JP5534745B2 - Conductive fine particles, anisotropic conductive material, and connection structure - Google Patents
Conductive fine particles, anisotropic conductive material, and connection structure Download PDFInfo
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Description
本発明は、導電層と低融点金属層との界面において破壊が生じにくく、高い接続信頼性を実現することが可能な導電性微粒子、該導電性微粒子を用いてなる異方性導電材料、及び、接続構造体に関する。 The present invention relates to conductive fine particles that are unlikely to break at the interface between the conductive layer and the low-melting-point metal layer, and that can realize high connection reliability, an anisotropic conductive material using the conductive fine particles, and The connection structure.
従来、電子回路基板において、ＩＣやＬＳＩは、電極をプリント基板にハンダ付けすることによって接続されていた。しかし、ハンダ付けでは、プリント基板と、ＩＣやＬＳＩとを効率的に接続することはできなかった。また、ハンダ付けでは、ＩＣやＬＳＩの実装密度を向上させることが困難であった。
これを解決するためにハンダを球状にした、いわゆる「ハンダボール」でＩＣやＬＳＩを基板に接続するＢＧＡ（ボールグリッドアレイ）が開発された。この技術によれば、チップ又は基板上に実装されたハンダボールを高温で溶融し基板とチップとを接続することで高生産性、高接続信頼性を両立した電子回路を構成することができる。
Conventionally, in an electronic circuit board, ICs and LSIs are connected by soldering electrodes to a printed circuit board. However, soldering cannot efficiently connect the printed circuit board to the IC or LSI. In addition, it is difficult to improve the mounting density of ICs and LSIs by soldering.
In order to solve this problem, a BGA (ball grid array) has been developed in which the solder is made into a spherical shape, so-called “solder balls” that connect the IC or LSI to the substrate. According to this technique, an electronic circuit that achieves both high productivity and high connection reliability can be configured by melting a solder ball mounted on a chip or a substrate at a high temperature and connecting the substrate and the chip.
しかし、近年、基板の多層化が進み、多層基板は使用環境の影響を受けやすいことから、基板に歪みや伸縮が発生し、基板間の接続部に断線が発生するという問題があった。 However, in recent years, since the number of substrates has been increased and multilayer substrates are easily affected by the use environment, there has been a problem that distortion and expansion / contraction occur in the substrates and disconnection occurs in the connection portion between the substrates.
このような問題に対し、特許文献１には、樹脂微粒子の表面に、導電性の高い金属が含まれる金属層（導電層）が形成され、さらに、金属層の表面に、錫等の金属からなる低融点金属層（ハンダ層）が形成された導電性微粒子が開示されている。このような導電性微粒子を用いれば、柔軟な樹脂微粒子が導電性微粒子に加わる応力を緩和でき、かつ、最表面に低融点金属層を形成することにより、電極間を容易に導電接続することができる。 For such a problem, Patent Document 1 discloses that a metal layer (conductive layer) containing a highly conductive metal is formed on the surface of resin fine particles, and further, a metal such as tin is formed on the surface of the metal layer. A conductive fine particle having a low melting point metal layer (solder layer) formed thereon is disclosed. If such conductive fine particles are used, the stress applied to the conductive fine particles by the flexible resin fine particles can be relaxed, and the low melting point metal layer can be formed on the outermost surface to easily conduct conductive connection between the electrodes. it can.
しかしながら、電解めっき等の方法によって金属層の表面に低融点金属層を形成した場合は、実装を行う際の加熱によって、金属層と低融点金属層との界面において割れ等の破壊が生じやすくなり、これに起因して得られる接続構造体等の接続信頼性が大幅に損なわれるという問題があった。 However, when a low melting point metal layer is formed on the surface of the metal layer by a method such as electrolytic plating, the heating during mounting tends to cause breakage such as cracking at the interface between the metal layer and the low melting point metal layer. As a result, there is a problem that the connection reliability of the connection structure and the like obtained due to this is greatly impaired.
本発明は、導電層と低融点金属層との界面において破壊が生じにくく、高い接続信頼性を実現することが可能な導電性微粒子、該導電性微粒子を用いてなる異方性導電材料、及び、接続構造体を提供することを目的とする。 The present invention relates to conductive fine particles that are unlikely to break at the interface between the conductive layer and the low-melting-point metal layer, and that can realize high connection reliability, an anisotropic conductive material using the conductive fine particles, and An object is to provide a connection structure.
本発明は、基材微粒子の表面に、導電層及び低融点金属層が順次形成されている導電性微粒子であって、１５０℃で３００時間加熱した後における導電層と低融点金属層との間の金属間拡散層の厚みが、導電層の厚みと低融点金属層の厚みとの合計に対して２０％以下である導電性微粒子である。
以下に本発明を詳述する。
The present invention is a conductive fine particle in which a conductive layer and a low melting point metal layer are sequentially formed on the surface of a substrate fine particle, and is heated between 150 ° C. for 300 hours between the conductive layer and the low melting point metal layer. The conductive fine particles in which the thickness of the intermetallic diffusion layer is 20% or less with respect to the total thickness of the conductive layer and the low melting point metal layer.
The present invention is described in detail below.
本発明は、鋭意検討した結果、電極間の導電接続において、金属層（導電層）と低融点金属層との界面に破壊が生じる要因として、導電層を構成する金属と低融点金属層を構成する金属との間に形成される金属間化合物からなる層（金属間拡散層）が関係していることを見出した。即ち、脆弱な金属間拡散層が形成されることで、外力に対して金属間拡散層が起点となって界面の破壊が発生することを見出した。
そして、本発明者らは更に鋭意検討した結果、１５０℃で３００時間加熱した後における導電層と低融点金属層との間の金属間拡散層の厚みを導電層の厚みと低融点金属層の厚みとの合計に対して２０％以下とした場合に、導電層と低融点金属層との界面での破壊を抑制して、接続信頼性を大幅に改善できることを見出し、本発明を完成させるに至った。
As a result of intensive studies, the present invention has been made up of the metal constituting the conductive layer and the low-melting-point metal layer as a factor that causes breakdown at the interface between the metal layer (conductive layer) and the low-melting-point metal layer in the conductive connection between the electrodes. The present inventors have found that a layer made of an intermetallic compound (intermetallic diffusion layer) formed between the metal and the metal to be related is involved. That is, it has been found that the formation of a fragile intermetallic diffusion layer causes the interface to break with the intermetallic diffusion layer as a starting point against external force.
As a result of further intensive studies, the present inventors have determined that the thickness of the intermetallic diffusion layer between the conductive layer and the low melting point metal layer after heating at 150 ° C. for 300 hours is the thickness of the conductive layer and the low melting point metal layer. In order to complete the present invention, it is found that when the thickness is 20% or less with respect to the total thickness, the connection reliability can be greatly improved by suppressing the breakage at the interface between the conductive layer and the low melting point metal layer. It came.
本発明の導電性微粒子は、基材微粒子の表面に、導電層及び低融点金属層が順次形成されている導電性微粒子であって、１５０℃で３００時間加熱した後における導電層と低融点金属層との間の金属間拡散層の厚みが、導電層の厚みと低融点金属層の厚みとの合計に対して２０％以下である。 The conductive fine particles of the present invention are conductive fine particles in which a conductive layer and a low-melting-point metal layer are sequentially formed on the surface of the substrate fine particles, and the conductive layer and the low-melting-point metal after heating at 150 ° C. for 300 hours. The thickness of the intermetallic diffusion layer between the layers is 20% or less with respect to the total thickness of the conductive layer and the low melting point metal layer.
上記基材微粒子は特に限定されず、例えば、樹脂微粒子、無機微粒子、有機無機ハイブリッド微粒子、金属微粒子等が挙げられる。上記基材微粒子としては、特に樹脂微粒子が好ましい。 The substrate fine particles are not particularly limited, and examples thereof include resin fine particles, inorganic fine particles, organic-inorganic hybrid fine particles, and metal fine particles. As the substrate fine particles, resin fine particles are particularly preferable.
上記樹脂微粒子は特に限定されず、例えば、ポリオレフィン樹脂、アクリル樹脂、ポリアルキレンテレフタレート樹脂、ポリスルホン樹脂、ポリカーボネート樹脂、ポリアミド樹脂、フェノールホルムアルデヒド樹脂、メラミンホルムアルデヒド樹脂、ベンゾグアナミンホルムアルデヒド樹脂、尿素ホルムアルデヒド樹脂等で構成される樹脂微粒子が挙げられる。
上記ポリオレフィン樹脂は特に限定されず、例えば、ポリエチレン樹脂、ポリプロピレン樹脂、ポリスチレン樹脂、ポリイソブチレン樹脂、ポリブタジエン樹脂等が挙げられる。上記アクリル樹脂は特に限定されず、例えば、ポリメチルメタクリレート樹脂、ポリメチルアクリレート樹脂等が挙げられる。これらの樹脂は、単独で用いられてもよいし、２種以上が併用されてもよい。
The resin fine particles are not particularly limited, and include, for example, polyolefin resin, acrylic resin, polyalkylene terephthalate resin, polysulfone resin, polycarbonate resin, polyamide resin, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, and the like. Resin fine particles.
The polyolefin resin is not particularly limited, and examples thereof include polyethylene resin, polypropylene resin, polystyrene resin, polyisobutylene resin, and polybutadiene resin. The acrylic resin is not particularly limited, and examples thereof include polymethyl methacrylate resin and polymethyl acrylate resin. These resins may be used alone or in combination of two or more.
上記樹脂微粒子を作製する方法は特に限定されず、例えば、重合法による方法、高分子保護剤を用いる方法、界面活性剤を用いる方法等が挙げられる。
上記重合法は特に限定されず、乳化重合、懸濁重合、シード重合、分散重合、分散シード重合等の重合法が挙げられる。
The method for producing the resin fine particles is not particularly limited, and examples thereof include a polymerization method, a method using a polymer protective agent, and a method using a surfactant.
The polymerization method is not particularly limited, and examples thereof include emulsion polymerization, suspension polymerization, seed polymerization, dispersion polymerization, and dispersion seed polymerization.
上記無機微粒子は特に限定されず、例えば、シリカ、アルミナ等の金属酸化物で構成される微粒子が挙げられる。上記有機無機ハイブリッド微粒子は特に限定されず、例えば、オルガノシロキサン骨格の中にアクリルポリマーを含有するハイブリッド微粒子が挙げられる。
上記金属微粒子は特に限定されず、例えば、アルミニウム、銅、ニッケル、鉄、金、銀等の金属からなる微粒子が挙げられる。なかでも、銅微粒子が好ましい。上記銅微粒子は、実質的に銅金属のみで形成された銅微粒子であってもよく、銅金属を含有する銅微粒子であってもよい。なお、上記基材微粒子が銅微粒子である場合は、後述する導電層を形成しなくてもよい。
The inorganic fine particles are not particularly limited, and examples thereof include fine particles composed of metal oxides such as silica and alumina. The organic-inorganic hybrid fine particles are not particularly limited, and examples thereof include hybrid fine particles containing an acrylic polymer in an organosiloxane skeleton.
The metal fine particles are not particularly limited, and examples thereof include fine particles made of metals such as aluminum, copper, nickel, iron, gold, and silver. Of these, copper fine particles are preferred. The copper fine particles may be copper fine particles formed substantially only of copper metal, or may be copper fine particles containing copper metal. In addition, when the said base material microparticles | fine-particles are copper microparticles, it is not necessary to form the conductive layer mentioned later.
上記基材微粒子が樹脂微粒子である場合、上記樹脂微粒子の１０％Ｋ値の好ましい下限は１０００ＭＰａ、好ましい上限は１５０００ＭＰａである。上記１０％Ｋ値が１０００ＭＰａ未満であると、樹脂微粒子を圧縮変形させると、樹脂微粒子が破壊されることがある。上記１０％Ｋ値が１５０００ＭＰａを超えると、導電性微粒子が電極を傷つけることがある。上記１０％Ｋ値のより好ましい下限は２０００ＭＰａ、より好ましい上限は１００００ＭＰａである。 When the substrate fine particles are resin fine particles, the preferred lower limit of the 10% K value of the fine resin particles is 1000 MPa, and the preferred upper limit is 15000 MPa. If the 10% K value is less than 1000 MPa, the resin fine particles may be destroyed when the resin fine particles are compressed and deformed. When the 10% K value exceeds 15000 MPa, the conductive fine particles may damage the electrode. The more preferable lower limit of the 10% K value is 2000 MPa, and the more preferable upper limit is 10,000 MPa.
なお、上記１０％Ｋ値は、微小圧縮試験器（例えば、島津製作所社製「ＰＣＴ−２００」）を用い、樹脂微粒子を直径５０μｍのダイアモンド製円柱の平滑圧子端面で、圧縮速度２．６ｍＮ／秒、最大試験荷重１０ｇの条件下で圧縮した場合の圧縮変位（ｍｍ）を測定し、下記式により求めることができる。
Ｋ値（Ｎ／ｍｍ２）＝（３／√２）・Ｆ・Ｓ−３／２・Ｒ−１／２
Ｆ：樹脂微粒子の１０％圧縮変形における荷重値（Ｎ）
Ｓ：樹脂微粒子の１０％圧縮変形における圧縮変位（ｍｍ）
Ｒ：樹脂微粒子の半径（ｍｍ）
The 10% K value is obtained by using a micro compression tester (for example, “PCT-200” manufactured by Shimadzu Corporation), and using a smooth indenter end face of a diamond cylinder having a diameter of 50 μm and a compression speed of 2.6 mN / The compression displacement (mm) when compressed under conditions of seconds and a maximum test load of 10 g can be measured and determined by the following equation.
K value (N / mm 2) = ( 3 / √2) · F · S -3/2 · R -1/2
F: Load value at 10% compression deformation of resin fine particles (N)
S: Compression displacement (mm) in 10% compression deformation of resin fine particles
R: radius of resin fine particles (mm)
上記基材微粒子の平均粒子径は特に限定されないが、好ましい下限は１μｍ、好ましい上限は２０００μｍである。上記基材微粒子の平均粒子径が１μｍ未満であると、基材微粒子が凝集しやすく、凝集した基材微粒子の表面に低融点金属層を形成した導電性微粒子を用いると、隣接する電極間を短絡させることがある。上記基材微粒子の平均粒子径が２０００μｍを超えると、回路基板等の電極間の接続に適した範囲を超えることがある。上記基材微粒子の平均粒子径のより好ましい下限は３μｍ、より好ましい上限は１０００μｍである。
なお、上記基材微粒子の平均粒子径は、光学顕微鏡又は電子顕微鏡を用いて無作為に選んだ５０個の基材微粒子の粒子径を測定し、測定した粒子径を算術平均することにより求めることができる。
The average particle diameter of the substrate fine particles is not particularly limited, but a preferable lower limit is 1 μm and a preferable upper limit is 2000 μm. When the average particle diameter of the above-mentioned substrate fine particles is less than 1 μm, the substrate fine particles are likely to aggregate. When conductive fine particles in which a low melting point metal layer is formed on the surface of the aggregated substrate fine particles are used, a gap between adjacent electrodes can be obtained. May cause a short circuit. When the average particle diameter of the base material fine particles exceeds 2000 μm, the range suitable for connection between electrodes such as a circuit board may be exceeded. The more preferable lower limit of the average particle diameter of the substrate fine particles is 3 μm, and the more preferable upper limit is 1000 μm.
The average particle size of the above-mentioned substrate fine particles is obtained by measuring the particle size of 50 randomly selected substrate fine particles using an optical microscope or an electron microscope and arithmetically averaging the measured particle sizes. Can do.
上記基材微粒子の平均粒子径の変動係数は特に限定されないが、１０％以下であることが好ましい。上記変動係数が１０％を超えると、導電性微粒子の接続信頼性が低下することがある。なお、上記変動係数とは、粒子径分布から得られる標準偏差を平均粒子径で除して得られる値を百分率（％）で示した数値である。 The coefficient of variation of the average particle diameter of the substrate fine particles is not particularly limited, but is preferably 10% or less. If the coefficient of variation exceeds 10%, the connection reliability of the conductive fine particles may be lowered. The coefficient of variation is a numerical value obtained by dividing the standard deviation obtained from the particle size distribution by the average particle size and expressed as a percentage (%).
上記基材微粒子の形状は、対向する電極の間隔を維持できる形状であれば特に限定されないが、真球形状であることが好ましい。また、上記基材微粒子の表面は平滑であってもよいし、突起を有していてもよい。 The shape of the substrate fine particles is not particularly limited as long as the distance between the opposing electrodes can be maintained, but a true spherical shape is preferable. Further, the surface of the substrate fine particles may be smooth or may have a protrusion.
本発明の導電性微粒子は、上記基材微粒子の表面に、導電層が形成されている。上記導電層は、下地金属層としての役割を有する。
上記導電層を形成する金属は特に限定されず、例えば、金、銀、銅、亜鉛、鉄、鉛、錫、アルミニウム、コバルト、インジウム、ニッケル、クロム、アンチモン、ビスマス、ゲルマニウム、カドミウム等が挙げられる。なかでも、導電性に優れることから、上記導電層を形成する金属は、金、銅又はニッケルであることが好ましい。
In the conductive fine particles of the present invention, a conductive layer is formed on the surface of the substrate fine particles. The conductive layer serves as a base metal layer.
The metal forming the conductive layer is not particularly limited, and examples thereof include gold, silver, copper, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, antimony, bismuth, germanium, and cadmium. . Especially, since it is excellent in electroconductivity, it is preferable that the metal which forms the said conductive layer is gold, copper, or nickel.
上記基材微粒子の表面に、上記導電層を形成させる方法は特に限定されず、例えば、無電解メッキ法、電解メッキ法、真空蒸着法、イオンプレーティング法、イオンスパッタリング法等が挙げられる。 The method for forming the conductive layer on the surface of the substrate fine particles is not particularly limited, and examples thereof include an electroless plating method, an electrolytic plating method, a vacuum deposition method, an ion plating method, and an ion sputtering method.
上記導電層の厚さは特に限定されないが、好ましい下限は０．１μｍ、好ましい上限は１００μｍである。上記導電層の厚さが０．１μｍ未満であると、導電性が充分に得られないことがある。上記導電層の厚さが１００μｍを超えると、導電性微粒子の柔軟性が低下することがある。上記導電層の厚さのより好ましい下限は０．２μｍ、より好ましい上限は５０μｍである。
なお、上記導電層の厚さは、無作為に選んだ１０個の導電性微粒子の断面を走査型電子顕微鏡（ＳＥＭ）により観察して測定し、これらを算術平均した厚さである。
Although the thickness of the said conductive layer is not specifically limited, A preferable minimum is 0.1 micrometer and a preferable upper limit is 100 micrometers. If the thickness of the conductive layer is less than 0.1 μm, sufficient conductivity may not be obtained. When the thickness of the conductive layer exceeds 100 μm, the flexibility of the conductive fine particles may be lowered. A more preferable lower limit of the thickness of the conductive layer is 0.2 μm, and a more preferable upper limit is 50 μm.
The thickness of the conductive layer is a thickness obtained by observing and measuring a section of 10 randomly selected conductive fine particles with a scanning electron microscope (SEM) and arithmetically averaging them.
本発明の導電性微粒子は、低融点金属を有する。上記低融点金属層は、リフロー工程により溶融して電極に接合し、電極間を導通させる役割を有する。 The conductive fine particles of the present invention have a low melting point metal. The low-melting-point metal layer has a role of melting and joining the electrodes by a reflow process and conducting between the electrodes.
上記低融点金属層を構成する低融点金属は特に限定されないが、錫、又は錫を含有する合金であることが好ましい。上記合金は、錫−銀合金、錫−銅合金、錫−銀−銅合金、錫−ビスマス合金、錫−亜鉛合金等が挙げられる。
なかでも、各電極材料に対し濡れ性が優れることから、低融点金属は、錫、錫−銀合金、錫−銀−銅合金が好適である。
The low melting point metal constituting the low melting point metal layer is not particularly limited, but is preferably tin or an alloy containing tin. Examples of the alloy include a tin-silver alloy, a tin-copper alloy, a tin-silver-copper alloy, a tin-bismuth alloy, and a tin-zinc alloy.
Among them, tin, tin-silver alloy, and tin-silver-copper alloy are suitable as the low melting point metal because wettability is excellent for each electrode material.
更に、上記低融点金属層と電極との接合強度を向上させるために、上記低融点金属層に、ニッケル、銅、アンチモン、アルミニウム、亜鉛、鉄、金、チタン、リン、ゲルマニウム、テルル、コバルト、ビスマス、マンガン、クロム、モリブデン、パラジウム等の金属を含有させてもよい。なかでも、上記低融点金属層と電極との接合強度を向上させる効果に優れていることから、上記低融点金属層に、ニッケル、銅、アンチモン、アルミニウム、亜鉛を含有させることが好適である。
上記低融点金属層中に含有される金属の合計に占める上記金属の含有量は特に限定されないが、好ましい下限は０．０００１重量％、好ましい上限は１重量％である。上記低融点金属層中に含有される金属の合計に占める上記金属の含有量が、０．０００１〜１重量％の範囲内であることにより、上記低融点金属層と電極との接合強度をより向上させることができる。
Furthermore, in order to improve the bonding strength between the low-melting-point metal layer and the electrode, the low-melting-point metal layer includes nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, Metals such as bismuth, manganese, chromium, molybdenum, and palladium may be included. Especially, since it is excellent in the effect which improves the joining strength of the said low melting metal layer and an electrode, it is suitable to make the said low melting metal layer contain nickel, copper, antimony, aluminum, and zinc.
The content of the metal in the total of metals contained in the low melting point metal layer is not particularly limited, but a preferable lower limit is 0.0001% by weight and a preferable upper limit is 1% by weight. When the content of the metal in the total of metals contained in the low-melting-point metal layer is within the range of 0.0001 to 1% by weight, the bonding strength between the low-melting-point metal layer and the electrode is further increased. Can be improved.
上記低融点金属層における上記錫の含有量は、４０重量％以上であることが好ましい。上記含有量が４０重量％未満であると、本発明の効果が充分に得られず、実装不良を招くことがある。なお、上記低融点金属層における錫の含有量とは、低融点金属層に含有される元素の合計に占める錫の割合を意味し、上記低融点金属層の錫含有量は、高周波誘導結合プラズマ発光分光分析装置（堀場製作所社製「ＩＣＰ−ＡＥＳ」）、蛍光Ｘ線分析装置（島津製作所社製「ＥＤＸ−８００ＨＳ」）等を用いて測定することができる。 The tin content in the low melting point metal layer is preferably 40% by weight or more. When the content is less than 40% by weight, the effects of the present invention cannot be sufficiently obtained, and mounting defects may be caused. The tin content in the low melting point metal layer means the ratio of tin to the total of the elements contained in the low melting point metal layer, and the tin content in the low melting point metal layer is the high frequency inductively coupled plasma. It can be measured using an emission spectroscopic analyzer (“ICP-AES” manufactured by Horiba, Ltd.), a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu).
上記低融点金属層の厚さは特に限定されないが、好ましい下限は０．１μｍ、好ましい上限は２００μｍである。上記低融点金属層の厚さが０．１μｍ未満であると、リフローして溶融させても充分に電極に接合できないことがあり、上記低融点金属層の厚さが２００μｍを超えると、上記低融点金属層を形成する際に凝集が生じやすく、凝集した導電性微粒子は隣接電極間の短絡を引き起こすことがある。上記低融点金属層の厚さのより好ましい下限は０．２μｍ、より好ましい上限は５０μｍである。
なお、上記低融点金属層の厚さは、無作為に選んだ１０個の導電性微粒子の断面を走査型電子顕微鏡（ＳＥＭ）により観察して測定し、測定値を算術平均した厚さである。
Although the thickness of the said low melting metal layer is not specifically limited, A preferable minimum is 0.1 micrometer and a preferable upper limit is 200 micrometers. When the thickness of the low-melting-point metal layer is less than 0.1 μm, it may not be able to be sufficiently bonded to the electrode even when reflowed and melted. When the thickness of the low-melting-point metal layer exceeds 200 μm, Aggregation tends to occur when the melting point metal layer is formed, and the aggregated conductive fine particles may cause a short circuit between adjacent electrodes. The minimum with more preferable thickness of the said low melting metal layer is 0.2 micrometer, and a more preferable upper limit is 50 micrometers.
The thickness of the low-melting-point metal layer is a thickness obtained by observing and measuring the cross section of 10 randomly selected conductive fine particles with a scanning electron microscope (SEM) and arithmetically averaging the measured values. .
上記低融点金属層は、上記導電層側に密着層を有する構成であってもよい。
上記密着層は、置換めっきによって形成されていることが好ましい。これにより、導電層と低融点金属層との密着性が大幅に向上するため、一次実装後に導電層が露出することに起因する接合不良の発生を効果的に防止できる。
The low melting point metal layer may have a close contact layer on the conductive layer side.
The adhesion layer is preferably formed by displacement plating. As a result, the adhesion between the conductive layer and the low-melting-point metal layer is greatly improved, so that it is possible to effectively prevent the occurrence of poor bonding due to the exposure of the conductive layer after the primary mounting.
上記密着層を形成する金属は、錫が好ましいが、錫以外の元素を含有してもよく、錫と他の金属との合金としてもよい。上記合金は特に限定されず、例えば、錫−銅合金、錫−銀合金、錫−ビスマス合金、錫−亜鉛合金、錫−インジウム合金等が挙げられる。 The metal forming the adhesion layer is preferably tin, but may contain an element other than tin, or may be an alloy of tin and another metal. The said alloy is not specifically limited, For example, a tin-copper alloy, a tin-silver alloy, a tin-bismuth alloy, a tin-zinc alloy, a tin-indium alloy etc. are mentioned.
上記置換めっきとは、金属塩溶液を含有するめっき液に被めっき物を浸漬し、被めっき物の素地金属と置換めっき液中の金属イオンとのイオン化傾向の差を利用して素地金属に金属イオンを析出させる方法である。例えば、イオン化傾向の小さい金属イオンを含有するめっき液に、イオン化傾向の大きい金属からなる導電層が形成された基材微粒子を浸漬させることで、イオン化傾向の大きい金属を溶解させ、イオン化傾向の小さい金属からなる密着層を形成することができる。
なお、上記置換めっきは、金属イオンを含有するめっき液中で被めっき物の素地金属を陰極として通電し、表面に金属被膜を析出させる電気めっきとは異なるめっき方法であり、また、還元補助剤を加えることで、めっき液中の金属イオンを化学的に還元析出させ、素地金属表面に金属被膜を形成する無電解還元めっきとも異なるめっき方法である。
The above displacement plating is a method of immersing an object to be plated in a plating solution containing a metal salt solution, and using the difference in ionization tendency between the substrate metal of the object to be plated and the metal ion in the displacement plating solution, This is a method for precipitating ions. For example, by immersing a substrate fine particle on which a conductive layer made of a metal having a high ionization tendency is formed in a plating solution containing metal ions having a low ionization tendency, the metal having a high ionization tendency is dissolved and the ionization tendency is low. An adhesion layer made of metal can be formed.
The above displacement plating is a plating method different from electroplating in which a base metal of an object to be plated is energized as a cathode in a plating solution containing metal ions, and a metal film is deposited on the surface. Is different from electroless reduction plating in which metal ions in the plating solution are chemically reduced and deposited to form a metal film on the surface of the base metal.
上記置換めっき工程において使用する置換めっき液については、金属イオンを含有するものであれば特に限定されず、例えば、錫イオンや銀イオン等を含有するもの等が挙げられる。また、金属イオンの濃度は、導電層の材質に応じて適宜変更することが好ましい。
また、上記置換めっき液には、素地金属の電位を下げ、素地金属よりイオン化傾向が高いめっき液中の金属イオンでも析出が可能となることを目的として、各種の酸や錯化剤、その他添加剤を加えてもよい。更に、上記金属イオンの対イオンとして、硫酸イオン、硝酸イオン、ハロゲン化物イオン等の各種対イオンを含有していてもよい。
The substitution plating solution used in the substitution plating step is not particularly limited as long as it contains metal ions, and examples thereof include those containing tin ions and silver ions. In addition, it is preferable that the concentration of metal ions is appropriately changed according to the material of the conductive layer.
In addition, various acids, complexing agents, and other additives are added to the above replacement plating solution for the purpose of lowering the potential of the base metal and allowing precipitation of metal ions in the plating solution, which has a higher ionization tendency than the base metal. An agent may be added. Furthermore, various counter ions such as sulfate ions, nitrate ions, halide ions may be contained as counter ions of the metal ions.
本発明の導電性微粒子は、１５０℃で３００時間加熱した後における導電層と低融点金属層との間の金属間拡散層の厚みの上限が、導電層の厚みと低融点金属層の厚みとの合計に対して２０％である。このことは、導電性微粒子の作製時に導電層を構成する金属と低融点金属層を構成する金属との原子単位での接触が極めて少ないことを意味する。これにより、金属間拡散層の形成を抑制し、界面の破壊を防止して、接続信頼性の高い導電性微粒子とすることができる。
上記金属間拡散層の厚みが、導電層の厚みと低融点金属層の厚みとの合計に対して２０％を超えると、金属間拡散層を起点とした界面の破壊が生じる。上記金属間拡散層の厚みの好ましい下限は導電層の厚みと低融点金属層の厚みとの合計の１％、好ましい上限は導電層の厚みと低融点金属層の厚みとの合計の１６．７％である。
なお、本発明において「金属間拡散層」とは、導電層を構成する金属元素と、低融点金属層を構成する金属元素とが結合した「金属間化合物」からなる層のことをいう。また、上記金属間拡散層の厚みは、走査電子顕微鏡（ＦＥ−ＳＥＭ、堀場製作所社製）を用いて電子顕微鏡写真撮影と元素線分析とを行い、その結果を用いて測定することができる。
In the conductive fine particles of the present invention, the upper limit of the thickness of the intermetallic diffusion layer between the conductive layer and the low melting point metal layer after heating at 150 ° C. for 300 hours is the thickness of the conductive layer and the thickness of the low melting point metal layer. It is 20% with respect to the sum total. This means that there is very little contact in atomic units between the metal constituting the conductive layer and the metal constituting the low melting point metal layer when the conductive fine particles are produced. Thereby, formation of an intermetallic diffusion layer can be suppressed, destruction of the interface can be prevented, and conductive fine particles having high connection reliability can be obtained.
When the thickness of the intermetallic diffusion layer exceeds 20% with respect to the total of the thickness of the conductive layer and the low melting point metal layer, the interface breaks from the intermetallic diffusion layer. The preferable lower limit of the thickness of the intermetallic diffusion layer is 1% of the total thickness of the conductive layer and the low melting point metal layer, and the preferable upper limit is 16.7 of the total thickness of the conductive layer and the low melting point metal layer. %.
In the present invention, the “intermetallic diffusion layer” refers to a layer made of an “intermetallic compound” in which a metal element constituting the conductive layer and a metal element constituting the low melting point metal layer are combined. The thickness of the intermetallic diffusion layer can be measured using a scanning electron microscope (FE-SEM, manufactured by HORIBA, Ltd.) by performing electron micrograph photography and element beam analysis.
本発明の導電性微粒子の製造方法は、上述のような金属間拡散層が得られる方法であれば特に限定されないが、例えば、基材微粒子の表面に無電解めっき法等により銅を含有する導電層を形成する工程と、上記導電層上に、錫又は錫と他の金属との合金からなる低融点金属層を形成する工程を有する方法が好ましい。
また、上記導電層上に置換めっきにより錫等を含有する密着層を形成する工程を行った後、更に、錫又は錫と他の金属との合金からなる層を形成することにより、低融点金属層を形成してもよい。
The method for producing the conductive fine particles of the present invention is not particularly limited as long as the above-described intermetallic diffusion layer can be obtained. For example, the conductive fine particles containing copper by electroless plating on the surface of the substrate fine particles are used. A method having a step of forming a layer and a step of forming a low melting point metal layer made of tin or an alloy of tin and another metal on the conductive layer is preferable.
Moreover, after performing the process of forming the contact | adherence layer containing a tin etc. by displacement plating on the said conductive layer, further, by forming the layer which consists of an alloy of tin or tin, and another metal, low melting-point metal A layer may be formed.
本発明の導電性微粒子を製造する方法において、上記銅等の金属を含有する導電層を形成する工程には、従来公知の方法を用いることができる。また、密着層を形成する工程としては、上述した方法を用いることができる。 In the method for producing conductive fine particles of the present invention, a conventionally known method can be used in the step of forming the conductive layer containing the metal such as copper. In addition, as the step of forming the adhesion layer, the above-described method can be used.
上記低融点金属層を形成する工程としては特に限定されないが、導電層が形成された基材微粒子に、錫又は錫と他の金属との合金を含有する低融点金属微粒子を接触させ、せん断圧縮によって低融点金属微粒子を溶融させることにより、低融点金属層を形成する工程を有する方法（乾式被覆法）を用いた場合、本発明の導電性微粒子は、特に優れた効果を発揮することができる。 The step of forming the low-melting-point metal layer is not particularly limited, but the low-melting-point metal fine particles containing tin or an alloy of tin and another metal are brought into contact with the substrate fine particles on which the conductive layer is formed, and shear compression is performed. In the case of using a method (dry coating method) having a step of forming a low melting point metal layer by melting the low melting point fine metal particles, the conductive fine particles of the present invention can exhibit particularly excellent effects. .
上記乾式被覆法では、例えば、シータコンポーザ（徳寿工作所社製）を用いる方法等が挙げられる。上記シータコンポーザは、楕円形のキャビティを備えるベッセルと、キャビティ内でこのベッセルと同一軸上において別個に回転されるローターとを備えており、混合に際しては、ベッセルとローターとを逆回転させることにより、キャビティの短径とローターの長径とが一致する付近の間隙内で、せん断圧縮力を作用することができる。このせん断圧縮によって低融点金属微粒子を溶融軟化させ、低融点金属微粒子を基材微粒子に付着させることを繰り返すことにより、基材微粒子の導電層の表面に低融点金属層が形成された導電性微粒子を製造することができる。 Examples of the dry coating method include a method using a theta composer (manufactured by Tokuju Kogakusho Co., Ltd.). The theta composer includes a vessel having an elliptical cavity, and a rotor that is separately rotated on the same axis as the vessel in the cavity. A shear compressive force can be applied in the gap in the vicinity where the minor axis of the cavity and the major axis of the rotor coincide. Conductive fine particles in which a low-melting-point metal layer is formed on the surface of the conductive layer of the base particle by repeatedly melting and softening the low-melting-point metal fine particle by this shear compression and attaching the low-melting-point metal fine particle to the base particle. Can be manufactured.
上記低融点金属層を形成するときに用いる低融点金属微粒子の平均粒子径は特に限定されないが、好ましい下限は０．１μｍ、好ましい上限は１００μｍである。上記低融点金属微粒子の平均粒子径が０．１μｍ未満であると、低融点金属微粒子が凝集しやすくなるため、低融点金属層を形成することが困難となることがある。上記低融点金属微粒子の平均粒子径が１００μｍを超えると、せん断圧縮時に溶融軟化しきらず、低融点金属層を形成することが困難となるときがある。なお、上記低融点金属微粒子の平均粒子径は、光学顕微鏡又は電子顕微鏡を用いて無作為に選んだ５０個の低融点金属微粒子の粒子径を測定し、測定した粒子径を算術平均することにより求めることができる。
また、上記低融点金属微粒子の平均粒子径は、上記基材微粒子の平均粒子径の１／１０以下であることが好ましい。上記低融点金属微粒子の平均粒子径が、上記基材微粒子の平均粒子径の１／１０を超えると、せん断圧縮時に上記低融点金属微粒子を上記基材微粒子の導電層に付着、皮膜化させることができないことがある。
The average particle diameter of the low melting point metal fine particles used when forming the low melting point metal layer is not particularly limited, but the preferred lower limit is 0.1 μm and the preferred upper limit is 100 μm. When the average particle diameter of the low melting point metal fine particles is less than 0.1 μm, the low melting point metal fine particles are likely to aggregate, and it may be difficult to form the low melting point metal layer. When the average particle diameter of the low melting point metal fine particles exceeds 100 μm, it may be difficult to form a low melting point metal layer without being melted and softened during shear compression. The average particle size of the low-melting-point metal fine particles is obtained by measuring the particle sizes of 50 low-melting-point metal fine particles selected at random using an optical microscope or an electron microscope, and arithmetically averaging the measured particle sizes. Can be sought.
Moreover, it is preferable that the average particle diameter of the said low melting metal fine particle is 1/10 or less of the average particle diameter of the said base particle. When the average particle size of the low-melting-point metal fine particles exceeds 1/10 of the average particle size of the substrate fine particles, the low-melting-point metal fine particles adhere to the conductive layer of the substrate fine particles and form a film during shear compression. May not be possible.
本発明の導電性微粒子をバインダー樹脂に分散させることにより異方性導電材料を製造することができる。このような異方性導電材料もまた、本発明の１つである。 An anisotropic conductive material can be produced by dispersing the conductive fine particles of the present invention in a binder resin. Such an anisotropic conductive material is also one aspect of the present invention.
本発明の異方性導電材料として、例えば、異方性導電ペースト、異方性導電インク、異方性導電接着剤、異方性導電フィルム、異方性導電シート等が挙げられる。 Examples of the anisotropic conductive material of the present invention include anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, anisotropic conductive film, and anisotropic conductive sheet.
上記バインダー樹脂は特に限定されないが、絶縁性の樹脂が用いられ、例えば、ビニル樹脂、熱可塑性樹脂、硬化性樹脂、熱可塑性ブロック共重合体、エラストマー等が挙げられる。
上記ビニル樹脂は特に限定されないが、例えば、酢酸ビニル樹脂、アクリル樹脂、スチレン樹脂等が挙げられる。
上記熱可塑性樹脂は特に限定されないが、例えば、ポリオレフィン樹脂、エチレン−酢酸ビニル共重合体、ポリアミド樹脂等が挙げられる。
上記硬化性樹脂は特に限定されないが、例えば、エポキシ樹脂、ウレタン樹脂、ポリイミド樹脂、不飽和ポリエステル樹脂等が挙げられる。なお、上記硬化性樹脂は、常温硬化型樹脂、熱硬化型樹脂、光硬化型樹脂、湿気硬化型樹脂であってもよい。上記硬化性樹脂は硬化剤と併用してもよい。
上記熱可塑性ブロック共重合体は特に限定されないが、例えば、スチレン−ブタジエン−スチレンブロック共重合体、スチレン−イソプレン−スチレンブロック共重合体、スチレン−ブタジエン−スチレンブロック共重合体の水素添加物、スチレン−イソプレン−スチレンブロック共重合体の水素添加物等が挙げられる。
上記エラストマーは特に限定されないが、例えば、スチレン−ブタジエン共重合ゴム、アクリロニトリル−スチレンブロック共重合ゴム等が挙げられる。
これらの樹脂は、単独で用いられてもよいし、２種以上が併用されてもよい。
The binder resin is not particularly limited, but an insulating resin is used, and examples thereof include a vinyl resin, a thermoplastic resin, a curable resin, a thermoplastic block copolymer, and an elastomer.
Although the said vinyl resin is not specifically limited, For example, a vinyl acetate resin, an acrylic resin, a styrene resin etc. are mentioned.
Although the said thermoplastic resin is not specifically limited, For example, polyolefin resin, ethylene-vinyl acetate copolymer, a polyamide resin etc. are mentioned.
Although the said curable resin is not specifically limited, For example, an epoxy resin, a urethane resin, a polyimide resin, an unsaturated polyester resin etc. are mentioned. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. The curable resin may be used in combination with a curing agent.
The thermoplastic block copolymer is not particularly limited. For example, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated product of styrene-butadiene-styrene block copolymer, styrene -Hydrogenated product of isoprene-styrene block copolymer.
The elastomer is not particularly limited, and examples thereof include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.
These resins may be used alone or in combination of two or more.
本発明の異方性導電材料は、本発明の導電性微粒子、及び、上記バインダー樹脂の他に、本発明の課題達成を阻害しない範囲で、例えば、増量剤、可塑剤、粘接着性向上剤、酸化防止剤、熱安定剤、光安定剤、紫外線吸収剤、着色剤、難燃剤、有機溶媒等を含有してもよい。 In addition to the conductive fine particles of the present invention and the above-mentioned binder resin, the anisotropic conductive material of the present invention is, for example, an extender, a plasticizer, and improved adhesiveness within a range that does not hinder the achievement of the present invention. Agents, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants, flame retardants, organic solvents, and the like.
本発明の異方性導電材料の製造方法は特に限定されず、例えば、上記バインダー樹脂に本発明の導電性微粒子を添加し、均一に混合して分散させ、例えば、異方性導電ペースト、異方性導電インク、異方性導電接着剤等を製造する方法が挙げられる。また、上記バインダー樹脂に本発明の導電性微粒子を添加し、均一に分散させるか、又は、加熱溶解させて、離型紙や離型フィルム等の離型材の離型処理面に所定のフィルム厚さとなるように塗工し、例えば、異方性導電フィルム、異方性導電シート等を製造する方法も挙げられる。
また、上記バインダー樹脂と、本発明の導電性微粒子とを混合することなく、別々に用いて異方性導電材料としてもよい。
The method for producing the anisotropic conductive material of the present invention is not particularly limited. For example, the conductive fine particles of the present invention are added to the binder resin, and the mixture is uniformly mixed and dispersed. Examples thereof include a method for producing an anisotropic conductive ink, an anisotropic conductive adhesive, and the like. Further, the conductive fine particles of the present invention are added to the binder resin and uniformly dispersed or dissolved by heating, and a predetermined film thickness is applied to a release treatment surface of a release material such as release paper or release film. For example, a method for producing an anisotropic conductive film, an anisotropic conductive sheet or the like by coating may be used.
Moreover, it is good also as an anisotropic conductive material by using separately the said binder resin and the electroconductive fine particles of this invention, without mixing.
本発明の導電性微粒子又は本発明の異方性導電材料を用いてなる接続構造体もまた、本発明の１つである。 A connection structure using the conductive fine particles of the present invention or the anisotropic conductive material of the present invention is also one aspect of the present invention.
本発明の接続構造体は、一対の回路基板間に、本発明の導電性微粒子又は本発明の異方性導電材料を充填することにより、一対の回路基板間を接続させた導電接続構造体である。 The connection structure of the present invention is a conductive connection structure in which a pair of circuit boards are connected by filling the pair of circuit boards with the conductive fine particles of the present invention or the anisotropic conductive material of the present invention. is there.
本発明によれば、導電層と低融点金属層との界面において破壊が生じにくく、高い接続信頼性を実現することが可能な導電性微粒子、該導電性微粒子を用いてなる異方性導電材料、及び、接続構造体を提供することができる。 According to the present invention, conductive fine particles that are less likely to be broken at the interface between the conductive layer and the low-melting-point metal layer and can realize high connection reliability, and anisotropic conductive materials using the conductive fine particles And a connection structure can be provided.
以下に実施例を掲げて本発明を更に詳しく説明するが、本発明はこれら実施例のみに限定されない。 Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
（実施例１）
テトラメチロールメタンテトラアクリレートとジビニルベンゼンとの共重合体からなる樹脂微粒子（平均粒子径２４０μｍ）の表面に、電気めっきにより厚さ１０μｍの銅層を形成し、基材微粒子を得た。
次いで、得られた銅層形成基材微粒子９０ｇに対して、下記組成の錫めっき液（めっき液温２０℃）５００ｇを用いて置換めっきを行い、銅層形成樹脂微粒子の表面に厚さ０．５μｍの錫層を形成した。
Example 1
A copper layer having a thickness of 10 μm was formed by electroplating on the surface of resin fine particles (average particle diameter of 240 μm) made of a copolymer of tetramethylolmethane tetraacrylate and divinylbenzene to obtain substrate fine particles.
Subsequently, substitution plating was performed on 90 g of the obtained copper layer forming substrate fine particles using 500 g of a tin plating solution (plating solution temperature 20 ° C.) having the following composition, and a thickness of 0. A 5 μm tin layer was formed.
（錫めっき液組成）
硫酸錫 １５ｇ
メタンスルホン酸 ７５ｇ
チオ尿素 ４５ｇ
水 ３６５ｇ
(Tin plating solution composition)
15 g of tin sulfate
Methanesulfonic acid 75g
Thiourea 45g
365g of water
次いで、銅層及び錫層を形成した樹脂微粒子と、錫９６．５銀３．５合金微粒子（粒子径分布５〜１５μｍ）１６５ｇとをシータコンポーザ（徳寿工作所社製）に投入して混合した。これにより、錫９６．５銀３．５合金微粒子を銅層及び錫層を形成した樹脂微粒子に付着、皮膜化させて、厚さ２５μｍの錫９６．５銀３．５合金層を形成し、導電性微粒子を得た。なお、シータコンポーザを用いて混合する際には、回転容器（ベッセル）を３５ｒｐｍ、回転翼（ローター）を３５００ｒｐｍで逆回転させ、せん断圧縮力が作用するようにした。混合時間は３００分間とした。 Next, resin fine particles on which a copper layer and a tin layer were formed and 165 g of tin 96.5 silver 3.5 alloy fine particles (particle size distribution: 5 to 15 μm) were put into a Theta composer (manufactured by Tokuju Kogakusha Co., Ltd.) and mixed. . Thereby, the tin 96.5 silver 3.5 alloy fine particles were adhered to the resin fine particles on which the copper layer and the tin layer were formed and formed into a film to form a tin 96.5 silver 3.5 alloy layer having a thickness of 25 μm. Conductive fine particles were obtained. When mixing using a theta composer, the rotating container (vessel) was rotated in reverse at 35 rpm and the rotating blade (rotor) was rotated in reverse at 3500 rpm so that the shear compression force was applied. The mixing time was 300 minutes.
（実施例２）
実施例１において、樹脂微粒子（平均粒子径２４０μｍ）に代えて、銅微粒子（平均粒子径２６０μｍ）を用い、銅層を形成しなかった以外は実施例１と同様にして導電性微粒子を作製した。
(Example 2)
In Example 1, conductive fine particles were produced in the same manner as in Example 1 except that copper fine particles (average particle size 260 μm) were used instead of resin fine particles (average particle size 240 μm) and no copper layer was formed. .
（実施例３）
実施例１において、錫９６．５銀３．５合金微粒子（粒子径分布５〜１５μｍ）に代えて、錫９６．５銀３．０銅０．５合金微粒子（粒子径分布５〜１５μｍ）を用いた以外は実施例１と同様にして導電性微粒子を作製した。
(Example 3)
In Example 1, instead of tin 96.5 silver 3.5 alloy fine particles (particle size distribution 5-15 μm), tin 96.5 silver 3.0 copper 0.5 alloy fine particles (particle size distribution 5-15 μm) were used. Conductive fine particles were produced in the same manner as in Example 1 except that they were used.
（実施例４）
実施例１において、錫９６．５銀３．５合金微粒子（粒子径分布５〜１５μｍ）に代えて、錫４２．０ビスマス５８．０合金微粒子（粒子径分布５〜１５μｍ）を用いた以外は実施例１と同様にして導電性微粒子を作製した。
Example 4
In Example 1, tin 42.0 bismuth 58.0 alloy fine particles (particle size distribution 5 to 15 μm) were used in place of tin 96.5 silver 3.5 alloy fine particles (particle size distribution 5 to 15 μm). Conductive fine particles were produced in the same manner as in Example 1.
（比較例１）
実施例１と同様の方法で、テトラメチロールメタンテトラアクリレートとジビニルベンゼンとの共重合体からなる樹脂微粒子（平均粒子径２４０μｍ）の表面に、銅層及び錫層を形成した。
次いで、得られた銅層及び錫層を形成した樹脂微粒子の表面に電気めっきにより厚さ２５μｍの錫９６．５銀３．５合金層を形成し、導電性微粒子を得た。
(Comparative Example 1)
In the same manner as in Example 1, a copper layer and a tin layer were formed on the surface of resin fine particles (average particle size 240 μm) made of a copolymer of tetramethylolmethane tetraacrylate and divinylbenzene.
Next, a tin 96.5 silver 3.5 alloy layer having a thickness of 25 μm was formed by electroplating on the surface of the resin fine particles on which the obtained copper layer and tin layer were formed, and conductive fine particles were obtained.
＜評価＞
実施例及び比較例で得られた導電性微粒子について、以下の評価を行った。結果を表１に示した。
<Evaluation>
The following evaluation was performed about the electroconductive fine particles obtained by the Example and the comparative example. The results are shown in Table 1.
（１）金属間拡散層厚み測定
得られた導電性微粒子について、走査電子顕微鏡（ＦＥ−ＳＥＭ、堀場製作所社製）を用いて、１５０℃で３００時間加熱する前後における導電性微粒子の厚み方向の切断面の電子顕微鏡写真を撮影し、同時に元素線分析を行った。次いで、導電性微粒子の厚み方向の直線上における銅元素及び錫元素の混在する長さから金属間拡散層の厚みを測定した。同様の厚み測定を１０回行い、厚みの平均値を求めることにより、金属間拡散層の厚みを決定した。また、銅層、錫層及び合金層の厚みの合計に対する金属間拡散層の厚みの膜厚比を表１に示した。
なお、実施例１で得られた導電性微粒子の加熱前における電子顕微鏡写真を図１、加熱後における電子顕微鏡写真を図２、比較例１で得られた導電性微粒子の加熱前における電子顕微鏡写真を図３、加熱後における電子顕微鏡写真を図４に示した。
また、実施例１で得られた導電性微粒子の加熱前における元素線分析の結果を図５、加熱後における元素線分析の結果を図６、比較例１で得られた導電性微粒子の加熱前における元素線分析の結果を図７、加熱後における元素線分析の結果を図８に示した。
(1) Intermetallic diffusion layer thickness measurement About the obtained conductive fine particles, using a scanning electron microscope (FE-SEM, manufactured by HORIBA, Ltd.), the thickness of the conductive fine particles before and after heating at 150 ° C. for 300 hours was measured. An electron micrograph of the cut surface was taken, and at the same time, element beam analysis was performed. Next, the thickness of the intermetallic diffusion layer was measured from the length of the copper element and the tin element mixed on the straight line in the thickness direction of the conductive fine particles. The thickness of the intermetallic diffusion layer was determined by performing the same thickness measurement 10 times and calculating the average thickness. Table 1 shows the thickness ratio of the thickness of the intermetallic diffusion layer to the total thickness of the copper layer, the tin layer, and the alloy layer.
The electron micrograph before heating of the conductive fine particles obtained in Example 1 is shown in FIG. 1, the electron micrograph after heating is shown in FIG. 2, and the electron micrograph before heating of the conductive fine particles obtained in Comparative Example 1 is shown. FIG. 3 shows an electron micrograph after heating.
5 shows the results of element beam analysis before heating of the conductive fine particles obtained in Example 1, FIG. 6 shows the results of element beam analysis after heating, and FIG. 6 shows the results of the element fine particle analysis before heating of the conductive fine particles obtained in Comparative Example 1. FIG. 7 shows the result of element beam analysis in FIG. 8, and FIG. 8 shows the result of element beam analysis after heating.
（２）信頼性評価
得られた導電性微粒子を１５０℃で３００時間加熱した後、銅電極を有するシリコンチップ上に１１２個搭載し、２７０℃に設定したリフロー炉に投入し溶融させた。次いで導電性微粒子を実装したシリコンチップを、銅電極を有する基板上に搭載し、２７０℃に設定したリフロー炉に投入し溶融させることで接続構造体を得た。
得られた接続構造体の落下強度試験をＪＥＤＥＣ規格ＪＥＳＤ２２−Ｂ１１１に従って行った。接続構造体の断線が確認されるまで落下を行い、断線が起こるまでの落下回数を求めた。落下回数が１５０回を超えても断線しない場合を○、１５０回以下で断線する場合を×と評価した。
(2) Reliability evaluation After the obtained conductive fine particles were heated at 150 ° C. for 300 hours, 112 pieces were mounted on a silicon chip having a copper electrode, and placed in a reflow furnace set at 270 ° C. to be melted. Next, a silicon chip on which conductive fine particles were mounted was mounted on a substrate having a copper electrode, and was put into a reflow furnace set at 270 ° C. and melted to obtain a connection structure.
A drop strength test of the obtained connection structure was performed according to JEDEC standard JESD22-B111. It dropped until the disconnection of the connection structure was confirmed, and the number of drops until the disconnection occurred was obtained. Even when the number of drops exceeded 150 times, the case where the wire was not broken was evaluated as ◯, and when the wire was broken below 150 times, the case was evaluated as x.
本発明によれば、導電層と低融点金属層との界面において破壊が生じにくく、高い接続信頼性を実現することが可能な導電性微粒子、該導電性微粒子を用いてなる異方性導電材料、及び、接続構造体を提供することができる。
According to the present invention, conductive fine particles that are less likely to be broken at the interface between the conductive layer and the low-melting-point metal layer and can realize high connection reliability, and anisotropic conductive materials using the conductive fine particles And a connection structure can be provided.
Claims (6)
前記低融点金属層は、前記導電層側に置換めっきによって形成された、錫又は錫と他の金属との合金からなる密着層を有し、
１５０℃で３００時間加熱した後における導電層と低融点金属層との間の、
導電層を構成する金属と低融点金属層を構成する金属との間に形成される金属間化合物からなる金属間拡散層の厚みが、導電層の厚みと低融点金属層の厚みとの合計に対して１〜２０％である
ことを特徴とする導電性微粒子。 Conductive fine particles in which a conductive layer and a low melting point metal layer composed of tin or an alloy of tin and other metals are sequentially formed on the surface of the base fine particles,
The low-melting-point metal layer has an adhesion layer made of tin or an alloy of tin and another metal formed by displacement plating on the conductive layer side,
Between the conductive layer and the low melting point metal layer after heating at 150 ° C. for 300 hours ,
The thickness of the intermetallic diffusion layer made of an intermetallic compound formed between the metal constituting the conductive layer and the metal constituting the low melting point metal layer is the sum of the thickness of the conductive layer and the thickness of the low melting point metal layer. 1 to 20% of the conductive fine particles.
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