JP2020153010A - Silver-coated copper powder with barrier layer - Google Patents
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- JP2020153010A JP2020153010A JP2019199938A JP2019199938A JP2020153010A JP 2020153010 A JP2020153010 A JP 2020153010A JP 2019199938 A JP2019199938 A JP 2019199938A JP 2019199938 A JP2019199938 A JP 2019199938A JP 2020153010 A JP2020153010 A JP 2020153010A
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- 229910052709 silver Inorganic materials 0.000 title claims abstract description 204
- 239000004332 silver Substances 0.000 title claims abstract description 204
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 184
- 230000004888 barrier function Effects 0.000 title claims abstract description 132
- 239000002245 particle Substances 0.000 claims abstract description 31
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- 238000010438 heat treatment Methods 0.000 claims description 52
- 239000000843 powder Substances 0.000 claims description 44
- 229910052759 nickel Inorganic materials 0.000 claims description 41
- 229910052802 copper Inorganic materials 0.000 claims description 18
- 239000010949 copper Substances 0.000 claims description 18
- 230000007423 decrease Effects 0.000 claims description 15
- 230000003647 oxidation Effects 0.000 abstract description 15
- 238000007254 oxidation reaction Methods 0.000 abstract description 15
- 238000001354 calcination Methods 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 177
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- 238000000034 method Methods 0.000 description 31
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- 239000002184 metal Substances 0.000 description 22
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- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 15
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- 229910000431 copper oxide Inorganic materials 0.000 description 13
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- GGCZERPQGJTIQP-UHFFFAOYSA-N sodium;9,10-dioxoanthracene-2-sulfonic acid Chemical compound [Na+].C1=CC=C2C(=O)C3=CC(S(=O)(=O)O)=CC=C3C(=O)C2=C1 GGCZERPQGJTIQP-UHFFFAOYSA-N 0.000 description 3
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- 239000002253 acid Substances 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 2
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- NDVLTYZPCACLMA-UHFFFAOYSA-N silver oxide Chemical compound [O-2].[Ag+].[Ag+] NDVLTYZPCACLMA-UHFFFAOYSA-N 0.000 description 2
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- WRIDQFICGBMAFQ-UHFFFAOYSA-N (E)-8-Octadecenoic acid Natural products CCCCCCCCCC=CCCCCCCC(O)=O WRIDQFICGBMAFQ-UHFFFAOYSA-N 0.000 description 1
- LQJBNNIYVWPHFW-UHFFFAOYSA-N 20:1omega9c fatty acid Natural products CCCCCCCCCCC=CCCCCCCCC(O)=O LQJBNNIYVWPHFW-UHFFFAOYSA-N 0.000 description 1
- TYOXIFXYEIILLY-UHFFFAOYSA-N 5-methyl-2-phenyl-1h-imidazole Chemical compound N1C(C)=CN=C1C1=CC=CC=C1 TYOXIFXYEIILLY-UHFFFAOYSA-N 0.000 description 1
- QSBYPNXLFMSGKH-UHFFFAOYSA-N 9-Heptadecensaeure Natural products CCCCCCCC=CCCCCCCCC(O)=O QSBYPNXLFMSGKH-UHFFFAOYSA-N 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 239000005750 Copper hydroxide Substances 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- ZQPPMHVWECSIRJ-UHFFFAOYSA-N Oleic acid Natural products CCCCCCCCC=CCCCCCCCC(O)=O ZQPPMHVWECSIRJ-UHFFFAOYSA-N 0.000 description 1
- 239000005642 Oleic acid Substances 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- FOIXSVOLVBLSDH-UHFFFAOYSA-N Silver ion Chemical compound [Ag+] FOIXSVOLVBLSDH-UHFFFAOYSA-N 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
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- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- GFHNAMRJFCEERV-UHFFFAOYSA-L cobalt chloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].[Cl-].[Co+2] GFHNAMRJFCEERV-UHFFFAOYSA-L 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
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- 229910001956 copper hydroxide Inorganic materials 0.000 description 1
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- SZXQTJUDPRGNJN-UHFFFAOYSA-N dipropylene glycol Chemical compound OCCCOCCCO SZXQTJUDPRGNJN-UHFFFAOYSA-N 0.000 description 1
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- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 1
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- QXJSBBXBKPUZAA-UHFFFAOYSA-N isooleic acid Natural products CCCCCCCC=CCCCCCCCCC(O)=O QXJSBBXBKPUZAA-UHFFFAOYSA-N 0.000 description 1
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- ZQPPMHVWECSIRJ-KTKRTIGZSA-N oleic acid Chemical compound CCCCCCCC\C=C/CCCCCCCC(O)=O ZQPPMHVWECSIRJ-KTKRTIGZSA-N 0.000 description 1
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- Powder Metallurgy (AREA)
- Non-Insulated Conductors (AREA)
Abstract
Description
本発明は、電子材料の配線形成用として好適なバリア層付銀コート銅粉に関する。 The present invention relates to silver-coated copper powder with a barrier layer suitable for forming wiring for electronic materials.
従来から、導電性ペーストのような電子部品の配線形成材料は、例えば、プリント配線、半導体の内部配線、プリント配線板と電子部品との接続等に利用されている。近年、例えば、太陽電池用電極等の分野では、導電性ペーストの低温焼成化と配線の細線化に対する需要が高まってきている。このため、低温焼成でも電気抵抗が低抵抗となり（以下、本明細書にて「抵抗」とは「電気抵抗」のことを指す。）、さらには配線の細線化に対応できる導電性ペーストが求められている。 Conventionally, wiring forming materials for electronic components such as conductive pastes have been used, for example, for printed wiring, internal wiring of semiconductors, connection between printed wiring boards and electronic components, and the like. In recent years, for example, in the field of electrodes for solar cells, there is an increasing demand for low-temperature firing of conductive paste and thinning of wiring. For this reason, the electrical resistance becomes low even in low-temperature firing (hereinafter, "resistance" refers to "electrical resistance" in the present specification), and a conductive paste that can cope with thinning of wiring is required. Has been done.
このような導電性ペースト向けの金属粉末として、従来は銀粉が用いられてきた。しかし、銀の地金価格が高価であることから、より安価で製造できる銅粉や銀コート銅粉への代替が活発に検討されている。 Conventionally, silver powder has been used as a metal powder for such a conductive paste. However, since the price of silver ingots is high, alternatives to copper powder and silver-coated copper powder, which can be produced at a lower cost, are being actively considered.
銅粉を低温焼成（例えば、３００℃以下）に用いられる細線用導電性ペーストに用いる場合、銅粉に求められる特性として、用途及び使用条件にもよるが、導電性ペーストとした際の抵抗値が従来使用されている銀粉に近いことが要求される。 When copper powder is used for a conductive paste for fine wires used for low-temperature firing (for example, 300 ° C or less), the resistance value of the conductive paste is a characteristic required for the copper powder, although it depends on the application and usage conditions. Is required to be close to the silver powder used conventionally.
しかしながら、銅粉は、それ自体の抵抗値は低いものの、空気中で容易に酸化されてその表面に高抵抗の酸化銅（ＣｕＯ）層が形成されるため、例えば、太陽電池用電極に用いられるような、空気中で加熱硬化するタイプの導電ペースト向けの導電フィラーには適さない。対して銀コート銅粉は空気中加熱で酸化しない銀で銅粉の表面を被覆保護しているため、銅粉と比較して、耐酸化性が向上して低抵抗化が図れる。しかしながら、従来の銀コート銅粉においては、低温焼成時の温度履歴による銀コート層の劣化や、銅原子の銀コート層中での拡散を防ぎようがなく、銅粉中の銅原子が、徐々に表面側（銀コート層側）に移動する。よって、空気中での加熱（焼成）温度が２００℃を超えてくると、銀コート層表面へ酸化銅が形成されるため、銀コート銅粉を導電性ペーストに用いた際の抵抗値が銀粉を導電性ペーストに用いた場合に比べ劣っている。また、酸化銅が形成された銀コート銅粉は、黒色の酸化銅による粉体色の黒化を生じる。 However, although copper powder itself has a low resistance value, it is easily oxidized in the air to form a high-resistance copper oxide (CuO) layer on its surface, so that it is used, for example, as an electrode for a solar cell. It is not suitable for conductive fillers for conductive pastes of the type that cure by heating in air. On the other hand, since the silver-coated copper powder covers and protects the surface of the copper powder with silver that does not oxidize by heating in air, the oxidation resistance is improved and the resistance can be lowered as compared with the copper powder. However, in the conventional silver-coated copper powder, deterioration of the silver-coated layer due to the temperature history during low-temperature firing and diffusion of copper atoms in the silver-coated layer cannot be prevented, and the copper atoms in the copper powder gradually increase. Moves to the surface side (silver coat layer side). Therefore, when the heating (baking) temperature in the air exceeds 200 ° C., copper oxide is formed on the surface of the silver-coated layer, so that the resistance value when the silver-coated copper powder is used as the conductive paste is the silver powder. Is inferior to the case where is used for the conductive paste. Further, the silver-coated copper powder on which copper oxide is formed causes blackening of the powder color due to black copper oxide.
例えば、特許文献１には銀コート銅粉の比表面積を画像解析から得られた粒径から算出される比表面積に近づけることで導電性を上げる方法が示されている。しなしながら、特許文献１の銀コート銅粉では、評価値は圧粉抵抗値でしか示されておらず、以下に説明するように、圧粉抵抗値が低くても導電性ペーストの抵抗率が低いとはいえない。 For example, Patent Document 1 discloses a method of increasing the conductivity by bringing the specific surface area of silver-coated copper powder close to the specific surface area calculated from the particle size obtained from image analysis. However, in the silver-coated copper powder of Patent Document 1, the evaluation value is shown only by the powder resistance value, and as described below, the resistivity of the conductive paste even if the powder resistance value is low. Is not low.
すなわち、例えば、非特許文献１に示されるとおり、金属微粒子集合体の導電率は、構成する金属粒子の金属自身の導電率（σｐ）と接触部の導電性低下を示す数式を含む複雑な関数で表すことができる。金属微粒子同士の接触部が融着してその接触層の抵抗増加が無視できるような場合には、上記複雑な関数は簡略化されて、金属微粒子集合体の導電率は、微粒子同士の接触領域を円と仮定するとその接触部の半径（ｒｃ）の微粒子の半径（ｒ）に対する比率（ｒｃ／ｒ）に比例した値（σｐ×ｒｃ／ｒ）で与えられる。圧粉抵抗測定では、物理的な外力印加により接触部の半径が大きくなり易いため（接触面積が大きくなり易いため）、樹脂の圧縮応力が主たる印可応力となる導電性ペーストの導電率との単純な比較はできず、圧粉抵抗値と導電性ペーストの抵抗率とは必ずしも対応しない。 That is, for example, as shown in Non-Patent Document 1, the conductivity of the metal fine particle aggregate is complicated including a mathematical formula showing the conductivity (σ p ) of the metal itself of the constituent metal particles and the decrease in the conductivity of the contact portion. It can be represented by a function. When the contact portion between the metal fine particles is fused and the increase in the resistance of the contact layer is negligible, the above complicated function is simplified and the conductivity of the metal fine particle aggregate is the contact region between the fine particles. It is given by the ratio (r c / r) proportional to the value (σ p × r c / r ) for the assuming circle the radius of the fine particles of the contact portion of the radius (r c) (r). In the powder resistivity measurement, since the radius of the contact portion tends to increase due to the application of a physical external force (because the contact area tends to increase), the compressive stress of the resin is the main applied stress, which is simple with the conductivity of the conductive paste. The powder resistance value and the resistivity of the conductive paste do not always correspond to each other.
さらに、特許文献１の銀コート銅粉では、１５０℃で７５時間保持後の圧粉抵抗値は示されているが、銀コート銅粉の表面の酸化銅形成については言及されておらず、耐酸化性については不明である。 Further, in the silver-coated copper powder of Patent Document 1, the powder resistance value after holding at 150 ° C. for 75 hours is shown, but the formation of copper oxide on the surface of the silver-coated copper powder is not mentioned, and acid resistance is not mentioned. It is unknown about the chemical nature.
一方、銀コート銅粉において、耐熱性を向上させるため、中心部（コア）の銅粉と表面の銀コート層との間にニッケル層を形成させる技術が知られている。ニッケルは銅や銀よりも高融点であり、銅と銀の間にニッケル層があることで銅が銀に拡散するのを抑制することができる。また、ニッケルは銀と不混和であるため、銀コート層中へのニッケル原子の拡散が起こらないという利点もある。 On the other hand, in silver-coated copper powder, a technique for forming a nickel layer between the copper powder in the center (core) and the silver-coated layer on the surface is known in order to improve heat resistance. Nickel has a higher melting point than copper and silver, and the presence of a nickel layer between copper and silver can prevent copper from diffusing into silver. Further, since nickel is immiscible with silver, there is an advantage that nickel atoms do not diffuse into the silver coat layer.
例えば、特許文献２には、最表面に銀コート層と、銀コート層と銅粉の間にニッケル合金層を有し、ニッケル合金の含有率が０．１〜１５質量％であり、銀の含有率が２〜２０質量％である被覆銅粉が開示されている。特許文献２によれば、ニッケル合金層により耐酸化性を向上させているとしている。 For example, Patent Document 2 has a silver-coated layer on the outermost surface and a nickel alloy layer between the silver-coated layer and copper powder, and the nickel alloy content is 0.1 to 15% by mass. Coated copper powder having a content of 2 to 20% by mass is disclosed. According to Patent Document 2, the nickel alloy layer improves the oxidation resistance.
しかしながら、特許文献２には、平均粒径１００μｍの銅粉にニッケル合金を被覆し、さらに銀を被覆した銀コート銅粉の実施例が開示されているのみであり、平均粒径１０μｍ以下の銀コート銅粉では十分な耐酸化性が得られないことがあった。 However, Patent Document 2 only discloses an example of a silver-coated copper powder in which a copper powder having an average particle size of 100 μm is coated with a nickel alloy and further coated with silver, and silver having an average particle size of 10 μm or less. Sufficient oxidation resistance may not be obtained with coated copper powder.
すなわち、例えば、３００℃以下の低温焼成で形成される配線材料には、平均粒径が１０μｍ以下の銀コート銅粉が好適に用いられるが、このような銀コート銅粉に上記技術を適用したとしても、銀粉と同等の耐酸化性と導電性を両立させるのは難しく、銀コート銅粉の適用領域が大きく制限されていた。 That is, for example, silver-coated copper powder having an average particle size of 10 μm or less is preferably used as a wiring material formed by low-temperature firing at 300 ° C. or lower, and the above technique is applied to such silver-coated copper powder. Even so, it is difficult to achieve both oxidation resistance and conductivity equivalent to those of silver powder, and the application range of silver-coated copper powder is greatly limited.
本発明は、従来技術の問題点に鑑み、低温焼成用導電性ペーストに用いる場合において、銀粉と同程度の低い抵抗率と、優れた耐酸化性とを有し、かつ、低コストである銀コート銅粉を提供することを目的とする。 In view of the problems of the prior art, the present invention has silver having a resistivity as low as silver powder, excellent oxidation resistance, and low cost when used in a conductive paste for low temperature firing. It is intended to provide coated copper powder.
本発明の第１の実施形態では、平均粒径が０．５μｍ以上１０μｍ以下の銅粉と、最表面に形成された銀コート層と、銅粉および銀コート層の間に形成されたバリア層とを有する、バリア層付銀コート銅粉であって、銀コート層の平均厚さは２０ｎｍ以上１５０ｎｍ以下であり、バリア層の平均厚さは２０ｎｍ以上１５０ｎｍ以下である、バリア層付銀コート銅粉が提供される。 In the first embodiment of the present invention, a copper powder having an average particle size of 0.5 μm or more and 10 μm or less, a silver coat layer formed on the outermost surface, and a barrier layer formed between the copper powder and the silver coat layer. A silver-coated copper powder with a barrier layer, wherein the silver-coated layer has an average thickness of 20 nm or more and 150 nm or less, and the barrier layer has an average thickness of 20 nm or more and 150 nm or less. Powder is provided.
また、バリア層はニッケルを主成分とすることが好ましい。また、銅粉は銅を主成分として５０質量％以上含有することが好ましい。また、バリア層付銀コート銅粉は、圧粉抵抗値が５０μΩ・ｃｍ以下であることが好ましい。また、バリア層付銀コート銅粉は、空気中で室温から３５０℃まで加熱した場合、加熱後の質量増加率が加熱前の質量に対して１質量％未満であることが好ましい。また、Ｌ＊ａ＊ｂ＊表色系における明度Ｌ＊値が７０以上であり、かつ、空気中で室温から３００℃まで加熱し、３００℃で１０分間保持した場合、加熱後のＬ＊値の低下が、加熱前のＬ＊値と比較して、１０未満であることが好ましい。また、バリア層付銀コート銅粉を含む、Ｌ＊ａ＊ｂ＊表色系における明度Ｌ＊値が７０以上ペースト膜を作製し、ペースト膜を空気中で室温から３００℃まで加熱し、３００℃で１時間保持した場合、加熱後のペースト膜のＬ＊値の低下が、加熱前のペースト膜のＬ＊値と比較して、１０未満であることが好ましい。 Further, the barrier layer preferably contains nickel as a main component. Further, the copper powder preferably contains copper as a main component in an amount of 50% by mass or more. Further, the silver-coated copper powder with a barrier layer preferably has a powder resistance value of 50 μΩ · cm or less. Further, when the silver-coated copper powder with a barrier layer is heated from room temperature to 350 ° C. in air, the mass increase rate after heating is preferably less than 1% by mass with respect to the mass before heating. Further, when the brightness L * value in the L * a * b * color system is 70 or more, and the product is heated from room temperature to 300 ° C. in air and held at 300 ° C. for 10 minutes, the L * value after heating. The decrease in L * is preferably less than 10 as compared with the L * value before heating. Further, a paste film having a brightness L * value of 70 or more in the L * a * b * color system containing silver-coated copper powder with a barrier layer was prepared, and the paste film was heated from room temperature to 300 ° C. in air to 300. When held at ° C. for 1 hour, the decrease in the L * value of the paste film after heating is preferably less than 10 as compared with the L * value of the paste film before heating.
本発明に係るバリア層付銀コート銅粉は、低温焼成用導電性ペーストに用いた際に、銀粉と同程度の低い抵抗値と、耐酸化性とを有し、低コストで得ることができる。また、略球状のバリア層付銀コート銅粉とした場合、略球状をしているので異方性がなく、電子部品の配線形成材料に用いた場合に、配線の細線化を行うことができる。 The silver-coated copper powder with a barrier layer according to the present invention has a resistance value as low as that of silver powder and oxidation resistance when used in a conductive paste for low-temperature firing, and can be obtained at low cost. .. Further, in the case of silver-coated copper powder with a substantially spherical barrier layer, since it is substantially spherical, there is no anisotropy, and when it is used as a wiring forming material for electronic components, wiring can be thinned. ..
以下、本発明の一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限定されるものではなく、本発明の要旨を逸脱しない限りにおいて適宜変更することができる。 Hereinafter, one embodiment of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be appropriately modified without departing from the gist of the present invention.
１．バリア層付銀コート銅粉
本実施の形態にかかるバリア層付銀コート銅粉は、中心部（コア）の銅粉と、最表面に銀コート層と、銅粉と銀コート層との間にバリア層とを有する。当該銅粉は、走査型電子顕微鏡で観察した画像より得られる平均粒径が０．５μｍ以上１０μｍ以下であり、銀コート層の平均厚さが２０ｎｍ以上１５０ｎｍ以下であり、かつ、バリア層の平均厚さが２０ｎｍ以上１５０ｎｍ以下である。また、銅粉は球状または略球状であることが好ましい。
1. 1. Silver-coated copper powder with barrier layer The silver-coated copper powder with barrier layer according to the present embodiment is between the copper powder in the center (core), the silver-coated layer on the outermost surface, and the copper powder and the silver-coated layer. It has a barrier layer. The copper powder has an average particle size of 0.5 μm or more and 10 μm or less, an average thickness of a silver coat layer of 20 nm or more and 150 nm or less, and an average of barrier layers obtained from an image observed with a scanning electron microscope. The thickness is 20 nm or more and 150 nm or less. Further, the copper powder is preferably spherical or substantially spherical.
従来使用されている銀粉の場合、銀同士の接触部において、比表面積によるものの１５０℃付近の低温でネッキングが生じ、導電性が向上することが知られている。しかしながら、低温焼成用導電性ペーストとして銀コート銅粉を用いた場合、低温焼成時の温度履歴による銀コート層の劣化や、銅の拡散による銀コート層表面への酸化銅の形成により、銀コート層同士の接触部でのネッキング形成が阻害されていると考えられる。また、上記ネッキングの形成には銀原子の物質移動が必須であるが、銀コート銅粉において、物質移動に十分な銀量が存在しない場合、ネッキング形成の不良が起こることが考えられる。また、銀コート層への銅の拡散を抑制するためバリア層（例、ニッケル層）を設けた場合においても、銅の拡散を抑制するに十分なバリア層が存在しない場合、銀コート層の表面に酸化銅が形成され、低い抵抗値を実現することが困難となる。 In the case of silver powder used conventionally, it is known that necking occurs at a low temperature of around 150 ° C. due to the specific surface area at the contact portion between silver, and the conductivity is improved. However, when silver-coated copper powder is used as the conductive paste for low-temperature firing, the silver-coated layer is deteriorated due to the temperature history during low-temperature firing, and copper oxide is formed on the surface of the silver-coated layer due to the diffusion of copper. It is considered that the necking formation at the contact portion between the layers is inhibited. Further, although mass transfer of silver atoms is indispensable for the formation of the necking, it is considered that poor necking formation occurs in the silver-coated copper powder when a sufficient amount of silver is not present for the mass transfer. Further, even when a barrier layer (eg, a nickel layer) is provided to suppress the diffusion of copper into the silver coat layer, if there is not enough barrier layer to suppress the diffusion of copper, the surface of the silver coat layer. Copper oxide is formed on the surface, making it difficult to achieve a low resistance value.
よって、物質移動に十分な銀量がコートされており、かつ銅と銀コート層の間に銅の拡散を抑制するに十分なニッケル層を有していれば、銀コート銅粉であっても、低温焼成用導電性ペーストに用いた際に、銀粉に近い抵抗値と耐酸化性を得ることができるものと考えられる。 Therefore, even if it is a silver-coated copper powder, if a sufficient amount of silver is coated for mass transfer and a nickel layer sufficient to suppress the diffusion of copper is provided between the copper and the silver-coated layer. When used in a conductive paste for low-temperature firing, it is considered that a resistance value close to that of silver powder and oxidation resistance can be obtained.
一方で銀コート層やバリア層を過剰に厚く形成することは、被覆に要する時間が増大して生産性が低下するとともに、特に銀量を増加することは原料コストの増大をもたらす。これは、バリア層付銀コート銅粉を用いる上で重要なコスト低減に反する。 On the other hand, forming the silver coat layer or the barrier layer excessively thick increases the time required for coating and lowers the productivity, and in particular, increasing the amount of silver brings about an increase in raw material cost. This goes against the cost reduction that is important in using silver-coated copper powder with a barrier layer.
そこで、本発明らは、鋭意検討した結果、銀粉を用いた場合に近い低い抵抗値を得ることのできる最低量の銀コート層やバリア層の厚みを明らかにし、銀粉を用いるよりも低コストで、かつ銀粉に近い低い抵抗値を得ることできるバリア層付銀コート銅粉を見出し、本発明を完成させた。 Therefore, as a result of diligent studies, the present inventions have clarified the thickness of the minimum amount of the silver coat layer and the barrier layer that can obtain a low resistance value close to that when silver powder is used, and at a lower cost than using silver powder. And, a silver-coated copper powder with a barrier layer capable of obtaining a low resistance value close to that of silver powder was found, and the present invention was completed.
なお、銀コート層やバリア層の平均厚さは、例えば、各層の被覆量から求めた各層の被覆厚みを指標としている。ここで被覆量は、例えばバリア層付銀コート銅粉の組成分析をすることで求められ、銅粉の平均粒径を用いて被覆厚みを求めることができる。以下、各構成について説明する。 The average thickness of the silver coat layer and the barrier layer is, for example, the coating thickness of each layer obtained from the coating amount of each layer as an index. Here, the coating amount can be determined, for example, by analyzing the composition of the silver-coated copper powder with a barrier layer, and the coating thickness can be determined using the average particle size of the copper powder. Each configuration will be described below.
（銀コート層）
本実施の形態に係るバリア層付銀コート銅粉は、最表面に銀コート層を有する。従来のバリア層を有さない銀コート銅粉では、ネッキングを生じるに必要な銀量が不足するという問題が生じるのに対して、本実施の形態では、銀コート層が特定の厚さを有し、かつ、バリア層が銅原子の銀コート層への移動を抑制することにより、ネッキングに必要な銀量を確保可能とする。
(Silver coat layer)
The silver-coated copper powder with a barrier layer according to the present embodiment has a silver-coated layer on the outermost surface. In the conventional silver-coated copper powder without a barrier layer, there is a problem that the amount of silver required for necking is insufficient, whereas in the present embodiment, the silver-coated layer has a specific thickness. In addition, the barrier layer suppresses the movement of copper atoms to the silver-coated layer, so that the amount of silver required for necking can be secured.
銀コート層の平均厚さは、２０ｎｍ以上１５０ｎｍ以下である。銀コート層の厚みが２０ｎｍより薄い場合、銀粉を用いた場合と比較して少なくとも抵抗値が２．０倍以上高くなり、銀粉に近い、低い抵抗値を有することが困難となる。ここで、銀粉に近い（ほぼ同等の）抵抗値とは、銀粉の抵抗値の２．０倍以内をいう。 The average thickness of the silver coat layer is 20 nm or more and 150 nm or less. When the thickness of the silver coat layer is thinner than 20 nm, the resistance value is at least 2.0 times higher than that when silver powder is used, and it becomes difficult to have a low resistance value close to that of silver powder. Here, the resistance value close to (almost equivalent to) silver powder means within 2.0 times the resistance value of silver powder.
バリア層付銀コート銅粉の抵抗値は、銀コート層の厚みが厚くなるに従い低下する。よって抵抗値を向上させるという観点から、銀コート層の平均厚さは、好ましくは４０ｎｍ以上、さらに好ましくは６０ｎｍ以上である。また、銀コート層の平均厚さの上限はコストとの兼ね合いでおのずと決まるものではあるが、１５０ｎｍ以下とする。なお、この上限は、バリア層付銀コート銅粉に求められる効果に基づくものではないので、上限を超えて銀コート層を厚くすることを妨げるものではない。 The resistance value of the silver-coated copper powder with a barrier layer decreases as the thickness of the silver-coated layer increases. Therefore, from the viewpoint of improving the resistance value, the average thickness of the silver coat layer is preferably 40 nm or more, more preferably 60 nm or more. The upper limit of the average thickness of the silver coat layer is 150 nm or less, although it is naturally determined in consideration of the cost. Since this upper limit is not based on the effect required for the silver-coated copper powder with a barrier layer, it does not prevent the silver-coated layer from being thickened beyond the upper limit.
（バリア層）
本実施系の形態に係るバリア層付銀コート銅粉は、銅粉と銀コート層との間にバリア層を有する。バリア層は、銅原子の銀コート層への移動を抑制することができる。
(Barrier layer)
The silver-coated copper powder with a barrier layer according to the embodiment of the present embodiment has a barrier layer between the copper powder and the silver-coated layer. The barrier layer can suppress the movement of copper atoms to the silver coat layer.
上述の通り、金属粒子集合体（金属粉末）の導電率は粒子同士の接触部を円と仮定した場合、その半径に比例する。銀粉を低温焼成用の導電性ペーストの導電粒子として用いる場合、その粒径にもよるが、低温で粒子同士のネッキングが生じることで低抵抗な接触部位が形成され、樹脂の熱収縮のみの圧縮応力下であっても、結果として安定した低抵抗を得ることができる。一方、例えば、バリア層を有しない銀コート銅粉を用いた場合は、粒子同士の接触部分に銀が存在するものの、低温焼成中の熱履歴によって、銀コート層中の粒界やピンホールを通じた銅原子の拡散現象が生じ、表面に銀のネッキングを阻害する酸化銅が生成しやすい。また、銀コート層の厚みが薄い場合にはネッキングを生じるに必要な銀量が不足し、ネッキングが生じにくくなる。以上の事象が重なることで、バリア層を有しない銀コート銅粉では、銀粉を用いる場合よりも低抵抗値を得ることが難しい。 As described above, the conductivity of the metal particle aggregate (metal powder) is proportional to the radius of the contact portion between the particles, assuming that the contact portion is a circle. When silver powder is used as conductive particles of a conductive paste for low-temperature firing, low-resistance contact sites are formed due to necking between the particles at low temperatures, depending on the particle size, and compression of only the heat shrinkage of the resin. As a result, stable low resistance can be obtained even under stress. On the other hand, for example, when silver-coated copper powder having no barrier layer is used, although silver is present at the contact portion between the particles, the heat history during low-temperature firing causes the grain boundaries and pinholes in the silver-coated layer to pass through. Diffusion phenomenon of copper atoms occurs, and copper oxide that inhibits silver necking is likely to be generated on the surface. Further, when the thickness of the silver coat layer is thin, the amount of silver required to cause necking is insufficient, and necking is less likely to occur. By overlapping the above events, it is difficult to obtain a lower resistance value in the silver-coated copper powder having no barrier layer than in the case of using the silver powder.
そこで、本発明では、バリア層を特定の厚みで有することにより、銀コート層中の粒界やピンホールを通じた銅の拡散現象に対しては、拡散で中心部（コア）の銅粉から銀コート層に到達する銅原子数を抑制することができ、酸化銅の生成が非常に抑制される。 Therefore, in the present invention, by having the barrier layer having a specific thickness, the copper powder in the central portion (core) is dispersed to silver against the diffusion phenomenon of copper through the grain boundaries and pinholes in the silver coat layer. The number of copper atoms reaching the coat layer can be suppressed, and the formation of copper oxide is greatly suppressed.
バリア層の平均厚さは、２０ｎｍ以上１５０ｎｍ以下である。バリア層の厚みを２０ｎｍ以上としているが、これより薄い場合には銀コート層表面まで拡散してしまう銅量が増大し、バリア層付銀コート銅粉を加熱した時に表面の酸化銅が形成され、耐酸化性が低下して抵抗値が増大してしまうことがある。また、上限についても銀コート層の厚さと同じくコストとの兼ね合いでおのずと決まるものではあるが１５０ｎｍ以下とする。 The average thickness of the barrier layer is 20 nm or more and 150 nm or less. The thickness of the barrier layer is 20 nm or more, but if it is thinner than this, the amount of copper that diffuses to the surface of the silver-coated layer increases, and copper oxide on the surface is formed when the silver-coated copper powder with the barrier layer is heated. , The oxidation resistance may decrease and the resistance value may increase. In addition, the upper limit is set to 150 nm or less, although it is naturally determined in consideration of cost as well as the thickness of the silver coat layer.
バリア層は、バリア層内の銅の拡散速度を銀中の銅の拡散速度よりも遅くすることが可能であり、かつ、銀と不混和の特性を有する金属（以降、「バリア金属」と称することもある。）を用いて形成することができる。バリア金属は、上記特性を有する金属であれば特に限定されないが、ニッケルを主成分とする金属が好適に用いられる。 The barrier layer can make the diffusion rate of copper in the barrier layer slower than the diffusion rate of copper in silver, and has the property of being immiscible with silver (hereinafter referred to as "barrier metal"). It can also be formed using). The barrier metal is not particularly limited as long as it is a metal having the above characteristics, but a metal containing nickel as a main component is preferably used.
ニッケルを主成分とするバリア金属としては、具体的には、コバルト、タングステン、モリブデン、パラジウム、白金、リン、及びボロンから選ばれる少なくとも１種以上の元素をあわせて５０質量％未満（０を含む）含有するニッケルを用いることができる。また、バリア金属としては、ニッケルに代えてコバルトを用いてもよく、コバルトを単独で用いてもよい。 Specifically, as the barrier metal containing nickel as a main component, less than 50% by mass (including 0) of at least one element selected from cobalt, tungsten, molybdenum, palladium, platinum, phosphorus, and boron is combined. ) The contained nickel can be used. Further, as the barrier metal, cobalt may be used instead of nickel, or cobalt may be used alone.
ここで、「ニッケルを主成分とする」とは、バリア層を構成する金属中、最も含有量の多い金属がニッケルであることをいい、例えば、ニッケルの含有量が、バリア層に含まれる金属全体に対して、５０質量％以上であってもよく、８０質量％以上であてもよく、１００質量％であってもよい。 Here, "containing nickel as a main component" means that the metal having the highest content among the metals constituting the barrier layer is nickel, for example, the metal having a nickel content contained in the barrier layer. It may be 50% by mass or more, 80% by mass or more, or 100% by mass with respect to the whole.
なお、バリア層の構成元素については、バリア層付銀コート銅粉の断面加工し、バリア層に相当する領域をＥＤＸ（エネルギー分散型Ｘ線分光分析）等の定性分析により、確認することができる。 The constituent elements of the barrier layer can be confirmed by cross-sectional processing of the silver-coated copper powder with the barrier layer and the region corresponding to the barrier layer by qualitative analysis such as EDX (energy dispersive X-ray spectroscopic analysis). ..
なお、バリア層の表面は、その上へ銀をコートする前に、バリア金属の酸化物や水酸化物（例えば、ＮｉＯ、Ｎｉ（ＯＨ）２など）を生じないように還元状態を保つことが好ましい。上記のような酸化物や水酸化物が、バリア層と銀コート層の界面に存在すると導電性を著しく悪化させるからである。また、同様の理由で、バリア層と銀コート層は、その界面に形成される隙間ができるだけ少ないことが好ましい。バリア層と銀コート層との界面に隙間が多い場合、後でその隙間の部分のバリア層が空気などで徐々に酸化していく可能性が高いからである。 The surface of the barrier layer may be kept in a reduced state so as not to generate oxides or hydroxides of barrier metals (for example, NiO, Ni (OH) 2, etc.) before coating silver on the barrier layer. preferable. This is because if the above-mentioned oxides and hydroxides are present at the interface between the barrier layer and the silver coat layer, the conductivity is significantly deteriorated. Further, for the same reason, it is preferable that the barrier layer and the silver coat layer have as few gaps formed at their interfaces as possible. This is because if there are many gaps at the interface between the barrier layer and the silver coat layer, there is a high possibility that the barrier layer in the gaps will be gradually oxidized by air or the like later.
（銅粉）
本実施の形態に係るバリア層付銀コート銅粉は、中心部（コア）に、平均粒径０．５μｍ以上１０μｍ以下の銅粉を有する。銅粉の平均粒径を０．５μｍ以上としているが、平均粒径が０．５μｍを下回ると、銀コート層の厚みを２０ｎｍとしても、相対的に銀量を増大させねばならず、バリア層を形成させるコストを含めるとコスト的に銀粉を用いることに近くなるからである。平均粒径の下限は、より好ましくは０．７μｍ以上、さらに好ましくは１．０μｍ以上である。上限については、用途に応じて決められるものであり特に限定はされないが、主として電子部品の配線形成材料に用いられることを考慮して１０μｍ以下とすればよい。電子部品の配線幅は細線化されつつあるので、平均粒径の上限としては８．０μｍ以下であることがより好ましく、５．０μｍ以下としてもよく、２．０μｍ以下としてもよい。
(Copper powder)
The silver-coated copper powder with a barrier layer according to the present embodiment has a copper powder having an average particle size of 0.5 μm or more and 10 μm or less in the central portion (core). The average particle size of the copper powder is 0.5 μm or more, but if the average particle size is less than 0.5 μm, the amount of silver must be relatively increased even if the thickness of the silver coat layer is 20 nm, and the barrier layer. This is because if the cost of forming the silver powder is included, it is close to using silver powder in terms of cost. The lower limit of the average particle size is more preferably 0.7 μm or more, still more preferably 1.0 μm or more. The upper limit is determined according to the application and is not particularly limited, but may be 10 μm or less in consideration of being mainly used as a wiring forming material for electronic components. Since the wiring width of electronic components is becoming thinner, the upper limit of the average particle size is more preferably 8.0 μm or less, and may be 5.0 μm or less, or 2.0 μm or less.
また中心部（コア）にある銅粉は、銅を主成分とすればよく、銅合金とすることもできる。具体的には、銅を５０質量％以上含有していればよい。 Further, the copper powder in the central portion (core) may be mainly composed of copper and may be a copper alloy. Specifically, it may contain 50% by mass or more of copper.
本実施の形態に係るバリア層付銀コート銅粉は、略球状であることが好ましい。銀コート銅粉としては、フレーク状や樹枝状のものも公知であり、これらを導電性ペーストの導電粒子として用いた時には粒子同士の接触部を確保しやすく、低抵抗の導電膜を得ることには有利である。しかし、異方性を持った導電粒子であるため配線材料に用いる場合には、配線幅を安定化させることが難しく、隣接する配線間の間隔を十分に広げておかないと短絡する恐れがある。従って、電子部品の配線の細線化、すなわち電子部品の高密度化に応えるのは困難であった。 The silver-coated copper powder with a barrier layer according to the present embodiment is preferably substantially spherical. Flake-shaped and dendritic-shaped silver-coated copper powders are also known, and when these are used as conductive particles of a conductive paste, it is easy to secure contact portions between the particles, and a low-resistance conductive film can be obtained. Is advantageous. However, since it is an anisotropy conductive particle, it is difficult to stabilize the wiring width when it is used as a wiring material, and there is a risk of a short circuit unless the distance between adjacent wirings is sufficiently widened. .. Therefore, it has been difficult to respond to the thinning of wiring of electronic components, that is, the increase in density of electronic components.
一方、略球状の導電粒子（銀コート銅粉）を導電性ペーストに用いた場合、配線幅はフレーク状や樹枝状の導電粒子よりも安定するので、配線の細線化は容易となる。略球状の形状には、真球のみならず、走査型電子顕微鏡（ＳＥＭ）観察で短径と長径の比（短径／長径）が０．８〜１．０となる楕円形状となる楕円体等も含む。 On the other hand, when substantially spherical conductive particles (silver-coated copper powder) are used for the conductive paste, the wiring width is more stable than that of the flake-shaped or dendritic conductive particles, so that the wiring can be easily thinned. The substantially spherical shape is not limited to a true sphere, but an ellipsoid having an ellipsoidal shape in which the ratio of minor axis to major axis (minor axis / major axis) is 0.8 to 1.0 when observed by a scanning electron microscope (SEM). Etc. are also included.
なお、銅粉は、上記特性を満たすものであれば、一般に市販されている銅粉を用いてもよい。 As the copper powder, commercially available copper powder may be used as long as it satisfies the above characteristics.
（バリア層付銀コート銅粉の特性）
本実施の形態に係るバリア層付銀コート銅粉は、銀粉の抵抗値の２．０倍以下であることが好ましく、具体的には、圧粉抵抗値が５０μΩ・ｃｍ以下であることが好ましい。バリア層付銀コート銅粉を上記説明した構成とすることで、銀粉と代替可能な圧粉抵抗値が５０μΩ・ｃｍ以下とすることができる。なお、圧粉抵抗値は、所定の容器（例えば円柱状）に粉末を充填して加圧（例、６３．７ＭＰａ）して抵抗値（Ω）を測定し、その抵抗値（Ω）に断面積（ｃｍ２）を掛け、高さ（ｃｍ）で除して得られる。
(Characteristics of silver-coated copper powder with barrier layer)
The silver-coated copper powder with a barrier layer according to the present embodiment preferably has a resistance value of 2.0 times or less of the silver powder, and specifically, the powder resistance value is preferably 50 μΩ · cm or less. .. By adopting the silver-coated copper powder with a barrier layer as described above, the powder resistance value that can replace the silver powder can be set to 50 μΩ · cm or less. The powder resistance value is determined by filling a predetermined container (for example, a columnar shape) with powder, pressurizing (eg, 63.7 MPa), measuring the resistance value (Ω), and cutting the resistance value (Ω). Obtained by multiplying by area (cm 2 ) and dividing by height (cm).
本実施の形態に係るバリア層付銀コート銅粉は銀粉と同等の耐酸化性を有することが好ましい。例えば、空気中で３５０℃まで加熱し、加熱後の質量増加率が加熱前に対して１質量％未満となることが好ましい。加熱後の質量増加率が低いほど、酸化銅の形成が抑制されることを示す。なお、加熱後の重量増加率は、試料を空気中、所定の昇温速度で加熱した熱重量測定（ＴＧ）により求められる。 The silver-coated copper powder with a barrier layer according to the present embodiment preferably has the same oxidation resistance as the silver powder. For example, it is preferable to heat to 350 ° C. in air and the mass increase rate after heating is less than 1% by mass with respect to that before heating. It is shown that the lower the mass increase rate after heating, the more the formation of copper oxide is suppressed. The rate of weight increase after heating is determined by thermogravimetric analysis (TG) in which the sample is heated in air at a predetermined heating rate.
また、本実施の形態に係るバリア層付銀コート銅粉は、バリア層付銀コート銅粉、または例えば後述する実施例に記載された方法により得られたペースト膜のいずれも、それらを空気中で加熱し、３００℃に１時間保持した後において、粉体色の黒化が観察されることはない。これらは、中心部（コア）の銅粉と表面の銀コート層の間に例えばニッケルを主成分とするバリア層を形成し、そのバリア層の厚みを２０ｎｍ以上とすることで、銀コート層表面に酸化銅が形成されることを抑制することにより得られている。なお、粉体色の詳細な評価は、例えば、以下のように、バリア層付銀コート銅粉を準備するか、バリア層付銀コート銅粉を含むペースト膜（評価用）を作製し、バリア層付銀コート銅粉、またはペースト膜表面をＬ＊ａ＊ｂ＊表色系における明度Ｌ＊値（「Ｌ＊値」と略すこともある）の測定することにより行うことができる。なお、ペースト膜の作製方法の詳細は、後述する実施例に記載される。 Further, the silver-coated copper powder with a barrier layer according to the present embodiment is either a silver-coated copper powder with a barrier layer or a paste film obtained by, for example, the method described in Examples described later, in the air. After heating at 300 ° C. and holding at 300 ° C. for 1 hour, no blackening of powder color is observed. In these, for example, a barrier layer containing nickel as a main component is formed between the copper powder in the center (core) and the silver coat layer on the surface, and the thickness of the barrier layer is 20 nm or more, so that the surface of the silver coat layer is formed. It is obtained by suppressing the formation of copper oxide in the silver oxide. For detailed evaluation of the powder color, for example, prepare a silver-coated copper powder with a barrier layer or prepare a paste film (for evaluation) containing the silver-coated copper powder with a barrier layer to obtain a barrier. It can be carried out by measuring the lightness L * value (sometimes abbreviated as "L * value") in the L * a * b * color system on the surface of the layered silver-coated copper powder or the paste film. The details of the method for producing the paste film will be described in Examples described later.
３００℃加熱前のバリア層付銀コート銅粉、またはペースト膜（表面）は、Ｌ＊値が７０以上であることが好ましい。加熱前のＬ＊値が７０未満である場合、銀コート層の厚みが薄く、抵抗値が低くならないことがある。なお、加熱前のＬ＊値の上限は、特に限定されることはない。 The silver-coated copper powder with a barrier layer or the paste film (surface) before heating at 300 ° C. preferably has an L * value of 70 or more. If the L * value before heating is less than 70, the thickness of the silver coat layer may be thin and the resistance value may not decrease. The upper limit of the L * value before heating is not particularly limited.
３００℃まで加熱し、３００℃で１０分保持後のバリア層付銀コート銅粉のＬ＊値の低下が１０未満であることが好ましく、９以下であることがより好ましく、８未満であることがさらに好ましい。また、３００℃まで加熱し、３００℃で1時間保持後のペースト膜（表面）のＬ＊値の低下が１０未満であることが好ましく、６以下であることがより好ましく、６未満であることがさらに好ましい。バリア層付銀コート銅粉、またはペースト膜（表面）のＬ＊値の低下が上記範囲である場合、銀コート層表面での酸化銅の形成が抑制されており、十分な耐酸化性を有することを示す。加熱後のペースト膜（表面）のＬ＊値の低下が１０以上になると、耐酸化性が十分でないため、銀コート層表面で酸化銅が形成され、空気中で３５０℃まで加熱した時に加熱後の質量増加率が加熱前に対して１質量％を超えることがある。なお、加熱後のペースト膜（表面）のＬ＊値の低下は小さいほど好ましく、下限は０である。 The decrease in L * value of the silver-coated copper powder with a barrier layer after heating to 300 ° C. and holding at 300 ° C. for 10 minutes is preferably less than 10, more preferably 9 or less, and less than 8. Is even more preferable. Further, the decrease in the L * value of the paste film (surface) after heating to 300 ° C. and holding at 300 ° C. for 1 hour is preferably less than 10, more preferably 6 or less, and less than 6. Is even more preferable. When the decrease in L * value of the silver-coated copper powder with a barrier layer or the paste film (surface) is within the above range, the formation of copper oxide on the surface of the silver-coated layer is suppressed and the paste film (surface) has sufficient oxidation resistance. Show that. When the decrease in L * value of the paste film (surface) after heating is 10 or more, the oxidation resistance is not sufficient, so copper oxide is formed on the surface of the silver coat layer, and after heating when heated to 350 ° C. in air. The rate of increase in mass may exceed 1% by mass with respect to that before heating. The smaller the decrease in the L * value of the paste film (surface) after heating is, the more preferable it is, and the lower limit is 0.
２．バリア層付銀コート銅粉の製造方法
本実施の形態に係るバリア層付銀コート銅粉の製造方法は、上記特性を有するバリア層付銀コート銅粉が得られれば特に限定されないが、例えば、銅粉の表面にバリア層を形成する工程（ステップＳ１０）と、表面にバリア層を形成した銅粉のさらに表面に銀コート層を形成する工程（ステップＳ２０）と、を備える。
2. 2. Method for Producing Silver Coated Copper Powder with Barrier Layer The method for producing silver coated copper powder with a barrier layer according to the present embodiment is not particularly limited as long as a silver coated copper powder with a barrier layer having the above characteristics can be obtained. A step of forming a barrier layer on the surface of the copper powder (step S10) and a step of forming a silver coat layer on the surface of the copper powder having the barrier layer formed on the surface (step S20) are provided.
ステップＳ１０及びステップＳ２０において、バリア層、及び、銀コート層は、湿式法である無電解めっき法を用いて形成することが好ましい。無電解めっき法を用いる場合、バリア層上にバリア金属の酸化物や水酸化物が形成されない状態で、バリア層上の全面を均一な銀コート層で隙間なく密着させた状態で被覆することができる。 In steps S10 and S20, the barrier layer and the silver coat layer are preferably formed by using an electroless plating method which is a wet method. When the electroless plating method is used, it is possible to coat the entire surface of the barrier layer with a uniform silver coat layer without gaps without forming barrier metal oxides or hydroxides on the barrier layer. it can.
無電解めっき法としては、例えば、還元めっき法、又は、置換めっき法を用いることができる。 As the electroless plating method, for example, a reduction plating method or a substitution plating method can be used.
還元めっき法は、還元剤により表面にバリア金属や銀を析出させるものであり、公知の方法を用いることができる。具体的には、表面を被覆しようとする金属粉末（例、銅粉）を水に分散させて、水スラリーを形成し、この水スラリーに被覆する金属のイオン源となる塩（例、バリア金属を含む塩、銀を含む塩）と、還元剤を添加して、処理する。また必要に応じて、伝導塩、ｐＨ調整剤、界面活性剤、光沢剤、結晶調整剤、安定剤、沈殿防止剤等を添加することもできる。 The reduction plating method deposits a barrier metal or silver on the surface with a reducing agent, and a known method can be used. Specifically, a metal powder (eg, copper powder) to be coated on the surface is dispersed in water to form an aqueous slurry, and a salt serving as an ion source of the metal to be coated on the aqueous slurry (eg, a barrier metal). (Salt containing metal, salt containing silver) and a reducing agent are added and treated. Further, if necessary, a conductive salt, a pH adjuster, a surfactant, a brightener, a crystal adjuster, a stabilizer, a precipitation inhibitor and the like can be added.
置換めっき法は、金属元素のイオン化傾向の違いを利用するものであり、析出させる金属イオン（錯イオンも含む）を含有する溶液中で粒子表面の別の金属溶解したときに発生する電子によって、溶液中の析出させる金属イオンを還元させて粒子表面に析出させるものであり、公知の方法を用いればよい。本実施の形態では表層にバリア層を有する銅粉の表面に銀を析出させることに用いることができる。例えば、バリア層を有する銅粉を水に分散させて水スラリーとし、この水スラリーに銀イオン源となる銀塩と錯化剤を添加して、処理する。銀塩としては水に可溶な銀塩であることが好ましく、硝酸銀を用いるのが好ましく、アンモニアの存在下で硝酸銀を用いるのがさらに好ましい。 The substitution plating method utilizes the difference in ionization tendency of metal elements, and is generated by electrons generated when another metal on the particle surface is dissolved in a solution containing metal ions (including complex ions) to be precipitated. The metal ions to be precipitated in the solution are reduced and precipitated on the particle surface, and a known method may be used. In this embodiment, it can be used to deposit silver on the surface of copper powder having a barrier layer on the surface layer. For example, copper powder having a barrier layer is dispersed in water to form an aqueous slurry, and a silver salt serving as a silver ion source and a complexing agent are added to the aqueous slurry for treatment. As the silver salt, a silver salt soluble in water is preferable, silver nitrate is preferably used, and silver nitrate is more preferably used in the presence of ammonia.
なお、より均一な厚みを有するコート層を得るために、各コート層を形成する前の表面を被覆しようとする粉末（例、銅粉）を洗浄してもよい。洗浄方法は特に限定されないが、表面を被覆しようとする粉末を水に分散させて水スラリーとした後、銅の酸化物や水酸化物を溶解除去可能な物質、例えば酒石酸やグリシンを添加、撹拌することにより洗浄処理を行い、洗浄処理後の水スラリーを、無電解めっき法を用いて各コート層を形成するのが好ましい。 In addition, in order to obtain a coat layer having a more uniform thickness, the powder (eg, copper powder) to be coated on the surface before forming each coat layer may be washed. The cleaning method is not particularly limited, but after the powder to be coated on the surface is dispersed in water to form an aqueous slurry, a substance capable of dissolving and removing copper oxide and hydroxide, for example, tartrate acid and glycine, is added and stirred. It is preferable to carry out the cleaning treatment by performing the cleaning treatment, and to form each coat layer of the water slurry after the cleaning treatment by using an electroless plating method.
また、得られたバリア層付銀コート銅粉の凝集を抑制するために、銀コート層を形成した（ステップＳ２０）後に、さらに、表面処理を施してもよい。表面処理剤としては、ステアリン酸やオレイン酸などのカルボン酸や、ポリビニルアルコールなどの分散剤として用いられる水溶性高分子化合物を使用することができる。またこれらを併用してもよい。 Further, in order to suppress the aggregation of the obtained silver-coated copper powder with a barrier layer, a surface treatment may be further performed after the silver-coated layer is formed (step S20). As the surface treatment agent, a carboxylic acid such as stearic acid or oleic acid, or a water-soluble polymer compound used as a dispersant such as polyvinyl alcohol can be used. Moreover, you may use these together.
銀コート層を形成した（ステップＳ２０）後、又は、表面処理した後は、得られたスラリーを洗浄、ろ過して乾燥することで、バリア層付銀コート銅粉を得る。洗浄、ろ過、及び乾燥方法については、公知の方法を用いることができる。 After forming the silver-coated layer (step S20) or surface-treating, the obtained slurry is washed, filtered and dried to obtain a silver-coated copper powder with a barrier layer. Known methods can be used for cleaning, filtration, and drying methods.
以下、本実施の形態について、実施例を用いてさらに具体的に説明するが、本発明は、以下の実施例に何ら限定されるものではない。なお、中心部（コア）となる銅粉の平均粒径およびバリア層付銀コート銅粉および銀コート銅粉の特性として、バリア層および銀コート層厚み、圧粉抵抗値、３５０℃加熱重量増加率、３００℃における変色の確認を、以下の通り評価している。 Hereinafter, the present embodiment will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. The average particle size of the copper powder as the core and the characteristics of the silver-coated copper powder with the barrier layer and the silver-coated copper powder include the thickness of the barrier layer and the silver-coated layer, the powder resistance value, and the increase in heating weight at 350 ° C. The rate and confirmation of discoloration at 300 ° C. are evaluated as follows.
（評価方法）
＜平均粒径＞
銅粉の平均粒径については、走査型電子顕微鏡（日本電子株式会社製、ＪＳＭ−７１００Ｆ）を用いて観察した画像より、全様が一様に観察できる粒子３００個以上の一次粒子の粒径を測長することによって、その個数平均値を求め平均粒径（ＳＥＭ径）とした。
(Evaluation method)
<Average particle size>
Regarding the average particle size of the copper powder, the particle size of 300 or more primary particles that can be uniformly observed from the image observed using a scanning electron microscope (JSM-7100F, manufactured by JEOL Ltd.) By measuring the length, the average value of the number was obtained and used as the average particle size (SEM diameter).
＜バリア層および銀コート層厚み＞
得られたバリア層付銀コート銅粉のニッケル、銀含有量については、ＩＣＰ発光分光分析法（アジレント・テクノロジー（株）製 ＩＣＰ−ＯＥＳ５１００ＳＶＤＶ）により求めた。得られたニッケルおよび銀含有量から体積を算出、上記方法で得たＳＥＭ径から、各被覆層の厚み（平均厚さ）を得た。
<Thickness of barrier layer and silver coat layer>
The nickel and silver contents of the obtained silver-coated copper powder with a barrier layer were determined by ICP emission spectroscopy (ICP-OES5100SVDV manufactured by Agilent Technologies, Inc.). The volume was calculated from the obtained nickel and silver contents, and the thickness (average thickness) of each coating layer was obtained from the SEM diameter obtained by the above method.
＜圧粉抵抗値＞
圧粉抵抗値は、粉末約５ｇを直径２０ｍｍの円筒内で２０ｋＮ（６３．７ＭＰａ）印加しながら三菱化学アナリテック社製粉体測定システムＭＣＰ−ＰＤ５１を用い、四探針法で測定した。
<Powder resistance value>
The powder resistance value was measured by a four-probe method using a powder measuring system MCP-PD51 manufactured by Mitsubishi Chemical Analytech Co., Ltd. while applying 20 kN (63.7 MPa) in a cylinder having a diameter of 20 mm with about 5 g of powder.
＜３５０℃加熱重量増加率＞
粉末の重量増加率はＮＥＴＺＳＣＨ ＪＡＰＡＮ社製ＴＧ−ＤＴＡ２０００ＳＲを用い、粉末約３０ｍｇをアルミナ容器中に入れ、装置に導入する空気流量１３０ｍｌ／ｍｉｎ、室温からの昇温速度１０℃／ｍｉｎの条件にて測定し、加熱前の試料重量に対する３５０℃時点の試料重量の増加率を求めた。
<350 ° C heating weight increase rate>
For the weight increase rate of the powder, use TG-DTA2000SR manufactured by NETZSCH JAPAN, put about 30 mg of the powder in an alumina container, and introduce it into the apparatus under the conditions of an air flow rate of 130 ml / min and a heating rate from room temperature of 10 ° C./min. The measurement was performed, and the rate of increase in the sample weight at 350 ° C. with respect to the sample weight before heating was determined.
＜３００℃における変色の確認＞
バリア層付銀コート銅粉を直接加熱し、黒化の程度を確認する測定では、得られた粉体を空気中３００℃に加熱したフルテック（株）製超小型簡易雰囲気炉ＦＴ−１０１中に投入、１０分後に取り出し、加熱前後の粉体を日本電色工業（株）社製の簡易型分光色差計（ＮＦ３３３）に粉体測定用アダプターを取り付け、Ｌ＊ａ＊ｂ＊表色系における明度Ｌ＊値を測定した。なお、測定条件は視野角１０°、光源Ｄ６５とした。
バリア層付銀コート銅粉を用いたペースト膜における粉体色の黒化の程度を確認する測定では、得られたバリア層付銀コート銅粉を再度イオン交換水中に分散し、ステアリン酸エマルジョン（中京油脂株式会社製セロゾール９２０）を銀コート銅粉に対しステアリン酸が０．４質量％になるよう投入し、２０分間混合後、ろ過、水洗後乾燥することにより表面処理を実施した。さらに、表面処理を施した銀コート銅粉９０．１９質量％に、エポキシ樹脂のビスフェノールＡ型エポキシ樹脂０．４５質量％、硬化剤のフェノールホルムアルデヒド型ノボラック樹脂０．２７質量％、溶剤のジプロピレングリコール９．０質量％、硬化促進剤の２−フェニル−４−メチルイミダゾ−ル０．０９質量％となるように各薬剤を混合し、自転・公転ミキサー（株式会社シンキー製あわとり練太郎）を用いてペースト化した。得られたペーストにジプロピレングリコールを添加して粘度調整をした後にアルミナ基板上に粘度調整後のペーストを印刷し、２００℃、３０分間大気中で熱硬化することで評価用ペースト膜とした。
<Confirmation of discoloration at 300 ° C>
In the measurement to directly heat the silver-coated copper powder with a barrier layer and check the degree of blackening, the obtained powder was heated to 300 ° C in the air in the ultra-compact simple atmosphere furnace FT-101 manufactured by Fulltec Co., Ltd. After 10 minutes of charging, take out the powder before and after heating by attaching a powder measurement adapter to a simple spectral color difference meter (NF333) manufactured by Nippon Denshoku Kogyo Co., Ltd., and in the L * a * b * color system. The brightness L * value was measured. The measurement conditions were a viewing angle of 10 ° and a light source D65.
In the measurement to confirm the degree of blackening of the powder color in the paste film using the silver-coated copper powder with the barrier layer, the obtained silver-coated copper powder with the barrier layer was dispersed again in the ion-exchanged water, and the stearic acid emulsion ( Serosol 920) manufactured by Chukyo Yushi Co., Ltd. was added to the silver-coated copper powder so that the amount of stearic acid was 0.4% by mass, mixed for 20 minutes, filtered, washed with water and dried to carry out surface treatment. Further, 90.19% by mass of surface-treated silver-coated copper powder, 0.45% by mass of bisphenol A type epoxy resin of epoxy resin, 0.27% by mass of phenol formaldehyde type novolak resin as curing agent, and dipropylene as solvent. Mix each drug so that the glycol content is 9.0% by mass and the curing accelerator 2-phenyl-4-methylimidazole 0.09% by mass, and the rotation / revolution mixer (Awatori Rentaro manufactured by Shinky Co., Ltd.) Was made into a paste using. Dipropylene glycol was added to the obtained paste to adjust the viscosity, and then the viscosity-adjusted paste was printed on an alumina substrate and heat-cured in the air at 200 ° C. for 30 minutes to obtain an evaluation paste film.
評価用ペースト膜を空気中３００℃に加熱されたホットプレート上に置き、１時間後のペースト膜表面の変色状態を確認することで変色の有無を確認した。具体的には、加熱前後のペースト膜表面を、日本電色工業（株）社製の簡易型分光色差計（ＮＦ３３３）を用いて、Ｌ＊ａ＊ｂ＊表色系における明度Ｌ＊値を測定することにより評価した。なお、測定条件は視野角１０°、光源Ｄ６５とした。 The presence or absence of discoloration was confirmed by placing the evaluation paste film on a hot plate heated to 300 ° C. in air and confirming the discolored state of the paste film surface after 1 hour. Specifically, the surface of the paste film before and after heating is measured by using a simple spectrocolorimeter (NF333) manufactured by Nippon Denshoku Kogyo Co., Ltd. to determine the brightness L * value in the L * a * b * color system. It was evaluated by measuring. The measurement conditions were a viewing angle of 10 ° and a light source D65.
（実施例１）
＜バリア層めっき工程＞
まず、ＳＥＭ径４．５μｍの銅粉（アトマイズ法で作製、株式会社高純度化学社製）をイオン交換水に分散させた。具体的には、銅粉１００ｇを３％酒石酸水溶液中で約１時間撹拌した後、ろ過、水洗して、２リットルのイオン交換水中に分散させた。銅粉を分散させたイオン交換水に、塩化ニッケル六水和物を４３ｇ、およびグリシンを１３ｇ投入し、撹拌して溶解させた。液温を６５℃、水酸化ナトリウム水溶液添加によってｐＨを１１．５に調整後、抱水ヒドラジンを１３．５ｇ添加し、ニッケルを還元して銅粉の表面にコートした。反応が終了した後、粉末をろ過、水洗し、エタノールを通じて乾燥させニッケルコート銅粉を得た。
＜銀めっき工程＞
次に、上記方法で得たニッケルコート銅粉約１１０ｇを３％酒石酸水溶液中で約１時間撹拌した後、ろ過、水洗して２リットルのイオン交換水中に分散させた。ここに抱水ヒドラジンを１３．８ｇ、ＥＤＴＡ（エチレンジアミン四酢酸）を１４０ｇ加えた後、５０℃に昇温した。一方で、イオン交換水２００ｍｌに硝酸銀３３ｇを添加した水溶液を準備し、所望の銀量に必要な液量を硝酸銀が１分間に１ｇ混合される速度で添加してニッケルコート銅粉の表面に無電解めっき法で銀をコートした。反応が終了した後、得られた粉末をろ過、水洗し、エタノールを通じて乾燥させ、ニッケルバリア層付銀コート銅粉を得た。
＜バリア層付銀コート銅粉＞
得られたニッケルバリア層付銀コート銅粉は、組成分析からニッケル含有量が７質量％、銀含有量が１２質量％であった。ニッケルバリア層厚みは６５ｎｍ、銀コート層厚みは９４ｎｍと計算される。得られたニッケルバリア層付銀コート銅粉の圧粉抵抗値、３５０℃加熱重量増加率、３００℃で１０分間加熱前後のＬ＊値、及び、ペースト膜の３００℃で１時間加熱前後のＬ＊値を確認した。結果を表１に示す。
(Example 1)
<Barrier layer plating process>
First, copper powder having an SEM diameter of 4.5 μm (produced by an atomizing method, manufactured by High Purity Chemical Co., Ltd.) was dispersed in ion-exchanged water. Specifically, 100 g of copper powder was stirred in a 3% aqueous tartaric acid solution for about 1 hour, filtered, washed with water, and dispersed in 2 liters of ion-exchanged water. 43 g of nickel chloride hexahydrate and 13 g of glycine were added to ion-exchanged water in which copper powder was dispersed, and the mixture was stirred and dissolved. The pH was adjusted to 11.5 by adjusting the liquid temperature to 65 ° C. and an aqueous sodium hydroxide solution, and then 13.5 g of hydrazine hydrate was added to reduce nickel and coat the surface of the copper powder. After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol to obtain nickel-coated copper powder.
<Silver plating process>
Next, about 110 g of the nickel-coated copper powder obtained by the above method was stirred in a 3% aqueous tartaric acid solution for about 1 hour, filtered, washed with water and dispersed in 2 liters of ion-exchanged water. After adding 13.8 g of hydrazine hydrate and 140 g of EDTA (ethylenediaminetetraacetic acid), the temperature was raised to 50 ° C. On the other hand, an aqueous solution prepared by adding 33 g of silver nitrate to 200 ml of ion-exchanged water is added at a rate of mixing 1 g of silver nitrate per minute to the desired amount of silver, and the surface of the nickel-coated copper powder is nonexistent. Silver was coated by electroless plating. After completion of the reaction, the obtained powder was filtered, washed with water, and dried through ethanol to obtain a silver-coated copper powder with a nickel barrier layer.
<Silver coated copper powder with barrier layer>
From the composition analysis, the obtained silver-coated copper powder with a nickel barrier layer had a nickel content of 7% by mass and a silver content of 12% by mass. The nickel barrier layer thickness is calculated to be 65 nm, and the silver coat layer thickness is calculated to be 94 nm. The powder resistance value of the obtained silver-coated copper powder with a nickel barrier layer, the heating weight increase rate at 350 ° C., the L * value before and after heating at 300 ° C. for 10 minutes, and the L * value before and after heating at 300 ° C. for 1 hour at 300 ° C. * Confirmed the value. The results are shown in Table 1.
（実施例２）
＜バリア層めっき工程＞
ＳＥＭ径４．５μｍの銅粉（アトマイズ法で作製、株式会社高純度化学社製）をイオン交換水に分散させた。具体的には、銅粉１００ｇを３％酒石酸水溶液中で約１時間撹拌した後、ろ過、水洗して、２リットルのイオン交換水中に分散させた。銅粉を分散させたイオン交換水に、塩化ニッケル六水和物を２３ｇ、塩化コバルト六水和物を６．３ｇおよびグリシンを８ｇ投入し、撹拌して溶解させた。液温を６５℃、水酸化ナトリウム水溶液添加によってｐＨを１１．５に調整後、抱水ヒドラジンを８．２ｇ添加し、ニッケルとコバルトを還元して銅粉の表面にコートした。反応が終了した後、粉末をろ過、水洗し、エタノールを通じて乾燥させニッケル・コバルトコート銅粉を得た。
＜銀めっき工程＞
次に、上記方法で得たニッケル・コバルトコート銅粉約１０７ｇを３％酒石酸水溶液中で約１時間撹拌した後、ろ過、水洗して１リットルのイオン交換水中に分散させた。ここに抱水ヒドラジンを５．８５ｇ、ＥＤＴＡを６０ｇ加えた後、５０℃に昇温した。一方で、イオン交換水１００ｍｌに硝酸銀１４ｇを添加した水溶液を準備し、所望の銀量に必要な液量を硝酸銀が１分間に１ｇ混合される速度で添加してニッケル・コバルトコート銅粉の表面に無電解めっき法で銀をコートした。反応が終了した後、得られた粉末をろ過、水洗し、エタノールを通じて乾燥させ、ニッケル・コバルトバリア層付銀コート銅粉を得た。
＜バリア層付銀コート銅粉＞
上記コート方法により作製し、得られたニッケル・コバルトバリア層付銀コート銅粉は、組成分析からニッケル含有量が５質量％、コバルト含有量が１質量％、銀含有量が１０質量％であった。ニッケル・コバルトバリア層厚みは５０ｎｍ、銀コート厚みは７５ｎｍと計算される。得られたニッケルバリア層付銀コート銅粉の圧粉抵抗値、３５０℃加熱重量増加率、３００℃で１０分間加熱前後のＬ＊値、及び、ペースト膜の３００℃で１時間加熱前後のＬ＊値を確認した。結果を表１に示す。
(Example 2)
<Barrier layer plating process>
Copper powder having an SEM diameter of 4.5 μm (produced by an atomizing method, manufactured by High Purity Chemical Co., Ltd.) was dispersed in ion-exchanged water. Specifically, 100 g of copper powder was stirred in a 3% aqueous tartaric acid solution for about 1 hour, filtered, washed with water, and dispersed in 2 liters of ion-exchanged water. 23 g of nickel chloride hexahydrate, 6.3 g of cobalt chloride hexahydrate and 8 g of glycine were added to ion-exchanged water in which copper powder was dispersed, and the mixture was stirred and dissolved. The pH was adjusted to 11.5 by adjusting the liquid temperature to 65 ° C. and an aqueous sodium hydroxide solution, and then 8.2 g of hydrazine hydrate was added to reduce nickel and cobalt and coat the surface of the copper powder. After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol to obtain nickel-cobalt-coated copper powder.
<Silver plating process>
Next, about 107 g of nickel-cobalt-coated copper powder obtained by the above method was stirred in a 3% aqueous tartaric acid solution for about 1 hour, filtered, washed with water and dispersed in 1 liter of ion-exchanged water. After adding 5.85 g of hydrazine hydrate and 60 g of EDTA, the temperature was raised to 50 ° C. On the other hand, an aqueous solution prepared by adding 14 g of silver nitrate to 100 ml of ion-exchanged water is added at a rate of mixing 1 g of silver nitrate per minute to the desired amount of silver, and the surface of the nickel-cobalt-coated copper powder is added. Was coated with silver by electroless plating. After completion of the reaction, the obtained powder was filtered, washed with water, and dried through ethanol to obtain a silver-coated copper powder with a nickel-cobalt barrier layer.
<Silver coated copper powder with barrier layer>
The silver-coated copper powder with a nickel-cobalt barrier layer produced by the above coating method had a nickel content of 5% by mass, a cobalt content of 1% by mass, and a silver content of 10% by mass based on composition analysis. It was. The nickel-cobalt barrier layer thickness is calculated to be 50 nm, and the silver coat thickness is calculated to be 75 nm. The powder resistance value of the obtained silver-coated copper powder with a nickel barrier layer, the heating weight increase rate at 350 ° C., the L * value before and after heating at 300 ° C. for 10 minutes, and the L * value before and after heating at 300 ° C. for 1 hour at 300 ° C. * Confirmed the value. The results are shown in Table 1.
（実施例３）
＜バリア層めっき工程＞
ＳＥＭ径２．６μｍの銅粉（アトマイズ法で作製、日本アトマイズ加工株式会社製）をイオン交換水に分散させた。具体的には、銅粉１００ｇを３％酒石酸水溶液中で約１時間撹拌した後、ろ過、水洗して、２リットルのイオン交換水中に分散させた。銅粉を分散させたイオン交換水に、塩化ニッケル六水和物を１００ｇおよびグリシンを３０ｇ投入し、撹拌して溶解させた。液温を６５℃、水酸化ナトリウム水溶液添加によってｐＨを１１．５に調整後、抱水ヒドラジンを２７ｇ添加し、ニッケルを還元して銅粉の表面にコートした。反応が終了した後、粉末をろ過、水洗し、エタノールを通じて乾燥させニッケルコート銅粉を得た。
＜銀めっき工程＞
次に、上記方法で得たニッケルコート銅粉約１２４ｇを３％酒石酸水溶液中で約１時間撹拌した後、ろ過、水洗して２リットルのイオン交換水中に分散させた。ここにＥＤＴＡを１９０ｇ加えた後、５０℃に昇温した。一方で、イオン交換水１２０ｍｌに硝酸銀１１５ｇを添加した水溶液を準備し、所望の銀量に必要な液量を硝酸銀が１分間に２ｇ混合される速度で添加してニッケルコート銅粉の表面に無電解めっき法で銀をコートした。反応が終了した後、得られた粉末をろ過、水洗し、エタノールを通じて乾燥させ、ニッケルバリア層付銀コート銅粉を得た。
＜バリア層付銀コート銅粉＞
上記コート方法により作製し、得られたニッケルバリア層付銀コート銅粉は、組成分析からニッケル含有量が１６質量％、銀含有量が３０質量％であった。ニッケルバリア層厚みは６１ｎｍ、銀コート厚みは１３０ｎｍと計算される。得られたニッケルバリア層付銀コート銅粉の圧粉抵抗値、３５０℃加熱重量増加率、３００℃で１０分間加熱前後のＬ＊値、及び、ペースト膜の３００℃で１時間加熱前後のＬ＊値を確認した。結果を表１に示す。
(Example 3)
<Barrier layer plating process>
Copper powder having an SEM diameter of 2.6 μm (produced by the atomizing method and manufactured by Nippon Atomizing Co., Ltd.) was dispersed in ion-exchanged water. Specifically, 100 g of copper powder was stirred in a 3% aqueous tartaric acid solution for about 1 hour, filtered, washed with water, and dispersed in 2 liters of ion-exchanged water. 100 g of nickel chloride hexahydrate and 30 g of glycine were added to ion-exchanged water in which copper powder was dispersed, and the mixture was stirred and dissolved. The pH was adjusted to 11.5 by adjusting the liquid temperature to 65 ° C. and an aqueous sodium hydroxide solution, and then 27 g of hydrazine hydrate was added to reduce nickel and coat the surface of the copper powder. After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol to obtain nickel-coated copper powder.
<Silver plating process>
Next, about 124 g of the nickel-coated copper powder obtained by the above method was stirred in a 3% aqueous tartaric acid solution for about 1 hour, filtered, washed with water and dispersed in 2 liters of ion-exchanged water. After adding 190 g of EDTA to this, the temperature was raised to 50 ° C. On the other hand, an aqueous solution prepared by adding 115 g of silver nitrate to 120 ml of ion-exchanged water is added at a rate of mixing 2 g of silver nitrate per minute to the desired amount of silver, and the surface of the nickel-coated copper powder is nonexistent. Silver was coated by electroless plating. After completion of the reaction, the obtained powder was filtered, washed with water, and dried through ethanol to obtain a silver-coated copper powder with a nickel barrier layer.
<Silver coated copper powder with barrier layer>
The silver-coated copper powder with a nickel barrier layer produced by the above coating method had a nickel content of 16% by mass and a silver content of 30% by mass from the composition analysis. The nickel barrier layer thickness is calculated to be 61 nm, and the silver coat thickness is calculated to be 130 nm. The powder resistance value of the obtained silver-coated copper powder with a nickel barrier layer, the heating weight increase rate at 350 ° C., the L * value before and after heating at 300 ° C. for 10 minutes, and the L * value before and after heating at 300 ° C. for 1 hour at 300 ° C. * Confirmed the value. The results are shown in Table 1.
（比較例１）
ニッケルめっき工程を省いた以外は実施例１と同様に処理を行い、ニッケルバリア層を含まない銀含有量１３質量％の銀コート銅粉を得た。銀コート厚みは９５ｎｍと計算される。得られた銀コート銅粉の圧粉抵抗値、３５０℃加熱重量増加率、３００℃で１０分間加熱前後のＬ＊値、及び、ペースト膜の３００℃で１時間加熱前後のＬ＊値を確認した。結果を表１に示す。
(Comparative Example 1)
The same treatment as in Example 1 was carried out except that the nickel plating step was omitted, to obtain a silver-coated copper powder having a silver content of 13% by mass, which did not contain a nickel barrier layer. The silver coat thickness is calculated to be 95 nm. Powder resistance of the resulting silver-coated copper powder, confirmed 350 ° C. heating rate of weight increase, before and after heating at 300 ° C. 10 minutes L * value, and the L * value of 1 hour before and after heating at 300 ° C. of paste film did. The results are shown in Table 1.
実施例１〜３および比較例１は、いずれも圧粉抵抗値は５０μΩ・ｃｍ以下と銀粉相当の抵抗値を示したが、比較例１は、銀コート銅粉及びペースト膜の両者において、３００℃加熱後のＬ＊値の低下が１０以上となり、黒化が確認された。比較例１は、銀コート銅粉の３５０℃加熱後の重量増加率も２．４質量％と高く、耐酸化性は不十分であった。一方、実施例１〜３のバリア層付銀コート銅粉及びペースト膜は、３００℃加熱後のＬ＊値の低下が１０未満であり、黒化も確認されていない。また、実施例１〜３のバリア層付銀コート銅粉では、３５０℃加熱後の重量増加率も０質量％〜０．３質量％と酸化による重量増分は抑制され、充分な耐酸化性を有していることが示された。
In Examples 1 to 3 and Comparative Example 1, the powder resistance value was 50 μΩ · cm or less, which was equivalent to that of silver powder, but Comparative Example 1 showed 300 in both the silver-coated copper powder and the paste film. The decrease in L * value after heating at ° C was 10 or more, and blackening was confirmed. In Comparative Example 1, the weight increase rate of the silver-coated copper powder after heating at 350 ° C. was as high as 2.4% by mass, and the oxidation resistance was insufficient. On the other hand, in the silver-coated copper powder with a barrier layer and the paste film of Examples 1 to 3, the decrease in L * value after heating at 300 ° C. was less than 10, and blackening was not confirmed. Further, in the silver-coated copper powders with a barrier layer of Examples 1 to 3, the weight increase rate after heating at 350 ° C. was 0% by mass to 0.3% by mass, and the weight increase due to oxidation was suppressed, and sufficient oxidation resistance was obtained. Shown to have.
Claims (7)
前記銀コート層の平均厚さは２０ｎｍ以上１５０ｎｍ以下であり、
前記バリア層の平均厚さは２０ｎｍ以上１５０ｎｍ以下である、
ことを特徴とするバリア層付銀コート銅粉。 Silver with a barrier layer having a copper powder having an average particle size of 0.5 μm or more and 10 μm or less, a silver-coated layer formed on the outermost surface, and a barrier layer formed between the copper powder and the silver-coated layer. Coated copper powder
The average thickness of the silver coat layer is 20 nm or more and 150 nm or less.
The average thickness of the barrier layer is 20 nm or more and 150 nm or less.
A silver-coated copper powder with a barrier layer.
かつ、空気中で室温から３００℃まで加熱し、３００℃で１０分間保持した場合、加熱後のＬ＊値の低下が、加熱前のＬ＊値と比較して、１０未満であることを特徴とする請求項１〜請求項５のいずれか一項に記載のバリア層付銀コート銅粉。 L * a * b * Brightness L * value in the color system is 70 or more,
Moreover, when heated from room temperature to 300 ° C. in air and held at 300 ° C. for 10 minutes, the decrease in L * value after heating is less than 10 as compared with the L * value before heating. The silver-coated copper powder with a barrier layer according to any one of claims 1 to 5.
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| JP2004052044A (en) * | 2002-07-19 | 2004-02-19 | Mitsui Mining & Smelting Co Ltd | Silver-coated copper powder and its manufacturing method |
| JP2014032921A (en) * | 2012-08-06 | 2014-02-20 | Natoko Kk | Electroconductive fine particle |
| JP2014105387A (en) * | 2012-11-30 | 2014-06-09 | Mitsui Mining & Smelting Co Ltd | Silver coat copper powder and manufacturing method thereof |
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| JP2002075057A (en) * | 2000-08-30 | 2002-03-15 | Mitsui Mining & Smelting Co Ltd | Coated copper powder |
| JP2004052044A (en) * | 2002-07-19 | 2004-02-19 | Mitsui Mining & Smelting Co Ltd | Silver-coated copper powder and its manufacturing method |
| JP2014032921A (en) * | 2012-08-06 | 2014-02-20 | Natoko Kk | Electroconductive fine particle |
| JP2014105387A (en) * | 2012-11-30 | 2014-06-09 | Mitsui Mining & Smelting Co Ltd | Silver coat copper powder and manufacturing method thereof |
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