Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure
Reexamination Certificate
2002-06-18
2004-03-16
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
C257S013000, C257S098000, C257S099000, C257S103000, C257S433000, C257S434000, C257S704000
Reexamination Certificate
active
06707069
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to light emission diode packages with reflective plates of metal and, more particularly, to a light emission diode package provided with a reflective plate of metal for accomplishing an improved heat dissipation effect, in addition to easily controlling its luminance and angular distribution of the luminance.
2. Description of the Prior Art
As well known to those skilled in the art, light emission diode packages (herein below, referred to simply as “LED packages”) are semiconductor devices, which have LED chips acting as light sources and produced by changing the physical and chemical characteristics of some compound semiconductor materials, such as GaAs, AlGaAs, GaN, InGaN and AlGaInP, and radiate colored lights from the LED chips when electrically activated.
The characteristics of such LED packages are typically determined in accordance with colors of emitted lights, luminance, and a viewing angle thereof. Such characteristics of LED packages are primarily determined by the physical and chemical characteristics of compound semiconductor materials of LED chips, and secondarily determined by their package structures for seating the LED chips therein. In the prior art, the improvement in the characteristics of LED packages accomplished by the development of compound semiconductor materials of LED chips is undesirably limited. Therefore, improved structures of LED packages have been actively studied in recent years, in addition to study of the semiconductor materials of LED chips, in an effort to meet the requirement of a high luminous intensity and a desired viewing angle (it may also be referred to an angular distribution of the luminance). That is, while designing LED packages in recent years, it is desired to consider the compound semiconductor materials of LED chips as a primary design factor, and the structures of LED packages as a secondary design factor.
Particularly, both the luminance and an angular distribution of the luminance of LED packages are mainly affected by the secondary design factor, that is, the structures of the LED packages.
For example, a conventional lamp type LED package of
FIG. 1
a
and a conventional surface mounted type LED package of
FIG. 1
b
are compared with each other in their package structures as follows: In the case of the conventional lamp type LED package
10
of
FIG. 1
a
with two leads
3
a
and
3
b
, the second lead
3
b
is provided at its top with a metal electrode surface, which is depressed to form a depression with inclined side surfaces having a predetermined inclination angle. An LED chip
5
is seated in the depression of the metal electrode surface. The two leads
3
a
and
3
b
with the LED chip
5
are packaged by a hemispherical casing
7
of transparent mold resin, thus producing a lamp type LED package
10
. The conventional surface mounted type LED package
20
of
FIG. 1
b
consists of a molded package body
11
of epoxy resin, and an LED chip
15
mounted on the surface of the body
11
at a chip mounting area. The LED chip
15
is connected to an electrode (not shown) through a plurality of wires
13
.
In the conventional lamp type LED package
10
, the hemispherical casing
7
acts as a lens capable of controlling the angular distribution of luminance. Particularly, the hemispherical casing
7
controls the angular distribution of luminance in a way such that the distribution becomes narrow, thus increasing the luminous intensity at a predetermined angle. In addition, the light radiated from the LED chip
5
is reflected by the metal electrode surface of the second lead
3
b
, thus increasing the luminous intensity of the LED chip
5
. In comparison with such a lamp type LED package
10
, the surface mounted type LED package
20
has a wider angular distribution of luminance and a lower luminous intensity. It is thus noted that the package structures affect the luminance and the angular distribution of the luminance of LED packages. Therefore, in an effort to accomplish desired characteristics of LED packages, there has been proposed a surface mounted type LED package, with an additional light reflecting surface formed by coating metal on an inclined side surface of the chip mounting area of a molded package body and having a predetermined reflective angle.
Different from such LED packages having molded resin bodies, it is almost impossible to desirably control the luminance or the angular distribution of luminance of another type LED package, having a ceramic body consisting of laminated ceramic substrates and widely used in recent years. That is, the chip mounting area of such a ceramic body must be formed through a punching process, a laminating process, and a cutting process, different from the molded resin bodies having chip mounting areas formed through an resin injection molding process. It is thus very difficult to form a side surface of the chip mounting area of the ceramic body in such a way that the side surface has a desired reflective angle.
FIG. 2
is a sectional view of a conventional LED package having such a ceramic body. As shown in the drawing, the ceramic body of the LED package
30
consists of two ceramic substrates
21
and
22
, each of which is formed by laminating a plurality of ceramic sheets. Of the two ceramic substrates
21
and
22
, the lower substrate
21
is provided at its top surface with a chip mounting area for seating an LED chip
25
thereon. An electrode
23
extends outward from the edge of the chip mounting area to the lower surface of the lower ceramic substrate
21
to cover a part of the lower surface after passing over the side surfaces of the lower ceramic substrate
21
. The LED chip
25
is electrically connected to the electrode
23
using a plurality of wires
27
through a wire bonding process. The upper ceramic substrate
22
is bonded to the top surface of the lower ceramic substrate
21
, and forms a predetermined cavity surrounding the chip mounting area.
The cavity surrounding the chip mounting area of the ceramic body is formed through a punching process or a cutting process, so the inside surface of the ceramic body defining the cavity is formed as a vertical surface. Therefore, different from the LED packages having the molded resin bodies, it is difficult to form a coated metal layer on the vertical inside surface of the ceramic body. An additional inclined surface made of resin may be formed on the vertical inside surface of the ceramic body, with a metal layer coated on the inclined resin surface in an effort to overcome the above-mentioned problems. However, the inclined resin surface may be easily deformed, so it is almost impossible to form a desired reflecting surface on the ceramic body.
In the conventional LED packages having such ceramic bodies, it is only possible to control the luminance and the angular distribution of the luminance by changing the dimension of the chip mounting area and/or the thickness of the upper ceramic substrate determining the height of the cavity. Therefore, it is difficult to produce LED packages having ceramic bodies and meeting the requirement of a high luminous intensity and a desired angular distribution of luminance. However, the ceramic substrates of such LED packages have high heat conductivity and a high heat dissipation effect, thus effectively solving the problems of thermal degradation of LED packages and thermal stress of package bodies caused by heat radiated from LED chips. Therefore, it is desired to propose more effective LED packages, which use such ceramic substrates having a high heat conductivity and a high heat dissipation effect, and overcome the structural faults experienced in the conventional LED packages with ceramic bodies due to the vertical inside surface of the ceramic body and leading to difficulty in the control of luminance and angular distribution of the luminance of the LED packages.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping in mind the above pro
Cheon Jong Pil
Song Kyung Sub
Huynh Andy
Lowe Hauptman & Gilman & Berner LLP
Samsung Electro-Mechanics Co., LTD
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