JP5795096B2 - Silver paste excellent in low-temperature sinterability and method for producing the silver paste - Google Patents

Silver paste excellent in low-temperature sinterability and method for producing the silver paste Download PDF

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JP5795096B2
JP5795096B2 JP2014034554A JP2014034554A JP5795096B2 JP 5795096 B2 JP5795096 B2 JP 5795096B2 JP 2014034554 A JP2014034554 A JP 2014034554A JP 2014034554 A JP2014034554 A JP 2014034554A JP 5795096 B2 JP5795096 B2 JP 5795096B2
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silver
metal paste
silver particles
particles
amine
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JP2015159096A (en
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勇一 牧田
勇一 牧田
久保　仁志
仁志 久保
優輔 大嶋
優輔 大嶋
淳一 谷内
淳一 谷内
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Tanaka Kikinzoku Kogyo KK
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Priority to JP2014034554A priority Critical patent/JP5795096B2/en
Priority to TW104103853A priority patent/TWI542711B/en
Priority to KR1020187009140A priority patent/KR20180036799A/en
Priority to MYPI2016702566A priority patent/MY178751A/en
Priority to KR1020167023468A priority patent/KR101866111B1/en
Priority to CN201580010191.2A priority patent/CN106062886B/en
Priority to PCT/JP2015/054723 priority patent/WO2015129562A1/en
Priority to DE112015000957.4T priority patent/DE112015000957B4/en
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Publication of JP5795096B2 publication Critical patent/JP5795096B2/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B22F1/056—Submicron particles having a size above 100 nm up to 300 nm
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/07—Metallic powder characterised by particles having a nanoscale microstructure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/107—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material containing organic material comprising solvents, e.g. for slip casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/30—Making metallic powder or suspensions thereof using chemical processes with decomposition of metal compounds, e.g. by pyrolysis
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/09—Use of materials for the conductive, e.g. metallic pattern
    • H05K1/092—Dispersed materials, e.g. conductive pastes or inks
    • H05K1/097—Inks comprising nanoparticles and specially adapted for being sintered at low temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2301/00—Metallic composition of the powder or its coating
    • B22F2301/25—Noble metals, i.e. Ag Au, Ir, Os, Pd, Pt, Rh, Ru
    • B22F2301/255—Silver or gold

Description

本発明は、銀粒子が溶剤に分散する金属ペーストに関する。詳しくは、粒径１００〜２００ｎｍの銀粒子を必須的に含む金属ペーストであって、１５０℃以下の比較的低温でも焼結可能であり、且つ、低抵抗の銀焼結体を生成可能な金属ペーストに関する。   The present invention relates to a metal paste in which silver particles are dispersed in a solvent. Specifically, it is a metal paste that essentially contains silver particles having a particle size of 100 to 200 nm, and can be sintered at a relatively low temperature of 150 ° C. or lower and can produce a low-resistance silver sintered body. Regarding paste.

導電性の金属粒子を固形分として溶剤に混練・分散させた金属ペーストが、プリンテッドエレクトロニクスにおける回路形成材や、各種半導体素子を基板へ接合するための導電性接合材として使用されている。この金属ペーストは、基板や被接合部材へ塗布後に加熱焼成して金属粒子を焼結させることで回路・電極や接合部・接着部を形成するものである。   A metal paste in which conductive metal particles are kneaded and dispersed in a solvent as a solid content is used as a circuit forming material in printed electronics and as a conductive bonding material for bonding various semiconductor elements to a substrate. This metal paste is applied to a substrate or a member to be joined and then heated and fired to sinter the metal particles, thereby forming circuits / electrodes, joints / bonding portions.

そして、上記用途に対して特に有用な金属ペーストとして着目されているのが、金属粒子として銀粒子を適用する金属ペーストである。銀は比抵抗の低い金属であり、適切に形成された焼結体は導電膜として有効に作用することができる。また、銀は熱伝導性に優れるという利点もあり、銀を適用する金属ペーストは、パワーデバイス等の大電流化され動作温度が高温となる半導体機器製造のための接合材、熱伝導材としても有効であるとされている。   And it is metal paste which applies silver particle as a metal particle that attracts attention as a metal paste especially useful for the said use. Silver is a metal having a low specific resistance, and an appropriately formed sintered body can effectively act as a conductive film. In addition, silver has the advantage of excellent thermal conductivity, and the metal paste to which silver is applied can be used as a bonding material and heat conduction material for manufacturing semiconductor devices in which the operating temperature is increased due to the large current of power devices and the like. It is supposed to be effective.

銀粒子を適用する金属ペーストとしては、例えば、特許文献１に、平均一次粒子径が１〜２００ｎｍの銀ナノ粒子と沸点２３０℃以上の分散媒とからなり、更に、０．５〜３．０μｍのサブミクロン銀粒子を含む接合材が記載されている。特許文献１記載の金属ペーストからなる接合材は、銀粒子焼結のための接合温度（焼成温度）を２００℃以上としている。この接合温度は、ろう材による接合温度に比べると低温ということもできるが、十分に低温であるとはいい難い。接合温度の高低は被接合材である半導体素子へ影響を及ぼし得る要素であり、できる限り低温での焼結が可能であるものが望ましい。   As a metal paste to which silver particles are applied, for example, Patent Document 1 includes silver nanoparticles having an average primary particle diameter of 1 to 200 nm and a dispersion medium having a boiling point of 230 ° C. or more, and further 0.5 to 3.0 μm. A bonding material comprising submicron silver particles of the following is described. The bonding material made of the metal paste described in Patent Document 1 has a bonding temperature (sintering temperature) for silver particle sintering of 200 ° C. or higher. This bonding temperature can be said to be lower than that of the brazing material, but it is difficult to say that the bonding temperature is sufficiently low. The level of the joining temperature is an element that can affect the semiconductor element that is the material to be joined, and it is desirable that the joining temperature be as low as possible.

ここで、金属粒子の焼結温度に関しては、そのサイズ（粒径）の制御による調整の可能性が知られている。これはいわゆるナノサイズ効果と称されており、金属粒子は数十ｎｍ以下のナノレベルの微粒子となるとバルク材に比べて著しく融点が降下するという現象である。特許文献１記載の金属ペーストは、サブミクロンサイズの比較的大粒径の銀粒子を含むため低温での焼結は難しいと考えられるが、このナノサイズ効果を利用すれば、より低温で焼結可能な金属ペーストを得ることができると考えられる。   Here, regarding the sintering temperature of the metal particles, the possibility of adjustment by controlling the size (particle size) is known. This is referred to as a so-called nano-size effect, and is a phenomenon in which the melting point of the metal particles is remarkably lowered as compared with the bulk material when the nano-particles are tens of nanometers or less. The metal paste described in Patent Document 1 contains silver particles with a relatively large particle size of submicron size, so it is considered difficult to sinter at low temperatures. However, if this nanosize effect is used, sintering is performed at a lower temperature. It is believed that a possible metal paste can be obtained.

ナノレベルの銀粒子として特許文献２等による銀錯体の熱分解法により製造されたものが報告されている。熱分解法は、シュウ酸銀（Ａｇ２Ｃ２０４）等の熱分解性の銀化合物を原料として適宜の有機物と反応させて前駆体となる錯体を形成し、これを加熱し銀粒子を得る方法である。熱分解法によれば、比較的粒径の揃った平均粒径が数ｎｍ〜十数ｎｍの微小なナノレベルの銀粒子を製造できる。 As nano-level silver particles, those produced by a thermal decomposition method of a silver complex according to Patent Document 2 have been reported. In the thermal decomposition method, a heat-decomposable silver compound such as silver oxalate (Ag 2 C 2 0 4 ) is used as a raw material to react with an appropriate organic substance to form a precursor complex, which is heated to form silver particles. How to get. According to the thermal decomposition method, fine nano-level silver particles having an average particle diameter of a few nm to a few tens nm can be produced.

国際公開第２０１１／１５５６１５号パンフレットInternational Publication No. 2011/155615 Pamphlet 特開２０１０−２６５５４３号公報JP 2010-265543 A

しかし、本発明者等によれば、このナノレベルの銀粒子で構成した金属ペーストにも問題があることが確認されている。ナノレベルの銀粒子は２００℃以下の低温で焼結が生じるものの、焼結体の抵抗値がバルク材よりも相当高くなる傾向がある。この問題は、回路材料や導電性接合材としての金属ペーストにとってその有用性を大きく損なうものである。   However, according to the present inventors, it has been confirmed that there is a problem with the metal paste composed of the nano-level silver particles. Although nano-level silver particles are sintered at a low temperature of 200 ° C. or lower, the resistance value of the sintered body tends to be considerably higher than that of the bulk material. This problem greatly impairs the usefulness of the metal paste as a circuit material or a conductive bonding material.

そこで、本発明は、銀粒子を含む金属ペーストについて、低温域で銀粒子を焼結させることができ、その上で抵抗の低い焼結体や熱伝導性に優れた焼結体を形成可能なものを提供する。本発明において焼結温度の目標値としては、１５０℃以下の低温域を設定した。   Therefore, the present invention can sinter silver particles in a low temperature range for a metal paste containing silver particles, and can form a sintered body with low resistance and a sintered body with excellent thermal conductivity. Offer things. In the present invention, a low temperature range of 150 ° C. or lower was set as the target value of the sintering temperature.

上記課題を解決する本発明は、銀粒子からなる固形分と溶剤とを混練してなる金属ペーストにおいて、前記固形分が、粒径１００〜２００ｎｍの銀粒子を粒子数基準で３０％以上含む銀粒子で構成されており、 更に、固形分を構成する銀粒子は、保護剤として炭素数の総和が４〜８のアミン化合物が結合したものである金属ペーストである。   The present invention for solving the above-mentioned problems is a metal paste obtained by kneading a solid content composed of silver particles and a solvent, wherein the solid content contains 30% or more of silver particles having a particle size of 100 to 200 nm based on the number of particles. Furthermore, the silver particle which comprises solid content is a metal paste which the amine compound with a total of 4-8 carbon atoms couple | bonded as a protective agent.

本発明に係る金属ペーストは、溶剤と混練される固形分を構成する銀粒子について、粒径１００〜２００ｎｍの中程度の粒径範囲を有するものを一定割合以上含むものである。また、それら銀粒子は特定のアミン化合物からなる保護剤が結合したものである。本発明者等によると、本願の課題である低温での焼結可能性及び焼結体の低抵抗化は、主要な銀粒子の粒径範囲を上記範囲とすることと、適切な保護剤を選定することとの組合せの結果として有効に達成される。以下、本発明についてより詳細に説明する。   The metal paste according to the present invention contains silver particles constituting a solid content kneaded with a solvent having a medium particle size range of 100 to 200 nm in a certain ratio or more. Further, these silver particles are obtained by binding a protective agent made of a specific amine compound. According to the present inventors, the possibility of sintering at low temperatures and the reduction in resistance of the sintered body, which are the problems of the present application, are to make the particle size range of the main silver particles within the above range, and to use an appropriate protective agent. Effectively achieved as a result of the combination with the selection. Hereinafter, the present invention will be described in more detail.

本発明に係る金属ペーストでは、粒径１００〜２００ｎｍの銀粒子が固形分となる銀粒子全体に対して粒子数基準で３０％以上存在していることを要する。かかる中程度に微細な銀粒子が低温焼結に寄与するからである。ペーストに含まれる全ての銀粒子が粒径１００〜２００ｎｍであること、即ち、割合が１００％であることが好ましいが、そうである必要はない。粒径１００〜２００ｎｍの銀粒子が、３０％以上あれば、この粒径範囲外の粒子が存在していても良い。例えば、粒径１００〜２００ｎｍの銀粒子と粒径２０〜３０ｎｍの銀粒子とが混在した金属ペーストであっても、粒径１００〜２００ｎｍの銀粒子の割合が３０％以上であれば１５０℃以下での焼結が可能であり、焼結体の抵抗値も低いものとなる。また、粒径１００〜２００ｎｍの銀粒子に粒径５００ｎｍ超の粗大な銀粒子が混在した金属ペーストであっても良い。通常、５００ｎｍ（０．５μｍ）を超える粗大な銀粒子は２００℃以下で焼結することはない。しかし、本発明で適用する粒径１００〜２００ｎｍの銀粒子が一定割合以上存在すると、こうした粗大粒子も含めて銀粒子全体が低温で焼結する。   In the metal paste according to the present invention, it is necessary that silver particles having a particle size of 100 to 200 nm are present in an amount of 30% or more on the basis of the number of particles with respect to the entire silver particles as a solid content. This is because such moderately fine silver particles contribute to low temperature sintering. It is preferable that all silver particles contained in the paste have a particle size of 100 to 200 nm, that is, a ratio of 100%, but this need not be the case. If silver particles having a particle size of 100 to 200 nm are 30% or more, particles outside this particle size range may be present. For example, even if it is a metal paste in which silver particles having a particle size of 100 to 200 nm and silver particles having a particle size of 20 to 30 nm are mixed, if the ratio of the silver particles having a particle size of 100 to 200 nm is 30% or more, 150 ° C. or less. Sintering is possible, and the resistance value of the sintered body is low. Further, a metal paste in which coarse silver particles having a particle diameter of more than 500 nm are mixed with silver particles having a particle diameter of 100 to 200 nm may be used. Usually, coarse silver particles exceeding 500 nm (0.5 μm) are not sintered at 200 ° C. or lower. However, when silver particles having a particle diameter of 100 to 200 nm applied in the present invention are present in a certain ratio or more, the entire silver particles including such coarse particles are sintered at a low temperature.

粒径１００〜２００ｎｍの銀粒子の粒子数割合については、３０％未満の場合、１５０℃以下で焼結が全く生じないか不十分なものとなる。金属ペースト中の全銀粒子が粒径１００〜２００ｎｍであるもの、即ち、数割合が１００％となるものも当然に本発明の効果を有する。このように、本発明では、粒径１００〜２００ｎｍを軸としつつ、粒径の相違する銀粒子群が混在する場合があるが、全ての銀粒子を対象とした平均粒径（数平均）は、６０〜８００ｎｍとなるものが好ましい。   As for the ratio of the number of silver particles having a particle size of 100 to 200 nm, if it is less than 30%, sintering does not occur at 150 ° C. or lower or is insufficient. Naturally, all the silver particles in the metal paste have a particle size of 100 to 200 nm, that is, those having a number ratio of 100%, have the effect of the present invention. As described above, in the present invention, silver particle groups having different particle diameters may be mixed while having a particle diameter of 100 to 200 nm as an axis, but the average particle diameter (number average) for all silver particles is , 60 to 800 nm is preferable.

本発明に係るペーストにおいて、粒径１００〜２００ｎｍの銀粒子の焼結性は、銀粒子と結合する保護剤の作用も関連する。保護剤とは、溶剤中で懸濁する金属粒子の一部又は全面に結合する化合物であって、金属粒子の凝集を抑制するものである。本発明において、銀粒子と結合する保護剤は、炭素数の総和が４〜８のアミン化合物である。   In the paste according to the present invention, the sinterability of silver particles having a particle size of 100 to 200 nm is also related to the action of a protective agent that binds to the silver particles. The protective agent is a compound that binds to a part or the whole surface of metal particles suspended in a solvent, and suppresses aggregation of the metal particles. In the present invention, the protective agent that binds to the silver particles is an amine compound having a total carbon number of 4 to 8.

銀粒子の保護剤としては、一般にはアミン以外にカルボン酸類等の有機物が適用可能であるが、本発明で適用する保護剤としてアミン化合物に限定するのは、アミン以外の保護剤を適用する場合、１５０℃以下での銀粒子の焼結が生じないからである。この点、銀粒子の粒径が１００〜２００ｎｍの範囲内にあっても、アミン以外の保護剤では低温焼結が生じない。   As a protective agent for silver particles, organic substances such as carboxylic acids are generally applicable in addition to amines, but the protective agent applied in the present invention is limited to amine compounds when a protective agent other than amine is applied. This is because sintering of silver particles at 150 ° C. or lower does not occur. In this regard, even if the silver particles have a particle size in the range of 100 to 200 nm, low-temperature sintering does not occur with a protective agent other than amine.

また、保護剤であるアミン化合物についてその炭素数の総和を４〜８とするのは、銀粒子の粒径との関連でアミンの炭素数が銀粒子の安定性、焼結特性に影響を及ぼすからである。これは、炭素数４未満のアミンは粒径１００ｎｍ以上の銀微粒子を安定的に存在させるのが困難であり、均一な焼結体を形成させるのが困難となる。一方、炭素数８超のアミンは、銀粒子の安定性を過度に増大させ焼結温度を高温にする傾向がある。これらから、本発明の保護剤としては炭素数の総和が４〜８のアミン化合物に限定される。   In addition, the total number of carbon atoms of the amine compound as a protective agent is set to 4-8 because the carbon number of the amine affects the stability and sintering characteristics of the silver particles in relation to the particle size of the silver particles. Because. This is because it is difficult for an amine having less than 4 carbon atoms to stably present silver fine particles having a particle diameter of 100 nm or more, and it is difficult to form a uniform sintered body. On the other hand, amines having more than 8 carbon atoms tend to increase the stability of silver particles excessively and increase the sintering temperature. From these, the protective agent of the present invention is limited to amine compounds having 4 to 8 carbon atoms in total.

更に、アミン化合物については、沸点２２０℃以下のアミン化合物が好ましい。かかる高沸点のアミン化合物が結合した銀粒子は、粒径範囲が適切範囲にあっても焼結の際にアミン化合物が分離し難くなり焼結の進行を阻害することとなる。   Furthermore, the amine compound is preferably an amine compound having a boiling point of 220 ° C. or lower. Silver particles to which such a high-boiling amine compound is bonded are difficult to separate during sintering even if the particle size range is in an appropriate range, thus inhibiting the progress of sintering.

保護剤であるアミン化合物中のアミノ基の数としては、アミノ基が１つである（モノ）アミンや、アミノ基を２つ有するジアミンを適用できる。また、アミノ基に結合する炭化水素基の数は、１つ又は２つが好ましく、すなわち、１級アミン（ＲＮＨ２）、又は２級アミン（Ｒ２ＮＨ）が好ましい。そして、保護剤としてジアミンを適用する場合、少なくとも１以上のアミノ基が１級アミン又は２級アミンのものが好ましい。アミノ基に結合する炭化水素基は、直鎖構造又は分枝構造を有する鎖式炭化水素の他、環状構造の炭化水素基であっても良い。また、一部に酸素を含んでいても良い。本発明で適用する保護剤の好適な具体例としては、下記のアミン化合物が挙げられる。 As the number of amino groups in the amine compound as the protective agent, (mono) amine having one amino group or diamine having two amino groups can be applied. Further, the number of hydrocarbon groups bonded to the amino group is preferably one or two, that is, primary amine (RNH 2 ) or secondary amine (R 2 NH) is preferable. And when applying diamine as a protective agent, the thing whose at least 1 or more amino group is a primary amine or a secondary amine is preferable. The hydrocarbon group bonded to the amino group may be a hydrocarbon group having a cyclic structure in addition to a chain hydrocarbon having a linear structure or a branched structure. Further, oxygen may be partially included. Preferable specific examples of the protective agent applied in the present invention include the following amine compounds.

上記したアミン化合物からなる保護剤は、金属ペースト中の全ての銀粒子に結合していることが好ましい。本発明では、粒径１００〜２００ｎｍの銀粒子を必須とするが、この範囲外の粒径の銀粒子が混在することも許容する。このような異なる粒径範囲の銀粒子が混在する場合であっても、粒径１００〜２００ｎｍの銀粒子の保護剤が上記アミン化合物であることが当然要求されるが、１００〜２００ｎｍの範囲外の銀粒子についても上記のアミン化合物の保護剤が結合していることが求められる。但し、全く同一の化合物である必要はなく、炭素数の総和が４〜８のアミン化合物（例えば、表１記載の範囲内）であれば相違する保護剤を含んでいても良い。   It is preferable that the protective agent made of the above-described amine compound is bonded to all the silver particles in the metal paste. In the present invention, silver particles having a particle size of 100 to 200 nm are essential, but it is allowed to mix silver particles having a particle size outside this range. Even when silver particles having such different particle size ranges are mixed, the silver particle protective agent having a particle size of 100 to 200 nm is naturally required to be the amine compound, but it is out of the range of 100 to 200 nm. The silver particles are required to have the amine compound protective agent bound thereto. However, the compounds are not necessarily the same, and different protective agents may be included as long as the total number of carbon atoms is 4 to 8 (for example, within the range shown in Table 1).

そして、本発明に係る金属ペーストにおいては、低温焼結性の確保のため、保護剤であるアミン化合物が過不足ない量で含まれており、銀粒子に対して結合していることが好ましい。保護剤が少ない場合、銀粒子への保護効果が足りず、保管時において銀粒子同士が凝集して低温焼結性が損なわれることとなる。また、過剰に保護剤が銀粒子に結合する場合、焼結時にアミン消失による銀焼結体の体積収縮が大きくなり、焼結体にひび割れが多く発生するおそれがある。従って、本発明に係るペースト中の保護剤（アミン化合物）の量に関しては、ペースト中の窒素濃度と銀濃度のバランスが重要である。具体的には、窒素濃度（質量％）と銀粒子濃度（質量％）との比（Ｎ（質量％）／Ａｇ（質量％））で０．０００３〜０．００３であるものが好ましい。０．０００３未満では銀粒子への保護効果が不足し、０．００３を超えると焼結体に割れが発生するおそれが生じる。尚、金属ペースト中の窒素濃度は、ペーストの元素分析（ＣＨＮ分析等）により測定可能であり、銀粒子濃度はペースト製造時に使用する銀粒子質量及び溶剤量から容易に求めることができる。   And in the metal paste which concerns on this invention, in order to ensure low temperature sinterability, it is preferable that the amine compound which is a protective agent is contained in the quantity which is not excessive and insufficient, and has couple | bonded with the silver particle. When the amount of the protective agent is small, the protective effect on the silver particles is insufficient, and the silver particles agglomerate during storage and the low-temperature sinterability is impaired. Moreover, when a protective agent couple | bonds with silver particle excessively, there exists a possibility that the volume shrinkage of the silver sintered compact by amine loss | disappearance at the time of sintering may become large, and many cracks may generate | occur | produce in a sintered compact. Therefore, regarding the amount of the protective agent (amine compound) in the paste according to the present invention, the balance between the nitrogen concentration and the silver concentration in the paste is important. Specifically, the ratio of nitrogen concentration (mass%) to silver particle concentration (mass%) (N (mass%) / Ag (mass%)) is preferably 0.0003 to 0.003. If it is less than 0.0003, the protective effect on silver particles is insufficient, and if it exceeds 0.003, the sintered body may be cracked. The nitrogen concentration in the metal paste can be measured by elemental analysis (CHN analysis or the like) of the paste, and the silver particle concentration can be easily obtained from the mass of silver particles and the amount of solvent used during paste production.

以上説明した銀粒子の保護剤が結合した銀粒子は、溶剤中で分散・懸濁して金属ペーストとなる。この溶剤としては、炭素数８〜１６で構造内にＯＨ基を有する沸点２８０℃以下の有機溶剤が好ましい。銀粒子の焼結温度の目標を１５０℃以下とする場合、沸点２８０℃を超える溶剤は揮発・除去が困難だからである。この溶剤の好ましい具体例としては、ターピネオール（Ｃ１０、沸点２１９℃）、ジヒドロターピネオール（Ｃ１０、沸点２２０℃）、テキサノール（Ｃ１２、沸点２６０℃）、２，４−ジメチル−１，５−ペンタジオール（Ｃ９、沸点１５０℃）、２，２，４−トリメチル−１，３−ペンタンジオールジイソブチレート（Ｃ１６、沸点２８０℃）が挙げられる。溶剤は複数種を混合して使用しても良く、単品で使用しても良い。   The silver particles combined with the silver particle protective agent described above are dispersed and suspended in a solvent to form a metal paste. As this solvent, an organic solvent having a carbon number of 8 to 16 and having an OH group in the structure and a boiling point of 280 ° C. or lower is preferable. This is because when the silver particle sintering temperature target is set to 150 ° C. or lower, it is difficult to volatilize and remove a solvent having a boiling point higher than 280 ° C. Preferred examples of this solvent include terpineol (C10, boiling point 219 ° C.), dihydroterpineol (C10, boiling point 220 ° C.), texanol (C12, boiling point 260 ° C.), 2,4-dimethyl-1,5-pentadiol ( C9, boiling point 150 ° C.) and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (C16, boiling point 280 ° C.). A plurality of solvents may be used as a mixture, or may be used alone.

ペースト全体における溶剤と固形分（銀粒子）との混合比率については、溶剤含有率を質量比で５％〜６０％とするのが好ましい。５％未満ではペーストの粘度が高くなりすぎる。また、６０％を超えると必要な厚さの焼結体を得るのが困難となる。   About the mixing ratio of the solvent and solid content (silver particle) in the whole paste, the solvent content is preferably 5% to 60% by mass ratio. If it is less than 5%, the viscosity of the paste becomes too high. If it exceeds 60%, it becomes difficult to obtain a sintered body having a required thickness.

次に、本発明に係る金属ペーストの製造方法について説明する。本発明に係る金属ペーストは、上記した粒径１００〜２００ｎｍの銀粒子を３０％以上含む固形分を溶剤に混練することで製造される。そして、粒径１００〜２００ｎｍの銀粒子を３０％以上含む銀粒子からなる固形分を製造するため、粒径及び粒度分布を調整しつつ銀粒子を製造することが要求される。   Next, the manufacturing method of the metal paste which concerns on this invention is demonstrated. The metal paste according to the present invention is produced by kneading a solid containing 30% or more of silver particles having a particle size of 100 to 200 nm in a solvent. And in order to manufacture solid content which consists of silver particles which contain 30% or more of silver particles having a particle size of 100 to 200 nm, it is required to manufacture silver particles while adjusting the particle size and particle size distribution.

ここで本発明では、銀粒子の製造方法として、銀錯体を前駆体とした熱分解法を採用する。熱分解法は、シュウ酸銀（Ａｇ２Ｃ２０４）等の熱分解性を有する銀化合物を出発原料とし、これに保護剤になる有機化合物とで銀錯体を形成し、これを前駆体として加熱し、銀粒子を得る方法である。熱分解法は上記特許文献２でも適用されている方法であり、液相還元法（特許文献１に記載の方法）等の他の銀粒子製造方法より粒径調整が容易であり、比較的粒径の揃った銀粒子の製造が可能である。 Here, in this invention, the thermal decomposition method which used the silver complex as the precursor is employ | adopted as a manufacturing method of silver particle. The thermal decomposition method uses a silver compound having thermal decomposability such as silver oxalate (Ag 2 C 2 0 4 ) as a starting material, and forms a silver complex with an organic compound that serves as a protective agent. Is heated to obtain silver particles. The thermal decomposition method is also a method applied in the above-mentioned Patent Document 2. The particle size adjustment is easier than other silver particle production methods such as a liquid phase reduction method (the method described in Patent Document 1), and comparatively grain size. Silver particles with a uniform diameter can be produced.

但し、本発明者等によれば、これまでの熱分解法は、平均粒径で数ｎｍ〜十数ｎｍとなる微細な銀粒子の製造に好適であるが、本発明の対象となる粒径１００〜２００ｎｍの中程度に大きな粒径範囲を有する銀粒子を優先的に製造することは困難であった。本発明者等は熱分解法による銀粒子の生成機構を考慮し、銀錯体を熱分解して銀粒子とする際の反応系中の水分量を調整することで、粒径１００〜２００ｎｍの銀粒子を優先的に製造できるとした。   However, according to the present inventors, the conventional pyrolysis method is suitable for the production of fine silver particles having an average particle diameter of several nanometers to several tens of nanometers. It was difficult to preferentially produce silver particles having a moderately large particle size range of 100-200 nm. The present inventors consider the generation mechanism of silver particles by the pyrolysis method, and adjust the amount of water in the reaction system when the silver complex is pyrolyzed to form silver particles, whereby silver having a particle size of 100 to 200 nm is obtained. The particles were preferentially manufactured.

即ち、本発明における銀粒子の製造方法は、熱分解性を有する銀化合物とアミンとを混合して前駆体である銀−アミン錯体を製造し、前記前駆体を含む反応系を加熱することで銀粒子を製造する方法であって、前記加熱前の反応系の水分含有量を銀化合物１００重量部に対して５〜１００重量部とする。   That is, the method for producing silver particles in the present invention is to produce a silver-amine complex as a precursor by mixing a silver compound having thermal decomposability and an amine, and heating the reaction system containing the precursor. In the method for producing silver particles, the water content of the reaction system before heating is set to 5 to 100 parts by weight with respect to 100 parts by weight of the silver compound.

本発明の銀粒子の製造方法において、出発原料となる熱分解性を有する銀化合物としては、シュウ酸銀、硝酸銀、酢酸銀、炭酸銀、酸化銀、亜硝酸銀、安息香酸銀、シアン酸銀、クエン酸銀、乳酸銀等を適用できる。これら銀化合物のうち、特に好ましいのは、シュウ酸銀（Ａｇ２Ｃ２Ｏ４）又は炭酸銀（Ａｇ２ＣＯ３）である。シュウ酸銀や炭酸銀は、還元剤を要することなく比較的低温で分解して銀粒子を生成することができる。また、分解により生じる二酸化炭素はガスとして放出されることから、溶液中に不純物を残留させることも無い。 In the silver particle production method of the present invention, the silver compound having thermal decomposability as a starting material is silver oxalate, silver nitrate, silver acetate, silver carbonate, silver oxide, silver nitrite, silver benzoate, silver cyanate, Silver citrate, silver lactate, etc. can be applied. Of these silver compounds, silver oxalate (Ag 2 C 2 O 4 ) or silver carbonate (Ag 2 CO 3 ) is particularly preferable. Silver oxalate and silver carbonate can be decomposed at a relatively low temperature without requiring a reducing agent to produce silver particles. Further, since carbon dioxide generated by the decomposition is released as a gas, no impurities remain in the solution.

尚、シュウ酸銀については、乾燥状態において爆発性があることから、水又は有機溶媒（アルコール、アルカン、アルケン、アルキン、ケトン、エーテル、エステル、カルボン酸、脂肪酸、芳香族、アミン、アミド、ニトリル等）を混合し、湿潤状態にしたものを利用するのが好ましい。湿潤状態とすることで爆発性が著しく低下し、取り扱い性が容易となる。このとき、シュウ酸銀１００重量部に対して、５〜２００重量部の分散溶媒を混合したものが好ましい。但し、上記のとおり、本発明は反応系の水分量を厳密に規定しているため、水の混合は、規定量を超えない範囲にする必要がある。   Since silver oxalate is explosive in the dry state, water or an organic solvent (alcohol, alkane, alkene, alkyne, ketone, ether, ester, carboxylic acid, fatty acid, aromatic, amine, amide, nitrile Etc.) are preferably mixed and wetted. By making it wet, explosiveness is remarkably lowered and handling becomes easy. At this time, what mixed 5 to 200 weight part of dispersion solvents with respect to 100 weight part of silver oxalate is preferable. However, as described above, since the present invention strictly regulates the amount of water in the reaction system, the mixing of water needs to be within a range not exceeding the specified amount.

銀粒子の前駆体となる銀−アミン錯体は、上記銀化合物とアミン化合物とを混合・反応させて生成する。ここで使用するアミンは、上記の炭素数の総和が４〜８のアミン化合物が適用される。   The silver-amine complex serving as the precursor of the silver particles is produced by mixing and reacting the silver compound and the amine compound. As the amine used here, an amine compound having 4 to 8 carbon atoms in total is applied.

アミン化合物の混合量は、アミン化合物（保護剤）の質量と銀化合物中の銀の質量との比（アミン化合物（保護剤）の質量／Ａｇ質量）で２〜５となるようにしてアミン化合物量を調整する。未反応の銀化合物を生じさせることなく、十分な銀−アミン錯体を生成させるためである。尚、銀粒子に過剰なアミン化合物が結合していても、銀粒子製造後の洗浄により除去されることとなる。   The mixing amount of the amine compound is such that the ratio of the mass of the amine compound (protective agent) and the mass of silver in the silver compound (the mass of the amine compound (protective agent) / Ag mass) is 2 to 5, so that the amine compound is mixed. Adjust the amount. This is because a sufficient silver-amine complex is formed without generating an unreacted silver compound. Even if an excessive amine compound is bonded to the silver particles, it is removed by washing after the silver particles are produced.

銀化合物とアミン化合物との反応により銀−アミン錯体が生成し、銀粒子製造のための反応系が形成される。その後、この反応系を加熱することで銀粒子は生成するが、本発明ではこの段階において反応系中の水分量を規定する。反応系中の水分は、錯体の分解工程において加熱を均一に進行させる緩衝剤として作用すると考えられる。本発明では、水の緩衝作用を利用して、加熱時の反応系内の温度差を緩和しつつ、銀粒子の核生成や核成長を均一化しつつ促進するものである。   A silver-amine complex is formed by the reaction of the silver compound and the amine compound, and a reaction system for producing silver particles is formed. Thereafter, the reaction system is heated to produce silver particles. In the present invention, the amount of water in the reaction system is defined at this stage. It is considered that the water in the reaction system acts as a buffering agent that causes heating to proceed uniformly in the complex decomposition step. In the present invention, the buffering action of water is used to relax the temperature difference in the reaction system during heating, and promote nucleation and growth of silver particles while making them uniform.

反応系の水分含有量は、銀化合物１００重量部に対して５〜１００重量部の範囲内であることが必要である。水分含有量の好適範囲は５〜９５重量部であり、さらに好適な範囲は５〜８０重量部である。水分量が少ない（５重量部未満）と、得られる銀粒子の粒径は１００ｎｍ未満の微小なものが主体となり、１００〜２００ｎｍの銀粒子の割合が少なくなる。一方、水分量が多い（１００重量部を超える）と、銀粒子の粒径バラつきが大きくなりすぎ１００〜２００ｎｍの銀粒子の割合が少なくなる傾向となる。   The water content of the reaction system needs to be in the range of 5 to 100 parts by weight with respect to 100 parts by weight of the silver compound. A preferable range of the water content is 5 to 95 parts by weight, and a more preferable range is 5 to 80 parts by weight. When the amount of water is small (less than 5 parts by weight), the silver particles obtained are mainly fine particles having a particle size of less than 100 nm, and the proportion of silver particles of 100 to 200 nm is reduced. On the other hand, when the amount of water is large (exceeding 100 parts by weight), the particle size variation of the silver particles becomes too large, and the ratio of the silver particles of 100 to 200 nm tends to decrease.

尚、この反応系の水分含有量とは、加熱工程の直前段階における水分量であり、それまでに反応系に添加された水の量を考慮する必要がある。上記の通り、銀化合物としてシュウ酸銀を適用するときには、予め水を添加した湿潤状態で使用する場合があるが、この予め添加した水の量も、水分量に含められる。このため、銀化合物や均一化剤に予め添加された量だけで、水分含有量の規定範囲内となる場合、別途反応系の水分量を調節することなく、そのまま加熱することができる。一方、予め添加された量が、水分含有量の下限値（５重量部）より少なければ、別途単独で水を添加する等、水分量の調整が必要となる。水を添加するタイミングは、加熱工程の前であればよく、銀−アミン錯体の形成前、あるいは錯体形成後の、いずれの段階で添加してもよい。   The water content of the reaction system is the water content immediately before the heating step, and it is necessary to consider the amount of water added to the reaction system so far. As described above, when silver oxalate is applied as the silver compound, it may be used in a wet state in which water has been added in advance. The amount of water added in advance is also included in the amount of water. For this reason, when only the amount added in advance to the silver compound or the homogenizing agent falls within the specified range of the water content, it can be heated as it is without separately adjusting the water content of the reaction system. On the other hand, if the amount added in advance is less than the lower limit (5 parts by weight) of the water content, it is necessary to adjust the amount of water, such as adding water separately. The timing of adding water may be before the heating step, and may be added at any stage before formation of the silver-amine complex or after formation of the complex.

本発明では、銀−アミン錯体と適正範囲の水分で反応系を構成していれば良く、他の添加物がなくとも好適な粒径範囲の銀粒子を製造可能である。但し、使用するアミン化合物の関係等により、粒径分布の調整（１００〜２００ｎｍの銀粒子の割合の増大）、銀錯体の更なる安定化を図るための添加剤の添加を排除するものではない。   In the present invention, it is sufficient that the reaction system is composed of a silver-amine complex and an appropriate range of moisture, and silver particles having a suitable particle size range can be produced without other additives. However, adjustment of the particle size distribution (increase in the proportion of silver particles of 100 to 200 nm) and addition of additives for further stabilization of the silver complex are not excluded depending on the relationship of the amine compound used. .

本発明で適用可能な添加剤は、粒径分布を調整するための均一化剤である。この均一化剤は、アミドを骨格として有する化１で示される有機化合物である。この均一化剤は、反応系中の銀−アミン錯体の安定性を均一なものとして、錯体分解により銀粒子が生成する際の核生成・成長のタイミングを揃えることで、銀粒子の粒径を揃える添加剤である。   The additive applicable in the present invention is a homogenizing agent for adjusting the particle size distribution. This homogenizing agent is an organic compound represented by Chemical Formula 1 having an amide as a skeleton. This homogenizing agent makes the particle size of the silver particles uniform by making the stability of the silver-amine complex in the reaction system uniform and by aligning the timing of nucleation and growth when silver particles are produced by complex decomposition. Additives to align.

均一化剤として機能する有機化合物は、その骨格にアミド（カルボン酸アミド）（Ｎ−Ｃ＝Ｏ）を有することを要件とする。アミドの置換基（Ｒ、Ｒ’、Ｒ’’）には、Ｒとして水素、炭化水素、アミノ基又はこれらの組合せからなるアミノアルキル等を、また、Ｒ’、Ｒ’’として水素又は炭化水素を適用できる。本発明者等によれば、均一化剤である有機化合物のアミドが、銀−アミン錯体のアミン部分に作用して錯体が安定する。均一化剤である有機化合物の具体例としては、尿素及び尿素誘導体の他、Ｎ，Ｎ−ジメチルフォルムアミド（ＤＭＦ：（ＣＨ３）２ＮＣＨＯ）、Ｎ，Ｎ−ジエチルフォルムアミド（ＤＥＦ：（Ｃ２Ｈ５）２ＮＣＨＯ）、Ｎ，Ｎ−ジメチルアセトアミド（Ｃ４Ｈ９ＮＯ）、Ｎ，Ｎ−ジメチルプロピオンアミド（Ｃ５Ｈ１１ＮＯ）、Ｎ，Ｎ−ジエチルアセトアミド（Ｃ６Ｈ１３ＮＯ）等が挙げられる。尿素誘導体としては、１，３-ジメチル尿素（Ｃ３Ｈ８Ｎ２Ｏ）、テトラメチル尿素（Ｃ５Ｈ１２Ｎ２Ｏ）、１，３-ジエチル尿素（Ｃ５Ｈ１２Ｎ２Ｏ）などが挙げられる。 An organic compound that functions as a homogenizing agent is required to have an amide (carboxylic amide) (N—C═O) in its skeleton. In the amide substituent (R, R ′, R ″), R represents hydrogen, hydrocarbon, aminoalkyl or an amino group comprising a combination thereof, and R ′, R ″ represents hydrogen or hydrocarbon. Can be applied. According to the present inventors, the amide of the organic compound, which is a homogenizing agent, acts on the amine moiety of the silver-amine complex and the complex is stabilized. Specific examples of the organic compound as the homogenizing agent include urea, urea derivatives, N, N-dimethylformamide (DMF: (CH 3 ) 2 NCHO), N, N-diethylformamide (DEF: (C 2 H 5) 2 NCHO), N, N- dimethylacetamide (C 4 H 9 NO), N, N- dimethyl-propionamide (C 5 H 11 NO), N, N- diethylacetamide (C 6 H 13 NO) Etc. Examples of urea derivatives include 1,3-dimethylurea (C 3 H 8 N 2 O), tetramethylurea (C 5 H 12 N 2 O), 1,3-diethylurea (C 5 H 12 N 2 O), and the like. Is mentioned.

均一化剤を反応系への添加する場合、その量は銀化合物の銀のモル数（ｍｏｌＡｇ）に対する均一化剤のモル数（ｍｏｌ均一化剤）の比（ｍｏｌ均一化剤／ｍｏｌＡｇ）で、０．１以上とするのが好ましい。均一化剤として複数の有機化合物を同時に用いる場合は、その合計添加量を０．１以上とするのが好ましい。上記モル比が０．１未満であると、その効果が生じ難い。一方、上記モル比の上限値（均一化剤の上限量）については特に規定されるものではないが、銀粒子の純度を考慮すると銀化合物の銀に対して４以下とするのが好ましい。均一化剤は、液体の有機化合物の場合はそのまま添加するのが好ましい。また、尿素等のような固体の化合物の場合、固体のまま添加しても良く、水溶液で添加しても良い。但し、水溶液とする場合には、反応系の水分量を考慮する必要がある。 When the homogenizing agent is added to the reaction system, the amount is the ratio of the number of moles of the homogenizing agent (mol homogenizing agent ) to the number of moles of silver (mol Ag ) in the silver compound (mol homogenizing agent / mol Ag ). Therefore, it is preferably 0.1 or more. When a plurality of organic compounds are used simultaneously as the homogenizing agent, the total addition amount is preferably 0.1 or more. If the molar ratio is less than 0.1, the effect is difficult to occur. On the other hand, the upper limit of the molar ratio (the upper limit of the homogenizing agent) is not particularly specified, but is preferably 4 or less with respect to silver of the silver compound in consideration of the purity of the silver particles. The homogenizing agent is preferably added as it is in the case of a liquid organic compound. Further, in the case of a solid compound such as urea, it may be added as a solid or may be added as an aqueous solution. However, when the aqueous solution is used, it is necessary to consider the water content of the reaction system.

そして、反応系について、水分含有量の確認がなされ、必要に応じて添加剤を添加した後、反応系を加熱することで銀粒子が析出する。このときの加熱温度は、銀−アミン錯体の分解温度以上とするのが好ましい。上述の通り、銀−アミン錯体の分解温度は、銀化合物に配位するアミンの種類によって相違するが、本発明で適用されるアミン化合物の銀錯体の場合、具体的な分解温度は、９０〜１３０℃となる。   Then, the water content of the reaction system is confirmed, and after adding an additive as necessary, silver particles are precipitated by heating the reaction system. It is preferable that the heating temperature at this time be equal to or higher than the decomposition temperature of the silver-amine complex. As described above, the decomposition temperature of the silver-amine complex varies depending on the type of amine coordinated to the silver compound, but in the case of the silver complex of the amine compound applied in the present invention, the specific decomposition temperature is 90 to 130 ° C.

反応系の加熱工程において、加熱速度は析出する銀粒子の粒径に影響を及ぼすことから、加熱工程の加熱速度の調整により銀粒子の粒径をコントロールすることができる。ここで、加熱工程における加熱速度は、設定した分解温度まで、２.５〜５０℃／ｍｉｎの範囲で調整することが好ましい。   In the heating step of the reaction system, the heating rate affects the particle size of the precipitated silver particles, and therefore the particle size of the silver particles can be controlled by adjusting the heating rate of the heating step. Here, it is preferable to adjust the heating rate in a heating process in the range of 2.5-50 degreeC / min to the set decomposition temperature.

以上の加熱工程を経て銀粒子が析出する。析出した銀粒子は、固液分離を経て回収されて金属ペーストの固形分となる。ここで重要なのは回収される銀粒子に過剰なアミン化合物が結合しないように洗浄を行うことである。上記の通り、本発明においては銀粒子に対するアミン化合物の結合量（ペースト中の窒素含有量）を適切にすることが好ましい。そのため、銀粒子表面の保護に必要最低限のアミン化合物を残し、余剰のアミン化合物を系外へ除去することが必要となる。そのため、本発明では析出した銀粒子の洗浄が重要となる。   Silver particles precipitate through the above heating process. The precipitated silver particles are recovered through solid-liquid separation and become a solid content of the metal paste. What is important here is that washing is performed so that excessive amine compounds do not bind to the recovered silver particles. As described above, in the present invention, it is preferable to make the binding amount of the amine compound to the silver particles (the nitrogen content in the paste) appropriate. Therefore, it is necessary to leave the minimum amine compound necessary for protecting the surface of the silver particles and to remove the excess amine compound from the system. Therefore, in the present invention, it is important to wash the precipitated silver particles.

この銀粒子の洗浄は、溶媒としてメタノール、エタノール、プロパノール等の沸点が１５０℃以下のアルコール適用するのが好ましい。そして、洗浄の詳細な方法としては、銀粒子合成後の溶液に溶媒を加え、懸濁するまで攪拌した後、デカンテーションで上澄み液を除去することが好ましい。アミンの除去量は、加える溶媒の体積と洗浄回数で制御可能である。上述の一連の洗浄作業を洗浄回数１回とする場合、好ましくは、銀粒子合成後の溶液に対して１／２０〜３倍の体積の溶媒を使用し、１〜５回洗浄する。   For the washing of the silver particles, it is preferable to apply an alcohol having a boiling point of 150 ° C. or lower such as methanol, ethanol, propanol or the like as a solvent. And as a detailed method of washing | cleaning, after adding a solvent to the solution after silver particle synthesis | combination and stirring until it suspends, it is preferable to remove a supernatant liquid by decantation. The amount of amine removed can be controlled by the volume of solvent added and the number of washings. When the above-described series of cleaning operations is performed once, it is preferable to use a solvent having a volume of 1/20 to 3 times that of the solution after silver particle synthesis and to wash 1 to 5 times.

回収した銀粒子は固形分として適宜の溶剤と共に混練することで金属ペーストとすることができる。溶剤については上記したものが適用できる。尚、上記の工程による銀粒子の製造を２系統以上で行い、それらで製造される２種以上の銀粒子を混合したものを固形分とし、これを溶剤と混練して金属ペーストを製造しても良い。   The recovered silver particles can be made into a metal paste by kneading with an appropriate solvent as a solid content. As the solvent, those described above can be applied. In addition, the production of silver particles by the above process is performed in two or more systems, and a mixture of two or more kinds of silver particles produced by them is used as a solid content, which is kneaded with a solvent to produce a metal paste. Also good.

本発明に係る粒径制御された銀粒子を含む金属ペーストは、１５０℃以下の低温域であっても焼結可能であり、生成する焼結体はバルクの銀と同等の低抵抗値を示す。本発明に係る金属ペーストは、導電性の接合材料としての応用が可能であり、パワーデバイス等の大電流を取り扱う電気機器の接合材としても有用である。   The metal paste containing silver particles with controlled particle size according to the present invention can be sintered even at a low temperature range of 150 ° C. or lower, and the resulting sintered body exhibits a low resistance value equivalent to that of bulk silver. . The metal paste according to the present invention can be applied as a conductive bonding material, and is also useful as a bonding material for electrical devices that handle large currents such as power devices.

本実施形態における銀粒子製造工程を説明する図。The figure explaining the silver particle manufacturing process in this embodiment. 本実施形態で製造した銀粒子の形態を示すＳＥＭ写真。The SEM photograph which shows the form of the silver particle manufactured by this embodiment. 本実施形態で製造した金属ペーストの粒径分布を示す図。The figure which shows the particle size distribution of the metal paste manufactured by this embodiment. 本実施形態で製造した金属ペーストのＤＴＡ分析の結果を示す図。The figure which shows the result of the DTA analysis of the metal paste manufactured by this embodiment. 本実施形態で製造した金属ペーストの焼結過程の形態変化を示す写真。The photograph which shows the form change of the sintering process of the metal paste manufactured by this embodiment. 本実施形態で製造した属ペーストの焼結体の微視的構造を示す写真。The photograph which shows the microscopic structure of the sintered compact of the genus paste manufactured by this embodiment.

以下、本発明の好適な実施形態について説明する。本実施形態では、原料となる銀化合物、保護剤であるアミン化合物等の各種条件を変更しつつ銀粒子を製造し、溶剤と混練して金属ペーストを製造した後、その熱分析、焼結特性及び焼結体の抵抗の評価を行った。本実施形態における銀粒子の製造工程の概略を図１に示し、銀粒子の製造工程について説明する。   Hereinafter, preferred embodiments of the present invention will be described. In the present embodiment, silver particles are produced while changing various conditions such as a silver compound as a raw material and an amine compound as a protective agent, and after kneading with a solvent to produce a metal paste, its thermal analysis and sintering characteristics And the resistance of the sintered compact was evaluated. The outline of the manufacturing process of the silver particle in this embodiment is shown in FIG. 1, and the manufacturing process of a silver particle is demonstrated.

銀粒子の製造
本実施形態では、原料となる銀化合物としてシュウ酸銀１．４１ｇ又は炭酸銀１．２８ｇを銀含有量で１ｇとなるようにして使用した。これらの銀化合物に関しては、乾燥品のまま使用する場合と、水０．３ｇ（シュウ酸銀１００重量部に対して２１重量部、炭酸銀１００重量部に対して２３重量部）を加えて湿潤状態にしたものを用意した。 Production of Silver Particles In this embodiment, 1.41 g of silver oxalate or 1.28 g of silver carbonate was used as a raw material silver compound so that the silver content was 1 g. When these silver compounds are used as they are, they are moistened by adding 0.3 g of water (21 parts by weight with respect to 100 parts by weight of silver oxalate and 23 parts by weight with respect to 100 parts by weight of silver carbonate). I prepared something in a state.

そして、銀化合物に保護剤として各種アミン化合物を加えて銀−アミン錯体を製造した。銀化合物とアミンとの混合は室温で行い、クリーム状になるまで混練した。次に、製造した銀−アミン錯体について、場合により均一化剤として尿素溶液、ＤＭＦを組み合わせて添加した。また、水分量を考慮し、場合により水の添加も行った。そして、加熱前に反応系の水分量をチェックした。尚、保護剤については、アミン以外のものとしてオレイン酸を適用した例も用意している。   And various amine compounds were added to the silver compound as a protective agent, and the silver-amine complex was manufactured. The silver compound and amine were mixed at room temperature and kneaded until creamed. Next, the produced silver-amine complex was added in combination with a urea solution and DMF as a homogenizing agent. In consideration of the amount of water, water was sometimes added. And the water content of the reaction system was checked before heating. In addition, about the protective agent, the example which applied oleic acid as things other than an amine is also prepared.

水分量の確認がなされた反応系について、室温から加熱して銀−アミン錯体を分解し銀粒子を析出させた。このときの加熱温度は錯体の分解温度として１１０〜１３０℃を想定し、これを到達温度とした。また、加熱速度は、１０℃／ｍｉｎとした。   About the reaction system by which the moisture content was confirmed, it heated from room temperature, the silver-amine complex was decomposed | disassembled, and silver particle was deposited. The heating temperature at this time assumed 110-130 degreeC as a decomposition temperature of a complex, and made this the ultimate temperature. The heating rate was 10 ° C./min.

加熱工程においては、分解温度近傍から二酸化炭素の発生が確認された。二酸化炭素の発生がとまるまで加熱を継続し、銀粒子が懸濁した液体を得た。銀粒子の析出後、反応液にメタノールを添加して洗浄し、これを遠心分離した。この洗浄と遠心分離は２回行った。   In the heating process, generation of carbon dioxide was confirmed from around the decomposition temperature. Heating was continued until the generation of carbon dioxide stopped to obtain a liquid in which silver particles were suspended. After precipitation of silver particles, methanol was added to the reaction solution for washing, and this was centrifuged. This washing and centrifugation were performed twice.

以上の銀粒子の製造工程に関し、本実施形態では下記の１２種の銀粒子を製造した。また、図２に製造した銀粒子のＳＥＭ写真を示す。   Regarding the above silver particle production process, the following 12 types of silver particles were produced in this embodiment. Moreover, the SEM photograph of the silver particle manufactured in FIG. 2 is shown.

金属ペーストの製造
そして、製造した１２種の銀粒子を基に単独又は複数組み合わせて固形分とし、これに溶剤としてテキサノールを混練して金属ペーストを製造した。このときの固形分の割合は８０〜９５質量％である。製造した金属ペーストについては、適宜にサンプリングしてＳＥＭ観察を行い粒径分布を測定した。また、ＣＨＮ元素分析によりＮ含有量を測定して、銀含有量との比（Ｎ質量％／Ａｇ質量％）を算出した。 Production of Metal Paste Based on the 12 kinds of produced silver particles, a single or a plurality of silver particles were combined to obtain a solid content, and texanol was kneaded as a solvent to produce a metal paste. The ratio of solid content at this time is 80-95 mass%. About the manufactured metal paste, it sampled suitably and observed SEM and measured the particle size distribution. Moreover, N content was measured by CHN elemental analysis and ratio (N mass% / Ag mass%) with silver content was computed.

低温焼結試験
そして、上記で製造した金属ペーストを低温で焼結させて、焼結の有無、焼結体の電気抵抗、密着性（接合力）を評価した。この低温焼結試験は、各金属ペーストをＳｉ基板（金めっき付）に５０ｍｇ塗布（膜厚５０μｍを目標とした）し、昇温速度２℃／ｍｉｎで１５０℃まで昇温し、１５０℃に達した段階で２時間保持して焼結させた。焼結体の評価は、まずＳＥＭ観察し焼結体形成の有無を評価した後、体積抵抗率を測定した。更に、密着性評価のためのピール試験を行った。ピール試験は、焼結体に１０本×１０本（１００マトリックス）の切込みをカッターで入れた後、焼結体に粘着テープを貼付けたに後一気に剥がし、残存する焼結体のマトリックスの個数を数えた。評価基準として残存率９５％〜１００％の場合を密着性良好（○）とし、それ以下を密着性不良（×）と評価した。本実施形態で製造した金属ペーストについての分析結果及び低温焼結試験の結果を表３に示す。また、図３に、粒径分布の測定結果の例としてペーストｃ、ｆ、ｉ、ｋの結果を示す。 Low-temperature sintering test The metal paste produced above was sintered at a low temperature, and the presence / absence of sintering, electrical resistance of the sintered body, and adhesion (bonding force) were evaluated. In this low-temperature sintering test, 50 mg of each metal paste was applied to a Si substrate (with gold plating) (targeted to a film thickness of 50 μm), the temperature was raised to 150 ° C. at a rate of 2 ° C./min, and the temperature was increased to 150 ° C. At that stage, it was held for 2 hours and sintered. The sintered body was evaluated by first observing SEM and evaluating the presence or absence of the sintered body formation, and then measuring the volume resistivity. Furthermore, a peel test for evaluating adhesion was performed. In the peel test, 10 × 10 (100 matrix) incisions were made in the sintered body with a cutter, and then the adhesive tape was applied to the sintered body and then peeled off at once. I counted. As an evaluation criterion, the case where the residual rate was 95% to 100% was evaluated as good adhesion (◯), and the lower ratio was evaluated as poor adhesion (×). Table 3 shows the analysis results and low-temperature sintering test results for the metal paste manufactured in this embodiment. FIG. 3 shows the results of pastes c, f, i, and k as examples of the particle size distribution measurement results.

表３から、１５０℃での低温焼結性についてのみ考慮すれば、粒径１００〜２００ｎｍの銀粒子割合が３０％未満で平均粒径２０〜３０ｎｍである金属ペーストａ、ｂ、ｃは容易に焼結している。一方、平均粒径が大きい傾向にある金属ペーストｍ、ｎ、ｏは焼結し難い。これらの結果から、粒径と焼結温度には一応の相関性があるといえる。しかし、金属ペーストａ〜ｃは、焼結体を形成するもその抵抗値が高く、密着性にも劣る。また、焼結はしていたが、焼結体中にクラックが多数発生しており、粉化していた箇所もあった。抵抗値に関しては、クラックという空隙により、バルク体の銀の抵抗値（１．６μΩ・ｃｍ）よりも抵抗が大きくなったことによると考えられる。また、密着性についてもクラックの存在による影響が考えられるが、そもそも、これらの微細な銀粒子を主体とする金属ペーストにおいては十分な焼結がなされていないものと考えられる（詳細は、後述する熱的挙動の検討結果で説明する）。これらの結果から、銀粒子の低温焼結性と焼結体の低抵抗化との両立を図るためには、平均粒径のみで論じることは好ましくないといえる。   From Table 3, if only considering low-temperature sinterability at 150 ° C., metal pastes a, b, and c having a particle size ratio of 100 to 200 nm and an average particle size of 20 to 30 nm are easily obtained. Sintered. On the other hand, metal pastes m, n, and o that tend to have a large average particle size are difficult to sinter. From these results, it can be said that there is a temporary correlation between the particle size and the sintering temperature. However, although the metal pastes a to c form a sintered body, the resistance value is high and the adhesion is inferior. Moreover, although sintered, many cracks were generated in the sintered body and there were some powdered portions. Regarding the resistance value, it is considered that the resistance is larger than the resistance value (1.6 μΩ · cm) of the bulk silver due to the voids called cracks. In addition, the influence of the presence of cracks can be considered on the adhesion, but in the first place, it is considered that the metal paste mainly composed of these fine silver particles is not sufficiently sintered (details will be described later). This will be explained by the results of thermal behavior studies). From these results, it can be said that it is not preferable to discuss only the average particle size in order to achieve both low-temperature sinterability of silver particles and low resistance of the sintered body.

これに対して、好適粒径の銀粒子（粒径１００〜２００ｎｍ）を適度に含み、保護剤も適切な金属ペースト（ｄ〜ｆ、ｈ、ｊ〜ｌ）は、低温焼結性が良好であり、また、クラックも発生していなかった。そして、抵抗値もバルク体の銀に近い値であり、密着性も良好である。従って、これらの金属ペーストは、１５０℃という低温域であっても速やかに焼結したといえる。   On the other hand, metal pastes (d to f, h, j to l) that appropriately contain silver particles having a suitable particle size (particle size of 100 to 200 nm) and that have suitable protective agents have good low-temperature sinterability. There were no cracks. And resistance value is also a value close | similar to silver of a bulk body, and adhesiveness is also favorable. Therefore, it can be said that these metal pastes were rapidly sintered even in a low temperature range of 150 ° C.

尚、金属ペーストｇは、粒径１００〜２００ｎｍの銀粒子割合は好適であるが、沸点が２２０℃を超えるヒドロキシエチルアミノプロピルアミン（沸点：２５０℃）を適用したため、低温での焼結性は劣るといえる。また、保護剤としてアミン化合物ではなくオレイン酸を適用した金属ペーストｉに関しても、粒径１００〜２００ｎｍの銀粒子割合は好適であるものの低温焼結はできなかった。   In addition, although the silver particle ratio with a particle size of 100-200 nm is suitable for the metal paste g, since the hydroxyethylaminopropylamine (boiling point: 250 degreeC) whose boiling point exceeds 220 degreeC was applied, sinterability at low temperature is It can be said that it is inferior. Further, regarding the metal paste i to which oleic acid was applied instead of an amine compound as a protective agent, low-temperature sintering could not be performed although the ratio of silver particles having a particle size of 100 to 200 nm was suitable.

熱的挙動の分析
上記の低温焼結試験において、微細な銀粒子（粒径２０〜３０ｎｍ）を主体とする金属ペースト（ａ〜ｃ）は、焼結するものの焼結体にはクラックが多数生じ、密着性も悪いことが確認された。これに対し、本発明の粒径１００〜２００ｎｍの粒子を主とする金属ペーストでは、焼結も問題なく生じクラックもなかった。ここでは、この各金属ペーストの熱的挙動の相違点、割れの発生メカニズムを確認するための分析を行うこととした。 Analysis of thermal behavior In the low-temperature sintering test described above, the metal paste (a to c) mainly composed of fine silver particles (particle size 20 to 30 nm) is sintered, but a large number of cracks are generated in the sintered body. It was confirmed that the adhesion was also poor. On the other hand, the metal paste mainly composed of particles having a particle diameter of 100 to 200 nm of the present invention produced no problems and no cracks. Here, it was decided to conduct an analysis to confirm the difference in thermal behavior of each metal paste and the crack generation mechanism.

ところで、金属ペーストの熱的挙動の分析に関して、上記の低温焼結試験で行った熱履歴（１５０℃に２時間保持）は、金属ペーストの実際の使用方法に近いものの、加熱温度に変化が無く熱的挙動の解析には不向きである。そこで、本実施形態では、一定の昇温速度をもって金属ペーストを加熱するＴＧ−ＤＴＡ分析（示差熱分析）を行い、銀粒子の焼結に起因する発熱ピークの数及び発生温度を確認した。この金属ペーストのＤＴＡ分析においては昇温速度を、５℃／分〜２０℃／分とするのが好ましい。本実施形態では、測定温度範囲を室温から５００℃とし、１０℃／分の昇温速度で測定を行った。   By the way, regarding the analysis of the thermal behavior of the metal paste, the thermal history (held at 150 ° C. for 2 hours) performed in the low-temperature sintering test is close to the actual usage of the metal paste, but there is no change in the heating temperature. Not suitable for analysis of thermal behavior. Therefore, in the present embodiment, TG-DTA analysis (differential thermal analysis) for heating the metal paste at a constant temperature increase rate was performed to confirm the number of exothermic peaks and the generated temperature due to the sintering of the silver particles. In the DTA analysis of this metal paste, the rate of temperature rise is preferably 5 ° C./min to 20 ° C./min. In this embodiment, the measurement temperature range was from room temperature to 500 ° C., and the measurement was performed at a rate of temperature increase of 10 ° C./min.

そして、各金属ペーストについてＴＧ−ＤＴＡ分析を行ったところ、銀粒子の焼結に起因する発熱ピークの数、及び、発生位置（発生温度）についてグループ分けができることがわかった。即ち、発熱ピークの数については１本又は２本現れるものが区別できた。また、発生温度については２００℃を境に区別できた。今回測定したＤＴＡ曲線のうち、代表的な例として図４に、ペーストｃ、ｆ、ｉ、ｍのＤＴＡ曲線を示す。また、表４には、各金属ペーストについて測定したＤＴＡ曲線についての、銀粒子の焼結に起因する発熱ピークの数と発生温度の測定結果を示す。   And when TG-DTA analysis was performed about each metal paste, it turned out that it can group into the number of the exothermic peak resulting from sintering of silver particle, and a generation | occurrence | production position (generation temperature). In other words, the number of exothermic peaks could be distinguished from one or two. Further, the generated temperature could be distinguished at 200 ° C. as a boundary. Among the DTA curves measured this time, FIG. 4 shows DTA curves of pastes c, f, i, and m as a representative example. Table 4 shows the number of exothermic peaks due to the sintering of silver particles and the measurement results of the generated temperature for the DTA curve measured for each metal paste.

ＤＴＡ分析によれば、粒径２０〜３０ｎｍの微細銀粒子を主体とする金属ペースト（ａ〜ｃ）は、２００℃未満（１８０℃、１９０℃）での発熱ピークに加えて、２００℃以上（２１０℃、２３０℃）でも発熱ピークが発現する。ナノサイズ効果により低温での焼結が可能と思われるこれら金属ペーストにおいて低温での発熱ピークは当然に予測されるものである。しかし、このように複数の発熱ピークが発現するのは、微細銀粒子の焼結挙動が多段階で進行するためと考えられる。   According to the DTA analysis, the metal paste (ac) mainly composed of fine silver particles having a particle diameter of 20 to 30 nm has an exothermic peak below 200 ° C. (180 ° C., 190 ° C.), and more than 200 ° C. ( Even at 210 ° C. and 230 ° C., an exothermic peak appears. Naturally, the exothermic peak at low temperature is expected in these metal pastes, which are considered to be sintered at low temperature due to the nanosize effect. However, a plurality of exothermic peaks appear in this way because the sintering behavior of fine silver particles proceeds in multiple stages.

これに対比すると、本発明に係る粒径１００〜２００ｎｍの粒子を主とする金属ペースト（ｄ〜ｆ、ｈ、ｊ〜ｌ）は、ＤＴＡの結果において特徴的な挙動を示といえる。即ち、この金属ペーストは、ＤＴＡ曲線の銀粒子焼結に由来する発熱ピークが２００℃未満（１８０℃、１９０℃）の温度域で１本のみ発現する。発熱ピークが１本のみ発生するのは、銀粒子の焼結が１段階で完全に完了することを示す。この低温域で単発の発熱ピークが発現する現象は特異的なものである。   In contrast to this, it can be said that the metal paste (d to f, h, j to l) mainly composed of particles having a particle diameter of 100 to 200 nm according to the present invention exhibits a characteristic behavior in the result of DTA. That is, in this metal paste, only one exothermic peak derived from the silver particle sintering of the DTA curve appears in a temperature range of less than 200 ° C. (180 ° C., 190 ° C.). The occurrence of only one exothermic peak indicates that the silver particles are completely sintered in one stage. The phenomenon in which a single exothermic peak appears in this low temperature range is unique.

尚、今回のＤＴＡ分析では、銀粒子焼結に由来する発熱ピークが１８０℃付近で発現しており、上記低温焼結試験の温度（１５０℃）より高温となっている。この相違は加熱条件の相違によるものである。即ち、ＤＴＡ分析は常に加熱温度を変化（上昇）させるものであり、熱的要因のみによる焼結挙動を捉える分析手法だからである。金属ペーストの用途（配線材料、接合材料等）を考えれば、実際の使用に当たっては一定温度に保持して時間経過と共に焼結を進行させるものである。ＤＴＡ分析では、経時的要因は結果に反映されないことから、温度差が見られたといえる。そして、本実施形態の低温焼結試験は、実際の使用に際した加熱条件（１５０℃に固定して一定時間保持）に相当するものであり、この試験結果から本実施形態で好適な金属ペーストは低温焼結性に優れることが理解できる。   In this DTA analysis, an exothermic peak derived from silver particle sintering appears around 180 ° C., which is higher than the temperature of the low-temperature sintering test (150 ° C.). This difference is due to the difference in heating conditions. In other words, the DTA analysis always changes (increases) the heating temperature, and is an analysis method that captures the sintering behavior based only on thermal factors. Considering the use of the metal paste (wiring material, bonding material, etc.), in actual use, the temperature is maintained at a constant temperature and sintering proceeds with time. In the DTA analysis, the time difference was not reflected in the results, so it can be said that a temperature difference was observed. And the low-temperature sintering test of this embodiment is equivalent to the heating conditions (fixed at 150 ° C. and held for a certain period of time) in actual use. From this test result, the metal paste suitable for this embodiment is It can be understood that the low temperature sintering property is excellent.

また、粒径２０〜３０ｎｍの微細銀粒子を主体とする金属ペースト（ａ〜ｃ）の焼結体で見られたクラックについて、その要因はこの金属ペーストは２段階の焼結挙動を示す点にあると考えられる。この点に関して、図５はペーストｃ、ｆの１８０℃と２１０℃の焼結体のＳＥＭ写真である。１段階目にあたる１８０℃ではペーストｃ、ｆとも焼結体にクラックは生じていない。しかし、ｃにとって２段階目に相当する２１０℃では、ｃにのみクラックが多数生じている。つまり、ペーストｃにおけるクラックは、２段階目の焼結の際に発生したこととなる。多段階の焼結をしないペーストｆには、このようなクラックは生じないといえる。   In addition, regarding the cracks observed in the sintered body of the metal paste (ac) mainly composed of fine silver particles having a particle size of 20 to 30 nm, the cause is that the metal paste exhibits a two-stage sintering behavior. It is believed that there is. In this regard, FIG. 5 is an SEM photograph of 180 ° C. and 210 ° C. sintered bodies of pastes c and f. At 180 ° C., which is the first stage, no cracks occurred in the sintered bodies for both pastes c and f. However, at 210 ° C. corresponding to the second stage for c, many cracks are generated only in c. That is, the crack in the paste c is generated during the second stage sintering. It can be said that such a crack does not occur in the paste f not subjected to multi-stage sintering.

もっとも、焼結体全体の観察ではクラックの有無という点で、ペーストｃとペーストｆとは相違するが、微視的には近似している。図６は、図５の２１０℃加熱の写真を拡大したものである。この写真によると、ペーストｃ、ｆは、焼結体を構成する個々の粒子の形状・粒径（約５００ｎｍ）がよく似ている。このことから、銀の焼結体において熱的に安定な単位粒子（ユニット）の径は、焼結前の銀粒子の粒径によらずにおおよそ決まっているとの仮説が成り立つ。この仮説によれば、焼結前の銀粒子がナノ単位の微細粒子のみで構成されていると、上記の安定なユニットに成長するまでは粒子の移動量が大きくそれにより空隙が生じやすくなり、空隙の体積が限界を超えるとユニット同士の結合が切れ、クラックを引き起こすと推察される。   However, in the observation of the entire sintered body, the paste c and the paste f are different from each other in terms of the presence or absence of cracks, but are close to each other microscopically. FIG. 6 is an enlarged view of the photograph of 210 ° C. heating in FIG. According to this photograph, the pastes c and f are very similar in shape and particle size (about 500 nm) of individual particles constituting the sintered body. From this, the hypothesis holds that the diameter of the thermally stable unit particles (units) in the silver sintered body is roughly determined regardless of the particle diameter of the silver particles before sintering. According to this hypothesis, if the silver particles before sintering are composed only of nano-sized fine particles, the amount of movement of the particles is large until it grows into the above stable unit, which tends to cause voids, If the volume of the void exceeds the limit, it is assumed that the units are disconnected from each other and cause cracks.

以上説明した微細銀粒子の熱的挙動の他、ＤＴＡ分析の結果からは、銀粒子の保護剤として適切なアミンを選択することが必要であることが再確認される。保護剤としてアミン化合物ではなくオレイン酸を適用した場合においては、焼結による発熱ピークが1本ではあるが、その温度が２００℃以上と高くなる（金属ペーストｉ）。また、金属ペーストｇは、粒径１００〜２００ｎｍの銀粒子割合は好適であるが、沸点が高いアミン化合物を適用したため、発熱ピークは２００℃以上で発現した。尚、粒径が大きすぎる場合も、発熱ピークは２００℃以上でなければ発現しない（金属ペーストｍ）。   In addition to the thermal behavior of the fine silver particles described above, the results of DTA analysis reconfirm that it is necessary to select an appropriate amine as a protective agent for the silver particles. When oleic acid is used as a protective agent instead of an amine compound, the temperature is as high as 200 ° C. or more (metal paste i) although there is only one exothermic peak due to sintering. Moreover, although the silver particle ratio with a particle size of 100-200 nm is suitable for the metal paste g, since the amine compound with a high boiling point was applied, the exothermic peak expressed at 200 degreeC or more. Even when the particle size is too large, the exothermic peak does not appear unless it is 200 ° C. or higher (metal paste m).

以上説明したように、本発明に係る銀ペーストは、主たる銀粒子の粒径範囲を適切なものとすることで低温焼結性を獲得するものである。本発明により形成される銀焼結体は抵抗も低く、また、接合力も十分である。低温での焼結処理を必要とする配線材料や接合材料や熱伝導材料として広く使用可能である。
As described above, the silver paste according to the present invention acquires low-temperature sinterability by adjusting the particle size range of the main silver particles. The silver sintered body formed according to the present invention has a low resistance and a sufficient bonding strength. It can be widely used as a wiring material, a bonding material or a heat conduction material that requires a sintering process at a low temperature.

Claims (7)

銀粒子からなる固形分と溶剤とを混練してなる金属ペーストにおいて、
前記固形分が、粒径１００〜２００ｎｍの銀粒子を粒子数基準で３０％以上含む銀粒子で構成されており、
固形分を構成する銀粒子全体の平均粒径が、６０〜８００ｎｍであり、
更に、固形分を構成する銀粒子は、保護剤として炭素数の総和が４〜８のアミン化合物が結合しており、
ＴＧ−ＤＴＡ分析における銀粒子の焼結に起因する発熱ピークが２００℃未満で発現する金属ペースト。 In a metal paste formed by kneading a solid content composed of silver particles and a solvent,
The solid content is composed of silver particles containing 30% or more of silver particles having a particle size of 100 to 200 nm on the basis of the number of particles,
The average particle diameter of the entire silver particles constituting the solid content is 60 to 800 nm,
Furthermore, the silver particles constituting the solid content are bonded with an amine compound having a total carbon number of 4 to 8 as a protective agent ,
A metal paste in which an exothermic peak due to the sintering of silver particles in TG-DTA analysis appears at less than 200 ° C. 金属ペースト中の窒素濃度（質量％）と銀粒子濃度（質量％）との比（Ｎ／Ａｇ）が０．０００３〜０．００３である請求項１記載の金属ペースト。 2. The metal paste according to claim 1 , wherein a ratio (N / Ag) of a nitrogen concentration (mass%) and a silver particle concentration (mass%) in the metal paste is 0.0003 to 0.003. 保護剤であるアミン化合物は、ブチルアミン、１，４−ジアミノブタン、３−メトキシプロピルアミン、ペンチルアミン、２，２−ジメチルプロピルアミン、３−エトキシプロピルアミン、Ｎ，Ｎ−ジメチル−１，３−ジアミノプロパン、３−エトキシプロピルアミン、ヘキシルアミン、ヘプチルアミン、Ｎ，Ｎ−ジエチル−１，３−ジアミノプロパン、ベンジルアミンである請求項１又は請求項２のいずれかに記載の金属ペースト。 The amine compound as a protective agent is butylamine, 1,4-diaminobutane, 3-methoxypropylamine, pentylamine, 2,2-dimethylpropylamine, 3-ethoxypropylamine, N, N-dimethyl-1,3- The metal paste according to claim 1, which is diaminopropane, 3-ethoxypropylamine, hexylamine, heptylamine, N, N-diethyl-1,3-diaminopropane, or benzylamine. 溶剤は、炭素数８〜１６で構造内にＯＨ基を有する沸点２８０℃以下の有機溶剤である請求項１〜請求項３のいずれかに記載の金属ペースト。 The metal paste according to any one of claims 1 to 3 , wherein the solvent is an organic solvent having 8 to 16 carbon atoms and an OH group in the structure and having a boiling point of 280 ° C or lower. 銀粒子からなる固形分を製造し、前記固形分と溶剤とを混練する金属ペーストの製造方法において、
前記銀粒子の製造工程は、
（１）熱分解性を有する銀化合物とアミン化合物とを混合して、前駆体である銀−アミン錯体と水分とからなる反応系を形成する工程と、
（２）前記前駆体を含む反応系を前記銀−アミン錯体の分解温度以上に加熱して銀粒子を析出させる工程とからなり、
前記（２）の加熱前に反応系の水分含有量を、銀化合物１００重量部に対して５〜１００重量部とすることを特徴とする金属ペーストの製造方法。 In the method for producing a metal paste for producing a solid content composed of silver particles and kneading the solid content and a solvent,
The production process of the silver particles is as follows:
(1) A step of mixing a thermally decomposable silver compound and an amine compound to form a reaction system comprising a precursor silver-amine complex and moisture ;
(2) a step of heating the reaction system containing the precursor to a temperature equal to or higher than the decomposition temperature of the silver-amine complex to precipitate silver particles;
The method for producing a metal paste, wherein the water content of the reaction system is 5 to 100 parts by weight with respect to 100 parts by weight of the silver compound before the heating (2). 更に、（２）の加熱前の反応系に、アミドを骨格として有する下記式で示される有機化合物を１種又は２種以上添加する工程を含む請求項５記載の金属ペーストの製造方法。
Furthermore, the manufacturing method of the metal paste of Claim 5 including the process of adding the organic compound shown by the following formula which has amide | amido as a skeleton to the reaction system before a heating of (2).
熱分解性を有する銀化合物は、シュウ酸銀、硝酸銀、酢酸銀、炭酸銀、酸化銀、亜硝酸銀、安息香酸銀、シアン酸銀、クエン酸銀、乳酸銀のいずれか１種である請求項５又は請求項６記載の金属ペーストの製造方法。
Silver compounds with pyrolytic is silver oxalate, silver nitrate, silver acetate, silver carbonate, silver oxide, silver nitrite, silver benzoate, silver cyanate, silver citrate, claim is any one of silver lactate The manufacturing method of the metal paste of Claim 5 or Claim 6 .
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