JP2004027246A - Copper powder for conductive paste, and its manufacturing method - Google Patents
Copper powder for conductive paste, and its manufacturing method Download PDFInfo
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- JP2004027246A JP2004027246A JP2002181171A JP2002181171A JP2004027246A JP 2004027246 A JP2004027246 A JP 2004027246A JP 2002181171 A JP2002181171 A JP 2002181171A JP 2002181171 A JP2002181171 A JP 2002181171A JP 2004027246 A JP2004027246 A JP 2004027246A
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 122
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 8
- 239000002245 particle Substances 0.000 claims abstract description 19
- 239000011164 primary particle Substances 0.000 claims abstract description 12
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 11
- 239000010959 steel Substances 0.000 claims abstract description 11
- 229910052802 copper Inorganic materials 0.000 abstract description 24
- 239000010949 copper Substances 0.000 abstract description 24
- 238000000034 method Methods 0.000 abstract description 13
- 235000014113 dietary fatty acids Nutrition 0.000 abstract description 4
- 229930195729 fatty acid Natural products 0.000 abstract description 4
- 239000000194 fatty acid Substances 0.000 abstract description 4
- 150000004665 fatty acids Chemical class 0.000 abstract description 4
- 239000000843 powder Substances 0.000 description 9
- 239000007864 aqueous solution Substances 0.000 description 7
- 235000021355 Stearic acid Nutrition 0.000 description 5
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 description 5
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 description 5
- 229920000642 polymer Polymers 0.000 description 5
- 239000007858 starting material Substances 0.000 description 5
- 239000008117 stearic acid Substances 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- IPCSVZSSVZVIGE-UHFFFAOYSA-N hexadecanoic acid Chemical compound CCCCCCCCCCCCCCCC(O)=O IPCSVZSSVZVIGE-UHFFFAOYSA-N 0.000 description 4
- 229910000365 copper sulfate Inorganic materials 0.000 description 3
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 3
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 2
- 239000005751 Copper oxide Substances 0.000 description 2
- 235000021314 Palmitic acid Nutrition 0.000 description 2
- 239000011324 bead Substances 0.000 description 2
- 229910000431 copper oxide Inorganic materials 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- WQEPLUUGTLDZJY-UHFFFAOYSA-N n-Pentadecanoic acid Natural products CCCCCCCCCCCCCCC(O)=O WQEPLUUGTLDZJY-UHFFFAOYSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000000059 patterning Methods 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000005749 Copper compound Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 150000001880 copper compounds Chemical class 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 229910000679 solder Inorganic materials 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、電子部品の実装分野において導電ペースト用金属粉として使用する銅粉に関するものである。詳しくは、スルーホール用あるいは外部電極用ポリマー型銅ペースト、ならびに焼成型銅ペーストとして高性能が得られる、単分散した微細な特有形状の銅粉及びその製造方法に関するものである。
【０００２】
【従来の技術】
従来から導電ペースト用としてアトマイズ法、電解法、還元法などの製造方法による球状あるいは粒状銅粉が使用されてきた。しかし、印刷性や沈降性改善のため、銅粉を機械的に片状加工する方法が提案されてきた。具体的には粒状アトマイズ粉を媒体撹拌ミルで円盤状にする方法（特開２００２−１５６２２号公報）が提案されているが、平均粒径が７μｍ以上と大きくスルーホール用ポリマー型銅ペーストには可能だが、近年のファインパターン印刷には５μｍ以下の粒子径が要求され使用が難しくなってきた。
【０００３】
また微細銅粉をスラリー状でビーズミルで片状にする方法（特開平４−５６７０１号公報、特開２０００−８０４０９号公報）が提案されているが、いずれも粒子径が大きくファインパターン印刷には使用が難しい。また扁平率も大きいため、ペースト中に銅粉を高充填できず、はんだ濡れ性など部品実装に多くの問題があった。電子部品の実装分野において、スクリーンのファインパターン化に対応でき、ペーストに銅粉を高充填しても印刷適性を悪くしない銅粉が要求されているが、まだ開発されていなかった。
【０００４】
【発明が解決しようとする課題】
本発明はポリマー型ペースト用ならびに焼成型ペースト用銅粉として、高充填でき、しかもファインパターン化にも対応可能な銅粉を提供するものである。
【０００５】
【問題を解決するための手段】
すなわち本発明は、一次粒子径が３μｍ以下の電解銅粉あるいは還元銅粉に物理的応力を加えた微細盤状銅粉であって、平均粒子径が０．５〜４μｍ、アスペクト比が１．２〜２であることを特徴とする導電ペースト用銅粉である。その好ましい製造方法として、一次粒子径が３μｍ以下の電解銅粉あるいは還元銅粉をボールミルに投入し、１／４〜５／６４インチ径のスチールボールを媒体とし、銅粉に対して脂肪酸を０．０２〜０．５ｗｔ％添加し、空気中あるいは不活性雰囲気中で銅粉を分散しながら物理的応力を加えることを特徴とする導電ペースト用銅粉の製造方法を提供するものである。
【０００６】
本発明の電解銅粉とは、水溶液から電解析出した電解銅粉（例えば特開昭６２−１９９７０５号公報）、微細電解銅粉（例えば特開平４−８８１０４号公報）で、析出した電解銅粉の一次粒子径が３μｍ以下の銅粉が使用できる。還元銅粉とは水溶液中の銅化合物を還元剤で還元析出した銅粉（例えば特開平１−２９０７０６号公報、特開平２−３４７０８号公報）で、還元銅粉の一次粒子径が３μｍ以下の銅粉が使用できる。
【０００７】
アトマイズ法による銅粉はファインパターンに対応できる３μｍ以下の粒子径の製造が難しく、また物理的応力を加え加工しても効果が少ない。ボールミルで加工する際に使用する媒体は１／４〜５／６４インチ径のスチールボールが好ましい。それよりも大きい径のスチールボールでは粉砕力が強い為、微細な粉砕粉が発生し片状化も進みアスペクト比が大きくなる。また微細銅粉同士が圧接し大きなフレークとなる。
【０００８】
またそれよりも小さい径のスチールボールでは銅粉に与える物理的応力が小さいため、目的とする形状の銅粉を得る為には長時間かかる。ボール径は加工する銅粉の一次粒子径の大きさやボールミルの回転数によって本発明の形状になるように選定すれば良い。凝集防止のための助剤はステアリン酸やパルミチン酸などの脂肪酸が好ましく、粒子径が大きくアスペクト比が小さい銅粉を製造する場合は０．０２ｗｔ％添加と少ない方が良い。
【０００９】
しかし平均粒子径が２μｍ以下でアスペクト比が１．５以上の導電ペースト用銅粉を製造する場合は、銅粉に対して０．０５〜０．２ｗｔ％添加するのが好ましい。脂肪酸を０．５％より多く銅粉に添加すると、粉砕が行われ微粉が発生したり、また焼成型銅ペースト用には不純物として好ましくない場合がある。ボールミル体内雰囲気は空気で良いが、窒素封入など不活性雰囲気中で加工しても良い。
【００１０】
このようにボールミルを微細銅粉に物理的応力を加える分散加工機として使用すると、本発明の平均粒子径０．５〜４μｍ、アスペクト比１．２〜２の導電ペースト用として最適な特有形状の銅粉が容易に製造できる。なお、アスペクト比とは粒子形状の相当直径／厚さの比で、球形の場合その数値は１．０で、片平状になると数値が大となる。ボールミル以外の媒体撹拌ミルやビーズミルでは粉砕力が強く微粉が多く発生し、また片状化も進み（アスペクト比１０以上）、本発明の形状の盤状銅粉を得るのが非常に難しい。
【００１１】
平均粒子径が０．５μｍより細かいと、物理的応力を加えアスペクト比１．２〜２の銅粉でもペースト中での分散性や銅粉の高充填が難しくなる。また平均粒子径が４μｍより大きいと、ファインパターン印刷では均一に印刷できない。平均粒子径が０．５〜４μｍでアスペクト比が１．２〜２であることが重要である。すなわち球形よりもやや片状形状である盤状であることが、ペーストに銅粉を高充填でき、かつ印刷性や塗膜の平滑性を向上する。
【００１２】
【発明の実施の形態】
本発明の導電ペースト用銅粉が優れた性能を示す理由として、
▲１▼電解あるいは還元銅粉は水溶液から析出した銅粉であるため、結晶粒が大きく、アトマイズ粉より軟らかい。また電解あるいは還元銅粉の表面は銅の結晶面となり平滑でない。また銅粉粒子内部もアトマイズ粉より緻密でない。このような特性を有する、電解銅粉あるいは還元銅粉に外部から物理的応力を加えると、容易に表面が平滑になる。その結果、吸油量が減少し、銅粉の分散性が向上し、充填率が上がるのであろう。
▲２▼アスペクト比が１．２〜２である事は、球形あるいは多面体形状から一方向が薄い、やや厚みのある盤状形状になっている。この形状が銅ペーストの流動性を良くし、印刷適性も向上するのであろう。また塗膜の平滑性も良くなり、電子部品の実装に好ましい効果が得られる。
【００１３】
【実施例】
本発明の構成を詳しく説明すれば次の通りである。尚、これにより発明の製造方法ならびに用途が限定されるものでない。
【００１４】
（実施例１）
本発明の出発原料として、硫酸銅水溶液から析出した一次粒子径３μｍの電解銅粉を使用した。この電解銅粉に物理的応力を加える方法としてボールミルを用いた。ボールミルによる加工条件は、電解銅粉投入量４ｋｇ、媒体として１／４インチ径のスチールボール１０ｋｇ、電解銅粉に対して０．０２ｗｔ％のステアリン酸を添加、空気中でボールミルの回転数４０ｒｐｍで２時間運転した。その結果、電子顕微鏡で観察すると平均粒子径４μｍでアスペクト比１．３の厚みのある盤状銅粉が得られた。本発明の銅粉をスルーホール用ポリマー型銅ペーストに使用したところ、高充填しても流動性に優れており、また焼成型銅ペースト用にも最適であった。
【００１５】
（実施例２）
本発明の出発原料として、硫酸銅水溶液から析出した一次粒子径１μｍの電解銅粉を使用した。この電解銅粉に物理的応力を加える方法としてボールミルを用いた。ボールミルによる加工条件は、電解銅粉投入量２ｋｇ、媒体として１／８インチ径のスチールボール１０ｋｇ、電解銅粉に対して０．１ｗｔ％のステアリン酸を添加、空気中でボールミルの回転数４０ｒｐｍで３時間運転した。その結果、電子顕微鏡で観察すると平均粒子径２μｍでアスペクト比２のやや厚みのある盤状銅粉が得られた。本発明の銅粉をポリマー型銅ペーストに使用したところ、高充填しても印刷適性に優れた銅ペーストが製造できた。
【００１６】
（実施例３）
本発明の出発原料として、硫酸銅水溶液から析出した一次粒子径１．５μｍの電解銅粉を使用した。この電解銅粉に物理的応力を加える方法としてボールミルを用いた。ボールミルによる加工条件は、電解銅粉投入量２ｋｇ、媒体として１／８インチ径のスチールボール１０ｋｇ、電解銅粉に対して０．０５ｗｔ％のステアリン酸を添加、空気中でボールミルの回転数４０ｒｐｍで１時間運転した。その結果、電子顕微鏡で観察すると平均粒子径１．８μｍでアスペクト比１．２の丸みのある盤状銅粉が得られた。本発明の銅粉をポリマー型銅ペーストに使用したところ、高充填しても印刷適性に優れた銅ペーストが製造できた。焼成型としても緻密な塗膜が得られる銅ペーストが製造できた。
【００１７】
（実施例４）
本発明の出発原料として、酸化銅を水溶液中で還元した一次粒子径２μｍの還元銅粉を使用した。この還元銅粉に物理的応力を加える方法としてボールミルを用いた。ボールミルによる加工条件は、還元銅粉投入量２ｋｇ、媒体として３／１６インチ径のスチールボール１０ｋｇ、還元銅粉に対して０．０５ｗｔ％のステアリン酸を添加、空気中でボールミルの回転数４０ｒｐｍで２時間運転した。その結果、電子顕微鏡で観察すると平均粒子径３μｍでアスペクト比１．５の厚みのある盤状銅粉が得られた。本発明の銅粉をスルーホール用ポリマー型銅ペーストに使用したところ、高充填しても流動性に優れており、また焼成型銅ペースト用にも最適であった。
【００１８】
（実施例５）
本発明の出発原料として、酸化銅を水溶液中で還元した一次粒子径０．３μｍの還元銅粉を使用した。この還元銅粉に物理的応力を加える方法としてボールミルを用いた。ボールミルによる加工条件は、還元銅粉投入量１ｋｇ、媒体として５／６４インチ径のスチールボール１０ｋｇ、還元銅粉に対して０．５ｗｔ％のパルミチン酸を添加、窒素を封入した雰囲気中でボールミルの回転数２５ｒｐｍで８時間運転した。その結果、電子顕微鏡で観察すると平均粒子径０．５μｍでアスペクト比１．６の厚みのある細かい盤状銅粉が得られた。本発明の銅粉をポリマー型銅ペーストに使用したところ、従来の還元粒状銅粉より高充填でき、しかもファインパターン印刷後の塗膜表面外観も平滑であった。
【００１９】
【発明の効果】
電子部品の実装分野では、安価な銅粉を使用したポリマー型銅ペーストあるいは焼成型銅ペーストの開発が進められている。本発明の導電ペースト用銅粉を使用すればペースト中に銅粉を高充填でき、新しい銅ペーストの開発が可能となった。また電子部品の高密度化にともなうファインパターン印刷にも対応可能な銅ペーストの製造もできるようになった。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to copper powder used as a metal powder for a conductive paste in the field of mounting electronic components. More specifically, the present invention relates to a monodispersed fine copper powder having a specific shape and a high performance as a through-hole or external electrode polymer copper paste and a fired copper paste, and a method for producing the same.
[0002]
[Prior art]
Conventionally, spherical or granular copper powders manufactured by an atomizing method, an electrolytic method, a reducing method or the like have been used for conductive pastes. However, a method of mechanically flake processing of copper powder has been proposed for improving printability and sedimentability. Specifically, a method has been proposed in which a granular atomized powder is made into a disk shape with a medium stirring mill (Japanese Patent Application Laid-Open No. 2002-15622). However, the average particle size is as large as 7 μm or more, and a polymer type copper paste for through holes is used. Although possible, recent fine pattern printing requires a particle diameter of 5 μm or less, which makes it difficult to use.
[0003]
In addition, a method has been proposed in which fine copper powder is slurried into a flake shape using a bead mill (Japanese Patent Application Laid-Open Nos. 4-56701 and 2000-80409). Difficult to use. In addition, since the oblateness is large, the paste cannot be filled with copper powder at a high level, and there are many problems in component mounting such as solder wettability. In the field of mounting electronic components, copper powder that can cope with fine patterning of a screen and does not degrade printability even when the paste is highly filled with copper powder has been demanded, but has not been developed yet.
[0004]
[Problems to be solved by the invention]
The present invention provides a copper powder that can be filled at a high filling rate and that can also be used for fine patterning as a copper powder for a polymer type paste and a firing type paste.
[0005]
[Means to solve the problem]
That is, the present invention is a fine disk-shaped copper powder obtained by applying a physical stress to an electrolytic copper powder or a reduced copper powder having a primary particle diameter of 3 μm or less, and has an average particle diameter of 0.5 to 4 μm and an aspect ratio of 1. It is a copper powder for conductive paste, which is characterized in that it is 2 to 2. As a preferable production method, an electrolytic copper powder or a reduced copper powder having a primary particle diameter of 3 μm or less is put into a ball mill, a steel ball having a diameter of 1/4 to 5/64 inches is used as a medium, and a fatty acid is reduced to 0 with respect to the copper powder. The present invention provides a method for producing a copper powder for a conductive paste, characterized by adding 0.02 to 0.5 wt% and applying a physical stress while dispersing the copper powder in the air or in an inert atmosphere.
[0006]
The electrolytic copper powder of the present invention includes electrolytic copper powder electrolytically deposited from an aqueous solution (for example, JP-A-62-199705) and fine electrolytic copper powder (for example, JP-A-4-88104). Copper powder having a primary particle diameter of 3 μm or less can be used. The reduced copper powder is a copper powder obtained by reducing and precipitating a copper compound in an aqueous solution with a reducing agent (for example, JP-A-1-290706 and JP-A-2-34708), and has a primary particle diameter of 3 μm or less. Copper powder can be used.
[0007]
It is difficult to produce a copper powder having a particle size of 3 μm or less that can correspond to a fine pattern by the atomizing method, and the effect is small even if a physical stress is applied and processed. The medium used in processing with a ball mill is preferably a steel ball having a diameter of 1/4 to 5/64 inch. Since a steel ball having a larger diameter has a strong crushing force, fine crushed powder is generated, flakes are formed, and the aspect ratio is increased. Further, the fine copper powders are pressed against each other to form large flakes.
[0008]
Further, since a steel ball having a smaller diameter has less physical stress applied to the copper powder, it takes a long time to obtain a copper powder having a desired shape. The ball diameter may be selected so as to have the shape of the present invention according to the size of the primary particle diameter of the copper powder to be processed and the rotation speed of the ball mill. The auxiliary agent for preventing aggregation is preferably a fatty acid such as stearic acid or palmitic acid. When producing a copper powder having a large particle diameter and a small aspect ratio, it is better to add as little as 0.02 wt%.
[0009]
However, when producing copper powder for a conductive paste having an average particle diameter of 2 μm or less and an aspect ratio of 1.5 or more, it is preferable to add 0.05 to 0.2 wt% to the copper powder. If more than 0.5% of a fatty acid is added to the copper powder, pulverization is performed to generate fine powder, and it may not be preferable as an impurity for a baked copper paste. The atmosphere inside the ball mill may be air, but it may be processed in an inert atmosphere such as nitrogen filling.
[0010]
When the ball mill is used as a dispersing machine for applying a physical stress to the fine copper powder as described above, it is possible to use a specially shaped conductive paste having an average particle diameter of 0.5 to 4 μm and an aspect ratio of 1.2 to 2 according to the present invention. Copper powder can be easily manufactured. The aspect ratio is the ratio of the equivalent diameter / thickness of the particle shape. The numerical value is 1.0 in the case of a spherical shape, and the numerical value becomes large in the case of a single flat shape. In a medium stirring mill or a bead mill other than a ball mill, the pulverizing power is strong, a large amount of fine powder is generated, and flakes are promoted (aspect ratio of 10 or more).
[0011]
If the average particle size is smaller than 0.5 μm, physical stress is applied, and it becomes difficult to disperse in the paste or to highly fill the copper powder even with the copper powder having an aspect ratio of 1.2 to 2. On the other hand, if the average particle diameter is larger than 4 μm, uniform printing cannot be performed by fine pattern printing. It is important that the average particle diameter is 0.5 to 4 μm and the aspect ratio is 1.2 to 2. In other words, the disk shape, which is slightly flaky rather than spherical, allows the paste to be filled with a high amount of copper powder, and improves the printability and the smoothness of the coating film.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The reason why the copper powder for conductive paste of the present invention exhibits excellent performance,
{Circle around (1)} Since the electrolytic or reduced copper powder is a copper powder precipitated from an aqueous solution, the crystal grains are large and are softer than the atomized powder. The surface of the electrolytic or reduced copper powder is a copper crystal plane and is not smooth. The inside of the copper powder particles is also less dense than the atomized powder. When a physical stress is externally applied to the electrolytic copper powder or the reduced copper powder having such characteristics, the surface can be easily smoothed. As a result, the oil absorption will decrease, the dispersibility of the copper powder will improve, and the filling rate will increase.
{Circle around (2)} The aspect ratio of 1.2 to 2 means that the shape is thin and slightly thick in one direction from a spherical or polyhedral shape. This shape may improve the flowability of the copper paste and improve the printability. In addition, the smoothness of the coating film is improved, and a favorable effect for mounting electronic components can be obtained.
[0013]
【Example】
The configuration of the present invention will be described in detail as follows. It should be noted that this does not limit the production method and use of the invention.
[0014]
(Example 1)
As a starting material of the present invention, electrolytic copper powder having a primary particle diameter of 3 μm precipitated from an aqueous solution of copper sulfate was used. A ball mill was used as a method for applying a physical stress to the electrolytic copper powder. The processing conditions by the ball mill were as follows: 4 kg of electrolytic copper powder charged, 10 kg of 1/4 inch diameter steel balls as a medium, 0.02 wt% of stearic acid based on the electrolytic copper powder, and a ball mill rotation speed of 40 rpm in air. Driving for 2 hours. As a result, when observed with an electron microscope, a thick plate-like copper powder having an average particle diameter of 4 μm and an aspect ratio of 1.3 was obtained. When the copper powder of the present invention was used for a polymer-type copper paste for through-holes, it was excellent in fluidity even at a high filling, and was also optimal for a fired-type copper paste.
[0015]
(Example 2)
As a starting material of the present invention, electrolytic copper powder having a primary particle diameter of 1 μm precipitated from an aqueous solution of copper sulfate was used. A ball mill was used as a method for applying a physical stress to the electrolytic copper powder. The processing conditions of the ball mill were as follows: 2 kg of electrolytic copper powder charged, 10 kg of 1/8 inch diameter steel ball as a medium, 0.1 wt% of stearic acid added to the electrolytic copper powder, and a ball mill rotating speed of 40 rpm in air. Driving for 3 hours. As a result, when observed with an electron microscope, a slightly thick disk-shaped copper powder having an average particle diameter of 2 μm and an aspect ratio of 2 was obtained. When the copper powder of the present invention was used for a polymer-type copper paste, a copper paste excellent in printability was produced even with high filling.
[0016]
(Example 3)
As a starting material of the present invention, electrolytic copper powder having a primary particle diameter of 1.5 μm precipitated from an aqueous copper sulfate solution was used. A ball mill was used as a method for applying a physical stress to the electrolytic copper powder. The processing conditions by the ball mill were as follows: 2 kg of electrolytic copper powder input, 10 kg of 1/8 inch diameter steel balls as a medium, 0.05 wt% of stearic acid added to the electrolytic copper powder, and a ball mill rotating speed of 40 rpm in air. Driving for 1 hour. As a result, a round disk-shaped copper powder having an average particle diameter of 1.8 μm and an aspect ratio of 1.2 was obtained by observation with an electron microscope. When the copper powder of the present invention was used for a polymer-type copper paste, a copper paste excellent in printability was produced even with high filling. A copper paste capable of obtaining a dense coating film as a firing type could be produced.
[0017]
(Example 4)
As a starting material of the present invention, reduced copper powder having a primary particle diameter of 2 μm obtained by reducing copper oxide in an aqueous solution was used. A ball mill was used as a method for applying a physical stress to the reduced copper powder. The processing conditions by the ball mill were as follows: 2 kg of reduced copper powder, 10 kg of 3/16 inch diameter steel balls as a medium, 0.05 wt% of stearic acid added to the reduced copper powder, and a ball mill rotating speed of 40 rpm in air. Driving for 2 hours. As a result, when observed with an electron microscope, a thick disk-shaped copper powder having an average particle diameter of 3 μm and an aspect ratio of 1.5 was obtained. When the copper powder of the present invention was used for a polymer-type copper paste for through-holes, it was excellent in fluidity even at a high filling, and was also optimal for a fired-type copper paste.
[0018]
(Example 5)
As a starting material of the present invention, reduced copper powder having a primary particle diameter of 0.3 μm obtained by reducing copper oxide in an aqueous solution was used. A ball mill was used as a method for applying a physical stress to the reduced copper powder. The processing conditions of the ball mill were as follows: 1 kg of reduced copper powder input, 10 kg of 5/64 inch diameter steel balls as a medium, 0.5 wt% of palmitic acid added to the reduced copper powder, and a ball mill in an atmosphere containing nitrogen. The operation was performed at a rotation speed of 25 rpm for 8 hours. As a result, when observed with an electron microscope, a fine disk-shaped copper powder having an average particle diameter of 0.5 μm and an aspect ratio of 1.6 was obtained. When the copper powder of the present invention was used for the polymer type copper paste, it could be filled more than the conventional reduced granular copper powder, and the coating film surface appearance after printing the fine pattern was smooth.
[0019]
【The invention's effect】
In the field of electronic component mounting, development of polymer type copper paste or calcined type copper paste using inexpensive copper powder has been advanced. By using the copper powder for a conductive paste of the present invention, the copper powder can be highly filled in the paste, and a new copper paste can be developed. In addition, it has become possible to manufacture a copper paste that can also be used for fine pattern printing accompanying the increase in the density of electronic components.
Claims (2)
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| JP2002181171A JP2004027246A (en) | 2002-06-21 | 2002-06-21 | Copper powder for conductive paste, and its manufacturing method |
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