JPH10112584A - Connecting method for circuit board, connecting structure for circuit board, and liquid crystal device using the structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a highly reliable connecting state by obtaining a sufficient bonding strength between a circuit board and flexible wiring board. SOLUTION: In a connecting method for circuit boards, interposing a bonding layer 4 between a circuit board 2 with a plurality of electrodes 3 and a flexible wiring board 5, the flexible wiring board 5 is pressed down on the circuit board 2 by a heated presser element 6 to connect both boards 2, 5 with each other. Further, interposing an elastic member 7 with a thermal conductivity between the presser element 6 and the flexible wiring board 5, the flexible wiring board 5 is pressed down on the circuit board 2 by the presser element 6 via the elastic member 7. In this case, deforming the elastic member 7 into an irregular form according to the irregularities of the electrodes 3, the bonding layer 4 is squeezed uniformly into inter-electrode recessed portions. Thereby, the bonding layer 4 bonds the flexible wiring board 5 to the circuit board 2 over a wide area without forming any void between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a connection method for connecting a flexible wiring board to a circuit board, a connection structure of a circuit board formed by using the connection method, and a liquid crystal device using the connection structure.

[0002]

2. Description of the Related Art As one type of liquid crystal device, a liquid crystal panel having a structure in which liquid crystal is sealed between a pair of opposed substrates, and a circuit having electrodes for transmitting and receiving signals between the liquid crystal panel and the liquid crystal panel have been known. 2. Description of the Related Art A liquid crystal device having a substrate and a flexible wiring board for connecting a circuit substrate and a liquid crystal panel is known. When manufacturing a liquid crystal device of this type, particularly when connecting a flexible wiring board and a circuit board, as shown in FIG. 6, for example, a circuit board 52 on which a plurality of electrodes 53 are formed is placed at a predetermined position on a support base 51. The flexible wiring board 55 is mounted on the circuit board 52 with the adhesive layer 54 interposed therebetween. Then, the pressing element 56 heated to a predetermined temperature is moved as shown by the arrow A, and the flexible wiring board 55 and the adhesive layer 54 are pressed against the circuit board 52 at a predetermined pressure while heating them. Thereby, as shown in FIG. 7, the flexible wiring board 55 is connected to the circuit board 52 by the adhesive layer 54.

[0003]

In the conventional connection method described above, the pressing surface of the pressing element 56 for pressing the flexible wiring board 55 is a flat surface, so that the flexible wiring board 55 and the adhesive layer 54 are It was simply pressed against the circuit board 52 in a planar manner. However, the circuit board 5
Since a plurality of electrodes 53 are provided on 2, irregularities corresponding to those electrodes are formed on the surface of the circuit board 52. Therefore, the adhesive layer 54 pressed in a planar manner against the circuit board 52 is formed on the convex portion of the circuit board 52, that is, the electrode 53.
Are strongly pressed against the electrodes 53 at the locations where they exist, whereas the pressing force on the adhesive layer 54 is insufficient at the concave portions of the circuit board 52, that is, where the electrodes 53 do not exist.
As a result, there is a possibility that a gap G is generated where the pressing force is insufficient, and the adhesive strength becomes insufficient.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional connection method for connecting a circuit board and a flexible wiring board. It is an object of the present invention to obtain a highly reliable connection state by obtaining a high bonding strength.

[0005]

In order to achieve the above object, a method of connecting a circuit board according to the present invention comprises the steps of: placing an adhesive layer between a circuit board having electrodes and a flexible wiring board; In a connection method of connecting the flexible wiring board to the circuit board by pressing the flexible wiring board against the circuit board via the adhesive layer by the pressing element,
An elastic member having thermal conductivity is arranged between the pressing element and the flexible wiring board, and the flexible wiring board is pressed against the circuit board by the pressing element via the elastic member.

According to this connection method, the pressing member does not directly press the flexible wiring board, but presses the flexible wiring board via the elastic member. The elastic member is elastically deformed when pressed by the pressing element so as to conform to irregularities formed by the plurality of electrodes provided on the circuit board. Due to the elastic deformation of the elastic member, the flexible wiring board and the adhesive layer are pressed evenly at a sufficient pressure not only where the electrode is present but also in the concave portion where the electrode is not present. And evenly adhere to the entire surface of the circuit board without forming a void. As a result, the circuit board and the flexible wiring board can be firmly connected with a sufficient adhesive strength.

[0007] The flexible wiring board can be made of any flexible material. For example, FPC (Flexib
le Printed Circuit (flexible printed circuit board) or heat seal. Since the heat seal is a flexible wiring board formed by coating a resin for thermocompression bonding on a resin film for wiring on which a wiring pattern is formed, when this heat seal is used, the resin for wiring of the heat seal is used. The film constitutes a flexible wiring board, while the adhesive layer is constituted by the heat-sealing pressure bonding resin.

On the other hand, when a flexible wiring board is formed by using an FPC, the flexible wiring board is formed by the FPC itself, and an adhesive layer is separately provided by an adhesive resin or ACF (Anisotropic conductive film: anisotropic conductive film). (Conductive film) and the like. The ACF is a film that realizes electrical connection having conductivity in a single direction and insulation in a direction perpendicular thereto by dispersing conductive particles in a resin film and thermocompression bonding the resin film. Therefore, when forming the adhesive layer using this ACF,
The wiring pattern of the flexible wiring board and the electrodes of the circuit board are electrically connected via conductive particles in the ACF. On the other hand, when the adhesive layer is formed using an adhesive resin that does not include conductive particles inside, the wiring pattern of the flexible wiring board and the electrode of the circuit board are in direct contact, and the area around the contact portion is adhesive. It will be bonded by resin.

A circuit board connection structure according to the present invention is a circuit board connection structure in which a circuit board having electrodes and a flexible wiring board are connected by an adhesive layer sandwiched therebetween. It has an uneven shape corresponding to the unevenness formed by the electrodes on the circuit board. As in the present connection structure, if the unevenness is given to the flexible wiring board in accordance with the unevenness of the circuit board, the adhesive layer sandwiched between the flexible wiring board and the circuit board also has the uneven shape like the flexible wiring board. As a result, the adhesive layer can be spread evenly over the concave portion of the circuit board, and thus a strong adhesive strength can be obtained.

A liquid crystal device according to the present invention is a liquid crystal device using the above connection structure, and specifically includes a liquid crystal panel having a structure in which liquid crystal is sealed between a pair of opposed substrates, and electrodes. A liquid crystal device includes a circuit board that transmits and receives signals to and from a liquid crystal panel, and a flexible wiring board that connects the circuit board and the liquid crystal panel. In this liquid crystal device, the flexible wiring board is connected to the electrode portion of the circuit board via the adhesive layer, and the portion of the flexible wiring board connected to the circuit board corresponds to the unevenness formed by the electrodes on the circuit board. It has an uneven state. Also in this liquid crystal device, by providing the unevenness on the flexible wiring board in accordance with the unevenness of the circuit board, the same unevenness as the flexible wiring board can be provided on the adhesive layer sandwiched between the flexible wiring board and the circuit board. As a result, a strong adhesive strength can be obtained between the flexible wiring board and the circuit board.

[0011]

FIG. 1 shows an embodiment of a liquid crystal device according to the present invention. This liquid crystal device has a liquid crystal panel 8, a circuit board 2, and a heat seal 11. As shown in FIG. 3, the liquid crystal panel 8 has a pair of glass substrates 13a and 13b bonded by a sealant 12 formed of a thermosetting resin or the like, and a cell gap formed between the glass substrates 13a and 13b. , Polarizers 15a and 15b adhered to the outer surfaces of both glass substrates 13a and 13b, and light guide plate 1 mounted on the outer surface of one glass substrate 13b.
6.

The left end of the light guide plate 16 has L
An ED (Light Emitting Diode) 17 is provided. The opposite surface of each of the glass substrates 13a and 13b has an ITO (Indi
um Tin Oxide) and the like, and the transparent electrodes 18a and 18b are formed. These transparent electrodes are connected to electrode terminals 18 formed on the overhang portion 13c of the one glass substrate 13b.
Continue to c.

The heat seal 11 is, as shown in FIG.
This is a wiring sheet formed by coating a thermocompression resin 4 on a wiring resin film 5 on which a wiring pattern is formed (lower in the figure). In FIG. 3, the heat seal 11 has an overhanging portion 1 of the glass substrate 13 b with the thermocompression bonding resin facing downward.
3c and is further heated and simultaneously pressed against the overhang 13c of the glass substrate from the upper surface thereof with a predetermined pressure. Thereby, the resin for thermocompression bonding of the heat seal 11 is adhered to the overhang portion 13c of the glass substrate, and the heat seal 11 is connected to the glass substrate 13b. In this embodiment, the wiring resin film 5 of the heat seal 11 forms a flexible wiring board, and the thermocompression resin 4 of the heat seal 11 forms an adhesive layer.

Returning to FIG. 1, the circuit board 2 includes a hard substrate 9, a plurality of electrodes 3 formed on the substrate 9, and a liquid crystal driving IC 19 adhered on the substrate 9. It is composed of The heat seal 11 is connected to the electrode 3 of the circuit board 2, and its cross-sectional structure is as shown in FIG. As shown in the figure, with respect to the circuit board 2, unevenness is formed by forming a plurality of electrodes 3 on the board 9. As for the heat seal 11, the wiring resin film 5 has an uneven shape corresponding to the unevenness. That is, the portion of the wiring resin film 5 corresponding to the electrode 3 shows a convex state, and the portion of the wiring resin film 5 corresponding to the concave portion between the electrodes shows a concave state. The thermocompression resin 4 in the portion where the wiring resin film 5 is in the concave state is also formed in the same concave state. As a result, the thermocompression resin 4 in the portion is evenly in the concave portion between the electrodes. The adhesive is spread over the entire surface of the recess, and FIG.
Does not occur. As a result, the wiring resin film 5 of the heat seal 11 is firmly connected to the circuit board 2.

FIG. 4 shows an example of a method for making the heat seal 11 uneven in accordance with the unevenness of the circuit board 2 as described above. More specifically, first, the circuit board 2 is positioned and placed at a predetermined position on the support table 1, and the heat seal 11 is placed thereon. Heat seal 11
As described above, is composed of the wiring resin film 5 as a flexible wiring board and the thermocompression resin 4 as an adhesive layer laminated on the wiring resin film 5. In the present embodiment, the elastic member 7 having thermal conductivity is mounted on the heat seal 11. The elastic member 7 can be made of any elastic material having thermal conductivity. For example, the elastic member 7 can be made by using a trade name “Sircon” (manufactured by Fuji Polymer Co., Ltd.). When this sircon is used as the elastic member 7, the elastic member 7
Is preferably about 0.3 mm.

After the elastic member 7 is placed on the heat seal 11, the presser 6 heated to a predetermined temperature by a heating device (not shown) is moved as shown by an arrow A, and the elastic member 7 and the heat seal 11 are connected to a circuit. It is pressed against the substrate 2 at a predetermined pressure. Thereby, the resin 4 for thermocompression bonding of the heat seal 11 is formed.
Is pressed against the circuit board 2 at a predetermined pressure while being heated to a predetermined temperature. At this time, as shown in FIG. 5, the elastic member 7 pressed by the pressing element 6 presses the heat seal 11 while deforming into an uneven shape according to the unevenness formed by the electrode 3 on the circuit board 2. As a result, the resin 4 for thermocompression bonding of the heat seal 11 can be evenly distributed in the concave portion between the pair of adjacent electrodes 3, so that the heat seal 11 can be firmly connected to the circuit board 2.

After the above-mentioned heat-compression treatment, the pressing force of the pressing element 6 is released, and the elastic member 7 is removed, so that the unevenness corresponding to the unevenness due to the electrodes 3 of the circuit board 2 as shown in FIG. Is obtained.

As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the embodiments, and can be variously modified within the technical scope described in the claims.

For example, in FIG. 1, the connection method according to the present invention is applied to the connection between the heat seal 11 and the circuit board 2, but the present invention is used for the connection between the heat seal 11 and the glass substrate 13b. You can also. However,
The electrode terminal 18c formed on the overhang 13c of the glass substrate 13b is lower in height than the electrode terminal 3 of the circuit board 2, so that the overhang 13c of the overhang 13c of the glass substrate is small. Therefore, a good connection state may be obtained without using the connection method according to the present invention for the connection between the overhang 13c of the glass substrate and the heat seal 11.

Although FIG. 1 shows an example in which a circuit board is connected to a liquid crystal device, the connection of the circuit board according to the present invention can also be performed when connecting the circuit board to any device other than the liquid crystal device. Of course, methods and connection structures can be used. In addition, the flexible wiring board is not limited to the heat seal, and the FPC itself does not have the adhesive layer.
(Flexible Printed Circuit).

[0021]

According to the circuit board connection method of the present invention, when the elastic member is pressed by the pressing element, the elastic member is elastically deformed so as to conform to the unevenness of the circuit board. Spreads evenly over the concave portions of the concave and convex portions of the circuit board, and thus adheres to the entire concave portions without forming voids. Therefore, the flexible wiring board can be firmly connected to the circuit board.

According to the circuit board connection method of the second aspect, the heat seal in which the flexible wiring board and the adhesive layer are integrated in advance can be accurately aligned with the unevenness of the circuit board.

According to the connection structure of the circuit board according to the third aspect and the liquid crystal device according to the fourth aspect, the flexible wiring board is formed to have an uneven shape according to the unevenness of the circuit board.
The adhesive layer placed between the flexible wiring board and the circuit board can also be formed into an uneven shape according to the unevenness of the circuit board, so that the adhesive layer can be accurately adhered to the entire concave portion of the circuit board, and The wiring board can be firmly connected to the circuit board.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an embodiment of a liquid crystal device according to the present invention.

FIG. 2 is a cross-sectional view showing a connection portion between the heat seal and the circuit board according to the line BB in FIG. 1, and is a cross-sectional view showing one embodiment of a circuit board connection structure according to the present invention. .

FIG. 3 is a diagram showing a cross-sectional structure of the liquid crystal panel according to line CC in FIG.

FIG. 4 is a cross-sectional view showing one step when an embodiment of a circuit board connection method according to the present invention is performed.

FIG. 5 is a sectional view showing another step of the method for connecting the circuit boards shown in FIG. 4;

FIG. 6 is a cross-sectional view showing one step when an example of a conventional method of connecting circuit boards is performed.

FIG. 7 is a cross-sectional view showing a connection structure of a circuit board obtained by using the conventional connection method shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Support stand 2 Circuit board 3 Electrode 4 Resin for thermocompression bonding of heat seal (adhesive layer) 5 Resin film for wiring of heat seal (flexible wiring board) 6 Presser 7 Elastic member 8 Liquid crystal panel 9 Substrate 11 Heat seal 12 Sealant 13a, 13b Glass substrate 13c Overhanging portion of glass substrate 14 Liquid crystal 18a, 18b Transparent electrode 18c Electrode terminal 19 Liquid crystal driving IC G Gap

Claims (4)

[Claims] An adhesive layer is disposed between a circuit board having electrodes and a flexible wiring board, and the flexible wiring board is connected to the circuit board by pressing the flexible wiring board against the circuit board with a heated pressing element. In the method for connecting a circuit board, an elastic member having thermal conductivity is arranged between the pressing element and the flexible wiring board, and the flexible wiring board is pressed against the circuit board by the pressing element via the elastic member. Circuit board connection method. 2. The method of connecting a circuit board according to claim 1, wherein the flexible wiring board is formed by coating a resin for thermocompression bonding on a resin film for wiring on which a wiring pattern is formed. A method for connecting circuit boards, comprising: a film; and the adhesive layer is formed of a resin for pressure bonding of the heat seal. 3. A connection structure of a circuit board for connecting a circuit board having electrodes and a flexible wiring board with an adhesive layer sandwiched therebetween, wherein the flexible wiring board is formed by electrodes on the circuit board. A connection structure for a circuit board, which has an uneven shape corresponding to the unevenness. 4. A liquid crystal panel having a structure in which liquid crystal is sealed between a pair of opposing substrates, a circuit substrate having electrodes and transmitting and receiving signals between the liquid crystal panel, and connecting the circuit substrate and the liquid crystal panel. In a liquid crystal device having a flexible wiring board, the flexible wiring board is connected to an electrode portion of a circuit board via an adhesive layer, and the flexible wiring board in a portion connected to the circuit board is formed by electrodes on the circuit board. A liquid crystal device having an uneven shape corresponding to the unevenness to be formed.