Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With housing or contact structure
Reexamination Certificate
2002-03-22
2004-12-21
Flynn, Nathan J. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With housing or contact structure
C257S098000, C257S100000, C257S103000
Reexamination Certificate
active
06833566
ABSTRACT:
The present application is based on Japanese Patent Applications Nos. 2001-091961 and 2001-308256, which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to what is called a flip-chip-type light emitting diode (hereunder sometimes abbreviated as “an LED”) adapted so that alight emitting element is electrically connected to leads through the rear surface electrode thereof. The present invention also relates to a light shielding/reflecting type device adapted so that light outputted from a light source is reflected by a concave reflecting mirror and that the reflected light is radiated from an optical opening portion provided in a light shielding plate, and to the light source therefore. Incidentally, in the present specification, an LED chip itself is referred to as “a light emitting element”. Further, a light emitter sealed with a resin lens is referred to as a “light source”. Further, the entire light emitting apparatus including an optical device, such as package resin, on which an LED chip is mounted, or as a lens system, is referred to as “a light emitting diode”, “an LED” or “a device”.
2. Description of the Related Art
Hitherto, a light emitting diode has been constructed by employing what is called a flip-chip structure adapted so that when a light emitting element, such as a GaN light emitting element, having both of an anode electrode and a cathode electrode provided on one side thereof is mounted on an LED diode, the mounting of the light emitting element thereon is performed through a zener diode with the (transparent) electrode side down (see WO98-34285).
An example of such a conventional light emitting diode is described hereinbelow with reference to FIG.
11
.
FIG. 11
is a sectional view illustrating the configuration of a part, on which a light emitting element of the conventional light emitting diode is mounted, of the conventional light emitting diode. As illustrated in
FIG. 11
, in this light emitting diode
51
, a reflecting mirror
53
c is formed from one
53
a
of a pair of leads
53
a
and
53
b
for supplying electric power to a GaN light emitting element
52
. A zener diode
54
is mounted on the bottom surface of this light emitting diode
51
by using silver paste. Two kinds of electrodes
54
a
and
54
b
are formed on the top surface of the zener diode
54
. Two sorts of electrodes provided on the bottom surface of the light emitting element
52
are connected onto those electrodes
54
a
and
54
b
by using gold bumps
55
a
and
55
b
. Moreover, the light emitting element
52
is mounted thereon. A wire
56
is bonded to one
54
b
of the electrodes formed on the top surface of the zener diode
54
and electrically connected to the lead
53
b
corresponding to the other electrode
54
b
. Thus, the light emitting element
52
is mounted on the zener diode
54
and emits light by being supplied with electric power by the pair of leads
53
a
and
53
b.
However, in such a light emitting diode
51
, the light emitting element
52
is mounted one
53
a
of the leads through the zener diode
54
. Thus, this conventional light emitting diode has drawbacks in that heat dissipation is poor, that consequently, the temperature of the light emitting element
52
rises to a high level, and luminous efficiency lowers, and device lifetime decreases. Further, even when the reflecting mirror
53
c
is provided in such a way as to surround the light emitting element
52
, as illustrated in
FIG. 11
, the reflecting mirror
53
c
is away from the light emitting element
52
owing to the zener diode
54
, and that thus, sufficient optical characteristics cannot be obtained.
Further, light emitting diodes include a reflective LED. An example of this reflective LED is described hereinbelow with reference to FIG.
12
.
FIG. 12
is a sectional view illustrating an example of a reflective LED. As illustrated in
FIG. 12
, this reflective LED
131
has a light emitting element
132
mounted at an end portion of one
133
b
of a pair of leads
133
a
and
133
b
for supplying electric power thereto. Further, the light emitting element
132
is electrically connected to the other lead
133
a
through wire bonding using a wire
134
. The light emitting element
132
, the pair of leads
133
a
and
133
b
, and the wire
134
are sealed with transparent epoxy resin
135
. A reflecting surface, which has a focal point at the position of the light emitting element
132
and is shaped like a paraboloid of revolution, is formed at a place at which the reflecting surface faces the light emitting element
132
. A concave reflecting mirror
136
is formed by evaporating aluminum on the outer reflecting surface thereof.
When light is emitted from the light emitting element
132
, the light is upwardly reflected by each part of the reflecting mirror
136
parallel to the central axis of the reflecting surface shaped like a paraboloid of revolution. Then, the reflected light is radiated from the top surface, which is a flat radiating surface
137
, of the reflective LED
131
to the outside. Thus, the reflective LED
131
can externally radiate the light, which is emitted from the light emitting element
132
, as light obtained by being condensed with high efficiency.
However, the conventional reflective LED
131
has problems in that because the area of the reflecting surface seen from the outside is large, large dark noises are caused (that is, what is called pseudo-lighting occurs) owing to the reflection of external light at each turn-off of the light source, and that consequently, the contrast between the intensity of the light, which is radiated during the light source is turned on, and that of the light reflected when the light source is turned off, is low.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a light emitting diode, which sufficiently shows the characteristics of a light emitting element, by forming a flip chip structure without using a zener diode, and to provide a manufacturing method therefor.
Another object of the present invention is to provide a light shielding/reflecting type device, which shows high efficiency in external radiation of light and high contrast between the intensity of light, which is radiated during the light source is turned on, and that of light reflected when the light source is turned off, and to provide a light source therefor.
To achieve the foregoing object, according to the invention, there is provided a light emitting diode(hereunder referred to as a first light emitting diode of the invention) having a flip-chip-type light emitting element. In this diode, a through hole of a through-hole substrate is filled with metal. Further, one of rear surface electrodes of the light emitting element is connected onto the through hole. Moreover, the other of the rear surface electrodes of the light emitting element is connected to a conductive pattern insulated from the through hole of the through-hole substrate.
In the case of the LED of such a configuration, fine and precise conductive patterns of the through hole substrate can be formed. Thus, two rear surface electrodes, the distance between which is very short, of the light emitting element can be adapted so that one of the rear surface electrodes is reliably connected onto the through hole, while the other of the rear surface electrodes is reliably connected onto the conductive pattern insulated from the through hole by maintaining the insulation therebetween. Further, because the through hole is filled with metal, the through hole can serve as a heat sink. Thus, the LED excels in heat radiation. Consequently, luminous efficiency is maintained at a high level. The device lifetime can be increased.
Thus, the LED, which sufficiently exhibits the characteristics of the light emitting element, is provided by forming a flip-chip structure without using a zener diode.
According to another aspect of the invention, there is provided a light emitting diode (hereunder referred to as a se
Hadame Kunihiro
Kato Hideaki
Suehiro Yoshinobu
Greene Pershelle
McGinn & Gibb PLLC
Toyoda Gosei Co,., Ltd.
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