JP2000111939A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device excellent in reliability, which is capable of always stably and electrically connecting each electrode pad of IC chip with a wiring pattern even on the unstable wiring pattern such as COF(chip on film) type. SOLUTION: Plural electrode pads 3 of a semiconductor chip 2 and plural wiring patterns 5 are each electrically connected by directly mounting IC chip 2 having plural electrode pads 3 having different areas on the wiring patterns 5, provided on a film substrate 4, which is electrically connected to a liquid crystal panel 1. In this structure, the widths of the wiring patterns 5 are formed according to the sizes(length of wiring patterns 5 which traverse the electrode pads 3) of the electrode pads 3 so that the contact area Sn(=Wn×Ln) of each wiring pattern 5 with each electrode pad 3 of the semiconductor chip 2 becomes equal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called so-called semiconductor chip mounted directly on a wiring pattern on a substrate such as glass constituting a liquid crystal panel or on a film substrate connected to the liquid crystal panel directly or through heat sealing. The present invention relates to a chip-on-glass (hereinafter, referred to as COG) or chip-on-film (hereinafter, referred to as COF) type liquid crystal display device. More specifically, the present invention relates to a liquid crystal display element capable of obtaining a uniform electrical connection between each electrode pad of a semiconductor chip and a wiring pattern while keeping the contact pressure between each electrode pad of the semiconductor chip and a wiring pattern constant.

[0002]

2. Description of the Related Art In a liquid crystal display element, for example, a transparent electrode pattern is formed on each of two glass substrates, and a liquid crystal panel is formed by opposing at a predetermined interval and sandwiching a liquid crystal material therebetween. (Pixel electrode)
By inputting a data signal to each of the electrodes, ON / OFF of each segment electrode is controlled, and a desired display can be performed. Conventionally, the input of the data signal to each segment electrode has a structure in which each segment electrode is connected to a circuit board and a data signal is directly sent to each segment electrode from a signal processing circuit provided on the circuit board. .

However, if the number of the segment electrodes is large, the number of connection wirings becomes very large. Therefore, recently, a COG type in which a semiconductor chip (IC chip) for signal processing is directly mounted on a glass substrate has been used. A COF type in which an IC chip is directly mounted on a wiring pattern of a film substrate electrically connected to a liquid crystal panel is used.

The electrical connection between such a COG type or COF type IC chip and a wiring pattern is shown in FIG.
As shown in a plan view of a connection portion between a part of the IC chip 2 and the wiring pattern 5 in FIG.
6B is very narrow, about 50 to 100 μm.
As shown in the cross-sectional explanatory view, an anisotropic conductive adhesive 6 is applied or affixed on the wiring pattern 5 of the film substrate 4, and the IC chip 2 is pressed at a constant pressure F to raise the temperature to cure. The connection is made by a thermocompression bonding method. The anisotropic conductive adhesive 6 is obtained by mixing metal conductive particles 6a into an epoxy resin or the like, and when pressed under a certain pressure, the epoxy resin is extruded in a horizontal direction, and the IC chip 2 Since the conductive particles 6a are sandwiched between the electrode pad 3 and the wiring pattern 5, the electrode pad 3 and the wiring pattern 5 are electrically connected. on the other hand,
In the horizontal direction, only the portion insulated by the epoxy resin and pressed against the conductive particles 6a is electrically connected.

On the other hand, with the recent miniaturization and high definition of liquid crystal display elements, the number of output terminals increases and the number of electrode pads 3 of the IC chip 2 connected to the wiring pattern 5 increases.
For example, when the number of electrode pads 3 provided on opposite sides of the IC chip 2 is different, the electrode pads 3 cannot be provided at a fixed interval and a fixed width, and the area of the electrode pads 3 tends to be different. is there. For example, FIG.
Thus, while the electrode pad C has a width of 85 μm, the electrode pad B has a width of only 47 μm. In this case, since the width of each wiring of the wiring pattern 5 is formed to be a width that can cover any of the electrode pads 3, the contact area between each electrode pad 3 and each wiring of the wiring pattern 5 is equal to the electrode pad. In the case of C, the size is 85 μm (width) × 85 μm (length), whereas the size of the electrode pad B is 47 μm × 85 μm, and the area ratio is about 9: 5, which is a large difference.

[0006]

As described above, when a plurality of electrode pads of an IC chip are provided, the area of the electrode pads may not be constant and the difference between the areas may be large. On the other hand, conventionally, each wiring of the wiring pattern is formed so as to cover the electrode pad. Therefore, the contact area between the electrode pad of the IC chip and the wiring pattern may differ depending on the electrode pad. Since the connection between the electrode pad and the wiring pattern is made by using an anisotropic conductive adhesive in which conductive particles are mixed into an epoxy resin or the like as described above, and applying a certain pressure, the bonding is performed by thermocompression bonding. If the contact area is different, the pressure applied to the conductive particles in contact with each electrode pad will be different. If the pressure is different, the conductive particles may not be sufficiently crushed by the electrode pad having a weak pressure, and a sufficient electrical contact may not be obtained.
There is a problem that poor contact is likely to occur. This tendency is particularly remarkable when an IC chip is mounted on a flexible film substrate such as a COF-type flexible film substrate.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and always stably connects each electrode pad of an IC chip and a wiring pattern on an unstable wiring pattern such as a COF type. It is an object of the present invention to provide a highly reliable liquid crystal display element which can be connected to a liquid crystal display device.

[0008]

According to the present invention, there is provided a liquid crystal display device comprising: a plurality of wiring patterns on a liquid crystal panel substrate in which a liquid crystal layer is sandwiched by two substrates on which electrode patterns are formed; A semiconductor chip having a plurality of electrode pads having different areas is directly mounted on a plurality of wiring patterns on a film substrate electrically connected to a liquid crystal panel, so that a plurality of electrode pads of the semiconductor chip are provided. And the plurality of wiring patterns are electrically connected to each other, and the area of the electrode pads is adjusted so that the contact area between each electrode pad of the semiconductor chip and the wiring pattern is equal. The wiring pattern is formed accordingly.

The term "electrode pad" as used herein means a portion where an electrode of an IC can be connected to an external wiring, and includes an electrode pad provided with a bump. Also,
The film substrate means a substrate in which a wiring pattern is formed by a thin metal film on an insulating film such as a flexible film.

With this structure, even if the area of the electrode pad of the IC chip is different, the contact area between the wiring pattern and the electrode pad is always the same. Even when a certain pressure is applied to the electrode pad and an IC chip is mounted on an unstable film such as COF, stable connection can be obtained, and a highly reliable liquid crystal display device can be obtained.

In each of the pair of the electrically connected electrode pad and the wiring pattern, the wiring pattern is formed such that the width of the electrode pad is at least 10 μm larger than the width of the electrode pattern. ,
Even if a positional shift occurs in the manufacturing process, a portion where the electrode pad and the wiring pattern do not overlap does not occur, and a constant contact area is always obtained, which is preferable. Also, preferably,
The semiconductor chip is characterized in that a region excluding the electrode pad forming region is covered with an insulating film. Thereby, a short circuit with the wiring pattern can be prevented.
Further, the surface of the insulating film is formed to be higher than the surface of the electrode pad. If an insulating film is formed, even if the electrode pad does not have a bump, since the area of the overlapping portion between the wiring pattern and the electrode pad is formed to be constant, the force is uniformly applied, and the reliability is ensured. It is possible to achieve reliability or other-world connection. Further, a bump forming step is not required, and the number of steps can be simplified. By forming the wiring pattern so as to be orthogonal to one side of the electrode pad at least in the vicinity of the connection portion with the electrode pad, it is possible to ensure the same area.

[0012]

Next, the liquid crystal display device of the present invention will be described with reference to the drawings.

As shown in FIG. 1A, a liquid crystal display device of the present invention has two substrates 1 on which an electrode pattern (not shown) is formed as shown in a plan view of one embodiment.
A liquid crystal panel 1 is formed by sandwiching a liquid crystal layer between the liquid crystal panels 1 and 12. A plurality of wiring patterns on a substrate constituting the liquid crystal panel 1 or a plurality of wiring patterns on a film substrate 4 on which a wiring pattern is formed on a flexible film or the like electrically connected to the liquid crystal panel. A semiconductor chip (hereinafter, referred to as an IC chip) 2 having a plurality of electrode pads 3 having different areas is directly mounted on the IC chip 5 (FIG. 1A).
Are mounted), whereby the plurality of electrode pads 3 of the semiconductor chip 2 and the plurality of wiring patterns 5 are electrically connected to each other. In the present invention, FIG.
As shown schematically in (b), a relationship diagram between a part of the IC chip 2 and the wiring pattern 5, the contact between the bump 3 b formed on each electrode pad 3 of the semiconductor chip 2 and the wiring pattern 5 is shown. The width Wn of the wiring pattern 5 is formed according to the size of the bump 3b (the length of the wiring pattern 5 traversing the bump 3b) so that the area Sn (= Wn × Ln) becomes equal. .

The liquid crystal panel 1 has a structure similar to that of a normal liquid crystal panel, and is constituted, for example, as shown in FIG. That is, the insulating substrate 11,
Electrode patterns 13 and 14 are formed on one surface of 12, respectively, and alignment films 15 and 16 for aligning liquid crystal molecules in a certain direction are further provided. The two insulating substrates 1 and 2 are adhered to each other by a sealing agent 17 around the electrode patterns 13 and 14 so as to oppose each other while maintaining a certain gap by a spacer (not shown). When the liquid crystal material is injected, the liquid crystal layer 18 becomes 2
It is sandwiched between the insulating substrates 11 and 12. Further, the polarizing plates 1 are provided outside the insulating substrates 11 and 12, respectively.
9a and 19b are provided, and the liquid crystal panel 1 is formed by these. The opposed electrode patterns 13 and 14
Is applied, the alignment direction of the liquid crystal molecules changes during that period, and the transmission and non-transmission of light from a backlight (not shown) are controlled together with the direction of the polarization axis of the polarizing plates 19a and 19b. It is turned on and off and a desired display is made.

The IC chip 2 processes an input data signal and applies an on / off signal to each segment electrode (pixel electrode) to control the segment electrode (pixel electrode) so that a desired display can be performed. A signal processing circuit is formed, and each electrode terminal of the signal processing circuit is led out on one surface of the IC chip 2 as an electrode pad 3. A bump 3b, which is a projection having a desired height, is formed on the surface of the electrode pad 3, and the bump 3b is connected to a wiring pattern on an insulating substrate. The electrode pads 3 are, as described above, schematically shown in FIG. 1B due to the number of electrode pads 3 led out to one end face side and the layout relationship of the electrode pads 3. The width Tn and the length Ln may not be formed to be constant. The present invention is to solve the problem of the IC chip 2 when the size of the electrode pad of the IC chip 2 is not constant. The electrode pad 3 may have a state in which an electrode metal is provided on one surface of the IC chip 2 by vapor deposition or the like. In this example, a bump metal 3b is further formed on the surface.

The film substrate 4 has flexibility, for example, through a heat seal (not shown) or directly connecting the terminal of the electrode pattern of the liquid crystal panel 1 to the circuit board side, and has a degree of freedom of arrangement of the circuit board. In this case, a wiring pattern 5 made of a conductive thin film such as a thin copper thin film is formed on an insulating film.

The wiring pattern 5 is formed by bonding a copper thin film having a film thickness of about 8 to 15 μm or the like formed by vapor deposition or the like on the film substrate 4 by etching. Wiring pattern 5
Are not uniformly formed with the same width, but the contact area with the electrode pad 3 (the hatched portion in FIG. 1B) is changed according to the size of the electrode pad 3 of the IC chip 2 described above. It is formed so as to be equal (S1 = S2 =... = Sn). That is, the IC chip to be mounted is known in advance, and the size and pitch of the electrode pad 3 and the bump 3b formed thereon are also known.
The width Wn of the wiring connected to the bump 3b is determined so as to be Wn × Ln = constant according to each of the electrode pads 3 and the bump 3b formed on the electrode pad 3, and is formed by patterning. I have. For example, I
The size of the electrode pad (bump) of the C chip is 80 μm
.Times.80 .mu.m, 70.times.80, and 50.times.80. For example, each of the electrode pads 3 indicated by S1 to S3 in FIG. 1B has L1 = 50 .mu.m (T1 = 80 .mu.m), L2
= 80 μm (T2 = 50 μm), L3 = 70 μm (T3
= 80 μm), W1 = 64 μm, W2
= 40 μm and W3 = 45.7 μm.

In order to make the contact area of the wiring pattern 5 with the electrode pad 3 (bump 3b) of the IC chip 2 always constant, as described above, the wiring pattern 5
It is necessary to perform patterning with a predetermined width, but if the patterning is further performed so as to satisfy the following conditions, the contact area can be kept constant even if manufacturing variations occur.

That is, first, it is preferable that the wiring pattern 5 is formed so as to be always perpendicular to the pattern of the electrode pad 3 at a portion where the wiring pattern 5 intersects with the electrode pad 3 of the IC chip 2. For example, when the wiring pattern 5 is formed so as to be oblique to the electrode pad 3 as shown in FIG. 3, a relative displacement easily occurs between the IC chip 2 and the wiring pattern 5. For this reason, the contact area is likely to change, and it is highly likely that the contact area will not be constant.

Further, the width W of the wiring pattern 5 is preferably set to be always smaller than the width of the electrode pad by about 10 μm. That is, even when the difference between the width of the electrode pad 3 and each wiring of the wiring pattern 5 is the smallest, 1
0 μm is set so that it can be secured. For example, in the above example, W1 + 10 ≦ T1, W2 + 10 ≦ T2, W3 + 1
It is set so as to satisfy the relationship of 0 ≦ T3. By setting in this manner, a slight displacement may occur when bonding the IC chip 2 (for example, ± 5 to 8).
However, by providing such a margin, there is no portion where the electrode pad 3 and the wiring pattern 5 do not overlap with each other even in the case of displacement during bonding. This is because the contact areas can be made equal.

The mounting of the IC chip 2 on the wiring pattern 5 of the film substrate 4 is performed as shown in the partial cross-sectional view of FIG. An anisotropic conductive adhesive 6 in which conductive particles 6a are mixed in an epoxy resin or the like is applied or pasted around the wiring pattern 5, and the IC chip 2 is mounted, and the IC chip 2 is pressed with a constant pressure F and heated. It is adhered by doing. At this time, between the electrode pad 3 and the wiring pattern 5, epoxy resin or the like is extruded laterally by pressure, and the conductive particles 6 a are sandwiched therebetween and partially crushed.
Are electrically connected to each other. In the present invention, since the area between the electrode pad 3 and the wiring pattern 5 is the same in every electrode pad 3, the number of conductive particles 6a sandwiched therebetween is substantially constant, and
A constant pressure is also applied to a, and the degree of crushing is also constant.

According to the present invention, since the width of the wiring pattern is set so that the contact area between the electrode pad and the wiring pattern is equal, when the IC chip is bonded as described above, the voltage is applied to each electrode pad. And the pressure applied to the conductive particles sandwiched between the electrode pad and the wiring pattern also becomes constant. Therefore, the conductive particles between any of the electrode pads and the wiring pattern are crushed by a certain pressure, so that poorly-contacted electrode pads are not generated, thereby improving the yield and greatly improving the reliability.

Further, as described above, since each wiring of the wiring pattern is formed at least in the vicinity of the electrode pad so as to be perpendicular to the electrode pad, the contact area between the two is always constant, and the IC chip is slightly positioned. Even if it shifts,
A constant contact area is always obtained. Further, even when the width of the wiring pattern is the smallest in difference with the width of the electrode pad,
Since the wiring pattern is formed small so as to have a thickness of about 0 μm, a part of the wiring pattern does not protrude from the electrode pad, and a constant contact area can be maintained at all times even if a positional shift similarly occurs. .

In the above-described example, the IC chip is provided on the film substrate. However, when the IC chip is provided on the film substrate, the elasticity of the film is particularly large. The effect of the present invention is great because the contact is apt to be weaker, but the reliability is similarly improved even when the IC chip is bonded on a glass substrate such as a COG type. Although the bumps 3b are formed in the same region with respect to the electrode pads 3, if the areas and shapes are not the same, it is necessary to determine the wiring pattern according to the size of the bumps. Next, a second embodiment of the present invention will be described. In this example, as shown in FIG. 4, without forming a bump, an area other than the area where the electrode pad 23 is formed is covered with a polyimide film 20 having a thickness t _{i of} about 5 μm and an electrode pad having a thickness t _p = 200-300 nm. The film thickness t _e formed on the film substrate 4 directly on the film substrate 4 via the anisotropic conductive film 26 is connected to the wiring pattern 5. Here, the diameter of the anisotropic conductive film 26 is 5 μm.
About 6 conductive particles 6a are used. Then, each of the electrode pads 23 is configured so as to include about five conductive particles 6a. In this way, by designing the wiring pattern so that the contact area between the electrode pad 23 and the wiring pattern is the same, reliable connection can be performed without forming a bump on the electrode pad. It becomes possible. In this example, the connection with the wiring pattern formed on the film substrate 4 has been described, but the connection is not limited to the film substrate. However, when a film substrate is used, it is difficult to make a good connection due to a pressure difference, but by using the configuration of the present invention, it is possible to easily achieve a reliable and stable connection. . In addition, as shown in FIG. 5, the wiring pattern may be formed so as to be orthogonal to the electrode pad only in the vicinity of the connection region with the IC chip, and the angle may be changed in the vicinity.

[0025]

According to the present invention, when an IC chip is directly bonded on a wiring pattern, the bonding can be always performed at a constant pressure even when the size of the electrode pad of the IC chip is different. Greatly improve the yield and reliability of the electrical connections. As a result, I
The margin of the pressure applied to the IC chip when bonding the C chip can be increased, the equipment for the bonding step can be inexpensive, and the reliability of the liquid crystal display element can be greatly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an electrode pad portion and a bonding portion of an IC chip of one embodiment of a liquid crystal display element of the present invention.

FIG. 2 is an explanatory sectional view of an example of the liquid crystal panel of FIG. 1;

FIG. 3 is a diagram showing an example of an unfavorable shape of a relationship between an electrode pad and a wiring pattern.

FIG. 4 is an explanatory sectional view of a second embodiment of the present invention.

FIG. 5 is a diagram showing an example of a preferable shape of a relationship between an electrode pad and a wiring pattern.

FIG. 6 is an explanatory diagram of a bonding portion of an IC chip of a conventional liquid crystal display element.

[Explanation of symbols]

 Reference Signs List 1 liquid crystal panel 2 IC chip 3 electrode pad 4 film substrate 5 wiring pattern

Claims (6)

[Claims] 1. A liquid crystal panel having a liquid crystal layer sandwiched between two substrates having electrode patterns formed thereon, on a plurality of wiring patterns on a substrate of the liquid crystal panel, or on a film substrate electrically connected to the liquid crystal panel. By directly mounting a semiconductor chip having a plurality of electrode pads having different areas on a plurality of wiring patterns, the plurality of electrode pads of the semiconductor chip and the plurality of wiring patterns are electrically connected to each other. A liquid crystal display element to be connected, wherein the wiring pattern is formed according to the area of the electrode pad so that the contact area between each electrode pad of the semiconductor chip and the wiring pattern is equal. . 2. The wiring pattern is formed such that the width of the electrode pad is at least 10 μm larger than the width of the wiring pattern in each set of the electrically connected electrode pad and the wiring pattern. The liquid crystal display device according to claim 1. 3. The liquid crystal display device according to claim 1, wherein a bump is formed on the electrode pad, and the bump and the wiring pattern are joined. 4. The liquid crystal display device according to claim 1, wherein a region of the semiconductor chip other than the electrode pad forming region is covered with an insulating film. 5. The liquid crystal display device according to claim 4, wherein the surface of the insulating film is formed to be higher than the surface of the electrode pad. 6. The liquid crystal display device according to claim 1, wherein the wiring pattern is formed so as to be orthogonal to one side of the electrode pad at least near a connection portion with the electrode pad.