JP3665467B2 - Display device and method for manufacturing display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a portable device having a function such as pen input, a display device used for an electronic notebook , and a method for manufacturing the same .
[0002]
[Prior art]
Conventionally, a liquid crystal display device has a structure in which a TCP (Tape Carrier Package) or COF (Chip On FPC) in which an IC is mounted on a film substrate is connected to a terminal of a liquid crystal panel with an anisotropic conductive film. TCP has a configuration similar to that of COF, but TCP is a semiconductor package, and COF is mounted as a chip on a bare chip, and is further positioned as a circuit block on which resistors, capacitors, and the like are mounted.
[0003]
The TCP substrate is obtained by laminating, for example, a 75 micron polyimide film with a 40 micron epoxy adhesive film and a 25 micron Cu foil, followed by patterning, resist coating, and plating.
The IC on which the Au bumps are formed is thermocompression bonded to this, and the TCP plating and the Au bumps of the IC are connected by metal bonding. The connection part is sealed with an epoxy adhesive to complete the TCP.
[0004]
As the film substrate used for COF, for example, approximately 18-micron Cu is vapor-deposited on a 25-micron polyimide film and patterned, resist-coated, and plated. In this case, the film substrate is a two-layer film, and the base film is thinner than the TCP, so that the bendability is high. Basically, the film substrate can be bent at any location.
[0005]
The mounting of the IC in the COF is the same as that of the TCP, and the IC formed with the Au bump is thermocompression bonded so that the plating formed on the electrode pattern on the film substrate and the Au bump of the IC are connected by metal bonding. Or it can also connect using an anisotropic electrically conductive film. Then, an underfill is poured into the connecting portion to perform sealing. Furthermore, according to the specifications, components such as resistors and capacitors are printed with cream solder, mounted on a film substrate, and reflowed to complete the COF.
[0006]
FIG. 3 shows a schematic cross section of a conventional display device in which the film substrate 2 such as COF and the liquid crystal panel 1 are connected by an anisotropic conductive film. A pattern 3 is formed on the film substrate 2 by a conductor, and a resist 7 is provided except for electrode terminal portions for external connection.
The anisotropic conductive film 6 used here is a film-like adhesive obtained by filming a mixture of 10 to 5 micron conductive particles dispersed in a thermosetting adhesive. In addition to metal particles such as nickel and solder, the conductive particles include those in which plastic balls are plated with nickel and gold. The anisotropic conductive film is temporarily attached to the terminals of the liquid crystal panel, and the electrode terminals of the COF or TCP pattern 3 are aligned with the terminals of the liquid crystal panel, and are connected by thermocompression bonding.
[0007]
[Problems to be solved by the invention]
However, ICs for driving liquid crystal display devices have been miniaturized year by year, and the connection pitch has been reduced to 50 to 60 microns, which has caused a problem that film substrate patterning and connection yields are reduced.
The patterning yield is improved by reducing the electrode thickness of the film substrate to about 8 microns (6 to 10 microns), particularly in COF. On the other hand, the thickness of the anisotropic conductive film, that is, the amount of the adhesive, is optimal to fill the space between the electrode gaps of the film substrate in the connected state, so that an electrode pattern having a thickness of about 8 microns is used. In the case where the spaces have almost the same design, the thickness of the anisotropic conductive film is optimally 6 to 4 microns. However, it is difficult to mass-produce anisotropic conductive films with a film thickness of 10 microns or less. Furthermore, since the conductive particles are smaller in thickness than the film thickness, the dispersibility is increased, so that the current conductive particles are unsuitable at the above film thickness. Thus, mass production of an anisotropic conductive film having a thickness of 4 to 6 microns is difficult at present.
[0008]
When a film substrate with an electrode pattern of about 8 microns in thickness is pressure-bonded using an anisotropic conductive film with a thickness of 15 microns that is currently used, the amount of adhesive that protrudes from the terminal area becomes very large. The conductive particles that do not contribute to the connection flow out between the leads. Therefore, the conductive particles are arranged in a bead shape at the edge of the crimping portion, and a short circuit occurs at this portion. If the space between the terminals is designed to be large, the problem may be solved, but it is difficult to prevent the pitch below 0.2 mm.
[0009]
The incidence of this short phenomenon increases as the connection pitch becomes finer.
As a technique that has been put into practical use as a method for preventing short-circuits by improving the anisotropic conductive film, there are a method of forming an insulating film on conductive particles, and a method in which insulating balls are mixed in a certain amount or more in a bead-like manner. There are means such as a method of cutting off or reducing the amount of mixed conductive particles itself. In the means using conductive particles with an insulating film, the anisotropic conductive film becomes expensive, and a method in which a certain amount of insulating film balls is inserted cannot completely prevent a short circuit due to a problem of probability. In addition, the method of reducing conductive particles is uneasy about reliability because the number of particles contributing to the connection is also reduced.
[0010]
In addition, when anisotropic conductive paste is used, it is a countermeasure against the above problems by controlling the coating amount. However, it is difficult to temporarily attach the film substrate in the production process, and it is difficult to manage the coating. Since it is difficult to cope with equipment, capital investment is required.
Therefore, in the present invention, even if the connection between the film substrate using a thin electrode of about 10 microns or less and the liquid crystal panel is crimped using an anisotropic conductive film having a thickness of about 14 to 30 microns that is sufficiently thicker than the electrode, a short circuit is caused. It is to realize a display device that does not occur.
[0011]
[Means for Solving the Problems]
In order to solve this problem, the present invention relates to a display device comprising a liquid crystal display device and a film substrate held by sandwiching liquid crystals between at least two transparent substrates.
The connection terminals of the liquid crystal display device and the film substrate are formed of a plurality of continuous linear terminals, and a spacer is formed at the end of the portion to be thermocompression bonded, either the liquid crystal display device terminal or the film substrate terminal. By arranging this spacer in the portion that was short-circuited with the conductive particles when thermocompression bonded with an anisotropic conductive film, a shortage was prevented by creating a pool of adhesive and dispersing the particles.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Spacers with a thickness of 10 to 15 microns are disposed at both ends of the connection portion of the connection terminals of the film substrate in the inter-lead direction, and are bonded to the substrate of the display device with an anisotropic conductive film. For this reason, the particles flowing out without contributing to the connection are collected together with the adhesive in the spacer portion, and a short circuit between the terminals can be prevented.
[0013]
The spacer to be arranged can be formed by printing or the like. It is sufficient to use a solder resist. Therefore, it is possible to mount with an existing anisotropic conductive film and an existing device without increasing the number of steps.
[0014]
【Example】
Embodiments of the present invention will be described below with reference to FIGS.
(Example 1)
FIG. 1 shows a schematic cross section of a display device of the present invention. FIG. 2 is a front and side view showing the COF used in the display device of the present invention.
[0015]
The liquid crystal panel 1 has a configuration in which a liquid crystal is sandwiched between a glass substrate having a thickness of 0.5 mm on which an ITO pattern is formed and a pattern surface facing each other. The COF has a pattern 3 made of Cu having a thickness of 8 microns formed on a polyimide film 2 having a thickness of 25 microns, and the surface thereof is subjected to electroless tin plating. A driver IC 4 is mounted face down on the film substrate. On the connection terminal portion of the film substrate, a spacer 5 made of an epoxy resin material is formed with a thickness of 10 to 15 microns by printing.
[0016]
The pitch between the connection terminals was 200 microns, and AC-7-73-25 from Hitachi Chemical Co., Ltd. was used for the anisotropic conductive film. The anisotropic conductive film has a thickness of 25 microns and the conductive particles have a diameter of 10 microns. The anisotropic conductive film used here must have high fluidity when crimped.
The spacers 5 are aligned at positions overlapping the terminals of the liquid crystal panel, and are connected by thermocompression bonding via the anisotropic conductive film 6. It is desirable to thermocompress the terminal portion where the spacer 5 does not exist. At this time, the conductive particles that do not contribute to the connection of the anisotropic conductive film 6 and flow out to the end portion are collected in the peripheral portion of the spacer, so that no short circuit occurs between the leads.
[0017]
Originally, the installation of the spacer 5 is not preferable in terms of connection reliability. However, there is no problem in reliability due to the characteristics of the adhesive of the anisotropic conductive film 6 and the use of soft materials for the film substrate and the Cu foil. In other words, the actual usage level can be obtained by balancing these.
The spacer 5 may be made of the same material as that of the resist 7. In this embodiment, the spacer 5 is formed separately. In this embodiment, the spacer is formed on the COF side, but it may be formed on a liquid crystal display device. The spacer material is preferably a non-corrosive material that is not deformed by pressure and heat when the anisotropic conductive film is pressure-bonded.
[0018]
【The invention's effect】
As described above, according to the present invention, a thin Cu foil pattern film substrate capable of high-definition patterning and a liquid crystal display device can be connected with an existing anisotropic conductive film, and the liquid crystal display is inexpensive and productive. The device can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a cross section of a display device according to the present invention.
FIG. 2 is a front view and a side view showing a film substrate according to an embodiment of the present invention.
FIG. 3 is a schematic view showing a cross section of a conventional display device.
[Explanation of symbols]
1 Liquid Crystal Display 2 Polyimide Film 3 Pattern 4 Driver IC
5 Spacer 6 Anisotropic conductive film 7 Resist

Claims (5)

Comprising a display device having a multiple connection terminals, and the film substrate having a plurality of electrode terminals, and an anisotropic conductive film provided between the connection terminal and the electrode terminals of the film substrate of the display device In the display device,
Together with the plurality of electrode terminals and the plurality of connection terminals are connected by the anisotropic conductive film thermocompression bonding, wherein the plurality of definitive to the end of the crimping portion to which the electrode terminal and the connecting terminal is thermocompression a display device, characterized in that spacers are provided between the connecting terminal and the plurality of electrode terminals. The display device according to claim 1, wherein the electrode terminals and wherein the kite is formed by 6-10 micron thick conductor. The display device according to claim 1 or 2, wherein the spacer is provided on one of the film substrate and the display element. The display device according to claim 1 or 2, characterized in that the spacer is formed with a resist material provided on the film substrate. A display device comprising: a step of aligning a plurality of connection terminals formed on a display element and an electrode terminal formed on a film substrate via an anisotropic conductive film; and a connection step of thermocompression bonding the anisotropic conductive film In the manufacturing method of the display device, a spacer is provided between the connection terminal and the electrode terminal, and a terminal portion where the spacer is not provided in the connection step is thermocompression bonded. Production method.

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