JP3675185B2 - Wiring board, liquid crystal device and electronic device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wiring board formed by directly forming a wiring pattern on a base layer. The present invention also relates to a liquid crystal device including the wiring board. The present invention also relates to an electronic apparatus including the liquid crystal device.
[0002]
[Prior art]
In recent years, a liquid crystal device has been widely used as a part of a mobile phone, a portable electronic terminal, an electronic notebook, and other electronic devices, for example, an image display unit. The liquid crystal device is formed, for example, as follows, that is, a pair of substrates (in many cases transparent substrates) each having an electrode (for example, a transparent electrode) are bonded 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 one inner surface of the pair of substrates as necessary.
[0003]
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 the electrodes facing each other across the liquid crystal. Etc. 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 these electrodes, and the applied voltage is controlled by the liquid crystal driving IC.
[0004]
Various methods for mounting a liquid crystal driving IC on a substrate have been conventionally known. For example, taking a well-known TAB (Tape Automated Bonding) method as an example, in this mounting method, first, a TAB (Tape Automated Bonding) technique is used to make an FPC (Flexible Printed Circuit). : A flexible printed circuit board) is bonded to a liquid crystal driving IC to form a TCP (Tape Carrier Package), and the TCP is connected to the liquid crystal panel substrate to form an electrode in the liquid crystal panel. Connect a liquid crystal drive IC.
[0005]
As shown in FIG. 9, for example, the FPC used in the conventional TAB technique includes 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. Generally it has a layer structure. The base layer 51 is made of, for example, PI (polyimide), and the metal film pattern 52 is made of, for example, Cu (copper). Since this three-layer FPC has a three-layer structure, it is difficult to reduce its thickness, and it is also relatively expensive.
[0006]
In order to solve the above-mentioned problems of the three-layer FPC, a two-layer FPC 3 in which the metal film pattern 2 is directly formed on the base layer 1 as shown in FIG. It was done. 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]
[Problems to be solved by the invention]
The wiring board using the FPC 3 having the two-layer structure as described above has an advantage that the thickness can be reduced compared to the FPC having the three-layer structure, and the manufacturing cost can be reduced by a smaller number of parts. . However, since the FPC 3 having the two-layer structure is thin, it has a problem that it has a low mechanical strength and is easily cut off.
[0008]
According to the experiments of the present inventors, when an external force is applied to the wiring board when a mounting part such as an IC chip, a chip resistor, a chip capacitor or the like is mounted on the wiring board, a crack occurs around the mounting part. As a result, it has been found that the wiring board is often damaged.
[0009]
The present invention has been made in view of the above problems, and an object of the present invention is to prevent breakage of a wiring board having a two-layer structure.
[0010]
[Means for Solving the Problems]
(1) In order to achieve the above object, a wiring board according to the present invention includes a base layer, a metal film pattern directly formed on the base layer, and a mounting component mounted on the base layer. The metal film pattern is conductively connected to the mounting component, and an underfill adhesive or ACF ( Anisotropic ) is provided at a joint portion between the mounting component and the base layer. Conductive Around the mounting component Film) is filled, a thin reinforcing member in thickness than the mounting part is provided, the reinforcement member covers the mounting part from protruding portions of the underfill adhesive or the ACF It is characterized by that.
[0011]
According to this wiring board, the mechanical strength around the mounted component in the two-layered wiring board is increased by the function of the reinforcing member, and as a result, damage to the wiring board can be reliably prevented.
[0012]
In the above configuration, the “base layer” is formed of an insulating material such as PI (polyimide). Further, the “metal film pattern” is formed of Cu to a thickness of about 5 to 8 μm, for example. As the “mounting component”, an arbitrary electronic element, for example, an IC chip, a chip resistor, a chip capacitor, or the like can be considered.
[0013]
In the above configuration, “the metal film pattern is directly formed on the base layer” means that the metal film pattern is not fixed to the base layer by the adhesive layer as in the conventional three-layer structure. Is formed directly on the base layer.
[0014]
Specifically, for example, first, a metal film such as Cu is formed on the base layer made of PI film with a uniform thickness using a known film forming method, such as a sputtering method or a roll coating method. Then, a wiring board can be produced by forming a desired metal film pattern by using a well-known patterning method such as an electrolytic plating method or a photolithography method.
[0015]
As the “reinforcing member”, any material that can improve the mechanical strength of the base layer can be used, and the material itself can be harder or softer than the base layer. Specifically, metal foil, PET (polyethylene terephthalate), PI (polyimide), and other plastics can be used.
[0021]
(2) Next, a liquid crystal device according to the present invention is a liquid crystal device having a pair of substrates facing each other across a gap and a liquid crystal sealed in the gap. It is characterized by having.
[0022]
According to this liquid crystal device, by providing the reinforcing member around the mounting component constituting the wiring board having the two-layer structure, the mechanical strength around the mounting component in the wiring board can be increased, and as a result, The damage to the wiring board can be reliably prevented. This means that the wiring board can be prevented from being damaged when the wiring board is assembled as one part of the liquid crystal device to another part.
[0023]
(3) Next, an electronic apparatus according to the present invention includes the liquid crystal device having the above-described configuration and a control unit that controls the operation of the liquid crystal device. According to this electronic apparatus, since the reinforcing member is provided around the mounting component included in the two-layer wiring board constituting the liquid crystal device, the mechanical strength around the mounting component in the wiring board is increased. As a result, it is possible to reliably prevent the wiring board from being damaged. This is to prevent the wiring board from being damaged when the wiring board is assembled to another part as one part of the liquid crystal device.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
(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 is configured by mounting, that is, mounting, a wiring board 7 on a liquid crystal panel 6 using an ACF (Anisotropic Conductive Film) 8.
[0025]
The liquid crystal panel 6 includes a pair of substrates 11 a and 11 b that are bonded to each other with a sealing material 9. These substrates are formed of a light-transmitting material such as glass or plastic. Polarizing plates 12 are attached to the outer surfaces of these substrates 11a and 11b, and if necessary, an illumination device such as a backlight, a light reflecting member, or the like is attached corresponding to any of the substrates.
[0026]
A minute gap, 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 made of, for example, ITO (Indium Tin Oxide). Further, the intersection of these electrodes 13a and 13b constitutes one pixel for displaying an image. Note that the electrodes 13a and 13b are not limited to linear electrodes, and may be appropriate patterns such as marks and pictures.
[0027]
The substrate 11b has a projecting portion that projects outward from the counterpart substrate 11a, and a plurality of substrate-side terminals 14 are formed of ITO or the like on the surface of the projecting portion. These substrate-side terminals 14 include one that extends integrally from the electrode 13b and one that is connected to the electrode 13a via a conductive material.
[0028]
The electrodes 13a and 13b and the substrate-side terminal 14 are actually formed on the substrate 11a and the substrate 11b at an extremely narrow interval, but in FIG. 1, these intervals are shown for easy understanding of the structure. Is schematically shown enlarged. Further, the connection state between the substrate-side terminal 14 and the electrodes 13a and 13b is also omitted in FIG.
[0029]
As shown in FIG. 8, the wiring substrate 7 is formed as a two-layer FPC (Flexible Printed Circuit) by directly forming a metal film pattern 2 on the base layer 1. The base layer 1 is formed of, for example, a PI (polyimide) film, and the metal film pattern 2 is formed of, for example, Cu. The metal film pattern 2 includes the output side terminal 2a and the input side terminal 2b shown in FIG. Further, chip components 16 such as a chip resistor and a chip capacitor are mounted at appropriate positions on the wiring board 7 as necessary.
[0030]
A liquid crystal driving IC 17 as a mounting component is provided on the wiring board 7. More specifically, as shown in FIG. 2, the bumps 18 of the liquid crystal driving IC 17 are 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 both are bonded by eutectic. The joint portion between the two is filled with an underfill adhesive 19, and the underfill adhesive 19 is used to bond the two and prevent rust.
[0031]
The liquid crystal driving IC 17 can be mounted on the base layer 1 by any mounting method other than the above gang bonding. For example, a method using ACF (Anisotropic Conductive Film) can be used.
[0032]
Further, in FIG. 1, on the base layer 1 of the wiring board 7, actually, an appropriate metal film pattern for connecting the elements such as the input side terminal 2b, the liquid crystal driving IC 17, the output side terminal 2a and the chip component 16 is provided. Although formed, the metal film pattern is omitted in the figure.
[0033]
When connecting the wiring board 7 to the protruding portion of the board 11b of the liquid crystal panel 6, first, an ACF (Anisotropic Conductive Film) 8 is attached to the board-side terminal 14 of the board 11b, and the wiring board is further formed thereon. 7 part of the output side terminal 2a is pressed, and in this state, the part is heated and pressurized, that is, crimped. Thereby, 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.
[0034]
Thus, after the wiring substrate 7 is connected to the liquid crystal panel 6, if a predetermined signal for driving the liquid crystal is input to the input side terminal 2 b of the wiring substrate 7, the electrodes 13 a of the liquid crystal panel 6 and the liquid crystal driving IC 17 are A predetermined voltage is selectively applied to 13b, whereby numbers and other images are displayed on the surface of the substrate 11a or 11b of the liquid crystal panel 6.
[0035]
In the present embodiment, a plate-like reinforcing member 22A having a hole 21 slightly larger than the liquid crystal driving IC 17 is prepared, and the reinforcing member 22A is placed so that the liquid crystal driving IC 17 fits in the hole 21 described above. It is fixed on the base layer 1 with an adhesive or an adhesive, in this embodiment, on the base layer 1 on the same side as the liquid crystal driving IC 17. 2 and 3 show a state in which the reinforcing member 22A is fixed in such a manner. (Similarly to the wiring board 7 of FIG. 1, on the base layer 1 of the wiring board 7, the elements such as the input side terminal 2 b, the liquid crystal driving IC 17, the output side terminal 2 a and the chip component 16 are actually connected. An appropriate metal film pattern is formed, but the metal film pattern is omitted in FIG.
In a conventional wiring board having a structure in which the reinforcing member 22A is not provided, when the liquid crystal driving IC 17 which is a hard member is mounted on the soft base layer 1, cracks are easily formed around the liquid crystal driving IC 17. Therefore, the wiring board 7 is easily damaged from the liquid crystal driving IC 17. On the other hand, if the reinforcing member 22A is provided around the liquid crystal driving IC 17 as in the present embodiment, the mechanical strength of the portion increases, and as a result, the occurrence of cracks in the portion is prevented. it can.
[0036]
Note that the reinforcing member 22A can be formed of any material that can increase the strength of the base layer 1. For example, the same PI (polyimide) film, metal foil, PET, and other materials as the base layer 1 can be used. Can be formed by plastic.
[0037]
(Second Embodiment)
4 and 5 show another embodiment of the wiring board according to the present invention. As shown in FIGS. 2 and 3, the wiring board 27 shown here is constituted by an FPC having a two-layer structure in which the metal film pattern 2 is directly formed on the base layer 1 without using an adhesive layer. This is the same as the case of the wiring board 7.
[0038]
In the wiring board 7 shown in FIGS. 2 and 3, a reinforcing member 22 </ b> A having a hole 21 for releasing the liquid crystal driving IC 17 is used as a reinforcing member for reinforcing the base layer 1, and this is the same as the liquid crystal driving IC 17. It was provided on the base layer 1 on the side. On the other hand, in the wiring board 27 of this embodiment, a reinforcing member 22B having a uniform thickness without such a hole for escape is prepared, and this is viewed from the back side of the base layer 1 when viewed from the liquid crystal driving IC 17. It is fixed to. Thus, even when the reinforcing member 22B is provided on the back side of the base layer 1, the strength of the wiring board 27 can be increased, and as a result, the wiring board 27 can be prevented from being damaged.
[0039]
In particular, in this embodiment, there is no need to form a relief hole for the liquid crystal driving IC 17 in the reinforcing member 22B. Therefore, compared to the case where the reinforcing member having such a relief hole is used, the liquid crystal driving is performed. The strength of the wiring board around the IC 17 can be further increased.
[0040]
According to the experiment of the present invention, in FIG. 4, the extension length of the portion of the reinforcing member 22B that protrudes from the liquid crystal driving IC 17 is d, and the total thickness of the base layer 1 and the metal film pattern 2 is obtained. Where d is t ≧ t
It was found that by setting as described above, the wiring board 27 can be reliably prevented from cracking.
[0041]
(Third embodiment)
FIG. 6 shows still another embodiment of the wiring board according to the present invention. The wiring board 37 is constituted by the FPC having a two-layer structure in which the metal film pattern 2 is directly formed on the base layer 1 without using an adhesive layer. The wiring board 7 shown in FIG. This is the same as the case of the wiring board 27 shown in FIG.
[0042]
The wiring board 37 is different from the wiring board 7 shown in FIG. 3 in that the reinforcing member 22A is provided on the same side as the liquid crystal driving IC 17 with respect to the base layer 1 in the wiring board 7. Then, the reinforcing member 22C is provided on the back side of the liquid crystal driving IC 17 with respect to the base layer 1.
[0043]
The wiring board 37 is different from the wiring board 27 shown in FIG. 5 in that the reinforcing member 22B is provided only around the liquid crystal driving IC 17 in the wiring board 27, whereas the wiring board 37 is provided. Then, the reinforcing member 22C is provided so as to correspond to both the liquid crystal driving IC 17 and the chip component 16. According to the present embodiment, the strength around the chip component 16 can also be increased by the reinforcing member 22C, and therefore the breakage of the wiring board 37 can be more reliably prevented.
[0044]
(Fourth embodiment)
FIG. 7 shows a mobile phone which is an embodiment of an electronic apparatus according to the invention. The cellular phone 40 shown here is configured by storing various components such as an antenna 41, a speaker 42, a liquid crystal device 4, a key switch 43, a microphone 44, and the like in an exterior case 46. In addition, a control circuit board 47 on which a control circuit for controlling the operation of each component described above is provided inside the outer case 46. The liquid crystal device 4 is constituted by the liquid crystal device 4 shown in FIG.
[0045]
In the cellular phone 40, a signal input through the key switch 43 and the microphone 44, reception data received by the antenna 41, and the like are input to the control circuit on the control circuit board 47. Then, the control circuit displays an image such as a number, a character, a picture, etc. on the display surface of the liquid crystal device 4 based on the inputted various data, and further transmits transmission data from the antenna 41.
[0046]
The liquid crystal device 4 used in the cellular phone 40 is provided with a reinforcing member 22A around the liquid crystal driving IC 17 as shown in FIG. 1, or a reinforcing member 22B around the liquid crystal driving IC 17 as shown in FIG. 6 or the reinforcing member 22C is provided around the liquid crystal driving IC 17 and the chip component 16 as shown in FIG. 6, so that the strength of the wiring board 7, the wiring board 27, and the wiring board 37 can be increased. Therefore, breakage of the wiring boards 7, 27 and 37 can be surely prevented.
[0047]
(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 can be made within the scope of the invention described in the claims.
[0048]
For example, FIG. 1 shows the case where the wiring board according to the present invention is used as a component of a liquid crystal device, but the wiring substrate according to the present invention can be used as a component of any device other than the liquid crystal device.
[0049]
In the embodiment shown in FIG. 1, the liquid crystal device having a structure in which one wiring board is connected to the liquid crystal panel is illustrated. However, the present invention is applied to a liquid crystal device having a structure in which a plurality of wiring boards are connected to the liquid crystal panel. Of course you can.
[0050]
In the embodiment of FIG. 7, the case where the liquid crystal device of the present invention is used in a mobile phone as an electronic device is illustrated. However, the liquid crystal device of the present invention can be used for other electronic devices such as a portable information terminal, an electronic notebook, and a video. It can also be applied to a camera finder or the like.
[0051]
【The invention's effect】
According to the wiring board, the liquid crystal device, and the electronic apparatus according to the present invention, the mechanical strength around the mounted component in the wiring board having the two-layer structure is increased by the function of the reinforcing member, and as a result, the wiring board is damaged. Can be reliably prevented.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing one embodiment of a liquid crystal device and a wiring board according to the present invention.
2 is an enlarged cross-sectional view showing a cross-sectional structure of a main part of the wiring board shown in FIG. 1;
FIG. 3 is a plan view of the wiring board of FIG. 2;
FIG. 4 is a cross-sectional view showing another embodiment of a wiring board according to the present invention.
5 is a plan view of the wiring board of FIG. 4. FIG.
FIG. 6 is a plan view showing still another embodiment of a wiring board according to the present invention.
FIG. 7 is a perspective view showing an embodiment of an electronic apparatus according to the invention.
FIG. 8 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. 9 is a cross-sectional view schematically showing an FPC having a three-layer structure, which is a main part of a conventional wiring board.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base layer 2 Metal film pattern 2a Output side terminal 2b Input side terminal 3 FPC of 2 layer structure
4 Liquid crystal device 6 Liquid crystal panel 7 Wiring board 8 ACF
11a, 11b Substrate 13a, 13b Electrode 14 Substrate side terminal 16 Chip component (mounting component)
17 Liquid crystal drive IC (mounting parts)
21 hole 22A, 22B, 22C reinforcing member 27 wiring board 37 wiring board

Claims (3)

In a wiring board having a base layer, a metal film pattern formed directly on the base layer, and a mounting component mounted on the base layer,
The metal film pattern is conductively connected to the mounting component,
An underfill adhesive or ACF ( Anisotropic) is used at the joint between the mounting component and the base layer. Conductive Film ) is provided, and a reinforcing member having a thickness smaller than that of the mounting component is provided around the mounting component ,
The wiring board, wherein the reinforcing member covers a portion of the underfill adhesive or the ACF that protrudes from the mounted component .   A liquid crystal device comprising the wiring substrate according to claim 1, wherein the liquid crystal device includes a pair of substrates facing each other with a gap therebetween and a liquid crystal sealed in the gap. An electronic apparatus comprising: the liquid crystal device according to claim 2; and a control unit that controls an operation of the liquid crystal device.

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