Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1997-02-19
2001-06-19
Mengistu, Amare (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S080000
Reexamination Certificate
active
06249267
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to display apparatuses which have light emitting elements arranged in a matrix form on a printed substrate so that the light emitting elements are individually turned on and off to display images such as characters, and more particularly to display apparatuses which is adapted to dissipate heat developed by electronic components such as light emitting elements mounted on a printed board.
Conventionally, there have been utilized display apparatuses involving information display boards installed at railway stations or public squares as well as inside displays provided in vehicular rooms. These display apparatuses have light emitting elements such as light emitting diodes (hereinafter referred to as LEDs) in a matrix form so that the LEDs are individually controlled of emission of light to display characters and so on for displaying information of news, time, temperature, etc. The display apparatus of this kind has a structure for example as shown in
FIG. 4
In
FIG. 4
,
1
is a printed board formed of a glass-epoxy resin or the like having interconnect patterns on opposite surfaces. The printed board
1
has chip LEDs
2
matrix-arranged on one surface and IC components (controlling components)
3
matrix-arranged on the other surface. The IC components comprise controlling and driving components for selectively turning on and off the LEDs
2
on the opposite side.
4
is a metal fixture for fixing the display apparatus on an assembly on which the display apparatus is installed without being interfered by the IC components. The display apparatus is mounted on a housing, etc., of such an assembly by fastening screws in attachment holes
4
a.
The printed board
1
on which LEDs
2
and IC components
3
are thus mounted is formed by an electrically insulative substrate such as a glass-epoxy resin substrate formed with interconnect patterns on the surfaces thereof. To mount LEDs and IC components on the printed board
1
, surface mounting is usually adopted wherein these parts are rested on a surface of the printed board
1
to directly solder lead wires or electrode terminals of these parts onto the interconnect pattern on the printed board
1
. In such cases, the connection between LEDs
2
and IC components
3
is carried out via through-holes formed in the printed board
1
or by way of lateral faces of the printed board
1
.
The technique of mounting electronic components on a electrically insulative printed board for electronic assemblies is being applied to various electronic devices and apparatuses. In recent, the surface mounting that electronic components are directly soldered on the surface of a printed board is becoming a main stream in the field of mounting electronic devices and apparatuses.
Where electronic components are mounted on a electrically insulative printed board, there is almost no problem for small consumption power of electronic components. On the contrary, where mounting with LEDs for large-sized displays as stated hereinbefore or a number of heat-dissipating electronic components such as high-power semiconductor devices, the heat generated from the components is difficult to dissipate outside because of poor heat conductivity of such an electrically insulative printed board. The remaining heat is accumulated in the insulative substrate to thereby raise the temperature of electronic components, badly influencing electrical characteristics of the display apparatus. To avoid this, there is necessity of reducing the operating power low to suppress heat development, making difficult to provide a sufficient level of brightness of light.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to solve the above stated problem and provide a display apparatus which is capable of efficiently dissipate heat developed by electronic components to the outside to suppress excessive heating of the temperature of the components, thereby preventing against lowering in display characteristics.
A display apparatus of the present invention comprising: a heat conductive substrate; electrically insulative members formed on respective surfaces of the heat conductive substrate; light emitting elements arranged in a matrix form on the surface of the electrically insulative member on one surface of the heat conductive substrate; and control components arranged on the surface of the electrically insulative member on the other surface of the heat conductive substrate.
Here, the light emitting element refers to as an electronic element such as an LED for radiating light, which involves a bare chip per se divided by a semiconductor substrate and light-source arrays formed on a substrate. The heat conductive substrate means substrate in which the heat conductivity is obviously higher than that of a conventional printed board formed of glass-epoxy resin.
With such structure, the heat generated from light emitting elements or controlling components is allowed to conduct through the conductive substrate to be dissipated to the outside. Accordingly, the temperature of the electronic components such as light emitting elements is prevented from rising to an excessively high temperature, and accordingly there is substantially no necessity of lowering the driving electric power for the electronic component.
Preferably, the electrically insulative member on the one surface is formed at least two layers of a first under layer and a second layer formed thereon, the first layer having an interconnect pattern formed on a surface thereof, the second layer being formed with blind through-holes through which the light emitting elements and the interconnect pattern are electrically connected. With such arrangement, the light emitting elements are arranged with high density on the upper second layer, i.e., on a light emitting side of the display apparatus, with interconnects therefore provided on the first layer, thereby improving display characteristics of the display apparatus.
Here, the blind through-hole means a through hole formed penetrating a layer or a part of layers in a plurality of layers provided as an electrically insulating member, and does not mean a through-hole penetrating the entire layers thereof.
More preferably, at least one of the electrically insulative members are partly removed to provide exposed surface to the heat conductive substrate. With such arrangement, the heat built up in the heat conductive substrate is to be released to the outside.
Further preferably, the heat conductive substrate has a metal fixture on the other surface thereof, the metal fixture being in contact with the exposed surface of the heat conductive substrate, and the metal fixture has a height higher than those of the control components. If so arranged, where the display apparatus is installed on a housing of external apparatus or device, connection is possible through the metal fixture between the heat conductive substrate and the housing. This connection provides formation of a path for heat conduction from the electronic components, such as light emitting elements or controlling components, as a heat source to the housing for dissipating heat. Thus, the heat if developed is efficiently dissipated to the outside.
Still further preferably, the metal fixture is formed by a sheet member, and the metal fixture includes an attaching portion projecting higher than the control component. The metal fixture is readily available with less material. In such cases, the sheet member may have a stepped portion formed projecting to be contacted with the exposed surface of the heat conductive substrate.
Preferably, the heat conductive substrate is formed of alumina having an interconnect pattern on the one surface thereof, the electrically insulative member on the one surface being formed with blind through-holes through which the light emitting elements and the interconnect pattern are in electrical connection. If so constructed, a multi-layer structure is also available in compact with using the heat conductive substrate and the electrically
Arent Fox Kintner & Plotkin & Kahn, PLLC
Mengistu Amare
Rohm Co. Ltd
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