JP2009094099A - Flexible substrate connection part structure, flexible substrate, flat panel display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connection part structure of a flexible substrate capable of preventing disconnection at low cost.
A connecting portion 1 is a portion of a flexible substrate 5 that electrically connects a driver 9 and a liquid crystal panel 3 and includes a base material 7, wiring pattern groups 12a and 12b, and a protective film 13. .
The wiring 11 constituting the wiring pattern groups 12a and 12b has a planar shape mainly composed of straight lines, and includes a covering portion 21 covered with the protective film 13 and a non-covering portion 23 not covered with the protective film 13. Have.
The non-covering portion 23 is provided with a wavy non-linear portion 22 for relaxing the tensile stress.
When a tensile stress parallel to the direction of the wiring 11 is applied to the connection portion 1, the non-linear portion 22 expands like a spring, thereby dispersing and relaxing the tensile stress applied to the wiring 11.
Therefore, disconnection of the wiring 11 can be prevented without providing a separate reinforcing tape or the like.
[Selection] Figure 4

Description

  The present invention relates to a structure of a connecting portion of a flexible substrate, a flexible substrate having a structure of a connecting portion of a flexible substrate, and a flat panel display device.

  In recent years, electronic devices have been reduced in size and thickness, and a flexible substrate may be used as a substrate for connecting circuits in order to increase the mounting density of electronic components as compared with the conventional case.

  The flexible substrate is a substrate using a bendable material such as polyimide as a base material, and the mounting density of electronic components can be made higher than before by bending and connecting to a circuit.

  On the other hand, in order to further reduce the size and thickness of electronic devices, it is necessary to further reduce the pitch of wiring on the substrate. However, narrowing the pitch leads to insufficient strength of the wiring. There is a risk of disconnection of wiring due to pulling.

  In particular, the connection portion between the flexible substrate and another circuit tends to cause disconnection of the wiring because the tensile stress generated by the difference in thermal expansion coefficient between the flexible substrate and the other substrate or an external force is concentrated.

  In particular, in the connection portion, the exposed portion of the wiring that is not covered with the protective film is likely to break.

  In addition, the wiring is likely to be disconnected due to bending stress in the bent portion.

  Therefore, in order to reduce the pitch of the wiring on the substrate, it is necessary to provide a structure that prevents the wiring from being disconnected.

  As a structure for preventing disconnection of the wiring of the connecting portion, a structure in which a reinforcing tape is first attached to a flexible substrate is known.

  For example, paragraph number [0017] of Patent Document 1 discloses a structure in which a reinforcing tape T is attached to a flexible substrate (Patent Document 1).

  Further, as a structure for preventing disconnection of the wiring at the bent portion, a structure in which the wiring at the bent portion is formed in a waveform is known.

  For example, FIG. 1 of Patent Document 2 discloses a structure in which a bent portion of a lead wiring on a TAB (Tape Automated Bonding) tape is formed in a waveform.

Japanese Patent Laid-Open No. 2004-62048 JP 2005-294388 A

  However, the structure as disclosed in Patent Document 1 has a problem in that an increase in material cost due to the addition of a reinforcing tape and an increase in manufacturing cost due to the addition of a sticking process.

  Further, the structure as in Patent Document 2 has a problem that it is not effective in preventing disconnection of a connection portion where no stress is generated due to bending.

  This invention is made | formed in view of such a problem, The objective is to provide the structure of the connection part of the flexible substrate which can prevent a disconnection at low cost.

  In order to achieve the above-described object, the first invention is a structure of a connecting portion of a flexible substrate that connects two circuits, and is provided on a flexible sheet-like base material and the base material. And a wiring that can be connected to the two circuits, wherein the wiring has a non-linear portion.

  The non-linear portion may have any one of a wave shape, a sawtooth shape, a curved shape, and a U-shape in plan view.

  The structure of the connection portion of the flexible substrate may further include a protective film provided so as to cover a part of the wiring. In this case, the wiring is a coating that is a region covered with the protective film. And a non-covering portion that is a region not covered with the protective film, and the non-linear portion may be provided in the non-covering portion.

  As for the said wiring, all the areas | regions may be formed as the said non-linear part.

  A second invention is a flexible substrate having the structure of the connecting portion of the flexible substrate described in the first invention.

  A third invention is a flat panel display device having the flexible substrate according to the second invention.

  In 1st invention-3rd invention, the structure of the connection part of a flexible substrate is provided with the wiring which has a non-linear part, and stress is relieve | moderated when a non-linear part expand | extends with respect to tensile stress.

  Therefore, disconnection of the wiring can be prevented without providing a separate reinforcing tape or the like.

  ADVANTAGE OF THE INVENTION According to this invention, the structure of the connection part of the flexible substrate which can prevent a disconnection at low cost can be provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

  First, with reference to FIG. 1 and FIG. 2, the structure of the liquid crystal display device 2 as a flat panel display device which has the connection part 1 which concerns on embodiment of this invention is demonstrated.

  The liquid crystal display device 2 shown in FIG. 1 and FIG. 2 has a liquid crystal panel 3 for displaying an image with liquid crystal as one of two circuits.

  In addition, the liquid crystal display device 2 includes a driver 9 as one of two circuits for applying a voltage for image display of the liquid crystal panel 3 to the liquid crystal, and further includes the driver 9 and the liquid crystal panel 3. A flexible substrate 5 having a connection portion 1 for electrical connection is provided.

  Next, the structure of the liquid crystal panel 3, the flexible substrate 5, and the driver 9 will be described in detail with reference to FIGS.

  First, the structure of the liquid crystal panel 3 will be described with reference to FIGS.

  As shown in FIGS. 1 to 3, the liquid crystal panel 3 includes a substrate 3 a and a display unit 3 b that is provided on the substrate 3 a and displays an image.

  The substrate 3a is a glass substrate, and an electrode (not shown) whose one end is electrically connected to the driver 9 via the connection portion 1 of the flexible substrate 5 is provided on the surface.

  An electrode (not shown) is also electrically connected to the display unit 3b.

  The display unit 3b has liquid crystal sealed therein. When a voltage is applied via an electrode (not shown) on the substrate 3a, the liquid crystal is aligned and selectively transmits light to display an image.

  Next, the structures of the flexible substrate 5 and the driver 9 will be described with reference to FIGS.

  As shown in FIGS. 1 to 4, the flexible substrate 5 includes a base material 7, wiring pattern groups 12 a and 12 b composed of a plurality of wirings 11 provided on the base material 7, a protective film 13 covering a part of the wiring 11, An adhesive 15 for connecting the wiring 11 and the substrate 3a of the liquid crystal panel 3 is provided.

  In the flexible substrate 5, the base material 7, the wiring 11, and the protective film 13 that are connected to the liquid crystal panel 3 constitute the connection portion 1.

  A driver 9 is provided on the flexible substrate 5, and one end of the wiring 11 is electrically connected to the driver 9.

  Specifically, the base material 7 is a sheet-like member that holds each member of the flexible substrate 5 and the driver 9, and is made of a flexible material such as polyimide.

  The wiring pattern groups 12a and 12b include a plurality of wirings 11. The wirings 11 electrically connect the driver 9 and the display unit 3b via electrodes (not shown) and an adhesive 15 on the substrate 3a.

  The wiring 11 has a structure in which copper is plated with tin (tin), gold or the like.

  The protective film 13 is a member that protects a part of the wiring 11 and is made of an insulating material.

  Although details will be described later, the wiring 11 has a non-linear portion 22 in the connection portion 1.

  The adhesive 15 is a member that connects the flexible substrate 5 and the liquid crystal display device 2 and also electrically connects the wiring 11 and an electrode (not shown) on the substrate 3a, and is composed of, for example, a thermosetting anisotropic conductive film. Has been.

  The driver 9 is an IC chip or the like, and upon receiving a command for displaying an image from a CPU (Central Processing Unit) (not shown) or the like, the driver 9 is connected to the display 3b via the wiring 11, the adhesive 15, and an electrode (not shown) on the substrate 3a. A voltage is applied to the liquid crystal.

  Next, the structure of the connection part 1 in the flexible substrate 5 will be described with reference to FIGS.

  As shown in FIGS. 1 to 3, the connecting portion 1 is a portion that electrically connects the driver 9 and the liquid crystal panel 3 in the flexible substrate 5, and includes a base material 7, wiring pattern groups 12 a and 12 b, and a protective film. 13.

  As shown in FIG. 4, the wiring 11 constituting the wiring pattern groups 12 a and 12 b has a planar shape mainly composed of straight lines, and is covered with the covering portion 21 that is a region covered with the protective film 13 and the protective film 13. And an uncovered portion 23 which is a non-covered region.

  The non-covering portion 23 is provided with a wavy non-linear portion 22 for relaxing the tensile stress.

  Here, a method of connecting the flexible substrate 5 and the liquid crystal display device 2 will be briefly described.

  First, the driver 9 is mounted on the flexible substrate 5, and the adhesive 15 is provided on the connection portion 1.

  Next, the wiring 11 of the connection part 1 and the position of the electrode (not shown) of the substrate 3 a are aligned, and the connection part 1 is attached to the substrate 3 a using the adhesive 15.

  Finally, the adhesive 15 is cured by applying pressure and heating.

  Thus, the flexible substrate 5 and the liquid crystal display device 2 are connected by connecting the connecting portion 1 and the substrate 3a.

  Next, the function of the non-linear part 22 is demonstrated with reference to FIG. 5 and FIG.

  For example, it is assumed that a tensile stress B parallel to the direction of the wiring 11 is applied to the connection portion 1 from the state shown in FIG. 5A (a state where no tensile stress is applied).

  The term “tensile stress” as used herein refers to either or both of a tensile stress generated by an external force and a tensile stress generated by a difference in thermal expansion coefficient between the base material 7 and the substrate 3a.

  The tensile stress B applied to the connecting portion 1 is applied to a portion having the weakest mechanical strength in the connecting portion 1, specifically, a portion having an uncovered portion 23 not covered with the protective film 13 (see FIG. 4). concentrate.

  Here, although the base material 7 is comprised with the material which has flexibility, since the wiring 11 is the structure which gave plating, such as tin (tin), gold | metal | money, etc. to copper, compared with the base material 7, the wiring 11 Has a large elastic modulus and is difficult to expand and contract.

  For this reason, when the tensile stress B is applied, the wiring 11 of the non-covered portion 23 cannot follow the tensile stress B and easily breaks.

  However, the wiring 11 of the non-covered portion 23 has a non-linear portion 22 having a waveform, and the non-linear portion 22 has a length 31 (see FIG. 5) following the tensile stress B as shown in FIG. (See (a)) to a length 33 like a spring, and the tensile stress B is dispersed and relaxed by an elastic effect.

  Therefore, disconnection of the wiring 11 can be prevented without separately providing a reinforcing tape or the like.

  Note that the shape of the non-linear portion 22 is not limited to a waveform as long as it extends like a spring following the tensile stress B and can disperse and relax the tensile stress B by an elastic effect. Absent.

  For example, a curved shape as shown in FIG. 6 (a), a saw shape as shown in FIG. 6 (b), or a U-shape as shown in FIG. 6 (c) may be used.

  Further, the non-linear portion 22 may be provided at least in the non-covering portion 23, but the entire area of the wiring 11 may be configured by the non-linear portion 22.

  As described above, according to this embodiment, the connection portion 1 of the flexible substrate 5 includes the base material 7 and the wiring 11, and the non-linear portion 22 of the wiring 11 extends like a spring against the tensile stress B. As a result, the tensile stress B is dispersed and relaxed.

  Therefore, disconnection of the wiring 11 can be prevented.

  Moreover, according to this embodiment, since the connection part 1 does not need the reinforcement tape which prevents the disconnection of the wiring 11, it can prevent the disconnection of the wiring 11 at lower cost than before.

  In the above-described embodiment, the case where the present invention is applied to the connection portion 1 of the flexible substrate 5 that electrically connects the liquid crystal panel 3 and the driver 9 has been described. However, the present invention is not limited to this. It can be used for connecting portions of all flexible boards that electrically connect two circuits.

  In the above-described embodiment, the wiring 11 electrically connects the driver 9 and the display unit 3b. However, the wiring 11 may be a dummy wiring for reinforcing the mechanical strength of the connection unit 1. .

FIG. 2 is a plan view showing a liquid crystal panel 3 and a flexible substrate 5 having a connection portion 1. It is a reverse view of FIG. FIG. 2 is a view taken in the direction of arrow A in FIG. FIG. 2 is an enlarged view of a partial region of the connection portion 1 in FIG. 1, and the liquid crystal panel 3 is not shown. FIG. 5A is a diagram showing the wiring 11 before the tensile stress B is applied, and FIG. 5B is a diagram showing the wiring 11 when the tensile stress B is applied. It is a figure which shows the modification of the wiring.

Explanation of symbols

1 ………… Connector 3 ………… Liquid crystal panel 3a ………… Substrate 3b ………… Display 5 ………… Flexible substrate 7 ………… Base material 9 ………… Driver 11 ……… Wiring 12a ...... Wiring pattern group 13 ...... Protective film 15 ...... Adhesive 21 ...... Covered part 23 ...... Uncovered part 31 ...... Length 33 ...... Length

Claims (6)

A structure of a connecting portion of a flexible substrate that connects two circuits,
A sheet-like base material having flexibility;
Wiring provided on the substrate and connectable to the two circuits;
Have
The wiring has a non-linear portion, and the structure of the connecting portion of the flexible substrate.   The structure of the connecting portion of the flexible substrate according to claim 1, wherein the non-linear portion has a planar shape of any one of a waveform, a saw shape, a curved shape, and a U-shape. It further has a protective film provided to cover a part of the wiring,
The wiring is
A covering portion which is a region covered with the protective film;
An uncovered portion which is a region not covered with the protective film;
Have
The structure of the connection part of the flexible substrate according to claim 1, wherein the non-linear part is provided in the non-covering part.   The structure of the connection part of the flexible substrate according to claim 1, wherein all the regions of the wiring are formed as the non-linear part.   A flexible substrate having the structure of the connecting portion of the flexible substrate according to claim 1.   A flat panel display device comprising the flexible substrate according to claim 5.

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