JP2000124575A - Wiring board, liquid crystal device and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board of two-layered structure which can be protected against damage. SOLUTION: A metal film pattern 2 is formed direct on a base layer 1 for the formation of a wiring board 7, where the recessed corner C1 of the base layer 1 is rounded or formed like a curved shape such as an arc. By rounding, fissures are prevented from occurring in the recessed corner C1, and as a result, the wiring board 7 can be protected against damage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wiring board having a wiring pattern formed directly on a base layer. The present invention also relates to a liquid crystal device including the wiring substrate. The invention also relates to an electronic device including the liquid crystal device.

[0002]

2. Description of the Related Art In recent years, liquid crystal devices have been widely used as a part of portable telephones, portable electronic terminals, electronic organizers, and other electronic devices, for example, as image display units. The liquid crystal device is formed, for example, as follows: a pair of substrates (often transparent substrates) each having an electrode (eg, a transparent electrode) are attached to each other and formed between the substrates. It is formed by enclosing liquid crystal in a gap, a so-called cell gap. A polarizing plate is further mounted on the outer surface of the substrate as necessary, and a color filter is provided on the inner surface of one of the pair of substrates as necessary.

In this liquid crystal device, the light supplied to the liquid crystal can be modulated by controlling the orientation of the liquid crystal by controlling the voltage applied to electrodes facing each other with the liquid crystal interposed therebetween. Images such as numbers and pictures can be displayed. In order to control the voltage applied between the opposing electrodes in this way, in a normal liquid crystal device, a liquid crystal driving IC is conductively connected to those electrodes, and the applied voltage is controlled by the liquid crystal driving IC.

Various methods have been known for mounting a liquid crystal driving IC on a substrate. For example,
Taking a mounting method of a TAB (Tape Automated Bonding: Tape Automated Mounting) method, which has been conventionally known, as an example, in this mounting method, first, a TAB (Tape Automated Bonding) method is used.
ding) technology and FPC (Flexible Printed Circuit)
It: A liquid crystal driving IC is bonded on a flexible printed circuit board to form a TCP (Tape Carrier Package), and the TCP is connected to a substrate of the liquid crystal panel, thereby forming an electrode in the liquid crystal panel. Is connected to a liquid crystal driving IC.

[0005] The FPC used in the conventional TAB technology is as follows.
For example, as shown in FIG. 7, it generally has a three-layer structure including a base layer 51, a metal film pattern 52, and an adhesive layer 55 for fixing the metal film pattern 52 to the base layer 51. . The base layer 51 is formed of, for example, polyimide, and the metal film pattern 52 is formed of, for example, C.
formed by u (copper). This three-layer FPC
However, because of the three-layer structure, there is a problem that it is difficult to reduce the thickness, and it is relatively expensive.

In order to solve the above problems of the three-layer FPC, recently, as shown in FIG. 6, a two-layer structure in which a metal film pattern 2 is directly formed on a base layer 1 is used. FPC3 has been proposed. In this FPC 3, the metal film pattern 2 is directly fixed on the base layer 1 by a sputtering method, a roll coating method or the like without using an adhesive.

[0007]

The wiring board using the FPC 3 having the two-layer structure as described above can have a smaller thickness and a smaller number of parts than the FPC having the three-layer structure. It has the advantage that it can be manufactured only at low cost.
However, since the FPC 3 having the two-layer structure has a small thickness, the FPC 3 has a problem in that the mechanical strength is weak and thus the FPC 3 is easily cut.

According to an experiment conducted by the inventor, when an external force is applied to a wiring board having a shape having a corner, a crack is generated at the corner and the wiring board is damaged due to the crack. Turned out to be common.
The damage may cause disconnection of the metal film pattern wired on the wiring board, or may impair the connection reliability of chip components mounted on the wiring board.

The present invention has been made in view of the above problems, and has as its object to prevent a wiring board having a two-layer structure from being damaged.

[0010]

(1) In order to achieve the above object, a wiring board according to the present invention is a wiring board in which a metal film pattern is directly formed on a base layer. The corners are rounded.

According to this wiring board, by making the corner round, it is possible to prevent a crack from being generated in the corner when an external force is applied to the wiring board, and as a result, it is possible to prevent the damage to the wiring board. .

In the above structure, the "base layer" is formed of an insulating material, for example, polyimide. Also,
The “metal film pattern” is, for example, 5 to 8 μm of Cu.
It is formed with a thickness of about m.

[0013] The term "roundness" means that a corner portion is not an acute angle but a circular shape, an elliptical shape, or another curved shape. If the current processing method is to be performed when processing the base layer, the corner portion of the base layer is not formed at a strictly acute angle state, but necessarily has a slightly curved shape. That is the fact. However, such inevitably formed curved shapes are usually considered to be very small, with a radius of less than 0.3 mm, and such small roundness may cause cracks in the corners. Is not very effective in preventing Therefore,
In the present invention, the “roundness” formed at the corner of the base layer is desirably a curved shape having a radius of 0.3 mm or more.

[0014] In the above structure, "the metal film pattern is formed directly on the base layer" does not mean that the metal film pattern is fixed to the base layer by an adhesive layer as in the conventional three-layer structure. This means that the metal film pattern is formed directly on the base layer. Specifically, for example,
First, a metal film such as Cu is formed to a uniform thickness on a polyimide film base layer using a known film forming method, for example, a sputtering method, a roll coating method, and the like, and further, a known patterning method. For example, a wiring substrate can be manufactured by forming a desired metal film pattern using, for example, an electrolytic plating method, a photo etching method, or the like.

(2) With respect to the wiring board having the above configuration,
A reinforcing plate can be provided at a corner of the base layer.
According to this configuration, the mechanical strength of the wiring board is increased by the reinforcing plate, so that the wiring board can be more reliably prevented from being damaged.

The reinforcing plate is provided in close contact with either the front or back surface of the wiring board or on both surfaces using, for example, an adhesive or an adhesive. This reinforcing plate, for example,
It can be formed using glass epoxy resin, PET (polyethylene terephthalate) resin, a relatively thick polyimide film, and other various resin materials.

(3) Next, the liquid crystal device according to the present invention comprises:
A liquid crystal device including a pair of substrates opposed to each other with a gap therebetween and liquid crystal sealed in the gap includes the wiring substrate according to the above (1) or (2).

According to this liquid crystal device, by making the corners of the wiring board round, it is possible to prevent the occurrence of cracks at the corners when an external force is applied to the wiring board. Can be prevented.

(4) Next, the electronic device according to the present invention
The liquid crystal device having the above structure and a control unit for controlling the operation of the liquid crystal device are provided. According to this electronic device, by rounding the corners of the wiring board constituting the liquid crystal device, it is possible to prevent cracks from being generated at the corners when an external force is applied to the wiring board. Can be prevented from being damaged.

[0020]

(First Embodiment) FIG. 1 shows an embodiment of a liquid crystal device using a wiring board according to the present invention. The liquid crystal device 4 shown here uses an ACF
(Anisotropic Conductive Film) 8 is attached to the liquid crystal panel 6 using an anisotropic conductive film.

The liquid crystal panel 6 has a pair of substrates 11a and 11b bonded to each other by a sealing material 9. These substrates are formed of a light-transmitting material such as glass, plastic, or the like. A polarizing plate 12 is adhered to the outer surfaces of the substrates 11a and 11b, and if necessary, an illuminating device such as a backlight or a light reflecting member is provided on one of the substrates.

A minute gap, a so-called cell gap, is formed between the substrate 11a and the substrate 11b, and liquid crystal is sealed in the cell gap. A linear transparent electrode 13a is formed on the inner surface of the substrate 11a, and a linear electrode 13b orthogonal to the electrode 13a is formed on the inner surface of the substrate 11b. These electrodes 13a and 13b are, for example, I
It is formed by TO (Indium Tin Oxide: indium tin oxide). The electrode 13a and the electrode 13
The intersection with b constitutes one pixel for displaying an image. The electrodes 13a and 13b are not limited to linear electrodes.
Appropriate patterns such as marks and patterns can also be used.

The substrate 11b has an overhanging portion that extends outside the mating substrate 11a, and a plurality of substrate-side terminals 14 are formed on the surface of the overhanging portion by ITO or the like. These substrate-side terminals 14 include those extending integrally from the electrode 13b and those connected to the electrode 13a via a conductive material.

The electrodes 13a and 13b and the substrate-side terminals 14 are actually provided on the substrate 11a at very narrow intervals.
It is formed on the upper side and on the substrate 11b. In FIG. 1, the interval between them is schematically shown in an enlarged manner for easy understanding of the structure. Also, the substrate side terminal 14 and the electrodes 13a, 13
The connection state with b is also omitted in FIG.

As shown in FIG. 6, the wiring substrate 7 is formed as a two-layer FPC (Flexible Printed Circuit) by directly forming the metal film pattern 2 on the base layer 1. The base layer 1 is formed of, for example, a polyimide film, and the metal film pattern 2 is formed of, for example, Cu.
Formed by The metal film pattern 2 includes the output terminal 2a and the input terminal 2b shown in FIG. In addition, chip components 16 such as resistors, capacitors, inductors, thermistors, ICs, and the like are mounted in appropriate places on the wiring board 7 as necessary.

A liquid crystal driving IC 17 is provided on the wiring board 7. More specifically, as shown in FIG. 2, the bump 18 of the liquid crystal driving IC 17 is conductively connected to the metal film pattern 2 on the base layer 1. In the embodiment shown in FIG. 2, the liquid crystal driving IC 17 is mounted on the wiring board 7 by gang bonding. That is, the bump 18 and the metal film pattern 2 are heated and pressed in a state where they are overlapped with each other, and they are joined by eutectic. An underfill adhesive 19 is filled in a joint portion between the two, and the underfill adhesive 19 is used for bonding the two and preventing rust.

A liquid crystal driving IC for the base layer 1
For mounting 17, any mounting method other than the gang bonding described above can be adopted. For example, ACF (Anisotropi
c Conductive Film).

In FIG. 1, the input terminal 2b and the liquid crystal driving I
An appropriate metal film pattern connecting the C17, the output terminal 2a, and the chip component 16 is formed, but the metal film pattern is omitted in the figure.

When connecting the wiring board 7 to the overhanging portion of the board 11b of the liquid crystal panel 6, first, an ACF (Anisotropic Conductive Filtration) is placed at the board side terminal 14 of the board 11b.
m) 8 is attached, and the portion of the output terminal 2a of the wiring board 7 is pressed thereon, and the portion is heated and pressurized, that is, crimped in this state. As a result, the wiring board side terminal 2a and the panel side terminal 14 are conductively connected by the conductive fine particles contained in the ACF 8, and the wiring board 7 and the board 11b are bonded by the adhesive portion of the ACF 8.

After the wiring board 7 is connected to the liquid crystal panel 6 in this manner, if a predetermined signal for driving the liquid crystal is inputted to the input terminal 2b of the wiring board 7, the operation of the liquid crystal driving IC 17 causes the liquid crystal panel 6 to operate. A predetermined voltage is selectively applied to the electrodes 13a and 13b, whereby numbers and other images are displayed on the surface of the substrate 11a or 11b of the liquid crystal panel 6.

In this embodiment, as shown in FIG. 1, the corner portion C1 of the base layer 1 of the wiring board 7 is rounded, and in this embodiment, an arc-shaped curved shape (so-called R shape) is provided. . Without such a roundness, if the corner portion C1 is left at an acute angle as in the related art,
When an external force is applied to the wiring board 7 during the assembling work of the liquid crystal device 4, cracks may be generated at these corners C1, and the wiring board 7 may be damaged. On the other hand, according to the present embodiment in which the corner portion C1 is rounded, the occurrence of such a crack can be reliably prevented.
The breakage of the wiring board 7 can be reliably prevented.

In the embodiment shown in FIG. 1, among the plurality of corner portions formed on the wiring board 7, only the concave corner portion C1, which is considered to be most susceptible to cracking, is rounded. If there is a possibility that a crack may also occur at the corner C2, the corner C2 may be rounded, for example, arcuately curved.

(Second Embodiment) FIG. 3 shows another embodiment of the wiring board according to the present invention. This wiring board 27
Is the same as the wiring board 7 shown in FIG.
By forming the metal film pattern 2 directly on the substrate 1 without using an adhesive, it is made as a two-layer FPC. (Similarly to the wiring board 7 of FIG. 1, on the base layer 1 of the wiring board 7, actually, an appropriate metal film connecting the input side terminal 2 b, the liquid crystal driving IC 17, the output side terminal 2 a, and the chip part 16 The pattern is formed, but the metal film pattern is omitted in FIG. 3.) The difference between the wiring board 27 of the present embodiment and the wiring board 7 of FIG. 1 is that the concave corner C1 of the base layer 21 is formed. This is a modification of the round shape attached to the. Specifically, in FIG. 1, the corner portion C1 is curved in a substantially 1/4 arc shape, that is, rounded in an R shape.
An arc-shaped curve over an angle of / 4 or more, so-called Φ-shaped roundness is provided. Even with such a Φ-shaped curved shape, the concave corner portion C1
Can be prevented from being cracked. In the present embodiment, the convex corner portion C2 can be rounded as necessary.

(Third Embodiment) FIG. 4 shows still another embodiment of the wiring board according to the present invention. In this wiring board 37, the same base layer 1 used in the embodiment of FIG. 1 is used, and a metal film pattern 2 is directly formed thereon to form a two-layer FPC. The difference between the wiring board 37 of this embodiment and the wiring board 7 of FIG. 1 is that the rounded concave corner portion C1 of the R shape has a rear side opposite to the surface on which the metal film pattern 2 is formed. The reinforcing plate 38 is fixed using an adhesive, an adhesive, or the like, and a planar region to which the reinforcing plate 38 is fixed (the surface of the base layer 1 opposite to the side where the reinforcing plate 38 is fixed, and the reinforcing plate The region where the metal film pattern 2 and the chip component 16 are mounted is included in the region where the region 38 is fixed.

These reinforcing plates 38 have the same roundness as the R-shaped roundness provided at the corner C1 of the base layer 1, and the base layer 1 is formed so that the roundness matches the corner C1 of the base layer 1. Affixed to 1. The reinforcing plate 38 is
It can be formed of glass epoxy resin, PET resin, a polyimide film thicker than the base layer 1, or the like.

Reinforcement plate 3 fixed to concave corner portion C1
8, the reinforcing plate 38 is fixed to the back side of the region including the region where the chip component 16 is mounted even if the chip component 16 is mounted near the concave corner portion C1. This does not cause disconnection of the metal film pattern wired to the wiring board, nor does it impair the connection reliability of the chip component 16 mounted on the wiring board.

According to the wiring board 37 of this embodiment, in addition to rounding the corner C1 of the base layer 1,
Since the reinforcing plate 38 is fixed to this portion, the breakage of the wiring board 37 can be more reliably prevented.

(Fourth Embodiment) FIG. 5 shows a mobile phone as one embodiment of an electronic apparatus according to the present invention. The mobile phone 40 shown here has an antenna 41 and a speaker 4
2, liquid crystal device 4, key switch 43, microphone 44
And the like are stored in the outer case 46. Further, inside the outer case 46, a control circuit board 47 on which a control circuit for controlling the operation of each of the above-described components is provided. Liquid crystal device 4
Is constituted by the liquid crystal device 4 shown in FIG.

In this portable telephone 40, the key switch 4
A signal input through the microphone 3 and the microphone 44 and data received by the antenna 41 are input to the control circuit on the control circuit board 47. Then, the control circuit displays images such as numbers, characters, patterns, etc. on the display surface of the liquid crystal device 4 based on the various input data.
The transmission data is transmitted from the antenna 41.

As shown in FIG. 1, the liquid crystal device 4 used in the portable telephone 40 has a rounded or R-shaped concave corner C1 of the base layer 1 of the wiring board 7, so that the liquid crystal device 4 When an external force is applied to the wiring board 7 during the assembling work, it is possible to prevent cracks from being generated in these corners C1, and thus prevent the wiring board 7 from being damaged.

(Other Embodiments) The present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the embodiments, and various modifications may be made within the scope of the invention described in the claims. Can be modified.

For example, FIG. 1 shows a case where the wiring board according to the present invention is used as a component of a liquid crystal device. However, the wiring board according to the present invention can be used as a component of any device other than the liquid crystal device. it can.

In the embodiment shown in FIG. 1, a liquid crystal device having a structure in which one wiring board is connected to a liquid crystal panel is exemplified. However, the present invention is applied to a liquid crystal device having a structure in which a plurality of wiring boards are connected to a liquid crystal panel. Of course, the invention can be applied.

Further, in the embodiment of FIG. 5, the case where the liquid crystal device of the present invention is used for a mobile phone as an electronic device is exemplified. However, the liquid crystal device of the present invention is applicable to other electronic devices such as a portable information terminal, The present invention can also be applied to a notebook, a finder of a video camera, and the like.

[0045]

According to the wiring board, the liquid crystal device, and the electronic device of the present invention, the corners of the base layer are rounded, so that when an external force is applied to the wiring board, the corners are cracked. Can be prevented, and as a result, damage to the wiring board can be prevented. Therefore, the wiring pattern on the wiring board is not broken, and the connection reliability of the electronic components mounted on the wiring board is not impaired.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a wiring substrate and a liquid crystal device according to the present invention.

FIG. 2 is a sectional view showing a main part of the wiring board of FIG. 1;

FIG. 3 is a plan view showing another embodiment of the wiring board according to the present invention.

FIG. 4 is a perspective view showing still another embodiment of the wiring board according to the present invention.

FIG. 5 is a perspective view showing an embodiment of an electronic device according to the present invention.

FIG. 6 is a cross-sectional view schematically showing an FPC having a two-layer structure, which is a main part of the wiring board according to the present invention.

FIG. 7 shows a three-layer FPC which is a main part of a conventional wiring board.
It is sectional drawing which shows typically.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base layer 2 Metal film pattern 2a Output side terminal 2b Input side terminal 3 Two layer FPC 4 Liquid crystal device 6 Liquid crystal panel 7 Wiring board 8 ACF 11a, 11b substrate 13a, 13b Electrode 14 Substrate terminal 17 Liquid crystal drive IC 21 Base layer 27 Wiring board 37 Wiring board 38 Reinforcement plate C1 Recessed corner C2 Convex corner

Claims (4)

[Claims] 1. A wiring board, wherein a metal film pattern is directly formed on a base layer having a corner portion, wherein the corner portion of the base layer is rounded. 2. The wiring board according to claim 1, wherein a reinforcing plate is provided at a corner of the base layer. 3. A liquid crystal device having a pair of substrates opposed to each other with a gap therebetween and a liquid crystal sealed in the gap, wherein the liquid crystal device has the wiring substrate according to claim 1 or 2. Liquid crystal devices. 4. An electronic apparatus comprising: the liquid crystal device according to claim 3; and a control unit that controls an operation of the liquid crystal device.