【０００１】
【発明の属する技術分野】
本発明は、２つの回路基板の電極同士を対向させ接着樹脂を介して圧着する回路基板の接続方法に関し、さらに詳しく言えば、接続される電極が銅のような厚膜電極である場合に好適な回路基板の接続方法に関するものである。
【０００２】
【従来の技術】
２つの回路基板の電極同士を対向させて接続する方法に一つに、ＡＣＦ（異方性導電フィルム），ＮＣＦ（非導電フィルム），ＡＣＰ（異方性導電ペースト），ＮＣＰ（非導電ペースト）などの接着樹脂を用いての熱圧着法がある。
【０００３】
例えば、ＡＣＦ（異方性導電フィルム）について説明すると、ＡＣＦは熱可塑性もしくは熱硬化性樹脂フィルム内に導電粒子を分散させたもので、熱圧着することにより導電粒子がつながって単一方向の導電性を示し、これにより電極間同士の導通がとられる。
【０００４】
【発明が解決しようとする課題】
このように、ＡＣＦ（他の接着樹脂も同じ）によれば、多数の電極同士を一括して接続することができるが、接続する電極が厚膜電極の場合、次のような問題がある。
【０００５】
これを説明するために、図２（ａ）の断面図に第１回路基板１０側の厚膜電極群１１と第２回路基板２０側の厚膜電極群２１とをＡＣＦ３０を介して対向させた熱圧着前の状態を示し、図２（ｂ）の断面図に熱圧着後の状態を示す。なお、熱圧着によりＡＣＦ３０の樹脂は流動し、その状態の作図が困難であるため、図２（ｂ）にはＡＣＦ３０が省略されている。
【０００６】
ＡＣＦ３０は、電極１１，２１間の電気的接続と回路基板１０，２０間の機械的接続の双方の役割を担うが、例えば銅からなる厚膜電極の場合、その厚さに起因してＩＴＯのような薄膜電極の場合よりも回路基板１０，２０間の間隔が広くなるため、接着樹脂による機械的接続（保持）力が十分でなくなり、剥離してしまうことがある。
【０００７】
これを防止するには、ＡＣＦ３０に膜厚の厚いものを使用して接着樹脂量を増やせばよいのであるが、このようにすると、電極１１，２１間に接着樹脂が残され接続不良が発生したり、また、余剰の接着樹脂がはみ出して周辺を汚すなどの別の問題が引き起こされることがある。
【０００８】
したがって、本発明の課題は、特に厚膜電極同士を接着樹脂を介して熱圧着する場合、電気的な接続不良を招くことなく、十分な機械的接続力が得られるようにすることにある。
【０００９】
【課題を解決するための手段】
上記課題を解決するため、本発明は、第１電極群を有する第１回路基板と、上記第１電極群と対向する第２電極群を有する第２回路基板とを含み、上記各電極群の間に接着樹脂を配置して圧着する回路基板の接続方法において、上記第１電極群の両側に、所定のピッチで配列された少なくとも２列のダミー電極を含む第１補強電極部を形成するとともに、上記第２電極群の両側に、上記第１補強電極部のダミー電極間と対向する少なくとも１列のダミー電極を含む第２補強電極部を形成し、上記各補強電極部間にも上記接着樹脂を配置して、上記各電極群同士および上記各補強電極部同士を同時に圧着することを特徴としている。
【００１０】
この構成によれば、第１補強電極部のダミー電極間に第２補強電極部のダミー電極が入り込むため、その分、接着面積が広くなり、接着樹脂による機械的接続力が高められる。
【００１１】
本発明の好ましい態様によれば、各補強電極部ともに同一ピッチで配列された複数のダミー電極を含み、一方のダミー電極に対して他方のダミー電極が１／２ピッチずらされる。
【００１２】
なお、本発明において、ダミー電極とはもっぱら機械的接続力を高めるための電極で、電気信号の授受には寄与しない電極のことを言う。また、厚膜電極には厚さ５μｍ以上の電極が含まれる。
【００１３】
【発明の実施の形態】
次に、図１（ａ），（ｂ）により、本発明の実施形態について説明する。なお、図１（ａ）は先の図２（ａ）に対応する熱圧着前の状態を示す断面図で、また、図１（ｂ）は先の図２（ｂ）に対応する熱圧着後の状態を示す断面図である。
【００１４】
本発明において、第１回路基板１０と第２回路基板２０は、両方とも硬質回路基板、一方が硬質回路基板で，他方がフレキシブル基板、両方ともフレキシブル基板のいずれの組み合わせであってもよい。また、各厚膜電極群１１，２１は図１の紙面に対して直交する方向に沿って形成されている。
【００１５】
厚膜電極群１１と厚膜電極群２１とを例えばＡＣＦ３０を介して熱圧着するにあたって、本発明によると、厚膜電極群１１の両側に第１補強電極部１２が設けられ、また、厚膜電極群２１の両側にも第２補強電極部２２が設けられる。
【００１６】
この例において、第１補強電極部１２は２列のダミー電極１２１，１２２を含み、また、第２補強電極部２２も２列のダミー電極２２１，２２２を含む。これらの各ダミー電極１２１，１２２；２２１，２２２の膜厚（高さ）は、厚膜電極群１１，２１と同一であることが好ましいが、それよりも若干薄く（低く）てもよい。
【００１７】
第１補強電極部１２と第２補強電極部２２は、その一方のダミー電極１２１，１２２と、他方のダミー電極２２１，２２２とが互いに噛み合うように配置される。このようにするには、一例として、まず、ダミー電極１２１，１２２とダミー電極２２１，２２２とを同一の断面形状とする。その断面形状は台形であることが好ましいが、これ以外に例えば四角断面形状もしくは半円断面形状としてもよい。
【００１８】
次に、ダミー電極１２１，１２２とダミー電極２２１，２２２とをともに、電極幅（線幅）と電極間幅（線間幅）を同一としたうえで、相対的に１／２ピッチずらす。これにより、図１（ｂ）に示すように、熱圧着時に正確な噛み合い状態が得られる。
【００１９】
したがって、厚膜電極群１１と厚膜電極群２１との間および第１補強電極部１２と第２補強電極部２２との間にＡＣＦ３０を配置して熱圧着することにより、厚膜電極群１１と厚膜電極群２１との導通が採られるとともに、ダミー電極１２１，１２２とダミー電極２２１，２２２との噛み合い部分にもＡＣＦ３０が入り込んでより広い面での接着が行われ、強固な機械的接続状態が得られることになる。
【００２０】
機械的接続強度をより高めるには、ダミー電極の数は多いほどよいが、最低限として、一方のダミー電極が２つで、他方のダミー電極がそれらの間に入り込む１つの電極、すなわち２：１の関係を満足すればよい。また、使用する接着樹脂はＡＣＦに限定されるものでなく、ＮＣＦ，ＡＣＰ，ＮＣＰなどの接着樹脂も適用可能である。さらに、接着樹脂は熱硬化性，熱可塑性に限られず、光硬化性の材料であってもよい。
【００２１】
【発明の効果】
以上説明したように、本発明によれば、第１電極群を有する第１回路基板と、第２電極群を有する第２回路基板とを、それらの各電極群の間に接着樹脂を配置して圧着するにあたって、第１電極群の両側に、所定のピッチで配列された少なくとも２列のダミー電極を含む第１補強電極部を形成するとともに、第２電極群の両側に、第１補強電極部のダミー電極間と対向する少なくとも１列のダミー電極を含む第２補強電極部を形成し、各補強電極部間にも接着樹脂を配置して、各電極群同士および各補強電極部同士を同時に圧着することにより、特に厚膜電極同士を接着樹脂を介して圧着する場合、電気的な接続不良を招くことなく、十分な機械的接続力を得ることができる。
【図面の簡単な説明】
【図１】本発明の実施形態を示す図で、（ａ）は熱圧着前の状態を示す断面図、（ｂ）は熱圧着後の状態を示す断面図である。
【図２】従来の接続方法を示す図で、（ａ）は熱圧着前の状態を示す断面図、（ｂ）は熱圧着後の状態を示す断面図である。
【符号の説明】
１０，２０ 回路基板
１１，２１ 厚膜電極群
１２，２２ 補強電極部
１２１，１２２，２２１，２２２ ダミー電極
３０ ＡＣＦ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a circuit board connection method in which electrodes of two circuit boards are opposed to each other and pressure-bonded via an adhesive resin, and more specifically, is suitable when the connected electrodes are thick-film electrodes such as copper. The present invention relates to a method for connecting various circuit boards.
[0002]
[Prior art]
One of the methods of connecting the electrodes of two circuit boards while facing each other is ACF (anisotropic conductive film), NCF (non-conductive film), ACP (anisotropic conductive paste), NCP (non-conductive paste) There is a thermocompression bonding method using an adhesive resin.
[0003]
For example, an ACF (anisotropic conductive film) will be described. ACF is a thermoplastic or thermosetting resin film in which conductive particles are dispersed, and the conductive particles are connected by thermocompression bonding to form a unidirectional conductive film. Property, whereby conduction between the electrodes is established.
[0004]
[Problems to be solved by the invention]
As described above, according to the ACF (the same applies to other adhesive resins), a large number of electrodes can be connected collectively. However, when the electrodes to be connected are thick-film electrodes, there are the following problems.
[0005]
In order to explain this, the thick film electrode group 11 on the first circuit board 10 side and the thick film electrode group 21 on the second circuit board 20 side are opposed to each other via the ACF 30 in the cross-sectional view of FIG. The state before thermocompression bonding is shown, and the state after thermocompression bonding is shown in the cross-sectional view of FIG. Note that the resin of the ACF 30 flows due to the thermocompression bonding, and it is difficult to draw the resin in that state. Therefore, the ACF 30 is omitted in FIG. 2B.
[0006]
The ACF 30 plays both roles of electrical connection between the electrodes 11 and 21 and mechanical connection between the circuit boards 10 and 20. For example, in the case of a thick-film electrode made of copper, the ACF 30 has a thickness of ITO due to its thickness. Since the distance between the circuit boards 10 and 20 is wider than in the case of such a thin film electrode, the mechanical connection (holding) force by the adhesive resin is not sufficient, and the thin film electrode may be peeled off.
[0007]
In order to prevent this, it is only necessary to use a thicker ACF 30 to increase the amount of the adhesive resin. However, in this case, the adhesive resin is left between the electrodes 11 and 21 and a connection failure occurs. Or another problem such as excessive adhesive resin protruding and soiling the surroundings.
[0008]
Therefore, an object of the present invention is to make it possible to obtain a sufficient mechanical connection force without causing electrical connection failure particularly when thermocompression bonding of thick film electrodes via an adhesive resin.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention includes a first circuit board having a first electrode group, and a second circuit board having a second electrode group facing the first electrode group. In a method of connecting a circuit board in which an adhesive resin is arranged and pressure-bonded, a first reinforcing electrode portion including at least two rows of dummy electrodes arranged at a predetermined pitch is formed on both sides of the first electrode group. Forming, on both sides of the second electrode group, a second reinforcing electrode portion including at least one row of dummy electrodes facing between the dummy electrodes of the first reinforcing electrode portion, and bonding the respective reinforcing electrode portions to each other; A resin is disposed, and the electrode groups and the reinforcing electrode portions are simultaneously pressure-bonded to each other.
[0010]
According to this configuration, since the dummy electrode of the second reinforcing electrode portion enters between the dummy electrodes of the first reinforcing electrode portion, the bonding area is accordingly increased, and the mechanical connection force by the adhesive resin is increased.
[0011]
According to a preferred aspect of the present invention, each reinforcing electrode portion includes a plurality of dummy electrodes arranged at the same pitch, and the other dummy electrode is shifted by ピ ッ チ pitch with respect to one dummy electrode.
[0012]
Note that, in the present invention, the dummy electrode is an electrode solely for increasing the mechanical connection force, and refers to an electrode that does not contribute to transmission and reception of an electric signal. The thick-film electrode includes an electrode having a thickness of 5 μm or more.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1A is a cross-sectional view showing a state before thermocompression corresponding to FIG. 2A, and FIG. 1B is a view after thermocompression corresponding to FIG. 2B. It is sectional drawing which shows the state of.
[0014]
In the present invention, both the first circuit board 10 and the second circuit board 20 may be any combination of a rigid circuit board, one is a rigid circuit board, the other is a flexible board, and both are a flexible board. The thick film electrode groups 11 and 21 are formed along a direction orthogonal to the plane of FIG.
[0015]
According to the present invention, when the thick-film electrode group 11 and the thick-film electrode group 21 are thermocompression-bonded via the ACF 30, for example, the first reinforcing electrode portions 12 are provided on both sides of the thick-film electrode group 11, and Second reinforcing electrode portions 22 are also provided on both sides of the electrode group 21.
[0016]
In this example, the first reinforcing electrode section 12 includes two rows of dummy electrodes 121 and 122, and the second reinforcing electrode section 22 also includes two rows of dummy electrodes 221 and 222. The thickness (height) of each of these dummy electrodes 121, 122; 221, 222 is preferably the same as that of the thick-film electrode groups 11, 21, but may be slightly thinner (lower).
[0017]
The first reinforcing electrode section 12 and the second reinforcing electrode section 22 are arranged such that one of the dummy electrodes 121 and 122 and the other of the dummy electrodes 221 and 222 mesh with each other. To do so, as an example, first, the dummy electrodes 121 and 122 and the dummy electrodes 221 and 222 have the same cross-sectional shape. The cross-sectional shape is preferably trapezoidal, but may be, for example, a square cross-sectional shape or a semicircular cross-sectional shape.
[0018]
Next, both the dummy electrodes 121 and 122 and the dummy electrodes 221 and 222 have the same electrode width (line width) and the same electrode width (line width), and are relatively shifted by ピ ッ チ pitch. Thereby, as shown in FIG. 1B, an accurate meshing state can be obtained at the time of thermocompression bonding.
[0019]
Therefore, the ACF 30 is disposed between the thick-film electrode group 11 and the thick-film electrode group 21 and between the first reinforcing electrode unit 12 and the second reinforcing electrode unit 22 and thermocompression-bonded. Between the dummy electrodes 121 and 122 and the dummy electrodes 221 and 222, and the ACF 30 enters into the area where the dummy electrodes 121 and 122 mesh with each other, thereby bonding over a wider surface, thereby providing a strong mechanical connection. A state will be obtained.
[0020]
In order to further increase the mechanical connection strength, it is better to increase the number of dummy electrodes. However, at a minimum, one dummy electrode is two, and the other dummy electrode is one electrode interposed therebetween, that is, 2: It suffices that the relationship of 1 is satisfied. Further, the adhesive resin to be used is not limited to ACF, and an adhesive resin such as NCF, ACP, NCP or the like can be applied. Further, the adhesive resin is not limited to thermosetting and thermoplastic, but may be a photocurable material.
[0021]
【The invention's effect】
As described above, according to the present invention, the first circuit board having the first electrode group and the second circuit board having the second electrode group are provided by disposing an adhesive resin between the respective electrode groups. When performing pressure bonding, first reinforcing electrode portions including at least two rows of dummy electrodes arranged at a predetermined pitch are formed on both sides of the first electrode group, and first reinforcing electrodes are formed on both sides of the second electrode group. Forming a second reinforcing electrode portion including at least one row of dummy electrodes opposed to the dummy electrode portions, and also placing an adhesive resin between the reinforcing electrode portions to connect the respective electrode groups and the respective reinforcing electrode portions. By performing pressure bonding at the same time, a sufficient mechanical connection force can be obtained without causing poor electrical connection, particularly when the thick film electrodes are pressed together via an adhesive resin.
[Brief description of the drawings]
FIG. 1 is a view showing an embodiment of the present invention, in which (a) is a cross-sectional view showing a state before thermocompression bonding, and (b) is a cross-sectional view showing a state after thermocompression bonding.
2A and 2B are views showing a conventional connection method, in which FIG. 2A is a cross-sectional view showing a state before thermocompression bonding, and FIG. 2B is a cross-sectional view showing a state after thermocompression bonding.
[Explanation of symbols]
10, 20 Circuit board 11, 21 Thick film electrode group 12, 22 Reinforcement electrode part 121, 122, 221, 222 Dummy electrode 30 ACF
