JP6295870B2 - Method for producing copper powder - Google Patents
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本発明は、銅粉末の製造方法に関し、より詳しくは、銅化合物をポリオール中で加熱還元し、得られた銅粉末を特定の条件で乾燥し、大気中で長期保存しても酸化し難い銅粉末が低コストかつ生産性よく製造でき、積層セラミックスコンデンサやチップ抵抗器などの電子素子やタッチパネルや太陽電池などの配線材料の原料粉末として有用な銅粉末の製造方法に関する。 The present invention relates to a method for producing copper powder, and more specifically, copper that is heat-reduced in a polyol and the obtained copper powder is dried under specific conditions and is not easily oxidized even if stored for a long time in the atmosphere. The present invention relates to a method for producing copper powder that can be produced at low cost and with high productivity and is useful as a raw material powder for wiring materials such as electronic devices such as multilayer ceramic capacitors and chip resistors, touch panels, and solar cells.
従来より、積層セラミックスコンデンサ（以後、ＭＬＣＣという）やチップ抵抗器などの電子素子に外部電極を付与したり、それを基板に接合させたり、絶縁基板の意図する位置に導電回路を配属するのに導電ペーストが使用されている。導電ペーストの導電材料としては、銀、ニッケル、銅などの金属粉末が使用されているが、銅粉末は廉価でありながら抵抗値が低く、かつ、銀のようなマイグレーションが起き難いという長所があるので、銅ペーストが多用されている。 Conventionally, an external electrode is applied to an electronic element such as a multilayer ceramic capacitor (hereinafter referred to as MLCC) or a chip resistor, it is bonded to a substrate, or a conductive circuit is assigned to an intended position of an insulating substrate. Conductive paste is used. As the conductive material of the conductive paste, metal powders such as silver, nickel, and copper are used. However, copper powder has the advantages of low resistance and low resistance and hardly causing migration like silver. Therefore, copper paste is frequently used.
近年、ＭＬＣＣの外部電極として、金属粉末をフィラーとした導電性ペーストを使用する場合には、高温で焼き固めた誘電体であるセラミックスに、外部電極として金属粉末を焼き付けている。例えば、セラミックス素体を導電ペーストにディップ後熱処理すると、加熱中にペースト中のビヒクル分が蒸発または分解除去すると共に金属粉末が焼結して外部電極が形成される。この金属粉末としても銅粉末が多く使用される。
また、スルーホールやビア埋め用のペーストとしても、低価格でメッキ付きの良いペーストとして銅ペーストが利用され（特許文献１参照）、さらには太陽電池やタッチパネル向けの配線用として銅ペーストが用いられている（特許文献２参照）。
In recent years, when a conductive paste using a metal powder as a filler is used as an external electrode of the MLCC, the metal powder is baked as an external electrode on a ceramic that is a dielectric material baked and hardened at a high temperature. For example, when the ceramic body is dipped into a conductive paste and then heat-treated, the vehicle content in the paste is evaporated or decomposed during heating, and the metal powder is sintered to form an external electrode. A copper powder is often used as this metal powder.
Also, as paste for filling through-holes and vias, copper paste is used as a low-priced paste with good plating (see Patent Document 1), and further, copper paste is used for wiring for solar cells and touch panels. (See Patent Document 2).
銅ペーストに配合される銅粉末の製造方法としては、いわゆる電解法が最も一般的である。しかし、この方法で得られる銅粉は粗大な凝集体となり易い。そのため微細で分散性が良好な銅粉を得る方法として、例えば、酸化銅をカップリング剤の存在下で湿式還元する方法（特許文献３）、塩化物を気相還元する方法（特許文献４）、そして不均化反応を利用した方法が提案されている。しかし、これらの方法で得られる銅粉末はいずれも表面活性が高く、銅粉末はペーストとして使用する際に樹脂硬化のための加熱や半田づけなどにより酸化されたり、有機物の揮散を目的とする焼成時に雰囲気中にわずかに存在する酸素によって酸化されてしまう。このようにして得られた銅粉末を用いてペースト化すると、銅粉末中の酸化物により得られる厚膜の導電性が低下し、半田の濡れ性も低下する。 The so-called electrolytic method is the most common method for producing a copper powder to be blended in a copper paste. However, the copper powder obtained by this method tends to be coarse aggregates. Therefore, as a method for obtaining a fine copper powder having good dispersibility, for example, a method in which copper oxide is wet-reduced in the presence of a coupling agent (Patent Document 3), and a method in which chloride is reduced in a gas phase (Patent Document 4). A method using a disproportionation reaction has been proposed. However, all of the copper powders obtained by these methods have high surface activity, and when used as a paste, the copper powder is oxidized by heating or soldering for resin curing or firing for the purpose of volatilization of organic substances. Sometimes it is oxidized by the slight oxygen present in the atmosphere. When the copper powder thus obtained is used to make a paste, the conductivity of the thick film obtained by the oxide in the copper powder is lowered, and the wettability of the solder is also lowered.
これを防止すべく表面処理により銅粉末の耐酸化性を向上させる方法が提案されている。この例として、銅粉末をアミンで処理した後に、ほう素−窒素複合型分散剤を被覆する方法（特許文献５）があり、それ以外にベンゾトリアゾールやクロム酸塩をペースト中に混入するものや、有機チタネートや有機アルミネートを被覆する方法も知られている。しかし、これらの方法では、添加物により導電性が悪化し、充分な耐酸化効果が得られないという欠点がある。また、銅微粒子を単結晶とし耐酸化性を付与する方法（特許文献６）が試みられているが、この方法では耐酸化効果が得られても生産性が低い。 In order to prevent this, a method for improving the oxidation resistance of copper powder by surface treatment has been proposed. As an example of this, there is a method (Patent Document 5) in which a copper powder is treated with an amine and then coated with a boron-nitrogen composite type dispersant, and in addition, benzotriazole or chromate is mixed in the paste. A method of coating organic titanate or organic aluminate is also known. However, these methods have the drawback that the conductivity is deteriorated by the additive and a sufficient oxidation resistance effect cannot be obtained. Moreover, although the method (patent document 6) which makes copper fine particle a single crystal and provides oxidation resistance is tried, even if an oxidation resistance effect is acquired by this method, productivity is low.
これらの欠点を解消するために、酸化銅をポリオール中で還元する方法（特許文献７）が提案されている。これによれば、酸化銅を液状のポリオールに懸濁させ反応温度以上に加熱するので、確かに耐酸化性の優れた銅粉末が得られる。しかし、この方法では、生成した銅析出物を単離した後の乾燥について具体的言及がなく、使用する原料酸化銅の差により得られる銅粉末の粒径、形状、分散性、酸素濃度に著しい差異が生じ、粒状で耐酸化性に優れた銅粉を安定的に得ることは難しい。 In order to eliminate these drawbacks, a method of reducing copper oxide in a polyol (Patent Document 7) has been proposed. According to this, since copper oxide is suspended in a liquid polyol and heated to a temperature equal to or higher than the reaction temperature, a copper powder having excellent oxidation resistance can be obtained. However, in this method, there is no specific mention about the drying after isolating the produced copper precipitate, and the particle size, shape, dispersibility, and oxygen concentration of the copper powder obtained by the difference in the raw material copper oxide used are remarkable. A difference arises and it is difficult to stably obtain a granular copper powder excellent in oxidation resistance.
さらに上記の問題点を改善した方法として、特許文献８が挙げられ、原料としてニッケル品位が１０ｐｐｍ未満で且つ水分率が１０％以下の酸化銅粉及び／又はその含水物を用いることにより、この原料の酸化銅の全量がＣｕ２Ｏの超微粒子となった後、Ｃｕ２ＯからＣｕに還元して均一なＣｕ微粒子とする。しかし、還元して得られた銅粉末の乾燥について具体的言及がなく、乾燥方法や条件によっては２５℃で２０００時間大気中に保存すると酸化が進んでしまい、所望の銅粉やそれを用いた銅ペーストが得られない場合がある。 Further, as a method for improving the above-mentioned problems, Patent Document 8 is cited. By using a copper oxide powder having a nickel quality of less than 10 ppm and a moisture content of 10% or less and / or its hydrate as a raw material, this raw material is used. After the total amount of copper oxide becomes Cu 2 O ultrafine particles, Cu 2 O is reduced to Cu to form uniform Cu fine particles. However, there is no specific mention about the drying of the copper powder obtained by reduction, and depending on the drying method and conditions, oxidation proceeds when stored in the atmosphere at 25 ° C. for 2000 hours, and the desired copper powder and the same were used. Copper paste may not be obtained.
こうした状況の下、使用する原料酸化銅の種類によらず、粒径、形状、分散性に著しい差異を生ずることなく、粒状で単分散性に優れた銅粉末が安定的に得られ、２５℃で２０００時間大気中に保存しても酸化が進まないことで、ＭＬＣＣやプリント基板、電磁波シールド、太陽電池やタッチパネルなどの配線材料に使用される還元後に酸化膜の形成を抑えた銅粉末およびその製造方法が切望されていた。 Under such circumstances, regardless of the type of raw material copper oxide to be used, a granular and excellent monodisperse copper powder can be stably obtained without causing a significant difference in particle size, shape, and dispersibility. The copper powder that suppresses the formation of an oxide film after reduction used in wiring materials such as MLCCs, printed boards, electromagnetic wave shields, solar cells, touch panels, etc. The manufacturing method was anxious.
本発明の目的は、前述した従来技術の問題点に鑑み、銅化合物をポリオール中で加熱還元し、得られた銅粉末を洗浄した後乾燥し、大気中で長期保存しても酸化し難い銅粉末が低コストで生産性よく製造できる、積層セラミックスコンデンサなどの電子素子の原料粉末として有用な銅粉末の製造方法を提供することにある。 In view of the above-mentioned problems of the prior art, the object of the present invention is to reduce a copper compound by heating in a polyol, wash the obtained copper powder, dry it, and prevent oxidation even if stored for a long time in the atmosphere. An object of the present invention is to provide a method for producing a copper powder useful as a raw material powder for an electronic device such as a multilayer ceramic capacitor, in which the powder can be produced at low cost with high productivity.
本発明者らは、上記課題を解決するために鋭意研究を重ねた結果、特定量の銅化合物またはその含水物をポリオール中に懸濁させ、１６０〜３２０℃に加熱して銅化合物を還元させて、得られた銅粉末を洗浄し脱水した後、特定条件の減圧雰囲気下で乾燥させることで、大気中で長期保存しても酸化し難い銅粉末が低コストでかつ生産性良く得られることを見出して、本発明を完成するに至った。 As a result of intensive studies to solve the above problems, the present inventors suspended a specific amount of a copper compound or a hydrated product thereof in a polyol, and heated it to 160 to 320 ° C. to reduce the copper compound. After washing and dehydrating the obtained copper powder, it is possible to obtain copper powder that is difficult to oxidize even if stored for a long time in the air at low cost and with high productivity by drying in a reduced pressure atmosphere under specific conditions. As a result, the present invention has been completed.
すなわち、本発明の第１の発明によれば、銅化合物またはその含水物をポリオール中に懸濁させ、１６０〜３２０℃ に加熱して銅粉末を得る工程（Ａ）と、該銅粉末を水で洗浄した後、脱水する工程（Ｂ）と、洗浄・脱水された該銅粉末を乾燥させる工程（Ｃ）を備えた銅粉末の製造方法であって、
前記工程（Ａ）において、前記酸化銅またはその含水物とポリオールを質量比が５：９５〜６０：４０の範囲内で混合し、また、前記工程（Ｃ）において、真空度が９０ｋＰａ以下で、温度が４０〜２００℃の範囲とした真空乾燥機内で銅粉末を１〜７２時間乾燥させ、２５℃で２０００時間大気雰囲気下にて保存したとき、その酸素濃度の増加量が、保存前に対して０．５質量％以下の銅粉末を得ることを特徴とする銅粉末の製造方法が提供される。
That is, according to the first invention of the present invention, the step (A) of obtaining a copper powder by suspending a copper compound or a hydrated product thereof in a polyol and heating to 160 to 320 ° C., and the copper powder in water A method for producing a copper powder, comprising: a step (B) of dehydrating after washing with a step (C); and a step (C) of drying the washed and dehydrated copper powder,
In the step (A), the copper oxide or its hydrate and the polyol are mixed within a mass ratio of 5:95 to 60:40, and in the step (C), the degree of vacuum is 90 kPa or less, When the copper powder was dried for 1 to 72 hours in a vacuum dryer at a temperature in the range of 40 to 200 ° C. and stored at 25 ° C. for 2000 hours in an air atmosphere, the increase in oxygen concentration was less than that before storage. A copper powder production method is provided, characterized in that a copper powder of 0.5 mass% or less is obtained .
また、本発明の第２の発明によれば、第１の発明において、前記工程（Ｃ）における、真空度が１Ｐａ以下であることを特徴とする銅粉末の製造方法が提供される。
また、本発明の第３の発明によれば、第１または２の発明において、前記工程（Ｃ）における、前記真空乾燥機は、被乾燥物を振動させる機構を具備していることを特徴とする銅粉末の製造方法が提供される。
According to a second aspect of the present invention, there is provided the method for producing a copper powder according to the first aspect, wherein the degree of vacuum in the step (C) is 1 Pa or less.
According to a third invention of the present invention, in the first or second invention, the vacuum dryer in the step (C) includes a mechanism for vibrating the material to be dried. A method for producing a copper powder is provided.
また、本発明の第４の発明によれば、第１〜３のいずれかの発明において、前記工程（Ａ）において、前記ポリオールは、２〜６個のＯＨ基を有する多価アルコールであることを特徴とする銅粉末の製造方法が提供される。
また、本発明の第５の発明によれば、第１〜４のいずれかの発明において、前記工程（Ｂ）において、洗浄された銅粉末が、遠心分離機で脱水されることを特徴とする銅粉末の製造方法が提供される。
According to a fourth invention of the present invention, in any one of the first to third inventions, in the step (A), the polyol is a polyhydric alcohol having 2 to 6 OH groups. A method for producing a copper powder is provided.
According to a fifth invention of the present invention, in any one of the first to fourth inventions, the washed copper powder is dehydrated in a centrifuge in the step (B). A method for producing copper powder is provided.
また、本発明の第６の発明によれば、第１〜５のいずれかの発明において、酸素濃度が１．０質量％以下であることを特徴とする銅粉末の製造方法が提供される。
また、本発明の第７の発明によれば、第１〜６のいずれかの発明において、平均粒径が０．１〜２０μｍであることを特徴とする銅粉末の製造方法が提供される。
また、本発明の第８の発明によれば、第１〜７のいずれかの発明において、連結粒子の長径が平均粒径の４倍以下であることを特徴とする銅粉末の製造方法が提供される。
According to a sixth aspect of the present invention, there is provided a method for producing a copper powder characterized in that, in any one of the first to fifth aspects, the oxygen concentration is 1.0% by mass or less.
According to a seventh aspect of the present invention, there is provided a method for producing a copper powder characterized in that in any one of the first to sixth aspects, the average particle size is 0.1 to 20 μm.
According to an eighth aspect of the present invention, there is provided the method for producing a copper powder according to any one of the first to seventh aspects , wherein the long diameter of the connected particles is 4 times or less of the average particle diameter. Is done.
本発明では、特定量の銅化合物またはその含水物をポリオール中に懸濁させ、１６０℃以上に加熱して還元し、得られた銅粉末を洗浄し脱水した後、特定の条件で真空乾燥させるために、２５℃で２０００時間放置しても酸素濃度の増加量が小さい銅粉末が得られる。この製造方法は、比較的低コストであり、しかも生産性が高い。
また、得られた銅粉末は、２５℃で２０００時間放置しても酸化が進まないことから、ＭＬＣＣやチップ抵抗器の外部電極、電磁波シールド、スルーホールやビア埋め用のプリント基板、太陽電池・タッチパネルなど電子素子の配線材料の原料として有用である。
In the present invention, a specific amount of a copper compound or a hydrated product thereof is suspended in a polyol, reduced by heating to 160 ° C. or higher, the obtained copper powder is washed and dehydrated, and then vacuum dried under specific conditions. Therefore, a copper powder having a small increase in oxygen concentration can be obtained even when left at 25 ° C. for 2000 hours. This manufacturing method is relatively low cost and has high productivity.
In addition, since the obtained copper powder does not oxidize even when left at 25 ° C. for 2000 hours, MLCC, chip resistor external electrode, electromagnetic wave shield, through hole and via filling printed circuit board, solar cell It is useful as a raw material for wiring materials for electronic elements such as touch panels.
以下、本発明の銅粉末の製造方法の実施形態について詳細に説明する。 Hereinafter, an embodiment of a method for producing a copper powder of the present invention will be described in detail.
１．銅粉末の製造方法
本発明により銅粉末を製造するには、特定量の銅化合物をポリオール中に懸濁させ、１６０〜３２０℃に加熱して銅粉末を得る工程（Ａ）において、銅化合物とポリオールをある特定質量比で混合し、次に、工程（Ｂ）において、得られた銅粉末を洗浄し脱水した後、工程（Ｃ）において、特定の減圧雰囲気下で乾燥させることで、酸化し難い銅粉末が得られるようにする。
1. To prepare a copper powder by the method the invention of the copper powder is suspended a specific amount of the copper compound in the polyol, in the step (A) to obtain a copper powder was heated to one hundred sixty to three hundred and twenty ° C., and copper compounds The polyol is mixed at a specific mass ratio, and then the obtained copper powder is washed and dehydrated in the step (B), and then oxidized in the step (C) by drying in a specific reduced-pressure atmosphere. Try to obtain difficult copper powder.
（Ａ）銅粉末の形成工程
本発明では、まず、下記の銅化合物（ａ）をポリオール（ｂ）と混合し、１６０〜３２０℃に加熱して銅化合物を還元し銅粉末を得る。
(A) Copper Powder Formation Step In the present invention, first, the following copper compound (a) is mixed with the polyol (b) and heated to 160 to 320 ° C. to reduce the copper compound to obtain a copper powder.
銅化合物（ａ）
本発明では、銅粉末の原料として銅化合物を使用する。銅化合物の種類は、加熱されたポリオール中で還元され、最終的に銅粉末として堆積されるものであれば特に限定されない。
例えば、酸化銅（酸化第一銅および酸化第二銅）、水酸化銅、炭酸銅、シュウ酸銅、硫酸銅などが挙げられる。好ましいのは酸化銅、水酸化銅である。また銅化合物は、水和物（含水物）でも構わない。一般に、銅化合物の含水率が多い場合、生産性が悪化してしまう場合がある。そのため、銅化合物の含水物を用いる場合は、含水率は２５質量％以下であることが好ましく、２０質量％以下であることがより好ましく、１０質量％以下であることがさらに好ましい。
Copper compound (a)
In the present invention, a copper compound is used as a raw material for the copper powder. The kind of copper compound is not particularly limited as long as it is reduced in a heated polyol and finally deposited as a copper powder.
Examples thereof include copper oxide (cuprous oxide and cupric oxide), copper hydroxide, copper carbonate, copper oxalate, and copper sulfate. Preferred are copper oxide and copper hydroxide. The copper compound may be a hydrate (hydrated product). Generally, when the moisture content of the copper compound is large, the productivity may be deteriorated. Therefore, when using a hydrated copper compound, the moisture content is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.
ポリオール（ｂ）
ポリオールは、銅化合物の還元機能を有する多価アルコールである。２〜６個のＯＨ基を有するものが好ましく、例えば、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、テトラエチレングリコール、プロピレングリコール、トリメチレングリコール、ポリエチレングリコール、フェニルジグリコールなどが挙げられる。中でもトリエチレングリコールやテトラエチレングリコールが好ましい。これらは複数種を混合しても構わないし、本発明の目的を損なわなければ、水や他の溶剤を添加しても差し支えない。
Polyol (b)
A polyol is a polyhydric alcohol having a reducing function of a copper compound. Those having 2 to 6 OH groups are preferred, and examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, trimethylene glycol, polyethylene glycol, and phenyl diglycol. Of these, triethylene glycol and tetraethylene glycol are preferable. A plurality of these may be mixed, and water and other solvents may be added as long as the object of the present invention is not impaired.
銅化合物は、ポリオールと混合し、１６０℃以上３２０℃以下に加熱し、熱せられたポリオール中で懸濁される。この範囲内の温度で撹拌することで、銅化合物の還元反応が促進され、銅粉末が形成される。
好ましい加熱温度は、１８０℃以上３１０℃以下であり、より好ましくは、１９０℃以上３００℃以下で、かつポリオールの沸点以下である。加熱温度が１６０℃未満の場合、還元反応が十分に進まず得られる銅粉末の酸素濃度が大幅に上昇するとともに、生産性も悪化する。一方、３２０℃を超えるとポリオールの分解揮発による減少が著しくなり、十分に還元できなくなる恐れがある。そのため、加熱温度を選択したポリオールの沸点より高く設定した場合は、上限の加熱温度を沸点よりも低くすることが望ましい。
The copper compound is mixed with the polyol, heated to 160 ° C. or higher and 320 ° C. or lower, and suspended in the heated polyol. By stirring at a temperature within this range, the reduction reaction of the copper compound is promoted and copper powder is formed.
A preferable heating temperature is 180 ° C. or higher and 310 ° C. or lower, more preferably 190 ° C. or higher and 300 ° C. or lower, and lower than the boiling point of the polyol. When the heating temperature is lower than 160 ° C., the reduction reaction does not proceed sufficiently, and the oxygen concentration of the obtained copper powder is significantly increased and the productivity is also deteriorated. On the other hand, when it exceeds 320 ° C., the decrease due to the decomposition and volatilization of the polyol becomes remarkable, and there is a possibility that it cannot be sufficiently reduced. Therefore, when the heating temperature is set higher than the boiling point of the selected polyol, it is desirable to set the upper limit heating temperature lower than the boiling point.
還元反応に供される銅化合物とポリオールの量は、質量比で５：９５〜６０：４０の範囲内とする。銅化合物の質量比が５未満の場合は、銅粉末の回収量が悪く、銅化合物の質量比が６０を超えると還元が十分に終了しない場合があり、いずれも生産性が低下する。また、銅化合物の質量比が高くなると、還元された銅粉末同士が連結しやすく（以降、連結粒子と呼ぶことがある）なり、特に銅化合物の重量比が６０を超えると、連結粒子の長径が銅粉末個々の平均粒径の４倍を超えるものも発生することがある。銅化合物とポリオールの質量比は、１０：９０〜５５：４５であることが好ましく、１５：８５〜５０：５０であることがより好ましい。 The amount of the copper compound and polyol used for the reduction reaction is in the range of 5:95 to 60:40 by mass ratio. When the mass ratio of the copper compound is less than 5, the recovered amount of the copper powder is poor, and when the mass ratio of the copper compound exceeds 60, the reduction may not be completed sufficiently, and the productivity decreases in any case. Further, when the mass ratio of the copper compound is increased, the reduced copper powders are easily connected to each other (hereinafter sometimes referred to as connected particles). Particularly, when the weight ratio of the copper compound exceeds 60, the major axis of the connected particles May exceed 4 times the average particle size of each copper powder. The mass ratio of the copper compound and the polyol is preferably 10:90 to 55:45, and more preferably 15:85 to 50:50.
（Ｂ）洗浄・脱水工程
工程（Ａ）で得られた銅粉末は、次の洗浄工程（Ｂ）で洗浄し脱水する。還元工程で得られた銅粉末の表面状態や共雑物を詳細に観察すると、銅化合物またはその含水物とポリオールとを１６０℃以上に加熱して生起する反応で、銅が析出し、銅粉末の表面や凝集物の内部に溶媒であるポリオールなどが、共雑物として懸濁している。そのため、反応後に銅粉末を分離し、純水などで洗浄する。
(B) Washing / Dehydration Step The copper powder obtained in the step (A) is washed and dehydrated in the next washing step (B). When the surface state and contaminants of the copper powder obtained in the reduction process are observed in detail, copper precipitates due to the reaction that occurs when the copper compound or its hydrate and polyol are heated to 160 ° C. or higher. A polyol or the like as a solvent is suspended as a contaminant on the surface or inside the aggregate. Therefore, after the reaction, the copper powder is separated and washed with pure water or the like.
洗浄に純水を用いる場合は、導電率が１．０μＳ／ｃｍ以下、より好ましくは、導電率が０．１μＳ／ｃｍ未満である超純水を洗浄に用いるのがより好ましい。洗浄温度は特に限定されないが、５〜５０℃が好ましく、１０〜４０℃がより好ましい。純水による洗浄温度が５０℃を超えると銅粉末が酸化してしまう恐れがあり、５℃未満では洗浄速度が遅く生産性が低下してしまう恐れがある。本発明の趣旨を逸脱しない範囲内であれば、超純水や水道水や工業用水などを使用してもよく、あるいは、純水の代わりにメタノール、エタノール、プロパノール等のアルコール類を洗浄に用いても差し支えない。 When pure water is used for cleaning, it is more preferable to use ultrapure water having an electric conductivity of 1.0 μS / cm or less, more preferably an electric conductivity of less than 0.1 μS / cm. The washing temperature is not particularly limited, but is preferably 5 to 50 ° C, more preferably 10 to 40 ° C. If the cleaning temperature with pure water exceeds 50 ° C., the copper powder may be oxidized, and if it is less than 5 ° C., the cleaning speed may be slow and the productivity may decrease. As long as it does not deviate from the gist of the present invention, ultrapure water, tap water, industrial water, or the like may be used, or alcohol such as methanol, ethanol, propanol or the like is used for cleaning instead of pure water. There is no problem.
洗浄方法、用いる装置、手段や条件は、銅粉末からポリオールやその他の不純物を洗い落とせれば特に限定されない。一例としては、純水で撹拌洗浄後、銅粉末を沈降させ上澄みを回収してから遠心分離機にて脱水する方法が挙げられる。遠心分離機により脱水する場合は、その回転数を装入する銅粉末の量によって調整する。銅粉末が液中に十分分散される回転数であれば特に限定されないが、５０〜３０００ｒｐｍ程度が好ましく、より好ましくは１００〜２５００ｒｐｍである。また本発明の目的を損なわない限り、貫通洗浄などの別の洗浄方法を利用しても差し支えない。 The washing method, the apparatus used, means and conditions are not particularly limited as long as polyol and other impurities can be washed off from the copper powder. As an example, after stirring and washing with pure water, the copper powder is settled and the supernatant is recovered, and then dehydrated with a centrifuge. When dewatering with a centrifuge, the number of revolutions is adjusted according to the amount of copper powder charged. Although it will not specifically limit if copper powder is fully disperse | distributed in a liquid, About 50-3000 rpm is preferable, More preferably, it is 100-2500 rpm. Further, another cleaning method such as through cleaning may be used as long as the object of the present invention is not impaired.
（Ｃ）乾燥工程
工程（Ｂ）で洗浄し脱水された銅粉末は、洗浄によりポリオールなどの共雑物が除去され、遠心分離機等により脱水されているが表面には、まだ水分が付着しているので、この乾燥工程（Ｃ）で、さらに水分などを乾燥させる。
(C) Drying step The copper powder washed and dehydrated in step (B) is dehydrated with a centrifuge etc. after removing contaminants such as polyol by washing, but moisture still adheres to the surface. In this drying step (C), moisture and the like are further dried.
従来、銅粉末の乾燥は、オーブンやスプレードライのような熱風乾燥が主に用いられていた。しかし、熱風乾燥の場合、乾燥後の銅粉末の酸素濃度が高くなり、また、経時変化で酸素濃度がさらに高くなってしまう。
そのため、本発明では、銅粉末を真空乾燥機に装入し、真空度が９０ｋＰａ以下の減圧雰囲気下とし、４０〜２００℃の温度範囲で１〜７２時間乾燥させて水分を除去する。
Conventionally, hot air drying such as oven or spray drying has been mainly used for drying copper powder. However, in the case of hot air drying, the oxygen concentration of the copper powder after drying is increased, and the oxygen concentration is further increased with time.
For this reason, in the present invention, the copper powder is charged into a vacuum dryer, and the moisture is removed by drying in a reduced pressure atmosphere having a vacuum degree of 90 kPa or less and drying in a temperature range of 40 to 200 ° C. for 1 to 72 hours.
真空乾燥機は、種類によって限定されず、少なくとも減圧機能と加熱機能を有する乾燥機であれば良い。しかし、さらに被乾燥物を振動させる機構を有している真空振動乾燥機を用いれば、乾燥中に銅粉末を振動させることで水分の蒸発を早める効果があり、生産性が向上する。 A vacuum dryer is not limited by a kind, What is necessary is just a dryer which has a pressure reduction function and a heating function at least. However, if a vacuum vibration dryer having a mechanism for further vibrating the object to be dried is used, the copper powder is vibrated during drying, which has the effect of accelerating the evaporation of moisture, thereby improving productivity.
真空度が９０ｋＰａを超えると、水分の蒸発が不十分で銅粉末の酸素濃度が高くなると共に、２５℃で２０００時間大気放置後の酸素濃度増加量が１質量％を超えてしまう。また、十分に乾燥するまでの時間が長くなるため、生産性が悪くなる。真空度は低いほど良好であり、１Ｐａ以下がより好ましく、１×１０−２Ｐａ以下がさらに好ましい。 If the degree of vacuum exceeds 90 kPa, the evaporation of moisture is insufficient and the oxygen concentration of the copper powder becomes high, and the increase in oxygen concentration after leaving in the atmosphere at 25 ° C. for 2000 hours exceeds 1% by mass. Moreover, since time until fully drying becomes long, productivity worsens. The lower the degree of vacuum, the better, and it is preferably 1 Pa or less, more preferably 1 × 10 −2 Pa or less.
乾燥温度は、４０℃未満であると水分の蒸発が不十分で、乾燥時間も長くなるので好ましくなく、２００℃を超えると水分の蒸発が早いが、銅粉末同士が焼結してしまうことが懸念され好ましくない。洗浄によりポリオールなどの共雑物を除去したうえで、真空度、乾燥温度、乾燥時間を本発明の範囲内で調整することによって酸素濃度が低く、２５℃で２０００時間大気放置しても酸素濃度の増加量１質量％以下の銅粉末を得ることができる。 If the drying temperature is less than 40 ° C., the evaporation of moisture is insufficient and the drying time becomes longer, which is not preferable. If the drying temperature exceeds 200 ° C., the evaporation of moisture is fast, but the copper powders may sinter. Concerned and undesirable. After removing contaminants such as polyol by washing, the oxygen concentration is low by adjusting the degree of vacuum, drying temperature and drying time within the scope of the present invention. A copper powder having an increase of 1% by mass or less can be obtained.
２．得られる銅粉末
上記により得られる銅粉末は、その酸素濃度が１．０質量％以下である。さらには、２５℃で２０００時間大気雰囲気下にて保存しても、保存後の酸素濃度と保存前の酸素濃度の差が１質量％以下となるのが好ましい。本発明では、上記の製造条件を最適化すれば、２５℃で２０００時間大気雰囲気下での保存後の酸素濃度の増加量を０．５質量％以下とすることも期待できる。
2. Obtained copper powder The copper powder obtained by the above has the oxygen concentration of 1.0 mass% or less. Furthermore, it is preferable that the difference between the oxygen concentration after storage and the oxygen concentration before storage is 1% by mass or less even when stored in the air at 2000C for 25 hours. In the present invention, if the above production conditions are optimized, it can be expected that the amount of increase in oxygen concentration after storage in the air atmosphere at 25 ° C. for 2000 hours is 0.5% by mass or less.
また本発明により得られる銅粉末の平均粒径は、０．１〜２０μｍで、微細な略球状の粉末である。平均粒径は、０．１〜１５μｍが好ましく、０．１〜１０μｍがより好ましい。また、連結粒子の長径が平均粒径の４倍以下であるために、溶剤や樹脂等からなるビヒクルに対して分散性が高い。 Moreover, the average particle diameter of the copper powder obtained by this invention is 0.1-20 micrometers, and is a fine substantially spherical powder. The average particle size is preferably from 0.1 to 15 μm, more preferably from 0.1 to 10 μm. Further, since the major axis of the connecting particles is 4 times or less of the average particle diameter, the dispersibility is high with respect to a vehicle made of a solvent, a resin, or the like.
２５℃で２０００時間大気放置後の酸素濃度の増加量が１質量％以下である銅粉末は、積層セラミックスコンデンサまたはチップ抵抗器、スルーホールやビア埋め用のプリント基板、電磁波シールド、太陽電池、タッチパネルなどの電子素子の原料粉末として有用である。 Copper powder with an oxygen concentration increase of 1% by mass or less after 2000 hours at 25 ° C. is a multilayer ceramic capacitor or chip resistor, printed circuit board for filling through-holes and vias, electromagnetic shielding, solar cells, touch panels It is useful as a raw material powder for electronic devices.
３．銅ペースト
本発明により得られる銅粉末は、溶剤や樹脂等からなるビヒクルと混合、混練させて銅ペーストとする。銅粉末以外に銅ペーストに混合される成分としては、用途に応じて、エポキシ化合物やフェノール、セルロース、アクリル化合物などの有機樹脂、分散剤、硬化剤や硬化促進剤などの添加剤、有機溶剤、Ａｇ、Ａｕ、ＡｌやＮｉなどの金属粉、シリカ、アルミナなど金属酸化物粉などを適宜選択することができる。
3. Copper paste The copper powder obtained by this invention is mixed and kneaded with the vehicle which consists of a solvent, resin, etc. to make a copper paste. In addition to the copper powder, the components mixed in the copper paste include, depending on the use, organic resins such as epoxy compounds, phenol, cellulose, and acrylic compounds, dispersants, additives such as curing agents and curing accelerators, organic solvents, Metal powders such as Ag, Au, Al and Ni, metal oxide powders such as silica and alumina, and the like can be appropriately selected.
銅粉末の平均粒径は、上記例示した外部電極や配線材料などの用途に応じて適宜設定すればよいが、本発明により得られる銅粉末は、平均粒径が０．１〜２０μｍであり、連結粒子の長径が平均粒径の４倍以下であるため分散性が高く、また、２５℃で２０００時間大気雰囲気下にて保存しても、酸素濃度の上昇が低いために、これを配合した銅ペーストは、ＭＬＣＣやチップ抵抗器の外部電極や電磁波シールド、スルーホールやビア埋め用のプリント基板、太陽電池やタッチパネルに代表される配線材料など電子素子の製造に好ましく使用できる。 The average particle diameter of the copper powder may be set as appropriate according to the applications such as the above exemplified external electrodes and wiring materials, but the copper powder obtained by the present invention has an average particle diameter of 0.1 to 20 μm, Since the long diameter of the connected particles is not more than 4 times the average particle diameter, the dispersibility is high, and the increase in oxygen concentration is low even when stored in the atmosphere at 25 ° C. for 2000 hours. The copper paste can be preferably used for the production of electronic elements such as MLCCs and external electrodes of chip resistors, electromagnetic wave shields, printed boards for filling through holes and vias, wiring materials typified by solar cells and touch panels.
以下に、実施例に基づき本発明を具体的に説明するが、本発明は、これら実施例によって何ら限定されるものではない。なお、銅粉末の製造、洗浄には、下記の原材料を使用し、物性を測定・評価した。 EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In addition, the following raw material was used for manufacture and washing | cleaning of copper powder, and the physical property was measured and evaluated.
「原料」
・酸化銅Ａ：酸化第二銅（含水率５質量％、住友金属鉱山株式会社製）
・酸化銅Ｂ：酸化第二銅（含水率２５質量％、住友金属鉱山株式会社製）
・水酸化銅Ａ：水酸化銅（和光純薬工業株式会社製）
・炭酸銅Ａ：炭酸銅（和光純薬工業株式会社製）
・シュウ酸銅Ａ：シュウ酸銅（和光純薬工業株式会社製）
"material"
-Copper oxide A: Cupric oxide (water content 5 mass%, manufactured by Sumitomo Metal Mining Co., Ltd.)
-Copper oxide B: cupric oxide (water content 25% by mass, manufactured by Sumitomo Metal Mining Co., Ltd.)
-Copper hydroxide A: Copper hydroxide (Wako Pure Chemical Industries, Ltd.)
・ Copper carbonate A: Copper carbonate (Wako Pure Chemical Industries, Ltd.)
-Copper oxalate A: Copper oxalate (Wako Pure Chemical Industries, Ltd.)
「ポリオール」
・ポリオールＡ：トリエチレングリコール（関東化学株式会社製、沸点：２８７℃）
・ポリオールＢ：テトラエチレングリコール（関東化学株式会社製、沸点：３２７℃）
"Polyol"
Polyol A: triethylene glycol (manufactured by Kanto Chemical Co., Inc., boiling point: 287 ° C.)
Polyol B: Tetraethylene glycol (manufactured by Kanto Chemical Co., Inc., boiling point: 327 ° C.)
（１）平均粒径、形状
得られた銅粉末は大きさと形状を走査型電子顕微鏡（以下、ＳＥＭ）で観察し、平均粒径は画像解析した粒径測定値の平均値を示す。
(1) Average particle diameter and shape The obtained copper powder was observed with a scanning electron microscope (hereinafter, SEM) for the size and shape, and the average particle diameter represents an average value of the particle diameter measurement values obtained by image analysis.
（２）酸素濃度
得られた銅粉末は、作製直後の酸素濃度（質量％）を、不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で測定した。また、２５℃で２０００時間大気雰囲気下に放置した後にも酸素濃度を同様に測定し、増加量を計算した。
(2) Oxygen concentration The obtained copper powder was measured for the oxygen concentration (mass%) immediately after production by an inert gas impulse heating and melting infrared absorption method (model: TC-436AR, manufactured by LECO). Further, the oxygen concentration was measured in the same manner after being left in the air atmosphere at 25 ° C. for 2000 hours, and the increase was calculated.
（３）連結粒子の長さ
得られた銅粉末をＳＥＭで１００００倍の視野で撮影し画像解析した結果、連結粒子の長径が平均粒径の４倍を超えるものがある場合を不可（×）とし、すべてが４倍以下である場合を良（○）とした。
(3) Length of connected particles As a result of photographing the obtained copper powder with a SEM with a field of view of 10,000 times and analyzing the image, it is impossible to have a case where the long diameter of the connected particles exceeds 4 times the average particle size (×) When all were 4 times or less, it was judged as good (◯).
（４）生産性
所定量の銅粉末を得るまでに要する時間を測定し、従来と比べ同等である場合を不可（×）、時間が短縮された場合を可（△）とし、時間が著しく短縮された場合を良（○）とした。
(4) Productivity Measures the time required to obtain a predetermined amount of copper powder. If it is equivalent to the conventional method, it is not possible (x), and if the time is shortened, it is acceptable (△), and the time is significantly shortened. The case where it was done was judged as good (◯).
（５）総合評価
上記の４項目において、平均粒径が０．１〜２０μｍ、酸素濃度の上昇が１％以下、連結粒子の長径が平均粒径の４倍以下、生産性の各条件を全て満たすか、可が一つあるものを良（○）とし、１つでも満たさないものがある場合は不可（×）とした。
(5) Comprehensive evaluation In the above four items, the average particle diameter is 0.1 to 20 μm, the increase in oxygen concentration is 1% or less, the long diameter of the connected particles is 4 times or less of the average particle diameter, and all the productivity conditions Satisfies or has one pass, passes (good), and if there is not even one, passes (No).
（実施例１）
酸化銅Ａ（含水率が５質量％の酸化第二銅）を原料とし、表１の条件で原料を溶媒中に供給し、所定の設定温度にして加熱し、１時間撹拌した。その後、還元後の銅粉末を沈降させ上澄みを回収した後、残留品に純水を供給し２５℃で撹拌洗浄（純水洗浄）し、再び銅粉末を沈降させ上澄みを回収後に、遠心分離機（２３００ｒｐｍ）で遠心脱水した。得られた銅粉を真空乾燥機に装入し、表１の条件で真空乾燥した。
作製した銅粉末は、平均粒径をＳＥＭ観察後、画像解析した。形状は略球形であった。酸素濃度を不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で分析した。これらの結果は表１に併記した。
Example 1
Using copper oxide A (cupric oxide having a water content of 5 mass%) as a raw material, the raw material was supplied into the solvent under the conditions shown in Table 1, heated to a predetermined set temperature, and stirred for 1 hour. Thereafter, the reduced copper powder is allowed to settle and the supernatant is recovered. Then, pure water is supplied to the remaining product and stirred and washed at 25 ° C. (pure water cleaning). After the copper powder is settled and the supernatant is recovered, the centrifuge Centrifugal dehydration was performed at 2300 rpm. The obtained copper powder was charged into a vacuum dryer and vacuum dried under the conditions shown in Table 1.
The prepared copper powder was subjected to image analysis after observation of the average particle diameter by SEM. The shape was substantially spherical. The oxygen concentration was analyzed by an inert gas impulse heating melting infrared absorption method (model: TC-436AR, manufactured by LECO). These results are also shown in Table 1.
（実施例２、３）
表１に記載したように原料の酸化銅とポリオールの比を変え、それ以外は実施例１と同様にして銅粉末を作製した。作製した銅粉末の平均粒径をＳＥＭの観察後、画像解析した。形状は略球形であった。酸素濃度を不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で分析した。これらの結果は表１に併記した。
(Examples 2 and 3)
As described in Table 1, copper powder was prepared in the same manner as in Example 1 except that the ratio of the raw material copper oxide and polyol was changed. The average particle size of the prepared copper powder was image-analyzed after SEM observation. The shape was substantially spherical. The oxygen concentration was analyzed by an inert gas impulse heating melting infrared absorption method (model: TC-436AR, manufactured by LECO). These results are also shown in Table 1.
（実施例４〜８）
表１に記載したように原料の銅化合物の種類を変えるか、ポリオールの種類を変えた以外は実施例１と同様にして銅粉末を作製した。作製した銅粉末の平均粒径をＳＥＭの観察後、画像解析した。形状は略球形であった。酸素濃度を不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で分析した。これらの結果は表１に併記した。
(Examples 4 to 8)
A copper powder was prepared in the same manner as in Example 1 except that the type of raw material copper compound was changed as shown in Table 1 or the type of polyol was changed. The average particle size of the prepared copper powder was image-analyzed after SEM observation. The shape was substantially spherical. The oxygen concentration was analyzed by an inert gas impulse heating melting infrared absorption method (model: TC-436AR, manufactured by LECO). These results are also shown in Table 1.
（実施例９、１０）
表１に記載したように反応温度を変え、それ以外は実施例１と同様にして銅粉末を作製した。作製した銅粉末の平均粒径をＳＥＭの観察後、画像解析した。形状は略球形であった。酸素濃度を不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で分析した。これらの結果は表１に併記した。
(Examples 9 and 10)
Copper powder was prepared in the same manner as in Example 1 except that the reaction temperature was changed as described in Table 1. The average particle size of the prepared copper powder was image-analyzed after SEM observation. The shape was substantially spherical. The oxygen concentration was analyzed by an inert gas impulse heating melting infrared absorption method (model: TC-436AR, manufactured by LECO). These results are also shown in Table 1.
（実施例１１〜１４）
表１に記載したように乾燥機の温度を変えるか、時間または真空度を変えるか、乾燥時に振動を加えた以外は実施例１と同様にして銅粉末を作製した。作製した銅粉末の平均粒径をＳＥＭの観察後、画像解析した。形状は略球形であった。酸素濃度を不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で分析した。これらの結果は表１に併記した。
(Examples 11-14)
A copper powder was prepared in the same manner as in Example 1 except that the temperature of the dryer was changed as shown in Table 1, the time or the degree of vacuum was changed, or vibration was applied during drying. The average particle size of the prepared copper powder was image-analyzed after SEM observation. The shape was substantially spherical. The oxygen concentration was analyzed by an inert gas impulse heating melting infrared absorption method (model: TC-436AR, manufactured by LECO). These results are also shown in Table 1.
（比較例１、２）
表２に記載したように酸化銅Ａとポリオールの比を変え、それ以外は実施例１と同様にして銅粉末を作製した。作製した銅粉末の平均粒径をＳＥＭの観察後、画像解析した。形状は略球形であったが、比較例２の銅粉末は連結粒子の長径が大きかった。酸素濃度を不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で分析した。これらの結果は表２に併記した。
(Comparative Examples 1 and 2)
Copper powder was prepared in the same manner as in Example 1 except that the ratio of copper oxide A and polyol was changed as described in Table 2. The average particle size of the prepared copper powder was image-analyzed after SEM observation. Although the shape was substantially spherical, the copper powder of Comparative Example 2 had a larger major axis of the connected particles. The oxygen concentration was analyzed by an inert gas impulse heating melting infrared absorption method (model: TC-436AR, manufactured by LECO). These results are also shown in Table 2.
（比較例３）
表２に記載したように反応温度を変え、それ以外は実施例１と同様にして銅粉末を作製した。作製した銅粉末の平均粒径をＳＥＭの観察後、画像解析した。形状は略球形であったが、平均粒径は１０μｍを超えていた。酸素濃度を不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で分析した。これらの結果は表２に併記した。
(Comparative Example 3)
Copper powder was prepared in the same manner as in Example 1 except that the reaction temperature was changed as described in Table 2. The average particle size of the prepared copper powder was image-analyzed after SEM observation. The shape was substantially spherical, but the average particle size exceeded 10 μm. The oxygen concentration was analyzed by an inert gas impulse heating melting infrared absorption method (model: TC-436AR, manufactured by LECO). These results are also shown in Table 2.
（比較例４〜６）
表２に記載したように真空乾燥機の設定温度と時間と真空度を変え、それ以外は実施例１と同様にして銅粉末を作製した。作製した銅粉末の平均粒径をＳＥＭの観察後、画像解析し、酸素濃度を不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で分析した。これらの結果は表２に併記した。
(Comparative Examples 4-6)
As described in Table 2, copper powder was prepared in the same manner as in Example 1 except that the set temperature, time, and degree of vacuum of the vacuum dryer were changed. The average particle size of the prepared copper powder was image-analyzed after SEM observation, and the oxygen concentration was analyzed by an inert gas impulse heating and melting infrared absorption method (model: TC-436AR, manufactured by LECO). These results are also shown in Table 2.
（比較例７）
表２に記載したように真空乾燥機の真空ポンプを稼働せずに、通常の乾燥機代わりとして真空乾燥機を用いた。それ以外は実施例１と同様にして銅粉末を作製した。作製した銅粉末の平均粒径をＳＥＭの観察後、画像解析し、酸素濃度を不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で分析した。これらの結果は表２に併記した。
(Comparative Example 7)
As described in Table 2, a vacuum dryer was used instead of a normal dryer without operating the vacuum pump of the vacuum dryer. Otherwise, a copper powder was produced in the same manner as in Example 1. The average particle size of the prepared copper powder was image-analyzed after SEM observation, and the oxygen concentration was analyzed by an inert gas impulse heating and melting infrared absorption method (model: TC-436AR, manufactured by LECO). These results are also shown in Table 2.
（参考例１〜３）
前記原料、ポリオールを用いて製造していない市販の銅粉末を用意し、平均粒径をＳＥＭの観察後、画像解析し、酸素濃度を不活性ガスインパルス加熱融解赤外吸収法（型式：ＴＣ−４３６ＡＲ，ＬＥＣＯ社製）で分析した。
参考例１は三井金属工業株式会社製の電解銅粉（品名：ＥＣＹ）、参考例２は三井金属工業株式会社製の湿式銅粉（品名：１１００Ｙ）、参考例３は三井金属工業株式会社製のアトマイズ銅粉（品名：ＭＡ−Ｃ０２５Ｋ）であり、それぞれの結果を表２に併記した。
(Reference Examples 1-3)
Commercially available copper powder not manufactured using the above raw materials and polyol was prepared, the average particle size was observed by SEM, image analysis was performed, and the oxygen concentration was determined by inert gas impulse heating and melting infrared absorption method (model: TC- 436AR, manufactured by LECO).
Reference Example 1 is an electrolytic copper powder (product name: ECY) manufactured by Mitsui Kinzoku Kogyo Co., Ltd., Reference Example 2 is a wet copper powder (product name: 1100Y) manufactured by Mitsui Kinzoku Kogyo Co., Ltd., and Reference Example 3 is manufactured by Mitsui Metal Industry Co., Ltd. Atomized copper powder (product name: MA-C025K), and the results are shown in Table 2.
「評価」
上記結果を示す表１から明らかなように、実施例１〜１４の銅粉末は、銅化合物とポリオールの比および反応温度を所定の範囲とし、適切な乾燥を行っているので、作製した銅粉末の粒径、酸素濃度の上昇が小さく、生産性、コストメリットが優れていることがわかる。なお、実施例３、１０、１３は酸素濃度上昇がやや高く、実施例２、１１は生産性の面でやや劣るが、いずれも実用上問題のないレベルである。
"Evaluation"
As is clear from Table 1 showing the above results, the copper powders of Examples 1 to 14 were appropriately dried with the ratio of the copper compound to the polyol and the reaction temperature within a predetermined range. It can be seen that the increase in particle size and oxygen concentration is small, and the productivity and cost merit are excellent. In Examples 3, 10 and 13, the increase in oxygen concentration is slightly high, and Examples 2 and 11 are slightly inferior in productivity, but both are at a level where there is no practical problem.
これに対し、比較例１は、銅化合物とポリオールの比で銅化合物を本発明の好ましい範囲よりも低くしたため、生産性が悪く、工業的に不利になり不可となった。比較例２は、銅化合物とポリオールの比で銅化合物を本発明の好ましい範囲よりも高くしたため、十分に還元反応が進まず生産性が悪く、連結粒子の長さ評価も悪くなった。比較例３は、反応温度が本発明の好ましい範囲より低いため、還元反応が適切に進まず生産性が悪くなった。
また、比較例４は、乾燥温度を本発明の好ましい範囲よりも低くしたため、乾燥が十分でなく酸素濃度上昇が高く、生産性も悪く不可となった。比較例５は、乾燥時間を本発明の好ましい範囲よりも短くしたため、乾燥が十分でなく酸素濃度上昇が高く不可となった。比較例６は、乾燥時の真空度が本発明よりも弱いため、乾燥が十分でなく酸素濃度上昇が高く不可となった。さらに、比較例７は、乾燥時に真空ポンプを使用しなかったため通常の温風乾燥機での乾燥となり、生産性が悪くなり酸素濃度上昇も高く不可となった。
On the other hand, since the comparative example 1 made the copper compound lower than the preferable range of this invention by the ratio of a copper compound and a polyol, productivity was bad and became industrially disadvantageous and became impossible. Since the comparative example 2 made the copper compound higher than the preferable range of this invention by the ratio of a copper compound and a polyol, reduction reaction did not fully advance but productivity was bad, and the length evaluation of the connection particle | grains also worsened. In Comparative Example 3, since the reaction temperature was lower than the preferred range of the present invention, the reduction reaction did not proceed properly and the productivity was poor.
In Comparative Example 4, since the drying temperature was lower than the preferred range of the present invention, the drying was not sufficient, the oxygen concentration was increased, the productivity was poor, and it was impossible. In Comparative Example 5, since the drying time was shorter than the preferable range of the present invention, the drying was not sufficient, and the increase in oxygen concentration was impossible. In Comparative Example 6, the degree of vacuum at the time of drying was weaker than that of the present invention. Furthermore, since the comparative example 7 did not use a vacuum pump at the time of drying, it was dried with a normal hot air dryer, resulting in poor productivity and high oxygen concentration, which was impossible.
また、参考例１〜３は、原材料として、銅化合物とポリオールを用いず、他の製法による銅粉末を用いており、いずれも２５℃で２０００時間大気保存後の酸素濃度の増加量が高くなり不可となった。 In addition, Reference Examples 1 to 3 do not use a copper compound and polyol as raw materials, but use copper powder produced by other production methods, and all increase the oxygen concentration after 2000 hours storage at 25 ° C. It became impossible.
本発明により得られる銅粉末は、平均粒径が０．１〜２０μｍと微細で、２５℃で２０００時間大気放置しても酸素濃度が上昇しないので、各種電子素子の原料として適用できる。
また、本発明により得られる銅粉末を配合した銅ペーストは、ＭＬＣＣの内部や外部電極、チップ抵抗器の外部電極、電磁波シールド、各種導電性接着剤、スルーホールやビア埋め用プリント基板、太陽電池・タッチパネルなどの配線材料として、作製後の銅粉末が酸化し難く、高い生産性を維持できるため、その工業的価値は極めて大きい。
The copper powder obtained according to the present invention has a fine average particle size of 0.1 to 20 μm, and the oxygen concentration does not increase even when left in the air at 25 ° C. for 2000 hours. Therefore, it can be applied as a raw material for various electronic devices.
Moreover, the copper paste which mix | blended the copper powder obtained by this invention is the inside of MLCC, an external electrode, the external electrode of a chip resistor, an electromagnetic wave shield, various conductive adhesives, a printed circuit board for filling a through hole or a via, a solar cell -As a wiring material for touch panels and the like, the manufactured copper powder is difficult to oxidize and can maintain high productivity, so its industrial value is extremely high.
Claims (8)
前記工程（Ａ）において、前記酸化銅またはその含水物とポリオールを質量比が５：９５〜６０：４０の範囲内で混合し、また、前記工程（Ｃ）において、真空度が９０ｋＰａ以下で、温度が４０〜２００℃の範囲とした真空乾燥機内で銅粉末を１〜７２時間乾燥させ、２５℃で２０００時間大気雰囲気下にて保存したとき、その酸素濃度の増加量が、保存前に対して０．５質量％以下の銅粉末を得ることを特徴とする銅粉末の製造方法。 A step (A) of obtaining a copper powder by suspending a copper compound or a hydrated product thereof in a polyol and heating to 160 to 320 ° C., a step (B) of dehydrating the copper powder after washing with water; A method for producing a copper powder comprising a step (C) of drying the washed and dehydrated copper powder,
In the step (A), the copper oxide or its hydrate and the polyol are mixed within a mass ratio of 5:95 to 60:40, and in the step (C), the degree of vacuum is 90 kPa or less, When the copper powder was dried for 1 to 72 hours in a vacuum dryer at a temperature in the range of 40 to 200 ° C. and stored at 25 ° C. for 2000 hours in an air atmosphere, the increase in oxygen concentration was less than that before storage. A method for producing a copper powder, comprising obtaining 0.5% by mass or less of copper powder .
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