JP5092630B2 - Fine silver powder, method for producing the same, and dispersion liquid for conductive paste using the fine silver powder - Google Patents
Fine silver powder, method for producing the same, and dispersion liquid for conductive paste using the fine silver powder Download PDFInfo
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- 239000010946 fine silver Substances 0.000 title claims description 89
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
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- WUOACPNHFRMFPN-UHFFFAOYSA-N alpha-terpineol Chemical compound CC1=CCC(C(C)(C)O)CC1 WUOACPNHFRMFPN-UHFFFAOYSA-N 0.000 description 3
- -1 aluminum alkoxide Chemical class 0.000 description 3
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- SQIFACVGCPWBQZ-UHFFFAOYSA-N delta-terpineol Natural products CC(C)(O)C1CCC(=C)CC1 SQIFACVGCPWBQZ-UHFFFAOYSA-N 0.000 description 3
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- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 3
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- DOIRQSBPFJWKBE-UHFFFAOYSA-N dibutyl phthalate Chemical compound CCCCOC(=O)C1=CC=CC=C1C(=O)OCCCC DOIRQSBPFJWKBE-UHFFFAOYSA-N 0.000 description 2
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- UODXCYZDMHPIJE-UHFFFAOYSA-N menthanol Chemical compound CC1CCC(C(C)(C)O)CC1 UODXCYZDMHPIJE-UHFFFAOYSA-N 0.000 description 2
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- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
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- XXJWXESWEXIICW-UHFFFAOYSA-N diethylene glycol monoethyl ether Chemical compound CCOCCOCCO XXJWXESWEXIICW-UHFFFAOYSA-N 0.000 description 1
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- 229910052708 sodium Inorganic materials 0.000 description 1
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- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 1
- 235000019982 sodium hexametaphosphate Nutrition 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、微粒銀粉およびその製造方法並びに導電性ペースト用分散液に係り、より詳しくは電子回路、特に低温焼成セラッミック基板の配線部材用として優れた電気特性が得られる微粒銀粉およびその製造方法と導電性ペースト用分散液に関する。 The present invention relates to a fine silver powder, a method for producing the same, and a dispersion for a conductive paste, and more particularly, a fine silver powder capable of obtaining excellent electrical characteristics for an electronic circuit, particularly a wiring member for a low-temperature fired ceramic substrate, and a method for producing the same. The present invention relates to a dispersion for conductive paste.
近年、大規模的に普及している携帯電話等の小型電子機器を製造するためにＬＴＣＣ（ｌｏｗ−ｔｅｍｐｅｒａｔｕｒｅ ｃｏｆｉｒｅｄ ｃｅｒａｍｉｃ、低温焼成セラッミック）を基板材料とした電子回路基板が採用され、最近ではこのＬＴＣＣを用いたパッケージ（一般に「ＬＴＣＣパッケージ」と称している）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, an electronic circuit board using LTCC (low-temperature coherent ceramic) as a substrate material has been adopted in order to manufacture small-sized electronic devices such as mobile phones that are widely used on a large scale. Recently, this LTCC has been adopted. In order to arrange small electronic components such as chip capacitors and chip inductors on a ceramic multilayer substrate of a package using the IC (generally referred to as “LTCC package”), a fine pitch wiring portion for an electronic circuit is formed. ing.
ＬＴＣＣパッケージでは、前記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製造される。
すなわち、まず微粒銀粉と有機溶剤等を混練して導電性ペースト（銀ペースト）が作製され、次いでこの導電性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製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。
In the LTCC package, it is necessary to improve the conductivity of the wiring part because of the demand for the fine pitch described above, and fine silver powder is used as a raw material for the wiring part as follows.
That is, a conductive paste (silver paste) is first prepared by kneading fine silver powder and an organic solvent, and then a wiring pattern is formed on a green sheet made of a ceramic material by screen printing using this conductive paste. Printed. Then, the conductive paste and the green sheet are simultaneously fired 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。
銀の融点は約９６０℃であるが、一般的に５００℃付近から微粒銀粉の粒子同士の焼結が始まり、それに伴って配線部の微粒銀粉の熱収縮が始まる。一方、ＬＴＣＣのセラミック材料も微粒銀粉とは別の挙動で収縮する。すなわち、焼結温度が高いセラミック材料は、微粒銀粉より高い温度から熱収縮を開始する。また、一般的にセラミック材料は、収縮量も少ない。したがって、焼成時に微粒銀粉とセラミック材料との間に熱収縮挙動の差が生じるため、電子回路基板においてクラックやデラミネーション等の不具合が発生し易く、この不具合を防止するため双方の熱収縮挙動を調整しつつ焼成工程を行う必要がある。
At this time, the following phenomenon occurs in the firing process of the LTCC package.
Although the melting point of silver is about 960 ° C., the sintering of fine silver powder particles starts generally from around 500 ° C., and the thermal shrinkage of the fine silver powder in the wiring portion starts accordingly. On the other hand, the LTCC ceramic material also shrinks in a behavior different from that of the fine silver powder. That is, the ceramic material having a high sintering temperature starts thermal shrinkage from a temperature higher than that of the fine silver powder. In general, ceramic materials also have a small amount of shrinkage. Therefore, since a difference in thermal shrinkage behavior occurs between the fine silver powder and the ceramic material during firing, defects such as cracks and delamination are likely to occur in the electronic circuit board. It is necessary to carry out the firing step while adjusting.
以上のように電子回路基板のファインピッチ化に対応した導電ペースト用微粒銀粉においては、焼成工程において微粒銀粉とセラミック材料との間の熱収縮挙動の差が少ない微粒銀粉が求められている。 As described above, in the fine silver powder for conductive paste corresponding to the fine pitch of the electronic circuit board, there is a demand for a fine silver powder having a small difference in thermal shrinkage behavior between the fine silver powder and the ceramic material in the firing step.
このような要請に対して、従来、より高温から熱収縮を開始するように改善された微粒銀粉が提案されている。例えば、特許文献１には、平均粒径が１０μｍ以下の金属銀粒子表面に原子番号１２〜８２の範囲内で周期表の２〜１４族に属する金属元素の少なくとも１種を含む酸化物および複合酸化物からなる群より選ばれる少なくとも１種が固着している表面修飾銀粉が提案されている。前記表面修飾銀粉は、微粒銀粉の表面を無機物で被覆して低温での微粒銀粉の粒子同士の焼結を防止し、熱収縮開始温度をより高温側にシフトさせて熱収縮挙動を改善したものである。 In response to such a demand, conventionally, a fine silver powder improved so as to start thermal contraction from a higher temperature has been proposed. For example, Patent Document 1 discloses an oxide and composite containing at least one metal element belonging to Groups 2 to 14 of the periodic table in the range of atomic numbers 12 to 82 on the surface of metal silver particles having an average particle diameter of 10 μm or less. A surface-modified silver powder to which at least one selected from the group consisting of oxides is fixed has been proposed. The surface-modified silver powder is coated with an inorganic substance on the surface of the fine silver powder to prevent sintering of the fine silver powder particles at low temperature, and the heat shrinkage starting temperature is shifted to a higher temperature side to improve the heat shrinkage behavior. It is.
しかしながら、表面修飾銀粉では、高抵抗の表面固着物によって焼成後の比抵抗が高くなるおそれがある上、表面修飾銀粉は、乾式固着法もしくは湿式固着法という製造方法で作製されるため、工程が複雑で高コストになるという問題がある。具体的に説明すると、乾式固着法では、酸化物および／または複合酸化物をオングミル、ハイブリタイザーなどの装置で処理して金属銀微粒子表面に固着する方法がとられる。また、湿式固着法では、まず金属銀微粒子表面にアンミン酸ナトリウム（Ａｌ２Ｏ３付着のため）、ケイ酸ナトリウム（ＳｉＯ２付着のため）などのような水溶性塩から誘導される金属酸化物および／または複合酸化物を付着させ、洗浄し、乾燥させた後、付着強度を得るため、追加の工程として、当該酸化物および／または複合酸化物が付着している金属銀粒子を、オングミル、ハイブリタイザーなどの装置で固着処理する方法がとられる。 このため、これらの製法では、廃液処理、乾燥工程、固着工程などが必要となり、工程が複雑で高コストになるという問題がある。 However, in the surface-modified silver powder, the specific resistance after firing may increase due to the high-resistance surface-fixed material, and the surface-modified silver powder is produced by a manufacturing method such as a dry-fixing method or a wet-fixing method. There is a problem that it is complicated and expensive. More specifically, in the dry fixing method, an oxide and / or composite oxide is processed by an apparatus such as an angmill, a hybridizer, etc., and fixed to the surface of the metal silver fine particles. In the wet fixing method, first, a metal oxide derived from a water-soluble salt such as sodium ammine (for Al 2 O 3 adhesion), sodium silicate (for SiO 2 adhesion) or the like on the surface of the metal silver fine particles. In order to obtain adhesion strength after depositing and / or composite oxide, and washing and drying, as an additional step, metal silver particles to which the oxide and / or composite oxide is adhered are ong mill, A method of fixing with a device such as a hybridizer is employed. For this reason, in these manufacturing methods, a waste liquid process, a drying process, a fixing process, etc. are needed, and there exists a problem that a process is complicated and becomes high-cost.
さらに、前記乾式法で固着させた場合には、熱収縮率が高くなり、セラミック基板として焼成した場合、クラックやデラミネーションの原因となることが知られている特許文献２で示唆されている。この特許文献２では、微粒銀粉をアルミニウムアルコキシド溶液中に分散し、アルミニウムアルコキシドを加熱分解し、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って、比表面積が０．５０〜４．０ｍ２／ｇ、平均粒径が０．５０〜１０．０μｍ、最大粒径が１．０〜３０．０μｍの酸化アルミニウム被覆微粒銀粉が提案されている。しかしながら、前記酸化アルミニウム被覆微粒銀粉も前記と同様に表面固着物によって焼成後の比抵抗が高くなるおそれがある上、この製造方法も洗浄、乾燥工程などの後工程があり、工程が複雑で高コストとなるという問題がある。 Furthermore, it is suggested in Patent Document 2 that it is known that, when fixed by the dry method, the thermal shrinkage rate is high, and when fired as a ceramic substrate, it causes cracks and delamination. In Patent Document 2, fine silver powder is obtained by dispersing fine silver powder in an aluminum alkoxide solution, thermally decomposing aluminum alkoxide, and coating aluminum oxide on the surface of the fine silver powder, and having a specific surface area of 0.50 to 4. An aluminum oxide-coated fine silver powder having 0 m 2 / g, an average particle size of 0.50 to 10.0 μm, and a maximum particle size of 1.0 to 30.0 μm has been proposed. However, the aluminum oxide-coated fine-grained silver powder may have a high specific resistance after firing due to the surface-fixed material as described above, and this manufacturing method also has post-processes such as a washing and drying process, which are complicated and expensive. There is a problem of cost.
一方、銀合金アトマイズ粉を導電フィラーとして含有する導電性ペースト組成物が特許文献３に提案されている。特許文献３は、アトマイズ法によって作製した銀合金微粉を用い、焼成中に銀合金微粉の表面を酸化物（銀以外の合金元素の酸化物）で被覆させることによって、熱収縮開始温度をより高温側にシフトさせて熱収縮挙動の改善を図ったものである。しかしながら、アトマイズ法を用いた場合、得られる銀合金粉の粒径は大きいものとならざるを得ず、電子回路基板のファインピッチ化に対応した１μｍ以下の微粉を作製するためには分級が必要であるが、分級効率が悪く、高コストとなるという問題がある。 On the other hand, Patent Document 3 proposes a conductive paste composition containing silver alloy atomized powder as a conductive filler. Patent Document 3 uses a silver alloy fine powder produced by an atomizing method, and coats the surface of the silver alloy fine powder with an oxide (an oxide of an alloy element other than silver) during firing, so that the heat shrinkage start temperature is higher. The heat shrinkage behavior is improved by shifting to the side. However, when the atomization method is used, the particle size of the obtained silver alloy powder must be large, and classification is necessary to produce fine powder of 1 μm or less corresponding to the fine pitch of the electronic circuit board. However, there is a problem that the classification efficiency is poor and the cost is high.
このため、電子回路基板のファインピッチ化に対応した導電ペースト用微粒銀粉においては、焼成工程における熱収縮挙動が改善され、セラミック材料との間の熱収縮挙動の差が少ない、すなわち、熱収縮開始温度が高く収縮量が少ない微粒銀粉と、効率的でかつ低コストな工業的に適した微粒銀粉の製造技術の開発が望まれている。
本発明は、前記した従来の事情に鑑みてなされたもので、高純度で熱収縮開始温度が高く、収縮量も少ないファインピッチ化した電子回路基板用導電性ペースト用として好適な微粒銀粉と、その微粒銀粉を効率的にかつ低コストで量産できる製造方法、並びにその微粒銀粉を用いた導電性ペースト用分散液を提供することを目的とするものである。 The present invention has been made in view of the above-described conventional circumstances, and is a fine silver powder suitable for use as a conductive paste for an electronic circuit board having a high purity, a high thermal shrinkage start temperature, and a small shrinkage amount, and It is an object of the present invention to provide a production method capable of mass-producing the fine silver powder efficiently and at low cost, and a conductive paste dispersion using the fine silver powder.
本願発明者は、微粒銀粉の熱収縮挙動の改善について鋭意検討した結果、特定の形状を有する表面に有機物を吸着させた微粒銀粉は熱収縮挙動が改善されること、その微粒銀粉は、銀微粒子を超高圧に加圧して対向衝突させることで得られるとの知見を得て、本発明を完成するに至ったものである。 The inventor of the present application diligently studied on the improvement of the heat shrinkage behavior of the fine silver powder. As a result, the fine silver powder having the organic substance adsorbed on the surface having a specific shape improves the heat shrinkage behavior. As a result, the present invention has been completed by obtaining the knowledge that it can be obtained by pressurizing the material with ultra high pressure and causing it to collide against each other.
すなわち、本発明に係る微粒銀粉は、表面に凹凸を有する略球状もしくは略多面体状の粒子であって、前記凹凸を有する表面に有機物が吸着していることを特徴とするものである。
また、この微粒銀粉は、銀粒子を超高圧に加圧して対向衝突させることにより、銀粒子の分散と銀粒子表面への有機物吸着を同時に行なうことにより得られるものであることを特徴とするものである。
さらに、本発明の微粒銀粉は、平均粒径が０．１〜２μｍで、最大粒径が１０μｍ以下であり、さらにまた、本発明の微粒銀粉は、熱収縮開始温度が８００℃以上であることを好ましい態様とするものである。
That is, the fine silver powder according to the present invention is a substantially spherical or substantially polyhedral particle having irregularities on the surface, and is characterized in that an organic substance is adsorbed on the irregular surface.
The fine silver powder is obtained by simultaneously dispersing silver particles and adsorbing organic substances on the surface of the silver particles by pressing the silver particles to an ultra high pressure and causing them to collide with each other. It is.
Further, the fine silver powder of the present invention has an average particle diameter of 0.1 to 2 μm and a maximum particle diameter of 10 μm or less, and the fine silver powder of the present invention has a heat shrinkage starting temperature of 800 ° C. or higher. Is a preferred embodiment.
本発明に係る微粒銀粉の製造方法は、湿式分散装置を用いて微粒銀粉を得る製造方法であって、銀粒子を有機溶媒中に分散させてスラリーを得るスラリー化工程、スラリーを１００ＭＰａ以上の超高圧で対向衝突させてスラリー中の銀粒子の衝突により分散と銀粒子表面への有機物吸着を同時に行なう分散化工程からなることを特徴とするものである。 The method for producing fine silver powder according to the present invention is a production method for obtaining fine silver powder using a wet dispersion device, wherein a slurry is obtained by dispersing silver particles in an organic solvent to obtain a slurry. It is characterized by comprising a dispersion step in which dispersion is carried out at the same time by high-pressure collision and silver particles in the slurry collide and adsorption of organic substances onto the surface of the silver particles.
また、前記分散化工程においては、スラリーの衝突部への繰り返し導入回数を５〜１５回とすることが好ましい。 Moreover, in the said dispersion | distribution process, it is preferable that the frequency | count of repeated introduction | transduction to the collision part of a slurry shall be 5-15 times.
本発明に係る導電性ペースト用分散液は、前記微粒銀粉を有機溶剤中に分散させたスラリーであることを特徴とするものである。 The dispersion for conductive paste according to the present invention is a slurry in which the fine silver powder is dispersed in an organic solvent.
本発明に係る微粒銀粉は、表面に吸着されている有機物が焼成時に分解してカーボンとなり、銀粒子間の拡散を防止すること、およびその形状が略球状もしくは略多面体状であるため銀粒子間の接触部分が減少することにより熱収縮開始温度が高温となり、また銀粒子を超高圧に加圧して対向衝突させて銀粒子の分散と銀粒子表面への有機物吸着を同時に行なうことにより得られるものであるから、収縮開始温度がさらに改善され、その上微細で粗粒を含まないため、ファインピッチ化が要求される電子回路基板用として特に好適である。 In the fine silver powder according to the present invention, the organic substance adsorbed on the surface is decomposed to become carbon upon firing, and the diffusion between the silver particles is prevented, and since the shape thereof is substantially spherical or substantially polyhedral, it is between the silver particles. The heat shrinkage starting temperature becomes high due to the reduction of the contact part of the material, and it is obtained by simultaneously dispersing silver particles and adsorbing organic matter on the silver particle surface by pressurizing silver particles to ultra high pressure and colliding with each other Therefore, the shrinkage start temperature is further improved, and furthermore, since it is fine and does not contain coarse particles, it is particularly suitable for an electronic circuit board that requires a fine pitch.
また、本発明に係る微粒銀粉の製造方法によれば、湿式分散装置を用いてスラリーを超高圧で対向衝突させることで、銀粒子の凝集を解砕するとともに、表面を凹凸にして略球状もしくは略多面体状とし、表面に有機物を吸着あるいは微粉自体を緻密化させることができることにより、高純度で熱収縮開始温度が高く、セラミック基板等の電子回路基板用として好適な微粒銀粉と導電性ペースト用分散液を効率よく低コストで製造することができる。 In addition, according to the method for producing fine silver powder according to the present invention, the slurry is collided with ultrahigh pressure using a wet dispersion device to crush the agglomeration of the silver particles, and the surface is roughly spherical or Highly pure and highly heat-shrinkable starting temperature due to its substantially polyhedral shape, which can adsorb organic substances on the surface or make the fine powder itself dense, and is suitable for fine silver powder and conductive paste for electronic circuit boards such as ceramic boards The dispersion can be produced efficiently and at low cost.
本発明に係る微粒銀粉において、表面に凹凸を形成するのは、当該微粒銀粉の表面に有機物を付着させやすくするためである。この表面に形成される凹凸は、サイズ的には有機物が十分に吸着される程度の大きさと定義することができる。この表面に有機物が吸着した略球状もしくは略多面体状の粒子の場合、熱収縮開始温度が高温側にシフトする機構は解明されていないが、次のように推察される。
略球状もしくは略多面体状の粒子の表面に形成された凹凸部に存在する有機物が、焼成時に分解してカーボンとなり、銀粒子間の拡散を防止して熱収縮開始温度を高温側にシフトさせるものと考えられる。また同時に、微粒銀粉を略球状もしくは略多面体状とすることで銀粒子間の接触部分が減少し、熱収縮開始温度に影響を及ぼしていると考えられる。
In the fine silver powder according to the present invention, the unevenness is formed on the surface in order to make it easy to attach organic matter to the surface of the fine silver powder. The unevenness formed on the surface can be defined in terms of size to the extent that organic substances are sufficiently adsorbed. In the case of approximately spherical or approximately polyhedral particles with organic substances adsorbed on the surface, the mechanism by which the heat shrinkage start temperature shifts to the high temperature side has not been elucidated, but is presumed as follows.
Organic substances present in the irregularities formed on the surface of substantially spherical or polyhedral particles are decomposed into carbon during firing, preventing diffusion between silver particles and shifting the heat shrinkage start temperature to the high temperature side it is conceivable that. At the same time, it is considered that the contact portion between the silver particles is reduced by making the fine silver powder into a substantially spherical shape or a substantially polyhedral shape, affecting the heat shrinkage starting temperature.
さらに、本発明に係る微粒銀粉として、銀粒子を超高圧に加圧して対向衝突させることにより、銀粒子の分散と銀粒子表面への有機物吸着を同時に行なうことにより得られるものとしたのは、超高圧に加圧して対向衝突させることにより、銀粒子表面に銀中にカーボンが均一に分散した複合層が形成されて銀粒子の焼結が阻害され、熱収縮開始温度を高温側にシフトさせる効果がより大きくなると考えられるためである。
なお、微粒銀粉表面への有機物吸着量は、カーボン量として０．２〜１．０質量％であることが好ましい。すなわち、０．２質量％未満では銀粒子の焼結を阻害する効果が十分でなく、他方、導電性を考慮しない場合にはカーボン量の上限は特に限定されるものではないが、導電性ペースト用として用いる場合には、１．０質量％を超えると焼成後の導電性が十分ではなくなり好ましくないためである。
Furthermore, as the fine silver powder according to the present invention, it was obtained by simultaneously performing dispersion of silver particles and adsorption of organic substances on the surface of the silver particles by pressurizing the silver particles to an ultrahigh pressure to collide with each other. By applying ultra-high pressure and making it face and collide, a composite layer in which carbon is uniformly dispersed in silver is formed on the surface of the silver particles, inhibiting the sintering of the silver particles and shifting the heat shrinkage start temperature to the high temperature side. This is because the effect is considered to be greater.
In addition, it is preferable that the organic substance adsorption amount to the fine silver powder surface is 0.2-1.0 mass% as a carbon amount. That is, if the amount is less than 0.2% by mass, the effect of inhibiting the sintering of silver particles is not sufficient. On the other hand, the upper limit of the amount of carbon is not particularly limited when the conductivity is not considered, but the conductive paste This is because when the amount is more than 1.0% by mass, the conductivity after firing is not sufficient and is not preferable.
本発明において、微粒銀粉の平均粒径を０．１〜２μｍ、最大粒径を１０μｍ以下としたのは、以下に記載する理由による。
すなわち、平均粒径が０．１μｍ未満では熱収縮開始温度の改善が十分でなく、他方、平均粒径が２μｍまたは最大粒径が１０μｍを超えると、電子回路のファインピッチ化に対応困難となるためである。なお、ファインビア埋め用の導電ペースト用フィラーとして使用する場合には、平均粒径を０．１〜１μｍとし、最大粒径を５μｍ以下とするのが好ましい。
In the present invention, the reason that the average particle size of the fine silver powder is 0.1 to 2 μm and the maximum particle size is 10 μm or less is as follows.
That is, when the average particle size is less than 0.1 μm, the heat shrinkage start temperature is not sufficiently improved. On the other hand, when the average particle size is 2 μm or the maximum particle size exceeds 10 μm, it is difficult to cope with fine pitches in electronic circuits. Because. In addition, when using as a filler for conductive pastes for filling fine vias, it is preferable that the average particle size is 0.1 to 1 μm and the maximum particle size is 5 μm or less.
また、本発明の微粒銀粉の熱収縮開始温度を８００℃以上としたのは、焼成時におけるセラミックス材料との熱収縮挙動の差が少なくなり、セラミック基板として焼成した場合にクラックやデラミネーションの発生を防止することができるためである。なお、熱収縮開始温度の上限は特に限定するものではないが、銀の融点（９６１．８℃）を考慮すると、本発明の微粒銀粉においては９５０℃が限度である。微粒銀粉の熱収縮開始温度は、熱機械分析装置（例えば、ブルカー・エイエックスエス（株）製、ＴＭＡ４０００ＳＡ）を用いて測定することができる。 In addition, the thermal shrinkage start temperature of the fine silver powder of the present invention is set to 800 ° C. or more because the difference in thermal shrinkage behavior with the ceramic material during firing is reduced, and cracks and delamination occur when fired as a ceramic substrate. It is because it can prevent. The upper limit of the heat shrink start temperature is not particularly limited, but considering the melting point of silver (961.8 ° C.), the upper limit is 950 ° C. in the fine silver powder of the present invention. The thermal shrinkage start temperature of the fine silver powder can be measured using a thermomechanical analyzer (for example, TMA4000SA manufactured by Bruker AXS Co., Ltd.).
本発明の微粒銀粉に係る製造方法において、スラリー化工程で得たスラリーを分散化工程で１００ＭＰａ以上の超高圧で対向衝突させることとしたのは、スラリーを超高圧で対向衝突させることにより、銀粒子を分散化し、表面改質を行うことができるためである。
すなわち、湿式分散装置を用いてスラリーを超高圧で対向衝突させることで、銀粒子の凝集を解砕するとともに、表面を凹凸にして略球状もしくは略多面体状とすること、表面に有機物を吸着させること、あるいは、微粉自体を緻密化させることなどの効果で熱収縮開始温度を高温側にシフトさせることができるためである。ここで、スラリーを対向衝突させる圧力を１００ＭＰａ以上の超高圧としたのは、１００ＭＰａ未満では、前記のような効果が十分に得られず熱収縮開始温度を高温側にシフトさせることができないためである。なお、対向衝突させる圧力としては、１００〜２４５ＭＰａとすることがより好ましく、２００〜２４５ＭＰａとすることが特に好ましい。現状では、２４５ＭＰａを超える圧力で対向衝突させる装置はないが、２４５ＭＰａを超える圧力でも前記のような効果は得られるものと考えられる。
In the manufacturing method according to the fine silver powder of the present invention, the slurry obtained in the slurrying step is made to collide with the ultrahigh pressure of 100 MPa or more in the dispersion step because the slurry is made to collide with the ultrahigh pressure by silver. This is because the particles can be dispersed and surface modification can be performed.
That is, the slurry is made to collide with the slurry at an ultrahigh pressure using a wet disperser to break up the aggregation of the silver particles, make the surface uneven and have a substantially spherical or substantially polyhedral shape, and adsorb organic substances on the surface. This is because the heat shrinkage start temperature can be shifted to the high temperature side by the effect of densifying the fine powder itself. Here, the pressure at which the slurry collides oppositely is set to an ultrahigh pressure of 100 MPa or more because if the pressure is less than 100 MPa, the above-described effects cannot be obtained sufficiently and the heat shrinkage start temperature cannot be shifted to the high temperature side. is there. In addition, it is more preferable to set it as 100-245 MPa as a pressure made to oppose, and it is especially preferable to set it as 200-245 MPa. At present, there is no device that collides oppositely at a pressure exceeding 245 MPa, but it is considered that the above-described effect can be obtained even at a pressure exceeding 245 MPa.
湿式分散装置としては、カウンタージェットミル方式の湿式分散装置を用いることができる。例えば、スギノマシン製スターバーストが挙げられる。他の方式としては、例えば、高圧を用いるアドバンスト・ナノ・テクノロジィ製ナノメーカーなどを用いることができるが、カウンタージェットミル方式の装置を用いることが好ましく、前記スターバーストを用いることが特に好ましい。 As the wet dispersion apparatus, a counter jet mill type wet dispersion apparatus can be used. For example, Starburst made by Sugino Machine can be mentioned. As another method, for example, a nano maker manufactured by Advanced Nano Technology using a high pressure can be used, but it is preferable to use a counter jet mill type device, and it is particularly preferable to use the starburst.
本発明の製造方法においては、銀粒子をスラリーとして衝突部へ導入して銀粒子の処理を行うが、その導入回数を１〜１５回と限定したのは、１回未満では分散性について最適化できず、他方、１５回を超えると凝集を起こす可能性があるためである。なお、好ましくは５〜１０回である。５回未満では、分散性の最適化が十分でないことがあり、５回以上とすることがより好ましい。 In the production method of the present invention, the silver particles are introduced into the collision part as a slurry to treat the silver particles, and the number of introductions is limited to 1 to 15 times. On the other hand, if it exceeds 15 times, aggregation may occur. In addition, Preferably it is 5-10 times. If it is less than 5 times, optimization of dispersibility may not be sufficient, and it is more preferably 5 times or more.
本発明の微粒銀粉の製造方法に用いる銀粒子は、元々結晶性が良い熱プラズマを用いた方法により作製した銀粒子を用いることが好ましい。また、本発明の製造方法では、ＳＥＭ観察等によって確認できる１次粒子より微細な微細銀粉を得ることができないため、前記１次粒子の平均粒径が０．１〜２μｍで最大粒径が１０μｍ以下の銀粒子を用いる必要がある。ただし、１μｍ以上の微粒銀粉を得ようとする場合には、アトマイズ法から作製した銀粒子を用いてもよい。なお、湿式法による銀粒子を用いても効果は得られるが、好ましくは高温熱処理を行う乾式法による銀粒子を用いることが好ましい。いうまでもなく銀合金粒子あるいは複合銀粒子を用いても本発明の製造方法による効果は得られる。 As the silver particles used in the method for producing fine silver powder of the present invention, it is preferable to use silver particles produced by a method using thermal plasma with good crystallinity. Further, in the production method of the present invention, fine silver powder finer than the primary particles that can be confirmed by SEM observation or the like cannot be obtained. Therefore, the average particle size of the primary particles is 0.1 to 2 μm and the maximum particle size is 10 μm. It is necessary to use the following silver particles. However, in order to obtain fine silver powder of 1 μm or more, silver particles produced by an atomizing method may be used. In addition, although the effect is acquired even if it uses the silver particle by a wet method, It is preferable to use the silver particle by the dry method which performs high temperature heat processing preferably. Needless to say, the effects of the production method of the present invention can be obtained even when silver alloy particles or composite silver particles are used.
スラリー化工程における有機溶媒と銀粒子のスラリーを得る方法としては、特に限定されるものではなく、超音波撹拌機、羽撹拌機、ミキサー等などの通常の方法が用いられる。 The method for obtaining the slurry of the organic solvent and silver particles in the slurrying step is not particularly limited, and usual methods such as an ultrasonic stirrer, a blade stirrer, and a mixer are used.
本発明の微粒銀粉の製造方法は、有機溶媒中に銀粒子を分散させたスラリー同士を衝突させるため、導電性ペーストに使われている有機溶剤を溶媒として使用すれば、分離工程を省略して、処理したスラリーをそのまま、熱収縮開始温度の高い熱収縮挙動が改善された導電性ペースト用分散液として使用できる。例えば、有機溶媒として導電性ペーストに使われている有機溶剤であるテルピネオールを用いれば、有機溶媒による表面被覆、あるいは、不純物混入がなく極めて有利であり、そのままペースト化できる利点があるため、低コストに製造できる。 In the method for producing fine silver powder of the present invention, the slurry in which silver particles are dispersed in an organic solvent collides with each other. Therefore, if the organic solvent used in the conductive paste is used as a solvent, the separation step is omitted. The treated slurry can be used as it is as a dispersion for conductive paste with improved heat shrinkage behavior having a high heat shrinkage starting temperature. For example, the use of terpineol, which is an organic solvent used in conductive pastes, as an organic solvent is extremely advantageous without surface coating with an organic solvent or contamination with impurities. Can be manufactured.
前記有機溶媒としては、芳香族系、アルコール系、エステル系、ケトン系などの有機溶剤、例えば、テルピネオール、ジヒドロテルピネオール、エチルセルソルブ、ブチルセルソルブ、エチルカルビトール、ブチルカルビトール、又はそれらの酢酸エステル、ペンタンジオールアルキルエーテル、ジブチルフタレート、γ−ブチロラクトン等が挙げられる。 Examples of the organic solvent include aromatic solvents, alcohol solvents, ester solvents, ketone solvents, and the like, such as terpineol, dihydroterpineol, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, or acetic acid thereof. Examples thereof include esters, pentanediol alkyl ethers, dibutyl phthalate, and γ-butyrolactone.
本発明の製造方法においては、導電ペーストに用いられる有機溶剤を用いた処理を行い、導電性ペースト用分散液を得るほうが、分離の必要もなく、コスト面を考慮すると好ましいが、分離して得られた乾粉状態の微粒銀粉を再度、有機溶媒に分散させて導電性ペースト用分散液を得ても特に問題はない。乾粉状態の微粒銀粉を得るためには、有機溶媒と微粒銀粉の分離が必要であるが、用いられる方法としては、特に限定されるものではなく、遠心分離、揮発性溶媒による洗浄等が用いられる。
［実施例］
In the production method of the present invention, it is preferable to perform the treatment using the organic solvent used for the conductive paste to obtain a dispersion for the conductive paste because there is no need for separation, but considering the cost, it can be obtained separately. There is no particular problem even if the obtained finely divided silver powder in a dry powder state is dispersed again in an organic solvent to obtain a dispersion for conductive paste. In order to obtain a fine silver powder in a dry powder state, it is necessary to separate the organic solvent and the fine silver powder, but the method used is not particularly limited, and centrifugation, washing with a volatile solvent, and the like are used. .
[Example]
次に、本発明の実施例について説明する。
本実施例では、原料の銀粒子として、熱プラズマを用いて作製した球状銀粒子を用いた。図１は熱プラズマを用いて作製した原料の略球状銀粒子を示す顕微鏡写真である。この球状銀粒子は、原料スラリーを例えばスギノマシン製スターバーストラボに導入し超音波を照射して分散化させて作製したものである。原料スラリーは、略球状銀粒子（粒度分布：Ｄ１０＝０．３７μｍ、Ｄ５０＝１．３２μｍ、Ｄ９０＝２．８２μｍ、Ｄ１００＝６．５４μｍ、純度＞９９．５％）２０重量部をテルピネオール８０重量部中に混合して、超音波を３分間照射して分散化させて作製した。本発明の実施例１〜２においては、前記スギノマシン製スターバーストラボを用い、超高圧に加圧した原料（スラリー）を超高速で噴射・衝突させて得た微細銀粉を採用した。
Next, examples of the present invention will be described.
In this example, spherical silver particles produced using thermal plasma were used as the raw material silver particles. FIG. 1 is a photomicrograph showing substantially spherical silver particles of a raw material produced using thermal plasma. The spherical silver particles are produced by introducing a raw slurry into, for example, a starburst laboratory manufactured by Sugino Machine and dispersing it by irradiating ultrasonic waves. The raw material slurry was 80 parts by weight of terpineol with 20 parts by weight of substantially spherical silver particles (particle size distribution: D10 = 0.37 μm, D50 = 1.32 μm, D90 = 2.82 μm, D100 = 6.54 μm, purity> 99.5%). The mixture was mixed in the part and irradiated with ultrasonic waves for 3 minutes for dispersion. In Examples 1 and 2 of the present invention, fine silver powder obtained by spraying and colliding a raw material (slurry) pressurized to an ultra-high pressure at an ultra-high speed using the above-mentioned Sugino Machine Starburst Lab.
なお、本実施例１、２における各種測定は、以下の方法にて行なった。
（１）走査型電子顕微鏡観察：走査型電子顕微鏡（（株）日立ハイテクノロジーズ製、Ｓ−４７００：以下ＦＥ−ＳＥＭと記載）を用いて観察した。
（２）粒度分布測定：微粒銀粉を約０．１ｇ採取し、分散媒として０．２重量％のヘキサメタリン酸ナトリウム水溶液を約５０ｍｌ添加した後、超音波ホモジナイザー（株式会社日本精機製作所社製、ＵＳ−３００Ｔ）により、３００μＡの出力で１分間分散させてサンプル液を調製した。レーザー回折法（日機装（株）製、ＭＩＣＲＯＴＲＡＣ ＨＲＡ ＭＯＤＥＬ：９３２０−Ｘ１００）によりサンプル液を測定した。平均粒径は、体積積算で５０％の値（Ｄ５０）を用いた。（３）熱機械分析（熱収縮挙動）：微粒銀粉をペレット状（φ約５×ｔ約１．５）に成型（加重２００ｋｇ、時間１分）した後、熱機械分析（ブルカー・エイエックスエス（株）製、ＴＭＡ４０００ＳＡ：以下ＴＭＡと記載）を用い、１０ｇの加重をかけながら、９８％窒素−２％水素混合ガス（２００ｍｌ／分）による還元性雰囲気中でおいて、熱収縮特性を測定した。熱収縮特性としては、０．５％収縮時の温度を熱収縮開始温度とし、８００℃における収縮率（％）とともに評価した。
Various measurements in Examples 1 and 2 were performed by the following methods.
(1) Scanning electron microscope observation: Observation was performed using a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, S-4700: hereinafter referred to as FE-SEM).
(2) Particle size distribution measurement: About 0.1 g of fine silver powder was collected, about 50 ml of 0.2 wt% sodium hexametaphosphate aqueous solution was added as a dispersion medium, and then an ultrasonic homogenizer (Nippon Seiki Seisakusho Co., Ltd., US -300T) to prepare a sample solution by dispersing for 1 minute at an output of 300 μA. The sample solution was measured by a laser diffraction method (manufactured by Nikkiso Co., Ltd., MICROTRAC HRA MODEL: 9320-X100). As the average particle size, a value of 50% (D50) in terms of volume integration was used. (3) Thermomechanical analysis (thermal shrinkage behavior): After molding fine silver powder into pellets (φ approx. 5 × t approx. 1.5) (loading 200 kg, time 1 minute), thermomechanical analysis (Bruker AXS) Using a TMA4000SA manufactured by Co., Ltd. (hereinafter referred to as TMA), the thermal shrinkage characteristics were measured in a reducing atmosphere with 98% nitrogen-2% hydrogen mixed gas (200 ml / min) while applying a weight of 10 g. did. As the heat shrinkage characteristics, the temperature at 0.5% shrinkage was regarded as the heat shrinkage start temperature, and the shrinkage rate (%) at 800 ° C. was evaluated.
前記原料スラリーを約０．５リットル／分で導入し、衝突圧力を２００ＭＰａとして衝突部への導入を１０回繰り返して処理を行い、微粒銀粉を得た。得られた微粒銀粉について、走査型電子顕微鏡観察（ＦＥ−ＳＥＭ）、粒度分布測定（レーザー回折法）、熱機械分析（ＴＭＡ）を行ない、評価した。
得られた微粒銀粉のＦＥ−ＳＥＭ写真を図２に示す。図２より、得られた微粒銀粉は、表面に凹凸があり凝集のない微粉末であることがわかる。また、この微粒銀粉の粒度分布は、体積積算でＤ１０＝０．２９μｍ、Ｄ５０＝０．４９μｍ、Ｄ９０＝１．５２μｍ、Ｄ１００＝４．６２μｍとなり、小粒径化していた。
微粒銀粉のＴＭＡ結果を図３に示す。得られた微粒銀粉の熱収縮開始温度は、９００℃以上と非常に高い温度を示し、８００℃における収縮率も０％であった。
The raw material slurry was introduced at a rate of about 0.5 liter / min, the collision pressure was set to 200 MPa, and the introduction into the collision part was repeated 10 times to obtain a fine silver powder. The obtained fine silver powder was evaluated by scanning electron microscope observation (FE-SEM), particle size distribution measurement (laser diffraction method), and thermomechanical analysis (TMA).
An FE-SEM photograph of the obtained fine silver powder is shown in FIG. FIG. 2 shows that the obtained fine silver powder is a fine powder having irregularities on the surface and no aggregation. In addition, the particle size distribution of the fine silver powder was D10 = 0.29 μm, D50 = 0.49 μm, D90 = 1.52 μm, D100 = 4.62 μm in volume integration, and the particle size was reduced.
The TMA result of the fine silver powder is shown in FIG. The heat shrinkage starting temperature of the obtained fine silver powder showed a very high temperature of 900 ° C. or higher, and the shrinkage rate at 800 ° C. was also 0%.
前記原料スラリーを約０．５リットル／分で導入し、衝突圧力を２００ＭＰａで衝突部への導入を５回繰り返して処理を行った以外は、実施例１と同様にして微粒銀粉を作製し、評価した。
得られた微粒銀粉は、実施例１とほぼ同様の粒度分布を示し、小粒径化されており、体積積算でＤ１０＝０．３２μｍ、Ｄ５０＝０．７６μｍ、Ｄ９０＝１．６２μｍ、Ｄ１００＝３．２７μｍとなっていた。また、得られた微粒銀粉のＴＭＡ結果を図３に併せて示す。得られた微粒銀粉の熱収縮開始温度は、８５３℃と高い温度を示し、８００℃における収縮率も０％であった。
［比較例１］
A fine silver powder was produced in the same manner as in Example 1 except that the raw material slurry was introduced at a rate of about 0.5 liters / minute, and the treatment was repeated 5 times by introducing the collision slurry at a collision pressure of 200 MPa. evaluated.
The obtained fine silver powder has almost the same particle size distribution as in Example 1 and has a reduced particle size. D10 = 0.32 μm, D50 = 0.76 μm, D90 = 1.62 μm, D100 = It was 3.27 μm. Moreover, the TMA result of the obtained fine silver powder is also shown in FIG. The heat shrinkage starting temperature of the obtained fine silver powder was as high as 853 ° C., and the shrinkage rate at 800 ° C. was also 0%.
[Comparative Example 1]
比較例として、原料の球状銀粒子についてＴＭＡを実施したところ、熱収縮開始温度は６０４℃と低く、８００℃における収縮率も６％と高い値であった。原料の球状銀粒子のＴＭＡ結果を図３に併せて示す。
［比較例２］
As a comparative example, when TMA was performed on the spherical silver particles of the raw material, the heat shrinkage start temperature was as low as 604 ° C., and the shrinkage rate at 800 ° C. was as high as 6%. The TMA results of the starting spherical silver particles are also shown in FIG.
[Comparative Example 2]
乾式法であるアトマイズ法で作製した球状銀粉（日本アトマイズ加工（株）製、ＨＸＲ―ＡＧ１．５、平均粒径１．５μｍ、純度＞９９．９％）をそのまま試料として用いた。その球状銀粉の粒径分布は、体積積算でＤ１０＝０．８８μｍ、Ｄ５０＝１．４７μｍ、Ｄ９０＝２．５８μｍ、Ｄ１００＝６．５４μｍであった。ＴＭＡ結果を図３に併せて示す。
本発明の微粒銀粉と比較すると、粒径分布が大きいにもかかわらず、熱収縮開始温度が６０６℃と低く、８００℃における収縮率も１２％と高かった。
［比較例３］
Spherical silver powder (manufactured by Nippon Atomization Co., Ltd., HXR-AG1.5, average particle size 1.5 μm, purity> 99.9%) produced by the atomization method, which is a dry method, was used as it was as a sample. The particle size distribution of the spherical silver powder was D10 = 0.88 μm, D50 = 1.47 μm, D90 = 2.58 μm, and D100 = 6.54 μm in volume integration. TMA results are also shown in FIG.
Compared with the fine silver powder of the present invention, although the particle size distribution was large, the thermal shrinkage start temperature was low at 606 ° C., and the shrinkage rate at 800 ° C. was also high at 12%.
[Comparative Example 3]
湿式法で作製した銀粉（同和鉱業（株）製、ＡＧ２−１Ｓ、平均粒径１．７μｍ、純度９９．６％）をそのまま試料として用いた。その球状銀粉の粒径分布は、体積積算でＤ１０＝０．７２μｍ、Ｄ５０＝１．６９μｍ、Ｄ９０＝３．４９μｍ、Ｄ１００＝１０．５μｍであった。ＴＭＡを図３に併せて示す。
本発明の微粒銀粉と比較すると、粒径分布が大きいにもかかわらず、熱収縮開始温度は２３２℃と低く、８００℃における収縮率も１０％と高かった。
Silver powder produced by a wet method (manufactured by Dowa Mining Co., Ltd., AG2-1S, average particle size 1.7 μm, purity 99.6%) was used as a sample as it was. The particle size distribution of the spherical silver powder was D10 = 0.72 μm, D50 = 1.69 μm, D90 = 3.49 μm, and D100 = 10.5 μm in volume integration. TMA is also shown in FIG.
Compared with the fine silver powder of the present invention, although the particle size distribution was large, the thermal shrinkage start temperature was as low as 232 ° C., and the shrinkage rate at 800 ° C. was also as high as 10%.
上記実施例から明らかなごとく、本発明によって得られる微粒銀粉は、解砕により原料の球状銀粒子と比較して粒度分布が小粒径化されているにもかかわらず、熱収縮開始温度が高温側にシフトして収縮率も低く、熱収縮挙動が改善されていることがわかる。したがって、本発明の微粒銀粉は主に電子回路基板の配線材料として使用される導電性ペースト用微粒銀粉として好適である。 As is clear from the above examples, the fine silver powder obtained by the present invention has a high heat shrinkage start temperature despite the fact that the particle size distribution is reduced by pulverization compared to the spherical silver particles of the raw material. It can be seen that the shrinkage rate is low and the heat shrinkage behavior is improved. Therefore, the fine silver powder of the present invention is suitable as a fine silver powder for conductive paste used mainly as a wiring material for electronic circuit boards.
本発明に係る微粒銀粉は、表面に吸着されている有機物が焼成時に分解してカーボンとなり、銀粒子間の拡散を防止すること、およびその形状が略球状もしくは略多面体状であるため銀粒子間の接触部分が減少することにより熱収縮開始温度が高温となり、また銀粒子を超高圧に加圧して対向衝突させて銀粒子の分散と銀粒子表面への有機物吸着を同時に行なうことにより得られるものであるから、収縮開始温度がさらに改善され、その上微細で粗粒を含まないため、ファインピッチ化が要求される電子回路基板用として特に好適である。さらに顔料、塗料、焼結助剤などとしての利用も可能である。
また、本発明に係る微粒銀粉の製造方法によれば、湿式分散装置を用いてスラリーを超高圧で対向衝突させることで、銀粒子の凝集を解砕するとともに、表面を凹凸にして略球状もしくは略多面体状とし、表面に有機物を吸着あるいは微粉自体を緻密化させることができることにより、高純度で熱収縮開始温度が高く、セラミック基板等の電子回路基板用として好適な微粒銀粉と導電性ペースト用分散液を効率よく低コストで製造することができ、その工業的価値は極めて大である。
In the fine silver powder according to the present invention, the organic substance adsorbed on the surface is decomposed to become carbon upon firing, and the diffusion between the silver particles is prevented, and since the shape thereof is substantially spherical or substantially polyhedral, it is between the silver particles. The heat shrinkage starting temperature becomes high due to the reduction of the contact part of the material, and it is obtained by simultaneously dispersing silver particles and adsorbing organic matter on the silver particle surface by pressurizing silver particles to ultra high pressure and colliding with each other Therefore, the shrinkage start temperature is further improved, and furthermore, since it is fine and does not contain coarse particles, it is particularly suitable for an electronic circuit board that requires a fine pitch. Further, it can be used as a pigment, paint, sintering aid, and the like.
In addition, according to the method for producing fine silver powder according to the present invention, the slurry is collided with ultrahigh pressure using a wet dispersion device to crush the agglomeration of the silver particles, and the surface is roughly spherical or Highly pure and highly heat-shrinkable starting temperature due to its substantially polyhedral shape, which can adsorb organic substances on the surface or make the fine powder itself dense, and is suitable for fine silver powder and conductive paste for electronic circuit boards such as ceramic boards The dispersion can be produced efficiently and at low cost, and its industrial value is extremely large.
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| JP2013196997A (en) * | 2012-03-22 | 2013-09-30 | Toray Ind Inc | Conductive composition |
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