JPH04362925A - Wiring board - Google Patents

Abstract

PURPOSE:To improve the reliability regarding electric and mechanical connections and suppress connection resistance as much as possible. CONSTITUTION:A connection conductor 31 formed on a glass substrate 22 is a laminate of a transparent electrode 24, a chromium layer 32, and an aluminum layer 33, and the width W3 of the chromium layer 32 and aluminum layer 33 is less than the width W2 of the transparent electrode 24. Consequently, even when the connection conductor 31 is covered with an anisotropic conductive layer which has shrinkability accompanying curing and the layer is cured, peeling from the glass substrate 22 due to shrinkage stress extends only to the chromium layer 32 and aluminum layer 33 and the transparent electrode 24 is not peeled, thereby preventing the connection conductor 31 from being disconnected by peeling off the glass substrate 22. Further, the chromium layer 32 and aluminum layer 33 are formed on the transparent electrode 24, so the electric resistance of the connection conductor 31 can be suppressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring substrate such as a glass substrate for, for example, a liquid crystal display device.

0002

2. Description of the Related Art FIG. 10 is a sectional view of a typical conventional liquid crystal display device 1. As shown in FIG. The liquid crystal display device 1 includes a pair of glass substrates 2 and 3, and on each glass substrate 2 and 3, ITO (indium tin oxide) extending in mutually orthogonal directions is disposed.
A plurality of transparent electrodes 4 and 5 are formed, and a display area 6
is set. The transparent electrode 4 on the glass substrate 2 is formed extending outward from the display area 6 on the glass substrate 2, and a chromium layer 7 and an aluminum layer 8 are laminated and formed in this part for the purpose of suppressing the resistance value. and is configured as circuit wiring 9. Chromium layer 7 includes transparent electrodes 4 and 5 and aluminum layer 8
Used to improve adhesion with

A flexible wiring board 13 having circuit wiring 12 formed on a support film 11 made of a resin material is connected to the connection area 10 of the circuit wiring 9 through an anisotropic conductive layer 14 . The vicinity of the connection area 10 is covered and fixed on both sides of the glass substrate 2 with a fixing resin layer 16.

FIG. 11 is a plan view of the circuit wiring 9 on the glass substrate 2, and FIG. 12 is a plan view of the circuit wiring 9 on the glass substrate 2, and FIG.
FIG. The transparent electrodes 4 and 5, the chromium layer 7, and the aluminum layer 8 that constitute the circuit wiring 9 are as follows:
As shown in FIGS. 11 and 12, they are formed to have the same width W1.

The anisotropic conductive layer 14 is formed by diffusing conductive fine particles into a synthetic resin material and pressing the flexible wiring board 13 and the circuit wiring 9 into contact with each other. It has a configuration that realizes electrical continuity only in the vertical direction in FIG.

Conventionally, thermoplastic synthetic resin materials have been used as this synthetic resin material, but since such synthetic resin materials soften when heated, the liquid crystal display device 1 cannot be used under relatively high temperature operating conditions. When used as a base, there is a problem in that the reliability of the electrical and mechanical connection between the glass substrate 2 and the flexible wiring board 13 is low. Therefore, it becomes difficult to bend the flexible wiring board 13 near the liquid crystal display device 1, resulting in a problem of low usability.

That is, using an anisotropic conductive resin made of a thermosetting synthetic resin material is superior in terms of the reliability of the electrical and mechanical connections. The material has a characteristic of high shrinkage stress upon curing. For this reason, it has the following problems.

FIG. 13 is a sectional view illustrating the problems of the conventional example. As described above, when the anisotropic conductive layer 14 made of a thermosetting synthetic resin material is coated on the aluminum layer 8 laminated on the glass substrate 2 and cured by heating, the anisotropic conductive layer 14 is formed as described above. A relatively large shrinkage stress, indicated by an arrow F1 in FIG. 13, acts on the conductive layer 14. The aluminum layer 8 is formed by sputtering, and it is known that the aluminum layer 8 grows in the form of relatively large grains during this film formation, and that many fine irregularities exist on the surface after the film formation is completed. Therefore, the anisotropic conductive layer 14 is strongly adhered to the aluminum layer 8.

The chromium layer 7 has the same surface properties, and therefore the transparent electrode 4, the chromium layer 7, the aluminum layer 8, and the anisotropic conductive layer 14 are strongly adhered to each other. On the other hand, it is known that the surface quality of ITO constituting the transparent electrode 4 is extremely smooth compared to the aluminum layer 8, etc. Therefore, the transparent electrode 4 has a lower peel strength than the adjacent chromium layer 7, for example. Also, glass substrate 2
This means that the peel strength is relatively low.

0010

[Problems to be Solved by the Invention] Therefore, due to the shrinkage stress F1 of the anisotropic conductive layer 14, the chromium layer 7
Forces indicated by arrows F2 are generated at both left and right ends, and this force may cause the transparent electrode 4 to peel off from the glass substrate 2 at its end portion 15 and break. Further, the chromium layer 7 is formed on the transparent electrode 4
, 5, the side surfaces are etched to form grooves as shown in the figure, and the anisotropic conductive layer 14 is caught in the grooves, increasing the peeling action of the transparent electrodes 4 and 5.

In order to prevent such a situation, the circuit wiring 9
A technique is conceivable that consists of only the transparent electrode 4. In this case, since the surface of ITO is smooth, even if the shrinkage stress F1 occurs during thermocompression bonding using the anisotropic conductive layer 14 made of a thermosetting resin, the anisotropic conductive layer 14 does not cover the transparent electrode 4. The occurrence of slipping and peeling is prevented. However, it is known that ITO that constitutes the transparent electrode 4 has a relatively high electrical resistance value, which causes a new problem that the connection resistance increases and the display quality deteriorates.

An object of the present invention is to solve the above-mentioned technical problems and to provide a wiring board that can improve the reliability of electrical and mechanical connections and suppress connection resistance as much as possible. It is to provide.

[0013]

[Means for Solving the Problems] The present invention provides a first conductor formed on a base material with a resin material formed on the first conductor such that at least a portion of the outer circumference of the first conductor is exposed. The wiring board is characterized in that a second conductor having a high adhesive strength is formed, and the first conductor and the second conductor are covered with a resin layer that has shrinkage properties when cured.

[0014]

[Operation] According to the present invention, at least a portion of the outer circumference of the first conductor on the base material is exposed, and a second conductor having a stronger adhesive force with the resin material than the first conductor is placed inwardly of the first conductor. form a conductor. The region on the base material that includes the first conductor is covered with a resin layer that has shrinkage properties when cured.

Therefore, even if the resin layer shrinks during curing, the resin layer slides on the first conductor in the exposed portion of the outer periphery of the first conductor, and the shrinkage causes the first conductor to shrink. It is possible to prevent the peeling from the outer periphery. Moreover, since the second conductor is formed on the first conductor, the electrical resistance of the laminate consisting of the first conductor and the second conductor can be significantly lowered than when only the first conductor is used.

[0016]

Embodiment FIG. 1 is a plan view of a portion of a liquid crystal display device 21 according to an embodiment of the present invention, and FIG.
FIG. 3 is a sectional view taken along the section line X3-X3 in FIG. 2. FIG. The liquid crystal display device 21 includes a pair of glass substrates 22 and 23, and on each glass substrate 22 and 23, a strip of ITO (indium tin oxide) is formed.
A plurality of transparent electrodes 2 each extending in mutually orthogonal directions.
4 and 25 are formed, and a display area 26 is set. Alignment films 27 and 28 are formed on each glass substrate 22 and 23, a liquid crystal layer 29 is injected between them, and the periphery is sealed with a sealant 30.

The transparent electrode 24 on the glass substrate 22 is formed extending outward from the display area 26 on the glass substrate 22, and a chromium layer 32 and an aluminum layer 33 are formed on this part for the purpose of suppressing the resistance value. , and are configured as connection wiring 31. The chromium layer 32 is used to improve the adhesion strength between the transparent electrodes 24 and 25 and the aluminum layer 33.

A flexible wiring board 37, in which the circuit wiring 36 is formed on a support film 35 made of a resin material, is connected to the connection area 34 of the circuit wiring 36 by an anisotropic conductive layer 38. The transparent electrode 24 constituting the connection wiring 31 is formed to have a width W2, and has a chromium layer 32 and an aluminum layer 3.
3 is formed to have a width W3 smaller than the width W2.

FIG. 4 is a plan view of the connection wiring 31 in the vicinity of the connection area 34, and FIG. 5 is a cross-sectional view taken along the section line X5-X5 in FIG. In this embodiment, as described above, the width W3 of the chromium layer 32 and the aluminum layer 33 is selected to be smaller than the width W2 of the transparent electrode 24 in the connection wiring 31. That is, the chromium layer 32 and the aluminum layer 33 have an exposed region 39 where both ends in the width direction of the transparent electrode 24 are not covered with the chromium layer 32 and the aluminum layer 33.
The transparent electrode 24 is formed inwardly so as to have the same shape.

By configuring the connection wiring 31 in this manner, the synthetic resin material constituting the anisotropic conductive layer 38 is made of a thermosetting resin material, which shrinks when cured, such as an ultraviolet curable resin material, as will be described later. Materials can be selected.

That is, as explained in the prior art section, I
The transparent electrode 24 made of TO has an extremely smooth surface, while the chromium layer 32 and the aluminum layer 3
The surface texture obtained by depositing 3 by sputtering is due to the fact that the deposition process grows in the form of relatively large grains.
It is known that there are many fine irregularities on the surface. Therefore, for example, when the connection wiring 31 is coated with an anisotropic conductive layer 38 comprising a thermosetting resin as shown in FIG. 6 and cured by heating, the anisotropic conductive layer 38 is A shrinkage stress indicated by F11 is generated.

The anisotropic conductive layer 38 is firmly adhered to the aluminum layer 33 due to the surface properties of the aluminum layer 33. Therefore, the transparent electrode 24 of the chromium layer 32
A force indicated by arrow F12 is generated at the end of . This power F
Although the chromium layer 32 and the aluminum layer 33 may peel off from the transparent electrode 24 due to F12, the compressive stress F11 acting near the exposed area 39 of the transparent electrode 24 causes the anisotropic conductive layer 38 to peel off from the transparent electrode 24. Based on the fact that the transparent electrode 24 is only relatively weakly bonded due to the surface properties of the transparent electrode 24, the shrinking anisotropic conductive layer 38 slides on the exposed area 39, and the glass substrate 22 is bonded to the transparent electrode 24.
This prevents the generation of forces that would cause it to peel off.

Therefore, as shown in FIGS. 4 and 5,
When the flexible wiring board 37 is thermocompression bonded to the connection wiring 31 on the glass substrate 22 via the anisotropic conductive layer 38, the chromium layer 32 and the aluminum layer 33 may peel off due to the shrinkage stress F11. In this case, at least the transparent electrode 24 remains on the glass substrate 22. Therefore, a situation in which the flexible wiring board 37 and the transparent electrode 24 in the display area 26 become electrically or mechanically disconnected or disconnected can be prevented.

Furthermore, as described above, at least the transparent electrode 24 remains on the glass substrate 22, so that the anisotropic conductive layer 38 is well fixed to the glass substrate 22. This significantly improves the reliability of the electrical and mechanical connection between the flexible wiring board 37 and the glass substrate 22. Furthermore, the connection wiring 31 connects the transparent electrode 24 and the chromium layer 3.
2 and the aluminum layer 33, the electrical resistance value can be suppressed compared to the case where it is constructed only from the transparent electrode 24, and the display quality can be improved.

FIG. 7 is a process diagram illustrating the manufacturing process of the liquid crystal display device 21. As shown in FIG. In step a1, an ITO layer 24, a chromium layer 32, and an aluminum layer 33 are formed on a relatively large glass substrate 22 using a thin film technique such as sputtering. In step a2, the three-layer laminate is patterned into a strip having the width W2 over the entire surface of the glass substrate 22 using a photo process using a well-known photoresist or the like.

In step a3, the chromium layer 32 and aluminum layer 33 within the display area 26 of the three-layer strip-shaped laminate are selectively etched and removed, and the connection wiring 31 outside the display area 26 is removed. In this step, the chromium layer 32 and the aluminum layer 33 are patterned to have a width W3 so that the exposed region 39 is formed. In step a4, the glass substrate 23 manufactured in the same steps as steps a1 to a3 is bonded, and step a5
In step a6, the individual liquid crystal display devices 21
Divide so as to obtain. In step a7, the liquid crystal layer 29 is injected, and in step a8, the anisotropic conductive layer 38 is thermocompression bonded and cured, thereby fixing the flexible wiring board 37 and the glass substrate 22.

FIG. 8 shows connection wiring 31 of another embodiment of the present invention.
FIG. This embodiment is similar to the previous embodiment, and corresponding parts are given the same reference numerals. The noteworthy point of this embodiment is that the chromium layer 32 and aluminum layer 33 on the transparent electrode 24 are selectively removed, and the exposed areas 39 shown with diagonal lines are made into mutually independent individual areas 40.
This is because they are arranged in a staggered manner.

That is, the anisotropic conductive layer 3 is formed on the transparent electrode 24.
When the shrinkage stress F11 due to 4 acts, the chromium layer 3
Even if 2 and the aluminum layer 33 are peeled off, the transparent electrode 24 adjacent in the width direction remains, and the chromium layer 3
Even if all of the aluminum layer 2 and the aluminum layer 33 are peeled off, the connection wiring 31a can achieve electrical continuity through the transparent electrode 24 and the glass substrate 2 of the anisotropic conductive layer 38.
Fixation to 2 is achieved.

[0029] Such an embodiment can also achieve the same effects as those described in the previous embodiments.

FIG. 9 is a sectional view showing the structure of still another embodiment of the present invention. This embodiment is similar to the previous embodiment, and corresponding parts are given the same reference numerals. This embodiment is an example in which, for example, in the liquid crystal display device 21 shown in FIG. 2, a drive circuit element 41 is connected on a glass substrate 22 in a so-called bare chip state by face-down bonding. The drive circuit element 41 includes bumps 4 for connection to a circuit element body 42 made of semiconductor crystal such as silicon, for example.
3 is formed.

For example, the connection wiring 31 on the glass substrate 22 is formed by laminating a chromium layer 32 and an aluminum layer 33 on a transparent electrode 24, as in the above embodiment, and the width W3 of the chromium layer 32 and the aluminum layer 33 is is formed smaller than the width W2 of the transparent electrode 24. The connection wiring 31 and the bump 43 of the drive circuit element 41 are brought into contact with each other with conductive particles 44 interposed between them, and the drive circuit element 41
For example, an ultraviolet curing resin (
UV resin) 45.

The ultraviolet curing resin 45 is a material that shrinks when cured by ultraviolet irradiation. Therefore, the drive circuit element 41 is always held in a pressed state against the glass substrate 22, and electrical continuity between the bumps 43 and the connection wiring 31 is reliably achieved. In such a configuration example, since the width W2 of the transparent electrode 24 and the width W3 of the chromium layer 32 and the aluminum layer 33 are set as described above, it is possible to achieve an effect similar to that described in the above embodiment. .

[0033]

As described above, according to the present invention, at least a portion of the outer circumference of the first conductor on the base material is exposed, and the first conductor is exposed to the resin material from the inside of the first conductor. A second conductor is formed that has a surface texture with high adhesive strength. The area on the base material including the first conductor is coated with a shrinkable adhesive upon completion of bonding.

Therefore, even if the adhesive contracts during the adhesive action, the adhesive will slide on the first conductor in the exposed portion of the outer periphery of the first conductor, and the contraction will cause the adhesive to shrink on the first conductor. It is possible to prevent the situation where the material peels off from the outer periphery. Moreover, a second conductor is formed on the first conductor,
The electrical resistance of the configuration consisting of the first conductor and the second conductor is
This can be much lower than in the case of only conductors.

[Brief explanation of drawings]

FIG. 1 is a partial plan view of a liquid crystal display device 21 according to an embodiment of the present invention.

FIG. 2 is a plan view of a liquid crystal display device 21. FIG.

FIG. 3 is a cross-sectional view of the liquid crystal display device 21. FIG.

FIG. 4 is a plan view of the vicinity of the connection region 34 of the connection wiring 31.

5 is a sectional view taken along the section line X5-X5 in FIG. 4. FIG.

FIG. 6 is an enlarged cross-sectional view of the connection wiring 31.

7 is a process diagram illustrating the manufacturing process of the liquid crystal display device 21. FIG.

FIG. 8 is a plan view showing connection wiring 31a according to another embodiment of the present invention.

FIG. 9 is a sectional view showing the structure of still another embodiment of the present invention.

FIG. 10 is a cross-sectional view of a typical conventional liquid crystal display device 1.

11 is a plan view of circuit wiring 9 on glass substrate 2. FIG.

12 is a sectional view taken along the section line X11-X11 in FIG. 10. FIG.

FIG. 13 is a sectional view illustrating problems in the conventional example.

[Explanation of symbols]

21 Liquid crystal display device 22, 23 Glass substrate 24, 25 Transparent electrode 31, 31a Connection wiring 32 Chromium layer 33 Aluminum layer 37 Flexible wiring board 38 Anisotropic conductive layer 39 Exposure area 40 Individual areas 41 Drive circuit element 45 Ultraviolet curing resin

Claims (1)

[Claims] 1. A second conductor having a stronger adhesive strength to the resin material than the first conductor, the second conductor being formed on the first conductor formed on the base material so as to expose at least a part of the outer circumference of the first conductor. 1. A wiring board, wherein the first conductor and the second conductor are coated with a resin layer that has shrinkage properties when cured.