JPH0394219A - Manufacture of liquid crystal electrooptical device - Google Patents

Abstract

PURPOSE:To obtain the lightweight, inexpensive device which has a large aperture rate by connecting conductors on a liquid crystal panel and conductors on a 3rd substrate by irradiating an ultraviolet-ray setting adhesive with ultraviolet rays while the substrates are put one over the other across the adhesive and pressed. CONSTITUTION:Electrodes are formed on the couple of substrates 1 and 3 which constitute a liquid crystal panel by forming a conductive films on the surfaces of the substrates, and then irradiating them with laser light and cutting the conductive films. Further, semiconductor chips for driving liquid crystal are mounted on a 3rd substrate 3 different from the 1st and 2nd substrates 1 and 2. The conductors on the substrate where the semiconductor chips are mounted and the conductors on the substrates which constitute the liquid crystal panel are connected by interposing the ultraviolet-ray setting adhesive 8 with which conductive particulates are mixed between the substrates 1 and 3 and irradiating the adhesive with ultraviolet rays while applying pressure. Consequently, the lightweight, inexpensive liquid crystal electrooptical device which has a high aperture rate, high contrast, and high yield is obtained.

Description

[Detailed Description of the Invention] [Prior Art] A liquid crystal electro-optical device is lighter than a conventional display element.
Because it has advantages such as low power consumption, it is used in various fields, such as calculators. clock. word processor. Used in pocket TVs, etc.

By the way, the arrangement of semiconductor elements for driving the liquid crystal in a liquid crystal electro-optical device was initially
Most of them were mounted on glass epoxy printed circuit boards in state C.

In this case, the connection between the electrodes of the printed circuit board on which the package IC is mounted and the electrodes formed on the liquid crystal panel is made using, for example, FPC (Flexible Print C).
It was carried out by ircuit.

Recently, T A B (Tape Auto
ed Bonding) methods have also been used. this is,
A semiconductor chip with bumps formed on the pad portion is bonded onto a polyimide film on which wiring is formed using Cu or the like by face down bonding (ILB: Inner L).
(referred to as ead bonding), and further connects the film and the electrodes fabricated on the liquid crystal panel (
OLB: Outer Lead Bonding
) method.

Another method is to directly mount a semiconductor chip on the substrate that hosts the liquid crystal panel. For example, wiring for manually transmitting signals to a semiconductor chip and wiring for supplying output signals from the semiconductor chip to the electrodes of the display section of the liquid crystal panel are formed on a substrate constituting a liquid crystal panel, and the wiring and the semiconductor A method of wire bonding with the chip using Au wire, or a method of forming bumps on the pad part of the IC chip,
There is also a method of performing face-down bonding with the wiring.

[Problems with conventional technology]

However, among the above methods, the method of mounting a package IC on a glass epoxy printed circuit board and connecting the printed circuit board and a liquid crystal panel using an FPC requires a large package IC and a heavy glass epoxy board. Because it is placed on the printed circuit board of the LCD electro-optical device,
Not only is the advantage of "light weight" not being utilized, but since FPC is used to connect the printed circuit board and the liquid crystal panel, the connection of the printed circuit board to the FPC on the one hand, and the FPC on the other hand
Since the PC and the liquid crystal panel must be connected, and the number of connections is twice as many as the number of wires to be connected, the yield is also lowered.

In addition, since FPCs are generally connected by thermocompression bonding,
The FPC thermally expands during connection, and the alignment before heating may shift slightly due to heating. This is 1
This phenomenon becomes more noticeable when the number of wires in a single FPC increases, so a large number of FPCs must be used when manufacturing a liquid crystal panel with a large number of wires. Naturally, this increases the time and effort required for alignment, resulting in an increase in cost.

Furthermore, glass substrates are usually used for liquid crystal panels, but in this case, the thermal expansion coefficients of FPC and glass are different, so
Even if a connection is established during crimping, changes in temperature will cause stress and reduce reliability.

Furthermore, the TAB method does not require a printed circuit board on which a semiconductor element for driving a liquid crystal is placed, so it is improved in terms of "lightness," but it is not preferable because the polyimide tape becomes extremely expensive.

Furthermore, since the ξ-d tape is used, the problem of thermal expansion mentioned above also arises.

Furthermore, when mounting a semiconductor chip on a substrate on which a liquid crystal panel is mounted, the manufacturing yield of the entire liquid crystal electro-optical device is the product of the manufacturing yield of the connection process between the semiconductor chip and wiring and the yield of the liquid crystal panel itself. , the overall production yield is significantly lowered, which is not preferable.

[Structure of the invention]

In order to solve the above-mentioned problems, the present invention provides that the electrodes formed on a pair of substrates that control the liquid crystal panel of a liquid crystal electro-optical device are formed by forming a conductive film on the surface of the substrate and then irradiating the conductive film with a laser beam. A semiconductor chip for driving the liquid crystal is mounted on a third substrate different from the pair of first and second substrates constituting the liquid crystal panel, and the semiconductor chip is manufactured by cutting. The wiring on the mounted board and the wiring on the board that controls the liquid crystal panel are interposed between the boards with an ultraviolet curing adhesive mixed with conductive fine particles.
The feature is that the connection is made by irradiating ultraviolet light while applying pressure.

In particular, in the present invention, it is preferable that conductive fine particles and slightly smaller fine particles are mixed in the ultraviolet curable adhesive because the yield of wiring connections is further increased.

In the present invention, a semiconductor chip is used instead of a packaged semiconductor element to drive the liquid crystal, so a glass epoxy printed circuit board on which the chip is mounted is not required. You can make the most of your strengths.

Furthermore, since the liquid crystal panel and the drive circuit section are connected without using an FPC, it is possible to eliminate the problem of the number of connection points being twice as many as the number of wiring lines and the problem of thermal expansion of the FPC, as described above.

Furthermore, the present invention does not require an expensive polyimide tape as in the TAB method, so a liquid crystal electro-optical device can be manufactured at low cost.

Furthermore, in the present invention, since the substrate constituting the liquid crystal panel and the substrate mounting the semiconductor chip are manufactured separately,
After the semiconductor chip is connected to the wiring on the board, it is possible to conduct an electrical test on the connection between the semiconductor chip and the wiring before connecting it to the liquid crystal panel, and as a result, the connection of the semiconductor chip is not perfect. Since there is no need to connect the liquid crystal panel to the liquid crystal panel, the yield can be greatly increased.

Further, in particular, in the present invention, since the electrodes of the liquid crystal panel are manufactured by cutting the conductive film using laser light, it is easier to reduce the interval between the l electrodes compared to the case where the electrodes are manufactured by photolithography. However, if we were to use FPC to connect a substrate on which semiconductor elements are mounted and a liquid crystal panel with a small electrode spacing, this would be undesirable because thermal expansion would occur as described earlier and adjacent wiring would short-circuit. . Therefore, only in the present invention, which has both the process of fabricating electrodes using a laser and the process of connecting the wiring on the substrate on which the semiconductor chip is mounted and the wiring on the liquid crystal panel using an ultraviolet curing adhesive, The above-mentioned problems can be solved by reducing the electrode spacing, in other words by increasing the aperture ratio of the liquid crystal panel.

The present invention will be explained below with reference to Examples.

[Example 1] This example is shown in Figs. 1(a) and (b). Figure 2,
This will be explained using FIG.

First, a liquid crystal panel is manufactured.

As the first substrate (1), ITO (Ind.
ium Tin Oxide).

Then, 640 striped electrodes (9) are produced using an excimer laser (FIG. 1(a)). however,
Only a few electrodes are shown in the construction drawing (a). and the second
As a substrate (2), 200 layers of ■T◯ were similarly deposited on a 1.1 mm thick soda glass, and 400 electrodes were also formed using an excimer laser (not shown). Here, the excimer laser irradiation conditions are: beam energy of 250 mJ, pulse width of 2 On seconds, and beam cross-sectional shape of 15 um x 400 mm. The repetition frequency was 10 Hz.

After cutting the ITO film in this manner, the ends of the ITO are cut again using an excimer laser (FIG. 1(b)). In this case, the excimer laser irradiation conditions are such that the cross-sectional shape of the beam is 30 μm x 400 mm, and the central part of the substrate (IT
Place a mask on the part where ○ is not to be cut to prevent IT○ from being cut. Other conditions may be the same as before.

Thereafter, boria ξ tuccinic acid was applied onto the first and second substrates using an offset printing method, and was placed in a clean oven for 35 minutes.
Heating was performed at 0°C for 3 hours to obtain a polyimide thin film. After rubbing the polyimide thin film formation surface on the first substrate (1) using cotton cloth, a baser with a diameter of 8 μm was applied.
m of SiOz particles were sprinkled. An epoxy adhesive was printed on the second substrate (2) using a screen printer. After the first and second substrates were bonded together, liquid crystal was injected by a known vacuum injection method, and the liquid crystal injection port was sealed using an ultraviolet curing adhesive. The LCD panel is now complete.

Next, the production of a substrate for mounting a liquid crystal driving 1c chip will be described.

As the third board (3), width 50mm, length 270mm
, After forming a film of ITO on soda glass having a thickness of 1.1 mm, wiring 09) is produced by photolithography. The wiring was then plated with Ni and further plated with Au.

This wiring consists of wiring (not shown) for inputting signals to the semiconductor chip (5) and wiring for transmitting output signals from the semiconductor chip (5) to the liquid crystal panel.

Then, a liquid crystal driving semiconductor chip (5) having Au bumps formed on the pad portion is connected. This connection method uses the dispensing method to drop UV-curable adhesive onto the semiconductor chip, aligns the wiring with the bump, and then
Heat to °C and irradiate with ultraviolet rays for 3 minutes. By this method, the required number of semiconductor chips and wiring were connected to both the common electrode side and the data electrode side.

Here, an electrical test was conducted regarding the connection of the semiconductor chip.

Then, a liquid crystal panel is connected only to those semiconductor chips arranged on the substrate that are completely connected. In this example, the method is as follows:
First, on the wiring formed on the first substrate of the liquid crystal panel and on the part (4) that does not overlap with the second substrate, conductive fine particles (6) and fine particles ( After applying the ultraviolet curing adhesive (8) mixed with 7) by the dispensing method, overlap the wiring on the liquid crystal panel so that the wiring on the part where the adhesive was applied and the wiring on the board on which the semiconductor chip is mounted face each other. , approx. 2.4kg/cm”
Apply pressure? UV rays were irradiated for 3 minutes. The conductive fine particles (6) used here are polystyrene particles having a diameter of 7.5 μm and are plated with Au. Further, as fine particles (7) slightly smaller than the conductive fine particles (6), SiO2 particles with a diameter of 5 μm were used. Further, the mixing ratio of the ultraviolet curable adhesive (8), the conductive fine particles (6), and the fine particles (7) is 107:14:4 by weight.

After this, -30°C. A heat shock test was conducted at 70''C (for 1 hour each), but no defects were observed, as was the case immediately after connection.

It should be noted that when connecting the wiring of the liquid crystal panel and the wiring on the board on which the semiconductor chip is mounted, it is sufficient to use only conductive fine particles, but as in this example, two types of fine particles were used. This allows for a more secure connection.

The liquid crystal electro-optical device fabricated in this example has a semiconductor chip mounted on a glass substrate, so it is very light and does not require a glass epoxy printed circuit board, and it is also very light in weight. Since the semiconductor chips are separate from each other, only those whose semiconductor chips are completely connected can be connected to the liquid crystal panel, which greatly increases manufacturing yields.

Furthermore, in this embodiment, since only one connection point is required for connection of one wire, the process can be simplified and the manufacturing yield can be increased compared to the case where FPC is used.

In particular, in this example, since the electrodes of the liquid crystal panel were produced using an excimer laser, a liquid crystal panel with a very small electrode interval could be produced.

In addition, in this example, irradiation with excimer laser light was performed twice, which made it possible to make the ITO electrode at the connection part with the substrate on which the semiconductor chip is mounted thinner and to sufficiently increase the insulation resistance of the adjacent electrodes. Ta.

[Example 2] First, a liquid crystal panel is manufactured.

As the first substrate (1), ITO (In
1,200 people made a film of dium tin oxide). Then, 640 strip-shaped electrodes (9) are produced using an excimer laser. In this example, the first
The state shown in Figure (a) is fine. Then, as a second substrate (2), 120% of ITO was similarly placed on 1.1 mm thick soda glass.
400 electrodes were fabricated using an excimer laser using 0 people. Here, the excimer laser irradiation conditions are the same as in Example 1, with a beam energy of 250 mJ,
Pulse width: 20 ns, beam cross-sectional shape: 15 μm x 4
00 mm, and the repetition frequency was 10 Hz.

Thereafter, polyamic acid was coated on the first and second substrates using an offset printing method, and then heated in a clean oven for 35 minutes.
Heating was performed at 0°C for 3 hours to obtain a boiled iron thin film. After rubbing the surface of the first substrate (1) on which the polygonal thin film is formed using a cotton cloth, a spacer with a diameter of 8 μm is applied.
m of Si02 particles were sprinkled. An epoxy adhesive was printed on the second substrate (2) using a screen printer. After the first and second substrates were bonded together, liquid crystal was injected by a known vacuum injection method, and the liquid crystal injection port was sealed using an ultraviolet curing adhesive. The LCD panel is now complete.

Next, the production of a substrate for mounting a liquid crystal driving IC chip will be described.

As the third board (3), width 50mm, length 270m
After coating ITO on soda glass with a thickness of 1.1 mm, wiring 09) is produced by photolithography. The wiring was then plated with Ni and further plated with Au.

This wiring consists of wiring (not shown) for inputting signals to the semiconductor chip (5) and wiring for transmitting output signals from the semiconductor chip (5) to the liquid crystal panel.

Then, a liquid crystal driving semiconductor chip (5) having Au bumps formed on the pad portion is connected. This connection method uses a dispensing method to drop UV-curable adhesive onto the semiconductor chip, aligns the wiring with the bumps, and then applies a pressure of 95g per bump to the semiconductor chip.
Heat to °C and irradiate with ultraviolet rays for 3 minutes. By this method, the required number of semiconductor chips and wiring were connected to both the common electrode side and the data electrode side.

Here, an electrical test was conducted regarding the connection of the semiconductor chip.

Then, a liquid crystal panel is connected only to those semiconductor chips arranged on the substrate that are completely connected. In this example, the method is as follows:
First, on the wiring formed on the first substrate of the liquid crystal panel and on the part (4) that does not overlap with the second substrate, conductive fine particles (6) and fine particles ( After applying the ultraviolet curing adhesive (8) mixed with 7) by the dispensing method, overlap the wiring on the liquid crystal panel so that the wiring on the part where the adhesive was applied and the wiring on the board on which the semiconductor chip is mounted face each other. , approx. 2.4kg/cm”
Ultraviolet rays were irradiated for 3 minutes while applying pressure. The conductive fine particles (6) used here were boristyrene particles with a diameter of 2.5 μm and were plated with Au to a thickness of 1000λ. Further, the fine particles (7) slightly smaller than the conductive fine particles (6) are Si02 particles with a diameter of 2 μm. The mixing ratio of the ultraviolet curable adhesive (8), the conductive fine particles (6), and the fine particles (7) is 98:13:3 by weight.

Thereafter, a heat shock test was conducted at -30°C and 70°C (for 1 hour each), but no defects were found, as was the case immediately after connection.

In this example, not only the effects obtained in Example 1 can be obtained, but also the excimer laser beam is irradiated one time when manufacturing the electrodes of the liquid crystal panel, so it is more effective than in Example 1. The process was shortened. However, in order to obtain sufficient insulation resistance between adjacent electrodes, conductive fine particles much smaller than those in Example 1 were used in this example.

[Example 3] When connecting a liquid crystal panel manufactured in exactly the same manner as in Example 1 to a substrate on which a semiconductor chip is mounted, as shown in FIG. 4, the substrate connected to the common electrode side of the liquid crystal panel, By bonding the data electrode side of the liquid crystal panel and the connected substrate at their intersections GO) using an ultraviolet curing adhesive, a liquid crystal electro-optic device with superior mechanical strength compared to the case of Example 1 can be obtained. We were able to create the device.

In this example, bonding at the intersection 00) was possible because the common electrode side substrate of the liquid crystal panel and the substrate on which the semiconductor chip connected to the data electrode side substrate is mounted form the same plane, and This is because the data electrode side substrate of the liquid crystal panel and the substrate on which the semiconductor chip connected to the common electrode side substrate is mounted form the same plane. Therefore,
As shown in Figure 5, one board 0 is placed across one board holding the liquid crystal panel and the board mounting the semiconductor chip.
8) can be bonded, thereby further increasing the mechanical strength.

In Figure 5, the substrate side is shown only between one of the two substrates on which the semiconductor chip is mounted and the substrate (1), but the substrate side is shown between the other substrate on which the semiconductor chip is mounted and the substrate. A similar arrangement is also provided between (2).

Since the substrate 08) is used as a reinforcing material for the connection between the liquid crystal panel and the substrate on which the semiconductor chip is mounted, its material is not particularly specified. The shape is not particularly specified, as long as it can function as a reinforcing material.

〔effect〕

As described above, by using the present invention, it is possible to manufacture a liquid crystal electro-optical device that is lightweight, inexpensive, has a high aperture ratio, provides high contrast, and has a high yield.

[Brief explanation of drawings]

Figures 1(a) and 1(b) show the electrode shapes. FIG. 2 shows a schematic cross-section of a connecting portion of a liquid crystal electro-optical device using the present invention. 3, 4, and 5 show schematic diagrams of the entire liquid crystal electro-optical device using the present invention. Substrate Semiconductor Chip Conductive Fine Particle Fine Particle Ultraviolet Curing Adhesive FPC ＾-Ichishu 2 Figure, -9 (Unused) (b) Figure 4/0 Figure ke/r

Claims (1)

[Claims] 1. A conductive thin film is formed on the surface of the substrate, and then the conductive thin film is irradiated with laser light to cut the conductive thin film, thereby forming electrodes on the first and second substrates. A method for manufacturing a liquid crystal electro-optical device with a liquid crystal interposed therebetween, comprising the steps of manufacturing a liquid crystal panel, forming wiring on a third substrate different from the substrate constituting the liquid crystal panel, and A step of connecting a driving semiconductor chip to the wiring on the third substrate, and connecting the wiring on the liquid crystal panel and the wiring on the third substrate to the liquid crystal via an ultraviolet curable adhesive mixed with conductive fine particles. A liquid crystal electro-optical device characterized by having a step of stacking the substrates so that the wiring on the panel and the wiring on the third substrate face each other and connecting them by irradiating ultraviolet rays while applying pressure. Fabrication method. 2. In claim 1, the ultraviolet curable adhesive contains first fine particles having at least a conductive surface;
A method for manufacturing a liquid crystal electro-optical device, characterized in that second fine particles slightly smaller than the fine particles are mixed therein.