JP4149385B2 - Aluminum oxide coated fine silver powder and method for producing the same - Google Patents
Aluminum oxide coated fine silver powder and method for producing the same Download PDFInfo
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- JP4149385B2 JP4149385B2 JP2004018237A JP2004018237A JP4149385B2 JP 4149385 B2 JP4149385 B2 JP 4149385B2 JP 2004018237 A JP2004018237 A JP 2004018237A JP 2004018237 A JP2004018237 A JP 2004018237A JP 4149385 B2 JP4149385 B2 JP 4149385B2
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- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 title claims description 202
- 239000010946 fine silver Substances 0.000 title claims description 123
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 title claims description 106
- 238000004519 manufacturing process Methods 0.000 title claims description 33
- 239000002245 particle Substances 0.000 claims description 91
- 239000000843 powder Substances 0.000 claims description 52
- 238000000034 method Methods 0.000 claims description 32
- 239000000243 solution Substances 0.000 claims description 32
- 238000009826 distribution Methods 0.000 claims description 25
- 229910052709 silver Inorganic materials 0.000 claims description 19
- 239000004332 silver Substances 0.000 claims description 19
- 239000002253 acid Substances 0.000 claims description 16
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims description 15
- 239000004327 boric acid Substances 0.000 claims description 15
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 claims description 14
- 238000011049 filling Methods 0.000 claims description 14
- 229910001388 sodium aluminate Inorganic materials 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- 238000006386 neutralization reaction Methods 0.000 claims description 11
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- FGUUSXIOTUKUDN-IBGZPJMESA-N C1(=CC=CC=C1)N1C2=C(NC([C@H](C1)NC=1OC(=NN=1)C1=CC=CC=C1)=O)C=CC=C2 Chemical compound C1(=CC=CC=C1)N1C2=C(NC([C@H](C1)NC=1OC(=NN=1)C1=CC=CC=C1)=O)C=CC=C2 FGUUSXIOTUKUDN-IBGZPJMESA-N 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 5
- 238000000691 measurement method Methods 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 4
- 230000018044 dehydration Effects 0.000 claims description 4
- 238000006297 dehydration reaction Methods 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- 239000011259 mixed solution Substances 0.000 claims description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 3
- 230000001186 cumulative effect Effects 0.000 claims description 3
- 230000003472 neutralizing effect Effects 0.000 claims description 3
- 229910017604 nitric acid Inorganic materials 0.000 claims description 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 2
- 238000001704 evaporation Methods 0.000 claims description 2
- 230000008020 evaporation Effects 0.000 claims description 2
- 239000007787 solid Substances 0.000 claims description 2
- 230000003647 oxidation Effects 0.000 claims 2
- 238000007254 oxidation reaction Methods 0.000 claims 2
- 238000000576 coating method Methods 0.000 description 31
- 239000011248 coating agent Substances 0.000 description 28
- 230000000052 comparative effect Effects 0.000 description 16
- 229910010272 inorganic material Inorganic materials 0.000 description 10
- 239000011147 inorganic material Substances 0.000 description 10
- 239000000758 substrate Substances 0.000 description 9
- 230000032798 delamination Effects 0.000 description 8
- 238000010304 firing Methods 0.000 description 8
- 230000008602 contraction Effects 0.000 description 7
- 239000000919 ceramic Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 239000008188 pellet Substances 0.000 description 6
- 229910010293 ceramic material Inorganic materials 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 238000012856 packing Methods 0.000 description 5
- 239000011162 core material Substances 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 238000004898 kneading Methods 0.000 description 4
- GNFTZDOKVXKIBK-UHFFFAOYSA-N 3-(2-methoxyethoxy)benzohydrazide Chemical compound COCCOC1=CC=CC(C(=O)NN)=C1 GNFTZDOKVXKIBK-UHFFFAOYSA-N 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000007865 diluting Methods 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 1
- 239000001856 Ethyl cellulose Substances 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- WUOACPNHFRMFPN-UHFFFAOYSA-N alpha-terpineol Chemical compound CC1=CCC(C(C)(C)O)CC1 WUOACPNHFRMFPN-UHFFFAOYSA-N 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
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- 238000001816 cooling Methods 0.000 description 1
- SQIFACVGCPWBQZ-UHFFFAOYSA-N delta-terpineol Natural products CC(C)(O)C1CCC(=C)CC1 SQIFACVGCPWBQZ-UHFFFAOYSA-N 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
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- 229920001249 ethyl cellulose Polymers 0.000 description 1
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- 230000008018 melting Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
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Landscapes
- Conductive Materials (AREA)
- Non-Insulated Conductors (AREA)
- Powder Metallurgy (AREA)
Description
本発明は、導電性粉末として使われる微粒銀粉およびその製造方法に関し、さらに詳細には、主に電子回路基板の配線に使用される銀ペースト用の酸化アルミニウム被覆微粒銀粉およびその製造方法に関する。 The present invention relates to a fine silver powder used as a conductive powder and a method for producing the same, and more particularly to an aluminum oxide-coated fine silver powder for silver paste used mainly for wiring of an electronic circuit board and a method for producing the same.
近年、携帯電話等の小型電子機器が普及している。かかる小型電子機器を製造するために低温焼成セラミック（ＬＴＣＣ（ｌｏｗ−ｔｅｍｐｅｒａｔｕｒｅ ｃｏｆｉｒｅｄ ｃｅｒａｍｉｃ））を基板材料とした電子回路用基板がしばしば用いられている。そして、当該ＬＴＣＣを用いたパッケージ（ＬＴＣＣパッケージ）のセラミック多層基板にチップコンデンサやチップインダクタ等の小型電子部品を配置するために、ファインピッチ化された電子回路用の配線部が形成されている。 In recent years, small electronic devices such as mobile phones have become widespread. In order to manufacture such a small electronic device, a substrate for an electronic circuit using a low-temperature fired ceramic (LTCC) as a substrate material is often used. In order to arrange small electronic components such as a chip capacitor and a chip inductor on a ceramic multilayer substrate of a package using the LTCC (LTCC package), a wiring portion for an electronic circuit having a fine pitch is formed.
さて、上記ＬＴＣＣパッケージでは、上述したファインピッチ化の要請のため、配線部の導電性を向上させる必要があり、原材料として微粒銀粉が以下のように配線部に用いられている。 In the LTCC package, it is necessary to improve the conductivity of the wiring part because of the above-mentioned demand for fine pitch, and fine silver powder is used as a raw material in the wiring part as follows.
すなわち、まず微粒銀粉と有機剤とを混練して得た導電性ペースト（銀ペースト）が作成される。次に、このペーストを用いてスクリーン印刷法等によりセラミック材料で作成されたグリーンシート上に配線パターンが印刷される。そして、導電性ペーストとグリーンシートとが焼成炉で同時に焼成されて、銀材料で配線部が形成されたＬＴＣＣパッケージが製造される。 That is, first, a conductive paste (silver paste) obtained by kneading fine silver powder and an organic agent is prepared. Next, using this paste, a wiring pattern is printed on a green sheet made of a ceramic material by a screen printing method or the like. Then, the conductive paste and the green sheet are fired at the same time in a firing furnace to manufacture an LTCC package in which a wiring portion is formed of a silver material.
この際、ＬＴＣＣパッケージの焼成工程において以下のような現象が生じる。銀の融点は９６０℃であるが、５００℃近辺から微粒銀粉の粒子（粉粒）同士の焼結が始まる。それに伴って導電性ペーストに含まれる銀の熱収縮が始まる。一方、ＬＴＣＣのセラミックス材料も別個な挙動で熱収縮する。よって、焼成工程時に微粒銀粉の銀とセラミックス材料との間に熱収縮挙動の差があるため電子回路基板においてクラックやデラミネーション等が発生し易く、これらの不具合を防止するため双方の熱収縮の挙動を調整しつつ焼成工程を行う要請がある。 At this time, the following phenomenon occurs in the firing process of the LTCC package. Although the melting point of silver is 960 ° C., sintering of fine silver powder particles (powder particles) starts around 500 ° C. Along with this, thermal shrinkage of silver contained in the conductive paste begins. On the other hand, the LTCC ceramic material also thermally shrinks in a separate behavior. Therefore, since there is a difference in thermal shrinkage behavior between the fine silver powder silver and the ceramic material during the firing process, cracks and delamination are likely to occur in the electronic circuit board. There is a request to perform the firing process while adjusting the behavior.
さて、例えば、上記不具合を防止するために微粒銀粉粒子上に無機物を被覆して微粒銀粉粒子の焼結温度をより高温にシフトさせた無機物被覆法が提案されている（特許文献１参照）。
その一つに、無機物を微粒銀粉の粒子の表面に対し物理的に乾式法で被覆する被覆方法（乾式法）が提案されている。
For example, in order to prevent the above problems, an inorganic coating method has been proposed in which fine silver powder particles are coated with an inorganic material and the sintering temperature of the fine silver powder particles is shifted to a higher temperature (see Patent Document 1).
As one of them, a coating method (dry method) in which an inorganic substance is physically coated on the surface of fine silver powder particles by a dry method has been proposed.
しかしながら、乾式法によれば、混練機等を用いて強い力を付与しながら混練してペーストを作成する際、微粒銀粉の粒子表面から被覆されていた無機物が剥離しまうことがあった。さらに、乾式法によれば微粒銀粉の粉粒が必ずしも略球形ではなく、例えば、表面に凹凸や突起部があるような異形粉粒の粉粒であった場合には、銀粉粒の粒子の全ての面を無機物で物理的に均一に被覆する被覆は困難であった。さらにまた、乾式法によれば無機物の被覆量が必要以上に多くなる傾向にあり、被覆された無機物の非導電性を起因として配線の導電性を低めてしまう被覆もあった。 However, according to the dry method, when a paste is prepared by kneading while applying a strong force using a kneader or the like, the inorganic material coated from the surface of the fine silver powder particles may be peeled off. Further, according to the dry method, the fine silver powder particles are not necessarily spherical, for example, when the surface is irregular shaped powder particles with irregularities or protrusions on the surface, all of the silver powder particles It was difficult to coat the surface of the surface with an inorganic material. Furthermore, according to the dry method, the coating amount of the inorganic material tends to increase more than necessary, and there is a coating that lowers the conductivity of the wiring due to the non-conductivity of the coated inorganic material.
従って、本発明の目的は、乾式法に比して微粒銀粉微粒子を含む導電性ペーストを作製するとき混練機の強い力で混練しても被覆された無機材料が剥離しにくい、微粒銀粉の粒子形状に関わらず粒子表面全体に均一に無機材料を被覆することにより無機物の被覆量がより少ない、さらに、導電性ペーストが基板上で基板材料のセラミックと同時焼成される際に上記クラックやデラミネーション等の不具合を起こさない、微粒銀粉およびその製造方法を提供することにある。 Therefore, the object of the present invention is to produce fine silver powder particles in which the coated inorganic material is difficult to peel off even when kneaded with a strong force of a kneader when producing a conductive paste containing fine silver powder fine particles as compared with the dry method. Regardless of the shape, the entire surface of the particle is uniformly coated with an inorganic material, so that the amount of inorganic coating is less. Furthermore, when the conductive paste is co-fired with the ceramic substrate material on the substrate, cracks and delamination are caused. An object of the present invention is to provide a fine silver powder and a method for producing the same that do not cause problems such as the above.
かかる実情において、本発明者等は、アルミン酸ナトリウム水溶液中で金属塩を中和することにより微粒銀粉粒子表面に無機材料たる酸化アルミニウム（Ａｌ２Ｏ３）を析出する湿式法において、諸プロセス条件を鋭意検討した結果、以下のような好適条件を見出し本発明を完成するに至った。以下、本発明に関して、「酸化アルミニウム被覆微粒銀粉」と「酸化アルミニウム被覆微粒銀粉の製造方法」とに分けて説明する。 In such a situation, the present inventors have made various process conditions in a wet method in which aluminum oxide (Al 2 O 3 ), which is an inorganic material, is precipitated on the surface of fine silver powder particles by neutralizing a metal salt in an aqueous sodium aluminate solution. As a result of intensive studies, the present inventors have found the following preferable conditions and completed the present invention. Hereinafter, the present invention will be described by dividing it into “aluminum oxide-coated fine silver powder” and “a manufacturing method of aluminum oxide-coated fine silver powder”.
＜酸化アルミニウム被覆微粒銀粉＞
本発明の酸化アルミニウム被覆微粒銀粉は、「湿式法で酸化アルミニウムを微粒銀粉の粒子表面に被覆した微粒銀粉。」である（本件における「微粒銀粉」の粒子は、その粒径が０．５〜３μｍ程度の銀粒子である。）。すなわち、湿式法における化学反応で酸化アルミニウムを微粒銀粉の粒子表面に被覆させることにより作製される。この際、本発明によれば、湿式法で被覆処理が行われるので乾式法に比べ均一かつ必要十分な量の酸化アルミニウムを微粒銀粉の粒子表面に被覆（析出）することができる。一方、乾式法では膜厚が不均一に、すなわち、例えば被覆膜が島状若しくは鱗状に、酸化アルミニウム被覆が微粒銀粉の粒子表面に固着する傾向がある。そのため、導電性ペースト作製の際の混練時に粒子同士が接触した時に酸化アルミニウム被覆が剥離し易かった。しかし、本発明によれば、酸化アルミニウムが均一に銀粉粒子に被覆されているため当該混練時の剥離現象を防止する被覆ができる。さらにまた、本発明によれば、酸化アルミニウムの量が不必要に多く銀粉微粒子表面に被覆しないため、導電性ペーストが焼成され形成される配線部の比抵抗を極端に低下させることもない。
<Aluminum oxide coated fine silver powder>
The aluminum oxide-coated fine silver powder of the present invention is “a fine silver powder in which aluminum oxide is coated on the surface of the fine silver powder by a wet method.” (The “fine silver powder” particles in this case have a particle size of 0.5 to 0.5. Silver particles of about 3 μm). That is, it is produced by coating aluminum oxide on the surface of fine silver powder by a chemical reaction in a wet method. At this time, according to the present invention, since the coating process is performed by a wet method, a uniform and necessary and sufficient amount of aluminum oxide can be coated (deposited) on the particle surface of the fine silver powder as compared with the dry method. On the other hand, in the dry method, the film thickness is non-uniform, that is, for example, the coating film tends to be in the form of islands or scales, and the aluminum oxide coating tends to adhere to the surface of the fine silver powder particles. Therefore, the aluminum oxide coating was easily peeled off when the particles were in contact with each other during kneading during the production of the conductive paste. However, according to the present invention, since the aluminum oxide is uniformly coated on the silver powder particles, a coating that prevents the peeling phenomenon during the kneading can be performed. Furthermore, according to the present invention, since the amount of aluminum oxide is unnecessarily large and does not cover the surface of the silver fine particles, the specific resistance of the wiring portion formed by firing the conductive paste is not extremely reduced.
（第１酸化アルミニウムコート微粒銀粉）
本発明の第１酸化アルミニウム被覆微粒銀粉の粉体特性を示す。
ａ．タップ充填密度（ｇ／ｃｍ３）が、３．５〜５．０
ｂ．Ｄ５０（μｍ）が、０．５〜５．０
ｃ．Ｄ９０−Ｄ１０（μｍ）が、１．０〜１０.０
(1st aluminum oxide coated fine silver powder)
The powder characteristic of the 1st aluminum oxide covering fine silver powder of the present invention is shown.
a. Tap filling density (g / cm 3 ) is 3.5 to 5.0
b. D 50 (μm) is 0.5 to 5.0
c. D 90 -D 10 (μm) is 1.0 to 10.0
上記の粉体特性により、本発明（実施例１および実施例２参照）の第１酸化アルミニウム被覆微粒銀粉は、銀の熱収縮開始温度よりも高い温度で熱収縮が開始し、熱機械分析装置により熱収縮開始温度が略６００℃から始まる特徴を示す。しかも熱収縮が始まった後は上に凸の曲線に沿って起きる。 Due to the above powder characteristics, the first aluminum oxide-coated fine silver powder of the present invention (see Example 1 and Example 2) starts thermal contraction at a temperature higher than the thermal contraction start temperature of silver. Thus, the heat shrinkage start temperature starts from about 600 ° C. Moreover, after heat shrinkage begins, it occurs along a convex curve.
上記熱収縮率の特性から、第１酸化アルミニウム被覆微粒銀粉によれば、酸化アルミニウムの被覆が施されていない微粒銀粉に比較して、クラックやデラミネーション等の不具合が起きにくくなる。以下、用語等の説明を行う。 From the characteristics of the heat shrinkage rate, according to the first aluminum oxide-coated fine silver powder, defects such as cracks and delamination are less likely to occur as compared to the fine silver powder not coated with aluminum oxide. Hereinafter, terms etc. will be explained.
最初に、芯材として用いる銀粉に関して説明する。この銀粉に関しては、第１酸化アルミニウム被覆微粒銀粉および後述する第２酸化アルミニウム被覆微粒銀粉の双方において、特に粉粒形状、粉体の製造方法は湿式法や乾式法等に限定を要するものではなく、以下に述べる粉体特性を持つ第１酸化アルミニウム被覆微粒銀粉および第２酸化アルミニウム被覆微粒銀粉を得ることが出来る限り、あらゆる銀粉の使用が可能である。 First, the silver powder used as the core material will be described. With respect to the silver powder thus, in both of the second aluminum oxide coating fine silver powder to the first aluminum oxide coating fine silver powder and below, no particular granular shape, manufacturing method of powder those requiring limited to a wet method or a dry method such as as long as it is possible to obtain a first aluminum oxide coating fine silver powder and the second aluminum oxide coating fine silver powder having powder properties described below, it is possible to use any silver powder.
ここで、順不同で粉体特性に関して説明する。まず、この第１酸化アルミニウム被覆微粒銀粉のＤ５０が０．５〜５．０μｍの範囲にあるものを対象としている。この第１酸化アルミニウム被覆微粒銀粉は、シャープな粒度分布を持つ粉体を対象としている。従って、最もシャープな粒度分布を得やすい粒径範囲を規定した。 Here, the powder characteristics will be described in any order. First, the first aluminum oxide-coated fine silver powder having a D50 in the range of 0.5 to 5.0 μm is targeted. The first aluminum oxide-coated fine silver powder is intended for a powder having a sharp particle size distribution. Therefore, the particle size range in which the sharpest particle size distribution can be easily obtained is defined.
そして、ここでＤ９０とＤ１０との値の差として（Ｄ９０−Ｄ１０）を規定している。この値の幅が小さくなるほど、体積累積粒径における粒度分布がシャープで粒径の揃ったものと言える。この（Ｄ９０−Ｄ１０）の値が１．０μｍ未満となるシャープな第１酸化アルミニウム被覆微粒銀粉を得ることは現段階では困難である。但し、芯材として用いる微粒銀粉の粒度分布を更に改善し、粉粒の凝集状態を適度に解消した粉体を用いることで、より良好な第１酸化アルミニウム被覆微粒銀粉を得ることは可能と考えられる。一方で、（Ｄ９０−Ｄ１０）の値が１０μｍを超えると、後述するブロードな粒度分布を持つ第２酸化アルミニウム被覆微粒銀粉と変わらない耐熱収縮特性を示すようになり、シャープな粉体の持つ特徴が薄れるのである。 And here it is defined as the difference value between D 90 and D 10 of (D 90 -D 10). It can be said that the smaller the range of this value, the sharper the particle size distribution in the volume cumulative particle size and the uniform particle size. It is difficult at this stage to obtain a sharp first aluminum oxide-coated fine silver powder having a value of (D 90 -D 10 ) of less than 1.0 μm. However, it is considered possible to obtain a better first aluminum oxide-coated fine silver powder by further improving the particle size distribution of the fine silver powder used as the core material and using a powder in which the agglomerated state of the powder is appropriately eliminated. It is done. On the other hand, when the value of (D 90 -D 10 ) exceeds 10 μm, the heat resistant shrinkage characteristic is the same as that of the second aluminum oxide-coated fine silver powder having a broad particle size distribution, which will be described later. The features it has faded.
更に、本件発明では、タップ充填密度が３．５〜５．０ｇ／ｃｍ３の範囲として規定している。このタップ充填密度は、第１酸化アルミニウム被覆微粒銀粉の粉粒の凝集状態を示す代替特性として、採用したものである。理想的には、第１酸化アルミニウム被覆微粒銀粉の粉粒の全てが一次粒子として分離した場合が最も高いタップ充填密度の値となるはずであり、これに対し粉粒の凝集状態が著しい二次粒子が多いほど、低いタップ充填密度の値となるはずである。従って、タップ充填密度が３．５ｇ／ｃｍ３未満の粒子の分散性の低い状態では、耐熱収縮性を制御することが困難となる。そして、タップ充填密度が５．０ｇ／ｃｍ３を超えるレベルとすることに耐熱収縮性という観点から見て特に問題はないが、シャープな粒度分布を持ち且つ上記平均粒径の粉体では、これ以上のタップ充填密度とすることが困難となる。 Furthermore, in this invention, tap filling density is prescribed | regulated as a range of 3.5-5.0 g / cm < 3 >. This tap filling density is adopted as an alternative characteristic indicating the aggregation state of the first aluminum oxide-coated fine silver powder. Ideally, when all of the particles of the first aluminum oxide-coated fine silver powder are separated as primary particles, the value of the highest tap packing density should be obtained. The more particles, the lower the tap packing density value should be. Therefore, it is difficult to control the heat shrinkage resistance in a state where the dispersibility of particles having a tap filling density of less than 3.5 g / cm 3 is low. And there is no particular problem from the viewpoint of heat shrinkage resistance when the tap filling density exceeds 5.0 g / cm 3 , but with a powder having a sharp particle size distribution and the above average particle size, It becomes difficult to obtain the above tap filling density.
（第２酸化アルミニウム被覆微粒銀粉）
次に、本発明の第２酸化アルミニウム被覆微粒銀粉の粉体特性を示す。
ａ．タップ充填密度（ｇ／ｃｍ３）が、２．０〜３．５
ｂ．Ｄ５０（μｍ）が、５．０〜１０．０
ｃ．Ｄ９０−Ｄ１０（μｍ）が、１０.０〜２５.０
(Second aluminum oxide coated fine silver powder)
Next, the powder characteristics of the second aluminum oxide-coated fine silver powder of the present invention will be shown.
a. Tap filling density (g / cm 3 ) is 2.0 to 3.5
b. D 50 (μm) is 5.0 to 10.0
c. D 90 -D 10 (μm) is 10.0 to 25.0
上記の粉体特性により、第２酸化アルミニウム被覆微粒銀粉は、銀の熱収縮開始温度よりも高い温度で熱収縮が開始し、酸化アルミニウム被覆微粒銀粉は、銀の熱収縮開始温度よりも高い温度で熱収縮が開始する微粒銀粉であって、熱収縮開始温度が８００℃超である特徴を示す。これにより、８００℃付近まで電子回路基板の配線部が収縮しないため８００℃付近まで配線部から電子回路基板のセラミック材への応力がかからず、電子回路基板においてクラックやデラミネーション等の不具合が起きにくくなる。 Due to the above powder characteristics, the second aluminum oxide-coated fine silver powder starts thermal shrinkage at a temperature higher than the heat shrinkage start temperature of silver, and the aluminum oxide-coated fine silver powder has a temperature higher than the heat shrinkage start temperature of silver. In this case, the heat shrinkage start temperature is higher than 800 ° C. As a result, the wiring portion of the electronic circuit board does not shrink up to about 800 ° C., so stress is not applied to the ceramic material of the electronic circuit board from the wiring portion up to about 800 ° C. It becomes difficult to get up.
ここで、上述したと同様に粉体特性に関して説明する。まず、この第２酸化アルミニウム被覆微粒銀粉のＤ５０が５．０〜１０．０μｍの範囲にあるものを対象としている。この第２酸化アルミニウム被覆微粒銀粉は、ブロードな粒度分布を持つ粉体を対象としている。そして、現在市場を流通している銀粉のうち、耐熱収縮特性に関する要求の顕著な粒径範囲を規定した。 Here, the powder characteristics will be described in the same manner as described above. First, D 50 of the second aluminum oxide coating fine silver powder is intended for those in the range of 5.0～10.0Myuemu. This second aluminum oxide-coated fine silver powder is intended for a powder having a broad particle size distribution. And among the silver powders currently circulating in the market, the remarkable particle size range of the requirement regarding the heat shrinkage characteristics was defined.
そして、第２酸化アルミニウム被覆微粒銀粉の（Ｄ９０−Ｄ１０）の範囲は、第１酸化アルミニウム被覆微粒銀粉に比べ広い値となっている。この（Ｄ９０−Ｄ１０）値が１０μｍ未満となれば、第１酸化アルミニウム被覆微粒銀粉と同様のものとなり、ブロード粉としての耐熱収縮特性の特徴が得られなくなるのである。一方、（Ｄ９０−Ｄ１０）の値が２５μｍを超えると、粒度分布の不均一さが際だつことになり、第２酸化アルミニウム被覆微粒銀粉を用いて製造する導電性ペーストの粘度管理が困難で、結果として回路等の導体を形成したときの膜密度の安定化が図れなくなるのである。 The range of (D 90 -D 10) of the second aluminum oxide coating fine silver powder has a wide value compared with the first aluminum oxide coating fine silver powder. If this (D 90 -D 10 ) value is less than 10 μm, it becomes the same as the first aluminum oxide-coated fine silver powder, and the characteristics of the heat shrinkage characteristic as a broad powder cannot be obtained. On the other hand, when the value of (D 90 -D 10 ) exceeds 25 μm, the non-uniformity of the particle size distribution becomes conspicuous, and it is difficult to manage the viscosity of the conductive paste produced using the second aluminum oxide-coated fine silver powder. As a result, the film density cannot be stabilized when a conductor such as a circuit is formed.
更に、タップ充填密度が２．０〜３．５ｇ／ｃｍ３の範囲として規定している。このタップ充填密度は、第２酸化アルミニウム被覆微粒銀粉の平均粒径が大きくブロードな粒度分布を持つものであるから、第１酸化アルミニウム被覆微粒銀粉の場合よりも低い値となっている。従って、タップ充填密度が２．０ｇ／ｃｍ３未満の粒子の分散性の低い状態では、平均粒径が大きくとも耐熱収縮性を制御することが困難となる。そして、タップ充填密度が３．５ｇ／ｃｍ３を超えるレベルとすることに耐熱収縮性という観点から見て特に問題はないが、ブロードな粒度分布を持ち且つ上記平均粒径の粉体では、これ以上のタップ充填密度とすることが困難となるのである。 Furthermore, the tap filling density is defined as 2.0 to 3.5 g / cm 3 . This tap filling density is lower than that of the first aluminum oxide-coated fine silver powder because the second aluminum oxide-coated fine silver powder has a large average particle size and a broad particle size distribution. Therefore, in a state where the dispersibility of particles having a tap packing density of less than 2.0 g / cm 3 is low, it is difficult to control the heat shrinkage resistance even if the average particle size is large. And, there is no particular problem from the viewpoint of heat shrinkage resistance when the tap filling density exceeds 3.5 g / cm 3 , but with a powder having a broad particle size distribution and the above average particle size, It is difficult to achieve the above tap filling density.
＜酸化アルミニウム被覆微粒銀粉の製造方法＞
実施例１〜４の酸化アルミニウム被覆微粒銀粉の製造方法は、以下に示す工程ａ〜ｇを含む。
工程ａ．水にアルミン酸ソーダを溶解し、溶解液を調整する溶解液調整工程、
工程ｂ．この溶解液に、微粒銀粉を投入し攪拌し、溶解液と微粒銀粉とを混合して混合溶液とする混合工程、
工程ｃ．上記混合溶液に、前記アルミン酸ソーダ１．６ｇ〜４．１ｇに対して０．９６ｍｏｌ〜２０．１ｍｏｌとなる量の酸を投入し該溶液を中和する中和工程、
工程ｄ．中和溶液を濾過し、銀粉と溶液とを固液分離する濾過工程、
工程ｅ．分離された銀粉を水（好適には純水、以下同様。）で洗浄する洗浄工程、
工程ｆ．洗浄された銀粉をアセトンに浸漬させ、アセトンの蒸発と共に銀粉上の付着水を脱水する脱水工程、および
工程ｇ．脱水された銀粉を乾燥させる乾燥工程。
<Method for producing aluminum oxide-coated fine silver powder>
The manufacturing method of the aluminum oxide coating | coated fine silver powder of Examples 1-4 includes the process ag shown below.
Step a. A solution adjusting step for dissolving sodium aluminate in water and adjusting the solution ,
Step b. This solution was stirred was charged with fine silver powder, mixing step of a mixed solution by mixing the solution and the fine silver powder,
Step c. A neutralization step of neutralizing the solution by charging the mixed solution with an amount of 0.96 mol to 20.1 mol with respect to 1.6 g to 4.1 g of sodium aluminate ,
Step d. A filtration step of filtering the neutralized solution and separating the silver powder and the solution into a solid and a liquid;
Step e. A washing step of washing the separated silver powder with water (preferably pure water, the same shall apply hereinafter);
Step f. A dehydration step of immersing the washed silver powder in acetone to dehydrate the water adhering to the silver powder along with evaporation of the acetone; and g. A drying process for drying the dehydrated silver powder.
この製法により、湿式法で酸化アルミニウムで均一に被覆された、第１および第２酸化アルミニウム被覆微粒銀粉が作製される。 By this production method, first and second aluminum oxide-coated fine silver powders uniformly coated with aluminum oxide by a wet method are produced.
さらに上述した酸化アルミニウム被覆微粒銀粉の製造方法おいては、
工程ａで、０．５〜３．０ｇ／Ｌの濃度となるように純水にアルミン酸ソーダを溶解し、
工程ｂで、この溶解液に、５０〜３００ｇ／Ｌの割合で微粒銀粉を投入し攪拌し溶液を調整し、
工程ｃで、この調整された溶液に、後述するように所定の濃度となるように希釈された酸を投入し該溶液を中和し銀粉粒子上にアルミニウム被覆微粒銀粉が作成されることを特徴とすることが好ましい。
Furthermore, in the manufacturing method of the above-described aluminum oxide-coated fine silver powder,
In step a, sodium aluminate is dissolved in pure water to a concentration of 0.5 to 3.0 g / L,
In step b, fine silver powder is added to the solution at a rate of 50 to 300 g / L and stirred to adjust the solution.
In step c, the adjusted solution is charged with an acid diluted to have a predetermined concentration as described later, and the solution is neutralized to produce aluminum-coated fine silver powder on the silver powder particles. It is preferable that
工程ａで、０．５〜３．０ｇ／Ｌの濃度となるように純水にアルミン酸ソーダを溶解するのは、０．５ｇ／Ｌ未満では、銀粉の酸化アルミニウムへの被覆が不十分となり、アルミニウム被覆微粒銀粉の熱収縮率が改善されず、一方、３．０ｇ／Ｌ大であると、アルミニウム被覆微粒銀粉を導電性ペーストの材料として混入して電子回路基板上で配線し焼成した後の比抵抗率が高くなりすぎて配線部の材料として実用的ではないからである。 In step a, sodium aluminate is dissolved in pure water so as to have a concentration of 0.5 to 3.0 g / L. If the concentration is less than 0.5 g / L, the coating of silver powder on aluminum oxide becomes insufficient. The thermal shrinkage rate of the aluminum-coated fine silver powder is not improved. On the other hand, if the size is 3.0 g / L, the aluminum-coated fine silver powder is mixed as a conductive paste material and wired on the electronic circuit board and fired. This is because the specific resistivity is too high to be practical as a material for the wiring portion.
工程ｂで、５０〜３００ｇ／Ｌの割合で微粒銀粉を投入するのは、５０ｇ／Ｌ未満では製造コスト面で不利であり、一方、３００ｇ／Ｌより超えると銀粉が凝集し易くなり均一な攪拌に支障をきたす。よって、銀粉濃度は５０〜３００ｇ／Ｌであることが望ましいからである。なお、本発明の酸化アルミニウム被覆銀粉では、酸化アルミニウムの濃度を、還元析出する場合の濃度よりも高濃度で被覆することが好適である。 In step b, the addition of fine silver powder at a rate of 50 to 300 g / L is disadvantageous in terms of production cost if it is less than 50 g / L, and on the other hand, if it exceeds 300 g / L, the silver powder tends to aggregate and uniform stirring Cause trouble. Therefore, the silver powder concentration is desirably 50 to 300 g / L. In addition, in the aluminum oxide coating silver powder of this invention, it is suitable to coat | cover the density | concentration of aluminum oxide with a density | concentration higher than the density | concentration in the case of carrying out reduction precipitation.
工程ｃで、中和に使用される酸としてホウ酸（３価の酸）を例にとると、本発明の実施にあたりホウ酸は中和時間（酸添加速度）を長めに設定するために適切に希釈するのがよい。もちろん当該中和時間を長く設定できるような微量にホウ酸を排出でき、かつ、定量性に優れたポンプを使用すれば高濃度のままでもホウ酸の添加が可能であることはいうまでもない。同時にホウ酸のＮＥＴ量がアルミン酸ソーダに対して中和が完了する量になっている事が必要である。なお、ホウ酸量は２０〜４０ｇ（水素イオン濃度（モル換算）＝０．３２×３ｍｏｌ（＝０．９６ｍｏｌ）〜０．６７×３ｍｏｌ（＝２０．１ｍｏｌ）「×３」の「３」はホウ酸の価数である。以下同様。）の範囲が好適である。２０ｇ未満だと中和不足で、４０ｇより大きいとコストの面で不利であるからである。例えば、アルミン酸ソーダ１．６〜４．１ｇに対して３３ｇ（＝０．５３×３ｍｏｌ（＝１．６ｍｏｌ））のホウ酸量で良い結果が出る傾向にある。 Taking boric acid (trivalent acid) as an example of the acid used for neutralization in step c, boric acid is suitable for setting a longer neutralization time (acid addition rate) in the practice of the present invention. It is better to dilute. Of course, boric acid can be discharged in a trace amount that can set the neutralization time long, and it is needless to say that boric acid can be added even at a high concentration if a pump with excellent quantitative properties is used. . At the same time, it is necessary that the NET amount of boric acid is such that neutralization is completed with respect to sodium aluminate. The amount of boric acid is 20 to 40 g (hydrogen ion concentration (mol conversion) = 0.32 × 3 mol (= 0.96 mol) to 0.67 × 3 mol (= 20.1 mol) “3” of “× 3” is The valence of boric acid, the same shall apply hereinafter). If it is less than 20 g, neutralization is insufficient, and if it is more than 40 g, it is disadvantageous in terms of cost. For example, a good result tends to be obtained with an amount of boric acid of 33 g (= 0.53 × 3 mol (= 1.6 mol)) with respect to 1.6 to 4.1 g of sodium aluminate.
なお、上記ホウ酸量を例とした酸量はアルミン酸ソーダ量との相対的な関係で決まるものである。本発明の実施例ではホウ酸を用いたが、ホウ酸以外の酸であってもアルミン酸ソーダ溶液を中和することができる酸であれば代替可能であり、使用される酸としてホウ酸に限定されるものではない。例えば、硝酸（一価の酸）、硫酸（二価の酸）、リン酸（三価の酸）等が使用可能であって、上記ホウ酸を例にした水素イオン濃度と同じ水素イオン濃度の値となるように各酸の重量を、各酸の価数に応じて換算することにより随時各酸の使用量を決めればよい。 The acid amount taking the boric acid amount as an example is determined by a relative relationship with the sodium aluminate amount. Although boric acid was used in the examples of the present invention, any acid other than boric acid can be used as long as it can neutralize the sodium aluminate solution. It is not limited. For example, nitric acid (monovalent acid), sulfuric acid (divalent acid), phosphoric acid (trivalent acid), etc. can be used, and the same hydrogen ion concentration as that of boric acid as an example. What is necessary is just to determine the usage-amount of each acid at any time by converting the weight of each acid according to the valence of each acid so that it may become a value.
この製法によれば、湿式法で、酸化アルミニウムで均一に被覆された、第１および第２の酸化アルミニウム被覆微粒銀粉が好適な条件で作製される。なお、当該製法では、中和時間を稼ぐために酸を希釈することにより酸の添加速度を遅くしている。これは溶液中で撹拌されている微粒銀粉の分散性を維持し、かつ、均一に酸化アルミニウムを被覆するためである。ちなみに、高濃度で酸を添加すると瞬時に中和沈殿物が生成したり、芯材である微粒銀粉同士が被覆材料である酸化アルミニウムにより互いに接着されたように凝集してしまう。このようにして、酸化アルミニウムの被覆が不均一となり、安定して好適な熱収縮特性も得られなくなってしまう。 According to this manufacturing method, the first and second aluminum oxide-coated fine silver powders uniformly coated with aluminum oxide are produced under suitable conditions by a wet method. In addition, in the said manufacturing method, in order to earn neutralization time, the addition rate of an acid is made slow by diluting an acid. This is for maintaining the dispersibility of the fine silver powder stirred in the solution and uniformly coating the aluminum oxide. By the way, when an acid is added at a high concentration, a neutralized precipitate is instantly formed, or fine silver powders that are core materials are aggregated together as if they are adhered to each other by aluminum oxide that is a coating material. In this way, the aluminum oxide coating becomes non-uniform, and stable heat shrinkage characteristics cannot be obtained.
本発明に係る粉粒銀粉によれば、酸化アルミニウム被覆銀粉の当該銀粉粒子をペースト化するときに強い力をかけて混練しても被覆された酸化アルミニウム（無機物）が剥離しにくく、かつ、銀粉粒子の表面全体に均一に無機材料を被覆できるため無機物の被覆量がより少なく、さらには、銀ペーストを電子回路基板上で回路基板のセラミックスと同時に焼成する際に、電子回路基板においてデラミネーションやクラック等の不具合を起こさないようにすることができる。 According to the granular silver powder according to the present invention, the coated aluminum oxide (inorganic matter) is difficult to peel off even when a strong force is applied when the silver powder particles of the aluminum oxide-coated silver powder are pasted, and the silver powder. Since the inorganic material can be uniformly coated on the entire surface of the particle, the amount of the inorganic material is less, and further, when the silver paste is fired simultaneously with the ceramic of the circuit board on the electronic circuit board, delamination or It is possible to prevent problems such as cracks.
以下、本発明の最良の実施形態を比較例１および２と対比しつつ、実施例１および２並びに実施例３および４を通じて詳細に説明する。なお、本発明は下記の実施例に限定されるものではない。 Hereinafter, the best embodiment of the present invention will be described in detail through Examples 1 and 2 and Examples 3 and 4 while comparing with Comparative Examples 1 and 2. In addition, this invention is not limited to the following Example.
＜実施例１および実施例２＞
以下、図１を参照して、湿式法で酸化アルミニウムの被覆が施される、第１酸化アルミニウム被覆微粒銀粉の製造方法について説明する。
<Example 1 and Example 2>
Hereinafter, with reference to FIG. 1, the manufacturing method of the 1st aluminum oxide covering fine grain silver powder by which the coating of aluminum oxide is given by the wet method is demonstrated.
実施例１および実施例２に係る製造方法は、図１に示されるように、工程ａ（溶解液調整工程）、工程ｂ（混合工程）、工程ｃ（中和工程）、工程ｄ（濾過工程）、工程ｅ（洗浄工程）、工程ｆ（脱水工程）、および工程ｇ（乾燥工程）を含み、これらの工程により、酸化アルミニウムで被覆された、第１酸化アルミニウム被覆微粒銀粉を得るものである。 As shown in FIG. 1, the manufacturing method according to Example 1 and Example 2 includes step a (dissolved liquid adjustment step), step b (mixing step), step c (neutralization step), step d (filtration step). ), Step e (cleaning step), step f (dehydration step), and step g (drying step). By these steps, the first aluminum oxide-coated fine silver powder coated with aluminum oxide is obtained. .
さらに、詳細に説明すると、
工程ａ：純水３０００ｍｌにアルミン酸ソーダ１．６ｇ（実施例１の場合）又は４．１ｇ（実施例２の場合）を溶解する（それぞれの濃度は０．５３ｇ／Ｌと１．３７ｇ／Ｌに換算される。）
In more detail,
Step a: Dissolve 1.6 g of sodium aluminate (in the case of Example 1) or 4.1 g (in the case of Example 2) in 3000 ml of pure water (the respective concentrations are 0.53 g / L and 1.37 g / L). Converted to.)
工程ｂ：この溶解液に銀粉（微粉）３００ｇを投入し（１００ｇ／Ｌ）、溶液全体に銀粉が分散するように攪拌しつつ、銀粉と溶液とを混合する。（工程ｂ）。この実施例１および２で投入された銀粉は、溶液中での分散性が良く、粒子も均一なものを使用している（以下、実施例１および２で用いられる銀粉を「ＴＹＰＥ１」とよぶ）。 Step b: Add 300 g of silver powder (fine powder) to this solution (100 g / L), and mix the silver powder and the solution while stirring so that the silver powder is dispersed throughout the solution. (Step b). The silver powder introduced in Examples 1 and 2 has good dispersibility in the solution and has uniform particles (hereinafter, the silver powder used in Examples 1 and 2 is referred to as “TYPE 1”). ).
ＴＹＰＥ１の銀粉の粉体特性は、図４（ａ）のＳＥＭ写真から観察されるように、粉体粒子が略球形であり分散性が良い。また、図４（ｂ）の棒グラフ（横軸；粒径（μｍ）、縦軸；各粒径（μｍ）の観察写真像中の存在頻度（％））から分るように、粉体粒子がシャープな粒度分布を呈している。なお、このＴＹＰＥ１の銀粉の元粉は、タップ充填密度が４．０（ｇ／ｃｍ３）、Ｄ５０が４．１（μｍ）、（Ｄ９０−Ｄ１０）が８．０（μｍ）である。ここでは、上記のように銀粉濃度を１００ｇ／Ｌとしたが、これに限定されるものではない。 As observed from the SEM photograph of FIG. 4A, the powder characteristics of the silver powder of TYPE 1 are substantially spherical and have good dispersibility. Further, as can be seen from the bar graph (horizontal axis: particle size (μm), vertical axis: presence frequency (%) in each observed particle size (μm)) of FIG. It exhibits a sharp particle size distribution. The original powder of TYPE 1 silver powder has a tap packing density of 4.0 (g / cm 3 ), D 50 of 4.1 (μm), and (D 90 -D 10 ) of 8.0 (μm). is there. Here, the silver powder concentration is set to 100 g / L as described above, but is not limited thereto.
工程ｃ：攪拌された状態を維持しつつ、溶液１５００ｍｌに対して３３ｇの濃度（２２ｇ／Ｌ）となるように希釈されたホウ酸を６０分間にわたり上記銀粉が分散された溶液に投入することにより、溶液を中和する。 Step c: While maintaining the stirring state, by adding boric acid diluted to a concentration of 33 g (22 g / L) to 1500 ml of the solution over 60 minutes into the solution in which the silver powder is dispersed Neutralize the solution.
工程ｄ：中和された溶液を、ヌッチェを用いて濾過し固液分離する。
工程ｅ：分離された銀粉を、純水５００ｍｌを用いて洗浄する。
工程ｆ：アセトン２００ｍｌを加えながら銀粉に含まれる水を脱水する。
工程ｇ：オートクレーブ内で７０℃×５時間、上記銀粉を乾燥する。
上記製法により、第１酸化アルミニウム被覆微粒銀粉を得た。
Step d: The neutralized solution is filtered and solid-liquid separated using a Nutsche.
Step e: The separated silver powder is washed with 500 ml of pure water.
Step f: Water contained in the silver powder is dehydrated while adding 200 ml of acetone.
Step g: Dry the silver powder in an autoclave at 70 ° C. for 5 hours.
By the above production method, a first aluminum oxide-coated fine silver powder was obtained.
次に、図２および図３を参照して、上記製造方法で得られた、第１酸化アルミニウム被覆微粒銀粉の諸粉体特性を説明する。 Next, with reference to FIGS. 2 and 3, various powder characteristics of the first aluminum oxide-coated fine silver powder obtained by the above production method will be described.
図２の表は、投入銀粉がＴＹＰＥ１である場合の実施例１および２の製法で得られた第１酸化アルミニウム被覆微粒銀粉の諸粉体特性値の結果および比較例１の諸特性が記されている。すなわち、酸化アルミニウム被覆量、比抵抗、比表面積（ＳＳＡ）、タップ充填密度（ＴＤ）、レーザー回折散乱式粒度測定法を用いて得られる体積累積５０％における粒径（Ｄ５０）、および最大粒径（Ｄｍａｘ）が記されている。 The table in FIG. 2 shows the results of various powder characteristic values of the first aluminum oxide-coated fine silver powder obtained by the production methods of Examples 1 and 2 when the input silver powder is TYPE 1 and the various characteristics of Comparative Example 1. ing. That is, aluminum oxide coating amount, specific resistance, specific surface area (SSA), tap packing density (TD), particle size (D 50 ) at 50% cumulative volume obtained using laser diffraction scattering particle size measurement method, and maximum particle size The diameter (Dmax) is marked.
アルミン酸ソーダ投入量は、上述したように、実施例１の場合は１．６ｇであり、実施例２の場合は４．１ｇである。比較例１の場合は０ｇ（酸化アルミニウム非被覆時の状態、すなわち元粉のままの状態の微粒銀粉）である。 As described above, the sodium aluminate input is 1.6 g in the case of Example 1 and 4.1 g in the case of Example 2. In the case of the comparative example 1, it is 0 g (a state when the aluminum oxide is not coated, that is, a fine silver powder in a state of the original powder).
比抵抗（Ω・cm）は、得られた銀粉を用いて銀ペーストを製造し、セラミック基板上に回路を引き回し、８７０℃の温度で１時間、焼結加工して得られた１ｍｍ幅回路を用いて測定した。なお、銀ペーストの組成は、微粒銀粉８５ｗｔ％、エチルセルロース０．７ｗｔ％、ターピネオール１４．２５ｗｔ％とした。 The specific resistance (Ω · cm) is obtained by manufacturing a silver paste using the obtained silver powder, drawing a circuit on a ceramic substrate, and sintering it at a temperature of 870 ° C. for 1 hour. And measured. The composition of the silver paste was 85 wt% fine silver powder, 0.7 wt% ethylcellulose, and 14.25 wt% terpineol.
酸化アルミニウム被覆量（％）は、得られた酸化アルミニウム被覆微粒銀粉を硝酸水溶液に加熱溶解し、フッ化水素酸およびホウ酸を加えてさらに加熱した後、常温まで冷却し希釈した液を島津製作所ＩＣＰＳ８０００により分析し、所定の換算方法により求めた。 The amount of aluminum oxide coating (%) was obtained by dissolving the resulting aluminum oxide-coated fine silver powder in an aqueous nitric acid solution, adding hydrofluoric acid and boric acid, further heating, cooling to room temperature, and diluting the diluted solution. The analysis was performed by ICPS8000, and determined by a predetermined conversion method.
ＳＳＡ（ｍ２／ｇ）は、銀粉の単位重量当りの表面積であり、いくつかの測定法があるが、ここではガス吸着法により粒子表面を測定し、ＳＳＡを求めている（ＢＥＴ法）。なお、公知の他の方法、すなわち、空気透過法や光透過粒度測定法によりＳＳＡを求めてもよい。 SSA (m 2 / g) is a surface area per unit weight of silver powder, and there are several measuring methods. Here, the particle surface is measured by a gas adsorption method to obtain SSA (BET method). The SSA may be obtained by other known methods, that is, the air transmission method or the light transmission particle size measurement method.
ＴＤ（ｇ／ｃｍ３）は、銀粉２００ｇを精秤し、１５０ｃｍ３のメスシリンダーに入れ、ストローク４０ｍｍで１０００回の落下を繰返しタッピングした後、銀粉の容積を測定することにより測定した。 TD (g / cm 3 ) was measured by accurately weighing 200 g of silver powder, placing it in a 150 cm 3 graduated cylinder, repeatedly tapping 1000 drops at a stroke of 40 mm, and then measuring the volume of the silver powder.
Ｄ１０、Ｄ５０、Ｄ９０、およびＤｍａｘ（μｍ）は、レーザー回折散乱式粒度測定法を用いて得られる体積累積が、１０％、５０％、９０％、および最大になったときの粒径のことであり、このＤ１０、Ｄ５０、Ｄ９０、およびＤｍａｘ（μｍ）の値は真に粒径の一つ一つの径を直接観察したものではなく、凝集した粒子を１個の粒子（凝集粒子）として捉えて粒径を算出したものである。なお、上記レーザー回折散乱式粒度測定法は、微粒銀粉０．１ｇをイオン交換水と混合し、超音波ホモジナイザ（日本精機製作所 ＵＳ−３００Ｔ）で５分間分散させた後、レーザー回折散乱式粒度分布測定 ＭｉｒｃｒｏＴｒａｃ ＨＲＡ ９３２０−Ｘ１００型（Ｌｅｅｄｓ＋Ｎｏｒｔｈｒｕｐ社製）を用いて測定を行った。 D 10 , D 50 , D 90 , and Dmax (μm) are the particle sizes when the volume accumulation obtained using the laser diffraction scattering particle size measurement method reaches 10%, 50%, 90%, and the maximum. The values of D 10 , D 50 , D 90 , and Dmax (μm) are not values obtained by directly observing the diameter of each particle, but agglomerated particles are expressed as one particle ( The particle diameter is calculated as agglomerated particles. The laser diffraction / scattering particle size measurement method described above is performed by mixing 0.1 g of fine silver powder with ion-exchanged water and dispersing with an ultrasonic homogenizer (Nippon Seiki Seisakusho US-300T) for 5 minutes, followed by laser diffraction / scattering particle size distribution. Measurements were performed using a MicroTrac HRA 9320-X100 model (Leeds + Northrup).
以上の粉体特性値を、図２に実施例１および２並びに比較例１について、各特性値毎まとめた。 The above powder characteristic values are summarized for each characteristic value in Examples 1 and 2 and Comparative Example 1 in FIG.
図３は、実施例１および２に係る第１酸化アルミニウム被覆微粒銀粉並びに比較例１に係る元粉である銀粉の熱収縮率（％）を示すグラフである。この実験結果は、各銀粉０．５ｇに９８ＭＰａの圧力を加え直径５ｍｍ、高さ約５ｍｍのペレットを成形し、このペレットを、熱機械分析（ＴＭＡ）装置を用いて窒素ガス雰囲気中、昇温速度２０℃／ｍｉｎで９００℃まで加熱し、熱収縮率（％）を測定して得られたものである。 FIG. 3 is a graph showing the thermal contraction rate (%) of the first aluminum oxide-coated fine silver powder according to Examples 1 and 2 and the silver powder that is the base powder according to Comparative Example 1. The result of this experiment was that a pressure of 98 MPa was applied to 0.5 g of each silver powder to form a pellet having a diameter of 5 mm and a height of about 5 mm, and this pellet was heated in a nitrogen gas atmosphere using a thermomechanical analysis (TMA) apparatus. It was obtained by heating to 900 ° C. at a rate of 20 ° C./min and measuring the heat shrinkage rate (%).
実施例１および２の実験結果によれば、被覆されていない微粒銀粉（元粉）のペレットの熱収縮曲線（比較例１）は、下に凸の状態で加熱温度４００℃から急激に低下している。すなわち４００℃位の低温度から熱収縮が急激に始まることが分かる。しかし、酸化アルミニウム被覆量（％）が０．１９％（実施例１）又は０．４９％（実施例２）の場合のペレットの熱収縮曲線から分かるとおり、略６００℃まで熱収縮はほとんど起こらず、全体的に上に凸の状態で、比較例１の熱収縮曲線と比較すると９００℃にかけて緩やかに減少している。これにより、第１酸化アルミニウム被覆微粒銀粉によって導電性ペーストを作成し、電子回路の配線に用いれば、焼成時の電子回路基板においてクラックやデラミネーション等の不具合が、酸化アルミニウムを被覆しない場合に比べ起きにくくなっていることが分かる。なお、参考までに、実施例１で作製された微粒銀粉のＳＥＭ写真観察像および粒度分布のグラフを図５（ａ）（ｂ）に、実施例２で作製された微粒銀粉のＳＥＭ写真観察像および粒度分布のグラフを図６（ａ）（ｂ）に示す。 According to the experimental results of Examples 1 and 2, the heat shrinkage curve (Comparative Example 1) of the uncoated fine silver powder (original powder) pellets rapidly decreases from the heating temperature of 400 ° C. in a convex state. ing. That is, it can be seen that the heat shrinkage starts abruptly from a low temperature of about 400 ° C. However, as can be seen from the heat shrinkage curve of the pellet when the aluminum oxide coating amount (%) is 0.19% (Example 1) or 0.49% (Example 2), heat shrinkage hardly occurs up to about 600 ° C. However, it is gradually convex toward 900 ° C. as compared with the heat shrinkage curve of Comparative Example 1 in a generally upwardly convex state. Thus, if a conductive paste is made from the first aluminum oxide-coated fine silver powder and used for the wiring of the electronic circuit, defects such as cracks and delamination in the electronic circuit board at the time of firing are compared to the case where the aluminum oxide is not coated. You can see that it is difficult to get up. For reference, the SEM photograph observation image and the particle size distribution graph of the fine silver powder prepared in Example 1 are shown in FIGS. 5 (a) and 5 (b), and the SEM photograph observation image of the fine silver powder prepared in Example 2 is shown in FIGS. And the graph of a particle size distribution is shown to Fig.6 (a) (b).
＜実施例３および実施例４＞
以下、図７を参照して、第２酸化アルミニウム被覆銀粉の製造方法について説明する。
<Example 3 and Example 4>
Hereinafter, with reference to FIG. 7, the manufacturing method of 2nd aluminum oxide covering silver powder is demonstrated.
実施例３および４に係る製造方法は、図７に示されるように、溶解液調整工程（工程ａ）、混合工程（工程ｂ）、中和工程（工程ｃ）、濾過工程（工程ｄ）、洗浄工程（工程ｅ）、脱水工程（工程ｆ）、および乾燥工程（工程ｇ）を経て、第２酸化アルミニウム被覆微粒銀粉を得るものである。以下、実施例３および４で投入される元粉である銀粉を「ＴＹＰＥ２」とよぶ）。すなわち、図１と比較して分かるように基本工程は同一である。よって工程の詳細な説明は省略する。ただし、以下の点で両実施例は異なる。すなわち、図１０（a）のＳＥＭ写真観察像から観察されるように、粒子が不均一の大きさであり、かつ分散性が悪く、図１０（ｂ）のグラフに示されるように、実施例１および２の元粉の微粒銀粉の場合に比べて、実施例３および４の元粉の銀粉の粒度がブロードに分布していることが分かる。なお、ＴＹＰＥ２の銀粉の元粉のタップ充填密度は３．０（ｇ／ｃｍ３）、Ｄ５０（μｍ）は６．１、および（Ｄ９０−Ｄ１０）は１６．２（μｍ）である。また、実施例１および２と同様に、工程ａにおける、実施例３および４のアルミン酸ソーダの投入量は、それぞれ１．６ｇ（０．５３ｇ／Ｌ）および４．１ｇ（１．３７ｇ／Ｌ）である。 As shown in FIG. 7, the production methods according to Examples 3 and 4 include a solution adjustment step (step a), a mixing step (step b), a neutralization step (step c), a filtration step (step d), The second aluminum oxide-coated fine silver powder is obtained through a washing step (step e), a dehydration step (step f), and a drying step (step g). Hereinafter, the silver powder that is the base powder charged in Examples 3 and 4 is referred to as “TYPE 2”). That is, as can be seen from comparison with FIG. 1, the basic process is the same. Therefore, detailed description of the process is omitted. However, the two embodiments are different in the following points. That is, as observed from the SEM photograph observation image of FIG. 10 (a), the particles have non-uniform sizes and poor dispersibility, and as shown in the graph of FIG. It can be seen that the particle sizes of the silver powders of the base powders of Examples 3 and 4 are broadly distributed as compared with the case of the fine silver powders of the base powders 1 and 2. The tap filling density of the original powder of TYPE2 silver powder is 3.0 (g / cm 3 ), D 50 (μm) is 6.1, and (D 90 -D 10 ) is 16.2 (μm). . Similarly to Examples 1 and 2, the amounts of sodium aluminate of Examples 3 and 4 in Step a were 1.6 g (0.53 g / L) and 4.1 g (1.37 g / L), respectively. ).
次に、図８および図９を参照して、上記製造方法で得られた、第２酸化アルミニウム被覆微粒銀粉の諸粉体特性を説明する。 Next, with reference to FIG. 8 and FIG. 9, various powder characteristics of the second aluminum oxide-coated fine silver powder obtained by the above production method will be described.
図８の表は、投入銀粉がＴＹＰＥ２である場合の実施例３および４の製法で得られた第２酸化アルミニウム被覆微粒銀粉の諸粉体特性値の結果および比較例２の諸特性が記されている。（諸特性の項目は、上述の実施例１および２の記載と同様の内容である。） The table of FIG. 8 shows the results of various powder characteristic values of the second aluminum oxide-coated fine silver powder obtained by the production methods of Examples 3 and 4 when the input silver powder is TYPE 2 and various characteristics of Comparative Example 2. ing. (Items of various characteristics are the same as those described in Examples 1 and 2 above.)
図９は、実施例３および４に係る第２酸化アルミニウム被覆微粒銀粉並びに比較例２に係る元粉である銀粉の熱収縮率（％）を示すグラフである。実施例３および４の実験結果によれば、酸化アルミニウムで被覆されていないＴＹＰＥ２の銀粉のペレットの熱収縮曲線（比較例２）は、下に凸の曲線で加熱温度３００℃付近から緩やかに低下している。すなわち３００℃位の低温度から熱収縮が始まることが分かる。しかし、酸化アルミニウム被覆量（％）が０．０２％（実施例３）および０．４７％（実施例４）の場合のペレットの熱収縮曲線から分かるとおり、双方とも、８００℃近辺まで熱収縮せず、８００℃を超えた近辺から熱収縮が始まる。すなわち、定量的には８００℃付近まで熱収縮率がほぼ０％であることがわかる。これにより、実施例３および４の銀粉を含む銀ペーストをセラミック材（基板）上で同時焼成したときに８００℃付近までは、当該基板へ熱収縮による応力を与えないことが分かる。よって、実施例３および４の製法から得られる第２酸化アルミニウム被覆微粒銀粉によれば、電子回路基板においてクラックやデラミネーション等の不具合が酸化アルミニウムを銀粉粒子へ被覆しない場合に比べ起きにくくなる。なお、参考までに、実施例３で作製された第２酸化アルミニウム被覆微粒銀粉のＳＥＭ写真観察像および粒度分布のグラフを図１１（ａ）（ｂ）に、実施例４で作製された第２酸化アルミニウム被覆微粒銀粉の微粒銀粉のＳＥＭ写真観察像および粒度分布のグラフを図１２（ａ）（ｂ）に示す。 FIG. 9 is a graph showing the thermal contraction rate (%) of the second aluminum oxide-coated fine silver powder according to Examples 3 and 4 and the silver powder that is the base powder according to Comparative Example 2. According to the experimental results of Examples 3 and 4, the heat shrinkage curve (Comparative Example 2) of the TYPE2 silver powder pellets not coated with aluminum oxide is a downwardly convex curve that gradually decreases from around 300 ° C. at the heating temperature. is doing. That is, it can be seen that thermal shrinkage starts from a low temperature of about 300 ° C. However, as can be seen from the heat shrinkage curves of the pellets when the aluminum oxide coating amount (%) is 0.02% (Example 3) and 0.47% (Example 4), both heat shrink to around 800 ° C. Without starting, heat shrinkage starts near 800 ° C. That is, it can be seen quantitatively that the thermal shrinkage rate is almost 0% up to around 800 ° C. Thus, the silver paste containing silver powder of Example 3 and 4 to the vicinity of 800 ° C. when co-fired on the ceramic material (substrate), it is found that does not give stress due to heat shrinkage to the substrate. Therefore, according to the second aluminum oxide-coated fine silver powder obtained from the production methods of Examples 3 and 4, defects such as cracks and delamination are less likely to occur in the electronic circuit board than when aluminum oxide is not coated on the silver powder particles. For reference, the SEM photograph observation image and the particle size distribution graph of the second aluminum oxide-coated fine silver powder prepared in Example 3 are shown in FIGS. 11 (a) and 11 (b), and the second image prepared in Example 4 is used. The SEM photograph observation image and the graph of particle size distribution of the fine silver powder of the aluminum oxide-coated fine silver powder are shown in FIGS.
以上、実施例１および２に係る第１酸化アルミニウム微粒銀粉、並びに実施例３および４に係る第２酸化アルミニウム微粒銀粉によれば、銀粉の粒子の表面に酸化アルミニウムを被覆した場合、銀粉の粒子の熱収縮がより高温側で始まるように改善されることが分る。その結果、これらの微粒銀粉を含む導電性ペーストを用いて配線された電子回路基板の焼成においてクラックやデラミネーション等の不具合を防止することができる微粒銀粉を提供することができる。 As described above, according to the first aluminum oxide fine silver powder according to Examples 1 and 2 and the second aluminum oxide fine silver powder according to Examples 3 and 4, when the surface of the silver powder particles is coated with aluminum oxide, the silver powder particles It can be seen that the heat shrinkage of the is improved so that it begins on the higher temperature side. As a result, it is possible to provide a fine silver powder capable of preventing defects such as cracks and delamination in firing of an electronic circuit board wired using a conductive paste containing these fine silver powders.
＜実施例１および２と、実施例３および４との比較＞
さらに、実施例１および２によって示された熱収縮率（％）の曲線（図３）と、実施例３および４によって示された熱収縮率（％）の曲線（図９）から分かるように、同一工程により酸化アルミニウムを銀粉の粒子に被覆しても、元粉たる微粒銀粉の粒度分布等の粉体特性によって熱収縮の挙動が異なることが分かる。このことは、元粉の銀粉の粉体特性、例えば粒度分布の状態、粒子の形状、および粒子の分散性を変化させることによって、実施例１および２のようにある温度から徐々に緩やかに熱収縮する熱収縮特性を得ることもできるし、実施例３および４のように所定温度まではほとんど熱収縮せずに、当該所定温度以降から熱収縮が始まるような熱収縮特性を得ることができる。このように、酸化アルミニウムを銀粉粒子表面へ被覆することによって収縮開始温度を高くするばかりでなく、熱収縮の挙動を元粉もしくは芯材銀粉粒子によって制御できることがわかる。これによりセラミック材の基板（グリーンシート）の熱収縮の挙動に応じて、微粒銀粉（粒子）の熱収縮を制御し、電子回路基板の焼成時のクラックやデラミネーション等の不具合を防ぐことができる。
<Comparison between Examples 1 and 2 and Examples 3 and 4>
Further, as can be seen from the heat shrinkage rate (%) curve (FIG. 3) shown by Examples 1 and 2, and the heat shrinkage rate (%) curve shown by Examples 3 and 4 (FIG. 9). Even when the aluminum oxide is coated on the silver powder particles in the same process, it can be seen that the behavior of heat shrinkage varies depending on the powder characteristics such as the particle size distribution of the fine silver powder as the original powder. This is achieved by gradually and gradually heating from a certain temperature as in Examples 1 and 2 by changing the powder characteristics of the original silver powder, such as the state of particle size distribution, the shape of the particles, and the dispersibility of the particles. It is possible to obtain a heat shrinkage characteristic that shrinks, and it is possible to obtain a heat shrinkage characteristic such that the heat shrinkage starts from the predetermined temperature or less without almost heat shrinking to a predetermined temperature as in the third and fourth embodiments. . Thus, it can be seen that by coating aluminum oxide on the surface of the silver powder particles, not only the shrinkage start temperature can be increased, but also the behavior of heat shrinkage can be controlled by the base powder or the core material silver powder particles. As a result, the thermal contraction of the fine silver powder (particles) can be controlled according to the thermal contraction behavior of the ceramic substrate (green sheet) to prevent problems such as cracks and delamination during firing of the electronic circuit board. .
本発明に係る銀粉およびその製造方法は、電子回路基板の配線パターン用の導電性ペーストに混入される導電性粉末およびその製造方法に用いることができる。 The silver powder and the manufacturing method thereof according to the present invention can be used for the conductive powder mixed in the conductive paste for the wiring pattern of the electronic circuit board and the manufacturing method thereof.
Claims (6)
ａ．タップ充填密度（ｇ／ｃｍ３）が、３．５〜５．０
ｂ．Ｄ５０（μｍ）が、０．５〜５．０
ｃ．Ｄ９０−Ｄ１０（μｍ）が、１．０〜１０．０
（なお、Ｄ１０、Ｄ５０、Ｄ９０は、レーザー回折散乱式粒度分布測定法による、１０％、５０％、９０％重量累積粒径を指す。以下同様に表記する。） The oxidation of aluminum a coated fine silver powder coated on the particle surfaces of the fine silver powder, aluminum oxide coated fine silver powder, characterized in that it comprises the following powder characteristics.
a. Tap filling density (g / cm 3 ) is 3.5 to 5.0
b. D 50 (μm) is 0.5 to 5.0
c. D 90 -D 10 is ([mu] m), 1.0 to 10.0
(D 10 , D 50 , and D 90 are 10%, 50%, and 90% weight cumulative particle diameters as measured by a laser diffraction scattering particle size distribution measurement method. The same applies hereinafter.)
該酸化アルミニウム被覆微粒銀粉の粒子の熱収縮が６００℃から始まることを特徴とする酸化アルミニウム被覆微粒銀粉。 The aluminum oxide-coated fine silver powder according to claim 1 is a fine silver powder whose thermal shrinkage starts at a temperature higher than the thermal shrinkage start temperature of silver,
The aluminum oxide-coated fine silver powder, wherein the heat shrinkage of the particles of the aluminum oxide-coated fine silver powder starts at 600 ° C.
ａ．タップ充填密度（ｇ／ｃｍ３）が、２．０〜３．５
ｂ．Ｄ５０（μｍ）が、５．０〜１０．０
ｃ．Ｄ９０−Ｄ１０（μｍ）が、１０．０〜２５．０ The oxidation of aluminum a coated fine silver powder coated on the particle surfaces of the fine silver powder, aluminum oxide coated fine silver powder, characterized in that it comprises the following powder characteristics.
a. Tap filling density (g / cm 3 ) is 2.0 to 3.5
b. D 50 (μm) is 5.0 to 10.0
c. D 90 -D 10 is ([mu] m), 10.0 to 25.0
該酸化アルミニウム被覆微粒銀粉の粒子の熱収縮が８００℃を超えた温度で始まることを特徴とする酸化アルミニウム被覆微粒銀粉。 The aluminum oxide-coated fine silver powder according to claim 3 is a fine silver powder whose thermal shrinkage starts at a temperature higher than the thermal shrinkage start temperature of silver,
The aluminum oxide-coated fine silver powder, wherein the heat shrinkage of the particles of the aluminum oxide-coated fine silver powder starts at a temperature exceeding 800 ° C.
工程ａ．水にアルミン酸ソーダを溶解し、溶解液を調整する溶解液調整工程、
工程ｂ．この溶解液に、微粒銀粉を投入し攪拌し、溶解液と微粒銀粉とを混合して混合溶液とする混合工程、
工程ｃ．上記混合溶液に、前記アルミン酸ソーダ１．６ｇ〜４．１ｇに対して０．９６ｍｏｌ〜２０．１ｍｏｌとなる量の酸を投入し該溶液を中和する中和工程、
工程ｄ．中和溶液を濾過し、微粒銀粉と溶液とを固液分離する濾過工程、
工程ｅ．分離された微粒銀粉を水で洗浄する洗浄工程、
工程ｆ．洗浄された微粒銀粉をアセトンに浸漬させ、アセトンの蒸発と共に微粒銀粉上の付着水を脱水する脱水工程、及び
工程ｇ．脱水された微粒銀粉を乾燥させる乾燥工程。 The manufacturing method of the aluminum oxide coat | cover fine silver powder containing process ag shown below.
Step a. A solution adjusting step for dissolving sodium aluminate in water and adjusting the solution,
Step b. A mixing step in which fine silver powder is added to and stirred in this solution, and the solution and fine silver powder are mixed to form a mixed solution,
Step c. A neutralization step of neutralizing the solution by charging the mixed solution with an amount of 0.96 mol to 20.1 mol with respect to 1.6 g to 4.1 g of sodium aluminate,
Step d. A filtration step of filtering the neutralized solution to separate the fine silver powder from the solution into a solid and a liquid;
Step e. A washing step of washing the separated fine silver powder with water,
Step f. A dehydration step of immersing the washed fine silver powder in acetone to dehydrate the water adhering to the fine silver powder along with evaporation of the acetone; and g. A drying process for drying the dehydrated fine silver powder.
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