JPH1065332A - Anistropic conductive thin film and method for connection of polymer board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an anistropic conductive films(ACF) for good electrical connection in a structure, wherein a flexible board is connected to a polymer board by thermo-compression bonding and a method for connecting a flexible board to thin film electrode patterns of the anistropic conductive films(ACF) by thermo-compression bonding. SOLUTION: An anistropic conductive film is provided with conductive particles dispersed in an adhesive layer, and a flexible wiring board for lead out is electrically and mechanically connected to a polymer board with wiring electrodes for lead out formed thereon. In this case, the total thickness of the adhesive layer (Ta) and the initial diameter of the conductive particles (D) satisfy the following formulas. D>Ta.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive thin film, and a mounting method for connecting a wiring electrode formed on a polymer substrate by the thin film, particularly a lead electrode of a liquid crystal display panel substrate and a terminal of a flexible substrate. And a mounting structure manufactured by the mounting method.

[0002]

2. Description of the Related Art In a mounting structure in which a lead electrode of a liquid crystal display panel and a terminal of a flexible substrate are connected by an anisotropic conductive film, the connection terminal of the flexible substrate has a protrusion of 1 × 10 ⁻² mm or less from a substrate material. It is known that the thickness of the anisotropic conductive film is set to be equal to the diameter of the conductive particles (JP-A-7-175078).

[0003]

SUMMARY OF THE INVENTION A thin film electrode (transparent conductive film such as ITO) pattern on a polymer substrate or a flexible wiring board [TCP (Tape Carrier P
package). same as below. In the case of performing thermocompression bonding using an anisotropic conductive film (ACF), FIG.
As shown in (1), dents 9 are generated in the polymer substrate 10 (the transparent conductive film 13 is also slightly cracked), and
Since the conductive particles 8 cannot push through the adhesive layer 2 of the anisotropic conductive film (ACF) 4 and break through, and the thin adhesive layer 12 remains between the conductive particles 8 and the transparent conductive film 13, the transparent conductive film No good electrical connection with No. 13 could be secured. The present invention utilizes an anisotropic conductive film (ACF) and an anisotropic conductive film (ACF) for ensuring good electrical connection in a structure in which the polymer and a TCP or a flexible substrate are thermocompression bonded to a substrate. Another object of the present invention is to provide a method for thermocompression bonding a TCP or a flexible substrate to a thin film electrode pattern on a polymer substrate.

[0004]

[MEANS FOR SOLVING THE PROBLEMS] Anisotropic conductive film (ACF)
A mixture of the adhesive and the conductive particles is used as a separator 1
In forming the adhesive layer 2 on which the conductive particles are dispersed, preferably uniformly dispersed, by printing on the adhesive particles, the adhesive layer thickness Ta is made smaller than the initial particle diameter D of the conductive particles, whereby the adhesion on the conductive particles 3 is reduced. The thickness of the agent layer 2 can be reduced. For this reason, FIG.
As shown in FIGS. 4 and 4, when the flexible wiring board 5 is thermocompression-bonded to the thin film electrode 13 such as ITO on the polymer substrate 10, the conductive particles 8 easily break through the adhesive layer 2, and the conductive particles 8 and the thin film electrode (ITO) Boundary 14 between 13
Has almost no adhesive, so that a good electrical connection can be obtained.

As shown in FIG. 5, the thickness (Tf) of the electrode 7 of the flexible wiring board 5 (including TCP) is usually 7 to 35 μm, while the thickness of the thin film electrode 13 on the polymer substrate 10 side is small. Since the film thickness (Tg) is about 0.1 μm, the anisotropic conductive film (ACF) 4 is sandwiched between the flexible wiring board 5 and the polymer substrate 11 with thin film electrodes, and both are connected by thermocompression bonding. As for the connection electrode step, almost only the film thickness (Tf) of the electrode 7 of the flexible wiring board 5 should be considered. In order to improve the peel strength of the flexible wiring board 5 and the polymer substrate 11 with thin-film electrodes after thermocompression bonding, it is preferable to fill the gap between the electrodes of the flexible wiring board 5 with the anisotropic conductive film 4. When the lower limit of the adhesive film thickness with respect to the electrode film thickness is obtained, the film thickness (Tf) of the electrode 7 of the flexible wiring board 5 is, for example, 18 μm.
The conductive particles 8 having a pattern width: gap ratio of, for example, 1: 1 and an initial particle diameter of, for example, φ21 μm are 1
/ C, for example, if it is crushed to 1/3, it is preferable to satisfy the following relationship.

## EQU4 ## 21 μm (D)> Ta ≧ 21/3 μm (D / C) +
18/2 μm (Tf × A) = 16 μm (where A is the same as above)

In order to further increase the thickness of the adhesive layer, it is necessary to increase the diameter of the conductive particles in order to satisfy the relationship of D ≧ Ta. However, as shown in FIG. 15 and the adhesive layer 16 to form a two-layer structure, and by dispersing the conductive particles 3 in the adhesive layer 16 on the surface side, the thickness between the conductive particles 3 and the thin film electrode (ITO) 13 is increased while increasing the total adhesive layer thickness. Since the adhesive layer 16 hardly remains on the boundary 14 of the flexible wiring board, the gap between the electrodes can be buried without increasing the diameter of the conductive particles even if the film thickness of the flexible wiring board electrode becomes large, and the good adhesion to the polymer substrate 10 can be achieved. Fine pitch connection becomes possible. As described in FIG. 5, when the flexible wiring board and the polymer substrate with thin-film electrodes are connected by thermocompression bonding via an anisotropic conductive film (ACF), only the film thickness (Tf) of the electrode of the flexible wiring board is used. Therefore, when the adhesive layer is taken as one layer and the lower limit of the adhesive film thickness with respect to this electrode film thickness is obtained, for example, when the electrode film thickness of the flexible wiring board is 35 μm and the pattern width: gap = 1: 1. In this case, in order to satisfy D> Ta,
According to D> D / 3 + 35/2, the initial particle diameter D of the conductive particles needs to be D> 26.25 μm. However, in the case of a two-layer structure, particles of 26.25 μm or less can be used. For example, if the thickness of the second layer is 16 μm, 16
μm particles can be used. When the adhesive layer is composed of a plurality of layers as described above, the adhesive layer may be composed of two or more layers. Particularly, by changing the adhesive composition of the first layer and the second layer, each of the adherends can be formed. A composition suitable for bonding can be selected, and the bonding strength at each interface can be improved.

The anisotropic conductive film (AC) shown in FIGS.
The thermocompression bonding between the polymer substrate (display element) and the flexible wiring board (TCP or the like) according to F) can be performed, for example, according to the process shown in FIG. By bringing it to the substrate side, the conductive particles can easily break through the adhesive layer during the thermocompression bonding. In addition, in the anisotropic conductive film shown in FIGS. 3 to 6, the anisotropic conductive film is applied to the polymer substrate with a pressing force equal to or more than the final compression before the final connection of the polymer substrate and the flexible wiring board (such as TCP). By pre-pressing, the conductive particles can break through the adhesive layer without softening of the polymer substrate, and a good connection can be obtained.

FIG. 8 shows a state in which the anisotropic conductive film (ACF) is pressed against the polymer substrate 10 in the step of attaching it. As for the pressure contact conditions, for example, assuming that the pressing force at the time of the final pressure bonding is 30 kgf / cm ² , the pressing force before the final pressure bonding connection is 30 to 40 kgf / cm ² , and the temperature is normal temperature to 8 ° C.
0 ° C. is suitable. FIG. 9 shows an anisotropic conductive film (ACF) having another configuration of the present invention. Since the surface of the conductive particles of this anisotropic conductive film is exposed on the side where the polymer substrate is thermocompression-bonded, the first one that has an adhesive or the like interposed when contacting a thin film electrode such as ITO on the polymer substrate during thermocompression bonding. And good connection can be obtained.

The anisotropic conductive film of the present invention is particularly effective for connecting a flexible wiring board to a polymer substrate on which the above-mentioned wiring electrodes are formed, but is not limited to such connection. However, it can be widely used in the technical field of electrically and mechanically connecting wirings to be connected, for example, a transparent conductive film on a glass substrate such as a liquid crystal display panel, a thin film head electrode for a thermal printer, and a TAB chip outer. It can be used for connecting leads and the like.

[0010] Such an anisotropic conductive film is, for example, shown in FIG.
Are obtained by the following steps. (A) Only the adhesive is printed on the separator to a predetermined thickness to form the adhesive layer 2. (B) Disposing conductive particles on the adhesive layer 2 before the adhesive is completely dried. As a method of arranging the conductive particles 3,
It is performed by spraying with air or the like. After the conductive particles 3 are arranged, the conductive particles 3 are buried in the adhesive layer 2 by the pressing means 18 and manufactured. As a method for embedding the conductive particles 3,
The thickness may be controlled by the total thickness from the lower surface of the separator to the pressing means, and the pressing means may be a roller or the like. (C) The finished product obtained through the steps (a) and (b) is shown.

FIG. 9 shows an anisotropic conductive film (A) shown in FIG.
3 shows another method for producing CF). This anisotropic conductive film (AC
The method F) is a method for producing an anisotropic conductive film in which the conductive particles are arranged and embedded in the adhesive at the same time, and the gap between the lower surface of the separator 1 and the transfer means (roller) 19 is managed and transferred. This is a method in which the conductive particles 3 arranged on the means (roller) 19 are transferred, and the conductive particles 3 are embedded in the adhesive layer 2 by pressure contact. Examples of a method for disposing the conductive particles 3 on the transfer means 19 include a method in which the transfer means is made of a porous member to attract and fix the conductive particles, or a method in which the conductive particles are magnetized and fixed by the magnetism of the transfer means. No.

Hereinafter, embodiments of the present invention will be described. 1. In an anisotropic conductive film in which conductive particles are dispersed in an adhesive layer, the total adhesive layer thickness (Ta) and the initial particle diameter (D) of the conductive particles satisfy the following relationship. Characteristic anisotropic conductive film.

D> Ta 2. The anisotropic conductive film according to 1 above, which is used to electrically and mechanically connect the polymer substrate on which the external lead-out wiring electrodes are formed and the external lead-out flexible wiring board by thermocompression bonding. 3. The polymer substrate is a liquid crystal display panel substrate;
Anisotropic conductive film. 4. The anisotropic conductive film according to any one of the above 2 to 3, wherein the total adhesive layer thickness (Ta), the initial particle diameter (D) of the conductive particles, and the electrode thickness (Tf) of the flexible wiring board satisfy the following relationships.

D> Ta ≧ D × 1 / C + Tf × A [where A is the ratio of the gap to the electrode pattern pitch of the flexible wiring board] The adhesive layer has a multilayer structure of two or more layers, and the conductive adhesive is contained only in the surface adhesive layer on the side where the polymer substrate is pressed, and the surface adhesive layer thickness (Tb) and the conductive particle diameter (D ) Satisfies the following relationship:

(7) D ≧ Tb 5. The anisotropic conductive film according to 5 above, wherein the adhesive layer has two layers, and the first layer and the second layer have different compositions. 7. The anisotropic conductive film according to the above 5 or 6, wherein the first layer and the second layer are of a composition suitable for bonding the respective adherends.

8. The anisotropic conductive film according to any one of 1 to 7, wherein a surface layer of the conductive particles protruding from the adhesive layer is exposed. 9. After the adhesive layer is formed on the separator, the conductive particles are arranged on the surface of the adhesive layer, and then the conductive particles are pressed against the adhesive layer by pressing means, and at least a part of the conductive particles is projected from the adhesive layer into the adhesive layer. 8. The method for producing an anisotropic conductive film according to the above item 8, wherein the method is embedded. 10. 9. The arrangement of the conductive particles is performed by spraying.
A method for producing an anisotropic conductive film.

11. After forming the adhesive layer on the separator,
8. The method for producing an anisotropic conductive film according to the above item 8, wherein the conductive particles arranged in the transfer means are embedded in the adhesive layer with at least a part of the conductive particles protruding from the adhesive layer by the transfer means. 12. 12. The method for producing an anisotropic conductive film according to the above item 11, wherein the transfer means is a transfer roller.

13. A method for electrically and mechanically connecting the polymer substrate on which the external lead-out wiring electrodes are formed and the flexible wiring electrode terminals by thermocompression bonding using the above-mentioned 1 to 12 anisotropic conductive films; A thermocompression bonding method, wherein the conductive particle protruding surface side is thermocompression bonded to a polymer substrate. 14． 13. A connection body between a polymer substrate on which a wiring electrode for external lead-out is formed and a flexible wiring board, which is manufactured by the thermocompression bonding method of the above 13.

15. The thermocompression bonding of the anisotropic conductive film of 2 to 8 to the polymer substrate on which the wiring electrode for external drawing is formed is performed before the actual compression bonding of the flexible wiring board. A thermocompression bonding method for an anisotropic conductive film and a polymer substrate, wherein the pressure bonding is performed at a lower temperature and a higher pressure. 16. 15. The thermocompression bonding method between the anisotropic conductive film and the polymer substrate, wherein the thermocompression bonding is performed without softening.

[0017]

【effect】

1. Claims 1 and 2 During thermocompression connection to a thin film electrode such as ITO on a polymer substrate, the conductive particles easily break through the adhesive, and good electrical connection is obtained. 2. Claim 2 By filling the gap between the electrodes of the flexible wiring board with the anisotropic conductive film adhesive, the peeling force after thermocompression bonding can be improved, and good connection to the thin film electrode on the polymer substrate can be obtained. 3. Claim 3 Since the adhesive layer has a multilayer structure, the thickness of the adhesive on the conductive particles on the polymer substrate connection side can be reduced while the thickness of the adhesive is increased. Even when the thickness is increased, the gap between the electrodes can be buried without increasing the diameter of the conductive particles, and good fine pitch connection to the polymer substrate can be achieved. 4. Claim 4 By changing the adhesive composition, an adhesive composition suitable for each adherend can be selected, and the adhesive force at each interface can be improved. 5. [5] Since the surface of the conductive particles is exposed, an intervening one can be eliminated from the beginning upon contact with a thin film electrode such as ITO on the polymer substrate at the time of thermocompression bonding, and a good connection can be obtained. 6. Claims 6 and 7 By bringing the projecting side of the conductive particles (the opposite side of the separator) to the polymer substrate side, the conductive particles can easily break through the adhesive during thermocompression bonding. 7. Claims 8 and 9 An anisotropic conductive film in which the surface of conductive particles is exposed at the connection surface on the polymer substrate side, and the anisotropic conductive film can be easily manufactured. 8. (10) The conductive particles can break through the adhesive layer without softening of the polymer substrate, and a good connection can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a conventional anisotropic conductive film.

FIG. 2 is a schematic sectional view of a connector obtained by thermocompression bonding a flexible wiring board and a polymer substrate using the anisotropic conductive film of FIG. 1;

FIG. 3 is a schematic cross-sectional view of an anisotropic conductive film during thermocompression bonding.

FIG. 4 is a schematic cross-sectional view of a connection body of a flexible wiring board and a polymer substrate using an anisotropic conductive film of the present invention.

FIG. 5 is a schematic sectional view showing a general electrode thickness of a flexible wiring board and a general thin film electrode thickness of a polymer substrate.

FIG. 6 is a schematic sectional view showing an anisotropic conductive film having two adhesive layers according to the present invention.

FIG. 7 is an explanatory diagram of a thermocompression bonding step between a polymer substrate and a flexible wiring board using an anisotropic conductive film.

FIG. 8 is a schematic cross-sectional view showing a pressure-contact state between the two in a step of attaching an anisotropic conductive film to a polymer substrate.

FIG. 9 is a schematic cross-sectional view of an anisotropic conductive film in which conductive particle surfaces are exposed on the side where a polymer substrate is thermocompression-bonded.

FIG. 10 is an explanatory diagram of a step of manufacturing the anisotropic conductive film of FIG. 9; (A) is a diagram showing an adhesive layer formed on a separator. FIG. 2 (b) is a view illustrating a step of arranging conductive particles on the adhesive layer of FIG. 1 and embedding the particles in the adhesive layer. (C) It is a cross-sectional schematic diagram of the finished product obtained by process (b).

FIG. 11 is an explanatory diagram of another process for manufacturing the anisotropic conductive film of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Separator 2 Adhesive layer 3 Conductive particle 4 Anisotropic conductive film 5 Flexible wiring board 6 Flexible wiring board substrate 7 Electrode 8 Conductive particle (there is crushing by pressurization) 9 Indentation of substrate by conductive particle 10 Polymer substrate 11 Polymer with thin film electrode Substrate 12 Thin adhesive layer between conductive particles / ITO 13 Thin film electrode (ITO) 15 First layer adhesive 16 Second layer adhesive 17 Exposed surface of conductive particles (there is no adhesive layer) 18 Pressing means 19 Transfer Means D Initial particle diameter of conductive particles of anisotropic conductive film Ta Thickness of total adhesive layer of anisotropic conductive film (ACF) Tf Film thickness of flexible wiring board electrode Tg Film thickness of thin film electrode 13 on polymer substrate 10 side

Claims (10)

[Claims] 1. A polymer substrate in which conductive particles are dispersed in an adhesive layer and on which an external lead-out wiring electrode is formed and an external lead-out flexible wiring board are electrically and mechanically connected by thermocompression bonding. An anisotropic conductive film characterized in that the total adhesive layer thickness (Ta) and the initial particle diameter (D) of the conductive particles satisfy the following relationship. ## EQU1 ## D> Ta 2. The thickness of the entire adhesive layer (Ta), the initial particle diameter of the conductive particles (D), and the electrode thickness of the flexible wiring board (T).
The anisotropic conductive film according to claim 1, wherein f) satisfies the following relationship. D> Ta ≧ D × 1 / C + Tf × A [where A is the ratio of the gap to the electrode pattern pitch of the flexible wiring board] 3. The adhesive layer has a multilayer structure of two or more layers,
In addition, conductive particles are contained only in the surface adhesive layer on the side where the polymer substrate is pressed, and the thickness (Tb) of the surface adhesive layer and the initial particle diameter (D) of the conductive particles satisfy the following relationship. The anisotropic conductive film according to claim 1, wherein [Formula 3] D ≧ Tb 4. The anisotropic conductive film according to claim 3, wherein at least the first adhesive layer and the surface adhesive layer on the side to which the polymer substrate is pressed are formed of different compositions. 5. The anisotropic conductive film according to claim 1, wherein the surface layer of the conductive particles protruding from the adhesive layer is exposed. 6. After the adhesive layer is formed on the separator, the conductive particles are arranged on the surface of the adhesive layer, and then the conductive particles are pressed by a pressing means, and at least a part of the conductive particles is projected from the adhesive layer. The method for producing an anisotropic conductive film according to claim 5, wherein the method is embedded in an adhesive layer. 7. After the adhesive layer is formed on the separator, the conductive particles arranged on the transfer means are embedded in the adhesive layer by the transfer means so that at least a portion thereof protrudes from the adhesive layer. The method for producing an anisotropic conductive film according to claim 5. 8. A polymer substrate on which an external lead-out wiring electrode is formed and a flexible wiring electrode terminal are electrically and thermally compressed by an anisotropic conductive film according to claim 1, 2, 3, 4 or 5. A thermocompression bonding method, wherein a method of mechanically connecting is performed by thermocompression bonding a conductive particle protruding surface side of an anisotropic conductive film to a polymer substrate. 9. A connection body between a polymer substrate on which a wiring electrode for external lead-out is formed and a flexible wiring board, which is manufactured by the thermocompression bonding method according to claim 8. 10. The thermocompression bonding of the anisotropic conductive film according to claim 1, 2, 3, 4, or 5 to a polymer substrate on which a wiring electrode for external drawing is formed, wherein the thermocompression bonding to a flexible wiring board is performed. A thermocompression bonding method between an anisotropic conductive film and a polymer substrate, wherein the anisotropic conductive film is pressed at a lower temperature and a higher pressure than at the time of main compression before connection.