JP2004323964A - Method for manufacturing electroless-plated electroconductive powder - Google Patents
Method for manufacturing electroless-plated electroconductive powder Download PDFInfo
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- JP2004323964A JP2004323964A JP2003124444A JP2003124444A JP2004323964A JP 2004323964 A JP2004323964 A JP 2004323964A JP 2003124444 A JP2003124444 A JP 2003124444A JP 2003124444 A JP2003124444 A JP 2003124444A JP 2004323964 A JP2004323964 A JP 2004323964A
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- 239000000843 powder Substances 0.000 title claims abstract description 139
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 238000000034 method Methods 0.000 title abstract description 13
- 239000011162 core material Substances 0.000 claims abstract description 68
- 239000006185 dispersion Substances 0.000 claims abstract description 65
- 238000007772 electroless plating Methods 0.000 claims abstract description 48
- 150000001875 compounds Chemical class 0.000 claims abstract description 42
- 229910052751 metal Inorganic materials 0.000 claims abstract description 10
- 239000002184 metal Substances 0.000 claims abstract description 10
- 238000007747 plating Methods 0.000 claims description 111
- 229910021645 metal ion Inorganic materials 0.000 claims description 8
- 238000006467 substitution reaction Methods 0.000 claims description 6
- 150000002500 ions Chemical class 0.000 claims description 5
- 230000000536 complexating effect Effects 0.000 claims description 2
- 239000007788 liquid Substances 0.000 abstract description 15
- 238000006073 displacement reaction Methods 0.000 abstract description 4
- 230000001112 coagulating effect Effects 0.000 abstract description 2
- 229910052737 gold Inorganic materials 0.000 description 73
- 239000010931 gold Substances 0.000 description 73
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 59
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 56
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 28
- 239000000243 solution Substances 0.000 description 28
- 239000002002 slurry Substances 0.000 description 27
- -1 gold ions Chemical class 0.000 description 19
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 18
- 239000008139 complexing agent Substances 0.000 description 15
- 239000007864 aqueous solution Substances 0.000 description 12
- 238000003756 stirring Methods 0.000 description 12
- 230000008021 deposition Effects 0.000 description 11
- 229910052759 nickel Inorganic materials 0.000 description 11
- 239000010408 film Substances 0.000 description 10
- UEUXEKPTXMALOB-UHFFFAOYSA-J tetrasodium;2-[2-[bis(carboxylatomethyl)amino]ethyl-(carboxylatomethyl)amino]acetate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]C(=O)CN(CC([O-])=O)CCN(CC([O-])=O)CC([O-])=O UEUXEKPTXMALOB-UHFFFAOYSA-J 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 229910052802 copper Inorganic materials 0.000 description 9
- 239000010949 copper Substances 0.000 description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 8
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 8
- 238000001914 filtration Methods 0.000 description 8
- 239000002245 particle Substances 0.000 description 8
- 230000002776 aggregation Effects 0.000 description 7
- 238000004220 aggregation Methods 0.000 description 7
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 6
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 6
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 239000001509 sodium citrate Substances 0.000 description 6
- HRXKRNGNAMMEHJ-UHFFFAOYSA-K trisodium citrate Chemical compound [Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O HRXKRNGNAMMEHJ-UHFFFAOYSA-K 0.000 description 6
- 229940038773 trisodium citrate Drugs 0.000 description 6
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 229910001431 copper ion Inorganic materials 0.000 description 5
- 239000000706 filtrate Substances 0.000 description 5
- 239000010409 thin film Substances 0.000 description 5
- 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
- VZCYOOQTPOCHFL-OWOJBTEDSA-N Fumaric acid Chemical compound OC(=O)\C=C\C(O)=O VZCYOOQTPOCHFL-OWOJBTEDSA-N 0.000 description 4
- AEMRFAOFKBGASW-UHFFFAOYSA-N Glycolic acid Chemical compound OCC(O)=O AEMRFAOFKBGASW-UHFFFAOYSA-N 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 4
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 4
- 150000003863 ammonium salts Chemical class 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- ISDDBQLTUUCGCZ-UHFFFAOYSA-N dipotassium dicyanide Chemical compound [K+].[K+].N#[C-].N#[C-] ISDDBQLTUUCGCZ-UHFFFAOYSA-N 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 4
- 229910017604 nitric acid Inorganic materials 0.000 description 4
- 229910052763 palladium Inorganic materials 0.000 description 4
- XNGIFLGASWRNHJ-UHFFFAOYSA-N phthalic acid Chemical compound OC(=O)C1=CC=CC=C1C(O)=O XNGIFLGASWRNHJ-UHFFFAOYSA-N 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 4
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 3
- 239000004471 Glycine Substances 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 239000007900 aqueous suspension Substances 0.000 description 3
- 150000007522 mineralic acids Chemical class 0.000 description 3
- 238000005065 mining Methods 0.000 description 3
- 229910001453 nickel ion Inorganic materials 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
- KWSLGOVYXMQPPX-UHFFFAOYSA-N 5-[3-(trifluoromethyl)phenyl]-2h-tetrazole Chemical compound FC(F)(F)C1=CC=CC(C2=NNN=N2)=C1 KWSLGOVYXMQPPX-UHFFFAOYSA-N 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 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
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 description 2
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 2
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 2
- KDYFGRWQOYBRFD-UHFFFAOYSA-N Succinic acid Natural products OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 description 2
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 150000003973 alkyl amines Chemical class 0.000 description 2
- 150000005215 alkyl ethers Chemical class 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
- 150000001412 amines Chemical class 0.000 description 2
- 150000001413 amino acids Chemical class 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 description 2
- 150000001735 carboxylic acids Chemical class 0.000 description 2
- 239000011231 conductive filler Substances 0.000 description 2
- XPPKVPWEQAFLFU-UHFFFAOYSA-N diphosphoric acid Chemical compound OP(O)(=O)OP(O)(O)=O XPPKVPWEQAFLFU-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000001530 fumaric acid Substances 0.000 description 2
- 239000000174 gluconic acid Substances 0.000 description 2
- 235000012208 gluconic acid Nutrition 0.000 description 2
- 229960004275 glycolic acid Drugs 0.000 description 2
- 239000004310 lactic acid Substances 0.000 description 2
- 235000014655 lactic acid Nutrition 0.000 description 2
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 description 2
- 239000011976 maleic acid Substances 0.000 description 2
- 239000001630 malic acid Substances 0.000 description 2
- 235000011090 malic acid Nutrition 0.000 description 2
- 230000005012 migration Effects 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 2
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 2
- 229920001281 polyalkylene Polymers 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 229940005657 pyrophosphoric acid Drugs 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- HELHAJAZNSDZJO-OLXYHTOASA-L sodium L-tartrate Chemical compound [Na+].[Na+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O HELHAJAZNSDZJO-OLXYHTOASA-L 0.000 description 2
- 229910001379 sodium hypophosphite Inorganic materials 0.000 description 2
- 239000001433 sodium tartrate Substances 0.000 description 2
- 229960002167 sodium tartrate Drugs 0.000 description 2
- 235000011004 sodium tartrates Nutrition 0.000 description 2
- 239000004094 surface-active agent Substances 0.000 description 2
- 239000011975 tartaric acid Substances 0.000 description 2
- 235000002906 tartaric acid Nutrition 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 239000005749 Copper compound Substances 0.000 description 1
- JJLJMEJHUUYSSY-UHFFFAOYSA-L Copper hydroxide Chemical compound [OH-].[OH-].[Cu+2] JJLJMEJHUUYSSY-UHFFFAOYSA-L 0.000 description 1
- 239000005750 Copper hydroxide Substances 0.000 description 1
- 229910001096 P alloy Inorganic materials 0.000 description 1
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 150000001346 alkyl aryl ethers Chemical class 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- RJTANRZEWTUVMA-UHFFFAOYSA-N boron;n-methylmethanamine Chemical compound [B].CNC RJTANRZEWTUVMA-UHFFFAOYSA-N 0.000 description 1
- 230000005587 bubbling Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 150000001880 copper compounds Chemical class 0.000 description 1
- 229910001956 copper hydroxide Inorganic materials 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 239000012776 electronic material Substances 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000007561 laser diffraction method Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000003002 pH adjusting agent Substances 0.000 description 1
- PIBWKRNGBLPSSY-UHFFFAOYSA-L palladium(II) chloride Chemical compound Cl[Pd]Cl PIBWKRNGBLPSSY-UHFFFAOYSA-L 0.000 description 1
- OFNHPGDEEMZPFG-UHFFFAOYSA-N phosphanylidynenickel Chemical compound [P].[Ni] OFNHPGDEEMZPFG-UHFFFAOYSA-N 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- NNFCIKHAZHQZJG-UHFFFAOYSA-N potassium cyanide Chemical compound [K+].N#[C-] NNFCIKHAZHQZJG-UHFFFAOYSA-N 0.000 description 1
- XTFKWYDMKGAZKK-UHFFFAOYSA-N potassium;gold(1+);dicyanide Chemical compound [K+].[Au+].N#[C-].N#[C-] XTFKWYDMKGAZKK-UHFFFAOYSA-N 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 238000000790 scattering method Methods 0.000 description 1
- 239000012279 sodium borohydride Substances 0.000 description 1
- 229910000033 sodium borohydride Inorganic materials 0.000 description 1
- 239000007779 soft material Substances 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- NCPXQVVMIXIKTN-UHFFFAOYSA-N trisodium;phosphite Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])[O-] NCPXQVVMIXIKTN-UHFFFAOYSA-N 0.000 description 1
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- Powder Metallurgy (AREA)
- Chemically Coating (AREA)
- Conductive Materials (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、分散性の良好なめっき粉体を得ることができる導電性無電解めっき粉体の製造方法に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
銅芯材の表面に、金からなる無電解めっき層が形成されてなる導電性無電解めっき粉体が知られている。例えば、金で被覆された９０％以上が平均粒径１００μｍ以下であり、平均アスペクト比が５以上のフレーク状であり、金の被覆量が３０〜５０重量％である銅芯材からなる導電性無電解めっき粉体が知られている（特許文献１参照）。このめっき粉体は、従来金やパラジウムの粉体が用いられていた導電性フィラーと同等の導電性を有し、また低コストであることから、金やパラジウムの導電性フィラーの代替物として用いられる。
【０００３】
また銅はマイグレーションを起こしやすいことからその防止を目的として、銅芯材の表面にニッケルめっきのバリア層を形成し、その上に金めっき層を形成することが行われている。しかしニッケルは銅と比較して比抵抗が高いため、ニッケル層が銅芯材に存在すると、銅の低抵抗の特徴が発現しにくくなる。また、ニッケルは無電解めっきの工程で凝集を起こしやすいことから、得られためっき粉体に対して機械的な分散処理を施してめっき粉体の分散性を高める必要がある。銅は金属の中では比較的に柔らかい部類に属する材料なので、機械的な分散処理によって銅芯材が変形しやすく、それによって金めっき層も損傷を受けやすい。なお機械的な分散処理には例えば気流式粉砕機、水流式粉砕機、ボールミル、ビースミル、その他機械的粉砕機が一般に使用される。
【０００４】
【特許文献１】
特開平６−１０８１０２号公報
【０００５】
従って本発明は、めっき粉体に損傷を与えることなく分散性が良好なめっき粉体を得ることができる導電性無電解めっき粉体の製造方法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明は、芯材粉体の表面を無電解めっきして得られためっき粉体の分散液に、該めっき粉体に含まれる金属のイオンと錯形成可能な化合物を添加し、凝集している該めっき粉体を分散させることを特徴とする導電性無電解めっき粉体の製造方法を提供することにより前記目的を達成したものである。
【０００７】
また本発明は、芯材粉体の表面を無電解めっきしてめっき粉体を製造するに先立ち、該芯材粉体を、該芯材粉体に含まれる金属のイオンと錯形成可能な化合物と混合し、該芯材粉体を分散させることを特徴とする導電性無電解めっき粉体の製造方法を提供するものである。
【０００８】
【発明の実施の形態】
以下本発明を、その好ましい実施形態に基づき説明する。以下の説明では本発明の一実施形態として、銅からなる芯材粒子（以下、銅芯材という）の表面に、金からなる無電解めっき層（以下、金めっき層という）を直接形成してめっき粉体を製造する方法をとりあげる。しかしながら、本発明の範囲はこの製造方法に限定されないことは言うまでもない。
【０００９】
本実施形態におけるめっき粉体の製造方法は（１）予備分散工程（２）金めっき工程および（３）分散処理工程に大別される。（１）予備分散工程ではめっきに先立ち銅芯材を分散させる工程である。（２）の金めっき工程では、錯化剤を含む水溶液に（１）の予備分散工程で得られた銅芯材を投入して混合分散させ、得られた分散液に金イオンを添加して金を銅芯材の表面に置換析出させる。（３）の分散処理工程においては、（２）の金めっき工程で得られためっき粉体（このめっき粉体は凝集の程度が高いことがある）を含む分散液に、該めっき粉体に含まれる金属のイオンと錯形成可能な化合物を混合して、該めっき粉体を分散させる。以下それぞれの工程について詳述する。
【００１０】
（１）予備分散工程
本工程はめっき前の銅芯材を分散させる工程であり、本発明の特徴の一つである。予備分散工程においては芯材粉体を、該芯材粉体に含まれる金属のイオンと錯形成可能な化合物と混合する。本実施形態においては芯材である銅のイオンと錯形成可能な化合物を銅芯材と混合する。芯材粉体の表面には酸化膜が存在している場合が多く、該酸化膜が存在しているとめっきが不均一になる。本予備分散工程を行うことで酸化膜が除去され、めっきを均一に行うことができることが判明した。錯化剤は、金属イオンの種類に応じて適切なものが用いられる。例えば本実施形態においては、後述する分散処理工程で用いられる錯化剤と同様のものを用いることができる。錯化剤は一般にその水溶液の形で芯材粉体と混合される。錯化剤の濃度は、酸化膜を除去でき且つ過剰の金属（本実施形態では銅）が溶出しないような濃度とする。
【００１１】
本予備分散工程において酸化膜を除去するために、前記錯化剤を無機酸と併用してもよい。無機酸としては例えば塩酸、硝酸、硫酸等を用いることができる。また酸化膜の除去の間、超音波と撹拌とを併用して除去反応が促進するようにしてもよい。ただし銅芯材に損傷を与えないように穏やかな条件で撹拌を行う。更に予備分散工程においては、例えば界面活性剤等の分散剤を必要に応じて用いることもできる。
【００１２】
銅芯材は、ほぼ球形のものや、フレーク状、針状のものなど、その形状に特に制限はない。銅芯材の大きさは本発明に従って製造されるめっき粉体の具体的用途に応じて適切に選択される。例えば、めっき粉体を電子回路接続用の電子材料として用いる場合には銅芯材はＤ５０値が０．５〜１０００μｍ、特に１〜２００μｍ程度の球状粒子であることが好ましい。或いは、アスペクト比の平均（長径と厚みの比の平均）が１〜１０００００、特に３〜２０００程度であって、長軸径の平均が、１〜１００００μｍ、特に３〜１０００μｍ程度であるフレーク状粒子であることが好ましい。
【００１３】
（２）金めっき工程
（１）の予備分散工程で得られた銅芯材を濾別、洗浄する。次いで銅芯材を、錯化剤を含む水溶液中に投入して分散液を得る。錯化剤はとしては、例えばクエン酸、ヒドロキシ酢酸、酒石酸、リンゴ酸、乳酸、グルコン酸、コハク酸、フタル酸、フマル酸、マレイン酸、マロン酸またはそのアルカリ金属塩やアンモニウム塩などの各種カルボン酸又はその塩、グリシンなどのアミノ酸、エチレンジアミン、アルキルアミンなどのアミン類、アンモニウム塩、エチレンジアミン四酢酸（ＥＤＴＡ）、ピロリン酸又はその塩など、金イオンや溶出する銅イオンと錯形成可能な化合物が使用される。これらの錯化剤は１種又は２種類以上を用いることができる。これらの錯化剤を用いることで銅芯材の表面全域を金めっき層で均一に被覆することが可能となる。
【００１４】
銅芯材を投入する前における前記水溶液中の錯化剤の濃度は、使用する錯化剤にもよるが、０．００１〜２モル／リットル、特に０．００５〜１モル／リットルであることが、銅芯材の表面全域を金めっき層で均一に被覆し得る点から好ましい。
【００１５】
次に、銅芯材を分散させた分散液に金イオンを含むめっき液を添加して置換型無電解めっきを行う。これによって銅芯材の表面に金を置換析出させる。錯化剤を含む水溶液に金イオンを予め添加しておくと、銅芯材を投入した時に、投入の時間差によって、金の置換析出にばらつきが生じることがしばしばある（後述する比較例１参照）。また前述したように、銅芯材の表面に酸化膜が存在している場合、金の置換反応が始まりにくくなり、金の析出にばらつきが生じることもしばしばある。これに対して銅芯材を分散させた分散液に金イオンを添加することでそのような不都合を回避し得ることが本発明者らの検討によって判明した。特に、錯化剤によって銅芯材の表面に存在している酸化膜を除去できることが判明した。但し銅を溶解させすぎると、不溶性の銅化合物が液中に蓄積することから、過度に酸化膜が形成されている銅芯材の場合は、先に述べた予備分散工程において酸化膜を予め除去しておくことが好ましい。
【００１６】
金イオンの添加速度は金の析出速度を制御するのに有効である。金の析出速度は均一な金の析出に影響を及ぼす。従って、金の析出速度はめっき液の添加速度を調整することによって、１〜３００ナノメーター／分、特に５〜１００ナノメーター／分に制御することが好ましい。金の析出速度は金イオンの添加速度から計算によって求めることができる。
【００１７】
銅芯材を投入する前の錯化剤溶液、銅を投入した後の分散液及びめっき液のｐＨは金の析出状態に影響する。ｐＨが低すぎると、銅芯材から溶出した銅イオンに由来する水酸化銅が形成されやすくなって、得られるめっき粉体が凝集しやすくなる。ｐＨが高すぎると金の析出が粗くなる。これらの観点から、めっき液のｐＨは３．５〜７．０、特に４．０〜６．０であることが好ましい。ｐＨ調整剤としては水酸化ナトリウム、水酸化カリウム、アンモニア水、塩酸、硫酸、硝酸、リン酸等が挙げられる。
【００１８】
めっき液を分散液に添加するときの温度も金の析出に影響する。温度が低すぎると、置換析出の反応速度が遅くなり、且つ析出が粗くなる。一方、温度が高すぎると、反応速度が速くなりすぎて金の析出にばらつきが生じる。また、めっき液が不安定となり分解を引き起こす場合もある。これらの観点から、めっき液が添加されている間での分散液の温度は５０〜９５℃、特に６５〜９０℃であることが好ましい。
【００１９】
（３）分散処理工程
本製造方法においてもっとも特徴となるのがこの分散処理工程である。具体的には、（２）の金めっき工程で得られためっき粉体の凝集状態が高い場合には、これを分散処理工程に付して単分散化させる必要がある。単分散化させるために、本発明においては（２）の金めっき工程で得られためっき粉体を含む分散液に、該めっき粉体に含まれる金属のイオンと錯形成可能な化合物（この化合物を以下「錯形成化合物」ともいう）を混合する。本発明者らの検討の結果、（２）の金めっき工程で得られためっき粉体凝集の一因は、該めっき粉体に含まれる金属のイオン、例えば銅芯材から溶出した銅イオンが水不溶性の化合物を形成し、該水不溶性の化合物がめっき粉体どうしを結合させることにあることが判明した。そこで本発明においては、凝集しているめっき粉体に錯形成化合物を添加することで、前記水不溶性の化合物を錯体に変化させて、凝集状態にあるめっき粉体を単分散化している。この観点から、本分散処理工程は、自己触媒型の無電解めっきよりも置換型の無電解めっきを行う場合に極めて有効である。本分散処理工程は、ミルや粉砕機を用いた機械的な分散方法に比べてめっき粉体に損傷を与えにくいという利点がある。特に銅芯材のように柔らかい材料を用いる場合には、その変形が起こらず、従って金めっき層も損傷を受けないので極めて有効である。また本分散処理工程は、めっき粉体に対する悪影響が少ないので、所望の分散状態が得られるまで数回繰り返すことができるという利点もある（後述する実施例１参照）。
【００２０】
錯形成化合物としては、特に無電解めっき前の芯材粉体に含まれる金属のイオンと錯形成可能な化合物を用いることが好ましい。本実施形態においては銅イオンと錯形成可能な化合物を用いることが好ましい。錯形成化合物の例としては、クエン酸、ヒドロキシ酢酸、酒石酸、リンゴ酸、乳酸、グルコン酸、コハク酸、フタル酸、フマル酸、マレイン酸、マロン酸又はそのアルカリ金属塩やアンモニウム塩などの各種カルボン酸又はその塩、グリシンなどのアミノ酸、エチレンジアミン、アルキルアミンなどのアミン類、アンモニウム塩、ＥＤＴＡ、ピロリン酸又はその塩などが挙げられる。これらの化合物は１種又は２種類以上を用いることができる。またこれらの化合物を、塩酸や硝酸、硫酸、リン酸などの無機酸と併用することができる。
【００２１】
錯形成化合物は一般に水溶液の形でめっき粉体と混合される。この水溶液の濃度（めっき粉体と混合する前の濃度）は、使用する化合物の種類にもよるが、一般に０．００５〜６モル／リットル、特に０．０１〜３モル／リットルであることが好ましい。この水溶液のｐＨは、化合物の種類にもよるが一般に３．５〜１４、特に５〜１２．５であることが好ましい。ｐＨの調整には、水酸化ナトリウム、水酸化カリウム、アンモニア水、塩酸、硫酸、硝酸、リン酸などが用いられる。
【００２２】
分散処理工程においては前記分散液の表面張力を低下させ得る化合物を更に添加することもできる（この化合物を以下「表面張力低下化合物」ともいう）。これによって、めっき粉体の分散性を一層高めることができる。表面張力低下化合物は錯形成化合物の添加と同時に、又は錯形成化合物の添加の前後に添加することができる。表面張力低下化合物の例としては、各種界面活性剤やアルコール類が挙げられる。これらのうち特にポリエチレングリコール（分子量２００〜２０００）、ポリアルキレンアルキルエーテル、ポリアルキレンアルキルアリールエーテルなどを用いることが好ましい。表面張力低下化合物は、分散処理工程にある前記分散液中に０．１〜１００００ｐｐｍ、特に１〜１０００ｐｐｍ含まれていることが好ましい。
【００２３】
分散処理の温度は５〜６０℃、特に１０〜３５℃であることが好ましい。この温度範囲であれば、銅芯材の溶解を生ずることなく比較的短時間で所望の分散状態となる。
【００２４】
分散処理工程においては補助的に超音波を用いたり、分散液を撹拌してもよい。但し、めっき粉体に損傷を与えないような穏やかな条件で行う。
【００２５】
分散処理が完了したら、分散液からめっき粉体を濾別し乾燥させることで最終製品が得られる。
【００２６】
本発明は前記実施形態に制限されない。例えば、銅芯材の表面にニッケルを無電解めっきした下地層を形成し、その下地層の上に金の無電解めっき層を形成してめっき粉体を得る方法や、非金属の芯材粉体の表面にニッケルの無電解めっき層を形成してめっき粉体を得る方法にも本発明を適用することができる。
【００２７】
また本発明の方法は置換型の無電解めっきを行う場合に特に有効な方法であるが、自己触媒型の無電解めっきを行う場合にも本発明の方法を適用することができる。更に必要に応じ、置換型無電解めっきによって金イオンを還元させた後、還元剤を用いた自己触媒型無電解めっきによって金イオンを更に還元させて金めっき層の厚みを大きくしてもよい。
【００２８】
また分散処理に用いられる錯形成化合物としては、無電解めっき前の芯材粉体に含まれる金属イオンと錯形成可能な化合物を用いることが特に好ましいが、それ以外にも、無電解めっき後の芯材粉体に含まれる金属のイオンと錯形成可能な化合物を用いることもできる。例えばめっき粉体が非金属の芯材粉体の表面にニッケルの無電解めっき層を形成してなるものである場合、錯形成化合物として、ニッケルイオンと錯形成可能な化合物を用いることができる。
【００２９】
また分散処理は、めっき粉体の製造工程における最後のめっき工程後に行われることに限られない。例えば、めっき工程を複数回行う製造方法においては、或るめっき工程とその次のめっき工程との間で分散処理を行うことができる。具体的には、芯材粉体の表面に第１の無電解めっき層を形成し、次いでその上に第２の無電解めっき層を形成する工程において、第１の無電解めっき層を形成した後、第２の無電解めっき層を形成する前に、分散処理を行うことができる。更に第２の無電解めっき層を形成した後にも分散処理を行ってもよい（この場合には、第１の無電解めっき層が形成されためっき粉体を、芯材粉体ととらえればよい）。
【００３０】
【実施例】
以下、実施例により本発明を更に詳細に説明する。しかしながら本発明の範囲はかかる実施例に制限されるものではない。
【００３１】
〔実施例１〕
（１）予備分散工程
Ｄ５０値が５μｍの銅粉〔三井金属鉱業（株）製 商品名”１５００ＹＭ”〕を芯材粉体に用いた。ＥＤＴＡ−４Ｎａ０．０２２モルを溶解した水２００ｍｌ中へ４３．５ｇの銅粉を分散させ、超音波を併用しながら３０℃で５分攪拌しスラリーを得た。次いでスラリーを濾別し、１回リパルプ洗浄した。
【００３２】
（２）金めっき工程
前記工程で得られた銅粉を水２００ミリリットルに分散させ、超音波を併用しながら常温で５分攪拌しスラリーを得た。０．０２７モル／リットルのＥＤＴＡ−４Ｎａ及び０．０３８モル／リットルのクエン酸三ナトリウムを含み、水酸化ナトリウム及びリン酸によりｐＨ５に調整された水溶液２リットル中へ、このスラリーを投入して分散液を得た。この分散液を１５分攪拌した。次いで０．４１モル／リットルのシアン化金カリウムを含むめっき液５０ミリリットルを、１０ミリリットル／分の添加速度で、この分散液に添加した。分散液の温度は８０℃に維持した。分散液を１０分間攪拌して銅粉の表面に金を置換析出させ、金めっき粉体を得た。
【００３３】
（３）分散処理工程
得られた金めっき粉体を濾別し、次いで金めっき粉体に水を加えて５００ミリリットルのスラリーにした。このスラリーに０．０４４モルのＥＤＴＡ−４Ｎａ及び１００ｍｇのポリオキシエチレンアルキルエーテル（旭電化製のアデカトールＴＮ（商品名））を加え、超音波を併用しながら２０℃で３０分間攪拌を続けた。この工程を３回繰り返し、金めっき粉体を分散処理した。次いで金めっき粉体を濾別し、３回リパルプ洗浄した後、８０℃の真空乾燥機で乾燥させた。金イオンの添加量から算出した金めっき層の厚さは３５ｎｍであった。得られた金めっき粉体を走査型電子顕微鏡で観察したところ、金めっき粉体の著しい凝集は観察されなかった。また得られた金めっき粉体の反射電子組成像を観察したところ、金めっき層が銅芯材の全面を均一に被覆していることが確認された。
【００３４】
〔実施例２〕
（１）触媒化処理工程
平均粒径４．６μｍ、真比重１．３９の球状ベンゾグアナミン−メラミン−ホルマリン樹脂〔（株）日本触媒製、商品名“エポスター”〕を芯材粉体として用いた。その２０ｇを４００ミリリットルのスラリーにし、６０℃に維持した。超音波を併用してスラリー攪拌しながら、０．１１モル／リットルの塩化パラジウム水溶液２ミリリットルを添加した。そのままの攪拌状態を５分間維持させ、芯材粉体の表面にパラジウムイオンを捕捉させる活性化処理を行った。次いで水溶液をろ過し、１回リパルプ湯洗した芯材粉体を２００ミリリットルのスラリーにした。超音波を併用しながらこのスラリーを攪拌し、そこへ０．０１７モル／リットルのジメチルアミンボランと０．１６モル／リットルのホウ酸との混合水溶液２０ミリリットルを加えた。常温で超音波を併用しながら２分攪拌してパラジウムイオンの還元処理を行った。
【００３５】
（２）初期薄膜形成工程
（１）の工程で得られた２００ミリリットルのスラリーを、０．０８７モル／リットルの酒石酸ナトリウムと０．００５モル／リットルの硫酸ニッケルと０．０１３モル／リットルの次亜リン酸ナトリウムからなる初期薄膜形成液に攪拌しながら添加して水性懸濁体となした。初期薄膜形成液は７５℃に加温されており、液量は１．８リットルであった。スラリー投入後、直ぐに水素の発生が認められ、初期薄膜形成の開始を確認した。１分後に０．０５１モル／リットルの次亜リン酸ナトリウムを投入し、さらに１分間攪拌を続けた。
【００３６】
（３）無電解めっき工程
初期薄膜形成工程で得られた水性懸濁体に０．８５モル／リットルの硫酸ニッケルと０．２６モル／リットルの酒石酸ナトリウムからなるニッケルイオン含有液及び２．６モル／リットル次亜リン酸ナトリウムと２．６モル／リットルの水酸化ナトリウムからなる還元剤含有液の２液を、それぞれ７ミリリットル／分の添加速度で添加した。添加量はそれぞれ３３７ミリリットルであった。２液の添加後すぐに水素の発生が認められ、めっき反応の開始が確認された。２液の添加が完了した後、水素の発泡が停止するまで７５℃の温度を保持しながら攪拌を続けた。次いで水性懸濁体をろ過し、ろ過物を３回リパルプ洗浄した後、１１０℃の真空乾燥機で乾燥させた。これにより、ニッケル−リン合金めっき層を有するめっき粉体を得た。ニッケルイオンの添加量から算出しためっき層の厚さは１００ｎｍであった。
【００３７】
（４）分散処理工程
前記工程で得られたニッケルめっき粉体３０ｇを、グリシン０．１３モルを溶解した水２００ｍｌ中へ分散させ、超音波を併用しながら３０℃で５分攪拌しスラリーを得た。これによってニッケルめっき粉体を分散させた。次いで前記スラリーを濾別し、１回リパルプ洗浄してニッケルめっきスラリーを得た。
【００３８】
（５）金めっき工程
金めっき用の無電解めっき液を４．１リットル調製した。無電解めっき液は、０．０２７モル／リットルのＥＤＴＡ−４Ｎａ、０．０３８モル／リットルのクエン酸三ナトリウム及び０．０１モル／リットルのシアン化金カリウムを含み、水酸化ナトリウム水溶液およびリン酸によってｐＨが６に調整されたものであった。液温６０℃の無電解めっき液を撹拌しながら、該めっき液に前記工程で得られたニッケルめっきスラリーを添加し、２０分間金めっき処理をした。次いで液をろ過し、ろ過物を３回リパルプ洗浄した後、１１０℃の乾燥機で乾燥させた。これによりニッケルめっき層上に無電解金めっき層が形成されためっき粉体が得られた。金イオンの添加量から算出した金めっき層の厚さは２５ｎｍであった。
【００３９】
（６）分散処理工程
得られた金めっき粉体を濾別し、次いで金めっき粉体に水を加えて５００ミリリットルのスラリーにした。このスラリーに０．０４４モルのＥＤＴＡ−４Ｎａを加え、超音波を併用しながら２０℃で３０分間攪拌を続けた。これによって金めっき粉体を分散させた。次いで金めっき粉体を濾別し、３回リパルプ洗浄した後、８０℃の真空乾燥機で乾燥させた。得られた金めっき粉体を走査型電子顕微鏡で観察したところ、金めっき粉体の著しい凝集は観察されなかった。また得られた金めっき粉体の反射電子組成像を観察したところ、金めっき層が銅芯材の全面を均一に被覆していることが確認された。
【００４０】
〔実施例３〕
（１）予備分散工程
Ｄ５０値が５μｍのニッケル粉を芯材粉体に用いた。ＥＤＴＡ−４Ｎａ０．０２２モルを溶解した水２００ｍｌ中へ６０．５ｇのニッケル粉を分散させ、超音波を併用しながら３０℃で５分攪拌しスラリーを得た。次いでスラリーを濾別し、１回リパルプ洗浄した。
【００４１】
（２）金めっき工程
金めっき用の無電解めっき液を２．０リットル調製した。無電解金めっき液は、０．０２７モル／リットルのＥＤＴＡ−４Ｎａ、０．０３８モル／リットルのクエン酸三ナトリウム及び０．０１モル／リットルのシアン化金カリウムを含み、水酸化ナトリウム水溶液およびリン酸によってｐＨが６に調整されたものであった。液温６０℃の無電解めっき液を撹拌しながら、該めっき液に前記工程で得られたニッケル粉のスラリーを添加し、２０分間金めっき処理をした。次いで液をろ過し、ろ過物を３回リパルプ洗浄した後、１１０℃の乾燥機で乾燥させた。これによりニッケル粉の表面上に金の無電解めっき層が形成されためっき粉体が得られた。金イオンの添加量から算出した金めっき層の厚さは２５ｎｍであった。
【００４２】
（３）分散処理工程
得られた金めっき粉体を濾別し、次いで金めっき粉体に水を加えて５００ミリリットルのスラリーにした。このスラリーに０．０４４モルのＥＤＴＡ−４Ｎａを加え、超音波を併用しながら２０℃で３０分間攪拌を続けた。これによって金めっき粉体を分散させた。次いで金めっき粉体を濾別し、３回リパルプ洗浄した後、８０℃の真空乾燥機で乾燥させた。得られた金めっき粉体を走査型電子顕微鏡で観察したところ、金めっき粉体の著しい凝集は観察されなかった。また得られた金めっき粉体の反射電子組成像を観察したところ、金めっき層がニッケル芯材の全面を均一に被覆していることが確認された。
【００４３】
〔比較例１〕
Ｄ５０値が５μｍの銅粉〔三井金属鉱業（株）製 商品名”１５００ＹＭ”〕を芯材粉体に用いた。０．０１３モル／リットルのシアン化金カリウム、０．１モル／リットルのシアン化カリウム及び０．０３モル／リットルのクエン酸三ナトリウムを含む一般的な金置換めっき液を２リットル調製した。銅粉４３．５ｇを水２００ミリリットルに分散させ、超音波を与えながら常温で５分攪拌してスラリーを得た。液温８５℃の金置換めっき液を攪拌しながら前記スラリーを投入し、５分間金めっき処理をした。次いでめっき液をろ過し、ろ過物を３回リパルプ洗浄した後、８０℃の真空乾燥機で乾燥させた。これにより銅粉の表面に金めっき層が形成された金めっき粉体が得られた。金イオンの添加量から算出した金めっき層の厚さは３５ｎｍであった。得られた金めっき粉体を走査型電子顕微鏡で観察したところ、金めっき粉体の著しい凝集が一部に観察された。また得られた金めっき粉体の反射電子組成像を観察したところ、金めっき層は銅芯材の表面を不連続にまばらな状態で被覆しており、銅が表面に露出していることが確認された。
【００４４】
〔比較例２〕
Ｄ５０値が５μｍの銅粉〔三井金属鉱業（株）製 商品名”１５００ＹＭ”〕を芯材粉体に用いた。銅粉４３．５ｇを水２００ミリリットルに分散させ、超音波を与えながら常温で５分攪拌してスラリーを得た。０．０２７モル／リットルのＥＤＴＡ−４Ｎａ及び０．０３８モル／リットルのクエン酸三ナトリウムを含み、水酸化ナトリウムによりｐＨ６に調整された水溶液２リットル中へ、このスラリーを投入して分散液を得た。次いで０．０３５モル／リットルのシアン化金カリウム、０．０２７モル／リットルのＥＤＴＡ−４Ｎａ及び０．０３８モル／リットルのクエン酸三ナトリウムからなる金属塩液と、０．７９モル／リットルの水素化ホウ素ナトリウム及び１．５モル／リットルの水酸化ナトリウムからなる還元液とを、送液ポンプを通して個別かつ同時に３０ミリリットル／分の添加速度でこの分散液に滴下した。滴下した液量は各々５８５ミリリットルであった。滴下終了後、めっき液をろ過し、ろ過物を３回リパルプ洗浄した後、８０℃の真空乾燥機で乾燥させた。これにより銅粉の表面に金めっき層が形成された金めっき粉体が得られた。金イオンの添加量から算出した金めっき層の厚さは３５ｎｍであった。得られた金めっき粉体を走査型電子顕微鏡で観察したところ、金めっき粉体の著しい凝集が一部に観察された。また得られた金めっき粉体の反射電子組成像を観察したところ銅粉の表面に金めっき層が形成されている粉体と、金めっき層が全く形成されていない銅粉とが観察された。また、金が単独で析出した微粒子が数多く観察された。
【００４５】
〔性能評価〕
実施例１〜３並びに比較例１及び２で得られた金めっき粉体について以下の方法で粒度分布を測定した。更に、体積固有抵抗値を測定し、また信頼性試験後の金めっき粉体の体積固有抵抗値を測定した。それらの結果を以下の表１に示す。
【００４６】
〔粒度分布〕
レーザー回折・散乱法による粒度分布測定装置（マイクロトラック ＨＲＡ Ｘ１００（商品名））により測定した。
【００４７】
〔体積固有抵抗値の測定〕
垂直に立てた内径１０ｍｍの樹脂製円筒内に、金めっき粉体１．０ｇを入れ、１０ｋｇの荷重をかけた状態で上下電極間の電気抵抗を測定し、体積固有抵抗値を求めた。
【００４８】
〔信頼性試験〕
金めっき粉体を６０℃・９５％ＲＨの環境下に２５０時間及び５００時間それぞれ保存した後の体積固有抵抗値を測定した。
【００４９】
【表１】
表１に示す結果から明らかなように、各実施例のめっき粉体（本発明品）は、分散性に優れていることが判る。まためっき粉体が損傷を受けておらず、更に金の析出が均一であることに起因して、電気抵抗値が十分に低い上に、信頼性が高いことが判る。一方、各比較例のめっき粉末は分散状態が良好でないことが判る。更に金の析出がばらついており、電気抵抗値が高く、信頼性が低いことが判る。
【００５１】
【発明の効果】
以上詳述した通り本発明の導電性無電解めっき粉体の製造方法によれば、めっき粉体に損傷を与えることなく分散性が良好なめっき粉体を得ることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a conductive electroless plating powder capable of obtaining a plating powder having good dispersibility.
[0002]
Problems to be solved by the prior art and the invention
A conductive electroless plating powder in which an electroless plating layer made of gold is formed on a surface of a copper core material is known. For example, a conductive material composed of a copper core material in which 90% or more covered with gold has a mean particle size of 100 μm or less, is in a flake shape having an average aspect ratio of 5 or more, and has a gold coverage of 30 to 50% by weight. An electroless plating powder is known (see Patent Document 1). This plating powder has the same conductivity as conductive fillers that used to be gold and palladium powders, and because of its low cost, it is used as a substitute for conductive fillers of gold and palladium. Can be
[0003]
Further, since copper is liable to cause migration, a nickel plating barrier layer is formed on the surface of a copper core material and a gold plating layer is formed thereon for the purpose of preventing migration. However, since nickel has a higher specific resistance than copper, if the nickel layer is present in the copper core material, the characteristic of low resistance of copper is hardly exhibited. Further, since nickel is apt to agglomerate in the electroless plating process, it is necessary to enhance the dispersibility of the plating powder by subjecting the obtained plating powder to a mechanical dispersion treatment. Copper is a material that belongs to a relatively soft class among metals, so that the copper core material is easily deformed by the mechanical dispersion treatment, whereby the gold plating layer is also easily damaged. For the mechanical dispersion treatment, for example, an air-flow crusher, a water-flow crusher, a ball mill, a bead mill, and other mechanical crushers are generally used.
[0004]
[Patent Document 1]
JP-A-6-108102
Accordingly, an object of the present invention is to provide a method for producing a conductive electroless plating powder capable of obtaining a plating powder having good dispersibility without damaging the plating powder.
[0006]
[Means for Solving the Problems]
The present invention provides a dispersion of a plating powder obtained by electroless plating the surface of a core material powder, adding a compound capable of forming a complex with ions of a metal contained in the plating powder, and coagulating the dispersion. The above object has been achieved by providing a method for producing a conductive electroless plating powder, characterized in that the plating powder is dispersed.
[0007]
Further, the present invention provides a compound capable of forming a complex with ions of a metal contained in the core material powder prior to producing a plating powder by electrolessly plating the surface of the core material powder. And dispersing the core material powder to provide a method for producing a conductive electroless plating powder.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on preferred embodiments. In the following description, as one embodiment of the present invention, an electroless plating layer made of gold (hereinafter, called a gold plating layer) is directly formed on the surface of core material particles made of copper (hereinafter, called a copper core material). The method of producing the plating powder is described. However, it goes without saying that the scope of the present invention is not limited to this manufacturing method.
[0009]
The method for producing a plating powder in the present embodiment is roughly divided into (1) a preliminary dispersion step, (2) a gold plating step, and (3) a dispersion treatment step. (1) The preliminary dispersion step is a step of dispersing a copper core material prior to plating. In the gold plating step (2), the copper core material obtained in the preliminary dispersion step (1) is put into an aqueous solution containing a complexing agent, mixed and dispersed, and gold ions are added to the obtained dispersion. Gold is substituted and deposited on the surface of the copper core material. In the dispersion treatment step (3), a dispersion containing the plating powder obtained in the gold plating step (2) (this plating powder may have a high degree of aggregation) is added to the dispersion liquid. The plating powder is dispersed by mixing a compound capable of forming a complex with the contained metal ion. Hereinafter, each step will be described in detail.
[0010]
(1) Preliminary dispersion step This step is a step of dispersing the copper core material before plating, and is one of the features of the present invention. In the preliminary dispersion step, the core material powder is mixed with a compound capable of forming a complex with the metal ion contained in the core material powder. In the present embodiment, a compound capable of forming a complex with copper ions as the core material is mixed with the copper core material. In many cases, an oxide film is present on the surface of the core material powder, and when the oxide film is present, plating becomes uneven. It was found that by performing the pre-dispersion step, the oxide film was removed, and the plating could be performed uniformly. An appropriate complexing agent is used depending on the type of the metal ion. For example, in the present embodiment, the same complexing agent used in the dispersion treatment step described later can be used. The complexing agent is generally mixed with the core powder in the form of its aqueous solution. The concentration of the complexing agent is set such that the oxide film can be removed and excess metal (copper in this embodiment) is not eluted.
[0011]
The complexing agent may be used in combination with an inorganic acid in order to remove an oxide film in the preliminary dispersing step. As the inorganic acid, for example, hydrochloric acid, nitric acid, sulfuric acid and the like can be used. During the removal of the oxide film, ultrasonic waves and stirring may be used in combination to promote the removal reaction. However, stirring is performed under mild conditions so as not to damage the copper core material. Further, in the preliminary dispersion step, for example, a dispersant such as a surfactant can be used as necessary.
[0012]
The shape of the copper core material is not particularly limited, such as a substantially spherical shape, a flake shape, and a needle shape. The size of the copper core material is appropriately selected according to the specific use of the plating powder produced according to the present invention. For example, Doshinzai in the case of using the plating powder as electronic materials for electronic circuit connection is preferably D 50 value 0.5～1000Myuemu, in particular spherical particles of about 1 to 200 [mu] m. Alternatively, flaky particles having an average aspect ratio (average of the ratio of the major axis to the thickness) of from 1 to 100,000, particularly about 3 to 2,000, and having an average of the major axis of about 1 to 10,000 μm, especially about 3 to 1,000 μm. It is preferable that
[0013]
(2) The copper core material obtained in the pre-dispersion step of the gold plating step (1) is separated by filtration and washed. Next, the copper core material is introduced into an aqueous solution containing a complexing agent to obtain a dispersion. Examples of complexing agents include various carboxylic acids such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid, succinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, and alkali metal salts and ammonium salts thereof. Compounds capable of complexing with gold ions or eluting copper ions, such as acids or salts thereof, amino acids such as glycine, amines such as ethylenediamine and alkylamine, ammonium salts, ethylenediaminetetraacetic acid (EDTA), pyrophosphoric acid and salts thereof. used. One or more of these complexing agents can be used. By using these complexing agents, the entire surface of the copper core material can be uniformly covered with the gold plating layer.
[0014]
The concentration of the complexing agent in the aqueous solution before charging the copper core material is 0.001 to 2 mol / L, particularly 0.005 to 1 mol / L, although it depends on the complexing agent used. Is preferred because the entire surface of the copper core material can be uniformly covered with the gold plating layer.
[0015]
Next, a plating solution containing gold ions is added to the dispersion liquid in which the copper core material is dispersed, and substitution type electroless plating is performed. Thereby, gold is substituted and precipitated on the surface of the copper core material. If gold ions are added in advance to the aqueous solution containing the complexing agent, when the copper core material is charged, variations in the displacement precipitation of gold often occur due to the time difference between the charges (see Comparative Example 1 described later). . In addition, as described above, when an oxide film is present on the surface of the copper core material, the substitution reaction of gold becomes difficult to start, and the deposition of gold often varies. On the other hand, the present inventors have found that such inconvenience can be avoided by adding gold ions to a dispersion liquid in which a copper core material is dispersed. In particular, it has been found that the complexing agent can remove the oxide film present on the surface of the copper core material. However, if the copper is excessively dissolved, the insoluble copper compound accumulates in the solution. In the case of a copper core material on which an oxide film is excessively formed, the oxide film is previously removed in the preliminary dispersion step described above. It is preferable to keep it.
[0016]
The rate of gold ion addition is effective in controlling the rate of gold deposition. Gold deposition rate affects uniform gold deposition. Therefore, it is preferable to control the gold deposition rate to 1 to 300 nanometers / minute, particularly 5 to 100 nanometers / minute by adjusting the rate of addition of the plating solution. The deposition rate of gold can be determined by calculation from the addition rate of gold ions.
[0017]
The pH of the complexing agent solution before the introduction of the copper core material, the dispersion after the introduction of the copper, and the pH of the plating solution influence the state of gold deposition. If the pH is too low, copper hydroxide derived from copper ions eluted from the copper core material is likely to be formed, and the resulting plated powder is likely to aggregate. If the pH is too high, the precipitation of gold becomes coarse. From these viewpoints, the plating solution preferably has a pH of 3.5 to 7.0, particularly preferably 4.0 to 6.0. Examples of the pH adjuster include sodium hydroxide, potassium hydroxide, aqueous ammonia, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like.
[0018]
The temperature at which the plating solution is added to the dispersion also affects gold deposition. If the temperature is too low, the reaction rate of the substitution precipitation becomes slow and the precipitation becomes coarse. On the other hand, if the temperature is too high, the reaction rate becomes too fast, and the deposition of gold varies. Further, the plating solution may become unstable and cause decomposition. From these viewpoints, the temperature of the dispersion during the addition of the plating solution is preferably from 50 to 95 ° C, particularly preferably from 65 to 90 ° C.
[0019]
(3) Dispersion treatment step This dispersion treatment step is the most characteristic of the present production method. Specifically, when the agglomerated state of the plating powder obtained in the gold plating step (2) is high, it is necessary to subject the powder to a dispersion treatment step to make it monodisperse. In order to make it monodisperse, in the present invention, a compound capable of forming a complex with the ion of the metal contained in the plating powder (this compound) is added to the dispersion containing the plating powder obtained in the gold plating step (2). Is also referred to as a “complex forming compound” below). As a result of the study of the present inventors, one cause of the aggregation of the plating powder obtained in the gold plating step of (2) is that ions of metal contained in the plating powder, for example, copper ions eluted from the copper core material. It has been found that a water-insoluble compound is formed and that the water-insoluble compound is in binding the plated powders together. Therefore, in the present invention, the water-insoluble compound is converted into a complex by adding a complex-forming compound to the agglomerated plating powder to monodisperse the agglomerated plating powder. From this viewpoint, the present dispersion treatment step is extremely effective when performing substitutional electroless plating rather than autocatalytic electroless plating. This dispersion treatment step has an advantage that the plating powder is hardly damaged as compared with a mechanical dispersion method using a mill or a crusher. In particular, when a soft material such as a copper core material is used, the deformation does not occur, and the gold plating layer is not damaged, which is extremely effective. This dispersion treatment step has an advantage that it can be repeated several times until a desired dispersion state is obtained because there is little adverse effect on the plating powder (see Example 1 described later).
[0020]
As the complex forming compound, it is particularly preferable to use a compound capable of forming a complex with a metal ion contained in the core material powder before electroless plating. In the present embodiment, it is preferable to use a compound capable of forming a complex with copper ions. Examples of complex-forming compounds include citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid, succinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, and various carboxylic acids such as alkali metal salts and ammonium salts thereof. Examples thereof include acids or salts thereof, amino acids such as glycine, amines such as ethylenediamine and alkylamine, ammonium salts, EDTA, pyrophosphoric acid and salts thereof. One or more of these compounds can be used. These compounds can be used in combination with inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid.
[0021]
The complex forming compound is generally mixed with the plating powder in the form of an aqueous solution. The concentration of this aqueous solution (the concentration before mixing with the plating powder) depends on the type of the compound used, but is generally from 0.005 to 6 mol / l, especially from 0.01 to 3 mol / l. preferable. Although the pH of this aqueous solution depends on the type of the compound, it is generally preferably from 3.5 to 14, particularly preferably from 5 to 12.5. For adjusting the pH, sodium hydroxide, potassium hydroxide, aqueous ammonia, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like are used.
[0022]
In the dispersion treatment step, a compound capable of lowering the surface tension of the dispersion may be further added (this compound is hereinafter also referred to as a “surface tension lowering compound”). Thereby, the dispersibility of the plating powder can be further enhanced. The surface tension reducing compound can be added at the same time as the addition of the complex-forming compound or before or after the addition of the complex-forming compound. Examples of the surface tension reducing compound include various surfactants and alcohols. Among these, it is particularly preferable to use polyethylene glycol (molecular weight: 200 to 2,000), polyalkylene alkyl ether, polyalkylene alkyl aryl ether, or the like. It is preferable that the surface tension-reducing compound is contained in the dispersion in the dispersion treatment step at 0.1 to 10000 ppm, particularly 1 to 1000 ppm.
[0023]
The temperature of the dispersion treatment is preferably 5 to 60C, particularly preferably 10 to 35C. Within this temperature range, the desired dispersion state can be achieved in a relatively short time without melting the copper core material.
[0024]
In the dispersion treatment step, ultrasonic waves may be used supplementarily or the dispersion liquid may be stirred. However, it is carried out under mild conditions so as not to damage the plating powder.
[0025]
When the dispersion treatment is completed, the plating powder is separated from the dispersion by filtration and dried to obtain a final product.
[0026]
The present invention is not limited to the above embodiment. For example, a method of obtaining a plating powder by forming an electroless plating layer of nickel on a surface of a copper core material and forming an electroless plating layer of gold on the underlayer, or a method of obtaining a nonmetallic core material powder The present invention is also applicable to a method of forming a nickel electroless plating layer on the surface of a body to obtain a plating powder.
[0027]
Although the method of the present invention is particularly effective when performing substitution type electroless plating, the method of the present invention can also be applied when performing autocatalytic electroless plating. Further, if necessary, after reducing gold ions by substitution type electroless plating, the thickness of the gold plating layer may be increased by further reducing gold ions by autocatalytic electroless plating using a reducing agent.
[0028]
Further, as the complex forming compound used in the dispersion treatment, it is particularly preferable to use a compound capable of forming a complex with the metal ion contained in the core material powder before electroless plating. A compound capable of forming a complex with a metal ion contained in the core material powder can also be used. For example, when the plating powder is formed by forming a nickel electroless plating layer on the surface of a nonmetallic core material powder, a compound capable of forming a complex with nickel ions can be used as the complex forming compound.
[0029]
Further, the dispersion treatment is not limited to being performed after the last plating step in the manufacturing process of the plating powder. For example, in a manufacturing method in which a plating step is performed a plurality of times, a dispersion process can be performed between a certain plating step and a subsequent plating step. Specifically, in the step of forming a first electroless plating layer on the surface of the core material powder and then forming a second electroless plating layer thereon, the first electroless plating layer was formed. Thereafter, before forming the second electroless plating layer, a dispersion treatment can be performed. Further, the dispersion treatment may be performed after the formation of the second electroless plating layer (in this case, the plating powder on which the first electroless plating layer is formed may be regarded as the core material powder). ).
[0030]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such an embodiment.
[0031]
[Example 1]
(1) Pre-dispersion Step D Copper powder having a 50 value of 5 μm [trade name “1500YM” manufactured by Mitsui Mining & Smelting Co., Ltd.] was used as the core material powder. 43.5 g of copper powder was dispersed in 200 ml of water in which 0.022 mol of EDTA-4Na was dissolved, and stirred at 30 ° C. for 5 minutes while using ultrasonic waves to obtain a slurry. The slurry was then filtered and washed once with repulping.
[0032]
(2) Gold Plating Step The copper powder obtained in the above step was dispersed in 200 ml of water and stirred at room temperature for 5 minutes while using ultrasonic waves to obtain a slurry. This slurry was introduced and dispersed in 2 liters of an aqueous solution containing 0.027 mol / l EDTA-4Na and 0.038 mol / l trisodium citrate and adjusted to pH 5 with sodium hydroxide and phosphoric acid. A liquid was obtained. This dispersion was stirred for 15 minutes. Next, 50 ml of a plating solution containing 0.41 mol / l potassium potassium cyanide was added to the dispersion at an addition rate of 10 ml / min. The temperature of the dispersion was maintained at 80 ° C. The dispersion was stirred for 10 minutes to replace and deposit gold on the surface of the copper powder to obtain a gold-plated powder.
[0033]
(3) Dispersion treatment step The obtained gold-plated powder was separated by filtration, and then water was added to the gold-plated powder to form a slurry of 500 ml. 0.044 mol of EDTA-4Na and 100 mg of polyoxyethylene alkyl ether (ADEKATOL TN (trade name) manufactured by Asahi Denka) were added to the slurry, and stirring was continued at 20 ° C. for 30 minutes while using ultrasonic waves. This step was repeated three times to disperse the gold-plated powder. Next, the gold-plated powder was separated by filtration, washed three times by repulping, and dried with a vacuum dryer at 80 ° C. The thickness of the gold plating layer calculated from the amount of gold ions added was 35 nm. When the obtained gold-plated powder was observed with a scanning electron microscope, no remarkable aggregation of the gold-plated powder was observed. Observation of the reflection electron composition image of the obtained gold-plated powder confirmed that the gold-plated layer uniformly covered the entire surface of the copper core material.
[0034]
[Example 2]
(1) Catalytic treatment step A spherical benzoguanamine-melamine-formalin resin having an average particle diameter of 4.6 µm and a true specific gravity of 1.39 [trade name “Eposter” manufactured by Nippon Shokubai Co., Ltd.] was used as the core material powder. Twenty grams were made into a 400 milliliter slurry and maintained at 60 ° C. 2 ml of an aqueous 0.11 mol / l palladium chloride solution was added while the slurry was stirred using ultrasonic waves. The stirring state was maintained for 5 minutes, and an activation treatment for capturing palladium ions on the surface of the core material powder was performed. Next, the aqueous solution was filtered, and the core material powder that had been washed once with repulp water was turned into a slurry of 200 ml. The slurry was stirred while using ultrasonic waves, and 20 ml of a mixed aqueous solution of 0.017 mol / l of dimethylamine borane and 0.16 mol / l of boric acid was added thereto. The mixture was stirred for 2 minutes at room temperature while using ultrasonic waves to reduce the palladium ions.
[0035]
(2) Initial thin film forming step: 200 ml of the slurry obtained in the step (1) was mixed with 0.087 mol / l sodium tartrate, 0.005 mol / l nickel sulfate and 0.013 mol / l It was added to the initial thin film forming solution composed of sodium phosphite with stirring to form an aqueous suspension. The initial thin film forming liquid was heated to 75 ° C., and the liquid volume was 1.8 liter. Immediately after the introduction of the slurry, generation of hydrogen was recognized, and the start of the initial thin film formation was confirmed. One minute later, 0.051 mol / liter of sodium hypophosphite was added, and stirring was continued for another minute.
[0036]
(3) Electroless Plating Step The aqueous suspension obtained in the initial thin film forming step contains a nickel ion-containing liquid composed of 0.85 mol / l nickel sulfate and 0.26 mol / l sodium tartrate and 2.6 mol. / Liter of sodium hypophosphite and 2.6 mol / liter of sodium hydroxide were added at a rate of 7 ml / min. The amount added was 337 ml each. Immediately after the addition of the two solutions, generation of hydrogen was recognized, and the start of the plating reaction was confirmed. After the addition of the two liquids was completed, stirring was continued while maintaining the temperature at 75 ° C. until the bubbling of hydrogen stopped. Next, the aqueous suspension was filtered, and the filtrate was washed three times by repulping, and then dried by a vacuum dryer at 110 ° C. Thus, a plating powder having a nickel-phosphorus alloy plating layer was obtained. The thickness of the plating layer calculated from the amount of nickel ions added was 100 nm.
[0037]
(4) Dispersion treatment step 30 g of the nickel-plated powder obtained in the above step was dispersed in 200 ml of water in which 0.13 mol of glycine was dissolved, and stirred at 30 ° C for 5 minutes while using ultrasonic waves to obtain a slurry. Was. Thereby, the nickel plating powder was dispersed. Next, the slurry was filtered and washed once with repulping to obtain a nickel plating slurry.
[0038]
(5) Gold Plating Step 4.1 L of an electroless plating solution for gold plating was prepared. The electroless plating solution contains 0.027 mol / L of EDTA-4Na, 0.038 mol / L of trisodium citrate and 0.01 mol / L of potassium potassium cyanide. PH was adjusted to 6. While stirring the electroless plating solution at a solution temperature of 60 ° C., the nickel plating slurry obtained in the above step was added to the plating solution, and gold plating treatment was performed for 20 minutes. Next, the liquid was filtered, and the filtrate was washed three times by repulping, and then dried by a dryer at 110 ° C. Thus, a plating powder in which an electroless gold plating layer was formed on the nickel plating layer was obtained. The thickness of the gold plating layer calculated from the amount of gold ions added was 25 nm.
[0039]
(6) Dispersing Step The obtained gold-plated powder was separated by filtration, and then water was added to the gold-plated powder to form a slurry of 500 ml. 0.044 mol of EDTA-4Na was added to the slurry, and stirring was continued at 20 ° C. for 30 minutes while using ultrasonic waves. Thereby, the gold plating powder was dispersed. Next, the gold-plated powder was separated by filtration, washed three times by repulping, and dried with a vacuum dryer at 80 ° C. When the obtained gold-plated powder was observed with a scanning electron microscope, no remarkable aggregation of the gold-plated powder was observed. Observation of the reflection electron composition image of the obtained gold-plated powder confirmed that the gold-plated layer uniformly covered the entire surface of the copper core material.
[0040]
[Example 3]
(1) Pre-dispersion step D Nickel powder having a 50 μm value of 5 μm was used as the core material powder. 60.5 g of nickel powder was dispersed in 200 ml of water in which 0.022 mol of EDTA-4Na was dissolved, and stirred at 30 ° C. for 5 minutes while using ultrasonic waves to obtain a slurry. The slurry was then filtered and washed once with repulping.
[0041]
(2) Gold Plating Step 2.0 L of an electroless plating solution for gold plating was prepared. The electroless gold plating solution contains 0.027 mol / L of EDTA-4Na, 0.038 mol / L of trisodium citrate and 0.01 mol / L of potassium potassium cyanide. The pH was adjusted to 6 with acid. While stirring the electroless plating solution at a solution temperature of 60 ° C., the nickel powder slurry obtained in the above step was added to the plating solution, and gold plating was performed for 20 minutes. Next, the liquid was filtered, and the filtrate was washed three times by repulping, and then dried by a dryer at 110 ° C. As a result, a plating powder in which a gold electroless plating layer was formed on the surface of the nickel powder was obtained. The thickness of the gold plating layer calculated from the amount of gold ions added was 25 nm.
[0042]
(3) Dispersion treatment step The obtained gold-plated powder was separated by filtration, and then water was added to the gold-plated powder to form a slurry of 500 ml. 0.044 mol of EDTA-4Na was added to the slurry, and stirring was continued at 20 ° C. for 30 minutes while using ultrasonic waves. Thereby, the gold plating powder was dispersed. Next, the gold-plated powder was separated by filtration, washed three times by repulping, and dried with a vacuum dryer at 80 ° C. When the obtained gold-plated powder was observed with a scanning electron microscope, no remarkable aggregation of the gold-plated powder was observed. Observation of the reflection electron composition image of the obtained gold-plated powder confirmed that the gold-plated layer uniformly covered the entire surface of the nickel core material.
[0043]
[Comparative Example 1]
D 50 value using copper powder 5μm to [Mitsui Mining & Smelting Co., trade name "1500YM"] the core material powder. Two liters of a common gold displacement plating solution containing 0.013 mol / l potassium potassium cyanide, 0.1 mol / l potassium cyanide and 0.03 mol / l trisodium citrate was prepared. 43.5 g of copper powder was dispersed in 200 ml of water and stirred at room temperature for 5 minutes while applying ultrasonic waves to obtain a slurry. The slurry was charged while stirring a gold displacement plating solution at a liquid temperature of 85 ° C., and a gold plating treatment was performed for 5 minutes. Next, the plating solution was filtered, and the filtrate was washed three times by repulping, and then dried with a vacuum dryer at 80 ° C. As a result, a gold-plated powder having a gold-plated layer formed on the surface of the copper powder was obtained. The thickness of the gold plating layer calculated from the amount of gold ions added was 35 nm. When the obtained gold-plated powder was observed with a scanning electron microscope, remarkable aggregation of the gold-plated powder was partially observed. Observation of the reflection electron composition image of the obtained gold-plated powder revealed that the gold-plated layer covered the surface of the copper core material discontinuously and sparsely, and that the copper was exposed on the surface. confirmed.
[0044]
[Comparative Example 2]
D 50 value using copper powder 5μm to [Mitsui Mining & Smelting Co., trade name "1500YM"] the core material powder. 43.5 g of copper powder was dispersed in 200 ml of water and stirred at room temperature for 5 minutes while applying ultrasonic waves to obtain a slurry. This slurry was introduced into 2 liters of an aqueous solution containing 0.027 mol / liter of EDTA-4Na and 0.038 mol / liter of trisodium citrate and adjusted to pH 6 with sodium hydroxide to obtain a dispersion. Was. Then a metal salt solution consisting of 0.035 mol / l potassium gold cyanide, 0.027 mol / l EDTA-4Na and 0.038 mol / l trisodium citrate, and 0.79 mol / l hydrogen A reducing solution consisting of sodium borohydride and 1.5 mol / l of sodium hydroxide was dropped into this dispersion separately and simultaneously at a rate of 30 ml / min through a liquid sending pump. The amount of the liquid dropped was 585 ml each. After the completion of dropping, the plating solution was filtered, and the filtrate was washed three times by repulping, and then dried by a vacuum dryer at 80 ° C. As a result, a gold-plated powder having a gold-plated layer formed on the surface of the copper powder was obtained. The thickness of the gold plating layer calculated from the amount of gold ions added was 35 nm. When the obtained gold-plated powder was observed with a scanning electron microscope, remarkable aggregation of the gold-plated powder was partially observed. When the reflection electron composition image of the obtained gold-plated powder was observed, a powder having a gold-plated layer formed on the surface of the copper powder and a copper powder having no gold-plated layer were observed. . Further, a large number of fine particles in which gold was solely precipitated were observed.
[0045]
(Performance evaluation)
The particle size distribution of the gold-plated powders obtained in Examples 1 to 3 and Comparative Examples 1 and 2 was measured by the following method. Further, the volume resistivity was measured, and the volume resistivity of the gold-plated powder after the reliability test was measured. The results are shown in Table 1 below.
[0046]
(Particle size distribution)
The particle size distribution was measured by a laser diffraction / scattering method particle size distribution analyzer (Microtrac HRA X100 (trade name)).
[0047]
(Measurement of volume resistivity)
1.0 g of the gold-plated powder was placed in a vertically-standing resin cylinder having an inner diameter of 10 mm, and an electric resistance between the upper and lower electrodes was measured with a load of 10 kg applied thereto, thereby obtaining a volume specific resistance value.
[0048]
〔Reliability test〕
After the gold-plated powder was stored in an environment of 60 ° C. and 95% RH for 250 hours and 500 hours, respectively, the volume resistivity value was measured.
[0049]
[Table 1]
As is clear from the results shown in Table 1, it is understood that the plated powders (products of the present invention) of the respective examples have excellent dispersibility. Further, it can be seen that the electrical resistance value is sufficiently low and the reliability is high because the plating powder is not damaged and the deposition of gold is uniform. On the other hand, it is found that the dispersion state of the plating powder of each comparative example is not good. Further, it can be seen that gold deposition varies, the electric resistance value is high, and the reliability is low.
[0051]
【The invention's effect】
As described in detail above, according to the method for producing a conductive electroless plating powder of the present invention, a plating powder having good dispersibility can be obtained without damaging the plating powder.
Claims (5)
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006080288A1 (en) * | 2005-01-25 | 2006-08-03 | Sekisui Chemical Co., Ltd. | Electrically conductive fine particles and anisotropic electrically conductive material |
| JP2007081141A (en) * | 2005-09-14 | 2007-03-29 | Nippon Steel Materials Co Ltd | Cu core ball and manufacturing method therefor |
| JP2011017067A (en) * | 2009-07-10 | 2011-01-27 | Asahi Glass Co Ltd | Method for producing surface-modified copper grain, composition for forming conductor, method for producing conductor film, and article |
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2003
- 2003-04-28 JP JP2003124444A patent/JP4247039B2/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006080288A1 (en) * | 2005-01-25 | 2006-08-03 | Sekisui Chemical Co., Ltd. | Electrically conductive fine particles and anisotropic electrically conductive material |
| JP2007081141A (en) * | 2005-09-14 | 2007-03-29 | Nippon Steel Materials Co Ltd | Cu core ball and manufacturing method therefor |
| JP2011017067A (en) * | 2009-07-10 | 2011-01-27 | Asahi Glass Co Ltd | Method for producing surface-modified copper grain, composition for forming conductor, method for producing conductor film, and article |
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