JP6225711B2 - Copper sulfide-coated copper powder, conductive paste, and methods for producing them - Google Patents
Copper sulfide-coated copper powder, conductive paste, and methods for producing them Download PDFInfo
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本発明は、硫化銅被覆銅粉、導電ペースト及びこれら製造方法に関する。 The present invention relates to a copper sulfide-coated copper powder, a conductive paste, and a production method thereof.
近年、回路形成等の電子部品用の導電ペーストに使用される導電性金属粉として、銅、ニッケル、銀、銀−パラジウム合金等の微粒子が用いられている。これらの金属微粒子中で、特に、銅微粒子は、銀、銀−パラジウム合金等の貴金属微粒子と比較すると安価であり、かつエレクトロマイグレーションを起こしにくい素材として注目されている。 In recent years, fine particles such as copper, nickel, silver, and silver-palladium alloys have been used as conductive metal powders used in conductive pastes for electronic components such as circuit formation. Among these fine metal particles, particularly, fine copper particles are attracting attention as materials that are less expensive than precious metal fine particles such as silver and silver-palladium alloys and are less likely to cause electromigration.
しかしながら、銅微粒子は、大気中において、比較的低温で酸化が進行しやすく、このため導電性や金属光沢が低下するという欠点があり、その使用範囲が制限されていた。また、金属微粒子をフィラーとして含む導電ペーストとしては、ペースト中の金属粉末を焼結させ、配線や電極等に使用する焼成ペーストと、硬化型のポリマーで固めるポリマーペーストとに大別されるが、いずれの場合でも１５０〜３５０℃の温度で熱処理が行われることが不可欠であり、この温度領域での耐酸化性に問題があった。特に、ポリマーペーストにおいては、硬化後に常温においても徐々に水分が進行することで酸化が進行する。これは耐湿性という問題で長期の信頼性においては大きな課題で、耐酸化性や耐湿性を向上させる手段が求められていた。 However, the copper fine particles tend to oxidize at a relatively low temperature in the atmosphere, and thus have a drawback that the conductivity and the metallic luster are lowered, and the use range thereof is limited. In addition, the conductive paste containing fine metal particles as a filler is roughly classified into a fired paste used to sinter the metal powder in the paste and used for wiring and electrodes, and a polymer paste hardened with a curable polymer. In any case, it is indispensable that the heat treatment is performed at a temperature of 150 to 350 ° C., and there is a problem in oxidation resistance in this temperature range. In particular, in the polymer paste, the oxidation proceeds as the moisture gradually proceeds even at room temperature after curing. This is a problem of moisture resistance, which is a big problem in long-term reliability, and means for improving oxidation resistance and moisture resistance has been demanded.
そこで、酸化物で被覆された金属微粒子を用いることが考えられる。例えば、金属粉末原料と、この金属粉末原料の主成分となる金属元素を主成分として含まない酸化物又は複酸化物又は酸素酸の塩の粉末原料とを混合し、得られた原料混合物を熱プラズマに供給して気相状態の混合物にした後、この気相状態の混合物を急冷して、前記金属粉末原料より微細化された金属微粒子を芯粒子とし、前記酸化物又は複酸化物又は酸素酸の塩、もしくは前記酸化物又は複酸化物又は酸素酸の塩と前記金属の酸化物との複酸化物又は複塩からなる、前記芯粒子を被覆する被覆層を形成することが提案されている（特許文献１参照）。また、酸化物被覆層中に貴金属等を含有させることにより、比抵抗を下げつつ、かつ耐酸化性を付与することが提案されている（特許文献２）。 Therefore, it is conceivable to use metal fine particles coated with an oxide. For example, a metal powder raw material and an oxide or double oxide or oxygen acid salt powder raw material containing no metal element as a main component of the metal powder raw material are mixed, and the resulting raw material mixture is heated. After being supplied to plasma to form a gas phase mixture, the gas phase mixture is rapidly cooled to form fine metal particles refined from the metal powder raw material as core particles, and the oxide, double oxide or oxygen It has been proposed to form a coating layer for covering the core particles, which consists of an acid salt, or an oxide or double oxide, or a double oxide or double salt of an oxyacid salt and the metal oxide. (See Patent Document 1). Further, it has been proposed to add oxidation resistance while lowering the specific resistance by including a noble metal or the like in the oxide coating layer (Patent Document 2).
また、大気雰囲気における加熱処理若しくは湿式の化学処理を用いて、芯材の銅粉の粉粒表面を酸化銅、亜酸化銅のいずれか一種若しくはこれらの二種からなる第１無機物コート層を形成し、その後、第１無機物コート層を形成した外殻に、無機酸化物からなる第２無機物コート層を形成することが提案されている（特許文献３）。 Moreover, the 1st inorganic substance coating layer which consists of a copper oxide, a cuprous oxide, or these 2 types is formed in the powder particle surface of the copper powder of a core material using the heat processing or wet chemical process in an atmospheric condition. Thereafter, it has been proposed to form a second inorganic coat layer made of an inorganic oxide on the outer shell on which the first inorganic coat layer is formed (Patent Document 3).
加えて、銅粉の耐酸化性を高めるため、硫酸銅水溶液と硫化ナトリウム水溶液とを反応させ、硫化銅粉を製造することが提案されている（特許文献４）。この方法では、硫酸銅水溶液と当該硫化ナトリウム水溶液とを混合した反応液に含まれる銅イオンの１当量に対し、硫黄イオンを１．１当量〜３．０当量として反応させている。 In addition, in order to improve the oxidation resistance of copper powder, it has been proposed to produce a copper sulfide powder by reacting an aqueous copper sulfate solution and an aqueous sodium sulfide solution (Patent Document 4). In this method, sulfur ions are reacted at 1.1 equivalents to 3.0 equivalents with respect to 1 equivalent of copper ions contained in a reaction solution obtained by mixing a copper sulfate aqueous solution and the sodium sulfide aqueous solution.
しかしながら、特許文献１及び２に記載の方法では、製法が複雑であり、高コストになることが予想される。 However, in the methods described in Patent Documents 1 and 2, the manufacturing method is complicated, and it is expected that the cost will increase.
また、特許文献３に記載の方法では、酸化物第二層はハイブリタイザーを用いてメカノケミカル反応により被覆されており、極めて薄い膜を均一に被覆することが困難なため、金属光沢や良好な比抵抗を維持することは困難であると考えられる。例えば、用途としては低温焼成ペースト用を想定しており、粉体の耐酸化性、体積抵抗率等は調査されておらず、製造される酸化物被覆金属微粒子が金属微粒子の優れた特性を維持したまま耐酸化性を高めたものとなるか不明である。 In the method described in Patent Document 3, the oxide second layer is coated by a mechanochemical reaction using a hybridizer, and it is difficult to uniformly coat a very thin film. It is considered difficult to maintain the specific resistance. For example, it is assumed that it is used for low-temperature fired paste, and the oxidation resistance and volume resistivity of the powder have not been investigated, and the manufactured oxide-coated metal fine particles maintain the excellent characteristics of metal fine particles It is unclear whether the oxidation resistance will be improved as it is.
また、特許文献４に記載の硫化銅粉は、硫化第二銅粉であり、その電気抵抗率（１．５×１０−６Ω・ｍ）は、銅の電気抵抗率（１．５５×１０−８Ω・ｍ）の約１００倍である。そのため、導電性をさらに高めることが求められる。 Moreover, the copper sulfide powder described in Patent Document 4 is cupric sulfide powder, and its electrical resistivity (1.5 × 10 −6 Ω · m) is copper electrical resistivity (1.55 × 10 6 ). About -8 Ω · m). Therefore, it is required to further increase the conductivity.
本発明は、耐酸化性を有し、かつ、導電性に優れた導電ペーストの用に供する硫化銅被覆銅粉を低コストで提供することを目的とする。 An object of the present invention is to provide copper sulfide-coated copper powder for use in a conductive paste having oxidation resistance and excellent conductivity at low cost.
本発明者らは、上記課題を解決すべく鋭意研究を重ねた結果、硫化銅被膜の厚さが０．０１μｍ以上０．０６μｍ以下になるように、平均粒子径が０．５〜１０μｍである銅粉の表面を硫化することで、耐酸化性を有し、かつ、導電性に優れた導電ペーストの用に供する硫化銅被覆銅粉を低コストで提供できることを見出し、本発明を完成するに至った。 As a result of intensive studies to solve the above problems, the present inventors have an average particle diameter of 0.5 to 10 μm so that the thickness of the copper sulfide coating is 0.01 μm or more and 0.06 μm or less. To sulfidize the surface of the copper powder, the copper sulfide-coated copper powder used for the conductive paste having oxidation resistance and excellent conductivity can be provided at a low cost, and the present invention is completed. It came.
具体的には、本発明では、以下のようなものを提供する。 Specifically, the present invention provides the following.
（１）本発明は、表面に硫化銅被膜が形成され、平均粒子径が０．５μｍ以上１０μｍ以下であり、硫化銅被膜の厚さが０．０１μｍ以上０．０６μｍ以下である硫化銅被覆銅粉である。 (1) The present invention is a copper sulfide-coated copper having a copper sulfide film formed on the surface, an average particle diameter of 0.5 μm to 10 μm, and a copper sulfide film thickness of 0.01 μm to 0.06 μm. It is powder.
（２）また、本発明は、前記硫化銅被膜が硫化第一銅被膜である、（１）に記載の硫化銅被覆銅粉である。 (2) Moreover, this invention is a copper sulfide covering copper powder as described in (1) whose said copper sulfide film is a cuprous sulfide film.
（３）また、本発明は、（１）又は（２）に記載の硫化銅被覆銅粉と、樹脂とを含む導電ペーストである。 (3) Moreover, this invention is an electrically conductive paste containing the copper sulfide covering copper powder as described in (1) or (2), and resin.
（４）また、本発明は、平均粒子径が０．５μｍ以上１０μｍ以下である銅粉の表面を硫化し、前記銅粉の表面に硫化銅被膜を形成する硫化銅被膜形成工程を含み、前記硫化銅被膜の厚さが０．０１μｍ以上０．０６μｍ以下である、硫化銅被覆銅粉の製造方法である。 (4) Moreover, this invention includes the copper sulfide film formation process which sulfides the surface of the copper powder whose average particle diameter is 0.5 micrometer or more and 10 micrometers or less, and forms the copper sulfide film on the surface of the said copper powder, It is a manufacturing method of copper sulfide covering copper powder whose thickness of a copper sulfide coat is 0.01 micrometer or more and 0.06 micrometer or less.
（５）また、本発明は、前記硫化銅被膜形成工程が、前記硫化銅被膜が目標の厚さになるような前記銅粉の硫化前後での重量変化率をあらかじめ予測し、その予測した重量になるまで前記銅粉を硫化する工程である、（４）に記載の硫化銅被覆銅粉の製造方法である。 (5) Further, in the present invention, the copper sulfide film forming step predicts in advance the weight change rate of the copper powder before and after sulfiding so that the copper sulfide film has a target thickness, and the predicted weight. It is the manufacturing method of the copper sulfide covering copper powder as described in (4) which is the process of sulfiding the said copper powder until it becomes.
（６）また、本発明は、前記重量変化率が、１−（１−０．５２ｄ１／Ｒ）３の値にしたがって予測される、（４）又は（５）に記載の硫化銅被覆銅粉の製造方法である。式中、Ｒは前記銅粉の平均粒子径の１／２であり、ｄ１は前記硫化銅被膜の目標の厚さである。 (6) Further, the present invention, the weight change ratio, 1 is predicted in accordance with the value of (1-0.52d 1 / R) 3, (4) or (5) Copper coated copper sulphide according to It is a manufacturing method of powder. In the formula, R is ½ of the average particle diameter of the copper powder, and d 1 is the target thickness of the copper sulfide coating.
（７）また、本発明は、前記硫化銅被膜形成工程の前に前記銅粉の表面にある酸化被膜を除去する酸化被膜除去工程をさらに含む、（４）から（６）のいずれかに記載の硫化銅被覆銅粉の製造方法である。 (7) Moreover, this invention further includes the oxide film removal process of removing the oxide film in the surface of the said copper powder before the said copper sulfide film formation process, It is in any one of (4) to (6) It is a manufacturing method of copper sulfide covering copper powder.
（８）また、本発明は、前記硫化銅被膜形成工程の後に前記硫化銅被覆銅粉を２２０℃以上の温度で加熱する加熱工程をさらに含む、（４）から（７）のいずれかに記載の硫化銅被覆銅粉の製造方法である。 (8) Moreover, this invention further includes the heating process which heats the said copper sulfide coating copper powder at the temperature of 220 degreeC or more after the said copper sulfide film formation process, In any one of (4) to (7) It is a manufacturing method of copper sulfide covering copper powder.
（９）また、本発明は、（４）から（８）のいずれかに記載の硫化銅被覆銅粉の製造方法によって製造された硫化銅被覆銅粉と、樹脂とを混合する混合工程を含む、導電ペーストの製造方法である。 (9) Moreover, this invention includes the mixing process which mixes the copper sulfide covering copper powder manufactured by the manufacturing method of the copper sulfide covering copper powder in any one of (4) to (8), and resin. A method for producing a conductive paste.
本発明によると、耐酸化性を有し、かつ、導電性に優れた導電ペーストの用に供する硫化銅被覆銅粉を低コストで提供できる。 According to the present invention, copper sulfide-coated copper powder used for a conductive paste having oxidation resistance and excellent conductivity can be provided at a low cost.
以下、本発明の具体的な実施形態について詳細に説明するが、本発明は以下の実施形態に何ら限定されるものではなく、本発明の目的の範囲内において、適宜変更を加えて実施することができる。 Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. Can do.
＜硫化銅被覆銅粉１＞
図１は、本発明に係る硫化銅被覆銅粉１を説明するための概略断面図である。硫化銅被覆銅粉１は、表面に硫化銅被膜２が形成され、平均粒子径２Ｒが０．５〜１０μｍであり、硫化銅被膜２の厚さｄ１が０．０１μｍ以上０．０６μｍ以下である。
<Copper sulfide-coated copper powder 1>
FIG. 1 is a schematic cross-sectional view for explaining a copper sulfide-coated copper powder 1 according to the present invention. The copper sulfide-coated copper powder 1 has a copper sulfide film 2 formed on the surface, an average particle diameter 2R of 0.5 to 10 μm, and a thickness d 1 of the copper sulfide film 2 of 0.01 μm or more and 0.06 μm or less. is there.
本発明では、表面に硫化銅被膜２が形成されていることを要する。硫化銅被膜２のない銅粉の状態であると、もともと優れた導電性を有するものの、短期間で酸化するため、一定期間が経過すると、本発明の硫化銅被覆銅粉１よりも導電性が劣るため、好ましくない。また、被膜が酸化被膜であると、本発明の硫化銅被覆銅粉１に比べて導電性が著しく劣るため、好ましくない。 In this invention, it is required that the copper sulfide film 2 is formed on the surface. In the state of copper powder without the copper sulfide coating 2, it originally has excellent conductivity, but since it oxidizes in a short period of time, the conductivity is higher than that of the copper sulfide-coated copper powder 1 of the present invention after a certain period of time. Since it is inferior, it is not preferable. Moreover, since an electroconductivity is remarkably inferior compared with the copper sulfide covering copper powder 1 of this invention as a film is an oxide film, it is unpreferable.
また、硫化銅被覆銅粉１の平均粒子径２Ｒは０．５μｍ以上１０μｍ以下であり、１．０μｍ以上５．０μｍ以下であることがより好ましい。平均粒子径２Ｒが小さすぎると、硫化銅被覆銅粉１を導電性ペーストとして利用する場合に、ペーストの粘性が高くなり得るため、好ましくない。平均粒子径２Ｒが大きすぎると、ペーストで配線を形成する場合に配線が太くなるため細線を求める用途には利用できなくなるため、好ましくない。なお、本明細書において、平均粒子径２Ｒは、レーザー粒度分布測定器マクロトラック（日機装社製）を用いて測定した、体積球相当径によるものとする。 Moreover, the average particle diameter 2R of the copper sulfide-coated copper powder 1 is 0.5 μm or more and 10 μm or less, and more preferably 1.0 μm or more and 5.0 μm or less. If the average particle diameter 2R is too small, the viscosity of the paste may increase when the copper sulfide-coated copper powder 1 is used as a conductive paste, which is not preferable. If the average particle diameter 2R is too large, the wiring becomes thick when the wiring is formed with a paste, so that it cannot be used for the purpose of obtaining a thin line, which is not preferable. In this specification, the average particle diameter 2R is based on a volume sphere equivalent diameter measured using a laser particle size distribution measuring instrument Macrotrac (manufactured by Nikkiso Co., Ltd.).
また、本発明では、硫化銅被膜２の厚さｄ１が０．０１μｍ以上０．０６μｍ以下であり、０．０１μｍ以上０．０５μｍ以下であることがより好ましく、０．０１μｍ以上０．０３μｍ以下であることが特に好ましい。硫化銅被膜２が薄すぎると、十分な耐酸化特性を有しない可能性があり、好ましくない。硫化第二銅の電気抵抗率は１．５×１０−６Ω・ｍであり、銅の電気抵抗率（１．５５×１０−８Ω・ｍ）の約１００倍である。硫化銅被膜２が厚すぎると、十分な導電性を有しない可能性があり、好ましくない。 In the present invention, the thickness d 1 of the copper sulfide coating 2 is 0.01 μm or more and 0.06 μm or less, more preferably 0.01 μm or more and 0.05 μm or less, and 0.01 μm or more and 0.03 μm or less. It is particularly preferred that If the copper sulfide coating 2 is too thin, it may not have sufficient oxidation resistance, which is not preferable. The electrical resistivity of cupric sulfide is 1.5 × 10 −6 Ω · m, which is about 100 times the electrical resistivity of copper (1.55 × 10 −8 Ω · m). If the copper sulfide coating 2 is too thick, it may not have sufficient conductivity, which is not preferable.
硫化銅被膜２の厚さは、硫化銅被覆銅粉１を切断し、切断面を研磨して平滑にした後、走査電子顕微鏡画像（ＳＥＭ画像）を観察することによって測定できる。 The thickness of the copper sulfide coating 2 can be measured by observing a scanning electron microscope image (SEM image) after cutting the copper sulfide-coated copper powder 1 and polishing and smoothing the cut surface.
硫化銅被膜２は、硫化第一銅被膜であっても硫化第二銅被膜であってもよいが、硫化第二銅は空気中の水分によって硫酸銅を徐々に生成するため、より高い安定性を得られる点で硫化第一銅被膜であることが好ましい。 The copper sulfide coating 2 may be a cuprous sulfide coating or a cupric sulfide coating, but since cupric sulfide gradually produces copper sulfate by moisture in the air, it has higher stability. It is preferable that it is a cuprous sulfide film at the point which can be obtained.
＜導電ペースト＞
本発明の導電ペーストは、上記硫化銅被覆銅粉１と、樹脂とを含む。樹脂の種類は特に限定されるものでなく、フェノール樹脂、ポリアセタール樹脂等、導電ペーストで用いられる樹脂を広く利用できる。また、本発明の導電ペーストは、本発明の効果を損なわない範囲で、溶剤、可塑剤、潤滑剤、分散剤、帯電防止剤等を含むものであってもよい。
<Conductive paste>
The conductive paste of the present invention includes the copper sulfide-coated copper powder 1 and a resin. The kind of resin is not particularly limited, and resins used in conductive pastes such as phenol resins and polyacetal resins can be widely used. In addition, the conductive paste of the present invention may contain a solvent, a plasticizer, a lubricant, a dispersant, an antistatic agent and the like as long as the effects of the present invention are not impaired.
本発明に係る導電ペーストを、厚さが乾燥膜厚で０．０２ｍｍになるように、金属スキージでガラス上に印刷し、大気雰囲気中にて２００℃で３０分間硬化させることによって得られる被膜の電気抵抗率は、１．０×１０−３Ω・ｃｍ以下である。そのため、本発明に係る導電ペーストは、極めて高い導電性を有するといえる。特に、硫化銅被膜２の厚さｄ１が０．０４μｍ以上０．０６μｍ以下であると、電気抵抗率が２．０×１０−４Ω・ｃｍ以下であり、硫化銅被膜２の厚さｄ１が０．０１μｍ以上０．０３μｍ以下であると、電気抵抗率が１．０×１０−４Ω・ｃｍ以下であるため、より好ましい。 The conductive paste according to the present invention is printed on a glass with a metal squeegee so that the thickness is 0.02 mm as a dry film thickness, and the coating obtained by curing at 200 ° C. for 30 minutes in an air atmosphere. The electrical resistivity is 1.0 × 10 −3 Ω · cm or less. Therefore, it can be said that the conductive paste according to the present invention has extremely high conductivity. In particular, when the thickness d 1 of the copper sulfide coating 2 is 0.04 μm or more and 0.06 μm or less, the electrical resistivity is 2.0 × 10 −4 Ω · cm or less, and the thickness d 1 of the copper sulfide coating 2 is It is more preferable that 1 is 0.01 μm or more and 0.03 μm or less because the electrical resistivity is 1.0 × 10 −4 Ω · cm or less.
加えて、硫化銅被膜２が硫化第一銅被膜であると、導電ペーストを硬化させた後の被膜を高温多湿下で放置しても高い導電性を保ち続けられる点で好ましい。 In addition, it is preferable that the copper sulfide coating 2 is a cuprous sulfide coating in that high conductivity can be maintained even if the coating after the conductive paste is cured is left under high temperature and high humidity.
＜硫化銅被覆銅粉の製造方法＞
以下、図２を参照しながら、硫化銅被覆銅粉１の製造工程について説明する。本発明は、少なくとも、平均粒子径が０．５μｍ以上１０μｍ以下である銅粉の表面を硫化し、銅粉の表面に硫化銅被膜２を形成する硫化銅被膜形成工程Ｓ４を含む。
<Method for producing copper sulfide-coated copper powder>
Hereinafter, the manufacturing process of the copper sulfide-coated copper powder 1 will be described with reference to FIG. The present invention includes at least a copper sulfide film forming step S4 in which the surface of a copper powder having an average particle diameter of 0.5 μm or more and 10 μm or less is sulfided to form a copper sulfide film 2 on the surface of the copper powder.
また、必須ではないが、本発明は、硫化銅被膜形成工程Ｓ４の前に銅粉の表面にある酸化被膜を除去する酸化被膜除去工程Ｓ３をさらに含むことが好ましい。また、硫化銅被膜形成工程Ｓ４の後に硫化銅被覆銅粉１を２２０℃以上の温度で加熱する加熱工程Ｓ５をさらに含むことが好ましい。以下、硫化銅被覆銅粉１の製造工程について、順を追って説明する。 Although not essential, the present invention preferably further includes an oxide film removing step S3 for removing the oxide film on the surface of the copper powder before the copper sulfide film forming step S4. Moreover, it is preferable that heating process S5 which heats copper sulfide covering copper powder 1 at the temperature of 220 degreeC or more is further included after copper sulfide film formation process S4. Hereinafter, the manufacturing process of the copper sulfide-coated copper powder 1 will be described in order.
〔電解工程Ｓ１〕
電解工程Ｓ１は、硫酸銅溶液中で銅の電気分解を行うことによって電極表面に電解銅粉を析出させ、回収する工程である。電解銅粉は、例えば、ＣｕＳＯ４・５Ｈ２Ｏ：５〜８０ｇ／Ｌ、遊離Ｈ２ＳＯ４：５０〜２５０ｇ／Ｌの浴組成で、電流密度５〜３０Ａ／ｄｍ２、浴温２０〜６５℃の条件で電解し、陰極上に電析させることによって製造できる。
[Electrolysis step S1]
The electrolysis process S1 is a process of depositing and collecting electrolytic copper powder on the electrode surface by performing electrolysis of copper in a copper sulfate solution. Electrolytic copper powder, for example, CuSO 4 · 5H 2 O: 5~80g / L, free H 2 SO 4: in bath composition of 50 to 250 g / L, current density 5~30A / dm 2, a bath temperature of 20 to 65 It can be produced by electrolysis under the condition of ° C. and electrodepositing on the cathode.
〔粉砕工程Ｓ２〕
粉砕工程Ｓ２は、電解工程Ｓ１で得られた電解銅粉を粉砕して銅微粉末にする工程である。
[Crushing step S2]
The pulverization step S2 is a step of pulverizing the electrolytic copper powder obtained in the electrolysis step S1 into a copper fine powder.
電解銅粉を粉砕する方法は特に限定されるものでないが、製造コストや効率等を考慮すると、ジェットミル、サイクロンミル等を利用し、流体中で原料粉同士を衝突又は衝突板に衝突させて粉砕させることが好ましい。また、量産コストを考慮すると、空気雰囲気下で処理することが好ましい。粉砕装置のほか、さらに分級装置を用い、生産をより効率的にしてもよい。 The method of pulverizing the electrolytic copper powder is not particularly limited, but considering the manufacturing cost and efficiency, etc., using a jet mill, a cyclone mill, etc., the raw material powder collides with each other or collides with the collision plate. It is preferable to grind. Moreover, when mass production cost is considered, it is preferable to process in an air atmosphere. In addition to the pulverizer, a classifier may be used to make production more efficient.
〔酸化被膜除去工程Ｓ３〕
酸化被膜除去工程Ｓ３は、銅粉の表面にある酸化被膜を除去する工程である。電解銅粉を空気雰囲気下で粉砕すると、電解銅粉を粉砕する間に、銅粉の表面に酸化被膜が形成される。酸化銅は硫化銅に比べて導電性が著しく劣るため、銅粉を硫化する前に酸化被膜を除去することが好ましい。
[Oxide film removal step S3]
The oxide film removal step S3 is a step of removing the oxide film on the surface of the copper powder. When the electrolytic copper powder is pulverized in an air atmosphere, an oxide film is formed on the surface of the copper powder while the electrolytic copper powder is pulverized. Since copper oxide is remarkably inferior to copper sulfide, it is preferable to remove the oxide film before sulfiding the copper powder.
具体的な除去方法は特に特定させるものではなく、酸化被膜を水素による還元反応に付し、酸化被膜を金属銅に変化させてもよいし、酸化被膜を化学的に溶解してもよい。酸化被膜を溶解する溶液として、硫酸、塩酸、硝酸等の酸溶液が挙げられる。中でも、酸化銅を溶解するが、銅を溶解しない点で、硫酸又は塩酸を用いることが好ましい。 The specific removal method is not particularly specified, and the oxide film may be subjected to a reduction reaction with hydrogen to change the oxide film to metallic copper, or the oxide film may be chemically dissolved. Examples of the solution for dissolving the oxide film include acid solutions such as sulfuric acid, hydrochloric acid, and nitric acid. Among them, it is preferable to use sulfuric acid or hydrochloric acid because it dissolves copper oxide but does not dissolve copper.
〔硫化銅被膜形成工程Ｓ４〕
硫化銅被膜形成工程Ｓ４は、酸化被膜を除去した後の銅粉の表面を硫化し、銅粉の表面に硫化第二銅被膜を形成する工程である。硫化反応に付す手法として、銅粉を硫化水素等の気体に接触させることのほか、銅粉を硫化アンモニウム、硫化カリウム、硫化ナトリウムの溶液に浸漬すること等が挙げられる。
[Copper sulfide coating forming step S4]
The copper sulfide coating forming step S4 is a step of sulfiding the surface of the copper powder after removing the oxide coating and forming a cupric sulfide coating on the surface of the copper powder. As a method for subjecting the sulfurization reaction, in addition to contacting the copper powder with a gas such as hydrogen sulfide, the copper powder is immersed in a solution of ammonium sulfide, potassium sulfide, or sodium sulfide.
上記したとおり、本発明では、酸化被膜の厚さを好適な範囲内にする必要があり、酸化被膜は、薄すぎても厚すぎても好適でない。しかしながら、被膜形成後の被覆銅粉を切断し、切断面を研磨して平滑にした後、走査電子顕微鏡画像（ＳＥＭ画像）を観察しなければ、酸化被膜の厚さを測定できない。そのため、銅粉の表面を硫化する間に被膜の厚さを好適に制御することは極めて難しい。 As described above, in the present invention, it is necessary to make the thickness of the oxide film within a suitable range, and it is not preferable that the oxide film is too thin or too thick. However, the thickness of the oxide film cannot be measured without observing a scanning electron microscope image (SEM image) after cutting the coated copper powder after forming the film and polishing and smoothing the cut surface. Therefore, it is extremely difficult to suitably control the thickness of the coating while sulfiding the surface of the copper powder.
本発明の好適な特徴として、硫化銅被膜２が目標の厚さになるような銅粉の硫化前後での重量変化率をあらかじめ予測し、その予測した重量になるまで銅粉を硫化することが挙げられる。 As a preferred feature of the present invention, the weight change rate of the copper powder before and after sulfiding so that the copper sulfide film 2 has a target thickness is predicted in advance, and the copper powder is sulfided until the predicted weight is reached. Can be mentioned.
このことについて、図１及び図３を参照しながら、より詳しく説明する。 This will be described in more detail with reference to FIGS.
図３に示すとおり、銅微粒子１１の平均粒子径を２Ｒとし、硫化しようとする銅の膜厚をｄとすると、硫化処理する前の銅微粒子１１の体積ＶＣｕは、（１）式で表すことができ、硫化処理後の硫化銅部分１２の体積ＶＣｕＳは、（２）式で表すことができる。
ＶＣｕ＝４／３πＲ３・・・・（１）
ＶＣｕＳ＝４／３πＲ３−４／３π（Ｒ−ｄ）３・・・・（２）
As shown in FIG. 3, when the average particle diameter of the copper fine particles 11 is 2R and the film thickness of the copper to be sulfided is d, the volume V Cu of the copper fine particles 11 before the sulfidation treatment is expressed by the equation (1). The volume V CuS of the copper sulfide portion 12 after the sulfidation treatment can be expressed by equation (2).
V Cu = 4 / 3πR 3 (1)
V CuS = 4 / 3πR 3 -4 / 3π (Rd) 3 (2)
すなわち、ＶＣｕＳのＶＣｕに対する比をｒａとすると、ｒａは（３）式で表すことができる。
ｒａ＝ＶＣｕＳ／ＶＣｕ＝１−（Ｒ−ｄ）３／Ｒ３・・・・（３）
In other words, if the ratio of V CuS to V Cu is ra, ra can be expressed by equation (3).
ra = V CuS / V Cu = 1− (R−d) 3 / R 3 ... (3)
この（３）式から、ｄのＲに対する比ｄ／Ｒを導出すると、（４）式で表すことができる。
ｄ／Ｒ＝１−（１−ｒａ）１／３・・・・（４）
If the ratio d / R of d to R is derived from this equation (3), it can be expressed by equation (4).
d / R = 1- (1-ra) 1/3 (4)
ここで、銅の比重は８．９ｇ／ｃｍ３であり、硫化第二銅の比重は４．６ｇ／ｃｍ３であるため、銅が硫化第二銅に変化すると、図１に示すとおり、比重差の分だけ被膜２が厚くなる。これを考慮すると、ｄと、硫化後の硫化第二銅の被膜厚ｄ１との関係は（５）式のとおりとなり、この（５）式を（４）式に代入することで、（６）式が得られる。
ｄ＝４．６／８．９×ｄ１＝０．５２ｄ１・・・・（５）
０．５２ｄ１／Ｒ＝１−（１−ｒａ）１／３・・・・（６）
Here, since the specific gravity of copper is 8.9 g / cm 3 and the specific gravity of cupric sulfide is 4.6 g / cm 3 , when copper is changed to cupric sulfide, the specific gravity is as shown in FIG. The coating 2 becomes thicker by the difference. With this in mind, and d, the relationship between the film thickness d 1 of the sulfide cupric after sulfurization be as (5), by substituting the equation (5) to (4), (6 ) Formula is obtained.
d = 4.6 / 8.9 × d 1 = 0.52d 1 (5)
0.52d 1 / R = 1- (1-ra) 1/3 (6)
そして、この（６）式をｒａについての式に変形すると、（７）式が得られる。
ｒａ＝１−（１−０．５２ｄ１／Ｒ）３・・・・（７）
Then, when this equation (6) is transformed into an equation for ra, equation (7) is obtained.
ra = 1- (1-0.52d 1 / R) 3 (7)
例えば、平均粒子径が５μｍである銅微粒子において、厚さ０．０５μｍの硫化銅被膜２を形成しようとすると、体積比ｒａは０．０３０となる。 For example, when a copper sulfide film 2 having a thickness of 0.05 μm is formed on copper fine particles having an average particle diameter of 5 μm, the volume ratio ra is 0.030.
ｒａは、硫化処理する前の銅微粒子の体積ＶＣｕと、硫化処理後の硫化銅部分の体積ＶＣｕＳとの比を示すほか、硫化前後での重量変化率を示すともいえる。例えば、ｒａが０．０３１である場合、硫化前後で重量が３．１％変化するといえる。このことから、硫化処理前後での重量変化を管理することで、硫化しようとする銅微粒子の平均粒子径ごとの硫化被膜の平均厚さを管理できるといえる。 It can be said that ra indicates the ratio of the volume V Cu of the copper fine particles before the sulfidation treatment and the volume V CuS of the copper sulfide portion after the sulfidation treatment, as well as the weight change rate before and after the sulfidation . For example, when ra is 0.031, it can be said that the weight changes by 3.1% before and after sulfiding. From this, it can be said that the average thickness of the sulfide film for each average particle diameter of the copper fine particles to be sulfided can be managed by managing the weight change before and after the sulfurization treatment.
したがって、硫化前後の重量変化を管理すれば、被膜の厚さを実際に測定することなく、被膜の厚さを好適に制御できる。 Therefore, if the weight change before and after sulfiding is managed, the thickness of the coating can be suitably controlled without actually measuring the thickness of the coating.
〔加熱工程Ｓ５〕
加熱工程Ｓ５は、硫化銅被覆銅粉１を２２０℃以上の温度で加熱する工程である。硫化第二銅は、湿った空気中では徐々に酸化されて硫酸銅を生成する。そして、硫化第二銅が硫酸銅に変化すると導電性が低下する。硫化銅被覆銅粉１を車載装置等での導電性材料として用いる場合、車載装置等では、高い耐湿性が求められるため、硫化第二銅からより安定性の高い硫酸第一銅に変化させることが好ましい。そのため、特に、高い耐湿性が求められる場合において、硫化銅被膜形成工程Ｓ４の後に加熱工程Ｓ５を行うことが好ましい。
[Heating step S5]
The heating step S5 is a step of heating the copper sulfide-coated copper powder 1 at a temperature of 220 ° C. or higher. Cupric sulfide is gradually oxidized in moist air to produce copper sulfate. And if cupric sulfide changes to copper sulfate, conductivity will fall. When copper sulfide-coated copper powder 1 is used as a conductive material in an in-vehicle device or the like, since the in-vehicle device or the like requires high moisture resistance, change from cupric sulfide to more stable cuprous sulfate. Is preferred. Therefore, particularly when high moisture resistance is required, it is preferable to perform the heating step S5 after the copper sulfide film forming step S4.
加熱温度は２２０℃以上であれば特に限定されるものでないが、粉砕した微粒子が凝集することを防ぐため、５００℃以下であることが好ましい。また、より速い反応を低コストで行うため、加熱温度を２５０℃以上４５０℃以下にすることがより好ましく、３００℃以上４００℃以下にすることがさらに好ましい。加熱温度が低すぎると、硫化第二銅から硫化第一銅への分解反応が生じないため、好ましくない。 The heating temperature is not particularly limited as long as it is 220 ° C or higher, but is preferably 500 ° C or lower in order to prevent the pulverized fine particles from aggregating. In order to perform a faster reaction at a low cost, the heating temperature is more preferably 250 ° C. or higher and 450 ° C. or lower, and further preferably 300 ° C. or higher and 400 ° C. or lower. When the heating temperature is too low, a decomposition reaction from cupric sulfide to cuprous sulfide does not occur, which is not preferable.
加熱する方法は、特に限定されるものでなく、硫化第二銅被覆銅微粉を炉内に投入した後に温度を徐々に上昇させるようにしてもよいし、所定の温度に調整された炉内に電解銅粉を投入するようにしてもよい。加熱する時間は、硫化第二銅被覆銅微粉の粒子径や処理量及び被覆した硫化第二銅の厚さ等によって適宜選択できる。また、加熱処理する設備は、温度制御できれば良く、公知の管状炉やボックス炉、ロータリーキルン等を用いることができる。また、加熱処理設備には発生ガスや粉塵を回収する装備を備えることで環境への負荷を少なくできる。 The method of heating is not particularly limited, and the temperature may be gradually increased after the cupric sulfide-coated copper fine powder is put into the furnace, or the furnace is adjusted to a predetermined temperature. You may make it throw in electrolytic copper powder. The heating time can be appropriately selected depending on the particle diameter and the processing amount of the cupric sulfide-coated copper fine powder, the thickness of the coated cupric sulfide, and the like. Moreover, the heat-treatment equipment should just be temperature-controllable, A well-known tubular furnace, a box furnace, a rotary kiln etc. can be used. In addition, it is possible to reduce the environmental load by providing the heat treatment equipment with equipment for collecting generated gas and dust.
＜導電ペーストの製造方法＞
導電ペーストは、上記硫化銅被覆銅粉１の製造方法によって製造された硫化銅被覆銅粉１を樹脂と混合することによって得られる。
<Method for producing conductive paste>
The conductive paste is obtained by mixing the copper sulfide-coated copper powder 1 produced by the method for producing the copper sulfide-coated copper powder 1 with a resin.
〔樹脂混合工程Ｓ６〕
樹脂混合工程Ｓ６の態様は特に限定されるものでなく、従来公知の混合方法で混合すればよい。例えば、ニーダーのよる混合、３本ロールミルでの混合等が挙げられる。
[Resin mixing step S6]
The aspect of resin mixing process S6 is not specifically limited, What is necessary is just to mix by a conventionally well-known mixing method. For example, mixing with a kneader, mixing with a three roll mill, and the like can be mentioned.
以下、実施例により、本発明をさらに詳細に説明するが、本発明はこれらの記載に何ら制限を受けるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention does not receive a restriction | limiting at all in these description.
＜実施例＞
〔電解工程Ｓ１〕
まず、ＣｕＳＯ４・５Ｈ２Ｏ濃度が８ｇ／Ｌであり、遊離Ｈ２ＳＯ４濃度が５５ｇ／Ｌである浴組成で、通電電流密度が１０Ａ／ｄｍ２であり、浴温が２５℃であるという条件下で電解銅粉を作製した。回収した電解銅粉の走査電子顕微鏡（ＳＥＭ）画像を図４に示す。
<Example>
[Electrolysis step S1]
First, the bath composition has a CuSO 4 .5H 2 O concentration of 8 g / L, a free H 2 SO 4 concentration of 55 g / L, an energization current density of 10 A / dm 2 , and a bath temperature of 25 ° C. Electrolytic copper powder was produced under the conditions. A scanning electron microscope (SEM) image of the recovered electrolytic copper powder is shown in FIG.
〔粉砕工程Ｓ２〕
回収した電解銅粉を、表１に示す粉砕装置で粉砕した。表１において、サイクロンミルは、サイクロンミル１５０Ｗ（静岡プラント社製）である。サイクロンミルを用いたときの粉砕条件は、空気雰囲気下、主軸回転数が表１に示す値である。粉砕後、レーザー粒度分布測定器マクロトラック（日機装社製）を用い、体積球相当径による平均粒子径を測定した。結果を表１に示す。
[Crushing step S2]
The recovered electrolytic copper powder was pulverized with a pulverizer shown in Table 1. In Table 1, the cyclone mill is a cyclone mill 150W (manufactured by Shizuoka Plant). The pulverization conditions when using a cyclone mill are the values shown in Table 1 for the spindle speed in an air atmosphere. After pulverization, an average particle diameter by the equivalent volume sphere diameter was measured using a laser particle size distribution measuring device Macrotrac (made by Nikkiso Co., Ltd.). The results are shown in Table 1.
また、表１において、ジェットミルは、ナノグラインディングミルＮＪ−５０（徳寿工作所社製）である。ジェットミルを用いたときの粉砕条件は、空気雰囲気下、粉砕圧力が１Ｍｐａである。そして、実施例５については、より粒子径を細かくするため、粉砕回数を４回に増やして粉砕した。そして、粉砕後、上記マクロトラックを用い、平均粒子径を測定した。結果を表１に示す。 In Table 1, the jet mill is a nano grinding mill NJ-50 (manufactured by Deoksugaku Kosakusha). The pulverization condition when using a jet mill is that the pulverization pressure is 1 Mpa in an air atmosphere. And about Example 5, in order to make a particle diameter finer, it grind | pulverized by increasing the frequency | count of grinding | pulverization to 4 times. And after grinding | pulverization, the said average particle diameter was measured using the said macro track. The results are shown in Table 1.
〔酸化被膜除去工程Ｓ３〕
次に、粉砕した銅微粉末の表面の酸化被膜を除去するため、粉砕後の銅粉を０．５ｇ／Ｌの希硫酸で溶解して酸化被膜を除去し、純水で十分洗浄した。
[Oxide film removal step S3]
Next, in order to remove the oxide film on the surface of the pulverized copper fine powder, the pulverized copper powder was dissolved in 0.5 g / L dilute sulfuric acid to remove the oxide film, and washed sufficiently with pure water.
〔硫化銅被膜形成工程Ｓ４〕
その後、硫化アンモニウムの１０％水溶液を用いて室温で１分〜１０分間撹拌しながら浸漬したあと、吸引ろ過して銅粉を回収、そのままの空気中に放置することで銅表面に硫化銅の被膜が形成された。空気中に放置する時間は３０秒で硫化反応が終了するため、ここでは十分な放置時間にするため、1分以上放置した後、それを十分な純水で水洗してから乾燥することで硫化処理を行った。これにより、実施例１〜６及び比較例１に係る硫化銅被覆銅粉を得た。
[Copper sulfide coating forming step S4]
Then, after being immersed in a 10% aqueous solution of ammonium sulfide at room temperature for 1 to 10 minutes with stirring, the copper powder is recovered by suction filtration and left in the air as it is to form a copper sulfide coating on the copper surface. Formed. Since the sulfidation reaction is completed in 30 seconds, the sulfurization reaction is completed in this case. Therefore, in order to make the time sufficient for this purpose, leave it for 1 minute or more, then wash it with enough pure water and dry it. Processed. Thereby, the copper sulfide covering copper powder concerning Examples 1-6 and comparative example 1 was obtained.
この方法で硫化処理した硫化銅被覆銅粉をエポキシ樹脂に埋め込み、これをダイヤモンドカッターで切断し、切断面をサンドペーパーで研磨して平滑にした後、平滑面を走査電子顕微鏡画像（ＳＥＭ画像）で観察した。そして、各々２０個の粒子について、粒子１個あたり４箇所の硫化被膜の厚さを測定した。結果を表２に示す。 Copper sulfide-coated copper powder that has been sulfurized by this method is embedded in an epoxy resin, cut with a diamond cutter, and the cut surface is polished and smoothed with sandpaper, and then the smooth surface is scanned with an electron microscope image (SEM image). Observed at. And about 20 particle | grains, the thickness of the sulfide film of 4 places per particle | grain was measured. The results are shown in Table 2.
〔加熱工程Ｓ５〕
実施例６に係る硫化銅被覆銅粉について、空気雰囲気下で３００℃、３時間熱処理した。
[Heating step S5]
The copper sulfide-coated copper powder according to Example 6 was heat-treated at 300 ° C. for 3 hours in an air atmosphere.
〔樹脂混合工程Ｓ６〕
実施例１〜６及び比較例１に係る硫化銅被覆銅粉８５重量部に、フェノール樹脂（製品名：ＰＬ−２２１１、群栄化学社製）１５重量部、ブチルセロソルブ（製品名：鹿特級、関東化学社製）１０重量部を混合し、小型ニーダー（装置名：ノンバブリングニーダーＮＢＫ−１、日本精機製作所社製）を用い、１２００ｒｐｍ、３分間の混錬を３回繰り返すことでペースト化した。これにより、実施例１〜６及び比較例１に係る導電ペーストを得た。
[Resin mixing step S6]
85 parts by weight of copper sulfide-coated copper powder according to Examples 1 to 6 and Comparative Example 1, 15 parts by weight of phenol resin (product name: PL-2211, manufactured by Gunei Chemical Co., Ltd.), butyl cellosolve (product names: deer special grade, Kanto) (Chemical Co., Ltd.) 10 parts by weight was mixed, and using a small kneader (device name: non-bubbling kneader NBK-1, manufactured by Nippon Seiki Seisakusho Co., Ltd.), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. Thereby, the electrically conductive paste which concerns on Examples 1-6 and the comparative example 1 was obtained.
＜比較例２＞
濃度が１２５ｇ／ＬであるＣｕＳＯ４・５Ｈ２Ｏ溶液５Ｌに、濃度が１００ｇ／Ｌである硫化ナトリウム溶液４Ｌを徐々に添加し、硫化第二銅の沈殿物を生成させた。硫化第二銅の平均粒子径を測定したところ、平均粒子径は０．１μｍであった。
<Comparative example 2>
4 L of a sodium sulfide solution having a concentration of 100 g / L was gradually added to 5 L of a CuSO 4 .5H 2 O solution having a concentration of 125 g / L, thereby producing a precipitate of cupric sulfide. When the average particle diameter of cupric sulfide was measured, the average particle diameter was 0.1 μm.
そして、上記硫化第二銅に対し、上記〔樹脂混合工程Ｓ６〕と同じ処理を行うことで、比較例２に係る導電ペーストを得た。 And the electrically conductive paste which concerns on the comparative example 2 was obtained by performing the same process as said [resin mixing process S6] with respect to the said cupric sulfide.
＜評価その１：導電性＞
実施例及び比較例に係る導電ペーストを、厚さが乾燥膜厚で０．０２ｍｍになるように、金属スキージでガラス上に印刷し、大気雰囲気中にて２００℃で３０分間硬化させた。そして、この硬化により得られた被膜の電気抵抗率を求めた。被膜の電気抵抗率は、低抵抗率計（装置名：Ｌｏｒｅｓｔａ−ＧＰＭＣＰ−Ｔ６００、三菱化学社製）を用いて四端子法によりシート抵抗値を測定し、表面粗さ形状測定器（装置名：ＳＵＲＦＣＯＭ１３０Ａ、東京精密社製）を用いて被膜の膜厚を測定した後、上記シート抵抗値を被膜の膜厚で除することによって求めた。結果を表２に示す。
<Evaluation 1: Conductivity>
The conductive paste according to the example and the comparative example was printed on a glass with a metal squeegee so that the thickness was 0.02 mm as a dry film thickness, and cured at 200 ° C. for 30 minutes in an air atmosphere. And the electrical resistivity of the film obtained by this hardening was calculated | required. The electrical resistivity of the film was measured by measuring the sheet resistance by a four-terminal method using a low resistivity meter (device name: Loresta-GPMCP-T600, manufactured by Mitsubishi Chemical Corporation), and a surface roughness shape measuring device (device name: The film thickness of the film was measured using SURFCOM130A (manufactured by Tokyo Seimitsu Co., Ltd.), and then obtained by dividing the sheet resistance value by the film thickness of the film. The results are shown in Table 2.
加えて、耐湿性による信頼性の影響を調べるため、実施例３及び６に係る導電ペーストについては、導電ペーストを上記の条件で硬化させた後の被膜を温度７０℃、湿度９５％中に１００時間保持し、電気抵抗率を測定した。結果を表２に示す。 In addition, in order to investigate the influence of reliability due to moisture resistance, for the conductive pastes according to Examples 3 and 6, the film after the conductive paste was cured under the above conditions was 100 ° C. at a temperature of 70 ° C. and a humidity of 95%. The electrical resistivity was measured by holding for a time. The results are shown in Table 2.
表面に硫化銅被膜が形成され、平均粒子径が０．５μｍ以上１０μｍ以下であり、硫化銅被膜の厚さが０．０１μｍ以上０．０６μｍ以下である硫化銅被覆銅粉からは、極めて高い導電性を有する導電ペーストを得られることが確認された（実施例）。特に、硫化銅被膜の厚さが０．０１μｍ以上０．０３μｍ以下であると、電気抵抗率が２．０×１０−４Ω・ｃｍ以下であり、より導電性に優れることが確認された（実施例３〜６）。 A copper sulfide coating is formed on the surface, the average particle diameter is 0.5 μm or more and 10 μm or less, and the copper sulfide coating copper powder having a copper sulfide coating thickness of 0.01 μm or more and 0.06 μm or less is extremely conductive. It was confirmed that a conductive paste having a property can be obtained (Example). In particular, when the thickness of the copper sulfide coating is 0.01 μm or more and 0.03 μm or less, the electrical resistivity is 2.0 × 10 −4 Ω · cm or less, and it was confirmed that the conductivity is more excellent ( Examples 3 to 6).
加えて、実施例３及び６の比較から分かるとおり、硫化処理後に加熱処理を行い、硫化銅被膜を硫化第二銅から硫化第一銅にすることで、耐湿熱性に優れることが確認された（実施例６）。 In addition, as can be seen from the comparison of Examples 3 and 6, heat treatment was performed after the sulfidation treatment, and it was confirmed that the copper sulfide film was changed from cupric sulfide to cuprous sulfide, thereby being excellent in heat and moisture resistance ( Example 6).
一方、硫化銅被膜が厚すぎると、電気抵抗率が１．０×１０−３Ω・ｃｍを超え、十分な導電性を得られないことが確認された（比較例）。 On the other hand, when the copper sulfide film was too thick, it was confirmed that the electrical resistivity exceeded 1.0 × 10 −3 Ω · cm, and sufficient conductivity could not be obtained (Comparative Example).
＜評価その２：重量変化率と硫化銅被膜の厚さとの相関性＞
硫化銅被膜形成工程Ｓ４において、硫化処理の前後での重量変化率を測定した。そして、下式のｒａに重量変化率を代入し、Ｒに平均粒子径の１／２を代入することで、硫化銅被膜の厚さを計算した。その結果を、硫化銅被膜の厚さの実測値とともに表３に示す。
ｒａ＝１−（１−０．５２ｄ１／Ｒ）３
In the copper sulfide film forming step S4, the weight change rate before and after the sulfiding treatment was measured. Then, the thickness of the copper sulfide coating was calculated by substituting the weight change rate for ra in the following formula and substituting 1/2 of the average particle diameter for R. The results are shown in Table 3 together with the measured values of the copper sulfide coating thickness.
ra = 1- (1-0.52d 1 / R) 3
表３から、重量変化率から予想される硫化銅被膜の厚さの予想値と、実際に計測した硫化銅被膜の厚さの実測値とがほぼ一致することが確認された。このことから、硫化前後での重量変化率を計測することで、硫化銅被膜の厚さを実際に計測することなく管理できるといえる。 From Table 3, it was confirmed that the predicted value of the thickness of the copper sulfide coating expected from the weight change rate and the actually measured value of the thickness of the copper sulfide coating actually measured substantially coincided with each other. From this, it can be said that the thickness of the copper sulfide coating can be managed without actually measuring by measuring the weight change rate before and after sulfiding.
１ 硫化銅被覆銅粉
２ 硫化銅被膜
1 Copper sulfide coated copper powder 2 Copper sulfide coating
Claims (9)
平均粒子径が０．５μｍ以上１０μｍ以下であり、
前記硫化銅被膜の厚さが０．０１μｍ以上０．０６μｍ以下である硫化銅被覆銅粉。 A copper sulfide film is formed on the surface,
The average particle size is 0.5 μm or more and 10 μm or less,
A copper sulfide-coated copper powder, wherein the copper sulfide film has a thickness of 0.01 μm or more and 0.06 μm or less.
前記硫化銅被膜の厚さが０．０１μｍ以上０．０６μｍ以下である、硫化銅被覆銅粉の製造方法。 Including a copper sulfide film forming step of sulfiding the surface of copper powder having an average particle size of 0.5 μm or more and 10 μm or less, and forming a copper sulfide film on the surface of the copper powder,
The manufacturing method of the copper sulfide coating | coated copper powder whose thickness of the said copper sulfide film is 0.01 micrometer or more and 0.06 micrometer or less.
（式中、Ｒは前記銅粉の平均粒子径の１／２であり、ｄ１は前記硫化銅被膜の目標の厚さである。） The weight change rate is 1 is predicted in accordance with the value of (1-0.52d 1 / R) 3, the manufacturing method of the copper sulfide-coated copper powder according to claim 5.
(In the formula, R is ½ of the average particle diameter of the copper powder, and d 1 is the target thickness of the copper sulfide coating.)
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