JP4894266B2 - Conductive powder surface treatment method, conductive powder and conductive paste - Google Patents
Conductive powder surface treatment method, conductive powder and conductive paste Download PDFInfo
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- 239000000843 powder Substances 0.000 title claims description 75
- 238000000034 method Methods 0.000 title claims description 36
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Description
本発明は、銅又は銅合金からなる導電性ペースト用の導電粉に関し、特に酸素品位が低く且つタップ密度の高い導電粉を得るための表面処理方法、その方法により得られる導電粉、及びその導電粉を用いる導電性ペーストに関する。 The present invention relates to a conductive powder for a conductive paste made of copper or a copper alloy, and in particular, a surface treatment method for obtaining a conductive powder having a low oxygen quality and a high tap density, a conductive powder obtained by the method, and a conductive powder thereof. The present invention relates to a conductive paste using powder.
基板回路形成用、スルーホール穴埋め用、積層コンデンサ電極形成用等の電子材料形成用の導電ペーストや導電フィラーとして、銅、ニッケル、銀あるいはこれらの合金の粉末が用いられている。これらの導電性粉末には、導電性が良好であること、印刷性に優れた粒子形状を有し、粒径が揃い凝集の少ない粒子であること、ペースト中での分散性が良いこと、またマイグレーションを起こしにくいことなどが求められている。 Copper, nickel, silver, or an alloy thereof is used as a conductive paste or conductive filler for forming electronic materials such as substrate circuit formation, through-hole filling, and multilayer capacitor electrode formation. These conductive powders have good conductivity, have a particle shape with excellent printability, have a uniform particle size and are less agglomerated, have good dispersibility in the paste, It is required that migration is difficult to occur.
これらの導電粉の中で、銅粉及び銅合金粉は最も安価であり、またマイグレーションを起こしにくい材料として優れている。しかし、銅粉及び銅合金粉は、特に耐熱・耐湿環境下において容易に酸化され、酸化されると導電性が低下しやすいという欠点があるため、その使用が制約されてきた。 Among these conductive powders, copper powder and copper alloy powder are the cheapest materials and are excellent as materials that hardly cause migration. However, the use of copper powder and copper alloy powder has been limited because it is easily oxidized particularly in a heat- and moisture-resistant environment, and when oxidized, the conductivity tends to decrease.
銅粉及び銅合金粉の耐酸化性を向上させる方法として、その表面を異種材料で被覆することが提案されている。例えば、特開平７−２７８６１４号公報には、ステアリン酸を直接混合して、銅粉表面をステアリン酸で被覆する方法が記載されている。また、特開２００２−３３２５０２号公報には、脂肪酸を含む有機溶媒中で処理して、銅粉表面を脂肪酸で被覆する方法が記載されている。しかしながら、一般に銅粉の表面は自然酸化膜や汚染層で覆われているため、その表面に上記方法により有機皮膜を形成したとしても、導電性を十分に向上させることはできなかった。 As a method for improving the oxidation resistance of copper powder and copper alloy powder, it has been proposed to coat the surface with a different material. For example, Japanese Patent Application Laid-Open No. 7-278614 describes a method in which stearic acid is directly mixed and the copper powder surface is coated with stearic acid. Japanese Patent Application Laid-Open No. 2002-332502 describes a method in which a copper powder surface is coated with a fatty acid by treatment in an organic solvent containing a fatty acid. However, since the surface of the copper powder is generally covered with a natural oxide film or a contaminated layer, even if an organic film is formed on the surface by the above method, the conductivity cannot be sufficiently improved.
そこで、特開平１１−１１１０５４号公報には、銅粉の表面を有機アルカリで清浄化し、次に還元剤により処理した後、有機皮膜を形成させる方法が提案されている。しかし、有機アルカリでの処理と還元剤での処理は、その都度水洗乾燥を行う必要があるうえ、その後の有機皮膜の形成は有機溶媒中で行うため、水洗乾燥の際や有機溶媒中に移す際に銅粉表面が大気に露出されて空気酸化を受けてしまう。また、この方法は、工程が極めて多く、コストも高くなるという問題があった。 Japanese Patent Application Laid-Open No. 11-111054 proposes a method of forming an organic film after the surface of copper powder is cleaned with an organic alkali and then treated with a reducing agent. However, treatment with organic alkali and treatment with a reducing agent require washing and drying each time, and since the subsequent formation of the organic film is carried out in an organic solvent, transfer to the organic solvent during washing and drying. At that time, the surface of the copper powder is exposed to the atmosphere and is subject to air oxidation. In addition, this method has a problem that the number of steps is extremely high and the cost is high.
また最近では、電子機器類などの小型化・軽量化に伴い、電子回路のファインピッチ化が進んでいる。その中で、配線幅、スルーホール径やビア径などがファイン化されており、それに使われる銅粉などの平均粒径は１０μｍから５μｍ以下へと移行している。同時に、スクリーン印刷やスルーホール用の導電ペースト用に使われている銅粉は、丸みのある形状のものが求められ、高タップ密度で良好な導電性を示すものが好まれている。 In recent years, fine pitches of electronic circuits have been advanced along with miniaturization and weight reduction of electronic devices. Among them, the wiring width, through-hole diameter, via diameter, and the like have been refined, and the average particle diameter of copper powder and the like used therefor has shifted from 10 μm to 5 μm or less. At the same time, the copper powder used for conductive pastes for screen printing and through-holes is required to have a round shape, and those having high tap density and good conductivity are preferred.
導電粉を用いた導電ペースト、特に低温で焼成する熱硬化型ペーストでは、導電性が粒子同士の接触によって得られるので、粒子間の抵抗を低減させるため表面酸化を抑えると同時に、粒子を密に接触させるためタップ密度を高くしたものが望まれている。この要望に対して、特開２００３−１４１９２９号公報には、小粒径（１〜５μｍ）の球状銅粉と大粒径（３〜１０μｍ）の多面体銅粉とを混合した低抵抗の銅粉ペーストが提案されている。しかしながら、この銅粉ペーストを焼成して形成した導電膜の体積抵抗値は、バルクの体積抵抗値の１０倍程度に留まっている。 In conductive pastes using conductive powder, especially thermosetting pastes that are fired at low temperatures, conductivity is obtained by contact between the particles. What made the tap density high in order to make it contact is desired. In response to this demand, Japanese Patent Application Laid-Open No. 2003-141929 discloses a low-resistance copper powder in which a spherical copper powder having a small particle size (1 to 5 μm) and a polyhedral copper powder having a large particle size (3 to 10 μm) are mixed. A paste has been proposed. However, the volume resistance value of the conductive film formed by firing this copper powder paste remains about 10 times the bulk volume resistance value.
また、特開平７−２２６１１０号公報には、レゾール型フェノール樹脂中で炭素数４〜１２の第１アミンを付着させながら、樹枝状電解銅粉を混合して導電性銅粉ペーストを製造する方法が記載されている。しかし、この方法では、熱風乾燥機で１５０℃、３０分間の熱処理が必要となり、また体積抵抗率はバルクの数十倍であった。特開昭６２−１９９７０５号公報、特開平２−１８２８０９号公報、特開２０００−８０４０８号公報には、樹枝状電解銅粉をジェットミルで粒径数μｍまで粉砕し、レゾール型フェノール樹脂を用いてペースト化した導電性銅粉ペーストが記載されているが、大気中において１５０℃あるいは２２０℃で焼成した膜の体積低効率は１００μｍΩ・ｃｍ以上であり、バルクの数十倍以上であった。 JP-A-7-226110 discloses a method for producing a conductive copper powder paste by mixing dendritic electrolytic copper powder while adhering a primary amine having 4 to 12 carbon atoms in a resol type phenol resin. Is described. However, this method requires heat treatment at 150 ° C. for 30 minutes with a hot air dryer, and the volume resistivity is several tens of times that of the bulk. In JP-A-62-199705, JP-A-2-182809, and JP-A-2000-80408, dendritic electrolytic copper powder is pulverized with a jet mill to a particle size of several μm, and a resol type phenol resin is used. The conductive copper powder paste made into a paste is described, but the volume low efficiency of the film fired at 150 ° C. or 220 ° C. in the atmosphere is 100 μmΩ · cm or more, which is several tens of times that of the bulk.
本発明は、上記した従来の事情に鑑み、酸素品位が低く、且つ優れた耐熱・耐湿性を有すると共に、タップ密度の高い銅粉又は銅合金粉を、簡単に且つ低コストで得るための表面処理方法、その方法で得られた導電性ペースト用の銅粉及び銅合金粉、並びにその銅粉及び銅合金粉を用いることで優れた導電性を有する焼成膜の形成に好適な導電性ペーストを提供することを目的とするものである。 In view of the above-described conventional circumstances, the present invention has a surface for obtaining oxygen powder having a low oxygen quality, excellent heat resistance and moisture resistance, and having a high tap density at a low cost. A conductive paste suitable for forming a fired film having excellent conductivity by using a treatment method, copper powder and copper alloy powder for conductive paste obtained by the method, and copper powder and copper alloy powder It is intended to provide.
上記目的を達成するため、本発明が提供する導電粉の表面処理方法は、銅又は銅合金からなる導電粉を、酸と還元剤と炭素数８以上の脂肪酸のアルカリ金属塩とを同時に含有する水溶液で処理することを特徴とする。 In order to achieve the above object, the surface treatment method for a conductive powder provided by the present invention comprises a conductive powder composed of copper or a copper alloy simultaneously with an acid, a reducing agent, and an alkali metal salt of a fatty acid having 8 or more carbon atoms. It is characterized by treating with an aqueous solution.
上記本発明の導電粉の表面処理方法においては、前記酸として、酢酸、ギ酸から選ばれた少なくとも１種を用いることができる。また、前記還元剤として、アスコルビン酸、ギ酸、及びそれらの塩から選ばれた少なくとも１種を用いることができる。 In the conductive powder surface treatment method of the present invention, at least one selected from acetic acid and formic acid can be used as the acid. Moreover, at least 1 sort (s) chosen from ascorbic acid, formic acid, and those salts can be used as said reducing agent.
また、本発明が提供する導電性ペースト用導電粉は、上記したいずれかの本発明の表面処理方法を施した銅又は銅合金からなる導電性ペースト用導電粉であって、炭素数８以上の脂肪酸の皮膜を有し、平均粒径が１〜３μｍの小粒径球状粉と平均粒径が３〜１０μｍの大粒径球状粉との混合粉からなることを特徴とするものである。この本発明の導電性ペースト用導電粉においては、前記小粒径球状粉が導電粉全体の１〜２０重量％であることが好ましい。 The conductive powder for conductive paste provided by the present invention is a conductive powder for conductive paste made of copper or a copper alloy subjected to any of the above-described surface treatment methods of the present invention, and having 8 or more carbon atoms. It has a fatty acid film, and is composed of a mixed powder of a small particle size spherical powder having an average particle size of 1 to 3 μm and a large particle size spherical powder having an average particle size of 3 to 10 μm. In the conductive powder for conductive paste of the present invention, the small particle size spherical powder is preferably 1 to 20% by weight of the entire conductive powder.
本発明は、更に、上記したいずれかの本発明の導電性ペースト用導電粉を用い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。 The present invention further provides a conductive paste characterized by using any one of the above-described conductive powders for a conductive paste of the present invention.
本発明によれば、銅又は銅合金からなる導電粉であって、酸素品位が低く、優れた耐熱・耐湿性を有し、且つタップ密度の高い導電粉を、簡単な方法により低コストで得ることができる。従って、本発明により得られる導電粉を用いた導電性ペーストは、従来に比べてはるかに優れた導電性を有する焼成膜の形成に好適である。 According to the present invention, conductive powder made of copper or a copper alloy, having low oxygen quality, excellent heat and humidity resistance, and high tap density can be obtained at a low cost by a simple method. be able to. Therefore, the conductive paste using the conductive powder obtained by the present invention is suitable for the formation of a fired film having much better conductivity than the conventional one.
本発明方法においては、銅粉及び銅合金粉の表面に存在している酸化膜や汚染層を酸の水溶液で除去する際に、その水溶液中に同時に還元剤と脂肪酸のアルカリ金属塩を含有させる。これにより、銅粉及び銅合金粉の表面の酸化膜や汚染層が酸で除去され、同時に水溶液中の溶存酸素による表面の再酸化が還元剤により抑制されるため、酸素品位を大幅に低減させることができる。また、酸化膜や汚染層を除去した表面には、直ちに脂肪酸イオンが配位して被覆するので、耐熱・耐湿性が向上し、後からの酸化を抑制すると共に、タップ密度を高めることができる。 In the method of the present invention, when the oxide film and the contaminated layer existing on the surface of the copper powder and the copper alloy powder are removed with an aqueous solution of an acid, the aqueous solution simultaneously contains a reducing agent and an alkali metal salt of a fatty acid. . As a result, the oxide film and the contamination layer on the surface of the copper powder and the copper alloy powder are removed with an acid, and at the same time, the reoxidation of the surface due to dissolved oxygen in the aqueous solution is suppressed by the reducing agent, thereby greatly reducing the oxygen quality. be able to. In addition, since the fatty acid ions are immediately coordinated and coated on the surface from which the oxide film and the contaminated layer have been removed, heat resistance and moisture resistance are improved, and oxidation can be suppressed later and the tap density can be increased. .
即ち、銅粉及び銅合金粉は、いかなる製法で作製したものであっても、特別な処理を施さない限り、その表面は酸化膜あるいは汚染層で覆われている。この表面の酸化膜や汚染層は酸で溶解除去することが可能であるが、酸で処理する際に水溶液中に存在する溶存酸素によって表面が直ちに酸化され、再び酸化膜が形成されてしまうため、酸素品位の大幅な低減は困難であった。 That is, the surface of the copper powder and the copper alloy powder is covered with an oxide film or a contaminated layer unless special treatment is performed. The surface oxide film and contaminated layer can be dissolved and removed with an acid, but the surface is immediately oxidized by the dissolved oxygen present in the aqueous solution when treated with an acid, and an oxide film is formed again. Therefore, it was difficult to significantly reduce the oxygen quality.
そこで、本発明方法では、銅粉や銅合金粉を処理する酸の水溶液中に還元剤を共存させることによって、溶存酸素による粉末粒子表面の酸化を抑制する。実際に酸のみで処理した銅粉と、酸と還元剤を共存させて処理した銅粉について、処理後の表面の化学状態をＸＰＳ分析した結果、還元剤を共存させて酸で処理した銅粉では表面でメタル状態の銅が検出され、酸化の程度が酸のみで処理した銅粉に比べて低減していることが確認できた。 Therefore, in the method of the present invention, the reducing agent coexists in the acid aqueous solution for treating the copper powder or the copper alloy powder, thereby suppressing the oxidation of the powder particle surface by dissolved oxygen. As a result of XPS analysis of the chemical state of the surface after treatment of copper powder actually treated with acid alone and copper powder treated with acid and reducing agent, copper powder treated with acid with coexisting reducing agent Then, copper in a metal state was detected on the surface, and it was confirmed that the degree of oxidation was reduced compared to copper powder treated with acid alone.
上記表面処理に用いる酸としては、酸化膜や汚染層を除去し得るものであれば特に制限はないが、酢酸、ギ酸から選ばれた少なくとも１種を用いることが好ましい。また、リン酸、硫酸、塩酸、硝酸なども使用できる。また、還元剤としては、アスコルビン酸、ギ酸、及びそれらの塩から選ばれた少なくとも１種を用いることが好ましい。また、シュウ酸、亜硫酸なども使用できる。尚、酸と還元剤の含有量や組合せは、銅粉や銅合金粉の処理量、その表面の酸化膜や汚染層の程度などに応じて適宜定めればよい。 The acid used for the surface treatment is not particularly limited as long as it can remove an oxide film and a contaminated layer, but at least one selected from acetic acid and formic acid is preferably used. Further, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid and the like can also be used. Moreover, it is preferable to use at least 1 sort (s) chosen from ascorbic acid, formic acid, and those salts as a reducing agent. Moreover, oxalic acid, sulfurous acid, etc. can also be used. In addition, what is necessary is just to determine suitably content and combination of an acid and a reducing agent according to the processing amount of copper powder or copper alloy powder, the oxide film of the surface, the grade of a contamination layer, etc.
また、銅粉や銅合金粉は、大気中で長期間保管すると表面の酸化が進行し、導電性が低下してしまう。そこで、耐酸化性を向上させるため、上述したように、表面に有機化合物を被覆することが知られている。しかし、有機化合物は一般に水溶液への溶解性がないので、有機化合物による被覆処理を行うためには、銅粉や銅合金粉を有機化合物と直接混合するか、又はアルコールなどの有機溶媒中で処理するのが一般的であった。しかも、有機化合物と直接混合するか又は有機溶媒中で処理する方法では、過剰の有機化合物が粉末表面に付着してしまい、その粉末を用いたペーストの粘度を上昇させるなどの不具合が生じていた。 In addition, when copper powder or copper alloy powder is stored in the atmosphere for a long period of time, the surface oxidation proceeds and the conductivity decreases. In order to improve the oxidation resistance, it is known to coat the surface with an organic compound as described above. However, since organic compounds are generally not soluble in aqueous solution, in order to perform coating treatment with organic compounds, copper powder or copper alloy powder is directly mixed with organic compounds or treated in an organic solvent such as alcohol. It was common to do. In addition, in the method of directly mixing with an organic compound or treating in an organic solvent, an excess of the organic compound adheres to the surface of the powder, causing problems such as increasing the viscosity of the paste using the powder. .
本発明者らは、脂肪酸が水溶液中ではカルボン酸イオンとして存在していることに着目し、前述の酸化膜及び汚染層を除去して清浄化処理した直後の粉末表面に、水溶液中で脂肪酸の皮膜を形成することを検討した。即ち、炭素数８以上の脂肪酸は、水に対してほとんど溶解しないが、脂肪酸のアルカリ金属塩であれば若干の溶解度がある。例えば、水に対する臨界ミセル濃度は、炭素数８のオクタン酸ナトリウムでは６.０ｇ／１００ｍｌ（２０℃）、炭素数１４のミリスチン酸ナトリウムでは１７５ｍｇ／１００ｍｍｌ（１７℃）、炭素数１８のステアリン酸カリウムでは１６ｍｇ／１００ｍｌ（６０℃）であり、それ以下の濃度では水溶液中でイオンとして存在できる。 The present inventors pay attention to the fact that fatty acids are present as carboxylate ions in an aqueous solution, and on the powder surface immediately after removing the above-mentioned oxide film and contamination layer and cleaning the fatty acid, The formation of a film was studied. That is, a fatty acid having 8 or more carbon atoms hardly dissolves in water, but has a slight solubility if it is an alkali metal salt of a fatty acid. For example, the critical micelle concentration for water is 6.0 g / 100 ml (20 ° C.) for sodium octanoate having 8 carbon atoms, 175 mg / 100 ml (17 ° C.) for sodium myristate having 14 carbon atoms, and potassium stearate having 18 carbon atoms. Is 16 mg / 100 ml (60 ° C.), and can be present as an ion in an aqueous solution at a lower concentration.
本発明においては、前述の酸と還元剤を同時に含有した水溶液に、更に上記臨界ミセル濃度付近の脂肪酸のアルカリ金属塩を溶解させることにより、酸化膜等を除去して清浄化された銅粉又は銅合金粉の表面に、脂肪酸のカルボン酸イオンを配位させることができる。このようにして生成した表面皮膜には分子1層分の脂肪酸イオンが配位し、表面が安定化すればそれ以上のイオンが吸着することはない。そのため、一つの水溶液を用いた１回の表面処理工程によって、銅粉又は銅合金粉の表面の清浄化と同時に、その表面に過剰な脂肪酸の付着のないきれいな脂肪酸の皮膜を形成することができる。 In the present invention, by dissolving the alkali metal salt of the fatty acid near the critical micelle concentration in the aqueous solution containing the acid and the reducing agent at the same time, the copper powder or the purified copper powder removed by removing the oxide film or the like A fatty acid carboxylate ion can be coordinated to the surface of the copper alloy powder. Fatty acid ions for one layer of molecules are coordinated to the surface film thus formed, and if the surface is stabilized, no more ions are adsorbed. Therefore, the surface of the copper powder or copper alloy powder can be cleaned simultaneously with a single surface treatment step using one aqueous solution, and at the same time, a clean fatty acid film without excessive fatty acid adhesion can be formed on the surface. .
上記脂肪酸としては、炭素数８以上の脂肪酸であればよく、飽和脂肪酸であっても不飽和脂肪酸であってもよい。例えば、オクタン酸（炭素数８）、デカン酸（炭素数１０）、ラウリン酸（炭素数１２）、ミリスチン酸（炭素数１４）、パルミチン酸（炭素数１６）、ステアリン酸（炭素数１８）、オレイン酸（炭素数１８、不飽和）などを好適に用いることができる。炭素数１８を超える脂肪酸も使用できるが、これらは薬品代が非常に高くなるため、炭素数１８の脂肪酸までが実用的である。また、これら脂肪酸のアルカリ金属塩としては、ナトリウム塩、カリウム塩などであってよい。 The fatty acid may be a fatty acid having 8 or more carbon atoms, and may be a saturated fatty acid or an unsaturated fatty acid. For example, octanoic acid (8 carbon atoms), decanoic acid (10 carbon atoms), lauric acid (12 carbon atoms), myristic acid (14 carbon atoms), palmitic acid (16 carbon atoms), stearic acid (18 carbon atoms), Oleic acid (18 carbon atoms, unsaturated) or the like can be preferably used. Fatty acids having more than 18 carbon atoms can also be used, but these have a very high chemical cost, so even fatty acids having 18 carbon atoms are practical. Further, the alkali metal salts of these fatty acids may be sodium salts, potassium salts and the like.
尚、有機溶媒中では脂肪酸は分子として存在しているため、銅粒子表面への吸着力は弱い。そのため、従来のように有機溶媒中で脂肪酸による被覆処理を行う場合には、脂肪酸濃度を高くする必要があった。また、粒子表面に吸着した脂肪酸の上には、次の脂肪酸分子が容易に付着するので過剰に付着しやすい。実際に水溶液中で脂肪酸の被覆層を形成した銅粉と、有機溶媒中で脂肪酸の被覆処理をした銅粉の表面状態をＳＥＭで観察比較すると、後者には過剰な脂肪酸の付着が認められたのに対し、前者は過剰な脂肪酸の付着がない清浄な粒状の表面であることが確認された。 In addition, since the fatty acid exists as a molecule in the organic solvent, the adsorptive power to the copper particle surface is weak. Therefore, when performing the coating treatment with a fatty acid in an organic solvent as in the prior art, it is necessary to increase the fatty acid concentration. Moreover, since the next fatty acid molecule adheres easily on the fatty acid adsorbed on the particle surface, it tends to adhere excessively. When the surface state of copper powder that actually formed a coating layer of fatty acid in an aqueous solution and copper powder that was coated with fatty acid in an organic solvent was observed and compared with SEM, the latter was found to have excessive fatty acid adhesion. On the other hand, the former was confirmed to be a clean granular surface without excessive fatty acid adhesion.
上記した本発明の表面処理方法によれば、全ての処理を一つの水溶液中で且つ１回の処理で同時に行うことができるので、従来の水溶液と有機溶媒による処理が混在した方法に比べ、初期投資費用や薬品、廃液処理及び人件費等のランニング費用を大きく削減できる。しかも、この表面処理により得られる銅粉又は銅合金粉は、酸素品位が低いうえに、耐熱・耐湿試験において酸化の進行が顕著に遅くなり、優れた耐酸化性を有している。また、この銅粉又は銅合金粉のタップ密度は、従来の有機溶媒中で被覆処理した銅粉あるいは被覆処理していない元の銅粉などに比べ、大幅に増大する。 According to the surface treatment method of the present invention described above, all treatments can be performed simultaneously in one aqueous solution and in a single treatment. Therefore, compared to a conventional method in which treatment with an aqueous solution and an organic solvent is mixed, Running costs such as investment costs, chemicals, waste liquid treatment, and labor costs can be greatly reduced. In addition, the copper powder or copper alloy powder obtained by this surface treatment has a low oxygen quality, and the progress of oxidation is remarkably slowed in a heat and moisture resistance test, and has excellent oxidation resistance. Further, the tap density of the copper powder or copper alloy powder is greatly increased as compared with the copper powder coated in a conventional organic solvent or the original copper powder not coated.
かかる銅又は銅合金からなる本発明の導電粉は、アトマイズ法やアンモニアスプラッシュ法などで作製できる球状粉が好適に用いられる。また、この球状の導電粉は、平均粒径が１〜３μｍの小粒径球状粉と、平均粒径が３〜１０μｍの大粒径球状粉との混合粉とすることによって、更にタップ密度を向上させることができる。上記小粒径球状粉と大粒径球状粉との混合粉においては、小粒径球状粉を全体の１〜２０重量％とすることが更に好ましい。尚、上記アンモニアスプラッシュ法は、窒素やアルゴンなどの雰囲気中において、溶融した銅にアンモニアを吹き付けて球状粉を作製する方法である。 As the conductive powder of the present invention made of copper or a copper alloy, spherical powder that can be produced by an atomizing method or an ammonia splash method is preferably used. In addition, the spherical conductive powder has a tap density further increased by using a mixed powder of a small particle size spherical powder having an average particle size of 1 to 3 μm and a large particle size spherical powder having an average particle size of 3 to 10 μm. Can be improved. In the mixed powder of the small particle size spherical powder and the large particle size spherical powder, the small particle size spherical powder is more preferably 1 to 20% by weight of the whole. The ammonia splash method is a method for producing spherical powder by spraying ammonia on molten copper in an atmosphere such as nitrogen or argon.
本発明による銅又は銅合金からなる導電粉は、通常のごとく有機ビヒクルと混練することにより、導電性ペーストとすることができる。また、この導電性ペーストを基材上に塗布して焼成することによって、基板回路や積層コンデンサ電極等の電子材料を形成することができる。 The conductive powder made of copper or copper alloy according to the present invention can be made into a conductive paste by kneading with an organic vehicle as usual. Further, by applying this conductive paste on a base material and baking it, electronic materials such as a substrate circuit and a multilayer capacitor electrode can be formed.
本発明の導電性ペーストにより得られる導電膜は、従来の導電性ペーストによる導電膜と比べて体積抵抗値を大幅に低減することができ、具体的にはバルクの体積抵抗値と同じ桁まで低減することが可能である。これは、酸と還元剤による粒子表面の清浄化と同時に、その表面への脂肪酸皮膜の形成による表面酸化の抑制、及びタップ密度の向上効果などによるものである。 The conductive film obtained by the conductive paste of the present invention can greatly reduce the volume resistance value compared to the conductive film by the conventional conductive paste, specifically, it is reduced to the same order of magnitude as the bulk volume resistance value. Is possible. This is because the particle surface is cleaned with an acid and a reducing agent, the surface oxidation is suppressed by forming a fatty acid film on the surface, and the tap density is improved.
よって、本発明による導電粉、あるいは本発明の導電粉を用いた導電ペーストは、スルーホール穴埋め用、ビア埋め用、基板回路形成用、積層コンデンサ電極形成用、その他の電子材料形成用として用いることにより、従来よりも高性能のものを得ることができる。 Therefore, the conductive powder according to the present invention or the conductive paste using the conductive powder of the present invention should be used for filling through holes, filling vias, forming substrate circuits, forming multilayer capacitor electrodes, and other electronic materials. Thus, a higher performance than the conventional one can be obtained.
［実施例１］
アンモニアスプラッシュ法により銅球状粉を作製した。即ち、窒素ガスを１５０リットル／分で流した雰囲気中において、管状型炉や高周波炉を用いて銅を１４００℃で加熱溶融し、その溶体にアンモニアガスを４０リットル／分で吹き付けることにより銅粉を得た。この銅粉（酸素品位０.２３重量％）を、下記表１に示す酸の水溶液で表面処理した。その際、試料ａ−１〜ａ−２では酸のみの水溶液を用い、試料ｂ−１〜ｂ−８では酸と還元剤を同時に含む水溶液を用いた。これらの表面処理により得られた銅粉について、その酸素品位を下記表1にまとめて示した。酸のみで表面処理を行った試料ａ−１〜ａ−２に比べて、酸と還元剤の両方を含む水溶液で表面処理した試料ｂ−１〜ｂ−８では銅粉の酸素品位が低減していることが分かる。
[Example 1]
Copper spherical powder was prepared by an ammonia splash method. That is, in an atmosphere in which nitrogen gas is flowed at 150 liters / minute, copper is heated and melted at 1400 ° C. using a tubular furnace or a high-frequency furnace, and ammonia gas is blown into the solution at 40 liters / minute to produce copper powder. Got. The copper powder (oxygen grade 0.23% by weight) was surface-treated with an acid aqueous solution shown in Table 1 below. At that time, samples a-1 to a-2 used an aqueous solution containing only an acid, and samples b-1 to b-8 used an aqueous solution containing an acid and a reducing agent simultaneously. The oxygen quality of the copper powder obtained by these surface treatments is summarized in Table 1 below. Compared with samples a-1 to a-2 that were surface-treated only with acid, samples b-1 to b-8 that were surface-treated with an aqueous solution containing both an acid and a reducing agent reduced the oxygen quality of the copper powder. I understand that
次に、上記と同じ銅粉を、下記表２に示すように、試料ｃ−１〜ｃ−７では、酸と還元剤と脂肪酸のナトリウム塩を同時に含む水溶液で表面処理した。得られた各銅粉について、初期酸素品位を求めると共に、８０℃で湿度８５％の雰囲気中に８時間保持する耐侯性試験を施した後の酸素品位を求め、その結果を下記表２に示した。また、比較のために、同じ銅粉で未処理のものと、同じ銅粉を酢酸のみを含む水溶液で表面処理した試料ａ−１についても、上記と同様に初期酸素品位と試験後酸素品位を求め、その結果を下記表２に併せて示した。 Next, as shown in Table 2 below, the same copper powder as described above was surface-treated with an aqueous solution containing an acid, a reducing agent, and a sodium salt of a fatty acid at the same time in Samples c-1 to c-7. About each obtained copper powder, while calculating | requiring an initial oxygen quality, the oxygen quality after performing the weather resistance test hold | maintained in the atmosphere of 85% of humidity at 80 degreeC was calculated | required, The result is shown in following Table 2 It was. For comparison, the initial oxygen grade and the post-test oxygen grade are also the same for the sample a-1 which has been surface-treated with an aqueous solution containing only acetic acid and the same copper powder untreated with the same copper powder. The results are also shown in Table 2 below.
上記の結果から、本発明方法により酸と還元剤と脂肪酸塩を同時に含む水溶液で表面処理した試料ｃ−１〜ｃ−７の銅粉は、表面の酸化膜などが除去されて清浄化されると同時に、その場で表面に脂肪酸皮膜が形成されるため、耐候性試験において酸化の進行が抑制されることが分かる。また、その酸化抑制効果は、炭素数が大きな脂肪酸で処理するほど顕著であることが分かる。一方、酢酸の水溶液で表面処理しただけの試料ａ−１では、耐候性試験における酸化の進行が著しかった。 From the above results, the copper powders of samples c-1 to c-7 that were surface-treated with an aqueous solution containing an acid, a reducing agent, and a fatty acid salt by the method of the present invention were cleaned by removing the oxide film on the surface. At the same time, since a fatty acid film is formed on the surface on the spot, it can be seen that the progress of oxidation is suppressed in the weather resistance test. Moreover, it turns out that the oxidation inhibitory effect is so remarkable that it processes with a fatty acid with a large carbon number. On the other hand, in the sample a-1 which was just surface-treated with an aqueous solution of acetic acid, the progress of oxidation in the weather resistance test was remarkable.
［実施例２］
上記実施例１の表面処理で得られた試料ｃ−４の銅粉について、そのタップ密度を下記表３に示した。また、参考のために、同じ銅粉をステアリン酸で処理して表面被覆した試料ａ−３についても、そのタップ密度を下記表３に併せて示した。尚、上記銅粉の処理前のタップ密度は４.２７ｇ／ｃｍ３である。
[Example 2]
Table 3 below shows the tap density of the copper powder of sample c-4 obtained by the surface treatment of Example 1. For reference, the tap density of Sample a-3, which is the same copper powder treated with stearic acid and surface-coated, is also shown in Table 3 below. In addition, the tap density before the process of the said copper powder is 4.27 g / cm < 3 >.
本発明方法により、酸と還元剤と脂肪酸塩を含む水溶液で表面処理した試料ｃ−１〜ｃ−７では、上述したように耐酸化性が向上するだけでなく、粒子表面に1分子層程度の非常にきれいな脂肪酸の皮膜が形成されるため、凝集を防止して、タップ密度が増大することが分かる。一方、ステアリン酸で表面被覆した試料ａ−３では、処理前よりもタップ密度が低くなった。これは、粒子表面に過剰の脂肪酸が付着したことにより、粒子の凝集が進んだためである。 Samples c-1 to c-7 surface-treated with an aqueous solution containing an acid, a reducing agent, and a fatty acid salt by the method of the present invention not only improve the oxidation resistance as described above, but also have about one molecular layer on the particle surface. It can be seen that a very clean fatty acid film is formed, preventing aggregation and increasing the tap density. On the other hand, in sample a-3 whose surface was coated with stearic acid, the tap density was lower than that before the treatment. This is because the aggregation of the particles has progressed due to the excessive fatty acid adhering to the particle surface.
［実施例３］
本発明方法により表面処理した銅粉を実際に使用して焼成膜を作製し、その電気抵抗値を比較した。即ち、上記実施例１のごとく表面処理した表２に示す試料ｃ−４の銅粉９５重量部を、バインダーとしてのエチルセルロース５重量部、溶媒としてのターピネオール３５重量部と混練して、それぞれ導電性ペーストを作製した。これらの導電性ペーストを、基材であるアルミナ基板上に塗布し、窒素―２％水素雰囲気中で６００℃又は７００℃で６０分間焼成して、それぞれ焼成膜を形成した。尚、焼成温度については、熱硬化型ペーストでの用途を想定し、導通が粒子間の接触で得られる粒子同士が焼結しない温度範囲とした。
[Example 3]
A fired film was prepared by actually using the copper powder surface-treated by the method of the present invention, and the electric resistance values were compared. That is, 95 parts by weight of the copper powder of the sample c-4 shown in Table 2 subjected to the surface treatment as in Example 1 was kneaded with 5 parts by weight of ethyl cellulose as a binder and 35 parts by weight of terpineol as a solvent, respectively. A paste was prepared. These conductive pastes were applied onto an alumina substrate as a base material and baked at 600 ° C. or 700 ° C. for 60 minutes in a nitrogen-2% hydrogen atmosphere to form a fired film. In addition, about the baking temperature, the use with a thermosetting type paste was assumed, and it was set as the temperature range in which the particle | grains obtained by contact between particle | grains do not sinter.
得られた各焼成膜について、焼成温度が６００℃の場合と７００℃の場合の電気抵抗を測定し、その結果を下記表４に示した。また、比較のために、同じ銅粉をそのまま用いた導電性ペースト、同じ銅粉を酢酸及びアスコルビン酸水溶液で処理した上記試料ｂ−１の銅粉を用いた導電性ペーストについても、上記と同様に焼成膜を作製し、その電気抵抗値を下記表４に併せて示した。 For each of the obtained fired films, the electrical resistance was measured when the firing temperature was 600 ° C. and 700 ° C., and the results are shown in Table 4 below. For comparison, a conductive paste using the same copper powder as it is, and a conductive paste using the copper powder of the sample b-1 obtained by treating the same copper powder with acetic acid and an ascorbic acid aqueous solution are the same as above. A fired film was prepared, and the electrical resistance values are shown in Table 4 below.
上記の結果から分かるように、本発明方法により表面処理した銅粉を使用して作製した焼成膜では、未処理の銅粉や比較例の銅粉の場合に比べて、電気抵抗値の低減効果が認められた。特に、酢酸とアスコルビン酸とステアリン酸を含む水溶液で表面処理した試料ｃ−４の銅粉の場合、焼成膜の電気抵抗値は未処理の銅粉の場合に対して３８〜６４倍の低減効果が得られた。これは、酸と還元剤による表面の清浄化により粒子間の接触抵抗が下がり、それに加えて、その清浄な表面に脂肪酸の皮膜を形成したことでタップ密度が増大し、粒子間の接点の数が増えたことによるものである。 As can be seen from the above results, in the fired film produced using the copper powder surface-treated by the method of the present invention, the electrical resistance value is reduced compared to the case of the untreated copper powder and the copper powder of the comparative example. Was recognized. In particular, in the case of the copper powder of sample c-4 surface-treated with an aqueous solution containing acetic acid, ascorbic acid and stearic acid, the electrical resistance value of the fired film is reduced by 38 to 64 times compared to the case of untreated copper powder. was gotten. This is because the surface resistance by the acid and the reducing agent reduces the contact resistance between the particles, and in addition, the tap density is increased by forming a film of fatty acid on the clean surface, and the number of contacts between the particles. Is due to the increase.
［実施例４］
アトマイズ法により作製した平均粒径５μｍの銅粉（タップ密度４.８５ｇ／ｃｍ３）を、上記実施例１の試料ｃ−６と同様に、酸及び還元剤としてのギ酸とステアリン酸ナトリウムとを含む水溶液を用いて表面処理した。その表面処理後の銅粉を、レゾール型フェノール樹脂（群栄化学（株）製、ＰＬ−２２１１）と下記表５に示す割合で混合し、この混合物１００重量部に溶剤としてブチルセロソルブ１０重量部を加え、小型ニーダーでペースト化した。
[Example 4]
A copper powder (tap density of 4.85 g / cm 3 ) having an average particle diameter of 5 μm prepared by an atomizing method was mixed with formic acid and sodium stearate as an acid and a reducing agent in the same manner as in sample c-6 of Example 1 above. Surface treatment was performed using an aqueous solution containing the solution. The copper powder after the surface treatment was mixed with a resol type phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) at a ratio shown in Table 5 below, and 10 parts by weight of butyl cellosolve as a solvent was added to 100 parts by weight of this mixture. In addition, it was made into a paste with a small kneader.
得られた各導電性ペーストをガラス基板上に印刷し、エアーオーブン中にて１５０℃又は２００℃でそれぞれ３０分間焼成した。尚、上記焼成温度は、ガラスエポキシ基板やポリイミド基板のような、耐熱温度が１６０℃あるいは２５０℃以下の基板材料を想定して設定した。 Each obtained electrically conductive paste was printed on the glass substrate, and it baked for 30 minutes at 150 degreeC or 200 degreeC in the air oven, respectively. The firing temperature was set assuming a substrate material having a heat resistant temperature of 160 ° C. or 250 ° C. or lower, such as a glass epoxy substrate or a polyimide substrate.
得られた各焼成膜について、体積抵抗値を測定した結果を下記表５に示した。この表５から分かるように、銅粉：樹脂の重量比が８０〜８５：２０〜１５の範囲で優れた体積抵抗値が得られた。特に、銅粉：樹脂の重量比が８５：１５のとき、焼成温度１５０℃で２６.０μΩ・ｃｍ、及び焼成温度２００℃で２１.４μΩ・ｃｍと極めて低抵抗であった。また、この銅粉のタップ密度は５.１１ｇ／ｃｍ３であった。尚、表面処理を行っていない銅粉の場合、焼成温度２００℃での体積抵抗値は、１０ｋΩ・ｃｍ以上であった。 Table 5 below shows the results of measuring the volume resistance values of the obtained fired films. As can be seen from Table 5, an excellent volume resistance value was obtained when the weight ratio of copper powder: resin was in the range of 80-85: 20-15. In particular, when the weight ratio of copper powder: resin was 85:15, the resistance was extremely low at 26.0 μΩ · cm at a firing temperature of 150 ° C. and 21.4 μΩ · cm at a firing temperature of 200 ° C. Moreover, the tap density of this copper powder was 5.11 g / cm 3 . In the case of copper powder that was not subjected to surface treatment, the volume resistance value at a firing temperature of 200 ° C. was 10 kΩ · cm or more.
［実施例５］
アトマイズ法で作製した銅粉で、平均粒径１.５μｍの小粒径球状粉と、平均粒径５μｍの大粒径球状粉を、下記表６に示す混合比で混合した。得られた各混合銅粉８５重量部を、レゾール型フェノール樹脂（群栄化学（株）製、ＰＬ−２２１１）１５重量部、溶剤（ブチルセロソルブ）１０重量部と配合し、小型ニーダーで混練して導電性ペーストとした。得られた各導電性ペーストをガラス基板上に印刷し、エアーオーブン中にて１５０℃あるいは２００℃でそれぞれ３０分間焼成した。
[Example 5]
The copper powder produced by the atomization method was mixed with a small particle size spherical powder having an average particle size of 1.5 μm and a large particle size spherical powder having an average particle size of 5 μm at a mixing ratio shown in Table 6 below. 85 parts by weight of each obtained mixed copper powder was blended with 15 parts by weight of a resol type phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by weight of a solvent (butyl cellosolve), and kneaded with a small kneader. A conductive paste was obtained. Each obtained conductive paste was printed on a glass substrate, and baked at 150 ° C. or 200 ° C. for 30 minutes in an air oven.
得られた各焼成膜について、体積抵抗値を測定した結果を下記表６に示した。この表６から分かるように、小粒径球状粉を全体の２０重量％以下混合した場合には、大粒径球状粉のみの場合とほぼ同等以上の導電性が得られた。例えば、大粒径球状銅粉：小粒径球状銅粉の混合比が９６：４の場合、焼成温度２００℃のとき、その体積抵抗率は９.５６μΩ・ｃｍと極めて低抵抗であった。 Table 6 below shows the results of measuring the volume resistance values of the obtained fired films. As can be seen from Table 6, when the small particle size spherical powder was mixed in an amount of 20% by weight or less, the conductivity almost equal to or higher than that of the large particle size spherical powder alone was obtained. For example, when the mixing ratio of the large particle size spherical copper powder to the small particle size spherical copper powder was 96: 4, the volume resistivity was extremely low at 9.56 μΩ · cm when the firing temperature was 200 ° C.
更に、上記大粒径球状銅粉：小粒径球状銅粉の混合比が９６：４の銅粉を用いて、上記と同様に焼成膜を形成し、その焼成膜について耐候性試験を行った。即ち、その焼成膜を２５℃の大気中に３０日間放置した後、その体積低効率を測定したところ、耐侯性試験前が９.５６μΩ・ｃｍであったのに対して、耐侯性試験後は１４.６μΩ・ｃｍであり、その増加量は＋５.１μΩ・ｃｍに過ぎなかった。
Furthermore, a fired film was formed in the same manner as described above using a copper powder having a mixing ratio of the above large particle size spherical copper powder: small particle size spherical copper powder of 96: 4, and a weather resistance test was performed on the fired film. . That is, after the fired film was left in the atmosphere at 25 ° C. for 30 days and its volume low efficiency was measured, it was 9.56 μΩ · cm before the weather resistance test, whereas after the weather resistance test, It was 14.6 μΩ · cm, and the increase was only +5.1 μΩ · cm.
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| JP5921808B2 (en) * | 2008-04-30 | 2016-05-24 | 日立化成株式会社 | Connection material and semiconductor device |
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| JP5439995B2 (en) * | 2009-07-10 | 2014-03-12 | 旭硝子株式会社 | Method for producing surface-modified copper particles, composition for forming conductor, method for producing conductor film and article |
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| KR101353149B1 (en) * | 2011-12-27 | 2014-01-27 | 삼성전기주식회사 | Manufacturing mehtod for copper powder |
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| JP6089175B2 (en) * | 2012-06-29 | 2017-03-08 | 荒川化学工業株式会社 | Method for producing conductive paste |
| JP2014194070A (en) * | 2013-02-28 | 2014-10-09 | Jsr Corp | Metal film formation method and conductive ink used for method |
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| CN104240841A (en) * | 2013-06-14 | 2014-12-24 | 中国振华集团云科电子有限公司 | Base metal conductor paste preparation method |
| JP6197504B2 (en) | 2013-09-04 | 2017-09-20 | 旭硝子株式会社 | Conductive paste and substrate with conductive film |
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| JP6704083B1 (en) * | 2019-11-22 | 2020-06-03 | 東邦チタニウム株式会社 | Copper powder and its manufacturing method |
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