal elements, alkaline earth metal elements and halogen elements are known to be harmful. In particular, when firing in a low temperature region of 300 ° C. or lower, removal by volatilization at the time of firing is hardly expected as compared with firing at a high temperature, and therefore it is necessary to reduce harmful impurities as much as possible in the synthesis stage of the metal fine powder.
上記した金属微粉の製造方法には、気相法によるものと、液相法によるものとが知られている。例えば、特開平３−３４２１１号公報には、原料となる金属を真空中又は微量のガス存在下で誘導加熱により蒸発させることによって、気相中から金属微粉を得る方法が開示されている。しかし、この方法では、高価な誘導加熱装置や真空装置等を必要とするうえ、金属微粉を真空装置内で生成するため一度に得られる金属微粉の量が少なく、工業的な大量生産には適していない。 As a method for producing the above-mentioned metal fine powder, a method using a gas phase method and a method using a liquid phase method are known. For example, Japanese Patent Application Laid-Open No. 3-34211 discloses a method of obtaining metal fine powder from a gas phase by evaporating a metal as a raw material by induction heating in a vacuum or in the presence of a small amount of gas. However, this method requires an expensive induction heating device, vacuum device, etc. and generates metal fines in the vacuum device, so the amount of metal fines obtained at a time is small and suitable for industrial mass production. Not.
上記の誘電加熱を利用する方法以外にも、金属を蒸発させ気相中から金属微粉を得る製造方法として、特開２００２−２４１８０６号公報にはアーク放電を利用したものが開示されているほか、電子ビームを利用したもの、レーザーを利用したもの等が知られている。しかしながら、これらの方法も上記の誘導加熱を利用した方法と同様の理由で高コストであるうえ、やはり工業的な大量生産に適した製造方法とは言い難い。 In addition to the above-described method using dielectric heating, as a production method for obtaining metal fine powder from the gas phase by evaporating metal, JP 2002-241806 discloses a method using arc discharge, Those using an electron beam and those using a laser are known. However, these methods are also costly for the same reason as the above-described method using induction heating, and it is difficult to say that these methods are also suitable for industrial mass production.
更に、気相法で合成する金属微粉は、金属が高温で気化して凝縮する過程を経るため、個々の微粒子がほぼ単結晶であり、液相から合成する微粒子よりも焼結活性が低いという特性を有するため、本質的に低温焼成による回路形成の用途には適していない。 Furthermore, the metal fine powder synthesized by the vapor phase method undergoes a process in which the metal vaporizes and condenses at a high temperature, so that the individual fine particles are almost single crystals, and the sintering activity is lower than the fine particles synthesized from the liquid phase. Due to its properties, it is essentially not suitable for use in circuit formation by low-temperature firing.
一方、液相中から金属微粉を製造する方法も提案されている。例えば、特開２００４−２５６７５７号公報には、クエン酸水素二アンモニウム水溶液の共存下に、塩化第二銅アンモニウム溶液をジメチルアミンボランで還元して、銅微粉を析出させる方法が開示されている。しかし、この方法では、得られる銅微粉に不純物として塩素の残留が予想されるため、電子部品の配線用材料としての用途には不適切である。また、還元剤として用いるジメチルアミンボランは還元力が高いため、安全面や環境面で取り扱いの難しい薬品であり、工業的な大量生産に適した製造方法ではない。 On the other hand, a method for producing metal fine powder from the liquid phase has also been proposed. For example, Japanese Patent Application Laid-Open No. 2004-256757 discloses a method of precipitating copper fine powder by reducing a cupric ammonium chloride solution with dimethylamine borane in the presence of a diammonium hydrogen citrate aqueous solution. However, this method is unsuitable for use as a wiring material for electronic parts because chlorine is expected to remain as impurities in the obtained copper fine powder. Further, dimethylamine borane used as a reducing agent is a chemical that is difficult to handle in terms of safety and environment because of its high reducing power, and is not a manufacturing method suitable for industrial mass production.
また、比較的粒子径が大きい銅粉の製造方法として、一価の銅化合物を酸で溶解することにより、金属銅と二価の銅化合物に分解する不均化反応を利用する方法が知られている。この不均化反応法は、取り扱いの容易な水溶液系において、安価な硫酸や酸化物原料を用いて銅粉が得られるという優れた特徴を有する。反応の副生成物は水であり、ガスの発生もなく、常温でも反応が可能であるため、安全且つエネルギー効率の良いプロセスである。 In addition, as a method for producing a copper powder having a relatively large particle size, a method utilizing a disproportionation reaction in which a monovalent copper compound is dissolved with an acid to decompose it into metallic copper and a divalent copper compound is known. ing. This disproportionation reaction method has an excellent feature that copper powder can be obtained using an inexpensive sulfuric acid or oxide raw material in an easily handled aqueous solution system. The reaction by-product is water, and it is a safe and energy-efficient process because it does not generate gas and can react at room temperature.
例えば、特開平５−９３２１４号公報には、オートクレーブを利用して高温とした硫酸銅(I)水溶液と室温の硫酸銅(II)水溶液を混合して、不均化反応により銅粉を得る方法が開示されている。この方法では、得られる銅粉は粒径の均一性と耐変色性に優れるが、サブミクロンメーター以上のものであるばかりか、オートクレーブという特殊な装置を用いて非酸化性雰囲気下で反応させ、しかも高温の液体を取り扱うという問題がある。 For example, Japanese Patent Laid-Open No. 5-93214 discloses a method of obtaining copper powder by a disproportionation reaction by mixing a copper (I) sulfate aqueous solution at a high temperature using an autoclave and a copper sulfate (II) aqueous solution at room temperature. Is disclosed. In this method, the obtained copper powder is excellent in uniformity of particle size and discoloration resistance, but it is not only a submicron meter or more, but it is reacted in a non-oxidizing atmosphere using a special device called an autoclave. Moreover, there is a problem of handling high-temperature liquids.
また、特開２００２−３６３６１８号公報には、銅(I)アンミン錯イオンを出発原料とし、溶液のｐＨの低下速度を制御する方法が開示されている。この方法では、特殊な装置を使用せず、反応温度も常温であるが、得られる銅粉はサブミクロンメーターのものである。更に、特開２００５−２５６０１２には、原料として亜酸化銅を用いてゼラチン等の天然樹脂を添加する方法が開示されているが、得られる銅粉はサブミクロンメーター以上のものである。 Japanese Patent Application Laid-Open No. 2002-363618 discloses a method of controlling the rate of pH reduction of a solution using a copper (I) ammine complex ion as a starting material. In this method, no special apparatus is used and the reaction temperature is room temperature, but the obtained copper powder is of a submicron meter. Furthermore, Japanese Patent Application Laid-Open No. 2005-256012 discloses a method of adding natural resin such as gelatin using cuprous oxide as a raw material, but the obtained copper powder is a submicron meter or more.
このように、不均化反応法は安全性や効率に優れ、焼結活性が高い金属微粉が得られるが、従来の方法では粒径１００ｎｍ以下の銅微粉の合成は極めて困難であった。そのため、粒径が１００ｎｍ以下で有害な不純物を含まず、電子材料の配線形成用として有用な銅微粉を、安全性が高く且つ低コストで製造することができ、工業的な大量生産に適した方法の提供が望まれている。 As described above, the disproportionation reaction method is excellent in safety and efficiency, and metal fine powder having high sintering activity can be obtained. However, synthesis of copper fine powder having a particle diameter of 100 nm or less was extremely difficult by the conventional method. Therefore, it is possible to produce a copper fine powder having a particle size of 100 nm or less and containing no harmful impurities, and useful for forming wiring of electronic materials at a high safety and at a low cost, and suitable for industrial mass production. It is desirable to provide a method.
本発明は、このような従来の事情に鑑みてなされたものであり、粒径が微細で且つ有害な不純物を含まず、低温焼成による電子材料の配線形成用として好適な銅微粉の製造方法、並びにその銅微粉、及びその銅微粉を用いた導電性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 such conventional circumstances, and has a fine particle diameter and does not contain harmful impurities, and is a method for producing copper fine powder suitable for wiring formation of electronic materials by low-temperature firing, And it aims at providing the electroconductive paste using the copper fine powder and the copper fine powder.
上記目的を解決するため、液相から銅微粉を製造する方法として、優れた特徴を有する不均化反応法に着目して鋭意検討した結果、特定の銅化合物と酸の組み合わせを用いることにより、更には銅化合物と酸との反応条件を制御することによって、従来の不均化反応法では得られなかった粒径１００ｎｍ以下の銅微粉が得られることを見出し、本発明を完成するに至ったものである。 In order to solve the above-mentioned purpose, as a method for producing copper fine powder from a liquid phase, as a result of intensive investigation focusing on a disproportionation reaction method having excellent characteristics, by using a combination of a specific copper compound and an acid, Furthermore, by controlling the reaction conditions between the copper compound and the acid, it was found that a copper fine powder having a particle size of 100 nm or less that could not be obtained by the conventional disproportionation reaction method was obtained, and the present invention was completed. Is.
即ち、本発明が提供する銅微粉の製造方法は、亜酸化銅粉のスラリーをヒドロキシカルボン酸と硫酸の混合酸と混合する工程と、混合溶液を撹拌保持する工程とからなり、亜酸化銅粉スラリーと混合酸の混合時間が５分未満であって、得られる銅微粉の平均粒径が１０〜５０ｎｍであり、且つ結晶子径と平均粒径の比が０.５以下であることを特徴とする。 That is, the method for producing copper fine powder provided by the present invention comprises a step of mixing a slurry of cuprous oxide powder with a mixed acid of hydroxycarboxylic acid and sulfuric acid, and a step of stirring and holding the mixed solution. The mixing time of the slurry and the mixed acid is less than 5 minutes, the average particle size of the obtained copper fine powder is 10 to 50 nm, and the ratio of the crystallite size to the average particle size is 0.5 or less And
上記本発明の銅微粉の製造方法においては、ヒドロキシカルボン酸としてクエン酸を用い、亜酸化銅粉中の銅に対して硫酸のモル比を１〜２０且つクエン酸のモル比を０.２〜６に調整し、亜酸化銅粉スラリーと混合酸の混合時間を２分未満とすることにより、平均粒径１０〜３０ｎｍの銅微粉を得ることができる。 In the method for producing the copper fine powder of the present invention, citric acid is used as the hydroxycarboxylic acid, the molar ratio of sulfuric acid is 1 to 20 and the molar ratio of citric acid is 0.2 to copper in the cuprous oxide powder. By adjusting to 6 and setting the mixing time of the cuprous oxide powder slurry and the mixed acid to less than 2 minutes, copper fine powder having an average particle size of 10 to 30 nm can be obtained.
また、本発明は、上記した銅微粉の製造方法により得られた銅微粉であって、平均粒径が１０〜５０ｎｍであり、且つ結晶子径と平均粒径の比が０.５以下であって、アルカリ金属元素及びアルカリ土類金属元素の含有量が１０重量ｐｐｍ以下であり、且つハロゲン元素の含有量が２０重量ｐｐｍ以下であることを特徴とする銅微粉を提供する。 Further, the present invention is a copper fine powder obtained by the above-described method for producing copper fine powder, wherein the average particle diameter is 10 to 50 nm, and the ratio of the crystallite diameter to the average particle diameter is 0.5 or less. The copper fine powder is characterized in that the content of alkali metal element and alkaline earth metal element is 10 ppm by weight or less and the content of halogen element is 20 ppm by weight or less.
更に、本発明は、上記した銅微粉の製造方法により得られた銅微粉に、有機溶剤を加えて混錬して得られるペーストであって、銅微粉の平均粒径が１０〜５０ｎｍであり、且つ結晶子径と平均粒径の比が０.５以下であって、アルカリ金属元素及びアルカリ土類金属元素の含有量が１０重量ｐｐｍ以下であり、且つハロゲン元素の含有量が２０重量ｐｐｍ以下であることを特徴とする導電性ペーストを提供するものである。 Furthermore, the present invention is a paste obtained by adding an organic solvent to the copper fine powder obtained by the above-described method for producing copper fine powder, and the average particle diameter of the copper fine powder is 10 to 50 nm, The ratio of the crystallite diameter to the average particle diameter is 0.5 or less, the content of alkali metal element and alkaline earth metal element is 10 ppm by weight or less, and the content of halogen element is 20 ppm by weight or less. The present invention provides a conductive paste characterized by the above.
本発明によれば、取り扱いの容易な水溶液系において、原料として安価な硫酸と亜酸化銅粉を用いて、電子材料の配線形成用として好適な銅微粉を得ることができる。しかも、常温で反応が可能であるうえ、水以外に反応副生成物がなく、工業的な大量生産に適した方法により、平均粒径が５０ｎｍ以下の微細粒子からなる銅微粉を低コストで製造することができる。 According to the present invention, it is possible to obtain copper fine powder suitable for wiring formation of electronic materials by using inexpensive sulfuric acid and cuprous oxide powder as raw materials in an easily handled aqueous solution system. In addition, it is possible to react at room temperature, and there are no reaction by-products other than water, and copper fine powder consisting of fine particles with an average particle size of 50 nm or less is produced at a low cost by a method suitable for industrial mass production. can do.
また、本発明の銅微粉は、上記のごとく粉末が微細なだけでなく、微細な粉末の各微粒子が更に微細な結晶子から構成される多結晶体である。従って、本発明の銅微粉を用いた導電性ペーストは、低温焼成による導電膜の形成に適しており、特に最近のスクリーン印刷やディスペンサー等を用いた配線密度のファインピッチ化に対応可能なものである。しかも、本発明の銅微粉は、アルカリ金属元素、アルカリ土類金属元素、ハロゲン元素などの有害な不純物を含まないため、マイグレーションの恐れも極めて少ない。 Further, the copper fine powder of the present invention is a polycrystalline body in which not only the powder is fine as described above but also each fine particle of the fine powder is composed of finer crystallites. Therefore, the conductive paste using the copper fine powder of the present invention is suitable for forming a conductive film by low-temperature firing, and is particularly compatible with finer pitches of wiring density using recent screen printing, dispensers and the like. is there. Moreover, since the copper fine powder of the present invention does not contain harmful impurities such as alkali metal elements, alkaline earth metal elements, and halogen elements, there is very little risk of migration.
本発明における銅微粉の製造方法は、公知の不均化反応法を応用して、一価の銅の化合物として安定な原料である亜酸化銅粉を、硫酸とヒドロキシカルボン酸の混合酸と急速に接触させて反応させることにより、従来の不均化反応法では得られなかった平均粒径５０ｎｍ以下の微細な銅微粉が得られる。しかも、得られる銅微粉は多結晶体であり、各粉末粒子を構成する結晶子の結晶子径ｃと上記平均粒径ｄの比ｃ／ｄは０.５以下である。 The method for producing copper fine powder in the present invention applies a known disproportionation reaction method to rapidly convert cuprous oxide powder, which is a stable raw material as a monovalent copper compound, to a mixed acid of sulfuric acid and hydroxycarboxylic acid. By making it contact and make it react, the fine copper fine powder with an average particle diameter of 50 nm or less which was not obtained by the conventional disproportionation reaction method is obtained. And the copper fine powder obtained is a polycrystal, and ratio c / d of the crystallite diameter c of the crystallite which comprises each powder particle, and the said average particle diameter d is 0.5 or less.
即ち、本発明方法は、亜酸化銅粉のスラリーをヒドロキシカルボン酸と硫酸の混合酸と混合する工程と、得られた混合溶液を撹拌保持する工程とからなる。上記亜酸化銅粉スラリーと混合酸との混合工程では、両者を急速に接触させて反応させることにより、反応初期に銅微粉の核が短時間に大量に発生する。この大量の微細な核の生成が、引き続いての撹拌保持の工程を経て得られる銅微粉の微細化に寄与するものと考えられる。尚、亜酸化銅粉スラリーに対して、硫酸とヒドロキシカルボン酸を個別に添加することもできるが、混合の均一性や安全性などを考慮すると、硫酸とヒドロキシカルボン酸を予め混合した混合酸を用いることが好ましい。 That is, the method of the present invention comprises a step of mixing a cuprous oxide powder slurry with a mixed acid of hydroxycarboxylic acid and sulfuric acid, and a step of stirring and holding the obtained mixed solution. In the mixing step of the cuprous oxide powder slurry and the mixed acid, a large amount of copper fine powder nuclei are generated in a short time in the initial stage of the reaction by rapidly bringing them into contact with each other for reaction. It is considered that the generation of a large amount of fine nuclei contributes to the refinement of the copper fine powder obtained through the subsequent stirring and holding step. In addition, sulfuric acid and hydroxycarboxylic acid can be added individually to the cuprous oxide powder slurry, but considering the uniformity and safety of mixing, a mixed acid prepared by mixing sulfuric acid and hydroxycarboxylic acid in advance is used. It is preferable to use it.
本発明方法で用いるヒドロキシカルボン酸は、析出した銅微粉の表面に吸着することにより、銅微粉の成長を妨げ、粒子間の凝集を防ぐ役割を担っている。ヒドロキシカルボン酸としては、クエン酸、リンゴ酸、酒石酸、乳酸などを使用できるが、銅への吸着力が高いクエン酸とリンゴ酸が好ましく、クエン酸が特に好ましい。また、ヒドロキシカルボン酸と混合酸を形成する硫酸としては、希硫酸を用いることが好ましい。 The hydroxycarboxylic acid used in the method of the present invention has a role of preventing the growth of copper fine powder and preventing aggregation between particles by adsorbing on the surface of the precipitated copper fine powder. As the hydroxycarboxylic acid, citric acid, malic acid, tartaric acid, lactic acid and the like can be used, but citric acid and malic acid having a high adsorptive power to copper are preferable, and citric acid is particularly preferable. Moreover, it is preferable to use dilute sulfuric acid as sulfuric acid which forms a mixed acid with hydroxycarboxylic acid.
上記亜酸化銅粉スラリーと混合酸との混合時間、即ち亜酸化銅粉スラリーと混合酸のいずれか片方の全量を他方に添加し終わるまでの時間は、５分以上になると１００ｎｍ以上の粗大な銅粒子が発生し、得られる銅微粉の平均粒径は５０ｎｍを超え、更には上記結晶子径ｃと平均粒径ｄの比ｃ／ｄも０.５を超えてしまう。従って、上記混合時間は５分未満とする必要があり、３分以内が好ましい。混合時間の下限は、特に限定されるものではないが、安全に且つ安定して添加混合できる範囲であれば、出来るだけ短いほうが良い。 The mixing time of the cuprous oxide powder slurry and the mixed acid, that is, the time until the addition of the total amount of either one of the cuprous oxide powder slurry and the mixed acid to the other is 100 nm or more when it is 5 minutes or more. Copper particles are generated, and the average particle diameter of the obtained copper fine powder exceeds 50 nm. Further, the ratio c / d of the crystallite diameter c to the average particle diameter d also exceeds 0.5. Therefore, the mixing time needs to be less than 5 minutes, and preferably within 3 minutes. The lower limit of the mixing time is not particularly limited, but is preferably as short as possible as long as it can be safely and stably added and mixed.
本発明の反応初期における核の大量発生からすれば、混合初期の混合速度が重要である。例えば、亜酸化銅粉スラリーに混合酸を添加混合する場合、混合開始から１分以内の亜酸化銅粉中の銅に対する硫酸の混合量を、モル比で０.２以上とすることが好ましい。この混合初期の硫酸のモル比が０.２未満であると、得られる銅微粉の平均粒径が５０ｎｍを超えやすく、結晶子径ｃと平均粒径ｄの比ｃ／ｄも０.５を超えるようになる。混合開始から１分以内の亜酸化銅粉中の銅に対する硫酸の混合量の上限は、特に限定されるものではないが、安全に且つ安定して添加混合できる範囲であれば、出来るだけ多いほうが良い。 From the viewpoint of mass generation of nuclei at the initial stage of the reaction of the present invention, the mixing speed at the initial stage of mixing is important. For example, when a mixed acid is added to and mixed with a cuprous oxide powder slurry, the amount of sulfuric acid mixed with copper in the cuprous oxide powder within 1 minute from the start of mixing is preferably 0.2 or more in terms of molar ratio. When the molar ratio of sulfuric acid at the initial stage of mixing is less than 0.2, the average particle diameter of the obtained copper fine powder tends to exceed 50 nm, and the ratio c / d between the crystallite diameter c and the average particle diameter d is 0.5. It will exceed. The upper limit of the amount of sulfuric acid mixed with copper in the cuprous oxide powder within 1 minute from the start of mixing is not particularly limited, but it should be as much as possible as long as it can be added and mixed safely and stably. good.
特に微細な銅微粉を得る場合には、上記混合酸中の硫酸及びヒドロキシカルボン酸の種類と濃度、及び混合初期における混合速度を調整することが好ましい。具体的には、特に微細な平均粒径１０〜３０ｎｍの銅微粉を得る場合には、ヒドロキシカルボン酸としてクエン酸を用い、亜酸化銅粉中の銅に対する硫酸のモル比を１〜２０の範囲とし、且つ亜酸化銅粉中の銅に対するクエン酸のモル比を０.２〜６の範囲に調整し、混合時間を２分未満とすることが好ましい。特に混合初期の硫酸の混合量として、例えば亜酸化銅粉スラリーに混合酸を添加混合する場合、混合開始から1分間以内に、亜酸化銅粉中の銅に対してモル比で０.５以上の硫酸を混合することが好ましい。 In particular, when obtaining fine copper fine powder, it is preferable to adjust the type and concentration of sulfuric acid and hydroxycarboxylic acid in the mixed acid, and the mixing speed in the initial stage of mixing. Specifically, when obtaining a fine copper powder having a fine average particle diameter of 10 to 30 nm, citric acid is used as the hydroxycarboxylic acid, and the molar ratio of sulfuric acid to copper in the cuprous oxide powder is in the range of 1 to 20. And the molar ratio of citric acid to copper in the cuprous oxide powder is preferably adjusted to a range of 0.2 to 6, and the mixing time is preferably less than 2 minutes. In particular, as the mixing amount of sulfuric acid at the initial stage of mixing, for example, when mixed acid is added to and mixed with the cuprous oxide powder slurry, within 1 minute from the start of mixing, the molar ratio to the copper in the cuprous oxide powder is 0.5 or more It is preferable to mix sulfuric acid.
尚、上記した亜酸化銅粉中の銅に対する硫酸のモル比が１未満では、硫酸量が不足するため、平均粒径３０ｎｍ以下の微細な銅微粉が得られず、逆に２０を超えると、工業的に意義のある銅濃度で反応させる場合には、液粘度が上昇するなど不具合が発生する。また、上記クエン酸のモル比が０.２未満では、後述する銅微粒子の分散効果が得られず、６を超えて添加しても更なる分散効果が認められない。上記硫酸のモル比は１〜１５の範囲が、及びクエン酸のモル比は０.２〜４の範囲が更に好ましい。尚、この場合においても、混合時間が２分以上になると平均粒径が３０ｎｍを超えてしまう。混合時間としては特に１分以内であることが好ましい。 If the molar ratio of sulfuric acid to copper in the above cuprous oxide powder is less than 1, the amount of sulfuric acid is insufficient, so fine copper powder with an average particle size of 30 nm or less cannot be obtained. When the reaction is carried out at an industrially significant copper concentration, problems such as an increase in liquid viscosity occur. Further, when the molar ratio of the citric acid is less than 0.2, the effect of dispersing the copper fine particles described later cannot be obtained, and even when added in excess of 6, no further dispersion effect is observed. The molar ratio of the sulfuric acid is more preferably in the range of 1 to 15, and the molar ratio of citric acid is more preferably in the range of 0.2 to 4. Even in this case, the average particle size exceeds 30 nm when the mixing time is 2 minutes or more. The mixing time is particularly preferably within 1 minute.
上記の亜酸化銅粉スラリーと混合酸を混合する工程及び混合溶液を撹拌保持する工程をとおして、反応温度に特に制約はない。しかしながら、反応温度が高すぎると、得られる銅微粒子が粗大化する傾向が認められるため、５０℃以下が好ましく、１０℃以下が更に好ましい。反応温度の下限については、混合溶液が撹拌可能な状態、即ち混合溶液の凝固点以上であればよい。 The reaction temperature is not particularly limited through the step of mixing the cuprous oxide powder slurry and the mixed acid and the step of stirring and holding the mixed solution. However, when the reaction temperature is too high, the resulting copper fine particles tend to be coarsened, and therefore, it is preferably 50 ° C. or lower, more preferably 10 ° C. or lower. The lower limit of the reaction temperature may be in a state where the mixed solution can be stirred, that is, above the freezing point of the mixed solution.
本発明方法では、出発原料として、常温常圧下の大気雰囲気にて安定な１価の銅化合物である亜酸化銅粉を用いる。亜酸化銅粉は、工業材料として販売されているものを利用してもよく、例えば、硫酸銅水溶液を水酸化ナトリウムなどで中和して酸化銅粉を析出させ、引き続きヒドラジンや還元糖などの適当な還元剤により還元して得られたものを用いても良い。亜酸化銅粉として、アルカリ金属元素、アルカリ土類金属元素及びハロゲン元素を含まないものを用いることにより、これらマイグレーションの原因となる不純物を含まない銅微粉が得られる。 In the method of the present invention, cuprous oxide powder, which is a monovalent copper compound that is stable in an air atmosphere at normal temperature and pressure, is used as a starting material. As the cuprous oxide powder, those sold as industrial materials may be used. For example, the aqueous solution of copper sulfate is neutralized with sodium hydroxide or the like to precipitate the copper oxide powder. You may use what was obtained by reducing with a suitable reducing agent. By using a cuprous oxide powder that does not contain an alkali metal element, an alkaline earth metal element, and a halogen element, a copper fine powder that does not contain impurities that cause migration is obtained.
特に、出発原料として、上記した有害なアルカリ金属元素、アルカリ土類金属元素及びハロゲン元素を含まない亜酸化銅を用いると共に、ハロゲン元素を含まない硫酸やヒドロキシカルボン酸を使用することによって、マイグレーションの原因となる有害な元素を含まず、電子部品の配線形成用材料として好適な銅微粉を得ることができる。尚、ハロゲン元素を含まない酸としては硝酸も挙げられるが、硝酸を用いると生成した銅微粒子を溶解してしまうため、銅微粉の収率が悪化し好ましくない。 In particular, using the above-mentioned harmful alkali metal element, alkaline earth metal element, and cuprous oxide containing no halogen element as the starting material, and using sulfuric acid or hydroxycarboxylic acid containing no halogen element, migration of Copper fine powder suitable as a wiring forming material for electronic parts can be obtained without containing harmful elements that cause the damage. In addition, although nitric acid is mentioned as an acid which does not contain a halogen element, since the produced | generated copper microparticle will be melt | dissolved if nitric acid is used, the yield of copper fine powder deteriorates and is not preferable.
原料として使用する亜酸化銅粉の粒径と、析出する銅微粉の粒径との間に相関があるため、微細な銅微粉を得るためには微細な亜酸化銅粉を用いることが好ましい。そのため、原料として使用する亜酸化銅粉は、粗大な亜酸化銅粉をボールミルやビーズミルなどで粉砕しても良く、湿式法で合成する場合には、反応条件を制御して得られる微細な亜酸化銅粉を用いることが好ましい。 Since there is a correlation between the particle size of the cuprous oxide powder used as a raw material and the particle size of the precipitated copper fine powder, it is preferable to use fine cuprous oxide powder in order to obtain fine copper fine powder. For this reason, the cuprous oxide powder used as a raw material may be obtained by pulverizing coarse cuprous oxide powder with a ball mill or bead mill. It is preferable to use copper oxide powder.
亜酸化銅粉の粒径については、特に限定されるものではないが、より微細な銅微粉を得るためには、その平均粒径としては３μｍ以下が好ましく、１μｍ以下が更に好ましい。微細な亜酸化銅粉を用いるほど微細な銅微粉が得られることから、使用する亜酸化銅粉の粒径の下限は特に制限はないが、通常の粉砕方法あるいは湿式合成方法で得られる安定な亜酸化銅粉の粒径の下限は通常１０ｎｍ程度である。 The particle size of the cuprous oxide powder is not particularly limited, but in order to obtain a finer copper fine powder, the average particle size is preferably 3 μm or less, and more preferably 1 μm or less. Since the finer copper fine powder is obtained as the fine cuprous oxide powder is used, the lower limit of the particle size of the cuprous oxide powder to be used is not particularly limited, but it is stable obtained by a normal pulverization method or a wet synthesis method. The lower limit of the particle size of the cuprous oxide powder is usually about 10 nm.
上記した本発明方法により得られる銅微粉は、平均粒径が１０〜５０ｎｍであり、好ましくは平均粒径が１０〜３０ｎｍである。銅微粉の粒径は焼結活性に与える影響が大きく、粒径を細かくすることで低温焼成が可能となる。平均粒径が５０ｎｍを超えると焼結活性が低下して、低温での焼成、例えば３００℃以下での焼成が困難となる。銅微粉の平均粒径が細かいほど、焼結活性は高くなるが、１０ｎｍ未満になると銅微粉の酸化が激しくなり、取り扱いが困難となるため好ましくない。 The copper fine powder obtained by the above-described method of the present invention has an average particle size of 10 to 50 nm, preferably an average particle size of 10 to 30 nm. The particle size of the copper fine powder has a great influence on the sintering activity, and low temperature firing is possible by reducing the particle size. When the average particle size exceeds 50 nm, the sintering activity is lowered, and firing at a low temperature, for example, firing at 300 ° C. or lower, becomes difficult. The smaller the average particle size of the copper fine powder is, the higher the sintering activity is. However, if it is less than 10 nm, the oxidation of the copper fine powder becomes intense and the handling becomes difficult.
しかも、本発明の銅微粉は、微粒子が更に微細な結晶子から構成される多結晶体からなり、上記のごとく平均粒径が微細であると同時に、結晶子の結晶子径ｃと上記平均粒径ｄの比ｃ／ｄが０.５以下である。結晶子径ｃと平均粒径ｄの比ｃ／ｄも焼結活性に与える影響が大きく、この比ｃ／ｄが小さくなるほど同じ粒径であっても焼結活性が高くなる。特に結晶子径ｃと平均粒径ｄの比ｃ／ｄが０.５以下であれば、低温焼成の好適な焼結活性を得ることができる。 Moreover, the copper fine powder of the present invention is composed of a polycrystal composed of finer crystallites, and the average particle size is fine as described above, and at the same time the crystallite diameter c of the crystallite and the average particle size are as described above. The ratio c / d of the diameter d is 0.5 or less. The ratio c / d between the crystallite diameter c and the average particle diameter d has a great influence on the sintering activity. The smaller the ratio c / d, the higher the sintering activity even if the particle diameter is the same. In particular, when the ratio c / d between the crystallite diameter c and the average particle diameter d is 0.5 or less, suitable sintering activity for low-temperature firing can be obtained.
また、本発明による銅微粉は、配線材料としてマイグレーションが懸念される元素、特にアルカリ金属元素、アルカリ土類金属元素、及びハロゲン元素が含まれないか、含まれてもアルカリ金属元素及びアルカリ土類金属元素の含有量が合計で１０重量ｐｐｍ以下、ハロゲン元素の含有量は２０重量ｐｐｍ以下であることが好ましく、特に上記いずれの元素も１０重量ｐｐｍ以下であることが更に好ましい。アルカリ元素及びアルカリ土類元素が合計で１０重量ｐｐｍを超えるか、あるいはハロゲン元素が２０重量ｐｐｍを超えて銅微粉中に含有される場合には、マイグレーションが発生しやすくなるため好ましくない。 In addition, the copper fine powder according to the present invention does not contain or contains an element that is feared to migrate as a wiring material, particularly an alkali metal element, an alkaline earth metal element, and a halogen element. The total content of metal elements is preferably 10 ppm by weight or less, and the content of halogen elements is preferably 20 ppm by weight or less. In particular, any of the above elements is more preferably 10 ppm by weight or less. When alkali elements and alkaline earth elements exceed 10 ppm by weight in total, or halogen elements exceed 20 ppm by weight and contained in copper fine powder, migration tends to occur, which is not preferable.
銅微粉中の上記各元素の含有量は、銅微粉を硝酸などで溶解した後、通常の化学分析法、例えば、ＩＣＰ発光分析法、蛍光Ｘ線分析法、原子吸光法などにより知ることができる。これらの分析方法において、上記したアルカリ元素、アルカリ土類元素、ハロゲン元素などの有害な元素、が検出されないことが好ましく、これらの元素の上記化学分析法による分析下限は通常５重量ｐｐｍ程度である。 The content of each element in the copper fine powder can be determined by dissolving the copper fine powder with nitric acid or the like and then using a conventional chemical analysis method such as ICP emission analysis, fluorescent X-ray analysis, atomic absorption, or the like. . In these analysis methods, it is preferable that the above-mentioned harmful elements such as alkali elements, alkaline earth elements and halogen elements are not detected, and the lower limit of analysis by these chemical analysis methods of these elements is usually about 5 ppm by weight. .
本発明の銅微粉は、有機溶剤を加えて混練することによって、導電性ペーストとすることができる。有機溶剤としては、エチレングリコール、ジエチレングリコール、トリエチレングリコール、グリセリン、ターピネオールなどが用いられる。有機溶剤の添加量は、特に限定されるものではないが、スクリーン印刷やディスペンサーなどの導電膜形成方法に適した粘度となるように、銅微粉の粒度を考慮して添加量を調整すればよい。 The copper fine powder of the present invention can be made into a conductive paste by adding an organic solvent and kneading. As the organic solvent, ethylene glycol, diethylene glycol, triethylene glycol, glycerin, terpineol, or the like is used. The addition amount of the organic solvent is not particularly limited, but the addition amount may be adjusted in consideration of the particle size of the copper fine powder so that the viscosity is suitable for a conductive film forming method such as screen printing or a dispenser. .
本発明の導電性ペーストは、銅微粉が極めて微細であると同時に、アルカリ元素、アルカリ土類元素及ハロゲン元素をほとんど含んでいないため、低温焼成による導電膜の形成に適している。しかも、配線密度のファインピッチ化に対応可能であって、得られる導電膜はマイグレーションの恐れが少なく、非常に信頼性が高いものである。 The conductive paste of the present invention is suitable for forming a conductive film by low-temperature firing because the copper fine powder is extremely fine and contains almost no alkali element, alkaline earth element or halogen element. In addition, it is possible to cope with finer wiring density, and the obtained conductive film is less likely to migrate and has very high reliability.
上記導電性ペーストには、粘度調整のために樹脂成分を添加することができる。添加する樹脂成分としては、例えば、エチルセルロースに代表されるセルロース系樹脂などが挙げられ、ターピネオールなどの有機溶剤に溶解した有機ビヒクルとして添加される。樹脂成分の添加量は、焼結性を阻害しない程度に抑える必要があり、好ましい添加量としては全体の５重量％以下である。 A resin component can be added to the conductive paste for viscosity adjustment. Examples of the resin component to be added include a cellulose resin typified by ethyl cellulose, and the resin component is added as an organic vehicle dissolved in an organic solvent such as terpineol. The addition amount of the resin component needs to be suppressed to such an extent that the sinterability is not hindered, and a preferable addition amount is 5% by weight or less.
また、上記導電性ペーストには、焼成後の導電性を改善するため、酸化防止剤としてヒドロキシカルボン酸を添加してもよい。酸化防止効果のある添加剤であればヒドロキシカルボン酸に限定されるものではないが、クエン酸、リンゴ酸、酒石酸、乳酸などのヒドロキシカルボン酸が好ましく、銅への吸着力が高いクエン酸またはリンゴ酸が特に好ましい。ヒドロキシカルボン酸の添加量は、１重量％未満では酸化防止効果が少なく、１５重量％を超えるとペーストの粘度が高くなり過ぎるため、１〜１５重量％が好ましい。 Moreover, in order to improve the electroconductivity after baking, you may add hydroxycarboxylic acid to the said electrically conductive paste as antioxidant. Although it is not limited to hydroxycarboxylic acid as long as it has an antioxidant effect, it is preferably a hydroxycarboxylic acid such as citric acid, malic acid, tartaric acid, lactic acid, etc., and citric acid or apple having high adsorptive power to copper Acid is particularly preferred. If the amount of hydroxycarboxylic acid added is less than 1% by weight, the antioxidant effect is small, and if it exceeds 15% by weight, the viscosity of the paste becomes too high.
以下の実施例において、銅原料として亜酸化銅（Ｃｕ２Ｏ）粉（Ｃｈｅｍｅｔ社製、ＵｌｔｒａＦｉｎｅ）を使用し、硫酸としては濃度７０％の希硫酸を使用した。また、ヒドロキシカルボン酸としては、無水クエン酸（和光純薬工業（株）製、試薬）、リンゴ酸（和光純薬工業（株）製、試薬）、酒石酸（和光純薬工業（株）製、試薬）、乳酸（和光純薬工業（株）製、試薬）を用いた。尚、亜酸化銅粉に含まれる可能性のある不純物として、アルカリ金属元素であるナトリウムとカリウム、アルカリ土類金属元素であるマグネシウム、ハロゲン元素である塩素について化学分析を行い、それぞれ１０重量ｐｐｍ未満の含有量であることを確認した。 In the following examples, cuprous oxide (Cu 2 O) powder (manufactured by Chemet, UltraFine) was used as a copper raw material, and dilute sulfuric acid having a concentration of 70% was used as sulfuric acid. Further, as hydroxycarboxylic acid, citric anhydride (manufactured by Wako Pure Chemical Industries, Ltd., reagent), malic acid (manufactured by Wako Pure Chemical Industries, Ltd., reagent), tartaric acid (manufactured by Wako Pure Chemical Industries, Ltd.), Reagent) and lactic acid (manufactured by Wako Pure Chemical Industries, Ltd., reagent) were used. Chemical analysis of sodium and potassium, which are alkali metal elements, magnesium, which is an alkaline earth metal element, and chlorine, which is a halogen element, as impurities that may be contained in cuprous oxide powder, each being less than 10 ppm by weight The content was confirmed.
［実施例１］
純水３５.６ｇに、予め遊星ボールミルにより粉砕したＣｕ２Ｏ粉２.４ｇを加え、混練して亜酸化銅粉スラリーとした。粉砕後の上記Ｃｕ２Ｏ粉をレーザー散乱式粒度分布測定法にて測定したところ、平均粒径は０.７μｍであった。また、純水２.５ｇに希硫酸７ｇと無水クエン酸２.５ｇを加えて、混合酸を調整した。尚、Ｃｕ２Ｏ粉中のＣｕに対して、硫酸のモル比は１.４９、クエン酸のモル比は０.３９である。
[Example 1]
To 35.6 g of pure water, 2.4 g of Cu 2 O powder previously ground by a planetary ball mill was added and kneaded to obtain a cuprous oxide powder slurry. When the Cu 2 O powder after pulverization was measured by a laser scattering particle size distribution measurement method, the average particle size was 0.7 μm. Further, 7 g of dilute sulfuric acid and 2.5 g of anhydrous citric acid were added to 2.5 g of pure water to prepare a mixed acid. In addition, the molar ratio of sulfuric acid is 1.49 and the molar ratio of citric acid is 0.39 with respect to Cu in the Cu 2 O powder.
上記亜酸化銅粉スラリーを撹拌しながら、室温（加熱又は冷却なし）にて上記混合酸を混合時間２秒で添加混合し、引き続き２時間撹拌を続けて銅微粉を析出させた。析出した銅微粉を濾過回収し、Ｘ線回折法（（株）リガク製、ＲＩＮＴ-１４００）により、銅単相であることを確認した。また、走査型電子顕微鏡（以下、ＳＥＭと記載。（株）日立製作所製、ＦＥ−ＳＥＭ Ｓ−４７００）で観察したところ、この銅微粉は単分散性の微粉であり、平均粒径ｄは２３ｎｍであった。尚、銅微粉の粒径は、ＳＥＭ観察（撮影倍率１０万倍）において、視野から２００個の粒子を無作為に選択して測定した。 While stirring the cuprous oxide powder slurry, the mixed acid was added and mixed at room temperature (without heating or cooling) at a mixing time of 2 seconds, and then the stirring was continued for 2 hours to precipitate copper fine powder. The deposited copper fine powder was collected by filtration, and confirmed to be a copper single phase by X-ray diffraction (manufactured by Rigaku Corporation, RINT-1400). Further, when observed with a scanning electron microscope (hereinafter referred to as SEM, manufactured by Hitachi, Ltd., FE-SEM S-4700), this copper fine powder was a monodisperse fine powder, and the average particle diameter d was 23 nm. Met. The particle size of the copper fine powder was measured by randomly selecting 200 particles from the field of view in SEM observation (imaging magnification: 100,000 times).
この銅微粉のＳＥＭ写真を図１に示す。また、この銅微粉について、Ｘ線回折パターンから結晶子径ｃをシェラーの式より算出したところ、９.４ｎｍであった。よって、この銅微粉の結晶子径ｃと平均粒径ｄの比ｃ／ｄは０.４１である。 An SEM photograph of this copper fine powder is shown in FIG. Further, for this copper fine powder, the crystallite diameter c was calculated from the X-ray diffraction pattern according to Scherrer's formula, and it was 9.4 nm. Therefore, the ratio c / d between the crystallite diameter c and the average particle diameter d of the copper fine powder is 0.41.
［実施例２］
上記実施例１において、混合時間を１分及び３分に変えた以外は同様にして、それぞれ上記混合酸を添加混合し、引き続き２時間撹拌を続けて銅微粉を析出させた。その際、反応開始から１分以内の亜酸化銅粉中の銅分に対する硫酸の混合量は、モル比でそれぞれ１.４９及び０.５とした。得られた銅微粉は、上記実施例１と同様にＸ線回折法により、いずれも銅単相であることを確認した。
[Example 2]
In Example 1, except that the mixing time was changed to 1 minute and 3 minutes, the mixed acid was added and mixed, respectively, and the stirring was continued for 2 hours to precipitate copper fine powder. At that time, the mixing amount of sulfuric acid with respect to the copper content in the cuprous oxide powder within 1 minute from the start of the reaction was 1.49 and 0.5, respectively, in molar ratio. The obtained copper fine powder confirmed that all were a copper single phase by the X ray diffraction method similarly to the said Example 1. FIG.
また、ＳＥＭで観察したところ、いずれの銅微粉も単分散性の微粉であり、平均粒径ｄは混合時間１分のものが２０ｎｍ、３分のものが４０ｎｍであった。混合時間１分のものについて、上記実施例１と同様に結晶子径を算出したところ、結晶子径は８.７ｎｍであり、結晶子径ｃと平均粒径ｄの比ｃ／ｄは０.４４であった。 Moreover, when observed by SEM, all the copper fine powders were monodisperse fine powders, and the average particle diameter d was 20 nm for the mixing time of 1 minute and 40 nm for the three minutes. When the crystallite size was calculated in the same manner as in Example 1 for the mixing time of 1 minute, the crystallite size was 8.7 nm, and the ratio c / d between the crystallite size c and the average particle size d was 0.8. 44.
［実施例３］
純水３５.６ｇにＣｕ２Ｏ粉２.４ｇを加え、混練して亜酸化銅粉スラリーとした。また、純水６ｇに希硫酸３.５ｇと無水クエン酸２.５ｇを加えて、混合酸を調整した。尚、Ｃｕ２Ｏ粉中のＣｕに対して、硫酸のモル比は０.７４、クエン酸のモル比は０.３９である
[Example 3]
2.4 g of Cu 2 O powder was added to 35.6 g of pure water and kneaded to obtain a cuprous oxide powder slurry. Further, mixed acid was prepared by adding 3.5 g of dilute sulfuric acid and 2.5 g of anhydrous citric acid to 6 g of pure water. The molar ratio of sulfuric acid to Cu in Cu 2 O powder is 0.74, and the molar ratio of citric acid is 0.39.
上記亜酸化銅粉スラリーを撹拌しながら、室温にて上記混合酸を２秒間で添加混合し、引き続き連続して２時間撹拌を続けることにより銅微粉を析出させた。 While stirring the cuprous oxide powder slurry, the mixed acid was added and mixed at room temperature for 2 seconds, and then continuously stirred for 2 hours to precipitate copper fine powder.
析出した銅微粉を濾過回収し、Ｘ線回折法により、銅単相であることを確認した。また、ＳＥＭ観察の結果、この銅微粉は単分散性の微粉であり、平均粒径ｄは３４ｎｍであった。更に、上記実施例１と同様に算出した結晶子径は１０.９ｎｍであり、結晶子径ｃと平均粒径ｄの比ｃ／ｄは０.３２であった。 The deposited copper fine powder was collected by filtration and confirmed to be a copper single phase by X-ray diffraction. As a result of SEM observation, the copper fine powder was a monodispersed fine powder, and the average particle diameter d was 34 nm. Further, the crystallite diameter calculated in the same manner as in Example 1 was 10.9 nm, and the ratio c / d between the crystallite diameter c and the average particle diameter d was 0.32.
［比較例１］
上記実施例３において、亜酸化銅粉スラリーを撹拌しながら、室温にて混合酸を５分間かけて添加混合し、引き続き２時間撹拌を続けた以外は同様にして、銅微粉を析出させた。その際、反応開始から1分以内の亜酸化銅粉中の銅に対する硫酸の混合量は０.１５とした。
[Comparative Example 1]
In Example 3 above, copper fine powder was precipitated in the same manner except that the mixed acid was added and mixed at room temperature over 5 minutes while stirring the cuprous oxide powder slurry, and the stirring was continued for 2 hours. At that time, the amount of sulfuric acid mixed with copper in the cuprous oxide powder within 1 minute from the start of the reaction was set to 0.15.
得られた銅微粉は、上記実施例１と同様にして評価したところ、Ｘ線回折法により銅単相であることが確認できたが、ＳＥＭ観察による平均粒径ｄが２２０ｎｍの粗大な銅粒子であった。 When the obtained copper fine powder was evaluated in the same manner as in Example 1, it was confirmed that the copper fine powder was a single phase of copper by an X-ray diffraction method. However, coarse copper particles having an average particle diameter d of 220 nm by SEM observation were confirmed. Met.
［実施例４］
純水３５.６ｇにＣｕ２Ｏ粉２.４ｇを加え、混練して亜酸化銅粉スラリーとした。また、純水８ｇに希硫酸３.５ｇと無水クエン酸０.５ｇを加えて、混合酸を調整した。尚、Ｃｕ２Ｏ粉中のＣｕに対して、硫酸のモル比は０.７４、クエン酸のモル比は０.０８である。
[Example 4]
2.4 g of Cu 2 O powder was added to 35.6 g of pure water and kneaded to obtain a cuprous oxide powder slurry. Further, 3.5 g of dilute sulfuric acid and 0.5 g of anhydrous citric acid were added to 8 g of pure water to prepare a mixed acid. The molar ratio of sulfuric acid to Cu in the Cu 2 O powder is 0.74, and the molar ratio of citric acid is 0.08.
上記亜酸化銅粉スラリーを撹拌しながら、室温にて上記混合酸を２秒間で添加混合し、引き続き連続して２時間撹拌を続けることにより、銅微粉を析出させた。 While stirring the cuprous oxide powder slurry, the mixed acid was added and mixed at room temperature for 2 seconds, and then continuously stirred for 2 hours to precipitate copper fine powder.
得られた銅微粉は、上記実施例１と同様にして評価したところ、Ｘ線回折法により銅単相であることが確認でき、またＳＥＭで観察したところ単分散性の微粉であり、平均粒径ｄは３９ｎｍであった。更に、上記実施例１と同様に算出した結晶子径は１１.６ｎｍであり、結晶子径ｃと平均粒径ｄの比ｃ／ｄは０.３０であった。 The obtained copper fine powder was evaluated in the same manner as in Example 1 above. As a result, it was confirmed that the copper fine powder was a single phase of copper by an X-ray diffraction method. The diameter d was 39 nm. Further, the crystallite diameter calculated in the same manner as in Example 1 was 11.6 nm, and the ratio c / d between the crystallite diameter c and the average particle diameter d was 0.30.
［実施例５］
純水３６.８ｇにＣｕ２Ｏ粉１.２ｇを加え、混練して亜酸化銅粉スラリーとした。また、純水２.５ｇに希硫酸７ｇと無水クエン酸２.５ｇを加えて、混合酸を調整した。尚、Ｃｕ２Ｏ粉中のＣｕに対して、硫酸のモル比は２.９８、クエン酸のモル比は０.７８である。
[Example 5]
1.2 g of Cu 2 O powder was added to 36.8 g of pure water and kneaded to obtain a cuprous oxide powder slurry. Further, 7 g of dilute sulfuric acid and 2.5 g of anhydrous citric acid were added to 2.5 g of pure water to prepare a mixed acid. The molar ratio of sulfuric acid to Cu in the Cu 2 O powder is 2.98, and the molar ratio of citric acid is 0.78.
上記亜酸化銅粉スラリーを撹拌しながら、冷却して液温を１０℃に下げ、上記混合酸を２秒間で添加混合し、引き続き連続して３時間撹拌を続けることにより、銅微粉を析出させた。 While stirring the cuprous oxide powder slurry, the liquid temperature is lowered to 10 ° C., the mixed acid is added and mixed in 2 seconds, and then continuously stirred for 3 hours to precipitate copper fine powder. It was.
得られた銅微粉は、上記実施例１と同様にして評価したところ、Ｘ線回折法により銅単相であることが確認でき、またＳＥＭで観察したところ単分散性の微粉であり、平均粒径ｄは２２ｎｍであった。更に、上記実施例１と同様に算出した結晶子径は１０.４ｎｍであり、結晶子径ｃと平均粒径ｄの比ｃ／ｄは０.４７であった。 The obtained copper fine powder was evaluated in the same manner as in Example 1 above. As a result, it was confirmed that the copper fine powder was a single phase of copper by an X-ray diffraction method. The diameter d was 22 nm. Further, the crystallite diameter calculated in the same manner as in Example 1 was 10.4 nm, and the ratio c / d between the crystallite diameter c and the average particle diameter d was 0.47.
［実施例６］
純水３７.７ｇにＣｕ２Ｏ粉０.３ｇを加え、混練して亜酸化銅粉スラリーとした。また、純水２.５ｇに希硫酸７ｇと無水クエン酸２.５ｇを加えて、混合酸を調整した。尚、Ｃｕ２Ｏ粉中のＣｕに対して、硫酸のモル比は１１.９２、クエン酸のモル比は３.１０である。
[Example 6]
To 37.7 g of pure water, 0.3 g of Cu 2 O powder was added and kneaded to obtain a cuprous oxide powder slurry. Further, 7 g of dilute sulfuric acid and 2.5 g of anhydrous citric acid were added to 2.5 g of pure water to prepare a mixed acid. In addition, the molar ratio of sulfuric acid is 11.92 and the molar ratio of citric acid is 3.10 with respect to Cu in the Cu 2 O powder.
上記亜酸化銅粉スラリーを撹拌しながら、室温にて上記混合酸を２秒間で添加混合し、引き続き連続して３時間撹拌を続けることにより、銅微粉を析出させた。 While stirring the cuprous oxide powder slurry, the mixed acid was added and mixed at room temperature for 2 seconds, and then continuously stirred for 3 hours to precipitate copper fine powder.
得られた銅微粉は、上記実施例１と同様にして評価したところ、Ｘ線回折法により銅単相であることが確認でき、またＳＥＭで観察したところ単分散性の微粉であり、平均粒径ｄは２５ｎｍであった。更に、上記実施例１と同様に算出した結晶子径は１１.８ｎｍであり、結晶子径ｃと平均粒径ｄの比ｃ／ｄは０.４７であった。 The obtained copper fine powder was evaluated in the same manner as in Example 1 above. As a result, it was confirmed that the copper fine powder was a single phase of copper by an X-ray diffraction method. The diameter d was 25 nm. Further, the crystallite diameter calculated in the same manner as in Example 1 was 11.8 nm, and the ratio c / d between the crystallite diameter c and the average particle diameter d was 0.47.
［実施例７］
純水３６.８ｇにＣｕ２Ｏ粉１.２ｇを加え、混練して亜酸化銅粉スラリーとした。また、純水２.５ｇに希硫酸７ｇとリンゴ酸２.５ｇを加えて、混合酸を調整した。尚、Ｃｕ２Ｏ粉中のＣｕに対して、硫酸のモル比は２.９８、リンゴ酸のモル比は１.１１である。
[Example 7]
1.2 g of Cu 2 O powder was added to 36.8 g of pure water and kneaded to obtain a cuprous oxide powder slurry. Further, 7 g of dilute sulfuric acid and 2.5 g of malic acid were added to 2.5 g of pure water to prepare a mixed acid. The molar ratio of sulfuric acid to Cu in the Cu 2 O powder is 2.98, and the molar ratio of malic acid is 1.11.
上記亜酸化銅粉スラリーを撹拌しながら、室温にて上記混合酸を２秒間で添加混合し、引き続き連続して２時間撹拌を続けることにより、銅微粉を析出させた。 While stirring the cuprous oxide powder slurry, the mixed acid was added and mixed at room temperature for 2 seconds, and then continuously stirred for 2 hours to precipitate copper fine powder.
得られた銅微粉は、上記実施例１と同様にして評価したところ、Ｘ線回折法により銅単相であることが確認でき、またＳＥＭで観察したところ単分散性の微粉であり、平均粒径ｄは４１ｎｍであった。更に、上記実施例１と同様に算出した結晶子径は１２.８ｎｍであり、結晶子径ｃと平均粒径ｄの比ｃ／ｄは０.３１であった。 The obtained copper fine powder was evaluated in the same manner as in Example 1 above. As a result, it was confirmed that the copper fine powder was a single phase of copper by an X-ray diffraction method. The diameter d was 41 nm. Further, the crystallite diameter calculated in the same manner as in Example 1 was 12.8 nm, and the ratio c / d between the crystallite diameter c and the average particle diameter d was 0.31.
［比較例２］
純水３９ｇにＣｕ２Ｏ粉１ｇを加え、混練して亜酸化銅粉スラリーとした。また、純水２３ｇに希硫酸７ｇのみを加えて、濃度４９％の硫酸溶液を調整した。尚、Ｃｕ２Ｏ粉中のＣｕに対して硫酸のモル比は３.５８であり、ヒドロキシカルボン酸は含まれていない。
[Comparative Example 2]
1 g of Cu 2 O powder was added to 39 g of pure water and kneaded to obtain a cuprous oxide powder slurry. Further, only 7 g of dilute sulfuric acid was added to 23 g of pure water to prepare a sulfuric acid solution having a concentration of 49%. The molar ratio of sulfuric acid with respect to Cu of Cu 2 O powder in is 3.58, hydroxycarboxylic acids are not included.
上記亜酸化銅粉スラリーを撹拌しながら、室温にて上記硫酸溶液を２秒間で添加混合し、引き続き連続して１時間撹拌を続けることにより、銅微粉を析出させた。 While stirring the cuprous oxide powder slurry, the sulfuric acid solution was added and mixed at room temperature for 2 seconds, and continuously stirred for 1 hour to precipitate copper fine powder.
得られた銅微粉は、上記実施例１と同様にして評価したところ、Ｘ線回折法により銅単相であることが確認できた。しかし、ＳＥＭで観察したところ、平均粒径ｄが１２４ｎｍの粗大なものであった。 When the obtained copper fine powder was evaluated in the same manner as in Example 1, it was confirmed that it was a copper single phase by an X-ray diffraction method. However, when observed with an SEM, the average particle diameter d was as large as 124 nm.
［比較例３］
純水４２.７５ｇにＣｕ２Ｏ粉１ｇを加え、混練して亜酸化銅粉スラリーとした。純水３.７５ｇに無水クエン酸２.５ｇのみを加えて、濃度４０％のクエン酸溶液を調整した。尚、Ｃｕ２Ｏ粉中のＣｕに対してクエン酸のモル比は０.９３であり、硫酸は含まれていない。
[Comparative Example 3]
1 g of Cu 2 O powder was added to 42.75 g of pure water and kneaded to obtain a cuprous oxide powder slurry. Only 2.5 g of anhydrous citric acid was added to 3.75 g of pure water to prepare a 40% strength citric acid solution. In addition, the molar ratio of citric acid with respect to Cu in the Cu 2 O powder is 0.93, and sulfuric acid is not included.
上記亜酸化銅粉スラリーを撹拌しながら、室温にて上記硫酸溶液を２秒間で添加混合し、引き続き連続して１時間撹拌を続けることにより、銅微粉を析出させた。 While stirring the cuprous oxide powder slurry, the sulfuric acid solution was added and mixed at room temperature for 2 seconds, and continuously stirred for 1 hour to precipitate copper fine powder.
得られた銅微粉は、上記実施例１と同様にして評価したところ、Ｘ線回折法により銅単相であることが確認できた。しかし、ＳＥＭで観察したところ、平均粒径ｄが３４０ｎｍの極めて粗大なものであった。 When the obtained copper fine powder was evaluated in the same manner as in Example 1, it was confirmed that it was a copper single phase by an X-ray diffraction method. However, when observed by SEM, the average particle diameter d was very coarse with 340 nm.
［実施例８］
上記実施例１で得られた銅微粉を純水中に再分散させた後、更に濾過回収することにより洗浄を行い、真空乾燥した。この銅微粉を秤量して、銅濃度として８０重量％になるように、エチレングリコール１２重量％及びクエン酸８重量％を添加し、自転公転式ミキサーを用いて混錬して導電性ペーストを得た。
[Example 8]
The copper fine powder obtained in Example 1 was redispersed in pure water, and further washed by filtration and recovery, and vacuum dried. The copper fine powder is weighed, and 12% by weight of ethylene glycol and 8% by weight of citric acid are added so that the copper concentration becomes 80% by weight, and kneaded using a rotating and rotating mixer to obtain a conductive paste. It was.
この銅微粉を導電粒子とする導電性ペーストは、その化学分析結果から、Ｎａ：１０重量ｐｐｍ以下、Ｍｇ：１０重量ｐｐｍ以下、Ｃｌ：１０重量ｐｐｍ以下であり、不純物として混入しうるアルカリ元素、アルカリ土類元素、ハロゲン元素を含まないことを確認した。 From the chemical analysis results, the conductive paste using the copper fine powder as conductive particles is Na: 10 ppm by weight or less, Mg: 10 ppm by weight or less, Cl: 10 ppm by weight or less, an alkali element that can be mixed as an impurity, It was confirmed that it did not contain alkaline earth elements and halogen elements.
この導電性ペーストを、バーコーターを用いて基板上に塗布した。その後、窒素雰囲気中において３００℃で１時間の熱処理を行うことによって、抵抗率が１×１０−５Ω・ｃｍである導電膜を形成することができた。また、同様に２００℃で１時間の熱処理を行うことにより、抵抗率が４×１０−５Ω・ｃｍである導電膜を形成することができた。 This conductive paste was applied onto a substrate using a bar coater. Thereafter, a heat treatment was performed at 300 ° C. for 1 hour in a nitrogen atmosphere, whereby a conductive film having a resistivity of 1 × 10 −5 Ω · cm could be formed. Similarly, by conducting a heat treatment at 200 ° C. for 1 hour, a conductive film having a resistivity of 4 × 10 −5 Ω · cm could be formed.
Claims (6)
The conductive paste according to claim 5, comprising a hydroxycarboxylic acid and a resin component.
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| JP7012630B2 (en) * | 2018-11-07 | 2022-01-28 | Ｊｘ金属株式会社 | Copper oxide particles |
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