JP4433449B2 - Anisotropic conductive film and manufacturing method thereof - Google Patents

Description

【００７８】
表１より、フレーク状のＮｉ粉末を２０体積％の金属充てん率で含有させた比較例１の異方導電膜、並びに樹脂粒子とＡｕ被覆の複合構造を有する球状の金属粉末を２０体積％の金属充てん率で含有させた比較例２の異方導電膜はともに絶縁抵抗が低く、面方向の絶縁性が悪いことがわかった。また、上記複合構造を有する球状の金属粉末の金属充てん率を１体積％に減少させた比較例３の異方導電膜は、接続抵抗が高く、厚み方向の導電性が悪いことがわかった。
【００７９】
これに対し、実施例１〜５の異方導電膜は何れも接続抵抗が低く、厚み方向の導電性に優れるとともに、絶縁抵抗が高く、面方向の絶縁性にも優れることがわかった。
また実施例１、２から、接続抵抗をより低く、かつ絶縁抵抗をより高くするためには、直鎖状の金属粉末の鎖の径を太くしつつ、金属充てん率を低くすればよいことが確認された。
【００８０】
また実施例１〜３から、接続抵抗をさらに低くするためには、金属粉末の鎖の表面に、導電性に優れた金属を被覆すればよいこと、実施例３〜５から、金属粉末の鎖を厚み方向に配向させればよいことが確認された。
実施例６
導電成分としては、微細なＮｉ粒が直鎖状に繋がれた形状を有し、Ｎｉ粒の粒径が４００ｎｍ、鎖の径Ｄが１μｍ、長さＬが９μｍ、比Ｌ／Ｄが９であるＮｉ粉末を用いた。
【００８１】
そしてこのＮｉ粉末と、結着剤としてのアクリル樹脂とを、金属充てん率が１体積％となるように混合し、メチルエチルケトンを加えてペースト状の複合材料を調製した。
次にこの複合材料を、下地としての磁石の上に塗布して、磁束密度２０００００μＴの磁場中で乾燥、固化させることによって、金属粉末を膜の厚み方向に配向させた状態で固定したのちはく離して、厚み２０μｍの異方導電膜を製造した。
【００８２】
参考例１
導電成分として、微細なＮｉ粒が直鎖状に繋がれた形状を有し、Ｎｉ粒の粒径が４００ｎｍ、鎖の径Ｄが３μｍ、長さＬが９μｍ、比Ｌ／Ｄが３であるＮｉ粉末を用いたこと以外は実施例６と同様にして、厚み２０μｍの異方導電膜を製造した。
比較例４
導電成分として、微細なＮｉ粒が直鎖状に繋がれた形状を有し、Ｎｉ粒の粒径が４００ｎｍ、鎖の径Ｄが１μｍ、長さＬが１５μｍ、比Ｌ／Ｄが１５であるＮｉ粉末を用いたこと以外は実施例６と同様にして、厚み２０μｍの異方導電膜を製造した。
【００８３】
比較例５
導電成分として、微細なＮｉ粒の集合体からなり、Ｎｉ粒の粒径が４００ｎｍ、短径Ｄが６μｍ、長径Ｌが９μｍ、比Ｌ／Ｄが１．５である粒状のＮｉ粉末を用いたこと以外は実施例６と同様にして、厚み２０μｍの異方導電膜を製造した。
接続抵抗の測定
幅１５μｍ、長さ５０μｍ、厚み５μｍのＡｕ電極が１０μｍ間隔で配列された電極パターンを有するＦＰＣの、上記電極パターン上に、各実施例、比較例で製造した異方導電膜を貼り付けた。
【００８４】
次に、片面にＡｌ膜を蒸着したガラス基板を、Ａｌ膜が異方導電膜と接するように重ねた状態で、１００℃に加熱しながら１電極あたり１０ｇの圧力で加圧して熱接着させた。
そして異方導電膜とＡｌ膜とを介して導電接続された隣り合う２つのＡｕ電極間の抵抗値を測定し、この測定値を１／２にして、異方導電膜の厚み方向の接続抵抗とした。
【００８５】
結果を表２に示す。なお表中の評価は、それぞれ下記のとおりとした。
◎：接続抵抗が０．１Ω以下。厚み方向の導電性は極めて良好。
○：接続抵抗が０．１Ω超で、かつ１Ω以下。厚み方向の導電性は良好。
×：接続抵抗が１Ω超。厚み方向の導電性は不良。
絶縁抵抗の測定
上記で使用したのと同じＦＰＣの電極パターン上に、各実施例、比較例で製造した異方導電膜を貼り付けた。
【００８６】
次にこの異方導電膜上に、今度はＡｌ膜を蒸着していないガラス基板を重ねた状態で、１００℃に加熱しながら１電極あたり１０ｇの圧力で加圧して熱接着させた。
そして異方導電膜を介してガラス基板が熱接着された、隣り合う２つのＡｕ電極間の抵抗値を測定して、異方導電膜の面方向の絶縁抵抗とした。
結果を表２に示す。なお表中の評価は、それぞれ下記のとおりとした。
【００８７】
◎：絶縁抵抗が１ＧΩ超。面方向の絶縁性は極めて良好。
○：絶縁抵抗が１ＭΩ超で、かつ１ＧΩ以下。面方向の絶縁性は良好。
×：絶縁抵抗が１ＭΩ以下。面方向の絶縁性は不良。
【００８８】
【表２】

【００８９】
表２より、鎖の長さが隣り合う電極間の距離よりも長い鎖状のＮｉ粉末を含有させた比較例４の異方導電膜は絶縁抵抗が低く、面方向の絶縁性が悪いことがわかった。そしてこの原因として、熱接着時にＮｉ粉末の横倒しが発生して、隣り合う電極間を短絡させたことが予測された。
また、比Ｌ／Ｄが小さすぎて鎖状でなく粒状を呈するＮｉ粉末を含有させた比較例５の異方導電膜は、接続抵抗が高く、厚み方向の導電性が低いことがわかった。
【００９０】
これに対し、実施例６の異方導電膜は接続抵抗が低く、厚み方向の導電性に優れるとともに、絶縁抵抗が高く、面方向の絶縁性にも優れることがわかった。そしてこのことから、鎖の長さを隣り合う電極間の距離未満とすることによって、たとえ熱接着時にＮｉ粉末の横倒しが発生しても、隣り合う電極間の短絡を確実に防止できることが確認された。
〔コンタクトプローブ実装用の異方導電膜〕
参考例２
導電成分としては、微細なＮｉ粒が直鎖状に繋がれた鎖が複数本、束状に凝集した形状を有し、Ｎｉ粒の粒径が１００ｎｍ、鎖の径Ｄが１０μｍ、長さＬが５０μｍ、比Ｌ／Ｄが５であるＮｉ粉末を用いた。
【００９１】
そしてこのＮｉ粉末と、結着剤としてのアクリル樹脂とを、金属充てん率が１体積％となるように混合し、メチルエチルケトンを加えてペースト状の複合材料を調製した。
次にこの複合材料を、下地としての磁石の上に塗布して、２０００００μＴの磁場中で乾燥、固化させることによって、金属粉末を膜の厚み方向に配向させた状態で固定したのちはく離して、厚み１２０μｍの異方導電膜を製造した。
【００９２】
参考例３
導電成分として、微細なＮｉ粒が直鎖状に繋がれた形状を有し、Ｎｉ粒の粒径が１μｍ、鎖の径Ｄが１０μｍ、長さＬが５０μｍ、比Ｌ／Ｄが５であるＮｉ粉末を用いたこと以外は参考例２と同様にして、厚み１２０μｍの異方導電膜を製造した。
参考例４
導電成分として、微細なＮｉ粒が直鎖状に繋がれた形状を有し、Ｎｉ粒の粒径が１μｍ、鎖の径Ｄが１０μｍ、長さＬが５０μｍ、比Ｌ／Ｄが５であるＮｉ粉末の表面を、厚み５０ｎｍのＡｇで被覆した複合構造を有する金属粉末を用いたこと以外は参考例２と同様にして、厚み１２０μｍの異方導電膜を製造した。
【００９３】
参考例５
導電成分として、微細なＮｉ粒が直鎖状に繋がれた形状を有し、Ｎｉ粒の粒径が３００ｎｍ、鎖の径Ｄが６００ｎｍ、長さＬが５０μｍ、比Ｌ／Ｄが８３．３であるＮｉ粉末を用いたこと以外は参考例２と同様にして、厚み１２０μｍの異方導電膜を製造した。
比較例６
導電成分として、直径５μｍの球状のＮｉ粉末を用い、このＮｉ粉末と、結着剤としてのアクリル樹脂とを、金属充てん率が１０体積％となるように混合し、メチルエチルケトンを加えてペースト状の複合材料を調製した。
【００９４】
次に、この複合材料をガラス基板上に塗布して乾燥、固化させたのち、はく離することで、厚み１２０μｍの異方導電膜を製造した。
比較例７
導電成分として、前記比較例２で使用したのと同じ、直径５μｍの球状の樹脂粒子の表面に、１００ｎｍのＡｕを被覆した金属粉末を用い、この金属粉末と、結着剤としてのアクリル樹脂とを、金属充てん率が１０体積％となるように混合し、メチルエチルケトンを加えてペースト状の複合材料を調製した。
【００９５】
次に、この複合材料をガラス基板上に塗布して乾燥、固化させたのち、はく離することで、厚み１２０μｍの異方導電膜を製造した。
比較例８
絶縁性の樹脂中に、直径２０μｍ、長さ１２０μｍの円柱状のＣｕ粉末を３０μｍ間隔で分布させた、厚み１２０μｍの市販の異方導電膜を、比較例８とした。
【００９６】
接続抵抗の測定
幅１００μｍ、長さ５０μｍ、厚み２μｍのＡｕ電極が４０μｍ間隔で配列された電極パターンを有するＦＰＣの、上記電極パターン上に、各参考例、比較例で製造した異方導電膜を貼り付けた。次に、片面にＡｌ膜を蒸着したガラス基板を、Ａｌ膜が異方導電膜と接するように重ねた状態で、１００℃に加熱しながら１電極あたり１ｇの圧力で加圧して熱接着させた。
【００９７】
そして異方導電膜とＡｌ膜とを介して導電接続された隣り合う２つのＡｕ電極間の抵抗値を測定し、この測定値を１／２にして、異方導電膜の厚み方向の接続抵抗とした。
結果を表３に示す。なお表中の評価は、それぞれ下記のとおりとした。
◎：接続抵抗が０．１Ω以下。厚み方向の導電性は極めて良好。
○：接続抵抗が０．１Ω超で、かつ１Ω以下。厚み方向の導電性は良好。
【００９８】
×：接続抵抗が１Ω超。厚み方向の導電性は不良。
絶縁抵抗の測定
幅１００μｍ、長さ５０μｍ、厚み２μｍのＡｕ電極が４０μｍ間隔で配列された電極パターンを有するＦＰＣの、上記電極パターン上に、各実施例、比較例で製造した異方導電膜を貼り付けた。
次にこの異方導電膜上に、今度はＡｌ膜を蒸着していないガラス基板を重ねた状態で、１００℃に加熱しながら１電極あたり１ｇの圧力で加圧して熱接着させた。
【００９９】
そして異方導電膜を介してガラス基板が熱接着された、隣り合う２つのＡｕ電極間の抵抗値を測定して、異方導電膜の面方向の絶縁抵抗とした。
結果を表３に示す。なお表中の評価は、それぞれ下記のとおりとした。
◎：絶縁抵抗が１０ＧΩ以上。面方向の絶縁性は極めて良好。
○：絶縁抵抗が１００ＭΩ超で、かつ１０ＧΩ未満。面方向の絶縁性は良好。
×：絶縁抵抗が１００ＭΩ以下。面方向の絶縁性は不良。
【０１００】
限界電流量の測定
幅１００μｍ、長さ５０μｍ、厚み２μｍのＡｕ電極が４０μｍ間隔で配列された電極パターンを有するＦＰＣの、上記電極パターン上に、各参考例、比較例で製造した異方導電膜を貼り付けた。次に、片面にＡｌ膜を蒸着したガラス基板を、Ａｌ膜が異方導電膜と接するように重ねた状態で、１００℃に加熱しながら１電極あたり１ｇの圧力で加圧して熱接着させた。
【０１０１】
そして異方導電膜とＡｌ膜とを介して導電接続された隣り合う２つのＡｕ電極間に電流を流すとともに、その電流値を徐々に増加させた際に、溶断による断線が発生した電流値を求めて限界電流量とした。
結果を表３に示す。なお表中の評価は、それぞれ下記のとおりとした。
◎：限界電流量が１．５Ａ超。耐電流特性は極めて良好。
○：限界電流値が１．０Ａ以上で、かつ１.５Ａ以下。耐電流特性は良好。
【０１０２】
×：限界電流値が１．０Ａ未満。耐電流特性は不良。
【０１０３】
【表３】

【０１０４】
表３より、球状のＮｉ粉末を１０体積％の金属充てん率で含有させた比較例６の異方導電膜、並びに樹脂粒子とＡｕ被覆の複合構造を有する球状の金属粉末を１０体積％の金属充てん率で含有させた比較例７の異方導電膜はともに接続抵抗が高く、厚み方向の導電性が悪いことがわかった。また比較例６の異方導電膜は絶縁抵抗が低いことから、面方向の絶縁性も悪いことがわかった。
また円柱状のＣｕ粉末を含有させた比較例８の異方導電膜は、やはり接続抵抗が高く、厚み方向の導電性が悪いことがわかった。
【０１０５】
これに対し、参考例２〜５の異方導電膜は何れも接続抵抗が低く、厚み方向の導電性に優れるとともに、絶縁抵抗が高く、面方向の絶縁性にも優れることがわかった。また参考例２〜４と参考例５から、異方導電膜の限界電流値を向上するためには、金属粉末の鎖の径を１μｍを超える範囲、特に５μｍ以上にするのが好ましいことが確認された。
【０１０６】
また参考例２、３と参考例４から、接続抵抗をさらに低くするためには、金属粉末の鎖の表面に、導電性に優れた金属を被覆すればよいことが確認された。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel anisotropic conductive film used for, for example, electronics mounting and a manufacturing method thereof.
[0002]
[Prior art]
For example, a semiconductor package is mounted on a mounting electrode provided on a conductor circuit such as a flexible printed wiring board (FPC) by so-called flip chip bonding, or two or more FPC conductor circuits are connected to each other. In the field of electronics mounting, in which the electrodes are connected via electrodes, high-density mounting is progressing, and the pitch between adjacent electrodes tends to become narrower.
[0003]
As one of the mounting methods in electronics mounting, there is a method using a film-like anisotropic conductive film having thermal adhesiveness (see, for example, Patent Documents 1 and 2).
An anisotropic conductive film, for example, a powdery conductive component, a function of forming a film by holding a conductive component such as a thermoplastic resin or a curable resin (film forming property), and an adhesive for heat bonding It has a structure in which it is dispersed in a film made of a binder having both functions (adhesiveness).
[0004]
An anisotropic conductive film having such a structure is formed by mixing the conductive component and a solid binder together with a solvent at a predetermined ratio to form a liquid composite material, and applying the composite material on a base. After drying and solidifying, it can be produced by peeling from the substrate. An anisotropic conductive film can also be produced by applying a composite material without a solvent by using a liquid curable resin as a binder, for example, and then solidifying the curable resin by semi-curing it. it can.
[0005]
In the anisotropic conductive film, the distribution density of the conductive component is set so that the conductive resistance in the surface direction (referred to as “insulation resistance”) is high in order to prevent short-circuiting between adjacent electrodes when thermally bonded. The metal filling rate represented by the ratio of the metal powder to the total amount of the specified metal powder and binder is adjusted.
Then, thermal bonding is performed with an anisotropic conductive film sandwiched between the FPC and the semiconductor package to be conductively connected or between the FPCs.
[0006]
Then, the anisotropic conductive film is compressed in the thickness direction by heating and pressurization at the time of thermal bonding, so that the distribution density of the conductive component in the thickness direction is increased, and the conductive components are close to each other or in contact with each other. As a result of forming the network, the conductive resistance in the thickness direction (referred to as “connection resistance”) is lowered.
However, at this time, the distribution density of the conductive component in the plane direction of the anisotropic conductive film does not increase. That is, the surface direction maintains the initial state where the insulation resistance is high and the conductivity is low.
[0007]
Therefore, according to the anisotropic conductive film, the insulation between adjacent electrodes is maintained by the insulation resistance in the plane direction to prevent a short circuit, while the connection resistance in the thickness direction allows a large number of electrodes-bumps or between the electrodes-electrodes. Since the conductive connection can be made at a time and independently, and the FPC and the semiconductor package or between the FPCs can be fixed by thermal bonding, the mounting operation is easy.
[0008]
[Patent Document 1]
JP-A-6-102523 (column 0009, column 0010, FIG. 2)
[Patent Document 2]
JP-A-8-115617 (column 0003, FIG. 1)
[0009]
[Problems to be solved by the invention]
As a conductive component contained in a conventional anisotropic conductive film, for example, Ni having an average particle diameter of about several μm to several tens of μm, and its shape is granular, spherical, flaky (flaky, flaky), etc. Various metal powders such as powders or resin powders whose surfaces are gold-plated have been put into practical use.
Moreover, in the conventional anisotropic conductive film, said metal powder is normally contained so that a metal filling rate may be 7-10 volume%.
[0010]
However, in the range of the metal filling rate, the value of the connection resistance at the time of thermal bonding is not sufficient, and there are increasing cases where it is required to further reduce the connection resistance. Therefore, in order to further lower the connection resistance during thermal bonding, it is conceivable to increase the metal filling rate from the above range. It will be lower. For this reason, for example, a new problem that a short circuit is likely to occur between electrodes adjacent to each other in the surface direction, which are arranged close to each other in accordance with the interval between the bumps of the semiconductor package, is caused.
[0011]
And since it is easy to produce such a problem, the conventional anisotropic conductive film cannot respond unless the pitch between adjacent electrodes is 50 μm or more, and cannot meet the demand for higher density mounting in the field of electronics mounting. is the current situation.
In addition, recently, the inventor has used a number of fine contact probes mounted on a mounting board in a probe card used to inspect whether a semiconductor chip such as a memory, IC, LSI, or ASIC has been normally manufactured. Separately, it was considered to use one anisotropic conductive film in place of a large number of wires used to connect to the electrodes on the circuit of the probe card body. In such connection, since the pitch of the pads of the semiconductor chip is about 100 to 200 μm, it was thought that a conventional anisotropic conductive film could sufficiently cope.
[0012]
That is, for example, the probe card is connected to a pad such as a semiconductor chip formed on a wafer before being cut into a predetermined size, and the contact probe is brought into conduction, whereby the circuit in the semiconductor chip is replaced with the circuit in the probe card body. This is intended for inspection by connecting to an external inspection circuit via a contact probe as the semiconductor chip is miniaturized, the pads themselves and their formation pitch are miniaturized due to multi-integration, or the number of pads is increased. There is a tendency to refine itself and to be multi-integrated on a mounting substrate.
[0013]
In particular, recently, probe cards in which a large number of very fine contact probes processed with a processing accuracy of micron units are mounted on a mounting substrate at a pitch of 100 to 200 μm according to the pitch of the pads of the semiconductor chip as described above. It has been put into practical use.
However, for example, in a probe card that inspects several tens to several hundreds of semiconductor chips formed on one wafer at a time, thousands of contact probes must be mounted on a mounting substrate. The same number is required for the wiring connecting the contact probe and the probe card body. Therefore, the number of wiring soldering operations is enormous.
[0014]
For this reason, there is a problem that it is very difficult to manufacture and manage the probe card.
Therefore, the inventor studied to substitute a large number of wirings and their soldering with a single anisotropic conductive film. However, if the conventional anisotropic conductive film was simply diverted, the following was obtained. It turned out that it was difficult to put it to practical use because it caused problems.
(1) If a short circuit has occurred in the internal circuit of the semiconductor chip to be tested, a large current of, for example, 1 A or more may flow locally in the anisotropic conductive film during the test. However, the conventional anisotropic conductive film does not consider the response to such a large current, and the allowable current value is only about several tens mA. For this reason, when a large current flows due to a short circuit or the like, Joule heat is generated, and the anisotropic conductive film becomes locally high in temperature, which may cause fusing.
[0015]
(2) As mentioned above, the contact probe is extremely small and fragile, so when using an anisotropic conductive film for its mounting, it is more than the usual connection between electrode and pad as described above. However, it is necessary to apply pressure at the time of thermal bonding at a low pressure. However, when the connection is made at a low pressure, the conventional anisotropic conductive film cannot reduce the connection resistance in the thickness direction to a sufficiently practical level, which may cause poor conduction.
[0016]
(3) Further, when the metal filling rate of the metal powder is increased in order to eliminate the conduction failure, the conventional anisotropic conductive film also decreases the insulation resistance in the surface direction as described above. Even if the pitch is, a short circuit may occur between adjacent electrodes.
(4) Further, in order to inspect a high-speed semiconductor chip such as a graphic board, a game semiconductor chip, or a Ga-As element at an actual operation speed, it is necessary to use a high-frequency signal. However, especially when the metal filling rate of the metal powder is increased so as to eliminate the conduction failure as described above, the impedance of the anisotropic conductive film increases, so that it is difficult to pass a high-frequency signal and it may not be possible to inspect. is there.
[0017]
(5) Since the semiconductor chip to be inspected by the probe card is often formed distributed over the entire surface of one wafer as described above, the contact probe mounting substrate and the probe card body are: It is formed in a large size that covers the wafer. Therefore, the anisotropic conductive film for connecting the probe card has to cover a considerably larger size than that for mounting a conventional semiconductor package, and, as described above, due to warping of these large members when connected at a low pressure. It is necessary to absorb variations in the thickness direction over the entire surface so as not to cause poor connection or poor conduction. However, it is difficult for conventional anisotropic conductive films to meet such requirements.
[0018]
An object of the present invention is to prevent a short circuit even when, for example, the pitch between adjacent electrodes is less than 50 μm, more preferably 40 μm or less. It is an object of the present invention to provide a novel anisotropic conductive film that can sufficiently cope with this.
Another object of the present invention is that the conductive connection can be made more reliably with a low-voltage connection than in the case of the semiconductor package described above, and it does not blow out even when a large current flows, and can also handle high-frequency signals. Accordingly, it is an object of the present invention to provide a novel anisotropic conductive film particularly suitable for mounting a contact probe or the like.
[0019]
Still another object of the present invention is to provide a method for producing such a novel anisotropic conductive film.
[0020]
[Means for Solving the Problems and Effects of the Invention]
  The invention described in claim 1Particle size is 400nm or lessA metal powder having a shape in which a large number of metal particles are connected in a chain, a ratio L / D of the chain length L to the diameter D is 3 or more, and D is 1 μm or less is included as a conductive component. An anisotropic conductive film characterized in that,The metal powder or the individual metal particles forming the metal powder may be a single metal having ferromagnetism, an alloy of two or more metals having ferromagnetism, an alloy of a metal having ferromagnetism and another metal, or It is formed of a composite containing a metal with ferromagnetism.It is a characteristic anisotropic conductive film.
  The metal powder used as the conductive component in the structure of claim 1 is formed into a shape in which a large number of fine metal particles of micron order or submicron order are connected in a chain form from the beginning by, for example, reduction precipitation described later. In particular, as will be described later, in a metal powder having a structure in which a metal film is further deposited around a large number of metal particles connected, individual metal particles are directly connected. For this reason, compared with the conventional granular metal powder, the increase in the contact resistance between each metal particle can be suppressed.
[0021]
  Further, the chain metal powder has a specific surface area larger than that of a conventional metal powder such as a granule, and therefore can be uniformly dispersed in the binder without causing aggregation or the like.
  Moreover, chain metal powderAs described above, the ratio L / D of the chain length L to the diameter D is 3 or more, preferablySince it is as large as about 10 to 100, a good conductive network can be formed in the anisotropic conductive film even when added in a small amount.
  For this reason, according to the configuration of the first aspect, the connection resistance in the thickness direction is reduced without increasing the packing density of the metal powder, that is, while maintaining the insulation resistance in the surface direction of the anisotropic conductive film at a high level. Can be greatly reduced.
  On the other hand, when the ratio L / D is less than 3, the chain length is too short, and the contact resistance of the anisotropic conductive film is lowered without causing a short circuit due to the effect of the density of the interaction between the metal powders. The effect is not obtained.
[0022]
Therefore, when the anisotropic conductive film according to claim 1 is used for mounting a semiconductor package or the like, a fine component having a pitch between adjacent electrodes of less than 50 μm, more preferably 40 μm or less, which could not be realized conventionally. Even the conductive connection can be reliably performed without causing a short circuit, and can sufficiently meet the demand for higher density mounting.
Further, when the anisotropic conductive film according to claim 1 is used for mounting a contact probe or the like, the packing density of the metal powder is not so high as described above, and therefore the impedance is maintained at a low level and the high frequency is maintained. In a state where signals can be passed, a large number of contact probes can be conductively connected more reliably by connection at a lower pressure.
[0023]
  The invention according to claim 2 is the anisotropic conductive film according to claim 1, wherein the chain of the metal powder is oriented in the thickness direction of the film.
  If the chain of metal powder is oriented in the thickness direction of the film, the connection resistance in the thickness direction can be further greatly reduced..
[0024]
In the above configuration, when fine metal particles of submicron order are deposited by the reduction precipitation method described below, the metal particles are magnetized, and a large number of metal particles are chained by a magnetic force. The metal powder is automatically formed.
Therefore, according to the structure of Claim 3, manufacture of a chain | strand-shaped metal powder is easy, and the improvement of manufacturing efficiency, a cost reduction, etc. of an anisotropic conductive film are attained.
In addition, the metal powder ranges from those in which a large number of fine metal particles are simply connected in a chain form by magnetic force, to those in which a metal layer is further deposited around the connected metal particles and the metal particles are firmly bonded. Although those having various structures are included, in any of these, the metal particles basically hold the magnetic force.
[0025]
For this reason, for example, when a composite material is manufactured or when an anisotropic conductive film is manufactured by applying on a base, the chain is not easily broken, and even if it is broken, no stress is applied. At this point, chain recombination is likely to occur. In addition, in the coated film after application, a plurality of metal powders easily come into contact with each other based on the magnetic force of the metal particles to form a conductive network.
Therefore, according to the configuration of claim 3, it is possible to further reduce the connection resistance in the thickness direction of the anisotropic conductive film.
[0026]
  Claim3In the described invention, the chain metal powder, or individual metal particles forming the metal powder, is added by adding ions of a metal having ferromagnetism as a forming material to a solution containing a reducing agent. A chain metal powder formed by precipitation in the metal powder or individual metal particles forming the metal powder.1 or 2It is an anisotropic conductive film of description.
[0027]
According to this reduction precipitation method, it becomes possible to automatically form a chain metal powder as described above.
Further, the metal particles formed by the reduction precipitation method have a uniform particle size and a sharp particle size distribution. This is because the reduction reaction proceeds uniformly in the system. Therefore, the metal powder produced from such metal grains is particularly excellent in the effect of making the connection resistance in the thickness direction of the anisotropic conductive film uniform over the entire surface of the anisotropic conductive film.
[0028]
The invention according to claim 5 is the anisotropic conductive film according to claim 4 using a trivalent titanium compound as a reducing agent.
Various compounds are conceivable as reducing agents for forming chain metal powders or individual metal particles forming the metal powders by the reduction precipitation method. However, among these, when a trivalent titanium compound such as titanium trichloride is used, the solution after the chain metal powder is deposited and formed is repeatedly used for the production of the chain metal powder by electrolytic regeneration. There is an advantage that it can be reproduced in a possible state.
[0029]
  Claim5The described invention includes a chain metal powder and a binder as solid content, and the metal filling rate represented by the ratio of the metal powder in the total amount of solid content is 0.05 to 20% by volume. Item 1 to4It is an anisotropic conductive film as described in any one of these. If the metal filling rate is less than 0.05%, there is too little metal powder that contributes to conduction in the thickness direction of the anisotropic conductive film, and thus there is a possibility that the connection resistance in the same direction due to thermal bonding cannot be sufficiently lowered. When the metal filling rate exceeds 20% by volume, the insulation resistance in the surface direction of the anisotropic conductive film becomes too low, and there is a possibility that a short circuit is likely to occur between adjacent electrodes.
[0030]
  Claim6The described invention is a metal powder,Particle size is 400nm or lessA metal particle having a shape in which a large number of metal grains are connected in a linear or needle shape is used.5It is an anisotropic conductive film as described in any one of these. When a linear or acicular metal powder is used, the connection resistance in the thickness direction of the anisotropic conductive film can be further reduced, and the insulation resistance in the plane direction can be further increased. In particular, when the metal powder chains are oriented in the thickness direction of the film, the interaction between the metal powders arranged along the orientation direction becomes closer and between the metal powders arranged in the transverse direction intersecting the orientation direction. Therefore, the above-described curing can be exhibited more remarkably.
[0031]
  The chain length of the metal powder is less than the distance between adjacent electrodes to be conductively joined.It is preferable to do.In particular, in the case of mounting a semiconductor package, if the length of the chain of the metal powder is defined to be less than the distance between the adjacent electrodes as described above, even if the chain metal powder is laid down during thermal bonding, There is no short circuit between the matching electrodes. For this reason, it can prevent reliably that a short circuit generate | occur | produces between adjacent electrodes.
[0032]
  In the case of mounting a semiconductor package, even if the pitch between adjacent electrodes is less than 50 nm, more preferably 40 μm or less.6In order to mount a semiconductor package or the like without causing a short circuit due to the effect of the density of the interaction between the metal powders, the chain diameter of the metal powder is preferably 1 μm or less.
[0033]
  In order to make the chain diameter 1 μm or less, it is preferable that the particle diameter of each metal particle forming the chain is 400 nm or less..
[0036]
  Further, in mounting the semiconductor package, it is necessary to sufficiently reduce the connection resistance in the thickness direction of the anisotropic conductive film by thermal bonding, and to further reduce the connection resistance during low-voltage connection in mounting the contact probe. Then, in either case, as the metal powder, for example,FerromagneticIt is preferable to use those having a composite structure in which the surface of the chain formed of a metal having a metal is coated with a metal having excellent conductivity.
[0037]
  Claims7In the described invention, the chain metal powder further comprises a single metal having ferromagnetism, an alloy of two or more metals having ferromagnetism, and an alloy of a metal having ferromagnetism and another metal. A chain metal powder on which a metal layer is deposited.6The anisotropic conductive film according to any one of the above.
  Further claims8In the described invention, the chain metal powder further deposits a metal layer made of at least one metal selected from the group consisting of Cu, Rb, Rh, Pd, Ag, Re, Pt and Au on the surface thereof. And a chain metal powder coated with the metal layer.7It is an anisotropic conductive film as described in any one of these.
[0038]
  Claim9The described invention is a method for producing the anisotropic conductive film according to claim 2, comprising at least a part of a chain metal powder formed of a ferromagnetic metal, and a binder. A composite material having fluidity is applied on a base to which a magnetic field is applied in a direction crossing the base surface, and the metal powder chains in the composite material are oriented in the thickness direction of the film along the magnetic field direction. The method for producing an anisotropic conductive film is characterized in that the orientation of the chain is fixed by solidifying or curing the composite material.
[0039]
  And claims10The invention described in the above is a method for producing the anisotropic conductive film according to claim 2, wherein at least a part of the chain-shaped metal powder formed of a ferromagnetic metal is crossed with the base surface. It is spread on a substrate to which a magnetic field is applied, and the metal powder chains are oriented in the direction of the magnetic field, and a fluid coating material containing a binder is applied thereon to solidify or cure. Thus, the anisotropic conductive film is produced by fixing the orientation of the chain.
[0040]
According to these manufacturing methods, the anisotropic conductive film in which the chain of the metal powder is oriented in the thickness direction of the film can be formed more efficiently.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described below.
The anisotropic conductive film of the present invention is characterized by containing, as a conductive component, metal powder having a shape in which a large number of fine metal particles are connected in a chain.
(Metal powder)
As the chain metal powder, any of various metal powders having a chain structure manufactured by various methods such as a gas phase method and a liquid phase method can be used. Those having a shape in which the grains are connected in a linear or needle shape are preferred.
[0042]
  In addition, as the chain metal powder, the metal powder, or individual metal particles forming the metal powder,FerromagneticA single metal havingFerromagneticAn alloy of two or more metals havingFerromagneticAn alloy of a metal with other metal andFerromagneticWhat was formed with the composite containing the metal which has this is preferable.
  FerromagneticSpecific examples of the metal powder containing a metal having the following can include any one of the following (a) to (e), or a mixture of two or more.
[0043]
  (a)FerromagneticA single metal havingFerromagneticAn alloy of two or more metals having, orFerromagneticA metal powder in which a large number of micron-order to sub-micron-order metal grains formed from an alloy of a metal having a metal and other metals are connected in a chain by its own magnetism.
  (b) Further on the surface of the metal powder of (a) above,FerromagneticA single metal havingFerromagneticAn alloy of two or more metals having, orFerromagneticThe metal powder which precipitated the metal layer which consists of an alloy of the metal which has this, and another metal, and couple | bonded the metal grain firmly.
[0044]
  (c) A metal powder in which a metal layer made of another metal or alloy is further deposited on the surface of the metal powder of (a) or (b), and the metal particles are firmly bonded.
  (d)FerromagneticA single metal havingFerromagneticAn alloy of two or more metals having, orFerromagneticThe surface of a granular core material formed from an alloy of a metal having a metal and another metal is coated with another metal or alloy to obtain a composite, and this composite is used as a metal particle to produce a large number of particles by the magnetism of the core , Metal powder linked in a chain.
[0045]
  (e) A metal powder in which a metal layer made of another metal or alloy is further deposited on the surface of the metal powder of (d), and the metal particles are firmly bonded.
  Of the aboveFerromagneticA single metal havingFerromagneticAn alloy of two or more metals having, orFerromagneticThe entire metal powder or metal particles formed by an alloy of a metal having a
  FerromagneticOf metal powder or metal particles formed by a composite containing a metal havingFerromagneticThe portion containing the metal having
  The material is formed by reduction depositionFerromagneticIt is preferable to form it by depositing in a solution by adding a reducing agent to a solution containing metal ions having the above.
[0046]
In the reduction precipitation method, first, a reducing agent, for example, a trivalent titanium compound such as titanium trichloride and a solution in which, for example, trisodium citrate is dissolved (hereinafter referred to as “reducing agent solution”), ammonia water or the like. To adjust the pH to 9-10. As a result, trivalent titanium ions are combined with citric acid as a complexing agent to form a coordination compound, and the activation energy when oxidized from Ti (III) to Ti (IV) is reduced. The potential increases. Specifically, the potential difference between Ti (III) and Ti (IV) exceeds 1V. This value is significantly higher than the reduction potential from Ni (II) to Ni (0), the reduction potential from Fe (II) to Fe (0), and the like. Therefore, various metal ions can be efficiently reduced to deposit and form metal particles, metal films, and the like.
[0047]
  Next, to the above reducing agent solution, such as Ni,FerromagneticA solution containing ions of a single metal havingFerromagneticAdd a solution containing two or more ions to form an alloy containing a metal having.
  Then, when Ti (III) functions as a reducing agent and oxidizes itself to Ti (IV), metal ions are reduced and deposited in the liquid. That is, metal particles composed of the above-mentioned simple metal or alloy are precipitated in the liquid, and a large number are connected in a chain by its own magnetism to form a chain metal powder. Further, if the precipitation is continued thereafter, a metal layer is further deposited on the surface of the metal powder, and the metal particles are firmly bonded to each other.
[0048]
That is, the metal powder such as (a) and (b), the metal particles that are the basis thereof, or the core material of the composite that is the basis of the metal powder of (d) can be manufactured by the above method. it can.
Among these, the metal particles and the core material have uniform particle sizes, and the particle size distribution is sharp. This is because the reduction reaction proceeds uniformly in the system. Therefore, the metal powder produced from such metal particles and core material is particularly excellent in the effect of making the conductive resistance in the thickness direction of the anisotropic conductive film uniform over the entire surface of the anisotropic conductive film.
[0049]
The reducing agent solution after the metal particles, the core material, and the like are deposited can be used for the production of chain metal powder by the reductive precipitation method by repeating the electrolytic regeneration any number of times. That is, by reducing the Ti (IV) to Ti (III) by applying a voltage, for example, by putting the reducing agent solution after depositing metal particles, cores, etc. into the electrolytic cell, electrolytic deposition again. Can be used as a reducing agent solution. This is because titanium ions are hardly consumed during electrolytic deposition, that is, they are not deposited together with the metal to be deposited.
[0050]
  Forming metal particles, cores, etc.FerromagneticExamples of the metal or alloy having Ni include Ni, iron, cobalt, and two or more of these alloys, and particularly Ni simple substance or Ni-iron alloy (Permalloy) is preferable. Particularly, metal particles formed of such metals and alloys have a strong effect of reducing the contact resistance between the metal particles because they have a strong magnetic interaction when connected in a chain.
  Also above,FerromagneticThe other metal that forms the composite of (c), (d), and (e) together with the metal or alloy having the above is selected from the group consisting of Cu, Rb, Rh, Pd, Ag, Re, Pt, and Au. Further, at least one kind of metal or an alloy thereof can be used. In consideration of improving the conductivity of the metal powder, the portion formed of these metals is preferably a portion exposed on the outer surface of the chain. That is, a composite having the structure of (c) and (e) in which the chain surface is coated with these metals is preferable. The coating can be formed by various film forming methods such as electroless plating, electrolytic plating, reduction deposition, and vacuum deposition.
[0051]
The metal powder used for mounting a semiconductor package or the like has any one of the structures (a) to (e), and the chain length is less than the distance between adjacent electrodes to be conductively bonded. Is preferred.
The metal powder preferably has a chain diameter of 1 μm or less, and individual metal particles forming the chain metal powder have a particle diameter of 400 nm or less.
These reasons are as described above.
[0052]
The length of the chain is more preferably 0.9 times or less of the distance between adjacent electrodes to be conductively bonded in consideration of further reliably preventing a short circuit due to sideways.
Also, if the chain diameter is too small, the chain diameter may be easily cut when the composite material is manufactured, or when it is applied on the base and the anisotropic conductive film is manufactured with a degree of stress. It is preferably 10 nm or more.
[0053]
  Also, if the particle size of the metal particles forming the chain is too small, the size of the metal powder itself connected in a chain shape may be too small, and the function as a conductive component may not be sufficiently obtained. The grain size is preferably 10 nm or more.
  UpThe lower limit of the chain length mentionedStipulate,Ratio L / D of chain length L to diameter DIs3 or moreNeed to be.
[0054]
  When the ratio L / D is less than 3, as described above, the effect of reducing the contact resistance of the anisotropic conductive film can be obtained without causing a short circuit due to the effect of the density of the interaction between the metal powders. RenaNo.
  In particular, as in the above (c) or (e), a composite structure in which the chain surface is coated with at least one metal selected from the group consisting of Cu, Rb, Rh, Pd, Ag, Re, Pt and Au. It is preferable to have conductivity because the conductivity can be improved.
[0055]
On the other hand, the metal powder used for mounting the contact probe or the like preferably has any one of the structures (a) to (e), and the chain diameter exceeds 1 μm and is 20 μm or less.
Moreover, it is preferable that the particle size of each metal particle which forms the said metal powder is 0.5-2 micrometers.
In particular, as in the above (c) or (e), a composite structure in which the chain surface is coated with at least one metal selected from the group consisting of Cu, Rb, Rh, Pd, Ag, Re, Pt and Au. It is preferable to have conductivity because the conductivity can be improved.
[0056]
However, as the metal powder for mounting the contact probe, there are many chains of the same diameter as those used for mounting the semiconductor package, and the diameter of the chain formed by agglomeration in a bundle shape. Can be used with a thickness exceeding 1 μm and not exceeding 20 μm. In consideration of improving conductivity, the surface of the aggregate may be coated with the metal.
There is an anisotropic conductive film in which a cylindrical Cu powder having a diameter similar to that of the above metal powder and having a diameter of about 20 μm and a length of about 120 μm is dispersed in a resin.
[0057]
However, when such an anisotropic conductive film is used for mounting a contact probe, the conductivity in the thickness direction of the film becomes insufficient as is apparent from the results of comparative examples described later. This is considered to be because it cannot be magnetically oriented in the thickness direction of the film because of the copper powder. That is, the copper powder cannot be oriented in the thickness direction of the film by applying a magnetic field, and is randomly oriented due to stress during film formation. For this reason, a sufficient conductive network cannot be formed by the low voltage connection when the contact probe is mounted, and the connection resistance in the same direction cannot be sufficiently lowered.
[0058]
(Binder)
As the binder for forming the anisotropic conductive film together with the chain metal powder, any of various conventionally known compounds having film-forming properties and adhesiveness can be used as the binder in the application. Examples of the binder include thermoplastic resins, curable resins, and liquid curable resins, and particularly preferable examples include acrylic resins, epoxy resins, fluorine resins, and phenol resins.
[0059]
(Composite material)
The composite material which becomes the base of the anisotropic conductive film is manufactured by blending a chain metal powder and a binder together with an appropriate solvent at a predetermined ratio. Further, the solvent may be omitted by using a liquid binder such as a liquid curable resin.
(Anisotropic conductive film and manufacturing method thereof)
The anisotropic conductive film of the present invention is applied to the above-mentioned composite material on a ground such as a glass plate and dried or solidified, or when the binder is a curable resin or a liquid curable resin. Can be manufactured by peeling off from the base after curing.
[0060]
In the case of mounting a semiconductor package, the thickness is preferably 10 μm to 100 μm in consideration of good conductive adhesion when the electrodes and the bumps are pressure-bonded via the anisotropic conductive film.
In the case of contact probe mounting, the thickness of the mounting board and probe card body should absorb variations in the thickness direction due to warpage, etc., over the entire surface so as not to cause poor connection or poor conduction. In consideration, it is preferably 100 to 300 μm.
[0061]
  Moreover, it is preferable that the anisotropic conductive film of this invention is fixing in the state which orientated the chain | strand of the metal powder in the thickness direction of the film | membrane in any use. Such anisotropic conductive film
  (A) At least some of the previously explainedFerromagneticBy applying a flowable composite material including a chain metal powder formed of a metal having a binder and a binder onto a base to which a magnetic field is applied in a direction crossing the base surface, the metal powder Fixing the orientation of the chain of the metal powder by solidifying or curing the composite material in a state where the chain is oriented in the thickness direction of the film along the direction of the magnetic field, or
  (B) The chain-like metal powder is dispersed on a base to which a magnetic field is applied in a direction crossing the base surface, and the binder is added in a state where the chains of the metal powder are oriented in the direction of the magnetic field. After fixing the chain orientation of the metal powder by applying and solidifying or hardening by applying a fluid coating agent,
It can be manufactured by peeling from the substrate.
[0062]
  The strength of the magnetic field applied when carrying out these methods is contained in the metal powder.FerromagneticIn consideration of sufficiently orienting the metal powder in the anisotropic conductive film in the thickness direction of the film, the magnetic flux density is 1000 μT or more, especially 10,000 μT or more. It is preferably 40,000 μT or more.
  Examples of a method for applying a magnetic field include a method of arranging magnets above and below a base such as a glass substrate, or a method of using the surface of a magnet as a base. The latter method utilizes the fact that the lines of magnetic force emerging from the surface of the magnet are substantially perpendicular to the surface of the magnet in the region from the surface to the thickness of the anisotropic conductive film. There is an advantage that the manufacturing apparatus can be simplified.
[0063]
In the anisotropic conductive film thus produced, the solid content, that is, the metal filling amount represented by the ratio of the metal powder to the total amount of the chain metal powder and the binder is 0.05 to 20% by volume. Is preferred.
In particular, in the case of contact probe mounting, in order to suppress the increase in impedance and allow high-frequency signals to pass, the filling rate of the metal powder is particularly 0.05 to 5% by volume even within the above range. Is preferred.
[0064]
In order to adjust the metal filling amount to the above range, in the case of not aligning the chain metal powder, and in the case of (A), a composite material containing the metal powder and the binder in the above ratio is used. And an anisotropic conductive film may be formed. In the case of (B), the amount of the metal powder sprayed, the binder concentration in the coating agent, the coating amount, etc. may be adjusted.
The anisotropic conductive film of the present invention has a function of a chain metal powder as a conductive component. For example, in mounting a semiconductor package, the pitch between adjacent electrodes may be less than 50 μm, more preferably 40 μm or less. There is no short circuit. Therefore, it is possible to sufficiently meet the demand for higher density mounting in the field of electronics mounting.
[0065]
In the case of contact probe mounting, in particular, by increasing the chain diameter and orienting the chain in the thickness direction of the film, it is possible to make a more reliable conductive connection at a lower pressure than in the case of a semiconductor package. Become. Moreover, it does not melt even when a large current flows, and it can be adapted to high-frequency signals.
Note that the anisotropic conductive film of the present invention can be used for, for example, pin mounting of IC sockets in addition to the above applications. It can also be used for three-dimensional packages that are currently connected by wire bonding or μBGA (μball grid array).
[0066]
【Example】
Hereinafter, the present invention will be described based on examples and comparative examples.
[Anisotropic conductive film for mounting semiconductor packages]
Example 1
The conductive component has a shape in which fine Ni particles are connected in a straight chain, the particle size of the Ni particles is 100 nm, the chain diameter D is 400 nm, the length L is 5 μm, and the ratio L / D is 12. 5 Ni powder was used.
[0067]
And this Ni powder and the acrylic resin as a binder were mixed so that a metal filling rate might be 20 volume%, methyl ethyl ketone was added, and the paste-form composite material was prepared.
Next, this composite material was applied on a glass substrate, dried and solidified, and then peeled off to produce an anisotropic conductive film having a thickness of 30 μm.
Example 2
As a conductive component, it has a shape in which fine Ni particles are connected in a straight chain, the particle size of Ni particles is 400 nm, the diameter D of the chain is 1 μm, the length L is 5 μm, and the ratio L / D is 5. Using Ni powder, mixing this Ni powder and acrylic resin as a binder so that the metal filling rate is 0.05% by volume, and adding methyl ethyl ketone to prepare a paste-like composite material Except for this, an anisotropic conductive film with a thickness of 30 μm was produced in the same manner as in Example 1.
[0068]
Example 3
The conductive component has a shape in which fine Ni particles are connected in a straight chain, the particle size of the Ni particles is 300 nm, the chain diameter D is 600 nm, the length L is 5 μm, and the ratio L / D is 8.3. The metal powder having a composite structure obtained by coating the surface of the Ni powder with 50 nm thick Ag and the metal powder and an acrylic resin as a binder have a metal filling rate of 1% by volume. An anisotropic conductive film having a thickness of 30 μm was manufactured in the same manner as in Example 1 except that methyl ethyl ketone was added to prepare a paste-like composite material.
[0069]
Example 4
The same composite material as prepared in Example 3 was applied on a magnet as a base, dried and solidified in a magnetic field having a magnetic flux density of 40000 μT, so that the metal powder was oriented in the thickness direction of the film. After fixing in the state, it was peeled off to produce an anisotropic conductive film having a thickness of 30 μm.
Example 5
The same metal powder as used in Example 3 was dispersed on the same magnet as used in Example 4, and was oriented in the thickness direction of the film in a magnetic field having a magnetic flux density of 40000 μT.
[0070]
Next, in this state, a coating material in which an acrylic resin as a binder was dissolved in methyl ethyl ketone was applied. The coating amount was adjusted so that the metal filling rate was 1% by volume.
Then, by drying and solidifying the coating agent, the metal powder was fixed in a state of being oriented in the thickness direction of the film, and then peeled to produce an anisotropic conductive film having a thickness of 30 μm.
Comparative Example 1
As a conductive component, a flaky Ni powder having a particle size distribution from 5 μm to 20 μm was used, and this Ni powder and an acrylic resin as a binder were mixed so that the metal filling rate was 20% by volume. Then, an anisotropic conductive film having a thickness of 30 μm was produced in the same manner as in Example 1 except that methyl ethyl ketone was added to prepare a pasty composite material.
[0071]
Comparative Example 2
A spherical metal powder having a composite structure in which 100 nm of Au is coated on the surface of spherical resin particles having a diameter of 5 μm as a conductive component, and this metal powder and an acrylic resin as a binder, An anisotropic conductive film having a thickness of 30 μm was manufactured in the same manner as in Example 1 except that mixing was performed so that the metal filling rate was 20% by volume and methyl ethyl ketone was added to prepare a pasty composite material.
[0072]
Comparative Example 3
The same metal powder used in Comparative Example 2 and an acrylic resin as a binder were mixed so that the metal filling rate was 1% by volume, and methyl ethyl ketone was added to prepare a paste-like composite material. Except for the above, an anisotropic conductive film with a thickness of 30 μm was produced in the same manner as in Comparative Example 2.
Connection resistance measurement
An anisotropic conductive film produced in each example and comparative example was attached to the above electrode pattern of an FPC having an electrode pattern in which Au electrodes having a width of 15 μm, a length of 50 μm, and a thickness of 2 μm were arranged at intervals of 15 μm.
[0073]
Next, a glass substrate having an Al film deposited on one side was heated and bonded at a pressure of 10 g per electrode while being heated to 100 ° C. with the Al film being in contact with the anisotropic conductive film. .
Then, the resistance value between two adjacent Au electrodes conductively connected via the anisotropic conductive film and the Al film is measured, and the measured value is halved to determine the connection resistance in the thickness direction of the anisotropic conductive film. It was.
[0074]
The results are shown in Table 1. The evaluations in the table were as follows.
A: Connection resistance is 0.1Ω or less. The conductivity in the thickness direction is very good.
○: Connection resistance is more than 0.1Ω and 1Ω or less. Good electrical conductivity in the thickness direction.
X: Connection resistance exceeds 1Ω. The conductivity in the thickness direction is poor.
Insulation resistance measurement
On the same FPC electrode pattern as used above, the anisotropic conductive films produced in the examples and comparative examples were attached.
[0075]
Next, on this anisotropic conductive film, a glass substrate on which an Al film was not deposited was overlapped, and pressure was applied at a pressure of 10 g per electrode while being heated to 100 ° C. to perform thermal bonding.
Then, the resistance value between two adjacent Au electrodes, to which the glass substrate was thermally bonded via the anisotropic conductive film, was measured to obtain the insulation resistance in the surface direction of the anisotropic conductive film.
The results are shown in Table 1. The evaluations in the table were as follows.
[0076]
A: Insulation resistance exceeds 1 GΩ. Insulation in the surface direction is very good.
○: Insulation resistance is more than 1 MΩ and 1 GΩ or less. Excellent insulation in the surface direction.
X: Insulation resistance is 1 MΩ or less. Insulation in the surface direction is poor.
[0077]
[Table 1]

[0078]
From Table 1, 20% by volume of the anisotropic conductive film containing 20% by volume of flaky Ni powder and 20% by volume of spherical metal powder having a composite structure of resin particles and Au coating. It was found that both of the anisotropic conductive films of Comparative Example 2 contained at a metal filling rate had low insulation resistance and poor planar insulation. Moreover, it turned out that the anisotropic conductive film of the comparative example 3 which reduced the metal filling rate of the spherical metal powder which has the said composite structure to 1 volume% has high connection resistance, and its electroconductivity of thickness direction is bad.
[0079]
On the other hand, it has been found that the anisotropic conductive films of Examples 1 to 5 each have low connection resistance and excellent conductivity in the thickness direction, high insulation resistance, and excellent surface insulation.
Also, from Examples 1 and 2, in order to lower the connection resistance and increase the insulation resistance, it is only necessary to reduce the metal filling rate while increasing the chain diameter of the linear metal powder. confirmed.
[0080]
Further, from Examples 1 to 3, in order to further reduce the connection resistance, the surface of the metal powder chain may be coated with a metal having excellent conductivity. From Examples 3 to 5, the metal powder chain It was confirmed that the film should be oriented in the thickness direction.
Example 6
The conductive component has a shape in which fine Ni particles are connected in a straight chain, the particle size of the Ni particles is 400 nm, the chain diameter D is 1 μm, the length L is 9 μm, and the ratio L / D is 9. Some Ni powder was used.
[0081]
And this Ni powder and the acrylic resin as a binder were mixed so that a metal filling rate might be 1 volume%, methyl ethyl ketone was added, and the paste-form composite material was prepared.
Next, this composite material is applied onto a base magnet, dried and solidified in a magnetic field having a magnetic flux density of 200,000 μT, and then fixed in a state where the metal powder is oriented in the thickness direction of the film, and then released. Thus, an anisotropic conductive film having a thickness of 20 μm was manufactured.
[0082]
  Reference example 1
  As a conductive component, it has a shape in which fine Ni particles are connected in a straight chain, the particle size of the Ni particles is 400 nm, the chain diameter D is 3 μm, the length L is 9 μm, and the ratio L / D is 3. An anisotropic conductive film having a thickness of 20 μm was produced in the same manner as in Example 6 except that Ni powder was used.
  Comparative Example 4
  As a conductive component, it has a shape in which fine Ni particles are connected in a straight chain, the particle size of Ni particles is 400 nm, the diameter D of the chain is 1 μm, the length L is 15 μm, and the ratio L / D is 15. An anisotropic conductive film having a thickness of 20 μm was produced in the same manner as in Example 6 except that Ni powder was used.
[0083]
Comparative Example 5
As the conductive component, a granular Ni powder comprising an aggregate of fine Ni particles, the particle size of Ni particles being 400 nm, the short diameter D being 6 μm, the long diameter L being 9 μm, and the ratio L / D being 1.5 was used. Except for this, an anisotropic conductive film having a thickness of 20 μm was produced in the same manner as in Example 6.
Connection resistance measurement
An anisotropic conductive film produced in each example and comparative example was attached to the above electrode pattern of an FPC having an electrode pattern in which Au electrodes having a width of 15 μm, a length of 50 μm, and a thickness of 5 μm were arranged at intervals of 10 μm.
[0084]
Next, a glass substrate having an Al film deposited on one side was heated and bonded at a pressure of 10 g per electrode while being heated to 100 ° C. with the Al film being in contact with the anisotropic conductive film. .
Then, the resistance value between two adjacent Au electrodes conductively connected via the anisotropic conductive film and the Al film is measured, and the measured value is halved to determine the connection resistance in the thickness direction of the anisotropic conductive film. It was.
[0085]
The results are shown in Table 2. The evaluations in the table were as follows.
A: Connection resistance is 0.1Ω or less. The conductivity in the thickness direction is very good.
○: Connection resistance is more than 0.1Ω and 1Ω or less. Good electrical conductivity in the thickness direction.
X: Connection resistance exceeds 1Ω. The conductivity in the thickness direction is poor.
Insulation resistance measurement
On the same FPC electrode pattern as used above, the anisotropic conductive films produced in the examples and comparative examples were attached.
[0086]
Next, on this anisotropic conductive film, a glass substrate on which an Al film was not deposited was overlapped, and pressure was applied at a pressure of 10 g per electrode while being heated to 100 ° C. to perform thermal bonding.
Then, the resistance value between two adjacent Au electrodes, to which the glass substrate was thermally bonded via the anisotropic conductive film, was measured to obtain the insulation resistance in the surface direction of the anisotropic conductive film.
The results are shown in Table 2. The evaluations in the table were as follows.
[0087]
A: Insulation resistance exceeds 1 GΩ. Insulation in the surface direction is very good.
○: Insulation resistance is more than 1 MΩ and 1 GΩ or less. Excellent insulation in the surface direction.
X: Insulation resistance is 1 MΩ or less. Insulation in the surface direction is poor.
[0088]
[Table 2]

[0089]
From Table 2, it can be seen that the anisotropic conductive film of Comparative Example 4 containing a chain-like Ni powder having a chain length longer than the distance between adjacent electrodes has low insulation resistance and poor planar insulation. all right. And as a cause of this, it was predicted that Ni powder laid down during thermal bonding, and the adjacent electrodes were short-circuited.
Moreover, it turned out that the anisotropic conductive film of the comparative example 5 which contained Ni powder which is too small in the ratio L / D and which is not a chain | strand shape but a granular form has high connection resistance, and its electroconductivity of the thickness direction is low.
[0090]
  On the other hand, it was found that the anisotropic conductive film of Example 6 had low connection resistance and excellent conductivity in the thickness direction, high insulation resistance, and excellent surface insulation. And from this, it was confirmed that short-circuiting between adjacent electrodes can be reliably prevented even if Ni powder lays down during thermal bonding by making the chain length less than the distance between adjacent electrodes. It was.
[Anisotropic conductive film for mounting contact probes]
  Reference example 2
  As a conductive component, it has a shape in which a plurality of chains in which fine Ni particles are connected in a straight line and aggregated in a bundle shape, the particle diameter of Ni particles is 100 nm, the diameter D of the chain is 10 μm, and the length L Ni powder having a ratio L / D of 5 was used.
[0091]
And this Ni powder and the acrylic resin as a binder were mixed so that a metal filling rate might be 1 volume%, methyl ethyl ketone was added, and the paste-form composite material was prepared.
Next, this composite material is applied on a magnet as a base, dried and solidified in a magnetic field of 200,000 μT, and then fixed in a state where the metal powder is oriented in the thickness direction of the film, and then released. An anisotropic conductive film having a thickness of 120 μm was manufactured.
[0092]
  Reference example 3
  As a conductive component, it has a shape in which fine Ni particles are connected in a straight chain, the particle size of Ni particles is 1 μm, the chain diameter D is 10 μm, the length L is 50 μm, and the ratio L / D is 5. Except for using Ni powderReference example 2In the same manner, an anisotropic conductive film having a thickness of 120 μm was manufactured.
  Reference example 4
  As a conductive component, it has a shape in which fine Ni particles are connected in a straight chain, the particle size of Ni particles is 1 μm, the chain diameter D is 10 μm, the length L is 50 μm, and the ratio L / D is 5. Except for using a metal powder having a composite structure in which the surface of Ni powder is coated with Ag having a thickness of 50 nm.Reference example 2In the same manner, an anisotropic conductive film having a thickness of 120 μm was manufactured.
[0093]
  Reference Example 5
  The conductive component has a shape in which fine Ni particles are connected in a straight chain, the particle size of the Ni particles is 300 nm, the chain diameter D is 600 nm, the length L is 50 μm, and the ratio L / D is 83.3. Except for using Ni powderReference example 2In the same manner, an anisotropic conductive film having a thickness of 120 μm was manufactured.
  Comparative Example 6
  As a conductive component, a spherical Ni powder having a diameter of 5 μm was used. This Ni powder and an acrylic resin as a binder were mixed so that the metal filling rate was 10% by volume, and methyl ethyl ketone was added to form a paste. A composite material was prepared.
[0094]
Next, this composite material was applied onto a glass substrate, dried and solidified, and then peeled to produce an anisotropic conductive film having a thickness of 120 μm.
Comparative Example 7
As the conductive component, the same metal powder coated with 100 nm of Au on the surface of spherical resin particles having a diameter of 5 μm, which is the same as that used in Comparative Example 2, was used. This metal powder and an acrylic resin as a binder were used. Were mixed so that the metal filling rate would be 10% by volume, and methyl ethyl ketone was added to prepare a paste-like composite material.
[0095]
Next, this composite material was applied onto a glass substrate, dried and solidified, and then peeled to produce an anisotropic conductive film having a thickness of 120 μm.
Comparative Example 8
A commercially available anisotropic conductive film having a thickness of 120 μm, in which cylindrical Cu powder having a diameter of 20 μm and a length of 120 μm was distributed in an insulating resin at intervals of 30 μm, was used as Comparative Example 8.
[0096]
  Connection resistance measurement
  Each of the FPCs having an electrode pattern in which Au electrodes having a width of 100 μm, a length of 50 μm, and a thickness of 2 μm are arranged at intervals of 40 μm,referenceAnisotropic conductive films produced in Examples and Comparative Examples were attached. Next, a glass substrate having an Al film deposited on one side was heated and bonded at a pressure of 1 g per electrode while heating at 100 ° C. with the Al film being in contact with the anisotropic conductive film. .
[0097]
Then, the resistance value between two adjacent Au electrodes conductively connected via the anisotropic conductive film and the Al film is measured, and the measured value is halved to determine the connection resistance in the thickness direction of the anisotropic conductive film. It was.
The results are shown in Table 3. The evaluations in the table were as follows.
A: Connection resistance is 0.1Ω or less. The conductivity in the thickness direction is very good.
○: Connection resistance is more than 0.1Ω and 1Ω or less. Good electrical conductivity in the thickness direction.
[0098]
X: Connection resistance exceeds 1Ω. The conductivity in the thickness direction is poor.
Insulation resistance measurement
An anisotropic conductive film manufactured in each of Examples and Comparative Examples was pasted on the above electrode pattern of FPC having an electrode pattern in which Au electrodes having a width of 100 μm, a length of 50 μm, and a thickness of 2 μm were arranged at intervals of 40 μm.
Next, on this anisotropic conductive film, a glass substrate on which an Al film was not deposited was overlapped, and pressure was applied at a pressure of 1 g per electrode while being heated to 100 ° C. to perform thermal bonding.
[0099]
Then, the resistance value between two adjacent Au electrodes, to which the glass substrate was thermally bonded via the anisotropic conductive film, was measured to obtain the insulation resistance in the surface direction of the anisotropic conductive film.
The results are shown in Table 3. The evaluations in the table were as follows.
A: Insulation resistance is 10 GΩ or more. Insulation in the surface direction is very good.
○: Insulation resistance is more than 100 MΩ and less than 10 GΩ. Excellent insulation in the surface direction.
X: Insulation resistance is 100 MΩ or less. Insulation in the surface direction is poor.
[0100]
  Limit current measurement
  Each of the FPCs having an electrode pattern in which Au electrodes having a width of 100 μm, a length of 50 μm, and a thickness of 2 μm are arranged at intervals of 40 μm,referenceAnisotropic conductive films produced in Examples and Comparative Examples were attached. Next, a glass substrate having an Al film deposited on one side was heated and bonded at a pressure of 1 g per electrode while heating at 100 ° C. with the Al film being in contact with the anisotropic conductive film. .
[0101]
A current is passed between two adjacent Au electrodes that are conductively connected via an anisotropic conductive film and an Al film, and when the current value is gradually increased, the current value at which disconnection due to fusing occurs The limit current amount was obtained.
The results are shown in Table 3. The evaluations in the table were as follows.
A: Limit current amount exceeds 1.5 A. Excellent current resistance.
◯: Limit current value is 1.0 A or more and 1.5 A or less. Good withstand current characteristics.
[0102]
X: Limit current value is less than 1.0A. Current resistance is poor.
[0103]
[Table 3]

[0104]
From Table 3, the anisotropic conductive film of Comparative Example 6 containing a spherical Ni powder with a metal filling rate of 10% by volume, and the spherical metal powder having a composite structure of resin particles and Au coating of 10% by volume of metal. It was found that both of the anisotropic conductive films of Comparative Example 7 contained at a filling rate had high connection resistance and poor conductivity in the thickness direction. Moreover, since the anisotropic conductive film of the comparative example 6 had low insulation resistance, it turned out that the insulation of a surface direction is also bad.
It was also found that the anisotropic conductive film of Comparative Example 8 containing columnar Cu powder had high connection resistance and poor conductivity in the thickness direction.
[0105]
  In contrast,Reference Examples 2-5These anisotropic conductive films were found to have low connection resistance, excellent conductivity in the thickness direction, high insulation resistance, and excellent surface direction insulation. AlsoReference Examples 2-4WhenReference Example 5Thus, in order to improve the limit current value of the anisotropic conductive film, it was confirmed that the chain diameter of the metal powder is preferably in a range exceeding 1 μm, particularly 5 μm or more.
[0106]
  AlsoReference examples 2 and 3WhenReference example 4Therefore, it was confirmed that the surface of the metal powder chain may be coated with a metal having excellent conductivity in order to further reduce the connection resistance.

Claims (10)

Metal powder having a shape in which a large number of metal particles having a particle size of 400 nm or less are connected in a chain, the ratio L / D of the chain length L to the diameter D is 3 or more, and D is 1 μm or less Is an anisotropic conductive film characterized by containing as a conductive component,
The metal powder or the individual metal particles forming the metal powder may be a single metal having ferromagnetism, an alloy of two or more metals having ferromagnetism, an alloy of a metal having ferromagnetism and another metal, or An anisotropic conductive film formed of a composite containing a metal having ferromagnetism .   The anisotropic conductive film according to claim 1, wherein the chain of the metal powder is oriented in the thickness direction of the film.   The metal powder or the individual metal particles forming the metal powder are formed by adding ferromagnetic metal ions, which are the forming material, to a solution containing a reducing agent to precipitate in the solution. The anisotropic conductive film according to claim 1 or 2. Anisotropically conductive film according to claim 3, wherein using a trivalent titanium compound as the reducing agent. And a chain metal powder and a binder as a solid content, and claims 1 and 0.05 to 20% by volume metal filling factor represented by the ratio of the metal powder relative to the total amount of solids of 4 The anisotropic conductive film as described in any one. The anisotropic conductive film according to any one of claims 1 to 5 , wherein the metal powder has a shape in which a large number of metal particles having a particle size of 400 nm or less are connected in a linear or needle shape.   The chain metal powder further deposits on its surface a metal layer comprising a single metal having ferromagnetism, an alloy of two or more metals having ferromagnetism, and an alloy of a metal having ferromagnetism and another metal. The anisotropic conductive film according to any one of claims 1 to 6, wherein the anisotropic conductive film is a chain metal powder. The chain metal powder further deposits a metal layer made of at least one metal selected from the group consisting of Cu, Rb, Rh, Pd, Ag, Re, Pt and Au on the surface of the metal powder. The anisotropic conductive film according to any one of claims 1 to 7 , wherein the anisotropic conductive film is a chain-like metal powder coated with.   3. A method for producing an anisotropic conductive film according to claim 2, wherein at least a part of the composite film has a fluidity and includes a chain-like metal powder formed of a ferromagnetic metal and a binder. The material is applied on a base to which a magnetic field is applied in a direction crossing the base surface, and the metal powder chains in the composite material are oriented in the thickness direction of the film along the magnetic field direction, and the composite material is solidified. Alternatively, a method for producing an anisotropic conductive film, wherein the chain orientation is fixed by curing.   3. A method for producing an anisotropic conductive film according to claim 2, wherein a chain-shaped metal powder, at least part of which is formed of a ferromagnetic metal, is applied with a magnetic field in a direction intersecting the base surface. Sprinkle on the ground to orient the metal powder chains in the direction of the magnetic field, and then apply a flowable coating material containing a binder to solidify or harden the chain orientation. A method for producing an anisotropic conductive film, comprising fixing.