Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure
Reexamination Certificate
2001-11-13
2003-07-22
Ho, Hoai (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
C250S552000, C257S084000, C257S085000, C257S099000, C257S603000, C438S025000, C438S028000
Reexamination Certificate
active
06597018
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a semiconductor light-emitting device and a flat panel display lighting system using the semiconductor light-emitting device. More particularly, the semiconductor light-emitting device is usable as, for example, a backlighting source that irradiates a liquid crystal display with light through a light guide plate.
BACKGROUND ART
A display that utilizes a liquid crystal has been generally applied to electronic devices such as cellular phones. The display using the liquid crystal has a structure in which the liquid crystal display is sealed with the liquid crystal and a light emitter such as a light-emitting diode (LED) is used as a backlighting source to display an image. A semiconductor light-emitting device of edge-lighting type, for example, is known as a light-emitting device used as the backlighting source.
FIGS.
7
(
a
) through
7
(
c
) are respectively perspective view of a semiconductor light-emitting device used for a flat panel display lighting system of edge-lit type, side view and front view, of the flat panel display lighting system.
As shown in FIG.
7
(
a
), a known semiconductor light-emitting device includes: blocklike insulating substrate
50
; pair of electrodes
51
a
and
51
b
, each of which is disposed to cover each end of the front face (i.e., the face on which a light emitter is placed), a side face and the back face (which is opposite to the face on which the light emitter is placed), of the substrate
50
; light emitter
52
bonded onto the electrode
51
a
with a conductive adhesive; wire
53
, which electrically connects the electrode
51
b
to the light emitter
52
; and resin package
54
, which is made of an epoxy resin and molds, for example, the light emitter
52
and wire
53
together on the front face of the substrate
50
.
As shown in FIGS.
7
(
b
) and
7
(
c
), the known flat panel display lighting system includes a board
55
on which the semiconductor light-emitting device and a light guide plate
56
of a polymer such as an acrylic polymer are disposed. The semiconductor light-emitting device is mounted on the board
55
and used as a backlighting source for a liquid crystal display
57
. The board
55
has a wiring pattern (not shown) for establishing continuity to the electrodes
51
a
and
51
b
of the semiconductor light-emitting device. The light guide plate
56
is used for guiding light, emitted from the light emitter
52
, to the liquid crystal display
57
and has a minute unevenness pattern on its bottom surface. Because of the existence of this minute unevenness pattern, light introduced into the edge of the light guide plate
56
is externally reflected toward the liquid crystal display
57
. That is to say, light generated by the light emitter
52
of the semiconductor light-emitting device is introduced into the edge of the light guide plate
56
. In other words, the light guide plate
56
is edge-lit. Thus, the light guide plate
56
functions as a backlighting source for the liquid crystal display
57
utilizing the light diffusion therein.
In such a surface-mounted flat panel display lighting system, the semiconductor light-emitting device is fixed onto the board
55
so as to be electrically connected to the electrode
51
a
and
51
b
and the wiring pattern using solders
58
a
and
58
b
. In this case, the height of the semiconductor light-emitting device is determined by the height (i.e., the vertical length shown in FIG.
7
(
a
)) of the substrate
50
. Specifically, the height of the light emitter
52
is set to be almost a half of that of the substrate
50
.
Problems to be Solved
The substrate
50
, however, has been diced so as to have a height and a thickness enough to retain the mechanical strength thereof. Therefore, the light emitter
52
is limited in height when mounted on the board
55
. Thus, the thickness of the light guide plate
56
also needs to be set in accordance with the height of the light emitter
52
. That is to say, to introduce light into almost the center of the edge face of the light guide plate
56
, the light guide plate
56
needs to have its thickness increased or to be mounted slightly apart from the upper surface of the board
55
. Accordingly, an unit made up of the flat panel display lighting system and liquid crystal display
57
has its thickness increased. As a result, the unit is less applicable to electronic devices such as cellular phones that have been tremendously downsized and thinned. In addition, the board
55
also has a space for the substrate
50
, and thus has its area as well as its thickness increased inevitably. Therefore, it becomes difficult to downsize the resultant device.
Though not shown in FIGS.
7
(
b
) and
7
(
c
), circuits such as drive and detector circuits for the light emitter
52
are formed on the lower surface of the board
55
. Thus, a solder reflow process step is required for such circuits on the lower surface of the board
55
. Moreover, as an example shown in FIGS.
7
(
b
) and
7
(
c
), if the light emitter
52
is mounted on the upper surface of the board
55
and fixed thereto with solders
58
a
and
58
b
, another solder reflow process step is required on the upper surface of the board
55
. Consequently, fabrication of the flat panel display lighting system includes two solder reflow process steps on the respective upper and lower surfaces of the board
55
. As a result, the number of process steps and items of control inspection increase, and thus increase in fabricating cost and decrease in production yield might eventually occur.
DISCLOSURE OF INVENTION
It is therefore an object of the present invention to have a structure for backlighting a liquid crystal display downsized and thinned. It is another object of the present invention to provide a semiconductor light-emitting device and a flat panel display lighting system of high productivity by reducing, for example, the number of the fabricating process steps.
An inventive semiconductor light-emitting device includes: a substrate having a base portion, which extends laterally, and a mounting portion, which extends longitudinally from an area located in a middle part of the base portion and has an element placing area in a position apart from the base portion; a pair of electrodes formed on the base portion and the mounting portion of the substrate, one of the pair of electrodes extending from an end of the base portion, the other of the pair of electrodes extending from the other end of the base portion; a light emitter, which is placed on the electrode placing area of the mounting portion and is electrically connected to each of the pair of electrodes; and a transparent encapsulant, which molds at least the light emitter and each part of the pair of electrodes together.
In this device, the light emitter is disposed in an area of the mounting portion located away from the base portion of the substrate, and light emitted from the light emitter can be taken out from the area. Therefore, light emission suitable for application can be obtained. Specifically, the known semiconductor light-emitting device needs to be mounted on a board with its upper surface attached to the board by vacuuming using, for example, a vacuum jig. Thus, the area in the board where the device is attached using a suction nozzle is limited in position and the board itself is also limited to a minimum dimension. Further, since the substrate of the semiconductor light-emitting device is limited in thickness, the resin package is also limited in size and shape and the light emitter is also limited in location, for example. As a result, there is little flexibility in designing, and thus emission characteristics have to be sacrificed to some extent. In contrast, the inventive semiconductor light-emitting device can be mounted through the board with the lower surface of the base portion attached to the board by vacuuming using a vacuuming jig. Thus, the inventive semiconductor light-emitting device does not have limitations such as those found in the known semiconductor
Ho Hoai
Tran Mai-Huong
LandOfFree
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