JP5176824B2 - Silver-coated copper fine particles, dispersion thereof, and production method thereof - Google Patents
Silver-coated copper fine particles, dispersion thereof, and production method thereof Download PDFInfo
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- JP5176824B2 JP5176824B2 JP2008247106A JP2008247106A JP5176824B2 JP 5176824 B2 JP5176824 B2 JP 5176824B2 JP 2008247106 A JP2008247106 A JP 2008247106A JP 2008247106 A JP2008247106 A JP 2008247106A JP 5176824 B2 JP5176824 B2 JP 5176824B2
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- 239000010949 copper Substances 0.000 title claims description 359
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims description 355
- 229910052802 copper Inorganic materials 0.000 title claims description 339
- 239000010419 fine particle Substances 0.000 title claims description 294
- 229910052709 silver Inorganic materials 0.000 title claims description 208
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 title claims description 207
- 239000004332 silver Substances 0.000 title claims description 205
- 239000006185 dispersion Substances 0.000 title claims description 100
- 238000004519 manufacturing process Methods 0.000 title claims description 33
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 115
- 239000002245 particle Substances 0.000 claims description 93
- 229910000510 noble metal Inorganic materials 0.000 claims description 62
- 229920003169 water-soluble polymer Polymers 0.000 claims description 57
- 229910052736 halogen Inorganic materials 0.000 claims description 40
- 150000002367 halogens Chemical class 0.000 claims description 38
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 claims description 37
- 229920002873 Polyethylenimine Polymers 0.000 claims description 32
- 239000002904 solvent Substances 0.000 claims description 30
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical compound OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 claims description 24
- FOIXSVOLVBLSDH-UHFFFAOYSA-N Silver ion Chemical compound [Ag+] FOIXSVOLVBLSDH-UHFFFAOYSA-N 0.000 claims description 23
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 23
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 23
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- 239000000084 colloidal system Substances 0.000 claims description 21
- 150000002736 metal compounds Chemical class 0.000 claims description 21
- 239000002798 polar solvent Substances 0.000 claims description 21
- 238000006467 substitution reaction Methods 0.000 claims description 19
- 239000011248 coating agent Substances 0.000 claims description 17
- 238000000576 coating method Methods 0.000 claims description 17
- 229920000083 poly(allylamine) Polymers 0.000 claims description 14
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 claims description 14
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 13
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 claims description 12
- 230000002829 reductive effect Effects 0.000 claims description 12
- 239000005751 Copper oxide Substances 0.000 claims description 10
- 229910001956 copper hydroxide Inorganic materials 0.000 claims description 10
- 229910000431 copper oxide Inorganic materials 0.000 claims description 10
- 150000002500 ions Chemical class 0.000 claims description 10
- 239000007788 liquid Substances 0.000 claims description 10
- 239000005750 Copper hydroxide Substances 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 9
- 230000006911 nucleation Effects 0.000 claims description 9
- 238000010899 nucleation Methods 0.000 claims description 9
- 150000003839 salts Chemical class 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 8
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 7
- 229920000642 polymer Polymers 0.000 claims description 7
- 239000000758 substrate Substances 0.000 claims description 7
- 238000001179 sorption measurement Methods 0.000 claims description 6
- 150000004679 hydroxides Chemical class 0.000 claims description 2
- 239000011859 microparticle Substances 0.000 claims 1
- 239000000243 solution Substances 0.000 description 67
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 33
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 23
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 21
- 238000000034 method Methods 0.000 description 20
- 239000002994 raw material Substances 0.000 description 18
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 18
- 238000010304 firing Methods 0.000 description 17
- 230000003647 oxidation Effects 0.000 description 17
- 238000007254 oxidation reaction Methods 0.000 description 17
- 230000000694 effects Effects 0.000 description 13
- 238000006722 reduction reaction Methods 0.000 description 13
- 239000002270 dispersing agent Substances 0.000 description 12
- 235000015165 citric acid Nutrition 0.000 description 11
- 229910052763 palladium Inorganic materials 0.000 description 11
- 238000003756 stirring Methods 0.000 description 11
- 238000000108 ultra-filtration Methods 0.000 description 11
- 230000002776 aggregation Effects 0.000 description 10
- 238000004220 aggregation Methods 0.000 description 10
- 239000000976 ink Substances 0.000 description 10
- 239000000843 powder Substances 0.000 description 9
- 229910001961 silver nitrate Inorganic materials 0.000 description 9
- -1 amine organic compound Chemical class 0.000 description 8
- 239000000460 chlorine Substances 0.000 description 8
- 239000010410 layer Substances 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 7
- 229910052801 chlorine Inorganic materials 0.000 description 7
- 229920005862 polyol Polymers 0.000 description 7
- 238000004917 polyol method Methods 0.000 description 7
- 150000003077 polyols Chemical class 0.000 description 7
- 230000009467 reduction Effects 0.000 description 7
- 238000005406 washing Methods 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- BERDEBHAJNAUOM-UHFFFAOYSA-N copper(I) oxide Inorganic materials [Cu]O[Cu] BERDEBHAJNAUOM-UHFFFAOYSA-N 0.000 description 5
- KRFJLUBVMFXRPN-UHFFFAOYSA-N cuprous oxide Chemical compound [O-2].[Cu+].[Cu+] KRFJLUBVMFXRPN-UHFFFAOYSA-N 0.000 description 5
- 229940112669 cuprous oxide Drugs 0.000 description 5
- 239000012776 electronic material Substances 0.000 description 5
- 150000002148 esters Chemical class 0.000 description 5
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 description 4
- RGHNJXZEOKUKBD-SQOUGZDYSA-N D-gluconic acid Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C(O)=O RGHNJXZEOKUKBD-SQOUGZDYSA-N 0.000 description 4
- 239000000654 additive Substances 0.000 description 4
- 230000000996 additive effect Effects 0.000 description 4
- 239000003957 anion exchange resin Substances 0.000 description 4
- 230000006866 deterioration Effects 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000011347 resin Substances 0.000 description 4
- 229920005989 resin Polymers 0.000 description 4
- 239000010944 silver (metal) Substances 0.000 description 4
- 238000005245 sintering Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000003786 synthesis reaction Methods 0.000 description 4
- 229910002651 NO3 Inorganic materials 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 239000010946 fine silver Substances 0.000 description 3
- 230000026030 halogenation Effects 0.000 description 3
- 238000005658 halogenation reaction Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 229940100890 silver compound Drugs 0.000 description 3
- 150000003379 silver compounds Chemical class 0.000 description 3
- BJEPYKJPYRNKOW-REOHCLBHSA-N (S)-malic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O BJEPYKJPYRNKOW-REOHCLBHSA-N 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- JJLJMEJHUUYSSY-UHFFFAOYSA-L Copper hydroxide Chemical class [OH-].[OH-].[Cu+2] JJLJMEJHUUYSSY-UHFFFAOYSA-L 0.000 description 2
- RGHNJXZEOKUKBD-UHFFFAOYSA-N D-gluconic acid Natural products OCC(O)C(O)C(O)C(O)C(O)=O RGHNJXZEOKUKBD-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 229910021607 Silver chloride Inorganic materials 0.000 description 2
- BJEPYKJPYRNKOW-UHFFFAOYSA-N alpha-hydroxysuccinic acid Natural products OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 229920001940 conductive polymer Polymers 0.000 description 2
- 150000001879 copper Chemical class 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 238000007429 general method Methods 0.000 description 2
- 239000000174 gluconic acid Substances 0.000 description 2
- 235000012208 gluconic acid Nutrition 0.000 description 2
- 150000002334 glycols Chemical class 0.000 description 2
- 239000004310 lactic acid Substances 0.000 description 2
- 235000014655 lactic acid Nutrition 0.000 description 2
- 239000001630 malic acid Substances 0.000 description 2
- 235000011090 malic acid Nutrition 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 230000005012 migration Effects 0.000 description 2
- 239000012046 mixed solvent Substances 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000007639 printing Methods 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000010301 surface-oxidation reaction Methods 0.000 description 2
- 238000002411 thermogravimetry Methods 0.000 description 2
- 239000013585 weight reducing agent Substances 0.000 description 2
- ZXSQEZNORDWBGZ-UHFFFAOYSA-N 1,3-dihydropyrrolo[2,3-b]pyridin-2-one Chemical compound C1=CN=C2NC(=O)CC2=C1 ZXSQEZNORDWBGZ-UHFFFAOYSA-N 0.000 description 1
- 101150113959 Magix gene Proteins 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 230000000274 adsorptive effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 239000006172 buffering agent Substances 0.000 description 1
- 238000011088 calibration curve Methods 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 229940047586 chemet Drugs 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000011362 coarse particle Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- OPQARKPSCNTWTJ-UHFFFAOYSA-L copper(ii) acetate Chemical compound [Cu+2].CC([O-])=O.CC([O-])=O OPQARKPSCNTWTJ-UHFFFAOYSA-L 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 238000010908 decantation Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- YNKVVRHAQCDJQM-UHFFFAOYSA-P diazanium dinitrate Chemical compound [NH4+].[NH4+].[O-][N+]([O-])=O.[O-][N+]([O-])=O YNKVVRHAQCDJQM-UHFFFAOYSA-P 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000000635 electron micrograph Methods 0.000 description 1
- 238000004993 emission spectroscopy Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000000445 field-emission scanning electron microscopy Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 125000000879 imine group Chemical group 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 150000004692 metal hydroxides Chemical class 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229940023462 paste product Drugs 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000003223 protective agent Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000010405 reoxidation reaction Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 150000003378 silver Chemical class 0.000 description 1
- 229910001958 silver carbonate Inorganic materials 0.000 description 1
- LKZMBDSASOBTPN-UHFFFAOYSA-L silver carbonate Substances [Ag].[O-]C([O-])=O LKZMBDSASOBTPN-UHFFFAOYSA-L 0.000 description 1
- 230000007847 structural defect Effects 0.000 description 1
- ACTRVOBWPAIOHC-XIXRPRMCSA-N succimer Chemical compound OC(=O)[C@@H](S)[C@@H](S)C(O)=O ACTRVOBWPAIOHC-XIXRPRMCSA-N 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
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Images
Landscapes
- Pigments, Carbon Blacks, Or Wood Stains (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
- Powder Metallurgy (AREA)
- Conductive Materials (AREA)
- Non-Insulated Conductors (AREA)
Description
本発明は、銀被覆銅微粒子及びその分散液、並びにその製造方法に関するものである。更に詳しくは、粒径が微細で、低温焼成が可能であり、特に電子材料の配線形成用として有用な銀被覆銅微粒子及びその分散液に関する。 The present invention relates to silver-coated copper fine particles, a dispersion thereof, and a production method thereof. More specifically, the present invention relates to a silver-coated copper fine particle and a dispersion thereof, which have a fine particle size and can be fired at a low temperature, and are particularly useful for wiring formation of electronic materials.
従来から、金属微粒子は、電子材料用の導電性ペーストのような配線形成材料として、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。特に粒径が１００ｎｍ以下の金属微粒子は、通常のサブミクロン以上の粒子と異なり焼成温度が極めて低くなるため、低温焼成ペースト等への応用が検討されている。 Conventionally, metal fine particles have been used as a wiring forming material such as a conductive paste for electronic materials for printed wiring, semiconductor internal wiring, connection between a printed wiring board and electronic components, and the like. In particular, metal fine particles having a particle size of 100 nm or less have an extremely low firing temperature unlike ordinary submicron or more particles, and therefore, application to a low-temperature fired paste or the like is being studied.
最近では、インクジェットプリンター等を用いて金属微粒子を含有するインクにより配線パターンを印刷し、低温焼成して配線を形成する技術が着目され、研究開発が進められている。低温焼成用のペーストやインクに用いる金属微粒子粉としては、抵抗値が低く耐酸化性の高い銀を用いる技術が数多く開示されている。例えば特開２００７−０１９０５５号公報には、粒子表面が有機保護剤で覆われた平均粒径５０ｎｍ以下の銀粒子分散液が提案されている。しかし、銀はエレクトロマイグレーション発生の問題があり、本質的には電子回路形成用途には適さない。また、高価であることも欠点として挙げられる。 Recently, a technique for printing a wiring pattern with an ink containing metal fine particles using an ink jet printer or the like and firing it at a low temperature to form a wiring has been paid attention and research and development have been advanced. Many techniques using silver having a low resistance value and high oxidation resistance have been disclosed as metal fine particle powders used in pastes and inks for low-temperature firing. For example, Japanese Patent Application Laid-Open No. 2007-019055 proposes a silver particle dispersion liquid having an average particle diameter of 50 nm or less whose particle surface is covered with an organic protective agent. However, silver has a problem of occurrence of electromigration and is essentially not suitable for use in forming electronic circuits. Another disadvantage is that it is expensive.
そのため、導電性に優れ且つエレクトロマイグレーションの発生が少ない金属である銅微粒子の開発が、近年盛んに行なわれている。例えば特開２００５−３０７３３５号公報には、銅の酸化物、水酸化物又は塩を、エチレングリコール、ジエチレングリコール又はトリエチレングリコールの溶液中において、核生成のために貴金属イオンを添加すると共に、分散剤としてポリビニルピロリドン、還元反応制御剤としてアミン系有機化合物を添加して加熱還元し、銅微粒子を得る方法が提案されている。また、特開２００５−３３０５５２号公報には、同様にポリオール溶液中で、核生成のためにパラジウムイオンを添加すると共に、分散剤としてポリエチレンイミンを添加して加熱還元し、銅微粒子を得る方法が提案されている。 For this reason, development of copper fine particles, which is a metal having excellent conductivity and less electromigration, has been actively conducted in recent years. For example, in Japanese Patent Application Laid-Open No. 2005-307335, a copper oxide, hydroxide, or salt is added to a solution of ethylene glycol, diethylene glycol, or triethylene glycol to add a noble metal ion for nucleation, and a dispersant. There has been proposed a method for obtaining copper fine particles by adding polyvinyl pyrrolidone and an amine organic compound as a reduction reaction control agent and reducing by heating. Similarly, JP-A-2005-330552 discloses a method in which palladium ions are added for nucleation in a polyol solution, and polyethyleneimine is added as a dispersant, followed by heat reduction to obtain copper fine particles. Proposed.
しかしながら、これらの方法では、平均粒径５０ｎｍ以下の銅微粒子が得られるが、導電膜を得るためには４％水素−窒素中にて２５０℃での加熱を必要とするため、適用できる分野が限定されている。また、得られた導電膜の体積抵抗率は２００μΩ・ｃｍ程度であり、比較的高い抵抗値となっている。その他にも銅微粒子に関する文献は多数存在するが、銅は耐酸化性に劣る欠点を有し、また銀と比べて焼結性が低いため、低温焼成時の体積抵抗率が銀に比べ高くなる傾向がある。 However, with these methods, copper fine particles having an average particle size of 50 nm or less can be obtained. However, in order to obtain a conductive film, heating at 250 ° C. in 4% hydrogen-nitrogen is required. Limited. The obtained conductive film has a volume resistivity of about 200 μΩ · cm, which is a relatively high resistance value. There are many other documents related to copper fine particles, but copper has the disadvantage of being inferior in oxidation resistance, and also has lower sinterability than silver, so the volume resistivity during low-temperature firing is higher than that of silver. Tend.
銅粉の耐酸化性を向上させ、良好な導電性を得る方法として、銅粒子表面に銀を被覆させる方法が提案されている。例えば特開２０００−２４８３０３号公報には、還元剤が溶存した水溶液中で金属銅粉と硝酸銀を反応させる銀被覆銅粉の製造方法が提案されている。また、置換反応を利用したものとして、特開２００６−１６１０８１号公報には、ＪＩＳ Ｚ ８７２９に規定される明度Ｌ＊が５０以上である銅粉と、銀イオンが存在する有機溶媒含有溶液中で、銀イオンと金属銅との置換反応により、銀を銅粒子の表面に被覆する銀被覆銅粉の製造方法が記載されている。 As a method of improving the oxidation resistance of copper powder and obtaining good conductivity, a method of coating the surface of copper particles with silver has been proposed. For example, JP 2000-248303 A proposes a method for producing silver-coated copper powder in which metal copper powder and silver nitrate are reacted in an aqueous solution in which a reducing agent is dissolved. Moreover, as a thing using a substitution reaction, in Unexamined-Japanese-Patent No. 2006-161081, in the organic solvent containing solution in which the copper powder whose brightness L * prescribed | regulated to JISZ8729 is 50 or more, and silver ion exist. The manufacturing method of the silver covering copper powder which coat | covers silver on the surface of a copper particle by substitution reaction of silver ion and metallic copper is described.
また、特開２００４−０５２０４４号公報には、銀コート銅粉における銀の重量パーセントとレーザー回折散乱式粒度分布測定による重量累積粒径Ｄ５０との積Ｘ及び、銀コート銅粉の色差測定によるＬ＊の関係が特定式となる銀コート粉と、銅粉とを酸性溶液中に分散し、その銅粉分散液にキレート化剤を加えて銅粉スラリーを調整した後、緩衝剤を添加してｐＨ調整を行い、銅粉スラリーに銀イオン溶液を連続的に添加することで、置換反応により銅粉表面へ銀層を形成する銀コート銅粉の製造方法が提案されている。 Further, JP 2004-052044, the product X and the weight cumulative particle diameter D 50 by weight percent and laser diffraction scattering particle size distribution measurement of silver in the silver-coated copper powder, according to the color difference measurement of the silver-coated copper powder Disperse silver coat powder and copper powder in which the relationship of L * is a specific formula in an acidic solution, add a chelating agent to the copper powder dispersion to adjust the copper powder slurry, and then add a buffering agent. A method for producing silver-coated copper powder has been proposed in which a pH is adjusted and a silver ion solution is continuously added to the copper powder slurry to form a silver layer on the surface of the copper powder by a substitution reaction.
しかし、これらの方法は、いずれも銅粉の耐酸化性を向上させ、良好な導電性を得ることを目的としているものの、粒径が数μｍと大きなものであり、粒径１００ｎｍ以下の微細な粒子を用いた低温焼成時の体積抵抗率の改善に着目したものではない。このように、従来の技術では、インクジェットプリンター等を用いた配線パターンの印刷への適応が可能であって、低温焼成時の体積抵抗率が十分に低い銅微粒子は開発されていないのが現状である。 However, all of these methods aim to improve the oxidation resistance of the copper powder and obtain good conductivity, but the particle size is as large as several μm, and the particle size is 100 nm or less. It does not focus on improving the volume resistivity during low-temperature firing using particles. As described above, in the conventional technology, it is possible to adapt to the printing of a wiring pattern using an ink jet printer or the like, and copper fine particles having a sufficiently low volume resistivity at the time of low-temperature firing have not been developed at present. is there.
本発明は、上記した従来の事情に鑑み、低温焼成が可能であって且つ低い体積抵抗率が得られ、配線材料用として好適な銀被覆銅微粒子及びその分散液を提供すること、並びに、その銀被覆銅微粒子及びその分散液の大量生産に適した簡便な製造方法を提供することを目的とするものである。 In view of the above-described conventional circumstances, the present invention provides a silver-coated copper fine particle suitable for wiring materials and a dispersion thereof, which can be fired at a low temperature and has a low volume resistivity, and its An object of the present invention is to provide a simple production method suitable for mass production of silver-coated copper fine particles and dispersions thereof.
本発明者は、上記目的を達成するため、低体積抵抗率が得られる低温焼結性に優れた銅微粒子について検討を重ね、平均粒径が１００ｎｍ以下で均一な銅微粒子表面に極めて薄い銀被膜を形成することによって、低温焼結性と体積抵抗率が改善されること、及び銅微粒子分散液に特定量の銀イオン含有溶液を添加する簡便な方法で上記銀被覆銅微粒子が得られることを見出し、本発明を完成したものである。 In order to achieve the above object, the present inventor has repeatedly studied copper fine particles excellent in low-temperature sinterability capable of obtaining a low volume resistivity, and an extremely thin silver coating on the surface of uniform copper fine particles having an average particle size of 100 nm or less. That the low-temperature sinterability and volume resistivity are improved, and that the silver-coated copper fine particles can be obtained by a simple method of adding a specific amount of silver ion-containing solution to the copper fine particle dispersion. The title and the present invention have been completed.
即ち、本発明が提供する銀被覆銅微粒子は、銅を主成分とする銅微粒子と銅微粒子表面の少なくとも一部を被覆している銀とからなる銀被覆銅微粒子であって、平均粒径が１０〜１００ｎｍ、相対標準偏差（標準偏差σ／平均粒径ｄ）が６０％以下であり、銀の銅に対する割合が０.３〜１５質量％であることを特徴とするものである。 That is, the silver-coated copper fine particles provided by the present invention are silver-coated copper fine particles composed of copper fine particles mainly composed of copper and silver covering at least a part of the surface of the copper fine particles. 10 to 100 nm, the relative standard deviation (standard deviation σ / average particle diameter d) is 60% or less, and the ratio of silver to copper is 0.3 to 15% by mass.
上記本発明の銀被覆銅微粒子においては、銀被覆銅微粒子の表面に、ポリエチレンイミン、ポリビニルピロリドン、ポリアリルアミンから選ばれた少なくとも１種の水溶性高分子が吸着していることが好ましく、その水溶性高分子の吸着量は銀被覆銅微粒子の１.５質量％以下であることが好ましい。また、上記本発明の銀被覆銅微粒子は、ハロゲン元素の合計含有量が銅に対して２０質量ｐｐｍ以下であることが好ましい。 In the silver-coated copper fine particles of the present invention, it is preferable that at least one water-soluble polymer selected from polyethyleneimine, polyvinylpyrrolidone and polyallylamine is adsorbed on the surface of the silver-coated copper fine particles. The adsorption amount of the conductive polymer is preferably 1.5% by mass or less of the silver-coated copper fine particles. The silver-coated copper fine particles of the present invention preferably have a total content of halogen elements of 20 mass ppm or less with respect to copper.
また、本発明が提供する銀被覆銅微粒子分散液は、上記本発明の銀被覆銅微粒子と溶媒とからなる銀被覆銅微粒子分散液であって、溶媒中にエチレングリコール、ジエチレングリコール、トリエチレングリコールの少なくとも１種と、水及びエタノールの少なくとも１種を含むことを特徴とする。 The silver-coated copper fine particle dispersion provided by the present invention is a silver-coated copper fine particle dispersion comprising the silver-coated copper fine particles of the present invention and a solvent, and contains ethylene glycol, diethylene glycol, triethylene glycol in the solvent. It contains at least one kind and at least one kind of water and ethanol.
上記本発明の銀被覆銅微粒子分散液においては、前記溶媒中に、更にヒドロキシカルボン酸を含むことが好ましい。また、上記本発明の銀被覆銅微粒子分散液は、基板に塗布後、窒素雰囲気中にて２２０℃で１時間焼成した際の体積抵抗率が４０μΩ・ｃｍ以下となることを特徴とするものである。 In the silver-coated copper fine particle dispersion of the present invention, it is preferable that the solvent further contains a hydroxycarboxylic acid. Further, the silver-coated copper fine particle dispersion of the present invention is characterized in that the volume resistivity is 40 μΩ · cm or less when applied to a substrate and then baked at 220 ° C. for 1 hour in a nitrogen atmosphere. is there.
本発明が提供する銀被覆銅微粒子の製造方法は、平均粒径が１０〜１００ｎｍ、相対標準偏差（標準偏差σ／平均粒径ｄ）が６０％以下の銅微粒子を含む銅微粒子分散液に、銅微粒子分散液中の銅に対する銀の割合が０.３〜１５質量％となるように銀イオン含有溶液を添加し、置換反応によって銀を銅微粒子表面に析出させることを特徴とするものである。 The method for producing silver-coated copper fine particles provided by the present invention comprises a copper fine particle dispersion containing copper fine particles having an average particle size of 10 to 100 nm and a relative standard deviation (standard deviation σ / average particle size d) of 60% or less. A silver ion-containing solution is added so that the ratio of silver to copper in the copper fine particle dispersion is 0.3 to 15% by mass, and silver is precipitated on the surface of the copper fine particles by a substitution reaction. .
上記本発明の銀被覆銅微粒子の製造方法において、前記銅微粒子は、エチレングリコール、ジエチレングリコール又はトリエチレングリコールに、ポリエチレンイミン、ポリビニルピロリドン、ポリアリルアミンから選ばれた少なくとも１種の水溶性高分子を添加した溶液中において、銅の酸化物、水酸化物又は塩を加熱還元して得られた銅微粒子であることを特徴とする。 In the method for producing silver-coated copper fine particles of the present invention, the copper fine particles are added with at least one water-soluble polymer selected from polyethyleneimine, polyvinylpyrrolidone, and polyallylamine to ethylene glycol, diethylene glycol, or triethylene glycol. In the solution, copper fine particles obtained by heating and reducing copper oxide, hydroxide or salt are characterized.
上記本発明の銀被覆銅微粒子の製造方法においては、前記溶液に、核生成のための貴金属化合物又は貴金属コロイドを添加することが好ましい。また、前記銅微粒子分散液にヒドロキシカルボン酸又はその溶液を添加することにより、銅微粒子に吸着している水溶性高分子の一部をヒドロキシカルボン酸で置換して、銅微粒子に吸着している水溶性高分子の量を１.５質量％未満とすることが好ましい。更に、前記銅微粒子分散液及び銀イオン含有溶液中におけハロゲン元素の合計含有量を、銅に対して２０質量ｐｐｍ未満に制御することが好ましい。 In the method for producing silver-coated copper fine particles of the present invention, it is preferable to add a noble metal compound or a noble metal colloid for nucleation to the solution. Further, by adding hydroxycarboxylic acid or a solution thereof to the copper fine particle dispersion, a part of the water-soluble polymer adsorbed on the copper fine particles is replaced with hydroxycarboxylic acid, and adsorbed on the copper fine particles. The amount of the water-soluble polymer is preferably less than 1.5% by mass. Furthermore, it is preferable to control the total content of halogen elements in the copper fine particle dispersion and the silver ion-containing solution to less than 20 ppm by mass with respect to copper.
また、本発明が提供する銀被覆銅微粒子分散液の製造方法は、エチレングリコール、ジエチレングリコール又はトリエチレングリコールに、ポリエチレンイミン、ポリビニルピロリドン、ポリアリルアミンから選ばれた少なくとも１種の水溶性高分子を添加した溶液中において、銅の酸化物、水酸化物又は塩を加熱還元して銅微粒子を生成させ、得られた銅微粒子分散液を極性溶媒で溶媒置換及び濃縮した後、銀イオン含有溶液を添加して銀を銅微粒子表面に析出させることを特徴とする。 Further, the method for producing a silver-coated copper fine particle dispersion provided by the present invention comprises adding at least one water-soluble polymer selected from polyethyleneimine, polyvinylpyrrolidone and polyallylamine to ethylene glycol, diethylene glycol or triethylene glycol. In this solution, copper oxide, hydroxide or salt is heated to reduce to produce copper fine particles, and the resulting copper fine particle dispersion is solvent-substituted and concentrated with a polar solvent, and then a silver ion-containing solution is added. Then, silver is deposited on the surface of the copper fine particles.
上記本発明の銀被覆銅微粒子分散液の製造方法においては、前記銅微粒子分散液に銀イオン含有溶液を添加して銀を銅微粒子表面に析出させた後、更に極性溶媒で溶媒置換及び濃縮することにより、前記銀イオン含有溶液より混入する余剰のイオンを洗浄除去することが好ましい。 In the method for producing a silver-coated copper fine particle dispersion according to the present invention, a silver ion-containing solution is added to the copper fine particle dispersion to precipitate silver on the surface of the copper fine particles, followed by solvent substitution and concentration with a polar solvent. Thus, it is preferable to wash away and remove excess ions mixed from the silver ion-containing solution.
本発明によれば、低温での焼結特性に優れると同時に、配線材料として使用した場合、低温焼成で良好な導電性を示す銀被覆銅微粒子、及びその分散液を提供することができる。しかも、本発明が提供する銀被覆銅微粒子は、平均粒径が１０〜１００ｎｍと微細であることから、インクジェットプリンター用のインクとしても好適であり、工業的価値は極めて大きい。 ADVANTAGE OF THE INVENTION According to this invention, when using as a wiring material while being excellent in the sintering characteristic at low temperature, the silver coating copper fine particle which shows favorable electroconductivity by low-temperature baking, and its dispersion liquid can be provided. Moreover, since the silver-coated copper fine particles provided by the present invention have a fine average particle diameter of 10 to 100 nm, they are suitable as inks for ink jet printers and have an extremely great industrial value.
＜銀被覆銅微粒子＞
本発明の銀被覆銅微粒子は、銅を主成分とする銅微粒子と、その銅微粒子表面の少なくとも一部を被覆している銀とからなる。そして、本発明の銀被覆銅微粒子は、平均粒径が１０〜１００ｎｍであり、相対標準偏差（標準偏差σ／平均粒径ｄ）が６０％以下であって、銅微粒子の表面を被覆する銀の銅に対する割合が０.３〜１５質量％であることを特徴とするものである。
<Silver-coated copper fine particles>
The silver-coated copper fine particles of the present invention are composed of copper fine particles mainly composed of copper and silver covering at least a part of the surface of the copper fine particles. The silver-coated copper fine particles of the present invention have an average particle size of 10 to 100 nm, a relative standard deviation (standard deviation σ / average particle size d) of 60% or less, and silver covering the surface of the copper fine particles. The ratio with respect to copper is 0.3 to 15% by mass.
上記本発明による銀被覆銅微粒子においては、平均粒径が１０〜１００ｎｍであること、銅微粒子表面を被覆する銀の銅に対する割合が０.３〜１５質量％であることが重要である。即ち、銀被覆銅微粒子の粒径については、粒径を微細化して平均粒径１０〜１００ｎｍとすることで、焼結温度を低温化することが可能となり、優れた低温焼結性を得ることができる。 In the silver-coated copper fine particles according to the present invention, it is important that the average particle diameter is 10 to 100 nm, and the ratio of silver covering the surface of the copper fine particles to copper is 0.3 to 15% by mass. That is, with respect to the particle diameter of the silver-coated copper fine particles, the sintering temperature can be lowered by reducing the particle diameter to an average particle diameter of 10 to 100 nm, thereby obtaining excellent low-temperature sinterability. Can do.
ただし、銅微粒子の場合は、粒径の微細化によって表面酸化が起こりやすくなるため、微細化による低温焼結性の改善効果が十分得られないという問題が発生する。一方、銅粒子表面を銀により被覆して、低温焼結性、更には体積抵抗率を改善する場合、通常は、銅粒子表面を被覆する銀はある程度以上の厚さが必要となる。特に、粒径を微細化した場合には、表面積の増加により被覆に必要な銀量が飛躍的に増加する、あるいは、小粒径化により銀被覆時の銅粒子の凝集が発生しやすくなる等の問題点があった。 However, in the case of copper fine particles, surface oxidation is likely to occur due to the refinement of the particle size, so that there is a problem that the effect of improving the low-temperature sinterability due to the refinement cannot be obtained sufficiently. On the other hand, when the surface of the copper particles is coated with silver to improve the low-temperature sinterability and further the volume resistivity, usually, the silver covering the surface of the copper particles needs to have a certain thickness. In particular, when the particle size is refined, the amount of silver necessary for coating increases dramatically due to the increase in surface area, or the aggregation of copper particles during silver coating tends to occur due to the reduction in particle size, etc. There was a problem.
例えば、上記特許文献４では、必要な銀量は金属銅粉の比表面積に依存し、比表面積が数／１０ｍ２／ｇで、粒径が数μｍに相当する銅粉の場合、銅に対して０.５〜１０質量％の銀量が好ましく、銀層の厚みにして数ｎｍ〜数１０ｎｍが好ましいとしている。しかし、このような厚みの銀層でナノオーダーの銅微粒子粉を被覆しようとした場合、銅に対して必要な銀量は大幅に増加して数１０質量％以上になると見込まれるため、耐マイグレーション性並びにコストなどの点から現実的なものではない。 For example, in the above-mentioned Patent Document 4, the required silver amount depends on the specific surface area of the metal copper powder, and in the case of copper powder having a specific surface area of several ten m 2 / g and a particle size of several μm, The silver amount of 0.5 to 10% by mass is preferable, and the thickness of the silver layer is preferably several nm to several tens of nm. However, when trying to coat nano-order copper fine particle powder with a silver layer with such a thickness, the amount of silver required for copper is expected to increase significantly to several tens of mass% or more, and therefore migration resistance It is not realistic in terms of sex and cost.
本発明は、このような相反する問題点を解決して、低温焼結性に優れると同時に、十分に低い体積抵抗率が得られる銀被覆銅微粒子を開発したものである。即ち、銅微粒子を微細化して低温焼結性を向上させると共に、微細化によって発生する表面酸化による焼結性や体積抵抗率の悪化に対しては、銅微粒子表面を被覆する銀層を極めて薄くすることにより抑制することができる。 The present invention solves such conflicting problems and has developed silver-coated copper fine particles that are excellent in low-temperature sinterability and at the same time have a sufficiently low volume resistivity. In other words, the copper fine particles are refined to improve the low-temperature sinterability, and the silver layer covering the surface of the copper fine particles is extremely thin against the deterioration of sinterability and volume resistivity caused by surface oxidation caused by the miniaturization. This can be suppressed.
具体的には、平均粒径を１０〜１００ｎｍとし、より好ましくは１０〜５０ｎｍとして、低温焼結性を向上させ、同時に、銅微粒子表面を被覆する銀の銅に対する割合を０.３〜１５質量％とすることで、焼結性及び体積抵抗率の悪化を抑制している。例えば、平均粒径が３０ｎｍの場合、銀量が上記範囲の最大量である１５質量％としても、粒子全体を被覆している銀層の厚みは０.６ｎｍと見積もることができる。更に、銀層の厚みは表面が平滑な粒子として比表面積から計算されたものであり、現実的な微細な凹凸がある粒子では比表面積が増加するため、更に銀層の厚みは薄くなることになる。 Specifically, the average particle size is 10 to 100 nm, more preferably 10 to 50 nm, the low temperature sinterability is improved, and at the same time, the ratio of silver covering the copper fine particle surface to copper is 0.3 to 15 mass. By making it%, the deterioration of sinterability and volume resistivity is suppressed. For example, when the average particle size is 30 nm, the thickness of the silver layer covering the entire particle can be estimated to be 0.6 nm even if the silver amount is 15% by mass which is the maximum amount in the above range. Further, the thickness of the silver layer is calculated from the specific surface area as particles having a smooth surface, and the specific surface area increases in the case of particles having realistic fine irregularities, so that the thickness of the silver layer is further reduced. Become.
このように非常に薄い銀層では、粒子表面全体を均一な厚さで被覆することは困難であり、粒子表面の一部が銀で被覆されない場合もある。そのような場合であっても、本発明の銀被覆銅微粒子は平均粒径が１０〜１００ｎｍと微細であるため、優れた低温焼結性を有していることに加え、銅微粒子表面の少なくとも一部が銀で被覆されることによって、上記した焼結性と体積抵抗率の悪化を抑制するという優れた効果を得ることができる。 With such a very thin silver layer, it is difficult to coat the entire particle surface with a uniform thickness, and a part of the particle surface may not be coated with silver. Even in such a case, since the silver-coated copper fine particles of the present invention have a fine average particle diameter of 10 to 100 nm, in addition to having excellent low-temperature sinterability, at least the surface of the copper fine particles By partially coating with silver, it is possible to obtain an excellent effect of suppressing deterioration of the sinterability and volume resistivity described above.
銀被覆銅微粒子の平均粒径が１０ｎｍ未満の場合は、粒子の表面積が増加するため十分な銀被覆が得られず、被覆による効果が減少して耐酸化性も悪化する。逆に１００ｎｍを超える場合には、焼結活性が低下するため、焼成後の体積抵抗率が増加する。また、銀被覆銅微粒子の相対標準偏差（標準偏差σ／平均粒径ｄ）が６０％を超える場合、粒径が１０ｎｍ以下あるいは１００ｎｍ以上の粒子が多量に存在している可能性が高いため、耐酸化性や焼結性が悪化するばかりか、インクジェットプリンターによる吐出時にノズルが閉塞する危険がある。 When the average particle diameter of the silver-coated copper fine particles is less than 10 nm, the surface area of the particles increases, so that a sufficient silver coating cannot be obtained, the effect of the coating is reduced, and the oxidation resistance is also deteriorated. On the other hand, when it exceeds 100 nm, the sintering activity decreases, and thus the volume resistivity after firing increases. Further, when the relative standard deviation of the silver-coated copper fine particles (standard deviation σ / average particle diameter d) exceeds 60%, it is highly possible that a large amount of particles having a particle diameter of 10 nm or less or 100 nm or more exist. In addition to deterioration in oxidation resistance and sinterability, there is a risk of nozzle clogging during ejection by an ink jet printer.
銅微粒子を被覆している銀の銅に対する割合は、０.３〜１５質量％とする。銀の銅に対する割合を０.３〜１５質量％の範囲とすることにより、上記した平均粒径１０〜１００ｎｍの微粒子の効果と相俟って、優れた上記効果が得られる。この割合が０.３質量％未満では低温焼成後の体積抵抗率を十分に低減することができず、また１５質量％を超えても体積抵抗率の低減効果に大きな差は見られず、銀の割合が増えることでコストが増大する。 The ratio of silver covering the copper fine particles to copper is 0.3 to 15% by mass. By setting the ratio of silver to copper in the range of 0.3 to 15% by mass, the above-described effect can be obtained in combination with the effect of the fine particles having an average particle diameter of 10 to 100 nm. If this proportion is less than 0.3% by mass, the volume resistivity after low-temperature firing cannot be sufficiently reduced, and if it exceeds 15% by mass, there is no significant difference in the effect of reducing the volume resistivity. The cost increases as the percentage increases.
また、銅微粒子表面の銀による被覆は、銀と銅の置換による銀の析出によって起こるため、銅に対する銀の割合が大きくなると、銀の析出に伴う銅の溶解量が増加し、銅微粒子の表面状態の変化や有機物の脱離により銅微粒子の凝集や酸化が起こりやすくなる。そのため、最良の体積抵抗率の低減効果を得るためには、上記銀の銅に対する割合を０.３〜５質量％とすることが更に好ましい。 In addition, since the coating of silver on the surface of the copper fine particles occurs due to the precipitation of silver by substitution of silver and copper, when the ratio of silver to copper increases, the amount of copper dissolved due to silver precipitation increases, and the surface of the copper fine particles Aggregation and oxidation of copper fine particles are likely to occur due to the change of state and the detachment of organic substances. Therefore, in order to obtain the best volume resistivity reduction effect, the ratio of silver to copper is more preferably 0.3 to 5% by mass.
本発明に係る銀被覆銅微粒子の表面には、水溶性高分子が吸着していることが好ましい。上記水溶性高分子としては、極性溶媒と親和性が高く、銀被覆銅微粒子に吸着して立体障害を形成し得るものであればよい。具体的には、ポリエチレンイミン、ポリビニルピロリドン、ポリアリルアミンの内の少なくとも１種を好適に使用することができ、その中でもポリエチレンイミンが特に好ましい。 It is preferable that a water-soluble polymer is adsorbed on the surface of the silver-coated copper fine particles according to the present invention. The water-soluble polymer is not particularly limited as long as it has high affinity with a polar solvent and can adsorb to silver-coated copper fine particles to form steric hindrance. Specifically, at least one of polyethyleneimine, polyvinylpyrrolidone, and polyallylamine can be suitably used, and among these, polyethyleneimine is particularly preferable.
これらの水溶性高分子で銀被覆銅微粒子を被覆することで、銀被覆銅微粒子を溶媒中に分散させて分散液とした場合、水溶性高分子の立体障害により銀被覆銅微粒子の凝集が抑制され、分散液の分散安定性が向上する。また、電子材料用として好適なものとするため、ハロゲン元素を銀被覆銅微粒子から極力除去した場合、銀被覆銅微粒子表面への水溶性高分子の吸着が進まず、立体障害による凝集防止効果が十分得られない場合がある。このような場合でも、ポリエチレンイミンは銅との親和性が高いイミン基を有することから、銀被覆銅微粒子への吸着能が高く、銅微粒子表面に吸着して上記効果を得ることができる。 By coating silver-coated copper fine particles with these water-soluble polymers, when the silver-coated copper fine particles are dispersed in a solvent to form a dispersion, aggregation of the silver-coated copper fine particles is suppressed due to steric hindrance of the water-soluble polymer. As a result, the dispersion stability of the dispersion is improved. In addition, when halogen elements are removed from silver-coated copper fine particles as much as possible in order to make them suitable for electronic materials, the adsorption of water-soluble polymers on the surface of silver-coated copper fine particles does not progress, and the effect of preventing aggregation due to steric hindrance is achieved. You may not get enough. Even in such a case, since the polyethyleneimine has an imine group having a high affinity with copper, the adsorption ability to the silver-coated copper fine particles is high, and the above effect can be obtained by being adsorbed on the surface of the copper fine particles.
ただし、水溶性高分子は焼成の阻害要因になると同時に、水溶性高分子の量が多いほど焼成後の導電性を低下させやすい。そのため、低温焼成後の良好な体積抵抗率を得るためには、銀被覆銅微粒子表面に吸着している水溶性高分子の量を１.５質量％未満とすることが好ましい。水溶性高分子の量が１.５質量％を超えると、低温焼成後の体積抵抗率が上昇するため配線材料として好ましくない。 However, the water-soluble polymer becomes an impediment to firing, and at the same time, the greater the amount of the water-soluble polymer, the lower the conductivity after firing. Therefore, in order to obtain a good volume resistivity after low-temperature firing, the amount of the water-soluble polymer adsorbed on the surface of the silver-coated copper fine particles is preferably less than 1.5% by mass. If the amount of the water-soluble polymer exceeds 1.5% by mass, the volume resistivity after low-temperature firing increases, which is not preferable as a wiring material.
そこで、本発明においては、銀被覆銅微粒子表面に吸着している水溶性高分子の量を低減させるため、ヒドロキシカルボン酸によって水溶性高分子を置換することができる。尚、水溶性高分子の量を低減させると、導電性が向上する一方で耐酸化性は低下するが、ヒドロキシカルボン酸による被覆により酸化を抑制することが可能である。上記ヒドロキシカルボン酸としては、乳酸、グルコン酸、リンゴ酸、クエン酸が好ましく、体積抵抗率を改善する効果に優れているクエン酸を用いることが特に好ましい。 Therefore, in the present invention, the water-soluble polymer can be substituted with hydroxycarboxylic acid in order to reduce the amount of the water-soluble polymer adsorbed on the surface of the silver-coated copper fine particles. When the amount of the water-soluble polymer is reduced, the conductivity is improved while the oxidation resistance is lowered, but the oxidation can be suppressed by coating with a hydroxycarboxylic acid. As the hydroxycarboxylic acid, lactic acid, gluconic acid, malic acid, and citric acid are preferable, and it is particularly preferable to use citric acid that is excellent in the effect of improving volume resistivity.
本発明の銀被覆銅微粒子は、ハロゲン元素の合計含有量が２０質量ｐｐｍ以下であることが好ましい。ハロゲン元素の合計含有量が２０質量ｐｐｍを超える銀被覆銅微粒子を配線パターン等の導電材料として使用すると、マイグレーションや他の電子材料を腐食させる可能性が有るため好ましくない。また、ハロゲン元素は焼結の阻害要因となり、焼成後の体積抵抗率が上昇する原因となることもあるため、合計含有量を２０質量ｐｐｍに調整することが好ましい。 The silver-coated copper fine particles of the present invention preferably have a total halogen element content of 20 mass ppm or less. Use of silver-coated copper fine particles having a total halogen element content of more than 20 ppm by mass as a conductive material such as a wiring pattern is not preferable because migration and other electronic materials may be corroded. Further, since the halogen element becomes an impediment to sintering and may increase the volume resistivity after firing, it is preferable to adjust the total content to 20 mass ppm.
＜銀被覆銅微粒子分散液＞
本発明の銀含有銅微粒子分散液は、上記銀被覆銅微粒子と溶媒からなる。溶媒中には、エチレングリコール、ジエチレングリコール、トリエチレングリコールの内の少なくとも１種のグリコールと、水及びエタノールの内の少なくとも１種が含まれている。尚、上記溶媒としては、溶媒相互の分離を防止するため、水、アルコール、エステルなどの極性溶媒が好ましい。
<Silver-coated copper fine particle dispersion>
The silver-containing copper fine particle dispersion of the present invention comprises the above silver-coated copper fine particles and a solvent. The solvent contains at least one glycol selected from ethylene glycol, diethylene glycol, and triethylene glycol, and at least one selected from water and ethanol. In addition, as said solvent, in order to prevent isolation | separation of a solvent, polar solvents, such as water, alcohol, and ester, are preferable.
上記水溶性高分子が吸着した銀被覆銅微粒子を溶媒中に分散させた分散液は、粒子表面に吸着した水溶性高分子の立体障害により、酸化並びに凝集を抑制することができる。また、水あるいはエタノールを主成分とする溶媒を使用することにより、非極性有機溶媒を主成分とした場合と比較して、廃液や大気汚染による環境負荷を低減することができる。上記溶媒中には、体積抵抗率の改善のため、更にヒドロキシカルボン酸を含むことが好ましく、その中でも酸化及び凝集の抑制効果が大きいクエン酸を含むことが特に好ましい。 The dispersion in which the silver-coated copper fine particles adsorbed with the water-soluble polymer are dispersed in a solvent can suppress oxidation and aggregation due to steric hindrance of the water-soluble polymer adsorbed on the particle surface. Further, by using a solvent containing water or ethanol as a main component, it is possible to reduce the environmental load due to waste liquid or air pollution as compared with the case where a nonpolar organic solvent is used as a main component. In order to improve the volume resistivity, the solvent preferably further contains a hydroxycarboxylic acid, and particularly preferably citric acid that has a large effect of suppressing oxidation and aggregation.
本発明の銀被覆銅微粒子分散液は、低温焼成においても良好な導電性を示す。具体的には、銀被覆銅微粒子分散液を基板に塗布した後、通常は乾燥させ、窒素雰囲気中において２２０℃で１時間焼成したとき、その体積抵抗率が４０μΩ・ｃｍ以下の導電膜となる。 The silver-coated copper fine particle dispersion of the present invention exhibits good conductivity even at low temperature firing. Specifically, after the silver-coated copper fine particle dispersion is applied to the substrate, it is usually dried and when baked at 220 ° C. for 1 hour in a nitrogen atmosphere, the volume resistivity becomes a conductive film having a volume resistivity of 40 μΩ · cm or less. .
＜銀被覆銅微粒子及びその分散液の製造方法＞
本発明の銀被覆銅微粒子の製造方法は、平均粒径が１０〜１００ｎｍ、相対標準偏差（標準偏差σ／平均粒径ｄ）が６０％以下である銅微粒子を含む銅微粒子分散液に、その銅微粒子分散液に含有される銅に対する銀の割合が０.３〜１５質量％となるように銀イオン含有溶液を添加し、置換反応によって銀を銅微粒子表面に析出させることを特徴とするものである。
<Method for producing silver-coated copper fine particles and dispersion thereof>
The method for producing silver-coated copper fine particles of the present invention comprises a copper fine particle dispersion containing copper fine particles having an average particle size of 10 to 100 nm and a relative standard deviation (standard deviation σ / average particle size d) of 60% or less. A silver ion-containing solution is added so that the ratio of silver to copper contained in the copper fine particle dispersion is 0.3 to 15% by mass, and silver is precipitated on the surface of the copper fine particles by a substitution reaction. It is.
上記銅微粒子分散液に銀イオン含有溶液を添加して、銀を銅微粒子表面の銅と置換反応させることで、容易に銅微粒子表面の少なくとも１部が銀で被覆された銀被覆銅微粒子を得ることができる。また、上記の銀添加量では、ほぼ全量が銅と置換して銅微粒子表面に析出するため、得ようとする銀被覆銅微粒子における銀の銅に対する割合と同等の割合で銀を添加すればよい。ただし、反応条件により質量割合が若干ずれる場合があるが、同一条件では銀の析出量が安定しているため、少量での予備試験を行うことで必要な添加量を簡単に求めることができる。 A silver ion-containing solution is added to the copper fine particle dispersion, and silver is substituted with copper on the surface of the copper fine particles to easily obtain silver-coated copper fine particles in which at least a part of the surface of the copper fine particles is coated with silver. be able to. In addition, since almost the entire amount is replaced with copper and deposited on the surface of the copper fine particles with the above-mentioned silver addition amount, it is only necessary to add silver at a ratio equivalent to the ratio of silver to copper in the silver-coated copper fine particles to be obtained. . However, although the mass ratio may slightly deviate depending on the reaction conditions, the amount of silver deposited is stable under the same conditions. Therefore, the necessary addition amount can be easily obtained by conducting a preliminary test with a small amount.
また、上記銀被覆銅微粒子の製造方法においては、平均粒径が１０〜１００ｎｍ、更に好ましくは５０ｎｍ以下であり、相対標準偏差（標準偏差σ／平均粒径ｄ）が６０％以下の銅微粒子の分散液を用いる。このような分散液は、平均粒径及び相対標準偏差が上記範囲のものであれば、市販の銅微粒子分散液を用いてもよく、あるいは銅微粒子を溶媒に分散させて作製した分散液を用いてもよい。 In the method for producing the silver-coated copper fine particles, the copper fine particles having an average particle diameter of 10 to 100 nm, more preferably 50 nm or less, and a relative standard deviation (standard deviation σ / average particle diameter d) of 60% or less. Use dispersion. As long as the average particle size and the relative standard deviation are within the above ranges, such a dispersion may be a commercially available copper fine particle dispersion, or a dispersion prepared by dispersing copper fine particles in a solvent. May be.
上記銅微粒子は、ポリオール法を用いることで容易に製造することができる。即ち、本発明においては、エチレングリコール、ジエチレングリコール又はトリエチレングリコールなどのグリコール溶液中において、銅の酸化物、水酸化物又は塩を加熱還元することにより、銅微粒子を得ることが好ましい。また、加熱還元時には、上記銅微粒子分散液に、分散剤としてポリエチレンイミン、ポリビニルピロリドン、ポリアリルアミンの内の少なくとも１種の水溶性高分子を添加しておくことが好ましい。 The copper fine particles can be easily produced by using a polyol method. That is, in the present invention, it is preferable to obtain copper fine particles by heating and reducing a copper oxide, hydroxide or salt in a glycol solution such as ethylene glycol, diethylene glycol or triethylene glycol. Further, at the time of heat reduction, it is preferable to add at least one water-soluble polymer of polyethyleneimine, polyvinylpyrrolidone, and polyallylamine as a dispersant to the copper fine particle dispersion.
このようなポリオール法を応用して合成した銅微粒子は、粒子の分散安定性や導電性、耐酸化性が良好であり、且つ大量生産に適したものである。また、銅微粒子は極性溶媒中に分散した状態で得られるため、銀被覆のために銀イオン含有溶液を添加する銅微粒子分散液として用いることができる。更に、分散剤として上記水溶性高分子を添加することで、生成した銅微粒子の凝集を抑制し、分散安定性が高い銅微粒子分散液を得ることができる。 Copper fine particles synthesized by applying such a polyol method have good dispersion stability, electrical conductivity, and oxidation resistance of the particles, and are suitable for mass production. Further, since the copper fine particles are obtained in a state dispersed in a polar solvent, they can be used as a copper fine particle dispersion in which a silver ion-containing solution is added for silver coating. Furthermore, by adding the water-soluble polymer as a dispersant, it is possible to suppress the aggregation of the produced copper fine particles and obtain a copper fine particle dispersion having high dispersion stability.
以下、上記ポリオール法を用いた銅微粒子の製造方法について更に詳細に説明する。ポリオール法は、銅原料である銅の酸化物、水酸化物又は塩を、上記グリコールなどのポリオール溶液中で加熱還元することにより、液相中で銅微粒子を合成するものである。銅原料として用いる銅の酸化物、水酸化物又は塩としては、例えば、酸化銅、亜酸化銅等の銅の酸化物、水酸化銅等の銅の水酸化物、酢酸銅等の銅の塩を用いることができる。 Hereinafter, the method for producing copper fine particles using the polyol method will be described in more detail. In the polyol method, copper fine particles are synthesized in a liquid phase by heat-reducing copper oxide, hydroxide or salt, which is a copper raw material, in a polyol solution such as glycol. Examples of the copper oxide, hydroxide or salt used as the copper raw material include copper oxides such as copper oxide and cuprous oxide, copper hydroxides such as copper hydroxide, and copper salts such as copper acetate. Can be used.
また、本発明ではポリオールとしてグリコールを使用し、具体的には、エチレングリコール（ＥＧ）、ジエチレングリコール（ＤＥＧ）、トリエチレングリコール（ＴＥＧ）のいずれか１種、又は２種以上の混合物を用いる。使用する装置は、通常のポリオール法で用いられる装置を使用することかできるが、装置内に銅微粒子が付着し難いものが好ましく、ガラス容器、フッ素樹脂等で被覆処理された金属容器などが好ましい。また、均一に還元反応を行わせるためには、撹拌手段を備えた装置が好ましい。 In the present invention, glycol is used as the polyol, and specifically, any one of ethylene glycol (EG), diethylene glycol (DEG), and triethylene glycol (TEG), or a mixture of two or more thereof is used. Although the apparatus used by the normal polyol method can be used for the apparatus to be used, it is preferable that copper fine particles do not easily adhere to the apparatus, and a glass container, a metal container coated with a fluororesin, or the like is preferable. . Moreover, in order to perform a reduction reaction uniformly, the apparatus provided with the stirring means is preferable.
本発明方法においては、ハロゲン元素を含有しない原料を用いることが重要である。一般に、ハロゲン元素、特に塩素は、合成された銅微粒子表面に吸着するだけでなく内部にまで含有されることから、電子材料用として許容可能な範囲、即ち銅微粒子の銅に対して２０質量ｐｐｍ未満まで除去することが極めて困難である。そのため、銅微粒子中のハロゲン元素の合計含有量を銅に対して２０質量ｐｐｍ以下にまで低ハロゲン化するためには、原料から混入するハロゲン元素の合計含有量を制御することが必要である。 In the method of the present invention, it is important to use a raw material containing no halogen element. Generally, a halogen element, particularly chlorine, is not only adsorbed on the surface of the synthesized copper fine particles but also contained inside, so that it is acceptable for an electronic material, that is, 20 mass ppm with respect to copper of the copper fine particles. It is extremely difficult to remove to less than. Therefore, in order to reduce the total halogen element content in the copper fine particles to 20 mass ppm or less with respect to copper, it is necessary to control the total halogen element content mixed from the raw material.
即ち、銅原料である銅の酸化物、水酸化物又は塩の他、エチレングリコール、ジエチレングリコール又はトリエチレングリコール、分散剤の水溶性高分子、更には後述する核生成のための貴金属化合物又は貴金属コロイドについてハロゲン元素の含有量を調べ、これらの原料を含むグリコール溶液中のハロゲン元素の合計含有量が銅に対して２０質量ｐｐｍ以下となるように制御することが好ましい。 That is, in addition to copper oxide, hydroxide or salt, which is a copper raw material, ethylene glycol, diethylene glycol or triethylene glycol, a water-soluble polymer of a dispersant, and a noble metal compound or noble metal colloid for nucleation described later It is preferable to control the content of the halogen element with respect to copper so that the total content of the halogen element in the glycol solution containing these raw materials is 20 ppm by mass or less with respect to copper.
また、上記の各銅原料については、ハロゲン元素含有量が５質量ｐｐｍ未満であることが好ましい。ハロゲン元素含有量が低ければ、通常のポリオール法で用いられる原料を用いることができる。銅原料については、ハロゲン元素含有量が高い場合でも、洗浄によってハロゲン元素含有量を５質量ｐｐｍ未満に低減できれば原料として用いることができる。尚、銅原料は、通常の粉末状態で使用することが好ましい。 Moreover, about each said copper raw material, it is preferable that halogen element content is less than 5 mass ppm. If the halogen element content is low, a raw material used in a normal polyol method can be used. The copper raw material can be used as a raw material even if the halogen element content is high if the halogen element content can be reduced to less than 5 ppm by washing. The copper raw material is preferably used in a normal powder state.
均一で微細な銅微粒子を得るためには、核生成のための貴金属化合物又は貴金属コロイドを上記グリコール溶液に添加することが好ましい。核形成に用いる貴金属化合物としては、溶液中で銅より容易に還元されるものであれば良い。低ハロゲン化の場合には、有害なハロゲン元素を排除する必要から、ハロゲン元素を成分元素としている化合物は用いることができない。また、ハロゲン元素を成分元素としない化合物を用いる場合であっても、不純物として混入する場合があるので注意を要する。 In order to obtain uniform and fine copper fine particles, it is preferable to add a noble metal compound or a noble metal colloid for nucleation to the glycol solution. Any noble metal compound used for nucleation may be used as long as it can be reduced more easily than copper in solution. In the case of low halogenation, since it is necessary to eliminate harmful halogen elements, compounds containing halogen elements as component elements cannot be used. In addition, even when a compound that does not contain a halogen element as a component element is used, care must be taken because it may be mixed as an impurity.
上記貴金属化合物は、粉末状態で添加することもできるが、水などの極性溶媒に溶解した状態で添加することによって、均一に溶液中に分散させることができるため、微細な貴金属粒子を均一に形成させることができ、得られる銅微粒子も均一で微細なものになるため好ましい。従って、極性溶媒に可溶性の貴金属化合物、即ち水溶性貴金属化合物を用いることが好ましく、例えば、塩化パラジウムアンモニウム、塩化パラジウム、硝酸パラジウム、硝酸パラジウムアンモニウムなどのパラジウム塩、硝酸銀、塩化銀などの銀塩が用いられる。特に、低ハロゲン化の場合には、ハロゲン元素を含まない硝酸パラジウム、硝酸パラジウムアンモニウムが好ましい。 The noble metal compound can be added in powder form, but it can be uniformly dispersed in the solution by adding it in a polar solvent such as water, thus forming fine noble metal particles uniformly. This is preferable because the resulting copper fine particles are uniform and fine. Therefore, it is preferable to use a noble metal compound that is soluble in a polar solvent, that is, a water-soluble noble metal compound. Used. In particular, in the case of low halogenation, palladium nitrate and palladium ammonium nitrate not containing a halogen element are preferable.
また、貴金属化合物として、溶解性が低い貴金属水酸化物や貴金属酸化物を用いることもできる。核生成物質として好適な貴金属化合物、例えば、上記した硝酸パラジウムや硝酸パラジウムアンモニウムは強酸化性の硝酸イオンを含んでいるが、水酸化物や酸化物は硝酸イオン等の強酸化性イオンを含まず、有害な元素も成分元素としていない。このため、酸化性イオンによる還元抑制作用がなく、より低い温度で還元が可能になるため工業的には有利である。 Further, as the noble metal compound, a noble metal hydroxide or noble metal oxide having low solubility can be used. Noble metal compounds suitable as nucleating substances, for example, palladium nitrate and ammonium ammonium nitrate described above contain strong oxidizing nitrate ions, but hydroxides and oxides do not contain strong oxidizing ions such as nitrate ions. Also, harmful elements are not included as component elements. For this reason, there is no reduction inhibitory action by oxidizing ions, and reduction is possible at a lower temperature, which is industrially advantageous.
更に、銅微粒子生成のための核の形成には、貴金属コロイドを用いることもできる。貴金属コロイドを用いる場合、貴金属コロイドの合成を銅微粒子の製造と分離することができるため、貴金属コロイドの合成を最適条件で行うことができ、コロイド中の微細な貴金属微粒子の制御も容易である。即ち、微細な貴金属微粒子は銅微粒子生成の核となることから、貴金属微粒子を制御することで、銅微粒子の粒径制御と粒径の均一性をより向上させることができる。 Furthermore, a noble metal colloid can also be used to form nuclei for producing copper fine particles. When the noble metal colloid is used, the synthesis of the noble metal colloid can be separated from the production of the copper fine particles. Therefore, the synthesis of the noble metal colloid can be performed under the optimum conditions, and the fine noble metal fine particles in the colloid can be easily controlled. That is, fine noble metal fine particles become the core of copper fine particle generation, and controlling the noble metal fine particles can further improve the particle size control and particle size uniformity of the copper fine particles.
また、貴金属コロイドを限外濾過膜などにより置換洗浄すれば、上記した有害な元素の他、銅微粒子の生成に不要な成分も反応系から極力排除することが可能である。低ハロゲン化する場合、特にハロゲン元素含有量は、上記貴金属化合物の場合と同様に、銅に対して２０質量ｐｐｍ未満に制御することが好ましい。 In addition, if the noble metal colloid is washed by substitution with an ultrafiltration membrane or the like, it is possible to remove from the reaction system as much as possible the components unnecessary for the production of copper fine particles in addition to the harmful elements described above. In the case of low halogenation, the halogen element content is preferably controlled to less than 20 ppm by mass with respect to copper, as in the case of the noble metal compound.
上記貴金属コロイドとしては、溶液中で置換反応を起こさせないため銅よりもイオン化傾向が低いものが好ましく、例えば、銀、パラジウム、白金、金のコロイドが好ましい。また、得られる銅微粒子の粒径は添加された貴金属核数に反比例すること、高価な貴金属の使用量は極力少ないことが望ましいことから、核として添加するコロイド中の貴金属微粒子の平均粒径は２０ｎｍ以下が好ましく、１０ｎｍ以下が更に好ましい。貴金属微粒子の平均粒径が２０ｎｍを越えると、得られる銅微粒子の粒径が大きくなり過ぎるばかりか、貴金属の使用量が増えて高コストとなる。 As the noble metal colloid, a colloid of silver, palladium, platinum, and gold is preferable because it does not cause a substitution reaction in the solution and has a lower ionization tendency than copper. In addition, since the particle size of the obtained copper fine particles is inversely proportional to the number of noble metal nuclei added and the amount of expensive noble metal used is preferably as small as possible, the average particle size of the noble metal fine particles in the colloid added as the nucleus is It is preferably 20 nm or less, and more preferably 10 nm or less. If the average particle diameter of the noble metal fine particles exceeds 20 nm, not only the particle diameter of the obtained copper fine particles will be too large, but also the amount of noble metal used will increase and the cost will increase.
上記貴金属コロイドとしては、市販のものを用いることもできるが、公知のポリオール法を用いることによって容易に合成できる。例えば、ポリオール溶液中に、水溶性貴金属化合物と水溶性高分子を添加すれば、貴金属コロイドが得られる。水溶性貴金属化合物としては、例えば硝酸パラジウムや硝酸パラジウムアンモニウムなどのハロゲン元素を成分元素としない化合物が好ましい。また、水溶性高分子としては、ポリビニルピロリドンなどが好ましい。水溶性貴金属化合物と水溶性高分子の添加量は、必要な粒径が得られるように温度などの合成条件を加味して定める。例えば、水溶性貴金属化合物の添加量をパラジウム濃度で５ｇ／ｌ、水溶性高分子の添加量を１０ｇ／ｌとすれば、粒径１０〜１５ｎｍの微粒子を含有したパラジウムコロイドが得られる。 As the precious metal colloid, a commercially available one can be used, but it can be easily synthesized by using a known polyol method. For example, a noble metal colloid can be obtained by adding a water-soluble noble metal compound and a water-soluble polymer to a polyol solution. The water-soluble noble metal compound is preferably a compound that does not contain a halogen element such as palladium nitrate or palladium ammonium nitrate. Moreover, as a water-soluble polymer, polyvinylpyrrolidone etc. are preferable. The addition amount of the water-soluble noble metal compound and the water-soluble polymer is determined in consideration of synthesis conditions such as temperature so that a necessary particle size can be obtained. For example, when the addition amount of the water-soluble noble metal compound is 5 g / l in terms of palladium concentration and the addition amount of the water-soluble polymer is 10 g / l, a palladium colloid containing fine particles having a particle diameter of 10 to 15 nm can be obtained.
上記した核生成用の貴金属化合物あるいは貴金属コロイドの添加量は、その形態にかかわらず、銅に対する貴金属の割合、例えば貴金属／Ｃｕ質量比で０.０００４〜０.０１の範囲とすることが好ましい。貴金属／Ｃｕ質量比が０.０００４未満では、貴金属微粒子の量が不足するため、銅の還元反応ないし銅微粒子の形成が十分に進まない。銅微粒子形成に至った場合でも、核となる貴金属微粒子数が不足しているため、粒径が粗大化する恐れがある。また、貴金属／Ｃｕ質量比が０.０１を超えても銅微粒子は得られるが、高価な貴金属の添加量が増える割には粒径の微細化効果は得られないため好ましくない。 Regardless of the form, the addition amount of the above-mentioned noble metal compound or noble metal colloid for nucleation is preferably in the range of 0.0004 to 0.01 in terms of the ratio of noble metal to copper, for example, the noble metal / Cu mass ratio. When the noble metal / Cu mass ratio is less than 0.0004, the amount of noble metal fine particles is insufficient, so that the reduction reaction of copper or the formation of copper fine particles does not proceed sufficiently. Even when copper fine particles are formed, the number of noble metal fine particles serving as nuclei is insufficient, so that the particle size may become coarse. Further, although the copper fine particles can be obtained even if the noble metal / Cu mass ratio exceeds 0.01, it is not preferable because the effect of refining the particle diameter cannot be obtained for an increase in the amount of expensive noble metal added.
特に好ましくは、核生成用の貴金属化合物あるいは貴金属コロイドの貴金属としてパラジウム（Ｐｄ）を用い、Ｐｄ／Ｃｕ質量比を０.０００６〜０.００５の範囲とする。これによって、平均粒径が１００ｎｍ以下であり、且つ粒径の均一性に優れた銅微粒子を得ることができる。 Particularly preferably, palladium (Pd) is used as the noble metal compound for nucleation or the noble metal colloid, and the mass ratio of Pd / Cu is in the range of 0.0006 to 0.005. As a result, copper fine particles having an average particle size of 100 nm or less and excellent particle size uniformity can be obtained.
上記銅微粒子の合成の際にグリコール溶液に分散剤として添加する高分子は、極性溶媒であるグリコール溶液中に溶解させるために水溶性高分子を使用する。水溶性高分子は、還元析出した若しくは添加した貴金属微粒子及び銅微粒子の表面に吸着し、立体障害により微粒子同士の接触を防止することによって、凝集がほとんどなく、分散性に優れた銅微粒子の生成を促進する。 The polymer added as a dispersant to the glycol solution during the synthesis of the copper fine particles uses a water-soluble polymer for dissolution in the glycol solution, which is a polar solvent. Water-soluble polymer adsorbs on the surface of noble metal fine particles and copper fine particles that have been reduced or precipitated, and prevents contact between fine particles due to steric hindrance, thereby producing copper particles with almost no aggregation and excellent dispersibility. Promote.
上記水溶性高分子としては、極性溶媒であるエチレングリコール、ジエチレングリコール又はトリエチレングリコールに溶解し、生成した貴金属微粒子及び銅微粒子に吸着して立体障害を形成し得るものであればよい。具体的には、ポリビニルピロリドン、ポリエチレンイミン、ポリアリルアミンから選ばれた少なくとも１種が好ましく、その中でも銅との親和性が高いポリエチレンイミンが特に好ましい。 The water-soluble polymer is not particularly limited as long as it is soluble in polar solvents such as ethylene glycol, diethylene glycol, or triethylene glycol and can be adsorbed on the produced noble metal fine particles and copper fine particles to form steric hindrance. Specifically, at least one selected from polyvinylpyrrolidone, polyethyleneimine, and polyallylamine is preferable, and among these, polyethyleneimine having a high affinity for copper is particularly preferable.
水溶性高分子であるポリエチレンイミン（ＰＥＩ）の添加量は、銅に対する質量比、即ちＰＥＩ／Ｃｕ質量比で、０.００５〜０.１の範囲が好ましく、０.０１〜０.０３の範囲が更に好ましい。ＰＥＩ／Ｃｕ質量比が０.００５未満では、微粒子への吸着ないし被覆の割合が低下して、核となる貴金属微粒子あるいは生成した銅微粒子が反応中に凝集し、結果的に得られる銅微粒子が粗大化する。また、ＰＥＩ／Ｃｕ質量比が０.１を越えると、溶液の粘性が高くなり過ぎ、後の極性溶媒との溶媒置換や濃縮に時間がかかるうえ、濃縮後に水溶性高分子の残存量が多くなるため好ましくない。 The addition amount of polyethyleneimine (PEI), which is a water-soluble polymer, is preferably in the range of 0.005 to 0.1 and in the range of 0.01 to 0.03 in terms of mass ratio to copper, that is, PEI / Cu mass ratio. Is more preferable. When the PEI / Cu mass ratio is less than 0.005, the ratio of adsorption or coating on the fine particles is reduced, and the noble metal fine particles serving as nuclei or the produced copper fine particles are aggregated during the reaction. It becomes coarse. In addition, when the PEI / Cu mass ratio exceeds 0.1, the viscosity of the solution becomes too high, and it takes time for solvent substitution and concentration with a polar solvent later, and a large amount of water-soluble polymer remains after concentration. Therefore, it is not preferable.
一般に、高分子分散剤は、吸着基によって対象となる微粒子の吸着能が異なっている。そのため、核として反応初期に生成し若しくは添加される貴金属微粒子用と、その貴金属微粒子に還元析出して生成する銅微粒子用として、異なる複数の高分子分散剤を混合して用いることが効果的である。具体的には、上記した銅微粒子用としてのポリエチレンイミンに加えて、貴金属微粒子用としてポリビニルピロリドンとポリアリルアミンの内の少なくとも１種を用いることが特に好ましい。 In general, the polymer dispersant has different adsorptive ability of the target fine particles depending on the adsorbing group. Therefore, it is effective to use a mixture of a plurality of different polymer dispersants for the noble metal fine particles that are generated or added at the initial stage of the reaction as nuclei and for the copper fine particles that are formed by reduction deposition on the noble metal fine particles. is there. Specifically, it is particularly preferable to use at least one of polyvinylpyrrolidone and polyallylamine for noble metal fine particles in addition to the above-described polyethyleneimine for copper fine particles.
その場合、ポリビニルピロリドン（ＰＶＰ）及び／又はポリアリルアミン（ＰＡＡ）の添加量は、銅に対する合計の質量比、即ち（ＰＶＰ＋ＰＡＡ）／Ｃｕの質量比で０.８未満とすることが好ましく、０.０１〜０.５の範囲が更に好ましい。ポリビニルピロリドンあるいはポリアリルアミンの添加により、核となる貴金属微粒子を更に微細にすることができるが、これらの合計添加量が上記質量比で０.８を超えると、ポリエチレンイミンと同様に溶液の粘性が高くなり過ぎ、後の極性溶媒との溶媒置換や濃縮に時間がかかるうえ、濃縮後に水溶性高分子の残存量が多くなるため好ましくない。 In that case, the addition amount of polyvinylpyrrolidone (PVP) and / or polyallylamine (PAA) is preferably less than 0.8 in terms of the total mass ratio with respect to copper, that is, (PVP + PAA) / Cu. A range of 01 to 0.5 is more preferable. By adding polyvinylpyrrolidone or polyallylamine, the noble metal fine particles as a core can be made finer. However, when the total addition amount thereof exceeds 0.8 by the above mass ratio, the viscosity of the solution is similar to that of polyethyleneimine. This is not preferable because it becomes too high, and it takes time for solvent substitution and concentration with a polar solvent later, and the residual amount of water-soluble polymer increases after concentration.
上記水溶性高分子からハロゲン元素が混入した場合も、最終的に作製した銅微粒子あるいは分散液にハロゲン元素が残留するため、低ハロゲン化する場合にはハロゲン含有量の低い水溶性高分子を使用する必要がある。即ち、水溶性高分子中のハロゲン元素の含有量についても、上記溶液中のハロゲン元素の合計含有量が銅に対して２０質量ｐｐｍ未満となるように制御することが好ましい。具体的には、水溶性高分子中のハロゲン元素含有量を１０００質量ｐｐｍ未満、好ましくは４００質量ｐｐｍ未満に低減することにより、最終的に作製される銅微粒子中のハロゲン含有量を２０質量ｐｐｍ未満にすることができる。 Even when a halogen element is mixed in from the above water-soluble polymer, the halogen element remains in the finally produced copper fine particles or dispersion, so when using a low halogen content, use a water-soluble polymer with a low halogen content. There is a need to. That is, the content of halogen elements in the water-soluble polymer is also preferably controlled so that the total content of halogen elements in the solution is less than 20 ppm by mass with respect to copper. Specifically, by reducing the halogen element content in the water-soluble polymer to less than 1000 ppm by mass, preferably less than 400 ppm by mass, the halogen content in the finally produced copper fine particles is 20 ppm by mass. Can be less than.
特にポリエチレンイミンは製造過程においてハロゲン元素が混入しやすいが、混入した場合には陰イオン交換樹脂を用いてハロゲン元素の多くを除去することができる。陰イオン交換樹脂としては、ＯＨ−形、ＮＯ３ −形等のハロゲンイオン形以外の樹脂を用いることができるが、還元反応に悪影響が出ないＯＨ−形の樹脂が好ましい。除去方法としては、水溶性高分子溶液を陰イオン交換樹脂と接触させ、ハロゲンイオンを交換吸着して除去する。樹脂との接触方法としては、バッチ式あるいはカラム式等の公知の方法を用いることができる。 In particular, polyethyleneimine is likely to be mixed with halogen elements in the production process, but when mixed, most of the halogen elements can be removed using an anion exchange resin. As the anion exchange resin, resins other than halogen ion type such as OH − form and NO 3 − form can be used, but OH − form resin which does not adversely affect the reduction reaction is preferable. As a removal method, a water-soluble polymer solution is brought into contact with an anion exchange resin, and halogen ions are removed by exchange adsorption. As a method for contacting the resin, a known method such as a batch method or a column method can be used.
次に、本発明による銀被覆銅微粒子の好ましい製造方法を、工程順に更に具体的に説明する。まず、エチレングリコール、ジエチレングリコール、トリエチレングリコールの少なくとも１種からなるグリコールの溶液に、銅原料と貴金属化合物又は貴金属コロイドを添加すると共に、分散剤として水溶性高分子を添加する。これらの原料を添加したグリコール溶液を撹拌しながら、所定の温度に昇温して保持することにより銅微粒子が生成する。昇温及び保持中は、反応を均一化させるため撹拌することが好ましい。グリコール溶液は酸化防止作用も持っているが、還元反応を促進させると共に銅微粒子の再酸化を防止するため、昇温及び保持中は窒素ガスを吹き込むことが好ましい。 Next, a preferred method for producing silver-coated copper fine particles according to the present invention will be described more specifically in the order of steps. First, a copper raw material and a noble metal compound or a noble metal colloid are added to a glycol solution comprising at least one of ethylene glycol, diethylene glycol, and triethylene glycol, and a water-soluble polymer is added as a dispersant. While stirring the glycol solution to which these raw materials are added, the copper fine particles are produced by raising the temperature to a predetermined temperature and holding it. It is preferable to stir during the temperature rising and holding to make the reaction uniform. Although the glycol solution also has an antioxidant action, nitrogen gas is preferably blown during temperature rise and holding in order to promote the reduction reaction and prevent reoxidation of the copper fine particles.
通常は、グリコール溶液に、銅原料、貴金属化合物又は貴金属コロイド、水溶性高分子を添加した後に加熱を開始する。ただし、銅微粒子形成の核を微細且つ均一に生成させるため、貴金属化合物あるいは貴金属コロイドについては、それ以外の原料を添加して昇温中のポリオール溶液に後から添加してもよい。また、水溶性高分子の一部あるいは全部についても、上記と同様に、昇温中のポリオール溶液に後から添加することができる。 Usually, heating is started after adding a copper raw material, a noble metal compound or a noble metal colloid, and a water-soluble polymer to a glycol solution. However, in order to finely and uniformly generate nuclei for forming copper fine particles, the noble metal compound or the noble metal colloid may be added later to the polyol solution being heated by adding other raw materials. Also, part or all of the water-soluble polymer can be added later to the polyol solution during the temperature rise, as described above.
均一な銅微粒子を合成するためには、グリコール溶液の最高到達温度として１２０〜２００℃の範囲が可能である。この最高到達温度が１２０℃未満では、銅の還元反応速度が遅くなり、反応完了まで長時間を要するだけでなく、得られる銅微粒子の粗大化を招く。また、温度が２００℃を超えると、高分子分散剤による保護効果が薄れ、凝集性の粗大な粒子に成長するため好ましくない。 In order to synthesize uniform copper fine particles, the maximum temperature of the glycol solution can be in the range of 120 to 200 ° C. When this maximum temperature is less than 120 ° C., the reduction reaction rate of copper is slow, and not only a long time is required until the reaction is completed, but also the resulting copper fine particles are coarsened. On the other hand, when the temperature exceeds 200 ° C., the protective effect by the polymer dispersant is reduced, and the particles grow to coarse cohesive particles, which is not preferable.
上記方法により、本発明の銀被覆銅微粒子の製造に好適な銅微粒子を得ることができる。また、本発明の銀被覆銅微粒子は粒子表面に吸着している水溶性高分子の量を１.５質量％未満とすることが好ましいが、上記方法により得られた銅微粒子表面の水溶性高分子の量を１.５質量％未満とすることによって、最終的な銀被覆銅微粒子表面の水溶性高分子の量を上記範囲とすることができる。 By the said method, the copper fine particle suitable for manufacture of the silver covering copper fine particle of this invention can be obtained. The silver-coated copper fine particles of the present invention preferably have an amount of water-soluble polymer adsorbed on the particle surface of less than 1.5% by mass. By setting the amount of the molecule to less than 1.5% by mass, the amount of the water-soluble polymer on the surface of the final silver-coated copper fine particles can be within the above range.
そこで、得られた銅微粒子表面に吸着している水溶性高分子の量を低減させるため、ヒドロキシカルボン酸によって水溶性高分子を置換することが好ましい。この操作は、銀被覆銅微粒子を得た後にも、同様の目的のために行うことができるが、前段階の銅微粒子に対して行うと効果的である。 Therefore, in order to reduce the amount of the water-soluble polymer adsorbed on the surface of the obtained copper fine particles, it is preferable to substitute the water-soluble polymer with hydroxycarboxylic acid. This operation can be performed for the same purpose after obtaining the silver-coated copper fine particles, but it is effective when performed on the copper fine particles in the previous stage.
即ち、得られた銅微粒子を含む溶液に、ヒドロキシカルボン酸あるいはヒドロキシカルボン酸溶液を添加して撹拌することにより、銅微粒子の分散性を維持しながら、銅微粒子表面に吸着被覆している水溶性高分子の１部をヒドロキシカルボン酸で置換することができる。遊離した水溶性高分子は、限外濾過により排出する。尚、水溶性高分子の量を低減させると銅微粒子は酸化されやすいが、ヒドロキシカルボン酸による被覆により酸化を抑制することが可能である。また、表面の水溶性高分子が減少するため、後の銀との置換反応が容易になる。 That is, by adding a hydroxycarboxylic acid or a hydroxycarboxylic acid solution to the obtained solution containing copper fine particles and stirring, the water-soluble matter that is adsorbed and coated on the surface of the copper fine particles while maintaining the dispersibility of the copper fine particles is maintained. One part of the polymer can be replaced with hydroxycarboxylic acid. The released water-soluble polymer is discharged by ultrafiltration. Note that when the amount of the water-soluble polymer is reduced, the copper fine particles are easily oxidized, but the oxidation can be suppressed by coating with a hydroxycarboxylic acid. Further, since the water-soluble polymer on the surface is reduced, the subsequent substitution reaction with silver is facilitated.
上記ヒドロキシカルボン酸としては、乳酸、グルコン酸、リンゴ酸、クエン酸が好ましく、溶媒への溶解性や粘度調整等を考慮して、これらの１種又は２種以上を適宜選択して用いることができる。ヒドロキシカルボン酸の添加量に関しては、溶液に対して２０質量％未満とすることが好ましく、１〜１０質量％とすることが更に好ましい。ヒドロキシカルボン酸の添加量が２０質量％以上になると、銅微粒子の溶解が進行して、酸化や凝集の原因となるため好ましくない。 As the hydroxycarboxylic acid, lactic acid, gluconic acid, malic acid, and citric acid are preferable. In consideration of solubility in a solvent and viscosity adjustment, one or more of these may be appropriately selected and used. it can. Regarding the addition amount of hydroxycarboxylic acid, it is preferable to set it as less than 20 mass% with respect to a solution, and it is still more preferable to set it as 1-10 mass%. When the amount of the hydroxycarboxylic acid added is 20% by mass or more, the dissolution of the copper fine particles proceeds to cause oxidation and aggregation, which is not preferable.
上記したヒドロキシカルボン酸での置換によって、表面が水溶性高分子及びヒドロキシカルボン酸で被覆され、吸着している水溶性高分子量が１.５質量％未満の銅微粒子が得られる。得られた銅微粒子は上記極性溶媒中に分散した銅微粒子を含むグリコール溶液として得られ、本発明の銀被覆銅微粒子の製造における銅微粒子分散液として用いることが可能である。 By substitution with hydroxycarboxylic acid as described above, copper fine particles having a surface coated with a water-soluble polymer and hydroxycarboxylic acid and having an adsorbed water-soluble polymer amount of less than 1.5% by mass are obtained. The obtained copper fine particles are obtained as a glycol solution containing copper fine particles dispersed in the polar solvent, and can be used as a copper fine particle dispersion in the production of the silver-coated copper fine particles of the present invention.
ただし、このグリコール溶液中には銅微粒子以外に余剰の水溶性高分子が含まれている。この水溶性高分子は、最終的に使用される配線材料用導電性ペースト製品中に過剰に存在すると、電気抵抗の上昇や構造欠陥などの不具合をもたらす原因となる。そこで、上記グリコール溶液を水やアルコール、エステル等の極性溶媒で溶媒置換して濃縮することにより、水溶性高分子をできるだけ除去することが好ましい。尚、溶媒置換に使用する極性溶媒としては、水、アルコール、エステルのいずれか１種、若しくはこれらの２種以上の混合物が好ましい。 However, this glycol solution contains excess water-soluble polymer in addition to the copper fine particles. If the water-soluble polymer is excessively present in the conductive paste product for wiring material that is finally used, it causes a problem such as an increase in electrical resistance or a structural defect. Therefore, it is preferable to remove the water-soluble polymer as much as possible by concentrating the glycol solution with a polar solvent such as water, alcohol, or ester and concentrating it. In addition, as a polar solvent used for solvent substitution, any 1 type of water, alcohol, ester, or a mixture of 2 or more types thereof is preferable.
このようなグリコール溶液を調整する一般的な方法としては、得られた銅微粒子を含むグリコール溶液を、水、アルコール、エステル等の極性溶媒で希釈した後、限外濾過等により溶媒置換及び濃縮を行う方法が用いられる。その際、成膜性の向上のために、ヒドロキシカルボン酸等の添加剤を上記極性溶媒に加えても良い。ヒドロキシカルボン酸の添加量は、上記した水溶性高分子の置換のため銅微粒子を含む溶液に添加する場合と同様に、分散液に対して２０質量％未満が好ましく、１〜１０質量％が更に好ましい。その後、必要に応じて、更に極性溶媒による希釈と、溶媒置換及び濃縮を繰り返し、所望の銅濃度と不純物含有量に調整した銅微粒子分散液を得る。 A general method for preparing such a glycol solution is to dilute the obtained glycol solution containing copper fine particles with a polar solvent such as water, alcohol, ester, etc., and then perform solvent substitution and concentration by ultrafiltration or the like. The method of doing is used. At that time, an additive such as hydroxycarboxylic acid may be added to the polar solvent in order to improve the film formability. The amount of hydroxycarboxylic acid added is preferably less than 20% by weight, preferably 1-10% by weight, based on the dispersion, as in the case of adding to the solution containing copper fine particles for the replacement of the water-soluble polymer. preferable. Thereafter, if necessary, further dilution with a polar solvent, solvent substitution, and concentration are repeated to obtain a copper fine particle dispersion adjusted to a desired copper concentration and impurity content.
上記調整を行ったグリコール溶液は、本発明の銀被覆銅微粒子の製造方法における銅微粒子分散液として好適に用いることができる。次に、この銅微粒子分散液に上記所定量の銀イオン含有溶液を添加し、置換反応によって銀を銅表面に析出させる。尚、本発明の銀被覆銅微粒子では銀被覆層が極めて薄いため、銀被覆前後での粒径の変化は測定不可能な程度に少ない。ただし、銅微粒子の粒径から算出した比表面積と上記銀イオン含有溶液の銀の銅に対する割合（質量比）から、粒径増加分である銀被覆層の厚さを容易に見積もることができる。 The glycol solution having been adjusted as described above can be suitably used as a copper fine particle dispersion in the method for producing silver-coated copper fine particles of the present invention. Next, the predetermined amount of silver ion-containing solution is added to the copper fine particle dispersion, and silver is deposited on the copper surface by a substitution reaction. In the silver-coated copper fine particles of the present invention, since the silver coating layer is very thin, the change in particle size before and after silver coating is so small that it cannot be measured. However, from the specific surface area calculated from the particle diameter of the copper fine particles and the ratio (mass ratio) of silver to the copper in the silver ion-containing solution, the thickness of the silver coating layer, which is an increase in particle diameter, can be easily estimated.
銅微粒子分散液に添加する銀イオン含有溶液は、硝酸銀、炭酸銀、塩化銀等の銀化合物及び銀メタルを溶解した溶液を用いることができる。用いる溶媒としては、水、アンモニア水、硝酸等の銀化合物及び銀の溶解度が高いものが好ましい。また、銀イオン含有溶液の添加は、均一に銀を析出させるため、撹拌しながら行うことが好ましい。添加速度に関しては、全体に均一に銀を析出させるため、可能な範囲で遅くすることが好ましく、銅１００ｇに対して銀０.１ｇ／分以下の添加速度とすることが好ましい。ただし、生産性を考慮すると、銀０.０１ｇ／分以上とすることが好ましい。 As the silver ion-containing solution added to the copper fine particle dispersion, a solution in which a silver compound such as silver nitrate, silver carbonate, or silver chloride and silver metal are dissolved can be used. As a solvent to be used, a silver compound such as water, aqueous ammonia and nitric acid and a solvent having high solubility of silver are preferable. Further, the addition of the silver ion-containing solution is preferably performed with stirring in order to precipitate silver uniformly. Regarding the addition rate, in order to deposit silver uniformly throughout, it is preferable to slow down as much as possible, and it is preferable to set the addition rate to 0.1 g / min or less with respect to 100 g of copper. However, considering productivity, it is preferable to set it as 0.01 g / min or more of silver.
銀イオン含有溶液を添加して得られた銀被覆銅微粒子分散液は、銀イオン含有溶液に含まれていた銀以外のイオン（以下、余剰イオンと記載）を含んでいる。余剰イオンは、銀被覆銅微粒子の酸化や凝集の原因となる可能性があるため、洗浄除去することが好ましい。洗浄を行うことで余剰イオンを除去し、銀被覆銅微粒子分散液を安定化することができる。洗浄方法としては、限外濾過、デカンテーション、遠心濾過等の一般的な方法を使用することができるが、数十ｎｍの粒子の沈降性及び濾過性の低さを考慮すると、限外濾過による洗浄が好ましい。 The silver-coated copper fine particle dispersion obtained by adding the silver ion-containing solution contains ions other than silver (hereinafter referred to as surplus ions) contained in the silver ion-containing solution. Since excess ions may cause oxidation or aggregation of the silver-coated copper fine particles, it is preferable to remove them by washing. By washing, excess ions can be removed and the silver-coated copper fine particle dispersion can be stabilized. As a washing method, general methods such as ultrafiltration, decantation, and centrifugal filtration can be used. However, in consideration of sedimentation property and low filterability of particles of several tens of nm, ultrafiltration is used. Cleaning is preferred.
特に極性溶媒中に分散させた上記銀被覆銅微粒子分散液を限外濾過により洗浄する場合、上記ポリオール溶液の調整と同様の方法を用いることができる。即ち、必要に応じてヒドロキシカルボン酸等の添加剤を加えた水、アルコール、エステル等の極性溶媒で希釈した後、限外濾過等により溶媒置換及び濃縮を必要に応じて繰り返すことで、所望の銅濃度と不純物含有量に調整した銀被覆銅微粒子分散液を得ることができる。更に、耐酸化性及び体積抵抗率の改善のため、銀被覆銅微粒子分散液には、分散液に対して２０質量％未満、より好ましくは１〜１０質量％のヒドロキシカルボン酸等の添加剤を加えても良い。 In particular, when the silver-coated copper fine particle dispersion dispersed in a polar solvent is washed by ultrafiltration, the same method as the preparation of the polyol solution can be used. That is, after diluting with a polar solvent such as water, alcohol, ester or the like with an additive such as hydroxycarboxylic acid as necessary, solvent substitution and concentration are repeated as necessary by ultrafiltration, etc. A silver-coated copper fine particle dispersion adjusted to have a copper concentration and an impurity content can be obtained. Furthermore, in order to improve oxidation resistance and volume resistivity, the silver-coated copper fine particle dispersion has an additive such as hydroxycarboxylic acid of less than 20% by weight, more preferably 1 to 10% by weight, based on the dispersion. May be added.
上記製造方法によって得られた銀被覆銅微粒子分散液は、銀被覆銅微粒子が微細で且つ粗大粒子を含まず、低温焼結性に優れ、低温焼成おいても良好な導電性が得られる。しかも、銀被覆銅微粒子が微粒であるため、分散液中での長期分散性にも優れたものである。このため、本発明の銀被覆銅微粒子分散液は、インクジェットプリンターやスクリーン印刷を用いた微細な配線パターンの印刷形成技術にける専用のインクあるいはペースト用材料として優れており、インクあるいはペースト中で良好な分散性を保つことができる。 The silver-coated copper fine particle dispersion obtained by the above production method has fine silver-coated copper fine particles and does not contain coarse particles, is excellent in low-temperature sinterability, and good conductivity is obtained even at low-temperature firing. In addition, since the silver-coated copper fine particles are fine particles, they have excellent long-term dispersibility in the dispersion. Therefore, the silver-coated copper fine particle dispersion of the present invention is excellent as a dedicated ink or paste material in a fine wiring pattern print forming technique using an ink jet printer or screen printing, and is excellent in an ink or paste. High dispersibility can be maintained.
以下の各実施例により、本発明の銀被覆銅微粒子及びその分散液を製造すると共に評価した。尚、各実施例で使用した原料は下記のとおりである。
銅原料：亜酸化銅（Ｃｕ２Ｏ）（Ｃｈｅｍｅｔ社製）
貴金属化合物：硝酸パラジウムアンモニウム（エヌ・イー・ケムキャット社製）
グリコール溶媒：エチレングリコール（ＥＧ）（日本触媒(株)製）
分散剤：ポリエチレンイミン（ＰＥＩ）（ＳＰ−０１８、日本触媒(株)製）、ポリビニルピロリドン（ＰＶＰ）（ＩＳＰ−Ｋ１５、アイエスピー・ジャパン（株）製）
添加剤：クエン酸（和光純薬(株)製、特級）
銀化合物：硝酸銀（和光純薬(株)製、特級）
In the following examples, the silver-coated copper fine particles of the present invention and dispersions thereof were produced and evaluated. In addition, the raw material used in each Example is as follows.
Copper raw material: Cuprous oxide (Cu 2 O) (Chemet)
Precious metal compound: Palladium ammonium nitrate (NEM Chemcat)
Glycol solvent: Ethylene glycol (EG) (manufactured by Nippon Shokubai Co., Ltd.)
Dispersant: Polyethyleneimine (PEI) (SP-018, manufactured by Nippon Shokubai Co., Ltd.), Polyvinylpyrrolidone (PVP) (ISP-K15, manufactured by ISP Japan Co., Ltd.)
Additive: Citric acid (Wako Pure Chemical Industries, special grade)
Silver compound: Silver nitrate (Wako Pure Chemical Industries, Ltd., special grade)
［実施例１］
塩素含有量４０質量ｐｐｍの亜酸化銅（Ｃｕ２Ｏ）粉６００ｇを、３リットルの０.１ｍｏｌ／ｌ水酸化ナトリウム水溶液に添加してサスペンションとし、８０℃で１時間撹拌した後、濾過した。得られた亜酸化銅を３リットルの純水に添加し、３０分間撹拌洗浄した後、濾過して得られた洗浄済みＣｕ２Ｏ粉を８０℃で真空乾燥した。この洗浄済みＣｕ２Ｏ粉の塩素含有量は、Ｃｕに対して２質量ｐｐｍであった。
[Example 1]
600 g of cuprous oxide (Cu 2 O) powder having a chlorine content of 40 mass ppm was added to 3 liters of a 0.1 mol / l sodium hydroxide aqueous solution to form a suspension, stirred at 80 ° C. for 1 hour, and then filtered. The obtained cuprous oxide was added to 3 liters of pure water, washed with stirring for 30 minutes, and then washed Cu 2 O powder obtained by filtration was vacuum-dried at 80 ° C. The chlorine content of this washed Cu 2 O powder was 2 ppm by mass with respect to Cu.
一方、塩素含有量が３０００質量ｐｐｍのポリエチレンイミン（ＰＥＩ）１０ｇを、１０質量％となるように水で希釈し、水酸化ナトリウム水溶液を用いてＯＨ−形に変換した陰イオン交換樹脂（三菱化学(株)製、ＳＡ−１０Ａ）１０ｇを添加して８時間撹拌した。その後、樹脂を濾別し、８０℃で真空乾燥させることにより、洗浄済みＰＥＩを得た。この洗浄済みＰＥＩの塩素含有量は２００質量ｐｐｍとなった。 On the other hand, 10 g of polyethyleneimine (PEI) having a chlorine content of 3000 mass ppm was diluted with water so as to be 10 mass%, and an anion exchange resin (Mitsubishi Chemical Co., Ltd.) converted into OH − form using an aqueous sodium hydroxide solution. 10 g of SA-10A (manufactured by Co., Ltd.) was added and stirred for 8 hours. Thereafter, the resin was filtered off and vacuum-dried at 80 ° C. to obtain washed PEI. The chlorine content of this washed PEI was 200 ppm by mass.
溶媒である１リットルのエチレングリコール（ＥＧ）に、１１０ｇの亜酸化銅（Ｃｕ２Ｏ）粉、４０ｇのポリビニルピロリドン（ＰＶＰ）、１.５ｇのポリエチレンイミン（ＰＥＩ）を加え、窒素ガスを吹き込みながら加熱撹拌した。このグリコール溶液に、硝酸パラジウムアンモニウムをアンモニア水で溶解したパラジウム溶液をパラジウム量で０.２ｇ加え、１５０℃で３０分保持して銅微粒子を還元析出させた。 While adding 110 g of cuprous oxide (Cu 2 O) powder, 40 g of polyvinylpyrrolidone (PVP), and 1.5 g of polyethyleneimine (PEI) to 1 liter of ethylene glycol (EG) as a solvent, while blowing nitrogen gas Stir with heating. To this glycol solution, 0.2 g of a palladium solution in which palladium ammonium nitrate was dissolved in aqueous ammonia was added in an amount of palladium, and maintained at 150 ° C. for 30 minutes to reduce and precipitate copper fine particles.
得られた銅微粒子を濾過し、ＳＥＭで観察したところ、凝集のない微粒子であった。この銅微粒子は、平均粒径ｄが２６ｎｍで、相対標準偏差（標準偏差σ／平均粒径ｄ）が５２％であった。尚、ＳＥＭ観察による粒径測定は、日立ハイテクノロジー(株)製の電界放出型電子顕微鏡（ＦＥ−ＳＥＭ、型式Ｓ−４７００）を用いて観察し、視野から２００個の銅微粒子を無作為に選択して粒径を測定し、平均粒径と相対標準偏差（標準偏差σ／平均粒径ｄ）を算出した。 The obtained copper fine particles were filtered and observed with an SEM. As a result, the fine particles were not aggregated. The copper fine particles had an average particle diameter d of 26 nm and a relative standard deviation (standard deviation σ / average particle diameter d) of 52%. In addition, the particle size measurement by SEM observation was observed using a field emission electron microscope (FE-SEM, model S-4700) manufactured by Hitachi High Technology Co., Ltd., and 200 copper fine particles were randomly selected from the field of view. The particle size was selected and measured, and the average particle size and relative standard deviation (standard deviation σ / average particle size d) were calculated.
次に、得られた銅微粒子を含む溶液を、０.６５μｍフィルターに通して残留原料を除去した後、溶媒のエチレングリコール（ＥＧ）の大部分を水で置換した銅微粒子分散液を調製した。具体的には、上記銅微粒子を含む溶液（Ｃｕ：１０質量％）１リットルに、純水とエチレングリコールの混合溶媒（純水：エチレングリコール：＝８：１）１リットルにクエン酸１０ｇを添加した洗浄液を追加し、限外濾過により１００ｃｃになるまで濃縮した。その後、１リットルになるまで上記と同じ洗浄液を追加し、限外濾過により余剰の分散剤等を含む混合濾液を系外へ排出して、銅微粒子を含む溶液を１００ｃｃまで濃縮した。更に、この濃縮液に、再び上記と同じ洗浄液を１リットルになるまで追加し、限外濾過により濾液を系外へ排出して１００ｃｃまで濃縮した。 Next, the obtained solution containing copper fine particles was passed through a 0.65 μm filter to remove residual raw materials, and then a copper fine particle dispersion in which most of the solvent, ethylene glycol (EG), was replaced with water was prepared. Specifically, 10 g of citric acid is added to 1 liter of a mixed solvent of pure water and ethylene glycol (pure water: ethylene glycol: = 8: 1) to 1 liter of the above solution containing copper fine particles (Cu: 10% by mass). The washing solution was added and concentrated to 100 cc by ultrafiltration. Thereafter, the same cleaning liquid as described above was added until the volume became 1 liter, and the mixed filtrate containing excess dispersant and the like was discharged out of the system by ultrafiltration, and the solution containing copper fine particles was concentrated to 100 cc. Furthermore, the same washing liquid as described above was added to this concentrated liquid again until 1 liter, and the filtrate was discharged out of the system by ultrafiltration and concentrated to 100 cc.
得られた銅微粒子分散液に、上記と同じ洗浄液を１リットルになるまで添加し、撹拌しながら予め作製しておいた１質量％硝酸銀水溶液２６５ｃｃを５ｃｃ／分の添加速度（銅１００ｇに対して銀０.０３２ｇ／分）で定量添加し、添加終了後１０分間撹拌しながら保持した。その後限外濾過により１００ｃｃになるまで濃縮し、上記と同様の洗浄工程を更に２回繰り返して硝酸イオンを除去し、試料１の銀被覆銅微粒子分散液１００ｃｃを得た。 To the obtained copper fine particle dispersion, the same cleaning liquid as described above was added until 1 liter, and 265 cc of a 1% by mass aqueous silver nitrate solution prepared in advance with stirring was added at a rate of 5 cc / min (based on 100 g of copper). Silver (0.032 g / min) was added quantitatively, and the mixture was held for 10 minutes while stirring. Thereafter, the solution was concentrated to 100 cc by ultrafiltration, and the same washing step as described above was further repeated twice to remove nitrate ions, whereby 100 cc of a silver-coated copper fine particle dispersion of Sample 1 was obtained.
得られた試料１の銀被覆銅微粒子のＳＥＭ写真を図１に示す。この銀被覆銅微粒子の平均粒径ｄは２８ｎｍ、相対標準偏差（標準偏差σ／平均粒径ｄ）は４９％であり、銀含有イオン溶液添加前の銅微粒子とほとんど変化が無かった。また、銀被覆銅微粒子分散液は、ＩＣＰ発光分析法による分析結果から、Ｃｕ：５７質量％、Ａｇ：１.１質量％、銅に対する銀含有量は１.９質量％であった。 An SEM photograph of the silver-coated copper fine particles of Sample 1 obtained is shown in FIG. The silver-coated copper fine particles had an average particle diameter d of 28 nm and a relative standard deviation (standard deviation σ / average particle diameter d) of 49%, which was almost unchanged from the copper fine particles before addition of the silver-containing ion solution. The silver-coated copper fine particle dispersion was found to be Cu: 57 mass%, Ag: 1.1 mass%, and the silver content with respect to copper was 1.9 mass%, based on the results of analysis by ICP emission spectrometry.
また、上記銀被覆銅微粒子分散液に硝酸を添加して粒子を溶解し、硝酸銀を加えて塩化銀を沈殿させ、沈殿物中の塩素（Ｃｌ）を検量線による蛍光Ｘ線定量分析(ＰｎＮａｌｙｔｉｃａｌ製、Ｍａｇｉｘ)にて測定することにより求めたところ、残留塩素量は９質量ｐｐｍであった。その他のハロゲン元素に関しては検出されず、残部が純水、エチレングリコール、クエン酸であって、銅に対するハロゲン元素の合計含有量は１６質量ｐｐｍであった。 Further, nitric acid is added to the above silver-coated copper fine particle dispersion to dissolve the particles, silver nitrate is added to precipitate silver chloride, and chlorine (Cl) in the precipitate is quantitatively analyzed by fluorescent X-rays using a calibration curve (manufactured by PnNalytical). , Magix), the residual chlorine content was 9 mass ppm. Other halogen elements were not detected, and the balance was pure water, ethylene glycol, and citric acid, and the total content of halogen elements relative to copper was 16 mass ppm.
この試料１の銀被覆銅微粒子分散液は、作製後１ヶ月間静置したが、沈降は認められなかった。また、この銀被覆銅微粒子分散液をガラス基板上に塗布し、乾燥後にＸ線回折分析を行った結果、銅と銀のピークのみであり、酸化銅のピークは検出されなかった。この結果から、銀被覆銅微粒子は平均粒径が５０ｎｍ以下という微粒子であるにもかかわらず、耐酸化性に優れていることが確認された。 The silver-coated copper fine particle dispersion of Sample 1 was allowed to stand for 1 month after preparation, but no sedimentation was observed. Moreover, as a result of apply | coating this silver covering copper fine particle dispersion on a glass substrate and performing X-ray diffraction analysis after drying, it was only a peak of copper and silver, and the peak of copper oxide was not detected. From this result, it was confirmed that the silver-coated copper fine particles are excellent in oxidation resistance despite being fine particles having an average particle diameter of 50 nm or less.
また、この試料１の銀被覆銅微粒子分散液を、真空中において８０℃で３時間乾燥させた後、窒素雰囲気中にて６００℃までの熱重量分析を行ったところ、３００℃〜６００℃にかけて１.１質量％の重量減少が検出された。別途実施したクエン酸、ＰＥＩ、ＰＶＰの各熱重量分析結果から、クエン酸に関しては１８０℃付近から分解し始めて３００℃でほぼ完全に分解蒸発し、ＰＥＩ及びＰＶＰに関しては３００℃付近から分解し始めて６００℃でほぼ完全に分解蒸発し、Ｃが固体として残留しないことが確認されている。よって、３００℃〜６００℃の重量減少は銅に吸着したＰＥＩ及びＰＶＰの分解に由来する重量減少であると考えられる。従って、この銀被覆銅微粒子に吸着している水溶性高分子量は１.１質量％となる。 Further, after the silver-coated copper fine particle dispersion of Sample 1 was dried at 80 ° C. for 3 hours in a vacuum, a thermogravimetric analysis was performed up to 600 ° C. in a nitrogen atmosphere. A weight loss of 1.1% by weight was detected. From the results of thermogravimetric analysis of citric acid, PEI, and PVP that were conducted separately, citric acid started to decompose at around 180 ° C, almost completely decomposed and evaporated at 300 ° C, and PEI and PVP started to decompose at around 300 ° C. It has been confirmed that almost completely decomposed and evaporated at 600 ° C., and C does not remain as a solid. Therefore, it is considered that the weight reduction from 300 ° C. to 600 ° C. is the weight reduction derived from the decomposition of PEI and PVP adsorbed on copper. Therefore, the water-soluble high molecular weight adsorbed on the silver-coated copper fine particles is 1.1% by mass.
この試料１の銀被覆銅微粒子分散液に焼成膜の膜質向上を目的としてクエン酸を分散液に対し５質量％添加して、バーコーターによりガラス基板上にパターン印刷を行った。得られたパターンを乾燥した後、窒素雰囲気中にて２２０℃×１時間の熱処理を行った結果、体積抵抗率が３２μΩ・ｃｍの導電膜が形成されていることが確認できた。尚、体積抵抗率は、日本電子(株)製の分析走査電子顕微鏡（ＳＥＭ、型式ＪＳＭ−６３６０ＬＡ）での基板断面観察により測定した膜厚と、(株)ダイアインスツルメンツ製の抵抗率計（ロレスターＧＰ）により測定した表面抵抗率とから求めた。 For the purpose of improving the film quality of the fired film, 5% by mass of citric acid was added to the silver-coated copper fine particle dispersion of Sample 1 and the pattern was printed on the glass substrate with a bar coater. After drying the obtained pattern, heat treatment was performed at 220 ° C. for 1 hour in a nitrogen atmosphere, and as a result, it was confirmed that a conductive film having a volume resistivity of 32 μΩ · cm was formed. The volume resistivity is determined by observing the cross section of the substrate with an analytical scanning electron microscope (SEM, model JSM-6360LA) manufactured by JEOL Ltd., and a resistivity meter (Lorester, Inc.) manufactured by Dia Instruments Co., Ltd. It was determined from the surface resistivity measured by GP).
上記した試料１の銀被覆銅微粒子及びその分散液について、銀の銅に対する質量割合（Ａｇ／Ｃｕ）、ハロゲン元素の銅に対する質量割合（ハロゲン／Ｃｕ）、平均粒径（ｄ）、相対標準偏差（標準偏差σ／平均粒径ｄ）、水溶性高分子量、及び導電膜の体積抵抗率を、下記表１にまとめて示した。 Regarding the silver-coated copper fine particles and dispersion thereof of Sample 1 described above, the mass ratio of silver to copper (Ag / Cu), the mass ratio of halogen to copper (halogen / Cu), average particle diameter (d), relative standard deviation Table 1 below collectively shows (standard deviation σ / average particle diameter d), water-soluble high molecular weight, and volume resistivity of the conductive film.
［実施例２］
上記実施例１と同様に実施したが、銅微粒子分散液に添加する１％硝酸銀水溶液の添加量を変更し、それぞれ試料２〜５の銀被覆銅微粒子分散液を得た。これら試料２〜５の銀被覆銅微粒子及びその分散液について、上記実施例１と同様に評価した。得られた結果を下記表１に併せて示した。
[Example 2]
Although it implemented similarly to the said Example 1, the addition amount of 1-% silver nitrate aqueous solution added to a copper fine particle dispersion was changed, and the silver covering copper fine particle dispersion of samples 2-5 was obtained, respectively. The silver-coated copper fine particles and their dispersions of Samples 2 to 5 were evaluated in the same manner as in Example 1 above. The obtained results are also shown in Table 1 below.
［比較例１］
上記実施例１と同様に実施したが、試料６では銅微粒子分散液に硝酸銀水溶液を添加せず、試料７〜８では銅微粒子分散液に添加する１％硝酸銀水溶液の添加量を変更して、それぞれ試料６〜８の銅微粒子あるいは銀被覆銅微粒子の分散液を得た。これら試料６〜８の銅微粒子あるいは銀被覆銅微粒子及びその分散液についても、上記実施例１と同様に評価した。得られた結果を下記表１に併せて示した。
[Comparative Example 1]
Although it implemented similarly to the said Example 1, in sample 6, silver nitrate aqueous solution was not added to copper fine particle dispersion, and in samples 7-8, the addition amount of 1% silver nitrate aqueous solution added to copper fine particle dispersion was changed, A dispersion of copper fine particles or silver-coated copper fine particles of Samples 6 to 8 was obtained. The copper fine particles or silver-coated copper fine particles of Samples 6 to 8 and the dispersions thereof were also evaluated in the same manner as in Example 1. The obtained results are also shown in Table 1 below.
［比較例２］
平均粒径ｄが０.１９μｍ、相対標準偏差（標準偏差σ／平均粒径ｄ）が２２％、ＢＥＴ比表面積が３.７ｍ２／ｇの球状の銅粉１００ｇを、純水１リットル中に懸濁させ、超音波洗浄器（アズワン製、ＵＳ−３Ｒ）中で１０分間分散させて銅微粒子分散液を得た。
[Comparative Example 2]
100 g of spherical copper powder having an average particle diameter d of 0.19 μm, a relative standard deviation (standard deviation σ / average particle diameter d) of 22%, and a BET specific surface area of 3.7 m 2 / g in 1 liter of pure water. Suspended and dispersed for 10 minutes in an ultrasonic cleaner (manufactured by ASONE, US-3R) to obtain a copper fine particle dispersion.
この銅微粒子分散液を撹拌しながら、予め作製しておいた１質量％硝酸銀水溶液４７０ｃｃを５ｃｃ／分の添加速度（銅１００ｇに対して銀０.０３２ｇ／分）で定量添加し、添加終了後１０分間撹拌しながら保持した。得られた粒子を吸引濾過により固液分離し、１リットルの純水中で３０分間撹拌洗浄した後、再び吸引濾過して試料９の銀被覆銅微粒子を得た。 While stirring this copper fine particle dispersion, 470 cc of a 1% by mass aqueous silver nitrate solution prepared in advance was quantitatively added at an addition rate of 5 cc / min (0.032 g / min of silver with respect to 100 g of copper), and after completion of the addition Hold with stirring for 10 minutes. The obtained particles were separated into solid and liquid by suction filtration, stirred and washed in 1 liter of pure water for 30 minutes, and then suction filtered again to obtain silver-coated copper fine particles of Sample 9.
この試料９の銀被覆銅微粒子を、純水とエチレングリコールの混合溶媒（純水：エチレングリコール：＝８：１）１００ｃｃにクエン酸を５ｇ添加した溶媒中に懸濁させ、超音波洗浄器で３０分間分散させることにより、試料９の銀被覆銅微粒子分散液を得た。 The silver-coated copper fine particles of Sample 9 were suspended in a solvent obtained by adding 5 g of citric acid to 100 cc of a mixed solvent of pure water and ethylene glycol (pure water: ethylene glycol: = 8: 1), and an ultrasonic cleaner. By dispersing for 30 minutes, a silver-coated copper fine particle dispersion of Sample 9 was obtained.
得られた試料９の銀被覆銅微粒子分散液を、上記実施例１と同様にガラス基板上に印刷し、窒素雰囲気中にて２２０℃×１時間の熱処理を行って導電膜を形成した。得られた導電膜の体積抵抗率は１Ω・ｃｍ以上と極めて高い値であった。これらの結果を、下記表１に併せて示した。 The obtained silver-coated copper fine particle dispersion of Sample 9 was printed on a glass substrate in the same manner as in Example 1 above, and heat-treated at 220 ° C. for 1 hour in a nitrogen atmosphere to form a conductive film. The volume resistivity of the obtained conductive film was an extremely high value of 1 Ω · cm or more. These results are also shown in Table 1 below.
上記表１に示す結果から分るように、本発明による試料１〜５の各銀被覆銅微粒子分散液は、窒素雰囲気中における２２０℃×１時間の低温焼成によって、４０μΩ・ｃｍ以下の非常に低い体積抵抗率を有する焼成膜が得られた。一方、比較例については、試料６の銀を被覆していない銅微粒子分散液、試料７のＡｇ／Ｃｕ質量比が本発明の範囲以下である各銀被覆銅微粒子分散液では、焼成膜の体積抵抗率が４０μΩ・ｃｍを越えた高い値となった。 As can be seen from the results shown in Table 1 above, each of the silver-coated copper fine particle dispersions of Samples 1 to 5 according to the present invention is very low of 40 μΩ · cm or less by low-temperature firing at 220 ° C. for 1 hour in a nitrogen atmosphere. A fired film having a low volume resistivity was obtained. On the other hand, with respect to the comparative example, in the copper fine particle dispersion of sample 6 not coated with silver, and in each silver-coated copper fine particle dispersion in which the Ag / Cu mass ratio of sample 7 is below the range of the present invention, the volume of the fired film The resistivity was a high value exceeding 40 μΩ · cm.
また、比較例である粒径が本発明の粒径範囲より大きい試料９の銀被覆銅微粒子分散液では、焼成後の体積抵抗率が本発明の銀被覆銅微粒子分散液より大幅に高い結果となった。尚、比較例であるＡｇ／Ｃｕ質量比が本発明の範囲を超えた試料８の銀被覆銅微粒子分散液は、銀析出時に銅微粒子が凝集し、沈降してしまったため、その後の評価が不可能であった。 Further, in the silver-coated copper fine particle dispersion of Sample 9 having a particle size that is a comparative example larger than the particle size range of the present invention, the volume resistivity after firing is significantly higher than that of the silver-coated copper fine particle dispersion of the present invention. became. In addition, the silver-coated copper fine particle dispersion of Sample 8 whose Ag / Cu mass ratio, which is a comparative example, exceeds the range of the present invention, the copper fine particles aggregated and settled during silver precipitation, and the subsequent evaluation was unsatisfactory. It was possible.
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| JP6033327B2 (en) * | 2011-12-15 | 2016-11-30 | ヘンケル アイピー アンド ホールディング ゲゼルシャフト ミット ベシュレンクテル ハフツング | Selective coating of exposed copper on silver-plated copper |
| WO2013108916A1 (en) | 2012-01-17 | 2013-07-25 | Ｄｏｗａエレクトロニクス株式会社 | Silver-coated copper alloy powder and method for manufacturing same |
| JP6181368B2 (en) * | 2012-12-14 | 2017-08-16 | ユニチカ株式会社 | Aggregates of fibrous silver particles |
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| KR101403371B1 (en) * | 2013-12-31 | 2014-06-03 | 충남대학교산학협력단 | Manufacturing method of metal particle and metal particle using thereof, and conductive paste and shielding electromagnetic wave containing the same |
| JP2016160455A (en) * | 2015-02-27 | 2016-09-05 | 日立化成株式会社 | Copper-containing particle, conductor forming composition, method for producing conductor, conductor and device |
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| JP6380255B2 (en) * | 2015-06-25 | 2018-08-29 | 住友金属鉱山株式会社 | Silver-coated copper-based fine particles and production method thereof, and silver-coated copper-based fine particle dispersion and production method thereof |
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