JP2827650B2 - Thermocompression bonding method and crimping member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for thermocompression bonding of a flexible circuit board (hereinafter referred to as "FPC") and an FPC for thermal expansion.
The present invention relates to a crimping member used to prevent displacement of a PC.

[0002]

2. Description of the Related Art In recent years, there has been a great demand for thin display devices such as liquid crystal displays and plasma displays as display devices for OA equipment. As a method of mounting the drive IC of these display devices, TAB using a flexible circuit board is used.
(Tape Automated Bonding) implementation. Hereinafter, a conventional method of mounting an FPC on a glass substrate will be described with reference to FIGS.

FIG. 5 is a schematic view showing an example in which an FPC 2 is thermocompression-bonded to a glass substrate 4 having a wiring pattern 12 using an anisotropic conductive film 3. Normally, a transparent electrode such as ITO, Al, C
A metal thin film such as r is used.

As the anisotropic conductive film 3, a material obtained by dispersing a conductive material in an adhesive resin film is used. As the conductive material, metal particles of Ni or solder, or plastic particles coated with metal such as carbon and Au are used. Adhesives can be broadly classified into thermoplastic and thermosetting adhesives. Styrene-based block copolymers such as SBS (styrene-butadiene-styrene) and SEBS (styrene-ethylene-butylene-styrene) are used as thermoplastic adhesives. Connection work is possible. Examples of the thermosetting adhesive include an epoxy resin, a polyurethane acrylic resin, and the like. Compared with a thermoplastic adhesive, the adhesive has high stability at high temperatures, is resistant to external stress, and has high reliability.
The thickness of the anisotropic conductive film 3 is usually about 10 to 40 μm,
A 3 mm tape is used.

[0005] As the FPC 2, a film formed by wiring a polyimide film called a base film with Cu or the like is used. As the thickness of the base film, 30 to 70 μ
m, and a Cu lead of 10 to 10 m is used.
35 μm is used.

As a method of mounting the FPC 2 on the glass substrate 4, first, the anisotropic conductive film 3 is temporarily attached to the wiring pattern 12 of the glass substrate 4 by applying pressure and heating. The heating temperature varies depending on the type of the adhesive, for example, 80 to 140 ° C. for a thermoplastic adhesive and 6 for a thermosetting adhesive.
It is heated at a temperature of 0-100 ° C. Pressure is 3-10
Kgf / cm ² .

Next, the electrodes of the FPC 2 are positioned and superimposed on the glass substrate 4 to which the anisotropic conductive film 3 has been temporarily attached, and then are completely pressed by the pressing tool 5. The heating temperature of the final compression depends on the type of adhesive.
About 20-150 ° C, 170-190 ° C for thermosetting system. The pressure is 20 to 60 kgf / cm ² and is applied for about 20 to 30 seconds.

As a result of the thermocompression bonding, the conductive fine particles in the anisotropic conductive film 3 are sandwiched between the electrode of the FPC 2 and the electrode of the glass substrate 4, and the two wirings mediate the conductive fine particles,
Electrically connected. Usually, the conductive fine particles after pressurization are 1-3
By crushing to about μm, a stable connection can be obtained. Between adjacent wiring patterns, the conductive fine particles are dispersed in the resin and have no conductivity. FIGS. 9 and 10 show the crimped state of the FPC.

However, in order to uniformly suppress the crushing of the thermocompression-bonded particles to 1 to 3 μm in the above-described conventional configuration, the flatness of the pressing surface of the pressing tool 5 needs to be 3 μm or less. As the pressing tool 5, stainless steel or the like is used, but it is difficult to reduce the flatness of the pressing surface to 3 μm or less. Further, as described above, in order to heat the anisotropic conductive film 3 to about 200 ° C., the pressure tool 5 itself needs to be heated to about 300 ° C. In such a high temperature state, it becomes more difficult to keep the flatness and the parallelism uniform.

In order to reduce the parallelism, for example, as shown in FIG. 11, a cushioning material 13 is provided between the pressing tool 5 and the FPC 2.
For example, a method of providing a high heat-resistant silicon rubber or Teflon film has been devised. By providing the cushioning material 13 on the pressure tool 5, the cushioning material 13 absorbs the unevenness of the pressure tool 5, and it is possible to apply pressure to the pressure surface of the FPC 2 to some extent evenly.

However, when pressure is applied by using the cushioning material 13, the edge portions at both ends of the FPC 2 receive a force that is pulled to both sides from the cushioning material 13, and as a result, a problem of electrode displacement due to the extension of the FPC 2 occurs. . FIG. 12 shows a pressurized state when a cushioning material is used.

FIGS. 13 and 14 show the positional relationship between the wiring pattern 12 of the glass substrate 4 and the wiring pattern 11 of the FPC 2. FIG. 13 shows a normal positional relationship, and FIG. pulled wiring patterns 11 of the FPC2 is a glass substrate 4 wiring pattern 12 or we are diagrams began seeing <br/>.

If only the pressing tool 5 is used, it is possible to uniformly press the FPC 2. However, when the cushioning material 13 is used, the tensile force of the cushioning material 13 acts on both ends of the FPC 2 to extend the FPC 2. I do. In order to solve this problem, there is a method of providing a thin metal plate between the cushioning member 13 and the FPC 2. In this case, since the temperature of the metal plate rises from room temperature to about 150 to 200 ° C. at the time of pressurization, the metal plate thermally expands and a tensile force is applied to the FPC 2, so that the metal needs to have a coefficient of thermal expansion as small as possible. is there.

[0014]

However, in the above configuration, when a plurality of FPCs are pressure-bonded to a large-sized substrate, the low-thermal-expansion metal also needs to have a length to be pressed. When the substrate size is 6 inches, 100 mm on one side,
For 10 inches, about 200 mm is required.

When a material having a thermal expansion coefficient of, for example, 4 × 10 ^-6 is used as the low thermal expansion metal at a length of 200 mm and the heating temperature is set at 200 ° C., the metal plate extends about 160 μm.

In the plurality of pressurized FPCs 2, the central FPC 2 in the longitudinal direction of the pressurized metal material is pressurized without any problem, but the FPCs 2 at both ends are shifted in the expansion direction due to the thermal expansion of the metal plate. Later, the adhesive hardens. As a result, the FPCs 2 near both sides are pressure-bonded and connected to each other with the wiring pattern 11 of the FPC 2 and the wiring pattern 12 of the glass substrate 4 being displaced from each other, resulting in poor connection due to protrusion from the pattern.

When the process is arranged, the metal plate 10 and the FPC 2 are pressed by the pressing tool 5. The metal plate 10 is heated from a room temperature to a tool temperature. The metal plate 10 thermally expands due to the temperature difference. FPC due to thermal expansion of metal plate 10
2 shifts sideways. The adhesive hardens with the lapse of time of pressurization and heating. As a result, a positional shift between the FPC 2 and the glass substrate 4 occurs.

As a countermeasure against the above-mentioned problem, a means for preventing the occurrence of thermal expansion by heating the metal plate 10 before pressurization can be considered, but it is not practical because of its fixing method and troublesome replacement.

Further, as a problem of the pressurization, there is a problem of adhesion of the adhesive to the pressurization tool. The mechanism of adhesion of the adhesive will be described with reference to FIGS.

FIG. 15 shows the glass substrate 4 and the anisotropic conductive film 3.
FIG. 4 is a diagram showing a positional relationship between the FPC2 and the FPC2. In order to prevent peeling of the FPC , the end face of the FPC 2 is located inside the end face of the anisotropic conductive film 3 . The pressing tool 5 is wider than the width of the anisotropic conductive film 3 , and has a structure in which a necessary portion can be pressed even if a positional shift occurs.

As a result of pressure bonding of the FPC 2, as shown in FIG. 16, the adhesive of the anisotropic conductive film 3 is softened by heating,
Further, the pressure is applied to the lifting tool 5 from the end face of the FPC and adheres to the pressing tool 5, which promotes hardening and adheres to the pressing surface of the pressing tool.

In a case where a plurality of FPCs 2 are pressed together at once , a gap is generated between adjacent FPCs 2 and the adhesive material is softened and adheres to the pressing tool 5 in the same manner as described above .
To cure. The pressing tool 5 has a surface parallelism of 1 to 3 μm.
m is required, but the fused adhesive is 1 to 10μ
m, which significantly impairs the parallelism of the pressing surface.

As a method for removing the adhered adhesive,
There is a method of rubbing with an organic solvent such as acetone, MEK, and toluene, but as described above, the pressing tool 5 is heated to a high temperature of 250 ° C. to 350 ° C. for heating, and cleaning in a high temperature state is also performed. It is also difficult. In order to prevent adhesion of the adhesive resin, a high heat-resistant film is
A method of interposing C2 has been devised, but in this case, the thermal expansion of the film causes the F
The result is that the PC itself extends laterally. FIG. 6 shows a schematic diagram of the displacement.

The present invention has been made to solve the above problems, and has as its object to provide a highly accurate mounting of an FPC.

[0025]

In order to achieve the above object, a divided flat plate-like crimping member 1 according to the present invention is provided by an FPC.
2 has a configuration capable of pressing only a portion that needs to be pressurized and pressurizing a plurality of FPCs 2. The crimping member can be freely attached to and detached from the apparatus, and is frequently replaced. Is possible.

[0026]

[Action] This arrangement only pressing surface pressed crimp member 1, FPC 2, no occurrence of positional displacement due to thermal expansion of the metal plate, further adhesive Anisotropic conductive film 3 is crimping portion
It can adhere to only the material 1 and prevent direct attachment to the pressing tool 5.

[0027]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the structure of a crimping member according to an embodiment of the present invention, and FIG. 2 is a diagram showing a thermocompression bonding method using the crimping member of the present invention. FIG. Also,
FIG. 7 is an explanatory view of the conventional and the present invention.

First, as shown in FIG.
The PC 2 fixes the glass substrate 4 stuck at a predetermined position to the stage 7. The glass block 8 is arranged under the pressurized portion of the stage in consideration of flatness and thermal conductivity.

As the crimping member 1 , for example, eight FPCs
Are collectively crimped, the linear portions having a length corresponding to the width of the FPC 2 are arranged so as to have the same positional relationship as the FPC 2, and they are connected by a common portion and integrated.
For the sample tested this time, an FPC 2 having a width of 25 mm was used, and the thickness of the crimping member 1 was 0.5 mm.

After fixing the glass substrate 4 at a predetermined position, the pressing member 1 is positioned, and is fixed on the anisotropic conductive film 3 via the FPC 2. At this time, the pressure bonding member 1 is integrated at a place other than the pressurized portion of the anisotropic conductive film 3,
It can be easily fixed without causing any trouble in pressurization.

[0032] Although not illustrated in the pressure tool 5, silicone rubber is fixed as a buffer for parallelism. The pressurizing tool 5 has a mechanism that moves up and down by an air cylinder 6. Adjust the air pressure of the air cylinder 6 ,
After the pressing force is set to 20 to 40 kgf / cm ² , the pressing tool 5 is lowered, the pressing member 1 and the FPC 2 are pressed, and after holding for 20 to 30 seconds, the pressing tool 5 is raised. The crimping operation is completed. For crimping of the present invention as described above
As a result of pressing the FPC 2 with the member 1 , the FPC 2 elongated by about 10 μm from the center of the FPC 2 , but no displacement occurred in any of the FPCs 2 . A schematic diagram of the extension is shown in FIG. Although the adhesive of the anisotropic conductive film 3 is adhered to Crawling crimping member 1 by applying pressure, into the pressure tool 5, as shown in FIG. 4, did not adhere <br/>.

[0033]

As described above, the present invention provides a plurality of FPCs.
In the thermocompression bonding method of (1), only the portion directly pressed between the pressing tool and the plurality of FPCs is divided into a plurality of pieces.
The parts are heat-compressed with an integrated crimping member interposed. This prevents the FPC from shifting due to the thermal expansion of the crimping member and realizes high-precision mounting. The adhesive in the conductive conductive film is prevented from adhering to the pressing tool, and stable thermocompression bonding can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a crimping member according to an embodiment of the present invention.

FIG. 2 is a view showing a state of thermocompression bonding using the crimping member of the embodiment.

FIG. 3 is an explanatory diagram of stress of an FPC in a thermocompression bonding state using the compression bonding member of the embodiment.

Sectional view showing a crimping state definitive in the Example 4]

FIG. 5 is a conventional thermocompression bonding state diagram.

[6] stress illustration of in the prior of the thermo-compression bonding FPC

FIG. 7 is an explanatory diagram of thermocompression bonding in a conventional example and an example of the present invention.

FIG. 8 is an external view showing an example of mounting an FPC on a glass substrate.

Description view before you Keru crimped using implements an anisotropic conductive film that are common to FIG. 9 prior and the present invention

Illustration after you Keru crimped using implements an anisotropic conductive film that are common to FIG. 10 prior and the present invention

FIG. 11 is an explanatory view when a cushioning material is used in conventional thermocompression bonding.

FIG. 12 is an explanatory view of a crimped state when the conventional cushioning material is used.

FIG. 13 is a wiring pattern diagram of a conventional example when thermocompression bonding is normal.

FIG. 14 is a wiring pattern diagram in a case where an FPC is extended by a buffer material in a conventional example.

FIG. 15 is an explanatory view of your Keru challenges to conventional thermal compression bonding

FIG. 16 is an explanatory view of your Keru challenges to conventional thermal compression bonding

[Explanation of symbols]

1 crimping member second flexible circuit board (FPC) 3 anisotropic conductive film 4 glass substrate 5 pressure tool 6 air cylinder 7 Stage 8 glass block 9 opening 10 the metal plate 11 FPC wiring pattern 12 of the glass substrate wiring patterns 13 Cushioning material

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hikaru Fujita 1006 Kadoma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-63-174328 (JP, A) JP-A-1-302735 (JP, A) JP-A-3-136260 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) H01L 21/603 H01L 21/60 311 H01L 25/00

Claims (2)

(57) [Claims] 1. A thermocompression bonding method for electrically connecting thermocompression bonding by a plurality of flexible circuit board pressurized tool having a circuit pattern on a glass substrate having a circuit pattern, said pressure tools and said plurality of flexible circuit board division of only the part which applies directly pressurizing it into a plurality between the
Other parts are heat-pressed with an integrated crimping member
A thermocompression bonding method characterized by wearing . 2. A crimping member for collectively crimping a plurality of flexible circuit boards, wherein only a portion to be directly pressed is divided and other portions are integrated. .