JP2009128779A - Liquid crystal display device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device with which a short circuit between an electrode terminal pad of a flexible circuit substrate and an edge etc. of a silicon substrate is prevented without using any insulating member. <P>SOLUTION: The liquid crystal display device has the silicon substrate 2 having a pixel electrode, a transparent substrate 1 having a transparent electrode, and a liquid crystal 2 interposed between the silicon substrate 2 and the transparent substrate 1. Also an electrode terminal pad 6 of the silicon substrate 2 and that of the flexible circuit substrate 3 are electrically connected with an anisotropic conductive adhesive 7. In this case, when a distance between the electrode terminal pad of the silicon substrate and the electrode terminal pad of the flexible circuit substrate is represented by d1, and a distance between the silicon substrate surface and the electrode terminal pad of the flexible circuit substrate is represented by d2, inequality d2>d1 holds with respect to the distance d1 and the distance d2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device using an anisotropic conductive adhesive (ACF) and a method for manufacturing the same, and more particularly to a method for connecting substrates.

  Conventionally, in a liquid crystal panel composed of an opposing transparent substrate and a silicon substrate, electrode terminal pads on the silicon substrate and electrode terminals on the flexible circuit substrate are connected by an anisotropic conductive adhesive (referred to as ACF). The applicant of the present application has proposed, for example, in Japanese Patent Laid-Open No. 11-125830 as a countermeasure against a short circuit between the edge of the silicon substrate and the electrode terminal pad on the flexible circuit board (Patent Document 1).

  The connection method of the publication will be described with reference to FIG. In the figure, 1 is a transparent substrate, 2 is a silicon substrate, and 3 is a flexible circuit board. A liquid crystal panel is constituted by the transparent substrate 1 and the silicon substrate 2 facing each other. The flexible circuit board 3 is covered with an insulating protective film 4 around the wiring 5, and one end of the flexible circuit board 3 is connected to the silicon substrate 2.

  That is, the electrode terminal pad 6 on the silicon substrate 2 and the electrode terminal pad on the flexible circuit board 3 (area where the insulating film 4 of the wiring 5 is not covered) are electrically connected by the anisotropic conductive adhesive (ACF) 7. Connected. At that time, by installing the insulating member 15 in a part near the edge of the silicon substrate 2 adjacent to the ACF 7, a short circuit defect between the edge of the silicon substrate 2 and the electrode terminal pad on the flexible circuit board 3 is prevented. Occurrence is prevented.

The ACF 7 is composed of an insulating base material and metal-plated insulator particles, and electrically connects the electrode pads via the metal-plated insulator particles when pressed between the electrode pads. The insulating member 15 is composed of a base material that is insulative with respect to the ACF 7 and an insulator that is not metal-plated, and is not electrically connected even if it is crimped. The other is the same material and dimensions, with the only difference being the presence or absence of metal plating.
JP-A-11-125830

  When the electrode terminal pads on the silicon substrate and the electrode terminal pads on the flexible circuit board are connected by the ACF, the following problems have been encountered in measures against shorting between the edge of the silicon substrate and the electrode terminal pads on the flexible circuit board.

  (1) Since an insulating member is placed in addition to the ACF, man-hours increase.

  (2) When both the ACF and the insulating member are attached to the liquid crystal panel, a part of the ACF and the insulating member overlaps, and the overlapped portion becomes uneven in thickness, resulting in insufficient pressurization. It is easy to generate.

  (3) The flexible circuit board is composed of a resin film such as polyimide and Cu wiring, and is characterized by its flexibility, but conversely, there are also defects such as warpage and undulation and poor flatness. For this reason, when there is no insulating member, warping or undulation of the flexible circuit board adversely affects when the electrode terminal pads on the silicon substrate and the electrode terminal pads on the flexible substrate are electrically connected by the ACF.

  In other words, the electrode terminal pad of the flexible circuit board may touch the edge of the silicon substrate or the like due to warping or undulation of the flexible circuit board, which may cause a short circuit or a leak. In particular, if there is silicon residue or the like due to dicing on the end surface of the silicon substrate, the probability of occurrence of defects becomes higher.

  An object of the present invention is to provide a liquid crystal display device capable of preventing a short circuit between an electrode terminal pad of a flexible circuit board and an edge of a silicon substrate without using an insulating member, and a manufacturing method thereof.

  The present invention includes a silicon substrate having a pixel electrode and a transparent substrate having a transparent electrode, wherein a liquid crystal is sandwiched between the silicon substrate and the transparent substrate, an electrode terminal pad of the silicon substrate, and the flexible circuit In the liquid crystal display device in which the electrode terminal pad of the substrate is electrically connected by an anisotropic conductive adhesive, the distance between the electrode terminal pad of the silicon substrate and the electrode terminal pad of the flexible circuit substrate is d1, and When the distance between the surface and the electrode terminal pad of the flexible circuit board is d2, the distance d1 and the distance d2 have a relationship of d2> d1.

  In the present invention, a liquid crystal is sandwiched between a silicon substrate having pixel electrodes and a transparent substrate having transparent electrodes, and the electrode terminal pads of the silicon substrate and the electrode terminal pads of the flexible circuit substrate are different from each other. In a method of manufacturing a liquid crystal display device that is electrically connected using an isotropic conductive adhesive, a state in which the anisotropic conductive adhesive is sandwiched between the electrode terminal pad of the flexible circuit board and the electrode terminal pad of the silicon substrate In the thermocompression bonding step, and in the thermocompression bonding step, an interval d1 between the electrode terminal pad of the silicon substrate and the electrode terminal pad of the flexible circuit substrate; The distance d2 between the surface of the silicon substrate and the electrode terminal pad of the flexible circuit board satisfies the relationship d2> d1. And butterflies.

  In the present invention, the silicon substrate and the flexible circuit board are connected, and at the same time, a larger gap is formed between the end surface of the silicon substrate and the flexible circuit board than between the electrode terminal pads. By doing so, a short circuit failure caused by a part of the passivation film missing during chipping or handling is prevented.

  In addition, by utilizing the characteristic of ACF that a conduction characteristic is generated only in a narrow gap, an insulation effect is produced by filling ACF in a large gap. Furthermore, the insulating effect can be enhanced by warping the flexible circuit board away from the silicon substrate. In addition, since only the ACF is used, the number of steps can be reduced, the pressure can be applied with good uniformity, and the connection failure due to the pressure unevenness can be prevented.

  According to the present invention, a short circuit failure between the electrode terminal pad of the flexible circuit board and the edge on the silicon substrate side can be prevented by using only the ACF. In particular, it is possible to stably prevent a short circuit by bending the flexible circuit board so that it is separated from the silicon substrate on the edge side of the silicon substrate with respect to the electrode terminal pad on the silicon substrate by the ACF. Furthermore, short-circuit prevention can be carried out without any special additional steps / members, and costs can be reduced.

  Next, the best mode for carrying out the invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a sectional view showing Embodiment 1 of a reflective liquid crystal display device according to the present invention, and FIG. 2 is an enlarged view showing a part thereof. In FIG. 1, the same parts as those of the conventional apparatus of FIG. In the figure, 1 is a transparent substrate having a transparent electrode, and 2 is a silicon substrate having a pixel electrode. A liquid crystal layer is sandwiched between the transparent substrate 1 and the silicon substrate 2 and sealed with a seal member 14.

  A liquid crystal panel is composed of the transparent substrate 1, the silicon substrate 2, and a liquid crystal layer sandwiched between the transparent substrate 1 and the silicon substrate 2. Then, by applying a driving voltage between the transparent electrode and the pixel electrode, the liquid crystal molecules are moved to control the polarization state of the light. The details of the liquid crystal display device are well known and will not be described. 3 is a flexible circuit board.

  The silicon substrate 2 is provided with a protruding electrode terminal pad 6 in a region where the transparent substrate 1 is not bonded. The flexible circuit board 3 has a structure in which the wiring 5 is protected by an insulating protective film 4. The electrode terminal pad of the flexible circuit board 3 is electrically connected to the electrode terminal pad 6 of the silicon substrate 2 by an anisotropic conductive adhesive (ACF) 7.

  FIG. 2 shows an enlarged view of a connection portion using anisotropic conductive adhesive (ACF) 7. As described above, the electrode terminal pads 6 of the silicon substrate 2 and the electrode terminal pads of the flexible circuit board 3 (regions not covered with the insulating protective film 4 of the wiring 5) are in the anisotropic conductive adhesive (ACF) 7. Are electrically connected through the conductive particles 8.

  At this time, as shown in FIG. 2, the distance between the electrode terminal pad 6 of the silicon substrate 2 and the electrode terminal pad of the flexible circuit board 3 (a region not covered with the insulating protective film 4 of the wiring 5) is defined as d1. Further, the distance between the surface of the silicon substrate 2 and the electrode terminal pad of the flexible substrate 3 (region not covered with the insulating protective film 4 of the wiring 5) is defined as d2.

  As shown in FIG. 2, the distance d1 and the distance d2 have a relationship of d2> d1, and the distance d2 is wider than the distance d1. In such a configuration, even when there is no insulating member, the conductive particles 8 do not cause a short circuit between the edges and side surfaces of the silicon substrate 2 and the electrode terminal pads of the flexible circuit board 3 after thermocompression bonding. That is, even when there is no conventional insulating member, it is possible to prevent a short circuit with only the ACF 7 and to reduce man-hours.

  Further, even if the ACF 7 protrudes from the end portion of the silicon substrate 2 due to the displacement of the anisotropic conductive adhesive (ACF) 7 or the like and goes around the side surface of the silicon substrate 2, no short-circuit defect occurs. Furthermore, since there is no conventional insulating member, quality defects due to the overlap between the ACF 7 and the insulating member can be eliminated, which can contribute to quality improvement and yield improvement.

(Embodiment 2)
FIG. 3 is a diagram showing Embodiment 2 of the present invention, and shows a cross-sectional view in the middle of manufacturing the reflective liquid crystal display device of the present invention. That is, the electrode terminal pad 6 on the silicon substrate 2 and the electrode terminal pad of the flexible circuit board 3 (regions not covered with the insulating protective film 4 of the wiring 5) are connected via an anisotropic conductive adhesive (ACF) 7. Shows the process of bonding. In FIG. 3, the same parts as those in FIG.

  That is, 1 is a transparent substrate having a transparent electrode, and 2 is a silicon substrate having a pixel electrode. A liquid crystal layer is sandwiched between the transparent substrate 1 and the silicon substrate 2 and sealed with a seal member 14. These transparent substrate 1, silicon substrate 2 and the like constitute a liquid crystal panel. 3 is a flexible circuit board. 9 is a heat source for thermocompression bonding, 10 is a backup heater, and 11 is a holding stage for holding the flexible circuit board 3.

  A stopper 12 is disposed between the silicon substrate 2 and the holding stage 11 for the flexible circuit board 3 at a position higher than the surface of the silicon substrate 2. When the silicon substrate 2 and the flexible circuit board 3 are thermocompression bonded, the flexible circuit board 3 is stopped at the position of the stopper 12. At this time, a heat source (heater tool) 9 for thermocompression bonding is pressed against the protruding electrode 6 side of the silicon substrate 2 so that the flexible circuit board 3 does not sag.

  On the edge side of the silicon substrate 2, as shown in FIG. 3, the flexible circuit board 3 is bent in the opposite direction to the silicon substrate 2, that is, is bent outward from the electrode terminal pads 6 of the silicon substrate 2. Excess anisotropic conductive adhesive (ACF) 7 flows into the bent gap portion. Then, the flexible circuit board 3 is fixed in a state of being bent away from the silicon substrate 2. Further, a backup heater 10 is installed on the back side of the silicon substrate 2 opposite to the heat source 9 so as to be applied to the end of the silicon substrate 2, and the ACF 7 in the gap not directly touching the heat source 9 is also cured. Can be promoted.

  Here, when the electrode size of the silicon substrate is small, the electrode of the silicon substrate must be completely covered (connected) to the flexible circuit board in order to obtain a connection resistance necessary for connection with the flexible circuit board. Therefore, the flexible circuit board is bent between the electrode of the silicon substrate and the edge of the silicon substrate. When the electrode size of the silicon substrate is sufficiently large, it is not necessary to be completely covered with the flexible circuit board, and the flexible circuit board may be bent from the middle of the electrode.

  In this embodiment, the distance d1 between the electrode terminal pad 6 of the silicon substrate 2 and the electrode terminal pad of the flexible circuit board 3 and the distance d2 between the surface of the silicon substrate 2 and the electrode terminal pad of the flexible board 3 are d2> after connection. The relationship of d1 is the same as in the first embodiment.

  In the present embodiment, the gap between the silicon substrate 2 and the flexible circuit board 3 can be arbitrarily selected by changing the height of the stopper 12. Therefore, even when the blade wears out during the dicing process and the chipping of the silicon edge becomes large, or when the height of the electrode terminal pad of the flexible circuit board 3 varies, it is possible to cope with the possibility of margin. Furthermore, even when there is warping or undulation of the flexible circuit board 3, it is possible to remarkably improve the reliability with respect to short-circuit failure by preventing the flexible circuit board 3 from sagging between the stopper 12 and the heat source 9. It becomes.

  The inventors of the present application set the height of the stopper 12 at a position 100 μm higher than the outermost surface of the silicon substrate 2 to electrically connect the electrode terminal pad 6 of the silicon substrate 2 and the wiring 5 of the flexible circuit board 3 by the ACF 7. went. At that time, the gap between the edge of the silicon substrate 2 and the electrode terminal pad of the flexible circuit board 3 was 20 μm. When ACF having a conductive particle diameter of 5 μm was used, sufficient insulation could be secured.

(Embodiment 3)
FIG. 4 is a sectional view showing Embodiment 3 of the present invention. In the present embodiment, the ACF protrudes outside the edge of the silicon substrate 2 in consideration of the position shift and the attachment position of the ACF. 4A is a sectional view showing a state after connection by ACF, and FIG. 4B is a perspective view showing a state before connection by ACF. 4, the same parts as those in FIGS. 1 to 3 are denoted by the same reference numerals.

  That is, 1 is a transparent substrate having a transparent electrode, and 2 is a silicon substrate having a pixel electrode. A liquid crystal layer is sandwiched between the transparent substrate 1 and the silicon substrate 2 and sealed with a seal member 14. A liquid crystal panel is composed of the transparent substrate 1, the silicon substrate 2, the liquid crystal layer, and the like. 3 is a flexible circuit board. Embodiments 1 and 2 are to electrically connect the electrode terminal pads of the flexible circuit board 3 (regions not covered with the insulating protective film 4 of the wiring 5) to the electrode terminal pads 6 of the silicon substrate 2 using the ACF 7. It is the same.

  In this embodiment, as shown in FIG. 4B, the ACF (shown by 13) is arranged on the electrode terminal pad 6 of the silicon substrate 2 before connection by the ACF. Next, thermocompression bonding is performed using the method described with reference to FIG. 3, and the electrode terminal pads of the flexible circuit board 3 (regions not covered with the insulating protective film 4 of the wiring 5) and the electrode terminal pads 6 of the silicon substrate 2 are bonded. It is electrically connected by ACF7. As a result, as shown in FIG. 4A, the ACF 7 protrudes outside the edge of the silicon substrate.

  Conventionally, in the manufacturing process, dust has entered a gap between the end of the silicon substrate 2 and the wiring of the flexible circuit board 3 to cause a short-circuit defect, thereby reducing the yield. Yield can be improved by protruding outside. In this way, when the flexible circuit board 3 and the silicon substrate 2 are electrically connected using the ACF 7, it is desirable that the ACF 7 protrude beyond the edge of the silicon substrate.

  The distance d1 between the electrode terminal pad 6 of the silicon substrate 2 and the electrode terminal pad of the flexible circuit board 3 and the distance d2 between the surface of the silicon substrate 2 and the electrode terminal pad of the flexible board 3 satisfy the relationship d2> d1. This is the same as in the first embodiment.

  In this embodiment, as shown in FIG. 4B, the ACF width (W) is set to 1.0 mm, the thickness (T) is set to 25 μm, and the ACF length (L) is set to 11.6 mm before connection. At that time, the width (W ′) after connection (after pressurization) in FIG. 4A was 1.3 mm, and the protrusion width (W ″) was 50 μm. (Distance between chip electrodes 11.7 mm, flexible) The distance (D) between the edge of the silicon substrate and the center of the ACF was set to 0.55 mm in consideration of the ACF sticking deviation Max 100 μm (one side 50 μm). Making the ACF 7 protrude outside the edge of the silicon substrate can also be used for the first and second embodiments.

(Embodiment 4)
FIG. 5 is a sectional view showing Embodiment 4 of the present invention. In FIG. 5, the same parts as those in FIGS. As one of the man-hours improving measures in the mounting process of the reflective liquid crystal panel, there is a method in which a transparent substrate of the same size is bonded to a semiconductor wafer and then separated into pieces by dicing or scribing.

  In general, if the gap between the silicon substrate 2 and the transparent substrate 1 is about several microns and the projecting electrodes 6 are provided on the silicon substrate 2, it is difficult to achieve the above manufacturing process. Further, if a protruding electrode having a thickness of about 10 μm is to be formed, a protruding electrode forming step must be prepared separately from the semiconductor process, which is more disadvantageous in terms of man-hours.

  In this embodiment, the electrode terminal pads 6 of the silicon substrate are arranged at a position lower than the surface of the silicon substrate, and can be formed only by a normal semiconductor process, and the wafer sizes can be bonded to each other.

  Specifically, as shown in FIG. 5, electrode terminal pads 6 are arranged on the silicon substrate 2 at a position lower than the surface thereof. At that time, a recess is formed in the surface of the silicon substrate 2 and the electrode terminal pad 6 is disposed in the recess. FIG. 5 is an enlarged view of the ACF connection as in FIG. Other configurations are the same as those in FIG.

  In the present embodiment, high elastic modulus 5 μm diameter plastic core particles are used, electrode terminal pads 6 are arranged at a position 1.5 μm lower than the surface of the silicon substrate 2, and the flexible circuit board 3 is connected using the connection method of FIG. 3. The wiring 5 and the electrode terminal pad were connected. The distance between the electrode of the silicon substrate 2 after connection and the wiring of the flexible circuit board 3 was about 3 to 4 μm.

  Further, as a result of disposing the stopper 12 of FIG. 3 at a position 0.1 mm higher than the surface of the silicon substrate 2, the gap between the end surface of the silicon substrate 2 and the wiring 5 of the flexible circuit board 3 is about 20 μm. In FIG. 5, the distance between the electrode terminal pad 6 of the silicon substrate 2 and the electrode terminal pad of the flexible circuit board 3 is d1, and the distance between the end surface of the silicon substrate 2 and the wiring 5 of the flexible wiring board 3 is d2. This indicates that the distance d2 has a relationship of d1 <d2.

(Embodiment 5)
FIG. 6 is a sectional view showing Embodiment 5 of the present invention. In FIG. 6, the same parts as those in FIGS. The electrode terminal pad 6 of the silicon substrate 2 is arranged at a position lower than the surface of the silicon substrate 2 as in FIG. Further, the anisotropic conductive adhesive (ACF) 7 is protruded outside the edge of the silicon substrate 2 as in FIG.

  In this embodiment, the length H1 of the electrode terminal pad 6 of the silicon substrate 2 is shorter than the length H2 of the heat source (heater tool) 9 for thermocompression bonding as shown in FIG. As a result, the electrode terminal pad 6 is always covered with the heat source 9 during thermocompression bonding, that is, the ACF 7 on the electrode 6 is sufficiently cured, so that a highly reliable apparatus such as moisture resistance can be provided. It becomes possible. The configuration of this embodiment can also be used in the embodiments of FIGS. Further, the distance d1 and the distance d2 are in the relationship of d1 <d2, as in the above embodiment.

It is sectional drawing which shows Embodiment 1 of the liquid crystal display device which concerns on this invention. It is an expanded sectional view which expands and shows a part of FIG. It is sectional drawing which shows Embodiment 2 of this invention. It is sectional drawing which shows Embodiment 3 of this invention. It is sectional drawing which shows Embodiment 4 of this invention. It is sectional drawing which shows Embodiment 5 of this invention. It is sectional drawing which shows the display apparatus of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Silicon substrate 3 Flexible circuit board 4 Insulating protective film 5 Wiring 6 Electrode terminal pad 7 Anisotropic conductive adhesive (ACF)
8 Conductive particles 9 Heat source for thermocompression bonding (heater tool)
10 Backup heater 11 Flexible circuit board stage 12 Stopper 13 ACF before connection
14 Sealing member 15 Insulating member

Claims (7)

A silicon substrate having a pixel electrode; and a transparent substrate having a transparent electrode, wherein a liquid crystal is sandwiched between the silicon substrate and the transparent substrate, an electrode terminal pad of the silicon substrate, and an electrode terminal of the flexible circuit substrate In a liquid crystal display device that is electrically connected to a pad by an anisotropic conductive adhesive,
When the distance between the electrode terminal pad of the silicon substrate and the electrode terminal pad of the flexible circuit board is d1, and the distance between the surface of the silicon substrate and the electrode terminal pad of the flexible circuit board is d2, the distance d1 and the distance d2 is a relationship of d2>d1; The liquid crystal display device according to claim 1, wherein the flexible circuit board is bent away from the silicon substrate toward an outside from an electrode terminal pad of the silicon substrate. The liquid crystal display device according to claim 1, wherein the anisotropic conductive adhesive protrudes outward from an edge of the silicon substrate. 4. The liquid crystal display device according to claim 1, wherein the electrode terminal pad of the silicon substrate is disposed at a position lower than a surface of the silicon substrate. 5. A liquid crystal is sandwiched between a silicon substrate having a pixel electrode and a transparent substrate having a transparent electrode, and the electrode terminal pad of the silicon substrate and the electrode terminal pad of the flexible circuit substrate are bonded with an anisotropic conductive adhesive. In the manufacturing method of the liquid crystal display device electrically connected using,
Electrically connecting the electrode terminal pads of the flexible circuit board and the electrode terminal pads of the silicon substrate by thermocompression bonding using a heat source for thermocompression bonding with the anisotropic conductive adhesive sandwiched therebetween. Including
In the thermocompression bonding step, an interval d1 between the electrode terminal pad of the silicon substrate and the electrode terminal pad of the flexible circuit substrate and an interval d2 between the surface of the silicon substrate and the electrode terminal pad of the flexible circuit substrate are d2. A manufacturing method of a liquid crystal display device characterized by satisfying a relationship of> d1. 6. The method of manufacturing a liquid crystal display device according to claim 5, wherein the heat source for thermocompression bonding is longer than an electrode terminal pad of the silicon substrate. A stopper is disposed outside the edge of the silicon substrate, and by setting the height of the stopper higher on the surface of the silicon substrate, the flexible circuit board is separated from the electrode terminal pad of the silicon substrate in the thermocompression bonding step. 6. The method of manufacturing a liquid crystal display device according to claim 5, wherein the liquid crystal display device is bent outwardly from the silicon substrate.

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