JP4362601B2 - Method for producing copper powder - Google Patents
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- JP4362601B2 JP4362601B2 JP2004117103A JP2004117103A JP4362601B2 JP 4362601 B2 JP4362601 B2 JP 4362601B2 JP 2004117103 A JP2004117103 A JP 2004117103A JP 2004117103 A JP2004117103 A JP 2004117103A JP 4362601 B2 JP4362601 B2 JP 4362601B2
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims description 219
- 238000004519 manufacturing process Methods 0.000 title claims description 22
- 239000000843 powder Substances 0.000 claims description 154
- 239000010949 copper Substances 0.000 claims description 113
- 229910052802 copper Inorganic materials 0.000 claims description 113
- 238000010438 heat treatment Methods 0.000 claims description 53
- 239000002245 particle Substances 0.000 claims description 40
- 238000005245 sintering Methods 0.000 claims description 39
- 238000007873 sieving Methods 0.000 claims description 25
- 239000012298 atmosphere Substances 0.000 claims description 16
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 9
- 239000001257 hydrogen Substances 0.000 claims description 8
- 229910052739 hydrogen Inorganic materials 0.000 claims description 8
- 239000002253 acid Substances 0.000 claims 1
- 239000000126 substance Substances 0.000 claims 1
- 239000012535 impurity Substances 0.000 description 71
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 44
- 229910052799 carbon Inorganic materials 0.000 description 44
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 38
- 239000001301 oxygen Substances 0.000 description 38
- 229910052760 oxygen Inorganic materials 0.000 description 38
- 238000010304 firing Methods 0.000 description 21
- 239000011231 conductive filler Substances 0.000 description 13
- 238000002156 mixing Methods 0.000 description 12
- 239000000463 material Substances 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 229910052573 porcelain Inorganic materials 0.000 description 8
- 238000004220 aggregation Methods 0.000 description 7
- 230000002776 aggregation Effects 0.000 description 7
- 239000011230 binding agent Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 239000000654 additive Substances 0.000 description 5
- 239000011521 glass Substances 0.000 description 5
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 4
- 239000000470 constituent Substances 0.000 description 4
- 239000002270 dispersing agent Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000009826 distribution Methods 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 239000004034 viscosity adjusting agent Substances 0.000 description 2
- 239000005751 Copper oxide Substances 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910000431 copper oxide Inorganic materials 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
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Description
本発明は、主としてセラミックス基板の導電路や積層セラミックス部品の電極の形成等に用いられる焼成型導電性ペースト用の導電フィラーとして適し、金属ペーストの添加剤、触媒材料、フィルター用材料にも適した銅粉末の製造方法および銅粉末並びに当該銅粉末を用いた焼成型導電性ペーストに関するものである。 The present invention is suitable as a conductive filler for firing-type conductive pastes used mainly for forming conductive paths of ceramic substrates and electrodes of laminated ceramic parts, and is also suitable for metal paste additives, catalyst materials, and filter materials. The present invention relates to a method for producing copper powder, copper powder, and a fired conductive paste using the copper powder.
近年、セラミックス基板の導電路や積層セラミックス部品の電極の形成等に用いられる、焼成型導電性ペースト用の導電フィラーとして、銀粉末に替わり、銅粉末を使用することが一般的となっている（例えば、特許文献１参照）。
一方、エレクトロニクス技術の進歩に伴う部品の実装技術の進歩により、焼成型導電性ペーストも、電子部品の様々な部分で使用されるようになった。
In recent years, it has become common to use copper powder in place of silver powder as a conductive filler for firing-type conductive pastes used for forming conductive paths of ceramic substrates and electrodes of laminated ceramic parts ( For example, see Patent Document 1).
On the other hand, with the progress of component mounting technology accompanying the advancement of electronics technology, fired conductive paste has also been used in various parts of electronic components.
この結果、焼成型導電性ペーストに要求される、焼成後の焼結密度等の焼成条件も多様化し、所望の焼成条件を有する焼成型導電性ペーストをオーダーメイド的に求められる場合が増加してきた。 As a result, firing conditions such as sintered density after firing required for firing-type conductive pastes are diversified, and there is an increasing number of custom-made firing-type conductive pastes having desired firing conditions. .
ところが、所望の焼成条件を提示され、当該焼成条件を満足する焼成型導電性ペーストを迅速に調製しようとしても困難な場合が多い。これは、焼成型導電性ペーストが、導電フィラー、ガラスフリット、バインダー、分散剤や粘度調製剤、等の多様な成分を有し、さらに、これらの成分を調合するのに際し、調合比率、混合条件等、多くの要素があり、一つの製品を開発するためにはこれら多くの要因を調整しながら最適化を図る必要があるためである。
本発明は上記の背景のもとに成されたものであり、要求される、焼成後の多様な焼結密度を発揮できる焼成型導電性ペーストを迅速に調製することを可能とし、併せて金属ペーストの添加剤、触媒材料、フィルター用材料にも適した銅粉末の製造方法、銅粉末、並びに当該銅粉末を用いた焼成型導電性ペーストを提供することを目的とする。 The present invention has been made based on the above-described background, and enables the rapid preparation of a fired conductive paste capable of exhibiting various sintered densities after firing, which is required. An object of the present invention is to provide a copper powder production method suitable for paste additives, catalyst materials, and filter materials, copper powder, and a fired conductive paste using the copper powder.
上述の課題を解決するために、本発明者らが研究をおこなった結果、当該焼成型導電性ペーストの主要成分であり導電フィラーの銅粉末のタップ密度を制御することができれば、導電フィラー、ガラスフリット、バインダー等の種類等を変更することなく、焼成時の脱バインダー特性を制御することができ、この結果として、焼成後の焼成密度を制御できることに想到した。 As a result of studies conducted by the present inventors in order to solve the above-mentioned problems, if the tap density of the copper powder of the conductive filler that is the main component of the baked conductive paste can be controlled, the conductive filler, glass It has been conceived that the debinding characteristics during firing can be controlled without changing the type of frit, binder, etc., and as a result, the firing density after firing can be controlled.
すなわち、課題を解決するための第１の手段は、平均粒径1〜１０μｍの銅微粉末を、還元性雰囲気下において、単独または焼結助剤の存在下で２００〜５５０℃の温度範囲にて熱処理することを特徴とする銅粉末の製造方法である。 That is, the first means for solving the problem is that copper fine powder having an average particle diameter of 1 to 10 μm is placed in a temperature range of 200 to 550 ° C. alone or in the presence of a sintering aid in a reducing atmosphere. And a heat treatment of the copper powder.
第２の手段は、前記熱処理後の銅粉末に、解砕と篩がけとの少なくとも一方を実施することを特徴する第１の手段に記載の銅粉末の製造方法である。 A 2nd means is a manufacturing method of the copper powder as described in a 1st means characterized by implementing at least one of crushing and sieving to the copper powder after the said heat processing.
第３の手段は、前記熱処理を、水素雰囲気下で行うことを特徴とする第１または第２の手段に記載の銅粉末の製造方法である。 The third means is the copper powder manufacturing method according to the first or second means, wherein the heat treatment is performed in a hydrogen atmosphere.
第４の手段は、前記焼結助剤は、表面にＣｕＯを含む酸化膜を有する銅粉であることを特徴とする第１〜第３の手段のいずれかに記載の銅粉末の製造方法である。 A fourth means is the copper powder manufacturing method according to any one of the first to third means, wherein the sintering aid is a copper powder having an oxide film containing CuO on its surface. is there.
第５の手段は、平均粒径1〜１０μｍの銅微粉末の表面の一部分が互いに結合した凝集体を含み、そのタップ密度が２〜５ｇ／ｃｍ３であることを特徴とする銅粉末である。 A fifth means is a copper powder characterized in that a part of the surface of a copper fine powder having an average particle diameter of 1 to 10 μm includes an aggregate bonded together, and the tap density is 2 to 5 g / cm 3. .
第６の手段は、銅および酸素以外の不純物濃度が、０．２ｗｔ％以下であることを特徴とする第５の手段に記載の銅粉末である。 A sixth means is the copper powder according to the fifth means, wherein an impurity concentration other than copper and oxygen is 0.2 wt% or less.
第７の手段は、第５または第６の手段に記載の銅粉末を含有することを特徴とする焼成型導電性ペーストである。 A seventh means is a baked conductive paste characterized by containing the copper powder described in the fifth or sixth means.
第１の手段によれば、平均粒径1〜１０μｍの銅微粉末を２００〜５５０℃の温度範囲にて熱処理し、その表面の一部分を互いに結合させて当該銅微粉末の凝集体とすることで、当該凝集体を構成粒子とし、所望のタップ密度を有する銅粉末を製造することができる。 According to the first means, copper fine powder having an average particle diameter of 1 to 10 μm is heat-treated in a temperature range of 200 to 550 ° C., and a part of the surface is bonded to each other to form an aggregate of the copper fine powder. Thus, a copper powder having a desired tap density can be produced using the aggregate as a constituent particle.
第２の手段によれば、解砕と篩がけとの少なくとも一方により、銅微粉末の凝集が進みすぎた銅粉末を解砕または除去できるので、銅粉末の性状を均一化することができる。 According to the second means, the copper powder in which the aggregation of the copper fine powder has progressed excessively can be crushed or removed by at least one of crushing and sieving, so that the properties of the copper powder can be made uniform.
第３の手段によれば、前記熱処理を、水素雰囲気下において行うことで、処理コストの低減、処理結果の安定性を得ることができる。 According to the third means, by performing the heat treatment in a hydrogen atmosphere, the processing cost can be reduced and the stability of the processing result can be obtained.
第４の手段によれば、焼結助剤として、表面にＣｕＯを含む酸化膜を有する銅粉を用いることで、銅粉末中の不純物を増加させることなく銅微粉末の凝集状態を制御できる。 According to the fourth means, the aggregation state of the copper fine powder can be controlled without increasing the impurities in the copper powder by using the copper powder having the oxide film containing CuO on the surface as the sintering aid.
第５の手段によれば、平均粒径1〜１０μｍの銅微粉末の表面の一部分が互いに結合した凝集体を含み、そのタップ密度が２〜５ｇ／ｃｍ３であることを特徴とする銅粉末から、所望のタップ密度を有する銅粉末を選択できるので、当該選択された所望のタップ密度を有する銅粉末と、ガラスフリット、バインダー、分散剤、粘度調製剤等とを、混合して焼成型導電性ペーストを調製する際、これらガラスフリット、バインダー、分散剤、粘度調製剤、等の成分は殆ど固定したまま、前記銅粉末のタップ密度を選択することにより、焼成後に所望の焼成密度を発揮する導電性ペーストを容易に短期間で調製できるとともに、当該銅粉末は、抵抗ペーストや静電遮蔽ペーストなどの金属ペーストへの添加剤として、あるいは触媒材料やフィルター用材料としても好個に使用できる。 According to a fifth means, a copper powder characterized in that a part of the surface of a copper fine powder having an average particle diameter of 1 to 10 μm includes an aggregate bonded together, and the tap density is 2 to 5 g / cm 3. From this, it is possible to select a copper powder having a desired tap density. Therefore, the copper powder having the selected desired tap density is mixed with a glass frit, a binder, a dispersant, a viscosity adjusting agent, etc. When preparing the paste, the desired density is achieved after firing by selecting the tap density of the copper powder while keeping these components such as glass frit, binder, dispersant, viscosity modifier, etc. almost fixed. Conductive paste can be easily prepared in a short period of time, and the copper powder can be used as an additive to metal pastes such as resistance pastes and electrostatic shielding pastes, or as catalyst materials and filters. It can also be used as an individual material.
第６の手段によれば、本発明に係る銅粉末は、銅および酸素以外の不純物濃度が、０．２ｗｔ％以下である銅粉末であるため、電気的特性に優れ、品質の安定性にも優れた焼成型導電性ペースト等を調製することができる。 According to the sixth means, since the copper powder according to the present invention is a copper powder having an impurity concentration other than copper and oxygen of 0.2 wt% or less, the electrical characteristics are excellent and the quality is stable. An excellent fired conductive paste or the like can be prepared.
第７の手段による当該焼成型導電性ペーストは、電子部品の様々な部分で使用することができる。 The fired conductive paste according to the seventh means can be used in various parts of electronic components.
以下、本発明を実施するための最良の形態を説明する。
まず、本発明に係る銅粉末について説明する。（以下、平均粒径1〜１０μｍの範囲から選択される銅微粉末を銅微粉末元粉と記載する場合がある。）
本発明に係る銅粉末は、平均粒径1〜１０μｍの範囲から選択される、ほぼ均一な粒径を有する銅微粉末元粉、または広範囲な粒径分布を有する銅微粉末元粉を熱処理し、当該銅微粉末元粉の表面の一部分を互いに結合させて凝集状態とし、当該凝集状態となった銅微粉末元粉を構成粒子とする銅粉末である。
Hereinafter, the best mode for carrying out the present invention will be described.
First, the copper powder according to the present invention will be described. (Hereinafter, copper fine powder selected from the range of average particle diameter of 1 to 10 μm may be referred to as copper fine powder base powder.)
The copper powder according to the present invention is obtained by heat-treating a copper fine powder base powder having a substantially uniform particle diameter, or a copper fine powder base powder having a wide particle size distribution, selected from a range of an average particle diameter of 1 to 10 μm. A part of the surface of the copper fine powder base powder is bonded to each other to form an agglomerated state, and the copper fine powder base powder in the agglomerated state is a copper powder having constituent particles.
ここで、銅微粉末元粉には、例えば、含銅塩水溶液を還元して銅微粉末を得る湿式法により製造された球状の銅粉（以下、湿式球状粉と記載する場合がある。）等が好個に用いられ、当該製造条件の制御により、湿式球状粉の粒径を所定のものに制御することができる。また、市販の球状の銅粉を用いることもできる。
銅微粉末元粉は、平均粒径が１μｍよりも大きいと単分散性が良くなるためタップ密度の制御範囲が広くなり、一方、平均粒径が１０μｍ以下であれば焼結が生ずる温度がバルクの銅の融点から離れるため、銅粉末におけるタップ密度以外の他の特性値が変化する恐れが少なくなり適切となる。したがって、銅微粉末元粉として選択される粒径は１〜１０μｍの範囲が好ましく、より好ましくは３〜７μｍの範囲である。当該範囲内であれば、ほぼ均一な粒径を有する銅微粉末元粉であっても良いし、広範囲な粒径分布を有する銅微粉末元粉であっても良い。但し、ほぼ均一な粒径を有する銅微粉末元粉を用いた場合の方が、製造される銅粉末のタップ密度の制御範囲が広くなる。
Here, the copper fine powder base powder is, for example, a spherical copper powder manufactured by a wet method in which a copper-containing salt aqueous solution is reduced to obtain a copper fine powder (hereinafter sometimes referred to as a wet spherical powder). And the like, and the particle size of the wet spherical powder can be controlled to a predetermined value by controlling the production conditions. Commercially available spherical copper powder can also be used.
The copper fine powder base powder has a monodispersibility that is good when the average particle size is larger than 1 μm, so the control range of the tap density is widened. On the other hand, if the average particle size is 10 μm or less, the temperature at which sintering occurs is bulky. Therefore, it is appropriate that the characteristic value other than the tap density in the copper powder is changed. Therefore, the particle size selected as the copper fine powder base powder is preferably in the range of 1 to 10 μm, more preferably in the range of 3 to 7 μm. If it is in the said range, the copper fine powder base powder which has a substantially uniform particle size may be sufficient, and the copper fine powder base powder which has a wide particle size distribution may be sufficient. However, the control range of the tap density of the produced copper powder becomes wider when the copper fine powder base powder having a substantially uniform particle size is used.
銅微粉末元粉の表面の一部分が互いに結合した凝集状態とは、前記銅微粉末元粉が有する、粒子形状、ＢＥＴ特性、酸素濃度特性、炭素を代表とする不純物濃度特性、熱収縮特性が、実質的に保たれたまま凝集体となり、本発明に係る銅粉末の構成粒子となっていることをいう。この結果、本発明に係る銅粉末は、前記銅微粉末元粉の形状、ＢＥＴ特性、不純物濃度、等を実質的に維持したままタップ密度が制御された銅粉末となっている。そして、銅微粉末元粉の凝集状態を制御することで、当該銅粉末のタップ密度を前記銅微粉末元粉が有するタップ密度の０．９８〜０．５０倍の範囲、即ち、タップ密度で２〜５ｇ／ｃｍ３の範囲で制御することができた。
尚、本発明において、タップ密度はＪＩＳ Ｚ ２５０４に準拠して測定したものであり、単位はｇ／ｃｍ３である。
The agglomerated state in which parts of the surface of the copper fine powder base powder are bonded to each other means that the copper fine powder base powder has the particle shape, BET characteristics, oxygen concentration characteristics, impurity concentration characteristics represented by carbon, and heat shrinkage characteristics. In other words, the agglomerates remain substantially maintained and constitute the constituent particles of the copper powder according to the present invention. As a result, the copper powder according to the present invention is a copper powder in which the tap density is controlled while substantially maintaining the shape, BET characteristics, impurity concentration, and the like of the copper fine powder base powder. And by controlling the aggregation state of the copper fine powder base powder, the tap density of the copper powder is in the range of 0.98 to 0.50 times the tap density of the copper fine powder base powder, that is, the tap density. Control was possible in the range of 2 to 5 g / cm 3 .
In the present invention, the tap density is measured in accordance with JIS Z 2504, and the unit is g / cm 3 .
たとえば、所定の平均粒径を有する銅微粉末元粉として平均粒径が３μｍ（タップ密度４．３５）の銅微粉末元粉を用い、タップ密度を銅微粉末元粉の０．９８〜０．５０倍の範囲で制御して、各種のタップ密度を有する銅粉末を製造したとき、各々の銅粉末を構成する銅微粉末元粉の形状はほとんど変化しなかった。この場合例えば、ＢＥＴ特性は０．３９から０．３３とほとんど変化せず、酸素濃度特性は０．０９ｗｔ％から０．１２ｗｔ％とほとんど変化せず、炭素濃度特性は０．１１ｗｔ％から０．０７ｗｔ％とほとんど変化せず、熱収縮特性を示す収縮開始温度も７５０±１０℃から７５０±１０℃とほとんど変化しなかった。さらに、各々の銅粉末において、銅および酸素以外の不純物濃度の総量（炭素を含む。）は０．２ｗｔ％以下であった。 For example, a copper fine powder base powder having an average particle diameter of 3 μm (tap density 4.35) is used as the copper fine powder base powder having a predetermined average particle diameter, and the tap density is 0.98 to 0 of the copper fine powder base powder. When copper powder having various tap densities was produced by controlling within a range of 50 times, the shape of the copper fine powder base powder constituting each copper powder hardly changed. In this case, for example, the BET characteristic hardly changes from 0.39 to 0.33, the oxygen concentration characteristic hardly changes from 0.09 wt% to 0.12 wt%, and the carbon concentration characteristic changes from 0.11 wt% to 0.12 wt%. There was almost no change at 07 wt%, and the shrinkage start temperature showing the heat shrinkage characteristic was hardly changed from 750 ± 10 ° C. to 750 ± 10 ° C. Furthermore, in each copper powder, the total amount (including carbon) of impurity concentrations other than copper and oxygen was 0.2 wt% or less.
次に、本発明に係る銅粉末の製造方法の一例について説明する。
本発明に係る銅粉末の製造方法は、銅微粉末元粉を還元性雰囲気中、単独で、または焼結助剤の存在下で銅微粉末元粉の表面の一部分が焼結する条件熱処理を実施し、当該銅微粉末元粉の表面の一部分を互いに結合させて凝集状態とし、当該凝集状態となった銅微粉末元粉を構成粒子とする銅粉末を得る。そして、好ましくは、この得られた銅粉末に解砕と篩がけの少なくとも一方を実施して銅粉末を製造するものである。
Next, an example of the copper powder manufacturing method according to the present invention will be described.
The method for producing a copper powder according to the present invention comprises subjecting a copper fine powder base powder to a heat treatment under a reducing atmosphere, alone or in the presence of a sintering aid, under a condition that a part of the surface of the copper fine powder base powder is sintered. The copper fine powder base powder is partially bonded to each other to form an aggregated state, and a copper powder having the aggregated copper fine powder base powder as constituent particles is obtained. And preferably, the obtained copper powder is subjected to at least one of crushing and sieving to produce a copper powder.
以下、銅微粉末元粉として平均粒径３μｍのものを用いた場合を例として説明する。
まず、平均粒径３μｍの銅微粉末元粉は、上述した湿式法により公知の条件で湿式球状粉を製造しても良いし、市販されている純度３Ｎ以上の球状銅粉を用いても良い。
Hereinafter, an example in which a copper fine powder base powder having an average particle diameter of 3 μm is used will be described.
First, as the copper fine powder base powder having an average particle diameter of 3 μm, wet spherical powder may be produced under known conditions by the wet method described above, or commercially available spherical copper powder having a purity of 3N or more may be used. .
次に、銅微粉末元粉への熱処理の保持温度および保持時間は、銅微粉末元粉の相互間の焼結の程度を左右し、銅微粉末元粉の凝集の度合いに影響を与えて、製造される銅粉末のタップ密度を変化させる要因である。つまり、この熱処理の保持温度は、１９０℃では銅微粉末元粉にほとんど焼結が生ぜず、また６００℃以下であれば、加熱されることによる銅微粉末元粉の表面状態の変化を無視することができる。したがって、熱処理の保持温度は、２００〜５５０℃の範囲が好ましく、より好ましくは２４０〜５２０℃の範囲である。保持時間は、２時間〜５時間が好ましい。熱処理時の雰囲気は、還元性雰囲気であれば良いが水素雰囲気とすることで、処理コストの低減、処理結果の安定性を得ることができ好ましい。 Next, the holding temperature and holding time of the heat treatment for the copper fine powder base powder influence the degree of sintering between the copper fine powder base powder and affect the degree of aggregation of the copper fine powder base powder. It is a factor which changes the tap density of the copper powder manufactured. That is, when the heat treatment holding temperature is 190 ° C., the copper fine powder base powder hardly sinters, and if it is 600 ° C. or lower, the change in the surface state of the copper fine powder base powder due to heating is ignored. can do. Therefore, the holding temperature of the heat treatment is preferably in the range of 200 to 550 ° C, more preferably in the range of 240 to 520 ° C. The holding time is preferably 2 hours to 5 hours. The atmosphere during the heat treatment may be a reducing atmosphere, but a hydrogen atmosphere is preferable because the processing cost can be reduced and the stability of the processing result can be obtained.
同様に、銅微粉末元粉への熱処理において、焼結助剤の添加もまた、銅微粉末元粉の凝集の度合いに影響を及ぼす要因である。この焼結助剤は、銅微粉末元粉同士よりも焼結しやすいもの、また逆に焼結しにくいものである。この焼結助剤に接する銅微粉末元粉の焼結が、選択的に促進されたり阻害されたりすることになるため、焼結助剤の種類や混合比率を変更することで、銅微粉末元粉の凝集の程度が精密に変更されて、製造される銅粉末のタップ密度を精密に制御できる。 Similarly, in the heat treatment of the copper fine powder base powder, the addition of a sintering aid is also a factor affecting the degree of aggregation of the copper fine powder base powder. This sintering aid is easier to sinter than copper fine powder base powders, and conversely, is difficult to sinter. Since the sintering of the copper fine powder base powder in contact with this sintering aid is selectively promoted or inhibited, the copper fine powder can be changed by changing the type and mixing ratio of the sintering aid. The tap powder density of the produced copper powder can be precisely controlled by precisely changing the degree of aggregation of the original powder.
この焼結助剤として、表面が強制酸化され、酸化銅（ＣｕＯ）の膜に覆われた銅粉（以下、酸化膜銅粉と記載する。）が好個に使用できる。即ち、焼結助剤として、酸化膜銅粉の様な銅酸化物を用いることで、銅微粉末元粉への熱処理において焼結助剤が存在しても、製造された銅粉末中へ、銅、酸素以外の望まれない不純物が混入することを抑制できる。酸化膜銅粉の添加により銅微粉末元粉の凝集状態はより精度よく制御可能となり、所望のタップ密度を有する銅粉末が製造される。 As the sintering aid, copper powder (hereinafter referred to as oxide film copper powder) whose surface is forcibly oxidized and covered with a copper oxide (CuO) film can be suitably used. That is, by using a copper oxide such as oxide film copper powder as a sintering aid, even if a sintering aid is present in the heat treatment of the copper fine powder base powder, into the produced copper powder, It is possible to suppress mixing of unwanted impurities other than copper and oxygen. By adding the oxide film copper powder, the aggregation state of the copper fine powder base powder can be controlled with higher accuracy, and a copper powder having a desired tap density is produced.
この酸化膜銅粉を用いることなく、熱処理の保持温度および保持時間の制御で、銅粉末のタップ密度を制御しても良いが、酸化膜銅粉を用いることで、用いない場合よりタップ密度の制御をより精密におこなえるようになる。銅微粉末元粉に対する添加量としては、銅微粉末元粉重量／酸化膜銅粉重量＝１９／１の添加から効果があり、生産コストの観点からは、銅微粉末元粉重量／酸化膜銅粉重量＝１０／１０程度までの添加が好ましい。
尚、当該酸化膜銅粉としては、上述の銅微粉末元粉と同程度、或いはそれ以下の粒径を有する市販の純度３Ｎ以上の湿式球状粉を、大気中にて攪拌しながら１５０℃前後の温度で加熱することで製造することができる。尚、処理温度と処理時間とを制御することで、当該酸化膜銅粉に含まれる酸素の量が調節可能である。
Without using this oxide film copper powder, the tap density of the copper powder may be controlled by controlling the holding temperature and holding time of the heat treatment, but by using the oxide film copper powder, the tap density is higher than when not using it. It becomes possible to perform control more precisely. The amount added to the copper fine powder base powder is effective from the addition of copper fine powder base powder weight / oxide film copper powder weight = 19/1. From the viewpoint of production cost, the copper fine powder base powder weight / oxide film Addition of copper powder weight = about 10/10 is preferable.
As the oxide film copper powder, a commercially available wet spherical powder having a particle size equal to or less than that of the above-mentioned copper fine powder base powder and having a purity of 3N or more is stirred at about 150 ° C. in the atmosphere. It can manufacture by heating at the temperature of. Note that the amount of oxygen contained in the oxide film copper powder can be adjusted by controlling the processing temperature and the processing time.
熱処理後に銅粉末の解砕や篩がけをおこない、凝集の進みすぎた銅粉末元粉の凝集体を、解砕、除去することも品質管理上の観点から好ましい構成である。本発明者らの知見によれば、銅粉末の製造方法における、これら解砕または篩がけは、銅微粉末元粉の有する前記諸特性に与える影響を無視できるものであった。 It is also preferable from the viewpoint of quality control that the copper powder is crushed or sieved after the heat treatment, and the aggregate of the copper powder base powder that has been excessively agglomerated is crushed and removed. According to the knowledge of the present inventors, these crushing or sieving in the copper powder production method can ignore the influence of the copper fine powder base powder on the above characteristics.
以上説明した製造方法により、平均粒径が３μｍ（タップ密度４．３５）の銅微粉末元粉より、前記銅粉末元粉のタップ密度の０．５〜０．９８倍、即ち、タップ密度２．１〜４．３の値を有する各種の銅粉末が調製できた。
By the manufacturing method explained above, from the copper fine powder base powder having an average particle diameter of 3 μm (tap density 4.35), the tap density of the copper powder base powder is 0.5 to 0.98 times, that is, the
以上の説明においては、銅微粉末元粉として平均粒径が３μｍのものを原料とした場合を例として説明したが、同様に、平均粒径７μｍ（タップ密度が４．８８）の銅微粉末元粉を使用した場合は、前記銅微粉末元粉のタップ密度の０．５〜０．９８倍、即ち、タップ密度２．４〜４．８の値を有する各種の銅粉末が調製できた。
以下同様に、平均粒径が１から１０μｍの範囲にある銅微粉末元粉を用い、当該範囲内であれば、ほぼ均一な粒径を有する銅微粉末元粉や、広範囲な粒径分布を有する銅微粉末元粉を用いて、タップ密度２〜５ｇ／ｃｍ３の範囲の値を有する各種の銅粉末が調製できた。
In the above description, the case where the raw material of the copper fine powder has an average particle diameter of 3 μm is described as an example. Similarly, the copper fine powder having an average particle diameter of 7 μm (tap density is 4.88). When the base powder was used, various copper powders having a value of 0.5 to 0.98 times the tap density of the copper fine powder base powder, that is, a tap density of 2.4 to 4.8 could be prepared. .
Similarly, a copper fine powder base powder having an average particle size in the range of 1 to 10 μm is used, and if within this range, a copper fine powder base powder having a substantially uniform particle size or a wide range of particle size distribution is obtained. Various copper powders having a tap density in the range of 2 to 5 g / cm 3 could be prepared using the copper fine powder base powder.
この結果、タップ密度２〜５ｇ／ｃｍ３の値を有する各種の銅粉末から所望のタップ密度を有する銅粉末を選択し、例えば、焼成型導電性ペーストの導電フィラーとして用いた場合、焼成特性が異なる多様な導電性ペーストを調製できるようになった。 As a result, when a copper powder having a desired tap density is selected from various copper powders having a tap density of 2 to 5 g / cm 3 , for example, when used as a conductive filler of a baking type conductive paste, the baking characteristics are A variety of different conductive pastes can be prepared.
ここで、本発明に係る銅粉末を用いることで、焼成後に所望の焼成密度を発揮する導電性ペーストを調製できる理由について説明する。
焼成型導電性ペーストの焼成特性には様々な要因が影響するが、具体的にはペーストの組成、ペーストの調整条件、ペーストの焼成条件の三つが主なものである。さらに、ペースト組成としては、ペーストを構成する導電フィラー、ガラスフリット、バインダー、分散剤や粘度調製剤などの添加剤の選択とその混合比率、調整条件としては、ペースト製造の際の混練と脱泡の方法と条件、焼成条件としては、ペースト塗布後の乾燥、脱バインダー、焼成の工程を含む時間−温度条件と酸素濃度の管理などである。一つの製品を開発するためにはこれら多くの要因を調整しながら最適化を図る必要がある。
Here, the reason why a conductive paste that exhibits a desired firing density after firing can be prepared by using the copper powder according to the present invention will be described.
Various factors influence the firing characteristics of the firing type conductive paste. Specifically, there are three main ones: paste composition, paste adjustment conditions, and paste firing conditions. Furthermore, the paste composition includes selection of additives such as conductive filler, glass frit, binder, dispersant and viscosity adjuster constituting the paste, and the mixing ratio, and adjustment conditions include kneading and defoaming during paste production. Examples of the method, conditions, and firing conditions include drying after binder application, debinding, and time-temperature conditions including the firing steps and management of oxygen concentration. In order to develop one product, it is necessary to optimize while adjusting many of these factors.
例えば、当該焼成型導電性ペーストの熱収縮特性や流動性を変化させるために、導電フィラーのタップ密度を変えようとすると、当該導電フィラーの粒径や形状、さらには不純物濃度まで変化してしまうため、上述の多くの要因を再度調製する必要が生じていたのである。さらに、導電フィラーに不純物として含まれる炭素濃度が、０．２ｗｔ％を超えた場合、当該焼成型導電性ペーストの焼結特性に不具合が発生する可能性もある。 For example, if the tap density of the conductive filler is changed in order to change the heat shrinkage characteristics and fluidity of the baked conductive paste, the particle size and shape of the conductive filler, and even the impurity concentration change. Therefore, it was necessary to prepare many of the above factors again. Furthermore, when the carbon concentration contained as an impurity in the conductive filler exceeds 0.2 wt%, there is a possibility that a problem occurs in the sintering characteristics of the fired conductive paste.
そこで、当該導電フィラーとして、本発明に係る、平均粒径1〜１０μｍの銅微粉末元粉の表面の一部分が互いに結合した凝集体を含み、そのタップ密度が２〜５ｇ／ｃｍ３である銅粉末から、所望のタップ密度を有する銅粉末を選択して用いれば、当該銅粉末を構成する銅微粉末元粉の形状、ＢＥＴ特性、不純物濃度、等を実質的に維持したままタップ密度だけを変えられるので、上述の多くの要因を再度調製することなく、所望のタップ密度を有する導電フィラーを含む焼成型導電性ペーストを、容易、迅速に調製できるようになった。そして、当該焼成型導電性ペーストは、焼成時に各々異なる脱バインダー特性を現し、焼成後には、各々異なる所望の焼成密度を発揮する。これらのデータから、最適な導電フィラーのタップ密度を求めれば、当該タップ密度を有する銅粉末を調製するだけで、容易、迅速に、求められる焼成型導電性ペーストを調製できるようになった。 Therefore, as the conductive filler, copper containing agglomerates in which parts of the surface of the copper fine powder base powder having an average particle diameter of 1 to 10 μm according to the present invention are bonded to each other, and the tap density is 2 to 5 g / cm 3. If copper powder having a desired tap density is selected and used from the powder, only the tap density is maintained while substantially maintaining the shape, BET characteristics, impurity concentration, etc. of the copper fine powder base powder constituting the copper powder. Since it can be changed, a fired conductive paste containing a conductive filler having a desired tap density can be easily and quickly prepared without re-preparing many of the above factors. The fired conductive paste exhibits different binder removal characteristics during firing, and exhibits different desired firing densities after firing. From these data, if the optimum tap density of the conductive filler is determined, the required fired conductive paste can be prepared easily and quickly simply by preparing a copper powder having the tap density.
以下、図面を参照しながら各実施例を用い本発明を具体的に説明する。
ここで、図１は、本発明にかかる銅粉末の製造方法が適用された各実施例における製造条件とタップ密度との関係を、比較例とともに示す図表であり、
図２は、各実施例における熱処理の保持温度とタップ密度との関係を示し、(Ａ)がその関係を示す図表、(Ｂ)がその関係を示すグラフであり、
図３は、各実施例における焼結助剤の混合比率（含有比率）とタップ密度との関係を示し、(Ａ)がその関係を示す図表、(Ｂ)がその関係を示すグラフであり、
図４は、各実施例における焼結助剤としての酸化膜銅粉の酸素濃度とタップ密度との関係を示し、(Ａ)がその関係を示す図表、(Ｂ)がその関係を示すグラフである。
Hereinafter, the present invention will be described in detail with reference to the drawings and using each embodiment.
Here, FIG. 1 is a chart showing the relationship between the manufacturing conditions and the tap density in each example to which the method for manufacturing a copper powder according to the present invention is applied, together with a comparative example,
FIG. 2 shows the relationship between the heat treatment holding temperature and the tap density in each example, (A) is a chart showing the relationship, and (B) is a graph showing the relationship.
FIG. 3 shows the relationship between the mixing ratio (content ratio) of the sintering aid and the tap density in each example, (A) is a chart showing the relationship, and (B) is a graph showing the relationship.
FIG. 4 shows the relationship between the oxygen concentration and tap density of the oxide film copper powder as the sintering aid in each example, (A) is a chart showing the relationship, and (B) is a graph showing the relationship. is there.
これらの各実施例および比較例においては、磁製皿に単分散の銅微粉末元粉を、できるだけ均等な厚みになるように２０ｇ程度入れ、雰囲気炉に入れて、一旦真空排気した後に１気圧の水素で置換し、１０リットル／分で水素ガスを流しながら、所定の熱処理プログラムによる熱処理を実施する。その後、雰囲気を窒素置換しながら自然冷却した後にサンプルを取り出し、乳鉢を用いた解砕処理と、目開き５０μｍの篩を用いた篩がけを実施して凝集状態の銅粉末を製造し、その特性値を評価した。 In each of these examples and comparative examples, about 20 g of monodispersed copper fine powder base powder is put in a porcelain dish so as to have a uniform thickness as much as possible, put in an atmosphere furnace, and once evacuated to 1 atm. Then, heat treatment by a predetermined heat treatment program is performed while flowing hydrogen gas at 10 liters / minute. Then, after naturally cooling the atmosphere with nitrogen, the sample was taken out, and pulverization using a mortar and sieving using a sieve with an opening of 50 μm were carried out to produce a coagulated copper powder. The value was evaluated.
前記製造過程において、焼結助剤を用いる場合には、予め篩がけを行った所定量の銅微粉末元粉と、良好に分散させた焼結助剤とを適当な容器に入れ、振とうにより均一になるまで混合を行う。得られた銅微粉末元粉と焼結助剤との混合物を磁製皿に入れ、前述と同様な熱処理および解砕などを実施して凝集状態の銅粉末を製造し、その特性値を評価した。その際、分散性の低い焼結助剤については、この焼結助剤と銅微粉末元粉の一部とを予め乳鉢で混合する前処理を追加した。 In the above manufacturing process, when using a sintering aid, put a predetermined amount of copper fine powder base powder previously screened and a well dispersed sintering aid in a suitable container and shake. Mix until uniform. The mixture of the obtained copper fine powder base powder and sintering aid is put into a porcelain dish, and heat treatment and pulverization similar to those described above are performed to produce an agglomerated copper powder, and its characteristic values are evaluated. did. In that case, about the sintering aid with low dispersibility, the pretreatment which mixes this sintering aid and a part of copper fine powder base powder with a mortar previously was added.
（実施例１）公知の湿式法にて製造した、タップ密度が４．３５ｇ／ｃｍ３で平均粒径３μｍの球状単分散銅微粉末２０ｇを磁製皿に取り分け、水素雰囲気中１時間で２４０℃まで昇温し、その温度を５時間保持する条件で熱処理をおこなった。解砕・篩がけ後のタップ密度は４．２５ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 1) 20 g of spherical monodispersed copper fine powder produced by a known wet method and having a tap density of 4.35 g / cm 3 and an average particle size of 3 μm was placed in a porcelain dish, and 240 hours in a hydrogen atmosphere for 1 hour. The temperature was raised to 0 ° C., and heat treatment was performed under the condition that the temperature was maintained for 5 hours. The tap density after crushing and sieving was 4.25 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例２）熱処理の保持温度が３００℃であることを除き、実施例１と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．５１ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 2) A heat treatment was performed under exactly the same conditions as in Example 1 except that the heat treatment holding temperature was 300 ° C. The tap density after crushing and sieving was 3.51 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例３）熱処理の保持温度が３４０℃であることを除き、実施例１と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．２７ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 3) A heat treatment was performed under exactly the same conditions as in Example 1 except that the heat treatment holding temperature was 340 ° C. The tap density after crushing and sieving was 3.27 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例４）熱処理の保持温度が４００℃で、４時間保持したことを除き、実施例１と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は２．９５ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 4) A heat treatment was performed under exactly the same conditions as in Example 1 except that the heat treatment was held at 400 ° C for 4 hours. The tap density after crushing and sieving was 2.95 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（比較例１）熱処理の保持温度が１９０℃であることを除き、実施例１と全く同一条件の熱処理をおこなった。焼結は見られず、解砕・篩がけ後のタップ密度は元粉と殆ど変わらぬ４．３６ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Comparative Example 1) Heat treatment was performed under exactly the same conditions as in Example 1 except that the heat treatment holding temperature was 190 ° C. Sintering was not observed, and the tap density after crushing and sieving was 4.36 g / cm 3 , which was almost the same as the original powder. Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（比較例２）熱処理の保持温度が５６０℃、１時間保持であることを除き、実施例１と全く同一条件の熱処理をおこなった。銅微粉末同士は激しく焼結しており、解砕・篩がけをおこなうことが出来なかった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Comparative Example 2) A heat treatment was performed under exactly the same conditions as in Example 1 except that the heat treatment was held at 560 ° C for 1 hour. The copper fine powders were vigorously sintered and could not be crushed and sieved. Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
上述の実施例１〜４および比較例１および２は、図２(Ａ)にも示すように、焼結助剤を使用せず、熱処理の保持温度および保持時間を変化させて、製造される凝集状態の銅粉末のタップ密度を制御したものである。この場合には、図２(Ｂ)に示すように、熱処理保持温度を２００〜５５０℃の範囲で上昇させることで、製造される銅粉末のタップ密度を低下させる制御をおこなうことができる。 As shown in FIG. 2A, Examples 1 to 4 and Comparative Examples 1 and 2 described above are manufactured without using a sintering aid and by changing the holding temperature and holding time of the heat treatment. The tap density of the agglomerated copper powder is controlled. In this case, as shown in FIG. 2 (B), it is possible to control to lower the tap density of the produced copper powder by raising the heat treatment holding temperature in the range of 200 to 550 ° C.
（実施例５）図１に示すように、湿式法にて製造した、タップ密度が４．３５ｇ／ｃｍ３で平均粒径３μｍの球状単分散銅微粉末１９ｇと、この球状銅微粉末の表面を酸素濃度５．２ｗｔ％まで酸化させた焼結助剤としての酸化膜銅粉１ｇとを充分均一になるように混合・分散させ（焼結助剤の含有比率５ｗｔ％）、これを磁製皿に取り分け、水素雰囲気中１時間で２４０℃まで昇温し、その温度を５時間保持する条件で熱処理をおこなった。解砕・篩がけ後のタップ密度は３．８８ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 Example 5 As shown in FIG. 1, 19 g of spherical monodispersed copper fine powder produced by a wet method and having a tap density of 4.35 g / cm 3 and an average particle size of 3 μm, and the surface of this spherical copper fine powder 1 g of oxide film copper powder as a sintering aid, which is oxidized to an oxygen concentration of 5.2 wt%, is mixed and dispersed so as to be sufficiently uniform (content ratio of sintering aid is 5 wt%). The plates were separated and heated to 240 ° C. in 1 hour in a hydrogen atmosphere, and heat treatment was performed under the condition of maintaining the temperature for 5 hours. The tap density after crushing and sieving was 3.88 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例６）銅微粉末と酸化膜銅粉の混合比率が１８ｇ：２ｇであること（焼結助剤の含有比率１０ｗｔ％）を除き、実施例５と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．８０ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。
(Example 6) A heat treatment was performed under exactly the same conditions as in Example 5 except that the mixing ratio of the copper fine powder and the oxide film copper powder was 18 g: 2 g (sintering
（実施例７）銅微粉末と酸化膜銅粉の混合比率が１６ｇ：４ｇであること（焼結助剤の含有比率２０ｗｔ％）を除き、実施例５と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．６６ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。
(Example 7) A heat treatment was performed under exactly the same conditions as in Example 5 except that the mixing ratio of copper fine powder and oxide film copper powder was 16 g: 4 g (sintering
（実施例８）銅微粉末と酸化膜銅粉の混合比率が１０ｇ：１０ｇであること（焼結助剤の含有比率５０ｗｔ％）を除き、実施例５と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．５６ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。
(Example 8) A heat treatment was performed under exactly the same conditions as in Example 5 except that the mixing ratio of the copper fine powder and the oxide film copper powder was 10 g: 10 g (sintering
（実施例９）銅微粉末の２０ｇすべてが酸化膜銅粉であること（焼結助剤の含有比率１００ｗｔ％）を除き、実施例５と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．１９ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。
(Example 9) A heat treatment was performed under exactly the same conditions as in Example 5 except that all 20 g of the copper fine powder was oxide film copper powder (sintering
上述の実施例５〜９は、図３(Ａ)にも示すように、熱処理の保持温度および保持時間を一定としつつ、銅微粉末元粉に対する同一種類の焼結助剤の混合比率(含有比率ｗｔ％)を変更して、製造される凝集状態の銅粉末のタップ密度を制御するものである。この場合には、図３(Ｂ)に示すように、焼結助剤の混合比率を上昇させることで、製造される銅粉末のタップ密度を低下させる制御をおこなうことができる。 In the above Examples 5 to 9, as shown in FIG. 3 (A), the mixing ratio of the same kind of sintering aid to the copper fine powder base powder (containing) while keeping the holding temperature and holding time of the heat treatment constant. The tap density of the agglomerated copper powder to be produced is controlled by changing the ratio wt%). In this case, as shown in FIG. 3 (B), it is possible to control to reduce the tap density of the produced copper powder by increasing the mixing ratio of the sintering aid.
（実施例１０）図１に示すように、湿式法にて製造した、タップ密度が４．３５ｇ／ｃｍ３で平均均粒径３μｍの球状単分散銅微粉末１９ｇと、この球状銅微粉末の表面を酸素濃度０．６１ｗｔ％まで酸化させた焼結助剤としての酸化膜銅粉１ｇとを充分均一になるように混合・分散させ、これを磁製皿に取り分け、水素雰囲気中１時間で３００℃まで昇温し、その温度を５時間保持する条件で熱処理をおこなった。解砕・篩がけ後のタップ密度は３．３５ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 Example 10 As shown in FIG. 1, 19 g of spherical monodispersed copper fine powder produced by a wet method and having a tap density of 4.35 g / cm 3 and an average particle size of 3 μm, and the spherical copper fine powder 1 g of oxide film copper powder as a sintering aid whose surface was oxidized to an oxygen concentration of 0.61 wt% was mixed and dispersed so as to be sufficiently uniform, and this was separated into a porcelain dish, and in one hour in a hydrogen atmosphere. The temperature was raised to 300 ° C., and heat treatment was performed under the condition that the temperature was maintained for 5 hours. The tap density after crushing and sieving was 3.35 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例１１）使用した酸化膜銅粉の酸素濃度が０．７５ｗｔ％であることを除き、実施例１０と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．４４ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 11) A heat treatment was performed under exactly the same conditions as in Example 10 except that the oxygen concentration of the oxide film copper powder used was 0.75 wt%. The tap density after crushing and sieving was 3.44 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例１２）使用した酸化膜銅粉の酸素濃度が１．２ｗｔ％であることを除き、実施例１０と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．３８ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 12) A heat treatment was performed under exactly the same conditions as in Example 10 except that the oxygen concentration of the used oxide film copper powder was 1.2 wt%. The tap density after crushing and sieving was 3.38 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例１３）使用した酸化膜銅粉が、平均粒径１μｍの球状単分散銅微粉末を酸素濃度が３．０ｗｔ％まで酸化させた酸化膜銅粉であることを除き、実施例１０と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．２７ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 13) Except that the oxide film copper powder used was an oxide film copper powder obtained by oxidizing a spherical monodispersed copper fine powder having an average particle diameter of 1 µm to an oxygen concentration of 3.0 wt%. The heat treatment was performed under exactly the same conditions. The tap density after crushing and sieving was 3.27 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例１４）再現性を調べるために実施例２と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．５６ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 14) In order to examine reproducibility, heat treatment was performed under exactly the same conditions as in Example 2. The tap density after crushing and sieving was 3.56 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例１５）再現性を調べるために実施例１３と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．３４ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．１１ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 15) In order to examine reproducibility, heat treatment was performed under exactly the same conditions as in Example 13. The tap density after crushing and sieving was 3.34 g / cm 3 . Further, the concentration of carbon as an impurity was 0.11 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
上述の実施例１０〜１５は、図４(Ａ)にも示すように、熱処理の保持温度および保持時間を一定としつつ、主に、酸化膜銅粉の酸素濃度を変更することで焼結助剤の種類を変更して、製造される凝集状態の銅粉末のタップ密度を制御するものである。この場合には、図４(Ｂ)に示すように、焼結助剤としての酸化膜銅粉の酸素濃度を上昇させることで、製造される銅粉末のタップ密度を低下させる制御をおこなうことができる。 In Examples 10 to 15 described above, as shown in FIG. 4A, the sintering aid is mainly changed by changing the oxygen concentration of the oxide film copper powder while keeping the holding temperature and holding time of the heat treatment constant. The tap density of the agglomerated copper powder to be produced is controlled by changing the type of the agent. In this case, as shown in FIG. 4 (B), it is possible to control to lower the tap density of the produced copper powder by increasing the oxygen concentration of the oxide film copper powder as the sintering aid. it can.
（実施例１６）図１に示すように、湿式法にて製造した、タップ密度が４．８８ｇ／ｃｍ３で平均粒径７μｍの球状単分散銅微粉末１９ｇと、実施例１１で使用したと同一の、酸素濃度０．７５ｗｔ％の酸化膜銅粉１ｇとを充分均一になるように混合・分散させ、これを磁製皿に取り分け、水素雰囲気中１時間で３４０℃まで昇温し、その温度を５時間保持する条件で熱処理をおこなった。解砕・篩がけ後のタップ密度は３．６９ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．０９ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 Example 16 As shown in FIG. 1, 19 g of spherical monodispersed copper fine powder produced by a wet method and having a tap density of 4.88 g / cm 3 and an average particle size of 7 μm was used in Example 11. 1 g of oxide film copper powder having the same oxygen concentration of 0.75 wt% was mixed and dispersed so as to be sufficiently uniform, and this was separated into a porcelain dish and heated to 340 ° C. in a hydrogen atmosphere for 1 hour. Heat treatment was performed under the condition of maintaining the temperature for 5 hours. The tap density after crushing and sieving was 3.69 g / cm 3 . The concentration of carbon as an impurity was 0.09 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例１７）熱処理の保持温度が４００℃、４時間保持であることを除き、実施例１６と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は３．６５ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．０９ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 17) A heat treatment was performed under exactly the same conditions as in Example 16 except that the heat treatment was held at 400 ° C for 4 hours. The tap density after crushing and sieving was 3.65 g / cm 3 . The concentration of carbon as an impurity was 0.09 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
（実施例１８）熱処理の保持温度が５００℃、２時間保持であることを除き、実施例１６と全く同一条件の熱処理をおこなった。解砕・篩がけ後のタップ密度は２．４６ｇ／ｃｍ３であった。また、不純物としての炭素の濃度は０．０９ｗｔ％であり、銅および酸素以外の不純物（炭素およびその他の不純物）濃度は、０．２ｗｔ％以下であった。 (Example 18) A heat treatment was performed under exactly the same conditions as in Example 16 except that the heat treatment was held at 500 ° C for 2 hours. The tap density after crushing and sieving was 2.46 g / cm 3 . The concentration of carbon as an impurity was 0.09 wt%, and the concentration of impurities (carbon and other impurities) other than copper and oxygen was 0.2 wt% or less.
これらの実施例１６〜１８は、銅微粉末元粉の平均粒子径を７μｍとし、同一種類の焼結助剤を使用し、熱処理の保持温度と保持時間をともに変更して、製造される銅粉末のタップ密度を制御するものである。この場合には、熱処理の保持温度を上昇させ、これに応じて保持時間を減少させることで、製造される銅粉末のタップ密度を低下させる制御をおこなうことができる。 In these Examples 16 to 18, the average particle size of the copper fine powder base powder is 7 μm, the same kind of sintering aid is used, and both the holding temperature and holding time of the heat treatment are changed, and the produced copper It controls the tap density of the powder. In this case, it is possible to control to lower the tap density of the produced copper powder by raising the holding temperature of the heat treatment and reducing the holding time accordingly.
尚、各実施例においては、磁製皿に銅微粉末元粉等のサンプルを２０ｇ取り分けるものを述べたが、この磁製皿よりも大きく、且つ不純物混入の恐れがない耐熱容器を前記磁製皿の代わりに使用し、また、ミキサーや解砕機、振動篩などの自動機器を使用することで、銅粉末を工業的規模で生産することが可能である。 In each of the examples, 20 g of a sample such as a copper fine powder base powder is separated on a porcelain dish. However, a heat-resistant container that is larger than this porcelain dish and has no fear of contamination is made of the porcelain dish. Copper powder can be produced on an industrial scale by using it in place of a dish and using automatic equipment such as a mixer, a crusher, and a vibrating sieve.
この銅微粉末は導電性ペーストの他、抵抗ペーストや静電遮蔽ペーストなどの他の金属ペーストへの添加剤として、あるいは触媒材料やフィルター用材料としても使用可能である。 The copper fine powder can be used as an additive to other metal pastes such as a resistance paste and an electrostatic shielding paste, or as a catalyst material or a filter material in addition to the conductive paste.
Claims (3)
化膜を有する銅粉である焼結助剤の存在下で２００〜５５０℃の温度範囲にて熱処理することを特徴とする銅粉末の製造方法。 Copper fine powder having an average particle diameter of 1 to 10 μm is subjected to an acid containing CuO on the surface in a reducing atmosphere.
A method for producing a copper powder, comprising heat-treating in a temperature range of 200 to 550 ° C. in the presence of a sintering aid that is a copper powder having a chemical film .
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