Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With reflector – opaque mask – or optical element integral...
Reexamination Certificate
1998-12-29
2001-02-06
Tran, Minh Loan (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With reflector, opaque mask, or optical element integral...
C257S099000, C257S100000, C257S103000
Reexamination Certificate
active
06184544
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a semiconductor light emitting device in which its cost is reduced, and the light emission efficiency is improved and which is made thin. U.S. patent application 09/221,838 entitled Light Emitting Diode Element and U.S. patent application 09/221,839 entitled Semiconductor Light Emitting Device both naming the inventors Hidekazu Toda and Shinji Isokawa. and both filed on the same day as the present application and incorporated herein by references.
2. Description of the Related Art
Semiconductor light emitting device of the surface mount type using light emitting elements have been used for various industrial and consumer's apparatuses.
An example of such a prior art semiconductor light emitting device will be described with reference to FIG.
1
.
The semiconductor light emitting device which is disclosed in Japanese Laid-open Patent Publication No. 9-283803 is also known other than that shown in FIG.
1
.
FIG. 1
is a sectional view showing a semiconductor light emitting device
11
using a light emitting diode element (hereinafter abbreviated as LED element) as a semiconductor light emitting element.
In
FIG. 1
, a reference numeral
1
denotes a rectangular insulating substrate made of an electrically insulating material such as ceramics or non-transparent synthetic resin, which is coated with a pair of metallized wiring layers
2
,
3
leading from the bottom of the rectangular insulating substrate
1
to it upper surface via its lateral side thereof. The LED element
6
is formed with a light emitting layer by the vapor phase growth of a nitride compound such as GaN on a sapphire substrate
6
a
and is formed with p and n side electrodes on one side thereof facing to the rectangular insulating substrate
1
.
A reference numeral
7
denotes a reflector which is formed with a cavity
7
a
for accommodating the LED element
6
. The reflector
7
is molded from a substrate of non-transparent synthetic resin to have a predetermined thickness. The cavity
7
a
is coated on its lateral side with a reflective coating to form a reflective layer. The reflector
7
is laminated on the rectangular insulating substrate
1
with a via bonding layers
9
,
10
.
Electrically conductive materials
4
,
5
are bonded on the surface of respective metallized wiring layers
2
,
3
. The LED element
6
is die-bonded on the rectangular insulating substrate
1
by using electrically conductive materials
4
,
5
as bonding material so that the LED element
6
is accommodated in the cavity
7
a
of the reflector
7
and the p and n side electrodes on one side
6
a
of the LED element
6
are electrically connected with a pair of metallized wiring layers
2
,
3
. A reference numeral
8
denotes a molded portion made of a transparent or semi-transparent synthetic resin, that is a light transmittable synthetic resin molded portion which covers the entire surface of the LED element
6
for sealing it.
The thus formed semiconductor light emitting device
11
comprising the LED element
6
which is die-bonded on the rectangular insulating substrate
1
is surface-mounted on a circuit board. The metallized wiring layers
2
,
3
made of an electrically conductive material are connected to wiring conductors formed on the circuit board.
The output light which is emitted from the surface of the sapphire substrate
6
b
of the semiconductor light emitting element
6
is transmitted through the molded portion
8
and then emitted externally. A part of the output light is reflected on the side of the cavity
7
a
of the reflector
7
. The reflected light is also transmitted through the molded portion
8
is emitted externally so that the light emission efficiency of the semiconductor light emitting device
11
is enhanced.
Since the reflective coating material is applied on the side wall of the cavity which is formed from the substrate of non-transparent synthetic resin to improve the light emitting efficiency in the prior art semiconductor light emitting device in such a manner, there is a problem that man-hour is increased thereby to increase the manufacturing cost. The output light which is emitted in a direction opposite to the light emitting face of the semiconductor light emitting device is considerably lost so that it is not effectively used.
Since the reflector of another member which is formed into a predetermined thickness is laminated on the insulating substrate, the thickness of the reflector may be larger than a necessary thickness even if the thickness of the semiconductor light emitting element is made thinner. This results in that the semiconductor light emitting device has a large elevational size T
1
.
SUMMARY OF THE INVENTION
The present invention is made to overcome such problems. It is an object of the present invention to provide a semiconductor light emitting device in which its manufacturing cost is reduced, and the light emission efficiency is improved and which is made in the thin form to reduce its size and weight and to provide a semiconductor light emitting device having an increased light emission efficiency by using, for example, a semiconductor (LED) having a high light emission efficiency which is described in Copending Japanese Patent Application No. 10-55662 incorporated herin by reference.
The above-mentioned objects are accomplished by semiconductor light emitting devices as follows:
1. A semiconductor light emitting device comprising first reflective substrate, a second reflective substrate having a cavity which is laminated on said first reflective substrate, a semiconductor light emitting element which is accommodated in said cavity of said second reflective substrate and is die-bonded on said first reflective substrate on the side opposite to the light emitting side, where p and n side electrodes are formed; and a light transmittable synthetic resin molded portion for sealing the semiconductor light emitting element.
2. A semiconductor light emitting device set forth in the paragraph 1, in which said semiconductor light emitting element may be die-bonded on a wiring pattern on the surface of said first reflective substrate facing to the cavity of said second reflective substrate so that the electrodes on the side opposite to the light emitting face of said semiconductor light emitting element are electrically connected to through-hole conductors on said first reflective substrate.
3. A semiconductor light emitting device set forth in the paragraph 1, in which said semiconductor light emitting element at least may comprise a sapphire substrate, a GaN based compound semiconductor layer including a light emitting layer laminated on said sapphire substrate, and a current diffusion film laminated on said semiconductor layer, and wherein said current diffusion film is made of an electrically conductive metal having a high light reflectance, and wherein said semiconductor light emitting element is mounted on said first reflective substrate so that an output light of the light emitting layer is emitted from the sapphire substrate together with the reflected light which is reflected on said current diffusion film.
4. A semiconductor light emitting device set forth in the paragraph 1 or 2, in which said first and second reflective substrate may be white substrates.
Since the second white (reflective) substrate which is formed with the cavity is laminated on the first white substrate and the semiconductor light emitting element is accommodated in the cavity of the second white substrate in accordance with the present invention, the output light emitted from the semiconductor light emitting element is also reflected on both the lateral side of the semiconductor light emitting element and its bottom side opposite to its light emitting face and is externally emitted. The light emission efficiency of the semiconductor light emitting device can be improved.
Since the first and second white substrates themselves are used as reflective layers for the output light emitted from the semiconductor
Isokawa Shinji
Toda Hidekazu
Rohm & Co., Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Tran Minh Loan
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