JP2000294895A - Circuit board, its manufacture, display device using the same board and electronics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board preventing degradation in the reliability and the performance of an electronic part such as a mounted IC chip. SOLUTION: In an FPC substrate 400, copper foil bonded to both faces of a base film 410 having insulating property and flexibility without a bonding layer is patterned, an input wiring 420a and an output wiring 420b are formed on the mounting face of an electronic part and a dummy wiring layer 422 on a face opposite to the mounting face. The dummy wiring layer 422 is installed to be slightly wider than an area where an IC chip 450 is mounted and it has moisture proof and light shielding property. The input electrode 450a of the IC chip 450 is electrically connected to the input wiring 420a and the output electrode 450b to the output wiring 420b through conductive particles 460a dispersed in the adhesive 460 of epoxy resin and the like at an appropriate rate, and they are sealed by adhesive 460.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board on which electronic components are mounted, a method for manufacturing the same, and a display device and an electronic apparatus using the circuit board.

[0002]

BACKGROUND OF THE INVENTION In recent years,
Electronic components, such as IC chips, are directly mounted on FPC (Flexible Printed Circuit) substrates because of their small size, thinness and lightness, adaptability to bendable structures, and realization of high productivity by roll-to-roll. Technology has come to be used. Moreover, with this technology, TA
Unlike the B (Tape Automated Bonding) technology, the inner lead is not required, so that the copper foil can be made thin, and the fine pitch of the wiring can be easily achieved.

FIG. 10 is a cross-sectional view showing a conventional structure when electronic components are mounted on an FPC board. As shown in this figure, the input electrode 450a of the IC chip 450 and the input wiring 420a formed in advance on the base film 410
Is electrically connected via conductive particles 460a dispersed in the adhesive 460, and similarly, the output electrode 450b of the IC chip 450 and the output wiring 420b formed in advance on the base film 410 are connected with the adhesive 460 Are electrically connected via conductive particles 460a dispersed in the substrate.

However, since the base film 410, which is the base material of the FPC board, is generally made of an organic film such as PI (polyimide) through which moisture easily penetrates, the base film 410 is opposite to the mounting surface (the lower side in the drawing). ), The moisture that has permeated the base film 410 reaches the wiring forming surface of the IC chip 450, thereby reducing the reliability of the IC chip or causing light leakage due to light transmitted through the base film 410. There is a disadvantage that the performance of the IC chip is reduced. This drawback becomes more prominent when the base film 410 is made thinner.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a circuit board capable of preventing a decrease in the reliability and performance of an electronic component such as an IC chip to be mounted and a manufacturing method thereof. It is an object of the present invention to provide a method, and a display device and an electronic device using the circuit board.

[0006]

Means for Solving the Problems (1) A circuit board according to the present invention comprises: a base material having insulation and flexibility;
A wiring board having a wiring layer provided on the base material, an electronic component electrically connected to the wiring layer, and mounted on the wiring board, and a region where the electronic component is mounted and a plan view thereof. A region that at least partially overlaps the electronic component, covers the substrate from a side opposite to the electronic component, and has a coating portion insulated from the wiring layer and the electronic component;

According to the present invention, moisture penetrating through the base material from the surface opposite to the mounting surface of the electronic component is completely blocked by the covering portion. Therefore, the possibility that the reliability or performance of the wiring layer or the electronic component in the region where the electronic component is mounted on the wiring board is reduced due to moisture is reduced.
For example, when a semiconductor device such as an IC chip is mounted on a wiring board as an electronic component, the wiring pattern of the wiring board often has a narrow pitch in the mounting area, and the wiring pattern between the wiring patterns is affected by moisture or the like. Short-circuits and pseudo short-circuits tend to occur. In the circuit board of the present invention, occurrence of such a problem can be reduced.

(2) In the circuit board according to the present invention, the covering portion is a dummy wiring layer.

According to the present invention, the covering portion can be formed with the same equipment as the equipment for forming the wiring layer.

(3) In the circuit board according to the present invention, the covering portion is a resin layer.

(4) In the circuit board according to the present invention, the covering portion has a light shielding property.

According to the present invention, light penetrating through the base material from the surface opposite to the mounting surface of the electronic component is completely blocked by the covering portion. Therefore, the performance of the electronic components mounted on the wiring board due to light leakage is reduced.

(5) The circuit board according to the present invention further has a resin sealing portion for sealing a portion where the electronic component and the wiring layer are electrically connected with a resin.

According to the present invention, since the portion where the electronic component and the wiring layer are electrically connected is sealed with the resin sealing portion, the electrical connection portion between the electronic component and the wiring layer is wet. The possibility of causing a decrease in reliability due to the influence of the above is reduced.

(6) The circuit board according to the present invention comprises (1)
Any of (4) to (4), further including an anisotropic conductive film interposed between the electronic component and the wiring layer and electrically connecting the electronic component and the wiring layer.

When the electronic component and the wiring board are joined by the anisotropic conductive film as described above, TAB (Tape Automated Boundary) is used.
Onding) The joining step and the molding step in mounting can be performed in one step, and there is an advantage that the manufacturing step can be shortened.

(7) In the circuit board according to the present invention, the base material and the wiring layer are directly joined without interposing an adhesive layer.

When the wiring layer is formed directly on the base material without the interposition of the adhesive layer, current leakage due to the adhesive can be reduced, swelling of the adhesive can be prevented, and the flexibility of the wiring board can be improved. It becomes possible.

(8) The circuit board according to the present invention comprises (1)
In any one of (7) to (7), the base material has a plurality of layers, and the covering portion is provided between the plurality of layers.

This circuit board is a multi-layer board having a base material composed of a plurality of layers, and a covering portion is provided between the layers of these base materials. When the covering portion is formed between a plurality of layers, it is easy to form the covering portion with an area equal to or larger than the bonding area of the electronic component. By forming the area of the covering portion equal to or larger than the bonding area of the electronic component, the possibility that moisture or light permeates from the outside of the covering portion can be further reduced.

(9) A display device according to the present invention includes any one of the circuit boards, and a flat panel including connection terminals to which the circuit boards are electrically connected.

(10) In the display device according to the present invention, the flat panel is a liquid crystal panel having a pair of opposed substrates and a liquid crystal sealed between the pair of substrates.
The connection terminal is formed on at least one of the pair of substrates.

(11) In the display device according to the present invention, the electronic components mounted on the circuit board include a driving semiconductor device.

(12) The electronic device according to the present invention is characterized in that (1)
1) a display device, and an image signal processing circuit that processes an image signal input to the display device.

(13) The method for manufacturing a circuit board according to the present invention is the method for manufacturing a circuit board according to any one of (1) to (7), wherein the electronic component is crimped on the surface side of the wiring board. An electronic component mounting step of mounting; and a covering part forming step of forming the covering part on the back surface side of the wiring board after the electronic component mounting step.

According to the present invention, after the electronic component is mounted on the front surface side of the wiring board by crimping, by forming the covering portion on the back surface side of the wiring board, damage is caused when the electronic component is mounted by crimping. It is possible to reinforce the base material of the wiring board that may have been damaged by the covering portion. by this,
Reduce the possibility of moisture entering from the back of the wiring board,
Moisture entering from the back side of the wiring board permeates the base material,
It is possible to reduce the possibility that a problem occurs in the electronic component mounting area. As such a problem, for example, there is a short circuit between patterns in the wiring layer or a pseudo short circuit.

(14) The method for manufacturing a circuit board according to the present invention is the method for manufacturing a circuit board according to any one of (1) to (7), wherein the covering portion is formed on a back surface side of the wiring board. After the covering portion forming step and the covering portion forming step,
An electronic component mounting step of mounting the electronic component on the surface side of the wiring board by crimping.

According to the present invention, after forming the covering portion on the back surface side of the wiring board, the electronic components are mounted on the front surface side of the wiring board by crimping. Since the covering portion is formed and reinforced on the back surface side of the wiring substrate, the possibility that the base material of the wiring substrate is damaged when the electronic component is mounted by crimping is reduced. This reduces the possibility of intrusion of moisture from the back surface of the wiring board, and reduces the possibility that moisture invading from the back surface side of the wiring board will pass through the base material and cause a problem in the electronic component mounting area. be able to. As such a problem, for example, there is a short circuit between patterns in the wiring layer or a pseudo short circuit.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below more specifically with reference to the drawings.

1. First Embodiment 1.1 Circuit Board First, a circuit board according to a first embodiment of the present invention will be described. FIG. 1 is a plan view showing the circuit board.
FIG. 2 is a cross-sectional view at a position along the line AA depicted in FIG. In these figures, F as a wiring board
The PC (Flexible Printed Circuit) substrate 400 is the first
Second, a copper thin film is formed on both sides of a base film 410 as a base material having insulation and flexibility by sputtering or vapor deposition. Second, the copper thin film is formed by a known photolithography technique or etching. Third, it is patterned into a predetermined shape, and thirdly, copper plating is applied on the patterned copper thin film. Further, as the FPC substrate 400, a substrate obtained by applying a polyamic acid, which is a precursor of a polyimide, to a copper foil, heating and polymerizing the polyamic acid to form a polyimide, and using the polyimide as a base film 410 to form a wiring substrate may be used. .

The FPC board 400 may be formed by laminating copper foil on both sides of a base film 410 with an adhesive and then patterning it into a predetermined shape, as described above. When the wiring pattern is directly formed on 410, the current leak due to the adhesive in the adjacent wiring pattern, the swelling of the adhesive does not occur, and the flexibility of the FPC board 400 is improved. Is advantageous.

As the base film 410 as a base material, other organic films such as polyethylene terephthalate and polyester may be used in addition to polyimide. On the other hand, the wiring pattern formed on the FPC board 400 includes an input wiring 420a for inputting a signal to the IC chip 450, an output wiring 420b for receiving an output signal from the IC chip 450, and a dummy wiring layer 422 as a covering part. And so on.

On the other hand, a rectangular parallelepiped IC as an electronic component
The chip 450 (semiconductor device) includes a plurality of input electrodes 450a and output electrodes 450b on a peripheral portion of one surface thereof, and is mounted on the FPC board 400 with the surface on which the input electrodes 450a and output electrodes 450b are formed facing downward. . Each input electrode 450a and each output electrode 450b
For example, bumps (protrusion electrodes) made of Au or the like are provided in advance. A film-like anisotropic conductive film in which conductive particles are uniformly dispersed in an adhesive such as epoxy is sandwiched between the IC chip 450 and the FPC board 400. Thereafter, the IC chip 450 is press-bonded to the FPC board 400 via the anisotropic conductive film while applying pressure and heat.
Thus, the FPC board 400 as a wiring board
Then, a circuit board on which an IC chip 450 as an electronic component is mounted is formed.

In this mounting, as shown in FIG. 2, the input electrode 450a is connected to the input wiring 420a, and the output electrode 450b is connected to the output wiring 420b, respectively, in an adhesive 460 such as epoxy resin or photocurable resin. The connection is made electrically through the conductive particles 460a dispersed at an appropriate ratio. Here, the adhesive 460 is applied to the IC chip 4
At 50, the input electrode 450a and the output electrode 450b
Also serves as a sealing material as a resin sealing portion for protecting the surface on which is formed from moisture, contamination, stress and the like.

When the IC chip 450 and the FPC board 400 are joined by the anisotropic conductive film, the conventional T
In the AB mounting, the joining step and the molding step can be performed in one step, and there is an advantage that the manufacturing step can be shortened.

Incidentally, the dummy wiring layer 422 as the covering portion in the present embodiment is provided on the surface opposite to the mounting surface slightly wider than the region where the IC chip 450 is mounted. For this reason, in the figure, moisture penetrating from below the base film 410 is completely blocked by the dummy wiring layer. Therefore, the FPC board 40
Thus, a decrease in the reliability of the IC chip 450 mounted on the IC chip 450 is prevented. Similarly to the moisture, light entering from below the base film 410 in the drawing is completely blocked by the dummy wiring layer 422, and
In this case, the IC chip 450 does not enter the surface (wiring forming surface) on which the input electrode 450a and the output electrode 450b are formed.

In the above embodiment, the input electrode 4
The connection between 50a and input wiring 420a and the connection between output electrode 450b and output wiring 420b are made via conductive particles 460a dispersed in adhesive 460, that is, anisotropic conductive films. Alternatively, other connection forms may be used. For example, the input wiring 420a and the output wiring 42
Au is applied to the copper foil forming
A between the 50a and the Au bump of the output electrode 450b
A u-Au junction may be used. Further, the copper foil forming the input wiring 420a and the output wiring 420b is plated with tin, and this is heated in contact with the Au bumps of the input electrode 450a and the output electrode 450b of the IC chip 450, so that Au-Sn eutectic bonding is achieved. May be. Further, the copper foil forming the input wiring 420a and the output wiring 420b is formed into a solderable pattern, and the material of the bumps on the input electrode 450a and the output electrode 450b of the IC chip 450 is solder, so that solder-solder bonding can be used. good. In such bonding, the IC chip 450 is molded using a sealing material as a resin sealing portion.

Further, what is mounted on the FPC board 400 is not limited to the IC chip 450. For example, FPC board 4
Other active elements and non-active elements may be used as long as they are likely to be affected by moisture or light penetrating through the base film 410 when mounted on the base film 410.

Further, the adhesive 460 in which the conductive particles 460a are dispersed is applied to the input electrode 450a of the IC chip 450.
And the output wiring 420b.
a and the input wiring 420a, and the output electrode 450b and the output wiring 420b, respectively, and then these connection portions may be molded with a sealing material as a resin sealing portion.

In addition, since the dummy wiring layer 422 is not used as a wiring, if the potential is not determined, a capacitance component is generated, which is not preferable. For this reason, it is actually desirable to connect to the wiring of the ground level.

1.2 Display Apparatus As described above, when the IC chip 450 is mounted on the FPC board 400, the time required for the process is longer regardless of the number of connection electrodes of the IC chip 450 as compared with wire bonding. It will be constant. Therefore, when the number of electrodes of the IC chip 450 is extremely large, the productivity is significantly improved. Here, as an IC chip having an extremely large number of electrodes, for example, a driving circuit (driver) for driving a data line or a scanning line in a display device is given. Therefore, as an application example of such a mounting structure, a liquid crystal device using an FPC board on which such a driver is mounted will be described.

As shown in FIG. 3, this liquid crystal device
It mainly includes a liquid crystal panel 100, two FPC boards 400X and 400Y connected to the liquid crystal panel 100, and a control circuit board (not shown) connected to these FPC boards 400X and 400Y. . this house,
The liquid crystal panel 100 includes an element substrate 200 on which a plurality of data lines and the like are formed, and an opposing substrate 300 on which a plurality of scanning lines and the like are formed. The structure is such that they are bonded together with their forming surfaces facing each other.

More specifically, as shown in FIG. 4, a plurality of pixel electrodes 234 arranged in a matrix and extending in the column direction on the surface of the element substrate 200 facing the counter substrate 300. A data line (signal line) 212 is formed, and each column of pixel electrodes 234 is
Each of the data lines 212 has a TFD (Thin Film Diod).
e) connected via element 220; Where TF
The D element 220 includes a first metal film 222 as viewed from the substrate side.
And an oxide film 224 obtained by anodizing the first metal film 222
And a second metal film 226 to form a metal / insulator / metal sandwich structure. Therefore, T
The FD element 220 has a switching characteristic as a diode in both positive and negative directions.

On the other hand, of the opposing substrate 300, the element substrate 2
The scanning line 312 is provided on the surface facing
Are arranged in such a manner as to extend in a row direction perpendicular to the pixel electrodes 234, and are arranged so as to be opposed to the pixel electrodes 234. Further, although not shown, a color filter is provided corresponding to each pixel electrode 234. ing. Therefore, the liquid crystal cell corresponding to one pixel is configured to include the pixel electrode 234, the scanning line 312 which is an opposite electrode, and the liquid crystal filled between these two substrates.

Then, the element substrate 200 and the counter substrate 300
Is that a certain gap (gap) is maintained by a sealing material applied along the periphery of the substrate and spacers appropriately dispersed, and for example, TN (Twis
ted Nematic) type liquid crystal is enclosed. In addition,
On the opposing surfaces of the element substrate 200 and the opposing substrate 300, an alignment film or the like rubbed in a predetermined direction is provided, and on the back surface, a polarizing plate corresponding to the alignment direction is provided. Omitted). However,
If a polymer-dispersed liquid crystal in which a liquid crystal is dispersed as fine particles in a polymer is used, the above-described alignment film, polarizing plate, and the like become unnecessary. The use of a polymer-dispersed liquid crystal enhances light use efficiency, which is advantageous in terms of high luminance and low power consumption.

In such a configuration, the data line 21
2 and the scanning line 312 are electrically coupled to each other at the intersection thereof via a series connection of the liquid crystal layer and the TFD element 220. Therefore, when a voltage equal to or higher than the threshold value is applied to the TFD element 220 by the scanning signal applied to the scanning line 312 and the data signal applied to the data line 212, the element is turned on and the element is turned on. A predetermined charge is stored in a liquid crystal layer connected to the liquid crystal layer. Then, even after the element is turned off after charge accumulation, if the resistance of the liquid crystal layer is sufficiently high, accumulation of charge in the liquid crystal layer is maintained. When the amount of charge to be stored is controlled by driving the TFD element 220 on and off in this manner, the alignment state of the liquid crystal changes for each pixel, and predetermined information can be displayed. At this time, since it is sufficient to accumulate electric charges in each liquid crystal layer during a part of the period, by selecting each scanning line 312 in a time-division manner, the data line 212 and the scanning line 31 are selected.
Time-division multiplex driving in which 2 is common to a plurality of pixels is possible. Note that the formation of the scanning lines and the data lines may be reversed, and the scanning lines may be formed on the element substrate 200 and the data lines may be formed on the opposite substrate.

Although not shown in FIG. 3, the element substrate 2
00 is provided with a data line terminal for leading each data line to the outside, while a terminal region 316 of the counter substrate 300 is provided with a data line terminal for leading each scanning line to the outside. It is provided below.

The FPC boards 400X and 400Y are
For example, it has the structure of the above-described circuit board including the FPC board 400, the IC chip 450, and the dummy wiring layer 422. Among them, FPC board 400X
In this case, the driver 450X for driving each data line is mounted as an IC chip in an upside down manner in FIG. Therefore, the dummy wiring layer 422 in the FPC board 400X
X will be provided on the upper side in FIG. On the other hand, on the FPC board 400Y, a driver 450Y for driving each scanning line is mounted as an IC chip in the same direction as the top and bottom in FIG. Therefore, the dummy wiring layer 422Y in the FPC board 400Y is provided on the lower side in FIG.

Here, in the FPC board 400X,
A terminal located at one end thereof and extending the input wiring is joined to the control circuit board, while a terminal located at the other end and extending the output wiring is provided in the terminal region 216 of the element substrate 200. It is joined to the formed data line terminal. Similarly, for the FPC board 400Y,
The terminal located at one end thereof and extending the input wiring is joined to the control circuit board, while the terminal located at the other end and extending the output wiring is located in the terminal region 316 of the counter substrate 300. It is joined to the formed scanning line terminal.

With such a configuration, the driver 450Y
Generates a scanning signal according to a control signal supplied from the control circuit board, and supplies the scanning signal to each scanning line of the element substrate 200. On the other hand, the driver 450X supplies a data signal according to a control signal supplied from the control circuit board to each data line of the counter substrate 300. At this time, the driver 4 mounted on each of the FPC boards 400X and 400Y
As described above, in the 50X and 450Y, the reduction in reliability and performance is prevented by the dummy wiring layers 424X and 422Y provided corresponding to the mounting area.

The FPC boards 400X and 400Y may have the structure of a second embodiment described later in addition to the first embodiment.

As a liquid crystal panel, in addition to the above,
Applicable to passive matrix method without TFD element or liquid crystal panel where scanning lines and data lines are provided on the element substrate and pixel electrodes are connected to their intersections via TFT (Thin Film Transistor) elements It is.

1.3 Electronic Apparatus Next, an example in which the liquid crystal panel of the above-described liquid crystal device is used for a display section of an electronic apparatus will be described. FIG. 5 is a plan view showing a configuration example of a projector using the liquid crystal panel as a light valve.

As shown in FIG.
Inside 100, a lamp unit 1102 composed of a white light source such as a halogen lamp is provided. The projection light emitted from the lamp unit 1102 is separated into three primary colors of RGB by four mirrors 1106 and two dichroic mirrors 1108 arranged in the light guide 1104, and is used as a light valve corresponding to each primary color. Liquid crystal panels 1110R, 1110B and 1110
G is incident.

The liquid crystal panels 1110R, 1110B and 1110G are the above-described liquid crystal panels, and are supplied from the image signal processing circuit (not shown) to the FPC boards 400X and 400C.
It is driven by R, G, and B primary color signals supplied via Y, respectively. Light modulated by these liquid crystal panels enters a dichroic prism 1112 from three directions. This dichroic prism 111
In 2, the R and B lights are refracted at 90 degrees, while the G light goes straight. Therefore, as a result of combining the images of each color, a color image is projected on a screen or the like via the projection lens 1114.

Here, the liquid crystal panels 1110R, 1110
B and 1110G have dichroic mirror 110
8, light corresponding to each of the primary colors of R, G, and B enters, so that it is not necessary to provide a color filter on the counter substrate 300.

In addition to the projector, a liquid crystal television, a viewfinder type / monitor direct-view type video tape recorder, a car navigation system, an electronic organizer, a calculator, a word processor, a workstation, a mobile phone, a pager, a video phone, a POS A (point-of-sales) terminal, a device including a touch panel, and the like are examples of the electronic device. The display device according to the present invention can be applied to these various electronic devices.

2. Second Embodiment The second embodiment is different from the first embodiment in the structure of a circuit board in which a wiring board having a base material and a wiring layer is provided with an electronic component and a cover. Otherwise, the configuration is the same as in the first embodiment, and a description thereof will be omitted. Further, in the drawings, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

FIG. 6 is a sectional view showing a circuit board of the present embodiment, and corresponds to FIG. 2 in the first embodiment. As shown in this figure, the FPC board 402 is a multi-layer board composed of two layers of base films 410a and 410b, and a dummy wiring layer 424 as a covering portion is provided between the base films 410a and 410b.
It is provided slightly wider than the area where 50 is mounted.

Therefore, similarly to the first embodiment, moisture and light penetrating from the surface opposite to the mounting surface of the IC chip 450 through the base film 410b are applied to the dummy wiring layer 4
24, the deterioration of the reliability of the IC chip 450 and the deterioration of the performance due to light leakage are prevented.

It should be noted that the base film is not limited to two layers, but may be three or more layers.

3. <Third Embodiment> 3.1 Liquid Crystal Device FIG. 7 is a plan view of a liquid crystal device according to the present embodiment, in which wiring patterns and the like are omitted, and FIG.
It is sectional drawing in the position along P. In FIG. 8, a liquid crystal panel 1 used in a liquid crystal device 500 as a display device of the present embodiment includes a transparent substrate 10 made of a transparent thin glass plate and a transparent substrate 20 made of a transparent thin glass plate. are doing. A sealing material 30 is disposed on the periphery of the transparent substrates 20 and 30, and a predetermined gap 31 is formed between the transparent substrate 10 and the transparent substrate 20 with the sealing material 30 interposed therebetween.
(Cell gap). Here, the cell gap, which is the distance between the transparent substrate 10 and the transparent substrate 20, is defined by a number of spacers 32 interposed between the transparent substrate 10 and the transparent substrate 20.

As shown in FIG. 7, a discontinuous portion used as a liquid crystal injection port 301 for injecting the liquid crystal 40 is formed in the sealing material 30, and the liquid crystal injection port 301 is used to inject the liquid crystal 40 under reduced pressure. After that, it is sealed with a sealing material 305 made of an ultraviolet curable resin.

As shown in FIG. 8, the transparent substrate 10
A liquid crystal 40 is sealed in a region defined by the transparent substrate 20 and the sealing material 30. Striped electrodes 105 are provided on both the transparent substrate 10 and the transparent substrate 20.
205 are formed, and their surfaces are oriented films 101, 2
01 and the liquid crystal 40 is covered with STN (Super TwistedNem).
atic) system.

Polarizing plates 102 and 202 are attached to the outer surfaces of the transparent substrate 10 and the transparent substrate 20, respectively. When the liquid crystal panel 1 is configured as a reflective liquid crystal panel 1, the polarizing plate 2 attached to the transparent substrate 20 is used.
A reflective plate 203 is attached to the outer surface of 02.

As described above, on the inner surface of the transparent substrate 10, for example, a plurality of stripe-shaped electrodes 105 extending in the lateral direction are formed of a transparent conductive film, such as ITO (Indium Tin Oxi).
de) A plurality of stripe-shaped electrodes 205 extending in the vertical direction are formed on the inner surface of the transparent substrate 20 by a film.
It is formed by a TO film. Pixels are formed at the intersections of these striped electrodes 105 and 205.

Since the transparent substrate 20 is larger than the transparent substrate 10, a part of the transparent substrate 20 projects from the lower edge of the transparent substrate 10, and the terminal 206 formed at the end of the projecting portion has The FPC board 2 as a wiring board constituting the circuit board of the present invention is connected via the anisotropic conductive film 3 and the like. Here, the terminal 206 is, for example,
Stripe electrode 205 formed on transparent substrate 20
Are formed as wiring (extended) even in the overhang portion, and the striped electrode 105 formed on the transparent substrate 10 is connected to the transparent substrate 1 by a conductive material (not shown).
Electrical connection is made between the two substrates of the 0 and the second transparent substrate 10, and the wiring formed at the overhang portion is arranged and used for connection.

Therefore, when various control signals and drive signals such as a power supply are input from an external circuit via the FPC board 2,
A voltage can be applied to desired desired striped electrodes 105 and 205 based on the drive signal. Therefore, the desired image can be displayed on the liquid crystal panel 1 by controlling the alignment state of the liquid crystal 40 in each pixel. In order to input such a drive signal, a drive IC 5 as an electronic component is mounted on the FPC board 2 and formed as a circuit board. The FPC board 2 is made of a base film 2 made of a thin polyimide film having a thickness of about 25 μm.
A wiring pattern 21 made of copper and covered with nickel-gold or the like is formed on the surface of the base material 2 (base material), and a driving IC 5 is mounted on the wiring pattern 21 via the anisotropic conductive film 3. Have been. Further, in the vicinity of the connection portion between the FPC board 2 and the terminal 206, the liquid crystal panel 1
A resin mold 34 is applied to the end of the resin mold 34.

In the FPC board 2, the anisotropic conductive film 3
, The driving IC 5 is mounted on a COF (Chip On Film). COF mounting is a well-known technology,
Detailed description is omitted. In this mounting, a sheet-like or paste-like anisotropic conductive film 3 in which conductive particles 33 formed by plating a surface of a plastic ball with gold or the like are dispersed in a resin 35 is bonded to the FPC board 2 and the driving IC 5. The driving IC 5 is pressed while being heated by the pressure bonding head in a state of being sandwiched therebetween. Then, the melted resin 35 is pushed away between the terminal 51 of the driving IC 5 and the wiring pattern 21 of the FPC board 2 to form a resin sealing portion, and the wiring of the terminal 51 of the driving IC 5 and the wiring of the FPC board 2 together therewith. The conductive particles 33 are pressed between the pattern 21 and the terminal 51 of the driving IC 5 and the wiring pattern 21 of the FPC board 2 are electrically connected. Such a mounting method can cope with a fine pitch of the wiring pattern 21 and the terminal 51,
In addition, there is an advantage that a large number of terminals 51 can be electrically connected collectively.

The FPC board 2 also has a surface-mount type ceramic capacitor 55 mounted thereon. A solder resist layer 56 is formed in a region of the surface of the FPC board 2 where no components are mounted. Further, at the end of the FPC board 2, terminals for mounting the liquid crystal device 500 on a mobile phone or the like and electrically connecting to the circuit board of the device main body are formed and arranged in a wiring pattern. A reinforcing plate 59 for reinforcing the connected terminal portion is provided in the region on the back surface of the FPC board 2 where the terminal portion is formed.
Is affixed.

In the IC mounting structure of the liquid crystal device 1 configured as described above, in the present embodiment, an IC is mounted on the back side (the side on which the base film 22 is formed) of the FPC board 2.
In a region including the back side of the mounting region 50, a coating layer 60 (a hatched region indicated by reference numeral 60 in FIG. 7) is formed as a covering portion, and constitutes a circuit board of the present invention. In other words, a region opposite to the surface on which the driving IC 5 of the FPC board 2 is mounted, and a region corresponding to the back surface of the region (mounting region) on which the driving IC 5 is mounted (the region overlapping in plan view) 2), a coating layer 60 is formed. The coating layer 60 is formed as a region at least 0.1 mm wider than the IC mounting region 50. The coating layer 60 used here is a resin layer having high moisture proof performance such as epoxy resin.

In the IC mounting structure of the present embodiment, the wiring pitch is small in the area (IC mounting area 50) where the base film 22 of the FPC board 2 is as thin as 25 μm or less and the driving IC 5 is mounted on the FPC board 2 by COF. Conventional 70μ
The pitch is set to be as narrow as about 50 μm compared to about m,
Moreover, there is a possibility that the base film 22 may be damaged by pressure bonding when the driving IC 5 is mounted using the anisotropic conductive film 3. As described above, in the circuit board according to the present embodiment, moisture infiltrates from the back surface of the FPC board 2 despite the condition that moisture and the like easily penetrate from the back surface of the base film 22 and are easily affected by the influence. Can be prevented by the coating layer 60. Therefore, the moisture invading from the back side of the FPC board 2 penetrates the base film 22 and the wiring pattern 2 is formed in the IC mounting area 50 where the wiring pattern 21 has a narrow pitch.
There is no short or pseudo short between the two.

In order to configure such an IC mounting structure, in the present embodiment, after the driving IC 5 is mounted on the front side of the FPC board 2 by pressure bonding via the anisotropic conductive film 3, the FPC board is mounted. 2 and the IC mounting area 5
The coating layer 60 is formed in a region at least 0.1 mm wider than 0. Thereby, the driving IC
It is possible to reinforce the base film 22 of the FPC board 2 that may have been damaged when the 60 has been mounted by crimping, and prevent the penetration of moisture by the coating layer 60.

3.2 Electronic Equipment Equipped with Liquid Crystal Device FIGS. 9A, 9B, and 9C are external views showing examples of electronic equipment using the liquid crystal device 500 of this embodiment as a display unit. It is. FIG. 9A illustrates a mobile phone 88,
A liquid crystal device 500 is provided above the front surface. FIG.
(B) shows a wristwatch 92, in which a display unit using a liquid crystal device 500 is provided at the center of the front of the main body. FIG. 9 (C)
Denotes a portable information device 96, which includes a display unit including a liquid crystal device 500 and an input unit 98. These electronic devices include, in addition to the liquid crystal device 500, various circuits (not shown) such as a display information output source, a display information processing circuit, and a clock generation circuit, and a power supply circuit that supplies power to these circuits. It is configured to include a display signal generation unit. The display unit includes, for example, the input unit 9 in the case of the portable information device 96.
The display image is formed by supplying the display signal generated by the display signal generation unit based on the information and the like input from 8.

The electronic devices into which the liquid crystal device 500 of the present embodiment is incorporated are not limited to portable telephones, wristwatches, and portable information devices, but may be notebook computers, electronic organizers, pagers, calculators, POS terminals, IC cards, Various electronic devices such as a mini-disc player are conceivable.

4. <Fourth Embodiment> A circuit board and a liquid crystal device using the same according to the present embodiment are as follows.
Since the structure is exactly the same as that of the third embodiment, the description of the structure is omitted.

In the present embodiment, unlike the third embodiment,
By mounting an IC (semiconductor device) by the method described below,
A liquid crystal device having the structure described with reference to FIGS. 7 and 8 is manufactured.

That is, in the present embodiment, the FPC board 2
Before mounting the driving IC 5 on the front side of the FPC board 2,
Area on which the driving IC 5 is to be mounted (I
The coating layer 60 is formed in an area at least 0.1 mm wider than the C mounting area 50). The coating layer 60 used here is also a resin layer having high moisture proof performance such as an epoxy resin, similarly to the third embodiment.

Next, the surface of the FPC board 2 and the driving IC 5
The driving IC 5 is pressed while being heated by a pressure bonding head (not shown) with the anisotropic conductive film 3 interposed therebetween.
The driving IC 5 is mounted.

According to such an IC mounting method, the FPC
Since the base film 22 of the substrate 2 is protected by the coating layer 60 formed in advance, the driving IC 5
When mounting by crimping, the possibility of damage is low. Further, since the coating layer 60 is formed on the back surface side of the FPC board 2, it is possible to prevent moisture from entering from the back surface of the FPC board 2. Therefore,
Moisture invading from the back side of the FPC board 2 penetrates the base film 22 and reduces the possibility of causing a short circuit or a pseudo short circuit between the wiring patterns 21 in the IC mounting area 50 where the wiring patterns 21 have a narrow pitch. be able to.

5. <Modification> Here, a modification applicable to the above-described embodiment will be described. In each of the following modifications, only points different from the above-described embodiments will be described and described.

5.1 In the above-described embodiment, the TF which is a two-terminal switching element is used as the liquid crystal panel.
A liquid crystal panel in which TN type liquid crystal is filled with electro-optical characteristics using an active matrix type driving method using D (Thin Film Diode), and an STN (Super Twisted Nematic) type with electro-optical characteristics using simple matrix driving. The liquid crystal panel in which liquid crystal was sealed was shown. However, the liquid crystal panel is not limited to this. In terms of the driving method, a static drive type liquid crystal panel, a three-terminal switching element such as a TFT (Thin Film Transistor) or a two-terminal switching element such as an MIM (Metal- In
active-matrix type liquid crystal panel using sulator-metal), in terms of electro-optical characteristics, guest-host type,
Various types of liquid crystal panels can be used, such as a phase transition type, a ferroelectric type, and a BTN type using a bistable nematic liquid crystal having memory properties.

5.2 Further, the flat display panel used in the present invention is not limited to a liquid crystal panel, but may be another flat display panel, for example, an EL (Electro-Luminescence) display panel, a PDP (Plasma Display Panel) display panel, FE
It may be a D (Field Emission Display) panel or the like.

5.3 In each of the above embodiments, an example has been described in which a semiconductor device as a drive circuit is mounted on a circuit board, and the circuit board is connected to a flat display panel. However, a circuit board of the present invention connected to the flat display panel includes a circuit board on which at least one of a semiconductor device of a driving circuit, a semiconductor device of an image signal processing circuit, and a semiconductor device of another circuit is mounted. There may be.

5.4 The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the present invention or within the equivalent scope of the claims.

[Brief description of the drawings]

FIG. 1 is a plan view showing a circuit board according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along a line AA shown in FIG.

FIG. 3 shows two Fs having the structure shown in FIGS. 1 and 2;
FIG. 2 is an exploded perspective view showing a PC board and a liquid crystal panel.

FIG. 4 is a partially cutaway perspective view showing the configuration of the liquid crystal panel according to the first embodiment.

FIG. 5 is a cross-sectional view illustrating a configuration of a liquid crystal projector as an example of an electronic apparatus to which the liquid crystal panel according to the first embodiment is applied.

FIG. 6 is a sectional view showing a circuit board according to a second embodiment of the present invention, and corresponds to FIG. 2 in the first embodiment.

FIG. 7 is a plan view of a liquid crystal device according to a third embodiment with wirings and the like omitted.

FIG. 8 is a cross-sectional view at a position along line PP drawn in FIG. 7;

FIGS. 9A and 9B are external views showing an electronic device using the display device of the third embodiment as a display unit, wherein FIG. 9A is a mobile phone, FIG. 9B is a wristwatch, and FIG. 9C is a mobile information device. It is.

FIG. 10 is a sectional view showing a conventional circuit board.

[Explanation of symbols]

 Reference Signs List 1 liquid crystal panel 2 FPC board (wiring board) 3 anisotropic conductive film 5 driving IC (electronic component) 10 transparent substrate 20 transparent substrate 21 wiring pattern (wiring layer) 22 base film (base material) 33 conductive particles 40 liquid crystal Reference Signs List 50 IC mounting area 60 Coating layer (resin layer, covering portion) 88 Cellular phone (electronic device) 92 Watch (electronic device) 96 Portable information device (electronic device) 100 Liquid crystal panel 200 Element substrate 206 Terminal (connection terminal) 300 Counter substrate 400 FPC board (wiring board) 410 Base film (base material) 420a Input wiring (wiring layer) 420b Output wiring (wiring layer) 422,424 Dummy wiring layer 450 IC chip (electronic component) 460 Adhesive (resin sealing part) 460a Conductive particles 500 Liquid crystal device 1100 Projector (electronic device)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 1/02 H05K 1/02 K

Claims (14)

[Claims] A substrate having an insulating property and flexibility, a wiring board having a wiring layer provided on the base, and electrically connected to the wiring layer and mounted on the wiring board. In the region where at least a part of the region where the electronic component is mounted overlaps at least a part in plan view, the electronic component is covered with the base material from the side opposite to the electronic component, and A circuit board comprising: an insulated covering portion; 2. The circuit board according to claim 1, wherein the covering portion is a dummy wiring layer. 3. The circuit board according to claim 1, wherein the covering portion is a resin layer. 4. The circuit board according to claim 1, wherein the cover has a light-shielding property. 5. The circuit board according to claim 1, further comprising a resin sealing portion for sealing a portion where the electronic component and the wiring layer are electrically connected with a resin. 6. The anisotropic conductive film according to claim 1, which is interposed between the electronic component and the wiring layer, and electrically connects the electronic component and the wiring layer. A circuit board further comprising: 7. The circuit board according to claim 1, wherein the base material and the wiring layer are directly joined without using an adhesive layer. 8. The circuit board according to claim 1, wherein the base has a plurality of layers, and the covering portion is provided between the plurality of layers. 9. A display device, comprising: the circuit board according to claim 1; and a flat panel including a connection terminal to which the circuit board is electrically connected. 10. The liquid crystal panel according to claim 9, wherein the flat panel is a liquid crystal panel including a pair of substrates facing each other and a liquid crystal sealed between the pair of substrates. The display device formed in at least one of the above. 11. The display device according to claim 9, wherein the electronic component mounted on the circuit board includes a driving semiconductor device. 12. An electronic apparatus, comprising: the display device according to claim 11; and an image signal processing circuit that processes an image signal input to the display device. 13. The method for manufacturing a circuit board according to claim 1, wherein the electronic component is mounted on a surface side of the wiring board by crimping; And a covering portion forming step of forming the covering portion on the back surface side of the wiring board after the component mounting step. 14. The method for manufacturing a circuit board according to claim 1, wherein the covering section is formed on the back side of the wiring board, and the covering section is formed. An electronic component mounting step of mounting the electronic component on the surface side of the wiring board by crimping after the step.