Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
2003-01-06
2004-09-14
Wilson, Allan R. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S432000, C257S436000
Reexamination Certificate
active
06791151
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a base of an optoelectronic device, and more particularly, to a base that can reflect light for an optoelectronic device, thereby promoting light emission intensity or increasing light reception intensity.
BACKGROUND OF THE INVENTION
Generally speaking, an optoelectronic device usually comprises an optoelectronic element, and the property of the optoelectronic device is closely related to that of the optoelectronic element. Currently, one of the most commonly-used optoelectronic elements is a diode, which can be roughly divided into a light-emitting element, such as a light-emitting diode (LED) chip, and a photosensitive element, such as a photo-detector or a solar cell, wherein the photo-detector can be a photodiode (PD) or a positive-intrinsic-negative (PIN) diode, etc.
Herein, a LED is taken as an example. Such as shown in
FIG. 1
, a LED comprises a coating resin
101
, a LED chip
102
, a conductive wire
103
, a molding material
104
, a lead frame
105
and an inner lead
106
, wherein the lead frame
105
comprises a base
105
a
and a lead
105
b
. The description of the aforementioned LED structure can be referred to U.S. Pat. No. 5,998,925.
Such as shown in
FIG. 1
, the coating resin
101
is filled in the base
105
a
to cover the LED chip
102
, so as to prevent the diode chip
102
from contacting oxygen or moisture, thereby protecting the LED chip
102
. The coating resin
101
is generally made of transparent material, such as epoxy resin, urea resin or glass, etc. However, the thermal expansion coefficient and heat conductivity of the coating resin
101
are apparently different from those of the LED chip
102
, so that the heat generated from the imperfect electro-optical conversion is easy to be accumulated on the interface between the coating resin
101
and the LED chip
102
, while the optoelectronic element is in operation. Moreover, in the manufacturing process, it is quite important about how to use proper temperature and process for the coating resin
101
to be stably coated on or filled in the area surrounding the LED chip
102
, and meanwhile, to assure that no extra chemical reaction between two different materials (the coating resin
101
and the LED chip
102
) will occur. However, with the current technology, it usually needs to perform a baking step on the coating resin
101
at 150° C. for about 40 minutes, so as cure the coating resin
101
. Hence, for fitting to the current process, the coating resin
101
of high purity has to be selected as the material used for coating or filling (since some elements are easy to be diffused into semiconductor material to change the original properties of the semiconductor material).
The aforementioned structure also causes another bad influence. As the coating resin
101
is a poor heat conductor, heat is accumulated on the interface between two different materials (the coating resin
101
and the LED chip
102
). Due to the difference in the thermal expansion coefficients between the coating resin
101
and the LED chip
102
, while the element is in operation, heat accumulated therein causes additional stress exerted on the LED chip
102
, wherein the stress is exactly proportional to the interface temperature (which is caused by the accumulated heat). While LED elements are developed towards the applications of high brightness and high power, the aforementioned problem will become more and more serious. Even on the current common applications, since the coating resin
101
and the LED chip
102
are different in material properties, the operation stability and life of the optoelectronic elements are affected directly or indirectly.
Further, please refer to
FIG. 2
, which is a detailed diagram showing the elements around the base
105
a
, wherein the LED chip
102
is a semiconductor element having a PN junction
107
. Hence, when a positive voltage is applied to two electrodes of the LED chip
102
, the light of light of specific wavelength will be emitted from the PN junction
107
of the LED chip
102
. In the aforementioned structure, the light emitted by the LED chip
102
towards the base
105
a
cannot be emitted again to the external, and thus the light emission intensity and efficiency of the entire LED device are affected. However, under the current structure, these shortcomings are inevitable.
Such as shown in
FIG. 2
, the coating resin
101
is used to fill in the base
105
a
to cover the LED chip
102
, and the coating resin
101
may comprise fluorescent matter, such as phosphor. Besides, the coating resin
101
can be transparent material, such epoxy resin, urine resin or glass, etc. Moreover, the fluorescent matter contained in the coating resin
101
can change the light emission wavelength by the way of energy conversion, and the porosity and coating thickness of the fluorescent matter also affect the color of the colored light emitted after the wavelengths respectively generated by the LED and the fluorescent matter are mixed. However, on one hand, due to the oxidization reaction and the deterioration scheme of the coating resin
101
itself, and on the other hand, due to the temperature influence and the UV light irradiation, the deterioration of the coating resin
101
and phosphor is thus accelerated. When the coating resin
101
is deteriorated and cured because of heat, or is damaged by the UV light in sunshine, the coating resin
101
has the phenomenon of curing and deteriorating. Once the coating resin
101
starts deteriorating, the LED chip
102
covered thereby will be affected and damaged. Especially for the element of which the waveband of light emitted is below that of blue light (wherein the wavelength of emitted light is smaller than 480 nm), because the LED chip thereof has the attribute of spontaneous light-emission, and additionally, the light traveling path thereof is concentrated within a specific angle, resulting in high light emission intensity, consequently, the damage to the coating resin is more sever. With the occurrence of these situations, the LED device has the chance to be functionally retarded.
Please refer
FIG. 1
again. In the process for manufacturing the conventional LED, the LED chip
102
has to first be fixed on the base
105
a
. Thereafter, the conductive wire
103
is formed between the LED chip
102
and the inner lead
106
in a manner of wiring. Then, the coating resin
101
is filled in the base
105
a
to cover the LED chip
102
and part of the conductive wire
103
. However, errors may occur in the process of fixing the LED chip
102
, and the conductive wire
103
may not be able to be formed accurately on the bonding pad of the LED chip
102
while being formed on the LED chip
102
, thus causing the LED chip
102
to be electrically nonconductive, resulting in manufacturing a defective LED.
On the other hand, as to a photosensitive element, the photosensitive element can be a photodiode, a PIN diode, a photo crystal or a solar cell. Referring to
FIG. 3
,
FIG. 3
is a schematic diagram showing a conventional photodiode of TO-CAN type.
FIG. 3
illustrates a photodiode
110
, a base
120
, a lead pin
130
, a lead pin
132
, a metal cover
144
, a light-emitting window
154
, a conductive wire
180
, a soldering pad
190
and an insulation part
195
, etc., wherein the photodiode
110
is fixed on one surface of the base
120
, and the lead pin
130
and the lead pin
132
are connected to the other surface of the base
120
for transmitting electrical signals.
As to the metal-can packaging of the photodiode
110
, it means that the metal cover
144
is fitted to the base
120
, so as to protect the photodiode
110
. Besides, the light-emitting window
154
is inset into the upper surface of the metal cover
144
, so that, when the metal cover
144
is fitted to the base
120
, an incident light
200
from the external can pass through the light-emitting window
154
and is refracted to become an incident light
202
, which is further focused on the photodiode
110
. Furth
Lin Ming-Der
Wang Kwang-Ru
Highlink Technology Corporation
Sughrue & Mion, PLLC
Wilson Allan R.
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