JPH0829799A - Picture display device - Google Patents

Abstract

PURPOSE:To electrically shield the noise from the outside or inside of a circuit board by coating at least a portion of electronic parts of the circuit board with a shielding sheet consisting of a fusible conductive layer held between thermosoftening insulation layers. CONSTITUTION:The shielding sheet 4 is constituted by holding the fusible conductive layer 2 between the two layers of thermosoftening insulation layer 1a and 1b. The shielding sheet 4 is placed on a PCB substrate 7 packed with an IC 5, a condenser 6 and various wirings. Then, the shielding sheet 4 is quickly heated with a hot air type heater, dryer, etc. At this time, the shielding sheet 4 is deformed conforming to the shape of the electronic parts packed on the PCB substrate 7 because the m.ps. of the thermosoftening insulation layers 1a and 1b such as paraffin are set above the m.p. of a low-m.p. metal layer which is the first material 2a for the easily fusible conductive layer 2. Thus, spacings between the electronic parts packed on the PCB substrate 7 are completely covered with the shielding sheet 4 without spacing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device comprising a display panel and a drive circuit board, and more particularly to a structure for shielding electric noise of the circuit board.

[0002]

2. Description of the Related Art As an image display device for displaying characters such as characters and graphic symbols, a flat panel display having a display surface which is an aggregate of a large number of pixels as a minimum unit arranged in a matrix is widely used. A liquid crystal display device is typically used as the flat panel display.

These display panels are connected to a circuit board on which a large number of electronic components and wirings for selectively driving and controlling each pixel are mounted to form an image display device. In addition, in order to improve the compactness of such a flat display that is thin, small, and lightweight, a circuit board for driving and controlling the display panel is provided close to or directly to the input terminal led to the board end of the display panel. Often connected.

For example, semiconductors such as driver ICs and control ICs, electronic components such as capacitors and resistors, and various wirings for connecting these are mounted on a flexible substrate. Then, this circuit board is connected to an input terminal led to the end of the display panel, and the circuit board and the display panel are housed in one case to form a compact image display device.

[0005]

In various electronic parts and wirings mounted on such a circuit board, for example, capacitors interfere with each other to generate electrical noise, or wirings with different potentials. Or signal wirings having different signal cycles influence each other to generate electrical noise. If such electrical noise alters the signal, it adversely affects the display function and deteriorates the image quality. Further, such electrical noise may adversely affect not only the image display device but also other electronic circuits in the vicinity.

Therefore, the portion of the circuit board that may generate such electrical noise and adversely affect the electronic circuit requires a means for shielding the noise. FIG. 3 shows an example of such noise shielding means. That is, IC5
The PCB board 7 on which electronic components such as a capacitor 6 and the like are mounted is entirely covered with a shield case 8 to be electrically shielded from the outside.

However, with such a shielding structure, the circuit can be electrically shielded from the outside, but there is a gap inside the PCB substrate 7, that is, between the capacitors 6 or ICs 5 or between various wirings (not shown). It is not possible to completely shield the influence of electrical noise inside the substrate.

Further, the structure in which the entire PCB substrate 7 is covered with the shield case 8 hinders compactness, and the degree of freedom in structural design as a flat panel display is limited.

The present invention has been made in view of the above problems, and in an image display device comprising a matrix type display panel and a circuit board on which electronic components for driving and controlling the display panel are mounted, An object of the present invention is to provide an image display device in which the adverse effects of noise from the outside or inside are electrically shielded.

[0010]

The present invention is directed to a display panel having a display surface which is an aggregate of a large number of pixels arranged in a matrix, and an electronic component for selectively driving and controlling the pixels of the display panel. In an image display device having a circuit board on which is mounted, at least a part of the electronic components of the circuit board is covered with a shielding sheet composed of a fusible conductive layer sandwiched by a heat-softening insulating layer. The easy-melting conductive layer is composed of a first material that controls the melting point and a second material that controls the degree of deformation when softened and deformed by heating, and the melting point of the first material is the thermal softening. The object is achieved by lowering the melting point of the conductive insulating layer.

[0011]

The shape of the electronic components mounted on the circuit board is not uniform and has various shapes.
Therefore, the mere flexible shielding sheet cannot effectively cover the gaps between these electronic components.

Further, in order to function as an electric shielding sheet, the shielding sheet must have an insulating property as well as an electrical conductivity for preventing charge-up such as static electricity.

Therefore, first, the electrical shielding sheet may have a structure in which an electrically conductive layer is sandwiched between insulating layers and the electrically conductive layer can be grounded. Next, in order to effectively cover the gaps between the electronic components, the shielding sheet is made of a low melting point material whose shape is irreversibly deformed in a heated state. That is, it can be deformed according to the shape of various electronic components by heating, and the gap between the electronic components can be effectively covered.

However, when the melting point of the insulating layer is lower than the melting point of the electrically conductive layer, the insulating layer may be softened and deformed first by heating, and a defective portion may be formed in the insulating layer to cause dielectric breakdown. Therefore, the melting point of the electrically conductive layer needs to be lower than the melting point of the insulating layer.

When the shielding sheet having a melting point of the electrically conductive layer lower than that of the insulating layer is heated at a temperature higher than the melting point of the insulating layer, the electrically conductive layer softened and deformed causes a large gap in the electronic component. It may flow in a large amount and may also cause dielectric breakdown. Therefore, the electrically conductive layer is composed of a material that controls the melting point of the electrically conductive layer and a material that controls the degree of deformation during softening deformation.

[0016]

EXAMPLES Examples of the present invention will be described in detail below. Since the display panel and the drive circuit itself applied to the image display device of the present invention are the same as those of the conventional one, the description thereof will be omitted.

FIG. 1 shows a schematic sectional structure of an electrical shielding sheet applied to the present invention. In FIG. 1, the shielding sheet 4
Has a structure in which the fusible conductive layer 2 is sandwiched between two thermosoftening insulating layers 1a and 1b.

The heat-softening insulating layers 1a and 1b must also have the function of an adhesive for sealing the gap between the electronic components mounted on the circuit board, and paraffin, vinyl, polyethylene or the like can be used.

Next, the easy-melting conductive layer 2 has a function of preventing charge-up of the insulating layers 1a and 1b by grounding, but in order to soften and deform the shielding sheet 4 by heating to seal the gap between electronic parts. It is composed of a first material 2a for controlling the melting point and a second material 2b for controlling the degree of deformation when softened and deformed by heating.

The first material 2a that constitutes the fusible conductive layer 2
As a low melting point metal layer for controlling the melting point,
A Newton alloy or a wood alloy that melts at a low temperature can be used. Newton alloy has a melting point of 95 ° C and wood alloy has a melting point of 70 ° C.
It has a melting point lower than that of paraffin, vinyl, polyethylene, or the like that constitutes 1a and 1b.

Also, for example, nickel particles are mixed in the low melting point metal layer as the second material 2b in order to control the degree of deformation when it is softened and deformed by heating. The amount of the nickel particles can be selected according to the shape of the circuit board and the electronic component to be applied, but can be selected within the range of about 30 to 80% by volume ratio of the fusible conductive layer 2.

Next, FIG. 2 shows a state in which such a shielding sheet 4 is heated. On the PCB board 7 on which the IC 5, the capacitor 6 and various wirings (not shown) are mounted,
First, the shielding sheet 4 having the structure as shown in FIG. 1 is placed.

Then, the shielding sheet 4 is quickly heated with a warm air blower or a dryer. At this time, the melting points of the heat-softening insulating layers 1a and 1b such as paraffin are set to be higher than the melting point of the low-melting metal layer which is the first material 2a of the fusible conductive layer 2.

Therefore, since the low-melting-point metal layer is already melted when the heat-softenable insulating layers 1a and 1b are softened or melted, the shielding sheet 4 conforms to the shape of the electronic component mounted on the PCB substrate 7. To transform. As a result, the gap between the electronic components mounted on the PCB substrate 7 can be completely covered by the shielding sheet 4 without any gap.

Further, since nickel particles or the like are mixed as the second material 2b in the easy-melting conductive layer 2, it is possible to control the degree of deformation when the easy-melting conductive layer 2 is heated. Therefore, there is no possibility that the fusible conductive layer 2 selectively remains in a large amount in a large gap of the electronic component and the insulating property is destroyed. Then, finally, a hole is formed in a part of the heat-softening insulating layer 1a of the shielding sheet 4, the lead wire is connected to the fusible conductive layer 2 with the conductive adhesive 9, and the lead wire is grounded.

[0026]

As described above, according to the present invention, the electronic components of the circuit board are heated and covered with the shielding sheet composed of the easy-melting conductive layer sandwiched by the heat-softening insulating layers, so that the gap between the electronic components can be improved. It is possible to provide an image display device in which the above can be completely covered with a shielding sheet without any gap, and the adverse effect of noise from the outside or the inside of the circuit board can be electrically shielded. Also, since this electrical shielding sheet is coated along the shape of the electronic components mounted on the board, the space for shielding is minimal and the conventional shield case is not required, so it is compact. And has a great degree of freedom in structural design as a flat panel display.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional configuration diagram showing an electrical shielding sheet applied to the present invention.

FIG. 2 is a schematic cross-sectional configuration diagram showing a state in which a circuit board is covered with the shielding sheet of FIG.

FIG. 3 is a schematic configuration diagram showing a conventional electrical shield case.

[Explanation of symbols]

 1a, 1b ... Thermosoftening insulating layer 2 ... Easy-melting conductive layer 2a ... First material 2b ... Second material 4 ... Shielding sheet 5 ... IC 6 ... Capacitor 7 ... PCB substrate

Claims (2)

[Claims] 1. A display panel having a display surface which is an aggregate of a large number of pixels arranged in a matrix, and a circuit board on which electronic parts for selectively driving and controlling the pixels of the display panel are mounted. In the image display device, at least a part of the electronic components of the circuit board is covered with a shielding sheet composed of a fusible conductive layer sandwiched by thermosoftening insulating layers. 2. The image display device according to claim 1,
The fusible conductive layer is composed of a first material for controlling the melting point and a second material for controlling the degree of deformation when softened and deformed by heating, and the melting point of the first material is the melting point of the thermosoftening insulating layer. An image display device characterized by being lower than the melting point.