Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With reflector – opaque mask – or optical element integral...
Reexamination Certificate
2003-03-18
2004-10-12
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With reflector, opaque mask, or optical element integral...
C257S013000, C257S103000, C438S022000, C438S029000
Reexamination Certificate
active
06803606
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting device and a manufacturing method thereof.
As shown in
FIG. 3
, a light emitting device has conventionally been made up of a substrate
101
, a semiconductor light emitting element
103
fixed onto the substrate
101
with use of Ag (silver) paste
102
, a gold wire
104
bonded to the semiconductor light emitting element
103
and connected to an unshown electrode, two reflectors
107
disposed around the semiconductor light emitting element
103
for reflecting a light beam from the semiconductor light emitting element
103
, and a resin
109
disposed between these two reflectors
107
,
107
for sealing the light emitting element
103
and the gold wire
104
. The reflector
107
is formed from a liquid crystal polymer having high heat resistance in consideration of influence of heat from the semiconductor light emitting element
103
. A light reflecting surface
107
a
of the reflector
107
located on the side of the semiconductor light emitting element
103
is left untreated or mirror-finished.
However, adherence between the reflector
107
and the resin
109
is poor because the conventional light emitting device is formed such that the light reflecting surface
107
a
of the reflector is left untreated or mirror-finished. Consequently, there is the possibility that the reflector
107
is detached from the resin
109
due to heat generated in mounting the light emitting device or heat generated in operating the light emitting device. Proceeding in detachment of the reflector
107
from the resin
109
induces detachment of the substrate
101
from the resin
109
. As a result, due to stress caused by the detachment of the substrate
101
from the resin
109
, there is imposed such serious problem as destruction in connection between the semiconductor light emitting element
103
and the gold wire
104
. Further, when adherence between the reflector
107
and the resin
109
is poor, water may disadvantageously invade into a detachment portion between the reflector
107
and the resin
109
.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a light emitting device capable of preventing detachment of a reflector from a resin.
In order to accomplish the above object, the present invention a light emitting device comprising:
a substrate;
a light emitting element on the substrate;
a reflector on the substrate for reflecting a light beam outgoing from the light emitting element; and
a resin disposed between the light emitting element and the reflector on the substrate,
wherein a face of the reflector that reflects a light beam outgoing from the light emitting element is formed into a rough surface.
According to the above configuration, the face of the reflector that reflects a light beam outgoing from the light emitting element is formed into a rough surface, so that adherence between the reflector and the resin through the rough surface of the reflector becomes relatively larger. Therefore, the reflector is hardly detached from the resin even if, for example, the light emitting device receives heat during mounting the light emitting device on the substrate or during operating the light emitting device. This ensures avoidance of such disadvantage as the substrate being detached from the resin, a bonding wire connected to the light emitting element being disconnected due to the detachment of the substrate from the resin, and water entering through a detachment portion between the reflector and the resin, thereby causing malfunction of the light emitting device.
In one embodiment of the present invention, the rough surface of the reflector has an arithmetic mean roughness ranging of 1 &mgr;m or more and 20 &mgr;m or less.
According to the above embodiment, adherence between the reflector and the resin through the rough surface of the reflector becomes appropriate. When the arithmetic mean roughness of the rough surface is smaller than 1 &mgr;m, adherence between the reflector and the resin becomes insufficient to unavoidably cause such a problem as detachment of the reflector from the resin. When the arithmetic mean roughness of the rough surface is larger than 20 &mgr;m, a reflecting amount of light on the rough reflecting surface becomes insufficient, which makes luminance of a light beam emitted by the light emitting device insufficient.
In one embodiment of the present invention, the reflector is made of a liquid crystal polymer.
According to the above embodiment, the liquid crystal polymer of which the reflector is made has good heat resistance, but has difficulty in adhering to the resin. However, since the reflector has a rough surface, sufficient adherence may be obtained between the reflector and the resin via the rough surface. Therefore, the reflector made of the liquid crystal polymer has a stable light reflecting function even if the temperature of the light emitting device is raised by light emitting operation and the like, and the problem of detachment of the reflector from the resin is avoided, which achieves stable provision of the light emitting device having good performance.
In one embodiment of the present invention, the liquid crystal polymer contains a glass at a rate of more than 0 wt % and equal to or less than 30 wt %.
According to the above embodiment, the reflector has good strength since the reflector is made of the liquid crystal polymer containing a glass. Here, when a rate of the glass contained in the liquid crystal polymer is more than 30 wt %, there increases a light beam outgoing from the light emitting element that transmits the reflector. Thereby, there is the possibility that luminance of the light emitting device may decrease and that a light beam may leak to the lateral side of the light emitting device. Also, there is a disadvantage that a mold is remarkably worn away where the reflector made of the liquid crystal polymer containing more than 30 wt % is manufactured by injection molding for example.
In one embodiment of the present invention, the liquid crystal polymer contains titanium oxide at a rate of more than 0 wt % and equal to or less than 30 wt %.
According to the above embodiment, reflectance of light increases since the reflector is made of a liquid crystal polymer containing titanium oxide. When a rate of titanium oxide contained in the liquid crystal polymer is more than 30 wt %, a resin flow of the liquid crystal polymer containing titanium oxide is deteriorated. Therefore, stable molding is not attainable when the reflector is manufactured by injection molding for example.
In one embodiment of the present invention, the liquid crystal polymer contains calcium oxide at a rate of more than 0 wt % and equal to or less than 50 wt %.
According to the above embodiment, the liquid crystal polymer containing not more than 50 wt % calcium oxide enables a rough surface to be stably formed. That is, the reflector made of the above-stated liquid crystal polymer enables formation of a rough surface having good adherence to resin. When a rate of calcium oxide contained in the liquid crystal polymer is more than 50 wt %, heat resistance and strength of the reflector decrease since a rate of the liquid crystal polymer decreases.
In one embodiment of the present invention, the liquid crystal polymer contains a glass at a rate of 20 wt % or more and 30 wt % or less, and also contains titanium oxide at a rate of 20 wt % or more and 30 wt % or less.
According to the above embodiment, the above liquid crystal polymer makes it possible to obtain a reflector having good strength and light reflectance. When the rate of the glass is less than 20 wt %, heat resistance and mechanical strength of the reflector are decreased. When the rate of the glass is more than 30 wt %, a light transmission amount of the reflector increases. Thereby, luminance of the light emitting device decreases, and a light beam leaks to the lateral side of the light emitting device. Also, When the rate of the glass is more than 30 wt %, a mold in molding the reflector is
Nelms David
Sharp Kabushiki Kaisha
Tran Long
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