Chip semiconductor light-emitting device

Details Chip semiconductor light-emitting device Chip semiconductor light-emitting device

2001-04-10

2003-06-03

Patel, Nimeshkumar D. (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

Solid-state type

C313S113000, C313S114000, C313S498000

Reexamination Certificate

active

06573653

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to chip semiconductor light-emitting devices and, more particularly, to a chip semiconductor light-emitting device for emitting color mixture of light by the use of light-emitting diode (LED) elements different in emission-light color.
PRIOR ART
Conventionally, there has been known a chip light-emitting device having a light source arranged with LED elements different in emission-light color to emit color mixture of light. FIG.
7
and
FIG. 8
depict an example of such a device, wherein
FIG. 7
shows a perspective view of a chip light-emitting device
10
while
FIG. 8
is a side view of
FIG. 7
as viewed in a section on line A—A. In
FIG. 7
, the chip light-emitting device
10
has a baseboard
2
on which electrodes
3
a
,
3
b
and electrodes
4
a
,
4
b
are formed of conductive material.
In one end of the baseboard
2
, semi-circular cutouts
8
a
,
8
a
are provided to form, thereon, conductive films, such as electroplated layers, respectively connected to the electrodes
3
b
and
4
b
. Also, in the other end of the baseboard
2
, semi-circular cutouts are similarly provided. The conductive films, such as electroplated layers, formed on the semi-circular cutouts extend down to a backside of the baseboard.
An LED element
1
a
is mounted by die bonding on the electrode
3
a
, and an LED element
1
b
is mounted by die bonding on the electrode
4
a
. The LED element
1
a
emits, e.g. red light. The LED element
1
b
emits light of different color from the light color by the LED element
1
a
, e.g. green light. The LED element
1
a
is electrically connected to the electrode
3
b
through wire bonding using a metal wire
5
a
. The LED element
1
a
is electrically connected to the electrode
4
b
through wire bonding using a metal wire
5
b.
The baseboard
2
mounting thereon the LED elements
1
a
,
1
b
is rested with a reflector
6
formed of opaque resin. Light-transmissive resin
7
such as epoxy resin is filled in an aperture defined in the reflector
6
as shown in
FIG. 8
, thereby forming a chip light-emitting device
10
. The reflector
6
is oval as viewed in plan and has a slant surface
6
a
having upward inclination with respect to a contact surface with the baseboard
2
. The reflector
6
is formed by injection-molding, e.g. of white-colored liquid-crystal polymer.
The chip light-emitting device
10
is surface-mounted on a printed circuit board. Electrical connection is made between the conductive films formed on the backside of the baseboard
2
through the semi-circular cutouts and the circuit pattern on the printed circuit board. By operating the LED element
1
a
for red-light emission and the LED element
1
b
for green-light emission, the chip light-emitting device
10
emits light mixed with red and green.
The operation of the chip light-emitting device
10
will be explained with reference to FIG.
8
. It is now assumed that the LED element
1
a
has a light source Sa. The output light of the light source Sa reflects upon a slant surface
6
a
of the reflector
6
at a lower side than a belly thereof and turns into reflection light Ra directed toward a luminous center P of the chip light-emitting device
10
. Also, the output light from the light source Sb of the LED element
1
b
reflects upon a slant surface
6
a
of the reflector
6
as a surface closer to the baseboard and turns into reflection light Rx directed toward the luminous center P of the chip light-emitting device
10
.
In this manner, the chip light-emitting device
10
has the reflector
6
formed with a vertically-penetrating slant surface
6
a
to reflect and radiate the output light of the LED element by the reflector. The reflection light is collected to a luminous center P, thereby improving luminous efficiency.
Also, the output light from the light source Sa of the LED element
1
a
and the output light from the light source Sb of the LED element
1
b
, in the vicinity of a top end of the slant surface
6
a
of the reflector
6
, respectively turn into reflection light Rb and Ry to be emitted from the chip light-emitting device
10
.
FIG. 9
is an explanatory view showing, in a vertical sectional view of
FIG. 8
, a luminous-intensity distribution given by the LED elements
1
a
,
1
b
. In
FIG. 9
, Ia is a luminous-intensity distribution of reflection light given by the LED element
1
a
while
1
b
is a luminous-intensity distribution of reflection light given by the LED element
1
b
. On a right side of the luminous center P, the LED element
1
a
arranged distant from the slant surface
6
a
provides reflection light upon nearly an upper half of the slant surface
6
a
.
Meanwhile, on a left side of the luminous center P, the LED element
1
b
arranged distant from the slant surface
6
a
provides reflection light nearly upon an upper half of the slant surface
6
a
. In this manner, the luminous-intensity distributions by the LED elements
1
a
,
1
b
are different in characteristic on between the left and right sides of the luminous center P.
As shown in
FIG. 9
, in the conventional chip light-emitting device, the reflector slant surface is set with a constant inclination angle &thgr;x. Consequently, the luminous-intensity distribution is different on left and right sides with respect to the luminous center P between the LED element arranged closer to the slant surface and the LED element arranged closer to the slant surface. Due to this, there is emphasis on any of light colors emitted by-the LED elements
1
a
and
1
b
depending upon a position viewing the light emission surface of the chip light-emitting device. Thus, there has been a problem that there is difference in color-mixture tone and hence difference in color of emission light from the chip light-emitting device.
As for the LED element arranged distant as viewed from the slant surface, the output light reflects almost on an upper half only of the slant surface. Thus, there has been a problem that there is decrease in amount of light directed toward a luminous center and hence decrease in a center luminous intensity of the chip light-emitting device
10
.
SUMMARY OF THE INVENTION
Therefore, it is a primary object of this invention to provide a novel chip semiconductor light-emitting device.
Another object of the invention to provide a chip light-emitting device capable of making even the degree of mixing colors.
A chip semiconductor light-emitting device according to the present invention comprises: a baseboard; first and second conductors formed on the baseboard; first and second semiconductor light-emitting elements respectively mounted on the first and second conductors and different in color of emission light; and a reflector placed on the baseboard such that a slant surface thereof surrounds the first and second semiconductor light-emitting elements; the slant surface including first and second reflection surfaces continuing in a thickness direction of the reflector and respectively having first and second inclination angles, the first reflection surface being closer to the baseboard and the second reflection surface more distant from the baseboard; the first and second angles being set such that first output light of the first semiconductor light-emitting element arranged closer to the first reflection surface provides a first angle, given between reflection light reflected on a lower side of the first reflection surface and reflection light reflected on an upper side of the first reflection surface, equal to a second angle, given between reflection light reflected on a lower side of the second reflection surface and reflection light reflected on an upper side of the second reflection surface that are provided by second output light of the second semiconductor light-emitting device arranged distant from the first reflection surface.
In an embodiment, the first angle is represented by &thgr;p and the second angle by &thgr;q. The first inclination angle &thgr;a and &thgr;b are set to have a relationship &thgr;p=&thgr;q. This makes equal the directiv

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